Bidirectional isolation DCDC circuit and common mode filter design method

Abstract

The invention provides a bidirectional isolation DCDC circuit and a common mode filter design method, and relates to the technical field of power supply circuits. The circuit comprises a first isolation transformer which comprises a first primary winding and a first secondary winding which are electrically isolated from each other; the primary side main circuit comprises a first common-mode filter and a first full-bridge circuit, and a second connecting end of the first common-mode filter is electrically connected with the first primary winding through the first full-bridge circuit; and the secondary side main circuit comprises a second common-mode filter and a second full-bridge circuit, and a second connecting end of the second common-mode filter is electrically connected with the first secondary winding through the second full-bridge circuit. According to the bidirectional isolation DCDC circuit supporting DC bidirectional energy transmission, the common-mode filters are respectively arranged on the primary side and the secondary side of the first isolation transformer, so that high-frequency common-mode interference introduced in an external power supply input or power device high-frequency switching operation process can be effectively inhibited; and the electromagnetic compatibility and the anti-interference capability of the circuit are improved.

Description

Technical Field

[0001] This invention relates to the field of power supply circuit technology, and more specifically, to a bidirectional isolated DC-DC circuit and a common-mode filter design method. Background Technology

[0002] With the rapid development of power electronics technology, high-voltage and high-power applications such as new energy vehicles and photovoltaic power generation are becoming increasingly popular. This has led to higher performance requirements for the required test power supply systems, especially in terms of high output voltage, high dynamic response, and electromagnetic compatibility.

[0003] To meet these high-performance specifications, the output stage of a test power supply typically employs a multi-module cascade structure, using multiple power modules connected in series to increase the overall output voltage level. Furthermore, to further reduce output ripple and improve dynamic response performance, a phase-shifting control strategy is used in the test power supply system. This strategy shifts the switching signals of each module in phase, achieving a higher equivalent switching frequency and a smoother output waveform. This strategy effectively increases control bandwidth and achieves a multi-level-like output effect. However, under this strategy, the intermediate-stage isolated DC-DC module in the test power supply system must withstand significant common-mode voltage surges. These common-mode voltages include both DC common-mode components generated by inter-module potential differences and high-frequency alternating components caused by phase-shifting control. High-frequency common-mode voltages, in particular, can cause significant electromagnetic compatibility (EMC) problems, such as difficulty in filtering high-frequency output ripple, common-mode interference coupling to internal sampling and control circuits leading to malfunctions, and in severe cases, even affecting the drive and protection functions of the isolated DC-DC module, threatening system stability and safety.

[0004] To reduce the impact of common-mode voltage interference, some related technologies employ a BUCK cascade topology with filtering followed by series connection. This involves each DC-DC module undergoing output filtering before being connected in series to form a high-voltage output. However, this approach requires independent sampling and control of the inductor current of each module to suppress LC resonance that may occur during load surges. Furthermore, based on this structure, phase-shift control can only reduce output ripple but cannot achieve a multi-level effect, resulting in a low overall LC cutoff frequency and limited improvement in control bandwidth. In contrast, some related technologies use a series-first, then filtering approach, which allows for unified output filtering after each DC-DC module is connected in series. This approach offers advantages such as a simpler structure and more centralized control loop. More importantly, this structure, combined with phase-shift control, can significantly increase the equivalent switching frequency, achieving equivalent multi-level output characteristics and effectively improving the filter cutoff frequency and system control bandwidth. However, this approach exposes the intermediate isolated DC-DC modules directly to a high-frequency common-mode voltage environment, making electromagnetic interference a particularly prominent issue, for which an effective solution is currently lacking. Summary of the Invention

[0005] The problem solved by this invention is: how to effectively suppress interference caused by high-frequency common-mode voltage.

[0006] To address the above problems, this invention provides a design method for a bidirectional isolated DC-DC circuit and a common-mode filter.

[0007] In a first aspect, the present invention provides a bidirectional isolated DC-DC circuit, comprising: The first isolation transformer includes a first primary winding and a first secondary winding that are electrically isolated from each other; The primary side main circuit includes a first common-mode filter and a first full-bridge circuit. The second connection terminal of the first common-mode filter is electrically connected to the first primary winding through the first full-bridge circuit. The secondary side main circuit includes a second common-mode filter and a second full-bridge circuit. The second connection terminal of the second common-mode filter is electrically connected to the first secondary winding through the second full-bridge circuit. Wherein, the first connection terminal of the first common-mode filter is used to connect to DC power, and the first connection terminal of the second common-mode filter is used to output DC power; or, the first connection terminal of the second common-mode filter is used to connect to DC power, and the first connection terminal of the first common-mode filter is used to output DC power.

[0008] Optionally, the first common-mode filter includes a first common-mode inductor, which includes a first inductor, a second inductor, a first damping winding, a first damping resistor, and a first magnetic core structure. The coils of the first inductor, the second inductor, and the first damping winding are respectively wound on the first magnetic core structure. The two ends of the first damping resistor are respectively electrically connected to the two ends of the first damping winding. The first full-bridge circuit is respectively electrically connected to the first inductor and the second inductor. And / or, the second common-mode filter includes a second common-mode inductor, which includes a third inductor, a fourth inductor, a second damping winding, a second damping resistor, and a second magnetic core structure. The coils of the third inductor, the fourth inductor, and the second damping winding are respectively wound on the second magnetic core structure. The two ends of the second damping resistor are respectively electrically connected to the two ends of the second damping winding. The second full-bridge circuit is respectively electrically connected to the third inductor and the fourth inductor.

[0009] Optionally, the first common-mode filter further includes a first capacitor, one end of which is electrically connected to the end of the first inductor away from the first full-bridge circuit, and the other end of which is electrically connected to the end of the second inductor away from the first full-bridge circuit; the primary-side main circuit further includes a second capacitor, one end of which is electrically connected to the end of the first inductor used for electrically connecting to the first full-bridge circuit, and the other end of which is electrically connected to the end of the second inductor used for electrically connecting to the first full-bridge circuit; And / or, the second common-mode filter further includes a fourth capacitor, one end of which is electrically connected to the end of the third inductor away from the second full-bridge circuit, and the other end of which is electrically connected to the end of the fourth inductor away from the second full-bridge circuit; the secondary-side main circuit further includes a fifth capacitor, one end of which is electrically connected to the end of the third inductor used for electrically connecting to the second full-bridge circuit, and the other end of which is electrically connected to the end of the fourth inductor used for electrically connecting to the second full-bridge circuit; And / or, the primary side main circuit further includes a third capacitor, the first inductor is used to electrically connect one end of the first full-bridge circuit to ground or control ground through the third capacitor, or the second inductor is used to electrically connect one end of the first full-bridge circuit to ground or control ground through the third capacitor; And / or, the secondary side main circuit further includes a sixth capacitor, the third inductor is used to electrically connect one end of the second full-bridge circuit to ground or control ground through the sixth capacitor, or the fourth inductor is used to electrically connect one end of the second full-bridge circuit to ground or control ground through the sixth capacitor.

[0010] Optionally, the bidirectional isolated DC-DC circuit further includes a resonant inductor and a resonant capacitor; The first full-bridge circuit includes a first switch, a second switch, a third switch, and a fourth switch. The first terminals of the first and third switches are electrically connected to one end of the first inductor, and the second terminals of the second and fourth switches are electrically connected to one end of the second inductor. The second terminal of the first switch and the first terminal of the second switch are electrically connected, and are electrically connected to one end of the first primary winding through one of the resonant inductor and the resonant capacitor. The second terminal of the third switch and the first terminal of the fourth switch are electrically connected, and are electrically connected to the other end of the first primary winding. The first full-bridge circuit includes a fifth switch, a sixth switch, a seventh switch, and an eighth switch. The first ends of the fifth and seventh switches are electrically connected to one end of the third inductor, and the second ends of the sixth and eighth switches are electrically connected to one end of the fourth inductor. The second end of the fifth switch and the first end of the sixth switch are electrically connected, and are also electrically connected to one end of the first secondary winding through another of the resonant inductor and the resonant capacitor. The second end of the seventh switch and the first end of the eighth switch are electrically connected, and are also electrically connected to the other end of the first secondary winding.

[0011] Optionally, the bidirectional isolated DC-DC circuit further includes a control circuit that is communicatively connected to the first full-bridge circuit and the second full-bridge circuit, respectively. The control circuit is used to control the on / off state of each switch in the first full-bridge circuit and the second full-bridge circuit.

[0012] Optionally, the control circuit includes a primary-side control circuit, a secondary-side control circuit, and a detection circuit. The primary-side control circuit includes a first isolation drive circuit, the input of which is electrically connected to the output of the detection circuit, and the output of which is electrically connected to the controlled terminals of each switch in the first full-bridge circuit. The secondary-side control circuit includes a second isolation drive circuit, the input of which is electrically connected to the output of the detection circuit, and the output of which is electrically connected to the controlled terminals of each switch in the second full-bridge circuit. The input of the detection circuit is used to receive drive signals.

[0013] Optionally, the primary-side control circuit further includes a first comparison circuit and a first fault clamping circuit. The output terminal of the detector circuit is electrically connected to the input terminal of the first isolation drive circuit through the first comparison circuit. The output terminal of the first fault clamping circuit is connected to the input terminal of the first comparison circuit. The input terminal of the first fault clamping circuit is used to receive a fault signal and clamp the potential of the input terminal of the first comparison circuit to a first preset clamping level according to the fault signal. And / or, the secondary side control circuit further includes a second comparison circuit and a second fault clamping circuit. The output terminal of the detector circuit is electrically connected to the input terminal of the second isolation drive circuit through the second comparison circuit. The output terminal of the second fault clamping circuit is connected to the input terminal of the second comparison circuit. The input terminal of the second fault clamping circuit is used to receive a fault signal and clamp the potential of the input terminal of the second comparison circuit to a second preset clamping level according to the fault signal.

[0014] Optionally, the control circuit further includes a second isolation transformer, the input terminal of the detection circuit is electrically connected to the second secondary winding of the second isolation transformer, and the second primary winding of the second isolation transformer is used to receive the drive signal; And / or, the control circuit further includes a third isolation transformer, the output terminal of the detector circuit is electrically connected to the third primary winding of the third isolation transformer, and the input terminal of the first isolation drive circuit is electrically connected to the third secondary winding of the third isolation transformer; And / or, the control circuit further includes a fourth isolation transformer, the output terminal of the detector circuit is electrically connected to the fourth primary winding of the fourth isolation transformer, and the input terminal of the second isolation drive circuit is electrically connected to the fourth secondary winding of the fourth isolation transformer.

[0015] Optionally, the detection circuit includes a first comparator, a second comparator, a seventh capacitor, and an eighth capacitor. The non-inverting input of the first comparator is electrically connected to one end of the second secondary winding, and the non-inverting input of the second comparator is electrically connected to the other end of the second secondary winding. The inverting inputs of the first and second comparators are respectively used to connect to a preset reference voltage. The output of the first comparator is connected to one end of the third primary winding, or connected to one end of the third primary winding through one of the seventh capacitors. The output of the second comparator is connected to the other end of the third primary winding, or connected to the other end of the third primary winding through another of the seventh capacitors. The midpoint of the second secondary winding is grounded through the eighth capacitor, and / or the midpoint of the second secondary winding is connected to control ground.

[0016] Secondly, the present invention provides a common-mode filter design method, including: Based on the first preset target performance requirements, determine the first design parameters of the first common-mode inductor of the first common-mode filter regarding the first inductor, the second inductor, and the first magnetic core structure; perform simulation analysis based on the first design parameters, and determine the second design parameters of the first common-mode inductor regarding the first damping winding and the first damping resistor based on the simulation analysis results; And / or, based on the second preset target performance requirements, determine the third design parameters of the second common-mode inductor of the second common-mode filter regarding the third inductor, the fourth inductor, and the second magnetic core structure; perform simulation analysis based on the second design parameters, and determine the fourth design parameters of the second common-mode inductor regarding the second damping winding and the second damping resistor based on the simulation analysis results.

[0017] The beneficial effects of the bidirectional isolated DC-DC circuit of the present invention are as follows: The bidirectional isolated DC-DC circuit of the present invention, which supports bidirectional DC energy transmission, is suitable for application scenarios with high requirements for high voltage output, high dynamic response capability, and electromagnetic compatibility, such as test power supplies, high-voltage charging and discharging systems, and photovoltaic energy storage converters. Specifically, by setting common-mode filters on the primary and secondary sides of the first isolation transformer, this circuit can effectively suppress high-frequency common-mode interference introduced by external power input or high-frequency switching operation of power devices, thereby improving the electromagnetic compatibility and anti-interference capability of the circuit. By using a full-bridge circuit to work in conjunction with the first isolation transformer, bidirectional high-efficiency conversion and isolated transmission of DC and high-frequency AC are achieved, which facilitates (e.g., combined with phase-shift control) improvement of the control bandwidth (or response speed) and energy transmission efficiency of this circuit and its applied circuits (e.g., the circuit topology of the corresponding power system). Thus, based on the aforementioned circuit structure, the optimized design of the common-mode voltage isolation path is achieved, enhancing the circuit's tolerance to high common-mode voltages. This improves the stability and reliability of the circuit and its applications in complex electromagnetic environments. When used as a submodule in a power supply system, this circuit significantly reduces the overall electromagnetic interference risk, simplifies system filtering and electromagnetic compatibility design requirements, and improves the stability and response speed of energy conversion under different operating modes. It also enhances the modular expansion capability of the power supply system, better meeting the multiple performance requirements of complex application environments such as high voltage, high power, and bidirectional energy flow. Furthermore, the primary and secondary functions of the first isolation transformer in this circuit are switchable, supporting forward and reverse energy flow, thereby meeting the flexibility requirements of different bidirectional power supply scenarios and expanding the application range of this circuit. Attached Figure Description

[0018] Figure 1 This is a partial circuit structure diagram of the bidirectional isolated DC-DC circuit in an embodiment of the present invention; Figure 2 This is a schematic diagram of the control circuit of the bidirectional isolated DC-DC circuit in an embodiment of the present invention; Figure 3 This is a timing diagram of the bidirectional isolated DC-DC circuit in an embodiment of the present invention. Figure 4 This is a timing diagram showing the fault operation of the bidirectional isolated DC-DC circuit in an embodiment of the present invention. Detailed Implementation

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in sequences other than those illustrated or described herein.

[0021] Combination Figure 1 As shown, an embodiment of the present invention provides a bidirectional isolated DC-DC circuit, comprising: The first isolation transformer includes a first primary winding and a first secondary winding that are electrically isolated from each other; The primary side main circuit includes a first common-mode filter and a first full-bridge circuit. The second connection terminal of the first common-mode filter is electrically connected to the first primary winding through the first full-bridge circuit. The secondary side main circuit includes a second common-mode filter and a second full-bridge circuit. The second connection terminal of the second common-mode filter is electrically connected to the first secondary winding through the second full-bridge circuit. Wherein, the first connection terminal of the first common-mode filter is used to connect to DC power, and the first connection terminal of the second common-mode filter is used to output DC power; or, the first connection terminal of the second common-mode filter is used to connect to DC power, and the first connection terminal of the first common-mode filter is used to output DC power.

