An isolated converter and method that can absorb spike voltage

Abstract

The present application relates to power supply technical field, particularly to a kind of isolated converter and method of absorbing sharp peak voltage, including: transformer, primary side circuit and secondary side circuit;Transformer includes primary winding and secondary winding, secondary winding is center-tapped type, and secondary winding includes first winding and second winding;Primary side circuit is used to convert DC voltage into AC voltage and then transmit to the primary winding of transformer;Secondary side circuit includes switch tube Q1, first absorption circuit, switch tube Q2, second absorption circuit, energy storage inductance Lo and filter capacitor Co;First absorption circuit includes absorption capacitor C1, first energy discharge component and second energy discharge component;Second absorption circuit includes absorption capacitor C2, third energy discharge component and fourth energy discharge component;It can effectively absorb sharp peak voltage generated by transformer leakage inductance, and release energy through first absorption circuit and second absorption circuit, improve the stability of entire converter system.

Description

Technical Field

[0001] This invention relates to the field of power supply technology, and in particular to an isolation converter and method capable of absorbing voltage spikes. Background Technology

[0002] Secondary-side center-tapped isolated power converters typically use transformers for isolation to improve power supply safety and reliability. The principle is to step down the input AC power through the transformer, then rectify and filter it to obtain DC output. At the output, a center tap splits the DC power into two equal parts, supplying the positive and negative terminals of the load respectively. This type of power converter is commonly used in applications requiring symmetrical power supply or high isolation and safety, such as audio amplifiers, instruments, medical equipment, computer networks, and industrial automation. It reduces output ripple and noise, improving power quality and stability.

[0003] The existing secondary-side center-tapped half-bridge isolation circuit is widely used due to its simple structure, few components, and low voltage stress. However, because of the leakage inductance of the transformer, the energy stored in the leakage inductance increases the peak voltage when the secondary rectifier switch is turned off, leading to overvoltage, damage to the switch or other electronic components, and system instability. Therefore, when designing the circuit, it is necessary to consider the impact of leakage inductance and take corresponding measures to reduce peak voltage.

[0004] Therefore, overcoming the shortcomings of the existing technology is an urgent problem to be solved in this technical field. Summary of the Invention

[0005] The technical problem to be solved by this invention is: how to absorb the energy stored in the leakage inductance of a transformer, and how to reduce the peak voltage generated by the leakage inductance of a transformer.

[0006] The present invention adopts the following technical solution: In one aspect, an isolation converter capable of absorbing peak voltages is provided, comprising: a transformer, a primary circuit, and a secondary circuit; The transformer includes a primary winding and a secondary winding. The secondary winding is a center-tapped type and includes a first winding and a second winding. The primary circuit is used to convert DC voltage into AC voltage and then transmit it to the primary winding of the transformer. The secondary circuit includes a switching transistor Q1, a first absorption circuit, a switching transistor Q2, a second absorption circuit, an energy storage inductor Lo, and a filter capacitor Co; the first absorption circuit includes an absorption capacitor C1, a first energy dissipation component, and a second energy dissipation component; the second absorption circuit includes an absorption capacitor C2, a third energy dissipation component, and a fourth energy dissipation component; One end of the first winding is connected to the drain of the switching transistor Q1 and one end of the absorption capacitor C1; the other end of the first winding is connected to one end of the energy storage inductor Lo and one end of the second winding; the other end of the energy storage inductor Lo is used to connect to the load; the other end of the absorption capacitor C1 is connected to one end of the first energy dissipation component and one end of the second energy dissipation component; the source of the switching transistor Q1 is connected to the other end of the first energy dissipation component and the load; the other end of the second energy dissipation component is used to connect to the load; the filter capacitor Co is connected in parallel across the load; The other end of the second winding is connected to the drain of the switching transistor Q2 and one end of the absorption capacitor C2, respectively; the other end of the absorption capacitor C2 is connected to one end of the third energy dissipation component and one end of the fourth energy dissipation component; the source of the switching transistor Q2 is connected to the other end of the third energy dissipation component and the load, respectively; the other end of the fourth energy dissipation component is used to connect to the load.

[0007] Preferably, the first energy dissipation component includes a resistor R1 and a diode D1, and the second energy dissipation component includes a diode D2 and a resistor R2; One end of resistor R1 is connected to the source of switch Q1, and the other end of resistor R1 is connected to the anode of diode D1. The cathode of diode D1 is connected to the anode of diode D2, and the cathode of diode D1 is also connected to the other end of absorption capacitor C1. The cathode of diode D2 is connected to one end of resistor R2, and the other end of resistor R2 is connected to the output terminal of transformer.

