Wireless charging system and control method thereof

Abstract

The present application relates to a kind of wireless charging system and its control method, belong to new energy wireless charging technical field.Control method includes: in the soft start process of wireless charging system, the phase shift angle of control transmitting coil side inverter and the phase shift angle of receiving coil side rectifier gradually reduce to 0;And in the reducing process, the phase shift angle of control rectifier=m*the phase shift angle of inverter, m>1;The phase shift angle of the inverter is the on-time difference of switch pipe of same group conduction in one control period of inverter, and the phase shift angle of the rectifier is the on-time difference of switch pipe of same group conduction in one control period of rectifier.The present application controls the phase shift angle of inverter and the phase shift angle of rectifier gradually reduce to 0 in the soft start process;And in the reducing process, the phase shift angle of rectifier is always equal to m times the phase shift angle of inverter, reduce the temperature rise of power device, solve the phenomenon of power device overheating.

Description

Technical Field

[0001] This invention relates to a wireless charging system and its control method, belonging to the field of new energy wireless charging technology. Background Technology

[0002] With the development of charging technology, low-power wireless charging technology is now widely used in daily life. High-end mobile phones are basically equipped with wireless charging. As wireless charging technology develops, its advantages such as convenience and safety have been gradually accepted by the market, and cars equipped with wireless charging systems have emerged.

[0003] In wireless charging systems, there are currently several topologies: SS, PP, LCL-LCL, and LCC-LCC. Because LCC-LCC has a constant current source output characteristic, its output current does not change with the output voltage, combining the advantages of SS and PP, making it a superior choice. In dual-sided LCC systems, the secondary-side control method is divided into active control and passive control. Compared to passive control, active control allows the secondary side to be controlled independently, without relying on communication, and can output normally, offering better control performance. The disadvantage is that it requires additional control circuitry on the secondary side, making the control method more complex than passive control.

[0004] In wireless charging systems based on active control dual-sided LCC, a high temperature rise often occurs in the power devices on one side (primary or secondary side) when the system is under no-load or light-load conditions (no-load means the system load is 0; light-load means the system load is small and has not yet reached full load). Summary of the Invention

[0005] The purpose of this application is to provide a wireless charging system and its control method to solve the problem of high temperature rise in existing wireless charging methods under no-load or light-load conditions.

[0006] To achieve the above objectives, this application proposes a technical solution for a control method of a wireless charging system, comprising the following steps:

[0007] During the soft-start process of the wireless charging system, the phase shift angle of the inverter on the transmitting coil side and the phase shift angle of the rectifier on the receiving coil side are gradually reduced to 0; and during the reduction process, the phase shift angle of the rectifier is controlled to be m * the phase shift angle of the inverter, where m > 1; the phase shift angle of the inverter is the conduction time difference of the switching transistors in the same group within one control cycle of the inverter, and the phase shift angle of the rectifier is the conduction time difference of the switching transistors in the same group within one control cycle of the rectifier.

[0008] In addition, this application also proposes a technical solution for a wireless charging system. The wireless charging system includes a transmitter, a receiver, and a controller. The transmitter includes an inverter and a transmitting coil, and the receiver includes a receiving coil and a rectifier. The input terminal of the inverter is used to connect to a DC bus, and the output terminal of the inverter is connected to the transmitting coil. The receiving coil is connected to the input terminal of the rectifier, and the output terminal of the rectifier is used to connect to a power battery. Resonant circuits are provided between the inverter and the transmitting coil, and between the receiving coil and the rectifier. The controller controls the connection between the inverter and the rectifier. The controller includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the control method of the wireless charging system described above.

[0009] The beneficial effects of the wireless charging system and its control method of the present invention are as follows: Based on the study of the phenomenon of high temperature rise of power devices under no-load and light-load conditions, it was found that the temperature rise was caused by the inappropriate control of the phase shift angle of the power devices. Through simulation of the wireless charging system, it was found that when the phase shift angle of the rectifier is a multiple of the set phase shift angle of the inverter, the temperature rise of the power devices is lower. Therefore, the present invention reduces the temperature rise of the power devices and solves the problem of overheating of the power devices by controlling the phase shift angle of the inverter and the phase shift angle of the rectifier to gradually decrease to 0 during the soft start process; and by controlling the phase shift angle of the rectifier to be always equal to m times the phase shift angle of the inverter during the reduction process.

