CN207200393U - The wireless charging system of portable electric appts - Google Patents

Abstract

The utility model provides a kind of wireless charging system of portable electric appts, including wireless charging transmitting terminal and wireless charging receiving terminal, wireless charging transmitting terminal includes power module, FET driver element, full bridge inverter, transmitting coil, main control chip circuit and signal deteching circuit, power module, FET driver element, full bridge inverter and transmitting coil are sequentially connected, and main control chip is all connected with power module, signal deteching circuit and FET driver element；Power module includes 5V mu balanced circuits and 3.3V mu balanced circuits；Wireless charging receiving terminal includes receiving coil, full bridge rectifier, voltage regulator circuit and the controller list being sequentially connected.The utility model solves the complex operation of traditional wire charging, very flexible, easily produces the shortcomings of spark, wire are exposed and plug wire part is easily worn, and with efficiency high, safety, control is simple and the low advantage of radiation.

Description

Wireless Charging System for Portable Electronic Devices

technical field

The utility model relates to the technical field of wireless charging, in particular to a wireless charging system for portable electronic equipment.

Background technique

With the development of electronic technology, the functions of portable electronic devices such as tablets and mobile phones have become more and more abundant, which has brought great convenience to our life, and the frequency of people using these portable electronic devices will also increase. high. Due to the limited battery life of lithium batteries, these devices will be charged more and more frequently. At present, most portable electronic devices use the traditional wired charging method, which needs to be connected to a data cable to charge the device, which brings great trouble to our charging. At this time, wireless charging came into being.

The research on wireless power transmission technology originated from the electromagnetic induction phenomenon discovered by Michael Faraday in the 1830s, that is, a conductor will generate an induced electromotive force in a magnetic field where the magnetic flux changes. If the wire is closed, there will be a current in the wire. In the 1890s, American physicist and inventor Nikola Tesla had already proved the feasibility of wireless energy transmission technology on the basis of experiments. The wireless energy transmission scheme conceived by Tesla is: use an amplifying transmitter to transmit electromagnetic waves in a radial oscillation mode between the earth and the ionosphere, the frequency of the electromagnetic waves is 8Hz, the earth can be regarded as an inner conductor, and the earth’s ionosphere can be regarded as The outer conductor, at this time, will produce low-frequency resonance between the earth and the ionosphere. Energy can be transmitted wirelessly using electromagnetic waves that circle the Earth's surface. Although Tesla's plan was not realized in the end, with the development of technology, people have theoretically proved the feasibility of this plan.

With the continuous development of electronic technology, portable electronic devices such as tablet computers and mobile phones have more and more functions, so the power consumption of these devices will also increase. These rich functions of portable electronic devices bring great convenience to our life, and people will use them more and more frequently. Due to the limited capacity of lithium batteries, people charge these devices more and more times, sometimes once a day or even several times a day. At present, the main charging method is wired charging, which requires one end to be connected to an AC power and the other end to be connected to an electronic device that needs to be charged.

Utility model content

The technical problem to be solved by the utility model is to provide a wireless charging system for portable electronic devices, which solves the disadvantages of traditional wired charging such as complex operation, poor flexibility, easy sparks, exposed wires, and easy wear and tear on plug-in parts, and has It has the advantages of high efficiency, safety, simple control and low radiation.

In order to solve the above technical problems, the utility model provides the following technical solutions: a wireless charging system for portable electronic devices, including a wireless charging transmitter and a wireless charging receiver, the wireless charging transmitter includes a power module, a field effect tube drive unit , a full-bridge inverter circuit, a transmitting coil, a main control chip circuit and a signal detection circuit, the power module, a field effect tube drive unit, a full-bridge inverter circuit and a transmitting coil are connected in sequence, and the main control chip is connected to the Power module, signal detection circuit and FET drive unit;

The wireless charging receiving end includes a receiving coil, a full-bridge rectifying circuit, a voltage regulating circuit and a controller unit connected in sequence.

Further, the wireless charging transmitter also includes a temperature detection circuit, a first buzzer and an LED light; the temperature detection circuit, the first buzzer and the LED light are all connected to the main control chip circuit;

The temperature detection circuit is used to detect the operating temperature of the wireless charging system;

The first buzzer is used to give a buzzer alarm when the temperature is too high and to make corresponding buzzers for each charging state;

The LED lights are used to take corresponding flashing indications according to the charging status.

Further, the main control chip circuit includes a main control chip, a power supply indicating circuit, a system status indicating circuit and an ISP program downloading circuit.

