Dimming Power Supply Short-Circuit Sensing for Inrush Immunity
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Solution Overview
Problem
Existing dimming power supplies falsely trigger short-circuit protection due to high inrush currents in capacitive or inductive lamp loads, leading to malfunction and potential damage to power devices.
Innovation Solution
A dimming power supply with a voltage sampling circuit and switching devices to detect short circuits, preventing false triggers by inrush currents and ensuring swift protection, while disconnecting the load from ground to prevent afterglow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current sampling time is increased to avoid false triggering, then false triggering rate is reduced, but response speed to actual short circuit decreases
Solution Approach 1:
The patent replaces the mechanical/time-based delay approach with an electronic voltage comparison mechanism. Instead of waiting for a predetermined time period to elapse before responding to current samples, the system immediately compares the sampled voltage against a reference voltage threshold. This electronic substitution enables instantaneous response to actual short-circuit conditions while using the voltage threshold comparison to filter out false triggers from inrush currents
2Reliability
If voltage sampling circuit is added, then false triggering is eliminated, but device complexity increases
Solution Approach 1:
The patent merges the voltage sampling function with the existing protection circuit by incorporating a sampling resistor into the current path and using its voltage drop as the detection signal. The comparator circuit is integrated with the control logic, combining multiple functions (voltage sampling, threshold comparison, and protection triggering) into a unified circuit architecture, thereby minimizing the increase in overall device complexity while achieving elimination of false triggering
Data Source
AI summary
The present disclosure discloses a dimming power supply, which includes a power supply circuit, a power control transistor, a control circuit, a driving circuit and a short-circuit protection circuit. The short-circuit protection circuit includes a voltage sampling circuit and a first switching device, an input end of the voltage sampling circuit is connected to the negative electrode of the load, an output end of the voltage sampling circuit is connected to a control end of the first switching device, and when the first switching device is turned on, a signal input to the gate of the power control transistor is pulled down or truncated. A second switching device is connected in series in the voltage sampling circuit, a control end of the second switching device is connected to the gate of the power control transistor, when the power control transistor is turned off, the second switching device is turned off.