Wireless charging system and control method thereof

Abstract

The invention discloses a wireless charging system and a control method of the wireless charging system. The wireless charging system includes a DC-to-DC converter, an inverter circuit, and a wireless power transmission circuit. The control method comprises the steps of setting a limiting range of a phase angle of the inverter circuit; the reference voltage is set as the input voltage of the DC-to-DC converter; sampling the DC output voltage of the DC-to-DC converter in real time; and calculating an error value between the DC output voltage and the reference voltage, generating a phase control signal based on the error value, and dynamically adjusting the phase angle of the inverter circuit.

Description

Technical Field

[0001] The present invention relates to a charging system and a control method for the charging system, and more particularly to a wireless charging system and a control method for the wireless charging system. Background Art

[0002] In the field of switching power supplies, wireless power transmission (WPT) technology faces the challenge of low transmission efficiency compared to traditional wired contact power supply methods. For WPT systems, achieving high efficiency over a wide power range is a fundamental requirement.

[0003] Take the SS compensation topology (series-series compensation topology) as an example, that is, the topology in which the transmitter side of wireless power transmission is series compensated and the receiver side is also series compensated. Figure 1 As shown in FIG, which is a block diagram of the structure of the wireless charging system of the present invention. In order to achieve wide-range regulation of the output voltage and power transmission under different coupling states, a DC-to-DC converter (DCDC) 20 and a power factor corrector (PFC) 30 are usually added to the front stage of the wireless power transmission unit 10 (including the inverter circuit 11 and the wireless power transmission circuit 12). However, the present invention is not limited to this, that is, the technical solution of the present invention is also applicable to SP (series-parallel), PS, PP topologies or composite compensation topologies such as LCC-S, C-LC, SS-LCC of wireless power transmission.

[0004] In conventional technology, to ensure zero voltage switching (ZVS) of the inverter bridge switches S1-S4 of the wireless power transmission unit 10, the phase angle between the output voltage fundamental and the inverter bridge output current is controlled to a fixed phase angle. In conventional control methods, the voltage of the DC-DC converter 20 is fixed to ensure the output voltage and adapt to different coupling conditions (such as coil distance and offset). However, under this control method, the output voltage of the DC-DC converter 20 cannot be dynamically adjusted. In this case, the losses of the DC-DC converter 20 and the losses of the inverter bridge switches S1-S4 of the inverter circuit 11 of the wireless power transmission unit 10 are both high.

[0005] See Figure 3 As shown in FIG, it is a conventional output voltage control block diagram of a DC-DC converter used in wireless power transmission. Figure 3 As shown, according to the target output voltage V bat , and the required output current setting value I set , and the output power P required by the wireless power transmission unit 10out The reference voltage value of the output voltage of the DC-DC converter 20 is obtained by controlling the loop, so as to adjust the power switch duty cycle of the DC-DC converter 20, and make the output voltage of the DC-DC converter 20 stable at the target output voltage V DCDC_out .

[0006] However, in the prior art, the output voltage of the DC-DC converter 20 is only dependent on the set output demand and cannot be dynamically optimized and adjusted, resulting in high loss of the DC-DC converter 20 and the wireless power transmission unit 10.

[0007] Therefore, how to design a wireless charging system and a control method of the wireless charging system, which can solve the problems and technical bottlenecks in the prior art under wide power range and wide coupling conditions, is an important subject studied by the present inventors. SUMMARY

[0008] An object of the present application is to provide a wireless charging system to solve the problems in the prior art.

[0009] To achieve the above object, the wireless charging system comprises a DC-DC converter, an inverter circuit, a wireless power transmission circuit, and a control unit. The DC-DC converter receives a DC input voltage and converts the DC input voltage into a DC output voltage. The inverter circuit receives the DC output voltage and converts the DC output voltage into an AC output voltage. The wireless power transmission circuit comprises a transmitting coil connected to the inverter circuit, for generating an alternating magnetic field through high-frequency AC, and a receiving end configured to receive electric energy through electromagnetic induction. The control unit samples the DC output voltage in real time, calculates an error value of the DC output voltage and a reference voltage, generates a phase control signal based on the error value, and dynamically adjusts the phase angle of the inverter circuit.

[0010] In an embodiment, the phase angle of the inverter circuit is set to a limited range, the limited range is set according to the phase difference between the AC output voltage and the AC output current of the inverter circuit, and the AC output voltage phase leads the AC output current phase.

