Contactless power transmission system capable of controlling power transmitter apparatus to stably supply load device with required power

A contactless power transmission system including a power transmitter apparatus and a power receiver apparatus, the contactless power transmission system transmitting power in a contactless manner from the power transmitter apparatus to the power receiver apparatus,

• wherein the power transmitter apparatus comprises:
• a transmitting coil;
• a power supply circuit configured to generate transmitting power having a variable voltage and a variable frequency, and supply the transmitting power to the transmitting coil;
• and a controller apparatus,
• wherein the power receiver apparatus comprises:
• a receiving coil;
• a voltage detector circuit configured to detect an output voltage of the power receiver apparatus;
• and a power-receiver communication device communicatively connected to the power transmitter apparatus, and configured to transmit a detected value of the output voltage of the power receiver apparatus to the power transmitter apparatus,
• wherein the controller apparatus comprises:
• a power-transmitter communication device communicatively connected to the power receiver apparatus, and configured to receive the detected value of the output voltage of the power receiver apparatus from the power receiver apparatus;
• and
• a first control circuit configured to control the power supply circuit based on the detected value of the output voltage of the power receiver apparatus,
• wherein the first control circuit is further configured to:
• control the power supply circuit to generate transmitting power having a frequency varying within a predetermined frequency range,
• receive the detected value of the output voltage of the power receiver apparatus from the power receiver apparatus using the power-transmitter communication device, the detected value being detected in the power receiver apparatus when generating the transmitting power using the power supply circuit,
• determine a stably transmitting frequency based on the detected value of the output voltage of the power receiver apparatus, the stably transmitting frequency indicating a frequency of the transmitting power at which dependency of the output voltage of the power receiver apparatus on a load value of the power receiver apparatus is at least locally minimized within the frequency range,
• determine a transmitting voltage based on the detected value of an output voltage of the power receiver apparatus, the transmitting voltage indicating a voltage of the transmitting power at which the output voltage of the power receiver apparatus reaches a predetermined target voltage when generating transmitting power having the stably transmitting frequency, and control the power supply circuit to generate transmitting power having the stably transmitting frequency and the transmitting voltage,
• wherein the power receiver apparatus further comprises:
• a load device having a variable load value:
• a first load element having a first load value;
• a second load element having a second load value larger than the first load value;
• and a first switch circuit configured to selectively supply the output voltage of the power receiver apparatus to one of the load device, the first load element, and the second load element,
• wherein the first control circuit is further configured to:
• when performing normal power transmission, transmit a control signal to the power receiver apparatus using the power-transmitter communication device, the control signal being provided for switching the first switch circuit to supply the output voltage of the power receiver apparatus to the load device, and
• when determining a frequency of the transmitting power, transmit a control signal to the power receiver apparatus using the power-transmitter communication device, the control signal being provided for switching the first switch circuit to supply the output voltage of the power receiver apparatus to the first or second load element, and
• wherein the first control circuit is further configured to:
• obtain a first voltage indicating a frequency characteristic of the output voltage of the power receiver apparatus, based on the detected value of the output voltage of the power receiver apparatus, when the output voltage of the power receiver apparatus is supplied to the first load element,
• obtain a second voltage indicating a frequency characteristic of the output voltage of the power receiver apparatus, based on the detected value of the output voltage of the power receiver apparatus, when the output voltage of the power receiver apparatus is supplied to the second load element, and
• determine a frequency of the transmitting power at which a difference between the first voltage and the second voltage is minimized, as the stably transmitting frequency.