Demodulator for wireless power transmitter
A demodulator is mounted on a wireless power transmitter that conforms to the Qi standard, and demodulates an amplitude modulated signal superimposed on a coil current I COIL that flows through a primary coil of a transmission antenna, or otherwise on a coil voltage across both ends of the primary coil. Multiple demodulating units are each configured to have respectively different configurations, to operate in parallel, to extract a demodulated component from the coil current I COIL or otherwise from the coil voltage, and to generate baseband signals as demodulated signals. A signal processing unit employs a baseband signal that is correctly received, from among the multiple baseband signals generated by the multiple demodulating units, based on an error detection result obtained using a checksum.
1. A demodulator mounted on a wireless power transmitter that conforms to a Qi standard, and configured to demodulate an amplitude modulated signal superimposed on a coil current that flows through a primary coil of a transmission antenna, or otherwise on a coil voltage across both ends of the primary coil, the demodulator comprising:
a plurality of demodulating units having respectively different demodulation characteristics, and each configured to operate in parallel, and to extract a modulated component from the coil current or otherwise from the coil voltage so as to generate a baseband signal as a demodulated signal; and
a signal processing unit configured to employ a baseband signal that has been correctly received, selected from among the plurality of baseband signals generated by the multiple demodulating units based on an error detection result obtained using a checksum.
2. The demodulator according to claim 1 , wherein the plurality of demodulating units are each configured to have a high reception rate in respectively different load current ranges.
3. The demodulator according to claim 1 , wherein the signal processing unit is configured to sequentially set each one of the plurality of baseband signals as a checksum target.
4. The demodulator according to claim 1 , wherein at least one from among the plurality of demodulating units comprises a diode rectifier circuit configured to perform diode rectification of the coil current or otherwise of the coil voltage.
5. The demodulator according to claim 1 , wherein at least one from among the plurality of demodulating units comprises a bridge circuit configured to perform synchronous detection of the coil current or otherwise of the coil voltage.
6. The demodulator according to claim 1 , further comprising a current transformer configured to generate a detection signal that corresponds to the coil current that flows through the transmission antenna.
7. The demodulator according to claim 1 , monolithically integrated on a single semiconductor substrate.
8. A control circuit employed in a wireless power transmitter configured to conform to a Qi standard, comprising a transmission antenna that comprises a primary coil, and a driver connected to the transmission antenna, the control circuit comprising:
the demodulator according to claim 1 , configured to demodulate an amplitude modulated signal superimposed on a coil current that flows through a primary coil of a transmission antenna, or otherwise on a coil voltage across both ends of the primary coil; and
a controller configured to control the driver based on a baseband signal received from the demodulator.
9. The control circuit according to claim 8 , monolithically integrated on a single semiconductor substrate.
10. A wireless power transmitter comprising:
a transmission antenna comprising a primary coil;
a driver connected to the transmission antenna;
a controller configured to control the driver; and
the demodulator according to claim 1 , configured to demodulate an amplitude modulated signal superimposed on a coil current that flows through the primary coil, or otherwise on a coil voltage across both ends of the primary coil.
11. A method employed in a wireless power transmitter that conforms to a Qi standard for demodulating an amplitude modulated signal superimposed on a coil current that flows through a primary coil of a transmission antenna, or otherwise on a coil voltage across both ends of the primary coil, the method comprising:
providing a plurality of demodulating units having respectively different demodulation characteristics;
operating the plurality of demodulating units in parallel so as to instruct each demodulating unit to extract a demodulated component from the coil current or otherwise from the coil voltage, and to generate a baseband signal as a demodulated signal; and
employing a baseband signal that is correctly received, from among the plurality of baseband signals generated by the plurality of demodulating units, based on an error detection result obtained using a checksum.