A DCDC converter

Abstract

The utility model discloses a DCDC converter, including four pipe BUCK BOOST circuit, full bridge circuit, BUCK BOOST drive circuit, full bridge drive circuit, isolation drive transmission circuit, synchronous rectification drive circuit, main control circuit, current detection circuit, bus voltage detection circuit and output voltage detection circuit. The utility model discloses through optimizing the control circuit and input positive direction impact current's control circuit such as output current back-priming, has effectively reduced the back-priming current of output to input and the positive direction impact current of input to output, and then effectively avoided the problem of the damage of power tube and other devices.

Description

Technical Field

[0001] This utility model relates to the field of electronic circuit technology, specifically to a DC-DC converter. Background Technology

[0002] For wide-voltage input isolation high-power (400W and above) DC-DC converters, a two-stage circuit topology is usually chosen for DC-DC converter design to reduce voltage / current stress on power devices, facilitate power device selection, optimize power transformer / inductor design, optimize power device thermal design, and improve the efficiency of DC-DC converters.

[0003] like Figure 1 The DC / DC converter circuit block diagram shown includes a four-transistor BUCK-BOOST circuit, a full-bridge circuit, a BUCK-BOOST drive circuit, a full-bridge drive circuit, an isolated drive transmission circuit, a synchronous rectification drive circuit, a main control circuit, a current detection circuit, a bus voltage detection circuit, and an output voltage detection circuit.

[0004] For high-power DC-DC converters with low-voltage, wide-range input, such as a 9-36V input, 24V output, and 1000W DC-DC converter, the front-end power circuit typically uses a four-transistor BUCK-BOOST circuit topology, while the rear-end power circuit typically uses a full-bridge circuit topology, with the full-bridge circuit employing synchronous rectification. This four-transistor BUCK-BOOST + full-bridge circuit can operate bidirectionally when the synchronous rectifier transistors have a drive signal.

[0005] The DC-DC converters composed of the above four-transistor BUCK-BOOST full-bridge circuits can all operate bidirectionally, but they have the following three problems:

[0006] Problem 1: The bidirectional DC-DC converter uses a two-stage circuit topology. When the output is unloaded or lightly loaded and has a large capacitor, the voltage of the large output capacitor will not discharge quickly after the input is powered off. When the input is powered off and then powered on again, generating a synchronous rectification drive signal, the large output capacitor will cause reverse current to flow into the input. In severe cases, the large reverse current can damage components such as the power transistors of the DC-DC converter.

[0007] Problem 2: The bidirectional DC-DC converter uses a two-stage circuit topology. When the input is powered off or briefly interrupted, if the synchronous rectification drive signal continues to be generated, it will cause the output to backflow into the input. In severe cases, the large backflow current will damage the power transistors and other components of the DC-DC converter.

[0008] Problem 3: The bidirectional DC-DC converter employs a two-stage circuit topology. During power-off, if the voltage on the input filter capacitor of the full-bridge circuit cannot effectively discharge, the input capacitor will discharge through the transformer to the output capacitor upon power-on. Because the AC impedance of the input and output filter capacitors is relatively low, a large forward inrush current will be generated. In severe cases, this large forward inrush current can damage components such as the power transistors in the full-bridge circuit.

[0009] Therefore, in order to solve the problem of damage to power transistors and other devices caused by the above three reasons, it is necessary to propose a technical solution to effectively reduce output reverse current and forward inrush current. Utility Model Content

[0010] The purpose of this invention is to provide a DC-DC converter that can overcome the problems of damage to power transistors and other devices caused by reverse current and forward surge current in the prior art.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] This utility model provides a circuit block diagram of a DC-DC converter, including a four-transistor BUCK-BOOST circuit, a full-bridge circuit, a BUCK-BOOST drive circuit, a full-bridge drive circuit, an isolated drive transmission circuit, a synchronous rectification drive circuit, a main control circuit, a current detection circuit, a bus voltage detection circuit, and an output voltage detection circuit.

[0013] The input terminal of the four-transistor BUCK-BOOST circuit is the input terminal of the DC-DC converter. The output terminal of the four-transistor BUCK-BOOST circuit is connected to the input terminal of the full-bridge circuit. The output terminal of the full-bridge circuit is the output terminal of the DC-DC converter. The BUCK-BOOST drive circuit is connected between the four-transistor BUCK-BOOST circuit and the main control circuit. The full-bridge drive circuit is connected between the full-bridge circuit and the main control circuit. The synchronous rectification circuit is connected between the full-bridge circuit and the isolated drive transmission circuit. The isolated drive transmission circuit is connected between the synchronous rectification circuit and the main control circuit. The current detection circuit is connected between the four-transistor BUCK-BOOST circuit and the main control circuit. The bus voltage detection circuit is connected between the output terminal of the four-transistor BUCK-BOOST circuit and the main control circuit. The output voltage detection circuit is connected between the output terminal of the DC-DC converter and the main control circuit.

[0014] Optionally, the four-transistor BUCK-BOOST circuit includes capacitor C1, capacitor C2, MOSFET Q1, MOSFET Q2, MOSFET Q3, MOSFET Q4, inductor L1, and resistor R1;

