Abstract:
A wireless power feed system with high transfer efficiency of electric power is disclosed. The wireless power feed system includes a power feeding device and a power receiving device, wherein the power feeding device includes a first electromagnetic coupling coil that is connected to an AC power source via a directional coupler; a first resonant coil; a switch connected to the opposite ends of the first resonant coil; a control circuit which conducts switching on/off of the switch based on a parameter of an amplitude of a reflective wave detected by the directional coupler; and an analog-digital converter provided between the first electromagnetic coupling coil and the control circuit; and the power receiving device includes a second resonant coil; and a second electromagnetic coupling coil, and wherein the first electromagnetic coupling coil is provided between the first resonant coil and the second resonant coil.
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.
Abstract:
There is provided a power transmission device which includes an antenna receiving a reflected power from a power receiving device, a power detection unit detecting a value of the reflected power received by the antenna, a control circuit determining a power adjustment value in accordance with the value of the reflected power, a power adjustment unit to which the reflected power whose value is detected is input and which adjusts impedance in accordance with the power adjustment value determined by the control circuit, and a demodulation circuit to which the reflected power having the power adjustment value determined by the control circuit is input via the power adjustment unit having the adjusted impedance, and relates to a power feeding system including the power transmission device.
Abstract:
A signal processing circuit that consumes less power by stop of supply of power for a short time. In a storage element, before supply of power is stopped, data in a first storage circuit is stored to a second storage circuit, and the data is read from the second storage circuit and a verification circuit can determine whether or not the data in the second storage circuit matches the data in the first storage circuit. After supply of power is restarted, the data in the second storage circuit is stored to the first storage circuit, and the verification circuit can determine whether or not the data in the second storage circuit matches the data in the first storage circuit. In such a manner, verification can be performed without requiring a time for verification.
Abstract:
Disclosed is a semiconductor device having a memory cell which comprises a transistor having a control gate and a storage gate. The storage gate comprises an oxide semiconductor and is able to be a conductor and an insulator depending on the potential of the storage gate and the potential of the control gate. Data is written by setting the potential of the control gate to allow the storage gate to be a conductor, supplying a potential of data to be stored to the storage gate, and setting the potential of the control gate to allow the storage gate to be an insulator. Data is read by supplying a potential for reading to a read signal line connected to one of a source and a drain of the transistor and detecting the change in potential of a bit line connected to the other of the source and the drain.
Abstract:
An object is to provide a power feeding system and a power feeding method which are more convenient for a power feeding user at the power receiving end, without causing increases in complexity and size of devices. An object is to provide a power feeding system and a power feeding method which also allow a power feeding provider (a company) which feeds power (at the power transmitting end) to supply power without waste. A power feeding device which wirelessly supplies power to a power receiver detects the position and the resonant frequency of the power receiver by receiving a position and resonant frequency detection signal using a plurality of sub-carriers having different frequencies from the power receiver, and controls the frequency of a power signal to be transmitted to the power receiver on the basis of the information. An efficient power feeding service can be offered by transmitting a power signal to the power receiver at an optimum frequency for high power transmission efficiency.
Abstract:
Provided is a power receiving device in which supply of power from a power supply device can be stopped while a reduction in Q-value is suppressed. The power receiving device includes a first antenna which forms resonant coupling with an antenna of the power supply device; a second antenna which forms electromagnetic induction coupling with the first antenna; a rectifier circuit including a plurality of switches and performing a first operation or a second operation depending on whether the plurality of switches is ON or OFF, the first operation being an operation in which voltage applied from the second antenna is rectified to be outputted, and the second operation being an operation in which a pair of power supply points is short-circuited; a load to which the voltage is applied; and a control circuit which generates a signal for selecting ON or OFF of the plurality of switches.
Abstract:
A contactless power feeding system includes a power transmitting device and a power receiving device. The power transmitting device includes a first AC power source configured to generate an AC power with a first frequency, a second AC power source configured to generate an AC power with a second frequency which is different from the first frequency, a first electromagnetic induction coil, and a first resonant coil. The power receiving device includes a second resonant coil, a second electromagnetic induction coil, and a power storage unit. Power is wirelessly supplied to the power storage unit at the second frequency by a magnetic resonance phenomenon which occurs between the first resonant coil and the second resonant coil.
Abstract:
A novel power receiving device and a novel power transmission device are provided. Power feeding and communication are performed using a magnetic resonance method. Specifically, in one embodiment of the present invention, power feeding is performed by generating a second high-frequency voltage based on a first high-frequency voltage induced in a resonant coil and communication is performed by modulating amplitude of the first high-frequency voltage induced in the resonant coil. Thus, it is possible to perform communication and power feeding based on data obtained by the communication in pseudo-parallel.
Abstract:
Provided is a power receiving device in which supply of power from a power supply device can be stopped while a reduction in Q-value is suppressed. The power receiving device includes a first antenna which forms resonant coupling with an antenna of the power supply device; a second antenna which forms electromagnetic induction coupling with the first antenna; a rectifier circuit including a plurality of switches and performing a first operation or a second operation depending on whether the plurality of switches is ON or OFF, the first operation being an operation in which voltage applied from the second antenna is rectified to be outputted, and the second operation being an operation in which a pair of power supply points is short-circuited; a load to which the voltage is applied; and a control circuit which generates a signal for selecting ON or OFF of the plurality of switches.