Locking type protection circuit, switching power supply and LED driving power supply

Abstract

The utility model relates to a locking type protection circuit, a switching power supply and an LED driving power supply. The locking type protection circuit comprises a current sampling module, a comparator module, a locking control module and a protection switch module. The current sampling module is used for collecting current signals output by the switching power supply; the comparator module is used for comparing the current signal with a preset reference signal and outputting a control signal when the current signal is greater than the preset reference signal; and the locking control module is used for disconnecting the protection switch module according to the control signal so as to cut off the output end of the switching power supply, and is used for controlling the protection switch module to maintain a disconnected state after being disconnected. The locking type protection circuit can realize quick response protection when the switching power supply outputs overcurrent or short circuit, safely and reliably cut off the output of the switching power supply, realize a locking type protection function, prevent self-recovery large current from impacting a power device, and reduce systematic safety problems caused by overcurrent or short circuit.

Description

Technical Field

[0001] This utility model relates to the field of power supply protection, and in particular to a lockout protection circuit, a switching power supply, and an LED driver power supply. Background Technology

[0002] In existing technology, the protection function of a switching power supply is self-recovering when a large current is generated due to output overcurrent or short circuit. When a short circuit or overcurrent occurs at the output terminal, the power supply will temporarily shut down the output to protect the circuit; when the short circuit or overcurrent condition disappears, the power supply will automatically resume output. Once a large current is generated due to output overcurrent or short circuit, entering the self-recovery state without resolving the overcurrent or short circuit issue will subject the power devices to extremely high current stress, which can easily lead to breakdown of the power devices, damage to the switching power supply, and even safety problems. Switching power supplies are used in LED driver lighting products, where the output voltage is very high; using a self-recovering output overcurrent or short circuit protection function can easily cause safety issues. Utility Model Content

[0003] The technical problem to be solved by this utility model is to provide a lockout protection circuit, a switching power supply, and an LED driver power supply.

[0004] The technical solution adopted by this utility model to solve its technical problem is: to provide a lockout protection circuit for use in switching power supplies, the lockout protection circuit including: a current sampling module, a comparator module, a lockout control module and a protection switch module;

[0005] The current sampling module and the protection switch module are connected to the output terminal of the switching power supply. The comparator module is connected to the current sampling module and the interlocking control module. The interlocking control module is connected to the protection switch module.

[0006] The current sampling module is used to collect the current signal output by the switching power supply;

[0007] The comparator module is used to compare the current signal with a preset reference signal, and output a control signal when the current signal is greater than the preset reference signal;

[0008] The interlocking control module is used to disconnect the protection switch module according to the control signal, thereby cutting off the output terminal of the switching power supply, and to control the protection switch module to maintain the disconnected state after disconnection.

[0009] Furthermore, the comparator module includes a comparator, a positive feedback unit, and a reference unit;

[0010] The non-inverting input of the comparator is connected to the current sampling module, the inverting input of the comparator is connected to the reference unit, the positive power supply of the comparator is connected to the input power supply voltage, the negative power supply of the comparator is grounded, and the output of the comparator is connected to the latching control module.

[0011] The positive feedback unit is connected between the non-inverting input and the output of the comparator.

[0012] The reference unit is used to provide the preset reference signal;

[0013] The comparator acquires the current signal from the current sampling module, acquires the preset reference signal from the reference unit, and compares the current signal with the preset reference signal.

[0014] Furthermore, the reference unit includes a Zener diode, a fourth resistor, a sixth resistor, and a seventh resistor;

[0015] The anode of the Zener diode is grounded, and the cathode of the Zener diode is connected to the input power supply voltage through the fourth resistor; one end of the sixth resistor is connected to the cathode of the Zener diode, and the other end is connected to the anode of the Zener diode through the seventh resistor. The other end of the sixth resistor is also connected to the inverting input terminal of the comparator.

