A light load mode switching control circuit for a switching power supply

Abstract

The present invention discloses a light load mode switching control circuit of a switching power supply, comprising a voltage detection module, a current detection module and a standby load module; the input end of the voltage detection module is used to connect the output end of the switching power supply, and the output end of the voltage detection module is connected to the control end of the standby load module; the input end of the current detection module is used to connect the output end of the switching power supply, and the output end of the current detection module is connected to the control end of the standby load module; the first input end of the standby load module is used to connect the power supply, the second input end of the standby load module is used to connect the output end of the switching power supply, and the output end of the standby load module is grounded. The present invention can improve the stability of mode switching by adding a standby load and setting a trigger circuit when the switching power supply leaves or enters the light load mode, thereby ensuring the output voltage quality of the switching power supply and improving the stability of the power load.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply control, and in particular to a light load mode switching control circuit of a switching power supply. Background Art

[0002] At present, in order to reduce light-load losses, many switching power supplies adopt control modes such as FCOT (Fast Constant On Time) and PSM (Pulse Skip Modulation) under light-load conditions. However, this will affect the voltage quality under light load. At the same time, due to changes in the load of the power supply circuit, the controller switches unevenly during the process of leaving or entering the light-load mode, which also causes the output voltage quality to deteriorate, thereby affecting the stability of the power load. Summary of the invention

[0003] The technical problem to be solved by the embodiments of the present invention is to provide a light load mode switching control circuit for a switching power supply, which can improve the stability of the mode switching by adding a backup load and setting a trigger circuit when the switching power supply leaves or enters the light load mode, thereby ensuring the output voltage quality of the switching power supply and improving the stability of the power load.

[0004] In order to solve the above technical problems, an embodiment of the present invention provides a light load mode switching control circuit of a switching power supply, including a voltage detection module, a current detection module and a standby load module;

[0005] The input end of the voltage detection module is used to connect to the output end of the switching power supply, and the output end of the voltage detection module is connected to the control end of the standby load module;

[0006] The input end of the current detection module is used to connect to the output end of the switching power supply, and the output end of the current detection module is connected to the control end of the standby load module;

[0007] The first input end of the standby load module is used to connect to a power supply, the second input end of the standby load module is used to connect to an output end of a switching power supply, and the output end of the standby load module is grounded.

[0008] Further, the voltage detection module includes a first capacitor, a maximum peak detection unit, a minimum peak detection unit, a peak-to-peak value calculation unit and a voltage comparison unit;

[0009] The first end of the first capacitor is connected to the input end of the voltage detection module, the second end of the first capacitor is connected to the input end of the maximum peak detection unit, and the output end of the maximum peak detection unit is connected to the first input end of the peak-to-peak value calculation unit;

[0010] The input end of the minimum peak detection unit is connected to the second end of the first capacitor, the output end of the minimum peak detection unit is connected to the second input end of the peak-to-peak value calculation unit, and the output end of the peak-to-peak value calculation unit is connected to the first input end of the voltage comparison unit;

[0011] The second input terminal of the voltage comparison unit is used to connect to a first reference voltage, and the output terminal of the voltage comparison unit is connected to the output terminal of the voltage detection module.

[0012] Further, the maximum peak detection unit includes a first operational amplifier, a first diode, a first resistor and a second capacitor;

[0013] The non-inverting input terminal of the first operational amplifier is connected to the input terminal of the maximum peak detection unit, the inverting input terminal of the first operational amplifier is connected to the cathode of the first diode, the output terminal of the first operational amplifier is connected to the anode of the first diode, and the cathode of the first diode is connected to the output terminal of the maximum peak detection unit;

[0014] A first end of the first resistor is connected to the cathode of the first diode, and a second end of the first resistor is grounded;

[0015] The positive electrode of the second capacitor is connected to the cathode of the first diode, and the negative electrode of the second capacitor is grounded.

[0016] Furthermore, the maximum peak detection unit also includes a second operational amplifier and a second resistor;

[0017] The non-inverting input terminal of the second operational amplifier is connected to the cathode of the first diode, the inverting input terminal of the second operational amplifier is connected to the output terminal of the maximum peak detection unit, and the output terminal of the second operational amplifier is connected to the output terminal of the maximum peak detection unit;

[0018] A first end of the second resistor is connected to an inverting input end of the first operational amplifier, and a second end of the second resistor is connected to a cathode of the first diode.

[0019] Further, the minimum peak detection unit includes a third operational amplifier, a second diode, a third resistor and a third capacitor;

[0020] The non-inverting input terminal of the third operational amplifier is connected to the input terminal of the minimum peak detection unit, the inverting input terminal of the third operational amplifier is connected to the anode of the second diode, the output terminal of the third operational amplifier is connected to the cathode of the second diode, and the anode of the second diode is connected to the output terminal of the minimum peak detection unit;

[0021] A first end of the third resistor is connected to the anode of the second diode, and a second end of the third resistor is grounded;

[0022] A cathode of the third capacitor is connected to an anode of the second diode, and a cathode of the third capacitor is grounded.

[0023] Further, the minimum peak detection unit also includes a fourth operational amplifier and a fourth resistor;

[0024] The non-inverting input terminal of the fourth operational amplifier is connected to the anode of the second diode, the inverting input terminal of the fourth operational amplifier is connected to the output terminal of the minimum peak detection unit, and the output terminal of the fourth operational amplifier is connected to the output terminal of the minimum peak detection unit;

[0025] A first end of the fourth resistor is connected to an inverting input end of the third operational amplifier, and a second end of the fourth resistor is connected to an anode of the second diode.

[0026] Further, the peak-to-peak value calculation unit includes a fifth operational amplifier, a fifth resistor, a sixth resistor, a seventh resistor and an eighth resistor;

[0027] The non-inverting input terminal of the fifth operational amplifier is connected to the first input terminal of the peak-to-peak value operation unit through the fifth resistor, the inverting input terminal of the fifth operational amplifier is connected to the second input terminal of the peak-to-peak value operation unit through the sixth resistor, and the output terminal of the fifth operational amplifier is connected to the output terminal of the peak-to-peak value operation unit;

[0028] A first end of the seventh resistor is connected to the non-inverting input end of the fifth operational amplifier, and a second end of the seventh resistor is connected to the output end of the fifth operational amplifier;

[0029] A first end of the eighth resistor is connected to the inverting input end of the fifth operational amplifier, and a second end of the eighth resistor is grounded.

[0030] Further, the voltage comparison unit includes a sixth operational amplifier;

[0031] The inverting input terminal of the sixth operational amplifier is connected to the first input terminal of the voltage comparison unit, the non-inverting input terminal of the sixth operational amplifier is connected to the second input terminal of the voltage comparison unit, and the output terminal of the sixth operational amplifier is connected to the output terminal of the voltage comparison unit.