[0010] Furthermore, in the aforementioned wireless charging system and its control method, in order to reduce the temperature rise of the resonant circuit, during the soft-start process, if the output voltage of the rectifier reaches the voltage set value, the resonant current on the transmitting coil side and the output voltage of the inverter and / or the resonant current on the receiving coil side and the output voltage of the rectifier are detected; if the phase difference between any resonant current and its corresponding output voltage exceeds the set range, the conduction angle of the rectifier is adjusted so that the phase difference is controlled within the set range, wherein the conduction angle is π-Φ, and Φ is the conduction time difference between the inverter and the rectifier within the same control cycle.

[0011] Furthermore, in the aforementioned wireless charging system and its control method, if the phase of any resonant current leads the phase of its corresponding output voltage outside the set phase range, the conduction angle of the rectifier is increased to keep the phase difference within the set range; if the phase of any resonant current lags the phase of its corresponding output voltage outside the set phase range, the conduction angle of the rectifier is decreased to keep the phase difference within the set range.

[0012] Furthermore, in order to ensure the normal operation of the wireless charging system and its control method, a self-test step of the wireless charging system is included before the soft start. If the wireless charging system malfunctions, an alarm will be triggered.

[0013] Furthermore, in the aforementioned wireless charging system and its control method, m is less than 3.

[0014] Furthermore, in the aforementioned wireless charging system and its control method, the system begins a soft start when the DC bus voltage reaches the set bus voltage value.

[0015] Furthermore, in the above wireless charging system, the resonant circuit is an LCC resonant circuit.

[0016] Furthermore, the wireless charging system described above also includes a PFC power corrector, with the input terminal of the inverter connected to the output terminal of the PFC power corrector, and the input terminal of the PFC power corrector connected to a three-phase power supply.

[0017] Furthermore, in the aforementioned wireless charging system, the inverter is a full-bridge inverter. Attached Figure Description

[0018] Figure 1 This is a structural block diagram of the wireless charging system of the present invention;

[0019] Figure 2 This is a circuit diagram of the inverter and rectifier of the present invention;

[0020] Figure 3 This is a flowchart of the control method for the wireless charging system of the present invention;

[0021] Figure 4 This is the control timing diagram of the inverter of the present invention;

[0022] Figure 5 This is the control timing diagram of the rectifier of the present invention. Detailed Implementation

[0023] Wireless charging system example:

[0024] The main concept of this invention is based on the problem of heat generation in switching devices during soft start. Research has shown that the temperature rise is caused by inappropriate control of the phase shift angle of the power devices. Through simulation of a wireless charging system, it was found that when the phase shift angle of the rectifier is a multiple of the phase shift angle of the inverter, the temperature rise of the power devices is lower. Therefore, this invention controls the phase shift angle of the rectifier to a multiple of the phase shift angle of the inverter during soft start, accurately controlling the phase shift angle and improving the heat generation phenomenon.

[0025] Wireless charging systems such as Figure 1 , Figure 2 As shown, the wireless charging system adopts a bilateral LCC topology and includes a transmitter, a receiver, and a controller.

[0026] The transmitter includes a PFC power corrector, an inverter, and a transmitting coil. The input of the PFC power corrector is connected to a three-phase power supply, the output of the PFC power corrector is connected to the input of the inverter, the output of the inverter is connected to the transmitting coil L3, and a first resonant circuit is provided between the output of the inverter and the transmitting coil L3.

[0027] The inverter is a full-bridge inverter, including a first filter circuit and a first full-bridge circuit. The first filter circuit includes capacitors C1 and C2. The first full-bridge circuit includes switching transistors Q1, Q2, Q3, and Q4. Switches Q1 and Q4 are connected in the same group; switches Q2 and Q3 are connected in the same group. The first resonant circuit includes inductor L1, capacitor C3, and capacitor C4.

[0028] The receiving end includes a receiving coil L4 and a rectifier. The receiving coil L4 is connected to the input terminal of the rectifier, and the output terminal of the rectifier is used to connect to the power battery. A second resonant circuit is provided between the receiving coil L4 and the rectifier.

