CN113866662B - Switch power supply output current detection circuit and switch power supply - Google Patents

Switch power supply output current detection circuit and switch power supply Download PDF

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Publication number
CN113866662B
CN113866662B CN202111129819.4A CN202111129819A CN113866662B CN 113866662 B CN113866662 B CN 113866662B CN 202111129819 A CN202111129819 A CN 202111129819A CN 113866662 B CN113866662 B CN 113866662B
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resistor
power supply
module
sampling
voltage
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CN113866662A (en
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杜勐
黎治民
张宏
宋彦超
陈宏源
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Shijiazhuang Tonghe Electronics Co Ltd
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Shijiazhuang Tonghe Electronics Co Ltd
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/40Testing power supplies

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  • General Physics & Mathematics (AREA)
  • Measurement Of Current Or Voltage (AREA)

Abstract

The invention provides a switching power supply output current detection circuit and a switching power supply. The switching power supply output current detection circuit includes: a sampling current differential amplifying module and a sampling voltage translation module; the sampling current differential amplifying module is connected with the voltage output end of the target switching power supply, the second input end of the sampling current differential amplifying module is connected with the input end of the load of the target switching power supply, the first output end of the sampling current differential amplifying module is connected with the first end of the sampling voltage translation module, and the second output end of the sampling current differential amplifying module is connected with the second end of the sampling voltage translation module; and the third end of the sampling voltage translation module is used for outputting a small-voltage sampling signal. The invention has the advantages of clear and concise circuit structure, low complexity and easy realization while reducing the cost without adopting a high-voltage current sampling operational amplifier.

Description

Switch power supply output current detection circuit and switch power supply
Technical Field
The present invention relates to the field of detection circuits, and in particular, to a switching power supply output current detection circuit and a switching power supply.
Background
The switching power supply is a power supply which uses the modern power electronic technology to control the time ratio of switching on and switching off of a switching tube and maintain stable output voltage, is widely applied to almost all electronic equipment with the characteristics of small size, light weight and high efficiency along with the development and innovation of the power electronic technology, and is an indispensable power supply mode for the rapid development of the electronic information industry at present.
The switching power supply basically comprises a main circuit, a control circuit, a detection circuit and an auxiliary power supply, wherein the detection circuit can provide various parameters and various instrument data in operation in the protection circuit. In a switching power supply outputting a negative voltage, an output current detection circuit generally uses a precision resistor string in a ground circuit to obtain a sampling voltage reflecting current variation, and since the sampling voltage is generally a small negative voltage, a required voltage is obtained by an inverting amplification circuit.
If the output negative voltage of the switching power supply is low, the differential operational amplifier can be directly used for sampling the output current. However, if the output negative voltage of the switching power supply is high, and the switching power supply is commonly grounded and multiplexing output, the sampling resistor string cannot sample current in the ground line loop, and the sampling resistor string usually needs to select a high-voltage current sampling operational amplifier in the negative voltage output loop, so that the cost of the high-voltage current sampling operational amplifier is high, and if the high-voltage current sampling operational amplifier is not adopted, the structure of the output current detection circuit is complex.
Disclosure of Invention
The embodiment of the invention provides a switching power supply output current detection circuit and a switching power supply, which are used for solving the problems of high cost and complex structure of the switching power supply output current detection circuit when the switching power supply is in common-ground multi-path output.
In a first aspect, an embodiment of the present invention provides a switching power supply output current detection circuit, including: a sampling current differential amplifying module and a sampling voltage translation module;
The sampling current differential amplifying module is characterized in that a first input end is connected with a voltage output end of a target switching power supply, a second input end is connected with an input end of a load of the target switching power supply, a first output end is connected with a first end of the sampling voltage translation module, and a second output end is connected with a second end of the sampling voltage translation module;
And the third end of the sampling voltage translation module is used for outputting a small-voltage sampling signal.
In one possible implementation, the sampling voltage translation module further includes a fourth terminal connected to the voltage output terminal of the target switching power supply.
