Power supply circuit with secondary side to primary side communication

An electrical circuit for a power supply, the electrical circuit comprising:

• a primary-side switch on a primary side of the power supply, the primary-side switch being connected to a primary winding of a flyback transformer;
• a secondary-side controller integrated circuit (IC) that is configured to monitor an output voltage on a secondary side of the power supply and to induce a detection signal from a secondary winding of the flyback transformer to the primary winding of the flyback transformer in response to the output voltage of the power supply dropping below a threshold;
• and
• a primary-side controller IC having a first pin that is connected to the primary-side switch, the primary-side controller IC being configured to control a switching operation of the primary-side switch to regulate the output voltage of the power supply, and to turn on the primary-side switch in response to sensing the detection signal at the first pin.