TWI623169B - Wireless charging circuit and charging board thereof - Google Patents

Abstract

A wireless charging circuit is coupled to an oscillating unit, and the wireless charging circuit comprises a balun unit, a multi-order filtering unit and a differential unit. The balun unit is coupled to the oscillating unit. The multi-stage filtering unit is coupled to the balun unit. The differential unit is coupled to the multi-stage filter unit, and the differential unit is coupled to a transmission coil. The oscillating unit generates a differential signal to the balun unit, and the balun unit converts the differential signal into a conversion signal and transmits the signal to the multi-stage filtering unit, and the multi-stage filtering unit filters the conversion signal to output a filtered signal to The differential unit converts the filtered signal into a differential output signal and is output by the transmission coil.

Description

Wireless charging circuit and charging board thereof

The present invention relates to a wireless charging circuit and a charging board thereof, and more particularly to a wireless charging circuit coupled to an oscillator and a charging board therefor.

FIG. 1 is a schematic diagram of a wireless charging circuit of a conventional wireless charging board. 1A is a waveform diagram of a conventional wireless charging board according to FIG. 1 before and after conversion of a switching switch in an oscillator. Please refer to FIG. 1 and FIG. 1A. 1 discloses a conventional wireless charging board including an oscillator OSC, a filter circuit FC, a differential circuit DU, and a transmission coil Co. The filter circuit FC is coupled between the oscillator OSC and the differential circuit DU. The differential circuit DU is coupled to the transmission coil Co. The transmission coil Co is used to transmit electrical energy to a wireless receiving device such as a wireless mouse, a keyboard or a headphone.

In practice, the switching on relationship in the oscillator OSC receives the square wave signal W1, and the square wave signal W1 indicates the on or off of the switching switch. Therefore, the oscillator OSC will generate a differential signal such as the sine wave W2 and transmit it to the filter circuit FC. In the process of converting the square wave signal W1 into the sine wave signal W2, the energy of the portion of the excess block Re as shown in FIG. 1A is still present in the circuit or in the capacitor. The energy of the excess block Re will be transmitted to the transmission coil Co, and the energy of the part of the excess block Re is transmitted by the transmission coil Co to the wireless receiving device, thereby causing electromagnetic interference to the wireless receiving device, or Extend other noise and other issues.

In addition, the conventional filter circuit FC is composed of a plurality of inductors and a plurality of capacitors. Capacitor energy storage or inductive energy storage will generate multiple frequency noise interference. Therefore, traditional wireless charging boards often cannot overcome electromagnetic interference (EMI) and other problems; or they often cannot overcome the safety problem of 6.78 MHz electromagnetic interference. By using the wireless charging pad It often causes inconvenience or concerns about electromagnetic interference safety.

In view of this, the present invention discloses a wireless charging circuit and a charging board thereof, which are designed through a balun unit and a multi-stage filtering unit, thereby improving the convenience in use of the wireless charging circuit and the charging board thereof.

The invention provides a wireless charging circuit coupled to an oscillating unit for generating a differential signal. The wireless charging circuit includes a balun unit, a multi-stage filtering unit and a differential unit. The balun unit is coupled to the oscillating unit. The multi-stage filtering unit is coupled to the balun unit. The differential unit is coupled to the multi-stage filter unit, and the differential unit is coupled to a transmission coil. The oscillating unit transmits a differential signal to the balun unit, and the balun unit converts the differential signal into a conversion signal and transmits the signal to the multi-stage filtering unit, and the multi-stage filtering unit filters the conversion signal to output a filtered signal to The differential unit converts the filtered signal into a differential output signal and is output by the transmission coil.

The invention provides a wireless charging board comprising an oscillating unit and a wireless charging circuit. The oscillating unit is coupled to a balun unit of the wireless charging circuit. The oscillating unit is used to generate a differential signal and transmit it to the balun unit.