[0015] Capacitor C1 is connected between the positive input terminal Vin and the input ground GND1 of the four-transistor BUCK-BOOST circuit. Capacitor C2 is connected between the positive output terminal V1 and the output ground GND of the four-transistor BUCK-BOOST circuit. The drain (D) of MOSFET Q1 is connected to the positive input terminal Vin of the four-transistor BUCK-BOOST circuit. The source (S) of MOSFET Q1 is connected to the drain (D) of MOSFET Q2. The gate (G) of MOSFET Q1 is connected to the output terminal GS1 of the BUCK-BOOST drive circuit. The source (S) of MOSFET Q2 is connected to the input ground GND1 of the four-transistor BUCK-BOOST circuit. The gate (G) of MOSFET Q2 is connected to the output terminal GS2 of the BUCK-BOOST drive circuit. The drain (D) of MOSFET Q3 is connected to... The source (S) terminal of MOSFET Q4 and the source (S) terminal of MOSFET Q3 are connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. The gate (G) terminal of MOSFET Q3 is connected to the output terminal GS3 of the BUCK-BOOST drive circuit. The source (S) terminal of MOSFET Q4 is connected to the drain (D) terminal of MOSFET Q3. The drain (D) terminal of MOSFET Q4 is connected to the positive output terminal V1 of the four-transistor BUCK-BOOST circuit. The gate (G) terminal of MOSFET Q4 is connected to the output terminal GS4 of the BUCK-BOOST drive circuit. The inductor L1 is connected between the source (S) terminals of MOSFET Q1 and Q4. The resistor R1 is connected between the input ground terminal GND1 and the output ground terminal GND of the four-transistor BUCK-BOOST circuit.

[0016] Optionally, the full-bridge circuit includes capacitor C3, capacitor C4, MOSFETs Q5, Q6, Q7, Q8, Q9, Q10, Q11, Q12 and transformer T1;

[0017] Capacitor C3 is connected between the positive input terminal V1 and the input ground terminal GND of the full-bridge circuit. Capacitor C4 is connected between the positive output terminal Vo and the output ground terminal GND2 of the full-bridge circuit. The drain of MOSFET Q5 is connected to the positive input terminal of transformer T1. The source of MOSFET Q5 is connected to the input ground terminal GND of the full-bridge circuit. The gate of MOSFET Q5 is connected to the output terminal GS5 of the full-bridge drive circuit. The drain of MOSFET Q6 is connected to the negative input terminal of transformer T1. The source (S) of the MOSFET Q6 is connected to the input ground GND of the full-bridge circuit. The gate (G) of the MOSFET Q6 is connected to the output GS6 of the full-bridge drive circuit. The drain (D) of the MOSFET Q7 is connected to the positive input V1 of the full-bridge circuit. The source (S) of the MOSFET Q7 is connected to the negative input of the transformer T1. The gate (G) of the MOSFET Q7 is connected to the output GS7 of the full-bridge drive circuit. The drain (D) of the MOSFET Q8 is connected to the positive input V1 of the full-bridge circuit. The source (S) of the MOSFET Q8 is connected to the positive input of the transformer T1. The gate (G) of MOSFET Q8 is connected to the output terminal GS8 of the full-bridge drive circuit. The drain (D) of MOSFET Q9 is connected to the positive output terminal of transformer T1. The source (S) of MOSFET Q9 is connected to the output ground GND2 of the full-bridge circuit. The gate (G) of MOSFET Q9 is connected to the output terminal GS9 of the full-bridge drive circuit. The drain (D) of MOSFET Q10 is connected to the negative output terminal of transformer T1. The source (S) of MOSFET Q10 is connected to the output ground GND2 of the full-bridge circuit. The gate (G) of MOSFET Q10 is connected to... The output terminal GS10 of the full-bridge drive circuit is connected to the positive output terminal Vo of the full-bridge circuit, the source terminal of the MOSFET Q11 is connected to the negative output terminal of the transformer T1, the gate terminal of the MOSFET Q11 is connected to the output terminal GS11 of the full-bridge drive circuit, the drain terminal of the MOSFET Q12 is connected to the positive output terminal Vo of the full-bridge circuit, the source terminal of the MOSFET Q12 is connected to the positive output terminal of the transformer T1, and the gate terminal of the MOSFET Q12 is connected to the output terminal of the full-bridge drive circuit.

[0018] Optionally, the current detection circuit includes resistors R2, R3, R4, R5, R6, and R7, capacitor C7, and chip U1;

[0019] The power supply terminal of chip U1 is connected to the voltage terminal VCC1, and the ground terminal of chip U1 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. The positive input terminal of chip U1 is connected to one end of resistors R2, R3, and R4, respectively. The other end of resistor R2 is connected to the voltage terminal VCC1, the other end of resistor R3 is connected to the output ground terminal GND of the four-transistor BUCK-BOOST circuit, and the other end of resistor R4 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. The negative input terminal of chip U1 is connected to the voltage terminal VCC1, the ground terminal of R3, and the ground terminal of R4. One end of resistor R5 and one end of resistor R6 are connected to the input ground GND1 of the four-transistor BUCK-BOOST circuit, and the other end of resistor R6 is connected to the output terminal of chip U1. One end of resistor R7 is connected to the output terminal of chip U1, and the other end of resistor R7 is connected to the output terminal Vcs of the current detection circuit. One end of capacitor C7 is connected to the input ground GND1 of the four-transistor BUCK-BOOST circuit, and the other end of capacitor C7 is connected to the output terminal of the current detection circuit. The output terminal of the current detection circuit is connected to the input terminal of the main control circuit.

[0020] Optionally, the current detection circuit further includes capacitors C5 and C6. Capacitor C5 is connected between the positive input terminal of the chip U1 and the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit, and capacitor C6 is connected between the negative input terminal of the chip U1 and the output terminal of the chip U1.

[0021] Optionally, the bus voltage detection circuit includes resistors R7 and R9;

[0022] One end of resistor R7 is connected to the positive output terminal V1 of the four-transistor BUCK-BOOST circuit, and the other end of resistor R7 is connected to the output terminal V1_S of the bus voltage detection circuit. One end of resistor R9 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit, and the other end of resistor R9 is connected to the output terminal of the bus voltage detection circuit. The output terminal of the bus voltage detection circuit is connected to the input terminal of the main control circuit.

[0023] Optionally, the bus voltage detection circuit further includes a capacitor C8, which is connected between the output terminal V1_S of the bus voltage detection circuit and the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit.

