Wireless charging overvoltage protection system

Abstract

This invention relates to a wireless charging overvoltage protection system, comprising a power supply, a transmitter module, a receiver module, and a load connected in sequence. The receiver module is equipped with a post-bridge overvoltage protection unit, which includes a protection circuit, a rectifier circuit, a detection circuit, a comparator circuit, and an isolation trigger circuit connected in sequence to form a loop. The rectifier circuit is used to acquire the post-bridge voltage; the detection circuit is used to detect the post-bridge voltage and divide it; the comparator circuit is used to compare the divided voltage with a preset reference voltage and output a corresponding level signal; the isolation trigger circuit is used to turn the protection circuit on or off according to the level signal output by the comparator circuit. Compared with the prior art, this invention can protect the circuit in a timely manner when the receiver voltage is too high, and the protection period is long and timely.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wireless charging technology, in particular to a wireless charging overvoltage protection system. BACKGROUND

[0002] Wireless charging technology has now become mature, and due to the reliability, safety and non-contact characteristics of wireless charging technology, it is applied in more and more occasions, and is constantly changing people's life and production mode. Wireless charging technology includes wireless charging transmitting end and receiving end, and energy is transmitted through magnetic field by transmitting coil and receiving coil, but when the voltage received by the receiving end is too high, the components will be damaged, and the overvoltage protection technology of the receiving end is very important.

[0003] When the distance between the receiving coil and the transmitting coil is different, or the load of the receiving end is different, the voltage will have a large range of change, such as from the heaviest load to the lightest load, or from the farthest coil to the closest coil, which will cause the voltage to rise sharply and cause damage to the components. Based on the protection of the circuit, the common method is to cut off the power supply circuit, start the auxiliary power supply circuit or consume energy with the protection device to achieve it.

[0004] The application number is CN202120243078.1, the application date is January 28, 2021, and the invention patent discloses a wireless charging overvoltage protection device and system. The patent forms a new receiving end resonance circuit by the MOS tube switch and the capacitor overvoltage detection module, which makes the output voltage of the receiving end not too high. But the circuit of this patent is more complex.

[0005] The application number is CN201610759372.1, the application date is August 30, 2016, and the invention patent discloses a wireless charging receiving end overvoltage protection circuit and overvoltage protection method. The patent sets up a standby capacitor that can be selectively accessed in the resonance matching network, and when the voltage amplitude exceeds the threshold value, the standby capacitor is accessed to the network, so that the frequency point of the receiving coil deviates from the working frequency point of the transmitting coil, and then the charging voltage is reduced. The patent accesses the standby circuit, which has a delay in protection, and the circuit is more complex. SUMMARY

[0006] The purpose of the present application is to overcome the defects of the prior art and provide a wireless charging overvoltage protection system. The application can protect the circuit in time when the voltage of the receiving end is too high, and the protection period is long and timely.

[0007] The purpose of the present application can be achieved by the following technical solutions:

[0008] The application provides a wireless charging overvoltage protection system, which comprises a power supply, a transmitting end module, a receiving end module and a load connected in sequence, the receiving end module is provided with a post-bridge overvoltage protection unit, and the post-bridge overvoltage protection unit comprises a protection circuit, a rectifier circuit, a detection circuit, a comparison circuit and an isolation trigger circuit connected in sequence to form a loop.

[0009] The rectifier circuit is used to obtain a post-bridge voltage.

[0010] The detection circuit is used to detect the post-bridge voltage and divide the post-bridge voltage.

[0011] The comparison circuit is used to compare the divided voltage with a preset reference voltage, and then output a corresponding level signal.

[0012] The isolation trigger circuit is used to turn on or turn off the protection circuit according to the level signal output by the comparison circuit.

[0013] Preferably, the receiving end module further comprises a receiving end coil and a second voltage adjusting circuit, the receiving end coil is connected to the protection circuit, and the second voltage adjusting circuit is connected to the load.

