Wireless power receiver, control method thereof, power receiving control circuit, and electronic apparatus

Patent metadata

Field	Value
Publication number	US-2018131234-A1
Application number	US-201715804548-A
Country	US
Kind code	A1
Filing date	Nov 6, 2017
Priority date	Nov 8, 2016
Publication date	May 10, 2018
Grant date	—

Abstract

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.

First claim

What is claimed is:

1 . A wireless power receiver that receives a power signal from a wireless power transmitter, comprising:
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.

2 . The wireless power receiver of claim 1 , further comprising a main controller configured to control the modulator and the discharging circuit in association with each other.

3 . The wireless power receiver of claim 1 , wherein the discharging circuit intermittently generates a discharge current in the enable state.

4 . The wireless power receiver of claim 3 , wherein the discharge current generated by the discharging circuit is synchronized with a switching operation of the modulator.

5 . The wireless power receiver of claim 3 , wherein the discharging circuit constantly generates the discharge current when the rectified voltage exceeds a sub-threshold which is lower than the overvoltage threshold during the communication period by the modulator.

6 . The wireless power receiver of claim 1 , further comprising a power supply circuit configured to receive the rectified voltage generated in the smoothing capacitor,
wherein the discharging circuit enters the disable state when a current flowing through the power supply circuit is larger than a predetermined threshold.

7 . The wireless power receiver of claim 1 , wherein the discharging circuit includes a discharge transistor interposed between an output terminal of the rectifying circuit and a ground.

8 . The wireless power receiver of claim 7 , wherein the discharging circuit further includes a discharge resistor interposed between the output terminal of the rectifying circuit and the ground and connected in series with the discharge transistor.

9 . The wireless power receiver of claim 1 , further comprising a clamp circuit configured to shift the parallel resonance frequency of the receiving antenna when the overvoltage detecting circuit detects an overvoltage state.

10 . The wireless power receiver of claim 1 , wherein the wireless power receiver conforms to at least one of the Qi standard and the PMA standard.

11 . An electronic apparatus comprising the wireless power receiver of claim 1 .

12 . 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 the 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.

13 . The power receiving control circuit of claim 12 , 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.

14 . The power receiving control circuit of claim 12 , wherein a discharge transistor constituting the discharging circuit is incorporated in the power receiving control circuit.

15 . The power receiving control circuit of claim 13 , wherein the discharging circuit includes a discharge resistor interposed between the rectification pin and the ground and connected in series with the discharge transistor.

16 . The power receiving control circuit of claim 13 , wherein the main controller switches the discharge transistor in an operation period of the discharging circuit.

17 . The power receiving control circuit of claim 16 , 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.

18 . The power receiving control circuit of claim 17 , 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.

19 . The power receiving control circuit of claim 12 , 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.

20 . A control method of a wireless power receiver that receives a power signal from a wireless power transmitter, comprising:
receiving the power signal by a receiving antenna including a receiving coil; rectifying an alternating current flowing through the receiving antenna by a rectifying circuit; smoothing an output of the rectifying circuit by a smoothing capacitor; comparing a rectified voltage generated in the smoothing capacitor with an overvoltage threshold; changing a parallel resonance frequency of the receiving antenna in response to a modulation signal; and discharging the smoothing capacitor in synchronization with the modulation signal.

Assignees

• Rohm Co Ltd

Inventors

• Uchimoto Daisuke

Classifications

• H02J50/12 Primary

  of the resonant type · CPC title

• G05F1/46

  wherein the variable actually regulated by the final control device is DC (G05F1/625 takes precedence) · CPC title

• H02J50/80

  involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices · CPC title

• H02M7/04

  by static converters · CPC title

• H04B5/26

  using coils · CPC title