Switching power supply and electrical equipment

Abstract

The utility model discloses a switching power supply and electrical equipment. The switching power supply comprises a main power supply circuit, a control chip, an overload protection circuit and an overload blanking circuit. Wherein the main power supply circuit is connected with a load and is configured to supply power to the load; the control chip is connected with the main power supply circuit and is configured to control the main power supply circuit to work to supply power to a load; the overload protection circuit is respectively connected with a load voltage detection end and a voltage feedback end of the control chip, and is configured to perform overload protection based on a first detection voltage of the load voltage detection end; the overload blanking circuit is connected with the load voltage detection end and the voltage feedback end of the control chip, and is configured to enable the overload protection circuit to be in a failure state at least before the blanking time of the control chip ends and the first detection voltage reaches a first voltage threshold value corresponding to the load rated voltage. According to the switching power supply, the blanking time of the built-in control chip can be prolonged, so that power can be supplied to a load with a high-capacity capacitor, and the applicability is relatively good.

Description

Technical Field

[0001] The utility model relates to the field of switching power supplies, in particular to a switching power supply and electrical equipment. Background Art

[0002] Among various switching power supplies, the overload protection function is one of the basic functions. Since the load of the switching power supply usually contains a capacitive load, when the power supply is turned on, the output voltage may not be able to rise to the rated voltage in a short time due to charging, so the overload protection function of the switching power supply may be triggered erroneously. Therefore, in the related technology, a blanking time is usually added during the design. During the blanking time, the switching power supply will not be able to trigger the overload protection function, thereby enabling the power supply to work normally. For example, the ICE5Q chip is usually used in the design of single-ended flyback auxiliary power supplies on the market. The chip specification states that the blanking time is up to about 30ms, which is a short duration. This makes it impossible for this type of switching power supply to start normally when supplying power to a large-capacitance capacitive load, resulting in poor applicability of this type of switching power supply. Utility Model Content

[0003] The utility model aims to solve one of the technical problems in the related art to at least a certain extent. To this end, the first purpose of the utility model is to provide a switching power supply, which can make the overload protection circuit in a disabled state from the end of the blanking time of the control chip to the first detection voltage reaching the first voltage threshold corresponding to the rated voltage of the load by arranging an overload protection circuit and an overload blanking circuit inside, thereby achieving the effect of extending the blanking time of the switching power supply, thereby enabling the switching power supply to supply power to a large-capacity capacitive load, and effectively improving the applicability of the switching power supply.

[0004] The second purpose of the utility model is to provide an electrical device.

[0005] To achieve the above-mentioned purpose, the first embodiment of the utility model proposes a switching power supply, including: a main power supply circuit, the main power supply circuit is connected to the load and is configured to supply power to the load; a control chip, the control chip is connected to the main power supply circuit and is configured to control the main power supply circuit to supply power to the load; an overload protection circuit, the overload protection circuit is respectively connected to the load voltage detection terminal and the voltage feedback terminal of the control chip, and is configured to perform load overload protection based on a first detection voltage of the load voltage detection terminal; an overload blanking circuit, the overload blanking circuit is respectively connected to the load voltage detection terminal and the voltage feedback terminal of the control chip, and is configured to put the overload protection circuit into an invalid state at least from the end of the blanking time of the control chip to the time when the first detection voltage reaches a first voltage threshold corresponding to the rated voltage of the load.

[0006] According to the switching power supply of the embodiment of the utility model, by arranging an overload protection circuit and an overload blanking circuit internally, the overload protection circuit can be put into a disabled state from the end of the blanking time of the control chip to before the first detection voltage reaches the first voltage threshold corresponding to the rated voltage of the load, thereby achieving the effect of extending the blanking time of the switching power supply, thereby enabling the switching power supply to supply power to a large-capacity capacitive load, and effectively improving the applicability of the switching power supply.

[0007] According to one embodiment of the utility model, the overload blanking circuit includes: a first voltage stabilizing circuit, one end of the first voltage stabilizing circuit is connected to the voltage feedback end, and one end of the first voltage stabilizing circuit is also connected to the power supply end of the control chip through a first resistor; a first switch, the first switch is connected in series between the other end of the first voltage stabilizing circuit and the ground; a second resistor, the second resistor is connected in parallel with the first switch; a charging delay circuit, the charging delay circuit is respectively connected to the load voltage detection end and the control end of the first switch, and is configured to perform charging delay based on the first detection voltage, so as to make the first switch in a conducting state at least from the end of the blanking time of the control chip to the first detection voltage reaching the first voltage threshold corresponding to the load rated voltage, so as to make the overload protection circuit in a failed state through the first voltage stabilizing circuit.

[0008] According to one embodiment of the utility model, the first voltage stabilizing circuit includes: a first voltage stabilizing diode, the cathode of the first voltage stabilizing diode is connected to the voltage feedback end, and the anode of the first voltage stabilizing diode is connected to the first switch; or, a first three-terminal voltage stabilizing tube, the cathode and control electrode of the first three-terminal voltage stabilizing tube are respectively connected to the voltage feedback end, and the anode of the first three-terminal voltage stabilizing tube is connected to the first switch.

[0009] According to an embodiment of the present invention, the first switch is a triode or a MOS tube.

[0010] According to one embodiment of the utility model, the charging delay circuit includes: a first capacitor, one end of the first capacitor is connected to the load voltage detection end; a third resistor, one end of the third resistor is connected to the other end of the first capacitor, and the other end of the third resistor is connected to the control end of the first switch; a fourth resistor, the fourth resistor is connected between the control end of the first switch and the ground.

[0011] According to an embodiment of the utility model, the charging delay circuit further includes: a first diode, a cathode of the first diode is connected to the other end of the first capacitor, and an anode of the first diode is grounded.

[0012] According to one embodiment of the utility model, the overload protection circuit includes: a first voltage divider circuit, which is connected to the load voltage detection terminal and is configured to divide the first detection voltage to obtain a first divided voltage; an overload trigger circuit, which is respectively connected to the load voltage detection terminal, the first voltage divider circuit and the voltage feedback terminal, and is configured to disconnect the first voltage stabilizing circuit and the second resistor when the first divided voltage does not reach a second voltage threshold corresponding to the load rated voltage, so as to trigger the control chip to perform load overload protection.

[0013] According to one embodiment of the utility model, the first voltage divider circuit includes: a fifth resistor, one end of the fifth resistor is connected to the load voltage detection end; a sixth resistor, one end of the sixth resistor is connected to the other end of the fifth resistor and forms a first connection point, the other end of the sixth resistor is grounded, and the first connection point is connected to the overload trigger circuit.

