An overcurrent protection circuit for a power supply with multiple outputs

Abstract

The present invention discloses an overcurrent protection circuit of a power supply with multiple outputs, which is connected between the power supply output terminal and the load power input terminal. The overcurrent protection circuit includes: at least one output circuit for outputting current; at least one overcurrent detection circuit, at least one primary trigger circuit, a common trigger circuit and a main control circuit. In the present invention, an overcurrent detection circuit is set on each output circuit, and the output current in each circuit is detected by the overcurrent detection circuit, and a comparison result is generated. When the comparison result indicates that the corresponding output current is greater than a predetermined value, the primary trigger circuit and the common trigger circuit are turned on in sequence, and the common trigger circuit sends a shutdown trigger signal to the main control circuit. The main control circuit controls the power supply to stop working, and can perform overcurrent protection on each output circuit, can timely detect overcurrent problems, and react to shut down the power supply, thereby improving safety performance and reducing the probability of safety accidents.

Description

Technical Field

[0001] The invention belongs to the technical field of circuits, and in particular relates to an overcurrent protection circuit for a power supply. Background Art

[0002] At present, AC-DC (AC input DC output) multi-channel output power supplies directly connected to the AC power grid are widely used in various electronic products, such as TVs, DVDs, set-top boxes, etc. In traditional multi-channel output power supplies, a transformer can provide multiple outputs. Under different conditions, the output power of each channel varies greatly. In order to ensure the stability of the multi-channel output voltage, the sampled voltage of each output is usually fed back to the input circuit to control the stability of the output voltage of each output branch.

[0003] As a power supply device for electronic products, the power supply must not only meet the requirements of the subsequent power-consuming equipment, but also have its own protection measures, such as overcurrent protection. At present, electronic products detect short-circuit problems by detecting the output voltage change, and only protect when the voltage value becomes low or high, without detecting the current. This will result in the power supply working process. When one or more output currents have problems due to output short circuit or other reasons, the problem cannot be discovered in real time. If the power supply keeps working, it will cause the power supply to burn out, or even cause fire and other problems.

[0004] An existing multi-channel output power supply circuit (such as two-channel output) includes an AC input protection module, a bridge rectifier module, a filter module, a transformer module, a control module, a switch detection unit, a first output circuit, a second output circuit and a feedback unit; the control module is connected to the transformer module through the switch detection unit, and controls the on and off of the transformer module by controlling the on and off of the switch detection unit through the control module; one end of the feedback unit is connected to the first output circuit, and the other end is connected to the control module; AC power is input from the AC input protection module, rectified by the bridge rectifier module to become pulsating DC power, and then processed by the filter module to filter out the clutter therein to obtain smooth pulsating DC power, which is supplied to the transformer module, and then the transformer outputs the pulsating DC power to the first output circuit and the second output circuit.

[0005] The transformer module includes a transformer, a first output circuit and a second output circuit are connected to the first transformer secondary side and the second transformer secondary side respectively, and the first transformer secondary side and the second transformer secondary side are coupled to the primary side of the transformer. When the voltage on the first output circuit increases, the feedback unit feeds back information to the control module, and the control module controls the switch detection unit to disconnect, so that the transformer module stops outputting, and then controls the power supply to stop working.

[0006] The existing technology can perform overvoltage protection, but it cannot perform overcurrent protection on each output circuit. This has the following disadvantages: when one or more output currents have an overcurrent problem due to an output short circuit or other reasons, this problem cannot be discovered in real time. If the power supply continues to work, it will cause the power supply to burn out and even cause a safety accident (such as a fire). Summary of the invention

[0007] In order to solve the above problems, the present invention provides an overcurrent protection circuit of a power supply with multiple outputs. By setting an overcurrent detection circuit on each output circuit, it is possible to perform overcurrent protection on each output circuit, and when one or more output currents have an overcurrent problem due to an output short circuit or other reasons, the problem can be discovered in time, and a response can be made to shut down the power supply, thereby improving safety performance and reducing the probability of safety accidents.