In one possible implementation, the sampling voltage translation module includes: triode N1, resistor R3 and resistor R7;
The base electrode of the triode N1 is used as the first end of the sampling voltage translation module, the emitter electrode of the triode N1 is used as the second end of the sampling voltage translation module, the emitter electrode of the triode N1 is connected with the first end of the resistor R7, and the collector electrode of the triode N1 is connected with the first end of the resistor R3;
The second end of the resistor R7 is used as a third end of the sampling voltage translation module;
The second end of the resistor R3 is used as the fourth end of the sampling voltage translation module.
In one possible implementation, the sampling voltage translation module further includes: a resistor R8 and a capacitor C4;
the first end of the resistor R8 is respectively connected with the second end of the resistor R3 and the first end of the capacitor C4, and the second end is used for being connected with a preset voltage source;
The second end of the capacitor C4 is grounded.
In one possible implementation manner, the sampling current differential amplification module includes a resistor R1, a resistor R4, a resistor R6, a resistor R9 and a differential operational amplifier U2;
the first end of the resistor R1 is used as a first input end of the sampling current differential amplification module and is connected with the first end of the resistor R6 and a negative power supply end of the differential operational amplifier U2, and the second end of the resistor R1 is used as a second input end of the sampling current differential amplification module and is connected with the first end of the resistor R4;
the second end of the resistor R4 is connected with the non-inverting input end of the differential operational amplifier U2;
The second end of the resistor R6 is respectively connected with the inverting input end of the differential operational amplifier U2 and the first end of the resistor R9;
The positive power end of the differential operational amplifier U2 is used for inputting a preset power supply, and the output end of the differential operational amplifier U2 is used as a first output end of the sampling current differential amplification module;
and the second end of the resistor R9 is used as a second output end of the sampling current differential amplification module.
In one possible implementation manner, the switching power supply output current detection circuit further includes: a voltage stabilizing module;
The first input end of the voltage stabilizing module is connected with the voltage output end of the target switching power supply, the second input end of the voltage stabilizing module is grounded, the first output end of the voltage stabilizing module is connected with the positive power end of the differential operational amplifier U2, and the second output end of the voltage stabilizing module is connected between the second end of the resistor R4 and the non-inverting input end of the differential operational amplifier U2.
In one possible implementation manner, the voltage stabilizing module includes a resistor R2, a resistor R5, a capacitor C3 and a voltage stabilizing tube U1;
the first end of the resistor R2 is used as a second output end of the voltage stabilizing module, and the second end is respectively connected with the first end of the resistor R5, the first end of the capacitor C3 and the negative electrode of the voltage stabilizing tube U1 and then used as a first output end of the voltage stabilizing module;
the second end of the resistor R5 is used as a second input end of the voltage stabilizing module;
and the second end of the capacitor C3 is connected with the positive electrode of the voltage stabilizing tube U1 and then used as a first input end of the voltage stabilizing module.
In one possible implementation manner, the switching power supply output current detection circuit further comprises an output filtering module;
And the first end of the output filter module is connected with the voltage output end of the target switching power supply, the second end of the output filter module is connected with the second input end of the sampling current differential amplification module, and the third end of the output filter module is grounded.
In one possible implementation, the output filter module includes a capacitor C1, a capacitor C2, and an inductance L6;
the first end of the capacitor C1 is connected with the first end of the inductor L6 and then used as the first end of the output filter module, and the second end of the capacitor C2 is connected with the second end of the capacitor C2 and then used as the third end of the output filter module;
and the first end of the capacitor C2 is connected with the second end of the inductor L6 and then is used as the second end of the output filter module.
In a second aspect, an embodiment of the present invention provides a switching power supply, including: the switching power supply output current detection circuit as described in the first aspect or any one of the possible implementation manners of the first aspect.
