CN108318738B - Phase detection circuit and parameter information detection method of wireless power transmission system - Google Patents

Abstract

The invention provides a phase detection circuit of a wireless power transmission system and a parameter information detection method, wherein the phase detection circuit includes a voltage dividing resistor, a bidirectional Zener diode, a comparator, an isolator, an AND gate, a single-pole double-throw analog switch and an RC filter. The voltage on the primary side capacitor of the wireless power transmission system is converted into a small amplitude signal by a voltage divider resistor and then input to the comparator to generate a square wave. The square wave signal after passing through the isolator and the controller generated are in phase with the primary side fundamental wave voltage The PWM wave phase and the phase detection signal are obtained. The signal modulates the phase information to the DC voltage signal through the single-pole double-throw analog switch and the RC filter circuit. The parameter calculation program can calculate parameters such as phase angle, impedance and mutual inductance in the electromagnetic coupling device based on the DC voltage signal obtained by the phase detection circuit. The present invention has the advantages of simplicity and high efficiency, low cost, reliable circuit, less susceptible to interference, and the like.

Description

A phase detection circuit and parameter information detection of a wireless power transmission system method

technical field

The invention relates to the technical field of power electronic converters, in particular to a phase detection circuit and a parameter information detection method of a wireless power transmission system.

Background technique

The mutual inductance of the coupling coil is very important for the widely used wireless power transmission system. To obtain the mutual inductance parameters of the coupled coil, first measure the phase difference of the voltage and current on the primary side. The traditional phase measurement method generally obtains the phase difference by dividing the time interval of two signals by the period: two signals of the same frequency are converted into digital signals by a comparator, and the time interval of the two digital signals is measured by a counter, and the time interval Divide by the period and multiply by 360° to get the phase difference. This method is limited by the frequency of the counter, and a large error will occur when measuring the phase difference of high-frequency signals. Therefore, in order to obtain the mutual inductance of the wireless power transmission system, it is necessary to improve the existing high-frequency signal phase detection technology.

After searching the prior art, it is found that the invention patent "Method for Measuring Phase Difference of High-Frequency Signal" (CN03543333A) discloses a method for measuring the phase of high-frequency signal. The invention adopts the frequency measuring circuit to obtain the frequency of the high frequency signal. The digital quadrature signal generation circuit is set up by the microcontroller circuit, and the sine signal and cosine signal with the same frequency as the high frequency signal are output. Two demodulators are used to demodulate the high frequency signal respectively, and four synchronous acquisition circuits are used. The 4 channels of down-converted signals are sampled synchronously, quantized sequentially, and finally the measurement of the phase difference of the high-frequency signal is completed by calculation.

On the one hand, the existing phase detection and mutual inductance estimation methods are difficult to meet the precision requirements of high-frequency signals, and on the other hand, the detection process is cumbersome and the cost is high. Therefore, at the present stage, a method for detecting parameter information of a wireless power transmission system is very much needed, which has the advantages of simplicity, efficiency, and low cost.

SUMMARY OF THE INVENTION

In view of the defects in the prior art, the purpose of the present invention is to provide a phase detection circuit and a parameter information detection method for a wireless power transmission system, based on the DC voltage signal obtained by the phase detection circuit, can accurately calculate parameters such as phase angle, impedance and mutual inductance.

The present invention is realized according to the following technical solutions:

A phase detection circuit for a wireless power transmission system, characterized by comprising: two voltage dividing resistors R3 and R4, a bidirectional Zener diode BZD, a comparator CMP, an isolator ISO, an AND gate AND, a single-pole double-throw analog switch SPDT , RC filter, in which one end of the first voltage dividing resistor R3 is used as the circuit input anode, and the other end is connected with one end of the second voltage dividing resistor R4, one end of the bidirectional Zener diode BZD, and one input end of the comparator CMP is connected; the second The other end of the voltage dividing resistor R4 is connected to the other end of the bidirectional Zener diode BZD and the other input end of the comparator CMP to form the negative pole of the circuit input; the output end of the comparator CMP is connected to the input end of the isolator ISO, and the isolator ISO The output terminal of the AND gate AND is connected to one input terminal of the AND gate AND; the other input terminal of the AND gate AND is used as the input terminal of the PWM signal, and the output terminal of the AND gate AND is connected to the input terminal of the SPDT analog switch SPDT. The output of the switch SPDT is connected to the input of the RC filter.

