CN215870743U - Fault protection circuit - Google Patents
Fault protection circuit Download PDFInfo
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- CN215870743U CN215870743U CN202121952994.9U CN202121952994U CN215870743U CN 215870743 U CN215870743 U CN 215870743U CN 202121952994 U CN202121952994 U CN 202121952994U CN 215870743 U CN215870743 U CN 215870743U
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Abstract
The present invention relates to a fault protection circuit. The fault protection circuit is suitable for a BUCK circuit and comprises an output voltage detection unit, a voltage comparison action unit, a return difference compensation unit, an isolation unit, a drive control unit and a switch tube Q2And (4) forming. When the circuit normally works, the drive control unit gets power from the input end, and the switch tube Q is switched on when the input voltage is established2And the input power supply circuit and the output circuit are established to ensure the normal and effective work of the circuit. When the BUCK circuit sends a fault, e.g. the main power switch Q1Short circuit, or output overvoltage, the fault protection circuit will input into the power supply circuitAnd the output loop is disconnected, so that the high output voltage caused by the fault is prevented from damaging a rear-stage circuit, meanwhile, the isolation unit in the protection circuit isolates the reference node AGND for input power supply from the reference node GND for the output loop, and the high voltage generated by the reference node GND for the output loop is prevented from being injected into the power supply unit to damage the power supply circuit.
Description
Technical Field
The utility model relates to the technical field of switching power supplies, in particular to a fault protection circuit suitable for a BUCK circuit.
Background
The BUCK circuit is used as a general BUCK DC/DC converter, is often applied to various low-voltage power supply occasions with higher requirements on efficiency, and is also widely applied to a plurality of wide-input voltage-drop type power factor correction circuits. However, the BUCK circuit in practical application generally has a single fault protection problem, that is, when a main power switch tube is short-circuited and broken down, an input high voltage is directly transmitted to two ends of an output capacitor through an inductor, so that the output capacitor is damaged by overvoltage or is exploded to cause fire, and meanwhile, a rear-stage circuit is directly damaged. Therefore, designing a suitable single fault protection circuit is crucial for the application of the BUCK circuit.
The design difficulty of the BUCK fault protection circuit is as follows:
1) when the circuit works normally, how to ensure the effective connection of an input power supply loop and an output loop of the fault protection circuit;
2) how to effectively disconnect the input power supply loop and the output loop after the fault occurs;
3) how to prevent the output circuit reference node from high-voltage pouring into the power supply circuit after the fault is removed, and the power supply circuit is damaged.
SUMMERY OF THE UTILITY MODEL
In view of the above, the present invention provides a fault protection circuit, which is used to solve the problems that the BUCK circuit cannot be protected quickly when the BUCK circuit fails, and the isolation scheme is adopted to protect the BUCK circuit, so as to prevent the high voltage from flowing into the power supply loop from the output reference node GND, which causes circuit damage.
In order to solve the technical problems, the technical scheme adopted by the utility model is as follows:
a fault protection circuit for use in a BUCK circuit, the fault protection circuit comprising: the circuit comprises a switching tube, an output voltage detection unit, a voltage comparison action unit, an isolation unit, a drive control unit and a return difference compensation unit;
the switching tube is connected between an input power supply loop and an output loop of the BUCK circuit;
the output voltage detection unit is provided with an output voltage sampling end, and the output voltage detection unit collects the output voltage of the output loop and provides the output voltage to the voltage comparison action unit through the output voltage sampling end;
the voltage comparison action unit compares the output voltage with a reference voltage, and if the output voltage is greater than the reference voltage, a level signal is output and is transmitted to the drive control unit through the isolation unit;
the driving control unit controls the switching tube to be switched off according to the level signal, so that the input power supply loop is disconnected with the output loop;
the return difference compensation unit is connected with the output voltage sampling end of the output voltage detection unit and used for providing compensation voltage for the output voltage sampling end so as to prevent the switching tube from being repeatedly switched on and off.