[0008] Preferably, the resistance value range of the resistor R1 is: Where R1 is the resistance value of resistor R1, L is the inductance value of the leakage inductance of the transformer, and C is the capacitance value of the absorption capacitor C1.

[0009] The resistance range of the resistor R2 is: Where R2 is the resistance of resistor R2, L is the inductance of the transformer leakage inductance, and C is the capacitance of absorption capacitor C1.

[0010] Preferably, the third energy dissipation component includes a resistor R3 and a diode D3, and the fourth energy dissipation component includes a diode D4 and a resistor R4; One end of the resistor R3 is connected to the source of the switching transistor Q2, and the other end of the resistor R3 is connected to the anode of the diode D3. The cathode of the diode D3 is connected to the anode of the diode D4, and the cathode of the diode D3 is also connected to the other end of the absorption capacitor C2. The cathode of the diode D4 is connected to one end of the resistor R4, and the other end of the resistor R4 is connected to the output terminal of the transformer.

[0011] Preferably, the resistance value range of the resistor R3 is: Where R3 is the resistance of resistor R3, L is the inductance of the transformer leakage inductance, and C is the capacitance of absorption capacitor C2.

[0012] The resistance range of the resistor R4 is: Where R4 is the resistance value of resistor R4, L is the inductance value of the leakage inductance of the transformer, and C is the capacitance value of the absorption capacitor C2.

[0013] Preferably, the isolation converter capable of absorbing peak voltages further includes a control circuit for controlling the switching on and off of the switching transistors Q1 and Q2.

[0014] Preferably, the primary-side circuit includes a voltage divider capacitor Ca, a voltage divider capacitor Cb, a switching transistor S1, and a switching transistor S2; The voltage dividing capacitors Ca and Cb are connected in series across the power supply, and the switching transistors S2 and S1 are also connected in series across the power supply; one end of the primary winding is connected between the switching transistors S1 and S2, and the other end of the primary winding is connected between the voltage dividing capacitors Ca and Cb. When the switch S1 is turned on and the switch S2 is turned off, the switch Q2 is turned on and the switch Q1 is turned off. When the switch S1 is off and the switch S2 is on, the switch Q1 is on and the switch Q2 is off.

[0015] Secondly, a method for absorbing voltage spikes is provided, including: When the switch Q1 is turned off, the energy generated by the leakage inductance of the transformer passes through the absorption capacitor C1 and the second energy dissipation component in sequence and is then transferred to the load to absorb the energy generated by the leakage inductance of the transformer; when the switch Q1 is turned on, the absorption capacitor C1 discharges through the switch Q1 and the first energy dissipation component. When the switch Q2 is turned off, the energy generated by the leakage inductance of the transformer passes through the absorption capacitor C2 and the fourth energy dissipation component in sequence and is then transferred to the load to absorb the energy generated by the leakage inductance of the transformer; when the switch Q2 is turned on, the absorption capacitor C2 discharges through the switch Q2 and the third energy dissipation component.

[0016] Preferably, when the switching transistor Q1 is turned off, the energy generated by the leakage inductance of the transformer passes sequentially through the absorption capacitor C1 and the second energy dissipation component before being transferred to the load to absorb the energy generated by the leakage inductance of the transformer, further comprising: After the absorption capacitor C1 is charged, the energy in the absorption capacitor C1 is discharged sequentially through the first winding, the energy storage inductor Lo, the load, and the first energy discharge component.