[0014] According to one embodiment of the utility model, the overload trigger circuit includes: a seventh resistor, one end of the seventh resistor is connected to the load voltage detection end; an eighth resistor, one end of the eighth resistor is connected to the other end of the seventh resistor; a second three-terminal voltage regulator, the cathode of the second three-terminal voltage regulator is connected to the other end of the eighth resistor, the anode of the second three-terminal voltage regulator is grounded, and the control electrode of the second three-terminal voltage regulator is connected to the first voltage divider circuit; a first optocoupler, the first input end of the first optocoupler is connected to one end of the eighth resistor, the second input end of the first optocoupler is connected to the other end of the eighth resistor, the first output end of the first optocoupler is connected to the voltage feedback end, and the second output end of the first optocoupler is grounded.

[0015] According to one embodiment of the utility model, the overload trigger circuit also includes: a ninth resistor, one end of the ninth resistor is connected to the control electrode of the second three-terminal voltage regulator; a second capacitor, one end of the second capacitor is connected to the other end of the ninth resistor, and the other end of the second capacitor is connected to the cathode of the second three-terminal voltage regulator.

[0016] According to one embodiment of the utility model, the switching power supply also includes: a starting circuit, which is respectively connected to the power supply ends of the main power supply circuit and the control chip, and is configured to provide a starting voltage to the control chip when the main power supply circuit is powered on; an auxiliary power supply circuit, the input end of the auxiliary power supply circuit is connected to the main power supply circuit, and the output end of the auxiliary power supply circuit is connected to the power supply end of the control chip through a second diode, and is configured to provide a working voltage to the control chip after the control chip is started, wherein the output end of the auxiliary power supply circuit serves as a load voltage detection end.

[0017] According to one embodiment of the utility model, the startup circuit includes: a third capacitor, one end of the third capacitor is respectively connected to the main power supply circuit and the power supply end of the control chip, and the other end of the third capacitor is grounded; a fourth capacitor, the fourth capacitor is connected in parallel with the third capacitor.

[0018] According to one embodiment of the utility model, the auxiliary power supply circuit includes: a fifth capacitor, one end of the fifth capacitor is connected to the anode of the second diode as the output end of the auxiliary power supply circuit, and the other end of the fifth capacitor is grounded; a tenth resistor, the tenth resistor is connected in parallel with the fifth capacitor; an eleventh resistor, one end of the eleventh resistor is connected to one end of the fifth capacitor; a third diode, the cathode of the third diode is connected to the other end of the eleventh resistor, and the anode of the third diode is connected to the main power supply circuit.

[0019] According to an embodiment of the utility model, the switching power supply further includes: an output current limiting circuit, which is respectively connected to the load and the overload blanking circuit and is configured to render the overload blanking circuit in a failure state when an overcurrent occurs in the load.

[0020] According to one embodiment of the utility model, the output current limiting circuit includes: a current detection circuit, which is connected to the load and configured to detect the current of the load to obtain a second detection voltage corresponding to the current; an overcurrent trigger circuit, which is respectively connected to the load, the current detection circuit and the overload blanking circuit, and is configured to put the first switch in an off state when the second detection voltage reaches a voltage threshold corresponding to the overcurrent protection threshold, so that the overload blanking circuit is in an invalid state.

[0021] According to one embodiment of the utility model, the current detection circuit includes: a twelfth resistor, one end of the twelfth resistor is connected to the load; a thirteenth resistor, one end of the thirteenth resistor is connected to the other end of the twelfth resistor and forms a second connection point, the other end of the thirteenth resistor is grounded, and the second connection point is connected to the overcurrent trigger circuit.

[0022] According to one embodiment of the utility model, the overcurrent trigger circuit includes: a fourteenth resistor, one end of the fourteenth resistor is connected to the load; a second optocoupler, a first input end of the second optocoupler is connected to the other end of the fourteenth resistor, a first output end of the second optocoupler is connected to the control end of the first switch, and a second output end of the second optocoupler is grounded; a third three-terminal Zener diode, a cathode of the third three-terminal Zener diode is connected to the second input end of the second optocoupler, an anode of the third three-terminal Zener diode is grounded, and a control electrode of the third three-terminal Zener diode is connected to the current detection circuit.

[0023] According to an embodiment of the present utility model, the overcurrent trigger circuit further includes: a fifteenth resistor, and the fifteenth resistor is connected between the first input terminal and the second input terminal of the second optocoupler.

[0024] According to one embodiment of the utility model, the overcurrent trigger circuit also includes: a fourth diode, the anode of the fourth diode is connected to the load, the cathode of the fourth diode is connected to one end of the fourteenth resistor; and a sixth capacitor, the sixth capacitor is connected between the cathode of the fourth diode and the ground.

[0025] According to one embodiment of the utility model, the output current limiting circuit also includes: a first filter circuit, which is arranged between the control electrode of the third three-terminal voltage regulator and the current detection circuit; or, a second filter circuit, which is respectively connected to the load and the current detection circuit.

[0026] To achieve the above-mentioned object, a second embodiment of the present invention provides an electrical device, including the aforementioned switching power supply.

[0027] According to the electrical device of the embodiment of the utility model, the restriction of the electrical device on the capacitance of the load can be removed through the aforementioned switching power supply, thereby reducing the design difficulty of the electrical device.

[0028] Additional aspects and advantages of the present invention will be given in part in the following description and in part will become apparent from the following description or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of the structure of a switching power supply according to an embodiment of the utility model;

[0030] Figure 2 is a circuit diagram of an overload blanking circuit according to an embodiment of the utility model;

[0031] Figure 3 is a circuit diagram of an overload protection circuit according to an embodiment of the utility model;

[0032] Figure 4 A circuit diagram of a switching power supply according to an embodiment of the utility model;

[0033] Figure 5 is a circuit diagram of an output current limiting circuit according to an embodiment of the utility model;

[0034] Figure 6 The figure is a schematic diagram of the structure of an electrical device according to an embodiment of the utility model. DETAILED DESCRIPTION

[0035] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0036] The switching power supply and electrical equipment provided in the embodiments of the present utility model are described below with reference to the accompanying drawings.

[0037] Figure 1is a schematic diagram of the structure of a switching power supply according to an embodiment of the utility model, referring to Figure 1 As shown, the switching power supply 100 includes: a main power supply circuit 110 , a control chip 120 , an overload protection circuit 130 and an overload blanking circuit 140 .

