Wide-range overcurrent protection circuit and switching power supply

Abstract

The utility model discloses a wide-range overcurrent protection circuit and a switching power supply, and relates to the field of switching power supply overcurrent protection, the circuit comprises a sampling module, a comparison module and a driving module, the comparison module is connected with the sampling module and the driving module, the driving module is connected with a control chip of the switching power supply, the sampling module is connected with a secondary circuit, and the secondary circuit is connected with the comparison module. The sampling module samples a current signal of the secondary circuit, converts the current signal into a first voltage signal and sends the first voltage signal to the comparison module, the comparison module receives the first voltage signal and sends an overcurrent signal to the driving module when the first voltage signal is larger than a preset threshold value, and the driving module sends the overcurrent signal to the secondary circuit when receiving the overcurrent signal. And the circuit connection between the soft start pin of the control chip and the ground is conducted. Compared with a traditional switching power supply which detects the output of a power switch tube through a power supply control chip of a primary circuit to carry out overcurrent protection, the switching power supply is applied to a secondary circuit of the switching power supply, is not influenced by input voltage, can accurately detect an output overcurrent point, and improves the reliability of the circuit.

Description

Technical Field

[0001] This application relates to the field of overcurrent protection technology for switching power supplies, and in particular to a wide-range overcurrent protection circuit and a switching power supply. Background Technology

[0002] In traditional switching power supply output overcurrent protection, the power control chip detects the output current of the power switching transistor and sets the threshold of its current pin. When the current in the secondary circuit (transformer secondary winding side circuit) increases, the induced current in the primary circuit (transformer primary winding side circuit) will also increase. When the current detected in the primary circuit exceeds the threshold set inside the chip and reaches a certain time, it is considered that the output load is too large and enters the protection mode.

[0003] However, when the output power of the switching power supply is large and the primary circuit does not have PFC (Power Factor Correction), the DC voltage difference after rectification of the upper and lower limit voltages will be large when the input voltage is in the full range of 90VAC-264VAC. Under the condition of large voltage difference in the primary circuit, the primary induced current will also be different, resulting in a large difference in the overcurrent protection point under different input voltage conditions. Utility Model Content

[0004] The main purpose of this application is to provide a wide-range overcurrent protection circuit and a switching power supply, which aims to solve the technical problem that different input voltages cause large differences in the overcurrent protection point when the primary circuit of the switching power supply does not have PFC.

[0005] To achieve the above objectives, this application proposes a wide-range overcurrent protection circuit, which is applied to the secondary circuit of a switching power supply. The wide-range overcurrent protection circuit includes: a sampling module, a comparison module, and a driving module.

[0006] The comparison module is connected to the sampling module and the driving module respectively. The driving module is connected to the control chip of the switching power supply, and the sampling module is connected to the secondary circuit.

[0007] The sampling module is used to sample the current signal of the secondary circuit and convert it into a first voltage signal, which is then sent to the comparison module.

[0008] The comparison module is used to receive a first voltage signal and send an overcurrent signal to the drive module when the voltage signal is greater than a preset threshold.

[0009] The drive module is used to connect the circuit between the soft-start pin of the control chip and ground when an overcurrent signal is received.

[0010] Optionally, the comparison module includes: a first comparison circuit and a second comparison circuit;

[0011] The first comparison circuit is connected to the second comparison circuit and the sampling module, respectively; the second comparison circuit is connected to the driving module.

[0012] The first comparison circuit is used to send a second voltage signal to the second comparison circuit when it receives a first voltage signal and the voltage signal is greater than a preset threshold.

[0013] The second comparison circuit is used to receive a second voltage signal and send an overcurrent signal to the drive module when the voltage signal is less than a preset threshold.

[0014] Optionally, the sampling module includes: a sampling resistor, a first resistor, and a second resistor;

[0015] The first end of the sampling resistor is connected to the first end of the first resistor and ground, the second end of the sampling resistor is connected to the first end of the second resistor, and the comparison module is connected to the second end of the first resistor and the second end of the second resistor, respectively.

[0016] Optionally, the sampling module further includes: a first capacitor, a second capacitor, and a third capacitor;

[0017] The first terminal of the first capacitor is connected to the output terminal of the secondary circuit. The second terminal of the first capacitor is connected to the second terminal of the sampling resistor and the first terminal of the second resistor. The first terminal of the second capacitor is connected to the second terminal of the first resistor and the comparison module. The first terminal of the third capacitor is connected to the second terminal of the second resistor and the comparison module. The second terminals of the second capacitor and the second terminals of the third capacitor are connected to ground.

