A control method of a vehicle voltage conversion circuit and a vehicle

Abstract

This disclosure provides a control method for a vehicle voltage conversion circuit and a vehicle. The voltage conversion circuit includes a phase-shifted full-bridge circuit, a transformer, and a rectifier circuit. The phase-shifted full-bridge circuit is connected to the first side of the transformer, and the rectifier circuit is connected to the second side of the transformer. The voltage on the first side is higher than the voltage on the second side. The control method includes: monitoring the output current on the second side of the transformer; when the output current is within a preset current range, controlling the rectifier circuit to be in synchronous rectification mode until the output current is lower than the lower limit of the preset current range or higher than the upper limit of the preset current range. The preset current range characterizes the current range in which the voltage conversion circuit radiates emissions exceeding a reference radiation value during operation. This method actively and forcibly controls the secondary side to synchronous rectification mode by identifying the current range exceeding the radiation limit, preventing the DC-DC converter from entering a high-noise combination mode within this range, thereby reducing switching noise and diode reverse recovery noise at the source.

Description

Technical Field

[0001] This disclosure relates to the field of vehicle technology, and more specifically, to a control method for a vehicle voltage conversion circuit and a vehicle in the field of vehicle technology. Background Technology

[0002] A voltage conversion circuit is a power electronic device that transforms direct current (DC) from one voltage level to another. Depending on their topology, voltage conversion circuits can be classified into various types, including buck, boost, buck-boost, flyback, forward, half-bridge, and full-bridge. Among these, the full-bridge voltage conversion circuit is particularly common in medium- to high-power applications due to its high power density and efficiency.

[0003] In full-bridge voltage converter circuits, phase-shifted full bridge (PSFB) control is commonly used. PSFB circuits offer high efficiency, high power density, a wide input voltage range, and good electromagnetic compatibility potential, making them particularly suitable for applications with high-voltage input and low-voltage, high-current output. PSFB circuits are widely used in vehicle electrical systems.

[0004] However, during actual vehicle operation, due to the dynamic connection and disconnection of loads such as engine start-stop, defrost, and air conditioning compressor, when the output current is within a certain current range, the output current of the voltage conversion circuit will change frequently, causing the vehicle's radiated emission at a specific frequency point, such as around 66MHz, to significantly exceed the limit, affecting the vehicle's electromagnetic compatibility certification and even interfering with the normal operation of other electronic devices in the vehicle.

[0005] Therefore, there is an urgent need for a control method that can reduce the radiated emissions of voltage conversion circuits, and avoid the simultaneous occurrence of hard switching and asynchronous rectification without significantly affecting efficiency, thereby improving electromagnetic compatibility. Summary of the Invention

[0006] In view of the above problems, this disclosure provides a control method for a vehicle voltage conversion circuit and a vehicle to solve one or more of the above problems. The technical solution is as follows: In a first aspect, this disclosure provides a control method for a vehicle voltage conversion circuit. The voltage conversion circuit includes a phase-shifting full-bridge circuit, a transformer, and a rectifier circuit. The phase-shifting full-bridge circuit is connected to a first side of the transformer, and the rectifier circuit is connected to a second side of the transformer. The voltage on the first side is higher than the voltage on the second side. Control methods include: Monitor the output current on the second side of the transformer; When the output current is within the preset current range, the control rectifier circuit is in synchronous rectification mode until the output current is lower than the lower limit of the preset current range or higher than the upper limit of the preset current range. The preset current range represents the range of currents in which the voltage conversion circuit radiates and emits currents exceeding the reference radiation value when it is working.

[0007] In one embodiment, controlling the rectifier circuit to be in synchronous rectification mode includes: When the output current reaches the rectification start threshold, the control rectifier circuit is in synchronous rectification mode. When the output current reaches the rectification shutdown threshold, the control rectifier circuit exits the synchronous rectification mode. Among them, the rectification start threshold is not less than the upper limit of the preset current range, the rectification stop threshold is less than the lower limit of the preset current range, or the rectification start threshold is not greater than the lower limit of the preset current range and the rectification stop threshold is not less than the upper limit of the preset current range.

[0008] In one embodiment, the method further includes: if the voltage conversion circuit is controlled by an analog controller, determining the rectification off threshold and the rectification on threshold by adjusting the resistance value of the resistor and the capacitance value connected to the analog controller.

[0009] In one embodiment, the analog controller is a phase-shifted full-bridge control chip, which includes a current detection pin and an intermittent conduction mode pin. The current detection pin is connected to a first capacitor, and the intermittent conduction mode pin is connected to a first resistor. By adjusting the resistance and capacitance parameters of the resistors connected to the analog controller, the rectification start-up and rectification stop-down thresholds are determined, including: By adjusting the resistance value of the first resistor to set the rectification shutdown threshold, the synchronous rectification mode is exited when the output current reaches the rectification shutdown threshold. By adjusting the capacitance of the first capacitor to set the rectification start threshold, the synchronous rectification mode is entered when the output current reaches the rectification start threshold.

[0010] In one embodiment, the output of the rectifier circuit is connected to a load, and the voltage conversion circuit further includes: an isolating switch and a control unit that drives the isolating switch, wherein the isolating switch is connected in series between the output of the rectifier circuit and the load. The control method also includes: detecting the voltage between the output terminal of the rectifier circuit and the positive terminal of the load; when the voltage at the positive terminal is higher than the voltage at the output terminal, the control unit generates a control signal to turn off the isolating switch.

[0011] In one embodiment, the phase-shifted full-bridge circuit includes a first bridge arm switching transistor group connected to the positive terminal of the power supply input and a second bridge arm switching transistor group connected to the negative terminal of the power supply input. The control method further includes: The dead time between the first bridge arm switching transistor group and the second bridge arm switching transistor group is adjusted according to the output current. The smaller the output current, the longer the dead time, and the larger the output current, the shorter the dead time.

[0012] In one embodiment, the method further includes: if the voltage conversion circuit uses a digital controller, determining the rectification enable threshold and the rectification disable threshold by configuring the register parameters of the digital controller.

[0013] In one embodiment, the rectifier circuit includes a synchronous rectifier diode, and the control method further includes: The drain-source voltage of the synchronous rectifier diode is detected; when the drain-source voltage jumps from negative to 0 or positive, a zero-crossing control signal is generated. The synchronous rectifier is turned off based on the zero-crossing control signal; the delay time between the generation of the zero-crossing control signal and the actual turn-off of the synchronous rectifier is obtained; based on the delay time, the turn-off delay setting parameter is adjusted so that the turn-off time of the synchronous rectifier is consistent with the current zero-crossing time.

[0014] In one embodiment, when the voltage conversion circuit is controlled by an analog controller, the analog controller is a phase-shifted full-bridge control chip. The phase-shifted full-bridge control chip includes a turn-off delay setting pin, which is connected to a resistor to ground, and a function to adjust the turn-off delay setting parameter, including adjusting the resistance value of the turn-off delay setting pin to ground to adjust the turn-off delay setting parameter.

[0015] Secondly, based on the same inventive concept, this disclosure also provides a vehicle, the vehicle including: a memory for storing executable program code; A processor is configured to call and execute the executable program code from the memory, causing the vehicle to perform a control method for a vehicle voltage conversion circuit as described in any of the first aspects.

[0016] The technical solution provided in this disclosure has the following advantages compared with the prior art: In existing vehicle electrical systems, when the output current of the DC-DC converter reaches a certain fixed range, strong electromagnetic noise is generated due to the primary side hard switching and the secondary side asynchronous rectification mode, resulting in excessive radiation emissions from the entire vehicle.