Based on the above, the present invention provides a wireless charging circuit, which is designed to pass a balun unit and a multi-stage filtering unit, so that the balun unit converts the differential signal into a conversion signal and transmits the signal to the multi-stage filtering unit, and then the multi-order filtering unit. The conversion signal is filtered, thereby enabling the wireless charging circuit to achieve multi-level attenuation and filtering power, and improving the convenience of use of the wireless charging circuit and its charging board.

In order to further understand the technology, method and function of the present invention in order to achieve the intended purpose, reference should be made to the detailed description and drawings of the invention. The drawings and the annexed drawings are to be considered as illustrative and not restrictive.

1‧‧‧Wireless charging circuit

OSC‧‧‧Oscillator

10‧‧‧Oscillation unit

S1‧‧‧ first switch

S2‧‧‧ second switch

S3‧‧‧ third switch

S4‧‧‧fourth switch

R1~R4‧‧‧ resistor

12‧‧‧ Barron unit

L1‧‧‧first inductance

C1‧‧‧first capacitor

T‧‧‧ center tap transformer

14, 14a, 14b‧‧‧ multi-stage filter unit

C2‧‧‧second capacitor

C3‧‧‧ third capacitor

L2‧‧‧second inductance

L3‧‧‧ third inductance

16‧‧‧Differential unit

L4‧‧‧Adjustable Inductors

C4‧‧‧fourth capacitor

C5‧‧‧ fifth capacitor

C6‧‧‧ sixth capacitor

C7‧‧‧ seventh capacitor

C8‧‧‧ eighth capacitor

C41~C46, C51~C55‧‧‧ capacitor

L41~L44, L51~L56‧‧‧Inductors

Co‧‧‧ transmission coil

BPF1‧‧‧First Bandpass Filter

BPF2‧‧‧Second bandpass filter

BPF3‧‧‧ third bandpass filter

LPF1‧‧‧ first low pass filter

LPF2‧‧‧ second low pass filter

FC‧‧‧Filter circuit

DU‧‧‧Differential circuit

W1‧‧‧ square wave signal

W2‧‧‧string signal

Re‧‧‧Excess block energy

FIG. 1 is a schematic diagram of a wireless charging circuit of a conventional wireless charging board.

1A is a waveform diagram of a conventional wireless charging board according to FIG. 1 before and after conversion of a switching switch in an oscillator.

2 is a functional block diagram of a wireless charging circuit according to an embodiment of the present invention.

3 is a circuit diagram of a wireless charging circuit in accordance with another embodiment of the present invention.

FIG. 3A is a schematic diagram of frequency-radiation power of each frequency multiplication of a wireless charging circuit according to another embodiment of the present invention.

4 is a circuit diagram of a multi-stage filtering unit of a wireless charging circuit according to another embodiment of the present invention.

FIG. 5 is a circuit diagram of a multi-stage filtering unit of a wireless charging circuit according to another embodiment of the present invention.

In the following, the invention will be described in detail by way of illustration of various exemplary embodiments of the invention. However, the inventive concept may be embodied in many different forms and should not be construed as being limited to the illustrative embodiments set forth herein. In addition, the same reference numerals may be used in the drawings to indicate similar elements.

2 is a functional block diagram of a wireless charging circuit according to an embodiment of the present invention. Please refer to Figure 2. A wireless charging circuit 1 is coupled to an oscillating unit 10. The wireless charging circuit 1 includes a balun unit 12, a multi-stage filtering unit 14, and a differential unit 16. In practice, the balun unit 12 is coupled to the oscillating unit 10 and the multi-stage filtering unit 14. The differential unit 16 is coupled to the multi-stage filtering unit 14 and the transmission coil Co.

In detail, the balun unit 12 is implemented, for example, by a balun circuit. Barron circuits are used between balanced circuits and unbalanced circuits. Therein, two balanced inputs are passed through the balun circuit of this embodiment to provide an unbalanced output. For example, two balanced inputs are inputs to the differential signal. An unbalanced output such as a turn A single output of the exchange number.