[0016] Furthermore, the positive feedback unit includes a third resistor and a second diode;

[0017] The anode of the second diode is connected to the output terminal of the comparator, and the cathode of the second diode is connected to the non-inverting input terminal of the comparator through the third resistor.

[0018] Furthermore, the comparator module also includes an anti-false triggering unit connected between the non-inverting input and the inverting input of the comparator.

[0019] Furthermore, the interlocking control module includes: a second resistor and a thyristor;

[0020] The cathode of the thyristor is grounded, the gate of the thyristor is connected to the comparator module, and the anode of the thyristor is connected to the input power supply voltage through the second resistor and is also connected to the protection switch module.

[0021] Furthermore, the current sampling module includes a sampling resistor, and the protection switch module includes a second switching transistor and an eighth resistor;

[0022] The sampling resistor and the second switching transistor are connected in series with the output terminal of the switching power supply; one end of the sampling resistor is grounded, and the other end is connected to the source of the second switching transistor and the comparator module; the gate of the second switching transistor is connected to the anode of the thyristor, and the eighth resistor is connected in parallel between the gate and the source of the second switching transistor.

[0023] Furthermore, the lockout protection circuit also includes a filter module connected between the comparator module and the lockout control module.

[0024] This utility model also provides a switching power supply, including the lockout protection circuit described in any of the above claims.

[0025] This utility model also provides an LED driver power supply, including the switching power supply described above.

[0026] The present invention has the following advantages: by acquiring the current signal output by the switching power supply through the current sampling module, the comparator module outputs a control signal when the current signal is greater than the preset reference signal, and the interlocking control module disconnects the protection switch module and maintains the disconnected state according to the control signal. This can achieve fast response protection when the switching power supply outputs overcurrent or short circuit, safely and reliably cut off the output of the switching power supply, realize the interlocking protection function, prevent self-recovering large current from impacting power devices, and reduce systemic safety problems caused by overcurrent or short circuit. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0028] Figure 1 This is a structural block diagram of an embodiment of the lockout protection circuit of this utility model;

[0029] Figure 2 This is a circuit diagram of an embodiment of the lockout protection circuit of this utility model;

[0030] Figure 3 This is a circuit diagram of an embodiment of the switching power supply of this utility model. Detailed Implementation

[0031] To provide a clearer understanding of the technical features, objectives, and effects of this utility model, the specific embodiments of this utility model are now described in detail with reference to the accompanying drawings. In the following description, the terms "first," "second," "third," etc., are used only for the convenience of describing this technical solution and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0032] The latching protection circuit of this invention can be applied to non-isolated switching power supplies, such as BUCK circuits.

[0033] like Figure 1 As shown, in one embodiment of the lockout protection circuit of this utility model, it includes: a current sampling module 11, a comparator module 12, a lockout control module 14, and a protection switch module 13. The current sampling module 11 and the protection switch module 13 are connected to the output terminal of the switching power supply, the comparator module 12 is connected to the current sampling module 11 and the lockout control module 14, and the lockout control module 14 is connected to the protection switch module 13.

[0034] The current sampling module 11 is used to acquire the current signal output by the switching power supply. The comparator module 12 is used to compare the current signal with a preset reference signal, and output a control signal when the current signal is greater than the preset reference signal. The interlocking control module 14 is used to disconnect the protection switch module 13 according to the control signal, thereby cutting off the output of the switching power supply, and to control the protection switch module 13 to remain in the disconnected state after disconnection.

[0035] In this embodiment, both the current sampling module 11 and the protection switch module 13 are connected between the input and output terminals of the switching power supply. The output terminal of the switching power supply is connected to the load, supplying power to the load. The current sampling module 11 is used to collect the current signal output by the switching power supply to the load. When an overcurrent or short circuit occurs, the current signal collected by the current sampling module 11 rises, and when it exceeds a preset reference signal, the comparator module 12 outputs a control signal. After receiving the control signal, the latching control module 14 disconnects the protection switch module 13, thereby cutting off the output terminal of the switching power supply and stopping the power supply. After the output terminal of the switching power supply is disconnected, the current signal decreases, the comparator module 12 stops outputting the control signal, and the latching control module 14 controls the protection switch module 13 to remain in the open state.

