Improved synchronous rectification circuit for vehicle

Abstract

The utility model discloses a kind of vehicle improved synchronous rectification circuit, including high-voltage DC bus, battery, first full-bridge unit, second full-bridge unit and isolation transformer. First full-bridge unit is connected with high-voltage DC bus, second full-bridge unit is connected with battery, the secondary winding of transformer connects first full-bridge, primary winding connects second full-bridge. The gate drive path of upper tube Q1 and Q3 in first full-bridge is respectively provided with electronic switch K1 and K2, for selectively turning on or turning off the drive signal of upper tube, realize the switching between synchronous rectification state and body diode rectification state. The structure effectively prevents Q1 and Q3 misdirect on when inverter is in inverting working state, improve the short-circuit resistance of system and operating safety, applicable to the vehicle-mounted power system with charge-discharge bidirectional function.

Description

Technical Field

[0001] This utility model belongs to the field of bidirectional inverter technology, specifically relating to an improved synchronous rectifier circuit for automotive applications. Background Technology

[0002] In existing vehicle-mounted power systems, a full-bridge inverter / rectifier is typically used to achieve energy conversion between the power battery and the external AC grid or high-voltage DC bus. Synchronous rectification technology, as a common method to improve efficiency, is widely used in high-power DC / DC and DC / AC converters. In synchronous rectification schemes, the switching transistors of the upper and lower bridge arms are usually precisely driven by PWM signals to achieve bidirectional conduction and freewheeling control, reducing conduction losses. However, in the vehicle operating environment, the inverter often simultaneously undertakes both discharging (inversion) and charging operations, and its input and output terminals may face abnormal situations such as poor contact, load short circuit, and sudden changes in battery voltage. In actual operation, especially at the moment of output short circuit or bridge arm malfunction, the upper bridge arm transistors (such as Q1 and Q3) may experience "misguided conduction" due to mis-triggered drive, thus forming a direct path with the lower transistor, causing serious consequences such as device explosion and uncontrolled bus current.

[0003] To address this, some synchronous rectification systems have attempted to implement "pseudo-shutdown" or delayed-drive methods through software strategies. However, these methods are limited by the complexity of the drive logic, the turn-off speed of the devices, and the execution cycle of the controller, and certain safety risks still exist. Furthermore, in traditional inverter architectures, the high- and low-voltage bridge arm control is integrated, lacking isolation and fault shielding mechanisms. Once the control signal is abnormal or the feedback is delayed, it can easily cause circuit surges and equipment damage. Therefore, improving the safety of the bridge arm drive and the operational stability of the rectifier devices without increasing control complexity and cost has become an important direction for technological improvement in the industry. Utility Model Content

[0004] To address the aforementioned issues, this invention provides an improved synchronous rectifier circuit for vehicles. Utilizing a full-bridge topology, transformer, and controllable upper transistor drive structure, it improves system stability and fault tolerance while maintaining conversion efficiency, making it suitable for on-board charging / discharging bidirectional power conversion scenarios in new energy vehicles.

[0005] The technical solution provided by this utility model is as follows: An improved synchronous rectifier circuit for automotive applications includes: High-voltage DC bus, including +BUS and -BUS; A battery, including the positive terminal and the negative terminal; The first full-bridge unit connected to the high-voltage DC bus includes switch Q1, switch Q2, switch Q3 and switch Q4; The second full-bridge unit connected to the battery includes switching transistors Q5, Q6, Q7, and Q8. Transformer T1, wherein the secondary winding of transformer T1 is connected to the first full-bridge unit, and the primary winding of transformer T1 is connected to the second full-bridge unit; The gate of the switching transistor Q1 is connected to pulse width modulation pulse PWM1, the gate of the switching transistor Q2 is connected to pulse width modulation pulse PWM2, the gate of the switching transistor Q3 is connected to pulse width modulation pulse PWM3, and the gate of the switching transistor Q4 is connected to pulse width modulation pulse PWM4. A switch K1 is provided between the switching transistor Q1 and the pulse width modulation pulse PWM1, and a switch K2 is provided between the switching transistor Q3 and the pulse width modulation pulse PWM3.

[0006] In some embodiments, pin 4 of the secondary winding of transformer T1 is connected to the node between switch Q1 and switch Q2, and pin 3 of the secondary winding of transformer T1 is connected to the node between switch Q3 and switch Q4.

[0007] In some embodiments, pin 1 of the primary winding of transformer T1 is connected to the node between switch Q5 and switch Q6, and pin 2 of the secondary winding of transformer T1 is connected to the node between switch Q7 and switch Q8.

[0008] In summary, the beneficial effects of this utility model are as follows: (1) This utility model adds controllable switches K1 and K2 to the PWM signal paths of the upper bridge arms Q1 and Q3 of the first full-bridge unit on the high-voltage side, respectively, to selectively turn on or off the gate drive in different operating modes. In inverter output mode, K1 and K2 can be disconnected, leaving only the body diodes of Q1 and Q3 to participate in rectification, thereby avoiding mis-conduction of the upper tubes, preventing short circuits in the bridge arms, and improving the system's anti-abnormal capability; in charging mode, by turning on K1 and K2, the normal switching operation of the upper tubes is restored, forming a full-bridge structure with the lower tubes, and realizing high-efficiency bidirectional energy conversion.

[0009] (2) This utility model has a simple structure and does not rely on complex control algorithms. It can achieve safety control in different states by switching hardware switches, which enhances the reliability and practicality of the rectifier system and is particularly suitable for vehicle application scenarios with high safety requirements. Attached Figure Description

[0010] Figure 1 This is the circuit diagram of this utility model. Detailed Implementation

[0011] To enhance understanding of this utility model, the present utility model will be further described in detail below with reference to the embodiments and accompanying drawings. These embodiments are only used to explain the present utility model and do not constitute a limitation on the scope of protection of the present utility model.