[0017] The control method for the vehicle voltage conversion circuit disclosed herein identifies the excessive current range and actively forces the secondary side to be controlled in synchronous rectification mode, thereby enabling the voltage conversion circuit to operate within this range. The internal circuit no longer enters a high-noise combination mode, thereby reducing switching noise and diode reverse recovery noise at the source.

[0018] The above description is merely an overview of the technical solution disclosed herein. In order to better understand the technical means of this disclosure and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this disclosure more apparent and understandable, specific embodiments of this disclosure are described below. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0020] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0021] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this disclosure. Furthermore, the same reference numerals denote the same devices throughout the drawings. In the drawings: Figure 1 This diagram shows a schematic of the voltage conversion circuit according to an optional embodiment of the present disclosure; Figure 2 This diagram illustrates a control method flowchart for a vehicle voltage conversion circuit according to an optional embodiment of the present disclosure. Figure 3 This diagram illustrates the structure of a phase-shifting full-bridge control chip according to another optional embodiment of this disclosure; Figure 4 A flowchart illustrating a control method for a vehicle voltage conversion circuit according to another optional embodiment of this disclosure is shown. Figure 5 This diagram illustrates the relationship between the preset current range and the rectification threshold range in an embodiment of the present disclosure. Figure 6 A schematic diagram of the frame of a vehicle according to an alternative embodiment of the present disclosure is shown.

[0022] Explanation of reference numerals in the attached figures: 10. Phase-shifted full-bridge circuit; 11. First bridge arm switch assembly; 12. Second bridge arm switch assembly; 20. Transformer; 30. Rectifier circuit; 31. Synchronous rectifier diode; 32. Schottky diode; 40. Analog controller; CS, current sensing pin; First capacitor; DCM, discontinuous conduction mode pin; First resistor; ADEL, first shutdown delay setting pin; First resistance to ground; ADELEF, second shutdown delay setting pin; Second ground resistance; DELAB, first bridge arm output delay pin; second resistor ; DELCD, second bridge arm output delay pin; third resistor ; 200. Vehicle; 201. Processor; 202. Internal bus; 203. Network interface; 204. Memory; 205. Non-volatile memory. Detailed Implementation

[0023] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0024] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0025] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0026] In vehicle electrical systems, the voltage of the power battery is typically 300V to 800V, while low-voltage loads such as headlights, air conditioning, audio systems, defrosting, and battery charging require a stable power supply of 12V or 48V, with load currents reaching tens to hundreds of amperes. Therefore, DC-DC converters with phase-shifted full-bridge circuits have become the core components for converting high and low voltage electrical energy in vehicles. In other words, the DC-DC converters widely used in vehicles are essentially a type of phase-shifted full-bridge voltage conversion circuit.

[0027] However, during actual vehicle operation, the output current of the DC-DC converter fluctuates frequently due to the dynamic connection and disconnection of loads such as engine start-stop, defrost, and air conditioning compressor. When the output current is within a specific current range, such as 35 amps to 40 amps, the converter simultaneously operates in a state of primary-side hard switching and secondary-side asynchronous rectification. At this time, the primary-side switching transistor is forcibly turned on when the voltage is not zero, generating wide-spectrum switching noise; the secondary-side diode 32 exhibits a reverse recovery current spike when turned off, causing strong radiation. The superposition of these two noises causes the vehicle's radiated emissions at specific frequencies, such as around 66MHz, to significantly exceed regulatory limits, affecting the vehicle's electromagnetic compatibility certification and even interfering with the normal operation of other electronic devices in the vehicle.

[0028] Based on the problems encountered in the above vehicle applications, the following experiments and studies were conducted: In vehicle electrical control systems, DC-DC converters are typically used as voltage conversion circuits to realize the energy conversion interface between high-voltage power batteries and low-voltage loads. For example... Figure 1 As shown, a DC-DC converter typically includes a phase-shifted full-bridge circuit 10, a transformer 20, and a rectifier circuit 30. The phase-shifted full-bridge circuit 10 is connected to the first side of the transformer 20, and the rectifier circuit 30 is connected to the second side of the transformer 20. The voltage on the first side is higher than the voltage on the second side. The phase-shifted full-bridge circuit 10, the transformer 20, and the rectifier circuit 30 together constitute a phase-shifted full-bridge topology. Zero-voltage switching of the primary-side switching transistor is achieved through phase-shift control, and combined with synchronous rectification technology on the secondary side, excellent conversion performance is obtained under high-frequency operating conditions.

[0029] like Figure 1 As shown, the phase-shifted full-bridge circuit 10 consists of four switching transistors, typically MOSFETs. In this embodiment, the four switching transistors are designated S1 to S4. The four switching transistors are divided into two groups: a first bridge arm switching transistor group 11 and a second bridge arm switching transistor group 12. Figure 1 S1 and S2 in the circuit constitute the leading arm, which is also the first arm switch group 11. Figure 1 S3 and S4 form the lagging bridge arm, also known as the second bridge arm switching transistor group 12. Among them, the leading bridge arm is generally easier to achieve zero-voltage turn-on, while the lagging bridge arm is relatively difficult to achieve zero-voltage turn-on and is more sensitive to load conditions.

[0030] The rectifier circuit 30 consists of two synchronous rectifier diodes 31 (31 including E and F) and two Schottky diodes 32 (32 including G and H), which are controlled by the drive signal and alternately conduct to rectify the low-voltage, high-frequency AC signal on the secondary side of the transformer 20 into a low-voltage DC signal. Compared with traditional diode 32 rectification, the synchronous rectifier diodes 31 are MOSFETs with low on-resistance, which can significantly reduce conduction losses under high current output conditions and improve conversion efficiency. The rectified DC signal is smoothed by a filter network composed of output inductors and capacitors to form a stable low-voltage DC output, which is connected to the load through the output terminal.

[0031] During operation, the high-voltage DC input signal is modulated into a high-frequency square wave signal by the phase-shifting full-bridge circuit 10 and input to the primary side of the isolation transformer 20. The secondary side of the transformer 20 induces a low-voltage, high-frequency AC signal, which is rectified and filtered by the rectifier circuit 30, supplying a stable low-voltage DC signal to the load. Output voltage regulation is achieved by adjusting the duty cycle through phase-shifting control. Soft switching and synchronous rectification work together to balance conversion efficiency and electromagnetic compatibility. Depending on the conduction conditions of the phase-shifting full-bridge circuit 10 and the rectifier circuit 30, there are four basic switching and rectification operating modes.

[0032] The primary side of this application is one side of the phase-shifted full-bridge circuit 10, and the secondary side is one side of the rectifier circuit 30. The four modes are described below.

[0033] 1. Primary-side soft-switching mode, also known as zero-voltage turn-on. Its working principle utilizes the leakage inductance of transformer 20 or an externally applied resonant inductor to resonate with the junction capacitance of switching transistors S1-S4. Before switching transistors S1-S4 need to be turned on, the resonance process gradually reduces the voltage between their drain and source to zero or near zero. At this point, triggering the switching transistors S1-S4 to turn on achieves zero-voltage turn-on. This soft-switching method fundamentally eliminates the overlap of voltage and current at the moment of turn-on, thus the switching losses are almost zero.

[0034] 2. Primary-side hard switching mode, corresponding to primary-side soft switching. In this mode, the switching transistors S1-S4 are forcibly turned on before the drain-source voltage drops to zero, or even when it is at a relatively high voltage. Because the voltage and current overlap at the moment of turn-on, significant switching losses are generated, and large voltage and current spikes are also introduced, which have an adverse effect on electromagnetic compatibility.

[0035] 3. Secondary-side synchronous rectification mode refers to replacing the traditional Schottky diode with a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) with a low on-resistance MOSFET as the synchronous rectifier 31. Since the MOSFET has extremely low channel resistance when it is turned on, its on-state voltage drop is much smaller than the forward voltage drop of the traditional Schottky diode 32. Therefore, it can significantly reduce the conduction loss on the secondary side, which is particularly advantageous in low-voltage, high-current output applications.