[0014] Preferably, the isolation trigger circuit comprises a monostable multivibrator and an optocoupler, an input end of the monostable multivibrator is connected to an output end of the comparison circuit, two input ends of the optocoupler are connected to an output end of the monostable multivibrator and a power supply respectively, one output end of the optocoupler is connected to an output end of the protection circuit, and the other output end is connected to an isolation power supply.

[0015] Preferably, the protection circuit comprises a first MOS tube and a second MOS tube, one output end of the optocoupler is connected to a gate of the first MOS tube and a gate of the second MOS tube, a source of the first MOS tube and a source of the second MOS tube are connected, the source of the first MOS tube and the source of the second MOS tube are connected to a first isolation power supply, and a drain of the first MOS tube and a drain of the second MOS tube are connected to two ends of the receiving end coil.

[0016] Preferably, the protection circuit comprises a diode and a third MOS tube, one output end of the optocoupler is connected to a gate of the third MOS tube, a negative electrode of the diode is connected to a drain of the third MOS tube, a source of the third MOS tube is connected to a second isolation power supply, and the source of the third MOS tube and a positive electrode of the diode are connected to two ends of the receiving end coil.

[0017] Preferably, the protection circuit includes a fourth MOSFET and a fifth MOSFET. The drains of the fourth MOSFET and the fifth MOSFET are connected. The gates of the fourth MOSFET and the fifth MOSFET are each connected to an optocoupler. Each optocoupler is connected to an isolation power supply. The sources of the fourth MOSFET and the fifth MOSFET are respectively connected to a fourth isolation power supply and a fifth isolation power supply. The sources of the fourth MOSFET and the fifth MOSFET are connected to the two ends of the receiving coil.

[0018] Preferably, a current-limiting resistor is provided between the optocoupler and the power supply, and between the optocoupler and the isolation power supply.

[0019] Preferably, the transmitter module includes a PFC circuit, a first voltage adjustment circuit, an inverter circuit, and a transmitter coil connected in sequence, and the transmitter coil is connected to the receiver coil.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. The wireless charging overvoltage protection system provided by the present invention sets up a post-bridge overvoltage protection unit between the connection between the receiving coil and the load. After the receiving coil receives the energy transmitted by the transmitting coil, it passes through the rectifier circuit, detection circuit, comparison circuit and isolation trigger circuit in sequence. The protection circuit then short-circuits the post-bridge overvoltage protection unit, the second voltage adjustment circuit and the load. The protection is timely and the circuit is simple. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a wireless charging overvoltage protection system provided in this embodiment.

[0023] Figure 2 for Figure 1 The protection circuit shown in the embodiment is a schematic diagram of the overvoltage protection unit after the bridge in Embodiment 1.

[0024] Figure 3 for Figure 2 The circuit connection diagram of the protection circuit in the embodiment shown is illustrated.

[0025] Figure 4 for Figure 1 The protection circuit shown in the embodiment is a schematic diagram of the overvoltage protection unit after the bridge in Embodiment 2.

[0026] Figure 5 for Figure 4 The circuit connection diagram of the protection circuit in the embodiment shown is illustrated.

[0027] Figure 6 for Figure 1The protection circuit shown in the embodiment is a schematic diagram of the overvoltage protection unit after the bridge in Embodiment 3.

[0028] Figure 7 for Figure 6 The circuit connection diagram of the protection circuit in the embodiment shown is illustrated.

[0029] Figure 8 for Figure 1 The circuit connection diagram of the rectifier circuit, detection circuit, comparison circuit and isolation trigger circuit in the embodiment shown is illustrated. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0031] Example

[0032] refer to Figure 1 As shown, this embodiment provides a wireless charging overvoltage protection system that protects the receiving circuit with a protection speed of a few μs to tens of μs to better prevent damage to components caused by excessive receiving voltage. The system includes: a power supply, a transmitter module, a receiver module, and a load connected in sequence; wherein the transmitter module includes a PFC circuit, a first voltage adjustment circuit, an inverter circuit, and a transmitter coil connected in sequence; the receiver module includes a receiver coil, a post-bridge overvoltage protection unit, and a second voltage adjustment circuit connected in sequence; the transmitter coil is connected to the receiver coil; and the voltage adjustment circuit is connected to the load.

