Wireless power receiver, control method thereof, power receiving control circuit, and electronic apparatus
A wireless power receiver that receives a power signal from a wireless power transmitter includes: a receiving antenna including a receiving coil for receiving the power signal; a rectifying circuit configured to rectify an alternating current flowing through the receiving antenna; a smoothing capacitor configured to smooth an output of the rectifying circuit; an overvoltage detecting circuit configured to compare a rectified voltage generated in the smoothing capacitor with an overvoltage threshold; a modulator configured to change a parallel resonance frequency of the receiving antenna; and a discharging circuit configured to be switched between an enable state and a disable state and configured to enter the enable state during a communication period by the modulator to discharge the smoothing capacitor.
1. A power receiving control circuit for use in a wireless power receiver, comprising:
a first AC input pin and a second AC input pin connected to a receiving antenna that receives a power signal from a wireless power transmitter;
a rectification pin to which a smoothing capacitor is externally attached;
a rectifying circuit having an input side connected to the first AC input pin and the second AC input pin and an output side connected to the rectification pin;
an overvoltage detecting circuit configured to compare a rectified voltage of the rectification pin with an overvoltage threshold;
a first communication pin connected to one end of the receiving antenna via an external capacitor;
a second communication pin connected to the other end of the receiving antenna via another external capacitor;
a first modulation transistor interposed between the first communication pin and a ground;
a second modulation transistor interposed between second communication pin and the ground; and
a main controller configured to switch the first modulation transistor and the second modulation transistor so as to transmit a packet from the receiving antenna to the wireless power transmitter and configured to operate, in a transmission period of the packet, a discharging circuit interposed between the rectification pin and the ground so as to discharge the smoothing capacitor connected to the rectification pin.
2. The power receiving control circuit of claim 1 , wherein the discharging circuit includes a discharge transistor installed outside the power receiving control circuit, and
wherein the power receiving control circuit further includes a control pin connected to a control terminal of the discharge transistor.
3. The power receiving control circuit of claim 1 , wherein a discharge transistor constituting the discharging circuit is incorporated in the power receiving control circuit.
4. The power receiving control circuit of claim 2 , wherein the discharging circuit includes a discharge resistor interposed between the rectification pin and the ground and connected in series with the discharge transistor.
5. The power receiving control circuit of claim 2 , wherein the main controller switches the discharge transistor in an operation period of the discharging circuit.
6. The power receiving control circuit of claim 5 , wherein the main controller constantly turns on the discharge transistor when the rectified voltage exceeds a sub-threshold lower than the overvoltage threshold during the transmission period of the packet.
7. The power receiving control circuit of claim 6 , further comprising an A/D converter configured to convert the rectified voltage into a digital value,
wherein the main controller compares the digital value from the A/D converter with the sub-threshold.
8. The power receiving control circuit of claim 1 , further comprising a power supply circuit configured to receive the rectified voltage of the rectification pin,
wherein the main controller causes the discharging circuit to enter a disable state when a current flowing through the power supply circuit is larger than a predetermined threshold.