In the above technical solution, the wireless power transmission system includes four capacitors C0-C3, eight power MOSFETs Q1-Q8, a resistor RL, two coils L1, L2, coil internal resistances R1 and R2, one end of the first capacitor C0 It is connected to the drain of the power MOSFET Q1 and the drain of the power MOSFET Q3 to form the positive pole of the circuit input, and the other end of the first capacitor C0 is connected to the source of the power MOSFET Q2 and the source of the power MOSFET Q4 to form the input terminal of the circuit. Cathode; the source of the power MOSFET Q1, the drain of the power MOSFET Q2, and one end of the coil L1 are connected; the source of the power MOSFET Q3 is connected to the drain of the power MOSFET Q4 and one end of the capacitor C1; the other end of the coil L1 is connected to the capacitor C1. The other end is connected; one end of the coil L2 is connected to one end of the capacitor C2; the other end of the coil L2 is connected to the source of the power MOSFET Q5 and the drain of the power MOSFET Q6; the other end of the capacitor C2 is connected to the source of the power MOSFET Q7, the power The drain of the MOSFET Q8 is connected to the drain of the power MOSFET Q5; the drain of the power MOSFET Q5 is connected to the drain of the power MOSFET Q7, one end of the capacitor C3, and one end of the resistor RL; One end and the other end of the resistor RL are connected.

In the above technical solution, the input DC power Vin is inverted into the AC power V1 through a single-phase bridge circuit composed of four power MOSFETs Q1-Q4, and the primary side coil L1 is connected in series with the capacitor C1. The secondary side coil L2 is connected in series with the capacitor C2, and the output voltage V0 is formed through the rectifier circuit composed of four power MOSFETs Q5-Q8, which acts on the load RL.

In the above technical solution, the voltage on the primary side capacitor of the wireless power transmission system is converted into a small amplitude signal by the voltage divider resistors R3 and R4 and then input to the comparator CMP, and the generated square wave passes through the isolator ISO, and the digital The signal processor DSP controls the phase of the PWM wave generated in the same phase as the fundamental voltage on the primary side and obtains a phase detection signal. The information of the detection signal is modulated to a DC voltage signal through the SPDT analog switch SPDT and the RC filter device. .

A method for detecting parameter information of a wireless power transmission system, implemented according to any of the above-mentioned phase detection circuits, characterized in that it includes the following steps:

电阻R2各项参数初始化；Step 1: Calculate the phase angle α of the primary side bridge arm, the phase angle β of the secondary side bridge arm, and the phase difference of the voltage and current of the secondary side

The parameters of resistor R2 are initialized;

Step 2: sampling the input voltage Vin, the input current Iin, the output voltage V0, the output current I0 and the phase modulation voltage Vphase based on the synchronization circuit and the phase detection circuit;

Step 3: Calculate the phase difference θ of the primary side voltage and current, and the load impedance RL;

Step 4: Calculate equivalent resistance Re and equivalent reactance Xe;

Step 5: Estimate the redundant impedance X ₂ and mutual inductance M on the secondary side to complete the mutual inductance estimation of the wireless power transmission system.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The phase detection circuit can effectively avoid signal interference and has high reliability;

(2) The whole scheme has good implementation effect and low cost;

(3) No additional control circuit is required, and the implementation is simple and convenient.

Description of drawings

Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a schematic diagram of a wireless power transmission system according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a phase detection circuit according to an embodiment of the present invention.

FIG. 3 is a flowchart of a parameter calculation program according to an embodiment of the present invention.

Detailed ways

The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the inventive concept. These all belong to the protection scope of the present invention.

FIG. 1 is a schematic diagram of the wireless power transmission system in this embodiment. The wireless power transmission system of the present invention includes four capacitors C0-C3, eight power MOSFETs Q1-Q8, a resistor RL, and two coils L1, L2. One end of the first capacitor C0 is connected to the drain of the power MOSFET Q1 and the drain of the power MOSFET Q3 to form the positive electrode of the input end of the circuit. The other end of the first capacitor C0 is connected to the source of the power MOSFET Q2 and the source of the power MOSFET Q4 to form the cathode of the input end of the circuit. The source of the power MOSFET Q1, the drain of the power MOSFET Q2, and one end of the coil L1 are connected. The source of the power MOSFET Q3 is connected to the drain of the power MOSFET Q4 and one end of the capacitor C1. The other end of the coil L1 is connected to the other end of the capacitor C1. One end of the coil L2 is connected to one end of the capacitor C2. The other end of the coil L2 is connected to the source of the power MOSFET Q5 and the drain of the power MOSFET Q6. The other end of the capacitor C2 is connected to the source of the power MOSFET Q7 and the drain of the power MOSFET Q8. The drain of the power MOSFET Q5 is connected to the drain of the power MOSFET Q7, one end of the capacitor C3, and one end of the resistor RL. The source of the power MOSFET Q6 is connected to the source of the power MOSFET Q8, the anode of the diode D8, the other end of the capacitor C3, and the other end of the resistor RL.

