Primary Side Shutdown Power Supply Circuit With Controlled Restart
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Solution Overview
Problem
Existing power supply systems for solid state light sources face challenges in efficiently shutting down the primary side during faults without rapid flashing or permanent failure, as current solutions either deplete secondary energy storage quickly or require AC power reconnection.
Innovation Solution
A power supply circuitry with a flyback converter topology and galvanic isolation, incorporating a fault detection circuit, isolated control circuit, and auxiliary power circuit to manage shutdown and restart of the primary AC side while maintaining secondary side operation, allowing controlled restart intervals and avoiding rapid flashing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the primary AC circuit is shut down to reduce energy delivery during a fault, then energy consumption is reduced, but the secondary energy storage is depleted quickly causing loss of shutdown signal and primary AC restart
Solution Approach 1:
The patent applies preliminary action by pre-charging the energy storage capacitor during normal operation to a voltage higher than the operating threshold. When a fault occurs and the primary side shuts down, this pre-stored energy in the capacitor provides sufficient power to maintain the shutdown signal through the optocoupler for an extended period, preventing premature restart and allowing time for fault resolution or safe system state maintenance.
2Reliability
If a latching circuit is used on the primary side to hold shutdown condition indefinitely, then shutdown reliability is improved, but the system cannot restart and AC power must be removed and re-connected
Solution Approach 1:
The patent implements dynamics by making the shutdown state controllable and reversible through software control rather than being permanently latched. The microcontroller can clear the shutdown condition and restore normal operation by re-enabling the primary side switching, allowing the system to restart automatically once the fault is cleared without requiring physical AC power disconnection and reconnection.
Solution Approach 2:
The patent uses feedback by continuously monitoring system conditions through the secondary side microcontroller and adjusting the primary side operation accordingly. The optocoupler provides isolated feedback from the secondary to primary side, enabling the system to detect faults, maintain shutdown when needed, and automatically restart when conditions permit, creating a dynamic responsive control system rather than a static latched state.
3Loss of energy
If the primary side shuts down during fault, then energy delivery to secondary side is reduced, but monitoring of detected fault becomes impossible
Solution Approach 1:
The patent introduces an intermediary by placing the microcontroller and fault detection circuitry on the secondary side of the isolation barrier, powered by the energy storage capacitor. This secondary side controller can continue monitoring fault conditions even when the primary side is shut down, and can communicate the fault status and control decisions back to the primary side through the optocoupler, maintaining monitoring capability while isolated from the primary power circuit.
Data Source
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AI summary
Fault protection circuitry and methodologies for isolated power supply topologies are provided. The circuitry is configured to shut down the primary side of the supply in case of a system fault, while keeping the secondary side circuit running, thus offering flexibility for restarting upon clearing of the fault. A lighting driver thus configured with safety isolation and a secondary side microcontroller or other control circuitry, is configured so that the circuit can shut down the primary side in response to system fault detection, while keeping the secondary microcontroller running from an energy storage circuit (e.g., bulk capacitor in parallel with load). The driver operation can resume with a controlled timing if the fault is cleared. The number of restarts may be limited, and/ or a timer may be used to space restarts. The driver may be used with loads other than lighting-based loads, as will be appreciated.