[0036] 4. Secondary-side asynchronous rectification mode, as opposed to synchronous rectification mode, is the traditional diode rectification method. The secondary side directly uses a diode 32 for rectification, such as a Schottky diode. The circuit structure is relatively simple and the cost is relatively low. However, under high current output, the forward voltage drop of the Schottky diode 32 will bring considerable conduction losses, leading to a decrease in overall efficiency. Furthermore, the reverse recovery phenomenon of the Schottky diode 32 during turn-off will also generate additional electromagnetic interference.

[0037] Depending on whether the load is light or heavy, the voltage conversion circuit will operate under four different conditions.

[0038] In Mode 1, under light load, the output current is approximately 18 amps. In this mode, the phase-shifted full-bridge circuit 10 operates in hard-switching mode, and the rectifier circuit 30 operates in asynchronous diode rectification mode. The operation in light-load mode is as follows: the load is very light, the energy flowing through the primary side is minimal, and the energy stored in the inductor is insufficient to completely remove the charge from the junction capacitance before the switching transistors S1-S4 are turned on. Therefore, zero-voltage switching (ZVS) cannot be achieved, resulting in hard-switching. Simultaneously, to prevent the synchronous rectifier diode 31 from generating reverse current and causing additional losses in discontinuous conduction mode (DCM), the controller actively shuts off the synchronous rectification drive, allowing current to flow only through its body diode. The characteristics of this mode are: switching losses exist on the primary side, diode conduction losses exist on the secondary side, and the efficiency is relatively low under light load.

[0039] Mode 2, the first heavy-load mode, outputs approximately 40 amps. In this mode, the phase-shifted full-bridge circuit 10 also operates in hard-switching mode, and the rectifier circuit 30 remains in asynchronous rectification. This mode typically occurs due to improper control parameters, such as an excessively short dead time, uncontrolled phase shift angle, or an abnormally high input voltage, causing the switching transistor to be forcibly turned on before resonance is complete, resulting in hard switching. Simultaneously, the secondary-side synchronous rectification function fails to activate, so rectification is still performed by the Schottky diode 32. The characteristics of this first heavy-load mode are: primary-side switching losses and secondary-side conduction losses coexist. Especially under heavy load, hard-switching losses increase dramatically, easily leading to device overheating and a severe decrease in efficiency.

[0040] Mode 3, the second heavy-load mode, outputs approximately 50 amps. In this mode, the phase-shifted full-bridge circuit 10 enters a soft-switching (ZVS) state, but the rectifier circuit 30 remains asynchronously rectified. The working mechanism is as follows: the load current is large enough that the energy stored in the resonant inductor is sufficient to easily charge and discharge the junction capacitances of the switching transistors S1-S4, achieving zero-voltage turn-on of all primary-side switching transistors S1-S4, thus eliminating primary-side switching losses. However, due to cost considerations, simplified control, or specific protection strategies, the secondary side still uses Schottky diode 32 for rectification, resulting in significant forward conduction losses for the Schottky diode 32. The characteristics of this mode are: high primary-side efficiency, but secondary-side losses are the primary concern; overall efficiency is acceptable, but not optimal.

[0041] Mode 4, the third heavy-load mode, outputs approximately 60 amps. In this mode, the phase-shifted full-bridge circuit 10 operates in soft-switching mode, and the rectifier circuit 30 is also synchronously rectifying. This is the ideal operating point for the phase-shifted full-bridge converter. The primary side stably achieves zero-voltage switching under heavy load; the secondary side synchronous rectifier 31 uses a low-on-resistance MOSFET for synchronous rectification, and its conduction loss is far lower than that of a diode. The controller precisely controls the switching sequence of the rectifier circuit 30, ensuring perfect synchronization with the secondary current. The characteristics of the third heavy-load mode are: both primary-side switching losses and secondary-side conduction losses are minimized, and system efficiency reaches its peak.

[0042] During narrowband radiated emissions testing of the entire vehicle, technicians discovered that the vehicle's radiated emissions exceeded the limit when the output current of the DC-DC converter changed. In response, the technicians conducted a systematic investigation and analysis. During the testing process, they found that the vehicle's radiated emissions at a frequency around 66MHz significantly exceeded the limit.

[0043] After locating the noise source, it was confirmed that the excessive radiated emissions were caused by the DC-DC module itself. To further investigate the operating conditions under which the DC-DC converter would produce excessive radiation, the vehicle load was adjusted, such as changing the engine operating status and turning the defrost function on and off, while the DC-DC output current was monitored in real time. It was found that when the DC-DC output current was greater than 50A, the radiated emissions test passed successfully; however, when the output current was less than 40A, the test failed. This phenomenon indicates that the root cause of excessive radiated emissions is closely related to the magnitude of the DC-DC output current, which in turn directly determines its operating mode.

[0044] Based on the above experimental process, further analysis reveals the following root causes of excessive radiation: When the vehicle is running under standard operating conditions, changes in engine start / stop and defrosting status will cause dynamic changes in the vehicle's load current. As the output current changes, the operating mode of the DC-DC converter will automatically switch between light load and heavy load, primary side soft switching and hard switching, and secondary side synchronous rectification and asynchronous rectification.

[0045] Detailed testing revealed that when the DC-DC output current is between 35A and 40A, the DC-DC converter enters a second heavy-load mode. In this mode, the phase-shifted full-bridge circuit 10 operates in a hard-switching state, meaning that the switching transistor is forcibly turned on before its drain-source voltage has resonated to zero, resulting in a large voltage-current overlap and causing strong noise. Simultaneously, the rectifier circuit 30 operates in a asynchronous rectification state, i.e., using diodes for freewheeling. The diodes undergo a reverse recovery process during switching, generating spike currents. These two noise sources, combined, leak outwards through the DC-DC output harness, which itself acts as an antenna, radiating high-frequency electromagnetic energy into space, ultimately causing the vehicle's radiated emissions to exceed the standard near 66MHz.

[0046] In view of this, the present disclosure proposes a control method for a vehicle voltage conversion circuit and a vehicle to solve one or more of the above-mentioned problems.

[0047] The first embodiment of this disclosure proposes a control method for a vehicle voltage conversion circuit, which is the aforementioned DC-DC converter, and will not be described again here. The phase-shifting full-bridge circuit 10 described in this application can be referred to as either the primary side or the first side, while the rectifier circuit 30 can be referred to as either the secondary side or the second side.

[0048] like Figure 1 and Figure 3 As shown, the voltage conversion circuit includes a phase-shifting full-bridge circuit 10, a transformer 20, and a rectifier circuit 30. The phase-shifting full-bridge circuit 10 is connected to the first side of the transformer 20, and the rectifier circuit 30 is connected to the second side of the transformer 20. The voltage on the first side is higher than the voltage on the second side.

[0049] like Figure 2 As shown, the control method for the vehicle voltage conversion circuit includes: S10, monitor the output current on the second side of transformer 20.

[0050] S20. When the output current is within the preset current range, the rectifier circuit 30 is controlled to be in synchronous rectification mode until the output current is lower than the lower limit of the preset current range or higher than the upper limit of the preset current range. The preset current range represents the range of currents in which the voltage conversion circuit radiates and emits currents exceeding the reference radiation value when it is working.

[0051] The control method of the voltage conversion circuit disclosed herein identifies the current range that causes the vehicle's radiated emissions to exceed the standard, i.e., the preset current range, and actively forces the secondary side to be controlled into synchronous rectification mode, so that the voltage conversion circuit will no longer enter the high-noise combination mode in this range, thereby reducing the switching noise and diode reverse recovery noise from the source.

