An overcurrent protection circuit for a bidirectional DCDC converter

Abstract

The utility model discloses a kind of overcurrent protection circuit of bidirectional DCDC converter, including power topology module, bidirectional current detection module and bidirectional fault protection and recovery module, the power topology module includes detection resistance Rs, field effect tube Q3 and field effect tube Q4;The bidirectional current detection module includes operational amplifier U1, the same phase input end of operational amplifier U1 is connected with the first end of the detection resistance Rs by resistance R3 and the opposite phase input end of operational amplifier U1 is connected with the second end of the detection resistance Rs by resistance R1;The bidirectional fault protection and recovery module includes operational amplifier U2, operational amplifier U3 and MCU.The utility model discloses a kind of overcurrent protection circuit of bidirectional DCDC converter, realizes bidirectional current detection, fault locking and unlocking by integration design, simplifies circuit structure, reduces cost, and improves protection reliability simultaneously.

Description

Technical Field

[0001] This utility model belongs to the field of automotive power technology, specifically relating to an overcurrent protection circuit for a bidirectional DC-DC converter. Background Technology

[0002] In automotive power systems, bidirectional DC-DC converters are core components for enabling bidirectional power transmission and are widely used in scenarios such as charging and discharging power batteries and supplying auxiliary power. However, during forward discharge and reverse charging, converters are prone to overcurrent due to sudden load changes, short circuits, and other situations. If effective protection is not implemented in time, it can lead to damage to power devices, circuit burnout, and even safety accidents.

[0003] Existing overcurrent protection technologies are mostly designed for unidirectional current. If bidirectional protection is required, two independent detection and protection circuits are often needed, which results in complex structure, high cost, and large space occupation. Moreover, some protection circuits lack fault locking and software unlocking functions, which can easily lead to false starts after the fault is cleared, reducing system reliability.

[0004] Therefore, there is an urgent need for a bidirectional overcurrent protection circuit that is simple in structure, low in cost, and highly reliable to meet the application requirements of automotive power systems. Utility Model Content

[0005] The main purpose of this invention is to provide an overcurrent protection circuit for a bidirectional DC-DC converter. Through integrated design, it achieves bidirectional current detection, fault locking and unlocking, simplifies the circuit structure, reduces costs, and improves protection reliability.

[0006] To achieve the above objectives, this utility model provides an overcurrent protection circuit for a bidirectional DC-DC converter, including a power topology module, a bidirectional current detection module, and a bidirectional fault protection and recovery module, wherein: The power topology module includes a sensing resistor Rs, a field-effect transistor Q3, and a field-effect transistor Q4. The first end of the sensing resistor Rs is connected to the voltage input terminal, and the second end of the sensing resistor Rs is connected to the voltage output terminal in sequence through the field-effect transistor Q2, the inductor L1, the field-effect transistor Q3, and the field-effect transistor Q4. The bidirectional current detection module includes an operational amplifier U1. The non-inverting input terminal of the operational amplifier U1 is connected to the first terminal of the detection resistor Rs through a resistor R3, and the inverting input terminal of the operational amplifier U1 is connected to the second terminal of the detection resistor Rs through a resistor R1. The bidirectional fault protection and recovery module includes operational amplifier U2, operational amplifier U3, and an MCU. The non-inverting input of operational amplifier U2 is connected to the output of operational amplifier U1. One inverting input of operational amplifier U2 is connected to the power supply through resistor R8, and the other is grounded through resistors R9 and R10. The output of operational amplifier U2 is connected to the first terminal of the MCU and the gate of field-effect transistor Q5, and the drain of field-effect transistor Q5 is connected to the gates of field-effect transistors Q3 and Q4, respectively. The inverting input of operational amplifier U3 is connected to the output of operational amplifier U1, and the non-inverting input of operational amplifier U3 is connected to the common terminal of resistors R9 and R10. The output of operational amplifier U3 is connected to the first terminal of the MCU. The second terminal of the MCU is connected to field-effect transistor Q6, and the third terminal of the MCU is connected to the first terminal of driver U5.

[0007] As a further preferred embodiment of the above technical solution, the second end of the detection resistor Rs is electrically connected to the drain of the field-effect transistor Q2, and the source of the field-effect transistor Q2 is connected to the drain of the field-effect transistor Q3 through the inductor L1. The source of the field-effect transistor Q3 and the source of the field-effect transistor Q4 are connected, and the gate of the field-effect transistor Q3 and the gate of the field-effect transistor Q4 are connected and both are connected to the second terminal of the driver U5.

