Reverse current protection circuit

Abstract

This invention provides a reverse current protection circuit. The reverse current protection circuit is applicable to both an upper bridge switch and a lower bridge switch. The first terminal of the upper bridge switch is coupled to an input voltage. The first terminal of the lower bridge switch is connected to the second terminal of the upper bridge switch. The reverse current protection circuit detects the input voltage received at the first terminal of the upper bridge switch and the output voltage at the second terminal of the lower bridge switch, and controls the lower bridge switch accordingly. Before a reverse current greater than a reverse current threshold flows sequentially from the output voltage at the second terminal of the lower bridge switch through the lower bridge switch and the upper bridge switch to the input voltage, the reverse current protection circuit shuts down the lower bridge switch.

Claims

1. A reverse current protection circuit, applicable to an upper bridge switch and a lower bridge switch, wherein a first terminal of the upper bridge switch is coupled to an input voltage, a control terminal of the upper bridge switch is coupled to an upper bridge charging voltage, and a first terminal of the lower bridge switch is connected to a second terminal of the upper bridge switch, the reverse current protection circuit comprising: a main reverse current protection circuit connected to the control terminal of the lower bridge switch, configured to detect the input voltage received at the first terminal of the upper bridge switch and an output voltage at the second terminal of the lower bridge switch, thereby controlling the lower bridge switch; wherein... Before a reverse current greater than a reverse current threshold flows sequentially from the output voltage at the second terminal of the lower bridge switch through the lower bridge switch and the upper bridge switch to the input voltage, the main reverse current protection circuit shuts off the lower bridge switch; wherein the main reverse current protection circuit includes: an output voltage detection circuit connected to the second terminal of the lower bridge switch, configured to detect the output voltage and convert the detected output voltage into an output detection conversion current; and an input voltage detection circuit connected to the first terminal of the upper bridge switch, configured to detect the input voltage and convert the detected input voltage into an input detection conversion current. A current comparison circuit is connected to the output voltage detection circuit, the input voltage detection circuit, and the control terminal of the lower bridge switch, configured to compare the output detected conversion current with the input detected conversion current to output a lower bridge master control signal to the control terminal of the lower bridge switch; and an output voltage clamping circuit is connected to the second terminal of the lower bridge switch and the current comparison circuit, configured to output a power supply voltage to the current comparison circuit based on the output voltage of the second terminal of the lower bridge switch.

2. The reverse current protection circuit as described in claim 1, wherein, When the current comparison circuit determines that the output detection conversion current is greater than the input detection conversion current, the current comparison circuit turns off the lower bridge switch.

3. The reverse current protection circuit as claimed in claim 1, wherein the main reverse current protection circuit further comprises: a current amplification circuit connected between the current comparison circuit and the control terminal of the lower bridge switch, configured to multiply the lower bridge main control signal by a gain to output a lower bridge control current amplification signal to the control terminal of the lower bridge switch.

4. The reverse current protection circuit as claimed in claim 1, wherein the output voltage detection circuit comprises: a first output transistor, a first terminal of the first output transistor being connected to a second terminal of the lower bridge switch, and a second terminal of the first output transistor being grounded; and a second output transistor, a control terminal of the second output transistor being connected to the first terminal and the control terminal of the first output transistor, a first terminal of the second output transistor being connected to the current comparison circuit, and a second terminal of the second output transistor being grounded; wherein the current comparison circuit is configured to use the current at the first terminal of the second output transistor as the output detection conversion current.

5. The reverse current protection circuit as claimed in claim 4, wherein the output voltage detection circuit further comprises: an output resistor connected between the second terminal of the lower bridge switch and the first terminal of the first output transistor.

6. The reverse current protection circuit as claimed in claim 4, wherein the input voltage detection circuit comprises: a first input transistor, a first terminal of the first input transistor being connected to a first terminal of the upper bridge switch, and a second terminal of the first input transistor being grounded; and a second input transistor, a control terminal of the second input transistor being connected to the first terminal and the control terminal of the first input transistor, the first terminal of the second input transistor being connected to the current comparison circuit, and a second terminal of the second input transistor being grounded; wherein the current comparison circuit is configured to use the current at the first terminal of the second input transistor as the input detection conversion current.