[0018] Optionally, the first comparison circuit includes: a first comparator, a fourth capacitor, a third resistor, and a fourth resistor;

[0019] The non-inverting input of the first comparator is connected to the sampling module and the third resistor, respectively. The inverting input of the first comparator is connected to the sampling module and the first terminal of the fourth capacitor, respectively. The second terminal of the fourth capacitor is connected to the first terminal of the fourth resistor, respectively. The second comparator circuit is connected to the second terminal of the third resistor and the second terminal of the fourth resistor, respectively.

[0020] Optionally, the second comparison circuit includes: a second comparator, a fifth capacitor, a fifth resistor, a sixth resistor, and a seventh resistor;

[0021] The non-inverting input of the second comparator is connected to the first terminal of the seventh resistor, the first comparator circuit, and the first terminal of the fifth capacitor, respectively. The inverting input of the second comparator is connected to the second terminal of the fifth resistor and the first terminal of the sixth resistor, respectively. The second terminal of the fifth resistor is connected to the first comparator circuit. The second terminal of the sixth resistor and the second terminal of the fifth capacitor are grounded. The second terminal of the seventh resistor is connected to the first power supply.

[0022] Optionally, the driving module includes: a photoelectric conversion unit and a switching unit;

[0023] The photoelectric conversion unit is connected to the comparison module and the switching unit respectively, and the switching unit is connected to the control chip;

[0024] The photoelectric conversion unit is used to send a drive signal to the switching unit when it receives an overcurrent signal;

[0025] The switching unit is used to connect the circuit between the soft-start pin of the control chip and ground when a drive signal is received.

[0026] Optionally, the photoelectric conversion unit includes: an optocoupler, an eighth resistor, and a ninth resistor;

[0027] The first end of the light source of the optocoupler is connected to the second end of the eighth resistor, the first end of the eighth resistor is connected to the comparison module, the second end of the light source of the optocoupler is grounded, the first end of the light receiver of the optocoupler is connected to the second power supply, the second end of the light receiver of the optocoupler is connected to the first end of the ninth resistor, and the second end of the ninth resistor is connected to the switching unit.

[0028] Optionally, the switching unit includes: a MOSFET, a tenth resistor, and an eleventh resistor;

[0029] The gate of the MOS transistor is connected to the photoelectric conversion unit and the first end of the tenth resistor, respectively. The second end of the tenth resistor and the source of the MOS transistor are grounded. The drain of the MOS transistor is connected to the second end of the eleventh resistor. The first end of the eleventh resistor is connected to the soft-start pin of the control chip.

[0030] In addition, to achieve the above objectives, this utility model also proposes a switching power supply, which includes the wide-range overcurrent protection circuit described above.

[0031] One or more technical solutions proposed in this application have at least the following effects:

[0032] This application proposes a wide-range overcurrent protection circuit and a switching power supply. The circuit is applied to the secondary circuit of the switching power supply. The wide-range overcurrent protection circuit includes a sampling module, a comparison module, and a driving module. The comparison module is connected to both the sampling module and the driving module. The driving module is connected to the control chip of the switching power supply. The sampling module is connected to the secondary circuit. The sampling module samples the current signal of the secondary circuit and converts it into a first voltage signal, which is then sent to the comparison module. The comparison module receives the first voltage signal and, when it exceeds a preset threshold, sends an overcurrent signal to the driving module. The driving module, upon receiving the overcurrent signal, connects the soft-start pin of the control chip to ground. Compared to traditional switching power supplies that use the power control chip in the primary circuit to detect the output of the power switching transistor for overcurrent protection, this circuit, applied to the secondary circuit of the switching power supply, is unaffected by any input voltage across the entire input voltage range. It can accurately detect the output overcurrent point, improving the overall reliability of the circuit. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the structure of the first embodiment of the wide-range overcurrent protection circuit proposed in this application.

[0035] Figure 2 This is a schematic diagram of the structure of a second embodiment of the wide-range overcurrent protection circuit proposed in this application.

[0036] Figure 3 This is a schematic diagram of the structure of the third embodiment of the wide-range overcurrent protection circuit proposed in this application.