The multi-stage filtering unit 14 is configured to perform multi-stage attenuation filtering on the converted signal. The multi-order filtering unit 14 is implemented, for example, by a Butterworth filter, a Chebyshev filter, or other filters. In practice, the multi-stage filtering unit 14 includes a plurality of band pass filters and one or more low pass filters. The low pass filter is coupled between two adjacent band pass filters.

In practice, a low-pass filter is used to filter high frequencies, such as filtering signals above the cutoff frequency. The low pass filter allows low frequency signals to pass. In addition, a band-pass filter preserves signals within a bandwidth of both sides of the cutoff frequency. The band pass filter is, for example, a resistor-inductor-capacitor circuit (RLC circuit).

Among them, the band pass filter can also be generated by combining a low pass filter with a high pass filter. An ideal bandpass filter should have a completely flat passband. For example, there is no gain or attenuation in the passband, and all frequencies outside the passband are completely attenuated. In addition, the conversion outside the passband is done in a very small frequency range.

In brief, the multi-stage filtering unit 14 is, for example, a frequency doubling attenuation circuit, which is implemented by using a plurality of capacitors and a plurality of inductors. Each octave exhibits an attenuation of two to six dB. For example, the multi-stage filtering unit 14 is, for example, an eighth-order filtering circuit. At the same frequency, the eighth-order filtering circuit can attenuate and filter out 48 dB of noise compared to the first-order filtering circuit. Among them, the higher the order, the greater the degree of attenuation, the closer to the ideal filter. In the case of a first-order filter, the signal with a frequency of 10 times the cutoff frequency is attenuated by about 20 dB. The same signal passes through the second-order filter, and the signal with a frequency of 10 times the cutoff frequency is attenuated by 40 dB.

Further, the multi-stage filtering unit 14 includes a tunable inductor L4. Among them, the number of turns of the adjustable inductor L4 can be set according to the demand of the transmission coil Co. That is to say, the tunable inductor L4 belongs to the impedance matching element of the transmission coil Co, so that the loss of the transmission power of the transmission coil Co is reduced, and the transmission power of the transmission coil Co is improved. This embodiment does not limit the aspect of the tunable inductor L4.

Next, the differential unit 16 is coupled to the multi-stage filtering unit 14, and the differential unit 16 is coupled to a transmission coil Co. In practice, the differential unit 16 is implemented, for example, by a plurality of capacitors, such that a differential output signal is generated to the transmission coil Co. Therefore, the transmission coil Co can output power to charge the wireless receiving device. The differential unit 16 can be freely designed by those skilled in the art.

For example, the oscillating unit 10 generates a differential signal to the balun unit 12. The balun unit 12 converts the differential signal into a conversion signal and transmits it to the multi-stage filtering unit 14. The multi-stage filtering unit 14 filters the converted signal to output a filtered signal to the differential unit 16. The differential unit 16 converts the filtered signal into a differential output signal and is output by the transmission coil Co.

Briefly, the present embodiment transmits the differential signal to the conversion signal through the balun unit 12. Among them, the balun unit 12 performs voltage conversion, and does not have the leakage of "the conventional wireless charging board stores energy in the capacitor", whereby the balun unit 12 can eliminate the electromagnetic interference of N times the frequency caused by storing energy in the capacitor. problem.

Furthermore, the embodiment further transmits the multi-stage filtering unit 14 to attenuate and filter the converted signal into a filtered signal. Among them, the first-order filter reduces the signal strength by half (about -6dB) when the frequency is doubled (increasing octave). The multi-stage filtering unit 14 can filter the noise of the triple frequency, the quadruple frequency, the fifth frequency or the multiple frequency, thereby causing the multi-level attenuation of the noise signal strength, and the wireless charging circuit 1 meets the electromagnetic interference. (EMI) Safety regulations.

3 is a circuit diagram of a wireless charging circuit in accordance with another embodiment of the present invention. Please refer to Figure 3. The wireless charging circuit 1 shown in FIG. 3 includes an oscillating unit 10, a balun unit 12, a multi-stage filtering unit 14, a differential unit 16, and a transmission coil Co.