[0032] Furthermore, the current detection module includes a current detection unit, a current calculation unit, an effective value detection unit and a current comparison unit;

[0033] The input end of the current detection unit is connected to the input end of the current detection module, the input end of the current detection unit is also connected to the first input end of the current operation unit, the first output end of the current detection unit is connected to the second input end of the current operation unit, and the second output end of the current detection unit is grounded;

[0034] The output end of the current calculation unit is connected to the input end of the effective value detection unit, and the output end of the effective value detection unit is connected to the first input end of the current comparison unit;

[0035] The second input terminal of the current comparison unit is used to connect to a second reference voltage, the third input terminal of the current comparison unit is used to connect to a third reference voltage, and the output terminal of the current comparison unit is connected to the output terminal of the current detection module.

[0036] Further, the current detection unit includes a ninth resistor;

[0037] A first end of the ninth resistor is connected to the input end of the current detection unit, and a second end of the ninth resistor is connected to the first output end of the current detection unit.

[0038] Further, the current detection unit also includes a tenth resistor;

[0039] The first end of the tenth resistor is connected to the second end of the ninth resistor, and the second end of the tenth resistor is connected to the second output end of the current detection unit.

[0040] Further, the current operation unit includes a seventh operational amplifier, an eleventh resistor, a twelfth resistor, a thirteenth resistor and a fourteenth resistor;

[0041] The inverting input terminal of the seventh operational amplifier is connected to the first input terminal of the current operation unit through the eleventh resistor, the non-inverting input terminal of the seventh operational amplifier is connected to the second input terminal of the current operation unit through the twelfth resistor, and the output terminal of the seventh operational amplifier is connected to the output terminal of the current operation unit;

[0042] A first end of the thirteenth resistor is connected to the inverting input end of the seventh operational amplifier, and a second end of the thirteenth resistor is connected to the output end of the seventh operational amplifier;

[0043] A first end of the fourteenth resistor is connected to the non-inverting input terminal of the seventh operational amplifier, and a second end of the fourteenth resistor is grounded.

[0044] Further, the effective value detection unit includes an eighth operational amplifier, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, a third diode and a fourth diode;

[0045] The inverting input terminal of the eighth operational amplifier is connected to the input terminal of the effective value detection unit through the fifteenth resistor, the non-inverting input terminal of the eighth operational amplifier is grounded through the sixteenth resistor, the output terminal of the eighth operational amplifier is connected to the cathode of the fourth diode, and the anode of the fourth diode is connected to the output terminal of the effective value detection unit;

[0046] A first end of the seventeenth resistor is connected to the inverting input end of the eighth operational amplifier, and a second end of the seventeenth resistor is connected to the anode of the fourth diode;

[0047] The cathode of the third diode is connected to the inverting input terminal of the eighth operational amplifier, and the anode of the third diode is connected to the cathode of the fourth diode.

[0048] Further, the effective value detection unit also includes a ninth operational amplifier, an eighteenth resistor, a nineteenth resistor, a twentieth resistor and a fourth capacitor;

[0049] The inverting input terminal of the ninth operational amplifier is connected to the anode of the fourth diode through the eighteenth resistor, the non-inverting input terminal of the ninth operational amplifier is grounded through the nineteenth resistor, and the output terminal of the ninth operational amplifier is connected to the output terminal of the effective value detection unit;

[0050] A first end of the 20th resistor is connected to the inverting input end of the ninth operational amplifier, and a second end of the 20th resistor is connected to the output end of the ninth operational amplifier;

[0051] A first end of the fourth capacitor is connected to a first end of the twentieth resistor, and a second end of the fourth capacitor is connected to a second end of the twentieth resistor.

[0052] Further, the current comparison unit includes a tenth operational amplifier and an eleventh operational amplifier;

[0053] The non-inverting input terminal of the tenth operational amplifier is connected to the first input terminal of the current comparison unit, the inverting input terminal of the tenth operational amplifier is connected to the second input terminal of the current comparison unit, and the output terminal of the tenth operational amplifier is connected to the output terminal of the current comparison unit;

[0054] The inverting input terminal of the eleventh operational amplifier is connected to the first input terminal of the current comparison unit, the non-inverting input terminal of the eleventh operational amplifier is connected to the third input terminal of the current comparison unit, and the output terminal of the eleventh operational amplifier is connected to the output terminal of the current comparison unit.

[0055] Further, the standby load module includes a twenty-first resistor, a first switch tube, a second switch tube and a third switch tube;

[0056] A first end of the twenty-first resistor is connected to the first input end of the standby load module, and a second end of the twenty-first resistor is connected to the input end of the first switch tube;

[0057] The control end of the first switch tube is connected to the second end of the twenty-first resistor, and the output end of the first switch tube is connected to the output end of the standby load module;

[0058] The control end of the second switch tube is connected to the second end of the twenty-first resistor, and the output end of the second switch tube is connected to the output end of the standby load module;

[0059] The input end of the third switch tube is connected to the second input end of the standby load module, the control end of the third switch tube is connected to the control end of the standby load module, and the output end of the third switch tube is connected to the input end of the second switch tube.

[0060] Compared with the prior art, an embodiment of the present invention provides a light load mode switching control circuit for a switching power supply, comprising a voltage detection module, a current detection module and a standby load module; the input end of the voltage detection module is used to connect to the output end of the switching power supply, and the output end of the voltage detection module is connected to the control end of the standby load module; the input end of the current detection module is used to connect to the output end of the switching power supply, and the output end of the current detection module is connected to the control end of the standby load module; the first input end of the standby load module is used to connect to a power supply, the second input end of the standby load module is used to connect to the output end of the switching power supply, and the output end of the standby load module is grounded; the control circuit can improve the stability of mode switching by adding a standby load and setting a trigger circuit when the switching power supply leaves or enters the light load mode, thereby ensuring the output voltage quality of the switching power supply and improving the stability of the power load. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is a structural schematic diagram of a preferred embodiment of a light-load mode switching control circuit of a switching power supply provided by the present invention;

[0062] Figure 2 It is a structural schematic diagram of another preferred embodiment of a light-load mode switching control circuit of a switching power supply provided by the present invention;

[0063] Figure 3 It is a circuit schematic diagram of a preferred embodiment of a light load mode switching control circuit of a switching power supply provided by the present invention;

[0064] Figure 4 It is an application circuit diagram of a light-load mode switching control circuit of a switching power supply provided by the present invention. DETAILED DESCRIPTION

[0065] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this technical field without creative work are within the scope of protection of the present invention.