[0037] Figure 4 This is a circuit schematic diagram of the first embodiment of the wide-range overcurrent protection circuit proposed in this application.

[0038] Explanation of icon numbers:

[0039]

[0040] The purpose, features, and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0041] It should be understood that the specific embodiments described herein are only used to explain the technical solutions of this application and are not intended to limit this application.

[0042] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0043] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0044] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0045] The main solution of this application embodiment is: when the sampling module 1 collects the current signal and sends it to the comparison module 2, and the current signal is greater than the preset threshold, the overcurrent signal is sent to the driving module 3 to drive the power control chip, thereby lowering the soft-start pin voltage of the power control chip and thus reducing the power output power.

[0046] In traditional switching power supply output overcurrent protection, the power control chip detects the output current of the power switching transistor and sets a threshold value for its current pin. An increase in the current in the secondary circuit (transformer secondary winding side circuit) leads to an increase in the induced current in the primary circuit (transformer primary winding side circuit). When the current detected in the primary circuit exceeds the threshold value set internally by the chip for a certain period, the output load is considered too large, and the system enters protection mode. However, when the output power of the switching power supply is high and the primary circuit lacks PFC (Power Factor Correction), the difference in the rectified DC voltage between the upper and lower limit voltages can be significant when the input voltage is within the full range of 90VAC-264VAC. This large voltage difference in the primary circuit results in different induced currents, causing significant variations in the overcurrent protection point under different input voltage conditions.

[0047] This application provides a solution: a wide-range overcurrent protection circuit and a switching power supply. The circuit is applied to the secondary circuit of the switching power supply and includes a sampling module 1, a comparison module 2, and a drive module 3. The comparison module 2 is connected to both the sampling module 1 and the drive module 3. The drive module 3 is connected to the control chip of the switching power supply. The sampling module 1 is connected to the secondary circuit. The sampling module 1 samples the current signal of the secondary circuit and converts it into a first voltage signal, which is then sent to the comparison module 2. The comparison module 2 receives the first voltage signal and, when it exceeds a preset threshold, sends an overcurrent signal to the drive module 3. The drive module 3, upon receiving the overcurrent signal, connects the soft-start pin of the control chip to ground. Compared to traditional switching power supplies that use the power control chip in the primary circuit to detect the output of the power switching transistor for overcurrent protection, this circuit, applied to the secondary circuit of the switching power supply, is unaffected by any input voltage across the entire input voltage range, accurately detecting the output overcurrent point and improving the overall circuit reliability.

[0048] Based on this, the embodiments of this application provide a wide-range overcurrent protection circuit.

[0049] refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of the first embodiment of the wide-range overcurrent protection circuit proposed in this application.

[0050] Considering that in the case of a switching power supply without PFC, different input voltages lead to significant differences in the rectified DC voltage, which in turn results in significant differences in the overcurrent protection point, such as... Figure 1 As shown, the wide-range overcurrent protection circuit described in this embodiment includes: a sampling module 1, a comparison module 2, and a driving module 3;

[0051] The comparison module 2 is connected to the sampling module 1 and the driving module 3 respectively. The driving module 3 is connected to the control chip of the switching power supply, and the sampling module 1 is connected to the secondary circuit.

[0052] The sampling module 1 is used to sample the current signal of the secondary circuit and convert it into a first voltage signal, which is then sent to the comparison module 2.

[0053] The comparison module 2 is used to receive a first voltage signal and send an overcurrent signal to the drive module 3 when the voltage signal is greater than a preset threshold.

[0054] The drive module 3 is used to connect the circuit between the soft-start pin of the control chip and ground when an overcurrent signal is received.

[0055] It should be noted that PFC (Power Factor Correction) circuits are circuits that can improve the power factor. By adjusting the phase and waveform of the current, they reduce the reactive power exchange between the power grid and the load, improve energy utilization efficiency, and reduce the heat loss of power equipment and interference to the power grid. Adding a PFC circuit can significantly improve power supply efficiency and power factor, thereby indirectly improving the stability of the rectified DC voltage.

