Isolated Power Supply Feedback-Loss Control for Overvoltage Protection
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Solution Overview
Problem
Existing isolated power supply modules face issues with overvoltage when the feedback loop fails due to isolation barrier failure, requiring additional components or strict topology structures for protection, limiting applicability.
Innovation Solution
A control circuit that outputs an open-loop control signal when feedback is absent and stops it based on preset conditions, such as duration or duty cycle, to prevent overvoltage without additional components, applicable to various circuit topologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional components are added to protect against overvoltage when feedback loop fails, then overvoltage protection is improved, but device complexity increases
Solution Approach 1:
The control circuit monitors its own feedback signal status and automatically switches between open-loop and closed-loop control modes. The system uses its existing feedback circuitry to detect faults and trigger protection, eliminating the need for separate protection components.
Solution Approach 2:
The control circuit continuously monitors the feedback signal from the isolation circuit to detect whether the feedback loop is functioning normally. When feedback is absent or abnormal, the control circuit automatically transitions to a protection mode, using the feedback signal status as the control input for mode switching.
2Reliability
If strict requirements are imposed on topology structure for overvoltage protection, then overvoltage protection is improved, but adaptability deteriorates
Solution Approach 1:
The control circuit implements a universal protection mechanism that works across different power supply topologies (flyback, forward, push-pull, half-bridge, full-bridge). The protection function is achieved through monitoring the feedback signal status rather than relying on topology-specific characteristics, making it broadly applicable.
Solution Approach 2:
The control circuit changes its operating parameters (control mode) based on the feedback signal status. When feedback is normal, it operates in closed-loop mode; when feedback is absent, it switches to open-loop mode with reduced duty cycle, providing adaptive protection without requiring topology-specific configurations.
3Device complexity
If open-loop control signal continues to be output after feedback loop failure, then power supply module simplicity is maintained, but harmful effects increase due to overvoltage
Solution Approach 1:
The control circuit takes preliminary action by monitoring the feedback signal status and proactively switching to protection mode before overvoltage can occur. The control circuit detects feedback loop failures and preemptively reduces the open-loop control signal duty cycle to prevent harmful overvoltage conditions.
Solution Approach 2:
The control circuit uses the presence or absence of the feedback signal as a control input to automatically adjust its output. When feedback is absent indicating a fault, the control circuit reduces the duty cycle of the open-loop control signal, creating a self-regulating protection mechanism without additional components.
Data Source
AI summary
A power supply module includes a voltage conversion circuit, a secondary-side feedback circuit, and an isolation circuit. The voltage conversion circuit is configured to convert a direct current input voltage into a direct current output voltage. The secondary-side feedback circuit is configured to obtain the direct current output voltage and output a sampling voltage based on the direct current output voltage. The isolation circuit is configured to output a feedback signal in response to the sampling voltage. The control circuit is configured to: in response to not receiving the feedback signal, output an open-loop control signal to the voltage conversion circuit; and in response to open-loop pule generation information meeting a preset condition, stop outputting the open-loop control signal.