[0036] Compared to existing self-resetting protection functions, the lockout protection circuit of this utility model can quickly cut off the circuit when an output overcurrent or output short circuit occurs. It will not automatically restore the output after the large current drops, but will continue to cut off the circuit to achieve lockout protection. This avoids the circuit from continuing to work before the short circuit problem is resolved during maintenance, prevents the self-resetting large current from impacting the power device, and reduces systemic safety problems caused by overcurrent or short circuit.

[0037] Furthermore, the lockout protection circuit also includes a filter module connected between the comparator module 12 and the lockout control module 14. The filter module filters the control signal output by the comparator module 12 and then sends the processed control signal to the lockout control module 14.

[0038] Furthermore, comparator module 12 includes a comparator, a positive feedback unit, and a reference unit. The comparator can be an LM324A model.

[0039] The comparator's non-inverting input is connected to the current sampling module 11, its inverting input is connected to the reference unit, its positive power supply is connected to the input power supply voltage VCC, its negative power supply is grounded, and its output is connected to the latching control module 14. A positive feedback unit is connected between the comparator's non-inverting input and output. The reference unit provides a preset reference signal. The comparator acquires a current signal from the current sampling module 11 and a preset reference signal from the reference unit, comparing the current signal with the preset reference signal.

[0040] Furthermore, the comparator module 12 also includes an anti-false triggering unit connected between the non-inverting input and the inverting input of the comparator.

[0041] refer to Figure 2 The following describes a specific embodiment of the lockout protection circuit.

[0042] In this embodiment, the positive feedback unit includes a third resistor R3 and a second diode D2. The anode of the second diode D2 is connected to the output terminal of the comparator, and the cathode of the second diode D2 is connected to the non-inverting input terminal of the comparator through the third resistor R3. The positive feedback unit enables the comparator to operate in saturation, with the output voltage approximately equal to the input power supply voltage VCC.

[0043] In this embodiment, the reference unit includes a Zener diode ZN, a fourth resistor R4, a sixth resistor R6, and a seventh resistor R7. The anode of the Zener diode ZN is grounded, and the cathode of the Zener diode ZN is connected to the input power supply voltage VCC through the fourth resistor R4. One end of the sixth resistor R6 is connected to the cathode of the Zener diode ZN, and the other end is connected to the anode of the Zener diode ZN through the seventh resistor R7. The other end of the sixth resistor R6 is also connected to the inverting input of the comparator. The Zener diode ZN provides a stable voltage of 1.25V, which, after being divided by the sixth resistor R6 and the seventh resistor R7, yields a preset reference signal.

[0044] In this embodiment, the anti-false triggering unit includes a first capacitor C1. The two ends of the first capacitor C1 are respectively connected to the non-inverting input terminal and the inverting input terminal of the comparator, which can prevent the circuit from being falsely triggered by the lockout protection when it is powered on.

[0045] In this embodiment, the filtering module includes a second capacitor C2 and a fifth resistor R5. One end of the second capacitor C2 is connected to the output of the comparator through the fifth resistor R5, and the other end is grounded.

[0046] In this embodiment, the current sampling module 11 includes a sampling resistor RS, and the protection switch module 13 includes a second switch transistor Q2 and an eighth resistor R8. The second switch transistor Q2 is an NMOS transistor. The sampling resistor RS and the second switch transistor Q2 are connected in series with the output terminal of the switching power supply; one end of the sampling resistor RS is grounded, and the other end is connected to the source of the second switch transistor Q2 and the comparator module 12; the gate of the second switch transistor Q2 is connected to the anode of the thyristor, and the eighth resistor R8 is connected in parallel between the gate and source of the second switch transistor Q2.

