Charging pads and methods for charging receiver devices having different frequency standards

A charging pad configured to wirelessly transfer electrical power to a plurality of receiver devices, wherein the charging pad comprises:

• a power drive unit comprising:
• an oscillator configured to generate a first AC voltage signal having a first frequency;
• a bridge converter configured to convert a DC voltage signal into a second AC voltage signal having a second frequency;
• an amplifier coupled to the oscillator and configured to amplify the first AC voltage signal having the first frequency;
• and
• a transformer operatively coupled to the amplifier and the bridge converter and configured to combine the amplified first AC voltage signal and the second AC voltage signal;
• and
• a transmitting unit operatively coupled to the power drive unit and comprising:
• at least one first frequency coil tuned to the first frequency to transmit the amplified first AC voltage signal having the first frequency;
• and
• at least one second frequency coil tuned to the second frequency to transmit the second AC voltage signal having the second frequency.

A charging pad, comprising:

• a power drive unit comprising:
• a first oscillator configured to generate a first AC voltage signal having a first frequency;
• a second oscillator configured to generate a second AC voltage signal having a second frequency;
• an adder operatively coupled to the first oscillator and the second oscillator, wherein the adder is configured to:
• combine the first AC voltage signal and the second AC voltage signal to produce a combined voltage signal;
• and
• amplify the combined voltage signal having the first frequency and the second frequency;
• and
• a transmitting unit operatively coupled to the power drive unit and comprising:
• at least one first frequency coil tuned to the first frequency and configured to receive the amplified combined voltage signal and transmit the first AC voltage signal having the first frequency;
• and
• at least one second frequency coil tuned to the second frequency and configured to receive the amplified combined voltage signal and transmit the second AC voltage signal having the second frequency.