[0052] The embodiments described in this disclosure do not require significant hardware modifications to the main power circuit of the voltage conversion circuit. By simply optimizing the control logic and peripheral parameters, the radiated emissions can be effectively reduced, enabling the vehicle to pass relevant tests smoothly and reduce radiation during use.

[0053] The steps of the control method for the vehicle voltage conversion circuit of this disclosure will now be described using an exemplary process, taking the application of the voltage conversion circuit as a DC-DC converter as an example: Step S10: Monitor the output current on the second side of transformer 20.

[0054] The output current on the second side of transformer 20 is the output current of the DC-DC converter. In practical engineering applications, the controllers of DC-DC converters are mainly divided into two types: digital controllers and analog controllers. The two types of controllers differ in the specific circuitry and implementation methods for output current monitoring, but their purpose is the same: to obtain the magnitude of the output current in real time, providing a basis for mode switching and protection logic. The following sections describe these two implementation methods respectively.

[0055] In an alternative embodiment, a digital controller (DSP) approach can be used to obtain the output current. In one embodiment, a sampling resistor, such as a manganin shunt, is connected in series in the output circuit of the DC-DC converter, or a Hall effect-based current sensor is used. The weak voltage signal across the sampling resistor is amplified by a differential amplifier and then fed into the built-in analog-to-digital converter (ADC) pin of the DSP. The ADC module performs analog-to-digital conversion on the current signal at a fixed sampling frequency to obtain a digitized output current value.

[0056] To improve measurement accuracy and anti-interference capability, an RC low-pass filter circuit can be added to the ADC input, and the sampled values ​​can be processed by moving average filtering or first-order low-pass filtering in the software. The digital controller can flexibly determine whether the current is within the preset current range based on the sampled current value through software algorithms, and execute the corresponding mode switching logic.

[0057] In another approach to obtaining the output current, an analog controller can be used. Optionally, the analog controller can be the UCC28950 phase-shifted full-bridge control chip. Monitoring the output current is typically achieved through a primary-side current transformer or a secondary-side current sensing resistor. Taking the UCC28950 phase-shifted full-bridge control chip as an example... Figure 3As shown, the current sensing pin CS of the UCC28950 phase-shifted full-bridge control chip receives a voltage signal from the current sensing network. This signal reflects the magnitude of the output current or the equivalent value of the primary-side current. Internally, the chip compares this voltage with an internal reference voltage to implement functions such as peak current control, overcurrent protection, and discontinuous conduction mode (DCM) detection. By adjusting the resistor and capacitor parameters of the peripheral circuitry of the current sensing pin CS, the gain and response speed of the current sensing signal can be changed, thereby indirectly setting the protection threshold and mode switching point corresponding to the output current.

[0058] Based on the above embodiments, regardless of whether a digital controller or an analog controller is used, the control method of this embodiment needs to continuously monitor the real-time output current during the operation of the vehicle in order to determine whether the current output current falls within the preset current range described in this disclosure.

[0059] It should be noted that this application does not limit the analog controller to the UCC28950 phase-shift full-bridge control chip. Any control chip with the pins used in this application can be used in this application, and will not be described in detail here.

[0060] It should be noted that due to the presence of filtering circuits and software filtering in the current sampling path, the actual current value used for mode determination will have a certain delay. Therefore, when setting the upper and lower limits of the preset current range and the corresponding rectification start and stop thresholds, it is necessary to fully consider the sampling delay and load dynamic characteristics to avoid untimely mode switching due to sampling lag, which could cause the DC-DC converter to briefly enter a high-noise asynchronous rectification mode within the exceeding range. In practical implementation, the output current waveform and mode switching flag can be monitored simultaneously using an oscilloscope to jointly calibrate the sampling filter parameters and thresholds.

[0061] S20. When the output current is within the preset current range, the rectifier circuit 30 is controlled to be in synchronous rectification mode until the output current is lower than the lower limit of the preset current range or higher than the upper limit of the preset current range. The preset current range represents the range of currents in which the voltage conversion circuit radiates and emits currents exceeding the reference radiation value when it is working.

[0062] In the actual implementation process, the preset current range needs to be determined through preliminary test calibration.

[0063] For example, a preset current range can be determined through radiated emission testing. When the output current is in the range of 35A to 40A, the DC-DC converter operates in the second heavy-load mode with primary-side hard switching and secondary-side asynchronous rectification, resulting in excessive radiated emissions near the 66MHz frequency point. Therefore, this 35A to 40A range is defined as the preset current range, with a lower limit of 35A and an upper limit of 40A.

[0064] It is worth noting that the preset current range, rectification turn-on threshold, rectification turn-off threshold, and other values ​​mentioned in this application are all illustrative examples. Different values ​​can be designed according to different needs, and will not be elaborated here.

[0065] Different DC-DC converters may have different values ​​for the preset current range due to differences in topology parameters, layout and wiring, and wiring harness routing. This application does not limit this, but the method for determining the preset current range is the same: by changing the load connected to the voltage conversion circuit and monitoring the output current of the voltage conversion circuit, while measuring the radiated emission, the current range in which the radiated emission exceeds the reference radiation value when the voltage conversion circuit is working is the preset current range.

[0066] When the monitored output current falls into the preset current range, such as 35A to 40A, the controller needs to actively switch the secondary rectification mode from the default asynchronous rectification to synchronous rectification and maintain it in this mode until the output current is lower than the lower limit of 35A or higher than the upper limit of 40A, at which point it exits the synchronous rectification mode.

[0067] To achieve smooth and stable mode switching and avoid oscillations at the boundaries of the preset current range, this disclosure introduces a hysteresis control strategy. Specifically, this disclosure sets a rectification turn-on threshold and a rectification turn-off threshold. In an optional embodiment, step S20, "controlling the rectifier circuit 30 to be in synchronous rectification mode," includes: When the output current reaches the rectification start threshold, the rectifier circuit 30 is controlled to be in synchronous rectification mode. When the output current reaches the rectification shutdown threshold, the control rectifier circuit 30 exits the synchronous rectification mode.

[0068] Among them, such as Figure 5 As shown, when the output current changes from high to low, the rectification turn-on threshold is greater than or equal to the upper limit of the preset current range, and the rectification turn-off threshold is less than the lower limit of the preset current range. When the output current changes from low to high, the rectification turn-on threshold is less than or equal to the lower limit of the preset current range, and the rectification turn-off threshold is greater than or equal to the upper limit of the preset current range.

[0069] For example, such as Figure 5 As shown, the preset current range is set to 35A to 40A. Based on different current change trends, corresponding rectification start-up and rectification stop-down thresholds are configured: when the output current decreases from high to low, the rectification start-up threshold is set to 40A, and the rectification stop-down threshold is set to 30A. At this time, the start-up threshold is greater than or equal to the upper limit of the preset current range, and the stop-down threshold is less than the lower limit of the preset current range. The preset current range falls entirely within the range of the start-up and stop-down thresholds.

[0070] If the output current decreases but remains above 40A, the rectifier circuit 30 remains off until the current drops back to 40A, triggering the turn-on action and activating the rectifier circuit 30. During the current decrease from 40A to 30A, the rectifier circuit 30 continues to operate within this range. As the current gradually decreases to 30A, the rectifier circuit 30 exits the operating mode. The 10A difference between the rectifier turn-on threshold of 40A and the rectifier turn-off threshold of 30A completely covers the preset current range of 40A to 35A, effectively avoiding high-noise operating conditions.

