A switching power supply circuit capable of detecting current

Abstract

The present invention relates to a switching power supply circuit capable of detecting current, comprising a current detection circuit, a logic control circuit and a switching power supply main circuit, wherein the input end of the current detection circuit is electrically connected to the output end of the switching power supply main circuit, the output end of the current detection circuit is electrically connected to one signal input end of the logic control circuit, a CPU control signal is connected to another signal input end of the logic control circuit, and the output end of the logic control circuit is electrically connected to the input end of the switching power supply main circuit. The present invention collects the current signal outputted by the switching power supply main circuit through the current detection circuit, and performs a logic comparison between the current signal and the CPU control signal through the logic control circuit, thereby outputting a logic level signal as a control signal for controlling the switching power supply main circuit, so as to control the working state of the switching power supply main circuit, thereby ensuring that the entire switching power supply circuit will not have overvoltage and overcurrent phenomena, and the entire circuit has low energy consumption, high detection accuracy, and stable power supply.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and in particular to a switching power supply circuit capable of detecting current. Background Art

[0002] Nowadays, the integration and precision of integrated circuit chips in intelligent electronic and communication equipment are getting higher and higher, and the requirements for power supply are also getting higher and higher. The main features are low energy consumption, high precision and stable power supply. In this way, the output voltage and current of the switching power supply are required to remain stable without overvoltage and overcurrent. However, there is no switching power supply circuit in the prior art that can detect whether the current is within the set range. In this way, when the output current of the switching power supply fluctuates or even exceeds the set range, it is usually not discovered in time, which has a certain impact on the safety and stability of the switching power supply in practical applications. If you want to detect the output current of the switching power supply, you usually need an external current detection circuit, which is not only very troublesome, but also the detection accuracy cannot be guaranteed. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a switching power supply circuit capable of detecting current in view of the above-mentioned deficiencies in the prior art.

[0004] The technical solution of the present invention to solve the above technical problems is as follows: a switching power supply circuit capable of detecting current, comprising a current detection circuit, a logic control circuit and a switching power supply main circuit, wherein the input end of the current detection circuit is electrically connected to the output end of the switching power supply main circuit and collects the current signal of the switching power supply main circuit, the output end of the current detection circuit is electrically connected to one signal input end of the logic control circuit, a CPU control signal is connected to another signal input end of the logic control circuit, the output end of the logic control circuit is electrically connected to the input end of the switching power supply main circuit, and the switching power supply main circuit outputs a stable voltage to the outside.

[0005] The beneficial effects of the present invention are as follows: the switching power supply circuit capable of detecting current of the present invention collects the current signal outputted by the switching power supply main circuit through the current detection circuit, and performs a logic comparison between the current signal and the CPU control signal through the logic control circuit, thereby outputting a logic level signal as a control signal for controlling the switching power supply main circuit, so as to control the working state of the switching power supply main circuit, realize the detection of the output current of the switching power supply main circuit, and automatically control the working state of the switching power supply main circuit when the current is not within the set range, thereby ensuring that the entire switching power supply circuit will not have overvoltage or overcurrent phenomena, and the entire circuit has low energy consumption, high detection accuracy, and stable power supply.

[0006] On the basis of the above technical solution, the present invention can also be improved as follows:

[0007] Further: the current detection circuit includes a comparison amplifier U1, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a capacitor C1, a capacitor C2 and a capacitor C3, the positive power input terminal of the comparison amplifier U1 is electrically connected to the current detection positive terminal VIN+ of the switching power supply main circuit through the resistor R1, the negative power input terminal of the comparison amplifier U1 is electrically connected to the current detection negative terminal VIN- of the switching power supply main circuit through the resistor R2, and the positive power input terminal and the negative power input terminal of the comparison amplifier U1 are electrically connected The comparison signal input terminal of the comparison amplifier U1 is grounded through the resistor R3, the resistor R4 and the resistor R5 are connected in series in sequence between the comparison voltage input terminal and the amplified signal output terminal of the comparison amplifier U1, the ground terminal of the comparison amplifier U1 is grounded, the comparison signal output terminal of the comparison amplifier U1 is electrically connected to the input terminal of the logic control circuit, the power supply input terminal of the comparison amplifier U1 is electrically connected to the external power supply, and the resistor capacitor C2 and the capacitor C3 are connected in parallel between the power supply input terminal of the comparison amplifier U1 and the ground.