[0029] The rectifier includes a second full-bridge circuit and a second filter circuit. The second full-bridge circuit includes switching transistors Q5, Q6, Q7, and Q8; switching transistors Q5 and Q8 are in the same group of conducting transistors; switching transistors Q6 and Q7 are in the same group of conducting transistors. The second filter circuit includes capacitors C7 and C8. The second resonant circuit includes capacitors C5 and C6 and inductor L2.

[0030] The controller controls the inverter and rectifier. The controller includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the control method for the wireless charging system. The controller of this invention can be a single controller, or it can include two control units respectively located inside the rectifier and inverter. Both control units are equipped with wireless communication modules, communicating wirelessly to implement the control method of this invention. This invention does not limit the specific structure of the controller.

[0031] Control methods of wireless charging systems, such as Figure 3 As shown, it includes the following steps:

[0032] 1) The wireless charging system is powered on and performs a self-test.

[0033] The self-test includes checking whether the drive waveforms of switching transistors Q1, Q2, Q3, Q4, Q5, Q6, Q7, and Q8 are normal. If not, there is an abnormality in the drive, and the abnormality is eliminated.

[0034] 2) The system is normal and three-phase power is supplied. Start the PFC power corrector and determine whether soft start is possible by the output voltage Vin of the PFC power corrector.

[0035] The PFC power corrector is used to convert three-phase electricity into DC electricity. The output voltage Vin of the PFC power corrector (also known as the DC bus voltage Vin) is input into the inverter.

[0036] 3) When the output voltage Vin of the PFC power corrector is equal to the DC bus voltage setting value, the system begins soft start.

[0037] 4) During the soft start process, the phase shift angles of the inverter and rectifier are gradually reduced from 180°; and during the reduction process, the phase shift angle of the rectifier = m * the phase shift angle of the inverter, where m > 1.

[0038] The phase shift angle of an inverter is the time difference between the turn-on of the switching transistors in the same group within one control cycle of the inverter. The phase shift angle of a rectifier is the time difference between the turn-on of the switching transistors in the same group within one control cycle of the rectifier.

[0039] Since switching transistors Q1 and Q4 are in the same group of conduction; switching transistors Q2 and Q3 are in the same group of conduction; switching transistors Q5 and Q8 are in the same group of conduction; and switching transistors Q6 and Q7 are in the same group of conduction, and the conduction sequence of the switching transistors in one control cycle of the inverter is as follows: Figure 4 The following are the switching transistors: Q1, Q4, Q2, and Q3; the conduction sequence of the switching transistors in one control cycle of the rectifier is as follows: Figure 5 The following are the switching transistors: Q5, Q8, Q6, and Q7. Therefore, adjusting the phase shift angle of the inverter is equivalent to adjusting the conduction time of switching transistors Q3 and Q4, and adjusting the phase shift angle of the rectifier is equivalent to adjusting the conduction time of switching transistors Q7 and Q8.

[0040] from Figure 4 As can be seen from this, the phase shift angle of the inverter is 'a', meaning that switch Q4 conducts a time interval 'a' behind switch Q1. Figure 5 It can be seen that the phase shift angle of the rectifier is b, that is, the switching transistor Q8 conducts b time intervals after the switching transistor Q5. In this invention, during the soft start process, the phase shift angles a and b are gradually reduced from 180°, and a = m * b, where m > 1. The value of m is not the same for different inverters and rectifiers, but 1 < m < 3. For the double-sided LCC topology in this embodiment, experiments show that when m = 1.5, the heat generation problem can be better solved.

[0041] During the soft-start process, the rectifier's output voltage Vout gradually reaches the set voltage value. When the rectifier's output voltage Vout reaches the set voltage value, the resonant current I0 on the transmitting coil side and the inverter's output voltage U0 are detected. The phase difference between the inverter's output voltage U0 and the resonant current I0 is determined, and the rectifier's conduction angle θ (that is, the conduction angle of the secondary power device; the rectifier is the primary power device) is adjusted based on the phase difference to ensure that the phase difference is within the set range.

[0042] If the phase of the resonant current I0 leads the phase of the inverter's output voltage U0 outside the set range, the system is in the capacitive region. The conduction angle θ of the control rectifier is increased to keep the phase difference within the set range.