[0056] It should be noted that the first voltage signal is a DC voltage, and the overcurrent signal can be a current signal or a voltage signal, or it can be set according to the actual situation. This embodiment does not impose any restrictions. The preset threshold is the overcurrent protection point, which refers to the maximum allowable current value of the secondary circuit of the switching power supply under normal operating conditions. It can be set according to the rated voltage, rated current, operating environment, and load characteristics of the secondary circuit of the switching power supply. The sampling module 1 can sample the current through a sampling resistor, a current transformer, or a Hall sensor. The control chip is a power control chip. By adjusting the voltage of the soft-start pin of the power control chip, precise control of the output voltage of the switching power supply can be achieved. By lowering the voltage of the soft-start pin of the power control chip (to ground), the output power of the switching power supply can be reduced. The comparison module 2 is used to determine whether the secondary circuit output of the switching power supply is overcurrent, and the drive module 3 is used to drive the power control chip to reduce the output of the switching power supply.

[0057] It is understood that the current signal in this embodiment is the resonant cavity current, which refers to the current flowing in the resonant circuit. The resonant circuit is composed of components such as inductors (L) and capacitors (C). When the current and voltage in the circuit oscillate sinusoidally at the same frequency, a resonance phenomenon is formed. The overcurrent protection circuit determines whether the circuit is in an overcurrent state by monitoring the magnitude of the resonant cavity current. When the resonant cavity current exceeds a preset threshold, the overcurrent protection circuit will trigger a protection mechanism to prevent circuit damage.

[0058] In a specific implementation, the sampling module 1 is used to sample the current signal of the secondary circuit and convert it into a first voltage signal, which is then sent to the comparison module 2. The comparison module 2 is used to receive the first voltage signal and, when it exceeds a preset threshold, send an overcurrent signal to the drive module 3. The drive module 3 is used to connect the circuit between the soft-start pin of the control chip and ground when it receives the overcurrent signal, thereby lowering the soft-start pin voltage of the power control chip and reducing the output power of the switching power supply. Under the input voltage range, it is not affected by any input voltage, can accurately check the output overcurrent point, and improves the reliability of the overall circuit operation.

[0059] Based on the first embodiment of this application, in the second embodiment of this application, the content that is the same as or similar to the first embodiment described above can be referred to the above description, and will not be repeated hereafter. Based on this, please refer to... Figure 2 , Figure 2 This is a schematic diagram of the structure of a second embodiment of the wide-range overcurrent protection circuit proposed in this application.

[0060] To accurately detect the overcurrent point of the switching power supply output, and in order to lower the soft-start pin voltage of the power control chip, thereby reducing the power supply output power, such as... Figure 2 As shown, the comparison module 2 in this embodiment includes: a first comparison circuit 21 and a second comparison circuit 22;

[0061] The first comparison circuit 21 is connected to the second comparison circuit 22 and the sampling module 1, respectively; the second comparison circuit 22 is connected to the driving module 3.

[0062] The first comparison circuit 21 is used to send a second voltage signal to the second comparison circuit 22 when it receives a first voltage signal and the voltage signal is greater than a preset threshold.

[0063] The second comparison circuit 22 is used to receive the second voltage signal and send an overcurrent signal to the drive module 3 when the voltage signal is less than a preset threshold.

[0064] It should be noted that the second voltage signal is a DC voltage. The first comparison circuit 21 outputs a low level (second voltage signal) to the second comparison circuit 22 when it receives the first voltage signal. The second comparison circuit 22 outputs a high level (overcurrent signal) to the drive module 3 when it receives the low voltage. The first comparison circuit 21 and the second comparison circuit 22 can be comparators, or they can be set according to actual conditions. This embodiment does not impose any restrictions.

[0065] In a specific implementation, the first comparison circuit 21 is used to send a second voltage signal to the second comparison circuit 22 when it receives a first voltage signal and the voltage is greater than a preset threshold. The second comparison circuit 22 is used to receive the second voltage signal and send an overcurrent signal to the drive module 3 when the voltage is less than a preset threshold. Under the condition of input voltage across the entire range, it is not affected by any input voltage, thereby improving the accuracy of overcurrent point detection at the output of the switching power supply.

[0066] Based on the second embodiment of this application, in the third embodiment of this application, the content that is the same as or similar to the second embodiment described above can be referred to the above description, and will not be repeated hereafter. Based on this, please refer to... Figure 3 , Figure 3 This is a schematic diagram of the third embodiment of the wide-range overcurrent protection circuit proposed in this application.