[0017] Preferably, when the switching transistor Q2 is turned off, the energy generated by the leakage inductance of the transformer passes sequentially through the absorption capacitor C2 and the fourth energy dissipation component before being transferred to the load to absorb the energy generated by the leakage inductance of the transformer, further comprising: After the absorption capacitor C2 is charged, the energy in the absorption capacitor C2 is discharged sequentially through the second winding, the energy storage inductor Lo, the load, and the third energy discharge component.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention reduces the voltage spike generated by the transformer leakage inductance when the switch Q1 is turned off and the absorption capacitor C1 is charging by cooperating with the second energy dissipation component; reduces the voltage spike generated by the transformer leakage inductance when the switch Q1 is turned off and the absorption capacitor C1 is discharging by cooperating with the first energy dissipation component; reduces the voltage spike generated by the transformer leakage inductance when the switch Q2 is turned off and the absorption capacitor C2 is charging by cooperating with the fourth energy dissipation component; and reduces the voltage spike generated by the transformer leakage inductance when the switch Q2 is turned off and the absorption capacitor C2 is discharging by cooperating with the third energy dissipation component. This effectively absorbs the voltage spike generated by the transformer leakage inductance and releases energy through the first and second absorption circuits, thereby improving the efficiency and stability of the entire converter system. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the topology of a secondary-side center-tapped half-bridge isolation circuit provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of an isolation converter capable of absorbing voltage spikes provided in an embodiment of the present invention; Figure 3 This is an equivalent schematic diagram of a partial structure of an isolation converter capable of absorbing voltage spikes, provided in an embodiment of the present invention. Figure 4 This is a schematic diagram of the oscillation voltage waveform of an isolation converter capable of absorbing peak voltages provided in an embodiment of the present invention when undamped. Figure 5 This is a schematic diagram of the oscillating current waveform of an isolation converter capable of absorbing peak voltages provided in an embodiment of the present invention when it is undamped. Figure 6 This is a schematic diagram of the oscillation voltage waveform of an isolation converter capable of absorbing peak voltages after adding damping, provided in an embodiment of the present invention. Figure 7 This is a schematic diagram of the oscillating current waveform of an isolation converter capable of absorbing peak voltages after adding damping, provided in an embodiment of the present invention. Figure 8 This is a schematic diagram of the drain-source voltage waveform of switch Q1 when the isolation converter capable of absorbing peak voltages provided in an embodiment of the present invention does not include resistors R1 and R2. Figure 9 This is a schematic diagram of the drain-source voltage waveform of switch Q1 when an isolation converter capable of absorbing peak voltages is provided in an embodiment of the present invention, including resistors R1 and R2. Figure 10 This is a schematic diagram of the structure of an isolation converter capable of absorbing voltage spikes provided in an embodiment of the present invention; Figure 11 This is a schematic flowchart of a method for absorbing voltage spikes provided in an embodiment of the present invention; Figure 12 This is a flowchart illustrating another method for absorbing peak voltages provided in an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] In this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0023] In this application, unless otherwise expressly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a direct connection or an indirect connection through an intermediate medium. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0024] Example 1: like Figure 1 The diagram shows a common topology of a center-tapped half-bridge isolation circuit on the secondary side. The primary circuit includes the input voltage Vin, upper voltage divider capacitor Ca, lower voltage divider capacitor Cb, switching transistors S1 and S2, and a transformer T. The secondary circuit includes switching transistors Q1 and Q2, an energy storage inductor Lo, a filter capacitor Co, and the output voltage Vout. When switching transistor S1 is on and switching transistor S2 is off, current flows from the input voltage Vin+ through switching transistor S1, the primary winding of transformer T, and the lower voltage divider capacitor Cb, forming a current loop. At this time, the voltage drop across the primary winding of the transformer is Vin / 2. The current flowing through the primary winding generates magnetic lines of force, which are transmitted through the iron core to the secondary winding. This induces an electromotive force in the secondary winding, resulting in an induced voltage Vi / (2*n) across it, which turns on switching transistor Q2, thus forming a current loop. When switch S1 is off and switch S2 is on, current flows from the input voltage Vin+ through the upper voltage divider capacitor Ca, the primary winding of transformer T, and switch S2 to form a current loop. At this time, the voltage drop across the primary winding of the transformer is Vin / 2, and the induced voltage across the secondary winding of the transformer is Vi / (2*n), causing switch Q1 to turn on, and the current loop is formed. The secondary center-tapped half-bridge isolation converter alternates between switching on and off in each half-cycle of switch S1 and switch S2 to form a complete cycle. When switch S1 is on and switch S2 is off, the voltage across the primary winding of the transformer is a positive voltage drop in half a cycle; when switch S2 is on and switch S1 is off, the voltage across the primary winding of the transformer is a negative voltage drop in half a cycle.

[0025] In this type of secondary-side center-tapped half-bridge isolation circuit, the leakage inductance of the transformer T causes an increase in the voltage spike when the secondary rectifier switch (Q1 or Q2) is turned off due to the energy stored in the transformer's leakage inductance. To absorb this energy and reduce the voltage spike, this embodiment provides an isolation converter capable of absorbing voltage spikes. Figure 2As shown, it includes: a transformer, a primary circuit, and a secondary circuit; the transformer includes a primary winding and a secondary winding, the secondary winding being a center-tapped type, the secondary winding including a first winding and a second winding; the primary circuit is used to convert DC voltage into AC voltage and transmit it to the primary winding of the transformer; the secondary circuit includes a switching transistor Q1, a first absorption circuit, a switching transistor Q2, a second absorption circuit, an energy storage inductor Lo, and a filter capacitor Co; the first absorption circuit includes an absorption capacitor C1, a first energy dissipation component, and a second energy dissipation component; the second absorption circuit includes an absorption capacitor C2, a third energy dissipation component, and a fourth energy dissipation component.

