Saturation prevention of current transformer

A power supply circuit comprising:

• a current transformer configured to wirelessly capture an AC signal from a conductor passing through the current transformer;
• a full bridge rectifier configured to receive the AC signal and provide a rectified signal;
• a first unidirectional pass circuit coupled with the full bridge rectifier and configured to receive the rectified signal and provide a output supply signal of the power supply circuit;
• a shunt switch configured to selectively shunt current from the rectified signal;
• a controller having an output coupled to a control node the shunt switch via a second unidirectional pass circuit;
• a feedback network coupled output supply signal, the feedback network configured to provide a representation of a voltage of the output supply signal to the controller;
• a PWM generator configured to provide a PWM signal to modify a control signal of the shunt switch to reduce an imbalance of load on the current transformer;
• and
• a third unidirectional pass circuit configured to pass the PWM signal.

A method of operating a power supply to prevent saturation of a current transformer of the power supply, the method comprising:

• generating an AC signal at an output of a current transformer;
• rectifying the AC signal to provide a rectified signal at an output of a rectifier;
• rectifying output current of the power supply using an unidirectional pass circuit coupled directly with the rectifier;
• providing a representation of an output voltage of the power supply via feedback network;
• generating a PWM signal;
• shunting current of the rectified signal from the output current when the representation is higher than a threshold, regardless of a state of the PWM signal;
• and
• shunting current of the rectified signal from the output current when the PWM signal is in a first state regardless of a relative relationship of the representation and the threshold.