[0067] Considering the need to lower the soft-start pin voltage of the power control chip, and thus in order to drive the power control chip, such as... Figure 3 As shown, the driving module 3 in this embodiment includes: a photoelectric conversion unit 31 and a switching unit 32;

[0068] The photoelectric conversion unit 31 is connected to the comparison module 2 and the switching unit 32 respectively, and the switching unit 32 is connected to the control chip;

[0069] The photoelectric conversion unit 31 is used to send a drive signal to the switching unit 32 when it receives an overcurrent signal;

[0070] The switching unit 32 is used to connect the circuit between the soft-start pin of the control chip and ground when a drive signal is received.

[0071] It should be noted that the driving signal can be a current signal or a voltage signal, or it can be set according to the actual situation. This embodiment does not impose any restrictions. The photoelectric conversion unit 31 can be an optocoupler U3, and the switching unit 32 can be a MOSFET U4, a transistor, or an IGBT. These can also be set according to the actual situation. This embodiment does not impose any restrictions.

[0072] In a specific implementation, the photoelectric conversion unit 31 is used to send a drive signal to the switching unit 32 when it receives an overcurrent signal. The switching unit 32 is used to connect the circuit between the soft-start pin of the control chip and ground when it receives the drive signal, thereby reducing the output power of the switching power supply and protecting it from overcurrent, thus improving the reliability of the overall circuit operation.

[0073] Based on the third embodiment of this application, in the fourth embodiment of this application, the content that is the same as or similar to the third embodiment described above can be referred to the above description, and will not be repeated hereafter. Based on this, please refer to... Figure 4 , Figure 4 This is a schematic diagram of the fourth embodiment of the wide-range overcurrent protection circuit proposed in this application.

[0074] Considering overcurrent protection for the output of the switching circuit, and in order to accurately detect the current, such as... Figure 4 As shown, the sampling module 1 in this embodiment includes: a sampling resistor RS1, a first resistor R1, and a second resistor R2;

[0075] The first end of the sampling resistor RS1 is connected to the first end of the first resistor R1 and ground, the second end of the sampling resistor RS1 is connected to the first end of the second resistor R2, and the comparison module 2 is connected to the second end of the first resistor R1 and the second end of the second resistor R2 respectively.

[0076] In the specific implementation, the sampling resistor RS1 is used to collect the secondary circuit current of the switching power supply. The second resistor R2 is closer to the secondary circuit than the first resistor R1 (the voltage at the second terminal of the second resistor R2 is greater than the voltage at the second terminal of the first resistor R1). When the current is too large, the voltage difference flowing through the sampling resistor RS1 will be greater, that is, the voltage at the inverting input terminal of the first comparator U1 is greater than the voltage at the non-inverting input terminal of the first comparator U1, thereby improving the accuracy of the overcurrent detection at the output of the switching power supply.

[0077] Furthermore, the sampling module 1 also includes: a first capacitor C1, a second capacitor C2, and a third capacitor C3;

[0078] The first terminal of the first capacitor C1 is connected to the output terminal of the secondary circuit. The second terminal of the first capacitor C1 is connected to the second terminal of the sampling resistor RS1 and the first terminal of the second resistor R2. The first terminal of the second capacitor C2 is connected to the second terminal of the first resistor R1 and the comparison module 2. The first terminal of the third capacitor C3 is connected to the second terminal of the second resistor R2 and the comparison module 2. The second terminals of the second capacitor C2 and the second terminals of the third capacitor C3 are connected to ground.

[0079] It should be noted that the first capacitor C1, the second capacitor C2, and the third capacitor C3 are used for filtering to ensure voltage stability.

[0080] Furthermore, the first comparison circuit 21 includes: a first comparator U1, a fourth capacitor C4, a third resistor R3, and a fourth resistor R4;

[0081] The non-inverting input of the first comparator U1 is connected to the sampling module 1 and the third resistor R3, respectively. The inverting input of the first comparator U1 is connected to the sampling module 1 and the first terminal of the fourth capacitor C4, respectively. The second terminal of the fourth capacitor C4 is connected to the first terminal of the fourth resistor R4, respectively. The second comparator circuit 22 is connected to the second terminal of the third resistor R3 and the second terminal of the fourth resistor R4, respectively.