[0008] The beneficial effect of the above further scheme is that the current output from the current detection terminal of the switching power supply main circuit can be converted into a voltage through the comparison amplifier U1, and then compared and amplified with the internal reference voltage of the comparison amplifier U1, so that the subsequent logic control circuit can perform logical operations on it and the CPU control signal to generate a logic level signal for controlling the switching power supply main circuit.

[0009] Further: the current detection circuit also includes a working reset circuit, the output end of the working reset circuit is electrically connected to the reset reverse input end of the comparison amplifier U1, the input end of the working reset circuit is electrically connected to an external power supply, and the reference judgment condition control end of the working reset circuit is electrically connected to the comparison output end of the comparison amplifier U1.

[0010] The beneficial effect of the above further solution is that: the working reset circuit can automatically reset when the voltage outputted from the comparison output terminal of the comparison amplifier U1 is abnormal, thereby ensuring the normal operation of the current detection circuit and improving the stability of the entire circuit.

[0011] Further: the working reset circuit includes resistor R6, resistor R7, resistor R8, resistor R9, resistor R10, capacitor C4, capacitor C5, diode D1 and transistor Q1, the capacitor C4 is electrically connected between the reset input terminal of the comparison amplifier U1 and the ground, the reset input terminal of the comparison amplifier U1 is electrically connected to the cathode of the diode D1, the resistor R6 is electrically connected between the positive and negative electrodes of the diode D1, the anode of the diode D1 is electrically connected to the external power supply through the resistor R7, the anode of the diode is also electrically connected to the collector of the transistor Q1, the emitter of the transistor Q1 is grounded, the capacitor C5 and the resistor R10 are connected in parallel between the base of the transistor Q1 and the ground, the resistor R9 and the resistor R8 are connected in series in sequence between the base of the transistor Q1 and the external power supply, and the common end of the resistor R9 and the resistor R8 is electrically connected to the comparison output terminal of the comparison amplifier U1.

[0012] Further: the logic control circuit includes an OR gate chip U2, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a resistor R16, a resistor R17, a resistor R18, a resistor R19, a resistor R20, a resistor R21, a resistor R22, a resistor R23, a resistor R24, a capacitor C6, a capacitor C7, a capacitor C8, a capacitor C9, a transistor Q2 and a transistor Q3, the comparison output end of the comparison amplifier U1 is electrically connected to an input end of the OR gate chip U2 through the resistor R11, the CPU control signal is connected to another input end of the OR gate chip U2, the other input end of the OR gate chip U2 is grounded through the resistor R13, the ground end of the OR gate chip U2 is grounded, the power input end of the OR gate chip U2 is electrically connected to an external power supply, the capacitor C6 and the capacitor C7 are connected in parallel between the power input end of the OR gate chip U2 and the ground, and the output end of the OR gate chip U2 is connected to the ground through the resistor R15 is electrically connected to the base of the transistor Q2, R16 and capacitor C18 are connected in parallel between the base and emitter of the transistor Q2, the emitter of the transistor Q2 is grounded, the resistor R14 and the resistor R17 are connected in series between the base and the collector of the transistor Q2, the collector of the transistor Q2 is electrically connected to the base of the transistor Q3 through the resistor R18, the common end of the resistor R14 and the resistor R17 is electrically connected to an external power supply, and the The resistor R19 is electrically connected between the emitter of the transistor Q3 and the external power supply, the capacitor C9, the resistor R20 and the resistor R21 are connected in parallel between the external power supply and the ground, the resistor R22, the resistor R23 and the resistor R24 ​​are connected in series in sequence between the external power supply and the ground, the common end of the resistor R22 and the resistor R23 is electrically connected to the collector of the transistor Q3, and the common end of the resistor R22 and the resistor R23 is electrically connected to the input control end of the switching power supply main circuit.