[0071] In other words, during the process of the output current decreasing from a high current to a low current, the synchronous rectification start-up node is set later than or simultaneously with the upper limit of the preset current range, and the stop-up node is set earlier than the lower limit of the preset current range. This ensures that synchronous rectification starts before the current falls into the preset current range and stops only after it leaves the preset current range. This guarantees that the current remains within the preset current range where radiation is likely to exceed the limit throughout the entire process, and the rectifier circuit 30 is always in the operating state and will not stop midway.

[0072] like Figure 5 As shown, during the process of the output current decreasing from a high current to a low current, the output current is susceptible to slight fluctuations due to load disturbances, sampling errors, and electromagnetic noise when it falls to near the lower limit of the preset range. If the rectification shutdown threshold coincides with the lower limit of the preset current range, the repeated fluctuations of the output current around the rectification start threshold of 35A will cause frequent start-stop of the synchronous rectification mode, introducing additional electromagnetic interference and device losses. This solution sets the shutdown threshold below the lower limit of the preset current range, forming a hysteresis buffer between the lower limit of the preset range and the shutdown threshold. The current must completely leave the preset range and drop below the shutdown threshold before exiting the synchronous rectification mode, thereby effectively avoiding mode jitter at the boundary, reducing additional noise and losses, and improving the stability of circuit operation.

[0073] In another embodiment, as the output current increases from low to high, the rectification turn-on threshold is set to 35A and the rectification turn-off threshold is set to 45A. In this case, the turn-on threshold is less than or equal to the lower limit of the preset current range, and the turn-off threshold is greater than or equal to the upper limit of the preset current range. The preset current range falls entirely within the range of the turn-on and turn-off thresholds.

[0074] When the current rises to 35A, the rectifier circuit 30 enters the working mode; when the current is within the preset current range of 35A to 40A and has not reached the 45A shutdown threshold, the rectifier circuit 30 continues to operate; when the current exceeds the upper limit of the preset current range of 40A but has not reached the rectification shutdown threshold, it still maintains the synchronous rectification working state until the current rises to 45A before exiting the mode, ensuring that the rectifier circuit 30 works stably within the preset current range and suppressing radiated noise.

[0075] In this embodiment, as the output current increases from a small current to a large current, synchronous rectification is initiated before reaching the lower limit of the preset current range, and then deactivated only after exceeding the upper limit of the preset current range. This ensures that the current is in synchronous rectification mode as soon as it enters the preset current range and remains in synchronous rectification mode until it completely leaves the range, thus fully covering and locking the high-noise current range. By optimizing the switching logic with bidirectional threshold margin, the smoothness of circuit operation under increasing load conditions is improved, continuously achieving noise reduction and radiation suppression control effects.

[0076] It should be noted that both of the above setting methods can be implemented independently and are suitable for different current change trends. In practical applications, one can be selected based on the typical operating conditions of the vehicle, or the threshold relationship can be adaptively switched by the controller detecting the direction of current change. Regardless of the method used, the core is to ensure that the secondary side is in synchronous rectification mode within the preset current range.

[0077] In some embodiments, the specific implementation of controlling the rectifier circuit 30 to be in synchronous rectification mode varies depending on the type of controller.

[0078] In an optional embodiment, for a scheme employing a digital controller to control the voltage conversion circuit, the rectification enable threshold and rectification disable threshold can be determined by configuring the rectification enable threshold parameter and rectification disable threshold parameter in the register parameters of the digital controller.

[0079] In one example, the digital controller typically uses the TIC2000 series digital processor as the control core, which integrates an enhanced pulse width modulation (ePWM) module, a high-precision analog-to-digital converter (ADC), an analog comparator, and a hardware trip zone.

[0080] Regarding the adjustment of the rectification enable and disable thresholds, the rectification enable threshold parameter (denoted as I_SR_on) and the rectification disable threshold parameter (denoted as I_SR_off) are defined by configuring the internal register parameters of the digital controller. These two threshold parameters are stored in non-volatile memory as software parameters and can be modified online via the CAN bus or debug interface without replacing the hardware.

[0081] During program execution, the high-precision ADC in the digital controller is used to collect the output current of the secondary side of transformer 20 in real time. The sampled output current value is logically compared with the preset threshold parameter in the register. If the sampled current is greater than the rectification start threshold parameter I_SR_on and the voltage conversion circuit is currently in asynchronous mode, the numerical controller outputs a drive signal to enable the rectifier circuit 30. If the sampled current is less than the rectification shutdown threshold parameter I_SR_off and the voltage conversion circuit is currently in synchronous mode, the numerical controller outputs a signal to cut off the synchronous rectification drive, forcing the voltage conversion circuit to enter diode rectification mode. For example, for a preset current range of 35A-40A, under the current decreasing condition, I_SR_on=40A and I_SR_off=30A can be set; or under the current increasing condition, I_SR_on=30A and I_SR_off=40A can be set. Software-based register parameter configuration adapts to different crane load conditions, achieving smooth and reliable switching between synchronous rectification modes. Simultaneously, the digital controller generates a phase-shifted full-bridge drive signal based on the master-slave working logic of multiple ePWM modules. The master ePWM module outputs a reference timing signal, and the phase shift angle is set by rewriting the value of the phase register inside the slave ePWM module. When load conditions fluctuate, the phase shift angle parameter in the phase register is updated in real time, dynamically regulating the output voltage of the voltage regulation circuit while stably maintaining the zero-voltage conduction condition of the switching transistor.

[0082] In an optional embodiment, such as Figure 3 As shown, if the voltage conversion circuit is controlled by an analog controller 40, the rectification off threshold and rectification on threshold are determined by adjusting the resistance value of the resistor and the capacitance value connected to the analog controller 40.

[0083] In this embodiment, the synchronous rectification start and stop thresholds can be set by adjusting the resistance and capacitance values ​​of the external resistor and capacitor connected to the analog controller 40. There is no need to write control programs or debug software code. The control logic is simple, intuitive, and easy to debug. The hardware circuit architecture is simple and reliable, low in cost, and has strong anti-electromagnetic interference capability, making it suitable for complex automotive electrical environments. By simply changing or fine-tuning the resistor and capacitor parameters, it can adapt to voltage conversion circuits with different power levels and different current threshold requirements. It has strong versatility, can quickly complete the calibration of operating parameters, and stably realize the control logic of automatically switching the synchronous rectification working mode according to the output current.

[0084] Here is a specific example to illustrate: In an optional embodiment, the analog controller 40 is a phase-shifted full-bridge control chip, such as... Figure 3 As shown, the phase-shifted full-bridge control chip includes a current sensing pin (CS) and an intermittent conduction mode pin (DCM). The current sensing pin (CS) is connected to the first capacitor. The intermittent conduction mode pin DCM is connected to the first resistor. .

[0085] The resistance value of the first resistor is positively correlated with the rectification shutdown threshold, and the capacitance value of the first capacitor is also positively correlated with the rectification shutdown threshold. That is, the larger the resistance value of the first resistor, the higher the rectification shutdown threshold; the smaller the resistance value of the first resistor, the lower the rectification shutdown threshold. Similarly, the larger the capacitance value of the first capacitor, the higher the rectification enable threshold; and the smaller the capacitance value of the first capacitor, the higher the rectification enable threshold.

[0086] Taking the UCC28950 phase-shifting full-bridge control chip as an example, such as Figure 3 As shown, the first resistor of the voltage divider resistor is adjusted by adjusting the intermittent conduction mode (DCM) pin. The resistance value can be used to set the rectification shutdown threshold. For example, the first resistor... The rectifier impedance was adjusted from 2kΩ to 1.7kΩ, reducing the rectifier shutdown threshold from 40A to 30A. Simultaneously, the first capacitor surrounding the current sensing pin CS was adjusted. The capacitance value is reduced, for example, from 1.5nF to 330pF, so that the rectification turn-on threshold is about 40A.

