A current detection circuit and method applied to a space buck-boost regulator

Abstract

The application discloses a current detection circuit and method applied to a space buck-boost regulator and belongs to the field of current detection circuits.The circuit comprises a current transformer and a rectifier circuit; the primary sides of each magnetic core on the current transformer are connected with the current flowing through the middle inductor connecting buck mode switch tubes and boost mode switch tubes on the space buck-boost regulator; the secondary sides of each magnetic core on the current transformer are connected with the rectifier circuit, the rectifier circuit proportionally reduces the amplitude of the current and converts the current signal into a voltage signal output. Through the application of the application, the linearity and precision of the current detection of the space buck-boost regulator are improved.

Description

Technical Field

[0001] This invention relates to a current detection circuit and method for use in a space buck-boost regulator, belonging to the field of current detection circuit technology. Background Technology

[0002] Aerospace power controllers often require high-precision current sampling technology for negative feedback control of bus regulation, thereby improving the regulator's dynamic response characteristics and conversion efficiency. For inductor current sampling technology in a space-use dual-transistor buck-boost regulator, the current main method is dual-mirror current source sampling. This involves sampling at both ends of the power inductor and taking the larger value to avoid affecting the feedback control signal when one side of the switch is off, as there is no current signal at the corresponding end of the inductor. However, while this method is simple in principle and easy to operate, the sampling ratio of the mirror current source is affected by the DC bias of the current, thus reducing sampling sensitivity and linearity, making it unsuitable for applications requiring high precision.

[0003] Current transformers employ isolated sampling and are based on the principle of electromagnetic induction. A conductive winding is wound around a high-permeability magnetic core to induce a detection current. After passing through a rectifier circuit and a sampling resistor, the detection current is converted into a voltage signal, which is then fed back to the control circuit. Due to a fixed turns ratio, the detected secondary current is in a fixed proportion to the primary current. Therefore, current transformers have advantages such as simple structure, low cost, and wide applicability.

[0004] In actual operation, current transformers mostly adopt a single winding form, which imposes many limitations on current detection: on the one hand, if the magnetic field generated by the measured current exceeds the maximum magnetic flux that the current transformer core can withstand, the core will enter saturation, causing the output electrical signal to be distorted; on the other hand, the magnetic field inside the current transformer core has nonlinear characteristics, and the linearity range of the output signal is limited. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a current detection circuit and method for space buck-boost regulators, thereby improving the linearity and accuracy of current detection in space buck-boost regulators.

[0006] The technical solution of this invention is:

[0007] A current detection circuit for use in a space buck-boost regulator includes a current transformer and a rectifier circuit.

[0008] The current transformer includes two independent magnetic cores, with the primary and secondary coils on each core having opposite directions of their corresponding terminals; the secondary coils on both cores have the same winding direction and the same direction of their corresponding terminals.

[0009] The primary side of each magnetic core of the current transformer is connected to the current flowing through the intermediate inductor connecting the buck mode switch and the boost mode switch in the spatial buck-boost regulator.

[0010] The secondary side of each magnetic core in the current transformer is connected to the rectifier circuit. The rectifier circuit proportionally reduces the amplitude of the current and converts the current signal into a voltage signal for output.

[0011] Preferably, the primary side of each magnetic core of the current transformer is wound with a coil of the same number of turns, and the secondary side is also wound with a coil of the same number of turns, so that the large inductive current passing through the magnetic core is converted into a small DC current inversely proportional to the number of turns.

[0012] Preferably, each magnetic core has a coil wound with one turn on its primary side, and the coil passes through the middle of the magnetic core.

[0013] Preferably, the two magnetic cores are made of the same material, and the coil wires on the magnetic cores are made of the same material; the two magnetic cores are separated by a double-layer insulating pad.