[0008] Another object of the present invention is to provide an overcurrent protection circuit for a power supply with multiple outputs. By connecting an overcurrent detection resistor to the positive electrode of the output circuit, the outputs of each channel are not interfered with by each other on the basis of a common ground. The overcurrent protection circuit can still work normally when the outputs of each channel share a common ground, while also reducing the difficulty and complexity of circuit wiring.

[0009] To achieve the above object, the technical solution of the present invention is as follows:

[0010] An overcurrent protection circuit for a power supply with multiple outputs is connected between the power supply output terminal and the load power input terminal, and the overcurrent protection circuit includes: at least one output circuit for outputting current; at least one overcurrent detection circuit, which is used to detect the output current and compare whether the output current is greater than a predetermined value, thereby generating a corresponding comparison result; the overcurrent detection circuit is connected to the corresponding output circuit; at least one primary trigger circuit, the primary trigger circuit is connected to the corresponding overcurrent detection circuit to receive the comparison result output by the corresponding overcurrent detection circuit, when the comparison result output by any overcurrent detection circuit indicates that the corresponding output current is greater than the predetermined value, the primary trigger circuit is turned on; a common trigger circuit is connected to each primary trigger circuit, when the primary trigger circuit is turned on, the common trigger circuit is turned on, and the common trigger circuit sends a shutdown trigger signal; a main control circuit is connected to the common trigger circuit and is used to control the current output by the power supply, when the main control circuit receives the shutdown trigger signal output by the common trigger circuit, the main control circuit controls the power supply to stop working.

[0011] In the present invention, an overcurrent detection circuit is provided on each output circuit, and the output current in each circuit is detected by the overcurrent detection circuit, and a comparison result is generated. When the comparison result indicates that the corresponding output current is greater than a predetermined value, the primary trigger circuit and the common trigger circuit are turned on in sequence, and the common trigger circuit sends a shutdown trigger signal to the main control circuit. The main control circuit controls the power supply to stop working, and can perform overcurrent protection on each output circuit. When one or more output currents have an overcurrent problem due to an output short circuit or other reasons, the problem can be discovered in time, and a response can be made to shut down the power supply, thereby improving safety performance and reducing the probability of safety accidents.

[0012] Specifically, the overcurrent detection circuit includes an overcurrent detection resistor, a first voltage-dividing resistor, a second voltage-dividing resistor, and an operational amplifier; one end of the overcurrent detection resistor is connected to the positive electrode of the output circuit, and the other end is connected to one end of the first voltage-dividing resistor; the other end of the voltage-dividing resistor is connected to the non-inverting input terminal of the operational amplifier; one end of the second voltage-dividing resistor is connected to the output positive electrode of the output circuit, and the other end is connected to the inverting input terminal of the operational amplifier; the output terminal of the operational amplifier is connected to the corresponding primary trigger circuit; the operational amplifier is used to compare the voltage on the non-inverting input terminal of the operational amplifier and the inverting input terminal of the operational amplifier to generate a comparison result so that the output terminal of the operational amplifier can output.

[0013] By connecting the overcurrent detection resistor to the positive electrode of the output circuit, the outputs of each channel can be free from interference with each other on the basis of a common ground. The overcurrent protection circuit can still work normally when the outputs of each channel share a common ground, and the difficulty and complexity of circuit wiring are also reduced.

[0014] Specifically, the primary trigger circuit includes a primary trigger transistor, a primary trigger resistor, a first resistor, a second resistor and a primary diode, one end of the first resistor is connected to the output end of the operational amplifier, and the other end is connected to the base of the primary trigger transistor; the two ends of the primary trigger resistor are respectively connected to the base of the primary trigger transistor and the emitter of the primary trigger transistor, and the emitter of the primary trigger transistor is also connected to the output circuit; one end of the second resistor is connected to the collector of the primary trigger transistor, and the other end is connected to the primary diode, and one end of the primary diode is grounded; the primary trigger transistor receives the comparison result output by the operational amplifier, and when the comparison result indicates that the corresponding output current is greater than a predetermined value, the primary trigger transistor is turned on.

[0015] The primary trigger resistor is set to enable the primary trigger transistor to work normally.