The embodiment of the invention provides a switching power supply output current detection circuit and a switching power supply, wherein a first input end of a sampling current differential amplification module in the switching power supply output current detection circuit is connected with a voltage output end of a target switching power supply, a second input end of the sampling current differential amplification module is connected with an input end of a load of the target switching power supply, a first output end of a sampling voltage translation module is connected with a first end of the sampling voltage translation module, and a second output end of the sampling voltage translation module is connected with a second end of the sampling voltage translation module; the third end of the sampling voltage translation module outputs a small voltage sampling signal. The sampling current differential amplification module string formed by the common differential operational amplifier and the sampling resistor can be used for sampling and differential amplifying the sampling voltage in the output loop of the target switching power supply, and then the sampling voltage after differential amplifying is subjected to voltage translation by the sampling voltage translation module, so that a small-voltage sampling signal convenient to process is obtained. The high-voltage current sampling operational amplifier is not needed, the cost is reduced, the circuit structure is clear and concise, the complexity is low, and the implementation is easy.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a switching power supply output current detection circuit according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a switching power supply output current detection circuit according to another embodiment of the present invention.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth such as the particular system architecture, techniques, etc., in order to provide a thorough understanding of the embodiments of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the following description will be made by way of specific embodiments with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of a switching power supply output current detection circuit according to an embodiment of the present invention. As shown in fig. 1, the switching power supply output current detection circuit includes: a sample current differential amplification module 100 and a sample voltage translation module 200.
The sampling current differential amplifying module 100 is connected with a voltage output end of the target switching power supply, a second input end of the sampling current differential amplifying module 100 is connected with an input end of a load of the target switching power supply, a first output end of the sampling current differential amplifying module is connected with a first end of the sampling voltage translation module 200, and a second output end of the sampling current differential amplifying module is connected with a second end of the sampling voltage translation module 200; the third terminal of the sampling voltage translation module 200 is used for outputting a small voltage sampling signal.
Optionally, the sampling voltage translation module 200 further includes a fourth terminal, and the fourth terminal is connected to the voltage output terminal of the target switching power supply.
The output current detection circuit of the target switching power supply generally needs to sample a low-voltage sampling signal to correspondingly reflect the output current change condition of the target switching power supply, and the low-voltage sampling signal is input to a subsequent current acquisition and current limiting control unit so as to protect and control the power part of the target switching power supply. For the case that the output negative voltage is higher and the switching power supply is commonly grounded multi-output, the sampling signal output by the common differential operational amplifier is a high-voltage signal relative to the common ground GND, so that the subsequent processing is inconvenient. In some cases, a path of positive and negative power supplies are required to be independently generated to supply power for the differential operational amplifier, so that the power consumption is increased, and the circuit is more complex.
According to the switching power supply output current detection circuit, a first input end of a sampling current differential amplification module in the switching power supply output current detection circuit is connected with a voltage output end of a target switching power supply, a second input end of the sampling current differential amplification module is connected with an input end of a load of the target switching power supply, a first output end of the sampling voltage translation module is connected with a first end of the sampling voltage translation module, and a second output end of the sampling voltage translation module is connected with a second end of the sampling voltage translation module; the third end of the sampling voltage translation module outputs a small voltage sampling signal. The sampling current differential amplification module string formed by the common differential operational amplifier and the sampling resistor can be used for sampling and differential amplifying the sampling voltage in the output loop of the target switching power supply, and then the sampling voltage after differential amplifying is subjected to voltage translation by the sampling voltage translation module, so that a small-voltage sampling signal convenient to process is obtained. The high-voltage current sampling operational amplifier is not needed, the cost is reduced, the circuit structure is clear and concise, the complexity is low, and the implementation is easy.
Optionally, referring to fig. 2, the sampling voltage translation module 200 includes: transistor N1, resistor R3 and resistor R7.
The base electrode of the triode N1 is used as a first end of the sampling voltage translation module 200, the emitter electrode of the triode N1 is used as a second end of the sampling voltage translation module 200, the emitter electrode of the triode N1 is connected with a first end of the resistor R7, and the collector electrode of the triode N1 is connected with a first end of the resistor R3. Resistor R7, the second terminal, acts as the third terminal of the sample voltage translation module 200. Resistor R3, the second terminal, serves as the fourth terminal of sample voltage translation module 200.
Optionally, the sampling voltage translation module 200 further includes: resistor R8 and capacitor C4.
The first end of the resistor R8 is connected with the second end of the resistor R3 and the first end of the capacitor C4 respectively, and the second end is used for being connected with a preset voltage source. Capacitor C4, the second terminal is grounded.