[0013] The beneficial effect of the above further scheme is that: the output signal of the comparison amplifier U1 and the CPU control signal can be subjected to an OR logic operation through the logic control circuit, and a corresponding logic level signal can be generated to control the working state of the switching power supply main circuit, so that the entire switching power supply circuit outputs a stable voltage and current.

[0014] Further: the switching power supply main circuit includes capacitor C10, capacitor C11, capacitor C12, capacitor C13, capacitor C14, diode D2, diode D3, diode D4, MOS tube Q4, resistor R25, resistor R26, resistor R27, resistor R28 and resistor R29, the cathode of the diode D2 is electrically connected to the external power supply, the anode of the diode D2 is electrically connected to the gate of the MOS tube Q4 through the resistor R26, the capacitor C10 is connected in parallel to both ends of the diode D2, the resistor R25 and the capacitor C11 are connected in series between the gate and the drain of the MOS tube Q4, and the cathode of the diode D2 is electrically connected to the gate of the MOS tube Q4 through the resistor R26. The capacitor C12 and the resistor R27 are connected in series with the drain and the external power supply in sequence, the resistor R28 and the resistor R29 are connected in parallel between the drain of the MOS tube Q4 and the positive electrode of the transistor D3, the positive electrode of the transistor D3 is grounded through the capacitor C14, the negative electrode of the transistor D3 is electrically connected to the external power supply, the diode D4 and the capacitor C13 are connected in parallel between the negative electrode of the transistor D3 and the ground, the drain of the MOS tube Q4 is electrically connected to the positive power input terminal of the current detection circuit as the current detection positive terminal VIN+, and the positive electrode of the transistor D3 is electrically connected to the negative power input terminal of the current detection circuit as the current detection negative terminal VIN-.

[0015] The beneficial effect of the above further scheme is: by controlling the working state of the MOS tube Q4 according to the logic level signal output by the logic control circuit, the MOS tube Q4 is turned on and outputs a stable voltage and current, or the MOS tube Q4 is turned off and outputs a current-limited output or does not output a voltage or current. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A module block diagram of a switching power supply circuit capable of detecting current according to the present invention;

[0017] Figure 2 is a circuit diagram of a current detection circuit capable of detecting current of the present invention;

[0018] Figure 3 A circuit diagram of a logic control circuit capable of detecting current according to the present invention;

[0019] Figure 4 The figure is a circuit diagram of the main circuit of the switching power supply capable of detecting current of the present invention. DETAILED DESCRIPTION

[0020] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0021] like Figure 1 As shown, a switching power supply circuit capable of detecting current includes a current detection circuit, a logic control circuit and a switching power supply main circuit, wherein the input end of the current detection circuit is electrically connected to the output end of the switching power supply main circuit and collects the current signal of the switching power supply main circuit, the output end of the current detection circuit is electrically connected to one signal input end of the logic control circuit, a CPU control signal is connected to another signal input end of the logic control circuit, the output end of the logic control circuit is electrically connected to the input control end of the switching power supply main circuit, and the switching power supply main circuit outputs a stable voltage to the outside.

[0022] The switching power supply circuit capable of detecting current of the present invention collects the current signal outputted by the switching power supply main circuit through the current detection circuit, and performs a logic comparison between the current signal and the CPU control signal through the logic control circuit, thereby outputting a logic level signal as a control signal for controlling the switching power supply main circuit, so as to control the working state of the switching power supply main circuit, realize the detection of the output current of the switching power supply main circuit, and automatically control the working state of the switching power supply main circuit when the current is not within a set range, thereby ensuring that the entire switching power supply circuit will not have overvoltage or overcurrent phenomena, and the entire circuit has low energy consumption, high detection accuracy, and stable power supply.

[0023] The specific circuit structures of the current detection circuit, the logic control circuit and the switching power supply main circuit in the switching power supply circuit capable of detecting current will be described in detail below.