[0016] Specifically, when the voltage at the non-inverting input terminal of the operational amplifier is less than the voltage at the inverting input terminal of the operational amplifier, the comparison result output by the output terminal of the operational amplifier indicates that the corresponding output current is greater than the predetermined value. Let the voltage at the non-inverting input terminal of the operational amplifier be U1, and the voltage at the inverting input terminal of the operational amplifier be U3. When the output current of the output circuit is greater than the predetermined value, U3>U1, then the operational amplifier outputs a low level to the primary trigger transistor (which is a PNP type transistor), turning on the primary trigger transistor.

[0017] Specifically, the common trigger circuit includes a first trigger triode, a second trigger triode, a first trigger resistor, a second trigger resistor, and a light-emitting element in an optical coupler; the base of the first trigger triode is connected to the collector of the primary trigger resistor, the emitter of the first trigger triode is grounded, and the two ends of the first trigger resistor are respectively connected to the base and emitter of the first trigger triode; the two ends of the second trigger resistor are respectively connected to the base and emitter of the second trigger triode; the base of the second trigger triode is connected to the collector of the first trigger triode, the collector of the second trigger triode is grounded, and the emitter of the second trigger triode is connected to the light-emitting element in the optical coupler; when the primary trigger triode is turned on, the first trigger triode and the second trigger triode are respectively turned on, so that the light-emitting element in the optical coupler emits light and generates a turn-off trigger signal. The first trigger resistor and the second trigger resistor are also set to respectively enable the first trigger triode and the second trigger triode to work normally.

[0018] Specifically, the main control circuit includes a control chip, a light-receiving element in an optocoupler, a MOS tube, a first detection unit and a second detection unit; the GATE pin of the control chip is connected to the gate of the MOS tube, the drain of the MOS tube is connected to a power supply, the source of the MOS tube is connected to one end of the first detection unit, and the other end of the first detection unit is grounded; the SENSE pin of the control chip is connected to one end of the second detection unit, and the other end of the second detection unit is also connected to the source of the MOS tube; one end of the light-receiving element in the optocoupler is connected to the FB pin of the control chip, and the other end is grounded; the VDD pin of the control chip is connected to the power supply; when the light-receiving element in the optocoupler receives a shutdown trigger signal, the light-receiving element in the optocoupler is turned on, so that the control chip controls the MOS tube to be disconnected, thereby controlling the power supply to stop working.

[0019] When the primary trigger transistor is turned on, the level of the collector of the primary trigger transistor is pulled high, and a high level will be output to the first trigger transistor (which is an NPN type transistor), so that the first trigger transistor is turned on, the level of the collector of the first trigger transistor is pulled low, and the first trigger transistor outputs a low level to the second trigger transistor, the second trigger transistor is turned on, the level of the emitter of the second trigger transistor is pulled low, and finally a low level is output, which pulls the light-receiving element in the optocoupler into a low level, strengthens the conduction of the light-receiving element in the optocoupler, and at the same time, the light-emitting element in the optocoupler emits light to generate a shutdown trigger signal, thereby increasing the current of the light-receiving element in the optocoupler and entering a protection state. At this time, the control chip outputs a signal to control the MOS tube to disconnect, thereby stopping the power supply from working, thereby achieving the protection of each path.

[0020] Specifically, the first detection unit includes a first detection resistor, a second detection resistor, a third detection resistor and a fourth detection resistor, which are connected in series in sequence, and an input end of the first detection resistor is connected to a source of the MOS tube, and an output end of the fourth detection resistor is grounded; the first detection unit includes a fifth detection resistor, one end of the fifth detection resistor is connected to the source of the MOS tube, and the other end is connected to a SENSE pin of a control chip; the power supply current is detected by detecting the current of the SENSE pin of the control chip.

[0021] Among them, the model of the control chip is OB2273 or LD7750.

[0022] The advantages of the present invention are:

[0023] Compared with the prior art, the overcurrent protection circuit of the power supply with multiple outputs of the present invention can provide overcurrent protection for each output circuit by setting an overcurrent detection circuit on each output circuit, and when one or more output currents have an overcurrent problem due to an output short circuit or other reasons, the problem can be discovered in time and a response can be made to shut down the power supply, thereby improving safety performance and reducing the probability of safety accidents.