In this embodiment, the sampling voltage translation module couples the output of the sampling current differential amplification module to the base of a small signal triode N1 (a low threshold voltage Vth, which is required to ensure that the triode is in a variable resistor area during operation), the triode N1 pulls down a resistor R7 to access a reference ground-CS, and pulls up a resistor R3 to output a small voltage sampling signal ICY relative to GND, thereby realizing sampling voltage translation. The output small voltage sample signal ICY is transmitted to a subsequent current collection and current limit control unit (i.e., a circuit part including a resistor R8 and a capacitor C4) for further processing.
As shown in fig. 2, in this embodiment, the resistor R8 is connected to a 3.3V preset voltage source to process the small voltage sampling signal ICY output by the sampling voltage translation module, so that the circuit structure is clear and concise, easy to operate, and good in practicality.
Optionally, the sampling current differential amplifying module 100 includes a resistor R1, a resistor R4, a resistor R6, a resistor R9, and a differential operational amplifier U2.
The first end of the resistor R1 is used as a first input end of the sampling current differential amplifying module 100 and is connected with the first end of the resistor R6 and a negative power supply end of the differential operational amplifier U2, and the second end of the resistor R1 is used as a second input end of the sampling current differential amplifying module 100 and is connected with the first end of the resistor R4. And the second end of the resistor R4 is connected with the non-inverting input end of the differential operational amplifier U2. The second end of the resistor R6 is respectively connected with the inverting input end of the differential operational amplifier U2 and the first end of the resistor R9. The differential operational amplifier U2, the positive power end is used for inputting the preset power, the output end is regarded as the first output end of the differential amplification module 100 of the sampling current; resistor R9, the second terminal, is used as the second output terminal of the sample current differential amplification module 100.
In this embodiment, the resistor R1 is used as a sampling resistor string on the output negative voltage loop of the target switching power supply, and the voltage signal of the sampling resistor R1 is transmitted to the differential operational amplifier U2 of the reference ground-CS for differential amplification.
Optionally, referring to fig. 2, the switching power supply output current detection circuit further includes a voltage stabilizing module 300.
The voltage stabilizing module 300 has a first input end connected to the voltage output end of the target switching power supply, a second input end grounded, a first output end connected to the positive power end of the differential operational amplifier U2, and a second output end connected between the second end of the resistor R4 and the non-inverting input end of the differential operational amplifier U2.
Optionally, the voltage stabilizing module 300 includes a resistor R2, a resistor R5, a capacitor C3, and a voltage stabilizing tube U1.
The first end of the resistor R2 is used as the second output end of the voltage stabilizing module 300, and the second end is connected with the first end of the resistor R5, the first end of the capacitor C3 and the negative electrode of the voltage stabilizing tube U1 respectively to be used as the first output end of the voltage stabilizing module 300. Resistor R5, the second terminal, is used as the second input terminal of voltage regulator module 300. The second end of the capacitor C3 is connected to the positive electrode of the voltage regulator U1 and then used as the first input end of the voltage regulator module 300.
In this embodiment, the first input end of the voltage stabilizing module is connected to the voltage output end-CS of the target switching power supply, the second input end is grounded to GND, the first output end is connected to the positive power end of the differential operational amplifier U2, and the second output end is connected between the second end of the resistor R4 and the non-inverting input end of the differential operational amplifier U2. The voltage stabilizing module divides the voltage between the voltage output end-CS of the target switching power supply and the ground GND through the resistor R2 and the resistor R5, a preset power supply is input to the positive power supply end of the differential operational amplifier U2, the power supply of the differential operational amplifier U2 is directly taken from the output voltage of the target switching power supply, and the power supply can be synchronously powered on and off along with the sampled target switching power supply, so that the problems of error sampling and high power consumption are avoided. The power supply voltage series resistor is connected to the positive phase input end of the operational amplifier and used as the bias voltage of the positive phase end of the operational amplifier.
For example, the voltage may be divided by the resistor R2 and the resistor R5, and the reference voltage ref_5v of 5V may be input to the positive power terminal of the differential operational amplifier U2. The voltage input by the positive power supply end of the differential operational amplifier U2 can be determined by adjusting the resistance values of the resistor R2 and the resistor R5 according to the output voltage of the target switching power supply and the working voltage of the differential operational amplifier U2. The embodiment of the present invention is not limited thereto.
Optionally, referring to fig. 2, the switching power supply output current detection circuit further includes an output filtering module 400.