[0024] like Figure 2As shown, in one or more embodiments provided by the present invention, the current detection circuit includes a comparison amplifier U1, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a capacitor C1, a capacitor C2 and a capacitor C3, the positive power input terminal of the comparison amplifier U1 is electrically connected to the current detection positive terminal VIN+ of the switching power supply main circuit through the resistor R1, the negative power input terminal of the comparison amplifier U1 is electrically connected to the current detection negative terminal VIN- of the switching power supply main circuit through the resistor R2, and the positive power input terminal of the comparison amplifier U1 is electrically connected to the negative power input terminal The capacitor C1 is electrically connected, the comparison signal input terminal of the comparison amplifier U1 is grounded through the resistor R3, the resistor R4 and the resistor R5 are connected in series in sequence between the comparison voltage input terminal and the amplified signal output terminal of the comparison amplifier U1, the ground terminal of the comparison amplifier U1 is grounded, the comparison signal output terminal of the comparison amplifier U1 is electrically connected to the input terminal of the logic control circuit, the power supply input terminal of the comparison amplifier U1 is electrically connected to the external power supply +3V3, and the resistor capacitor C2 and the capacitor C3 are connected in parallel between the power supply input terminal of the comparison amplifier U1 and the ground.

[0025] The current output from the current detection terminal of the switching power supply main circuit can be converted into a voltage through the comparison amplifier U1, and then compared and amplified with the internal reference voltage of the comparison amplifier U1, so that the subsequent logic control circuit can perform logic operations on it and the CPU control signal to generate a logic level signal for controlling the switching power supply main circuit.

[0026] In the present invention, the comparison amplifier U1 adopts the INA200AID chip produced by Texas Instruments. INA200AID is a high-side current measurement parallel monitor and has an open-drain comparator and a reference amplifier. Its characteristics include: complete current detection solution, 0.6V internal reference voltage, internal open-drain comparison, latching capability comparator, common mode voltage range: -16V to +80V, high accuracy: 3.5% maximum error ultra-high temperature, 500KHZ bandwidth, quiescent current: maximum 1800mA.

[0027] In the present invention, the resistors R1, R2 and the capacitor C1 form a common-mode voltage input circuit. The main function of the current detection circuit is to convert the drain current of the MOS tube Q4 in the main circuit of the switching power supply into voltages VIN+ and VIN-, and then pass through the common-mode amplifier G inside the chip and divide the voltage from pin 2 (OUT end) through resistors R3, R4, and R5 to pin 3 (CMPIN) for input, and compare and amplify with the internal reference voltage of 0.6V. The amplification value of the INA200AID chip amplifier circuit is 20 (times), and then output to the logic OR gate chip U2 for logic calculation.

[0028] Preferably, in one or more embodiments provided by the present invention, the current detection circuit also includes a working reset circuit, the output end of the working reset circuit is electrically connected to the reset reverse input end of the comparison amplifier U1, the input end of the working reset circuit is electrically connected to the external power supply +3V3, and the reference judgment condition control end of the working reset circuit is electrically connected to the comparison output end of the comparison amplifier U1.

[0029] The working reset circuit can automatically reset when the voltage output from the comparison output terminal of the comparison amplifier U1 is abnormal, thereby ensuring the normal operation of the current detection circuit and improving the stability of the entire circuit.

[0030] In one or more embodiments provided by the present invention, the working reset circuit includes a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a capacitor C4, a capacitor C5, a diode D1 and a transistor Q1, the capacitor C4 is electrically connected between the reset input terminal of the comparison amplifier U1 and the ground, the reset input terminal of the comparison amplifier U1 is electrically connected to the cathode of the diode D1, the resistor R6 is electrically connected between the positive and negative electrodes of the diode D1, the anode of the diode D1 is electrically connected to the external power supply +3V3 through the resistor R7, the anode of the diode is also electrically connected to the collector of the transistor Q1, the emitter of the transistor Q1 is grounded, the capacitor C5 and the resistor R10 are connected in parallel between the base of the transistor Q1 and the ground, the resistor R9 and the resistor R8 are connected in series in sequence between the base of the transistor Q1 and the external power supply +3V3, and the common end of the resistor R9 and the resistor R8 is electrically connected to the comparison output terminal of the comparison amplifier U1.