[0066] The embodiment of the present invention provides a light load mode switching control circuit of a switching power supply, see Figure 1 , which is a structural schematic diagram of a preferred embodiment of a light-load mode switching control circuit of a switching power supply provided by the present invention, wherein the control circuit comprises a voltage detection module 100, a current detection module 200 and a standby load module 300;

[0067] The input end of the voltage detection module 100 is used to connect to the output end Udc of the switching power supply, and the output end of the voltage detection module 100 is connected to the control end of the standby load module 300;

[0068] The input end of the current detection module 200 is used to connect to the output end Udc of the switching power supply, and the output end of the current detection module 200 is connected to the control end of the standby load module 300;

[0069] The first input end of the standby load module 300 is used to connect to the power supply Vcc, the second input end of the standby load module 300 is used to connect to the output end Udc of the switching power supply, and the output end of the standby load module 300 is grounded.

[0070] Specifically, the control circuit is mainly composed of a voltage detection module 100, a current detection module 200 and a standby load module 300. In actual applications, the control circuit detects the output voltage of the controlled switching power supply (such as a DC-DC power supply chip, etc.) through the voltage detection module 100 to determine the output voltage quality of the switching power supply, and detects the output current of the switching power supply through the current detection module 200 to determine the load state and control mode of the switching power supply. When it is determined that the load of the switching power supply is in a light load mode and the peak-to-peak value of the output voltage dynamic response exceeds a preset voltage threshold, the standby load module 300 is triggered to function, forming a "load bias". By increasing the load of the switching power supply, the switching power supply is freed from the unstable state of switching to the light load mode, and the output voltage is stabilized to protect the output voltage quality.

[0071] See also Figure 2, which is a structural schematic diagram of another preferred embodiment of a light-load mode switching control circuit of a switching power supply provided by the present invention. In another preferred embodiment, the voltage detection module 100 includes a first capacitor C1, a maximum peak detection unit, a minimum peak detection unit, a peak-to-peak value calculation unit and a voltage comparison unit;

[0072] The first end of the first capacitor C1 is connected to the input end of the voltage detection module 100, the second end of the first capacitor C1 is connected to the input end of the maximum peak detection unit, and the output end of the maximum peak detection unit is connected to the first input end of the peak-to-peak value calculation unit;

[0073] The input end of the minimum peak detection unit is connected to the second end of the first capacitor C1, the output end of the minimum peak detection unit is connected to the second input end of the peak-to-peak value calculation unit, and the output end of the peak-to-peak value calculation unit is connected to the first input end of the voltage comparison unit;

[0074] The second input terminal of the voltage comparison unit is used to connect to the first reference voltage V1 , and the output terminal of the voltage comparison unit is connected to the output terminal of the voltage detection module 100 .

[0075] Specifically, in combination with the above embodiments, the voltage detection module 100 is mainly composed of a first capacitor C1, a maximum peak detection unit, a minimum peak detection unit, a peak-to-peak value calculation unit and a voltage comparison unit. In actual applications, the control circuit obtains the dynamic response waveform of the output voltage of the switching power supply through the AC coupling of the first capacitor C1, obtains the maximum peak voltage of the output voltage according to the dynamic response waveform of the output voltage through the maximum peak detection unit, obtains the minimum peak voltage of the output voltage according to the dynamic response waveform of the output voltage through the minimum peak detection unit, and calculates the voltage peak-to-peak value of the dynamic response waveform of the output voltage according to the maximum peak voltage and the minimum peak voltage through the peak-to-peak value calculation unit, transmits the voltage peak-to-peak value to the voltage comparison unit, and compares it with the preset first reference voltage V1 to determine whether to trigger the standby load module 300 according to the comparison result.

[0076] For example, the first reference voltage V1 represents the threshold of the dynamic response peak-to-peak value of the output voltage of the switching power supply. When the voltage peak-to-peak value of the dynamic response waveform of the output voltage of the switching power supply is greater than the first reference voltage V1, the voltage comparison unit outputs a high level, which can trigger the backup load module 300 to function.

[0077] It should be noted that whether to trigger the backup load module 300 depends not only on the output result of the voltage comparison unit in the voltage detection module 100, but also on the output result of the current detection module 200. The two are in an "AND" relationship, that is, certain threshold conditions must be met at the same time to finally confirm that the backup load module 300 is triggered to take effect.

[0078] See also Figure 3 , which is a circuit schematic diagram of a preferred embodiment of a light-load mode switching control circuit of a switching power supply provided by the present invention. As an improvement of the above scheme, the maximum peak detection unit includes a first operational amplifier U1, a first diode D1, a first resistor R1 and a second capacitor C2;

[0079] The non-inverting input terminal of the first operational amplifier U1 is connected to the input terminal of the maximum peak detection unit, the inverting input terminal of the first operational amplifier U1 is connected to the cathode of the first diode D1, the output terminal of the first operational amplifier U1 is connected to the anode of the first diode D1, and the cathode of the first diode D1 is connected to the output terminal of the maximum peak detection unit;

[0080] A first end of the first resistor R1 is connected to the cathode of the first diode D1, and a second end of the first resistor R1 is grounded;

[0081] An anode of the second capacitor C2 is connected to a cathode of the first diode D1 , and a cathode of the second capacitor C2 is grounded.

[0082] Specifically, in combination with the above embodiments, the maximum peak detection unit is mainly composed of a first operational amplifier U1, a first diode D1, a first resistor R1 and a second capacitor C2. In practical applications, the maximum peak voltage detection of the output voltage is mainly achieved by charging and discharging the second capacitor C2. The maximum peak voltage is obtained when the second capacitor C2 is charged, and the sampling time interval of the maximum peak voltage can be controlled by utilizing the discharge reset time when the parallel first resistor R1 is discharged.

[0083] When the voltage at the non-inverting input terminal of the first operational amplifier U1 is greater than the voltage at the inverting input terminal, the first operational amplifier U1 outputs a positive voltage, causing the first diode D1 to be turned on to charge the second capacitor C2; when the voltage at the non-inverting input terminal of the first operational amplifier U1 is equal to the voltage at the inverting input terminal, the first diode D1 is turned off and the charging process stops. At this time, the voltage corresponding to the positive electrode of the second capacitor C2 is the maximum peak voltage of the output voltage.

[0084] It should be noted that the first operational amplifier U1 is powered by a dual power supply (i.e., +V and -V) in actual applications; the function of the first diode D1 is forward conduction and reverse shutdown, so it is necessary to select a diode with a smaller forward conduction voltage to reduce the sampling value error; the second capacitor C2 needs to be charged quickly to maintain the peak voltage data. Since the electrical characteristics of its connection interface are high-impedance, it is necessary to select a capacitor with a smaller capacitance, generally at the level of several hundred pF; the first resistor R1 provides a discharge circuit for the second capacitor C2 to achieve peak data reset, and the value can be set accordingly according to the RC time constant and the sampling and holding required time.