[0008] As a further preferred technical solution of the above technical solution, the non-inverting input terminal of the operational amplifier U1 is also connected to one end of the resistor R4, and the other end of the resistor R4 is grounded through resistor R5 and connected to the power supply terminal through resistor R6. A resistor R2 is connected between the inverting input terminal and the output terminal of the operational amplifier U1.

[0009] As a further preferred embodiment of the above technical solution, a resistor R12 and a diode D1 are connected between the non-inverting input terminal and the output terminal of the operational amplifier U2, and the output terminal of the operational amplifier U2 is connected to the gate of the field-effect transistor Q5 in sequence through a diode D3 and a resistor R14. The cathode of the diode D3 is connected to the first terminal of the MCU. A resistor R13 and a diode D2 are connected between the non-inverting input and output terminals of the operational amplifier U3, and the output terminal of the operational amplifier U3 is connected to the gate of the field-effect transistor Q5 through a diode D4 and a resistor R14 in sequence.

[0010] As a further preferred embodiment of the above technical solution, a diode D11 is connected between the non-inverting input terminal of the operational amplifier U2 and the inverting input terminal of the operational amplifier U3. The second terminal of the MCU is connected to the gate of the field-effect transistor Q6 through a resistor R15, and the drain of the field-effect transistor Q6 is connected to the cathode of the diode D11.

[0011] The beneficial effects of this utility model are as follows: 1. High versatility: The power topology module is compatible with various topologies such as synchronous rectification, boost, and buck. The sensing resistor can be flexibly installed at the input or output terminals, making it suitable for various bidirectional DC-DC conversion scenarios.

[0012] 2. Low cost: Bidirectional current detection and protection are achieved through a single circuit, eliminating the need for two independent systems, which simplifies the structure and reduces hardware costs.

[0013] 3. High reliability: It has a fault locking function to avoid accidental startup when the fault has not been resolved; it adopts MCU software unlocking to ensure the safe recovery of the system after fault diagnosis and improves the overall stability.

[0014] 4. High flexibility: The overcurrent threshold can be set by adjusting the resistance value of the voltage divider resistor, which can be adapted to application scenarios with different power and protection requirements. Attached Figure Description

[0015] Figure 1 This is the overall circuit block diagram of this utility model; Figure 2 This is a circuit diagram of the bidirectional current detection module of this utility model; Figure 3 This is a circuit diagram of the bidirectional fault protection and recovery module of this utility model. Detailed Implementation

[0016] The following description is intended to disclose the present invention so that those skilled in the art can implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. The basic principles of the present invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the present invention.

[0017] This utility model discloses an overcurrent protection circuit for a bidirectional DC-DC converter. The specific embodiments of the utility model are further described below with reference to preferred embodiments.

[0018] In the embodiments of this utility model, those skilled in the art will note that the MCU and driver involved in this utility model can be regarded as prior art.

[0019] Preferred embodiment.

[0020] like Figure 1-3 As shown, this utility model discloses an overcurrent protection circuit for a bidirectional DC-DC converter, including a power topology module, a bidirectional current detection module, and a bidirectional fault protection and recovery module, wherein: The power topology module includes a sensing resistor Rs, a field-effect transistor Q3, and a field-effect transistor Q4. The first end of the sensing resistor Rs is connected to the voltage input terminal (Vin), and the second end of the sensing resistor Rs is connected to the voltage output terminal in sequence through the field-effect transistor Q2, the inductor L1, the field-effect transistor Q3, and the field-effect transistor Q4. The bidirectional current detection module includes an operational amplifier U1. The non-inverting input terminal of the operational amplifier U1 is connected to the first terminal of the detection resistor Rs through a resistor R3, and the inverting input terminal of the operational amplifier U1 is connected to the second terminal of the detection resistor Rs through a resistor R1. The bidirectional fault protection and recovery module includes operational amplifiers U2 and U3, and an MCU (U4). The non-inverting input of operational amplifier U2 (through resistor R7) is connected to the output of operational amplifier U1. One inverting input of operational amplifier U2 is connected to the power supply (Vs) through resistor R8, and the other is grounded through resistors R9 and R10. The output of operational amplifier U2 is connected to the first terminal of the MCU and the gate of field-effect transistor Q5, and the drain of field-effect transistor Q5 is connected to the gates of field-effect transistors Q3 and Q4, respectively. The inverting input of operational amplifier U3 (through resistor R11) is connected to the output of operational amplifier U1, and the non-inverting input of operational amplifier U3 is connected to the common terminal of resistors R9 and R10. The output of operational amplifier U3 is connected to the first terminal of the MCU. The second terminal of the MCU is connected to field-effect transistor Q6, and the third terminal of the MCU is connected to the first terminal of driver U5.

