Digital DAC adjusting BUCK chip output variable voltage circuit for wireless charging

Abstract

The invention provides a circuit for adjusting the output variable voltage of a BUCK chip through a digital DAC for wireless charging. The circuit comprises a BUCK circuit, an MCU controller, an ADC sampling circuit, a low-pass RC filter circuit and a feedback network circuit. One end of the MCU controller is connected with one end of the low-pass RC filter circuit, the other end of the low-pass RC filter circuit is connected with one end of the feedback network circuit and one end of the BUCK circuit, one end of the BUCK circuit is further connected with a power supply, the other end of the BUCK circuit is connected with the other end of the feedback network circuit, one end of the ADC sampling circuit collects the output voltage of the BUCK circuit at the other end of the BUCK circuit, and the other end of the ADC sampling circuit is connected with the power supply. And the other end of the ADC sampling circuit is connected with the other end of the MCU controller. The method is low in cost and easy to implement, the slope of the BUCK output voltage is adjustable, and the wireless charging carrier wave requirement can be better met.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless charging, and in particular to a circuit for adjusting a variable voltage output by a BUCK chip using a digital DAC for wireless charging. Background Art

[0002] With the extensive application of wireless charging technology in vehicles, wireless charging technology has brought convenience, safety, stability, strong compatibility, and improved driving and riding experience to car owners. And with the continuous development of technology, wireless charging technology will bring more surprises and convenience to users in the future. In many vehicle-side wireless charging product systems, the wireless charging transmitter terminal system needs to use a variable DC voltage output circuit, which relies on this circuit to output variable DC voltage, and then transfers the power of the transmitter to the wireless charging receiver through electromagnetic induction technology, thereby meeting the needs of the receiving device for different charging power under different lithium battery power conditions.

[0003] At present, the mainstream design of the on-board wireless charging transmitter on the market to meet the different charging power requirements of the receiver lithium battery under different power conditions is to use a digital BUCK separation circuit or select a BUCK chip circuit with a bus control function. The digital BUCK separation circuit is usually composed of 2 half-bridges or 1 full-bridge driver + 2 N-MOSFETs, but the use of a digital BUCK separation circuit will have the disadvantages of low efficiency, high cost, high complexity, poor electromagnetic interference resistance, large output ripple, large volume and weight, poor reliability and stability; and the BUCK chip circuit with a bus control function usually needs to integrate a bus function, such as I2C bus, SPI bus, UART, etc. It can be seen that the use of a BUCK chip circuit with a bus control function has the disadvantages of high complexity, high cost, and limited by bus control. In order to better meet the needs of the wireless charging transmission system, a new idea needs to be adopted.

[0004] For example, the invention patent with application number 202210954333.2 discloses a multi-port output three-in-one power supply, including an AC-DC circuit, a DC-DC circuit, a mobile power circuit, a wireless charging circuit and a charging port; wherein the DC-DC circuit is electrically connected to the ACDC circuit and the wireless charging circuit respectively, and reduces the voltage of the wireless charging circuit of the AC-DC circuit; the mobile power circuit and the DCDC circuit are electrically connected to the charging port and discharge. The above invention has more discrete device failure modes, low power transmission efficiency, complex control strategy, special selection requirements for the module processor MCU, and high design difficulty. Summary of the invention

[0005] Aiming at the problems of high circuit complexity and high cost of the existing variable DC voltage output circuit, the present invention provides a digital DAC for wireless charging to adjust the variable voltage output circuit of the BUCK chip, which outputs PWM through the MCU controller and affects the feedback circuit of the BUCK through the RC low-pass filter to output the voltage required by the system, with low cost and easy implementation.

[0006] In order to achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] A circuit for adjusting the output variable voltage of a BUCK chip using a digital DAC for wireless charging: comprising a BUCK circuit, an MCU controller, an ADC sampling circuit, a low-pass RC filter circuit and a feedback network circuit;

[0008] One end of the MCU controller is connected to one end of the low-pass RC filter circuit, the other end of the low-pass RC filter circuit is connected to one end of the feedback network circuit and one end of the BUCK circuit, one end of the BUCK circuit is also connected to the power supply, the other end of the BUCK circuit is connected to the other end of the feedback network circuit, one end of the ADC sampling circuit collects the BUCK circuit output voltage at the other end of the BUCK circuit, and the other end of the ADC sampling circuit is connected to the other end of the MCU controller.