[0011] In an embodiment, the phase angle of the inverter circuit is positively correlated with the operating frequency of the inverter circuit within the limited range.

[0012] In an embodiment, the upper limit of the limited range of the phase angle of the inverter circuit is set according to the voltage stress of the power switch in the inverter circuit, so that the AC output voltage is less than the voltage stress of the power switch in the inverter circuit.

[0013] In an embodiment, the lower limit of the limited range of the phase angle of the inverter circuit is set according to the zero voltage condition of the inverter circuit, and the determination method calculates the minimum phase angle according to the resonance parameters of the inverter circuit, so that the power switch of the inverter circuit realizes zero voltage turn-on.

[0014] In one embodiment, the topology of the DC-DC converter comprises at least one of a boost circuit, a buck circuit and a buck-boost circuit, and the reference voltage is determined according to the DC input voltage.

[0015] In one embodiment, the topology of the DC-DC converter is a buck-boost circuit, and when the DC-DC converter is configured in a boost mode, the control unit sets the reference voltage as a first reference voltage; when the DC-DC converter is configured in a buck mode, the control unit sets the reference voltage as a second reference voltage, the first reference voltage being greater than the second reference voltage.

[0016] In one embodiment, the first reference voltage is set according to the DC input voltage when the DC-DC converter is configured in a boost mode, and the second reference voltage is set according to the DC input voltage when the DC-DC converter is configured in a buck mode.

[0017] In one embodiment, when the DC-DC converter is configured in a boost mode, the control unit dynamically adjusts the phase angle of the inverter circuit to decrease, so that the DC output voltage decreases, and within the limit range of the phase angle of the inverter circuit, the DC output voltage is closest to the input voltage.

[0018] In one embodiment, when the DC-DC converter is configured in a buck mode, the control unit dynamically adjusts the phase angle of the inverter circuit to increase, so that the DC output voltage increases, and within the limit range of the phase angle of the inverter circuit, the DC output voltage is closest to the input voltage.

[0019] Another object of the present application is to provide a control method of a wireless charging system to solve the problems of the prior art.

[0020] To achieve the above object, the control method of the wireless charging system provided by the present application comprises a DC-DC converter, an inverter circuit and a wireless power transmission circuit. The control method comprises: setting a limit range of the phase angle of the inverter circuit; setting a reference voltage as the input voltage of the DC-DC converter; real-time sampling the DC output voltage of the DC-DC converter; and calculating the error value of the DC output voltage and the reference voltage, generating a phase control signal based on the error value, and dynamically adjusting the phase angle of the inverter circuit.

[0021] In one embodiment, the limit range is set according to the phase difference between the AC output voltage and the AC output current of the inverter circuit, and the AC output voltage phase leads the AC output current phase.

[0022] In one embodiment, the phase angle of the inverter circuit is positively correlated with the operating frequency of the inverter circuit within the limit range.

[0023] In one embodiment, the upper limit of the limited range of the phase angle of the inverter circuit is set according to the voltage stress of the power switch in the inverter circuit, so that the AC output voltage of the inverter circuit is less than the voltage stress of the power switch in the inverter circuit.

[0024] In one embodiment, the lower limit of the limited range of the phase angle of the inverter circuit is set according to the zero voltage condition of the inverter circuit, and the minimum phase angle is calculated according to the resonance parameters of the inverter circuit, so that the power switch of the inverter circuit realizes zero voltage turn-on.

[0025] In one embodiment, the topology of the DC-DC converter includes at least one of a boost circuit, a buck circuit and a buck-boost circuit, and the reference voltage is determined according to the DC input voltage.

[0026] In one embodiment, the topology of the DC-DC converter is a buck-boost circuit, and when the DC-DC converter is configured in a boost mode, the control unit sets the reference voltage as a first reference voltage; when the DC-DC converter is configured in a buck mode, the control unit sets the reference voltage as a second reference voltage, and the first reference voltage is greater than the second reference voltage.

[0027] In one embodiment, the first reference voltage is set according to the DC input voltage when the DC-DC converter is configured in a boost mode, and the second reference voltage is set according to the DC input voltage when the DC-DC converter is configured in a buck mode.

