Demodulation circuit and wireless charging device having the same

A wireless charging device, used to receive a pulse width modulation signal, the wireless charging device performs near distance wireless charging, the wireless charging device comprising:

• a coil, for receiving the pulse width modulation signal;
• a power stage circuit, electrically connected to the coil, for outputting a voltage or an electromagnetic energy to the coil;
• and
• a demodulation circuit, electrically connected to the coil and the power stage circuit, the demodulation circuit comprising:
• a control unit, electrically connected to the power stage circuit, for controlling the power stage circuit;
• a detection unit, electrically connected to the coil and the power stage circuit for detecting the pulse width modulation signal received by the coil and outputting a modulation signal, the modulation signal is an analog data signal;
• a switch unit, electrically connected to the detection unit;
• a delay unit, electrically connected to the switch unit for delaying the modulation signal and generating a delay signal;
• a demodulation unit, electrically connected to the switch unit and the delay unit for comparing the modulation signal and the delay signal so as to generate a first demodulation signal, wherein the first demodulation signal is a binary data signal;
• an amplifier, electrically connected to the switch unit for amplifying the modulation signal, the switch unit is used to output the modulation signal to the amplifier, the delay unit or the demodulation unit;
• an analog digital convertor, electrically connected to the amplifier, the analog digital convertor transforms an analog modulation signal into a digital modulation signal;
• and
• a digital demodulation unit, electrically connected to the analog digital convertor for generating a second demodulation signal;
• wherein when the voltage level of the modulation signal is higher than or equal to a voltage level of the delay signal, the demodulation unit outputs a high logic level first demodulation signal to the control unit. When the voltage level of the modulation signal is lower than the voltage level of the delay signal, the demodulation unit outputs a low logic level first demodulation signal to the control unit. When the control unit detects the first demodulation signal is lower than a demodulation success rate in a time period, the control unit outputs a first switch signal to the switch unit, the first switch signal is used to control the switch unit to output the modulation signal to the amplifier.;
• wherein when the control unit detects the second demodulation signal is lower than the demodulation success rate in the time period, the control unit outputs a second switch signal to the switch unit, the second switch signal is used to control the switch unit to output the modulation signal to the delay unit and the demodulation unit.