[0043] If the phase of the resonant current I0 lags behind the phase setting range of the inverter's output voltage U0, the system is in the inductive region. The conduction angle θ of the rectifier is reduced to keep the phase difference within the set range.

[0044] By adjusting the conduction angle θ, the phase relationship between the inverter's output voltage U0 and resonant current I0 is improved, reducing the resonant current and coil current, and lowering the temperature rise of the resonant inductor and coil. When the phase difference between the inverter's output voltage U0 and resonant current I0 is within a set range, the system is in a resonant state, with minimum current and minimum reactive power.

[0045] Based on the synchronous changes of the resonant current I0 on the transmitting coil side, the inverter's output voltage U0, the resonant current I1 on the receiving coil side, and the rectifier's output voltage U1 (Vout and U1 are numerically different, but both are the rectifier's output voltages; Vout is U1 plus two parallel capacitors C7 and C8), the conduction angle can be adjusted by detecting the resonant current I1 on the receiving coil side and the rectifier's output voltage U1. Alternatively, the output voltages and resonant currents on both sides can be detected simultaneously. If the phase difference on either side exceeds the set range, the conduction angle is adjusted. The adjustment process is the same and will not be elaborated here. The rectifier's conduction angle θ is π-Φ. In practice, adjusting the conduction angle θ is achieved by changing the control angle Φ, such as... Figure 5 As shown, the control angle Φ is the difference in conduction time between the inverter and the rectifier within the same control cycle, that is, the difference in conduction time between switching transistors Q1 and Q5, which causes the conduction time of switching transistor Q5 to lag behind the conduction time of switching transistor Q1 by a time interval Φ.

[0046] 5) As the load increases, the phase shift angle α of the inverter and the phase shift angle b of the rectifier decrease to 0, the startup is complete, and full-load charging begins.

[0047] In this step, although the phase shift angle 'a' of the inverter and the phase shift angle 'b' of the rectifier are multiples of each other, in the actual adjustment process, the phase shift angle 'a' of the inverter is first reduced to 0. Then, the phase shift angle 'b' of the rectifier can be adjusted separately to control the current output. When both the phase shift angles of the inverter and the rectifier are 0, it is also necessary to increase the DC bus voltage Vin to improve the load-carrying capacity and finally achieve system balance.

[0048] In the above embodiments, controlling the phase shift angle α of the inverter and the phase shift angle b of the rectifier to be a multiple relationship can not only reduce the heating phenomenon of power devices, but also reduce the phase difference between the resonant current I0 on the transmitting coil side and the output voltage U0 of the inverter. Therefore, the conduction angle θ is only adjusted when the phase difference is still large and exceeds the set range during the phase shift angle adjustment process. Thus, the adjustment of the conduction angle θ is generally carried out in the later stage of soft start, and the soft start is basically completed when the phase difference adjustment is within the set range.

[0049] The control method of the present invention is not limited to wireless charging systems with a bilateral LCC topology, but is also applicable to wireless charging systems with a bilateral LCC topology, and has a wide range of applications.

[0050] This invention does not limit the specific structure of the inverter and rectifier, as long as the control method of this invention can be used to achieve the corresponding effect.

[0051] This invention controls the phase shift angle of the rectifier to be a multiple of the phase shift angle of the inverter, which can solve the system oscillation caused by frequent adjustment of the phase shift angle, reduce the voltage and current phase difference, reduce the temperature rise of power devices under light load, reduce the loss of power devices, and optimize the working state of the wireless charging system.

[0052] Example of a control method for a wireless charging system:

[0053] The specific implementation process and effects of the control method of the wireless charging system have been described in the above wireless charging system embodiments, and will not be repeated here.