[0082] In a specific implementation, when the voltage at the inverting input terminal of the first comparator U1 is greater than the voltage at the non-inverting input terminal of the first comparator U1, a low level (second voltage signal) is output to the second comparator circuit 22.

[0083] Furthermore, the second comparator circuit 22 includes: a second comparator U2, a fifth capacitor C5, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7;

[0084] The non-inverting input of the second comparator U2 is connected to the first terminal of the seventh resistor R7, the first comparator circuit 21, and the first terminal of the fifth capacitor C5, respectively. The inverting input of the second comparator U2 is connected to the second terminal of the fifth resistor R5 and the first terminal of the sixth resistor R6, respectively. The second terminal of the fifth resistor R5 is connected to the first comparator circuit 21. The second terminal of the sixth resistor R6 and the second terminal of the fifth capacitor C5 are grounded. The second terminal of the seventh resistor R7 is connected to the first power supply.

[0085] It should be noted that the voltage value of the first power supply is equal to the preset threshold, which can be set according to the overcurrent point of the secondary circuit of the switching power supply.

[0086] In the specific implementation, when the voltage at the inverting input terminal of the second comparator U2 is less than the voltage at the non-inverting input terminal of the second comparator U2, a high level (overcurrent signal) is output to the drive module 3.

[0087] Furthermore, the photoelectric conversion unit 31 includes: an optocoupler U3, an eighth resistor R8, and a ninth resistor R9;

[0088] The first end of the light source of the optocoupler U3 is connected to the second end of the eighth resistor R8. The first end of the eighth resistor R8 is connected to the comparison module 2. The second end of the light source of the optocoupler U3 is grounded. The first end of the light receiver of the optocoupler U3 is connected to the second power supply. The second end of the light receiver of the optocoupler U3 is connected to the first end of the ninth resistor R9. The second end of the ninth resistor R9 is connected to the switching unit 32.

[0089] It should be noted that the light source of optocoupler U3 can be a light-emitting diode. When a high-level signal (overcurrent signal) is received, it transmits an optical signal to the receiver of optocoupler U3. Optocoupler U3 is used for electrical isolation to ensure circuit stability. Resistors R8 (eighth) and R9 (ninth) are used for voltage divider protection.

[0090] In a specific implementation, when the light source of the optocoupler U3 receives a high level (overcurrent signal), it transmits an optical signal to the light receiver of the optocoupler U3 to make the circuit between the second power supply and the switching unit 32 conduct, thereby ensuring the reliability of the circuit.

[0091] Furthermore, the switching unit 32 includes: a MOS transistor U4, a tenth resistor R10, and an eleventh resistor R11;

[0092] The gate of the MOS transistor U4 is connected to the first end of the photoelectric conversion unit 31 and the tenth resistor R10, respectively. The second end of the tenth resistor R10 and the source of the MOS transistor U4 are grounded. The drain of the MOS transistor U4 is connected to the second end of the eleventh resistor R11. The first end of the eleventh resistor R11 is connected to the soft-start pin of the control chip.

[0093] It should be noted that MOSFET U4 can be an NMOS transistor or a PMOS transistor, or it can be set according to the actual situation; this embodiment does not impose any restrictions. The tenth resistor R10 and the eleventh resistor R11 are used for voltage divider protection. The voltage of the second power supply is set according to the specifications of MOSFET U4.

[0094] In the specific implementation, when the gate of MOSFET U4 receives the voltage from the second power supply, it turns on the circuit between the soft-start pin of the power control chip and ground, thereby reducing the output power of the switching power supply and thus achieving overcurrent protection for the output of the switching power supply.

[0095] To achieve the above objectives, this application also proposes a switching power supply, which includes the wide-range overcurrent protection circuit described above.

[0096] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A wide-range overcurrent protection circuit, characterized by comprising: The circuit is applied to a secondary circuit of a switching power supply, and the wide-range overcurrent protection circuit comprises a sampling module, a comparison module and a driving module; The comparison module is connected with the sampling module and the driving module respectively, the driving module is connected with a control chip of the switching power supply, and the sampling module is connected with the secondary circuit; The sampling module is used for sampling a current signal of the secondary circuit and converting the current signal into a first voltage signal and sending the first voltage signal to the comparison module; The comparison module is used for receiving the first voltage signal and sending an overcurrent signal to the driving module when the first voltage signal is greater than a preset threshold value; The driving module is used for turning on a connection between a soft start pin of the control chip and the ground when the overcurrent signal is received.