[0014] Preferably, the rectifier circuit includes a trigger, a switching transistor, a diode, and a sampling resistor;

[0015] The non-inverting output terminals of the triggers are respectively connected to the switching transistors M. 1_1 Switching transistor M 1_2 The driving end; the switching transistor M 1_1 One end is connected to the positive output signal of the secondary coil A of the first magnetic core of the current transformer, and the other end is connected to the DC power supply; the switching transistor M 1_2 One end is connected to the negative output signal of coil A, and the other end is connected to the output sampling resistor R. samp Connected; Diode D 3_1 The negative terminal is connected to the DC power supply, and the positive terminal is connected to the negative output signal of coil A; diode D 3_2 The positive terminal is connected to ground, and the negative terminal is connected to the positive output signal of coil A;

[0016] The inverting output of the trigger is connected to the switching transistor M. 2_1 Switching transistor M 2_2 The driving end; the switching transistor M 2_1 One end is connected to the positive output signal of the secondary coil B of the second magnetic core of the current transformer, and the other end is connected to the DC power supply; the switching transistor M 2_2 One end is connected to the negative output signal of coil B, and the other end is connected to the output and the sampling resistor R. samp Connected; Diode D 4_1The negative terminal is connected to the DC power supply, and the positive terminal is connected to the coil B to output the negative signal; diode D 4_2 The positive terminal is connected to ground, and the negative terminal is connected to the positive output signal of coil B.

[0017] Preferably, the two magnetic cores of the current transformer are controlled by the inverting and non-inverting outputs of the trigger, and the two magnetic cores operate with a 180° phase shift.

[0018] Preferably, the CLK terminal of the trigger is connected to a clock generator, which emits a square wave signal with a frequency less than 1 / 100 of the switching frequency of the buck-mode switch and less than 1 / 100 of the switching frequency of the boost-mode switch; the trigger input terminal... Both are connected to a high level; the non-inverting output of the trigger outputs the square wave signal; the inverting output of the trigger... Connected to input terminal D, it outputs the inverted square wave signal;

[0019] Preferably, the rectifier circuit proportionally reduces the amplitude of the current and converts the current signal into a voltage signal, which is then output to the drive control circuit. The drive control circuit drives the buck mode switch and the boost mode switch according to the voltage signal to perform negative feedback regulation on the inductor current.

[0020] Preferably, the drive control circuit includes a compensator and a comparator; the output terminal of the rectifier circuit and the reference signal are respectively connected to the two input terminals of the compensator, and the output terminal of the compensator is connected to the input terminals of the first comparator and the second comparator. It is compared with two preset carrier signals and outputs two PWM signals, which drive the buck mode switch and the boost mode switch, respectively.

[0021] A current detection method for a space buck-boost regulator includes:

[0022] During the high-level output of the trigger, the inductor current flows through the secondary coil A of the first magnetic core of the current transformer, and the inductor current is transformed into a small DC current I inversely proportional to the number of turns. 2aver ; Switching transistor M 1_1 and M 1_2 When the circuit is turned on, the DC power supply passes through the switching transistor M. 1_1 The positive output signal of coil A is connected, and the negative output signal of coil A is connected through the switching transistor M. 1_2 Connect sampling resistor R samp And the current information I on the negative output signal 2aver With sampling resistor R samp The voltage obtained from the diode D is detected in the form of the voltage across the diode. 3_1 and diode D 3_2 Cut-off, switching transistor M 2_1 and M 2_2When disconnected, current information is not collected on the secondary coil B of the second magnetic core of the current transformer;

[0023] During the low-level period of the flip-flop output, the switching transistor M 1_1 and M 1_2 When disconnected, the positive and negative output signal currents of coil A remain unchanged and flow to the sampling resistor R. samp Direction; Diode D 3_1 The positive terminal voltage is the current I. 2aver The product of the sampling resistor and the diode D 3_1 When the circuit is turned on, the current in coil A flows through diode D. 3_1 Released, demagnetization complete; diode D 3_2 Prevent the reverse saturation current on the positive output signal of coil A from flowing to the sampling resistor R. samp ; Switching transistor M 2_1 and M 2_2 When the circuit is turned on, the DC current in the inductor changes the inductive reactance in coil B, and the inductor current is transformed into a small DC current I inversely proportional to the number of turns. 2aver DC power supply through switching transistor M 2_1 The positive output signal of coil B is connected, and the negative output signal of coil B is connected through the switching transistor M. 2_2 Connect sampling resistor R samp The current information on the negative output signal of coil B is then sampled using resistor R. samp The voltage obtained from the diode D is detected in the form of the voltage across the diode. 4_1 and diode D 4_2 Deadline.