[0085] Combination Figure 3 As shown, as an improvement of the above solution, the maximum peak detection unit further includes a second operational amplifier U2 and a second resistor R2;

[0086] The non-inverting input terminal of the second operational amplifier U2 is connected to the cathode of the first diode D1, the inverting input terminal of the second operational amplifier U2 is connected to the output terminal of the maximum peak detection unit, and the output terminal of the second operational amplifier U2 is connected to the output terminal of the maximum peak detection unit;

[0087] A first end of the second resistor R2 is connected to the inverting input end of the first operational amplifier U1 , and a second end of the second resistor R2 is connected to the cathode of the first diode D1 .

[0088] Specifically, in combination with the above embodiment, the maximum peak detection unit also includes a second operational amplifier U2 and a second resistor R2; wherein the second operational amplifier U2 plays an isolation role, and the second resistor R2 is connected in series in the negative feedback loop of the first operational amplifier U1, which can reduce the output bias voltage of the first operational amplifier U1, thereby reducing the sampling deviation, and at the same time can limit the current of the negative feedback loop to protect the circuit.

[0089] It should be noted that the second resistor R2 is a negative feedback circuit resistor, and its value is generally preferably 10 kΩ.

[0090] Combination Figure 3 As shown, as an improvement of the above solution, the minimum peak detection unit includes a third operational amplifier U3, a second diode D2, a third resistor R3 and a third capacitor C3;

[0091] The non-inverting input terminal of the third operational amplifier U3 is connected to the input terminal of the minimum peak detection unit, the inverting input terminal of the third operational amplifier U3 is connected to the anode of the second diode D2, the output terminal of the third operational amplifier U3 is connected to the cathode of the second diode D2, and the anode of the second diode D2 is connected to the output terminal of the minimum peak detection unit;

[0092] A first end of the third resistor R3 is connected to the anode of the second diode D2, and a second end of the third resistor R3 is grounded;

[0093] A cathode of the third capacitor C3 is connected to an anode of the second diode D2, and a cathode of the third capacitor C3 is grounded.

[0094] Specifically, in combination with the above embodiments, the minimum peak detection unit is mainly composed of a third operational amplifier U3, a second diode D2, a third resistor R3 and a third capacitor C3. In practical applications, the minimum peak voltage detection of the output voltage is mainly achieved by charging and discharging the third capacitor C3. The minimum peak voltage is obtained when the third capacitor C3 is charged, and the sampling time interval of the minimum peak voltage can be controlled by utilizing the discharge reset time when the parallel third resistor R3 is discharged.

[0095] For the output voltage after AC coupling, since its minimum peak voltage is a negative voltage, the positive electrode of the third capacitor C3 is grounded; when the voltage at the non-inverting input terminal of the third operational amplifier U3 is less than the voltage at the inverting input terminal, the third operational amplifier U3 outputs a negative voltage, causing the second diode D2 to be turned on, thereby pulling down the negative electrode voltage of the third capacitor C3 and charging the third capacitor C3; when the voltage at the non-inverting input terminal of the third operational amplifier U3 is equal to the voltage at the inverting input terminal, the second diode D2 is turned off, and the charging process stops. At this time, the voltage corresponding to the negative electrode of the third capacitor C3 is the minimum peak voltage of the output voltage.

[0096] It should be noted that the third operational amplifier U3 is powered by a dual power supply (i.e., +V and -V) in actual applications; the function of the second diode D2 is forward conduction and reverse shutdown, so it is necessary to select a diode with a smaller forward conduction voltage to reduce the sampling value error; the third capacitor C3 needs to be charged quickly to maintain the peak voltage data. Since the electrical characteristics of its connection interface are high-impedance, it is necessary to select a capacitor with a smaller capacitance, generally at the level of several hundred pF; the third resistor R3 provides a discharge circuit for the third capacitor C3 to achieve peak data reset, and the value can be set accordingly according to the RC time constant and the sampling and holding required time.

[0097] Combination Figure 3 As shown, as an improvement of the above solution, the minimum peak detection unit further includes a fourth operational amplifier U4 and a fourth resistor R4;

[0098] The non-inverting input terminal of the fourth operational amplifier U4 is connected to the anode of the second diode D2, the inverting input terminal of the fourth operational amplifier U4 is connected to the output terminal of the minimum peak detection unit, and the output terminal of the fourth operational amplifier U4 is connected to the output terminal of the minimum peak detection unit;

[0099] A first end of the fourth resistor R4 is connected to the inverting input end of the third operational amplifier U3 , and a second end of the fourth resistor R4 is connected to the anode of the second diode D2 .

[0100] Specifically, in combination with the above embodiment, the minimum peak detection unit also includes a fourth operational amplifier U4 and a fourth resistor R4; wherein the fourth operational amplifier U4 plays an isolation role, and the fourth resistor R4 is connected in series in the negative feedback loop of the third operational amplifier U3, which can reduce the output bias voltage of the third operational amplifier U3, thereby reducing the sampling deviation, and at the same time can limit the current of the negative feedback loop to protect the circuit.

[0101] It should be noted that the fourth resistor R4 is a negative feedback circuit resistor, and its value is generally preferably 10 kΩ.

[0102] Combination Figure 3 As shown, as an improvement of the above solution, the peak-to-peak value calculation unit includes a fifth operational amplifier U5, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7 and an eighth resistor R8;

[0103] The non-inverting input terminal of the fifth operational amplifier U5 is connected to the first input terminal of the peak-to-peak value operation unit through the fifth resistor R5, the inverting input terminal of the fifth operational amplifier U5 is connected to the second input terminal of the peak-to-peak value operation unit through the sixth resistor R6, and the output terminal of the fifth operational amplifier U5 is connected to the output terminal of the peak-to-peak value operation unit;

[0104] The first end of the seventh resistor R7 is connected to the non-inverting input end of the fifth operational amplifier U5, and the second end of the seventh resistor R7 is connected to the output end of the fifth operational amplifier U5;

[0105] A first end of the eighth resistor R8 is connected to the inverting input end of the fifth operational amplifier U5, and a second end of the eighth resistor R8 is grounded.

[0106] Specifically, in combination with the above embodiments, the peak-to-peak value operation unit is mainly composed of a fifth operational amplifier U5, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7 and an eighth resistor R8, and a subtraction operation structure is correspondingly formed. In practical applications, it is mainly used to perform a subtraction operation on the maximum peak voltage output by the minimum peak detection unit and the minimum peak voltage output by the minimum peak detection unit, and correspondingly obtain the voltage peak-to-peak value of the dynamic response waveform of the output voltage.

[0107] It should be noted that the values ​​of the fifth resistor R5, the sixth resistor R6, the seventh resistor R7 and the eighth resistor R8 are preferably: R5=R7, R6=R8, R5=k1*R6, k1>0, and the k1 times value is used to amplify the sampling voltage and reduce circuit interference.

