Pre-bias startup of a converter

A DC-to-DC converter, comprising:

• a power transformer having a primary side and a secondary side;
• an output voltage control loop coupled to an output voltage node at the secondary side of the power transformer and configured to generate a first signal to control a first switch at the primary side of the power transformer, the first signal having a first duty cycle;
• and
• a voltage-second (VS) controller coupled to the output voltage control loop and configured to generate a second signal to control a second switch at the secondary side of the power transformer, the second signal having a second duty cycle;
• wherein while the first duty cycle is less than a threshold, the second duty cycle is calculated by the VS controller;
• wherein while the first duty cycle is greater than the threshold, the second duty cycle is determined based on the first duty cycle in a complementary manner.

A method, comprising:

• comparing, by a voltage-second (VS) controller, a first duty cycle used to control a first switch at a primary side of a power transformer of a DC-to-DC converter with a threshold;
• if a value of the first duty cycle is less than the threshold, controlling, by the VS controller, a second duty cycle used to control a second switch at a secondary side of the power transformer, and maintaining a voltage level at an output voltage node at a non-zero value;
• and
• if the value of the first duty cycle is greater than the threshold, controlling, by an output voltage loop, the second duty cycle based on the first duty cycle, and monotonically increasing the voltage level the at the output voltage node from the non-zero value to a predetermined value.