[0024] The advantages of this invention compared to the prior art are:

[0025] (1) The current detection circuit designed in this invention can meet the stability requirements of high-frequency circuits and improve the power density of the circuit. Since the secondary side of the current transformer has two negative feedback windings, its internal magnetic field is maintained in a very low-intensity equilibrium state, avoiding the magnetic core from entering a saturation state, thereby improving the linearity of current detection.

[0026] (2) The present invention uses analog signals for current detection. The current signal is converted into a voltage signal through a sampling resistor and then connected to the input terminal of the compensator to perform negative feedback regulation on the inductor current, so as to improve the response rate and stability of the loop, which meets the requirements of the aerospace power controller for the current sampling circuit. Attached Figure Description

[0027] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0028] Figure 1 This is a schematic diagram of the power circuit of the space buck-boost regulator in an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of the winding of a current transformer according to an embodiment of the present invention;

[0030] Figure 3 This is a diagram illustrating the control strategy of the spatial buck-boost regulator in an embodiment of the present invention.

[0031] Figure 4 This is a schematic diagram of the current detection principle of a dual-winding current transformer according to an embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of the trigger in an embodiment of the present invention;

[0033] Figure 6 This is a simulation waveform diagram of the current transformer's working process according to an embodiment of the present invention. Detailed Implementation

[0034] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] This invention proposes a current detection circuit and method for use in space buck-boost regulators. The power circuit of the space buck-boost regulator is applied to aerospace power controllers, such as... Figure 1As shown, the circuit consists of a power supply, buck switch Q1, boost switch Q2, rectifier diodes D1 and D2, power inductor L, output capacitor Co, and output resistor Ro. It primarily transforms and regulates the output voltage of the photovoltaic solar array and controls the charging of the output battery pack. The magnitude of the DC current flowing through the inductor is denoted as I1. The current transformer has one primary winding and two secondary windings for sampling the DC current of the inductor. The positive and negative output signals of the secondary winding A of the current transformer are Img+L and Img+L, respectively; the positive and negative output signals of the secondary winding B of the current transformer are Img+R and Img+R, respectively.

[0036] The current transformer is a zero-flux current transformer, capable of linear current-to-current conversion over a wide frequency range. The current transformer consists of two independent magnetic cores, each connected to a primary inductor with one turn, and wound with N turns of the same type. This results in two secondary output currents for the transformer's detection. The two sets of windings are wound in the same direction on the current transformer, and the corresponding terminals of the two secondary windings are in the same direction, while the corresponding terminals of the primary and secondary windings are in opposite directions. The two magnetic cores and windings are made of the same material. For ease of description, the two magnetic cores on the current transformer are designated as the first magnetic core and the second magnetic core, with the secondary coil of the first magnetic core designated as coil A and the secondary coil of the second magnetic core designated as coil B.

[0037] refer to Figure 3 The document provides a schematic diagram of a current transformer winding according to one embodiment. The current transformer has a dual-core structure, with secondary coils of the same number of turns and size N wound around them. The primary coil passes through the middle of the core and has only one turn. The secondary core is required to saturate very easily, so that the inductive reactance of the secondary coil with the iron core can be changed using the DC current of the inductance. This transforms the large inductive current through the core into a small DC current, i.e., I, inversely proportional to the number of turns. 2aver =I1 / N. The middle of the dual magnetic core is isolated by a double-layer insulating pad to avoid crosstalk between signals. The outer side of the dual magnetic core is fixed by two windings.

[0038] Based on the fundamental principle of magnetic current detection. Figure 4 A schematic diagram of a current detection principle using a dual-winding current transformer is provided. The non-inverting output terminal of the trigger is connected to the switching transistor M. 1_1 and M 1_2 The driving end controls the switching transistor M 1_1 and M 1_2 The switching transistor M is simultaneously turned on or off. 1_1 One end is connected to the positive output signal Img+L of the secondary core coil A of the current transformer, and the other end is connected to a +12V DC power supply. The switching transistor M 1_2One end is connected to the negative output signal Img-L of the secondary core coil A of the current transformer, and the other end is connected to the output sampling resistor R. samp Connected, diode D 3_1 The negative terminal is connected to the +12V DC power supply, and the positive terminal is connected to the output signal Img-L of the DC transformer, forming a freewheeling circuit for Img-L. Diode D 3_2 The positive terminal is connected to ground, and the negative terminal is connected to the output signal Img+L of the DC transformer, forming a freewheeling circuit for Img+L.