2. The wide-range overcurrent protection circuit of claim 1, wherein, The comparison module comprises a first comparison circuit and a second comparison circuit; The first comparison circuit is connected with the second comparison circuit and the sampling module respectively, and the second comparison circuit is connected with the driving module; The first comparison circuit is used for sending a second voltage signal to the second comparison circuit when the first voltage signal is received and the first voltage signal is greater than a preset threshold value; The second comparison circuit is used for receiving the second voltage signal and sending an overcurrent signal to the driving module when the second voltage signal is less than the preset threshold value.

3. The wide-range overcurrent protection circuit of claim 1, wherein, The sampling module comprises a sampling resistor, a first resistor and a second resistor; A first end of the sampling resistor is connected with a first end of the first resistor and the ground, a second end of the sampling resistor is connected with a first end of the second resistor, and the comparison module is connected with a second end of the first resistor and a second end of the second resistor respectively.

4. The wide-range overcurrent protection circuit of claim 3, wherein, The sampling module further comprises a first capacitor, a second capacitor and a third capacitor; A first end of the first capacitor is connected with an output end of the secondary circuit, a second end of the first capacitor is connected with the second end of the sampling resistor and the first end of the second resistor, a first end of the second capacitor is connected with the second end of the first resistor and the comparison module respectively, a first end of the third capacitor is connected with the second end of the second resistor and the comparison module respectively, and a second end of the second capacitor and a second end of the third capacitor are connected with the ground.

5. The wide-range overcurrent protection circuit of claim 2, wherein, The first comparison circuit comprises a first comparator, a fourth capacitor, a third resistor and a fourth resistor; A non-inverting input end of the first comparator is connected with the sampling module and the third resistor respectively, an inverting input end of the first comparator is connected with the sampling module and a first end of the fourth capacitor respectively, a second end of the fourth capacitor is connected with a first end of the fourth resistor, and the second comparison circuit is connected with a second end of the third resistor and a second end of the fourth resistor respectively.

6. The wide-range overcurrent protection circuit of claim 2, wherein, The second comparison circuit comprises a second comparator, a fifth capacitor, a fifth resistor, a sixth resistor and a seventh resistor; The non-inverting input of the second comparator is connected with the first end of the seventh resistor, the first end of the first comparison circuit and the first end of the fifth capacitor respectively, the inverting input of the second comparator is connected with the second end of the fifth resistor and the first end of the sixth resistor respectively, the second end of the fifth resistor is connected with the first comparison circuit, the second end of the sixth resistor and the second end of the fifth capacitor are grounded, and the second end of the seventh resistor is connected with the first power supply.

7. The wide-range overcurrent protection circuit of claim 1, wherein, The driving module comprises a photoelectric conversion unit and a switching unit. The photoelectric conversion unit is connected with the comparison module and the switching unit respectively, and the switching unit is connected with the control chip. The photoelectric conversion unit is configured to send a driving signal to the switching unit when receiving an overcurrent signal. The switching unit is configured to turn on the connection between the soft start pin of the control chip and the ground when receiving the driving signal.

8. The wide-range overcurrent protection circuit of claim 7, wherein, The photoelectric conversion unit comprises an optoelectronic coupler, an eighth resistor and a ninth resistor. The first end of the light source of the optoelectronic coupler is connected with the second end of the eighth resistor, the first end of the eighth resistor is connected with the comparison module, the second end of the light source of the optoelectronic coupler is grounded, the first end of the light receiver of the optoelectronic coupler is connected with the second power supply, the second end of the light receiver of the optoelectronic coupler is connected with the first end of the ninth resistor, and the second end of the ninth resistor is connected with the switching unit.

9. The wide-range overcurrent protection circuit of claim 7, wherein, The switching unit comprises a MOS transistor, a tenth resistor and an eleventh resistor. The gate of the MOS transistor is connected with the photoelectric conversion unit and the first end of the tenth resistor respectively, the second end of the tenth resistor and the source of the MOS transistor are grounded, the drain of the MOS transistor is connected with the second end of the eleventh resistor, and the first end of the eleventh resistor is connected with the soft start pin of the control chip.

10. A switching power supply, characterized by comprising: The switching power supply comprises the wide-range overcurrent protection circuit according to any one of claims 1 to 9.

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