[0031] Here, when the comparison output terminal of the comparison amplifier U1 outputs a low level (i.e., normal operation), the base of the transistor Q1 is at a low level, the transistor Q1 does not work, the collector is at a high level, and the reset reverse input terminal of the comparison amplifier U1 does not receive a reset signal, i.e., the comparison amplifier U1 does not reset during normal operation; when the comparison output terminal of the comparison amplifier U1 outputs a high level (i.e., abnormal operation), the base of the transistor Q1 is at a high level, the transistor Q1 works, the collector is at a low level, and the reset reverse input terminal of the comparison amplifier U1 receives a reset signal, i.e., the comparison amplifier U1 automatically resets during normal operation. The diode adopts a BAV70 diode.

[0032] like Figure 3As shown, in one or more embodiments provided by the present invention, the logic control circuit includes an OR gate chip U2, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a resistor R16, a resistor R17, a resistor R18, a resistor R19, a resistor R20, a resistor R21, a resistor R22, a resistor R23, a resistor R24, a capacitor C6, a capacitor C7, a capacitor C8, a capacitor C9, a transistor Q2 and a transistor Q3, the comparison output end of the comparison amplifier U1 is electrically connected to an input end of the OR gate chip U2 through the resistor R11, the CPU control signal is connected to another input end of the OR gate chip U2, the other input end of the OR gate chip U2 is grounded through the resistor R13, the ground end of the OR gate chip U2 is grounded, the power input end of the OR gate chip U2 is electrically connected to an external power supply +3V3, the capacitor C6 and the capacitor C7 are connected in parallel between the power input end of the OR gate chip U2 and the ground, and the output end of the OR gate chip U2 is connected to the ground through the resistor R 15 is electrically connected to the base of the transistor Q2, the R16 and the capacitor C18 are connected in parallel between the base and the emitter of the transistor Q2, the emitter of the transistor Q2 is grounded, the resistor R14 and the resistor R17 are connected in series in sequence between the base and the collector of the transistor Q2, the collector of the transistor Q2 is electrically connected to the base of the transistor Q3 through the resistor R18, the common end of the resistor R14 and the resistor R17 is electrically connected to the external power supply +13.5V, the transistor Q3 The resistor R19 is electrically connected between the emitter and the external power supply +13.5V, the capacitor C9, the resistor R20 and the resistor R21 are connected in parallel between the external power supply +13.5V and the ground, the resistor R22, the resistor R23 and the resistor R24 ​​are connected in series in sequence between the external power supply +13.5V and the ground, the common end of the resistor R22 and the resistor R23 is electrically connected to the collector of the transistor Q3, and the common end of the resistor R22 and the resistor R23 is electrically connected to the input end of the switching power supply main circuit.

[0033] The logic control circuit can perform an OR logic operation on the output signal of the comparison amplifier U1 and the CPU control signal, and generate a corresponding logic level signal to control the working state of the switching power supply main circuit, so that the entire switching power supply circuit outputs a stable voltage and current.

[0034] like Figure 4As shown, in one or more embodiments provided by the present invention, the switching power supply main circuit includes a capacitor C10, a capacitor C11, a capacitor C12, a capacitor C13, a capacitor C14, a diode D2, a diode D3, a diode D4, a MOS tube Q4, a resistor R25, a resistor R26, a resistor R27, a resistor R28 and a resistor R29, the cathode of the diode D2 is electrically connected to an external power supply +13.5V, the anode of the diode D2 is electrically connected to the gate of the MOS tube Q4 through the resistor R26, the capacitor C10 is connected in parallel to both ends of the diode D2, the resistor R25 and the capacitor C11 are connected in series between the gate and the drain of the MOS tube Q4, The drain of the MOS tube Q4 and the external power supply +13.5V are connected in series with the capacitor C12 and the resistor R27 in sequence. The resistor R28 and the resistor R29 are connected in parallel between the drain of the MOS tube Q4 and the positive electrode of the transistor D3. The positive electrode of the transistor D3 is grounded through the capacitor C14. The negative electrode of the transistor D3 is electrically connected to the external power supply +12VB. The diode D4 and the capacitor C13 are connected in parallel between the negative electrode of the transistor D3 and the ground. The drain of the MOS tube Q4 is electrically connected to the positive power input terminal of the comparison amplifier U1 as a current detection positive terminal, and the positive electrode of the transistor D3 is electrically connected to the negative power input terminal of the comparison amplifier U1 as a current detection negative terminal.