[0087] When the output current decreases from heavy load to light load but exceeds 30A, the internal DCM comparator of the chip is not triggered, the synchronous rectification drive remains on, and the secondary side is in synchronous rectification mode. When the output current drops below 30A, the DCM comparator is triggered, the chip automatically shuts off the synchronous rectification drive, and the secondary side switches to asynchronous rectification mode. In this way, within the preset current range of 35A to 40A, the secondary side always operates in synchronous rectification mode.

[0088] In the actual operation of the voltage conversion circuit, in addition to the problem of excessive radiation under medium load, there is a current backflow problem under light load mode, especially the current backflow problem under intermittent conduction mode. When the voltage conversion circuit operates under extremely light load and in intermittent conduction mode, if the secondary rectifier circuit 30 is not turned off in time, the current of the output filter inductor will flow in reverse after zero crossing, flowing back from the output terminal to the transformer 20. This not only causes additional energy loss and reduces light load efficiency, but may also cause abnormal heating or even damage to the rectifier circuit 30. To this end, this disclosure further introduces a zero-crossing detection and turn-off delay adjustment mechanism to precisely control the turn-off timing of the synchronous rectifier tube.

[0089] Continue to refer to Figure 1 The rectifier circuit 30 includes a synchronous rectifier diode 31 (including E and F). The synchronous rectifier diode 31 is typically an N-channel MOSFET. When it is turned on, the current flows from the source to the drain, and the drain-source voltage Vds of the synchronous rectifier diode 31 is negative. When the current gradually decreases to zero crossing, the drain-source voltage Vds rises from negative to 0V. If the current reverses, the drain-source voltage Vds becomes positive. Therefore, by detecting the moment when the drain-source voltage Vds jumps from negative to 0V or to positive, the zero-crossing point of the current can be accurately determined.

[0090] In specific implementation, such as Figure 4 As shown, the control method also includes the following sub-steps: S30, Detect the drain-source voltage of synchronous rectifier diode 31; S40. When the drain-source voltage jumps from negative to 0 or positive, a zero-crossing control signal is generated. S50, based on the zero-crossing control signal, controls the rectifier circuit 30 to turn off; S60, Obtain the delay time from the generation of the zero-crossing control signal to the actual turn-off of the rectifier circuit 30; S70. Based on the delay time, adjust the turn-off delay setting parameter so that the turn-off time of the rectifier circuit 30 is consistent with the current zero-crossing time.

[0091] Due to signal transmission delay, driver circuit response delay, and the turn-off delay of the power transistor itself in the actual hardware circuit, even after the zero-crossing detection signal has been issued, the drive signal of the rectifier circuit 30 still needs a certain delay before it can actually turn off the power transistor. If this delay is too long, the current will have already reversed, leading to reverse current flow. Therefore, it is necessary to adjust the turn-off delay setting parameter. The turn-off delay setting parameter is a configurable parameter inside the controller. By adjusting the turn-off delay setting parameter, the turn-off time can be made to fall exactly at the current zero-crossing point.

[0092] For solutions employing digital controllers, zero-crossing detection can be implemented using the analog comparator module within the DSP. The drain-source voltage differential signal from the rectifier circuit 30 is connected to the positive input of the comparator, and the inverting input is connected to a 0V reference. When the drain-source voltage Vds changes from negative to positive, the comparator output flips, generating a current zero-crossing control signal. This zero-crossing control signal can directly trigger the trip zone (TZ) of the pulse width modulation module, achieving rapid hardware-level shutdown.

[0093] Meanwhile, the DSP has an internal digital comparator delay register. This register allows adjustment of the turn-off delay setting parameters, specifying the delay duration from the generation of the zero-crossing control signal to the turn-off of the rectifier circuit 30 drive signal. The delay adjustment step is a single system clock cycle. In actual debugging, the Vds waveform and drive waveform can be measured simultaneously with an oscilloscope to calculate the actual turn-off delay time. Then, the corresponding delay register value can be set for compensation, ensuring the turn-off time precisely falls at the current zero-crossing point.

[0094] In an optional embodiment, when the voltage conversion circuit is controlled by an analog controller 40, the analog controller 40 is a phase-shifted full-bridge control chip, such as... Figure 3 As shown, the phase-shifted full-bridge control chip has a dedicated shutdown delay setting pin, which includes a first shutdown delay setting pin ADEL and a second shutdown delay setting pin ADELEF.

[0095] The first shutdown delay setting pin ADEL is connected to the first ground resistor. This is used to set the turn-off delay of rectifier E in synchronous rectifier 31, and this delay is proportional to the resistance value. The second turn-off delay setting pin ADELEF is connected to a second ground resistor via ground. The turn-off delay of rectifier F in synchronous rectifier 31 is set, and the delay is proportional to the resistance value.

[0096] Since the current paths, device characteristics, and timing requirements of the secondary rectifier circuit 30 are not symmetrical in the positive and negative half-cycles, it is necessary to configure independent delay parameters for the two rectifier circuits 30 (E and F) to achieve precise zero-crossing turn-off.

[0097] In this example, step S70, "adjusting the shutdown delay setting parameter", includes: adjusting the shutdown delay setting parameter by adjusting the resistance value of the ground resistor connected to the shutdown delay setting pin, wherein the delay time is proportional to the resistance value of the ground resistor connected to the shutdown delay setting pin.

[0098] This solution is limited to an analog control architecture and uses a dedicated phase-shifting full-bridge control chip as the main control device. The chip has reserved a dedicated turn-off delay setting pin, which includes a first turn-off delay setting pin ADEL and a second turn-off delay setting pin ADELEF, which are used to set the turn-off delay of the E rectifier and the F rectifier in the synchronous rectifier 31, respectively.

[0099] The turn-off delay of synchronous rectifier 31 is determined by the resistance value of the external resistor connected to ground corresponding to the turn-off delay setting pin. The actual delay time increases synchronously with the increase of the resistance value. The operator can adjust the turn-off delay parameter by simply replacing or fine-tuning the resistance value, thereby matching the actual inherent delay time of the circuit and calibrating the turn-off sequence of the synchronous rectifier.

[0100] This embodiment utilizes chip hardware pins paired with ground resistors to achieve delay adjustment, eliminating the need for program burning and software configuration. Debugging is simple, requiring no additional delay conditioning circuitry. It features low hardware cost, small PCB space footprint, strong anti-interference capabilities, and suitability for harsh automotive operating environments.

[0101] In circuit design, appropriate resistor values ​​can be selected based on the power transistor model and the delay characteristics of the drive circuit. For example, 10kΩ corresponds to a delay of approximately 50ns, 24.9kΩ corresponds to a delay of approximately 120ns, 50kΩ corresponds to a delay of approximately 250ns, and 100kΩ corresponds to a delay of approximately 500ns.

[0102] In practical debugging applications, the resistance value can be selected by combining waveform measurement. For example, by measuring the actual delay between the Vds waveform and the drive waveform with an oscilloscope, a suitable value of the first resistor to ground can be selected so that the turn-off time falls at the current zero-crossing point. Taking the turn-off delay debugging of rectifier E in synchronous rectifier 31 as an example, if Vds is still negative for more than 50ns after the drive is turned off, it indicates that the turn-off is too early, and the first resistor to ground of the first turn-off delay setting pin ADEL should be reduced. If Vds has become positive but the drive is not turned off, it means the turn-off is too late. The first resistance to ground of the first turn-off delay setting pin ADEL should be increased. Similarly, the second ground resistance of the ADELEF pin can be set via the second shutdown delay. The turn-off delay of rectifier F is independently adjusted. By repeatedly fine-tuning the corresponding resistor values ​​through the above process to complete timing calibration, precise zero-crossing turn-off of the synchronous rectifier can be achieved, effectively avoiding current backflow problems under light load conditions.