[0026] One end of the first winding is connected to the drain of the switching transistor Q1 and one end of the absorption capacitor C1, respectively; the other end of the first winding is connected to one end of the energy storage inductor Lo and one end of the second winding, respectively; the other end of the energy storage inductor Lo is used to connect to the load; the other end of the absorption capacitor C1 is connected to one end of the first energy dissipation component and one end of the second energy dissipation component; the source of the switching transistor Q1 is connected to the other end of the first energy dissipation component and the load, respectively; the other end of the second energy dissipation component is used to connect to the load; the filter capacitor Co is connected in parallel across the load.

[0027] The other end of the second winding is connected to the drain of the switching transistor Q2 and one end of the absorption capacitor C2, respectively; the other end of the absorption capacitor C2 is connected to one end of the third energy dissipation component and one end of the fourth energy dissipation component; the source of the switching transistor Q2 is connected to the other end of the third energy dissipation component and the load, respectively; the other end of the fourth energy dissipation component is used to connect to the load.

[0028] Specifically, based on existing technology, this embodiment adds a first absorption circuit and a second absorption circuit to the secondary circuit of the transformer. The specific electronic components included in the first absorption circuit and the second absorption circuit may depend on the specific application and are not specifically limited here.

[0029] This embodiment reduces the voltage spike generated by the transformer leakage inductance when the switch Q1 is turned off and the absorption capacitor C1 is charging by cooperating with the second energy dissipation component; it also reduces the voltage spike generated by the transformer leakage inductance when the switch Q1 is turned off and the absorption capacitor C1 is discharging by cooperating with the first energy dissipation component; further, it reduces the voltage spike generated by the transformer leakage inductance when the switch Q2 is turned off and the absorption capacitor C2 is charging by cooperating with the fourth energy dissipation component; and finally, it reduces the voltage spike generated by the transformer leakage inductance when the switch Q2 is turned off and the absorption capacitor C2 is discharging by cooperating with the third energy dissipation component. This effectively absorbs the voltage spikes generated by the transformer leakage inductance and releases energy through the first and second absorption circuits, thereby improving the efficiency and stability of the entire converter system.

[0030] When the isolation converter operates in the first half of the cycle, it absorbs the energy stored in the transformer leakage inductance through the absorption capacitor C1, the switching transistor Q1, the first energy dissipation component, and the second energy dissipation component. Similarly, when the isolation converter operates in the second half of the cycle, it absorbs the energy stored in the transformer leakage inductance through the absorption capacitor C2, the switching transistor Q3, the third energy dissipation component, and the fourth energy dissipation component. The specific process will not be described in detail in this embodiment.

[0031] See Figure 3 , Figure 3 for Figure 2 The equivalent circuit diagram of the first absorption circuit and the transformer leakage inductance is shown below; the second absorption circuit is similar. Among them, Equivalent to the voltage across the leakage inductance of a transformer. The voltage across the absorption capacitor C1 is equivalent to the voltage across the capacitor, and R is equivalent to the impedance of either the first or second energy dissipation component. The charging and discharging process of the absorption capacitor C1 can be equivalent to the oscillation process of a second-order circuit, which yields a second-order linear constant homogeneous differential equation with Uc as the variable: The corresponding characteristic equation is: We can obtain two solutions, S1 and S2, where Damping coefficient: , The undamped oscillation frequency is: , For transformer leakage inductance, The capacitance of the absorption capacitor C1, For damping.

[0032] when When S1 and S2 are both distinct real roots, the response of Uc(t) is non-oscillatory, which is called overdamped; when When S1 and S2 are two equal negative real roots, the Uc(t) response is non-oscillatory, which is called critical damping; when When S1 and S2 are a pair of conjugate complex roots, the response of Uc(t) is oscillatory, which is called underdamped; when When the equivalent resistance R equals 0, S1 and S2 are a pair of conjugate imaginary roots, and the response of Uc(t) is oscillatory, which is called undamped. Assuming the initial voltage of capacitor C is 1, the oscillating voltage waveform of Uc in the undamped state is as follows: Figure 4 As shown, the oscillating current waveform is as follows Figure 5 As shown; by Figure 4 and Figure 5 It is known that under undamped conditions, both voltage and current undergo undiminished, constant-amplitude oscillations, which is detrimental to the energy absorption of the first absorption circuit, and the same applies to the second absorption circuit. For example... Figure 6 and Figure 7 The figures show the voltage and current waveforms under different damping conditions. Figure 6 and Figure 7 It can be seen that adding a resistance value R will reduce both the number of voltage oscillations and the amplitude of current oscillations. The larger the voltage, the smaller the number of voltage oscillations and the smaller the current oscillation amplitude, which is more conducive to the absorption of energy generated by the transformer leakage inductance.