[0024] Optionally, the output voltage detection circuit includes resistors R10 and R11 and chip U2;

[0025] The input power supply terminal of chip U2 is connected to voltage terminal VCC2, the output power supply terminal of chip U2 is connected to voltage terminal VCC2, the input ground terminal of chip U2 is connected to the output ground terminal GND2 of the full-bridge circuit, the output ground terminal of chip U2 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit, the input terminal of chip U2 is connected to one end of resistor R10 and resistor R11 respectively, the other end of resistor R10 is connected to the positive output terminal Vo of the full-bridge circuit, the other end of resistor R11 is connected to the output ground terminal GND2 of the full-bridge circuit, the output terminal of chip U2 is connected to the output terminal of the output voltage detection circuit, and the output terminal of the output voltage detection circuit is connected to the output terminal of the output voltage detection circuit.

[0026] Optionally, the output voltage detection circuit further includes capacitors C9 and C10. Capacitor C9 is connected between the output terminal of the output voltage detection circuit and the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit, and capacitor C10 is connected between the input terminal of the chip U2 and the output ground terminal GND2 of the full-bridge circuit.

[0027] The beneficial effects of this utility model are as follows:

[0028] 1. When the DC-DC converter is turned off and then turned on again, the reverse current from the output to the input can be effectively reduced, thereby effectively avoiding damage to power transistors and other devices.

[0029] 2. When the input is powered off or briefly interrupted, the DC-DC converter can effectively reduce the reverse current from the output to the input, thereby effectively preventing damage to power transistors and other devices.

[0030] 3. When the DC-DC converter is powered off and then restarted, the positive impact current from the input of the full-bridge circuit to the output can be effectively reduced, thereby effectively preventing damage to power transistors and other components. Attached Figure Description

[0031] Figure 1 This is a circuit block diagram of a DC-DC converter according to the present invention.

[0032] Figure 2 This is a circuit diagram of a four-transistor BUCK-BOOST circuit in a DC-DC converter according to the present invention.

[0033] Figure 3 This is a circuit diagram of a full-bridge circuit in a DC-DC converter according to the present invention.

[0034] Figure 4 This is a circuit diagram of a current detection circuit in a DC-DC converter according to the present invention.

[0035] Figure 5 This is a circuit diagram of a bus voltage detection circuit in a DC-DC converter according to the present invention.

[0036] Figure 6 This is a circuit diagram of the output voltage detection circuit in a DC-DC converter according to the present invention.

[0037] Figure 7 This is a circuit diagram of the main control circuit in a DC-DC converter according to the present invention.

[0038] Figure 8 This is a circuit diagram of a BUCK-BOOST drive circuit in a DC-DC converter according to the present invention.

[0039] Figure 9 This is a circuit diagram of a full-bridge drive circuit in a DC-DC converter according to the present invention.

[0040] Figure 10 This is a circuit diagram of an isolated drive transmission circuit in a DC-DC converter according to the present invention.

[0041] Figure 11 This is a circuit diagram of a synchronous rectification drive circuit in a DC-DC converter according to the present invention. Detailed Implementation

[0042] The present invention and its beneficial effects will be further described in detail below with reference to specific embodiments and accompanying drawings. However, the specific embodiments of the present invention are not limited thereto.

[0043] First Embodiment

[0044] Figures 1 to 11 The diagram shown is a circuit diagram of a first embodiment of a DC-DC converter according to this utility model, including a four-transistor BUCK-BOOST circuit, a full-bridge circuit, a current detection circuit, a bus voltage detection circuit, an output voltage detection circuit, a BUCK-BOOST drive circuit, a full-bridge drive circuit, an isolated drive transmission circuit, a synchronous rectification drive circuit, and a main control circuit.

[0045] The positive input terminal Vin of the four-transistor BUCK-BOOST circuit is connected to the positive input terminal of the DC-DC converter, the ground input terminal GND1 of the four-transistor BUCK-BOOST circuit is connected to the ground input terminal of the DC-DC converter, the positive output terminal V1 of the four-transistor BUCK-BOOST circuit is connected to the positive input terminal of the full-bridge circuit, and the ground output terminal GND of the four-transistor BUCK-BOOST circuit is connected to the ground input terminal of the full-bridge circuit.

[0046] The four-transistor BUCK-BOOST circuit includes capacitor C1, capacitor C2, MOSFET Q1, MOSFET Q2, MOSFET Q3, MOSFET Q4, inductor L1, and resistor R1.

[0047] Capacitor C1 is connected between the positive input terminal Vin and the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. Capacitor C2 is connected between the positive output terminal V1 and the output ground terminal GND of the four-transistor BUCK-BOOST circuit. The drain of MOSFET Q1 is connected to the positive input terminal Vin of the four-transistor BUCK-BOOST circuit. The source terminal of MOSFET Q1 is connected to the drain of MOSFET Q2. The gate terminal of MOSFET Q1 is connected to the output terminal GS1 of the BUCK-BOOST drive circuit. The drain terminal of MOSFET Q2 is connected to the source terminal of MOSFET Q1. The source terminal of MOSFET Q2 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. The gate terminal of MOSFET Q2 is connected to the output terminal GS2 of the BUCK-BOOST drive circuit. The drain (D) of MOSFET Q3 is connected to the source (S) of MOSFET Q4. The source (S) of MOSFET Q3 is connected to the input ground GND1 of the four-transistor BUCK-BOOST circuit. The gate (G) of MOSFET Q3 is connected to the output GS3 of the BUCK-BOOST driver circuit. The source (S) of MOSFET Q4 is connected to the drain (D) of MOSFET Q3. The drain (D) of MOSFET Q4 is connected to the positive output V1 of the four-transistor BUCK-BOOST circuit. The gate (G) of MOSFET Q4 is connected to the output GS4 of the BUCK-BOOST driver circuit. The inductor L1 is connected between the source (S) of MOSFET Q1 and the source (S) of MOSFET Q4. The resistor R1 is connected between the input ground GND1 and the output ground GND of the four-transistor BUCK-BOOST circuit.