[0033] refer to Figure 2 As shown, the overvoltage protection unit after the bridge includes a protection circuit, a rectifier circuit, a detection circuit, a comparator circuit, and an isolation trigger circuit connected in sequence to form a loop. The protection circuit is connected to the receiving coil, and the isolation trigger circuit is connected to the protection circuit.

[0034] The rectifier circuit is used to obtain the voltage after the bridge;

[0035] The detection circuit is used to detect the voltage after the bridge and divide the voltage after the bridge.

[0036] The comparator circuit is used to compare the voltage after voltage division with the preset reference voltage, and then output the corresponding level signal;

[0037] The isolation trigger circuit is used to turn the protection circuit on or off according to the level signal output by the comparison circuit.

[0038] Specifically, both the first voltage adjustment circuit and the second voltage adjustment circuit adopt DC-DC voltage adjustment circuit, the inverter circuit adopts DC-AC inverter circuit, and the rectifier circuit adopts AC-DC rectifier circuit.

[0039] The isolation trigger circuit includes a monostable oscillator and an optocoupler. The input terminal of the monostable oscillator is connected to the output terminal of the comparator circuit. The two input terminals of the optocoupler are connected to the output terminal of the monostable oscillator and the power supply, respectively. The two output terminals of the optocoupler are connected to the output terminal of the protection circuit and the isolation power supply, respectively. The detection circuit, the comparator circuit, and the monostable oscillator are all connected to the power supply.

[0040] As an optional implementation, current-limiting resistors are provided between the optocoupler and the power supply, as well as between the optocoupler and the isolation power supply.

[0041] Specifically, refer to Figure 8 As shown, the rectifier circuit includes multiple rectifier diodes, and the detection circuit includes multiple voltage divider resistors. One end of the voltage divider resistor is connected to the rectifier diode, and the other end of the voltage divider resistor is connected to the comparator circuit.

[0042] Working principle: When the receiving coil receives the energy transmitted by the transmitting coil, it is rectified by the rectifier circuit to generate a bridge voltage. The bridge voltage enters the detection circuit, which detects and divides the bridge voltage before it enters the comparator circuit. The comparator circuit compares the divided voltage with the reference voltage. When the divided voltage exceeds the reference voltage, it indicates that the amplitude of the bridge voltage is high. The output of the comparator circuit changes from high level to low level, i.e., a falling edge is generated. This falling edge is connected to the falling edge trigger terminal of the monostable oscillator.

[0043] When a monostable oscillator receives a falling edge signal, its output changes from low to high. The duration of the high level can be adjusted by the delay capacitor and the delay resistor. After the monostable oscillator outputs a high level, it triggers the optocoupler to conduct. After the optocoupler conducts, it triggers the protection circuit to conduct, which short-circuits the overvoltage protection unit after the bridge, the second voltage adjustment circuit, and the load. This causes the resonant circuit at the receiving end to detune, thereby reducing the induced voltage to ensure that the voltage of the entire system is not too high and will not damage the components.

[0044] The protection circuit includes a first switching transistor and a second switching transistor. There are various implementation methods for the first and second switching transistors in terms of components. The following is a detailed description of each implementation method:

[0045] Implementation Method 1: Reference Figure 2 and Figure 3 As shown, the first switching transistor is a first MOSFET, the second switching transistor is a second MOSFET, one output terminal of the optocoupler is connected to the gate of the first MOSFET and the gate of the second MOSFET, the source of the first MOSFET is connected to the source of the second MOSFET, the source of the first MOSFET and the source of the second MOSFET are connected to a +12V first isolation power supply, and the drain of the first MOSFET and the drain of the second MOSFET are connected to the two ends of the receiving coil.

[0046] Working principle: After the monostable oscillator circuit triggers the optocoupler to conduct, the gates and sources of the first and second MOSFETs are both subjected to positive voltages, which in turn turns the two MOSFETs on, short-circuiting the overvoltage protection unit after the bridge, the second voltage adjustment circuit and the load. The total output power of the entire system drops sharply. The transmitter module detects the power change and shuts down, ensuring the safety and stability of the system.