[0033] Based on the foregoing analysis, if the first and second absorption circuits are to better absorb the energy generated by the leakage inductance, both the voltage and current need to oscillate with attenuation; therefore, the equivalent resistance R cannot be equal to 0. Thus, in one embodiment, see [further details omitted]. Figure 2 The first energy dissipation component includes a resistor R1 and a diode D1, and the second energy dissipation component includes a diode D2 and a resistor R2. One end of the resistor R1 is connected to the source of the switching transistor Q1, and the other end of the resistor R1 is connected to the anode of the diode D1. The cathode of the diode D1 is connected to the anode of the diode D2, and the cathode of the diode D1 is also connected to the other end of the absorption capacitor C1. The cathode of the diode D2 is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to the output terminal of the transformer. The third energy dissipation component includes a resistor R3 and a diode D3, and the fourth energy dissipation component includes a diode D4 and a resistor R4. One end of the resistor R3 is connected to the source of the switching transistor Q2, and the other end of the resistor R3 is connected to the anode of the diode D3. The cathode of the diode D3 is connected to the anode of the diode D4, and the cathode of the diode D3 is also connected to the other end of the absorption capacitor C2. The cathode of the diode D4 is connected to one end of the resistor R4, and the other end of the resistor R4 is connected to the output terminal of the transformer.

[0034] Because the energy dissipation component includes a resistor, in Figure 3 In the equivalent circuit, the damping factor Increasing the resistance reduces the number of voltage and current oscillations and their amplitude. This is because the resistor provides a path for energy dissipation, reducing the system's oscillation capability. In an undamped or poorly damped system, this energy conversion can occur an infinite number of times, leading to continuous oscillations. In a damped system, however, each energy conversion is accompanied by energy dissipation, thus reducing the number of oscillations. Because energy is lost in each oscillation, the amplitude of the oscillation (whether voltage or current) gradually decreases over time. The greater the damping, the faster the energy loss and the faster the oscillation amplitude decreases. The added resistors R1 and R2 provide this damping effect, reducing voltage and current oscillations, making the circuit more stable, and protecting other components in the circuit from excessive oscillations.

[0035] like Figure 8 As shown, when the first energy dissipation component does not include resistor R1 and the second energy dissipation component does not include resistor R2, the drain-source voltage waveform of the switch Q1 shows that the highest voltage at this time is above 120V; Figure 9 As shown, when the first energy dissipation component includes resistor R1 and the second energy dissipation component includes resistor R2, the drain-source voltage waveform of the switch Q1 is shown. The highest voltage at this time is between 90V and 100V. Figure 8 and Figure 9 It can be seen that after adding resistors R1 and R2 to the first and second energy dissipation components respectively, the drain-source voltage of the switch Q1 is significantly reduced, and the oscillation amplitude is also reduced accordingly. This design may help reduce the oscillation amplitude of the system, reduce the spike voltage generated when the switch Q1 is turned off, and improve the stability of the system. Similarly, the third and fourth energy dissipation components will not be described in detail here.

[0036] In practical applications, the structures of the first, second, third, and fourth energy dissipation components can be modified. For example, Schottky diodes, Zener diodes, or other types of semiconductor devices can be used to replace standard diodes to improve specific parameters, such as forward voltage drop and reverse recovery time. In a preferred embodiment, additional capacitors or inductors can be added to the energy dissipation components to improve performance. For example, a small capacitor connected in series can help filter out high-frequency noise. Further details are not provided in this embodiment.

[0037] In a preferred embodiment, the resistance values ​​of resistors R1 and R2 can be designed according to the following scheme: when the leakage inductance L and the absorption capacitor C1 are constant, the larger the value of R, the better. The larger the value, the better; the resistor R2 in the second energy dissipation component is a charging resistor. Considering that capacitor C1 is used to absorb voltage spikes, it is necessary to suppress voltage spikes in a timely manner; the resistance value of R2 should be as small as possible; considering both factors, the resistance range of R2 is: Where R2 is the resistance of resistor R2, L is the inductance of the transformer leakage inductance, and C is the capacitance of absorption capacitor C1; that is, when absorption capacitor C1 is charging, the RLC circuit composed of transformer leakage inductance, absorption capacitor C1, and resistor R2 is in an underdamped state. In the underdamped state, the circuit response will exhibit oscillating decay. That is, the voltage and current will gradually subside in an exponentially decaying oscillating manner.

[0038] The resistor R1 in the first energy dissipation component is a discharge resistor, and a relatively large resistance value range can be selected. The resistance value range of R1 is: Where R1 is the resistance of resistor R1, L is the inductance of the transformer leakage inductance, and C is the capacitance of absorption capacitor C1. That is, when the absorption capacitor C1 discharges, the RLC circuit composed of the transformer leakage inductance, absorption capacitor C1, and resistor R1 is in an overdamped state. In the overdamped state, the circuit response does not oscillate, but gradually reaches a steady state in a monotonic manner.