The first end of the output filter module 400 is connected to the voltage output end of the target switching power supply, the second end of the output filter module is connected to the second input end of the sampling current differential amplifying module 100, and the third end of the output filter module is grounded.
Optionally, the output filter module includes a capacitor C1, a capacitor C2, and an inductor L6;
The first end of the capacitor C1 is connected to the first end of the inductor L6 and then serves as the first end of the output filter module 400, and the second end of the capacitor C2 is connected to the second end of the capacitor C2 and then serves as the third end of the output filter module 400. The first end of the capacitor C2 is connected to the second end of the inductor L6 and then used as the second end of the output filter module 400.
According to a specific target switching power supply, an output filter module may be provided, and the sampling resistor R1 may be provided at a later stage of the output filter module.
The principle of this embodiment will be described with reference to fig. 2, and the following can be obtained according to the circuit shown in fig. 2:
The above can be simplified as:
V+CS=A1+B1*IO
Wherein I O is the output current of the target switching power supply, V REF_5V is the reference voltage of 5V, R 1、R2、R4 is the resistance corresponding to the resistor R1, the resistor R2, and the resistor R4, V +CS、V-CS is the voltage marked in fig. 2, and a 1、B1 is the coefficient obtained by simplifying the operation.
The voltage at the non-inverting input of the differential operational amplifier U2 is thus obtained:
The above can be simplified as:
U+=A2+B2*V+CS
The inverting input voltage of differential operational amplifier U2: u -=U+;
Where U +、U- is the voltage indicated in fig. 2, and a 2、B2 is the coefficient obtained by the simplified operation.
The output of the differential operational amplifier U2 is a small signal triode N1 which is used as an emitter follower to bear larger voltage drop during voltage translation.
Emitter output voltage of small signal triode: The simplified process is as follows: v O_U2=A3+B3*U-.
Wherein R 6、R9 is the resistance corresponding to the resistor R6 and the resistor R9, and A 3、B3 is the coefficient obtained by simplifying the operation.
For ease of calculation, assuming R9+R6 > R7, the current through resistor R7 is approximately equal to the current through resistor R8. The voltage at ICY can be found:
The above can be simplified as:
VICY=A4+B4*VO_U2
Wherein R 7、R8 is the resistance value corresponding to the resistor R7 and the resistor R8, V +3.3VS is 3.3V power supply relative to GND, and A 4、B4 is the coefficient obtained by simplifying the operation.
To integrate the above simplified expression, V ICY=A5+B5*IO,A5、B5 is the coefficient obtained by the simplified operation. The output current signal I O of the target switching power supply can be linearly transferred with the small voltage sampling signal V ICY.
In the above embodiments, the capacitance and resistance values of the respective capacitor resistors may be different according to different actual target switching power supplies, and in particular, the embodiment of the present invention is not limited to this.
In the embodiment, the switching power supply output current detection circuit is formed by a general differential operational amplifier, a small-signal triode, a voltage stabilizing diode, a corresponding resistor and capacitor and the like, so that the required components are few, the size is small, the cost is low, the circuit structure is clear and concise, the operation is easy, and the practicability is good. The output current detection circuit of the switching power supply can synchronously power on and off along with the sampled target switching power supply, so that the problems of error sampling and high power consumption are solved, the level transfer of a sampling current signal is realized, and the output small-voltage sampling signal is convenient for subsequent processing.
As a further embodiment of the present invention, the present invention further includes a switching power supply including the switching power supply output current detection circuit according to any one of the above embodiments, and has the same beneficial effects as the switching power supply output current detection circuit according to any one of the above embodiments.
In the foregoing embodiments, the descriptions of the embodiments are emphasized, and in part, not described or illustrated in any particular embodiment, reference is made to the related descriptions of other embodiments.
The above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention, and are intended to be included in the scope of the present invention.