[0024] The overcurrent protection circuit connects the overcurrent detection resistor to the positive electrode of the output circuit so that the outputs of each channel are not interfered with by each other on the basis of a common ground. The overcurrent protection circuit can still work normally when the outputs of each channel share a common ground, and also reduces the difficulty and complexity of circuit wiring. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of an overcurrent protection circuit of a power supply with multiple outputs implemented by the present invention.

[0026] Figure 2 yes Figure 1 Schematic diagram of the circuit structure of part A.

[0027] Figure 3 yes Figure 1 Schematic diagram of the circuit structure of part B.

[0028] Figure 4 It is the existing technology Figure 1 Part A corresponds to the structural diagram of the circuit.

[0029] Figure 5 It shows Figure 2 and Figure 4 Differentiate the structural diagram of the circuit. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] The technical solution of the present invention is as follows:

[0032] like Figure 1-5 The overcurrent protection circuit of the power supply with multiple outputs implemented by the present invention is connected between the power supply output terminal and the load power input terminal, and the overcurrent protection circuit includes:

[0033] At least one output circuit 1 for outputting current;

[0034] At least one over-current detection circuit 2, which is used to detect the output current and compare whether the output current is greater than a predetermined value, thereby generating a corresponding comparison result; the over-current detection circuit 2 is connected to a corresponding output circuit 1;

[0035] At least one primary trigger circuit 3, the primary trigger circuit 3 is connected to the corresponding over-current detection circuit 2 to receive the comparison result output by the corresponding over-current detection circuit 2, when the comparison result output by any over-current detection circuit 2 indicates that the corresponding output current is greater than a predetermined value, the primary trigger circuit 3 is turned on;

[0036] A common trigger circuit 4 is connected to each primary trigger circuit 3. When the primary trigger circuit 3 is turned on, the common trigger circuit 4 is turned on, and the common trigger circuit 4 sends a shutdown trigger signal.

[0037] The main control circuit 5 is connected to the common trigger circuit 4 and is used to control the current output by the power supply. When the main control circuit 5 receives the shutdown trigger signal output by the common trigger circuit 4, the main control circuit 5 controls the power supply to stop working.

[0038] In the present invention, an overcurrent detection circuit 2 is provided on each output circuit 1, and the output current in each circuit is detected by the overcurrent detection circuit 2, and a comparison result is generated. When the comparison result indicates that the corresponding output current is greater than a predetermined value, the primary trigger circuit 3 and the common trigger circuit 4 are turned on in sequence, and the common trigger circuit 4 sends a shutdown trigger signal to the main control circuit 5. The main control circuit 5 controls the power supply to stop working, and can perform overcurrent protection on each output circuit. When one or more output currents have an overcurrent problem due to an output short circuit or other reasons, the problem can be discovered in time, and a response can be made to shut down the power supply, thereby improving safety performance and reducing the probability of safety accidents.

[0039] In this embodiment, the output circuit 1 may include two output circuits, namely a first output circuit 11 and a second output circuit 12; the overcurrent protection circuit 2 can be applied to a circuit including an AC input protection module 01, a bridge rectifier module 02, a filter module 03, a transformer protection module 04 and a transformer 05 to perform overcurrent protection.

[0040] The AC power is input from the AC power input protection module 01, rectified by the bridge rectifier module 02 and converted into pulsating DC power, and then processed by the filter module 03 to filter out the noise, so as to obtain smooth pulsating DC power, which is supplied to the transformer 05 through the transformer protection module 04; the transformer protection module 04 is connected to the primary side of the transformer 05 to perform overcurrent protection on the transformer 05 to prevent the transformer 05 from being broken down due to excessive current.

[0041] The first output circuit 11 and the second output circuit 12 are connected to the first transformer secondary side and the second transformer secondary side respectively. The first transformer secondary side and the second transformer secondary side are both coupled to the primary side of the transformer 05 .

