Power transmission device and waveform monitor circuit for use in power transmission device
View Patent ↗A power transmission device in a power transmission system including the power transmission device including a primary coil and a power reception device including a secondary coil, the primary coil being electromagnetically coupled to the secondary coil, to receive in the power reception device AC power transmitted from the power transmission device, comprises a waveform monitor circuit configured to detect an electric potential at one end of the primary coil and output a waveform monitor signal formed by restricting the detected electric potential to an electric potential which is equal to or higher than a ground electric potential; a waveform detection circuit configured to detect a waveform change in the waveform monitor signal input from the waveform monitor circuit; and a data detection circuit configured to detect data transmitted by load change by a load modulation unit in the power reception device based on a result of detection of the waveform change detected by the waveform detection circuit.
1. A power transmission device comprising:
a primary coil;
a waveform monitor circuit configured to detect an electric potential at one end of the primary coil, and output a waveform monitor signal formed by restricting the detected electric potential to an electric potential which is equal to or higher than a reference electric potential;
a waveform detection circuit configured to detect a waveform change in the waveform monitor signal input from the waveform monitor circuit; and
a data detection circuit configured to detect data transmitted from a power reception device to the power transmission device based on a result of detection of the waveform change detected by the waveform detection circuit, wherein:
the waveform monitor circuit includes:
a rectification circuit including a diode, the diode being provided in series between the one end of the primary coil and an input end of the waveform detection circuit such that a direction from the one end of the primary coil to the input end of the waveform detection circuit is a forward direction of the diode; and
a first resistor, one end of which is connected to a node on a signal line between a cathode side of the diode and the input end of the waveform detection circuit, and another end of which is connected to a ground terminal held at a ground electric potential.
2. The power transmission device according to claim 1 ,
wherein the rectification circuit further includes a second resistor provided between the cathode side of the diode and the node.
3. The power transmission device according to claim 1 ,
wherein the rectification circuit further includes a second resistor provided between the one end of the primary coil and an anode side of the diode.
4. A power transmission device comprising:
a primary coil;
a waveform monitor circuit configured to detect an electric potential at one end of the primary coil, and output a waveform monitor signal formed by restricting the detected electric potential to an electric potential which is equal to or higher than a reference electric potential;
a waveform detection circuit configured to detect a waveform change in the waveform monitor signal input from the waveform monitor circuit; and
a data detection circuit configured to detect data transmitted from a power reception device to the power transmission device based on a result of detection of the waveform change detected by the waveform detection circuit, wherein:
the waveform monitor circuit includes:
a rectification circuit including a diode and a second resistor, the diode being provided in series between the one end of the primary coil and an input end of the waveform detection circuit such that a direction from the one end of the primary coil toward the input end is a forward direction of the diode, and the second resistor being provided at an anode side of the diode;
a first resistor, one end of which is connected to a node on a signal line between the anode side of the diode and the second resistor, and another end of which is connected to a ground terminal held at a ground electric potential; and
a third resistor, one end of which is connected to a cathode side of the diode and another end of which is connected to the ground terminal.
5. The power transmission device according to claim 4 ,
wherein the rectification circuit further includes a fourth resistor provided between the cathode side of the diode and the input end of the waveform detection circuit.
6. The power transmission device according to claim 4 ,
wherein the rectification circuit further includes a fifth resistor provided between the anode side of the diode and the node.
7. The power transmission device according to claim 1 ,
wherein the diode is a Schottky barrier diode.
8. The power transmission device according to claim 1 ,
wherein the diode is a Zener diode.
9. A waveform monitor circuit comprising:
an input terminal to be connected to one end of a primary coil of a power transmission device;
an output terminal to be connected to an waveform detection circuit of the power transmission device;
a rectification circuit including a diode, the diode being provided in series between the input terminal and the output terminal such that a direction from the input terminal to the output terminal is a forward direction of the diode; and
a first resistor, one end of which is connected to a node on a signal line between an output end of the rectification circuit and the output terminal, and the other end of which is connected to a ground terminal held at a ground electric potential.
10. A waveform monitor circuit comprising:
an input terminal to be connected to one end of a primary coil of a power transmission device;
an output terminal to be connected to an waveform detection circuit of the power transmission device;
a rectification circuit including a diode and a second resistor, the diode being provided in series between the input terminal and the output terminal such that a direction from the input terminal to the output terminal is a forward direction of the diode, and the second resistor being provided at an anode side of the diode;
a first resistor, one end of which is connected to a signal line between an anode side of the diode and the second resistor, and the other end of which is connected to a ground terminal held at a ground electric potential; and
a third resistor, one end of which is connected to a cathode side of the diode and the other end of which is connected to the ground terminal.
11. The power transmission device according to claim 4 , wherein the diode is a Schottky barrier diode.
12. The power transmission device according to claim 4 , wherein the diode is a Zener diode.