[0039] By setting the values ​​of resistors R1 and R2, the damping during the oscillation process of an RLC circuit can be effectively controlled, thus affecting the circuit's dynamic response. Different damping states have a significant impact on the circuit's performance and stability.

[0040] Similarly, in a preferred embodiment, the resistance values ​​of resistors R3 and R4 can be designed as follows: when the leakage inductance L and the absorption capacitor C2 are constant, the larger the value of R, the better. The larger the value, the better; the resistor R4 in the fourth energy dissipation component is a charging resistor. Considering that capacitor C2 is used to absorb voltage spikes, it is necessary to suppress voltage spikes in a timely manner; the resistance value of R4 should be as small as possible; considering both factors, the resistance range of R4 is: Where R4 is the resistance of resistor R4, L is the inductance of the transformer leakage inductance, and C is the capacitance of absorption capacitor C2; that is, when absorption capacitor C2 is charging, the RLC circuit composed of transformer leakage inductance, absorption capacitor C2, and resistor R4 is in an underdamped state. In the underdamped state, the circuit response will exhibit oscillating decay. That is, the voltage and current will gradually subside in an exponentially decaying oscillating manner.

[0041] The resistor R3 in the third energy dissipation component is a discharge resistor, and a relatively large resistance value range can be selected. The resistance value range of R3 is: Where R3 is the resistance of resistor R3, L is the inductance of the transformer leakage inductance, and C is the capacitance of absorption capacitor C2. That is, when the absorption capacitor C2 discharges, the RLC circuit composed of the transformer leakage inductance, absorption capacitor C2, and resistor R3 is in an overdamped state. In the overdamped state, the circuit response does not oscillate, but gradually reaches a steady state in a monotonic manner.

[0042] By controlling the values ​​of resistors R3 and R4, the damping during the oscillation of the RLC circuit can be effectively controlled, thus affecting the circuit's dynamic response. Different damping states have a significant impact on the circuit's performance and stability.

[0043] In a preferred embodiment, refer to Figure 2 The primary circuit includes a primary winding, voltage divider capacitors Ca and Cb, and switching transistors S1 and S2. Voltage divider capacitors Ca and Cb are connected in series across the power supply, and switching transistors S2 and S1 are also connected in series across the power supply. One end of the primary winding is connected between switching transistors S1 and S2, and the other end is connected between voltage divider capacitors Ca and Cb. When switching transistor S1 is on and switching transistor S2 is off, switching transistor Q2 is on and switching transistor Q1 is off. When switching transistor S1 is off and switching transistor S2 is on, switching transistor Q1 is on and switching transistor Q2 is off.

[0044] In this circuit, the isolation converter alternates between switching transistors S1 and S2 in each half-cycle, forming a complete cycle. When S1 is on and S2 is off, transistor Q2 is on. At this time, the isolation converter operates in the first half-cycle, and the voltage across the primary winding of the transformer is a positive voltage drop within that half-cycle. During this time, the first absorption circuit can absorb the energy stored in the transformer's leakage inductance.

[0045] When switch S2 is on and switch S1 is off, switch Q1 is on. At this time, the isolation converter operates in the second half-cycle, and the voltage across the primary winding of the transformer is a negative voltage drop during the half-cycle. The second absorption circuit can then absorb the energy stored in the transformer's leakage inductance.

[0046] Meanwhile, in the preferred embodiment, such as Figure 10 As shown, the isolation converter capable of absorbing peak voltages also includes a control circuit, which is used to control the on / off state of the switching transistors Q1 and Q2.

[0047] The control circuit is connected to the gates of both switching transistors Q1 and Q2. During the first half-cycle of the isolation converter's operation, the control circuit can control switching transistor Q1 to turn off and control the switching transistor Q2 to turn on. During the second half-cycle of the isolation converter's operation, the control circuit can control switching transistor Q2 to turn off and control the switching transistor Q1 to turn on. The specific control method will not be described in detail in this embodiment.

[0048] Example 2: An isolation converter capable of absorbing voltage spikes was proposed in Example 1. In this example, a method for absorbing voltage spikes will be proposed, including: like Figure 11 As shown, during the first half-cycle of the isolation converter's operation: Step 101: When the switching transistor Q1 is turned off, the energy generated by the leakage inductance of the transformer passes sequentially through the absorption capacitor C1 and the second energy dissipation component, and is then transferred to the load to absorb the energy generated by the leakage inductance of the transformer. Simultaneously, the absorption capacitor C1 is charged. After charging, the energy in the absorption capacitor C1 is discharged sequentially through the first winding, the energy storage inductor Lo, the load, and the first energy dissipation component; this constitutes one charge-discharge oscillation process of the absorption capacitor C1.