[0103] By repeatedly fine-tuning the resistor value through the above process to complete the timing calibration, the synchronous rectifier can be accurately turned off at zero crossing, effectively avoiding the problem of current backflow under light load conditions.

[0104] To further expand the operating range of the primary-side soft switching and reduce switching noise, in an optional embodiment, this disclosure also dynamically adjusts the dead time between the first bridge arm switching transistor group 11 and the second bridge arm switching transistor group 12 of the phase-shifted full-bridge circuit 10 according to the output current.

[0105] like Figure 1 and Figure 3 As shown, the phase-shifted full-bridge circuit 10 includes a first bridge arm switching transistor group 11 (11 includes S1 and S2) connected to the positive terminal of the power supply input and a second bridge arm switching transistor group 12 (12 includes S3 and S4) connected to the negative terminal of the power supply input. Dead time refers to the interval between the turn-off of both upper and lower switching transistors on the same bridge arm. The length of the dead time directly affects whether the second bridge arm switching transistor group 12 can achieve zero-voltage turn-on. If the dead time is too short, resonance has not yet been completed, and the synchronous rectifier 31 conducts before the drain-source voltage drops to zero, resulting in hard switching. If the dead time is too long, the current may reverse after resonance is completed, increasing additional losses. Therefore, the dead time needs to be optimized according to the load current.

[0106] In this disclosure, the dead time is negatively correlated with the output current: the smaller the output current, the longer the dead time; the larger the output current, the shorter the dead time. This is because under light load, the leakage inductance of transformer 20 stores less energy, requiring a longer dead time for the junction capacitance of the switching transistor to discharge and for the drain-source voltage to resonate to zero; while under heavy load, the energy is sufficient, and the dead time can be shortened accordingly.

[0107] In an optional embodiment, when the voltage conversion circuit is controlled by a digital controller, a table (two-dimensional array) mapping load current to dead time can be pre-established and stored in the DSP's memory. For example, when the output current is less than 5A, the dead time is set to 300-400ns; when the output current is between 5A and 15A, the dead time is set to 200-300ns; when the output current is between 15A and 50A, the dead time is set to 150-200ns; and when the output current is greater than 50A, the dead time is set to 100-150ns. During operation, the DSP samples the output current in real time through the ADC, looks up the corresponding dead time value in the table, and then updates the dead time registers (such as DBRED and DBFED) of the pulse width modulation module, thereby dynamically adjusting the dead time. This dynamic adjustment allows the primary-side switching transistor to maintain soft switching over a wider load range, reducing noise generated by hard switching and further improving electromagnetic compatibility.

[0108] In another alternative embodiment, when the voltage conversion circuit is controlled by an analog controller 40, the dead time is typically fixed by an external resistor. For example, the UCC28950 has a first bridge arm output delay pin DELAB and a second bridge arm output delay pin DELCD, with the first bridge arm output delay pin DELAB connected to the second resistor. DELAB is used to set the dead time of the lead arm, that is, to set the dead time of the first arm switching transistor group 11; the second arm output delay pin DELCD is connected to the third resistor. The DELCD pin is used to set the dead time of the hysteresis bridge arm, that is, to set the dead time of the second bridge arm switch group 12.

[0109] DELAB and DELCD are respectively connected through a second resistor. and the third resistor The dead time is set by the resistance value. Since the second bridge arm switch group 12 is more sensitive to the load, the dead time of the second bridge arm switch group 12 is longer than that of the first bridge arm switch group 11.

[0110] To further improve the reliability of the voltage conversion circuit and prevent current backflow under abnormal conditions such as controller failure or short circuit of the synchronous rectifier diode, in an optional embodiment, this disclosure also connects an isolating switch and a control unit that drives the isolating switch in series between the output terminal of the rectifier circuit 30 and the load. The isolating switch is typically an N-channel power MOSFET, with its source connected to the positive output terminal of the rectifier circuit 30 and its drain connected to the positive terminal of the load. The control unit detects the voltage between the output terminal of the rectifier circuit 30 and the positive terminal of the load.

[0111] Under normal operating conditions, the output voltage of rectifier circuit 30 is higher than the positive terminal voltage of the load. The control unit drives the isolating switch to conduct, and current flows from the voltage conversion circuit to the load with minimal voltage drop. When an abnormal situation occurs, such as the load voltage being higher than the output voltage of rectifier circuit 30, resulting in a reverse voltage trend, the control unit turns off the isolating switch within a short time. Since the body diode of the isolating switch is oriented from the source to the drain, it cannot conduct in reverse, thus physically and completely blocking the reverse current.

[0112] The isolating switch and its control unit essentially constitute an ideal diode. In a preferred embodiment, the control unit is an ideal diode controller chip LM74700. The anode pin (ANODE) ​​of this chip is connected to the positive output terminal of the voltage conversion circuit, the cathode pin (CATHODE) is connected to the positive terminal of the load, and the gate drive pin (GATE) is connected to the gate of the isolating switch. When the ANODE voltage is higher than the CATHODE voltage, the chip drives the isolating switch to conduct; when the CATHODE voltage is higher than the ANODE voltage, the chip quickly turns off the isolating switch. This protection, together with the active shutdown inside the analog or digital controller, forms dual redundancy, ensuring that the system will not suffer backflow damage under any operating condition.

[0113] In summary, the technical solution disclosed herein has at least the following beneficial effects: By identifying the excessive current range, the secondary side is actively and forcibly controlled to synchronous rectification mode, so that the DC converter no longer enters the high-noise combination mode in this range, thereby reducing the switching noise and diode reverse recovery noise from the source.

[0114] Furthermore, this disclosure avoids frequent mode switching of the voltage conversion circuit at critical load points by setting hysteresis control rectifier turn-on threshold and rectifier turn-off threshold, thus ensuring control stability.

[0115] For the two different implementation paths of analog controllers and digital controllers, this disclosure provides specific methods for adjusting the parameters of the external resistors and capacitors of the analog controller or configuring the register parameters of the digital controller, which have good versatility and implementability.

[0116] Furthermore, this disclosure introduces a zero-crossing turn-off mechanism based on drain-source voltage detection and a turn-off delay compensation method to precisely control the turn-off time of the synchronous rectifier diodes, preventing current backflow or additional losses caused by premature or delayed turn-off. By dynamically adjusting the dead time of the primary-side switching transistors, the operating range of soft switching can be extended, enabling the DC-DC converter to achieve zero-voltage turn-on even under lower loads, further reducing switching noise.

[0117] To prevent voltage backflow under extreme light loads or abnormal operating conditions, this disclosure also connects a control unit and an isolating switch in series at the output end, forming a double-insurance protection mechanism with the analog controller, which ensures both light load efficiency and absolute system safety.

[0118] Based on the same inventive concept, a second exemplary embodiment of this disclosure provides a control device for a vehicle voltage conversion circuit. The voltage conversion circuit includes a phase-shifting full-bridge circuit 10, a transformer 20, and a rectifier circuit 30. The phase-shifting full-bridge circuit 10 is connected to a first side of the transformer 20, and the rectifier circuit 30 is connected to a second side of the transformer 20. The voltage on the first side is higher than the voltage on the second side. The device includes: The monitoring module monitors the output current on the second side of the transformer. The function of this module corresponds to step S10.

[0119] The control module controls the rectifier circuit to operate in synchronous rectification mode when the output current is within a preset current range, until the output current falls below the lower limit of the preset current range or exceeds the upper limit of the preset current range. The preset current range represents the range of radiated emissions exceeding the reference radiation value when the voltage conversion circuit is operating. The function of this module corresponds to step S20.

