Power transmission control device, power transmission device, electronic instrument, and non-contact power transmission system
A power transmission control device provided in a power transmission device of a non-contact power transmission system includes a drive clock signal generation circuit that generates a drive clock signal specifying a drive frequency of a primary coil, a driver control circuit that generates a driver control signal based on the drive clock signal, and outputs the driver control signal to a transmission driver, a waveform detection circuit that detects a change in waveform of an induced voltage signal of the primary coil, and a control circuit that performs foreign object detection based on a detection result of the waveform detection circuit. The drive clock signal generation circuit outputs the drive clock signal set at a foreign object detection frequency during foreign object detection, the foreign object detection frequency being a frequency differing from a normal power transmission frequency.
1. A power transmission control device provided in a power transmission device included in a non-contact power transmission system, the non-contact power transmission system transmitting power from the power transmission device to a power reception device by electromagnetically coupling a primary coil and a secondary coil to transmit the power to a load of the power reception device, the power transmission control device comprising:
a drive clock signal generation circuit that generates a drive clock signal that specifies a drive frequency of the primary coil;
a driver control circuit that generates and outputs a driver control signal based on the drive clock signal, and outputs the driver control signal to a transmission driver that drives the primary coil;
a waveform detection circuit that detects a change in waveform of an induced voltage signal of the primary coil; and
a control circuit that performs foreign object detection based on a detection result of the waveform detection circuit,
the drive clock signal generation circuit outputting the drive clock signal set at a foreign object detection frequency during foreign object detection, the foreign object detection frequency being a frequency differing from a normal power transmission frequency.
2. The power transmission control device as defined in claim 1 ,
the drive clock signal generation circuit outputting the drive clock signal set at the foreign object detection frequency during foreign object detection, the foreign object detection frequency being a frequency between the normal power transmission frequency and a coil resonance frequency.
3. The power transmission control device as defined in claim 1 ,
the waveform detection circuit including a pulse width detection circuit that detects pulse width information relating to the induced voltage signal; and
the control circuit performing foreign object detection based on the pulse width information.
4. The power transmission control device as defined in claim 1 ,
the waveform detection circuit including a first pulse width detection circuit that measures a first pulse width period to detect first pulse width information, the first pulse width period being a period between a first edge timing of the drive clock signal and a first timing, the first timing being a timing when a first induced voltage signal of the primary coil that has changed from a low-potential-side power supply voltage exceeds a first threshold voltage; and
the control circuit performing foreign object detection based on the first pulse width information.
5. The power transmission control device as defined in claim 4 ,
the waveform detection circuit including a first waveform adjusting circuit that adjusts a waveform of the first induced voltage signal and outputs a first waveform-adjusted signal; and
the first pulse width detection circuit measuring the first pulse width period based on the first waveform-adjusted signal and the drive clock signal.
6. The power transmission control device as defined in claim 5 ,
the first pulse width detection circuit including a first counter that increments or decrements a count value in the first pulse width period and measures the first pulse width period based on the resulting count value.
7. The power transmission control device as defined in claim 6 ,
the first pulse width detection circuit including a first enable signal generation circuit that receives the first waveform-adjusted signal and the drive clock signal and generates a first enable signal that becomes active in the first pulse width period; and
the first counter incrementing or decrementing the count value when the first enable signal is active.
8. The power transmission control device as defined in claim 7 ,
the first enable signal generation circuit including a first flip-flop circuit, the drive clock signal being input to a clock terminal of the first flip-flop circuit, a high-potential-side power supply voltage or a low-potential-side power supply voltage being input to a data terminal of the first flip-flop circuit, and the first waveform-adjusted signal being input to a reset terminal or a set terminal of the first flip-flop circuit.
9. The power transmission control device as defined in claim 4 ,
the control circuit performing primary foreign object detection based on the first pulse width information, the primary foreign object detection being foreign object detection before normal power transmission starts.
10. The power transmission control device as defined in claim 9 ,
the waveform detection circuit including a second pulse width detection circuit that measures a second pulse width period to detect second pulse width information, the second pulse width period being a period between a second edge timing of the drive clock signal and a second timing, the second timing being a timing when a second induced voltage signal of the primary coil that has changed from a high-potential-side power supply voltage exceeds a second threshold voltage; and
the control circuit performing secondary foreign object detection based on the second pulse width information, the secondary foreign object detection being foreign object detection after normal power transmission has started.
11. The power transmission control device as defined in claim 10 ,
the waveform detection circuit including a second waveform adjusting circuit that adjusts a waveform of the second induced voltage signal and outputs a second waveform-adjusted signal; and
the second pulse width detection circuit measuring the second pulse width period based on the second waveform-adjusted signal and the drive clock signal.
12. The power transmission control device as defined in claim 11 ,
the second pulse width detection circuit including a second counter that increments or decrements a count value in the second pulse width period and measures the second pulse width period based on the resulting count value.
13. The power transmission control device as defined in claim 11 ,
the waveform detection circuit including a first waveform adjusting circuit that adjusts a waveform of the first induced voltage signal and outputs a first waveform-adjusted signal to the first pulse width detection circuit; and
the second waveform adjusting circuit adjusting a waveform of the second induced voltage signal differing from the first induced voltage signal, and outputting the second waveform-adjusted signal to the second pulse width detection circuit.
14. A power transmission device comprising:
the power transmission control device as defined in claim 1 ; and
a power transmission section that generates an alternating-current voltage and supplies the alternating-current voltage to the primary coil.
15. An electronic instrument comprising the power transmission device as defined in claim 14 .
16. A non-contact power transmission system comprising a power transmission device and a power reception device, the non-contact power transmission system transmitting power from the power transmission device to the power reception device by electromagnetically coupling a primary coil and a secondary coil to transmit the power to a load of the power reception device,
the power reception device including a power reception section that converts an induced voltage in the secondary coil into a direct-current voltage; and
the power transmission device including:
a drive clock signal generation circuit that generates a drive clock signal that specifies a drive frequency of the primary coil;
a driver control circuit that generates a driver control signal based on the drive clock signal, and outputs the driver control signal to a transmission driver that drives the primary coil;
a waveform detection circuit that detects a change in waveform of an induced voltage signal of the primary coil; and
a control circuit that performs foreign object detection based on a detection result of the waveform detection circuit,
the drive clock signal generation circuit outputting the drive clock signal set at a foreign object detection frequency during foreign object detection, the foreign object detection frequency being a frequency differing from a normal power transmission frequency.