Power Supply Error Latch Circuit for Persistent Overcurrent Protection
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Solution Overview
Problem
Power supplies with error latch protection often have their latch mode easily released, allowing potential errors such as overcurrent or overvoltage to be ignored by users, as they can be reset by simply pressing a power button, which compromises safety and reliability.
Innovation Solution
A power supply design incorporating an AC to DC converter, main and standby power converters, a power switch circuit, an error detecting circuit, and a latch trigger circuit that enters a persistent latch mode upon detecting overvoltage or overcurrent, forcing the main power converter to shut off and the standby power to remain at a low level until AC power is removed, eliminating the need for an expansive controller IC and preventing accidental reset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a controller IC with error latch function is used to provide latch mode protection, then the power supply can enter latch mode when error occurs, but the latch mode can be easily released by pressing the power button, resulting in the error being ignored by the user
Solution Approach 1:
The invention extracts the error latch function from the controller IC and implements it through a dedicated error latch circuit with specific components (resistors, capacitors, transistors). This separate implementation allows the latch mode to be maintained independently of the power button reset function, resolving the contradiction between latch persistence and ease of reset operation
Solution Approach 2:
The invention introduces an intermediary error latch circuit that acts as a mediator between the error detection and the power switch control. This circuit uses RC time constants and transistor switching to maintain the latch state independently, preventing the power button from directly resetting the error condition while still allowing proper error protection
2Ease of operation
If the latch mode is easily released by pressing the power button, then the power supply can be reset quickly, but the error protection is compromised and safety is reduced
Solution Approach 1:
The invention applies preliminary anti-action by designing the error latch circuit to automatically prevent reset operations during error conditions. The circuit proactively blocks the power button's ability to reset the error state until the error condition is cleared, ensuring that users cannot accidentally ignore safety errors while still allowing intentional reset after proper troubleshooting
3Reliability
If an expansive controller IC with error latch protection is used, then the power supply can provide comprehensive protection functions, but the device complexity and cost increase
Solution Approach 1:
The invention segments the error protection function from the main controller IC and implements it through a separate, simpler error latch circuit. This segmentation allows the controller IC to focus on power conversion control while the dedicated latch circuit handles error detection and latching, reducing overall system complexity and cost while maintaining comprehensive protection
Solution Approach 2:
The invention creates a simplified copy of the error latch function using basic electronic components (resistors, capacitors, transistors) instead of requiring a complex controller IC. This copying approach implements the essential error protection functionality with much simpler hardware, reducing device complexity and cost
Data Source
AI summary
A power supply employs an error detecting circuit to output an error signal when detecting an overvoltage or overcurrent occurred in one of output powers and employs a latch trigger circuit to cause the power supply to enter a latch mode when receiving the error signal. The power supply will keep the latch mode when entering the latch mode until the AC power VAC is removed. In addition, the power supply employs the error detecting circuit to provide the accurate safety threshold value by the constant current source with temperature compensation function and stable constant current output.