[0022] In this embodiment, the bidirectional isolated DC-DC circuit is used to realize bidirectional transmission of DC power, supporting forward transmission (primary side main circuit → secondary side main circuit) or reverse transmission (secondary side main circuit → primary side main circuit). It can be used as a sub-module in corresponding power systems (such as test power supply, high voltage charging and discharging power supply, photovoltaic energy storage converter, etc.). Through this circuit, high-efficiency and high-isolation energy exchange can be achieved between the input side and the output side.

[0023] A bidirectional isolated DC-DC circuit includes a primary-side main circuit, a secondary-side main circuit, and a first isolation transformer (e.g., for electrically connecting the primary-side main circuit and the secondary-side main circuit) for electrical connection. Figure 1(T1). The first isolation transformer is located between the primary main circuit and the secondary main circuit to realize the isolated coupling transmission of electrical energy between the primary main circuit and the secondary main circuit. The first isolation transformer includes a primary winding (denoted as the first primary winding) and a secondary winding (denoted as the first secondary winding) that are electrically isolated from each other. In bidirectional transmission mode, the functions of the primary and secondary windings can be switched according to the direction of electrical energy flow. The primary side main circuit includes a first common-mode filter and a first full-bridge circuit. The corresponding connection terminal of the first common-mode filter (denoted as the second connection terminal) is electrically connected to the first primary winding through the first full-bridge circuit. This is to suppress the high-frequency common-mode interference components in the DC power input to the first full-bridge circuit through the first common-mode filter, thereby preventing high-frequency common-mode noise from the external power supply input from coupling to the full-bridge circuit or control loop, thus affecting the normal operation of the bidirectional isolation DC-DC circuit; or to suppress the high-frequency common-mode interference components in the DC power input to the first common-mode filter through the first full-bridge circuit, thereby preventing the high-frequency common-mode voltage generated by the power devices in the first full-bridge circuit during high-frequency switching operation from coupling to the external load or corresponding devices, thereby causing electromagnetic interference (EMI) or control circuit malfunction. Similarly, the secondary-side main circuit includes a second common-mode filter and a second full-bridge circuit. The corresponding connection terminal of the second common-mode filter (denoted as the second connection terminal) is electrically connected to the first secondary winding through the second full-bridge circuit. This allows the second common-mode filter to suppress high-frequency common-mode interference components in the DC power input to the second full-bridge circuit, thereby preventing high-frequency interference from the secondary power supply terminal from entering the bidirectional isolation DC-DC circuit. Alternatively, it can suppress high-frequency common-mode interference components in the DC power input to the second common-mode filter through the second full-bridge circuit, thereby reducing the risk of common-mode voltage leakage caused by high-frequency switching operations on the secondary side and improving the overall electromagnetic compatibility of the bidirectional isolation DC-DC circuit.

[0024] In the bidirectional operating mode of the bidirectional isolated DC-DC circuit, the roles of the first full-bridge circuit and the second full-bridge circuit can be dynamically switched according to actual needs: When the first connection terminal of the first common-mode filter is used to input DC power and the first connection terminal of the second common-mode filter is used to output DC power, electrical energy is transferred from the primary side main circuit to the secondary side main circuit. The first full-bridge circuit operates as an inverter (DC-AC), responsible for converting DC power into high-frequency AC power, and coupling it to the second full-bridge circuit through the first isolation transformer. The second full-bridge circuit then operates as a rectifier (AC-DC), rectifying the received high-frequency AC power into DC power. Conversely, when the first connection terminal of the second common-mode filter is used to input DC power and the first connection terminal of the first common-mode filter is used to output DC power, electrical energy is transferred from the secondary side main circuit to the primary side main circuit. The second full-bridge circuit operates as an inverter and the first full-bridge circuit operates as a rectifier, thereby realizing the bidirectional transmission function of electrical energy between the two sides and meeting the bidirectional power supply needs under different application scenarios.

[0025] In summary, the bidirectional isolated DC-DC converter circuit supporting bidirectional DC energy transmission in this embodiment is suitable for applications requiring high-voltage output, high dynamic response, and electromagnetic compatibility, such as test power supplies, high-voltage charging and discharging systems, and photovoltaic energy storage converters. Specifically, by setting common-mode filters on both the primary and secondary sides of the first isolation transformer, this circuit can effectively suppress high-frequency common-mode interference introduced by external power input or high-frequency switching operations of power devices, thereby improving the electromagnetic compatibility and anti-interference capability of this circuit. By employing a full-bridge circuit to work in conjunction with the first isolation transformer, it achieves efficient bidirectional conversion and isolated transmission of DC and high-frequency AC, facilitating (e.g., combined with phase-shift control) improvement of the control bandwidth (or response speed) and energy transmission efficiency of this circuit and its applied circuits (e.g., the circuit topology of the corresponding power system). Thus, based on the aforementioned circuit structure, the optimized design of the common-mode voltage isolation path is achieved, enhancing the circuit's tolerance to high common-mode voltages. This improves the stability and reliability of the circuit and its applications in complex electromagnetic environments. When used as a submodule in a power supply system, this circuit significantly reduces the overall electromagnetic interference risk, simplifies system filtering and electromagnetic compatibility design requirements, and improves the stability and response speed of energy conversion under different operating modes. It also enhances the modular expansion capability of the power supply system, better meeting the multiple performance requirements of complex application environments such as high voltage, high power, and bidirectional energy flow. Furthermore, the primary and secondary functions of the first isolation transformer in this circuit are switchable, supporting forward and reverse energy flow, thereby meeting the flexibility requirements of different bidirectional power supply scenarios and expanding the application range of this circuit.

[0026] Optionally, combined Figure 1 As shown, the first common-mode filter includes a first common-mode inductor, which includes a first inductor, a second inductor, a first damping winding, a first damping resistor, and a first magnetic core structure. The coils of the first inductor, the second inductor, and the first damping winding are respectively wound on the first magnetic core structure. The two ends of the first damping resistor are respectively electrically connected to the two ends of the first damping winding. The first full-bridge circuit is respectively electrically connected to the first inductor and the second inductor. And / or, the second common-mode filter includes a second common-mode inductor, which includes a third inductor, a fourth inductor, a second damping winding, a second damping resistor, and a second magnetic core structure. The coils of the third inductor, the fourth inductor, and the second damping winding are respectively wound on the second magnetic core structure. The two ends of the second damping resistor are respectively electrically connected to the two ends of the second damping winding. The second full-bridge circuit is respectively electrically connected to the third inductor and the fourth inductor.

[0027] In this embodiment, to further improve the common-mode interference suppression capability of the bidirectional isolated DC-DC circuit, the first common-mode filter is provided with a first common-mode inductor. The first common-mode inductor (e.g.) Figure 1L1 includes a first inductor, a second inductor, a first damping winding, and a first damping resistor (e.g., ...). Figure 1 The first common-mode filter consists of a first inductor (R1) and a first magnetic core structure, wherein one end of the first inductor and one end of the second inductor serve as the first connection terminals of the first common-mode filter, for connection to external corresponding devices (such as DC power supply or load); the other ends of the first inductor and the second inductor serve as the second connection terminals of the first common-mode filter, for connection to the first full-bridge circuit. The windings of the first inductor and the second inductor are respectively wound on the first magnetic core structure. For example, the two windings have the same number of turns and are wound in opposite directions (that is, when the current directions are opposite, they generate magnetic flux in opposite directions in the magnetic core). For the normal current (differential mode current) flowing through the first inductor and the second inductor, they generate opposite magnetic fields in the first inductor and the second inductor, which cancel each other out, so that the total magnetic flux in the magnetic core tends to be zero, avoiding magnetic core saturation and improving the transmission efficiency of differential mode signals. At this time, the normal current is mainly affected by the coil resistance (and a small amount of damping caused by leakage inductance). For the common mode current flowing through the first inductor and the second inductor, due to the unidirectional nature of the common mode current, a unidirectional magnetic field will be generated in the coil, which will increase the inductive reactance of the coil, making the coil exhibit high impedance and producing a strong damping effect, thereby attenuating the common mode current, effectively suppressing the propagation of common mode interference current, and improving the common mode filtering effect. In addition, the first damping winding is also wound on the first magnetic core structure and magnetically coupled to the first inductor and the second inductor respectively. The two ends of the first damping winding are connected to the first damping resistor respectively, forming a damping branch. When a high-frequency common-mode interference signal acts on the first inductor and the second inductor, the first damping winding induces a corresponding voltage and discharges the interference energy through the damping resistor, thereby effectively suppressing common-mode resonance and high-frequency noise spikes, further improving the filtering capability of the first common-mode inductor for high-frequency common-mode interference, enhancing the electromagnetic compatibility and anti-interference capability of the bidirectional isolation DC-DC circuit, and thus ensuring the stable operation of the bidirectional isolation DC-DC circuit in high-voltage, high-power and complex electromagnetic environments.

[0028] And / or, to further enhance the common-mode interference suppression capability of the bidirectional isolated DC-DC circuit, the second common-mode filter is provided with a second common-mode inductor. The second common-mode inductor (e.g.) Figure 1 L2) includes the third inductor, the fourth inductor, the second damping winding, and the second damping resistor (e.g., Figure 1The second magnetic core structure includes a third inductor (R2) and a fourth inductor, wherein one end of the third inductor and one end of the fourth inductor serve as the first connection terminals of the second common-mode filter for connection to external corresponding devices (such as DC power supply or load); the other end of the third inductor and the other end of the fourth inductor serve as the second connection terminals of the second common-mode filter for connection to the second full-bridge circuit. The windings of the third and fourth inductors are respectively wound on the second magnetic core structure. For example, the two windings have the same number of turns and are wound in opposite directions (i.e., when the current directions are opposite, they generate magnetic flux in opposite directions in the magnetic core). For the normal current (differential mode current) flowing through the third and fourth inductors, they generate opposite magnetic fields in the third and fourth inductors, which cancel each other out, so that the total magnetic flux in the magnetic core tends to be zero, avoiding magnetic core saturation and improving the transmission efficiency of differential mode signals. At this time, the normal current is mainly affected by the coil resistance (and a small amount of damping caused by leakage inductance). For the common mode current flowing through the third and fourth inductors, due to the unidirectional nature of the common mode current, a unidirectional magnetic field will be generated in the coil, which will increase the inductive reactance of the coil, making the coil exhibit high impedance and producing a strong damping effect, thereby attenuating the common mode current, effectively suppressing the propagation of common mode interference current, and improving the common mode filtering effect. In addition, the second damping winding is also wound on the second magnetic core structure and is magnetically coupled to the third and fourth inductors respectively. The two ends of the second damping winding are connected to the second damping resistor respectively, forming a damping branch. When a high-frequency common-mode interference signal acts on the third and fourth inductors, the second damping winding induces a corresponding voltage and discharges the interference energy through the damping resistor, thereby effectively suppressing common-mode resonance and high-frequency noise spikes, further improving the filtering capability of the second common-mode inductor for high-frequency common-mode interference, enhancing the electromagnetic compatibility and anti-interference capability of the bidirectional isolation DC-DC circuit, and thus ensuring the stable operation of the bidirectional isolation DC-DC circuit in high-voltage, high-power and complex electromagnetic environments.

[0029] Thus, based on the above structural design, the first common-mode filter and / or the second common-mode filter can achieve strong common-mode interference suppression and reduce the risk of common-mode resonance. They can maintain a good and stable working state in complex application environments such as high voltage, high frequency, and high speed response, and improve the applicability of bidirectional isolated DC-DC circuits with high requirements for electromagnetic compatibility and interference control in corresponding power supply systems.

[0030] For ease of understanding, the structure of the first common-mode filter is illustrated below. The first common-mode inductor includes a first inductor, a second inductor, a first damping winding, a first damping resistor, and a first magnetic core structure. The first magnetic core structure is toroidal (e.g., a toroidal ferrite core). The first and second inductors are symmetrically wound on the first magnetic core structure, with the two windings having the same number of turns and opposite winding directions (i.e., when the current directions are opposite, they generate magnetic flux in opposite directions in the magnetic core). Thus, when the normal operating current (i.e., differential-mode current) flows through the first and second inductors respectively, the magnetic flux generated by the two windings in the magnetic core is in opposite directions and cancels each other out, thereby avoiding magnetic flux saturation in the magnetic core, reducing the suppression of differential-mode signals, and improving the transmission efficiency of differential-mode signals. When a common-mode interference current exists, this common-mode current will flow through the first and second inductors simultaneously in the same direction. At this time, the two windings generate magnetic flux in the same direction in the magnetic core, causing the magnetic flux in the magnetic core to superimpose, thereby significantly improving the common-mode inductive reactance, forming a high-impedance path, effectively suppressing the conduction of common-mode interference current, and enhancing the common-mode filtering effect. Furthermore, to further enhance the suppression capability of high-frequency common-mode noise, the first damping winding is also wound on the first magnetic core structure and magnetically coupled with the first inductor and the second inductor to form an auxiliary induction winding. The two ends of the first damping winding are connected to a first damping resistor to form a damping absorption circuit. When high-frequency common-mode noise excites a rapidly changing magnetic field in the first inductor and the second inductor, the first damping winding can induce a corresponding voltage signal. The interference energy is discharged through the first damping resistor to prevent the generation of common-mode resonance, further enhancing the suppression capability of the first common-mode inductor against high-frequency spike interference, thereby enhancing the electromagnetic compatibility performance and anti-interference capability of the entire bidirectional isolated DC-DC circuit.

[0031] Optionally, combined Figure 1 As shown, the first common-mode filter further includes a first capacitor, one end of which is electrically connected to the end of the first inductor away from the first full-bridge circuit, and the other end of which is electrically connected to the end of the second inductor away from the first full-bridge circuit; the primary side main circuit further includes a second capacitor, one end of which is electrically connected to the end of the first inductor used for electrically connecting to the first full-bridge circuit, and the other end of which is electrically connected to the end of the second inductor used for electrically connecting to the first full-bridge circuit; And / or, the second common-mode filter further includes a fourth capacitor, one end of which is electrically connected to the end of the third inductor away from the second full-bridge circuit, and the other end of the third capacitor is electrically connected to the end of the fourth inductor away from the second full-bridge circuit; the secondary-side main circuit further includes a fifth capacitor, one end of which is electrically connected to the end of the third inductor used for electrically connecting to the second full-bridge circuit, and the other end of the fifth capacitor is electrically connected to the end of the fourth inductor used for electrically connecting to the second full-bridge circuit.