[0047] Implementation Method Two: Reference Figure 4 and Figure 5 As shown, the first switching transistor is a diode, the second switching transistor is a third MOSFET, the cathode of the diode is connected to the drain of the third MOSFET, one output terminal of the optocoupler is connected to the gate of the third MOSFET, and the +12V second isolation power supply is connected to the source of the third MOSFET. The source of the third MOSFET and the anode of the diode are connected to the two ends of the receiving coil.

[0048] When the optocoupler receives a protection signal from the monostable oscillator circuit, the first isolation power supply connected to the optocoupler is turned on, causing the source and gate of the third MOSFET to experience a forward voltage. This turns on the third MOSFET, short-circuiting the overvoltage protection unit after the bridge, the second voltage adjustment circuit, and the load. The diode short-circuits half of the AC waveform, preventing that half-wave from passing through.

[0049] Implementation Method 3: Reference Figure 6 and Figure 7 As shown, the first switching transistor is the fourth MOSFET, and the second switching transistor is the fifth MOSFET. The drains of the fourth and fifth MOSFETs are connected. The sources of the fourth and fifth MOSFETs are connected to the fourth and fifth isolation power supplies, respectively. Each of the fourth and fifth MOSFETs is connected to an optocoupler. The outputs of both optocouplers are connected to an isolation power supply, and the inputs of both optocouplers are connected to a monostable oscillator. The sources of the fourth and fifth MOSFETs are connected to the two ends of the receiving coil.

[0050] The difference between this implementation method and the second implementation method is that the positions of the source and drain of the two MOSFETs are swapped. Since the positions of the source and drain are swapped, it is not possible to use the same power supply to apply positive voltage to the gate and drain of the two MOSFETs. Therefore, two 12V isolated power supplies are needed to apply positive voltage to the gate and drain of the two MOSFETs respectively to make them conduct, so as to short-circuit the overvoltage protection unit after the bridge, the second voltage adjustment circuit and the load when the voltage at the receiving end is too high.

[0051] When using the second implementation method, due to the presence of the diode, only half of the coil input AC waveform is short-circuited, while the other half can still be transmitted to the back-end circuit through the resonant capacitor. Although the voltage generated at this time is theoretically half that of the circuit without protection, it can protect the circuit devices in most cases. However, in some extreme cases, it may still cause the system to be unstable. In this case, it is necessary to completely short-circuit the overvoltage protection unit after the bridge, the second voltage adjustment circuit, and the load.

[0052] One approach is to replace the diodes with MOSFETs. The overvoltage after the bridge causes both MOSFETs to conduct simultaneously, short-circuiting the overvoltage protection unit, the second voltage adjustment circuit, and the load. The voltage after the bridge becomes very low, and the system protects the receiver circuit by shutting down the power supply to the transmitter.

[0053] Alternatively, implementation method three can be adopted: replace the diodes with MOSFETs, and add a MOSFET control signal. Overvoltage after the bridge causes both MOSFETs to conduct simultaneously. The protection signal is simultaneously received by the optocouplers, and both 12V isolation power supplies of the two optocouplers are turned on, so that the source and gate of the two MOSFETs are subjected to positive voltage, thereby turning on both MOSFETs and short-circuiting the overvoltage protection unit after the bridge, the second voltage adjustment circuit, and the load.

[0054] The first MOSFET in Implementation 1 has its source and the second MOSFET connected together, which is the best implementation in this embodiment. This implementation can completely isolate the circuit and only requires one isolated power supply to drive it. The diode in Implementation 2 may allow general AC to pass through the system, resulting in incomplete conduction and turn-off, but it can still achieve the purpose. The fourth MOSFET in Implementation 3 has its drain and the fifth MOSFET connected together, which can completely isolate the circuit, but requires two independent isolated power supplies to drive it, increasing the cost.