[0028] In one embodiment, when the DC-DC converter is configured in a boost mode, the control unit dynamically adjusts the phase angle of the inverter circuit to decrease, so that the DC output voltage decreases, and under the limited range of the phase angle of the inverter circuit, the DC output voltage is closest to the input voltage.

[0029] In one embodiment, when the DC-DC converter is configured in a buck mode, the control unit dynamically adjusts the phase angle of the inverter circuit to increase, so that the DC output voltage increases, and under the limited range of the phase angle of the inverter circuit, the DC output voltage is closest to the input voltage.

[0030] The wireless charging system and the control method of the wireless charging system have the following characteristics and advantages: 1. The output voltage and the input voltage of the DC-DC converter are controlled to be as equal as possible, so that the loss is reduced as much as possible, and thus the wireless power transmission system can obtain high efficiency in a wide power range; 2. In order to control the output voltage and the input voltage of the DC-DC converter to be as equal as possible, the DC-DC converter will be switched between the boost mode and the buck mode, so as to avoid the current working condition and the working state of the converter from being unable to match due to frequent switching between the boost mode and the buck mode, and two different levels are set; 3. By detecting the output voltage of the DC-DC converter and comparing it with a given reference voltage, a closed-loop control of the phase angle of the inverter circuit is introduced, so that the input voltage of the DC-DC converter is closest to the limit range of the phase angle change set in the front, so as to reduce the loss of the DC-DC converter as much as possible.

[0031] In order to further understand the technology, means and technical effects adopted by the present application to achieve the predetermined purpose, please refer to the following detailed description and drawings of the present application. It is believed that the purpose, features and characteristics of the present application can be deeply and specifically understood from the drawings. However, the drawings are provided for reference and illustration only, and are not used to limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 Fig. 1 is a structural block diagram of the wireless charging system of the present application.

[0033] Figure 2 Fig. 3 is a schematic diagram of the relationship between the phase angle and the working frequency of the inverter circuit of the wireless power transmission of the present application.

[0034] Figure 3 Fig. 6 is an output voltage control block diagram of the conventional DC-DC converter applied to the wireless power transmission.

[0035] Figure 4 Fig. 9 is a control block diagram of dynamically adjusting the phase angle of the inverter circuit of the present application.

[0036] Figure 5 Fig. 12 is a flow chart of the control method of the wireless charging system of the present application.

[0037] BRIEF DESCRIPTION OF DRAWINGS

[0038] 10: wireless power transmission unit

[0039] 11: inverter circuit

[0040] 12: wireless power transmission circuit

[0041] 20: DC-DC converter

[0042] 30: Power Factor Corrector

[0043] 40: Control unit

[0044] 41: Limiter

[0045] S1-S4: Inverter bridge switch tube

[0046] φ: Phase angle

[0047] f s : Operating frequency

[0048] P out : Output power

[0049] V DCDC_out : DC output voltage

[0050] V DCDC_ref : DC output voltage reference value

[0051] V AC_out : AC output voltage

[0052] I AC_out : AC output current

[0053] V DCDC_opt_ref : Reference voltage

[0054] φ sample : Actual phase angle value

[0055] φ ref : Reference phase angle value

[0056] V bat : Output voltage setting value

[0057] I set : Output current setting value

[0058] S10~S40: steps. DETAILED DESCRIPTION

[0059] The technical content and detailed description of the present invention are described as follows with reference to the accompanying drawings.

[0060] See Figure 1 and Figure 4 As shown, they are respectively a structural block diagram of the wireless charging system of the present invention and a control block diagram of the phase angle of the dynamic adjustment inverter circuit of the present invention. An embodiment of the wireless charging system of the present invention includes a DC to DC converter 20, an inverter circuit 11, a wireless power transmission circuit 12 and a control unit 40 (see Figure 4 The DC to DC converter 20 receives a DC input voltage and converts it into a DC output voltage V DCDC_outThe inverter circuit 11 receives the DC output voltage V DCDC_out , and the DC output voltage V DCDC_out Converted to AC output voltage V AC_out .

[0061] The wireless power transmission circuit 12 includes a transmitting coil connected to the inverter circuit 11 and a receiving end for receiving power through electromagnetic induction.