[0108] Combination Figure 3 As shown, as an improvement of the above solution, the voltage comparison unit includes a sixth operational amplifier U6;

[0109] The inverting input terminal of the sixth operational amplifier U6 is connected to the first input terminal of the voltage comparison unit, the non-inverting input terminal of the sixth operational amplifier U6 is connected to the second input terminal of the voltage comparison unit, and the output terminal of the sixth operational amplifier U6 is connected to the output terminal of the voltage comparison unit.

[0110] Specifically, in combination with the above embodiments, the voltage comparison unit is mainly composed of a sixth operational amplifier U6. In practical applications, a single-limit comparator operational amplifier can be used, which is mainly used to compare the peak-to-peak value of the dynamic response waveform of the output voltage with the preset first reference voltage V1 to determine whether to trigger the standby load module 300 based on the comparison result.

[0111] Combination Figure 2 As shown, in another preferred embodiment, the current detection module 200 includes a current detection unit, a current calculation unit, an effective value detection unit and a current comparison unit;

[0112] The input end of the current detection unit is connected to the input end of the current detection module 200, the input end of the current detection unit is also connected to the first input end of the current operation unit, the first output end of the current detection unit is connected to the second input end of the current operation unit, and the second output end of the current detection unit is grounded;

[0113] The output end of the current calculation unit is connected to the input end of the effective value detection unit, and the output end of the effective value detection unit is connected to the first input end of the current comparison unit;

[0114] The second input terminal of the current comparison unit is used to connect to the second reference voltage V2 , the third input terminal of the current comparison unit is used to connect to the third reference voltage V3 , and the output terminal of the current comparison unit is connected to the output terminal of the current detection module 200 .

[0115] Specifically, in combination with the above embodiments, the current detection module 200 is mainly composed of a current detection unit, a current calculation unit, an effective value detection unit and a current comparison unit. In actual applications, the control circuit detects the output current of the switching power supply through the current detection unit, and performs corresponding calculations on the detected output current of the switching power supply through the current calculation unit to improve the sampling accuracy, and obtains the DC effective value of the output current of the switching power supply according to the output calculation of the current calculation unit through the effective value detection unit, and transmits the DC effective value of the output current to the current comparison unit, and compares it with the preset second reference voltage V2 and the preset third reference voltage V3 to determine whether to trigger the standby load module 300 according to the comparison result.

[0116] For example, the second reference voltage V2 and the third reference voltage V3 represent the value range of the light load switching value of the switching power supply. When the DC effective value of the output current of the switching power supply is less than the second reference voltage V2 and greater than the third reference voltage V3, the current comparison unit outputs a high level, which can trigger the backup load module 300 to function.

[0117] It should be noted that the size of the value interval is not only related to the consistency of the light load value of the switching power supply, but also determined by the hysteresis interval of the load current. When the load of the switching power supply gradually increases, or gradually decreases to the light load switching value, the role of the value interval is to make the circuit load current avoid the light load switching point; when the value interval conditions are met, the current comparison unit outputs a high level, which can trigger the backup load module 300 to function.

[0118] Combination Figure 3 As shown, as an improvement of the above solution, the current detection unit includes a ninth resistor R9;

[0119] A first end of the ninth resistor R9 is connected to the input end of the current detection unit, and a second end of the ninth resistor R9 is connected to the first output end of the current detection unit.

[0120] Preferably, the current detection unit further includes a tenth resistor R10;

[0121] The first end of the tenth resistor R10 is connected to the second end of the ninth resistor R9 , and the second end of the tenth resistor R10 is connected to the second output end of the current detection unit.

[0122] Specifically, in combination with the above embodiment, the current detection unit is mainly composed of a ninth resistor R9 and may also include a tenth resistor R10; wherein the ninth resistor R9 is generally a small precision resistor to improve the accuracy of current sampling, and the tenth resistor R10 is a conventional load.

[0123] Combination Figure 3As shown, as an improvement of the above solution, the current operation unit includes a seventh operational amplifier U7, an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13 and a fourteenth resistor R14;

[0124] The inverting input terminal of the seventh operational amplifier U7 is connected to the first input terminal of the current operation unit through the eleventh resistor R11, the non-inverting input terminal of the seventh operational amplifier U7 is connected to the second input terminal of the current operation unit through the twelfth resistor R12, and the output terminal of the seventh operational amplifier U7 is connected to the output terminal of the current operation unit;

[0125] The first end of the thirteenth resistor R13 is connected to the inverting input end of the seventh operational amplifier U7, and the second end of the thirteenth resistor R13 is connected to the output end of the seventh operational amplifier U7;

[0126] A first end of the fourteenth resistor R14 is connected to the non-inverting input end of the seventh operational amplifier U7, and a second end of the fourteenth resistor R14 is grounded.

[0127] Specifically, in combination with the above embodiments, the current operation unit is mainly composed of a seventh operational amplifier U7, an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13 and a fourteenth resistor R14, and a subtraction operation structure is formed accordingly. In practical applications, it is mainly used to perform a subtraction operation on the voltage across the ninth resistor R9.

[0128] It should be noted that the values ​​of the eleventh resistor R11, the twelfth resistor R12, the thirteenth resistor R13 and the fourteenth resistor R14 are preferably: R11=R13, R12=R14, R11=k2*R12, k2>0, and the k2 times value is used to amplify the sampling voltage and reduce circuit interference.

[0129] Combination Figure 3 As shown, as an improvement of the above solution, the effective value detection unit includes an eighth operational amplifier U8, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, a third diode D3 and a fourth diode D4;

[0130] The inverting input terminal of the eighth operational amplifier U8 is connected to the input terminal of the effective value detection unit through the fifteenth resistor R15, the non-inverting input terminal of the eighth operational amplifier U8 is grounded through the sixteenth resistor R16, the output terminal of the eighth operational amplifier U8 is connected to the cathode of the fourth diode D4, and the anode of the fourth diode D4 is connected to the output terminal of the effective value detection unit;

[0131] A first end of the seventeenth resistor R17 is connected to the inverting input end of the eighth operational amplifier U8, and a second end of the seventeenth resistor R17 is connected to the anode of the fourth diode D4;

[0132] The cathode of the third diode D3 is connected to the inverting input terminal of the eighth operational amplifier U8, and the anode of the third diode D3 is connected to the cathode of the fourth diode D4.

[0133] Preferably, the effective value detection unit further includes a ninth operational amplifier U9, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20 and a fourth capacitor C4;

[0134] The inverting input terminal of the ninth operational amplifier U9 is connected to the anode of the fourth diode D4 through the eighteenth resistor R18, the non-inverting input terminal of the ninth operational amplifier U9 is grounded through the nineteenth resistor R19, and the output terminal of the ninth operational amplifier U9 is connected to the output terminal of the effective value detection unit;

[0135] A first end of the twentieth resistor R20 is connected to the inverting input end of the ninth operational amplifier U9, and a second end of the twentieth resistor R20 is connected to the output end of the ninth operational amplifier U9;

[0136] A first end of the fourth capacitor C4 is connected to a first end of the twentieth resistor R20 , and a second end of the fourth capacitor C4 is connected to a second end of the twentieth resistor R20 .