[0009] Preferably, the feedback network circuit includes an upper resistor, a lower resistor, and a feedback capacitor, one end of the upper resistor and one end of the feedback capacitor are both connected to the other end of the BUCK circuit, the other end of the upper resistor and the other end of the feedback capacitor are both connected to one end of the lower resistor, and the other end of the lower resistor is connected to the system ground.

[0010] Preferably, the low-pass RC filter circuit includes a first resistor and a first capacitor, one end of the first resistor is connected to one end of the MCU controller, the other end of the first resistor is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the system ground.

[0011] Preferably, the ADC sampling circuit includes resistor I, resistor II, resistor III and capacitor I, one end of resistor I is respectively connected to one end of resistor II and one end of resistor III, the other end of resistor II is connected to the system ground, the other end of resistor III is respectively connected to one end of capacitor I and the other end of the MCU controller, and the other end of capacitor I is connected to the system ground.

[0012] Preferably, an input capacitor is provided between the BUCK circuit and the power supply, one end of the input capacitor is connected to the system ground GND, and the other end of the input capacitor is respectively connected to one end of the BUCK circuit and the power supply.

[0013] Preferably, an output inductor is provided between the BUCK circuit and the feedback network circuit, one end of the output inductor is connected to the other end of the BUCK circuit, and the other end of the output inductor is connected to one end of the upper resistor and one end of the feedback capacitor of the feedback network circuit.

[0014] Preferably, a feedback resistor is provided between the feedback network circuit and the low-pass RC filter circuit, one end of the feedback resistor is connected to one end of the first resistor and one end of the first capacitor of the low-pass RC filter circuit, and the other end of the feedback resistor is connected to the other end of the BUCK circuit, one end of the feedback capacitor of the feedback network circuit, one end of the upper resistor, and one end of the lower resistor.

[0015] Preferably, an output capacitor is provided at the other end of the BUCK circuit, one end of the output capacitor is connected to the other end of the output inductor, and the other end of the output capacitor is connected to the system ground.

[0016] Preferably, the resistance of the first resistor and the capacitance of the first capacitor are based on Select, where F c is the cut-off frequency, and F c <20Hz, R is the resistance of the first resistor, and C is the capacitance of the first capacitor;

[0017] The resistance value of the upper resistor and the resistance value of the lower resistor are based on Make a selection, V out is the output voltage of the BUCK circuit, VFB_REF is the BUCK reference voltage, RUP is the upper resistor value, and RDOWN is the lower resistor value;

[0018] The inductance of the output inductor is based on Select, where L is the inductance of the output inductor L3, VIN is the input voltage, I out is the output current, f sw This is the default switching frequency of the BUCK circuit.

[0019] Preferably, the MCU controller outputs a PWM square wave so that the BUCK circuit outputs an adjustable voltage that changes with the duty cycle of the PWM square wave. The MCU controller adjusts the duty cycle of the output PWM square wave according to the received charging power requirement of the receiver to meet the charging power requirement of the receiver, and dynamically adjusts through the PID strategy to ultimately achieve a dynamic balance between receiving and transmitting power.

[0020] Compared with the prior art, the present invention has the following beneficial effects: the present invention outputs PWM square waves with different duty cycles through the MCU controller, which are filtered by RC low-pass to affect the feedback circuit of the BUCK, thereby outputting the voltage required by the system, which is low-cost and easy to implement. The output voltage harmonic rate of the BUCK of the present invention is adjustable, which can better meet the needs of wireless charging carrier. The present invention makes the wireless charging hardware circuit more concise, makes the vehicle-mounted wireless charging transmitter module a standardized design, and comprehensively improves the performance and cost-effectiveness of the voltage regulation output circuit of the vehicle-mounted wireless charging transmitter module. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 The circuit diagram of the digital DAC for wireless charging of the present invention is to adjust the output variable voltage circuit of the BUCK chip.