Further, the main control chip adopts ATmega328 chip;

The power indicating circuit includes three sets of resistors connected in series and LED lights, wherein one end of the resistors is connected to the VCC interface of the main control chip;

The system state indicating circuit includes a triode, a second buzzer and a resistor, wherein the emitter of the triode is connected to the VCC interface of the main control chip, the base of the triode is connected to a resistor, and the collector of the triode is connected to the second buzzer.

Further, the full-bridge inverter circuit adopts a voltage type inverter circuit, which includes 4 switching devices, capacitor C, inductor L and capacitor C1, and the 4 switching devices are Q1, Q2, Q3 and Q4 respectively; wherein, the switch The devices Q1, Q2, Q3 and Q4 are connected in a closed loop, the capacitor C is connected in series with the inductor L, the other end of the capacitor C is connected to the switching devices Q1 and Q2, the other end of the inductor L is connected to the switching devices Q3 and Q4, and the capacitor C1 is connected to the switching devices Q1 and Q3.

Further, the switching devices Q1, Q2, Q3 and Q4 are all IRF7822 switching devices, and the capacitor C1 is a high-voltage ceramic capacitor.

Further, the field effect transistor drive unit adopts a field effect transistor drive chip TPS28225, and the signal detection circuit includes a current detection circuit and a power supply voltage detection circuit.

Further, the power supply module includes a 5V voltage stabilizing circuit and a 3.3V voltage stabilizing circuit; wherein, the input of the 5V voltage stabilizing circuit is connected to a DC power supply, and the output of the 5V voltage stabilizing circuit is connected to a 3.3V voltage stabilizing circuit and the FET driver unit.

Further, the 5V voltage stabilizing circuit adopts LM2596S-ADJ DC-DC power supply voltage stabilizing circuit, and the 3.3V voltage stabilizing circuit adopts ASM1117 forward low-dropout regulator.

Further, the controller unit adopts TI's wireless power receiving chip BQ51020.

After adopting the above technical solution, the utility model has at least the following beneficial effects: the transmitting end of the wireless charging system of the present invention has over-current, over-voltage, under-voltage and high-temperature protection functions, and is easy to operate and safe to use, and can be applied to mobile phones, tablet computers, etc. For wireless charging of consumer electronics, the charging current can reach up to 1A.

Description of drawings

FIG. 1 is a schematic structural diagram of a wireless charging transmitter in a wireless charging system for a portable electronic device of the present invention;

FIG. 2 is a schematic structural diagram of a wireless charging receiving end in a wireless charging system for a portable electronic device of the present invention;

3 is a schematic circuit diagram of the main control chip circuit in the wireless charging system of the portable electronic device of the present invention;

4 is a schematic circuit diagram of a full-bridge inverter circuit in a wireless charging system for a portable electronic device of the present invention;

5 is a pin diagram of the IRF7822 switch device of the full-bridge inverter circuit in the wireless charging system of the portable electronic device of the present invention;

6 is a pin diagram of the field effect tube driver chip TPS28225 of the wireless charging system of the portable electronic device of the present invention;

7 is a schematic circuit diagram of the current detection circuit in the wireless charging system of the portable electronic device of the present invention;

8 is a schematic circuit diagram of a power supply voltage detection circuit in a wireless charging system for a portable electronic device of the present invention;

9 is a schematic circuit diagram of the temperature detection circuit in the wireless charging system of the portable electronic device of the present invention;

10 is a schematic circuit diagram of a 5V voltage stabilizing circuit in the wireless charging system of the portable electronic device of the present invention;

11 is a schematic circuit diagram of a 3.3V voltage stabilizing circuit in a wireless charging system for a portable electronic device of the present invention;

Fig. 12 is a graph showing the relationship between the efficiency of the BA51020 chip and the output current in the wireless charging system of the portable electronic device of the present invention.

Detailed ways

It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be further described in detail below in conjunction with the drawings and specific embodiments.

Example

The utility model provides a wireless charging system for portable electronic equipment, which mainly includes a wireless charging transmitting end and a wireless charging receiving end, and magnetic resonance wireless energy transmission is performed between the wireless charging transmitting end and the wireless charging receiving end through respective coils , thereby charging portable electronic devices.

As shown in Figure 1, the wireless charging transmitter mainly includes a power module, a field effect transistor drive unit, a full-bridge inverter circuit, a transmitting coil, a main control chip circuit, and a signal detection circuit. Among them, the power module, FET drive unit, full-bridge inverter circuit and transmitting coil are connected in sequence, and the main control chip is connected to the power module, signal detection circuit and FET drive unit; in addition, the wireless charging transmitter also includes a temperature detection circuit, the first buzzer and LED lights; the power supply module is divided into 5V regulator circuit and 3.3V regulator circuit, the input of the 5V regulator circuit is connected to the DC power supply, the output of the 5V regulator circuit is connected to the 3.3V regulator circuit and all The field effect tube drive unit; the signal detection circuit includes a current detection circuit and a power supply voltage detection circuit.

