Communicating fault indications between primary and secondary controllers in a secondary-controlled flyback converter

A method comprising:

• receiving, by a primary-side controller of a Universal Serial Bus Power Delivery (USB-PD) device from a secondary-side controller of the USB-PD device, a control signal across a galvanic isolation barrier;
• converting, by the primary-side controller, the control signal into a first pulse signal with a first pulse width;
• applying, by the primary-side controller, the first pulse signal to a primary-side power switch to control the primary-side power switch;
• detecting, by the primary-side controller, that a first fault condition has occurred;
• communicating, by the primary-side controller, a first information signal about the first fault condition to the secondary-side controller across the galvanic isolation barrier, wherein the first information signal is generated by converting the control signal into a second pulse signal with a second pulse width that is different than the first pulse width;
• and
• applying the second pulse signal to the primary-side power switch to control the primary-side power switch.

A Universal Serial Bus Power Delivery (USB-PD) device, the USB-PD device comprising:

• a primary-side integrated circuit (IC) controller;
• a primary-side power switch coupled to the primary-side IC controller;
• a flyback transformer coupled to the primary-side power switch;
• a secondary-side power switch coupled to the flyback transformer;
• and
• a secondary-side IC controller coupled to the secondary-side power switch;
• wherein the primary-side IC controller is configured to:
• receive a control signal from the secondary-side IC controller across a galvanic isolation barrier;
• convert the control signal into a first pulse signal with a first pulse width;
• apply the first pulse signal to control the primary-side power switch;
• detect that a first fault condition has occurred;
• communicate a first information signal about the first fault condition to the secondary-side IC controller across the galvanic isolation barrier, wherein the first information signal is generated by converting the control signal into a second pulse signal with a second pulse width that is different than the first pulse width;
• and
• apply the second pulse signal to control the primary-side power switch.