[0048] The positive input terminal V1 of the full-bridge circuit is connected to the positive output terminal V1 of the four-transistor BUCK-BOOST circuit, the ground input terminal GND of the full-bridge circuit is connected to the ground output terminal GND of the four-transistor BUCK-BOOST circuit, the positive output terminal Vo of the full-bridge circuit is connected to the positive output terminal of the DC-DC converter, and the ground output terminal GND2 of the full-bridge circuit is connected to the ground output terminal of the DC-DC converter.

[0049] The full-bridge circuit includes capacitor C3, capacitor C4, MOSFETs Q5, Q6, Q7, Q8, Q9, Q10, Q11, Q12 and transformer T1.

[0050] The capacitor C3 is connected between the positive input terminal V1 and the input ground terminal GND of the full-bridge circuit, and the capacitor C4 is connected between the positive output terminal Vo and the output ground terminal GND2 of the full-bridge circuit. The transformer T1 has four ports: positive input, negative input, positive output, and negative output. The positive input and positive output are the same type of terminals, and the negative input and negative output are also the same type of terminals. The drain (D) of MOSFET Q5 is connected to the positive input terminal of transformer T1, the source (S) of MOSFET Q5 is connected to the input ground GND of the full-bridge circuit, and the gate (G) of MOSFET Q5 is connected to the output terminal GS5 of the full-bridge drive circuit. The drain (D) of MOSFET Q6 is connected to the negative input terminal of transformer T1, the source (S) of MOSFET Q6 is connected to the input ground GND of the full-bridge circuit, and the gate (G) of MOSFET Q6 is connected to the output terminal GS6 of the full-bridge drive circuit. The drain (D) of MOSFET Q7 is connected to the positive input terminal V1 of the full-bridge circuit, the source (S) of MOSFET Q7 is connected to the negative input terminal of transformer T1, and the gate (G) of MOSFET Q7 is connected to the output terminal GS7 of the full-bridge drive circuit. The drain (D) of MOSFET Q8 is connected to the positive input terminal V1 of the full-bridge circuit, the source (S) of MOSFET Q8 is connected to the positive input terminal of transformer T1, and the gate (G) of MOSFET Q8 is connected to the output terminal GS8 of the full-bridge drive circuit. The drain (D) of MOSFET Q9 ... input ground GND of the full-bridge circuit, and the gate (G The drain (D) of the MOSFET Q9 is connected to the positive output terminal of the transformer T1. The source (S) of the MOSFET Q9 is connected to the output ground GND2 of the full-bridge circuit. The gate (G) of the MOSFET Q9 is connected to the output terminal GS9 of the full-bridge drive circuit. The drain (D) of the MOSFET Q10 is connected to the negative output terminal of the transformer T1. The source (S) of the MOSFET Q10 is connected to the output ground GND2 of the full-bridge circuit. The gate (G) of the MOSFET Q10 is connected to the output terminal GS10 of the full-bridge drive circuit. The drain (D) of the MOSFET Q11 is connected to the positive output terminal Vo of the full-bridge circuit. The source (S) of the MOSFET Q11 is connected to the negative output terminal of the transformer T1. The gate (G) of the MOSFET Q11 is connected to the output terminal GS11 of the full-bridge drive circuit. The drain (D) of the MOSFET Q12 is connected to the positive output terminal Vo of the full-bridge circuit. The source (S) of the MOSFET Q12 is connected to the positive output terminal T1 of the transformer T1. The gate (G) of the MOSFET Q12 is connected to the output terminal GS12 of the full-bridge drive circuit.

[0051] The current detection circuit includes resistors R2, R3, R4, R5, R6, R7, capacitor C7, and chip U1.

[0052] The chip U1 has five ports: power supply, ground, positive input, negative input, and output. The power supply port of chip U1 is connected to voltage terminal VCC1. The ground port of chip U1 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. The positive input port of chip U1 is connected to one end of resistors R2, R3, and R4. The other end of resistor R2 is connected to voltage terminal VCC1. The other end of resistor R3 is connected to the output ground terminal GND of the four-transistor BUCK-BOOST circuit. The other end of resistor R4 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. The negative input terminal of chip U1 is connected to one end of resistors R5 and R6. The other end of resistor R5 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. The other end of resistor R6 is connected to the output terminal of chip U1. One end of resistor R7 is connected to the output terminal of chip U1. The other end of resistor R7 is connected to the output terminal Vcs of the current detection circuit. One end of capacitor C7 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. The other end of capacitor C7 is connected to the output terminal Vcs of the current detection circuit. The output terminal Vcs of the current detection circuit is connected to the input terminal Vcs of the main control circuit.

[0053] Preferably, the current detection circuit further includes capacitors C5 and C6. Capacitor C5 is connected to the positive input terminal of the chip U1 and the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit, and capacitor C6 is connected to the negative input terminal of the chip U1 and the output terminal Vcs of the chip U1.

[0054] The bus voltage detection circuit includes resistors R7 and R9.

[0055] One end of resistor R7 is connected to the positive output terminal V1 of the four-transistor BUCK-BOOST circuit, and the other end of resistor R7 is connected to the output terminal V1_S of the bus voltage detection circuit. One end of resistor R9 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit, and the other end of resistor R9 is connected to the output terminal V1_S of the bus voltage detection circuit. The output terminal V1_S of the bus voltage detection circuit is connected to the input terminal V1_S of the main control circuit.

[0056] Preferably, the bus voltage detection circuit further includes a capacitor C8, which is connected to the output terminal V1_S of the bus voltage detection circuit and the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit.

[0057] The output voltage detection circuit includes resistors R10 and R11 and chip U2.