[0023] Figure 2 FIG. 4 is a circuit diagram of an ADC sampling circuit of the present invention.

[0024] Figure 3 The circuit diagram of the MCU controller of the present invention outputting PWM square wave.

[0025] Figure 4 This is a flow chart of wireless charging power regulation.

[0026] Figure 5 It is a partial circuit diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] like Figure 1 As shown, a circuit for adjusting the output variable voltage of a BUCK chip using a digital DAC for wireless charging includes a BUCK circuit, an MCU controller, an ADC sampling circuit, a low-pass RC filter circuit, and a feedback network circuit.

[0029] One end of the MCU controller is connected to one end of the low-pass RC filter circuit, the other end of the low-pass RC filter circuit is connected to one end of the feedback network circuit and one end of the BUCK circuit, one end of the BUCK circuit is also connected to the power supply BAT_SW, the other end of the BUCK circuit is connected to the other end of the feedback network circuit, one end of the ADC sampling circuit collects the BUCK circuit output voltage at the other end of the BUCK circuit, and the other end of the ADC sampling circuit is connected to the other end of the MCU controller.

[0030] Furthermore, the BUCK circuit is used to convert a high-voltage DC power supply into a required low-voltage DC power supply; the MCU controller controls the PWM square wave duty cycle through the internal program of the MCU controller, thereby controlling the BUCK output required voltage; the ADC sampling circuit divides the voltage through resistance to make the voltage range within the voltage range that the MCU controller can withstand and require, and the MCU controller converts the voltage value into an ADC value for program control; the low-pass RC filter circuit can effectively smooth the PWM square wave and reduce the high-frequency component, thereby converting the PWM square wave to a voltage level that is not close to DC; the feedback network circuit is used to stabilize the output voltage, control the voltage within the voltage range that the BUCK chip pin can withstand and require, adjust the control, suppress interference, and achieve efficiency optimization.

[0031] Furthermore, an input capacitor is provided between the BUCK circuit and the power supply BAT_SW, one end of the input capacitor is connected to the system ground GND, and the other end of the input capacitor is respectively connected to one end of the BUCK circuit and the power supply BAT_SW. The input capacitor is used for filtering, stabilizing the power supply voltage, and suppressing electromagnetic interference.

[0032] Furthermore, if Figure 1 As shown, the feedback network circuit includes an upper resistor R31, a lower resistor R37, and a feedback capacitor C50, one end of the upper resistor R31 and one end of the feedback capacitor C50 are both connected to the other end of the BUCK circuit, the other end of the upper resistor R31 and the other end of the feedback capacitor C50 are both connected to one end of the lower resistor R37, and the other end of the lower resistor R37 is connected to the system ground GND.

[0033] Specifically, the resistance values ​​of the upper resistor R31 and the lower resistor R37 are selected according to the buck circuit principle and the general buck circuit output voltage formula:

[0034]

[0035] V out is the output voltage of the BUCK circuit, VFB_REF is the BUCK reference voltage, RUP is the resistance value of the upper resistor R31, and RDOWN is the resistance value of the lower resistor R37.

[0036] Furthermore, if Figure 1 As shown, the low-pass RC filter circuit includes a first resistor R36 and a first capacitor C52. The first resistor R36 and the first capacitor C52 constitute an RC low-pass filter. One end of the first resistor R36 is connected to one end of the MCU controller, the other end of the first resistor R36 is connected to one end of the first capacitor C52, and the other end of the first capacitor C52 is connected to the system ground GND.

[0037] Specifically, according to the cut-off frequency formula of the RC low-pass filter, the resistance value of the first resistor R36 and the capacitance value of the first capacitor C52 are selected:

[0038]

[0039] In the formula, F c is the cut-off frequency (unit: Hz), R is the resistance of the first resistor R36 (unit: ohm), and C is the capacitance of the first capacitor C52 (unit: Farad).