[0038] Among them, the main power supply circuit 110 is connected to the load 200 and is configured to supply power to the load 200; the control chip 120 is connected to the main power supply circuit 110 and is configured to control the main power supply circuit 110 to operate so as to supply power to the load 200; the overload protection circuit 130 is respectively connected to the load voltage detection terminal VDD and the voltage feedback terminal FB of the control chip 120, and is configured to perform load overload protection based on the first detection voltage of the load voltage detection terminal VDD; the overload blanking circuit 140 is respectively connected to the load voltage detection terminal VDD and the voltage feedback terminal FB of the control chip 120, and is configured to put the overload protection circuit 130 into an invalid state at least from the end of the blanking time of the control chip 120 to the time when the first detection voltage reaches a first voltage threshold corresponding to the rated voltage of the load.

[0039] Specifically, the main power supply circuit 110 usually includes a plurality of switch tubes. When the switching power supply 100 is working normally, the control chip 120 can control the operation of the switch tubes in the main power supply circuit 110 so that the main power supply circuit 110 supplies power to the load 200. At the same time, the load voltage is detected through the voltage feedback terminal FB, and then the PWM wave of the switch tube is adjusted and controlled according to the load voltage to achieve negative feedback regulation, thereby supplying power to the load 200. At the same time, the switching power supply 100 has an overload protection circuit 130. When the switching power supply 100 is working, the overload protection circuit 130 will obtain a first detection voltage corresponding to the load voltage from the load voltage detection terminal VDD. When the first detection voltage is abnormal, for example, it can never rise to the first voltage threshold corresponding to the rated voltage of the load, at this time, the overload protection circuit 130 will be triggered, causing the switching power supply 100 to stop working, thereby achieving overload protection and ensuring the safe operation of the switching power supply 100.

[0040] During the power-on process of the switching power supply 100, when there is a large-capacity capacitor in the load 200, the first detection voltage will gradually rise to the first voltage threshold corresponding to the rated voltage of the load, and the voltage rise time is relatively long, which may erroneously trigger the overload protection circuit 130. In this regard, the control chip 120 in the related art usually sets a blanking time internally. During the blanking time, the control chip 120 allows the first detection voltage to be less than the first voltage threshold corresponding to the rated voltage of the load to alleviate the above-mentioned problem of false triggering of the overload protection. However, when the capacitance of the load 200 is large, the first detection voltage of the switching power supply 100 may still not rise to the first voltage threshold after the blanking time ends, so the problem of false triggering of the overload protection still occurs, which makes the switching power supply in the related art unable to supply power to the load with a large-capacity capacitor, which is relatively limited.

[0041] In the embodiment of the utility model, an overload blanking circuit 140 is provided in the switching power supply 100. The overload blanking circuit 140 can make the overload protection circuit 130 in a disabled state at least from the end of the blanking time of the control chip 120 to the time when the first detection voltage reaches the first voltage threshold, thereby effectively avoiding the aforementioned false triggering problem of the overload protection, thereby eliminating the problem of the switching power supply 100 limiting the capacitance of the load 200.

[0042] In the above embodiment, by arranging an overload protection circuit and an overload blanking circuit internally, the overload protection circuit can be put into a disabled state from the end of the blanking time of the control chip to before the first detection voltage reaches the first voltage threshold corresponding to the rated voltage of the load, thereby achieving the effect of extending the blanking time of the switching power supply, thereby enabling the switching power supply to supply power to a large-capacity capacitive load, and effectively improving the applicability of the switching power supply.

[0043] In some embodiments, reference Figure 2 As shown, the overload blanking circuit 140 includes: a first voltage stabilizing circuit 141, a first switch Q1, a second resistor R2 and a charging delay circuit 142. Among them, one end of the first voltage stabilizing circuit 141 is connected to the voltage feedback terminal FB, and one end of the first voltage stabilizing circuit 141 is also connected to the power supply terminal VCC of the control chip 120 through the first resistor R1; the first switch Q1 is connected in series between the other end of the first voltage stabilizing circuit 141 and the ground GND; the second resistor R2 is connected in parallel with the first switch Q1; the charging delay circuit 142 is respectively connected to the load voltage detection terminal VDD and the control terminal of the first switch Q1, and is configured to perform charging delay based on the first detection voltage, so as to make the first switch Q1 in a conducting state at least from the end of the blanking time of the control chip 120 to the first detection voltage reaching the first voltage threshold corresponding to the load rated voltage, so as to make the overload protection circuit 130 in a failure state through the first voltage stabilizing circuit 141.

[0044] Specifically, refer to Figure 2 As shown, the first switch Q1 can be an NMOS tube. When the switching power supply 100 starts working, the control chip 120 is first powered on so that the voltage VCC of the power supply terminal of the control chip 120 reaches the starting voltage value, wherein the starting voltage value can be 16V, etc. At this time, the voltage of the power supply terminal of the control chip 120 can be grounded GND through the first resistor R1, the first voltage stabilizing circuit 141 and the second resistor R2 to provide a stable working voltage to both ends of the first switch Q1, so that the voltage at both ends of the first switch Q1 can drive the first switch Q1, and the first switch Q1 is in the off state at this time. Subsequently, the first detection voltage output by the load voltage detection terminal VDD gradually rises, charging the internal components of the charging delay circuit 142, so that the voltage of the control terminal of the first switch Q1 gradually rises. When the first detection voltage reaches the first voltage threshold corresponding to the rated voltage of the load, the voltage at the control terminal of the first switch Q1 reaches the conduction voltage threshold, so that the first switch Q1 is turned on. At this time, the voltage at the voltage feedback terminal FB depends on the reverse conduction voltage drop of the first voltage stabilizing circuit 141. The reverse voltage drop of the first voltage stabilizing circuit 141 can be set to prevent the voltage value of the voltage feedback terminal FB from being too large, so as to ensure that the overload protection circuit 130 does not trigger the overload protection and realize the overload blanking function. At the same time, the length of the overload blanking time can be determined by adjusting the charging speed of the internal components of the charging delay circuit 142. When the charging delay circuit 142 is fully charged, the voltage at the control terminal of the first switch Q1 disappears, causing the first switch Q1 to be disconnected. As a result, the overload blanking circuit realizes the aforementioned function of extending the overload blanking time.

[0045] It should be noted that the first switch Q1 may also be a variety of switch elements such as a triode, a switch tube, etc. The use of an NMOS tube as the first switch Q1 in the embodiment of the utility model is exemplary and is not a limitation of the present application.