In detail, the oscillating unit 10 includes four switches S1 S S4 and four resistors R1 R R4, for example, including a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, and a plurality of Resistors R1~R4. The base and the first of the first switch S1 The bases of the three switches S3 are respectively coupled to a controller (not shown). The emitter of the first switch S1 is coupled to the gate of the second switch S2. The emitter of the third switch S3 is coupled to the gate of the fourth switch S4.

The source of the second switch S2 is coupled to the center tap transformer T. The source of the fourth switch S4 is coupled to the ground. The drain of the second switch S2 is coupled to ground. The drain of the fourth switch S4 is coupled to the center tap transformer T. The first switch S1 and the third switch S3 are respectively realized by a bipolar junction transistor (BJT), and the third switch S3 and the fourth switch S4 are respectively realized by a gold oxide half field effect transistor (MOSFET).

In addition, the first resistor R1 is coupled between the base and the emitter of the first switch S1. The second resistor R2 is coupled to the first resistor R1, the emitter of the first switch S1, and the gate of the second switch S2. The third resistor R3 is coupled between the base and the emitter of the third switch S3. The fourth resistor R4 is coupled to the third resistor R3, the emitter of the third switch S3, and the gate of the fourth switch S4.

Next, the balun unit 12 includes, for example, a first inductor L1, a first capacitor C1, a voltage source, and a center tap transformer T. The primary side of the center tapped transformer T is coupled to the oscillating unit 10, and the secondary side of the center tapped transformer T is coupled to the multi-stage filtering unit 14 and to the ground. In practice, the differential signal is input from both ends of the primary side of the center tapped transformer T, and the switching signal is output from one end of the secondary side of the center tapped transformer T, and enters the multi-stage filtering unit 14.

The center tapped transformer T is realized, for example, by an iron powder core transformer, a magnetic powder core transformer, a nickel zinc ferrite transformer, a manganese zinc ferrite transformer or other transformer. The turns ratio of the winding of the center tapped transformer T is 1:1, and the voltage of the voltage source is converted to a voltage of twice the voltage source through the center tapped transformer T. For example, if the voltage source is, for example, 5 volts, the voltage on the primary side of the center-tapped transformer T is 10 volts, and the voltage on the secondary side of the center-tapped transformer T is 20 volts.

In addition, the center tap of the primary side of the center tapped transformer T is coupled to a first inductor L1 and a first capacitor C1. The first inductor L1 is coupled to a voltage source and a first capacitor C1. The first capacitor C1 of the balun unit 12 is coupled to the ground to eliminate the first capacitor The capacitive reactance of C1. That is to say, the balun unit 12 is a center tapped transformer T that does not have a capacitive reactance, thereby overcoming the problem that "the energy of the excess block of the conventional wireless charging circuit is stored in the electromagnetic interference caused by the capacitor".

The multi-stage filtering unit 14 includes three capacitors C2 to C4, two inductors L2 to L3, and a tunable inductor L4. In practice, the multi-stage filtering unit 14 includes a second capacitor C2, a second inductor L2, a third capacitor C3, a third inductor L3, a tunable inductor L4, and a fourth capacitor C4.

The second capacitor C2 is coupled to the secondary side of the center tap transformer T and the second inductor L2. The second inductor L2 is coupled to the second capacitor C2, the third capacitor C3, and the third inductor L3. The third capacitor C3 is coupled between the ground, the second inductor L2, and the third inductor L3. The third inductor L3 is coupled to the center tap of the adjustable inductor L4. The first end of the adjustable inductor L4 is coupled to the fourth capacitor C4 and the fifth capacitor C5. The second end of the adjustable inductor L4 is coupled to the seventh capacitor C7 and to the ground.

The number of coils of the adjustable inductor L4 can be adjusted according to the output power requirement of the transmission coil Co. For example, before the factory leaves the manufacturer, the ratio of the number of coils of the fixed adjustable inductor L4, for example, the center tap of the adjustable inductor L4, distinguishes the number of upper and lower coils, respectively, is a ratio of turns of the coil of 1 to 1; or X ratio Y turns the turns ratio, X and Y are arbitrary integers, respectively. This embodiment does not limit the aspect of the tunable inductor L4.