[0049] When the switch Q1 is turned off, the energy generated by the transformer leakage inductance can be absorbed by the absorption capacitor C1 and the second energy dissipation component. Simultaneously, the absorption capacitor C1 will charge. When the switch Q1 is turned off, the energy stored in the transformer leakage inductance can no longer flow to the secondary side, and therefore will be released through the absorption capacitor C1 and the second energy dissipation component to prevent the transformer leakage inductance from affecting the circuit and to ensure system stability. The structure and implementation principle of the second energy dissipation component are described in Example 1, and will not be elaborated further in this example.

[0050] Step 102: When the switch Q1 is turned on, the absorption capacitor C1 discharges through the switch Q1 and the first energy dissipation component.

[0051] When the switch Q1 is turned on, the absorption capacitor C1 discharges through the switch Q1 and the first energy dissipation component. In this case, the energy stored in the absorption capacitor C1 is released through the switch Q1 and the first energy dissipation component. The structure and implementation principle of the first energy dissipation component are described in Example 1, and will not be explained in detail in this example.

[0052] In a preferred embodiment, such as Figure 12 As shown, during the second half of the operation cycle of the isolation converter: Step 201: When the switching transistor Q2 is turned off, the energy generated by the leakage inductance of the transformer passes sequentially through the absorption capacitor C2 and the fourth energy dissipation component, and is then transferred to the load to absorb the energy generated by the leakage inductance of the transformer. Simultaneously, the absorption capacitor C2 is charged. After charging, the energy in the absorption capacitor C2 is discharged sequentially through the second winding, the energy storage inductor Lo, the load, and the third energy dissipation component; this constitutes one charge-discharge oscillation process of the absorption capacitor C2.

[0053] When the switch Q2 is turned off, the absorption capacitor C2 and the fourth energy dissipation component absorb the energy generated by the transformer leakage inductance. Simultaneously, the absorption capacitor C2 charges. When the switch Q2 is turned off, the energy stored in the transformer leakage inductance can no longer flow to the secondary side, and is therefore released through the absorption capacitor C2 and the fourth energy dissipation component to prevent the transformer leakage inductance from affecting the circuit and to ensure system stability. The structure and implementation principle of the fourth energy dissipation component are described in Example 1, and will not be elaborated further in this example.

[0054] Step 202: When the switch Q2 is turned on, the absorption capacitor C2 discharges through the switch Q2 and the third energy dissipation component.

[0055] When switch Q2 is turned on, the absorption capacitor C2 discharges through switch Q2 and the third energy dissipation component. In this case, the energy stored in the absorption capacitor C2 is released through switch Q2 and the third energy dissipation component. The structure and implementation principle of the third energy dissipation component are described in Example 1, and will not be elaborated further in this example.

[0056] The specific structure of the isolation converter capable of absorbing peak voltages is described in Example 1, and will not be repeated in this example.

Claims

1. An isolation converter capable of absorbing voltage spikes, characterized in that, include: Transformer, primary circuit, and secondary circuit; The transformer includes a primary winding and a secondary winding. The secondary winding is a center-tapped type and includes a first winding and a second winding. The primary circuit is used to convert DC voltage into AC voltage and then transmit it to the primary winding of the transformer. The secondary circuit includes a switching transistor Q1, a first absorption circuit, a switching transistor Q2, a second absorption circuit, an energy storage inductor Lo, and a filter capacitor Co; the first absorption circuit includes an absorption capacitor C1, a first energy dissipation component, and a second energy dissipation component; the second absorption circuit includes an absorption capacitor C2, a third energy dissipation component, and a fourth energy dissipation component; One end of the first winding is connected to the drain of the switching transistor Q1 and one end of the absorption capacitor C1; the other end of the first winding is connected to one end of the energy storage inductor Lo and one end of the second winding; the other end of the energy storage inductor Lo is used to connect to the load; the other end of the absorption capacitor C1 is connected to one end of the first energy dissipation component and one end of the second energy dissipation component; the source of the switching transistor Q1 is connected to the other end of the first energy dissipation component and the load; the other end of the second energy dissipation component is used to connect to the load; the filter capacitor Co is connected in parallel across the load; The other end of the second winding is connected to the drain of the switching transistor Q2 and one end of the absorption capacitor C2, respectively; the other end of the absorption capacitor C2 is connected to one end of the third energy dissipation component and one end of the fourth energy dissipation component; the source of the switching transistor Q2 is connected to the other end of the third energy dissipation component and the load, respectively; the other end of the fourth energy dissipation component is used to connect to the load.

