Method and apparatus for input charge control of a power supply

A controller for a power supply, the controller comprising:

• a constant current control circuit to be coupled to receive an input current sense signal, an input voltage sense signal, and an output voltage sense signal and adapted to regulate an output current of the power supply by generating a control signal to control switching of a switch of the power supply;
• an integrator included in the constant current control circuit and coupled to integrate the input current sense signal during a switching period of the control signal to generate an integrated signal representative of a charge taken from an input voltage source of the power supply;
• an arithmetic operator circuit coupled to generate a reference signal that is proportional to a ratio of the output voltage sense signal to the input voltage sense signal;
• and
• a comparator coupled to the integrator and the arithmetic operator, wherein the comparator is to be coupled to turn the switch to an OFF state in response to the integrated signal reaching a value of the reference signal.

A controller for a power supply, the controller comprising:

• a constant current control circuit to be coupled to receive an input current sense signal, an input voltage sense signal, and an output voltage sense signal and adapted to regulate an output current of the power supply by generating a control signal to control switching of a switch of the power supply;
• an integrator included in the constant current control circuit and coupled to integrate the input current sense signal during a switching period of the control signal to generate an integrated signal representative of a charge taken from an input voltage source of the power supply;
• an arithmetic operator circuit coupled to generate a multiplication signal that is proportional to the input voltage sense signal multiplied by the integrated signal;
• and
• a comparator coupled to receive the output voltage sense signal and coupled to the arithmetic operator, wherein the comparator is to be coupled to turn the switch to an OFF state in response to the integrated signal reaching a value of the output voltage sense signal.