The input DC power Vin is converted into AC power V1 through a single-phase bridge circuit composed of four power MOSFETs Q1-Q4. The primary side coil L1 is connected in series with the capacitor C1. The secondary side coil L2 is connected in series with the capacitor C2, and the output voltage V0 is formed through the rectifier circuit composed of four power MOSFETs Q5-Q8, which acts on the load RL.

FIG. 2 is a circuit diagram of the phase detection in this embodiment. The phase detection circuit diagram includes two voltage divider resistors R3 and R4, a bidirectional Zener diode BZD, a comparator CMP, an isolator ISO, an AND gate AND, a single-pole double-throw analog switch SPDT, and an RC filter. One end of the first voltage dividing resistor R3 is used as the circuit input anode, and the other end is connected to one end of the second voltage dividing resistor R4, one end of the bidirectional Zener diode BZD, and one input end of the comparator CMP. The other end of the second voltage dividing resistor R4 is connected to the other end of the bidirectional Zener diode BZD and the other input end of the comparator CMP to form the negative electrode of the circuit input. The output of the comparator CMP is connected to the input of the isolator ISO. The output terminal of the isolator ISO is connected to one input terminal of the AND gate AND. The other input end of the AND gate AND serves as the input end of the PWM signal. The output end of the AND gate AND is connected with the input end of the SPDT analog switch. The output end of the SPDT analog switch SPDT is connected to the input end of the RC filter.

Collect the voltage on the primary side capacitor C1 in the wireless power transmission system, convert it into a small-amplitude signal after being divided by resistors R3 and R4, and then input it to the comparator CMP. DSP controls the phase of the PWM wave generated in the same phase as the primary side fundamental voltage V1 and obtains the phase detection signal. After the detection signal passes through the SPDT analog switch SPDT and the RC filter device, the phase information is modulated to the DC voltage signal Vphase.

FIG. 3 is a flowchart of a method for detecting parameter information according to an embodiment of the present invention. The parameter information detection method is based on the DC voltage signal obtained by the phase detection circuit, and can accurately calculate parameter values such as phase angle, impedance and mutual inductance in the wireless power transmission system, which includes the following steps:

等参数是通过控制器给定的，电阻R2是线圈的内阻，其值基本保持不变，线圈制作完成后即可通过LCR表测定，因此以上参数在系统初始化阶段即已知；Step 1: Primary side arm phase angle α, secondary side bridge arm phase angle β, secondary side voltage and current phase difference

The other parameters are given by the controller. The resistance R2 is the internal resistance of the coil, and its value remains basically unchanged. After the coil is made, it can be measured by the LCR meter, so the above parameters are known in the system initialization stage;

Step 2: The input voltage Vin, the input current Iin, the output voltage V0, the output current I0 and the phase modulation voltage Vphase are sampled based on the synchronization circuit and the phase detection circuit. The above signals are all DC signals, and the measurement technology is very mature and easy to implement;

Step 3: The controller calculates the phase difference θ of the primary side voltage and current according to the conversion relationship between the phase and the DC voltage, and calculates the load impedance RL according to the output voltage V0 and the output current I0;

计算等效电阻Re、等效电抗Xe；Step 4: According to the load impedance RL, the secondary side bridge arm phase angle β and the secondary side voltage and current phase difference

Calculate the equivalent resistance Re and equivalent reactance Xe;

Step 5: Estimate the redundant impedance X ₂ and mutual inductance M on the secondary side to complete the mutual inductance estimation of the wireless power transmission system.

The parameters of the main components in the example are as follows:

Voltage divider resistors R3, R4: 10kΩ and 2MΩ;

Comparator CMP: TLV3502;

Isolator ISO: ISO7710;

AND gate AND: SN74LVCLG08;

SPDT analog switch SPDT: NC7SB3157, 250MHz;

Digital signal processor DSP: TMS320F28335.