In addition, the second capacitor C2 and the second inductor L2 may form a band pass filter. The adjustable inductor L4 and the fifth capacitor C5 form a band pass filter. The adjustable inductor L4 and the seventh capacitor C7 form a band pass filter. The second inductor L2, the third inductor L3, and the third capacitor C3 form a low pass filter. The third inductor L3, the adjustable inductor L4, and the fourth capacitor C4 form a low pass filter. That is, the present embodiment may have a plurality of band pass filters and a plurality of low pass filters, thereby forming a multi-stage filter circuit.

The differential unit 16 includes, for example, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, and an eighth capacitor C8. In practice, the fifth capacitor C5 is coupled to the fourth capacitor. C4, seventh capacitor C7 and adjustable inductor L4. The sixth capacitor C6 is coupled to the fifth capacitor C5 and the transmission coil Co. The seventh capacitor C7 is coupled to the adjustable inductor L4, the eighth capacitor C8, and the ground. The eighth capacitor C8 is coupled to the seventh capacitor C7 and the transmission coil Co.

The fourth capacitor C4 is coupled to the ground to eliminate the capacitive reactance of the fourth capacitor C4, the fifth capacitor C5, the sixth capacitor C6, the seventh capacitor C7, and the eighth capacitor C8. One end of the adjustable inductor L4 is coupled to the ground to eliminate the inductive reactance of the adjustable inductor L4. That is to say, the multi-stage filter circuit transmits the fourth capacitor C4 to overcome the problem of "the conventional wireless charging circuit has capacitive reactance"; and the multi-stage filter circuit transmits the adjustable inductor L4 to overcome the "known wireless charging circuit has The problem of feeling resistance.

It is worth noting that the inductance of the balun unit 12 is a high inductance value, and the inductance of the multi-stage filtering unit 14 is a low inductance value. The multi-stage filtering unit 14 is configured to attenuate and filter out noise of N times frequency, and N is a positive integer greater than or equal to two. That is, in order to make the wireless charging circuit 1 or the wireless charging board comply with the electromagnetic interference (EMI) safety regulation, the multi-order filtering unit 14 may be second-order, third-order, fourth-order, eighth-order, sixteen-order or more-order filtering. The circuit is used to filter out multi-frequency noise. The embodiment does not limit the mode and operation mode of the oscillating unit 10, the balun unit 12, the multi-stage filtering unit 14, the differential unit 16, and a transmission coil Co.

FIG. 3A is a schematic diagram of frequency-radiation power of each frequency multiplication of a wireless charging circuit according to another embodiment of the present invention. Please refer to FIG. 3A. For convenience of explanation, the wireless charging board of this embodiment transmits a resonant frequency of 6.78 MHz for wireless charging. And the main power output of the wireless charging board is 1 watt, so the radiant power of the wireless charging board is calculated by the formula to be 30 dBm. Among them, the double frequency 2F, the triple frequency 3F, the quadruple frequency 4F and the fifth frequency 5F are about 13.56 MHz, 20.34 MHz, 27.12 MHz and 33.9 MHz, respectively. The attenuation at 5F 5F is about -14dB, which is known by the formula 20 × log (1/5). Therefore, there is 16dB of radiated power in the five-frequency 5F fashion.

In addition, the specifications for electromagnetic interference (EMI) safety of wireless charging boards are -34 dB. Therefore, this embodiment needs to achieve a total attenuation value greater than 50 dB. Therefore, this embodiment transmits The circuit design of Figure 3, and the impedance of the tunable inductor L4 of Figure 3 is set to 100 ohms. Therefore, the wireless charging circuit 1 of the present embodiment can achieve an attenuation of -60 dB at five times the frequency of 5F. That is to say, in this embodiment, the circuit design of the balun unit 12 and the multi-stage filtering unit 14 is adopted to filter out noise of 5 times or more and 5F or more.

