DC-DC converter, power receiving device, and power feeding system

• US 9,998,003 B2
• Filed: 10/21/2016
• Issued: 06/12/2018
• Est. Priority Date: 12/16/2011
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Takahashi, Kei, Kamata, Koichiro, Miwa, Misako, Maeda, Shuhei
• Primary Examiner(s): Fantu, Yalkew
• Application Number:
  US15/331,029
• Publication Number:
  US 20170040891A1
• Time in Patent Office: 599 Days
• Field of Search: 320108
• CPC Class Codes: G05F 3/08 wherein the variable is dc
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 7/00034 Charger exchanging data with an electronic device, i.e. telephone, whose internal battery is under charge
• CPC Class Codes: H02M 1/0022 the disturbance parameters being input voltage fluctuations
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

A circuit capable of keeping input impedance constant is provided. Further, a circuit which can contribute to improvement in power feeding efficiency in power feeding by a magnetic resonance method is provided. A voltage (a former voltage) proportional to a direct-current voltage input to a DC-DC converter from the outside and a voltage (a latter voltage) proportional to a current input from the outside are detected, and the ratio of the former voltage and the latter voltage are held constant. Accordingly, input impedance can be kept constant. Further, impedance conversion is performed in the DC-DC converter. Thus, even when the battery in which power feeding is performed exists on an output side of the DC-DC converter, input impedance can be kept constant. Consequently, power can be supplied to a power receiving device including the DC-DC converter and the battery with high power feeding efficiency by a magnetic resonance method.

Claims

1. A power receiving device comprising:

a first coil;

a rectifier circuit electrically connected to the first coil; and

a DC-DC converter electrically connected to the rectifier circuit, the DC-DC converter comprising a load, a first switch, and a first to third circuits,

wherein the first circuit is configured to output a first voltage to the third circuit,

wherein the second circuit is configured to output a second voltage to the third circuit,

wherein the first voltage is proportional to an input voltage input to the DC-DC converter,

wherein the second voltage is proportional to a current generated in the load, and

wherein the third circuit is configured to hold a ratio of the first voltage and the second voltage constant by controlling switching of the first switch.

2. The power receiving device according to claim 1, further comprising a battery electrically connected to an output side of the DC-DC converter.

3. The power receiving device according to claim 1, wherein the third circuit comprises a triangle wave oscillator, an error amplifier, and a comparator,

wherein the triangle wave oscillator and the error amplifier are electrically connected to the comparator.

4. The power receiving device according to claim 3, wherein the comparator is electrically connected to the first switch.

5. The power receiving device according to claim 3, further comprising a buffer in the third circuit,

wherein the buffer is provided between the comparator and the first switch.

6. The power receiving device according to claim 1, wherein the first switch is a transistor.

7. The power receiving device according to claim 1, further comprising a second switch electrically connected to the third circuit,

wherein a phase of a voltage input to the first switch is opposite to a phase of a voltage input to the second switch.

8. The power receiving device according to claim 1, further comprising a charge and discharge unit,

wherein the charge and discharge unit is provided between a first output node of the DC-DC converter and a second output node of the DC-DC converter.

9. A power feeding system comprising:

a power transmitting device comprising;

a power supply; and

a second coil electrically connected to the power supply, and the power receiving device according to claim 1.

10. A power receiving device comprising:

a first coil;

a rectifier circuit electrically connected to the first coil; and

a DC-DC converter electrically connected to the rectifier circuit, the DC-DC converter comprising a diode, a load, a first switch, and a first to third circuits,

wherein the first circuit is configured to output a first voltage to the third circuit,

wherein the second circuit is configured to output a second voltage to the third circuit,

wherein the first voltage is proportional to an input voltage input to the DC-DC converter,

wherein the second voltage is proportional to a current generated in the load,

wherein the third circuit is configured to hold a ratio of the first voltage and the second voltage constant by controlling switching of the first switch, and

wherein one end of the diode is electrically connected to one end of the first switch.

11. The power receiving device according to claim 10, further comprising a battery electrically connected to an output side of the DC-DC converter.

12. The power receiving device according to claim 10, wherein the third circuit comprises a triangle wave oscillator, an error amplifier, and a comparator,

wherein the triangle wave oscillator and the error amplifier are electrically connected to the comparator.

13. The power receiving device according to claim 12, wherein the comparator is electrically connected to the first switch.

14. The power receiving device according to claim 12, further comprising a buffer in the third circuit,

wherein the buffer is provided between the comparator and the first switch.

15. The power receiving device according to claim 10, wherein the first switch is a transistor.

16. The power receiving device according to claim 10, further comprising a second switch electrically connected to the third circuit,

wherein a phase of a voltage input to the first switch is opposite to a phase of a voltage input to the second switch.

17. The power receiving device according to claim 10, further comprising a charge and discharge unit,

wherein the charge and discharge unit is provided between a first output node of the DC-DC converter and a second output node of the DC-DC converter.

18. A power feeding system comprising:

a power transmitting device comprising;

a power supply; and

a second coil electrically connected to the power supply, and the power receiving device according to claim 10.