[0032] In this embodiment, to further improve the common-mode filtering effect of the first common-mode filter and optimize its electromagnetic compatibility, the first common-mode filter is also provided with a first capacitor (e.g., Figure 1 In section C1, the first capacitor is used to construct a discharge path for high-frequency common-mode interference between the two inductors of the first common-mode inductor (i.e., the first inductor and the second inductor). Specifically, one end of the first capacitor is electrically connected to the end of the first inductor furthest from the first full-bridge circuit, and the other end is electrically connected to the end of the second inductor furthest from the first full-bridge circuit, thus realizing that the capacitor is connected across the corresponding connection ends of the first and second inductors. When high-frequency common-mode interference occurs, since the first capacitor has low impedance to high-frequency signals, the potential change at its two ends is almost the same, which can provide an effective bypass path for common-mode interference, so that the high-frequency common-mode current forms a closed loop in the first capacitor and is suppressed, thereby preventing its further propagation. In this way, by setting the first capacitor, not only is the high-frequency filtering capability of the first common-mode filter for common-mode interference enhanced, but it can also weaken the radiated interference introduced by the external power supply to a certain extent, improve the overall electromagnetic compatibility performance, and based on the setting of the first common-mode inductor, the first common-mode filter has basically no effect on differential-mode signals, ensuring the stability and integrity of normal signal transmission. In addition, to further enhance the filtering capability of the primary-side main circuit and stabilize the bus voltage, the primary-side main circuit also includes a DC bus capacitor (denoted as the second capacitor, e.g., ...). Figure 1 In the first inductor (C2), one end of the second capacitor is connected to one end of the first inductor used for electrical connection to the first full-bridge circuit, and the other end is connected to one end of the second inductor used for electrical connection to the first full-bridge circuit. This allows the second capacitor to bridge the connection points of the first and second inductors facing the first full-bridge circuit. On one hand, the second capacitor can construct a DC bus filter path on the primary side, effectively filtering out high-frequency ripple voltages output to the first full-bridge circuit via the first common-mode filter or output from the first full-bridge circuit to the first common-mode filter, smoothing the bus voltage waveform, and reducing high-frequency spikes and noise interference to subsequent circuits. On the other hand, the second capacitor has a certain energy storage capacity, providing short-term energy support under dynamic conditions such as load changes or operating state switching, suppressing bus voltage fluctuations, thereby improving the dynamic response performance and power supply stability of the primary side main circuit. Furthermore, the second capacitor also helps improve the commutation conditions of the first full-bridge circuit, alleviating voltage stress during the switching process of various power devices (or switching transistors) in the first full-bridge circuit, extending the service life of power devices, and improving the electromagnetic compatibility and reliability of the primary side main circuit and bidirectional isolated DC-DC circuits.

[0033] And / or, to further improve the common-mode filtering effect of the second common-mode filter and optimize its electromagnetic compatibility, the second common-mode filter is also provided with a fourth capacitor (e.g., Figure 1The fourth capacitor (C4) is used to construct a high-frequency common-mode interference discharge path between the two inductors (i.e., the third and fourth inductors) of the second common-mode inductor. Specifically, one end of the fourth capacitor is electrically connected to the end of the third inductor furthest from the second full-bridge circuit, and the other end is electrically connected to the end of the fourth inductor furthest from the second full-bridge circuit, thus bridging the corresponding connection ends of the third and fourth inductors. When high-frequency common-mode interference occurs, because the fourth capacitor has low impedance to high-frequency signals, the potential change at its two ends is almost uniform, providing an effective bypass path for common-mode interference. This allows the high-frequency common-mode current to form a closed loop in the fourth capacitor and be suppressed, thereby preventing its further propagation. In this way, by setting the fourth capacitor, not only is the high-frequency filtering capability of the second common-mode filter enhanced for common-mode interference, but it can also weaken the radiated interference introduced by the external power supply to a certain extent, improving the overall electromagnetic compatibility performance. Furthermore, based on the setting of the second common-mode inductor, the second common-mode filter has virtually no impact on differential-mode signals, ensuring the stability and integrity of normal signal transmission. In addition, to further enhance the filtering capability of the secondary-side main circuit and stabilize the bus voltage, the secondary-side main circuit also includes a DC bus capacitor (denoted as the fifth capacitor, e.g., ...). Figure 1 In the circuit, the fifth capacitor (C5) is connected at one end to the third inductor (used for electrical connection to the second full-bridge circuit) and at the other end to the fourth inductor (used for electrical connection to the second full-bridge circuit). This allows the fifth capacitor to bridge the connection points of the third and fourth inductors facing the second full-bridge circuit. Firstly, the fifth capacitor can construct a DC bus filter path on the primary side, effectively filtering out high-frequency ripple voltages from the second common-mode filter to the second full-bridge circuit or vice versa, smoothing the bus voltage waveform, and reducing high-frequency spikes and noise interference to subsequent circuits. Secondly, the fifth capacitor has a certain energy storage capacity, providing short-term energy support under dynamic conditions such as load changes or operating state switching, suppressing bus voltage fluctuations, thereby improving the dynamic response performance and power supply stability of the secondary main circuit. Thirdly, the fifth capacitor also helps improve the commutation conditions of the second full-bridge circuit, alleviating voltage stress during the switching process of power devices (or switching transistors) in the second full-bridge circuit, extending the lifespan of power devices, and improving the electromagnetic compatibility and reliability of the secondary main circuit and bidirectional isolated DC-DC circuits.

[0034] Optionally, combined Figure 1 As shown, the primary side main circuit also includes a third capacitor. One end of the first inductor is used to electrically connect to the first full-bridge circuit and is grounded or connected to control ground through the third capacitor. Alternatively, one end of the second inductor is used to electrically connect to the first full-bridge circuit and is grounded or connected to control ground through the third capacitor. And / or, the secondary side main circuit also includes a sixth capacitor, and a third inductor is used to electrically connect one end of the second full-bridge circuit to ground or control ground through the sixth capacitor, or a fourth inductor is used to electrically connect one end of the second full-bridge circuit to ground or control ground through the sixth capacitor.

[0035] In this embodiment, to further enhance the primary-side main circuit's ability to suppress common-mode interference and improve its electromagnetic compatibility, the primary-side main circuit is also equipped with a third capacitor (such as...). Figure 1 (C3). Specifically, one end of the first or second inductor in the first common-mode inductor, which is used to electrically connect to the first full-bridge circuit, is grounded or connected to control ground through the third capacitor to achieve stable control of the DC bus negative terminal relative to ground potential, and to discharge the residual high-frequency common-mode noise in the DC bus to ground through the low-impedance path constructed by the capacitor, thereby constructing an effective common-mode filtering circuit. The DC bus refers to the two high-voltage conductive paths, positive and negative, connected to the first full-bridge circuit via the first common-mode filter. These paths carry and transmit high-voltage DC power, forming the energy channel in the entire power conversion link of the primary circuit. To ensure the stability of power transmission and the uniformity of the overall control reference, the negative terminal of the DC bus is grounded or connected to control ground via a third capacitor. The third capacitor provides a high-frequency common-mode current discharge path, effectively bypassing common-mode noise caused by high-speed switching of power devices or parasitic parameters of the topology, reducing its accumulation and outward radiation risk on the bus, and avoiding interference with drive signal sampling, communication, and driving. Simultaneously, choosing the grounding location on the negative side of the DC bus helps avoid common-mode voltage drift problems that may occur when the positive terminal is grounded. This aligns better with the mainstream grounding strategy of negative grounding and positive floating in high-voltage DC circuits, improving the overall electrical safety and electromagnetic compatibility of the circuit. To accommodate different polarity connections, if the ends of the first and second inductors furthest from the first full-bridge circuit are used to connect to the positive and negative terminals of the power supply (or serve as the positive and negative output terminals respectively), then the second inductor can be used to electrically connect to one end of the first full-bridge circuit, grounded through the third capacitor, to effectively discharge common-mode interference. Conversely, if the ends of the first and second inductors furthest from the first full-bridge circuit are used to connect to the negative and positive terminals of the power supply (or serve as the negative and positive output terminals respectively), then the first inductor can be used to electrically connect to one end of the first full-bridge circuit, grounded through the third capacitor. This ensures that the common-mode interference current is discharged to ground from the low-potential side of the DC bus, avoiding common-mode voltage shift or electrical safety risks that may be caused by grounding on the high-potential side, thereby improving the overall electromagnetic compatibility performance and operational stability of the circuit.

[0036] And / or, to further enhance the secondary-side main circuit's ability to suppress common-mode interference and improve its electromagnetic compatibility, the secondary-side main circuit is also equipped with a sixth capacitor (such as...). Figure 1(C6). Specifically, one end of the third or fourth inductor in the second common-mode inductor, which is used to electrically connect to the second full-bridge circuit, is grounded or connected to control ground through the sixth capacitor to achieve stable control of the DC bus negative terminal relative to ground potential, and to discharge the residual high-frequency common-mode noise in the DC bus to ground through the low-impedance path constructed by the capacitor, thereby constructing an effective common-mode filtering circuit. The DC bus refers to the two high-voltage conductive paths, positive and negative, connected to the second full-bridge circuit via the second common-mode filter. These paths carry and transmit high-voltage DC power, forming the energy channel in the entire power conversion link of the secondary-side main circuit. To ensure the stability of power transmission and the uniformity of the overall control reference, the negative terminal of the DC bus is grounded or connected to control ground via the sixth capacitor. The sixth capacitor provides a high-frequency common-mode current discharge path, effectively bypassing common-mode noise caused by high-speed switching of power devices or parasitic parameters of the topology, reducing its accumulation and outward radiation risk on the bus, and avoiding interference with drive signal sampling, communication, and driving. Simultaneously, choosing the grounding location on the negative side of the DC bus helps avoid common-mode voltage drift problems that may occur when the positive terminal is grounded. This aligns better with the mainstream grounding strategy of negative grounding and positive floating in high-voltage DC circuits, improving the overall electrical safety and electromagnetic compatibility of the circuit. To accommodate different polarity connections, if the ends of the third and fourth inductors furthest from the second full-bridge circuit are used to connect to the positive and negative terminals of the power supply (or serve as the positive and negative output terminals respectively), then the fourth inductor can be used to electrically connect to one end of the second full-bridge circuit and grounded through the sixth capacitor to effectively discharge common-mode interference. Conversely, if the ends of the third and fourth inductors furthest from the second full-bridge circuit are used to connect to the negative and positive terminals of the power supply (or serve as the negative and positive output terminals respectively), then the third inductor can be used to electrically connect to one end of the second full-bridge circuit and grounded through the sixth capacitor. This ensures that the common-mode interference current is discharged to ground from the low-potential side of the DC bus, avoiding common-mode voltage shift or electrical safety risks that may be caused by grounding on the high-potential side, thereby improving the overall electromagnetic compatibility performance and operational stability of the circuit.

[0037] For example, when each switch in the first full-bridge circuit is an NMOS transistor, with the drain, source, and gate of the NMOS transistor serving as the first, second, and third terminals respectively, then: the drains of the first switch S1 and the third switch S3 are connected to one end of the first inductor L1 in the first common-mode inductor; the sources of the second switch S2 and the fourth switch S4 are connected to one end of the second inductor L2; and the source of the first switch S1 is connected to the drain of the second switch S2, and the source of the third switch S3 is connected to the drain of the fourth switch S4. When each switch in the first full-bridge circuit is a PMOS transistor, and the source, drain, and gate of the NMOS transistor are used as the first, second, and third terminals respectively, then: the source of the first switch S1 and the third switch S3 are connected to one end of the first inductor L1 in the first common-mode inductor; the drain of the second switch S2 and the fourth switch S4 are connected to one end of the second inductor L2; and the drain of the first switch S1 is connected to the source of the second switch S2, and the drain of the third switch S3 is connected to the source of the fourth switch S4.

[0038] Optionally, the main circuit on the low common-mode voltage side (such as the main circuit connected to the DC input) is grounded through the negative terminal of the DC bus of the corresponding full-bridge circuit, and the main circuit on the high common-mode voltage side (such as the main circuit outputting DC power) is connected to the control ground through the negative terminal of the DC bus of the corresponding full-bridge circuit, so as to effectively divide and manage the common-mode potential on different voltage levels, and further enhance the electrical isolation and common-mode interference immunity of the bidirectional isolation DC-DC circuit.

[0039] Optionally, the third and sixth capacitors can be Y-capacitors (i.e., safety capacitors), which have good high-frequency common-mode interference suppression capabilities and stable withstand voltage performance, suitable for the dual requirements of common-mode noise discharge and electrical safety in isolation structures. The primary and secondary main circuits are grounded using Y-capacitors to provide a low-impedance discharge path for high-frequency noise, effectively filtering out high-frequency spike interference caused by common-mode voltage. For example, the third capacitor connects the negative terminal of the DC bus of the first full-bridge circuit to ground (PE), short-circuiting the high-frequency common-mode voltage to prevent it from affecting the primary control circuit; the sixth capacitor connects the negative terminal of the DC bus of the second full-bridge circuit to the secondary control ground (SGND), short-circuiting the high-frequency common-mode voltage between them to prevent excessive high-frequency common-mode voltage from being applied to the second isolated drive circuit in the secondary control circuit, thus avoiding any impact.

[0040] Optionally, combined Figure 1 As shown, the bidirectional isolated DC-DC circuit also includes a resonant inductor and a resonant capacitor; The first full-bridge circuit includes a first switch, a second switch, a third switch, and a fourth switch. The first terminals of the first and third switches are electrically connected to one end of a first inductor, and the second terminals of the second and fourth switches are electrically connected to one end of a second inductor. The second terminal of the first switch and the first terminal of the second switch are electrically connected, and are electrically connected to one end of the first primary winding through one of a resonant inductor and a resonant capacitor. The second terminal of the third switch and the first terminal of the fourth switch are electrically connected, and are electrically connected to the other end of the first primary winding. The first full-bridge circuit includes a fifth, a sixth, a seventh, and an eighth switch. The first terminals of the fifth and seventh switches are electrically connected to one end of the third inductor, and the second terminals of the sixth and eighth switches are electrically connected to one end of the fourth inductor. The second terminal of the fifth switch and the first terminal of the sixth switch are electrically connected, and are also electrically connected to one end of the first secondary winding through another of the resonant inductor and the resonant capacitor. The second terminal of the seventh switch and the first terminal of the eighth switch are electrically connected, and are also electrically connected to the other end of the first secondary winding.

[0041] In this embodiment, the bidirectional isolated DC-DC circuit is further provided with a resonant inductor (such as...). Figure 1 (Lr) and resonant capacitor (such as Lr) Figure 1 (Cr) to construct an energy transmission structure based on resonant topology, thereby improving power conversion efficiency, reducing switching losses and optimizing overall electromagnetic compatibility performance.