[0039] The inverting output of the trigger is connected to the switching transistor M. 2_1 and M 2_2 The driving end controls the switching transistor M 2_1 and M 2_2 The switching transistor M is simultaneously turned on or off. 2_1 One end is connected to the positive output signal Img+R of the secondary core coil B of the current transformer, and the other end is connected to the +12V DC power supply. The switching transistor M 2_2 One end is connected to the negative output signal Img-R of the secondary core coil B of the current transformer, and the other end is connected to the output sampling resistor R. samp Connected, diode D 4_1 The negative terminal is connected to the +12V DC power supply, and the positive terminal is connected to the output signal Img-R of the DC transformer, forming a freewheeling circuit for Img-R. Diode D 4_2 The positive terminal is connected to ground, and the negative terminal is connected to the output signal Img+R of the DC transformer, forming a freewheeling circuit for Img+R.

[0040] The regulator's control strategy is determined by Figure 2 The current transformer acquires the inductor current signal I1, and its output is connected to the input of the rectifier circuit. The rectifier circuit proportionally reduces the amplitude of the measured inductor current, and the current signal is converted into a voltage signal output through a sampling resistor. The output of the current detection circuit and the reference signal are connected to the two inputs of the first compensator. The output of the compensator is connected to the inputs of the first comparator and the second comparator, respectively, and compared with the two carrier waves to output two PWM signals, which drive the switching transistors Q1 and Q2 respectively.

[0041] The current transformer has two operating phases: a current induction phase and a core demagnetization phase. The dual-core structure alternately acquires the sampling resistor R within one switching cycle. samp This process improves the accuracy of current sampling by preventing the saturation current of the magnetic core from interfering with the primary inductance current collected by the DC transformer. The specific working process is as follows:

[0042] Step 1: During the high-level output of the trigger, the inductor current I1 flows through the iron core coil A. Since the DC current of the inductor changes the inductive reactance in the iron core coil A, the inductor current is transformed into a small DC current I inversely proportional to the number of turns. 2aver The switching transistor M 1_1 and M 1_2 When the circuit is turned on, the +12V DC power supply passes through the switching transistor M. 1_1 Connect Img+L, wherein Img-L is connected through the switching transistor M. 1_2 Connect the sampling resistor R samp and the current information I at Img-L 2aver With the sampling resistor R samp The voltage obtained from the upper diode is detected in the form of the current; the freewheeling diode D 3_1 and reverse protection diode D 3_2 Cut off, the switching transistor M 2_1 and M 2_2 When disconnected, current information is not collected on magnetic core B.

[0043] Step 2: During the period when the trigger outputs a low level, the switching transistor M... 1_1 and M 1_2 Disconnected because the inductor current cannot change abruptly, the output signals Img+L and Img-L of the DC transformer remain in the same direction and still flow to the sampling resistor R. samp The direction of the freewheeling diode D 3_1 The positive terminal voltage is the current I. 2aver The product of the sampling resistor and the freewheeling diode D, therefore, 3_1 When the circuit is turned on, the current in the iron core coil A flows through the freewheeling diode D. 3_1 Release the magnetizer to complete demagnetization and prevent the magnetic core from saturating and affecting the current detection in the next cycle; the diode D 3_2 Its function is to prevent the reverse saturation current on the output signal Img+L of the DC transformer from flowing to the sampling resistor R. samp This stabilizes the magnitude of the sampling current. Simultaneously, the switching transistor M... 2_1 and M 2_2 When the circuit is turned on, the DC current in the inductor changes the inductive reactance in the iron core coil B. Therefore, the inductor current is transformed into a small DC current I inversely proportional to the number of turns. 2aver The switching transistor M 2_1 and M 2_2 When the circuit is turned on, the +12V DC power supply passes through the switching transistor M. 2_1 Connect Img+R, wherein Img-R is connected through the switching transistor M. 2_2 Connect the sampling resistor R samp and the current information on Img-R is expressed using the sampling resistor R.samp The voltage obtained from the upper diode is detected. The freewheeling diode D... 4_1 and reverse protection diode D 4_2 Deadline.