It can be seen that the circuit design of the balun unit 12 and the multi-stage filtering unit 14 in this embodiment overcomes the problems of electromagnetic interference such as wireless charging through a frequency of 6.78 MHz. In addition, the problem of electromagnetic interference generated at a wireless resonance frequency of 30 MHz to 1 GHz is known to those skilled in the art. According to the technical spirit of the present embodiment, the multi-stage filtering unit 14 can be freely designed to eliminate N times. For noise above the frequency, N is a positive integer greater than or equal to two. That is to say, the wireless charging circuit 1 of the present embodiment can overcome the electromagnetic interference problem at a wireless resonance frequency of 30 MHz to 1 GHz and operates at a wireless resonance frequency of 30 MHz to 1 GHz.

4 is a circuit diagram of a multi-stage filtering unit of a wireless charging circuit according to another embodiment of the present invention. Please refer to Figure 4. The multi-stage filtering units 14a, 14 in FIG. 4 and FIG. 3 are similar in structure. The difference between the multi-stage filtering units 14a and 14 is that the multi-stage filtering unit 14a includes six capacitors C41 to C46 and four inductors L41 to L44.

Further, the first capacitor C41 is coupled to the balun unit 12 and the first inductor L41. The first inductor L41 is coupled to the second inductor L42, the first capacitor C41, and the second capacitor C42. The second inductor L42 is coupled to the first inductor L41, the second capacitor C42, and the third capacitor C43. The third capacitor C43 is coupled to the second inductor L42, the third inductor L43, and the fourth capacitor C44. The third inductor L43 is coupled to the third capacitor C43, the fourth capacitor C44, and the fifth capacitor C45. The fifth capacitor C45 is coupled to the third inductor L43, the fourth inductor L44, the sixth capacitor C46, and the differential unit 16. The second capacitor C42, the fourth capacitor C44, the sixth capacitor C46, and the fourth inductor L44 are respectively coupled to the ground.

The first capacitor C41 and the first inductor L41 form a band pass filter. The second inductor L42 and the third capacitor C43 form a band pass filter. Third inductance L43 and The fifth capacitor C45 forms a band pass filter. The first inductor L41, the second inductor L42, and the second capacitor C42 form a low pass filter. The third inductor L43, the fourth inductor L44, the fifth capacitor C45, and the sixth capacitor C46 form a low pass filter. The function of the sixth capacitor C46 is similar to the fourth capacitor C4 of FIG. The fourth inductor L44 functions similarly to the tunable inductor L4 of FIG.

Briefly, the multi-stage filtering unit 14 of the present embodiment has three band pass filters and two low pass filters. Among them, three band-pass filters are counted as fourth-order filters, and two low-pass filters are counted as fourth-order filters, which are total eight-order filters. The first-order filter reduces the signal strength by half (approximately -6dB) when the frequency is doubled (increasing octave). That is to say, the multi-stage filtering unit 14 of the embodiment is, for example, a filter circuit capable of attenuating the eighth order, thereby attenuating and filtering out 48 dB (decibel) of noise, so that the wireless charging circuit has multiple-order attenuation to comply with electromagnetic interference (EMI). ) The specification of safety regulations.

FIG. 5 is a circuit diagram of a multi-stage filtering unit of a wireless charging circuit according to another embodiment of the present invention. Please refer to Figure 5. The multi-stage filtering units 14b and 14 in FIG. 5 and FIG. 3 are similar in structure. However, the difference between the multi-stage filtering units 14b, 14 is that the multi-order filtering unit 14b in FIG. 5 includes five capacitors C51 to C55 and six inductors L51 to L56.