[0040] Taking 100kHz as an example, in order to filter the 100kHz PWM square wave into a DC level, a cutoff frequency much lower than 100kHz is selected. Usually, in a DC circuit requiring RC filtering, the cutoff frequency F is generally required. c <20Hz, in this embodiment, 5Hz (near DC level) is selected, that is, F c =5Hz, select R=150k ohms, and it can be calculated that the capacitance of the first capacitor C52 is about 0.22uF.

[0041] Furthermore, a feedback resistor R35 is provided between the feedback network circuit and the low-pass RC filter circuit, one end of the feedback resistor R35 is connected to one end of the first resistor R36 of the low-pass RC filter circuit and one end of the first capacitor C52, and the other end of the feedback resistor R35 is connected to the other end of the BUCK circuit, one end of the feedback capacitor C50 of the feedback network circuit, one end of the upper resistor R31, and one end of the lower resistor R37. The feedback resistor R35 is used for voltage division, so that the voltage after the PWM square wave output by the MCU controller passes through the RC low-pass filter is more likely to bias the feedback circuit. The resistance value selection method of the feedback resistor R35 is: according to formula (1), the relationship between the upper resistor R31 and the lower resistor R37 is obtained. In addition, the present invention can output and cover all voltages from 0 to VIN by adjusting PWM, so the resistance value of the feedback resistor R35 can be obtained according to Table 1-Vrail calculation table.

[0042] Vrail is the output voltage of the BUCK circuit, which is V in the expression out The PWM square wave output by the MCU controller biases the voltage of the BUCK feedback circuit, thereby controlling the BUCK to output the required BUCK circuit output voltage Vrail.

[0043] Table 1 - Vrail calculation table

[0044]

[0045] Furthermore, if Figure 1 , 2As shown, the ADC sampling circuit includes resistor ⅠR4, resistor ⅡR8, resistor ⅢR111 and capacitor ⅠC3. Capacitor ⅠC3 is used to filter out high-frequency signals to make ADC acquisition more accurate. One end of resistor ⅠR4 is connected to one end of resistor ⅡR8 and one end of resistor ⅢR111 respectively. The other end of resistor ⅡR8 is connected to the system ground GND. The other end of resistor ⅢR111 is connected to one end of capacitor ⅠC3 and the other end of MCU controller respectively. The other end of capacitor ⅠC3 is connected to the system ground GND. The ADC sampling circuit uses resistor ⅠR4, resistor ⅡR8 and resistor ⅢR111 to divide the output voltage Vrail of the BUCK circuit, and uses the MCU controller to sample the voltage after the voltage division of the output voltage Vrail of the BUCK circuit. The software monitors the digital DAC and the BUCK output voltage V out The digital DAC converts digital information into a continuous analog signal.

[0046] Furthermore, an output inductor L3 is provided between the BUCK circuit and the feedback network circuit, one end of the output inductor L3 is connected to the other end of the BUCK circuit, and the other end of the output inductor L3 is connected to one end of the upper resistor R31 of the feedback network circuit and one end of the feedback capacitor C50. The output inductor L3 is used to provide a freewheeling function to prevent current interruption. According to:

[0047]

[0048] Select the inductance of the output inductor L3. Where L is the inductance of the output inductor L3, VIN is the input voltage, I out is the output current, f sw This is the default switching frequency of the BUCK circuit.

[0049] Furthermore, an output capacitor is provided at the other end of the BUCK circuit, one end of the output capacitor is connected to the other end of the output inductor L3, and the other end of the output capacitor is connected to the system ground GND.

[0050] Specifically, the output filter capacitor is based on the formula:

[0051]

[0052] Make your selection. esr is the equivalent resistance of the series capacitor. The output capacitor can be selected by knowing the relationship between the equivalent resistance of the output filter capacitor and its capacitance through the formula.