7. The reverse current protection circuit as claimed in claim 6, wherein the input voltage detection circuit further comprises: an input resistor connected between the input voltage and the first terminal of the first output transistor.

8. The reverse current protection circuit as claimed in claim 6, wherein the current comparison circuit comprises: a first comparator transistor, a first terminal of the first comparator transistor being coupled to a power supply voltage, and a second terminal of the first comparator transistor being connected to the first terminal of a second output transistor; and a second comparator transistor, a control terminal of the second comparator transistor being connected to the second terminal and a control terminal of the first comparator transistor, a first terminal of the second comparator transistor being coupled to the power supply voltage, and a second terminal of the second comparator transistor being connected to the first terminal of the second input transistor.

9. The reverse current protection circuit as claimed in claim 8, wherein the main reverse current protection circuit further comprises: a current amplification circuit, wherein the current amplification circuit comprises: a current input transistor, a first terminal of the current input transistor being connected to a node between the second terminal of the second comparator transistor and the first terminal of the second input transistor, the second terminal of the current input transistor being grounded; and a current output transistor, a control terminal of the current output transistor being connected to the first terminal and the control terminal of the current input transistor, the first terminal of the current output transistor being connected to the control terminal of the lower bridge switch, the second terminal of the current output transistor being grounded.

10. The reverse current protection circuit as claimed in claim 9, wherein the current amplification circuit further comprises: a second current output transistor, the control terminal of the second current output transistor being coupled to the power supply voltage, a first terminal of the second current output transistor being connected to the control terminal of the lower bridge switch, and a second terminal of the second current output transistor being connected to the first terminal of the current output transistor.

11. The reverse current protection circuit as claimed in claim 10, wherein the main reverse current protection circuit further comprises: an output voltage clamping circuit, wherein the output voltage clamping circuit comprises: a Zener diode, the cathode of the Zener diode being connected to the second terminal of the lower bridge switch, and the anode of the Zener diode being grounded; and a clamping transistor, the control terminal of the clamping transistor being connected to the cathode of the Zener diode, the first terminal of the clamping transistor being connected to the second terminal of the lower bridge switch, and the second terminal of the clamping transistor being connected to the first terminal of the first comparator transistor, the first terminal of the second comparator transistor, and the control terminal of the second current output transistor.

12. The reverse current protection circuit as claimed in claim 11, wherein the output voltage clamping circuit further comprises: a clamping resistor connected between the second terminal of the lower bridge switch and the cathode of the Zener diode.

13. The reverse current protection circuit as claimed in claim 1 further comprises: an initial reverse current protection circuit configured to compare the output voltage with an input detection modulation voltage to control the lower bridge switch; wherein the input detection modulation voltage is equal to the input voltage plus a preset modulation voltage.

14. The reverse current protection circuit as claimed in claim 13, wherein the initial reverse current protection circuit further comprises: an initial comparator, a first input terminal of the initial comparator being connected to a second terminal of the lower bridge switch, the second input terminal of the initial comparator being coupled to the input detection modulation voltage; and an initial transistor, a control terminal of the initial transistor being connected to an output terminal of the initial comparator, a first terminal of the initial transistor being connected to the control terminal of the lower bridge switch, and a second terminal of the initial transistor being coupled to a reference voltage.

15. The reverse current protection circuit as claimed in claim 1 further comprises: a charging circuit connected to the control terminal of the upper bridge switch and the control terminal of the lower bridge switch, configured to output the upper bridge charging voltage to the control terminal of the upper bridge switch and output the lower bridge charging voltage to the control terminal of the lower bridge switch.

16. The reverse current protection circuit of claim 15 further comprises: an oscillation circuit connected to the charging circuit and configured to output a clock signal to the charging circuit; wherein the charging circuit is configured to control the output frequency of the upper bridge charging voltage and the lower bridge charging voltage according to the frequency of the clock signal.

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