The present invention provides a phase detection circuit and a parameter information detection method of a wireless power transmission system, which have the advantages of simple and efficient calculation method, cheap and reliable circuit, less susceptible to interference, and obvious application value.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above-mentioned specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essential content of the present invention. The embodiments of the present application and features in the embodiments may be combined with each other arbitrarily, provided that there is no conflict.

Claims (3)

1. a phase detection circuit of a wireless power transmission system, is characterized in that, comprising: two voltage dividing resistors R3 and R4, bidirectional Zener diode BZD, comparator CMP, isolator ISO, AND gate AND, SPDT analog Switch SPDT, RC filter, wherein one end of the first voltage dividing resistor R3 is used as the circuit input anode, and the other end is connected with one end of the second voltage dividing resistor R4, one end of the bidirectional Zener diode BZD, and an input end of the comparator CMP; The other end of the second voltage dividing resistor R4 is connected with the other end of the bidirectional Zener diode BZD and the other input end of the comparator CMP to form the negative electrode of the circuit input; the output end of the comparator CMP is connected with the input end of the isolator ISO to isolate the The output end of the ISO is connected with one input end of the AND gate AND; the other input end of the AND gate AND is used as the input end of the PWM signal, and the output end of the AND gate AND is connected with the input end of the SPDT analog switch SPDT. The output end of the throw analog switch SPDT is connected to the input end of the RC filter; The wireless power transmission system includes four capacitors C0-C3, eight power MOSFETs Q1-Q8, a resistor RL, two coils L1, L2, coil internal resistances R1 and R2, and one end of the first capacitor C0 is connected to the power MOSFET Q1. The drain of the power MOSFET Q3 is connected to the drain of the power MOSFET Q3 to form the positive electrode of the input end of the circuit, and the other end of the first capacitor C0 is connected to the source electrode of the power MOSFET Q2 and the source electrode of the power MOSFET Q4 to form the cathode of the input end of the circuit; the power MOSFET The source of Q1, the drain of power MOSFET Q2, and one end of coil L1 are connected; the source of power MOSFET Q3 is connected to the drain of power MOSFET Q4 and one end of capacitor C1; the other end of coil L1 is connected to the other end of capacitor C1; One end of the coil L2 is connected to one end of the capacitor C2; the other end of the coil L2 is connected to the source of the power MOSFET Q5 and the drain of the power MOSFET Q6; the other end of the capacitor C2 is connected to the source of the power MOSFET Q7 and the drain of the power MOSFET Q8 The drain of the power MOSFET Q5 is connected to the drain of the power MOSFET Q7, one end of the capacitor C3, and one end of the resistor RL; the source of the power MOSFET Q6 is connected to the source of the power MOSFET Q8, the other end of the capacitor C3, and the resistor RL connected to the other end; The voltage on the primary side capacitor of the wireless power transmission system is converted into a small-amplitude signal by the voltage dividing resistors R3 and R4 and then input to the comparator CMP, and the generated square wave passes through the isolator ISO and is controlled by the digital signal processor DSP. The generated PWM wave that is in phase with the primary side fundamental voltage is summed to obtain a phase detection signal. The information of the detection signal is modulated to a DC voltage signal after passing through the SPDT analog switch SPDT and the RC filter device. 2. the phase detection circuit of a kind of wireless power transmission system according to claim 1 is characterized in that, input DC power source Vin is inverted into alternating current V1 through the single-phase bridge circuit that is formed by four power MOSFETs Q1-Q4, The primary side coil L1 is connected in series with the capacitor C1. The secondary side coil L2 is connected in series with the capacitor C2, and the output voltage V0 is formed through the rectifier circuit composed of four power MOSFETs Q5-Q8, which acts on the load RL. 3. A parameter information detection method of a wireless power transmission system, realized according to the phase detection circuit described in any one of claims 1-2, characterized in that, comprising the steps: Step 1: Initialize the parameters of the primary side bridge arm phase angle α, the secondary side bridge arm phase angle β, and the secondary side voltage and current phase difference resistance R2; Step 2: sampling the input voltage Vin, the input current Iin, the output voltage V0, the output current I0 and the phase modulation voltage Vphase based on the synchronization circuit and the phase detection circuit; Step 3: Calculate the phase difference θ of the primary side voltage and current, and the load impedance RL; Step 4: Calculate equivalent resistance Re and equivalent reactance Xe; Step 5: Estimate the redundant impedance X2 and mutual inductance M on the secondary side to complete the mutual inductance estimation of the wireless power transmission system.

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