[0137] Specifically, in combination with the above embodiments, the effective value detection unit is mainly composed of an eighth operational amplifier U8, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, a third diode D3 and a fourth diode D4, and may also include a ninth operational amplifier U9, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20 and a fourth capacitor C4.

[0138] In practical applications, the effective value detection unit is mainly used for effective value calculation; the effective value detection unit can be divided into two parts, one part uses the eighth operational amplifier U8 as the core device to form a precise half-wave rectifier circuit, and the other part uses the ninth operational amplifier U9 as the core device to form an average value calculation circuit (integral operation circuit). In the average value calculation circuit, the average value can be converted into an effective value by setting the ratio of related resistors.

[0139] It can be understood that there is generally a transmission inductor at the output end of the switching power supply. The voltage corresponding to the inductor current sampling is a quasi-triangular periodic wave. The DC pulsating signal can be first obtained through a precise half-wave rectifier circuit, and then a smooth DC waveform can be obtained using an average value calculation circuit. The amplitude of the DC waveform is the average value of the half-wave rectification, and the effective value of the input signal can be obtained through the relationship between the average value and the effective value.

[0140] It should be noted that the third diode D3 and the fourth diode D4 in the effective value detection unit have the function of forward conduction and reverse shutdown, so it is necessary to select a diode with a smaller forward conduction voltage to reduce the sampling value error; the fifteenth resistor R15 and the seventeenth resistor R17 are the gain of the half-wave rectifier circuit, and R15 / R17 constitute the ratio of the output voltage to the input voltage. At the same time, in order to limit the current, the value is generally 10kΩ~100kΩ; the eighteenth resistor R18 and the twentieth resistor R20 are the gain of the average value calculation circuit; the sixteenth resistor R16 and the nineteenth resistor R19 are grounding resistors, and the conventional value is about 10kΩ~100kΩ; the fourth capacitor C4 is the key to the integral operation circuit, and the eighteenth resistor R18 and the fourth capacitor C4 constitute an integral time constant, which is related to the period of the measured waveform.

[0141] Combination Figure 3 As shown, as an improvement of the above solution, the current comparison unit includes a tenth operational amplifier U10 and an eleventh operational amplifier U11;

[0142] The non-inverting input terminal of the tenth operational amplifier U10 is connected to the first input terminal of the current comparison unit, the inverting input terminal of the tenth operational amplifier U10 is connected to the second input terminal of the current comparison unit, and the output terminal of the tenth operational amplifier U10 is connected to the output terminal of the current comparison unit;

[0143] The inverting input terminal of the eleventh operational amplifier U11 is connected to the first input terminal of the current comparison unit, the non-inverting input terminal of the eleventh operational amplifier U11 is connected to the third input terminal of the current comparison unit, and the output terminal of the eleventh operational amplifier U11 is connected to the output terminal of the current comparison unit.

[0144] Specifically, in combination with the above embodiments, the current comparison unit is mainly composed of a tenth operational amplifier U10 and an eleventh operational amplifier U11. In practical applications, the tenth operational amplifier U10 and the eleventh operational amplifier U11 can adopt window comparator operational amplifiers, which are mainly used to compare the effective value of the voltage output by the effective value detection unit with a preset second reference voltage V2 and a preset third reference voltage V3, so as to determine whether to trigger the standby load module 300 according to the comparison result.

[0145] Combination Figure 3 As shown, in another preferred embodiment, the standby load module 300 includes a twenty-first resistor R21, a first switch tube Q1, a second switch tube Q2 and a third switch tube Q3;

[0146] A first end of the twenty-first resistor R21 is connected to the first input end of the standby load module 300 , and a second end of the twenty-first resistor R21 is connected to the input end of the first switch tube Q1 ;

[0147] The control end of the first switch tube Q1 is connected to the second end of the twenty-first resistor R21, and the output end of the first switch tube Q1 is connected to the output end of the standby load module 300;

[0148] The control end of the second switch tube Q2 is connected to the second end of the twenty-first resistor R21, and the output end of the second switch tube Q2 is connected to the output end of the standby load module 300;

[0149] The input end of the third switch tube Q3 is connected to the second input end of the standby load module 300 , the control end of the third switch tube Q3 is connected to the control end of the standby load module 300 , and the output end of the third switch tube Q3 is connected to the input end of the second switch tube Q2 .

[0150] Specifically, in combination with the above embodiments, the standby load module 300 is mainly composed of a twenty-first resistor R21, a first switch tube Q1, a second switch tube Q2 and a third switch tube Q3, and is essentially a complete constant current source circuit, wherein the first switch tube Q1 and the second switch tube Q2 are in an amplified state, and only the third switch tube Q3 is in a controlled switch state to serve as a control switch of the standby load module 300. The power supply Vcc provides base current for the first switch tube Q1 and the second switch tube Q2 and turns on the first switch tube Q1 and the second switch tube Q2. The current flowing through the twenty-first resistor R21 is determined by the power supply Vcc and the tube voltage drop of the first switch tube Q1. Since the circuit structure of the standby load module 300 is a mirror structure, the current flowing through the third switch tube Q3 is the same as the current flowing through the twenty-first resistor R21, thereby forming a current source effect, and the twenty-first resistor R21 also has a certain temperature compensation effect.

[0151] It should be noted that Figure 3 The circuit shown is shown by taking the example that the first switch tube Q1, the second switch tube Q2 and the third switch tube Q3 all adopt NPN-type triodes. Those skilled in the art can understand that the first switch tube Q1, the second switch tube Q2 and the third switch tube Q3 can also adopt other types of switching devices, and the embodiment of the present invention does not make specific limitations.

[0152] See also Figure 4FIG. 1 is an application circuit diagram of a light-load mode switching control circuit of a switching power supply provided by the present invention. Figure 4 The outputs L0, C0, Cf, r1 and r2 in the control circuit are all common peripheral circuit components of the switching power supply, L0 is the output inductor, C0 is the output capacitor, r1 and r2 are the output voltage voltage-dividing sampling resistors, and Cf is the sampling feedforward capacitor for adjusting the loop stability; the control circuit is connected to the output end of the switching power supply. In combination with the above embodiments, it can be seen that the control circuit obtains the dynamic response waveform of the output voltage of the switching power supply through the first capacitor C1 AC coupling, obtains the maximum peak voltage of the output voltage according to the dynamic response waveform of the output voltage through the maximum peak detection unit, obtains the minimum peak voltage of the output voltage according to the dynamic response waveform of the output voltage through the minimum peak detection unit, and obtains the output voltage according to the maximum peak voltage and the minimum peak voltage through the peak-to-peak value calculation unit. The peak-to-peak value of the voltage of the dynamic response waveform of the voltage is transmitted to the voltage comparison unit, and compared with the preset first reference voltage V1, and a first comparison result is obtained accordingly; at the same time, the control circuit detects the output current of the switching power supply through the current detection unit, and calculates the detected output current of the switching power supply through the current calculation unit, and obtains the DC effective value of the output current of the switching power supply according to the output of the current calculation unit through the effective value detection unit, and transmits the DC effective value of the output current to the current comparison unit, and compares it with the preset second reference voltage V2 and the preset third reference voltage V3, and a second comparison result is obtained accordingly; according to the obtained first comparison result and the second comparison result, it is determined whether to trigger the standby load module 300.