As shown in FIG. 2 , the wireless charging receiving end includes a receiving coil, a full-bridge rectifier circuit, a voltage regulating circuit, and a controller unit connected in sequence.

Each module circuit of the wireless charging transmitter and the wireless charging receiver will be described in detail below.

As shown in FIG. 3 , the main control chip circuit of the wireless charging transmitter of the present invention includes a main control chip, a power supply indicating circuit, a system status indicating circuit and an ISP program downloading circuit. Among them, the main control chip is the ATmega328 chip packaged by Atmel's TQPF. This chip is an 8-bit AVR microprocessor with advanced RISC structure and high performance and low power consumption. It has 32K bytes of in-system programmable Flash, 2K bytes of on-chip SRAM. The power indicating circuit includes three sets of resistors in series and LED lights, wherein one end of the resistors is connected to the VCC interface of the main control chip; the system status indicating circuit includes a triode, a second buzzer and a resistor, wherein the emitter of the triode is connected to the main control chip. The VCC interface of the control chip, the base of the triode is connected to the resistor, and the collector of the triode is connected to the second buzzer.

The LED lights in the above power indicating circuit include a 3mm red LED light, a 5mm red LED light and a green LED light; among them, the 3mm red LED light indicates the connection status of the 3.3V regulated power supply, and the 5mm red LED light and the green LED light indicate charging Status; the second buzzer of the system status indication circuit is also used to indicate the charging status. Since the driving current of the I/O port of the single-chip microcomputer is relatively small, a driving circuit designed with a PNP transistor is used to drive the second buzzer.

The output voltage waveform of the full-bridge inverter circuit in the wireless charging transmitting end of the utility model should not change with the change of the load impedance angle. Comparing the characteristics of the voltage-type inverter circuit and the current-type inverter circuit, the full-bridge inverter circuit is selected to use the voltage-type inverter circuit, as shown in Figure 4. C1 in the figure is a high-voltage ceramic capacitor, which can reduce the pulsation of the input voltage and buffer the reactive energy.

The full bridge inverter circuit can flow a maximum current of 2A. According to the parameters of the field effect tube on the official website of International Rectification Corporation, IRF7822 is selected as the switching device of the full-bridge inverter circuit. IRF7822 is an N-channel enhanced field effect transistor, and a Schottky diode is connected in parallel between the source and the drain. Therefore, each bridge arm of the voltage-type full-bridge inverter circuit composed of IRF7822 does not need additional parallel diodes. The circuit easier.

The IRF7822 pin diagram is shown in Figure 5.

The field effect tube drive unit of the wireless charging transmitting end of the utility model adopts the field effect tube drive chip TPS28225, and the pin diagram of the field effect tube drive chip TPS28225 is shown in FIG. 6 .

The signal detection circuit in the wireless charging transmitter of the utility model includes a current detection circuit and a power supply voltage detection circuit.

Among them, the current detection circuit requires that it does not affect the original current path and has a relatively small impact on the loop. The current detection circuit generally adopts the method of indirect measurement, that is, the voltage drop of the sampling resistor in the current path is measured, and then the voltage value is converted into a current value according to the circuit parameters. In order to reduce the impact of the current detection circuit on the current loop and reduce the power consumption of the sampling circuit, the sampling resistor should be a high-precision resistor with a small resistance, generally several mΩ to several hundred mΩ. Since the sampling resistor is relatively small and the sampling current is not large, the voltage of the sampling resistor needs to be detected by the single-chip analog-to-digital converter through an amplifying circuit built with an op amp.

According to the position between the sampling resistor, ground, power supply, and load, current detection can be divided into two types: low-side current detection and high-side current detection. In the low-side current detection circuit, the load is connected to the positive pole of the power supply, and the sampling resistor is grounded and connected in series with the load. High-end current detection means that the sampling resistor is connected between the power supply and the load. Compared with the low-side current detection circuit, the load is directly connected to the ground, which will improve the reliability of the ground. In the high-end current detection circuit, since the common-mode voltage at both ends of the sampling resistor is high, which is close to the voltage of the op amp power supply, the op amp of the amplifying circuit needs to use a rail-to-rail op amp to amplify the voltage of the sampling resistor.