[0044] After continuous magnetization and demagnetization processes, the sampling resistor R samp It will always output a stable converted current detection signal.

[0045] The dual magnetic cores are controlled by the inverting and non-inverting outputs of a flip-flop, and the dual magnetic cores operate with a 180° phase shift, which is achieved using a clock generator. The flip-flop schematic diagram is shown below. Figure 5 As shown. This clock generator outputs a 1kHz square wave signal with a duty cycle D = 0.5. The frequency of the 1kHz square wave signal is determined by resistor R. t and capacitor C t The frequency f is determined by the time constant. AC =1 / (R) t ·C t ), accuracy is determined by R adj1 and R adj2 Adjustment. Connect the square wave signal to the CLK terminal of the trigger, input terminal. and If both are connected to a high level, then the non-inverting output terminal Q will output a 1kHz square wave signal, and the inverting output terminal... Connected to input terminal D, it outputs an inverted 1kHz square wave signal. Since the frequency of the square wave signal output by the trigger is much lower than the switching frequency of the primary-side switching transistor, typically 1 / 100th of the switching frequency, the frequency noise of the feedback control loop is much lower than the switching frequency when the output current detection signal is used for feedback control. This ensures that the control loop bandwidth meets the requirements for closed-loop control stability. Furthermore, as the switching frequency increases, the inductance of the coil and the volume of the magnetic core can be made smaller, thereby reducing the size and weight of the current transformer. Therefore, the current detection circuit designed in this invention can meet the stability requirements of high-frequency circuits and improve the power density of the circuit.

[0046] The effectiveness of this technical solution can be verified by simulating the circuit using Plesc software. (Refer to...) Figure 6 The paper presents a simulation waveform diagram of the operation of a current transformer according to an embodiment. In the simulation, the DC component of the primary inductor current is set to 10A, the AC component to 0.5A, the number of turns of the secondary coil N = 500, and the sampling resistor R... samp =100Ω. The figure shows the waveform of the inductor current and the voltage across the sampling resistor. It can be seen that the voltage signal sampled stabilizes at 2V after 0.4s, and the current sampling ratio is k = R. samp / N. This invention ensures the stability of current detection.

[0047] The embodiments described above are merely preferred embodiments of the present invention. Ordinary variations and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A current detection circuit for use in a space buck-boost regulator, characterized in that, Including current transformers and rectifier circuits; The current transformer includes two independent magnetic cores, with the primary and secondary coils on each core having opposite directions of their corresponding terminals; the secondary coils on both cores have the same winding direction and the same direction of their corresponding terminals. The primary side of each magnetic core of the current transformer is connected to the current flowing through the intermediate inductor connecting the buck mode switch and the boost mode switch in the spatial buck-boost regulator. The secondary side of each magnetic core in the current transformer is connected to the rectifier circuit. The rectifier circuit proportionally reduces the amplitude of the current and converts the current signal into a voltage signal for output.

2. The current detection circuit for a space buck-boost regulator according to claim 1, characterized in that, In a current transformer, the primary side of each magnetic core is wound with the same number of turns of coil, and the secondary side is also wound with the same number of turns of coil, so that the large inductive current passing through the magnetic core is transformed into a small DC current inversely proportional to the number of turns.

3. A current detection circuit for a space buck-boost regulator according to claim 1 or 2, characterized in that, Each magnetic core has a coil wound with one turn on its primary side, and the coil passes through the middle of the magnetic core.

4. The current detection circuit for a space buck-boost regulator according to claim 1, characterized in that, The two magnetic cores are made of the same material, and the coil wires on the magnetic cores are made of the same material; the two magnetic cores are separated by a double-layer insulating pad.