[0153] For example, the first reference voltage V1 represents the threshold value of the dynamic response peak-to-peak value of the output voltage of the switching power supply. When the voltage peak-to-peak value of the dynamic response waveform of the output voltage of the switching power supply is greater than the first reference voltage V1, the voltage comparison unit outputs a high level; the second reference voltage V2 and the third reference voltage V3 represent the value range of the light load switching value of the switching power supply. When the DC effective value of the output current of the switching power supply is less than the second reference voltage V2 and greater than the third reference voltage V3, the current comparison unit outputs a high level; when the voltage comparison unit outputs a high level and the current comparison unit outputs a high level, it is confirmed that the backup load module 300 is triggered to function.

[0154] Assume that after both trigger conditions are met, the current source (i.e., the standby load module 300) works, and the switching power supply leaves the light-load high-efficiency mode. At this time, the dynamic response deterioration caused by the mode switching disappears; when the actual load value (i.e., the DC effective value of the output current of the switching power supply) increases to the second reference voltage V2, the window comparator outputs a low level, the current source disconnects the main power circuit, and the switching power supply enters the normal PWM mode; when the actual load value decreases to the third reference voltage V3, the window comparator outputs a low level, and the switching power supply enters the normal FCOT / PSM mode.

[0155] In summary, a light load mode switching control circuit of a switching power supply provided in an embodiment of the present invention changes the circuit load by monitoring the operating condition of the switching power supply, and designs a light load and high-efficiency mode switching circuit. When the switching power supply leaves or enters the light load mode, the circuit can be separated from the unstable switching state by adding a backup load and setting a trigger circuit, thereby improving the stability of the mode switching, thereby ensuring the output voltage quality of the switching power supply and improving the stability of the power load.

[0156] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A light load mode switching control circuit of a switching power supply, characterized in that: It includes a voltage detection module, a current detection module and a standby load module; The input end of the voltage detection module is used to connect to the output end of the switching power supply, and the output end of the voltage detection module is connected to the control end of the standby load module; The input end of the current detection module is used to connect to the output end of the switching power supply, and the output end of the current detection module is connected to the control end of the standby load module; The first input end of the standby load module is used to connect to the power supply, the second input end of the standby load module is used to connect to the output end of the switching power supply, and the output end of the standby load module is grounded; The voltage detection module is used to detect the output voltage of the switching power supply, and the current detection module is used to detect the output current of the switching power supply. When it is determined according to the output result of the voltage detection module that the dynamic response peak-to-peak value of the output voltage is greater than the first reference voltage, and when it is determined according to the output result of the current detection module that the DC effective value of the output current is between the second reference voltage and the third reference voltage, the backup load module is triggered to function; wherein the second reference voltage and the third reference voltage represent the value range of the light load switching value of the switching power supply.

2. The light load mode switching control circuit of the switching power supply according to claim 1, characterized in that: The voltage detection module includes a first capacitor, a maximum peak detection unit, a minimum peak detection unit, a peak-to-peak value calculation unit and a voltage comparison unit; The first end of the first capacitor is connected to the input end of the voltage detection module, the second end of the first capacitor is connected to the input end of the maximum peak detection unit, and the output end of the maximum peak detection unit is connected to the first input end of the peak-to-peak value calculation unit; The input end of the minimum peak detection unit is connected to the second end of the first capacitor, the output end of the minimum peak detection unit is connected to the second input end of the peak-to-peak value calculation unit, and the output end of the peak-to-peak value calculation unit is connected to the first input end of the voltage comparison unit; The second input terminal of the voltage comparison unit is used to connect to a first reference voltage, and the output terminal of the voltage comparison unit is connected to the output terminal of the voltage detection module.

3. The light load mode switching control circuit of the switching power supply according to claim 2, characterized in that: The maximum peak detection unit includes a first operational amplifier, a first diode, a first resistor and a second capacitor; The non-inverting input terminal of the first operational amplifier is connected to the input terminal of the maximum peak detection unit, the inverting input terminal of the first operational amplifier is connected to the cathode of the first diode, the output terminal of the first operational amplifier is connected to the anode of the first diode, and the cathode of the first diode is connected to the output terminal of the maximum peak detection unit; A first end of the first resistor is connected to the cathode of the first diode, and a second end of the first resistor is grounded; The positive electrode of the second capacitor is connected to the cathode of the first diode, and the negative electrode of the second capacitor is grounded.

4. The light load mode switching control circuit of the switching power supply according to claim 3, characterized in that: The maximum peak detection unit also includes a second operational amplifier and a second resistor; The non-inverting input terminal of the second operational amplifier is connected to the cathode of the first diode, the inverting input terminal of the second operational amplifier is connected to the output terminal of the maximum peak detection unit, and the output terminal of the second operational amplifier is connected to the output terminal of the maximum peak detection unit; A first end of the second resistor is connected to an inverting input end of the first operational amplifier, and a second end of the second resistor is connected to a cathode of the first diode.

5. The light load mode switching control circuit of the switching power supply according to claim 2, characterized in that: The minimum peak detection unit includes a third operational amplifier, a second diode, a third resistor and a third capacitor; The non-inverting input terminal of the third operational amplifier is connected to the input terminal of the minimum peak detection unit, the inverting input terminal of the third operational amplifier is connected to the anode of the second diode, the output terminal of the third operational amplifier is connected to the cathode of the second diode, and the anode of the second diode is connected to the output terminal of the minimum peak detection unit; A first end of the third resistor is connected to the anode of the second diode, and a second end of the third resistor is grounded; A cathode of the third capacitor is connected to an anode of the second diode, and a cathode of the third capacitor is grounded.

6. The light load mode switching control circuit of the switching power supply according to claim 5, characterized in that: The minimum peak detection unit also includes a fourth operational amplifier and a fourth resistor; The non-inverting input terminal of the fourth operational amplifier is connected to the anode of the second diode, the inverting input terminal of the fourth operational amplifier is connected to the output terminal of the minimum peak detection unit, and the output terminal of the fourth operational amplifier is connected to the output terminal of the minimum peak detection unit; A first end of the fourth resistor is connected to an inverting input end of the third operational amplifier, and a second end of the fourth resistor is connected to an anode of the second diode.