[0053] Specifically, the circuit for the MCU controller to output PWM square waves with different duty cycles is as follows: Figure 3As shown in the figure, the implementation method of the MCU controller outputting PWM square waves with different duty cycles is as follows: ① Select PWM pin: select a GPIO pin of a wireless charging MCU controller that supports PWM function; ② Set PWM frequency: configure the timer or PWM module of the wireless charging MCU controller to generate the required frequency, which usually involves setting the prescaler, cycle value and automatic reload value of the timer, taking the 100kHz frequency PWM square wave as an example; ③ Set PWM duty cycle: define the proportion of the high level time of the PWM square wave issued by the wireless charging MCU controller to the total cycle time. A mechanism is needed here to adjust this proportion, which is generally achieved by modifying the comparison match value of the timer; ④ Initialization code: write initialization code to configure the PWM pin, timer and duty cycle; ⑤ Dynamically adjust the duty cycle: write a function to dynamically change the duty cycle of the PWM square wave.

[0054] Furthermore, the MCU implementing this solution needs to meet -M33 and above core processors, package with 64 pins and above, main frequency above 80MHz.

[0055] The principle of the above technical solution is that the MCU controller dynamically controls the PWM circuit to output a PWM square wave through the pin with TIM function of the MCU controller. The duty cycle value of this PWM square wave can be dynamically changed through the software code variable, and then the PWM square wave is filtered into a DC signal through the RC low-pass filter and input into the BUCK chip. Since the duty cycle of the PWM square wave can control the switch element inside the BUCK chip, the voltage output by the BUCK chip is controlled by controlling the opening time of the switch element. According to V DAC =V gpio *Duty_cycle calculates the different V corresponding to the PWM square wave with different duty cycles DAC value, then according to The BUCK circuit output voltage V out The output voltage can be adjusted as the duty cycle changes. The wireless charging then sends out different charging power requirements according to the changes in the receiver load. The transmitter demodulates the carrier signal, analyzes the carrier signal content, and adjusts the duty cycle of the output PWM square wave through the MCU controller to meet the charging power requirement of the receiver. Dynamic adjustment is performed through the PID strategy to ultimately achieve a dynamic balance between receiving and transmitting power.

[0056] Specifically, according to formula (5), different V corresponding to different duty cycle PWM square waves are calculated. DAC value.

[0057] V DAC =V gpio *Duty_cycle (5)

[0058] Where V gpio is the output voltage of the MCU controller io port, Duty_cycle is the PWM square wave duty cycle, V DAC is the product of the MCU controller IO port output voltage and the PWM square wave duty cycle. In the application of the present invention, the MCU power supply is 5V, then V gpio The output voltage is 5V, and the Duty_cycle range varies between 0-90%, so V out Equivalent relationship with Duty_cycle.

[0059] Then according to the formula:

[0060]

[0061] Change the value of the PWM square wave duty cycle Duty_cycle in the program to affect the BUCK circuit output voltage V out .

[0062] The specific steps of implementing the method of power regulation of wireless charging in software are as follows Figure 4 As shown, the power transmitter refers to the wireless charging device, and the power receiver refers to the device that needs to be charged, such as a mobile phone.

[0063] The PID strategy is:

[0064] Proportional (P): Proportional to the current error, providing a fast response. If the charging power is lower than the set value, the proportional control will increase the output power.

[0065] Integration (I): Accumulates historical errors and is used to eliminate steady-state errors. It ensures that the output power can be maintained at the set value in long-term operation.

[0066] Derivative (D): predicts the rate of change of the error, which helps to suppress system overshoot and improve the stability of the response.

[0067] like Figure 5 As shown, it is a partial circuit diagram of an embodiment, the input capacitor is composed of capacitors C36, C37, C38, C39, C40, and C41 connected in parallel, one end of the input capacitor is connected to the system ground GND, and the other end of the input capacitor is respectively connected to the VIN pin of the BUCK chip for stabilizing the input voltage, reducing power supply noise, providing transient current, reducing input current ripple, and improving system efficiency, and the power supply BAT_SW. The input capacitor is used for filtering, stabilizing the power supply voltage, and suppressing electromagnetic interference;

[0068] One end of the resistor R28 is connected to the MCU controller, and the other end of the resistor R28 is connected to the EN pin of the BUCK chip for controlling the start and stop of the BUCK chip. The resistor R28 is used to stabilize the level and prevent noise interference;

[0069] One end of the resistor R29 is connected to the system ground GND, and the other end of the resistor R29 is connected to the EN pin of the BUCK chip to ensure that the pin remains in a logic low state when no external signal is connected. When SC_EN is pulled low, it is grounded through the resistor R29 for discharge to prevent the BUCK from being unable to shut down.