[0120] The above modules can be integrated into an electronic control unit, which can be a standalone HUD controller or integrated into the smart cockpit domain controller.

[0121] When using integrated units, the vehicle may include a processing module and a storage module. The processing module is used to control and manage the vehicle's actions. The storage module supports the vehicle in executing program code and data.

[0122] Based on the same concept, this disclosure also provides a vehicle, the vehicle comprising: Memory, used to store executable program code; A processor is configured to retrieve and execute executable program code from memory, causing the vehicle to perform the control method of the vehicle voltage conversion circuit described in the above embodiments.

[0123] A processor can also be a combination of functions that perform computation, such as a combination of one or more microprocessors, digital signal processing (DSP) and microprocessors, etc.

[0124] Figure 6A schematic block diagram of a vehicle 200 according to an embodiment of this application is shown. The vehicle 200 includes a processor 201, an internal bus 202, a network interface 203, a memory 204, and a non-volatile memory 205, and may also include other hardware required for business operations. The processor 201 can read the corresponding computer program from the non-volatile memory 205 into the memory 204 and then run it to implement the steps of the method described above. Of course, in addition to the software implementation, this application does not exclude other implementation methods, such as logic devices or a combination of hardware and software, etc. That is to say, the execution subject of the following processing flow is not limited to each logic unit, but can also be hardware or logic devices.

[0125] The aforementioned memory may include, but is not limited to: USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, optical disks, and other media that can store computer programs.

[0126] The vehicle can be a traditional gasoline-powered vehicle, a hybrid vehicle, or a pure electric vehicle. By equipping it with the aforementioned device, the vehicle can actively sense the status of the headlights of the vehicle ahead and intelligently adjust the content of the HUD display and provide the driver with precise safety warnings, thereby significantly improving driving safety at night or in low-light conditions.

[0127] This embodiment also provides a computer-readable storage medium (including but not limited to disk storage, CD-ROM, optical storage, etc.) storing computer program code. When the computer program code is run on a computer, the computer executes the above-mentioned related method steps to implement the control method for a vehicle voltage conversion circuit provided in the above embodiment.

[0128] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0129] Through the above description of the embodiments, those skilled in the art will understand that, for the sake of convenience and brevity, only the division of the above functional modules is used as an example. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above.

[0130] In the embodiments provided in this disclosure, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another device, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection of devices or units may be electrical, mechanical, or other forms.

[0131] In the description of this disclosure, it should be understood that if the terms "upper", "lower", "front", "rear", "left" and "right" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the position or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.

[0132] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0133] The above are merely embodiments of this disclosure and are not intended to limit the scope of this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of the claims of this disclosure.

Claims

1. A control method of a vehicle voltage conversion circuit, characterized by, The voltage conversion circuit includes a phase-shifted full-bridge circuit, a transformer, and a rectifier circuit. The phase-shifted full-bridge circuit is connected to a first side of the transformer, and the rectifier circuit is connected to a second side of the transformer. The voltage on the first side is higher than the voltage on the second side. The control method includes: Monitor the output current on the second side of the transformer; When the output current is within a preset current range, the rectifier circuit is controlled to be in synchronous rectification mode until the output current is lower than the lower limit of the preset current range or higher than the upper limit of the preset current range. The preset current range represents the range of currents in which the voltage conversion circuit radiates and emits currents exceeding the reference radiation value when it is working.

2. The control method as described in claim 1, characterized in that, Controlling the rectifier circuit to be in synchronous rectification mode includes: When the output current reaches the rectification start threshold, the rectifier circuit is controlled to be in synchronous rectification mode. When the output current reaches the rectification shutdown threshold, the rectifier circuit is controlled to exit the synchronous rectification mode; wherein... When the output current changes from high to low, the rectification turn-on threshold is greater than or equal to the upper limit of the preset current range, and the rectification turn-off threshold is less than the lower limit of the preset current range. When the output current changes from low to high, the rectification turn-on threshold is less than or equal to the lower limit of the preset current range, and the rectification turn-off threshold is greater than or equal to the upper limit of the preset current range.

3. The control method as described in claim 2, characterized in that, The method further includes: If the voltage conversion circuit is controlled by an analog controller, the rectification off threshold and rectification on threshold are determined by adjusting the resistance value of the resistor and the capacitance value connected to the analog controller.

4. The control method as described in claim 3, characterized in that, The analog controller is a phase-shifted full-bridge control chip, which includes a current detection pin and an intermittent conduction mode pin. The current detection pin is connected to a first capacitor, and the intermittent conduction mode pin is connected to a first resistor. The step of determining the rectification start-up threshold and rectification shutdown threshold by adjusting the resistance parameters of the resistor and the capacitance parameters connected to the analog controller includes: By adjusting the resistance value of the first resistor to set the rectification shutdown threshold, the synchronous rectification mode is exited when the output current reaches the rectification shutdown threshold. The resistance value of the first resistor is positively correlated with the rectification shutdown threshold. By adjusting the capacitance of the first capacitor to set the rectification start threshold, the output current enters the synchronous rectification mode when it reaches the rectification start threshold. The capacitance of the first capacitor is positively correlated with the rectification start threshold.

5. The control method as described in claim 1, characterized in that, The output terminal of the rectifier circuit is connected to the load. The voltage conversion circuit further includes an isolation switch and a control unit that drives the isolation switch. The isolation switch is connected in series between the output terminal of the rectifier circuit and the load. The control method further includes: Detect the voltage between the output terminal of the rectifier circuit and the positive terminal of the load; When the voltage at the positive terminal is higher than the voltage at the output terminal, the control unit generates a control signal to turn off the isolation switch.

6. The control method as described in claim 1, characterized in that, The phase-shifted full-bridge circuit includes a first bridge arm switch group connected to the positive terminal of the power supply input and a second bridge arm switch group connected to the negative terminal of the power supply input. The control method further includes: The dead time between the first bridge arm switching transistor group and the second bridge arm switching transistor group is adjusted according to the output current, wherein the smaller the output current, the longer the dead time, and the larger the output current, the shorter the dead time.

7. The control method as described in claim 2, characterized in that, The method further includes: If the voltage conversion circuit uses a digital controller, the rectification enable threshold parameter in the register parameters of the digital controller is configured to determine the rectification enable threshold, and the rectification disable threshold parameter is configured to determine the rectification disable threshold.

8. The control method as described in any one of claims 1, 3, or 7, characterized in that, The rectifier circuit includes synchronous rectifier diodes. The control method further includes: Detect the drain-source voltage of the synchronous rectifier diode; When the drain-source voltage jumps from negative to 0 or positive, a zero-crossing control signal is generated; The synchronous rectifier is turned off based on the zero-crossing control signal; Obtain the delay time from the generation of the zero-crossing control signal to the actual turn-off of the synchronous rectifier tube; Based on the aforementioned delay time, the turn-off delay setting parameter is adjusted so that the turn-off time of the synchronous rectifier tube coincides with the current zero-crossing time.

9. The control method as described in claim 8, characterized in that, When the voltage conversion circuit is controlled by an analog controller, the analog controller is a phase-shifted full-bridge control chip. The phase-shifted full-bridge control chip includes a turn-off delay setting pin, which is connected to a resistor to ground. The adjustment of the shutdown delay setting parameters includes: The shutdown delay setting parameter is adjusted by adjusting the resistance value of the resistor to ground connected to the shutdown delay setting pin. The delay time is proportional to the resistance value of the resistor to ground connected to the shutdown delay setting pin.

10. A vehicle, characterized in that, The vehicles include: Memory, used to store executable program code; A processor is configured to call and execute the executable program code from the memory, causing the vehicle to perform the control method for the vehicle voltage conversion circuit as described in any one of claims 1 to 9.

Images