[0046] Furthermore, the first voltage stabilizing circuit 141 includes: a first voltage stabilizing diode Z1, wherein the cathode of the first voltage stabilizing diode Z1 is connected to the voltage feedback terminal, and the anode of the first voltage stabilizing diode Z1 is connected to the first switch Q1; or, a first three-terminal voltage stabilizing tube SZ1, wherein the cathode and control electrode of the first three-terminal voltage stabilizing tube SZ1 are respectively connected to the voltage feedback terminal VDD, and the anode of the first three-terminal voltage stabilizing tube SZ1 is connected to the first switch Q1.

[0047] Specifically, refer to Figure 2 and Figure 3As shown, both the first voltage stabilizing diode Z1 and the first three-terminal voltage stabilizing tube SZ1 can achieve the voltage stabilizing effect of the first voltage stabilizing circuit 141, so the first voltage stabilizing tube Z1 can be used to form the first voltage stabilizing circuit 141, and the first three-terminal voltage stabilizing tube SZ1 can also be used to form the first voltage stabilizing circuit 141. At the same time, the first voltage stabilizing tube Z1 has a cost advantage, and the three-terminal voltage stabilizing tube has an advantage of high precision, so one of them can be selected based on actual needs, thereby improving the flexibility of the switching power supply 100.

[0048] In some embodiments, reference Figure 2 As shown, the charging delay circuit 142 includes: a first capacitor C1, a third resistor R3 and a fourth resistor R4. Among them, one end of the first capacitor C1 is connected to the load voltage detection terminal VDD; one end of the third resistor R3 is connected to the other end of the first capacitor C1, and the other end of the third resistor R3 is connected to the control end of the first switch Q1; the fourth resistor R4 is connected between the control end of the first switch Q1 and the ground GND.

[0049] Specifically, refer to Figure 2 As shown, when the switching power supply 100 is just powered on, the voltage at the load voltage detection terminal is 0, the first capacitor C1 is not charged, and can be regarded as an open circuit, and the first switch Q1 is in the off state. After the control chip 120 of the switching power supply 100 is powered on, the voltage at the load voltage detection terminal VDD gradually rises, and the load voltage detection terminal VDD provides a high level to the control terminal of the first switch Q1 through the first capacitor C1 and the third resistor R3, thereby turning on the first switch Q1, wherein the first switch Q1 can be a MOS tube or a triode, such as an NMOS tube. When the first capacitor C1 is fully charged, the control terminal of the first switch Q1 becomes a high impedance state, thereby turning off the first switch Q1, thereby realizing the charging delay function of the charging delay circuit 142. At the same time, the charging delay time of the first switch Q1 can be determined according to the following formulas (1) and (2):

[0050] t=(R3+R4)*C1*Ln(VDD / (VDD-VC1') (1)

[0051] VC1'=VDD-VG_TH*R4 / (R3+R4) (2)

[0052] Wherein, t is the charging delay time, C1 is the capacitance of the first capacitor, R3 is the resistance of the third resistor, R4 is the resistance of the fourth resistor, VDD is the first detection voltage, VG_TH is the threshold voltage of the first switch Q1, and VC1' is the voltage across the capacitor when the third capacitor C3 is fully charged. It can be seen from the above formula that the charging delay time of the first switch Q1 can be adjusted by adjusting the capacitance of the first capacitor C1, thereby improving the convenience of the switching power supply 100. In addition, continue to refer to Figure 2As shown, the third resistor R3 is mainly used for current limiting to prevent the charging current of the first capacitor C1 from being too large and damaging the circuit; at the same time, the third resistor R3 and the fourth resistor R4 can also form a voltage divider circuit, which can ensure that during the charging process of the first capacitor C1, the control terminal voltage of the first switch Q1 can reach the target voltage to ensure that the charging delay circuit 142 can work normally.

[0053] For further reference, Figure 2 As shown, the charging delay circuit 142 further includes: a first diode D1, a cathode of the first diode D1 is connected to the other end of the first capacitor C1, and an anode of the first diode D1 is grounded GND.

[0054] Specifically, refer to Figure 2 As shown, the first diode D1 is mainly used to form a clamping circuit so that a stable voltage difference exists between the control terminal and the ground terminal of the first switch Q1 to ensure that the first switch Q1 is stably turned on. Figure 4 As shown, the first switch Q1 is an NMOS tube, and the first diode can ensure that the gate-source voltage of the first switch Q1 is the reverse voltage drop of the first diode D1, further ensuring that the charging delay circuit 142 can work normally and improving the reliability of the charging delay circuit.

[0055] In the above embodiment, by setting a first voltage stabilizing circuit, a first switch, a second resistor and a charging delay circuit in the overload blanking circuit, and setting a first capacitor, a third resistor and a fourth resistor in the charging delay circuit, the overload blanking circuit makes the first switch turned on after the blanking time of the control chip ends and before the first detection voltage reaches the first voltage threshold corresponding to the rated voltage of the load, thereby short-circuiting the second resistor and invalidating the overload protection circuit, thereby extending the blanking time and removing the restriction of the switching power supply on the capacitance of the load, thereby effectively improving the reliability of the switching power supply.

[0056] In some embodiments, reference Figure 3 As shown, the overload protection circuit 130 includes: a first voltage divider circuit 131 and an overload trigger circuit 132. The first voltage divider circuit 131 is connected to the load voltage detection terminal VDD, and is configured to divide the first detection voltage to obtain a first divided voltage; the overload trigger circuit 132 is respectively connected to the load voltage detection terminal VDD, the first voltage divider circuit 131 and the voltage feedback terminal FB, and is configured to disconnect the first voltage stabilizing circuit 141 and the second resistor R2 when the first divided voltage does not reach the second voltage threshold corresponding to the load rated voltage, so as to trigger the control chip 120 to perform load overload protection.

[0057] Specifically, refer to Figure 3As shown, the load voltage detection terminal VDD can be connected to the overload trigger circuit 132 through the first voltage divider circuit 131, and the first voltage divider circuit 131 can output a first divided voltage corresponding to the first detection voltage, and output it to the overload trigger circuit 132. During the normal operation of the switching power supply 100, when the voltage of the first divided voltage does not reach the second voltage threshold corresponding to the load rated voltage, it indicates that the current switching power supply 100 is at risk of overload. At this time, the overload trigger circuit 132 can disconnect the first voltage stabilizing circuit 141 and the second resistor R2. At this time, the power supply terminal VCC of the control chip 120 can be grounded GND through the first resistor R1, the load feedback terminal FB, the first voltage stabilizing circuit 141 and the second resistor R2. At this time, the voltage of the load feedback terminal FB can be determined by the following formula (1):

[0058] VFB=VSZ1+R2*VCC / (R1+R2) (3)

[0059] Among them, VFB is the load feedback terminal voltage, R2 is the resistance value of the second resistor, R1 is the resistance value of the first resistor, VCC is the power supply terminal voltage of the control chip 120, and VSZ1 is the reverse voltage drop of the first three-terminal voltage regulator SZ1. By adjusting the resistance values ​​of the first resistor R1 and the second resistor R2, the load feedback terminal voltage VFB can be made greater than the preset voltage range of the load feedback terminal FB, thereby triggering the control chip 120 to perform load overload protection. When the first divided voltage reaches the second voltage threshold, it indicates that the current switching power supply 100 is working normally, and the overload trigger circuit 132 will be connected in parallel with the first voltage regulator circuit 141 and the second resistor R2, thereby pulling down the load feedback terminal FB voltage so that it is within the preset voltage range to maintain the normal operation of the switching power supply 100. In this way, the overload protection function of the overload protection circuit is realized.