[0070] One end of the resistor R32 is connected to the system ground GND, and the other end of the resistor R32 is connected to the VDRP pin of the BUCK chip which is kept in a logic low state. The resistor R32 is used as a pull-down resistor for frequency compensation inside the BUCK circuit to ensure that the BUCK chip can work normally and stably at a specific frequency.

[0071] One end of the resistor R33 is connected to the system ground GND, and the other end of the resistor R33 is connected to the PWR pin of the BUCK chip. It is used to limit the output power of the BUCK. When the rear-end load is short-circuited or working abnormally, the BUCK chip limits the output power to ensure that the BUCK chip will not burn out.

[0072] One end of the resistor R34 is connected to the system ground GND, and the other end of the resistor R34 is connected to the FREQ pin of the BUCK chip, which is used to set the BUCK working switching frequency to ensure that the BUCK works within the frequency range required by the system.

[0073] One end of capacitor C51 is connected to the system ground GND, and the other end of capacitor C51 is respectively connected to the VCC pin of the BUCK chip for internal voltage regulation output, which supplies 5.2V to SNSP and SNSN, the SNSP pin of the BUCK chip output measurement positive end, and the SNSN pin of the BUCK chip output measurement negative end. Capacitor C51 is used for filtering and stabilizing the power supply voltage; the chip ground pin AGND pin and the chip ground pin PGND pin of the BUCK chip are both connected to the system ground GND to form a loop;

[0074] The switching node SW pin of the BUCK chip is connected to one end of the capacitor C43, the other end of the capacitor C43 is connected to one end of the resistor R30, the other end of the resistor R30 is connected to the BOOT pin of the BUCK chip, and the capacitor C43 is connected between the SW pin and the BOOT pin of the BUCK chip to ensure that the bootstrap circuit can be charged during the conduction period of the low-side MOSFET and provide the necessary gate bias voltage during the conduction period of the high-side MOSFET;

[0075] One end of resistor R36 is connected to the PWM_DCDC end of the MCU controller, and the other end of resistor R36 is connected to one end of resistor R35 and capacitor C52 respectively. The other end of capacitor C52 is connected to the system ground. Resistor R36 and capacitor C52 form an RC low-pass filter; the other end of resistor R35 is connected to one end of capacitor C50, one end of resistor R31, one end of resistor R37, and the feedback pin FB of the BUCK chip. One end of resistor R31 is connected to one end of resistor R37, and the other end of resistor R37 is connected to the system ground GND. The other end of resistor R31 is connected to one end of inductor L3, and the other end of capacitor C50 is connected to one end of inductor L3 and one end of output capacitor respectively. The other end of inductor L3 is connected to the SW pin of the BUCK chip, and the other end of the output capacitor is connected to the system ground GND. The output capacitor is composed of capacitor C45, capacitor C46, ​​capacitor C47, capacitor C48, capacitor C49, and capacitor C44 connected in parallel. An ideal capacitor has no resistance, but in actual applications, due to process reasons, there will always be a certain resistance inside the capacitor and in the connector circuit. Connecting multiple capacitors in parallel can reduce power loss, heat generation, optimize costs, and provide more flexible circuit design. Output capacitors are used to stabilize output voltage, reduce noise, improve transient response, and provide current buffering.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A digital DAC for wireless charging to adjust the output voltage of a BUCK chip, characterized in that: Including BUCK circuit, MCU controller, ADC sampling circuit, low-pass RC filter circuit and feedback network circuit; One end of the MCU controller is connected to one end of the low-pass RC filter circuit, the other end of the low-pass RC filter circuit is connected to one end of the feedback network circuit and one end of the BUCK circuit, one end of the BUCK circuit is also connected to the power supply, the other end of the BUCK circuit is connected to the other end of the feedback network circuit, one end of the ADC sampling circuit collects the BUCK circuit output voltage at the other end of the BUCK circuit, and the other end of the ADC sampling circuit is connected to the other end of the MCU controller.