[0042] Specifically, the first full-bridge circuit includes a first switch S1, a second switch S2, a third switch S3, and a fourth switch S4. Each switch has a first terminal and a second terminal for connecting to the DC bus, and a third terminal (controlled terminal, used to receive drive signals for controlling the on / off state) for receiving drive signals. The first terminals of the first switch S1 and the third switch S3 are connected to one end of the first inductor L1 in the first common-mode inductor; the second terminals of the second switch S2 and the fourth switch S4 are connected to one end of the second inductor L2; the second terminal of the first switch S1 is interconnected with the first terminal of the second switch S2, and is connected to one end of the first primary winding of the first isolation transformer through one of the resonant inductor Lr and the resonant capacitor Cr; the second terminal of the third switch S3 is interconnected with the first terminal of the fourth switch S4, and is connected to the other end of the first primary winding, thus constructing a full-bridge resonant energy transmission structure. Accordingly, the second full-bridge circuit includes a fifth switch S5, a sixth switch S6, a seventh switch S7, and an eighth switch S8. Each switch has a first terminal and a second terminal for connecting to the DC bus, and a third terminal (controlled terminal) for receiving drive signals. The first terminals of the fifth switch S5 and the seventh switch S7 are electrically connected to one end of the third inductor L3, respectively. The second terminals of the sixth switch S6 and the eighth switch S8 are electrically connected to one end of the fourth inductor L4, respectively. The second terminal of the fifth switch S5 is connected to the first terminal of the sixth switch S6, and is connected to one end of the first secondary winding of the first isolation transformer through another of the resonant inductor and the resonant capacitor. The second terminal of the seventh switch S7 is connected to the first terminal of the eighth switch S8, and is connected to the other end of the first secondary winding, so as to construct a full-bridge resonant energy transmission structure.

[0043] Thus, based on the above structure, the first full-bridge circuit and the second full-bridge circuit achieve magnetic coupling with the isolation transformer through resonant elements, thereby constructing a resonant energy transfer path and realizing efficient DC-DC conversion functions such as soft-switching control, resonant energy transfer, and bidirectional power flow. Specifically, in the bidirectional isolated DC-DC circuit, resonant inductors and resonant capacitors are respectively set on the primary and secondary sides of the first isolation transformer, which can work together to form a resonant circuit. Among them, the primary-side resonant element can effectively reduce the conduction or turn-off losses of switching devices, realize soft-switching characteristics such as ZVS (zero voltage switching) or ZCS (zero current switching), thereby improving energy conversion efficiency and suppressing high-frequency electromagnetic interference; while the secondary-side resonant element can improve the commutation conditions in the rectification stage, reduce the switching voltage stress of power devices, improve their reliability, and optimize the electromagnetic compatibility performance of the circuit in which it is located. By reasonably configuring the position and parameter combination of the primary and secondary resonant elements, better resonance characteristics and topology matching can be achieved, further improving the overall circuit's energy transfer efficiency, dynamic response performance, and operational stability, meeting the needs of different topologies and applications.

[0044] For example, both the first full-bridge circuit and the second full-bridge circuit include switching transistors suitable for automatic control of the on and off states, such as bipolar transistors, field-effect transistors, insulated-gate bipolar transistors, etc., to improve the degree of automatic control of the first full-bridge circuit and the second full-bridge circuit.

[0045] To facilitate understanding, the topology of a bidirectional isolated DC-DC circuit is illustrated below. (Combined with...) Figure 1 As shown, the bidirectional isolation DC-DC circuit includes a primary side main circuit, a secondary side main circuit, and a first isolation transformer. The primary side main circuit and the secondary side main circuit are isolated by the first isolation transformer T1. One end of the primary side of the first isolation transformer T1 is 1 (i.e., Figure 1 The first isolation transformer T1 shown in the figure has its first primary winding connection terminal 1 and one secondary winding connection terminal 3 (i.e., ... Figure 1 The connection terminals 3) of the first secondary winding of the first isolation transformer T1 shown are identical terminals. If the primary side main circuit is used to connect to the low common-mode voltage side (i.e., connected to DC power, serving as the primary side of the first isolation transformer T1), and the secondary side main circuit is used to connect to the high common-mode voltage side (i.e., output DC power, serving as the secondary side of the first isolation transformer T1), the positive and negative terminals of the DC input voltage V1 of the primary side main circuit are connected in parallel to the two ends of the first capacitor C1 and one end 1 and 4 of the first common-mode inductor L1 (i.e., one end 1 of the first inductor and one end 4 of the second inductor), and the other end 2 of the first common-mode inductor L1 (i.e., the other end 2 of the first inductor) is connected to the second capacitor (DC bus capacitor) C. One end of the first switch S1 and the first end of the third switch S3 are connected to the other end of the first common-mode inductor L1 (i.e., the other end of the second inductor 3). The other end of the first common-mode inductor L1 (i.e., the other end of the second inductor 3) is connected to the other end of the second capacitor C2, one end of the third capacitor C3, and the second ends of the second switch S2 and the fourth switch S4. The other end of the third capacitor C3 is connected to ground PE. The second end of the first switch S1 and the first end of the second switch S2 are connected to one end 1 of the resonant inductor Lr. The second end of the third switch S3 and the first end of the fourth switch S4 are connected to one end 2 of the primary side of the first isolation transformer T1 (i.e., the other end of the second inductor 3). Figure 1The first primary winding of the first isolation transformer T1 shown in the figure is connected at the connection end 2), the other end 2 of the resonant inductor Lr is connected to one end 1 of the primary winding of the first isolation transformer T1, and the two ends 5 and 6 of the first damping winding of the first common mode inductor L1 are respectively connected to the two ends of the first damping resistor R1. The positive and negative terminals of the secondary side main circuit DC output voltage V2 are connected in parallel to the two ends of the fourth capacitor C4 and one end 1 and 4 of the second common-mode inductor L2 (i.e., one end 1 of the third inductor and one end 4 of the fourth inductor). The other end 2 of the second common-mode inductor L2 (i.e., the other end 2 of the third inductor) is connected to one end of the fifth capacitor (DC bus capacitor) C5 and the first end of the fifth switch S5 and the seventh switch S7. The other end 3 of the second common-mode inductor L2 (i.e., the other end 3 of the fourth inductor) is connected to the other end of the fifth capacitor C5, one end of the sixth capacitor C6, the second end of the sixth switch S6 and the eighth switch S8. The other end of the sixth capacitor C6 is connected to the secondary side control ground SGND. The second end of the fifth switch S5 is connected to the first end of the sixth switch S6 and one end 1 of the resonant capacitor Cr. The second end of the seventh switch S7 and the first end of the eighth switch S8 are connected to one end 4 of the secondary side of the first isolation transformer T1 (i.e., the other end 2 of the third inductor). Figure 1 The first secondary winding of the first isolation transformer T1 shown in the figure is connected at terminal 4), the other end 2 of the resonant capacitor Cr is connected to terminal 3 of the secondary winding of the first isolation transformer T1, and the two ends 5 and 6 of the second damping winding of the second common mode inductor L2 are respectively connected to the two ends of the second damping resistor R2.

[0046] Optionally, the bidirectional isolated DC-DC circuit also includes a control circuit that is communicatively connected to the first full-bridge circuit and the second full-bridge circuit, respectively. The control circuit is used to control the on / off state of each switch in the first full-bridge circuit and the second full-bridge circuit.

[0047] In this embodiment, the bidirectional isolated DC-DC circuit also includes a control circuit. The control circuit is communicatively connected to the first full-bridge circuit and the second full-bridge circuit, respectively, and is used to control the on / off state of each switch in the first and second full-bridge circuits to achieve orderly energy transmission and bidirectional regulation of power flow. Specifically, the control circuit is electrically connected to the control terminals of the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 in the first full-bridge circuit to transmit drive signals for each switch and control the on / off state of each switch. Through the coordination of the on / off states of each switch, rectification or inversion functions are achieved. Furthermore, the control circuit is electrically connected to the control terminals of the fifth switch S5, the sixth switch S6, the seventh switch S7, and the eighth switch S8 in the second full-bridge circuit to transmit drive signals for each switch and control the on / off state of each switch. Through the coordination of the on / off states of each switch, rectification or inversion functions are achieved.

[0048] For example, in the bidirectional operating mode of the bidirectional isolated DC-DC circuit, the operating roles of the first full-bridge circuit and the second full-bridge circuit can be dynamically switched according to actual needs, and the control circuit cooperates accordingly: when the first connection terminal of the first common-mode filter is used to input DC power and the first connection terminal of the second common-mode filter is used to output DC power, electrical energy is transmitted from the primary side main circuit to the secondary side main circuit. The control circuit controls the first full-bridge circuit to operate as an inverter (DC-AC), responsible for converting DC power into high-frequency AC power, and coupling it to the second full-bridge circuit through the first isolation transformer. The control circuit controls the second full-bridge circuit to operate as a rectifier (AC-DC) at this time, rectifying the received high-frequency AC power into DC power. Conversely, when the first connection terminal of the second common-mode filter is used to input DC power and the first connection terminal of the first common-mode filter is used to output DC power, electrical energy is transmitted from the secondary side main circuit to the primary side main circuit. The control circuit controls the second full-bridge circuit to operate as an inverter and controls the first full-bridge circuit to operate as a rectifier. In this way, the control circuit can dynamically switch the power flow direction and control logic in different application scenarios, ensuring the efficient and stable operation of the bidirectional isolated DC-DC circuit in the corresponding application scenarios. Moreover, by setting the control circuit, precise control of each switch in the bidirectional isolated DC-DC circuit can be achieved, enabling the bidirectional isolated DC-DC circuit to have stable and controllable bidirectional energy transmission capability, and providing guarantees in terms of efficient energy conversion, wide input and output range support, and improved electromagnetic compatibility.

[0049] Optionally, combined Figure 1 , Figure 2 As shown, the control circuit includes a primary-side control circuit and a detection circuit. The primary-side control circuit includes a first isolation drive circuit. The input terminal of the first isolation drive circuit is electrically connected to the output terminal of the detection circuit. The output terminal of the first isolation drive circuit is electrically connected to the controlled terminal of each switch in the first full-bridge circuit. The input terminal of the detection circuit is used to receive drive signals.

[0050] In this embodiment, the control circuit includes a primary-side control circuit and a detection circuit, which can be used to achieve reliable drive control of each switching transistor in the first full-bridge circuit, thereby improving the response speed, control accuracy, and electromagnetic compatibility of the bidirectional isolated DC-DC circuit.

[0051] Specifically, the detection circuit is used to perform pre-processing on the raw drive signal input from the outside, such as common-mode interference suppression, logic level shaping, pulse width adjustment, timing correction, and dead-time control, to ensure that the drive signal received by the subsequent drive circuit (such as the first isolation drive circuit) meets the corresponding requirements in terms of level amplitude, logic relationship, and timing characteristics. For example, the detection circuit can adopt a differential detection structure, based on two mutually inverted drive signal inputs, and effectively suppresses common-mode interference components in the input signal through differential amplification and reference voltage comparison, thereby improving the signal's anti-interference capability. This structure is particularly suitable for maintaining the consistency of drive signal timing and logical correctness in high dv / dt, high di / dt, and high-frequency electromagnetic interference environments.

[0052] The input of the first isolation drive circuit is electrically connected to the output of the detector circuit. It receives the drive signal after detection and further isolates, amplifies, buffers, and shapes the drive signal to form an effective drive signal with gate drive capability that meets the requirements of the switching transistors and has a high rising / falling edge switching speed. The output of the first isolation drive circuit is electrically connected to the controlled terminals of the first to fourth switching transistors in the first full-bridge circuit. This allows for the control of the on / off state of each switching transistor, creating a symmetrical bridge arm, reasonable dead time, and precise timing switching control mode. This ensures stable and reliable inverter or rectification operation of the first full-bridge circuit during bidirectional power conversion, meeting the drive control requirements of different operating modes.

[0053] Thus, the detector circuit effectively eliminates common-mode interference and noise signals in the original drive signal, ensuring the accuracy and stability of the input drive signal logic; while the first isolation drive circuit provides a gate signal with sufficient drive capability while achieving electrical isolation, meeting the drive requirements of high-voltage, high-speed switching devices. Working together, the two significantly improve the control response speed, switching synchronization, and electromagnetic compatibility of the first full-bridge circuit, ensuring stable operation and efficient power conversion of the bidirectional isolated DC-DC circuit in complex electromagnetic environments.

[0054] Optionally, combined Figure 2 As shown, the control circuit also includes a secondary-side control circuit, which includes a second isolation drive circuit. The input terminal of the second isolation drive circuit is electrically connected to the output terminal of the detector circuit, and the output terminal of the second isolation drive circuit is electrically connected to the controlled terminals of each switching transistor in the second full-bridge circuit.

[0055] In this embodiment, the control circuit also includes a secondary control circuit, which is used to precisely drive and control each switch in the second full-bridge circuit to meet the different operating modes and control strategies of the bidirectional isolated DC-DC circuit in the bidirectional power transmission process.

[0056] Specifically, the secondary-side control circuit includes a second isolation drive circuit. The input of the second isolation drive circuit is electrically connected to the output of the detector circuit. It receives the drive signal after detection and further isolates, amplifies, buffers, and shapes the drive signal to form an effective drive signal with gate drive capability that meets the requirements of the switching transistors and has a high rising / falling edge switching speed. The output of the second isolation drive circuit is electrically connected to the controlled terminals of the fifth to eighth switches in the second full-bridge circuit, respectively, to control the on / off state of each switch. This constructs a symmetrical bridge arm switching control mode with reasonable dead time and precise timing, thereby ensuring stable and reliable inverter or rectification operation of the second full-bridge circuit during bidirectional power conversion and meeting the drive control requirements under different operating modes.

[0057] Thus, the second isolation drive circuit, while achieving electrical isolation, can provide a gate signal with sufficient driving capability to meet the driving requirements of high-voltage, high-speed switching devices. Furthermore, the detector circuit and the second isolation drive circuit work together to significantly improve the control response speed, switching synchronization, and electromagnetic compatibility of the second full-bridge circuit, ensuring stable operation and efficient power conversion of the bidirectional isolated DC-DC circuit in complex electromagnetic environments. Moreover, both the first and second isolation drive circuits respond to the original drive signal output from the same input detector circuit, ensuring a high degree of consistency and timing synchronization in the on / off control of each bridge arm on the primary and secondary sides. This avoids problems such as switching offset, bridge arm asymmetry, or dead-time mismatch caused by inconsistent control clock sources or differences in signal transmission paths, thereby improving the overall accuracy, stability, and reliability of the bidirectional isolated DC-DC circuit's power conversion.

[0058] Optionally, combined Figure 2 As shown, the primary control circuit also includes a first comparison circuit and a first fault clamping circuit. The output of the detector circuit is electrically connected to the input of the first isolation drive circuit through the first comparison circuit. The output of the first fault clamping circuit is connected to the input of the first comparison circuit. The input of the first fault clamping circuit is used to receive a fault signal and clamp the potential of the input of the first comparison circuit to a first preset clamping level according to the fault signal.

