Small size buck converter circuit suitable for low power applications

Abstract

The present invention relates to a small-volume BUCK converter circuit suitable for low-power applications, which includes a voltage stabilizing circuit, a BUCK converter main topology circuit, a feedback and control circuit, and an overcurrent protection circuit; the voltage stabilizing circuit includes a first resistor, a first capacitor, and a voltage stabilizing tube; the BUCK converter main topology circuit includes a first triode, a freewheeling diode, a filter inductor, and a filter capacitor; the feedback and control circuit includes a third capacitor, a second triode, a second resistor, and a third resistor; the overcurrent protection circuit includes a fourth resistor, a fifth resistor, a sixth resistor, and a third triode. The present invention uses capacitors and triodes to form a feedback circuit, and uses resistors and triodes to form a protection circuit, thereby reducing the complexity of the control and protection circuits and reducing the area of ​​the printed circuit board of the power supply system.

Description

Technical Field

[0001] The invention relates to a small-power and small-volume BUCK converter circuit, in particular to a small-volume BUCK converter circuit suitable for small-power applications. Background Art

[0002] In the power supply system of aerospace applications, the secondary power supply usually uses a shelf power supply module to convert the aircraft power supply 28V to 5V, and then convert it to 3.3V and 1.8V through a linear power supply to power digital processing chips. Therefore, the entire secondary power supply system is large in size. When the required power system power is small, or the controller volume and printed circuit board area are limited, it will restrict the design of the secondary power supply system. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a small-volume BUCK converter circuit suitable for low-power applications that can reduce the number of components and greatly reduce the required printed circuit board area.

[0004] According to the technical solution provided by the present invention, the small-volume BUCK converter circuit suitable for low-power applications includes a voltage stabilizing circuit, a BUCK converter main topology circuit, a feedback and control circuit, and an overcurrent protection circuit;

[0005] The voltage stabilizing circuit includes a first resistor, a first capacitor and a voltage stabilizing tube; the main topology circuit of the BUCK converter includes a first transistor, a freewheeling diode, a filter inductor and a filter capacitor; the feedback and control circuit includes a third capacitor, a second transistor, a second resistor and a third resistor; the overcurrent protection circuit includes a fourth resistor, a fifth resistor, a sixth resistor and a third transistor;

[0006] A DC power supply is connected to the emitter of the first triode, a collector of the first triode is connected to one end of the inductor and the cathode of the freewheeling diode, the other end of the inductor is connected to one end of the filter capacitor and one end of the sixth resistor, the other end of the filter capacitor is connected to the anode of the diode and one end of the load and is grounded, and the other end of the sixth resistor is connected to the other end of the load;

[0007] A second resistor is connected in parallel between the emitter and base of the first triode, one end of the third resistor is connected to the base of the first triode, the other end of the third resistor is connected to the collector of the second triode, the emitter of the second triode is connected to the emitter of the third triode, one end of the third capacitor is connected to the base of the second triode, and the other end of the third capacitor is connected to the collector of the first triode;

[0008] One end of the first resistor is connected to a DC power supply, the other end of the first resistor is connected to one end of the first capacitor and the cathode of the voltage regulator tube and the base of the second transistor, and the other end of the first capacitor C1 and the anode of the voltage regulator tube are connected to the ground terminal of the DC power supply;

[0009] One end of the fifth resistor is connected to one end of the inductor, the other end of the fifth resistor is connected to the base of the third transistor, one end of the fourth resistor is connected to the cathode of the voltage regulator, and the other end of the fourth resistor is connected to the collector of the third transistor.

[0010] Preferably, the first transistor is of PNP type, and the second transistor and the third transistor are both of NPN type.

[0011] The present invention uses capacitors and triodes to form a feedback circuit, and uses resistors and triodes to form a protection circuit, thereby reducing the complexity of the control and protection circuits and reducing the area of ​​the printed board of the power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a circuit schematic diagram of the present invention. DETAILED DESCRIPTION

[0013] The present invention will be further described below in conjunction with specific embodiments.

[0014] A small-size BUCK converter circuit suitable for low-power applications, such as Figure 1 As shown, it includes a voltage stabilizing circuit 1, a BUCK converter main topology circuit 2, a feedback and control circuit 3 and an overcurrent protection circuit 4;

[0015] The voltage stabilizing circuit 1 includes a first resistor R1, a first capacitor C1 and a voltage stabilizing tube VE1; wherein the first resistor R1 is equal to 12 kΩ, the first capacitor C1 is equal to 47 nF, and the voltage stabilizing tube VE1 is (G)2CW5234. The voltage regulation value of the voltage regulator VE1 is used to determine the output voltage of the circuit. When the circuit outputs normally, the third transistor V3 is turned off, and the first transistor V1 and the second transistor V2 both work in the switch state. When the second transistor V2 is turned on, the output voltage of the circuit is the voltage regulation value of the voltage regulator VE1 minus the PN junction voltage drop of 0.6V between the base and the emitter of the second transistor V2. The conduction of the second transistor V2 causes the first transistor V1 to be turned on, and the output voltage rises. When the output voltage rises to a value greater than the voltage regulation value of the voltage regulator VE1 minus 0.6V, the second transistor V2 is turned off, causing the first transistor V1 to be turned off, and the BUCK converter enters the freewheeling state, and the output voltage decreases. When the voltage decreases to less than the voltage regulation value of the voltage regulator VE1 minus 0.6V, the second transistor V2 is turned on again, so the voltage regulation value of the voltage regulator VE1 minus 0.6V is the average value of the output voltage.

