Dynamic discharge current control for improving power supply output regulation

A method during a communication period for a flyback converter:

• transmitting a message as a series of pulses from a secondary-side controller to a primary-side controller;
• in the primary-side controller, acknowledging the series of pulses by cycling a power switch through a series of cycles;
• measuring a deviation of a power supply voltage from a desired value for the power supply voltage responsive to the cycling of the power switch through the series of cycles;
• and
• adjusting a discharge current to ground from an output voltage rail supplying the power supply voltage to maintain the power supply voltage within a regulation range that includes the desired value for the power supply voltage.

A flyback converter, comprising:

• a plurality of selectable resistor circuits coupled between an output voltage rail for the flyback converter, each selectable resistor circuit comprising a resistor in series with a switch;
• and
• a secondary-side controller configured to enumerate a mobile device regarding whether the mobile device supports a fast charge mode and configured to transmit a message to a primary-side controller during a communication period confirming that the fast charge mode is supported by the mobile device, the secondary side controller including:
• a discharge control logic circuit configured to select from the plurality of selectable resistor circuits responsive to a deviation of a power supply voltage from a desired value of the power supply voltage during the communication period to adjust a discharge current conducted from the output voltage rail to ground.