Preferably, the output voltage detecting unit includes: diode and resistor R5And a resistance R6；
The anode of the diode is connected with the output voltage of the output loop, and the cathode of the diode is connected with the resistor R5Is connected to one end of the resistor R5And the other end of (2) and the resistor R6Is connected to one end of the resistor R6Is connected to a first reference node, the resistor R5And the resistance R6The connection node of the voltage sampling circuit is used as an output voltage sampling end;
the return difference compensation unit comprises: triode, resistance R1And a resistance R4；
The collector of triode with output voltage detection unit's output voltage sampling end is connected, the base of triode with resistance R4's one end is connected, the projecting pole of triode passes through resistance R41Is connected with a voltage source;
the voltage comparison action unit comprises: one end of the capacitor is connected with the first reference node, and the other end of the capacitor is connected with a collector electrode of the triode; a first pin of a reference source is connected with the output voltage sampling end, and a second pin of the reference source is connected with the resistor R4Is connected with the other end of the reference source, and a second pin of the reference source is connected with the resistor R4The connection point of the reference source is used as the output end of the voltage comparison action unit, and the third pin of the reference source is connected with the first reference node;
when the voltage of the output voltage sampling end is greater than the reference voltage in the first pin of the reference source, the second pin and the third pin of the reference source are in a low impedance state, at the moment, the level signal output by the output end of the voltage comparison action unit is a low level signal, the low level signal is transmitted to the driving control unit through the isolation unit, and the driving control unit controls the switching tube to be switched off according to the low level signal; and after the switch tube is switched off for a period of time, the voltage source provides the compensation voltage for the output voltage sampling end to prevent the switch tube from being repeatedly switched on and off.
Preferably, the fault protection circuit is further provided with a resistor R2And a resistance R3Said resistance R2One end of (2) and the resistor R3Connection, the resistance R2Is connected with the voltage source, the resistor R3The other end of the first pin is connected with a second pin of the reference source;
the isolation unit is a linear optocoupler, and is provided with a first input end, a second input end, a first output end and a second output end; the first input end and the second input end of the isolation unit and the resistor R3Parallel connection;
the drive control unit includes: voltage stabilizing diode and resistor R7Resistance R8And a resistance R9；
The voltage stabilizing diode is connected with the first output end and the second output end of the isolation unit in parallel; the resistor R7Is connected to the input voltage, the resistor R7The other end of the diode is connected with the voltage stabilizing diode; the resistor R8And the resistance R9After being connected in series, the resistor R is connected with a voltage stabilizing diode in parallel9The connection point of the voltage stabilizing diode is connected with a second reference node, and the resistor R8And a resistance R9Is used as an output port of the drive control unit and is connected with the switch tube.
Preferably, the first reference node is a reference node of the output voltage of the BUCK circuit; the second reference node is a reference node of the input voltage of the BUCK circuit, and the first reference node and the second reference node are both grounded points.
Compared with the prior art, the utility model has the following advantages and beneficial effects:
1) the drive control unit in the fault protection circuit provided by the utility model can realize the starting logic and the fault protection logic only by three resistors and one voltage stabilizing diode, and has the advantages of simple structure, low cost and the like;
2) the fault protection circuit provided by the utility model can realize the electrical isolation between the reference node (AGND) of the input voltage and the reference node (GND) of the output voltage reference, and prevent a high voltage from being injected into a power supply loop from the reference node (GND) of the output voltage after the fault occurs to damage related devices;
3) the scheme provided by the utility model can effectively protect the BUCK circuit with a fault, prevent the post-stage circuit from being damaged due to output high voltage after the fault occurs, and simultaneously change the power supply form of the voltage source according to the actual application requirement to realize fault locking protection or self-recovery protection.
Drawings
Fig. 1 is a block diagram of a circuit structure of a fault protection circuit according to the present invention;
fig. 2 is a schematic circuit diagram of a fault protection circuit according to the present invention.
Detailed Description
In order to make the technical solution and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings.
Fig. 2 is a schematic diagram of a fault protection circuit of the present invention, which is used in a BUCK circuit, and includes: switch tube, output voltage detection unit, voltage comparison action unit, isolation unit, drive control unit, return difference compensation unit and resistor R2And a resistance R3Wherein, the switch tube Q2The input power supply circuit is connected between the input power supply loop and the output loop of the BUCK circuit.
The output voltage detection unit is provided with an output voltage sampling end and supplies the sampled output voltage to the voltage comparison action unit.
In this embodiment, the output voltage detection unit includes: diode VD2Resistance R5And a resistance R6Diode VD2Is connected with the output voltage of the output circuit, and a diode VD2Cathode connection resistance R5One terminal of (1), resistance R5The other end and a resistor R6One end connected to a resistor R6The other end is connected with a first reference node GND, and a resistor R5And a resistance R6The first reference node GND is a reference node of the output voltage of the BUCK circuit and is also a ground point.
The return difference compensation unit is connected with the output voltage sampling end of the output voltage detection unit and used for providing compensation voltage for the output voltage sampling end so that the switching tube Q is enabled to be connected2And then the power is turned on again after being turned off.
The return difference compensation unit includes: triode Q3Resistance R1And a resistance R4(ii) a Triode Q3The collector of the triode Q is connected with the output voltage sampling end of the output voltage detection unit3Base and resistor R of4Is connected to a transistor Q3Emitter through resistor R1And a voltage source VCC(power supply unit) connection.