[0035] The working state of the MOS tube Q4 is controlled according to the logic level signal output by the logic control circuit, so that the MOS tube Q4 is turned on and outputs a stable voltage and current, or the MOS tube Q4 is turned off and outputs a current-limited output or does not output a voltage or current.

[0036] In the present invention, the resistor R27 and the capacitor C12 form a filter circuit for removing the source and drain ripples of the MOS tube Q4, the resistor R28 and the resistor R29 form a current measurement circuit for converting the current flowing into a voltage difference, and the diode D4 and the capacitor C13 form an output filter circuit. The diode D4 is a SMBJ6.0CA chip TVS tube.

[0037] Here, when the CPU control signal is at a low level, if the output current of the main circuit of the switching power supply is too large, the OR gate chip U2 outputs a high level, the transistor Q2 is turned on, the transistor Q3 is turned off, and the current flows through the resistor R20 and the resistor R21, thereby turning off the MOS tube Q4, so that the switching power supply is current-limited or does not output; if the output current of the main circuit of the switching power supply is normal, the OR gate chip U2 outputs a low level, the transistor Q2 is turned off, the transistor Q3 is turned on, the current flows through the gate of Q4, and the MOS tube Q4 is turned on, so that the switching power supply works and outputs normally. When the CPU control signal is at a high level, regardless of whether the output current of the main circuit of the switching power supply is normal, the MOS tube Q4 is in a turned-off state, so that the switching power supply is current-limited or does not output.

[0038] The current-detectable switching power supply circuit of the present invention solves the problem of overvoltage and overcurrent in the output voltage and current of the switching power supply. The voltage and current control accuracy is high, and the technical requirements of this type of current detection and comparison switching power supply are met. In addition, the circuit can be widely used in the actual circuit of the integrated circuit chip power supply.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A switching power supply circuit capable of detecting current, characterized in that: It includes a current detection circuit, a logic control circuit and a switching power supply main circuit, wherein the input end of the current detection circuit is electrically connected to the output end of the switching power supply main circuit and collects the current signal of the switching power supply main circuit, the output end of the current detection circuit is electrically connected to one signal input end of the logic control circuit, the CPU control signal is connected to another signal input end of the logic control circuit, the output end of the logic control circuit is electrically connected to the input control end of the switching power supply main circuit, and the switching power supply main circuit outputs a stable voltage to the outside; The logic control circuit includes an OR gate chip U2, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a resistor R16, a resistor R17, a resistor R18, a resistor R19, a resistor R20, a resistor R21, a resistor R22, a resistor R23, a resistor R24, a capacitor C6, a capacitor C7, a capacitor C8, a capacitor C9, a transistor Q2 and a transistor Q3. The current detection circuit includes a comparison amplifier U1. The comparison output end of the comparison amplifier U1 is electrically connected to an input end of the OR gate chip U2 through the resistor R11. The CPU control signal is connected to the other input end of the OR gate chip U2. The other input end of the OR gate chip U2 is grounded through the resistor R13. The ground end of the OR gate chip U2 is grounded. The power input end of the OR gate chip U2 is electrically connected to an external power supply. The capacitor C6 and the capacitor C7 are connected in parallel between the power input end of the OR gate chip U2 and the ground. The output end is electrically connected to the base of the transistor Q2 through the resistor R15, the R16 and the capacitor C18 are connected in parallel between the base and the emitter of the transistor Q2, the emitter of the transistor Q2 is grounded, the resistor R14 and the resistor R17 are connected in series between the base and the collector of the transistor Q2, the collector of the transistor Q2 is electrically connected to the base of the transistor Q3 through the resistor R18, and the common end of the resistor R14 and the resistor R17 is electrically connected to the external power supply. The resistor R19 is electrically connected between the emitter of the transistor Q3 and the external power supply, the capacitor C9, the resistor R20 and the resistor R21 are connected in parallel between the external power supply and the ground, the resistor R22, the resistor R23 and the resistor R24 ​​are connected in series in sequence between the external power supply and the ground, the common end of the resistor R22 and the resistor R23 is electrically connected to the collector of the transistor Q3, and the common end of the resistor R22 and the resistor R23 is electrically connected to the input end of the main circuit of the switching power supply.