[0059] In this embodiment, the primary control circuit is further provided with a first comparison circuit and a first fault clamping circuit, which are used to improve fault response capability and safety protection level while ensuring normal drive control.

[0060] The output of the detector circuit is electrically connected to the input of the first isolation drive circuit via a first comparator circuit. Specifically, the output of the detector circuit is electrically connected to the input of the first comparator circuit to input the detected drive signal to the first comparator circuit. The output of the first comparator circuit is electrically connected to the input of the first isolation drive circuit to transmit the compared drive signal to the first isolation drive circuit, which then drives the switches in the first full-bridge circuit. The first comparator circuit can perform amplitude filtering, validity determination, or logic modulation on the input drive signal based on the comparison result with a reference level, thereby ensuring that the drive signal input to the isolation drive circuit meets the level and logic requirements.

[0061] To ensure safe signal control under fault conditions, the primary control circuit also includes a first fault clamping circuit. Its input receives fault signals from external systems or the host controller, and its output is connected to the input of the first comparator circuit. When a fault signal is triggered and the first fault clamping circuit receives the signal, it pulls the output voltage to a preset clamping level (denoted as the first preset clamping level) and applies this level to the input of the first comparator circuit. This forces the normal drive signal output from the detector circuit to be suppressed from entering the isolation drive circuit, preventing the first isolation drive circuit from outputting a drive signal. Ultimately, this keeps all switches in the first full-bridge circuit in the off state, preventing device damage or malfunctions caused by mis-driving and ensuring the safe shutdown of the bidirectional isolated DC-DC circuit under abnormal conditions.

[0062] Thus, by setting a fault clamping path between the comparator circuit and the isolation drive circuit, not only is the redundancy of the control link enhanced, but also a controllable disconnection mechanism for the drive signal is realized, which is beneficial to improving the response speed to faults, control accuracy, and overall safety and reliability.

[0063] Optionally, combined Figure 2 As shown, the secondary side control circuit also includes a second comparison circuit and a second fault clamping circuit. The output terminal of the detector circuit is electrically connected to the input terminal of the second isolation drive circuit through the second comparison circuit. The output terminal of the second fault clamping circuit is connected to the input terminal of the second comparison circuit. The input terminal of the second fault clamping circuit is used to receive the fault signal and clamp the potential of the input terminal of the second comparison circuit to the second preset clamping level according to the fault signal.

[0064] In this embodiment, the secondary side control circuit is further provided with a second comparison circuit and a second fault clamping circuit, which are used to improve fault response capability and safety protection level while ensuring normal drive control.

[0065] The output of the detector circuit is electrically connected to the input of the second isolation drive circuit via a second comparator circuit. Specifically, the output of the detector circuit is electrically connected to the input of the second comparator circuit to input the detected drive signal to the second comparator circuit. The output of the second comparator circuit is electrically connected to the input of the second isolation drive circuit to transmit the compared drive signal to the second isolation drive circuit, which then drives the switches in the second full-bridge circuit. The second comparator circuit can perform amplitude filtering, validity determination, or logic modulation on the input drive signal based on the comparison result with a reference level, thereby ensuring that the drive signal input to the isolation drive circuit meets the level and logic requirements.

[0066] To ensure safe signal control under fault conditions, the secondary control circuit also includes a second fault clamping circuit. Its input receives fault signals from external systems or the host controller, and its output is connected to the input of the second comparator circuit. When a fault signal is triggered and the input of the second fault clamping circuit receives the signal, the circuit pulls its output to a preset clamping level (denoted as the second preset clamping level) and applies this level to the input of the second comparator circuit. This forces the normal drive signal from the detector circuit to be suppressed from entering the isolation drive circuit, preventing the second isolation drive circuit from outputting a drive signal. Ultimately, this keeps all switches in the second full-bridge circuit in the off state, preventing device damage or malfunctions caused by mis-driving and ensuring the safe shutdown of the bidirectional isolated DC-DC circuit under abnormal conditions.

[0067] Thus, by setting a fault clamping path between the comparator circuit and the isolation drive circuit, not only is the redundancy of the control link enhanced, but also a controllable disconnection mechanism for the drive signal is realized, which is beneficial to improving the response speed to faults, control accuracy, and overall safety and reliability.

[0068] Optionally, combined Figure 2 As shown, the control circuit also includes a second isolation transformer. The input terminal of the detector circuit is electrically connected to the second secondary winding of the second isolation transformer. The second primary winding of the second isolation transformer is used to receive the drive signal. And / or, the control circuit also includes a third isolation transformer, the output of the detector circuit is electrically connected to the third primary winding of the third isolation transformer, and the input of the first isolation drive circuit is electrically connected to the third secondary winding of the third isolation transformer. And / or, the control circuit also includes a fourth isolation transformer, the output of the detector circuit is electrically connected to the fourth primary winding of the fourth isolation transformer, and the input of the second isolation drive circuit is electrically connected to the fourth secondary winding of the fourth isolation transformer.

[0069] In this embodiment, the control circuit is equipped with corresponding isolation transformers for signal isolation and conversion, such as the second isolation transformer, the third isolation transformer and the fourth isolation transformer, to enhance the overall electrical isolation capability and anti-interference performance of the control circuit and the bidirectional isolation DC-DC circuit.

[0070] Specifically, if a second isolation transformer (such as...) is installed at the input of the detector circuit... Figure 2 The input terminal of the detector circuit (T2) is electrically connected to the second secondary winding of the second isolation transformer, while the second primary winding of the second isolation transformer receives the drive signal. The second isolation transformer provides primary electrical isolation to the external original drive signal received at its input terminal (or second primary winding), which is then input to the detector circuit through its output terminal (or second secondary winding). In this way, without affecting signal integrity, primary isolation of the external drive signal is achieved, allowing it to be input to the detector circuit, thus improving the control circuit's common-mode interference immunity and signal security.

[0071] And / or, if a third isolation transformer is provided between the detector circuit and the first isolation drive circuit (e.g. Figure 2 The third isolation transformer (T3) connects the detector circuit to the first isolation drive circuit via a third isolation transformer. The third isolation transformer adds an electrical isolation layer between the detector circuit and the first isolation drive circuit. Its third primary winding is connected to the output terminal of the detector circuit, and its third secondary winding is connected to the input terminal of the first isolation drive circuit. This ensures that the first isolation drive circuit can still stably receive drive signals under high voltage or strong interference conditions, and effectively protects the internal logic circuit of the first isolation drive circuit from damage.

[0072] And / or, if a fourth isolation transformer (e.g., ...) is provided between the detector circuit and the second isolation drive circuit Figure 2 The fourth isolation transformer (T4) connects the detector circuit to the second isolation drive circuit via a fourth isolation transformer. This fourth isolation transformer adds an electrical isolation layer between the detector circuit and the second isolation drive circuit. Its fourth primary winding is connected to the output of the detector circuit, and its fourth secondary winding is connected to the input of the second isolation drive circuit. This ensures that the second isolation drive circuit can still stably receive drive signals under high voltage or strong interference conditions, effectively protecting the internal logic circuits of the second isolation drive circuit from damage. Thus, when there is a large ground potential difference or different operating voltage domains between the secondary control circuit and the primary control circuit, the fourth isolation transformer provides an independent isolated signal path, improving drive stability and EMC performance.

[0073] Thus, by introducing the aforementioned isolation transformer, not only is multi-level isolation and transmission of drive signals in multiple critical paths achieved, but the risk of mutual interference between different voltage domains is also effectively reduced, enhancing the adaptability and operational safety of the control circuit and the entire bidirectional isolated DC-DC circuit in complex electromagnetic environments.

[0074] Optionally, the third and fourth isolation transformers can be pulse transformers to achieve rapid isolated transmission of drive signals. Pulse transformers offer advantages such as fast high-frequency response, small size, and tight coupling, effectively improving the anti-interference capability and real-time performance of drive signal transmission. The third and fourth isolation transformers can be used to transmit drive signals or fault blocking signals. When a fault is detected on one side, the blocking signal can be quickly synchronized to the other side via the pulse transformer, thereby achieving linkage blocking and safety clamping of the control circuit. Thus, by using pulse transformers, not only can effective signal isolation and coupling be achieved, but the dependence of the control circuit and bidirectional isolated DC-DC circuit on optocouplers, digital isolators, and other devices can also be reduced, simplifying the circuit structure, reducing costs, and simultaneously improving the overall circuit's response speed and common-mode interference immunity.

[0075] Optionally, based on the configuration of the third and fourth isolation transformers, when a fault occurs on either the primary or secondary side, the fault signal will trigger the corresponding clamping circuit to conduct, thereby rapidly pulling the two ends of the secondary winding of the connected isolation transformer down to the control ground potential, thus blocking the corresponding drive signal. Simultaneously, utilizing the magnetic coupling characteristics of the isolation transformers, this clamping process will also short-circuit the primary signal of the transformer, and then transmit a blocking signal through the mutually coupled isolation transformer on the other side, synchronously blocking the drive signal on the other side as well. In this way, when a fault is detected on either side, synchronous blocking of the primary and secondary drive signals can be achieved, avoiding risks such as bridge arm shoot-through or power device damage caused by asynchronous blocking responses, significantly improving the safety and robustness of the circuit.

[0076] Optionally, combined Figure 2 As shown, the control circuit also includes a second isolation transformer and a third isolation transformer, and a fifth isolation transformer. The output of the detection circuit is electrically connected to the third primary winding of the third isolation transformer through the fifth isolation transformer.

[0077] In this embodiment, a fifth isolation transformer (such as...) is provided between the detection circuit and the third isolation transformer. Figure 2The T5 isolation transformer is used to further introduce isolation nodes in the drive signal transmission link, enhancing the electrical isolation strength and anti-interference capability of the signal transmission. Specifically, the output of the detector circuit is electrically connected to the primary winding of the fifth isolation transformer (denoted as the fifth primary winding), and the secondary winding of the fifth isolation transformer (denoted as the fifth secondary winding) is electrically connected to the third primary winding of the third isolation transformer, used to relay the detected drive signal. In this way, an additional isolation barrier can be provided in systems with high common-mode voltage, complex ground potential offset, or multiple ground references, effectively reducing the impact of cross-domain noise conduction and ground potential difference on the integrity of the drive signal, and further improving the electrical safety, electromagnetic compatibility, and long-term operational stability of the control circuit.

[0078] Optionally, combined Figure 2 As shown, the control circuit also includes a second isolation transformer and a fourth isolation transformer, and a fifth isolation transformer. The output of the detection circuit is electrically connected to the fourth primary winding of the fourth isolation transformer through the fifth isolation transformer.

[0079] In this embodiment, a fifth isolation transformer is provided between the detection circuit and the fourth isolation transformer to further introduce an isolation node in the drive signal transmission link, enhancing the electrical isolation strength and anti-interference capability of the signal transmission. Specifically, the output terminal of the detection circuit is electrically connected to the primary winding of the fifth isolation transformer (denoted as the fifth primary winding), and the secondary winding of the fifth isolation transformer (denoted as the fifth secondary winding) is electrically connected to the fourth primary winding of the fourth isolation transformer, for relaying the drive signal after detection processing. This provides an additional isolation barrier in high common-mode voltage, complex ground potential offset, or multi-ground reference systems, effectively reducing the impact of cross-domain noise conduction and ground potential difference on the integrity of the drive signal, further improving the electrical safety, electromagnetic compatibility, and long-term operational stability of the control circuit.

[0080] Optionally, combined Figure 2 As shown, the detection circuit includes a first comparator, a second comparator, a seventh capacitor, and an eighth capacitor. The non-inverting input of the first comparator is electrically connected to one end of the second secondary winding, and the non-inverting input of the second comparator is electrically connected to the other end of the second secondary winding. The inverting inputs of the first and second comparators are respectively used to connect to a preset reference voltage. The output of the first comparator is connected to one end of the third primary winding, or connected to one end of the third primary winding through a seventh capacitor. The output of the second comparator is connected to the other end of the third primary winding, or connected to the other end of the third primary winding through another seventh capacitor. The midpoint of the second secondary winding is grounded through the eighth capacitor, and / or the midpoint of the second secondary winding is connected to control ground.

[0081] In this embodiment, the detection circuit includes a multi-stage processing circuit for receiving the drive signal (differential signal) output from the secondary side of the second isolation transformer and performing logic shaping and processing on it, specifically including a first comparator (such as...). Figure 2 N1), the second comparator (such as N1), and the second comparator (such as N1) Figure 2 N2), the seventh capacitor (such as N2), Figure 2 C7) and the eighth capacitor (such as Figure 2 (C8). The two ends of the second secondary winding of the second isolation transformer are respectively connected to the non-inverting inputs of the first and second comparators, thus forming a pre-stage input channel for differential signal sampling. The inverting inputs of the first and second comparators are respectively connected to a preset reference voltage (denoted as the preset reference voltage, such as 0.5V or 1.25V, used to set the switching threshold level) for logical judgment of the input differential signal. The outputs of the first and second comparators are electrically connected to the two ends of the third primary winding of the third isolation transformer. Specifically, the output of the first comparator is directly electrically connected to one end of the third primary winding, or connected to one end of the third primary winding via a seventh capacitor, to enhance the rising / falling edge characteristics of the drive signal or provide AC coupling isolation; the output of the second comparator is directly electrically connected to the other end of the third primary winding, or connected to the other end of the third primary winding via another seventh capacitor, to enhance the rising / falling edge characteristics of the drive signal or provide AC coupling isolation. In this way, a set of differential drive paths can be formed to drive the third primary winding of the third isolation transformer in a differential manner, thereby improving the anti-common-mode interference capability and edge fidelity of the drive signal during isolation transmission, and ensuring that the subsequent drive circuit obtains a drive signal with accurate timing and stable amplitude.

[0082] Furthermore, to improve the common-mode interference immunity and midpoint potential stability of the control circuit, the midpoint of the second secondary winding can be grounded through the eighth capacitor to provide a stable AC reference point, thereby reducing the impact of common-mode noise on the sampling accuracy of the differential signal; and / or, the midpoint can also be connected to control ground (PGND) to keep the signal reference consistent with the logic reference potential of the control circuit, further enhancing the accuracy of logic judgment and the overall electrical consistency of the circuit.

[0083] Thus, based on the above circuit structure, while receiving and shaping the differential drive signal output from the second isolation transformer, the detection circuit effectively improves the logical clarity and anti-interference capability of the input signal (drive signal) by using comparator threshold judgment, AC coupling, and capacitor filtering. Furthermore, the shaped drive signal is differentially excited by the third isolation transformer and sent to the first isolation drive circuit with high common-mode rejection ratio and good transmission consistency. This ensures that each switching device in the first full-bridge circuit still has accurate and reliable drive control capability under high-frequency, high dv / dt environments, significantly enhancing the overall performance and stability of the bidirectional isolation DC-DC circuit.

