Switching Power Supply Protection Circuit with Redundant Voltage Feedback

The feedback function is segmented into two independent paths: the traditional optocoupler feedback path and a new voltage detection path using a voltage detection circuit with resistive divider and voltage reference. This segmentation ensures that failure in one path does not compromise the entire feedback system, as the voltage detection circuit independently monitors the secondary output voltage and provides feedback to the control chip through a dedicated detection pin.

The voltage detection circuit is designed with a voltage reference and resistive divider that continuously monitors the secondary output voltage before it can reach dangerous levels. When the optocoupler fails, this pre-established detection mechanism immediately detects the voltage deviation and triggers protective action by the control chip, cushioning against the potential damage before it occurs.

The voltage detection circuit uses universal components (resistors, voltage reference, and existing control chip detection pins) that can be integrated into the existing power supply design without requiring entirely new circuit topologies. The control chip's existing detection pin is utilized for its dual purpose: normal operation monitoring and failure condition detection, reducing the need for additional dedicated components.

The voltage detection circuit creates a simplified copy of the secondary output voltage through a resistive divider network, scaling down the high voltage to a safe level that can be processed by the control chip's detection pin. This copied voltage signal provides the necessary feedback information without requiring direct connection to the high-voltage secondary side, reducing complexity while maintaining reliability.