According to the characteristics of the high-end current detection circuit and the low-end current detection circuit, in order to reduce the impact of the detection circuit on the load, the current detection circuit of the present invention uses a high-end current detection method to detect the current flowing through the full-bridge inverter circuit. The current detection circuit is as follows: Figure 7 shows. In the figure, R8 and C12 form an RC low-pass filter network to suppress high-frequency signals generated by the full-bridge inverter circuit. The magnitude of the current flowing through the sampling resistor in the circuit is That is, I=V*5*10 ² where V is the voltage at both ends of the sampling resistor, and R is the equivalent resistance of R1 and R2 connected in parallel, which is 20mΩ. The magnitude of the voltage at PC1 is V _PC1 =V*(R6/R8), V _PC1 =V*5*10 ² , and I is equal to V _PC1 in value.

In the wireless charging transmitting device of the present invention, the power supply voltage of the full-bridge inverter circuit is 5V. When the voltage is too low, the receiving end will fail to charge due to the low voltage; when the voltage is too high, the components of the wireless charging transmitter and receiver will be damaged due to high voltage. Therefore, it is necessary to detect the input voltage of the power supply to ensure that the input voltage is within a reasonable range. The power supply voltage detection circuit of the signal detection circuit is shown in Figure 8. In the figure, R13 and R14 form a voltage divider circuit, and C15 can filter out the high-frequency harmonics of the power supply. The voltage at PC0 is half of the power supply voltage.

When metals such as keys and coins are placed on the wireless charging transmitter, under the action of a magnetic field, eddy currents will be generated inside the metal, causing the temperature to rise continuously. When the temperature rises to a certain level, there will be a fire hazard. Therefore, the utility model designs a temperature detection circuit to prevent fires caused by excessive temperature at the transmitting end.

The temperature detection circuit uses a negative temperature coefficient thermistor (NTC) as an element to detect temperature. When the temperature decreases, the number of carriers in the metal oxide in the negative temperature coefficient thermistor will decrease, and the conductivity will weaken, so the resistance will increase; when the temperature rises, the number of carriers will increase, and the conductivity will increase. Will increase, so the resistance will become smaller. A thermistor with a resistance value ranging from 100 ohms to 1 megohm can be selected according to the actual usage. The relationship between the resistance of a negative temperature coefficient thermistor and temperature is:

Among them, R _T is the resistance value when the temperature is T, R _N is the resistance value at the rated temperature, B is the material constant of the negative temperature coefficient thermistor, and T _N is the rated temperature. According to the characteristics of NTC resistance changing with temperature, design the temperature detection circuit as shown in Figure 9. Using the analog-to-digital conversion module of the single-chip microcomputer to measure the voltage at PC2 can estimate the temperature value according to the relationship between the resistance value of the negative temperature coefficient thermistor and the voltage.

The power supply module in the utility model includes a 5V voltage stabilizing circuit and a 3.3V voltage stabilizing circuit, wherein the 5V voltage stabilizing circuit adopts the LM2596S-ADJ DC-DC power supply voltage stabilizing circuit, and when in use, adjust the potentiometer to make the output voltage 5V. As shown in FIG. 10 , it is a schematic structural diagram of a 5V voltage stabilizing circuit. In the figure, LM2596 is a step-down switching integrated voltage regulator chip, which can output a maximum current of 3A. The device integrates frequency compensation and a 150KHz fixed switching frequency generator to reduce filter device specifications. When the input voltage and output load are within the specified range, the error of the output voltage will not exceed ±4%, and the error of the oscillation frequency will not exceed ±15%. The integrated voltage stabilizing chip constitutes the step-down circuit and only needs to connect four devices outside, which makes the design of the switching power supply circuit extremely simple.

The 3.3V voltage regulator circuit uses ASM1117 forward low dropout voltage regulator. ASM1117 is a positive low-dropout voltage regulator with current limiting and thermal shutdown functions. 1.2V dropout at 1A; 1% accuracy at a fixed output voltage of 3.3V. The 3.3V regulator circuit is shown in Figure 11.

The controller unit of the wireless charging receiving end of the utility model adopts the wireless power receiving chip BQ51020 of TI. The BQ51020 device is TI's fully enclosed inductor-less receiver for the thinnest solution, featuring a fully synchronous rectifier with up to 96% efficiency and a high-efficiency post regulator with up to 97% efficiency, which can regulate the output voltage ( 4.5 to 8V) for coil and thermal optimization.