[0047] In this embodiment, the interlocking control module 14 includes a second resistor R2 and a silicon controlled rectifier (SCR). The cathode of the SCR is grounded, the gate of the SCR is connected to the comparator module 12, and the anode of the SCR is connected to the input power supply voltage VCC through the second resistor R2 and is also connected to the protection switch module 13. The gate of the SCR is connected to a fifth resistor R5, which in turn connects to the output of the comparator.

[0048] The specific working principle of the latching protection circuit in this embodiment is as follows:

[0049] The load is connected between the positive output terminal OUT+ and the negative output terminal OUT- of the switching power supply. When the load experiences overcurrent or a short circuit, the current flowing through the sampling resistor RS increases. The CS potential (i.e., the current signal) is applied to the non-inverting input of the comparator and compared with the potential of the inverting input. The potential of the inverting input is obtained by dividing the 1.25V provided by the Zener diode ZN through resistors R6 and R7 (i.e., the preset reference signal). When the potential of the non-inverting input is higher than that of the inverting input, the comparator outputs a high level (i.e., the control signal); when the potential of the non-inverting input is lower than that of the inverting input, the comparator outputs a low level.

[0050] A high-level signal triggers the SCR to turn on, pulling down the gate potential of the second switching transistor Q2 and turning it off, thus cutting off the output circuit of the switching power supply and achieving the protection purpose. After protection is triggered, the input power supply voltage VCC flows through the second resistor R2 and the SCR. Even if the high-level signal disappears, the SCR remains on, keeping the second switching transistor Q2 off, thus achieving a latch-up protection. When the input power supply voltage VCC is disconnected and the system restarts, the SCR returns to the off state, and the switching power supply resumes output.

[0051] The protection circuit of this invention is simple to control. By subtracting a preset reference signal from the sampled current signal and combining it with a positive feedback compensation signal, the conduction control of the SCR is achieved, thereby realizing the disconnection protection of the second switching transistor Q2. This allows the switching power supply to respond quickly to protection under overcurrent or short-circuit conditions. In addition, the protection current threshold can be flexibly set by adjusting the voltage division ratio of the sixth resistor R6 and the seventh resistor R7.

[0052] This utility model also provides a switching power supply, including the lockout protection circuit disclosed in any of the above embodiments.

[0053] In one specific embodiment, the switching power supply employs a BUCK circuit. For example... Figure 3 As shown, the BUCK circuit includes a first diode D1, a third diode D3, an inductor L, a first switching transistor Q1, a first electrolytic capacitor EC1, a second electrolytic capacitor EC2, and a ninth resistor RL.

[0054] The anode of the first diode D1 is connected to the positive input terminal VIN+. The cathode of the first diode D1 is connected to the positive terminal of the first electrolytic capacitor EC1 and the drain of the first switching transistor Q1. The cathode of the first electrolytic capacitor EC1 is connected to the negative input terminal VIN- and one end of the sampling resistor RS grounded. The other end of the sampling resistor RS is connected to the negative output terminal OUT- of the switching power supply through the second switching transistor Q2. The gate of the first switching transistor Q1 is connected to the PWM signal. The source of the first switching transistor Q1 is connected to one end of the inductor L and to the cathode of the third diode D3. The anode of the third diode D3 is connected to the drain of the second switching transistor Q2. The other end of the inductor is connected to the positive output terminal OUT+ of the switching power supply, the positive terminal of the second electrolytic capacitor EC2, and one end of the ninth resistor RL. The cathode of the second electrolytic capacitor EC2 and the other end of the ninth resistor RL are connected to the negative output terminal OUT- of the switching power supply.

[0055] The switching power supply of this invention can achieve rapid response protection in the event of output overcurrent or short circuit, safely and reliably cut off the output of the switching power supply, realize the lockout protection function, prevent self-resetting large current from impacting power devices, and reduce systemic safety problems caused by overcurrent or short circuit.

[0056] This invention also provides an LED driver power supply, including the switching power supply disclosed in the above embodiments. The LED driver power supply of this invention can achieve rapid response protection in the event of output overcurrent or short circuit, safely and reliably cutting off the output, realizing a lockout protection function, preventing self-resetting high current from impacting power devices, and reducing systemic safety problems caused by overcurrent or short circuit.