[0060] It should be noted that, when the switching power supply is powered on, the first switch Q1 in the overload blanking circuit 140 has not yet been turned on, the overload protection circuit 130 is in a triggered state, and the voltage of the load feedback terminal FB is relatively high. However, this is within the built-in blanking time of the control chip 120, so the high voltage of the load feedback terminal FB will not trigger the control chip 120 to perform load overload protection. When the blanking time of the control chip 120 ends, the control terminal voltage of the first switch Q1 has risen to the turn-on voltage, and the first switch Q1 has been turned on. Due to the voltage stabilizing effect of the first voltage stabilizing circuit 141, the circuit breaker function of the overload protection circuit 130 will not be able to pull up the voltage of the load feedback terminal FB, and the overload protection circuit 130 will fail. When the delay of the overload blanking circuit 140 ends, the overload protection circuit 130 restores the overload protection function of the switching power supply 100 in the above manner to ensure the power supply safety of the switching power supply 100.

[0061] Optionally, the first voltage divider circuit 131 includes: a fifth resistor R5 and a sixth resistor R6. One end of the fifth resistor R5 is connected to the load voltage detection terminal VDD; one end of the sixth resistor R6 is connected to the other end of the fifth resistor R5 and forms a first connection point J1, the other end of the sixth resistor R6 is grounded GND, and the first connection point J1 is connected to the overload trigger circuit 132.

[0062] Furthermore, the overload trigger circuit 132 includes: a seventh resistor R7, an eighth resistor R8, a second three-terminal voltage regulator SZ2 and a first optical coupler OC1. Among them, one end of the seventh resistor R7 is connected to the load voltage detection terminal VDD; one end of the eighth resistor R8 is connected to the other end of the seventh resistor R7; the cathode of the second three-terminal voltage regulator SZ2 is connected to the other end of the eighth resistor R8, the anode of the second three-terminal voltage regulator SZ2 is grounded GND, and the control electrode of the second three-terminal voltage regulator SZ2 is connected to the first voltage divider circuit 131; the first input end of the first optical coupler OC1 is connected to one end of the eighth resistor R8, the second input end of the first optical coupler OC1 is connected to the other end of the eighth resistor R8, the first output end of the first optical coupler OC1 is connected to the voltage feedback end FB, and the second output end of the first optical coupler OC1 is grounded GND.

[0063] Specifically, refer to Figure 5 As shown, the first input terminal and the second input terminal of the first optical coupler OC1 are connected to the two ends of the eighth resistor R8, respectively. When the first detection voltage output by the load voltage detection terminal VDD gradually rises, according to the voltage-dividing effect of the fifth resistor R5 and the sixth resistor R6, the control electrode voltage of the second three-terminal voltage regulator SZ2, that is, the first voltage-dividing voltage gradually rises until the second three-terminal voltage regulator SZ2 is reversely conducted. When the first voltage-dividing voltage does not reach the second voltage threshold corresponding to the rated voltage of the load, the second three-terminal voltage regulator SZ2 is not conducted, the resistance at both ends of the eighth resistor R8 is zero, and the first optical coupler OC1 is in a disconnected state, so the first voltage-stabilizing circuit 141 and the second resistor R2 can be disconnected. When the first divided voltage reaches the second voltage threshold corresponding to the rated voltage of the load, the second three-terminal voltage regulator SZ2 is reversely conducted, and the voltage across the eighth resistor R8 causes the first optical coupler OC1 to be in the amplification region. At this time, the first optical coupler OC1 can be regarded as a resistor connected in parallel to the first voltage regulator circuit 141 and the second resistor R2, which can pull down the voltage of the load feedback terminal FB, so that the voltage of the load feedback terminal FB will not be greater than the preset voltage range. In this way, the overload protection function is realized. In addition, the first optical coupler OC1 can effectively isolate the load feedback terminal FB from the load 200, thereby preventing the output of the switching power supply 100 from being affected by the output overload circuit 130, thereby effectively improving the stability of the switching power supply.

[0064] Furthermore, the overload trigger circuit 132 further includes: a ninth resistor R9 and a second capacitor C2. One end of the ninth resistor R9 is connected to the control electrode of the second three-terminal voltage regulator SZ2; one end of the second capacitor C2 is connected to the other end of the ninth resistor R9, and the other end of the second capacitor C2 is connected to the cathode of the second three-terminal voltage regulator SZ2.

[0065] Specifically, the second capacitor C2 is mainly used to isolate the control machine and cathode of the three-terminal voltage regulator, thereby ensuring that the three-terminal voltage regulator can be smoothly turned on and improving the circuit stability. At the same time, the three-terminal voltage regulator also has the advantage of high precision. The ninth resistor R9 is used to limit the current of the circuit where the second capacitor C2 is located to avoid the problem of excessive charging current in the circuit where the second capacitor C2 is located during charging, thereby ensuring the stable operation of the overload protection circuit 130.

[0066] In some embodiments, reference Figure 4 As shown, the switching power supply 100 further includes: a startup circuit 150 and an auxiliary power supply circuit 160. The startup circuit 150 is connected to the power supply terminals VCC of the main power supply circuit 110 and the control chip 120, respectively, and is configured to provide a startup voltage to the control chip 120 when the main power supply circuit 110 is powered on; the input terminal of the auxiliary power supply circuit 160 is connected to the main power supply circuit 110, and the output terminal of the auxiliary power supply circuit 160 is connected to the power supply terminal VCC of the control chip 120 through the second diode D2, and is configured to provide a working voltage to the control chip 120 after the control chip 120 is started, wherein the output terminal of the auxiliary power supply circuit 160 serves as a load voltage detection terminal VDD.