[0062] The control unit 40 samples the DC output voltage V in real time. DCDC_out , calculate the DC output voltage V DCDC_out With reference voltage V DCDC_opt_ref The error value is then used to generate a phase control signal based on the error value to dynamically adjust the phase angle φ of the inverter circuit 11. Specifically, the phase angle φ of the inverter circuit 11 is set to a limit range, wherein the limit range must meet the AC output voltage V AC_out The phase leads the AC output current I AC_out The phase of the resonant cavity is thereby ensured to operate in the inductive region, and the inverter circuit 11 is made to operate in the inductive region.

[0063] like Figure 2 As shown, the phase angle φ of the inverter circuit 11 is related to the operating frequency f of the inverter circuit 11. s This means that increasing the phase angle φ usually requires a corresponding increase in the operating frequency f s , and vice versa. In addition, the operating frequency of the wireless power transmission unit 10 is related to the system voltage gain characteristics. If the operating frequency f s Due to changes in the operating frequency f, the output voltage of the DC-DC converter 20, that is, the input voltage of the wireless power transmission unit 10, can be dynamically adjusted to offset the operating frequency f. s The effect of changes on the gain is reduced, thereby maintaining the stability of the output power or voltage.

[0064] Therefore, based on the above principles, in the topology control of the front-stage DC-DC converter 20 of the wireless power transmission unit 10, the present invention can achieve optimal control of the system operating point through the following adjustment mechanism: the operating frequency f can be changed by controlling the change of the phase angle φ of the inverter circuit 11 of the wireless power transmission unit 10. s , thereby affecting the input voltage of the wireless power transmission unit 10.

[0065] When the phase angle between the resonant current and voltage of the wireless power transmission unit 10 changes, the control system will adjust the operating frequency of the wireless power transmission unit 10 to maintain the system in the optimal resonant state, thereby ensuring the power transmission efficiency. When the gap or offset between the coils of the transmitter and receiver changes, resulting in a change in the coupling coefficient, the phase angle φ and the operating frequency f under a certain output condition are s Relationships such as Figure 2is shown. At this time, the adjustment of the operating frequency f s synchronously influences the impedance characteristic and the voltage gain characteristic of the resonant cavity. Therefore, the output power needs to be maintained stable by dynamically adjusting the DC output voltage V DCDC_out .

[0066] Although the relationship curve between the phase angle φ and the operating frequency f s presents different slopes under different output conditions, the two always maintain a positive correlation within a preset limit range. The specific specification of the limit range is as follows: the phase angle φ of the inverter circuit 11 is greater than zero, and the upper limit of the limit range is set according to the voltage stress of the power switch in the inverter circuit 11, thereby making the alternating output voltage V AC_out less than the voltage stress of the power switch in the inverter circuit 11.

[0067] In addition, the lower limit of the limit range of the phase angle φ of the inverter circuit 11 is set according to the zero voltage condition of the inverter circuit 11, and the determination method is to calculate the minimum phase angle according to the resonant parameters of the inverter circuit 11, so that the power switch of the inverter circuit 11 realizes zero voltage switching (ZVS).

[0068] By the way, in the present application, the topology of the DC-DC converter 20 can include at least one of a boost circuit, a buck circuit or a buck-boost circuit. The boost circuit has a boost mode, the buck circuit has a buck mode, and the buck-boost circuit has both the buck mode and the boost mode. And the setting of the reference voltage V DCDC_opt_ref is related to the operating mode of the DC-DC converter 20. Therefore, according to the different boost-buck modes of the DC-DC converter, the setting of the reference voltage V DCDC_opt_ref is also different. For example, when the DC-DC converter 20 is configured in the boost mode, the control unit 40 sets the reference voltage V DCDC_opt_ref as a first reference voltage. Or, when the DC-DC converter 20 is configured in the buck mode, the control unit 40 sets the reference voltage V DCDC_opt_ref as a second reference voltage. The first reference voltage is greater than the second reference voltage. Specifically, the first reference voltage is set according to the DC input voltage V DCDC_ref1 when the DC-DC converter 20 is configured in the boost mode, and the second reference voltage is set according to the DC input voltage V DCDC_ref2 when the DC-DC converter 20 is configured in the buck mode.