The voltage comparison action unit compares the output voltage with the reference voltage, if the output voltage is greater than the reference voltage, a low level signal is output and is transmitted to the drive control unit through the isolation unit so as to control the switching tube Q2And (6) turning off.
The voltage comparison operation unit includes: capacitor C1And a reference source U1Capacitor C1Is connected to a first reference node GND, a capacitor C1And the other end of the transistor Q3Is connected with the collector of the collector; a first pin of the reference source U1 is connected with the output voltage sampling end, a second pin of the reference source U1 is connected with the resistor R4Is connected with the other end of the resistor R, and a second pin of a reference source U1 is connected with the resistor R4The connection point of the reference source U1 and the first reference is used as the output end of the voltage comparison action unitThe node GND is connected.
Isolation unit coupler U2Is a linear optocoupler U2Linear optocoupler U2Having a first input, a second input, a first output and a second output; linear optocoupler U2First input terminal, second input terminal and resistor R3In parallel, and a resistance R3One terminal of (1) and a resistor R2Is connected to a resistor R2And the other end of which is connected to a voltage source Vcc.
The drive control unit includes: zener diode ZD1Resistance R7Resistance R8And a resistance R9(ii) a Zener diode ZD1The first output end and the second output end of the isolation unit are connected in parallel; resistance R7Is connected to the input voltage Vin, a resistor R7And the other end of (1) and a zener diode ZD1Connecting; resistance R8And a resistance R9Connected in series with a zener diode ZD1In parallel, and a resistance R9And a zener diode ZD1Is connected with a second reference node AGND, and the connection point of the resistor R8 and the resistor R9 is used as the output port of the driving control unit and is used for being connected with the switch tube Q2And (4) connecting.
The working principle analysis of the embodiment is as follows:
when the BUCK circuit in FIG. 1 works normally, the input voltage Vin is loaded on the resistor R7And a zener diode ZD1At both ends, via a resistance R8And a resistance R9After voltage division, a switch tube Q is formed2The drive signal of the circuit is conducted, an input loop and an output loop are established, and the normal and effective work of the BUCK circuit is ensured.
When BUCK circuit is faulty, e.g. main power transistor Q1Short-circuiting, the input high voltage is applied directly across the output capacitor C1 and the load. At this time, the voltage u of the voltage sampling terminal A is output1Rises when its voltage u1Greater than reference source U1When the reference voltage in the first pin is detected, the voltage u at the output end B point of the voltage comparison action unit2Pulled down, reference source U1The second pin and the third pin are in a low impedance state, and current passes through the resistor R at the moment2Flow direction linear optical coupler U2Such that the linear optocoupler U2The primary side diode is turned on to emit light. Linear optocoupler U at the moment2The first output end is conducted with the second output end, and the linear optocoupler U2Voltage u at point C3Pulled-down, voltage-stabilizing diode ZD1Short circuit, resistance R8And a resistance R9Is also short-circuited, the voltage at the output port D of the drive control unit is close to 0 and is not enough to drive the switching tube Q2Switching tube Q2And turning off the circuit to disconnect the input power supply loop and the output loop of the BUCK circuit, so as to realize quick protection when the BUCK circuit has a fault.
When the voltage comparison action unit outputs a low level, the triode Q3The return difference compensation unit passes through a resistor R when being conducted1Injecting a compensation voltage delta u into the A point of the output voltage sampling end1So that the input voltage of the voltage comparison operation unit becomes u11＝u1+Δu1Therefore, when the output voltage is reduced to a lower value, the protection circuit is recovered, and the situation that the protection circuit bounces back and forth at a set overvoltage protection point and the work is unstable is prevented. The single fault protection circuit of the BUCK circuit can be used for different voltage sources VCCAnd the power supply mode realizes the fault locking protection or hiccup protection.
In summary, the protection circuit provided by the utility model enables the circuit to be driven by the control unit when the BUCK circuit has no fault.
The fault protection circuit applicable to the BUCK circuit can be used according to different voltage sources VCCAnd the power supply mode realizes the fault locking protection or hiccup protection.
In summary, the fault protection circuit provided by the utility model enables the circuit to work normally by driving the control unit when the BUCK circuit has no fault; when the BUCK circuit breaks down, the input power supply circuit and the output circuit can be effectively disconnected, the situation that the output high voltage damages a rear-stage circuit after the fault occurs is prevented, and in practical application, the scheme can be slightly improved according to practical conditions to achieve the purpose.
The above-described embodiments of the present invention are merely examples for illustrating the present invention, and are not intended to limit the embodiments of the present invention. Variations and modifications in other variations will occur to those skilled in the art upon reading the foregoing description. Not all embodiments are exhaustive. All obvious changes and modifications of the present invention are within the scope of the present invention.