[0067] In some embodiments, the startup circuit 150 includes: a third capacitor C3 and a fourth capacitor C4. One end of the third capacitor C3 is respectively connected to the main power supply circuit 110 (part of the main power supply circuit is not shown) and the power supply terminal VCC of the control chip 120, and the other end of the third capacitor C3 is grounded GND; the fourth capacitor C4 is connected in parallel with the third capacitor C3.

[0068] Furthermore, the auxiliary power supply circuit 160 includes: a fifth capacitor C5, a tenth resistor R10, an eleventh resistor R11 and a third diode D3. One end of the fifth capacitor C5 is connected to the anode of the second diode D2 as the output end of the auxiliary power supply circuit 160, and the other end of the fifth capacitor C5 is grounded GND; the tenth resistor R10 is connected in parallel with the fifth capacitor C5; one end of the eleventh resistor R11 is connected to one end of the fifth capacitor C5; the cathode of the third diode D3 is connected to the other end of the eleventh resistor R11, and the anode of the third diode D3 is connected to the main power supply circuit 110.

[0069] Specifically, refer to Figure 4As shown, the startup circuit 150 is mainly used to provide an initial startup voltage to the control chip 120 when the control chip 120 starts itself, wherein the startup voltage source may be part of the main power supply circuit 110 connected to the third capacitor C3, such as the AC side part of the main power supply circuit 110, including the AC side, the rectifier side, etc., which are not shown in detail here. The voltage is stabilized and filtered by the third capacitor C3 and the fourth capacitor C4 to provide the startup voltage to the control chip 120 to complete the power-on process of the control chip 120. Subsequently, the auxiliary power supply circuit 160 may use the output side power supply of the main power supply circuit 110 to power the control chip 120 after the control chip 120 starts. For example, referring to Figure 4 As shown, the auxiliary power supply circuit 160 may include a fifth capacitor C5, a tenth resistor R10, an eleventh resistor R11 and a third diode D3, wherein the fifth capacitor C5 is used for filtering, the third diode D3 is used for rectification, the main power supply circuit 110 has a transformer and a secondary winding, and the main power supply circuit 110 can output the load side voltage to the anode of the second diode D2 through the third diode D3, the tenth resistor R10, the eleventh resistor R11 and the fifth capacitor C5, thereby achieving the effect of supplying power to the control chip 120 from the output side power supply, and realizing the function of supplying power to the control chip 120 using the output side power supply. In addition, the tenth resistor R10 and the eleventh resistor R11 mainly play a role in current limiting, preventing the current when the capacitor is powered on from damaging the switching power supply 100, so as to improve the safety of the switching power supply 100.

[0070] It should be noted that the operation of the auxiliary power supply circuit 160 does not require the support of a transformer. The fact that the main power supply circuit 110 in the embodiment of the utility model is equipped with a transformer is exemplary and does not limit the present application.

[0071] In some embodiments, reference Figure 4 As shown, the switching power supply 100 further includes: an output current limiting circuit 170, which is connected to the load 200 and the overload blanking circuit 140 respectively, and is configured to put the overload blanking circuit 140 into a failure state when an overcurrent occurs in the load 200.

[0072] Specifically, refer to Figure 4As shown, the output current limiting circuit 170 is mainly arranged on one side of the load 200 and is connected to the overload blanking circuit 140. When the large-capacity capacitor in the load 200 is powered on, the capacitor will generate a large output current, which is very likely to burn the switching power supply 100. Therefore, the switching power supply 100 needs to be provided with an output current limiting circuit 170 on the output side. During the power-on process of the switching power supply 100, if the output current is too large, the output current limiting circuit 170 can make the overload blanking circuit 140 invalid, and the overload protection circuit 130 can normally trigger the overload protection function of the control chip 120 to avoid burning the main power supply circuit 110 due to excessive output current, thereby effectively improving the safety of the switching power supply.

[0073] It should be noted that when the first switch Q1 in the overload blanking circuit 140 is not turned on, the output current limiting circuit 170 will make the overload blanking circuit 140 in an invalid state. However, this is usually within the built-in blanking time of the control chip 120, so the output current limiting circuit 170 will not affect the normal power-on process of the switching power supply 100. If the output current is still too large at the end of the blanking time of the control chip 120, it means that the main power supply circuit 110 has been running overcurrent for too long, and the output current limiting circuit 170 will protect the normal operation of the switching power supply 110 by making the overload blanking circuit 140 invalid.

[0074] In some embodiments, the output current limiting circuit 170 includes: a current detection circuit 171 and an overcurrent trigger circuit 172. The current detection circuit 171 is connected to the load 200 and is configured to detect the current of the load 200 to obtain a second detection voltage corresponding to the current; the overcurrent trigger circuit 172 is respectively connected to the load 200, the current detection circuit 171 and the overload blanking circuit 140, and is configured to make the first switch Q1 in a disconnected state when the second detection voltage reaches a voltage threshold corresponding to the overcurrent protection threshold, so that the overload blanking circuit Q1 is in a disabled state.

[0075] Furthermore, the current detection circuit 171 includes: a twelfth resistor R12 and a thirteenth resistor R13. One end of the twelfth resistor R12 is connected to the load 200; the thirteenth resistor R13, one end of the thirteenth resistor R13 is connected to the other end of the twelfth resistor R12 and forms a second connection point J2, the other end of the thirteenth resistor R13 is grounded GND, and the second connection point J2 is connected to the overcurrent trigger circuit 172.

[0076] Furthermore, the overcurrent trigger circuit 172 includes: a fourteenth resistor R14, a second optocoupler OC2 and a third three-terminal zener diode SZ3, one end of the fourteenth resistor R14 is connected to the load 200; the first input end of the second optocoupler OC2 is connected to the other end of the fourteenth resistor R14, the first output end of the second optocoupler OC2 is connected to the control end of the first switch Q1, and the second output end of the second optocoupler OC2 is grounded GND; the cathode of the third three-terminal zener diode SZ3 is connected to the second input end of the second optocoupler OC2, the anode of the third three-terminal zener diode SZ3 is grounded, and the control electrode of the third three-terminal zener diode SZ3 is connected to the current detection circuit 172.

