Patent ID: 11942871
Assignee: CYPRESS SEMICONDUCTOR CORPORATION
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H  G | IPC G  H

Claim 16:
17. A system, comprising:
a transformer comprising a primary side and a secondary side;
a first controller coupled to the secondary side of the transformer;
a discharge circuit configured to discharge an external capacitor based on an undervoltage threshold; and
a second controller coupled to the discharge circuit, the second controller coupled to receive a rectified alternating current (AC) voltage on the primary side of the transformer in an AC-DC converter and configured to receive control signals from the first controller, the second controller comprising:
a gate driver configured to turn on a primary field effect transistor (FET) that operates at a duty cycle; and
a startup controller coupled to the gate driver, the startup controller configured to:
determine whether a control signal has been received from the first controller;
in response to determining that the control signal has not been received, increase the duty cycle of the primary FET;
determine whether a voltage of the AC-DC converter is below the undervoltage threshold;
in response to determining that the voltage of the AC-DC converter is below the undervoltage threshold:
determine a current duty cycle of the primary FET; and
turn off the primary FET.