[0069] When the DC-DC converter 20 is configured in the boost mode, the control unit 40 dynamically adjusts the phase angle φ of the inverter circuit 11 to decrease, so that the DC output voltage V DCDC_outReduced, and within the limited range of the phase angle φ of the inverter circuit 11, the DC output voltage V DCDC_out On the contrary, when the DC-DC converter 20 is configured in the buck mode, the control unit 40 dynamically adjusts the phase angle φ of the inverter circuit 11 to increase so that the DC output voltage V DCDC_out Increases, and within the limited range of the phase angle φ of the inverter circuit 11, the DC output voltage V DCDC_out Closest to the input voltage.

[0070] Therefore, the wireless charging system proposed by the present invention has a phase angle φ of the inverter circuit 11 and an operating frequency f within a preset limit range. s There is a positive correlation (i.e. φ∝f s ), this relationship is valid under different output conditions. Working frequency f s Directly affects the impedance characteristics and voltage gain characteristics of the resonant cavity, and needs to be adjusted by adjusting the DC output voltage V DCDC_out To maintain the output power stable. By dynamically adjusting the phase angle φ, the operating frequency f is changed. s , thereby controlling the DC output voltage V of the DC-DC converter 20 DCDC_out Optimize and form closed-loop control.

[0071] Therefore, the present invention designs a limit of phase angle change, that is, a limit range, such as Figure 4 The limiter 41 of the control unit 40 is implemented, and the interval must simultaneously meet the following core constraints: First, it is necessary to ensure that the AC output voltage V AC_out The phase leads the AC output current I AC_out The phase of the resonant cavity is ensured to operate in the inductive region. Second, it is necessary to ensure that the power switch of the inverter circuit 11 achieves zero voltage conduction (ZVS). Therefore, the phase angle cannot be infinitely small. When the phase angle is too small, the current of the power switch will not be enough to turn off the power switch. If it is less than the minimum phase angle, a relatively large switching loss will be generated. Third, the phase angle cannot be infinitely large. It is necessary to ensure that the AC output voltage V AC_out Less than the voltage stress of the power switch in the inverter circuit 11. Therefore, a phase angle variation limit range is set based on the above conditions. In other words, the phase angle variation limit range includes the minimum requirement for ZVS and the maximum requirement for switching tube stress.

[0072] Incidentally, the phase angle cannot change infinitely. If the phase angle is infinitely reduced, it may affect the zero voltage conduction (ZVS) of the power switch of the inverter circuit 11. On the contrary, if it is infinitely increased, the output voltage will exceed the working stress of the switch tube. Therefore, by designing the limit range of the phase angle change, such as Figure 4 The limiter 41 of the control unit 40 is implemented to sample the DC output voltage V in real time.DCDC_out With reference voltage V DCDC_opt_ref The error value is adjusted by the PI controller, and the output result is limited by the limiter 41, so that the phase angle φ of the inverter circuit 11 is limited to a lower limit and an upper limit. The lower limit of the limit range is greater than zero to ensure that the resonant cavity operates in the inductive region and is greater than the minimum phase angle required to ensure ZVS of the switch tube. The upper limit of the limit range is set according to the voltage stress of the power switch in the inverter circuit 11. Therefore, through the control loop, a new DC output voltage V of the DC-DC converter 20 can be obtained. DCDC_out , thus according to the new DC output voltage V DCDC_out With reference voltage V DCDC_opt_ref By continuous comparison, the phase angle φ of the inverter circuit 11 is dynamically adjusted.

[0073] like Figure 4 As shown, the actual phase angle value φ of the inverter circuit 11 is further sampled. sample , and with the set reference phase angle value φ ref Calculate the error value, that is, Figure 4 The actual phase angle value φ shown sample With the set reference phase angle value φ ref Then the PI controller is used to adjust the operating frequency f of the inverter circuit 11. s .

[0074] Incidentally, the DC output voltage V of the DC-DC converter 20 is sampled. DCDC_out With reference voltage V DCDC_opt_ref The error value is adjusted by PI to change the output. This loop achieves phase angle tracking through negative feedback and is a typical closed-loop control. Although under certain working conditions, the PI output is constrained by the limiter 41 within the phase angle limit range, so that the phase angle φ cannot change freely to completely eliminate the voltage error, it is also a constrained closed-loop optimization. In other words, the actual DC output voltage V DCDC_out With reference voltage V DCDC_opt_ref There will be an error between the two, and the system is not pursuing the DC output voltage V DCDC_out and reference voltage V DCDC_opt_ref Equal, but by adjusting the phase angle φ, the DC output voltage V DCDC_out Approaching the theoretically achievable value determined by the phase angle boundary forms a closed-loop control for optimizing power output efficiency.