[0042] A Schottky diode D11 is usually connected to the first output circuit 11 to protect the first output circuit 11. When a reverse current flows through the Schottky diode D11 in the circuit, the Schottky diode D11 will be broken down, causing the circuit to stop working. When a new Schottky diode D11 is replaced, the circuit can resume working, thereby improving the safety performance of the circuit. Since the pulsating direct current from the primary side of the transformer 05 may also contain clutter, a filter protection unit 06 composed of filter capacitors EC7 and EC8 is usually connected to the output end of the Schottky diode D11 to filter out the clutter. Similarly, the second output circuit 12 can also be provided with a corresponding Schottky diode D12 and a filter protection unit as described above.

[0043] In this embodiment, the overcurrent detection circuit 2 includes a first overcurrent detection circuit 21 and a second overcurrent detection circuit 22, which are respectively connected to the output ends of the first output circuit 11 and the second output circuit 12; the primary trigger circuit 3 includes a first primary trigger circuit 31 and a second primary trigger circuit 32.

[0044] In this embodiment, the first overcurrent detection circuit 21 includes a first overcurrent detection resistor D11-K, a first voltage-dividing resistor R65, a second voltage-dividing resistor R50 and a first operational amplifier IC4; one end of the first overcurrent detection resistor D11-K is connected to the positive electrode of the first output circuit 11, and the other end is connected to one end of the first voltage-dividing resistor R65; the other end of the first voltage-dividing resistor R65 is connected to the non-inverting input terminal of the first operational amplifier IC4; one end of the second voltage-dividing resistor R50 is connected to the output positive electrode of the first output circuit 11, and the other end is connected to the inverting input terminal of the first operational amplifier IC4; the output terminal of the first operational amplifier IC4 is connected to the first primary trigger circuit 31; the first operational amplifier IC4 is used to compare the voltage on the non-inverting input terminal of the first operational amplifier IC4 and the inverting input terminal of the operational amplifier IC4 to generate a comparison result so that the output terminal of the first operational amplifier IC4 can be output.

[0045] In this embodiment, the first primary trigger circuit 31 includes a first primary trigger transistor Q7, a first primary trigger resistor R52, a first resistor R53 and a second resistor R54. One end of the first resistor R53 is connected to the output end of the first operational amplifier IC4, and the other end is connected to the base of the first primary trigger transistor Q7. The two ends of the first primary trigger resistor R52 are respectively connected to the base of the first primary trigger transistor Q7 and the emitter of the first primary trigger transistor Q7, and the emitter of the first primary trigger transistor Q7 is also connected to the first output circuit 11. One end of the second resistor R54 is connected to the collector of the first primary trigger transistor Q7, and the other end is grounded. The first primary trigger transistor Q7 receives the comparison result output by the first operational amplifier IC4, and when the comparison result indicates that the corresponding output current is greater than a predetermined value, the first primary trigger transistor Q7 is turned on. The first primary trigger resistor R52 is set to enable the first primary trigger transistor Q7 to work normally.

[0046] When the voltage at the non-inverting input terminal of the first operational amplifier IC4 is less than the voltage at the inverting input terminal of the first operational amplifier IC4, the comparison result outputted by the output terminal of the first operational amplifier IC4 indicates that the corresponding output current is greater than the predetermined value. Let the voltage at the non-inverting input terminal of the first operational amplifier IC4 be U1, and the voltage at the inverting input terminal of the first operational amplifier IC4 be U3. When the output current of the first output circuit 11 is greater than the predetermined value, U3>U1, then the first operational amplifier IC4 outputs a low level to the first primary trigger transistor Q7 (which is a PNP type transistor), so that the first primary trigger transistor Q7 is turned on.

[0047] Similarly, the second overcurrent detection circuit 21 includes a second overcurrent detection resistor R75, a third voltage-dividing resistor R68, a fourth voltage-dividing resistor R78 and a second operational amplifier IC8; one end of the second overcurrent detection resistor R75 is connected to the positive electrode of the second output circuit 12, and the other end is connected to one end of the third voltage-dividing resistor R68; the other end of the third voltage-dividing resistor R68 is connected to the non-inverting input terminal of the second operational amplifier IC8; one end of the third voltage-dividing resistor R68 is connected to the output positive electrode of the second output circuit 12, and the other end is connected to the inverting input terminal of the second operational amplifier IC8; the output terminal of the second operational amplifier IC8 is connected to the second primary trigger circuit 32; the second operational amplifier IC8 is used to compare the voltage on the non-inverting input terminal of the second operational amplifier IC8 and the inverting input terminal of the second operational amplifier IC8 to generate a comparison result so that the output terminal of the second operational amplifier IC8 can be output.

