Increasing efficiency in wireless chargers

A wireless charging system comprising:

• a transmitter configured to generate a magnetic field;
• and
• a receiver comprising:
• an inductive coil configured to generate an AC signal in the presence of the magnetic field;
• a conversion circuit configured to convert the AC signal generated by the inductive coil to a DC output signal, wherein the voltage level of the DC output signal is a function of one or more characteristics of the AC signal generated by the inductive coil;
• a charging circuit configured to:
• convert the DC output signal to a DC charging signal, wherein the voltage level of the DC charging signal has a fixed relationship to the voltage level of the DC output signal and the voltage level of the DC charging signal is less than the voltage level of the DC output signal;
• and
• provide the DC charging signal to a battery;
• and
• a controller configured to:
• measure a signal of the battery that indicates a charge level of the battery;
• based on the signal of the battery, determine that a relationship between the signal of the battery and the DC charging signal satisfies a predetermined criterion;
• and
• based on determining that the relationship between the DC charging signal and the signal of the battery satisfies the predetermined criterion, generate a control signal to adjust the magnetic field;
• wherein the receiver is configured to provide the control signal to adjust the magnetic field to the transmitter.

A method for wirelessly charging a battery, the method comprising:

• measuring, by a controller, a signal of the battery that corresponds to a charge level of the battery;
• receiving, by the controller, a signal representing a characteristic of a DC charging signal, wherein the DC charging signal is generated by a receiver, the receiver comprising:
• an inductive coil configured to generate an AC signal in the presence of a magnetic field;
• a conversion circuit configured to convert the AC signal generated by the inductive coil to a DC output signal, wherein a voltage level of the DC output signal is a function of one or more characteristics of the AC signal generated by the inductive coil;
• a charging circuit configured to:
• convert the DC output signal to the DC charging signal, wherein a voltage level of the DC charging signal has a fixed relationship to the voltage level of the DC output signal and the voltage level of the DC charging signal is less than the voltage level of the DC output signal;
• and
• provide the DC charging signal to the battery;
• and
• based on the signal of the battery and the signal representing the characteristic of the DC charging signal, determining, by the controller, that a relationship between the DC charging signal and the signal of the battery satisfies a predetermined criterion;
• and
• based on determining that the relationship between the DC charging signal and the signal of the battery satisfies the predetermined criterion, generating, by the controller a control signal to adjust the AC signal.