[0075] Two different reference voltage levels are set according to the output voltage of the power factor corrector (PFC) 30, that is, the reference voltage V DCDC_opt_refis a first reference voltage, used to correspond to the boost mode of the DC-DC converter 20 (based on the DC-DC converter 20 being a boost circuit or a buck-boost circuit) and to set the reference voltage V DCDC_opt_ref The second reference voltage corresponds to the buck mode of the DC-DC converter 20 (based on the buck mode of the DC-DC converter 20 being a buck-type circuit or a buck-boost type circuit). This is because, if two different reference voltage levels are not set, the DC-DC converter 20 will switch back and forth between the boost mode and the buck mode in order to control the output voltage and input voltage of the DC-DC converter 20 to be as equal as possible. Therefore, two levels are set to avoid switching back and forth between the two modes.

[0076] Furthermore, by detecting the output voltage of the DC-DC converter 20 and comparing it with a given reference voltage, a closed-loop control of the phase angle φ of the inverter circuit 11 is introduced, so that the DC output voltage V DCDC_out Within the specified phase angle variation range, the voltage is closest to the input voltage of the DC-DC converter 20, thereby minimizing losses in the DC-DC converter 20. In other words, the two voltage levels set for the boost and buck modes are intended to control the output voltage of the DC-DC converter 20 to be as equal as possible to the input voltage. Ideally, the DC-DC converter 20 is in a direct-flow state. However, in some operating conditions, it is not possible to completely eliminate voltage errors to meet power output requirements. However, it is possible to minimize the output voltage rise of the DC-DC converter 20 in boost mode and minimize the output voltage drop of the DC-DC converter 20 in buck mode. This maintains the DC-DC converter 20 in a high-efficiency operating range, thereby minimizing losses.

[0077] See Figure 5 As shown in FIG, which is a flow chart of the control method of the wireless charging system of the present invention. The control method of the wireless charging system includes, first, setting the phase angle limit range of the inverter circuit 11 (step S10), that is, setting the limit of the phase angle change. The limit range is based on the AC output voltage V AC_out and AC output current I AC_out Phase difference setting, and meet the AC output voltage V AC_out The phase leads the AC output current I AC_out The phase of the resonant cavity is ensured to operate in the inductive region. As for the limiting range, there are certain regulations, that is, the lower limit of the limiting range of the phase angle φ of the inverter circuit 11 is greater than zero, and the upper limit of the limiting range is set according to the voltage stress of the power switch in the inverter circuit 11, so that the AC output voltage V AC_out Smaller than the voltage stress of the power switch in the inverter circuit 11.

[0078] Then, the reference voltage V DCDC_opt_ref The input voltage of the DC-DC converter 20 is set (step S20), i.e. the reference voltage V DCDC_opt_ref is set as the first reference voltage (based on the DC-DC converter 20 being in the boost mode) or the pre-set reference voltage V DCDC_opt_ref is set as the second reference voltage (based on the DC-DC converter 20 being in the buck mode), wherein the first reference voltage is greater than the second reference voltage. In this way, by setting two different levels (the first reference voltage and the second reference voltage), the back and forth switching of the DC-DC converter 20 between the boost mode and the buck mode during the operation of controlling the output voltage of the DC-DC converter 20 to be equal to the input voltage can be avoided.

[0079] Then, the DC output voltage V DCDC_out of the DC-DC converter 20 is sampled in real time (step S30). Finally, the error value of the DC output voltage V DCDC_out and the reference voltage V DCDC_opt_ref is calculated, and the phase control signal is generated based on the error value, which is adjusted by the PI controller and controlled in the control loop, so as to obtain the new DC output voltage V DCDC_out of the DC-DC converter 20, so as to achieve the dynamic adjustment of the phase angle of the inverter circuit 11 according to the continuous comparison between the new DC output voltage V DCDC_out and the reference voltage V DCDC_opt_ref (step S40), i.e. by detecting the DC output voltage V DCDC_out of the DC-DC converter 20 and comparing it with the given reference voltage V DCDC_opt_ref , a closed-loop control of the phase angle is realized, so as to dynamically adjust the phase angle of the inverter circuit 11, so that under the condition of the limit range of the phase angle change set in the front, the input voltage of the DC-DC converter is most close, so as to minimize the loss of the DC-DC converter.