[0048] Similarly, in the present embodiment, the second primary trigger circuit 32 includes a second primary trigger transistor Q10, a second primary trigger resistor R80, a third resistor R81, a fourth resistor R82 and a first primary diode D21, one end of the third resistor R81 is connected to the output end of the second operational amplifier IC8, and the other end is connected to the base of the second primary trigger transistor Q10; the two ends of the second primary trigger resistor R80 are respectively connected to the base of the second primary trigger transistor Q10 and the emitter of the second primary trigger transistor Q10, and the emitter of the second primary trigger transistor Q10 is also connected to the second output circuit 12; one end of the fourth resistor R82 is connected to the collector of the second primary trigger transistor Q10, and the other end is connected to the first primary diode D21, and one end of the first primary diode D21 is grounded; the second primary trigger transistor Q10 receives the comparison result output by the second operational amplifier IC8, and when the comparison result indicates that the corresponding output current is greater than the predetermined value, the second primary trigger transistor Q10 is turned on. The second primary trigger resistor R80 is provided to enable the second primary trigger transistor Q10 to work normally.

[0049] The working principles of the second overcurrent detection circuit 22 and the second primary trigger circuit 32 are the same as those of the first overcurrent detection circuit 21 and the first primary trigger circuit 31; by connecting the first overcurrent detection resistor D11-K to the positive electrode of the first output circuit 11, and connecting the second overcurrent detection resistor R75 to the positive electrode of the second output circuit 12, the outputs of each channel can be free from interference with each other on the basis of a common ground, and the overcurrent protection circuit can still work normally when the outputs of each channel share a common ground, while also reducing the difficulty and complexity of circuit wiring.

[0050] In this embodiment, the common trigger circuit 4 includes a first trigger transistor Q16, a second trigger transistor Q15, a first trigger resistor R55, a second trigger resistor R64, and a light-emitting element PC1A in an optical coupler; the base of the first trigger transistor Q16 is connected to the collector of the primary trigger resistor, the emitter of the first trigger transistor Q16 is grounded, the two ends of the first trigger resistor R55 are connected to the base and emitter of the first trigger transistor Q16 respectively; the two ends of the second trigger resistor R64 are connected to the second trigger transistor Q16 respectively. The base and emitter of the transistor Q15 are connected; the base of the second trigger transistor Q15 is connected to the collector of the first trigger transistor Q16, the collector of the second trigger transistor Q15 is grounded, and the emitter of the second trigger transistor Q15 is connected to the light-emitting element in the optical coupler; when the first primary trigger transistor Q7 or the second primary trigger transistor Q10 is turned on, the first trigger transistor Q16 and the second trigger transistor Q15 are turned on respectively, so that the light-emitting element PC1A in the optical coupler emits light and generates a shutdown trigger signal. The first trigger resistor R55 and the second trigger resistor R64 are also set to respectively make the first trigger transistor Q16 and the second trigger transistor Q15 work normally, so that this embodiment can be realized.

[0051] In this embodiment, the main control circuit 4 includes a control chip U101, a light receiving element PC1B in an optical coupler, a MOS tube Q101, a first detection unit 41, and a second detection unit 42; the GATE pin of the control chip U101 is connected to the gate of the MOS tube Q101, the drain of the MOS tube Q101 is connected to the primary side of the transformer 05, the source of the MOS tube Q101 is connected to one end of the first detection unit 41, and the other end of the first detection unit 41 is grounded; the SENSE pin of the control chip U101 is connected to the second detection unit 42. One end of the light receiving element PC1B in the optocoupler is connected to the FB pin of the control chip U101, and the other end is grounded; the VDD pin of the control chip U101 is connected to the AC input protection module 01; when the light receiving element PC1B in the optocoupler receives the shutdown trigger signal, the light receiving element PC1B in the optocoupler is turned on, so that the control chip U101 controls the MOS tube Q101 to be disconnected, thereby controlling the power supply to stop working.

