Comparator Latch Reset Circuit for Power Converter Overvoltage
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Solution Overview
Problem
Existing overvoltage protection circuits for power supplies face challenges in designing latching functionality that does not occur at start-up, requiring critical component dimensioning and making the circuit design difficult.
Innovation Solution
Incorporating a reset circuit with a high-pass filter and edge-triggered switching element in the comparator feedback loop, allowing for controlled latching and resetting of the shutdown signal, independent of start-up conditions, using a microprocessor for intelligent reset signal generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rectifier element is used in the feedback loop of the comparator to implement latching functionality, then the overvoltage protection circuit can latch the shutdown signal, but the circuit design becomes very difficult and requires critical component dimensioning to prevent unintended latching at start-up
Solution Approach 1:
The patent introduces a reset circuit as an intermediary element between the comparator and the shutdown output. This reset circuit includes a switching element (such as a transistor) that acts as a mediator to control the latching behavior. The switching element is controlled by a reset signal to selectively connect or disconnect the feedback path containing the rectifier element, thereby enabling controlled latching without the design complexity of preventing unintended latching at start-up.
Solution Approach 2:
The patent applies preliminary action by providing a reset signal that is generated in advance (e.g., during power-up or through a microprocessor) to pre-configure the switching element in the reset circuit. This preliminary action ensures that the feedback path is properly controlled before the comparator begins its overvoltage detection function, preventing unintended latching at start-up while maintaining reliable latching when needed.
2Reliability
If component dimensions are optimized to prevent latching at start-up, then unintended latching is avoided, but the design requires very critical narrow specifications and becomes difficult to implement
Solution Approach 1:
The reset circuit with its controlled switching element serves as an intermediary that decouples the reliability of preventing unintended latching from the complexity of component dimensioning. Instead of relying on critical component values, the switching element provides explicit control over the feedback path, making the design much easier to manufacture while maintaining high reliability.
3Reliability
If the overvoltage protection circuit is designed to latch at start-up, then latching functionality is achieved, but the circuit may produce unintended resets or require complex reset control logic
Solution Approach 1:
The reset circuit acts as an intermediary control mechanism that simplifies reset management. The switching element in the reset circuit, when controlled by a simple reset signal (such as a microprocessor output or power-up signal), provides clean control over the latching behavior without requiring complex reset control logic. This intermediary structure eliminates the need for sophisticated reset sequences while maintaining reliable latching functionality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Simplifies the circuit design by eliminating the need for critical component dimensioning, ensuring reliable latching and resetting, and making the system more robust against unintended resets.
Implementation Method 1
The reset circuit comprises a high-pass filter coupled to an input of a switching element
Implementation Method 2
Such latching functionality may be implemented by using a rectifier element in the feedback loop of the comparator
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to an overvoltage protection circuit (40', 41, 42) for a power supply (100) comprising a power converter (20), the overvoltage protection circuit (40') comprising a comparator (OA2). The overvoltage protection circuit (40', 41, 42) is configured for using the comparator (OA2) for comparing the power supply voltage (VDC) with the reference voltage, and for producing a power supply shutdown signal (S41 s) on the shutdown output terminal (41 s) when the power supply voltage (VDC) exceeds the maximal power supply voltage, and for latching said power supply shutdown signal (S41 s) on the shut down output terminal (41 s) even if said power supply voltage (VDC) subsequently drops to a level below the maximal power supply voltage. The overvoltage protection circuit (40') further comprises a reset circuit (41 rc) coupled to the first input (+) of the comparator (OA2), the reset circuit (41 rc) being configured for pulling the signal level on the first input (+) below said reference value such that the power supply shutdown signal (S41 s) is reset when a reset signal (S41 r) is given to the reset circuit (41 rc).