[0077] Specifically, refer to Figure 4 As shown, when the load 200 works normally, the twelfth resistor R12 and the thirteenth resistor R13 in the current detection circuit 170 can convert the current signal at the load 200 into a voltage signal after voltage division to realize the current detection function, and transmit the second detection voltage to the control end of the third three-terminal voltage regulator SZ3 in the overcurrent trigger circuit 172 through the second connection point J2. Subsequently, during the continuous rise of the second detection voltage, the voltage across the third three-terminal voltage regulator SZ3 will stagnate at the reverse voltage drop of the three-terminal voltage regulator, and the voltage across the fourteenth resistor R14 will continue to rise, that is, the voltage across the second optical coupler OC2 will continue to rise. When the second detection voltage reaches the voltage threshold corresponding to the overcurrent protection threshold, the second optical coupler OC2 is turned on, and the first output end and the second output end of the second optical coupler OC2 are connected, so that the voltage at the control end of the first switch Q1 is forced to be pulled down, causing the first switch Q1 to be turned off, and the overload blanking circuit 140 is invalid. At this time, the output overload circuit 130 can be triggered normally, thereby protecting the normal operation of the switching power supply 100. Therefore, the function of the output current limiting circuit to limit the output current during the power-on process is realized, thereby improving the reliability of the switching power supply.

[0078] Optional, reference Figure 5 As shown, the overcurrent trigger circuit 172 further includes: a fifteenth resistor R15, and the fifteenth resistor R15 is connected between the first input terminal and the second input terminal of the second optical coupler OC2.

[0079] Specifically, refer to Figure 5 As shown, the overcurrent trigger circuit 172 may further include a fifteenth resistor R15. By setting two resistors in the overcurrent trigger circuit 172, the overcurrent protection threshold can be adjusted more conveniently, which is convenient for debugging, thereby improving the convenience of the switching power supply.

[0080] Optional, reference Figure 4As shown, the overcurrent trigger circuit 172 also includes: a fourth diode D4 and a sixth capacitor C6, the anode of the fourth diode D4 is connected to the load 200, and the cathode of the fourth diode D4 is connected to one end of the fourteenth resistor R14; the sixth capacitor C6 is connected between the cathode of the fourth diode D4 and the ground GND.

[0081] Specifically, the fourth diode D4 mainly plays a role in preventing backflow, thereby preventing the overcurrent trigger circuit from affecting the normal operation of the load 200, and the sixth capacitor C6 mainly plays a filtering and voltage stabilization effect to ensure that the overcurrent trigger circuit 172 can be reliably triggered.

[0082] In some embodiments, reference Figure 4 and Figure 5 As shown, the output current limiting circuit also includes: a first filter circuit 173, which is arranged between the control electrode of the third three-terminal voltage regulator SZ3 and the current detection circuit 171; or, a second filter circuit 174, which is connected to the load 200 and the current detection circuit 171 respectively.

[0083] Specifically, the first filter circuit 173 and the second filter circuit 174 are used to filter out the AC part of the load current to ensure that the output current limiting circuit 170 can work normally and improve the reliability of the output current limiting circuit. The specific principle is not expanded here. In addition, the specific structure of the first filter circuit 173 and the second filter circuit 174 may include a variety of situations, for example, referring to Figure 4 As shown, the first filtering circuit 173 may include a capacitor and a resistor, which is not specifically limited here.

[0084] In summary, according to the switching power supply of the embodiment of the utility model, by arranging an overload protection circuit and an overload blanking circuit internally, the overload protection circuit can be put into a disabled state from the end of the blanking time of the control chip to before the first detection voltage reaches the first voltage threshold corresponding to the rated voltage of the load, thereby achieving the effect of extending the blanking time of the switching power supply, thereby enabling the switching power supply to supply power to a large-capacity capacitive load, and effectively improving the applicability of the switching power supply; at the same time, by arranging an output current limiting circuit on the load side of the switching power supply, during the power-on process of the switching power supply, the output current limiting circuit can ensure that the switching power supply will not be burned due to excessive output current, thereby improving the applicability and reliability of the switching power supply.

[0085] Corresponding to the above embodiment, the utility model example also provides an electrical device, referring to Figure 6 As shown, the electrical device 1000 includes the aforementioned switching power supply 100 .

[0086] According to the electrical equipment of the embodiment of the utility model, the restriction of the electrical equipment on the capacitance of the load can be removed through the aforementioned switching power supply, thereby reducing the design difficulty of the electrical equipment and improving the reliability of the switching power supply.

[0087] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection portion with one or more wirings (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0088] It should be understood that the various parts of the utility model can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiment, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0089] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0090] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present utility model, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0091] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0092] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations of the present invention. Ordinary technicians in the field can change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A switching power supply, characterized in that: include: A main power supply circuit, the main power supply circuit is connected to a load and is configured to supply power to the load; A control chip, the control chip is connected to the main power supply circuit and is configured to control the main power supply circuit to supply power to the load; an overload protection circuit, the overload protection circuit being connected to a load voltage detection terminal and a voltage feedback terminal of the control chip respectively, and being configured to perform load overload protection based on a first detection voltage of the load voltage detection terminal; An overload blanking circuit, wherein the overload blanking circuit is respectively connected to the load voltage detection terminal and the voltage feedback terminal of the control chip, and is configured to put the overload protection circuit into a failure state at least from the end of the blanking time of the control chip to the time when the first detection voltage reaches a first voltage threshold corresponding to the load rated voltage.

2. The switching power supply according to claim 1, characterized in that: The overload blanking circuit comprises: a first voltage stabilizing circuit, wherein one end of the first voltage stabilizing circuit is connected to the voltage feedback end, and one end of the first voltage stabilizing circuit is also connected to the power supply end of the control chip through a first resistor; A first switch, wherein the first switch is connected in series between the other end of the first voltage stabilizing circuit and the ground; a second resistor, the second resistor being connected in parallel with the first switch; A charging delay circuit, wherein the charging delay circuit is respectively connected to the load voltage detection terminal and the control terminal of the first switch, and is configured to perform charging delay based on the first detection voltage, so as to enable the first switch to be in an on state at least from the end of the blanking time of the control chip to the time when the first detection voltage reaches a first voltage threshold corresponding to the load rated voltage, so as to enable the overload protection circuit to be in an invalid state through the first voltage stabilizing circuit.

3. The switching power supply according to claim 2, characterized in that: The first voltage stabilizing circuit comprises: a first voltage stabilizing diode, wherein a cathode of the first voltage stabilizing diode is connected to the voltage feedback terminal, and an anode of the first voltage stabilizing diode is connected to the first switch; or A first three-terminal voltage regulator tube, wherein a cathode and a control electrode of the first three-terminal voltage regulator tube are respectively connected to the voltage feedback terminal, and an anode of the first three-terminal voltage regulator tube is connected to the first switch.

4. The switching power supply according to claim 2, characterized in that: The first switch is a triode or a MOS tube.

5. The switching power supply according to claim 2, characterized in that: The charging delay circuit comprises: A first capacitor, one end of which is connected to the load voltage detection end; a third resistor, one end of the third resistor being connected to the other end of the first capacitor, and the other end of the third resistor being connected to the control end of the first switch; A fourth resistor is connected between the control end of the first switch and ground.