[0084] Optionally, the eighth capacitor can be a Y capacitor (i.e., a safety capacitor), which has good high-frequency common-mode interference suppression capability and stable withstand voltage performance, suitable for the dual requirements of common-mode noise discharge and electrical safety in isolation structures. The detection circuit is grounded through the eighth capacitor, and the eighth capacitor is used to connect the primary side control ground PGND and ground (such as PE ground), which can effectively discharge the high-frequency common-mode voltage coupled to ground in the control circuit, suppress the driving signal that interferes with the external input, and improve the anti-interference capability and stability of the control circuit.

[0085] Optionally, the control circuit further includes a third isolation transformer. The first comparison circuit includes a third comparator and a fourth comparator. The non-inverting input of the third comparator is electrically connected to one end of the third secondary winding, and the non-inverting input of the fourth comparator is electrically connected to the other end of the third secondary winding. The inverting inputs of the first and second comparators are respectively used to connect to a preset reference voltage. The outputs of the third and fourth comparators are electrically connected to the first isolation drive circuit. The midpoint of the third secondary winding is connected to control ground.

[0086] In this embodiment, the control circuit includes a third isolation transformer, and the first comparison circuit includes a third comparator (such as...). Figure 2 (N3) and the fourth comparator (e.g., N3) Figure 2The non-inverting inputs of the third and fourth comparators (N4) are electrically connected to the two ends of the third secondary winding of the third isolation transformer, respectively, to receive the differential signal (drive signal) output from the secondary winding of the third isolation transformer and perform level shaping and logic judgment on it. To achieve accurate level discrimination, a preset reference voltage (e.g., 1.25V) is connected to the inverting inputs of the third and fourth comparators as the judgment threshold level. Thus, when the input signal is higher than the preset reference voltage, the comparator outputs a high level, and vice versa, thus outputting a standard logic drive signal. The outputs of the third and fourth comparators are electrically connected to the inputs of the first isolation drive circuit. Based on the signal processed by the differential comparison, the first isolation drive circuit outputs a gate drive signal with high drive capability, steep rise / fall edges, and precise timing to drive the corresponding switching transistors in the first full-bridge circuit to turn on and off. This helps to achieve efficient and stable operation of the first full-bridge circuit in the bidirectional power conversion process, ensuring the synchronization of its switching actions, the consistency of dead-time control, and the drive reliability under high-frequency operation, thus meeting the application requirements of high-voltage, high-frequency, and high-efficiency power conversion.

[0087] Furthermore, the midpoint of the third secondary winding of the third isolation transformer is connected to control ground (PGND) to provide a stable potential reference for the differential drive signal, thereby improving the common-mode rejection capability of the differential input signal and the discrimination accuracy of the comparator. Simultaneously, by connecting the midpoint to control ground, the risk of level misjudgment and signal jumps caused by ground potential drift or common-mode interference is effectively reduced, further enhancing the anti-interference capability and control logic stability of the entire drive signal chain in high dV / dt, high di / dt, and complex electromagnetic environments.

[0088] Optionally, the control circuit further includes a fourth isolation transformer, and the second comparison circuit includes a fifth comparator and a sixth comparator. The non-inverting input of the fifth comparator is electrically connected to one end of the fourth secondary winding, and the non-inverting input of the sixth comparator is electrically connected to the other end of the fourth secondary winding. The inverting inputs of the fifth and sixth comparators are respectively used to connect to a preset reference voltage. The outputs of the fifth and sixth comparators are electrically connected to the first isolation drive circuit. The midpoint of the fourth secondary winding is connected to control ground.

[0089] In this embodiment, the control circuit includes a fourth isolation transformer, and the second comparison circuit includes a fifth comparator (such as...). Figure 2 (N5) and the sixth comparator (e.g., N5) Figure 2(N6). The non-inverting inputs of the fifth and sixth comparators are electrically connected to the two ends of the fourth secondary winding of the fourth isolation transformer, respectively, to receive the differential drive signal output by the transformer and to perform level shaping and logic discrimination on the differential signal. To achieve accurate logic level identification, a preset reference voltage (e.g., 1.25V) is connected to the inverting inputs of the fifth and sixth comparators as the threshold value for level judgment. Thus, when the voltage at a certain input is higher than the reference voltage, the corresponding comparator outputs a high level, and vice versa, thus outputting standard logic drive signals. The outputs of the fifth and sixth comparators are electrically connected to the inputs of the second isolation drive circuit. The second isolation drive circuit generates gate drive signals for driving each switching device in the second full-bridge circuit based on the received differential logic drive signals. These drive signals have strong driving capability, fast rise / fall edge characteristics, and precise timing control capability, enabling precise control of the on / off state of each switching transistor in the second full-bridge circuit. This helps ensure that the second full-bridge circuit has good switching synchronization, dead-time control consistency, and drive reliability under high-frequency operating conditions during bidirectional power conversion, meeting the performance requirements of high-voltage, high-power, and high-frequency power conversion.

[0090] Furthermore, to improve the level consistency and common-mode noise immunity of the drive signal processing, the midpoint of the fourth secondary winding is connected to control ground (SGND) to provide a stable DC reference potential. This connection not only helps improve the level recognition accuracy of the differential signal in the comparator preamplifier stage, but also significantly enhances the control circuit's ability to suppress common-mode interference (such as ground potential shift and electromagnetic coupling noise), further ensuring the stability and signal fidelity of the second isolated drive circuit in complex electromagnetic environments with high dV / dt and high di / dt.

[0091] Optionally, by grounding the primary-side main circuit and the secondary-side main circuit respectively, or connecting them to control ground, and by correspondingly grounding the detection circuit, the primary-side control circuit, and the secondary-side control circuit in the control circuit to ground or connect them to control ground, effective division and control of common-mode potentials at different voltage levels can be achieved. This limits high common-mode voltages to specific paths and regions, preventing high-frequency common-mode voltages from randomly distributing within the circuit and coupling to relatively weak devices or signal nodes, thus avoiding malfunctions or insulation risks. Furthermore, based on a two-stage isolation strategy: the first stage isolates the low common-mode voltage driving signals (corresponding to the primary-side main circuit and the primary-side control circuit), and the second stage further isolates the high common-mode voltage driving signals (corresponding to the secondary-side main circuit and the secondary-side control circuit), layer by layer shielding interference paths, significantly improving the overall circuit's common-mode interference immunity and signal stability.

[0092] Optionally, combined Figure 2As shown, the first fault clamping circuit includes a first diode, a second diode, a first transistor, a third resistor, and a fourth resistor. The non-inverting input of the third comparator is electrically connected to the anode of the second diode, and the cathode of the second diode is electrically connected to the first terminal of the first transistor, and connected to a preset potential through the third resistor. The non-inverting input of the fourth comparator is electrically connected to the anode of the first diode, and the cathode of the first diode is electrically connected to the first terminal of the first transistor. The second terminal of the first transistor is connected to control ground, and the third terminal of the first transistor is electrically connected to one end of the fourth resistor. The other end of the fourth resistor is used to receive fault signals.

[0093] In this embodiment, the first fault clamping circuit of the control circuit is used to clamp the input signals of the third comparator and the fourth comparator when a corresponding fault signal is detected or received, thereby blocking the generation path of the subsequent drive signal, so as to prevent the primary side control circuit from continuing to drive the power device in the fault state, and improve the overall safety and anti-abnormal capability of the control circuit.

[0094] Specifically, the first fault clamping circuit includes a first diode (such as...). Figure 2 D1), second diode (such as D1), and second diode (such as D1) Figure 2 D2), the first transistor (such as D2), Figure 2 Q1), the third resistor (such as Q1), Figure 2 R3) and the fourth resistor (such as Figure 2(R4 in the diagram). The non-inverting input of the third comparator is electrically connected to the anode of the second diode, and the cathode of the second diode is electrically connected to the first terminal of the first transistor, and connected to a preset potential (e.g., a stable DC reference voltage, such as 5V) through a third resistor. The non-inverting input of the fourth comparator is electrically connected to the anode of the first diode, and the cathode of the first diode is also connected to the first terminal of the first transistor, and connected to the preset potential through a third resistor. The second terminal of the first transistor is connected to control ground (PGND), and the third terminal is connected to the fault signal input terminal through the fourth resistor to receive externally provided fault signals. Under normal operating conditions, when there is no fault signal input or the fault signal input is invalid (such as the first transistor failing to conduct), the first transistor is in the off state. At this time, the non-inverting input terminals of the third and fourth comparators are stabilized at their respective potentials through their corresponding diodes and third resistors, ensuring the comparator input level is stable and effectively participating in the comparison and judgment of the drive signal. However, when in a fault state, when the fault signal is validly input, the first transistor conducts, thereby rapidly pulling the cathode potentials of the first and second diodes down to near control ground (PGND). This causes the two ends of the third secondary winding of the third isolation transformer to be connected to control ground through their corresponding diodes, forming an equivalent short-circuit path. At this time, the potential of the non-inverting input terminals of the third and fourth comparators is lower than the preset reference voltage of the inverting input terminals, causing the outputs of the third and fourth comparators to remain at a low level or in an invalid logic state, thereby blocking the subsequent transmission path of the entire drive signal chain and realizing fault suppression and safety protection of the control circuit.

[0095] For example, the first transistor is an NPN transistor, with its first terminal being the collector, the second terminal being the emitter, and the third terminal being the base. The collector is connected to the cathodes of the first and second diodes, used to rapidly pull down their cathode potentials through a conduction path when a fault signal is valid. The emitter is connected to control ground to provide a stable low-potential reference. The base is connected to an external fault signal input terminal via a fourth resistor to receive a fault drive signal. Under normal operating conditions, there is no fault level input at the base, the transistor is cut off, and the collector potential is stable at the corresponding potential, ensuring normal comparator input. Under fault conditions, a valid fault signal provides a sufficient forward bias voltage to the base, the first transistor conducts, and rapidly pulls down the collector potential, thereby pulling the non-inverting inputs of the third and fourth comparators to a low level, realizing fault clamping logic control, and improving the circuit's abnormal response speed and control safety.

[0096] Optionally, the first and second diodes can be diodes with low forward voltage drop and short reverse recovery time, such as Schottky diodes and fast recovery diodes, to improve the response speed and sensitivity of the fault clamping circuit. The low forward voltage drop of the first and second diodes allows them to pull the non-inverting inputs of the third and fourth comparators to a low level more quickly when the first transistor is turned on, ensuring timely interruption of the drive link under fault conditions and effectively suppressing the risk of mis-drive. The short reverse recovery time reduces interference caused by recovery current in high-frequency or fast-switching scenarios, improving the overall stability and anti-interference performance of the circuit.

[0097] Optionally, combined Figure 2 As shown, the second fault clamping circuit includes a fourth diode, a third diode, a second transistor, a fifth resistor, and a sixth resistor. The non-inverting input of the fifth comparator is electrically connected to the anode of the third diode, and the cathode of the third diode is electrically connected to the first terminal of the second transistor, and connected to a preset potential through the fifth resistor. The non-inverting input of the sixth comparator is electrically connected to the anode of the fourth diode, and the cathode of the fourth diode is electrically connected to the first terminal of the second transistor. The second terminal of the second transistor is connected to control ground, and the third terminal of the second transistor is electrically connected to one end of the sixth resistor. The other end of the sixth resistor is used to receive fault signals.

[0098] In this embodiment, the second fault clamping circuit of the control circuit is used to clamp the input signals of the fifth and sixth comparators when a corresponding fault signal is detected or received, thereby blocking the generation path of subsequent drive signals, so as to prevent the secondary control circuit from continuing to drive the power device in the fault state, and improve the overall safety and anti-abnormal capability of the control circuit.

[0099] Specifically, the second fault clamping circuit includes a fourth diode (such as...). Figure 2 D4), third diode (such as D4), Figure 2 D3), ​​second transistor (such as D3), Figure 2 Q2), the fifth resistor (such as Q2), and the fifth resistor (such as Q2) Figure 2 (R5) and the sixth resistor (such as Figure 2(R6 in the diagram). The non-inverting input of the fifth comparator is electrically connected to the anode of the third diode, and the cathode of the third diode is electrically connected to the first terminal of the second transistor, and connected to a preset potential (e.g., a stable DC reference voltage, such as 5V) through the fifth resistor. The non-inverting input of the sixth comparator is electrically connected to the anode of the fourth diode, and the cathode of the fourth diode is also connected to the first terminal of the second transistor, and connected to the preset potential through the fifth resistor. The second terminal of the second transistor is connected to control ground, and the third terminal is connected to the fault signal input terminal through the sixth resistor to receive externally provided fault signals. Under normal operating conditions, when there is no fault signal input or the fault signal input is invalid (such as the second transistor failing to conduct), the second transistor is in the off state. At this time, the non-inverting input terminals of the fifth and sixth comparators are stabilized at their respective potentials through their corresponding diodes and the fifth resistor, ensuring the comparator input level is stable and effectively participating in the comparison and judgment of the drive signal. However, when in a fault state, when the fault signal is validly input, the second transistor conducts, thereby rapidly pulling the cathode potentials of the fourth and third diodes down to near the control ground. This causes the two ends of the fourth secondary winding of the fourth isolation transformer to be connected to the control ground through their corresponding diodes, forming an equivalent short-circuit path. At this time, the potential of the non-inverting input terminals of the fifth and sixth comparators is lower than the preset reference voltage of the inverting input terminals, causing the outputs of the fifth and sixth comparators to remain at a low level or in an invalid logic state, thereby blocking the subsequent transmission path of the entire drive signal chain and realizing fault suppression and safety protection of the control circuit.

[0100] For example, the second transistor is an NPN transistor with its first terminal as the collector, second terminal as the emitter, and third terminal as the base. The collector is connected to the cathodes of the fourth and third diodes, used to quickly pull down their cathode potentials through the conduction path when a fault signal is valid. The emitter is connected to control ground to provide a stable low-potential reference. The base is connected to the external fault signal input terminal via a sixth resistor to receive the fault drive signal. Under normal operating conditions, there is no fault level input at the base, the transistor is cut off, and the collector potential is stable at the corresponding potential, ensuring normal comparator input. Under fault conditions, the valid fault signal provides a sufficient forward bias voltage to the base, the second transistor conducts, and quickly pulls down the collector potential, thereby pulling the non-inverting inputs of the fifth and sixth comparators to a low level, realizing fault clamping logic control, and improving the circuit's abnormal response speed and control safety.

[0101] Optionally, the fourth and third diodes can be diodes with low forward voltage and short reverse recovery time, such as Schottky diodes and fast recovery diodes, to improve the response speed and sensitivity of the fault clamping circuit. Specifically, the low forward voltage of the fourth and third diodes allows them to pull the non-inverting inputs of the fifth and sixth comparators to a low level more quickly when the second transistor is turned on, ensuring timely interruption of the drive link under fault conditions and effectively suppressing the risk of mis-drive. The short reverse recovery time reduces interference caused by recovery current in high-frequency or fast-switching scenarios, improving the overall stability and anti-interference performance of the circuit.