2. The circuit for adjusting the output variable voltage of the BUCK chip using a digital DAC for wireless charging according to claim 1, characterized in that: The feedback network circuit includes an upper resistor, a lower resistor, and a feedback capacitor. One end of the upper resistor and one end of the feedback capacitor are both connected to the other end of the BUCK circuit, the other end of the upper resistor and the other end of the feedback capacitor are both connected to one end of the lower resistor, and the other end of the lower resistor is connected to the system ground.

3. The circuit for adjusting the output variable voltage of the BUCK chip using a digital DAC for wireless charging according to claim 2, characterized in that: The low-pass RC filter circuit includes a first resistor and a first capacitor, one end of the first resistor is connected to one end of the MCU controller, the other end of the first resistor is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the system ground.

4. The circuit for adjusting the output variable voltage of the BUCK chip using a digital DAC for wireless charging according to claim 3, characterized in that: The ADC sampling circuit includes resistor I, resistor II, resistor III and capacitor I, one end of resistor I is respectively connected to one end of resistor II and one end of resistor III, the other end of resistor II is connected to the system ground, the other end of resistor III is respectively connected to one end of capacitor I and the other end of the MCU controller, and the other end of capacitor I is connected to the system ground.

5. The circuit for adjusting the output variable voltage of the BUCK chip using a digital DAC for wireless charging according to any one of claims 1 to 4, characterized in that: An input capacitor is provided between the BUCK circuit and the power supply, one end of the input capacitor is connected to the system ground GND, and the other end of the input capacitor is respectively connected to one end of the BUCK circuit and the power supply.

6. The circuit for adjusting the output variable voltage of the BUCK chip using a digital DAC for wireless charging according to claim 5, characterized in that: An output inductor is provided between the BUCK circuit and the feedback network circuit, one end of the output inductor is connected to the other end of the BUCK circuit, and the other end of the output inductor is connected to one end of the upper resistor and one end of the feedback capacitor of the feedback network circuit.

7. The circuit for adjusting the output variable voltage of the BUCK chip using a digital DAC for wireless charging according to claim 6, characterized in that: A feedback resistor is provided between the feedback network circuit and the low-pass RC filter circuit, one end of the feedback resistor is connected to one end of the first resistor and one end of the first capacitor of the low-pass RC filter circuit, and the other end of the feedback resistor is connected to the other end of the BUCK circuit, one end of the feedback capacitor of the feedback network circuit, one end of the upper resistor, and one end of the lower resistor.

8. The circuit for adjusting the output variable voltage of the BUCK chip using a digital DAC for wireless charging according to claim 7, characterized in that: An output capacitor is arranged at the other end of the BUCK circuit, one end of the output capacitor is connected to the other end of the output inductor, and the other end of the output capacitor is connected to the system ground.

9. The circuit for adjusting the output variable voltage of the BUCK chip using a digital DAC for wireless charging according to claim 3 or 8, characterized in that: The resistance value of the first resistor and the capacitance value of the first capacitor are based on Select, where F c is the cut-off frequency, and F c <20Hz, R is the resistance of the first resistor, and C is the capacitance of the first capacitor; The resistance value of the upper resistor and the resistance value of the lower resistor are based on Make a selection, V out is the output voltage of the BUCK circuit, VFB_REF is the BUCK reference voltage, RUP is the upper resistor value, and RDOWN is the lower resistor value; The inductance of the output inductor is based on Select, where L is the inductance of the output inductor L3, VIN is the input voltage, I out is the output current, f sw This is the default switching frequency of the BUCK circuit.

10. The circuit for adjusting the output variable voltage of the BUCK chip using a digital DAC for wireless charging according to claim 9, characterized in that: The MCU controller outputs a PWM square wave to enable the BUCK circuit to output an adjustable voltage that changes with the duty cycle of the PWM square wave. The MCU controller adjusts the duty cycle of the output PWM square wave according to the received charging power requirement of the receiver to meet the charging power requirement of the receiver, and dynamically adjusts through the PID strategy to ultimately achieve a dynamic balance between receiving and transmitting power.

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