[0016] The BUCK converter main topology circuit 2 includes a first transistor V1, a freewheeling diode VD1, a filter inductor L1 and a filter capacitor C2; wherein, the first transistor V1 adopts BCX53, the freewheeling diode VD1 adopts MURS360BT3G, the filter inductor L1 adopts SM5845-101, and the filter capacitor C2 is equal to 22uF. The first transistor V1 works in a switching state, and when it is turned on, it charges the filter inductor L1, and the current flowing through the filter inductor L1 increases. When it is turned off, the current flows through the freewheeling diode VD1, and the current flowing through the filter inductor L1 decreases. When the circuit works in a stable state, the average value of the current flowing through the filter inductor L1 is a constant value, and the filter inductor L1 and the filter capacitor C2 form an LC filter to provide a stable DC voltage for the load.

[0017] The feedback and control circuit 3 includes a third capacitor C3, a second transistor V2, a second resistor R2 and a third resistor R3; wherein the third capacitor C3 is equal to 1nF, the second transistor V2 adopts MMBT5551, the second resistor R2 is equal to 2kΩ, and the third resistor R3 is equal to 2kΩ. The third capacitor C3 feeds back the voltage of the connection point A of the first transistor V1, the filter inductor L1 and the freewheeling diode VD1 to the base of the second transistor V2, thereby determining the switch state of the first transistor V1.

[0018] The overcurrent protection circuit 4 includes a fourth resistor R4, a fifth resistor R5, a sixth resistor R6 and a third transistor V3; wherein the fourth resistor R4 is equal to 100Ω, the fifth resistor R5 is equal to 200Ω, the sixth resistor R6 is equal to 2kΩ, and the third transistor V3 adopts MMBT5551. The sixth resistor R6 is used to collect the load current, and the overcurrent protection point Ip is determined by the resistance value of the sixth resistor R6.

[0019] A direct current power supply DC with a voltage of 28V is connected to the emitter of the first transistor V1, the collector of the first transistor V1 is connected to one end of the inductor L1 and the cathode of the freewheeling diode VD1, the other end of the inductor L1 is connected to one end of the filter capacitor C2 and one end of the sixth resistor R6, the other end of the filter capacitor C2 is connected to the anode of the freewheeling diode VD1 and one end of the load RL and is grounded, and the other end of the sixth resistor R6 is connected to the other end of the load RL;

[0020] A second resistor R2 is connected in parallel between the emitter and base of the first triode V1, one end of the third resistor R3 is connected to the base of the first triode V1, the other end of the third resistor R3 is connected to the collector of the second triode V2, the emitter of the second triode V2 is connected to the emitter of the third triode V3, one end of the third capacitor C3 is connected to the base of the second triode V2, and the other end of the third capacitor C3 is connected to the collector of the first triode V1;

[0021] One end of the first resistor R1 is connected to the DC power supply DC, the other end of the first resistor R1 is connected to one end of the first capacitor C1, the cathode of the voltage regulator tube VE1 and the base of the second transistor V2, and the other end of the first capacitor C1 and the anode of the voltage regulator tube VE1 are connected to the ground end of the DC power supply DC;

[0022] One end of the fifth resistor R5 is connected to one end of the inductor L1, the other end of the fifth resistor R5 is connected to the base of the third transistor V3, one end of the fourth resistor R4 is connected to the cathode of the voltage regulator tube VE1, and the other end of the fourth resistor R4 is connected to the collector of the third transistor V3.

[0023] The first transistor V1 is of PNP type, and the second transistor V2 and the third transistor V3 are both of NPN type.