Claims (4)
1. A fault protection circuit for use in a BUCK circuit, the fault protection circuit comprising: the circuit comprises a switching tube, an output voltage detection unit, a voltage comparison action unit, an isolation unit, a drive control unit and a return difference compensation unit;
the switching tube is connected between an input power supply loop and an output loop of the BUCK circuit;
the output voltage detection unit is provided with an output voltage sampling end, and the output voltage detection unit collects the output voltage of the output loop and provides the output voltage to the voltage comparison action unit through the output voltage sampling end;
the voltage comparison action unit compares the output voltage with a reference voltage, and if the output voltage is greater than the reference voltage, a level signal is output and is transmitted to the drive control unit through the isolation unit;
the driving control unit controls the switching tube to be switched off according to the level signal, so that the input power supply loop is disconnected with the output loop;
the return difference compensation unit is connected with the output voltage sampling end of the output voltage detection unit and used for providing compensation voltage for the output voltage sampling end so as to prevent the switching tube from being repeatedly switched on and off.
2. The fault protection circuit of claim 1, wherein the output voltage detection unit comprises: diode and resistor R5And a resistance R6；
The anode of the diode is connected with the output voltage of the output loop, and the cathode of the diode is connected with the resistor R5Is connected to one end of the resistor R5And the other end of (2) and the resistor R6Is connected to one end of the resistor R6Is connected to a first reference node, the resistor R5And the resistance R6The connection node of the voltage sampling circuit is used as an output voltage sampling end;
the return difference compensation unit includes: triode, resistance R1And a resistance R4；
The collector of the triode is connected with the output voltage sampling end of the output voltage detection unit, and the base of the triode is connected with the resistor R4Is connected with the other end of the triode, and the emitting electrode of the triode passes through the resistor R1Is connected with a voltage source;
the voltage comparison operation unit includes: one end of the capacitor is connected with the first reference node, and the other end of the capacitor is connected with a collector electrode of the triode; a first pin of a reference source is connected with the output voltage sampling end, and a second pin of the reference source is connected with the resistor R4Is connected with the other end of the reference source, and a second pin of the reference source is connected with the resistor R4The connection point of the reference source is used as the output end of the voltage comparison action unit, and the third pin of the reference source is connected with the first reference node;
when the voltage of the output voltage sampling end is greater than the reference voltage in the first pin of the reference source, the second pin and the third pin of the reference source are in a low impedance state, at the moment, the level signal output by the output end of the voltage comparison action unit is a low level signal, the low level signal is transmitted to the driving control unit through the isolation unit, and the driving control unit controls the switching tube to be switched off according to the low level signal; and after the switch tube is switched off, the voltage source provides the compensation voltage for the output voltage sampling end to prevent the switch tube from being switched on and off repeatedly.
3. A fault protection circuit according to claim 2, wherein: and is also provided with a resistor R2And a resistance R3Said resistance R2One end of (2) and the resistor R3Connection, the resistance R2Is connected with the voltage source, the resistor R3The other end of the first pin is connected with a second pin of the reference source;
the isolation unit is a linear optocoupler, and is provided with a first input end, a second input end, a first output end and a second output end; the first input end and the second input end of the isolation unit and the resistor R3Parallel connection;
the drive control unit includes: voltage stabilizing diode and resistor R7Resistance R8And a resistance R9；
The voltage stabilizing diode is connected with the first output end and the second output end of the isolation unit in parallel; the resistor R7Is connected to the input voltage, the resistor R7The other end of the diode is connected with the voltage stabilizing diode; the resistor R8And the resistance R9After being connected in series, the resistor R is connected with the voltage stabilizing diode in parallel9The connection point of the voltage stabilizing diode is connected with a second reference node, and the resistor R8And a resistance R9Is used as an output port of the drive control unit and is connected with the switch tube.
4. A fault protection circuit according to claim 3, wherein: the first reference node is a reference node of the output voltage of the BUCK circuit; the second reference node is a reference node of the input voltage of the BUCK circuit, and the first reference node and the second reference node are both grounded points.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121952994.9U CN215870743U (en) | 2021-08-19 | 2021-08-19 | Fault protection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121952994.9U CN215870743U (en) | 2021-08-19 | 2021-08-19 | Fault protection circuit |
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| Publication Number | Publication Date |
|---|---|
| CN215870743U true CN215870743U (en) | 2022-02-18 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202121952994.9U Active CN215870743U (en) | 2021-08-19 | 2021-08-19 | Fault protection circuit |
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| CN (1) | CN215870743U (en) |
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- 2021-08-19 CN CN202121952994.9U patent/CN215870743U/en active Active
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