[0055] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A wireless charging overvoltage protection system, comprising a power supply, a transmitter module, a receiver module, and a load connected in sequence, characterized in that, The receiving module is equipped with a post-bridge overvoltage protection unit, which includes a protection circuit, a rectifier circuit, a detection circuit, a comparator circuit, and an isolation trigger circuit connected in sequence to form a loop. The rectifier circuit is used to obtain the voltage after the bridge. The detection circuit is used to detect the voltage after the bridge and divide the voltage after the bridge. The comparison circuit is used to compare the voltage after voltage division with the preset reference voltage, and then output the corresponding level signal; The isolation trigger circuit is used to turn the protection circuit on or off according to the level signal output by the comparison circuit; The receiving module further includes a receiving coil and a second voltage adjustment circuit. The receiving coil is connected to the protection circuit, and the second voltage adjustment circuit is connected to the load. The isolation trigger circuit includes a monostable oscillator and an optocoupler. The input terminal of the monostable oscillator is connected to the output terminal of the comparator circuit. The two input terminals of the optocoupler are respectively connected to the output terminal of the monostable oscillator and the power supply. One output terminal of the optocoupler is connected to the output terminal of the protection circuit, and the other output terminal is connected to the isolation power supply. The working process of the protection system is as follows: When the receiving coil receives the energy transmitted by the transmitting coil, it is rectified by the rectifier circuit to generate a bridge voltage. The bridge voltage enters the detection circuit, which detects and divides the bridge voltage before it enters the comparator circuit. The comparator circuit compares the divided voltage with the reference voltage. When the divided voltage exceeds the reference voltage, it indicates that the amplitude of the bridge voltage is high. The output of the comparator circuit changes from high level to low level, i.e., a falling edge is generated. This falling edge is connected to the falling edge trigger terminal of the monostable oscillator. After receiving a falling edge signal, the output of the monostable oscillator changes from low to high. The duration of the high level can be adjusted by the delay capacitor and the delay resistor. After the monostable oscillator outputs a high level, it triggers the optocoupler to conduct. After the optocoupler conducts, it triggers the protection circuit to conduct, which causes the protection circuit to short-circuit the overvoltage protection unit after the bridge, the second voltage adjustment circuit and the load, causing the resonant circuit at the receiving end to detune.

2. The wireless charging overvoltage protection system according to claim 1, characterized in that, The protection circuit includes a first MOSFET and a second MOSFET. One output terminal of the optocoupler is connected to the gate of the first MOSFET and the gate of the second MOSFET. The source of the first MOSFET and the source of the second MOSFET are connected. The source of the first MOSFET and the source of the second MOSFET are connected to a first isolation power supply. The drain of the first MOSFET and the drain of the second MOSFET are connected to the two ends of the receiving coil.

3. The wireless charging overvoltage protection system according to claim 1, characterized in that, The protection circuit includes a diode and a third MOSFET. One output terminal of the optocoupler is connected to the gate of the third MOSFET. The cathode of the diode is connected to the drain of the third MOSFET. The source of the third MOSFET is connected to a second isolation power supply. The source of the third MOSFET and the anode of the diode are connected to the two ends of the receiving coil.

4. The wireless charging overvoltage protection system according to claim 1, characterized in that, The protection circuit includes a fourth MOSFET and a fifth MOSFET. The drains of the fourth MOSFET and the fifth MOSFET are connected. The gates of the fourth MOSFET and the fifth MOSFET are each connected to an optocoupler. Each optocoupler is connected to an isolation power supply. The sources of the fourth MOSFET and the fifth MOSFET are respectively connected to a fourth isolation power supply and a fifth isolation power supply. The sources of the fourth MOSFET and the fifth MOSFET are connected to the two ends of the receiving coil.

5. The wireless charging overvoltage protection system according to claim 1, characterized in that, A current-limiting resistor is provided between the optocoupler and the power supply, and between the optocoupler and the isolation power supply.

6. The wireless charging overvoltage protection system according to claim 1, characterized in that, The transmitter module includes a PFC circuit, a first voltage adjustment circuit, an inverter circuit, and a transmitter coil connected in sequence, and the transmitter coil is connected to the receiver coil.

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