[0058] The chip U2 has six ports: input power supply VDD2, output power supply VDD1, input ground GND2, output ground GND1, input IN, and output OUT. The input power supply of chip U2 is connected to voltage terminal VCC2, the output power supply of chip U2 is connected to voltage terminal VCC2, the input ground of chip U2 is connected to the output ground GND2 of the full-bridge circuit, the output ground of chip U2 is connected to the input ground GND1 of the four-transistor BUCK-BOOST circuit, the input of chip U2 is connected to one end of resistors R10 and R11, the other end of resistor R10 is connected to the positive output Vo of the full-bridge circuit, the other end of resistor R11 is connected to the output ground GND2 of the full-bridge circuit, the output of chip U2 is connected to the output Vo_S of the output voltage detection circuit, and the output Vo_S of the output voltage detection circuit is connected to the output Vo_S of the output voltage detection circuit.

[0059] Preferably, the output voltage detection circuit further includes capacitors C9 and C10. Capacitor C9 is connected between the output terminal Vo_S of the output voltage detection circuit and the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. Capacitor C10 is connected between the input terminal of chip U2 and the output ground terminal GND2 of the full-bridge circuit.

[0060] The main control circuit includes one power supply terminal, one ground terminal, four input terminals, and eight output terminals. The power supply terminal of the main control circuit is connected to the voltage terminal VCC1, and the ground terminal of the main control circuit is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. The four input terminals of the main control circuit include input terminal Vin, input terminal V1_S, input terminal Vo_S, and input terminal Vcs. Input terminal Vin of the main control circuit is connected to the positive input terminal Vin of the four-transistor BUCK-BOOST circuit. Input terminal V1_S of the main control circuit is connected to the output terminal V1_S of the bus voltage detection circuit. Input terminal Vo_S of the main control circuit is connected to the output terminal Vo_S of the output voltage detection circuit. Input terminal Vcs of the main control circuit is connected to the output terminal Vcs of the current detection circuit. The main control circuit has eight output terminals, including output terminal GS_1, output terminal GS_2, output terminal GS_3, output terminal GS_4, output terminal GS_5, output terminal GS_6, output terminal GS_7, and output terminal GS_8. Output terminal GS_1 is connected to input terminal GS_1 of the BUCK-BOOST driver circuit. Output terminal GS_2 is connected to input terminal GS_2 of the BUCK-BOOST driver circuit. Output terminal GS_3 is connected to input terminal GS_3 of the BUCK-BOOST driver circuit. Output terminal GS_4 is connected to input terminal GS_4 of the BUCK-BOOST driver circuit. Output terminal GS_5 is connected to input terminal GS_5 of the full-bridge driver circuit. Output terminal GS_6 is connected to input terminal GS_6 of the full-bridge driver circuit. Output terminal GS_7 is connected to input terminal GS_7 of the isolation driver circuit. Output terminal GS_8 is connected to input terminal GS_8 of the isolation driver circuit.

[0061] The BUCK-BOOST driver circuit includes chip U4 and chip U5.

[0062] The chip U4 includes six ports: a power supply terminal, a ground terminal, two input terminals, and two output terminals. The power supply terminal of chip U4 is connected to power supply VCC3. The ground terminal of chip U4 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. One input terminal of chip U4 is connected to the input terminal GS_1 of the BUCK-BOOST driver circuit, and the other input terminal of chip U4 is connected to the input terminal GS_2 of the BUCK-BOOST driver circuit. One output terminal of chip U4 is connected to the output terminal GS1 of the BUCK-BOOST driver circuit, and the other output terminal of chip U4 is connected to the output terminal GS2 of the BUCK-BOOST driver circuit.

[0063] The chip U5 includes six ports: a power supply terminal, a ground terminal, two input terminals, and two output terminals. The power supply terminal of chip U5 is connected to power supply VCC3. The ground terminal of chip U5 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. One input terminal of chip U5 is connected to input terminal G3_2 of the BUCK-BOOST driver circuit, and the other input terminal of chip U5 is connected to input terminal G4_2 of the BUCK-BOOST driver circuit. One output terminal of chip U5 is connected to output terminal GS3 of the BUCK-BOOST driver circuit, and the other output terminal of chip U5 is connected to output terminal GS4 of the BUCK-BOOST driver circuit.

[0064] The full-bridge drive circuit includes chip U6 and chip U7.

[0065] The chip U6 includes six ports: a power supply terminal, a ground terminal, two input terminals, and two output terminals. The power supply terminal of chip U6 is connected to power supply VCC3. The ground terminal of chip U6 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. One input terminal of chip U6 is connected to the input terminal GS_6 of the BUCK-BOOST driver circuit, and the other input terminal of chip U6 is connected to the input terminal GS_5 of the BUCK-BOOST driver circuit. One output terminal of chip U6 is connected to the output terminal GS8 of the BUCK-BOOST driver circuit, and the other output terminal of chip U6 is connected to the output terminal GS5 of the BUCK-BOOST driver circuit.

[0066] The chip U7 includes six ports: a power supply terminal, a ground terminal, two input terminals, and two output terminals. The power supply terminal of chip U7 is connected to power supply VCC3. The ground terminal of chip U7 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. One input terminal of chip U7 is connected to the input terminal GS_5 of the BUCK-BOOST driver circuit, and the other input terminal of chip U7 is connected to the input terminal GS_6 of the BUCK-BOOST driver circuit. One output terminal of chip U7 is connected to the output terminal GS7 of the BUCK-BOOST driver circuit, and the other output terminal of chip U7 is connected to the output terminal GS6 of the BUCK-BOOST driver circuit.

[0067] The isolation drive circuit includes chip U8.

[0068] The chip U8 has 8 ports, namely an input power supply terminal, an output power supply terminal, an input ground terminal, an output ground terminal, 2 input terminals, and 2 output terminals.