Claims (8)

1. The utility model provides a switching power supply output current detection circuitry which is characterized in that is applied to the switching power supply that output negative voltage is higher, and has the multiplexing output of sharing ground, includes: a sampling current differential amplifying module and a sampling voltage translation module;
The sampling current differential amplifying module is characterized in that a first input end is connected with a voltage output end of a target switching power supply, a second input end is connected with an input end of a load of the target switching power supply, a first output end is connected with a first end of the sampling voltage translation module, and a second output end is connected with a second end of the sampling voltage translation module;
The third end of the sampling voltage translation module is used for outputting a small-voltage sampling signal;
The sampling current differential amplification module comprises a resistor R1, a resistor R4, a resistor R6, a resistor R9 and a differential operational amplifier U2;
The first end of the resistor R1 is used as a first input end of the sampling current differential amplification module and is connected with the first end of the resistor R4 and a negative power supply end of the differential operational amplifier U2, and the second end of the resistor R1 is used as a second input end of the sampling current differential amplification module and is connected with the first end of the resistor R6;
the second end of the resistor R4 is connected with the non-inverting input end of the differential operational amplifier U2;
The second end of the resistor R6 is respectively connected with the inverting input end of the differential operational amplifier U2 and the first end of the resistor R9;
The positive power end of the differential operational amplifier U2 is used for inputting a preset power supply, and the output end of the differential operational amplifier U2 is used as a first output end of the sampling current differential amplification module;
The second end of the resistor R9 is used as a second output end of the sampling current differential amplification module;
further comprises: a voltage stabilizing module;
The first input end of the voltage stabilizing module is connected with the voltage output end of the target switching power supply, the second input end of the voltage stabilizing module is grounded, the first output end of the voltage stabilizing module is connected with the positive power end of the differential operational amplifier U2, and the second output end of the voltage stabilizing module is connected between the second end of the resistor R4 and the non-inverting input end of the differential operational amplifier U2.
2. The switching power supply output current detection circuit of claim 1, wherein the sampling voltage translation module further comprises a fourth terminal connected to the voltage output terminal of the target switching power supply.
3. The switching power supply output current detection circuit of claim 2, wherein the sampling voltage translation module comprises: triode N1, resistor R3 and resistor R7;
The base electrode of the triode N1 is used as the first end of the sampling voltage translation module, the emitter electrode of the triode N1 is used as the second end of the sampling voltage translation module, the emitter electrode of the triode N1 is connected with the first end of the resistor R7, and the collector electrode of the triode N1 is connected with the first end of the resistor R3;
The second end of the resistor R7 is used as a third end of the sampling voltage translation module;
The second end of the resistor R3 is used as the fourth end of the sampling voltage translation module.
4. The switching power supply output current detection circuit of claim 3 wherein the sampling voltage translation module further comprises: a resistor R8 and a capacitor C4;
the first end of the resistor R8 is respectively connected with the second end of the resistor R3 and the first end of the capacitor C4, and the second end is used for being connected with a preset voltage source;
The second end of the capacitor C4 is grounded.
5. The switching power supply output current detection circuit according to claim 1, wherein the voltage stabilizing module comprises a resistor R2, a resistor R5, a capacitor C3 and a voltage stabilizing tube U1;
the first end of the resistor R2 is used as a second output end of the voltage stabilizing module, and the second end is respectively connected with the first end of the resistor R5, the first end of the capacitor C3 and the negative electrode of the voltage stabilizing tube U1 and then used as a first output end of the voltage stabilizing module;
the second end of the resistor R5 is used as a second input end of the voltage stabilizing module;
and the second end of the capacitor C3 is connected with the positive electrode of the voltage stabilizing tube U1 and then used as a first input end of the voltage stabilizing module.
6. The switching power supply output current detection circuit of claim 1, further comprising an output filter module;
And the first end of the output filter module is connected with the voltage output end of the target switching power supply, the second end of the output filter module is connected with the second input end of the sampling current differential amplification module, and the third end of the output filter module is grounded.
7. The switching power supply output current detection circuit according to claim 6, wherein the output filter module includes a capacitor C1, a capacitor C2, and an inductor L6;
the first end of the capacitor C1 is connected with the first end of the inductor L6 and then used as the first end of the output filter module, and the second end of the capacitor C2 is connected with the second end of the capacitor C2 and then used as the third end of the output filter module;
and the first end of the capacitor C2 is connected with the second end of the inductor L6 and then is used as the second end of the output filter module.
8. A switching power supply comprising the switching power supply output current detection circuit according to any one of claims 1 to 7.
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