2. The isolation converter capable of absorbing voltage spikes according to claim 1, characterized in that, The first energy dissipation component includes a resistor R1 and a diode D1, and the second energy dissipation component includes a diode D2 and a resistor R2; One end of resistor R1 is connected to the source of switch Q1, and the other end of resistor R1 is connected to the anode of diode D1. The cathode of diode D1 is connected to the anode of diode D2, and the cathode of diode D1 is also connected to the other end of absorption capacitor C1. The cathode of diode D2 is connected to one end of resistor R2, and the other end of resistor R2 is connected to the output terminal of transformer.

3. The isolation converter capable of absorbing peak voltages according to claim 2, characterized in that, The resistance range of the resistor R1 is: Where R1 is the resistance value of resistor R1, L is the inductance value of the leakage inductance of the transformer, and C is the capacitance value of the absorption capacitor C1. The resistance range of the resistor R2 is: Where R2 is the resistance of resistor R2, L is the inductance of the transformer leakage inductance, and C is the capacitance of absorption capacitor C1.

4. The isolation converter capable of absorbing peak voltages according to claim 1, characterized in that, The third energy dissipation component includes a resistor R3 and a diode D3, and the fourth energy dissipation component includes a diode D4 and a resistor R4; One end of the resistor R3 is connected to the source of the switching transistor Q2, and the other end of the resistor R3 is connected to the anode of the diode D3. The cathode of the diode D3 is connected to the anode of the diode D4, and the cathode of the diode D3 is also connected to the other end of the absorption capacitor C2. The cathode of the diode D4 is connected to one end of the resistor R4, and the other end of the resistor R4 is connected to the output terminal of the transformer.

5. The isolation converter capable of absorbing peak voltage according to claim 4, characterized in that, The resistance range of the resistor R3 is: Where R3 is the resistance of resistor R3, L is the inductance of the transformer leakage inductance, and C is the capacitance of absorption capacitor C2. The resistance range of the resistor R4 is: Where R4 is the resistance value of resistor R4, L is the inductance value of the leakage inductance of the transformer, and C is the capacitance value of the absorption capacitor C2.

6. The isolation converter capable of absorbing peak voltages according to claim 1, characterized in that, The isolation converter capable of absorbing peak voltages also includes a control circuit for controlling the switching on and off of the switching transistors Q1 and Q2.

7. The isolation converter capable of absorbing peak voltages according to claim 1, characterized in that, The primary circuit includes voltage divider capacitor Ca, voltage divider capacitor Cb, switching transistor S1, and switching transistor S2. The voltage dividing capacitors Ca and Cb are connected in series across the power supply, and the switching transistors S2 and S1 are also connected in series across the power supply; one end of the primary winding is connected between the switching transistors S1 and S2, and the other end of the primary winding is connected between the voltage dividing capacitors Ca and Cb. When the switch S1 is turned on and the switch S2 is turned off, the switch Q2 is turned on and the switch Q1 is turned off. When the switch S1 is off and the switch S2 is on, the switch Q1 is on and the switch Q2 is off.

8. A method for absorbing voltage spikes, characterized in that, The method is applied to the isolation converter capable of absorbing spike voltages as described in any one of claims 1-7, comprising: When the switch Q1 is turned off, the energy generated by the leakage inductance of the transformer passes through the absorption capacitor C1 and the second energy dissipation component in sequence and is then transferred to the load to absorb the energy generated by the leakage inductance of the transformer; when the switch Q1 is turned on, the absorption capacitor C1 discharges through the switch Q1 and the first energy dissipation component. When the switch Q2 is turned off, the energy generated by the leakage inductance of the transformer passes through the absorption capacitor C2 and the fourth energy dissipation component in sequence and is then transferred to the load to absorb the energy generated by the leakage inductance of the transformer; when the switch Q2 is turned on, the absorption capacitor C2 discharges through the switch Q2 and the third energy dissipation component.

9. The method for absorbing peak voltages according to claim 8, characterized in that, When the switching transistor Q1 is turned off, the energy generated by the leakage inductance of the transformer passes sequentially through the absorption capacitor C1 and the second energy dissipation component, and is then transferred to the load to absorb the energy generated by the leakage inductance of the transformer. The method further includes: After the absorption capacitor C1 is charged, the energy in the absorption capacitor C1 is discharged sequentially through the first winding, the energy storage inductor Lo, the load, and the first energy discharge component.

10. The method for absorbing voltage spikes according to claim 8, characterized in that, When the switching transistor Q2 is turned off, the energy generated by the leakage inductance of the transformer passes sequentially through the absorption capacitor C2 and the fourth energy dissipation component before being transferred to the load to absorb the energy generated by the leakage inductance of the transformer. The method further includes: After the absorption capacitor C2 is charged, the energy in the absorption capacitor C2 is discharged sequentially through the second winding, the energy storage inductor Lo, the load, and the third energy discharge component.

Images