5. A current detection circuit for a space buck-boost regulator according to claim 1, characterized in that, The rectifier circuit includes a trigger, a switching transistor, a diode, and a sampling resistor; The non-inverting output terminals of the triggers are respectively connected to the switching transistors. Switching transistor The driving end; the switching transistor One end is connected to the positive output signal of the secondary coil A of the first magnetic core of the current transformer, and the other end is connected to the DC power supply; the switching transistor One end is connected to the negative output signal of coil A, and the other end is connected to the output sampling resistor. Connected; diode The negative terminal is connected to the DC power supply, and the positive terminal is connected to the negative output signal of coil A; diode The positive terminal is connected to ground, and the negative terminal is connected to the positive output signal of coil A; The inverting output terminals of the triggers are respectively connected to the switching transistors. Switching transistor The driving end; the switching transistor One end is connected to the positive output signal of the secondary coil B of the second magnetic core of the current transformer, and the other end is connected to the DC power supply; the switching transistor One end is connected to the negative output signal of coil B, and the other end is connected to the output and the sampling resistor. Connected; diode The negative terminal is connected to the DC power supply, and the positive terminal is connected to the coil B to output the negative signal; diode The positive terminal is connected to ground, and the negative terminal is connected to the positive output signal of coil B.

6. A current detection circuit for a space buck-boost regulator according to claim 5, characterized in that, The two magnetic cores of the current transformer are controlled by the inverting and non-inverting outputs of the trigger, and the two magnetic cores operate with a 180° phase shift.

7. A current detection circuit for a space buck-boost regulator according to claim 6, characterized in that, The CLK terminal of the flip-flop is connected to a clock generator, which outputs a square wave signal with a frequency less than 1 / 100 of the switching frequency of the buck-mode switch and less than 1 / 100 of the switching frequency of the boost-mode switch; the flip-flop input terminal... , Both are connected to a high level; the non-inverting output of the trigger outputs the square wave signal; the inverting output of the trigger... With input terminal Connect to output the inverted square wave signal.

8. A current detection circuit for a space buck-boost regulator according to claim 1, characterized in that, The rectifier circuit proportionally reduces the amplitude of the current and converts the current signal into a voltage signal, which is then output to the drive control circuit. The drive control circuit drives the buck mode switch and the boost mode switch according to the voltage signal to perform negative feedback regulation on the inductor current.

9. A current detection circuit for a space buck-boost regulator according to claim 8, characterized in that, The drive control circuit includes a compensator and a comparator. The output of the rectifier circuit and the reference signal are respectively connected to the two inputs of the compensator. The output of the compensator is connected to the inputs of the first comparator and the second comparator. It is compared with two preset carrier signals and outputs two PWM signals, which drive the buck mode switch and the boost mode switch, respectively.

10. A current detection method for a space buck-boost regulator, employing a current detection circuit for a space buck-boost regulator as described in claim 5, characterized in that... include: During the high-level output of the trigger, the inductor current flows through the secondary coil A of the first magnetic core of the current transformer, and the inductor current is transformed into a small DC current inversely proportional to the number of turns. Switching transistor and When the circuit is turned on, the DC power supply passes through the switching transistor. The positive output signal of coil A is connected, and the negative output signal of coil A is connected through a switching transistor. Connect sampling resistor and the current information on the negative output signal With sampling resistor The voltage obtained from the diode is detected in the form of the voltage across the diode. and diodes Cut-off, switching transistor and When disconnected, current information is not collected on the secondary coil B of the second magnetic core of the current transformer; During the low-level period of the trigger output, the switching transistor and When disconnected, the positive and negative output signal currents of coil A remain unchanged and flow to the sampling resistor. Direction; Diode The positive terminal voltage is the current. The product of the diode and the sampling resistor. When the circuit is turned on, the current in coil A flows through the diode. Release, complete demagnetization; diode Prevent the reverse saturation current on the positive output signal of coil A from flowing to the sampling resistor. Switching transistor and When the circuit is turned on, the DC current in the inductor changes the inductive reactance in coil B, and the inductor current is transformed into a small DC current inversely proportional to the number of turns. DC power supply through switching transistor The positive output signal of coil B is connected, and the negative output signal of coil B is connected through the switching transistor. Connect sampling resistor The current information on the negative output signal of coil B is then sampled using the resistor. The voltage obtained from the diode is detected in the form of the voltage across the diode. and diodes Deadline.

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