[0080] Therefore, the wireless charging system and the control method of the wireless charging system provided by the application can achieve the following technical effects: because the wireless charging system has different application scenarios, the phase angle of the inverter circuit 11 of the wireless power transmission can be dynamically adjusted under different output voltages and different coupling conditions, so as to control the output voltage of the DC-DC converter 20, and the optimal loss is achieved, that is, the loss of the DC-DC converter 20 can be reduced to the minimum. In addition, because the DC-DC converter 20 is configured to operate in the boost mode and the buck mode, the change of the phase angle is in different directions. If the DC-DC converter 20 operates in the boost mode, the output of the DC-DC converter 20 can be reduced by reducing the phase angle, so that the loss of the inverter bridge switch tube of the inverter circuit 11 is reduced. If the DC-DC converter 20 operates in the buck mode, the output of the DC-DC converter 20 can be increased by increasing the phase angle, although the loss of the inverter bridge switch tube of the inverter circuit 11 is slightly increased at this time, but the increase is less than the loss of the DC-DC converter 20, so the total loss is reduced. Therefore, the transmission efficiency of the whole machine under different working conditions can be improved by the scheme of the two working modes.

[0081] In summary, the application has the following advantages:

[0082] 1. Controlling the output voltage and the input voltage of the DC-DC converter to be as equal as possible can reduce the loss as much as possible, so that the wireless power transmission system can obtain high efficiency in a wide power range.

[0083] 2. In order to control the output voltage and the input voltage of the DC-DC converter to be as equal as possible, the DC-DC converter will be switched between the boost mode and the buck mode, so as to avoid the frequent switching of the converter between the boost mode and the buck mode, which causes the current working condition to be unmatched with the working state of the converter, and two different levels are set.

[0084] 3. By detecting the output voltage of the DC-DC converter and comparing it with a given reference voltage, a closed-loop control of the phase angle of the inverter circuit is introduced, so that the input voltage of the DC-DC converter is closest to the limit range of the phase angle change set in the front, so as to reduce the loss of the DC-DC converter as much as possible.

[0085] The above merely describes preferred specific embodiments of the present application with reference to the accompanying drawings, and the features of the present application are not limited thereto, and are not intended to limit the present application, and all ranges of the present application shall be subject to the following claims, and any embodiments of the present application that are similar to the concept of the claims of the present application and have similar changes shall be included in the scope of the present application, and any changes or modifications that can be easily thought of by any person skilled in the art in the field of the present application can be covered by the claims of the present disclosure.

Claims

1. A wireless charging system, characterized in that: include: A DC-to-DC converter receives a DC input voltage and converts the DC input voltage into a DC output voltage; an inverter circuit receiving the DC output voltage and converting the DC output voltage into an AC output voltage; a wireless power transmission circuit comprising a transmitting coil connected to the inverter circuit and configured to generate an alternating magnetic field by a high-frequency alternating current, and a receiving end configured to receive power by electromagnetic induction; as well as A control unit samples the DC output voltage in real time, calculates an error value between the DC output voltage and a reference voltage, generates a phase control signal based on the error value, and dynamically adjusts the phase angle of the inverter circuit.

2. The wireless charging system according to claim 1, wherein: The phase angle of the inverter circuit is set within a limited range, which is set according to the phase difference between the AC output voltage and an AC output current of the inverter circuit and satisfies that the phase of the AC output voltage leads the phase of the AC output current.

3. The wireless charging system according to claim 2, wherein: The phase angle of the inverter circuit is positively correlated with the operating frequency of the inverter circuit within the limited range.

4. The wireless charging system according to claim 2, wherein: The upper limit of the limiting range of the phase angle of the inverter circuit is set according to the voltage stress of the power switch in the inverter circuit, so that the AC output voltage is smaller than the voltage stress of the power switch in the inverter circuit.

5. The wireless charging system according to claim 2, wherein: The lower limit of the limiting range of the phase angle of the inverter circuit is set according to the zero voltage condition of the inverter circuit. The determination method calculates the minimum phase angle according to the resonance parameters of the inverter circuit so that the power switch of the inverter circuit can achieve zero voltage conduction.

6. The wireless charging system according to claim 1, wherein: The topology of the DC-DC converter includes at least one of a boost circuit, a buck circuit and a buck-boost circuit, and the reference voltage is determined according to the DC input voltage.