[0069] The input power supply terminal of chip U8 is connected to voltage terminal VCC1, the output power supply terminal of chip U8 is connected to voltage terminal VCC2, the input ground terminal of chip U8 is connected to the input ground terminal GND1 of the power supply four-transistor BUCK-BOOST circuit, the output ground terminal of chip U8 is connected to the output ground terminal GND2 of the power supply full-bridge circuit, one input terminal GS_8 of chip U8 is connected to the input terminal GS_8 of the isolation driver circuit, the other input terminal GS_7 of chip U8 is connected to the input terminal GS_7 of the isolation driver circuit, one output terminal GS_8S of chip U8 is connected to the output terminal GS_8S of the isolation driver circuit, and the other output terminal GS_7S of chip U8 is connected to the output terminal GS_7S of the isolation driver circuit.

[0070] The output terminal GS_8S of the isolation drive circuit is connected to the input terminal GS_8S of the synchronous drive circuit, and the output terminal GS_7S of the isolation drive circuit is connected to the input terminal GS_7S of the synchronous drive circuit.

[0071] The synchronous rectification drive circuit includes chip U9 and chip U10.

[0072] The chip U9 includes six ports: a power supply terminal, a ground terminal, two input terminals, and two output terminals. The power supply terminal of chip U9 is connected to power supply VCC3. The ground terminal of chip U9 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. One input terminal of chip U9 is connected to the input terminal GS_8S of the synchronous rectification drive circuit, and the other input terminal of chip U9 is connected to the input terminal GS_7S of the synchronous rectification drive circuit. One output terminal of chip U9 is connected to the output terminal GS12 of the synchronous rectification drive circuit, and the other output terminal of chip U9 is connected to the output terminal GS9 of the BUCK-BOOST drive circuit.

[0073] The chip U10 includes six ports: a power supply terminal, a ground terminal, two input terminals, and two output terminals. The power supply terminal of chip U10 is connected to power supply VCC3. The ground terminal of chip U10 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. One input terminal of chip U10 is connected to the input terminal GS_7S of the synchronous rectification drive circuit, and the other input terminal of chip U10 is connected to the input terminal GS_8S of the synchronous rectification drive circuit. One output terminal of chip U10 is connected to the output terminal GS11 of the synchronous rectification drive circuit, and the other output terminal of chip U9 is connected to the output terminal GS10 of the BUCK-BOOST drive circuit.

[0074] The working principle of this utility model is analyzed in detail below:

[0075] 1. The DC-DC converter detects the output current I1 of the four-transistor BUCK-BOOST circuit through a current detection circuit, the output voltage V1 of the four-transistor BUCK-BOOST circuit through a bus voltage detection circuit, and the output voltage Vo of the DC-DC converter through an output voltage detection circuit. Given that the efficiency of the full-bridge circuit is η and the output current of the DC-DC converter is Io, by the law of conservation of energy, we know that: V1*I1*η=Vo*Io, that is, Io=V1*I1*η / Vo.

[0076] When the output is unloaded or lightly loaded and has a large capacitor, the voltage of the large output capacitor will not discharge quickly after the DC-DC converter is powered off. When the power is turned on again after a power-off and a synchronous rectification drive signal is generated, the large output capacitor will cause reverse current to flow into the input. The current value of Io can be indirectly calculated by detecting the current value of I1, without needing to directly detect the output current Io. If the output current Io were directly detected, it would require isolation and transmission to the primary-side main control circuit. Using an indirect output current detection scheme optimizes the circuit design, reduces PCB board area, and lowers the cost of the DC-DC converter.

[0077] When the DC-DC converter is working normally, the current flowing through resistor R1 is I1. The positive voltage drop across resistor R1 is VR1, which is the voltage drop from the output GND of the four-transistor BUCK-BOOST circuit to the input GND1 of the four-transistor BUCK-BOOST circuit, equal to I1 * R1. Resistor R2 acts as a compensation, transmitting the negative current to the main control circuit through the current detection circuit. The current detection circuit amplifies the lower detected voltage VR1 and outputs it through the chip's output terminal. Resistors R7 and C7 act as filters, converting the AC voltage signal into a DC voltage signal.

[0078] The current detection circuit transmits the detected output current Io of the DC-DC converter to the main control circuit in real time. The main control circuit compares the output current Io with a certain set current value. When the current Io is less than the set current value, the main control circuit does not generate a synchronous rectification drive signal. Furthermore, through the isolation drive transmission circuit and the synchronous rectification drive circuit, the synchronous rectifier diodes in the full-bridge circuit are left without a drive signal, remaining in a unidirectional conduction state. Therefore, when the DC-DC converter is restarted after being turned off, the reverse current from the output to the input can be effectively reduced, thus effectively preventing damage to power transistors and other components.

[0079] 2. The aforementioned DC-DC converter detects the output voltage V1 of the four-transistor BUCK-BOOST circuit through a bus voltage detection circuit, and the output voltage Vo of the DC-DC converter through an output voltage detection circuit. The output voltage Vo is referred to the input voltage of the full-bridge circuit through a transformer, which is Vo'. When V1 is less than Vo', reverse current may occur.

[0080] The bus voltage detection circuit transmits the output voltage V1 of the four-transistor BUCK-BOOST circuit and the output voltage Vo of the DC-DC converter detected by the bus voltage detection circuit to the main control circuit in real time. The main control circuit compares V1 and Vo'. When the voltage V1-Vo' is lower than a certain value, the main control circuit does not generate a synchronous rectification drive signal. Through the isolation drive transmission circuit and the synchronous rectification drive circuit, the synchronous rectifier tubes in the full-bridge circuit have no drive signal and are in a unidirectional conduction state.

[0081] The aforementioned DC-DC converter also detects the output current I1 of the four-transistor BUCK-BOOST circuit through a current detection circuit. When the output current I1 is a negative current, it indicates that there is a reverse current flow from the output to the input.