Further, the first capacitor C51 is coupled to the balun unit 12 and the first inductor L51. The first inductor L51 is coupled to the first capacitor C51 and the second inductor L52. The second inductor L52 is coupled to the first inductor L51, the third inductor L53, and the second capacitor C52. The third inductor L53 is coupled to the second inductor L52, the fourth inductor L54, and the second capacitor C52. The fourth inductor L54 is coupled to the third capacitor C53 and the third inductor L53. The third capacitor C53 is coupled to the fourth inductor L54 and the fifth inductor L55. The fifth inductor L55 is coupled to the third capacitor C53, the fourth capacitor C54, and the sixth inductor L56. The sixth inductor L56 is coupled to the fifth inductor L55, the fourth capacitor C54, and the fifth capacitor C55. The fifth capacitor C55 is coupled to the sixth inductor L56 and the differential unit 16. The second capacitor C52 and the fourth capacitor C54 are respectively coupled to the ground.

The first capacitor C51 and the first inductor L51 form a first band pass filter. BPF1. The fourth inductor L54 and the third capacitor C53 form a second band pass filter BPF2. The sixth inductor L56 and the fifth capacitor C55 form a third band pass filter BPF3. The first inductor L51, the second inductor L52, the third inductor L53, the fourth inductor L54, and the second capacitor C52 form a first low pass filter LPF1. The fifth inductor L55, the sixth inductor L56, and the fourth capacitor C54 may form a second low pass filter LPF2.

Briefly, the multi-stage filtering unit 14b of the present embodiment has three band pass filters and two low pass filters. Among them, three band-pass filters are counted as fourth-order filters, and two low-pass filters are counted as fourth-order filters, which are total eight-order filters. The first-order filter reduces the signal strength by half (approximately -6dB) when the frequency is doubled (increasing octave). That is to say, the multi-stage filtering unit 14b of the embodiment is, for example, a filter circuit capable of attenuating the eighth order, thereby attenuating and filtering out 48 dB (dB) of noise, so that the multi-stage attenuation reaches the electromagnetic interference (EMI) safety regulation. Specification.

In addition, in other embodiments, the first inductor L51 and the second inductor L52 may be combined into one inductor. The third inductor L53 and the fourth inductor L54 can be combined into one inductor. The fifth inductor L55 and the sixth inductor L56 can be combined into one inductor. Therefore, the multi-stage filtering unit 14b of FIG. 5 can be simplified to form the multi-order filtering unit 14a of FIG. This embodiment does not limit the aspect of the multi-order filtering unit 14b.

In summary, the present invention is a wireless charging circuit having a circuit design of a balun unit and a multi-stage filtering unit. Among them, the balun unit is a center tapped transformer for voltage conversion. Therefore, the balun unit does not have the drawback that the conventional wireless charging board stores energy in the capacitor, so that the balun unit can eliminate the problem of doubling the electromagnetic interference caused by storing the energy in the capacitor. Furthermore, the multi-stage filtering unit transmits a circuit design of a plurality of band pass filters and one or more low-pass filters, and the multi-order filtering unit attenuates and filters the converted signals into filtered signals. The multi-stage filtering unit can filter the noise of N times or more, causing multi-level attenuation of the noise signal intensity, and the wireless charging circuit meets the specifications of electromagnetic interference (EMI) safety. In addition, the tunable inductor belongs to the impedance matching component of the transmission coil and the fourth electrical component coupled to the ground. The circuit design of the capacitor, thereby eliminating the capacitive reactance and inductive reactance of the differential unit and the transmission coil. In this way, the wireless charging circuit of the embodiment can overcome the problem that the conventional wireless charging circuit has capacitive reactance and inductive reactance, and improves the usability of the wireless charging circuit.

The above description is only an embodiment of the present invention, and is not intended to limit the scope of the invention.