Claims

1. A control method for a wireless charging system, characterized in that, Includes the following steps: During the soft-start process of the wireless charging system, the phase shift angle of the inverter on the transmitting coil side and the phase shift angle of the rectifier on the receiving coil side are gradually reduced to 0; and during the reduction process, the phase shift angle of the rectifier is controlled to be m * the phase shift angle of the inverter, where m > 1; the phase shift angle of the inverter is the conduction time difference of the switching transistors in the same group within one control cycle of the inverter, and the phase shift angle of the rectifier is the conduction time difference of the switching transistors in the same group within one control cycle of the rectifier. Furthermore, during the soft-start process, if the rectifier's output voltage reaches the set voltage value, the resonant current on the transmitting coil side and the inverter's output voltage and / or the resonant current on the receiving coil side and the rectifier's output voltage are detected; if the phase difference between any resonant current and its corresponding output voltage exceeds the set range, the rectifier's conduction angle is adjusted so that the phase difference is controlled within the set range. The conduction angle is π-Φ, where Φ is the conduction time difference between the inverter and the rectifier within the same control cycle.

2. The control method for the wireless charging system according to claim 1, characterized in that, The resonant circuit in the wireless charging system is an LCC resonant circuit.

3. The control method for the wireless charging system according to claim 1, characterized in that, If the phase of any resonant current leads the phase of its corresponding output voltage outside the set phase range, the conduction angle of the rectifier is increased to keep the phase difference within the set range; if the phase of any resonant current lags the phase of its corresponding output voltage outside the set phase range, the conduction angle of the rectifier is decreased to keep the phase difference within the set range.

4. The control method for the wireless charging system according to claim 1, characterized in that, The soft start process includes a self-test step for the wireless charging system. If a fault occurs in the wireless charging system, an alarm will be triggered.

5. The control method for the wireless charging system according to claim 1, characterized in that, m is less than 3.

6. The control method for the wireless charging system according to claim 1, characterized in that, When the DC bus voltage reaches the set bus voltage value, the system begins a soft start.

7. A wireless charging system, characterized in that, The system includes a transmitter, a receiver, and a controller. The transmitter includes an inverter and a transmitting coil, and the receiver includes a receiving coil and a rectifier. The inverter's input is connected to a DC bus, and its output is connected to the transmitting coil. The receiving coil is connected to the rectifier's input, and its output is connected to a power battery. Resonant circuits are provided between the inverter and the transmitting coil, and between the receiving coil and the rectifier. The controller controls the inverter and the rectifier, and includes a processor, a memory, and a computer program stored in the memory. When the processor executes the computer program, it implements the following method: During the soft-start process of the wireless charging system, the phase shift angles of the inverter and rectifier are gradually reduced to 0; and during the reduction process, the phase shift angle of the rectifier is controlled by m * the phase shift angle of the inverter, where m > 1; the phase shift angle of the inverter is the conduction time difference of the switching transistors in the same group within one control cycle of the inverter, and the phase shift angle of the rectifier is the conduction time difference of the switching transistors in the same group within one control cycle of the rectifier. Furthermore, during the soft-start process, if the rectifier's output voltage reaches the set voltage value, the resonant current on the transmitting coil side and the inverter's output voltage and / or the resonant current on the receiving coil side and the rectifier's output voltage are detected. If the phase difference between any resonant current and its corresponding output voltage exceeds the set range, the rectifier's conduction angle is adjusted to control the phase difference within the set range. The conduction angle is π-Φ, where Φ is the conduction time difference between the inverter and the rectifier within the same control cycle.

8. The wireless charging system according to claim 7, characterized in that, The resonant circuit is an LCC resonant circuit.

9. The wireless charging system according to claim 7, characterized in that, It also includes a PFC power corrector, with the inverter's input terminal connected to the PFC power corrector's output terminal, and the PFC power corrector's input terminal connected to a three-phase power supply.

10. The wireless charging system according to claim 7, characterized in that, The inverter is a full-bridge inverter.

11. The wireless charging system according to claim 7, characterized in that, If the phase of any resonant current leads the phase of its corresponding output voltage outside the set phase range, the conduction angle of the rectifier is increased to keep the phase difference within the set range; if the phase of any resonant current lags the phase of its corresponding output voltage outside the set phase range, the conduction angle of the rectifier is decreased to keep the phase difference within the set range.

12. The wireless charging system according to claim 7, characterized in that, The soft start process includes a self-test step for the wireless charging system. If a fault occurs in the wireless charging system, an alarm will be triggered.

13. The wireless charging system according to claim 7, characterized in that, m is less than 3.

14. The wireless charging system according to claim 7, characterized in that, When the DC bus voltage reaches the set bus voltage value, the system begins a soft start.

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