[0024] The working principle of the control circuit and the protection circuit of the present invention is:

[0025] Since the base voltage of the second transistor V2 is clamped at its regulated value by the voltage regulator VE1, when the output voltage increases, the voltage between the base and emitter of the second transistor V2 decreases, which reduces the current flowing through the second transistor V2, thereby promoting the shutdown of the first transistor V1, and the BUCK converter enters the freewheeling state. The voltage at point A is clamped at -0.7V by the freewheeling diode VD1. Since the voltage across the third capacitor C3 cannot change suddenly, the base voltage of the second transistor V2 decreases rapidly, which further reduces the base current of the second transistor V2, accelerates the shutdown of the second transistor V2, and also accelerates The first transistor V1 is turned off, the inductor L continues to flow through the load and the freewheeling diode VD1, and the output voltage gradually decreases. When it decreases to the voltage value of the voltage regulator VE1 minus 0.6V, the PN junction voltage drop between the base and the emitter of the second transistor V2 is established, and the second transistor V2 is turned on, and the first transistor V1 is turned on. At this time, the voltage at point A rises to the input voltage. Since the voltage across the third capacitor C3 cannot change suddenly, the base voltage of the second transistor V2 rises rapidly, and the base current of the second transistor V2 increases, further promoting the conduction of the second transistor V2, thereby accelerating the conduction of the first transistor V1. After the first transistor V1 is turned on, the output voltage increases, and then the above process is repeated. Through the positive feedback of the third capacitor C3, the conduction and shutdown process of the first transistor V1 and the second transistor V2 is accelerated, so that the first transistor V1 works in a switching state, reducing the loss of the first transistor V1. The sixth resistor R6 is used to collect the load current. When the load current is greater than the set overcurrent protection point Ip (Ip=0.6V / R6), the PN junction voltage drop between the base and the emitter of the third transistor V3 is established, and the third transistor V3 is turned on, so that the output voltage becomes the regulated value of the voltage regulator VE1. The PN junction voltage drop between the base and the emitter of the second transistor V2 cannot be established, and the second transistor V2 is turned off. Then, the first transistor V1 is turned off, and the load current is reduced. When the load current is reduced to the point where the third transistor V3 cannot be turned on, the second transistor V2 continues to be turned on, and the circuit returns to normal.

[0026] When the voltage at the connection point A of the first transistor V1, the filter inductor L1 and the freewheeling diode VD1 remains unchanged, the first transistor V1 works in the amplification region. At this time, the BUCK converter enters the linear power supply working state. However, as long as the load is disturbed, the working state of the second transistor V2 changes, and the first transistor V1 enters the switch working state. In view of the fact that in actual applications, the output voltage is usually supplied to the CPU, FPGA or other ICs through a linear power supply, the load state does not remain unchanged, so this circuit will not work in the linear power supply state for a long time, which is acceptable in most applications.

Claims

1. A small-volume BUCK converter circuit suitable for low-power applications, characterized by: It includes a voltage stabilizing circuit (1), a BUCK converter main topology circuit (2), a feedback and control circuit (3) and an overcurrent protection circuit (4); The voltage stabilizing circuit (1) comprises a first resistor (R1), a first capacitor (C1) and a voltage stabilizing tube (VE1); the BUCK converter main topology circuit (2) comprises a first triode (V1), a freewheeling diode (VD1), a filter inductor (L1) and a filter capacitor (C2); the feedback and control circuit (3) comprises a third capacitor (C3), a second triode (V2), a second resistor (R2) and a third resistor (R3); the overcurrent protection circuit (4) comprises a fourth resistor (R4), a fifth resistor (R5), a sixth resistor (R6) and a third triode (V3); A direct current power supply (DC) is connected to the emitter of the first transistor (V1), the collector of the first transistor (V1) is connected to one end of the inductor (L1) and the cathode of the freewheeling diode (VD1), the other end of the inductor (L1) is connected to one end of the filter capacitor (C2) and one end of the sixth resistor (R6), the other end of the filter capacitor (C2) is connected to the anode of the freewheeling diode (VD1) and one end of the load (RL) and is grounded, and the other end of the sixth resistor (R6) is connected to the other end of the load (RL); A second resistor (R2) is connected in parallel between the emitter and base of the first triode (V1), one end of the third resistor (R3) is connected to the base of the first triode (V1), the other end of the third resistor (R3) is connected to the collector of the second triode (V2), the emitter of the second triode (V2) is connected to the emitter of the third triode (V3), one end of the third capacitor (C3) is connected to the base of the second triode (V2), and the other end of the third capacitor (C3) is connected to the collector of the first triode (V1); One end of the first resistor (R1) is connected to a direct current power supply (DC), the other end of the first resistor (R1) is connected to one end of a first capacitor (C1), a cathode of a voltage regulator tube (VE1) and a base of a second transistor (V2), and the other end of the first capacitor (C1) and an anode of the voltage regulator tube (VE1) are connected to a ground terminal of the direct current power supply (DC); One end of the fifth resistor (R5) is connected to one end of the inductor (L1), the other end of the fifth resistor (R5) is connected to the base of the third triode (V3), one end of the fourth resistor (R4) is connected to the cathode of the voltage regulator tube (VE1), and the other end of the fourth resistor (R4) is connected to the collector of the third triode (V3).

2. The small-volume BUCK converter circuit suitable for low-power applications according to claim 1 is characterized in that: The first transistor (V1) is of PNP type, and the second transistor (V2) and the third transistor (V3) are both of NPN type.

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