Claims (10)

A wireless charging circuit is coupled to an oscillating unit, wherein the oscillating unit is configured to generate a differential signal, the wireless charging circuit includes: a balun unit coupled to the oscillating unit; and a multi-stage filtering unit coupled to the balun And a differential unit coupled to the multi-stage filtering unit, wherein the differential unit is coupled to a transmission coil; wherein the oscillating unit transmits the differential signal to the balun unit, the balun unit The signal is converted into a conversion signal and transmitted to the multi-stage filtering unit. The multi-stage filtering unit filters the conversion signal to output a filtered signal to the differential unit, and the differential unit converts the filtered signal into a differential output signal outputted by the transmission coil; wherein the balun unit is a center tapped transformer, the primary side of the center tapped transformer is coupled to the oscillating unit, and the secondary side of the center tapped transformer is coupled to the multi-stage And a filter unit, the center tap of the primary side of the center tapped transformer is coupled to a first inductor and a first capacitor, and the first inductor is coupled to a voltage source and the first capacitor. The wireless charging circuit of claim 1, wherein the differential signal is input from both ends of the primary side of the center tap transformer, and the switching signal is output from one end of the secondary side of the center tap transformer, and enters the multi-step a filtering unit, and the turns ratio of the winding of the center tapped transformer is 1:1, and the voltage of the voltage source is converted to twice the voltage of the voltage source through the center tap transformer. The wireless charging circuit of claim 1, wherein the first capacitance of the balun unit is coupled to ground to cancel the capacitive reactance of the first capacitor, and the inductance of the balun unit is a high inductance value. The inductance of the multi-stage filtering unit is a low inductance value, and the multi-order filtering unit is used to filter out a noise of N times frequency, and N is a positive integer greater than or equal to two. The wireless charging circuit of claim 1, wherein the multi-level filtering unit comprises a second capacitor, a second inductor, a third capacitor, a third inductor, a tunable inductor, and a fourth capacitor coupled to the secondary side of the center-tapped transformer and the second inductor The third capacitor is coupled between the second inductor and the third inductor, the third inductor is coupled to the center tap of the adjustable inductor, and the first end of the adjustable inductor is coupled to the fourth capacitor and The multi-stage filtering unit has a second end coupled to the ground and the multi-stage filtering unit. The wireless charging circuit of claim 1 or 4, wherein the multi-order filtering unit performs multi-stage attenuation filtering on the conversion signal, the multi-order filtering unit comprising a plurality of band pass filters and one or more low pass filters The low pass filter is coupled between two adjacent band pass filters, and the wireless charging circuit operates at a wireless resonant frequency of 30 MHz to 1 GHz. The wireless charging circuit of claim 4, wherein the differential unit comprises a fifth capacitor, a sixth capacitor, a seventh capacitor, and an eighth capacitor, wherein the fifth capacitor is coupled to the fourth capacitor, the third a seventh capacitor and the adjustable inductor, the sixth capacitor is coupled to the fifth capacitor and the transmission coil, the seventh capacitor is coupled to the adjustable inductor, the eighth capacitor and the ground, and the eighth capacitor is coupled to the The seventh capacitor and the transmission coil. The wireless charging circuit of claim 6, wherein the fourth capacitor is coupled to the ground to cancel the capacitance of the fourth capacitor, the fifth capacitor, the sixth capacitor, the seventh capacitor, and the eighth capacitor The adjustable inductor is coupled to ground to eliminate the inductive reactance of the adjustable inductor. The wireless charging circuit of claim 1, wherein the center tap transformer is an iron powder core transformer, a magnetic powder core transformer, a nickel zinc ferrite transformer or a manganese zinc ferrite transformer, and the center tap transformer is wound. The turns ratio of the line is 1 to 1. The wireless charging circuit of claim 1, wherein the oscillating unit comprises a first switch, a second switch, a third switch, a fourth switch and a plurality of resistors, a base of the first switch and the first The bases of the three switches are respectively coupled to the controller, The emitter of the first switch is coupled to the gate of the second switch, the emitter of the third switch is coupled to the gate of the fourth switch, the source of the second switch, and the source of the fourth switch The first switch and the third switch are respectively coupled to the balun unit, and the first switch and the third switch are respectively bipolar junction transistors, and the first switch and the third switch are respectively coupled to the ground. The third switch and the fourth switch are respectively gold oxide half field effect transistors. A wireless charging board comprising: a wireless charging circuit as in one of claims 1 to 9; and an oscillating unit coupled to a balun unit of the wireless charging circuit, the oscillating unit for generating a differential signal, And transmitted to the balun unit.