[0021] Specifically, the second end of the detection resistor Rs is electrically connected to the drain of the field-effect transistor Q2, and the source of the field-effect transistor Q2 is connected to the drain of the field-effect transistor Q3 through the inductor L1. The source of the field-effect transistor Q3 and the source of the field-effect transistor Q4 are connected, and the gate of the field-effect transistor Q3 and the gate of the field-effect transistor Q4 are connected and both are connected to the second terminal of the driver U5.

[0022] More specifically, the non-inverting input terminal of the operational amplifier U1 is also connected to one end of the resistor R4, and the other end of the resistor R4 is grounded through the resistor R5 and connected to the power supply terminal (Vs) through the resistor R6. A resistor R2 is connected between the inverting input terminal and the output terminal of the operational amplifier U1.

[0023] Furthermore, a resistor R12 and a diode D1 are connected between the non-inverting input terminal and the output terminal of the operational amplifier U2, and the output terminal of the operational amplifier U2 is connected to the gate of the field-effect transistor Q5 in sequence through a diode D3 and a resistor R14. The cathode of the diode D3 is connected to the first terminal of the MCU. A resistor R13 and a diode D2 are connected between the non-inverting input and output terminals of the operational amplifier U3, and the output terminal of the operational amplifier U3 is connected to the gate of the field-effect transistor Q5 through a diode D4 and a resistor R14 in sequence.

[0024] Furthermore, a diode D11 is connected between the non-inverting input terminal of the operational amplifier U2 and the inverting input terminal of the operational amplifier U3. The second terminal of the MCU is connected to the gate of the field-effect transistor Q6 through a resistor R15, and the drain of the field-effect transistor Q6 is connected to the cathode of the diode D11.

[0025] The principle of this utility model is as follows: For the power topology module, the core function is to realize bidirectional power flow. Its logic revolves around two scenarios: "forward discharge" and "reverse charging," specifically relying on the on / off control of the switching devices (MOSFETs Q3 and Q4) in the power topology. The conduction / cutoff of MOSFETs Q3 and Q4 is controlled by the gate (G) voltage. When the MCU outputs a high-level drive signal to the gate, a voltage difference is formed between the gate and the source (S), causing the MOSFET to conduct, and current flows from the drain (D) to the source (forward transmission) or from the source to the drain (reverse transmission). When there is no drive signal to the gate or a fault protection occurs (such as Q5 being turned on), the gate voltage disappears, the MOSFET is turned off, and the current path is cut off. Current sampling is performed using a current sensing resistor Rs, which can be placed at either the input or output terminal for bidirectional overcurrent protection.

[0026] For the bidirectional current detection module, differential amplification with a midpoint offset voltage is used. The detection direction is defined as 0 to the offset voltage (positive), and the direction from the offset voltage to the power supply voltage (reverse). Specifically, it follows... Figure 2 From the perspective of emptiness and shortness, we know And formulas (1) and (2), where: (1); (2); make = , = , (2)-(1) yields: (3); Greater than When the time is positive, the magnification factor is The output range is ~ .

[0027] Less than The time is reversed, the amplification factor is R2 / R1, and the output range is 0~ .

[0028] yes and partial pressure It is understood that 5V systems generally... It is 2.5V.

[0029] For the bidirectional fault protection and recovery module, through Divide the 5V voltage. and The intermediate voltage point is the positive voltage threshold. , and The intermediate voltage divider point is the reverse voltage divider threshold. .

[0030] When a forward overcurrent occurs > When the op-amp U2 outputs a high level, the input of U2 is pulled high through D1 and R12, keeping the output high. This drives Q5 to turn on and forces Q3 and Q4 to turn off, thus achieving the forward overcurrent protection lockout function.

[0031] When reverse overcurrent occurs < When the op-amp U3 outputs a high level, the positive threshold of U2 is pulled up through D2 and R13, keeping the output at a high level and driving Q5 to turn on, thus forcibly turning off Q3 and Q4 to achieve the reverse current overcurrent protection lock-up function. Furthermore, after bidirectional overcurrent protection, a high-level fault frequency is synchronously sent to the MCU to execute actions such as recording the fault and stopping the drive. Once it is confirmed that the fault has been cleared and the action can be resumed, the MCU sends a high-level drive to turn on Q6, and the positive input of U2 is less than... , A negative input greater than U3 and low outputs of U2 and U3 unlock the output fault.