6. The switching power supply according to claim 5, characterized in that: The charging delay circuit also includes: A first diode, wherein a cathode of the first diode is connected to the other end of the first capacitor, and an anode of the first diode is grounded.

7. The switching power supply according to claim 2, characterized in that: The overload protection circuit comprises: a first voltage-dividing circuit, the first voltage-dividing circuit being connected to the load voltage detection terminal and configured to divide the first detection voltage to obtain a first divided voltage; An overload trigger circuit is respectively connected to the load voltage detection terminal, the first voltage divider circuit and the voltage feedback terminal, and is configured to disconnect the first voltage stabilizing circuit and the second resistor when the first voltage divider voltage does not reach a second voltage threshold corresponding to the load rated voltage, so as to trigger the control chip to perform load overload protection.

8. The switching power supply according to claim 7, characterized in that: The first voltage divider circuit comprises: a fifth resistor, one end of which is connected to the load voltage detection end; A sixth resistor, one end of the sixth resistor is connected to the other end of the fifth resistor to form a first connection point, the other end of the sixth resistor is grounded, and the first connection point is connected to the overload trigger circuit.

9. The switching power supply according to claim 7, characterized in that: The overload trigger circuit comprises: a seventh resistor, one end of which is connected to the load voltage detection end; an eighth resistor, one end of the eighth resistor being connected to the other end of the seventh resistor; a second three-terminal voltage regulator tube, wherein a cathode of the second three-terminal voltage regulator tube is connected to the other end of the eighth resistor, an anode of the second three-terminal voltage regulator tube is grounded, and a control electrode of the second three-terminal voltage regulator tube is connected to the first voltage divider circuit; A first optocoupler, wherein a first input terminal of the first optocoupler is connected to one end of the eighth resistor, a second input terminal of the first optocoupler is connected to the other end of the eighth resistor, a first output terminal of the first optocoupler is connected to the voltage feedback terminal, and a second output terminal of the first optocoupler is grounded.

10. The switching power supply according to claim 9, characterized in that: The overload trigger circuit also includes: a ninth resistor, one end of which is connected to the control electrode of the second three-terminal voltage regulator tube; A second capacitor, one end of the second capacitor is connected to the other end of the ninth resistor, and the other end of the second capacitor is connected to the cathode of the second three-terminal voltage regulator.

11. The switching power supply according to any one of claims 1 to 10, characterized in that: The switching power supply further comprises: A startup circuit, the startup circuit being connected to the power supply terminals of the main power supply circuit and the control chip respectively, and being configured to provide a startup voltage to the control chip when the main power supply circuit is powered on; An auxiliary power supply circuit, wherein the input end of the auxiliary power supply circuit is connected to the main power supply circuit, the output end of the auxiliary power supply circuit is connected to the power supply end of the control chip through a second diode, and is configured to provide a working voltage to the control chip after the control chip is started, wherein the output end of the auxiliary power supply circuit serves as the load voltage detection end.

12. The switching power supply according to claim 11, characterized in that: The startup circuit comprises: A third capacitor, one end of which is connected to the main power supply circuit and the power supply end of the control chip respectively, and the other end of which is grounded; A fourth capacitor is connected in parallel with the third capacitor.

13. The switching power supply according to claim 11, characterized in that: The auxiliary power supply circuit comprises: a fifth capacitor, one end of the fifth capacitor being connected to the anode of the second diode as the output end of the auxiliary power supply circuit, and the other end of the fifth capacitor being grounded; a tenth resistor, the tenth resistor being connected in parallel with the fifth capacitor; an eleventh resistor, one end of the eleventh resistor being connected to one end of the fifth capacitor; A third diode, wherein a cathode of the third diode is connected to the other end of the eleventh resistor, and an anode of the third diode is connected to the main power supply circuit.

14. The switching power supply according to any one of claims 2 to 10, characterized in that: The switching power supply further comprises: An output current limiting circuit is connected to the load and the overload blanking circuit respectively, and is configured to put the overload blanking circuit into a failure state when an overcurrent occurs in the load.

15. The switching power supply according to claim 14, characterized in that: The output current limiting circuit comprises: a current detection circuit, the current detection circuit being connected to the load and configured to detect the current of the load to obtain a second detection voltage corresponding to the current; An overcurrent trigger circuit, wherein the overcurrent trigger circuit is respectively connected to the load, the current detection circuit and the overload blanking circuit, and is configured to put the first switch in an off state when the second detection voltage reaches a voltage threshold corresponding to an overcurrent protection threshold, so as to put the overload blanking circuit in an invalid state.

16. The switching power supply according to claim 15, characterized in that: The current detection circuit comprises: a twelfth resistor, one end of which is connected to the load; A thirteenth resistor, one end of the thirteenth resistor is connected to the other end of the twelfth resistor and forms a second connection point, the other end of the thirteenth resistor is grounded, and the second connection point is connected to the overcurrent trigger circuit.

17. The switching power supply according to claim 15, characterized in that: The overcurrent trigger circuit comprises: a fourteenth resistor, one end of which is connected to the load; a second optical coupler, wherein a first input end of the second optical coupler is connected to the other end of the fourteenth resistor, a first output end of the second optical coupler is connected to the control end of the first switch, and a second output end of the second optical coupler is grounded; A third three-terminal voltage regulator, wherein the cathode of the third three-terminal voltage regulator is connected to the second input terminal of the second optocoupler, the anode of the third three-terminal voltage regulator is grounded, and the control electrode of the third three-terminal voltage regulator is connected to the current detection circuit.

18. The switching power supply according to claim 17, characterized in that: The overcurrent trigger circuit also includes: A fifteenth resistor is connected between the first input terminal and the second input terminal of the second optical coupler.

19. The switching power supply according to claim 17, characterized in that: The overcurrent trigger circuit also includes: a fourth diode, wherein an anode of the fourth diode is connected to the load, and a cathode of the fourth diode is connected to one end of the fourteenth resistor; A sixth capacitor is connected between the cathode of the fourth diode and the ground.

20. The switching power supply according to claim 17, characterized in that: The output current limiting circuit further includes: A first filter circuit, wherein the first filter circuit is provided between the control electrode of the third three-terminal voltage regulator and the current detection circuit; or A second filtering circuit is connected to the load and the current detection circuit respectively.

21. An electrical device, characterized in that: Comprising a switching power supply according to any one of claims 1-20.

Images