2. The switching power supply circuit capable of detecting current according to claim 1, characterized in that: The current detection circuit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a capacitor C1, a capacitor C2 and a capacitor C3. The positive power input terminal of the comparison amplifier U1 is electrically connected to the current detection positive terminal VIN+ of the switching power supply main circuit through the resistor R1, the negative power input terminal of the comparison amplifier U1 is electrically connected to the current detection negative terminal VIN- of the switching power supply main circuit through the resistor R2, and the capacitor C1 is electrically connected between the positive power input terminal and the negative power input terminal of the comparison amplifier U1, the comparison signal input terminal of the comparison amplifier U1 is grounded through the resistor R3, the resistor R4 and the resistor R5 are connected in series between the comparison voltage input terminal and the amplified signal output terminal of the comparison amplifier U1, the ground terminal of the comparison amplifier U1 is grounded, the comparison signal output terminal of the comparison amplifier U1 is electrically connected to the input terminal of the logic control circuit, the power supply input terminal of the comparison amplifier U1 is electrically connected to the external power supply, and the capacitor C2 and the capacitor C3 are connected in parallel between the power supply input terminal of the comparison amplifier U1 and the ground.

3. The switching power supply circuit capable of detecting current according to claim 2, characterized in that: The current detection circuit also includes a working reset circuit, the output end of the working reset circuit is electrically connected to the reset inverting input end of the comparison amplifier U1, the input end of the working reset circuit is electrically connected to an external power supply, and the reference judgment condition control end of the working reset circuit is electrically connected to the comparison output end of the comparison amplifier U1.

4. The switching power supply circuit capable of detecting current according to claim 3, characterized in that: The working reset circuit includes a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a capacitor C4, a capacitor C5, a diode D1 and a transistor Q1. The capacitor C4 is electrically connected between the reset input terminal of the comparison amplifier U1 and the ground. The reset input terminal of the comparison amplifier U1 is electrically connected to the cathode of the diode D1. The resistor R6 is electrically connected between the positive and negative electrodes of the diode D1. The anode of the diode D1 is electrically connected to the external power supply through the resistor R7. The anode of the diode is also electrically connected to the collector of the transistor Q1. The emitter of the transistor Q1 is grounded. The capacitor C5 and the resistor R10 are connected in parallel between the base of the transistor Q1 and the ground. The resistor R9 and the resistor R8 are connected in series in sequence between the base of the transistor Q1 and the external power supply, and the common end of the resistor R9 and the resistor R8 is electrically connected to the comparison output terminal of the comparison amplifier U1.

5. The switching power supply circuit capable of detecting current according to claim 1, characterized in that: The switching power supply main circuit includes capacitor C10, capacitor C11, capacitor C12, capacitor C13, capacitor C14, diode D2, diode D3, diode D4, MOS tube Q4, resistor R25, resistor R26, resistor R27, resistor R28 and resistor R29. The cathode of the diode D2 is electrically connected to the external power supply, the anode of the diode D2 is electrically connected to the gate of the MOS tube Q4 through the resistor R26, the capacitor C10 is connected in parallel to both ends of the diode D2, the resistor R25 and the capacitor C11 are connected in series between the gate and the drain of the MOS tube Q4, and the drain of the MOS tube Q4 is connected in series. The capacitor C12 and the resistor R27 are connected in series with the external power supply in sequence, the resistor R28 and the resistor R29 are connected in parallel between the drain of the MOS tube Q4 and the anode of the diode D3, the anode of the diode D3 is grounded through the capacitor C14, the cathode of the diode D3 is electrically connected to the external power supply, the diode D4 and the capacitor C13 are connected in parallel between the cathode of the diode D3 and the ground, the drain of the MOS tube Q4 is electrically connected to the positive power input terminal of the current detection circuit as the current detection positive terminal VIN+, and the anode of the diode D3 is electrically connected to the negative power input terminal of the current detection circuit as the current detection negative terminal VIN-.

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