7. The light load mode switching control circuit of the switching power supply according to claim 2, characterized in that: The peak-to-peak value calculation unit includes a fifth operational amplifier, a fifth resistor, a sixth resistor, a seventh resistor and an eighth resistor; The non-inverting input terminal of the fifth operational amplifier is connected to the first input terminal of the peak-to-peak value operation unit through the fifth resistor, the inverting input terminal of the fifth operational amplifier is connected to the second input terminal of the peak-to-peak value operation unit through the sixth resistor, and the output terminal of the fifth operational amplifier is connected to the output terminal of the peak-to-peak value operation unit; A first end of the seventh resistor is connected to the non-inverting input end of the fifth operational amplifier, and a second end of the seventh resistor is connected to the output end of the fifth operational amplifier; A first end of the eighth resistor is connected to the inverting input end of the fifth operational amplifier, and a second end of the eighth resistor is grounded.

8. The light load mode switching control circuit of the switching power supply according to claim 2, characterized in that: The voltage comparison unit includes a sixth operational amplifier; The inverting input terminal of the sixth operational amplifier is connected to the first input terminal of the voltage comparison unit, the non-inverting input terminal of the sixth operational amplifier is connected to the second input terminal of the voltage comparison unit, and the output terminal of the sixth operational amplifier is connected to the output terminal of the voltage comparison unit.

9. The light load mode switching control circuit of the switching power supply according to claim 1, characterized in that: The current detection module includes a current detection unit, a current calculation unit, an effective value detection unit and a current comparison unit; The input end of the current detection unit is connected to the input end of the current detection module, the input end of the current detection unit is also connected to the first input end of the current operation unit, the first output end of the current detection unit is connected to the second input end of the current operation unit, and the second output end of the current detection unit is grounded; The output end of the current calculation unit is connected to the input end of the effective value detection unit, and the output end of the effective value detection unit is connected to the first input end of the current comparison unit; The second input terminal of the current comparison unit is used to connect to a second reference voltage, the third input terminal of the current comparison unit is used to connect to a third reference voltage, and the output terminal of the current comparison unit is connected to the output terminal of the current detection module.

10. The light load mode switching control circuit of the switching power supply according to claim 9, characterized in that: The current detection unit includes a ninth resistor; A first end of the ninth resistor is connected to the input end of the current detection unit, and a second end of the ninth resistor is connected to the first output end of the current detection unit.

11. The light load mode switching control circuit of the switching power supply according to claim 10, characterized in that: The current detection unit also includes a tenth resistor; The first end of the tenth resistor is connected to the second end of the ninth resistor, and the second end of the tenth resistor is connected to the second output end of the current detection unit.

12. The light load mode switching control circuit of the switching power supply according to claim 9, characterized in that: The current operation unit includes a seventh operational amplifier, an eleventh resistor, a twelfth resistor, a thirteenth resistor and a fourteenth resistor; The inverting input terminal of the seventh operational amplifier is connected to the first input terminal of the current operation unit through the eleventh resistor, the non-inverting input terminal of the seventh operational amplifier is connected to the second input terminal of the current operation unit through the twelfth resistor, and the output terminal of the seventh operational amplifier is connected to the output terminal of the current operation unit; A first end of the thirteenth resistor is connected to the inverting input end of the seventh operational amplifier, and a second end of the thirteenth resistor is connected to the output end of the seventh operational amplifier; A first end of the fourteenth resistor is connected to the non-inverting input terminal of the seventh operational amplifier, and a second end of the fourteenth resistor is grounded.

13. The light load mode switching control circuit of the switching power supply according to claim 9, characterized in that: The effective value detection unit includes an eighth operational amplifier, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, a third diode and a fourth diode; The inverting input terminal of the eighth operational amplifier is connected to the input terminal of the effective value detection unit through the fifteenth resistor, the non-inverting input terminal of the eighth operational amplifier is grounded through the sixteenth resistor, the output terminal of the eighth operational amplifier is connected to the cathode of the fourth diode, and the anode of the fourth diode is connected to the output terminal of the effective value detection unit; A first end of the seventeenth resistor is connected to the inverting input end of the eighth operational amplifier, and a second end of the seventeenth resistor is connected to the anode of the fourth diode; The cathode of the third diode is connected to the inverting input terminal of the eighth operational amplifier, and the anode of the third diode is connected to the cathode of the fourth diode.

14. The light load mode switching control circuit of the switching power supply according to claim 13, characterized in that: The effective value detection unit also includes a ninth operational amplifier, an eighteenth resistor, a nineteenth resistor, a twentieth resistor and a fourth capacitor; The inverting input terminal of the ninth operational amplifier is connected to the anode of the fourth diode through the eighteenth resistor, the non-inverting input terminal of the ninth operational amplifier is grounded through the nineteenth resistor, and the output terminal of the ninth operational amplifier is connected to the output terminal of the effective value detection unit; A first end of the 20th resistor is connected to the inverting input end of the ninth operational amplifier, and a second end of the 20th resistor is connected to the output end of the ninth operational amplifier; A first end of the fourth capacitor is connected to a first end of the twentieth resistor, and a second end of the fourth capacitor is connected to a second end of the twentieth resistor.

15. The light load mode switching control circuit of the switching power supply according to claim 9, characterized in that: The current comparison unit includes a tenth operational amplifier and an eleventh operational amplifier; The non-inverting input terminal of the tenth operational amplifier is connected to the first input terminal of the current comparison unit, the inverting input terminal of the tenth operational amplifier is connected to the second input terminal of the current comparison unit, and the output terminal of the tenth operational amplifier is connected to the output terminal of the current comparison unit; The inverting input terminal of the eleventh operational amplifier is connected to the first input terminal of the current comparison unit, the non-inverting input terminal of the eleventh operational amplifier is connected to the third input terminal of the current comparison unit, and the output terminal of the eleventh operational amplifier is connected to the output terminal of the current comparison unit.

16. The light load mode switching control circuit of the switching power supply according to any one of claims 1 to 15, characterized in that: The standby load module includes a twenty-first resistor, a first switch tube, a second switch tube and a third switch tube; A first end of the twenty-first resistor is connected to the first input end of the standby load module, and a second end of the twenty-first resistor is connected to the input end of the first switch tube; The control end of the first switch tube is connected to the second end of the twenty-first resistor, and the output end of the first switch tube is connected to the output end of the standby load module; The control end of the second switch tube is connected to the second end of the twenty-first resistor, and the output end of the second switch tube is connected to the output end of the standby load module; The input end of the third switch tube is connected to the second input end of the standby load module, the control end of the third switch tube is connected to the control end of the standby load module, and the output end of the third switch tube is connected to the input end of the second switch tube.

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