[0082] The current detection circuit transmits the detected output current I1 of the four-transistor BUCK-BOOST circuit to the main control circuit in real time. The main control circuit compares the output current I1 with a certain set current value. When the current of I1 is lower than a certain set current value, the main control circuit does not generate a synchronous rectification drive signal. Instead, through the isolation drive transmission circuit and the synchronous rectification drive circuit, the synchronous rectifier tubes in the full-bridge circuit are left without a drive signal and are in a unidirectional conduction state.

[0083] Therefore, when the DC-DC converter is turned off and then turned on again, the reverse current from the output to the input can be effectively reduced, thereby effectively preventing damage to power transistors and other devices.

[0084] 3. During the power-off process of the DC-DC converter, if the voltage on the input filter capacitor of the full-bridge circuit cannot be effectively discharged, the input capacitor of the full-bridge circuit will discharge to the output capacitor through the transformer when the power is turned on again after the input is turned off. Since the AC impedance of the input and output filter capacitors is small, a large positive inrush current will be generated.

[0085] Therefore, during the power-off process of the DC-DC converter input, the main control circuit continues to generate a drive signal for a certain period of time. This drive signal is transmitted to the primary-side power transistors of the full-bridge drive circuit, allowing them to continue operating for a short period. The output capacitor of the four-transistor BUCK-BOOST circuit can be effectively discharged through the losses of the primary-side power transistors in the two-stage power circuit, transformer losses, and the output load of the DC-DC converter. Even when the output of the DC-DC converter is unloaded, it can still be effectively discharged through the losses of the primary-side power transistors and transformer losses. Furthermore, this scheme does not affect the efficiency or other performance characteristics of the DC-DC converter during normal operation.

[0086] Therefore, when the DC-DC converter is turned off and then turned on again, the positive impact current from the input of the full-bridge circuit to the output can be effectively reduced, thereby avoiding damage to power transistors and other devices.

[0087] The above-described embodiments of this utility model are merely illustrative examples and not intended to limit the implementation of this utility model. Those skilled in the art can make other variations and modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this utility model are still within the protection scope of this utility model.

Claims

1. A DC-DC converter, characterized in that, The DC-DC converter includes a four-transistor BUCK-BOOST circuit, a full-bridge circuit, a BUCK-BOOST drive circuit, a full-bridge drive circuit, an isolated drive transmission circuit, a synchronous rectification drive circuit, a main control circuit, a current detection circuit, a bus voltage detection circuit, and an output voltage detection circuit. The input terminal of the four-transistor BUCK-BOOST circuit is the input terminal of the DC-DC converter. The output terminal of the four-transistor BUCK-BOOST circuit is connected to the input terminal of the full-bridge circuit. The output terminal of the full-bridge circuit is the output terminal of the DC-DC converter. The BUCK-BOOST drive circuit is connected between the four-transistor BUCK-BOOST circuit and the main control circuit. The full-bridge drive circuit is connected between the full-bridge circuit and the main control circuit. The synchronous rectification drive circuit is connected between the full-bridge circuit and the isolated drive transmission circuit. The isolated drive transmission circuit is connected between the synchronous rectification drive circuit and the main control circuit. The current detection circuit is connected between the four-transistor BUCK-BOOST circuit and the main control circuit. The bus voltage detection circuit is connected between the output terminal of the four-transistor BUCK-BOOST circuit and the main control circuit. The output voltage detection circuit is connected between the output terminal of the DC-DC converter and the main control circuit.

2. A DC-DC converter according to claim 1, characterized in that: The four-transistor BUCK-BOOST circuit includes capacitor C1, capacitor C2, MOSFET Q1, MOSFET Q2, MOSFET Q3, MOSFET Q4, inductor L1, and resistor R1; Capacitor C1 is connected between the positive input terminal Vin and the input ground GND1 of the four-transistor BUCK-BOOST circuit. Capacitor C2 is connected between the positive output terminal V1 and the output ground GND of the four-transistor BUCK-BOOST circuit. The drain (D) of MOSFET Q1 is connected to the positive input terminal Vin of the four-transistor BUCK-BOOST circuit. The source (S) of MOSFET Q1 is connected to the drain (D) of MOSFET Q2. The gate (G) of MOSFET Q1 is connected to the output terminal GS1 of the BUCK-BOOST drive circuit. The source (S) of MOSFET Q2 is connected to the input ground GND1 of the four-transistor BUCK-BOOST circuit. The gate (G) of MOSFET Q2 is connected to the output terminal GS2 of the BUCK-BOOST drive circuit. The drain (D) of MOSFET Q3 is connected to... The source (S) terminal of MOSFET Q4 and the source (S) terminal of MOSFET Q3 are connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. The gate (G) terminal of MOSFET Q3 is connected to the output terminal GS3 of the BUCK-BOOST drive circuit. The source (S) terminal of MOSFET Q4 is connected to the drain (D) terminal of MOSFET Q3. The drain (D) terminal of MOSFET Q4 is connected to the positive output terminal V1 of the four-transistor BUCK-BOOST circuit. The gate (G) terminal of MOSFET Q4 is connected to the output terminal GS4 of the BUCK-BOOST drive circuit. The inductor L1 is connected between the source (S) terminals of MOSFET Q1 and Q4. The resistor R1 is connected between the input ground terminal GND1 and the output ground terminal GND of the four-transistor BUCK-BOOST circuit.