[0052] Take the working process when the first primary trigger transistor Q7 is turned on as an example: when the first primary trigger transistor Q7 is turned on, the level of the collector of the first primary trigger transistor Q7 is pulled high, and a high level is output to the first trigger transistor Q16 (which is an NPN type transistor), so that the first trigger transistor Q16 is turned on, the level of the collector of the first trigger transistor Q16 is pulled low, and the first trigger transistor Q16 outputs a low level to the second trigger transistor Q15, the second trigger transistor Q15 is turned on, and the second trigger transistor Q15 is turned on. The level of the emitter of the transistor Q15 is pulled down, and finally a low level is output, which pulls the light receiving element PC1A in the optocoupler into a low level, strengthens the conduction of the light receiving element PC1B in the optocoupler, and at the same time, the light emitting element PC1A in the optocoupler emits light to generate a shutdown trigger signal, thereby increasing the current of the light receiving element PC1B in the optocoupler and entering a protection state. At this time, the control chip U101 outputs a signal to control the MOS tube Q101 to disconnect, thereby stopping the transformer 05 from working, thereby achieving the protection of each circuit.

[0053] In this embodiment, the first detection unit 41 includes a first detection resistor R109, a second detection resistor R114, a third detection resistor R117 and a fourth detection resistor R118, which are connected in series in sequence, and an input end of the first detection resistor R109 is connected to the source of the MOS tube Q101, and an output end of the fourth detection resistor R118 is grounded; the first detection unit 41 includes a fifth detection resistor R111, one end of the fifth detection resistor R111 is connected to the source of the MOS tube Q101, and the other end is connected to the SENSE pin of the control chip U101; the power supply current is detected by detecting the current of the SENSE pin of the control chip U101.

[0054] Among them, the model of the control chip U101 is OB2273 or LD7750.

[0055] The advantages of the present invention are:

[0056] Compared with the prior art, the overcurrent protection circuit of the power supply with multiple outputs implemented by the present invention can provide overcurrent protection for each output circuit by setting an overcurrent detection circuit on each output circuit, and when one or more output currents have an overcurrent problem due to an output short circuit or other reasons, the problem can be discovered in time and a response can be made to shut down the power supply, thereby improving safety performance and reducing the probability of safety accidents.

[0057] The overcurrent protection circuit connects the overcurrent detection resistor to the positive electrode of the output circuit so that the outputs of each channel are not interfered with by each other on the basis of a common ground. The overcurrent protection circuit can still work normally when the outputs of each channel share a common ground, and also reduces the difficulty and complexity of circuit wiring.