7. The wireless charging system according to claim 1, wherein: The topology of the DC-DC converter is a buck-boost circuit, and when the DC-DC converter is configured in a boost mode, the control unit sets the reference voltage to a first reference voltage; when the DC-DC converter is configured in a buck mode, the control unit sets the reference voltage to a second reference voltage, wherein the first reference voltage is greater than the second reference voltage.

8. The wireless charging system according to claim 7, wherein: The first reference voltage is set according to the DC input voltage when the DC-DC converter is configured in a boost mode, and the second reference voltage is set according to the DC input voltage when the DC-DC converter is configured in a buck mode.

9. The wireless charging system according to claim 2, wherein: When the DC-to-DC converter is configured in boost mode, the control unit dynamically adjusts the phase angle of the inverter circuit to reduce so that the DC output voltage decreases, and within the limited range of the phase angle of the inverter circuit, the DC output voltage is closest to the input voltage.

10. The wireless charging system according to claim 2, wherein: When the DC-to-DC converter is configured in step-down mode, the control unit dynamically adjusts the phase angle of the inverter circuit to increase, so that the DC output voltage increases, and within the limited range of the phase angle of the inverter circuit, the DC output voltage is closest to the input voltage.

11. A control method for a wireless charging system, characterized in that: The wireless charging system includes a DC-to-DC converter, an inverter circuit, and a wireless power transmission circuit. The control method includes: Setting a limit range of the phase angle of the inverter circuit; Setting a reference voltage as an input voltage of the DC-DC converter; sampling a DC output voltage of the DC-to-DC converter in real time; and An error value between the DC output voltage and the reference voltage is calculated, and a phase control signal is generated based on the error value to dynamically adjust the phase angle of the inverter circuit.

12. The control method of the wireless charging system according to claim 11, wherein: The limiting range is set according to a phase difference between an AC output voltage and an AC output current of the inverter circuit, and satisfies the requirement that the AC output voltage phase leads the AC output current phase.

13. The control method of the wireless charging system according to claim 12, wherein: The phase angle of the inverter circuit is positively correlated with the operating frequency of the inverter circuit within the limited range.

14. The control method of the wireless charging system according to claim 11, wherein: The upper limit of the limiting range of the phase angle of the inverter circuit is set according to the voltage stress of the power switch in the inverter circuit, so that an AC output voltage of the inverter circuit is smaller than the voltage stress of the power switch in the inverter circuit.

15. The control method of the wireless charging system according to claim 11, wherein: The lower limit of the limiting range of the phase angle of the inverter circuit is set according to the zero voltage condition of the inverter circuit. The determination method calculates the minimum phase angle according to the resonance parameters of the inverter circuit so that the power switch of the inverter circuit can achieve zero voltage conduction.

16. The control method of the wireless charging system according to claim 11, wherein: The topology of the DC-DC converter includes at least one of a boost circuit, a buck circuit and a buck-boost circuit, and the reference voltage is determined according to the DC input voltage.

17. The control method of the wireless charging system according to claim 11, wherein: The topology of the DC-DC converter is a buck-boost circuit, and when the DC-DC converter is configured in a boost mode, the control unit sets the reference voltage to a first reference voltage; when the DC-DC converter is configured in a buck mode, the control unit sets the reference voltage to a second reference voltage, wherein the first reference voltage is greater than the second reference voltage.

18. The control method of the wireless charging system according to claim 17, wherein: The first reference voltage is set according to the DC input voltage when the DC-DC converter is configured in a boost mode, and the second reference voltage is set according to the DC input voltage when the DC-DC converter is configured in a buck mode.

19. The control method of the wireless charging system according to claim 11, wherein: When the DC-to-DC converter is configured in boost mode, the control unit dynamically adjusts the phase angle of the inverter circuit to reduce so that the DC output voltage decreases, and within the limited range of the phase angle of the inverter circuit, the DC output voltage is closest to the input voltage.

20. The control method of the backup power supply system according to claim 11, wherein: When the DC-to-DC converter is configured in step-down mode, the control unit dynamically adjusts the phase angle of the inverter circuit to increase, so that the DC output voltage increases, and within the limited range of the phase angle of the inverter circuit, the DC output voltage is closest to the input voltage.

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