[0032] This invention is applicable to various bidirectional DC-DC converter topologies and circuits requiring bidirectional current signal detection and bidirectional hardware overcurrent protection. It utilizes differential amplification to detect current magnitude and distinguishes between forward and reverse current by adjusting the op-amp reference voltage. Overcurrent thresholds are set via resistor divider; protection is initiated when the detected current output exceeds the threshold, and a comparator outputs a reverse lockout to confirm the fault status. Once the MCU confirms the fault can be eliminated, it releases the fault. This achieves bidirectional current detection and fault status locking, with a single MCU signal enabling bidirectional overcurrent fault unlocking. It is primarily used in bidirectional converter power supply products, improving product reliability and effectively reducing product costs.

[0033] It is worth mentioning that the technical features such as MCU and driver involved in this utility model patent application should be regarded as prior art. The specific structure, working principle and possible control method and spatial arrangement of these technical features can be adopted by conventional choices in the field and should not be regarded as the inventive point of this utility model patent. This utility model patent will not be further elaborated in detail.

[0034] For those skilled in the art, modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. An overcurrent protection circuit for a bidirectional DC-DC converter, characterized in that, It includes a power topology module, a bidirectional current detection module, and a bidirectional fault protection and recovery module, wherein: The power topology module includes a sensing resistor Rs, a field-effect transistor Q3, and a field-effect transistor Q4. The first end of the sensing resistor Rs is connected to the voltage input terminal, and the second end of the sensing resistor Rs is connected to the voltage output terminal in sequence through the field-effect transistor Q2, the inductor L1, the field-effect transistor Q3, and the field-effect transistor Q4. The bidirectional current detection module includes an operational amplifier U1. The non-inverting input terminal of the operational amplifier U1 is connected to the first terminal of the detection resistor Rs through a resistor R3, and the inverting input terminal of the operational amplifier U1 is connected to the second terminal of the detection resistor Rs through a resistor R1. The bidirectional fault protection and recovery module includes operational amplifier U2, operational amplifier U3, and an MCU. The non-inverting input of operational amplifier U2 is connected to the output of operational amplifier U1. One inverting input of operational amplifier U2 is connected to the power supply through resistor R8, and the other is grounded through resistors R9 and R10. The output of operational amplifier U2 is connected to the first terminal of the MCU and the gate of field-effect transistor Q5, and the drain of field-effect transistor Q5 is connected to the gates of field-effect transistors Q3 and Q4, respectively. The inverting input of operational amplifier U3 is connected to the output of operational amplifier U1, and the non-inverting input of operational amplifier U3 is connected to the common terminal of resistors R9 and R10. The output of operational amplifier U3 is connected to the first terminal of the MCU. The second terminal of the MCU is connected to field-effect transistor Q6, and the third terminal of the MCU is connected to the first terminal of driver U5.

2. The overcurrent protection circuit for a bidirectional DC-DC converter according to claim 1, characterized in that, The second end of the detection resistor Rs is electrically connected to the drain of the field-effect transistor Q2, and the source of the field-effect transistor Q2 is connected to the drain of the field-effect transistor Q3 through the inductor L1. The source of the field-effect transistor Q3 and the source of the field-effect transistor Q4 are connected, and the gate of the field-effect transistor Q3 and the gate of the field-effect transistor Q4 are connected and both are connected to the second terminal of the driver U5.

3. The overcurrent protection circuit for a bidirectional DC-DC converter according to claim 2, characterized in that, The non-inverting input terminal of the operational amplifier U1 is also connected to one end of the resistor R4. The other end of the resistor R4 is grounded through resistor R5 and connected to the power supply terminal through resistor R6. A resistor R2 is connected between the inverting input terminal and the output terminal of the operational amplifier U1.

4. The overcurrent protection circuit for a bidirectional DC-DC converter according to claim 3, characterized in that, A resistor R12 and a diode D1 are connected between the non-inverting input terminal and the output terminal of the operational amplifier U2, and the output terminal of the operational amplifier U2 is connected to the gate of the field-effect transistor Q5 through a diode D3 and a resistor R14 in sequence. The cathode of the diode D3 is connected to the first terminal of the MCU. A resistor R13 and a diode D2 are connected between the non-inverting input and output terminals of the operational amplifier U3, and the output terminal of the operational amplifier U3 is connected to the gate of the field-effect transistor Q5 through a diode D4 and a resistor R14 in sequence.

5. The overcurrent protection circuit for a bidirectional DC-DC converter according to claim 4, characterized in that, A diode D11 is connected between the non-inverting input terminal of the operational amplifier U2 and the inverting input terminal of the operational amplifier U3. The second terminal of the MCU is connected to the gate of the field-effect transistor Q6 through a resistor R15, and the drain of the field-effect transistor Q6 is connected to the cathode of the diode D11.

Images