The BQ51020 is capable of operating under the WPC v1.1 protocol, which enables wireless power systems to deliver up to 5W of power to the system when used with a Qi inductive transmitter. At 5W, the system efficiency is 79%. With market-leading efficiency and adjustable output voltage, the bq51020 also enables unique efficiency and system optimization. In-device I2C enables system designers to perform functions such as receiver alignment on the transmitter surface, detection of foreign objects on the receiver, and more. It can be applied to devices such as smartphones, tablets and headsets, Wi-Fi hotspots, and power banks.

The output efficiency of the BQ51020 chip is related to the output current. In the range where the output current is less than 1A, the greater the output current, the higher the efficiency. The relationship between BA51020 chip efficiency and output current is shown in Figure 12.

Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various modifications can be made to these embodiments without departing from the principle and spirit of the present invention. For equivalent changes, modifications, substitutions and variations, the scope of the present invention is defined by the appended claims and their equivalents.

Claims (10)

1. A wireless charging system for portable electronic equipment, comprising a wireless charging transmitter and a wireless charging receiver, characterized in that the wireless charging transmitter includes a power module, a field effect tube drive unit, a full-bridge inverter circuit, a transmitter The coil, the main control chip circuit and the signal detection circuit, the power module, the field effect tube drive unit, the full bridge inverter circuit and the transmitting coil are connected in sequence, and the main control chip is connected to the power module, the signal detection circuit and the field Effect tube drive unit; The wireless charging receiving end includes a receiving coil, a full-bridge rectifying circuit, a voltage regulating circuit and a controller unit connected in sequence. 2. The wireless charging system of portable electronic equipment as claimed in claim 1, wherein the wireless charging transmitter also includes a temperature detection circuit, a first buzzer and an LED light; the temperature detection circuit, the first Both the buzzer and the LED light are connected to the main control chip circuit; The temperature detection circuit is used to detect the operating temperature of the wireless charging system; The first buzzer is used to give a buzzer alarm when the temperature is too high and to make corresponding buzzers for each charging state; The LED lights are used to take corresponding flashing indications according to the charging status. 3. The wireless charging system for portable electronic devices according to claim 1, wherein the main control chip circuit comprises a main control chip, a power supply indicating circuit, a system status indicating circuit and an ISP program downloading circuit. 4. The wireless charging system of portable electronic equipment as claimed in claim 3, is characterized in that, described main control chip adopts ATmega328 chip; The power indicating circuit includes three sets of resistors connected in series and LED lights, wherein one end of the resistors is connected to the VCC interface of the main control chip; The system state indicating circuit includes a triode, a second buzzer and a resistor, wherein the emitter of the triode is connected to the VCC interface of the main control chip, the base of the triode is connected to a resistor, and the collector of the triode is connected to the second buzzer. 5. The wireless charging system for portable electronic equipment according to claim 1, wherein the full-bridge inverter circuit adopts a voltage-type inverter circuit, which includes four switching devices, a capacitor C, an inductor L, and a capacitor C1 , the four switching devices are Q1, Q2, Q3 and Q4 respectively; among them, the switching devices Q1, Q2, Q3 and Q4 are connected in a closed loop, the capacitor C is connected in series with the inductor L, and the other end of the capacitor C is connected to the switching devices Q1 and Q2, and the inductor L is another One end is connected to the switching devices Q3 and Q4, and the capacitor C1 is connected to the switching devices Q1 and Q3. 6 . The wireless charging system for portable electronic devices according to claim 5 , wherein the switching devices Q1 , Q2 , Q3 and Q4 are all IRF7822 switching devices, and the capacitor C1 is a high-voltage ceramic capacitor. 7. The wireless charging system for portable electronic devices according to claim 1, wherein the field effect transistor drive unit adopts a field effect transistor drive chip TPS28225, and the signal detection circuit includes a current detection circuit and a power supply voltage detection circuit . 8. The wireless charging system for portable electronic devices according to claim 1, wherein the power module includes a 5V voltage regulator circuit and a 3.3V voltage regulator circuit; wherein, the input of the 5V voltage regulator circuit is connected to a DC power supply, and the 5V voltage regulator circuit The output of the voltage stabilizing circuit is connected with the 3.3V stabilizing circuit and the field effect transistor driving unit. 9. The wireless charging system for portable electronic devices as claimed in claim 8, wherein the 5V regulator circuit adopts LM2596S-ADJ DC-DC power regulator circuit, and the 3.3V regulator circuit adopts ASM1117 forward low dropout voltage regulator. 10. The wireless charging system for portable electronic devices according to claim 1, wherein the controller unit adopts TI's wireless power receiving chip BQ51020.