[0058] The above lists the preferred embodiments of the present invention, which are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An overcurrent protection circuit for a power supply with multiple outputs, connected between the power supply output terminal and the load power input terminal, characterized in that: The overcurrent protection circuit comprises: At least one output circuit for outputting current; At least one over-current detection circuit, which is used to detect the output current and compare whether the output current is greater than a predetermined value, thereby generating a corresponding comparison result; the over-current detection circuit is connected to a corresponding output circuit; at least one primary trigger circuit, the primary trigger circuit being connected to the corresponding overcurrent detection circuit to receive a comparison result output by the corresponding overcurrent detection circuit, and the primary trigger circuit being turned on when the comparison result output by any one of the overcurrent detection circuits indicates that the corresponding output current is greater than a predetermined value; A common trigger circuit connected to each of the primary trigger circuits, when the primary trigger circuit is turned on, the common trigger circuit is turned on, and the common trigger circuit sends a shutdown trigger signal; A main control circuit is connected to the common trigger circuit and is used to control the current output by the power supply. When the main control circuit receives a shutdown trigger signal output by the common trigger circuit, the main control circuit controls the power supply to stop working; The overcurrent detection circuit comprises an overcurrent detection resistor, a first voltage-dividing resistor, a second voltage-dividing resistor, and an operational amplifier; one end of the overcurrent detection resistor is connected to the positive electrode of the output circuit, and the other end is connected to one end of the first voltage-dividing resistor; the other end of the voltage-dividing resistor is connected to the non-inverting input end of the operational amplifier; one end of the second voltage-dividing resistor is connected to the output positive electrode of the output circuit, and the other end is connected to the inverting input end of the operational amplifier; The output end of the operational amplifier is connected to the corresponding primary trigger circuit; the operational amplifier is used to compare the voltage on the non-inverting input end of the operational amplifier with the voltage on the inverting input end of the operational amplifier to generate a comparison result so that the output end of the operational amplifier can output; The primary trigger circuit includes a primary trigger transistor, a primary trigger resistor, a first resistor, a second resistor and a primary diode, one end of the first resistor is connected to the output end of the operational amplifier, and the other end is connected to the base of the primary trigger transistor; The two ends of the primary trigger resistor are respectively connected to the base of the primary trigger transistor and the emitter of the primary trigger transistor, and the emitter of the primary trigger transistor is also connected to the output circuit. One end of the second resistor is connected to the collector of the primary trigger transistor, and the other end is connected to the primary diode, one end of the primary diode is grounded; the primary trigger transistor receives the comparison result output by the operational amplifier, and when the comparison result indicates that the corresponding output current is greater than a predetermined value, the primary trigger transistor is turned on; The common trigger circuit includes a first trigger triode, a second trigger triode, a first trigger resistor, a second trigger resistor, and a light-emitting element in an optical coupler; the base of the first trigger triode is connected to the collector of the primary trigger resistor, the emitter of the first trigger triode is grounded, and the two ends of the first trigger resistor are respectively connected to the base and emitter of the first trigger triode; the two ends of the second trigger resistor are respectively connected to the base and emitter of the second trigger triode; The base of the second trigger transistor is connected to the collector of the first trigger transistor, the collector of the second trigger transistor is grounded, and the emitter of the second trigger transistor is connected to the light-emitting element in the optocoupler; when the primary trigger transistor is turned on, the first trigger transistor and the second trigger transistor are turned on respectively, so that the light-emitting element in the optocoupler emits light and generates a shutdown trigger signal.

2. The overcurrent protection circuit of a power supply with multiple outputs as claimed in claim 1, characterized in that: When the voltage at the non-inverting input terminal of the operational amplifier is less than the voltage at the inverting input terminal of the operational amplifier, the comparison result output by the output terminal of the operational amplifier indicates that the corresponding output current is greater than a predetermined value.

3. The overcurrent protection circuit of a power supply with multiple outputs as claimed in claim 1, characterized in that: The main control circuit includes a control chip, a light-receiving element in an optocoupler, a MOS tube, a first detection unit and a second detection unit; the GATE pin of the control chip is connected to the gate of the MOS tube, the drain of the MOS tube is connected to a power supply, the source of the MOS tube is connected to one end of the first detection unit, and the other end of the first detection unit is grounded; the SENSE pin of the control chip is connected to one end of the second detection unit, and the other end of the second detection unit is also connected to the source of the MOS tube; one end of the light-receiving element in the optocoupler is connected to the FB pin of the control chip, and the other end is grounded; the VDD pin of the control chip is connected to the power supply; when the light-receiving element in the optocoupler receives a shutdown trigger signal, the light-receiving element in the optocoupler is turned on, so that the control chip controls the MOS tube to be disconnected, thereby controlling the power supply to stop working.

4. The overcurrent protection circuit of a power supply with multiple outputs as claimed in claim 3, characterized in that: The first detection unit includes a first detection resistor, a second detection resistor, a third detection resistor and a fourth detection resistor, wherein the first detection resistor, the second detection resistor, the third detection resistor and the fourth detection resistor are connected in series in sequence, and an input end of the first detection resistor is connected to a source of the MOS tube, and an output end of the fourth detection resistor is grounded; the first detection unit includes a fifth detection resistor, one end of the fifth detection resistor is connected to the source of the MOS tube, and the other end is connected to a SENSE pin of a control chip; The power supply current is detected by detecting the current of the SENSE pin of the control chip.

5. The overcurrent protection circuit of a power supply with multiple outputs as claimed in claim 3, characterized in that: The model of the control chip is OB2273 or LD7750.

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