3. A DC-DC converter according to claim 1, characterized in that: The full-bridge circuit includes capacitor C3, capacitor C4, MOSFETs Q5, Q6, Q7, Q8, Q9, Q10, Q11, Q12 and transformer T1; Capacitor C3 is connected between the positive input terminal V1 and the input ground terminal GND of the full-bridge circuit. Capacitor C4 is connected between the positive output terminal Vo and the output ground terminal GND2 of the full-bridge circuit. The drain of MOSFET Q5 is connected to the positive input terminal of transformer T1. The source of MOSFET Q5 is connected to the input ground terminal GND of the full-bridge circuit. The gate of MOSFET Q5 is connected to the output terminal GS5 of the full-bridge drive circuit. The drain of MOSFET Q6 is connected to the negative input terminal of transformer T1. The source (S) of the MOSFET Q6 is connected to the input ground GND of the full-bridge circuit. The gate (G) of the MOSFET Q6 is connected to the output GS6 of the full-bridge drive circuit. The drain (D) of the MOSFET Q7 is connected to the positive input V1 of the full-bridge circuit. The source (S) of the MOSFET Q7 is connected to the negative input of the transformer T1. The gate (G) of the MOSFET Q7 is connected to the output GS7 of the full-bridge drive circuit. The drain (D) of the MOSFET Q8 is connected to the positive input V1 of the full-bridge circuit. The source (S) of the MOSFET Q8 is connected to the positive input of the transformer T1. The gate (G) of MOSFET Q8 is connected to the output terminal GS8 of the full-bridge drive circuit. The drain (D) of MOSFET Q9 is connected to the positive output terminal of transformer T1. The source (S) of MOSFET Q9 is connected to the output ground GND2 of the full-bridge circuit. The gate (G) of MOSFET Q9 is connected to the output terminal GS9 of the full-bridge drive circuit. The drain (D) of MOSFET Q10 is connected to the negative output terminal of transformer T1. The source (S) of MOSFET Q10 is connected to the output ground GND2 of the full-bridge circuit. The gate (G) of MOSFET Q10 is connected to... The output terminal GS10 of the full-bridge drive circuit is connected to the positive output terminal Vo of the full-bridge circuit, the source terminal of the MOSFET Q11 is connected to the negative output terminal of the transformer T1, the gate terminal of the MOSFET Q11 is connected to the output terminal GS11 of the full-bridge drive circuit, the drain terminal of the MOSFET Q12 is connected to the positive output terminal Vo of the full-bridge circuit, the source terminal of the MOSFET Q12 is connected to the positive output terminal of the transformer T1, and the gate terminal of the MOSFET Q12 is connected to the output terminal of the full-bridge drive circuit.

4. A DC-DC converter according to claim 1, characterized in that: The current detection circuit includes resistors R2, R3, R4, R5, R6, and R7, capacitor C7, and chip U1. The power supply terminal of chip U1 is connected to the voltage terminal VCC1, and the ground terminal of chip U1 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. The positive input terminal of chip U1 is connected to one end of resistors R2, R3, and R4, respectively. The other end of resistor R2 is connected to the voltage terminal VCC1, the other end of resistor R3 is connected to the output ground terminal GND of the four-transistor BUCK-BOOST circuit, and the other end of resistor R4 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit. The negative input terminal of chip U1 is connected to the voltage terminal VCC1, the ground terminal of R3, and the ground terminal of R4. One end of resistor R5 and one end of resistor R6 are connected to the input ground GND1 of the four-transistor BUCK-BOOST circuit, and the other end of resistor R6 is connected to the output terminal of chip U1. One end of resistor R7 is connected to the output terminal of chip U1, and the other end of resistor R7 is connected to the output terminal Vcs of the current detection circuit. One end of capacitor C7 is connected to the input ground GND1 of the four-transistor BUCK-BOOST circuit, and the other end of capacitor C7 is connected to the output terminal of the current detection circuit. The output terminal of the current detection circuit is connected to the input terminal of the main control circuit.

5. A DC-DC converter according to claim 4, characterized in that: The current detection circuit also includes capacitors C5 and C6. Capacitor C5 is connected between the positive input terminal of chip U1 and the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit, and capacitor C6 is connected between the negative input terminal of chip U1 and the output terminal of chip U1.

6. A DC-DC converter according to claim 1, characterized in that: The bus voltage detection circuit includes resistors R7 and R9; One end of resistor R7 is connected to the positive output terminal V1 of the four-transistor BUCK-BOOST circuit, and the other end of resistor R7 is connected to the output terminal V1_S of the bus voltage detection circuit. One end of resistor R9 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit, and the other end of resistor R9 is connected to the output terminal of the bus voltage detection circuit. The output terminal of the bus voltage detection circuit is connected to the input terminal of the main control circuit.

7. A DC-DC converter according to claim 6, characterized in that: The bus voltage detection circuit also includes a capacitor C8, which is connected between the output terminal V1_S of the bus voltage detection circuit and the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit.

8. A DC-DC converter according to claim 1, characterized in that: The output voltage detection circuit includes resistor R10, resistor R11, and chip U2; The input power supply terminal of chip U2 is connected to voltage terminal VCC2, the output power supply terminal of chip U2 is connected to voltage terminal VCC2, the input ground terminal of chip U2 is connected to the output ground terminal GND2 of the full-bridge circuit, the output ground terminal of chip U2 is connected to the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit, the input terminal of chip U2 is connected to one end of resistor R10 and resistor R11 respectively, the other end of resistor R10 is connected to the positive output terminal Vo of the full-bridge circuit, the other end of resistor R11 is connected to the output ground terminal GND2 of the full-bridge circuit, the output terminal of chip U2 is connected to the output terminal of the output voltage detection circuit, and the output terminal of the output voltage detection circuit is connected to the output terminal of the output voltage detection circuit.

9. A DC-DC converter according to claim 8, characterized in that: The output voltage detection circuit also includes capacitors C9 and C10. Capacitor C9 is connected between the output terminal of the output voltage detection circuit and the input ground terminal GND1 of the four-transistor BUCK-BOOST circuit, and capacitor C10 is connected between the input terminal of the chip U2 and the output ground terminal GND2 of the full-bridge circuit.

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