[0102] Optionally, the first and second isolation drive circuits are used to generate complementary timing drive signals based on the input differential drive signals, respectively, to drive the switch pairs in the corresponding bridge arms. For example, the drive signal generated by the first isolation drive circuit is used to drive the first and third switches to turn on simultaneously and drive the second and fourth switches to turn off simultaneously; or it is used to drive the first and third switches to turn off simultaneously and drive the second and fourth switches to turn on simultaneously. The drive signal generated by the second isolation drive circuit is used to drive the fifth and eighth switches to turn on simultaneously and drive the sixth and seventh switches to turn off simultaneously; or it is used to drive the fifth and eighth switches to turn off simultaneously and drive the sixth and seventh switches to turn on simultaneously.

[0103] For ease of understanding, the control circuit of the bidirectional isolated DC-DC converter is described below as an example. The control circuit includes a detector circuit, a primary-side control circuit, and a secondary-side control circuit. The primary-side control circuit drives the switches S1-S4 of the first full-bridge circuit in the primary-side main circuit. The secondary-side control circuit drives the switches S5-S8 of the second full-bridge circuit in the secondary-side main circuit. The primary-side control circuit uses external input signals (original drive signals) A and B, which are connected to terminals 1 and 2 of the primary side of the second isolation transformer T2, respectively. Terminal 3 of the secondary side of the second isolation transformer T2 outputs signal a1, which is connected to the non-inverting input of the first comparator N1. Terminal 5 of the secondary side of the second isolation transformer T2 outputs signal b1, which is connected to the non-inverting input of the second comparator N2. Terminal 4 of the secondary side of the second isolation transformer T2 is the winding midpoint connected to the control ground PG of the primary-side control circuit. ND, the primary side terminal 1 and the secondary side terminal 3 of the second isolation transformer T2 are identical terminals. The control circuit ground PGND is connected to the earth PE through the Y capacitor C8. The inverting input terminals of the first comparator N1 and the second comparator N2 are respectively connected to the internal reference voltage 1.25V of the primary control circuit. The output terminal of the first comparator N1 outputs signal a2, which is connected to the primary side terminal 1 of the fifth isolation transformer T5. The output terminal of the second comparator N2 outputs signal b2, which is connected to the seventh capacitor (DC blocking capacitor). One end of capacitor C7 is connected to the other end of the primary winding of the fifth isolation transformer T5, and the other end of capacitor C7 is connected to the other end 2 of the primary winding of the fifth isolation transformer T5. One end 3 and the other end 4 of the secondary winding of the fifth isolation transformer T5 output signals a3 and b3 respectively. One end 1 of the primary winding and one end 3 of the secondary winding of the fifth isolation transformer T5 are terminals with the same name. Signal a3 is connected to one end 1 of the primary winding of the third isolation transformer T3 and one end 1 of the primary winding of the fourth isolation transformer T4 respectively. Signal b3 is connected to one end 2 of the primary winding of the third isolation transformer T3 and one end 2 of the primary winding of the fourth isolation transformer T4 respectively. The secondary winding of the third isolation transformer T3 outputs signals a5 and b5 from one end 3 and the other end 5, respectively. The midpoint 4 of the secondary winding of the third isolation transformer T3 is connected to the primary control ground PGND. Signal a5 is connected to the non-inverting input of the third comparator N3 and the anode of the second diode D2, respectively. Signal b5 is connected to the non-inverting input of the fourth comparator N4 and the anode of the first diode D1, respectively. The inverting inputs of the third comparator N3 and the fourth comparator N4 are connected to the internal reference voltage 1 of the primary control circuit, respectively.25V, the output of the third comparator N3 outputs signal PWMA1, and the output of the fourth comparator N4 outputs signal PWMB1. Signal PWMA1 generates drive signals DR1 and DR4 through the first isolation drive circuit. DR1 is used to drive the first switch S1, and DR4 is used to drive the fourth switch S4. Signal PWMB1 generates drive signals DR2 and DR3 through the first isolation drive circuit. DR2 is used to drive the second switch S2, and DR3 is used to drive the third switch S3. The cathodes of the first diode D1 and the second diode D2 are respectively connected to the collector of the first transistor (such as an NPN transistor) Q1. The collector of the first transistor Q1 is connected to the 5V power supply of the primary side control circuit through the pull-up resistor (i.e., the third resistor) R3. The emitter of the first transistor Q1 is connected to the control ground PGND of the primary control circuit. The fault signal ERR1 of the primary side control circuit is connected to the base of the first transistor Q1 in series with the current-limiting resistor (i.e., the fourth resistor) R4. The logic of the primary side fault signal ERR1 is high level to block the drive pulse signal. The drive signal for the secondary control circuit is transmitted by the fourth isolation transformer T4. One end 3 and the other end 5 of the secondary winding of the fourth isolation transformer T4 output signals a4 and b4 respectively. The midpoint 4 of the secondary winding of the fourth isolation transformer T4 is connected to the secondary control ground SGND. Signal a4 is connected to the non-inverting input of the fifth comparator N5 and the anode of the third diode D3. Signal b4 is connected to the non-inverting input of the sixth comparator N6 and the anode of the fourth diode D4. The inverting inputs of the fifth and sixth comparators N5 are connected to the internal reference voltage 1.25V of the secondary control circuit. The output of the fifth comparator N5 outputs signal PWMA2, and the output of the sixth comparator N6 outputs signal PWMB2. Signal PWMA2 generates the drive signal DR through the second isolation drive circuit. DR5 and DR8 are used to drive the fifth switch S5 and the eighth switch S8, respectively. The signal PWMB2 generates drive signals DR6 and DR7 through the second isolation drive circuit. DR6 drives the sixth switch S6 and DR7 drives the seventh switch S7. The cathodes of the third diodes D3 and D4 are connected to the collector of the second transistor (e.g., an NPN transistor) Q2. The collector of the second transistor Q2 is connected to the 5V power supply of the secondary control circuit through a pull-up resistor (i.e., the fifth resistor) R5. The emitter of the second transistor Q2 is connected to the control ground SGND of the secondary control circuit. The secondary control circuit fault signal ERR2 is connected to the base of the second transistor Q2 in series with a current-limiting resistor (i.e., the sixth resistor) R6. The logic of the secondary fault signal ERR2 is high level to block the drive pulse signal.

[0104] Based on the above control circuit, combined with Figure 3 As shown, Figure 3The key signal timing of the control circuit under normal operating conditions is shown, which reflects the corresponding situation of the drive signal from the input terminal through isolation, comparison, transmission and drive in a step-by-step process. It can demonstrate the complete logical path of the consistency, symmetry and transmission isolation of the drive signal. Specifically, during normal operation, external input signals A and B are pulse signals with a 180-degree phase difference and a duty cycle of 0-45% (5% being the dead time). After passing through the second isolation transformer T2, the resulting signals a1 and b1 are differential waveforms with opposite polarities. These are compared with a preset reference voltage of 1.25V by the first comparator N1 and the second comparator N2 to obtain signals a2 and b2. a2 is the same as signal A, and b2 is the same as signal B. This detection method eliminates common-mode voltage interference on the input signals. Signals a2 and b2 pass through the fifth isolation transformer T5 to obtain signals a3 and b3. After passing through the third isolation transformer T3, they generate signals a5 and b5 with opposite polarities. These signals are then compared with the preset reference voltage of 1.25V by the comparator detection circuit (which includes the third comparator N3 and the fourth comparator N4) to output signals PWMA1 and PWMB1. PWMA1 is the same as signal A, and PWMB1 is the same as signal B. PWMA1 is then... DR1 and DR4 are generated by the first isolation drive circuit, corresponding to the first switch S1 and the fourth switch S4 in the primary main circuit, respectively. PWMB1 then generates DR2 and DR3 through the first isolation drive circuit, corresponding to the second switch S2 and the third switch S3 in the primary main circuit, respectively. Signals a3 and b3 generate opposite signals a4 and b4 after passing through the fourth isolation transformer T4. These signals are then compared with a preset reference voltage of 1.25V by a comparator detection circuit (which includes the fifth comparator N5 and the sixth comparator N6) to obtain PWMA2 and PWMB2. PWMA2 is the same as signal A, and PWMB2 is the same as signal B. PWMA2 then generates DR5 and DR8 through the second isolation drive circuit, corresponding to the fifth switch S5 and the eighth switch S8 in the secondary main circuit, respectively. PWMB2 then generates DR6 and DR7 through the second isolation drive circuit, corresponding to the sixth switch S6 and the seventh switch S7 in the secondary main circuit, respectively.

[0105] Combination Figure 4 As shown, Figure 4The diagram illustrates the key signal timing of the control circuit when it enters a fault state, demonstrating the linkage clamping and fault blocking mechanism between the primary and secondary control circuits based on the fault signal. This effectively blocks the generation path of the drive signal when the corresponding fault occurs, preventing the corresponding power device (switching transistor) from being falsely triggered, thereby improving the overall circuit safety. Specifically, when a fault occurs in the primary main circuit or the primary control circuit, for example, when the fault signal ERR1 changes from low to high, the corresponding first transistor Q1 turns on, pulling down the cathode potential of the first diode D1 and the second diode D2. Therefore, terminals 3 and 5 of the secondary side of the third isolation transformer T3 are short-circuited to the primary control ground PGND, and signals a5 and b5 are lower than the preset reference voltage of 1.25V. The outputs PWMA1 and PWMB1 of the third comparator N3 and the fourth comparator N4 become low, thus the output drives DR1~DR4 become low; simultaneously, due to the transformer... The clamping effect of the primary and secondary sides causes the secondary side terminals 3 and 5 of the third isolation transformer T3 to short-circuit to the control ground PGND, resulting in a short circuit between terminals 1 and 2 of the primary side of the third isolation transformer T3. Signal a3 short-circuits to b3, which in turn causes the secondary side terminals 3, 4, and 5 of the fourth isolation transformer T4 to short-circuit (where terminal 4 is the midpoint of the fourth secondary winding of T4). Therefore, signals a4 and b4 are short-circuited to ground, and the voltage level is lower than 1.25V. Consequently, the outputs of the fifth comparator N5 and the sixth comparator N6, PWMA2 and PWMB2, become low, thus driving the outputs DR5~DR8 to become low. Similarly, when a fault occurs in the secondary-side main circuit or secondary-side control circuit, for example, when ERR2 changes from low to high, the corresponding second transistor Q2 turns on, pulling down the cathodes of the third diode D3 and the fourth diode D4. Therefore, terminals 3 and 5 of the secondary side of the fourth isolation transformer T4 are short-circuited to the secondary-side control ground SGND, and signals a4 and b4 fall below 1.25V. The outputs PWMA2 and PWMB2 of the fifth comparator N5 and the sixth comparator N6 become low, thus the output drives DR5~DR8 become low. Simultaneously, due to the fault in the primary and secondary sides of the transformer... The clamping effect causes the secondary windings 3 and 5 of the third isolation transformer T3 to be short-circuited to PGND, resulting in a short circuit between terminals 1 and 2 of the primary winding of the fourth isolation transformer T4. Signal a3 is short-circuited to b3, which in turn causes a short circuit between terminals 3, 4, and 5 of the secondary winding of the third isolation transformer T3 (where terminal 4 is the midpoint of the third secondary winding of T3). As a result, signals a5 and b5 are short-circuited to ground, and the voltage level is lower than 1.25V. Consequently, the outputs PWMA1 and PWMB1 of the third comparator N3 and the fourth comparator N4 become low, thus driving DR1~DR4 to become low.

[0106] Another embodiment of the present invention provides a common-mode filter design method, comprising: Based on the first preset target performance requirements, determine the first design parameters of the first common-mode inductor of the first common-mode filter regarding the first inductor, the second inductor, and the first magnetic core structure; perform simulation analysis based on the first design parameters, and determine the second design parameters of the first common-mode inductor regarding the first damping winding and the first damping resistor based on the simulation analysis results; And / or, based on the second preset target performance requirements, determine the third design parameters of the second common-mode inductor of the second common-mode filter regarding the third inductor, the fourth inductor, and the second magnetic core structure; perform simulation analysis based on the second design parameters, and determine the fourth design parameters of the second common-mode inductor regarding the second damping winding and the second damping resistor based on the simulation analysis results.

[0107] The method described in this embodiment can be used to select parameters and design the structure of the first common-mode inductor of the first common-mode filter and / or the second common-mode inductor of the second common-mode filter in the above-mentioned bidirectional isolated DC-DC circuit. This enables the synergistic optimization of the core structure, inductance, damping network, and magnetic materials of the corresponding common-mode inductors, allowing the corresponding common-mode filters to effectively block high-frequency common-mode noise while possessing good inductance linearity and damping absorption capabilities. This, in turn, improves the anti-interference performance and operational reliability of the entire bidirectional isolated DC-DC circuit in complex electromagnetic environments.

[0108] Specifically, when designing the first common-mode inductor of the first common-mode filter, the first design parameters of the first common-mode inductor are determined based on the preset target performance requirements (denoted as the first preset target performance requirements), such as the common-mode interference suppression capability, electromagnetic compatibility, and high-voltage adaptability required by the primary-side main circuit and the bidirectional isolation DC-DC circuit. These first design parameters include design parameters for the first inductor, the second inductor, and the first magnetic core structure, such as the target inductance values ​​of the first and second inductors (used for differential-mode offsetting and common-mode coupling), and the first magnetic core structure parameters (such as the cross-sectional area of ​​the magnetic core). magnetic permeability Effective magnetic circuit length (etc.) These first design parameters are used for selection and size design. Then, the aforementioned first design parameters are input into the corresponding electromagnetic simulation model for performance simulation analysis. For example, the frequency response characteristics, resonant point, and impedance distribution of the first common-mode inductor using the first design parameters in the target frequency band are simulated and analyzed. Based on the simulation analysis results, second design parameters for the first common-mode inductor regarding the first damping winding and the first damping resistor are further determined. These parameters are used to improve the common-mode interference suppression capability and electromagnetic compatibility performance of the first common-mode inductor in the target operating frequency band. For example, the second design parameters include the winding parameters of the first damping winding (such as the number of coil turns, winding method, and impedance characteristics), and the resistance value of the first damping resistor used to absorb common-mode resonance energy. Thus, based on the determined first and second design parameters, the structural construction and parameter finalization of the first common-mode inductor can be completed, resulting in a first common-mode inductor that meets the required performance, ensuring that the designed first common-mode inductor has good common-mode suppression effect, electromagnetic compatibility performance, and operating stability in a bidirectional isolated DC-DC circuit.