[0057] It is understood that the above embodiments only illustrate preferred embodiments of the present utility model, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present utility model patent. It should be noted that for those skilled in the art, the above technical features can be freely combined, and several modifications and improvements can be made without departing from the concept of the present utility model, all of which fall within the protection scope of the present utility model. Therefore, all equivalent transformations and modifications made within the scope of the claims of the present utility model should fall within the coverage of the claims of the present utility model.

Claims

1. A latching protection circuit, characterized in that, Applied to switching power supplies, the latching protection circuit includes: a current sampling module, a comparator module, a latching control module, and a protection switch module; The current sampling module and the protection switch module are connected to the output terminal of the switching power supply. The comparator module is connected to the current sampling module and the interlocking control module. The interlocking control module is connected to the protection switch module. The current sampling module is used to collect the current signal output by the switching power supply; The comparator module is used to compare the current signal with a preset reference signal, and output a control signal when the current signal is greater than the preset reference signal; The interlocking control module is used to disconnect the protection switch module according to the control signal, thereby cutting off the output terminal of the switching power supply, and to control the protection switch module to maintain the disconnected state after disconnection.

2. The interlocking protection circuit according to claim 1, characterized in that, The comparator module includes a comparator, a positive feedback unit, and a reference unit; The non-inverting input of the comparator is connected to the current sampling module, the inverting input of the comparator is connected to the reference unit, the positive power supply of the comparator is connected to the input power supply voltage, the negative power supply of the comparator is grounded, and the output of the comparator is connected to the latching control module. The positive feedback unit is connected between the non-inverting input and the output of the comparator. The reference unit is used to provide the preset reference signal; The comparator acquires the current signal from the current sampling module, acquires the preset reference signal from the reference unit, and compares the current signal with the preset reference signal.

3. The interlocking protection circuit according to claim 2, characterized in that, The reference unit includes a Zener diode, a fourth resistor, a sixth resistor, and a seventh resistor; The anode of the Zener diode is grounded, and the cathode of the Zener diode is connected to the input power supply voltage through a fourth resistor; One end of the sixth resistor is connected to the cathode of the Zener diode, and the other end is connected to the anode of the Zener diode through the seventh resistor. The other end of the sixth resistor is also connected to the inverting input of the comparator.

4. The interlocking protection circuit according to claim 2, characterized in that, The positive feedback unit includes a third resistor and a second diode; The anode of the second diode is connected to the output terminal of the comparator, and the cathode of the second diode is connected to the non-inverting input terminal of the comparator through the third resistor.

5. The interlocking protection circuit according to claim 2, characterized in that, The comparator module also includes a false trigger prevention unit connected between the non-inverting input and the inverting input of the comparator.

6. The interlocking protection circuit according to claim 1, characterized in that, The interlocking control module includes: a second resistor and a silicon controlled rectifier; The cathode of the thyristor is grounded, the gate of the thyristor is connected to the comparator module, and the anode of the thyristor is connected to the input power supply voltage through the second resistor and is also connected to the protection switch module.

7. The latching protection circuit according to claim 6, characterized in that, The current sampling module includes a sampling resistor, and the protection switch module includes a second switching transistor and an eighth resistor. The sampling resistor and the second switching transistor are connected in series with the output terminal of the switching power supply; one end of the sampling resistor is grounded, and the other end is connected to the source of the second switching transistor and the comparator module; the gate of the second switching transistor is connected to the anode of the thyristor, and the eighth resistor is connected in parallel between the gate and the source of the second switching transistor.

8. The interlocking protection circuit according to claim 1, characterized in that, The lockout protection circuit further includes a filter module connected between the comparator module and the lockout control module.

9. A switching power supply, characterized in that, Includes the latching protection circuit as described in any one of claims 1-8.

10. An LED driver power supply, characterized in that, Includes the switching power supply as described in claim 9.

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