[0012] like Figure 1 As shown, an improved synchronous rectifier circuit for vehicles is suitable for inverter and charging systems of electric vehicles, and is especially suitable for DC / AC inverters with bidirectional energy conversion capabilities.

[0013] The rectifier circuit includes a high-voltage DC bus and a battery interface. The high-voltage DC bus includes +BUS and -BUS, used to connect the filter circuit and the inverter circuit. The battery interface includes the battery positive terminal and the battery negative terminal, used to connect the vehicle battery. The first full-bridge unit is located between +BUS and -BUS for energy exchange with the high-voltage side. This full-bridge unit includes four power switches Q1, Q2, Q3, and Q4, which form the upper and lower transistors of the left and right bridge arms, respectively. The second full-bridge unit is connected between the positive and negative terminals of the battery and includes switches Q5, Q6, Q7, and Q8, also forming a full-bridge circuit structure, used to achieve voltage transformation on the low-voltage side.

[0014] Transformer T1 connects the first full-bridge unit and the second full-bridge unit. Its secondary winding is connected to the first full-bridge unit, and its primary winding is connected to the second full-bridge unit. Secondary winding pin 4 of transformer T1 is connected to the midpoint between Q1 and Q2, and secondary winding pin 3 is connected to the midpoint between Q3 and Q4. Primary winding pin 1 is connected to the midpoint between Q5 and Q6, and primary winding pin 2 is connected to the midpoint between Q7 and Q8. Through this connection method, transformer T1 can achieve bidirectional energy transmission and provide electrical isolation.

[0015] The gate of switch Q1 is connected to pulse width modulation pulse PWM1, the gate of switch Q2 is connected to pulse width modulation pulse PWM2, the gate of switch Q3 is connected to pulse width modulation pulse PWM3, and the gate of switch Q4 is connected to pulse width modulation pulse PWM4.

[0016] To improve the safety and adaptability of the rectifier system under different operating conditions, electronic switches K1 and K2 are connected in series in the gate drive circuits of switching transistors Q1 and Q3, respectively. Switch K1 is located between the PWM1 signal and Q1, and switch K2 is located between the PWM3 signal and Q3.

[0017] With the above structural arrangement, when the inverter is in the inverter operation state, K1 and K2 can be disconnected, and the switching transistors Q1 and Q3 will not perform switching operation, with only the body diodes of Q1 and Q3 participating in the rectification operation; when the inverter is in the charging operation state, K1 and K2 are connected, and the switching transistors Q1 and Q3 resume PWM control to perform switching operation. They, together with the lower transistors Q2 and Q4, form a full-bridge inverter circuit, which provides high-frequency excitation to the secondary winding of transformer T1 to charge the battery.

[0018] This circuit structure utilizes a full-bridge topology, a transformer, and a controllable upper transistor drive structure to improve system stability and fault resistance while maintaining conversion efficiency. It is suitable for on-board charging / discharging bidirectional power conversion scenarios in new energy vehicles.

[0019] It should be noted that implementations not shown or described in the accompanying drawings or the main text of the specification are all forms known to those skilled in the art and are not described in detail. Furthermore, the definitions of the elements and methods described above are not limited to the various specific structures, shapes, or methods mentioned in the embodiments.

[0020] It should also be noted that this document may provide examples of parameters containing specific values, but these parameters need not be exactly equal to the corresponding values, but can approximate the corresponding values ​​within acceptable error tolerances or design constraints. Directional terms mentioned in the embodiments, such as "up," "down," "front," "back," "left," "right," "inner," and "outer," are only for reference to the directions in the accompanying drawings and are not intended to limit the scope of protection of this application.

[0021] The foregoing description illustrates and describes preferred embodiments of the present invention. As previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or related technical or knowledge. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. An improved synchronous rectifier circuit for automotive applications, characterized in that, include: High-voltage DC bus, including +BUS and -BUS; A battery, including the positive terminal and the negative terminal; The first full-bridge unit connected to the high-voltage DC bus includes switch Q1, switch Q2, switch Q3 and switch Q4; The second full-bridge unit connected to the battery includes switching transistors Q5, Q6, Q7, and Q8. Transformer T1, wherein the secondary winding of transformer T1 is connected to the first full-bridge unit, and the primary winding of transformer T1 is connected to the second full-bridge unit; The gate of the switching transistor Q1 is connected to pulse width modulation pulse PWM1, the gate of the switching transistor Q2 is connected to pulse width modulation pulse PWM2, the gate of the switching transistor Q3 is connected to pulse width modulation pulse PWM3, and the gate of the switching transistor Q4 is connected to pulse width modulation pulse PWM4. A switch K1 is provided between the switching transistor Q1 and the pulse width modulation pulse PWM1, and a switch K2 is provided between the switching transistor Q3 and the pulse width modulation pulse PWM3.

2. The improved synchronous rectifier circuit for vehicles according to claim 1, characterized in that, Pin 4 of the secondary winding of transformer T1 is connected to the node between switch Q1 and switch Q2, and pin 3 of the secondary winding of transformer T1 is connected to the node between switch Q3 and switch Q4.

3. The improved synchronous rectifier circuit for vehicles according to claim 1, characterized in that, Pin 1 of the primary winding of transformer T1 is connected to the node between switch Q5 and switch Q6, and pin 2 of the secondary winding of transformer T1 is connected to the node between switch Q7 and switch Q8.

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