[0109] When designing the second common-mode inductor of the second common-mode filter, the third design parameters of the second common-mode inductor are first determined based on the preset target performance requirements (denoted as the second preset target performance requirements), such as the common-mode interference suppression capability, electromagnetic compatibility, and high-voltage adaptability required by the secondary-side main circuit and the bidirectional isolation DC-DC circuit. These third design parameters include design parameters for the third inductor, the fourth inductor, and the second magnetic core structure, such as the target inductance values ​​of the third and fourth inductors (for differential-mode offsetting and common-mode coupling), and the second magnetic core structure parameters (such as the cross-sectional area of ​​the magnetic core). magnetic permeability Effective magnetic circuit length (etc.) These parameters are used for selection and size design. Then, the aforementioned third design parameters are input into the corresponding electromagnetic simulation model for performance simulation analysis. For example, the frequency response characteristics, resonant point, and impedance distribution of the second common-mode inductor using the third design parameters are simulated and analyzed within the target frequency band. Based on the simulation analysis results, fourth design parameters for the second common-mode inductor regarding the second damping winding and the second damping resistor are further determined. These parameters are used to improve the common-mode interference suppression capability and electromagnetic compatibility performance of the second common-mode inductor within the target operating frequency band. For example, the fourth design parameters include the winding parameters of the second damping winding (such as the number of coil turns, winding method, and impedance characteristics), and the resistance value of the second damping resistor used to absorb common-mode resonance energy. Thus, based on the determined third and fourth design parameters, the structural construction and parameter finalization of the second common-mode inductor can be completed, resulting in a second common-mode inductor that meets the required performance, ensuring that the designed second common-mode inductor has good common-mode suppression, electromagnetic compatibility performance, and operational stability in a bidirectional isolated DC-DC circuit.

[0110] In summary, through a phased design process, the basic magnetic design of the common-mode inductor is first preliminarily determined to identify the inductor winding parameters and core structure that meet the high-frequency common-mode voltage suppression requirements. Then, based on electromagnetic characteristic simulation analysis of the preliminary magnetic design model, the configuration parameters of the damping network are further determined, including the turns ratio of the damping winding and the selection and matching of the corresponding damping resistors. This adjusts the frequency response characteristics of the common-mode filter, suppresses spike resonances and high-frequency oscillations, and improves its common-mode interference absorption and dissipation capabilities in the target frequency band, thereby forming an overall common-mode filter structure with excellent common-mode filtering performance, stability, and engineering feasibility. This approach helps to systematically achieve the coordinated configuration of common-mode inductor structure design and damping optimization, ensuring its electromagnetic compatibility and long-term operational reliability in practical bidirectional isolated DC-DC circuits.

[0111] For example, in the design of common-mode inductors L1 and L2, the first or third design parameters (including the cross-sectional area of ​​the common-mode inductor core) can be determined based on the preset target performance requirements, taking into account factors such as satisfying Faraday's law of electromagnetic induction, ensuring that the maximum volt-second product under the design common-mode voltage does not lead to core saturation, controlling core losses within an acceptable range, and ensuring that the inductance meets the common-mode filtering requirements. Number of winding turns and the permeability of the core material (etc.). Among them, according to Faraday's law of electromagnetic induction, the corresponding formula is... ; Indicates the number of turns in a single main winding of a common-mode inductor (i.e., the number of turns in the winding coil of the first or second inductor; when the first and second inductors are wound symmetrically, it is assumed that the two main windings have the same number of turns). This represents the change in magnetic flux density, and is usually chosen as the maximum permissible amplitude of magnetic flux density swing to avoid core saturation. Indicates the effective cross-sectional area of ​​the magnetic core; This represents the common-mode voltage acting on the inductor; Indicates the duration of the common-mode voltage effect ( × This refers to the maximum volt-second product designed to constrain the core from saturation within that time period. This formula ensures the core remains unsaturated under the influence of the maximum volt-second product, preventing the magnetic flux density from exceeding the core's saturation point and ensuring safe operation. Based on this, the core cross-sectional area is determined first. and number of winding turns This ensures that the core does not saturate under the designed maximum common-mode volt-second product. Simultaneously, based on the set common-mode current requirements, the minimum required inductance is determined, and then calculated using the corresponding formula. Select a permeability that meets the requirements. The magnetic core material is selected to obtain the desired inductance performance, wherein... LThis represents the target minimum inductance (determined by common-mode current filtering requirements). Represents the free permeability, which is a constant; Indicates the relative permeability of the core material (a key parameter for design and selection); This represents the average length of the magnetic path (i.e., the effective magnetic path length) of the magnetic core. This is used after initially determining the common-mode inductance parameters (i.e., the cross-sectional area of ​​the magnetic core). Number of winding turns and the permeability of the selected core material Afterwards, these parameters are input into a simulation model for modeling and simulation analysis to further optimize the common-mode filtering performance and determine the required design parameters for the damping winding and damping resistor. For example, the initial resistance value of the damping resistor required for the common-mode inductor can be determined in the simulation. Its power consumption, and further design the number of turns of the damping winding. Based on the turns ratio of the damping winding to the main winding, Converted to the equivalent resistance value connected in parallel across the damping winding Satisfying the relation (This formula is derived based on the impedance reflection relationship of an ideal transformer, considering the equivalent resistance of the damping resistance reflected from the main winding side to the damping winding side.) Typically... The range is from 1kΩ to 100kΩ, with a typical power consumption of approximately 10W; after conversion The range is generally from 1Ω to 100Ω, and power resistors in TO-220 or TO-247 packages can be selected. The power rating is mostly above 50W to ensure the reliability of electrical performance and thermal management.

[0112] Thus, in common-mode inductor design, by optimizing the core size, materials, and winding parameters, it is ensured that magnetic saturation does not occur under high-frequency common-mode voltage, effectively avoiding the problem of degraded common-mode rejection performance. Simultaneously, by introducing a damping winding in parallel with a damping resistor, not only can the high-frequency resonance peak of the common-mode path be suppressed, preventing abnormal amplification of the common-mode current, but the impact of the damping resistor's parasitic parameters on filtering performance can also be reduced, improving the stability and reliability of the common-mode inductor. Furthermore, properly setting the core volt-second product and optimizing the winding structure helps prevent saturation of high-permeability cores under low-frequency conditions. In addition, to meet practical application requirements, power resistors in TO-220 or TO-247 packages can be selected, which have good heat dissipation capabilities and structural layout flexibility, facilitating heat dissipation and improving space utilization.

[0113] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A bidirectional isolated DC-DC circuit, characterized in that, include: The first isolation transformer includes a first primary winding and a first secondary winding that are electrically isolated from each other; The primary side main circuit includes a first common-mode filter and a first full-bridge circuit. The second connection terminal of the first common-mode filter is electrically connected to the first primary winding through the first full-bridge circuit. The secondary side main circuit includes a second common-mode filter and a second full-bridge circuit. The second connection terminal of the second common-mode filter is electrically connected to the first secondary winding through the second full-bridge circuit. Wherein, the first connection terminal of the first common-mode filter is used to connect to DC power, and the first connection terminal of the second common-mode filter is used to output DC power; or, the first connection terminal of the second common-mode filter is used to connect to DC power, and the first connection terminal of the first common-mode filter is used to output DC power.

2. The bidirectional isolated DC-DC circuit as described in claim 1, characterized in that, The first common-mode filter includes a first common-mode inductor, which includes a first inductor, a second inductor, a first damping winding, a first damping resistor, and a first magnetic core structure. The coils of the first inductor, the second inductor, and the first damping winding are respectively wound on the first magnetic core structure. The two ends of the first damping resistor are respectively electrically connected to the two ends of the first damping winding. The first full-bridge circuit is electrically connected to the first inductor and the second inductor, respectively; And / or, the second common-mode filter includes a second common-mode inductor, the second common-mode inductor includes a third inductor, a fourth inductor, a second damping winding, a second damping resistor, and a second magnetic core structure, the coils of the third inductor, the fourth inductor, and the second damping winding are respectively wound on the second magnetic core structure; the two ends of the second damping resistor are respectively electrically connected to the two ends of the second damping winding. The second full-bridge circuit is electrically connected to the third inductor and the fourth inductor, respectively.

3. The bidirectional isolated DC-DC circuit as described in claim 2, characterized in that, The first common-mode filter further includes a first capacitor, one end of which is electrically connected to the end of the first inductor away from the first full-bridge circuit, and the other end of which is electrically connected to the end of the second inductor away from the first full-bridge circuit; the primary-side main circuit further includes a second capacitor, one end of which is electrically connected to the end of the first inductor used for electrically connecting to the first full-bridge circuit, and the other end of which is electrically connected to the end of the second inductor used for electrically connecting to the first full-bridge circuit; And / or, the second common-mode filter further includes a fourth capacitor, one end of which is electrically connected to the end of the third inductor away from the second full-bridge circuit, and the other end of which is electrically connected to the end of the fourth inductor away from the second full-bridge circuit; the secondary-side main circuit further includes a fifth capacitor, one end of which is electrically connected to the end of the third inductor used for electrically connecting to the second full-bridge circuit, and the other end of which is electrically connected to the end of the fourth inductor used for electrically connecting to the second full-bridge circuit; And / or, the primary side main circuit further includes a third capacitor, the first inductor is used to electrically connect one end of the first full-bridge circuit to ground or control ground through the third capacitor, or the second inductor is used to electrically connect one end of the first full-bridge circuit to ground or control ground through the third capacitor; And / or, the secondary side main circuit further includes a sixth capacitor, the third inductor is used to electrically connect one end of the second full-bridge circuit to ground or control ground through the sixth capacitor, or the fourth inductor is used to electrically connect one end of the second full-bridge circuit to ground or control ground through the sixth capacitor.

4. The bidirectional isolated DC-DC circuit as described in claim 2, characterized in that, It also includes resonant inductors and resonant capacitors; The first full-bridge circuit includes a first switch, a second switch, a third switch, and a fourth switch. The first terminals of the first and third switches are electrically connected to one end of the first inductor, and the second terminals of the second and fourth switches are electrically connected to one end of the second inductor. The second terminal of the first switch and the first terminal of the second switch are electrically connected, and are electrically connected to one end of the first primary winding through one of the resonant inductor and the resonant capacitor. The second terminal of the third switch and the first terminal of the fourth switch are electrically connected, and are electrically connected to the other end of the first primary winding. The first full-bridge circuit includes a fifth switch, a sixth switch, a seventh switch, and an eighth switch. The first ends of the fifth and seventh switches are electrically connected to one end of the third inductor, and the second ends of the sixth and eighth switches are electrically connected to one end of the fourth inductor. The second end of the fifth switch and the first end of the sixth switch are electrically connected, and are also electrically connected to one end of the first secondary winding through another of the resonant inductor and the resonant capacitor. The second end of the seventh switch and the first end of the eighth switch are electrically connected, and are also electrically connected to the other end of the first secondary winding.

5. The bidirectional isolated DC-DC circuit as described in any one of claims 1-4, characterized in that, It also includes a control circuit that is communicatively connected to the first full-bridge circuit and the second full-bridge circuit respectively. The control circuit is used to control the on / off state of each switch in the first full-bridge circuit and the second full-bridge circuit.

6. The bidirectional isolated DC-DC circuit as described in claim 5, characterized in that, The control circuit includes a primary-side control circuit, a secondary-side control circuit, and a detection circuit. The primary-side control circuit includes a first isolation drive circuit, the input of which is electrically connected to the output of the detection circuit, and the output of which is electrically connected to the controlled terminals of each switch in the first full-bridge circuit. The secondary-side control circuit includes a second isolation drive circuit, the input of which is electrically connected to the output of the detection circuit, and the output of which is electrically connected to the controlled terminals of each switch in the second full-bridge circuit. The input of the detection circuit is used to receive drive signals.

7. The bidirectional isolated DC-DC circuit as described in claim 6, characterized in that, The primary control circuit further includes a first comparison circuit and a first fault clamping circuit, and the output terminal of the detector circuit is electrically connected to the input terminal of the first isolation drive circuit through the first comparison circuit. The output terminal of the first fault clamping circuit is connected to the input terminal of the first comparison circuit. The input terminal of the first fault clamping circuit is used to receive the fault signal and clamp the potential of the input terminal of the first comparison circuit to the first preset clamping level according to the fault signal. And / or, the secondary side control circuit further includes a second comparison circuit and a second fault clamping circuit, and the output terminal of the detector circuit is electrically connected to the input terminal of the second isolation drive circuit through the second comparison circuit; The output terminal of the second fault clamping circuit is connected to the input terminal of the second comparison circuit. The input terminal of the second fault clamping circuit is used to receive the fault signal and clamp the potential of the input terminal of the second comparison circuit to the second preset clamping level according to the fault signal.

8. The bidirectional isolated DC-DC circuit as described in claim 7, characterized in that, The control circuit also includes a second isolation transformer. The input terminal of the detection circuit is electrically connected to the second secondary winding of the second isolation transformer. The second primary winding of the second isolation transformer is used to receive the drive signal. And / or, the control circuit further includes a third isolation transformer, the output terminal of the detector circuit is electrically connected to the third primary winding of the third isolation transformer, and the input terminal of the first isolation drive circuit is electrically connected to the third secondary winding of the third isolation transformer; And / or, the control circuit further includes a fourth isolation transformer, the output terminal of the detector circuit is electrically connected to the fourth primary winding of the fourth isolation transformer, and the input terminal of the second isolation drive circuit is electrically connected to the fourth secondary winding of the fourth isolation transformer.

9. The bidirectional isolated DC-DC circuit as described in claim 8, characterized in that, The detection circuit includes a first comparator, a second comparator, a seventh capacitor, and an eighth capacitor. The non-inverting input of the first comparator is electrically connected to one end of the second secondary winding, and the non-inverting input of the second comparator is electrically connected to the other end of the second secondary winding. The inverting inputs of the first and second comparators are respectively used to connect to a preset reference voltage. The output of the first comparator is connected to one end of the third primary winding, or connected to one end of the third primary winding through one of the seventh capacitors. The output of the second comparator is connected to the other end of the third primary winding, or connected to the other end of the third primary winding through another of the seventh capacitors. The midpoint of the second secondary winding is grounded through the eighth capacitor, and / or the midpoint of the second secondary winding is connected to control ground.

10. A common-mode filter design method, characterized in that, include: Based on the first preset target performance requirements, determine the first design parameters of the first common-mode inductor of the first common-mode filter with respect to the first inductor, the second inductor, and the first magnetic core structure; Based on the first design parameters, a simulation analysis is performed, and based on the simulation analysis results, the second design parameters of the first common-mode inductor regarding the first damping winding and the first damping resistor are determined. And / or, based on the second preset target performance requirements, determine the third design parameters of the second common-mode inductor of the second common-mode filter with respect to the third inductor, the fourth inductor, and the second magnetic core structure; Based on the second design parameters, a simulation analysis is performed, and based on the simulation analysis results, the fourth design parameters of the second common-mode inductor regarding the second damping winding and the second damping resistor are determined.

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