Transistor Protection Circuit for LED Light String Overload Cutoff
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Solution Overview
Problem
Existing LED light string connection methods lead to voltage reduction or increased load when devices are connected in parallel, and failure or damage when connected in series, necessitating improved overcurrent and overload protection to prevent fires and extend service life.
Innovation Solution
An overcurrent and overload protection circuit using switch transistors and a wireless receiving circuit to disconnect the LED light string control circuit when overloaded or short-circuited, incorporating a step-down voltage stabilization circuit and field effect transistors for efficient current management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If multiple LED devices are connected in parallel, then the light string can operate continuously, but voltage reduction occurs leading to overcurrent and overload problems
Solution Approach 1:
The patent introduces a protection circuit as an intermediary between the power supply and LED light string. This circuit includes transistors (Q1-Q4), resistors (R1-R7), and a sampling resistor (R6) that monitor current and voltage levels, automatically disconnecting the circuit when overcurrent or overload conditions are detected, thus preventing damage while allowing parallel connection for continuous operation
Solution Approach 2:
The protection circuit implements feedback control by continuously monitoring the electrical parameters (current through sampling resistor R6, voltage across LEDs) and automatically adjusting the circuit state. When abnormal conditions are detected, the feedback signal triggers the transistor switching mechanism to cut off power, resolving the contradiction between continuous operation and safety protection
2Reliability
If multiple LED devices are connected in series, then voltage distribution is improved, but failure of one device causes voltage rise and damage to other devices
Solution Approach 1:
The protection circuit applies preliminary anti-action by pre-establishing protection mechanisms before damage occurs. The circuit monitors voltage and current levels in advance, and when series connection causes voltage rise beyond safe levels, the protection circuit automatically disconnects the circuit before damage can occur to any LED devices
Solution Approach 2:
The protection circuit acts as an intermediary that decouples the direct relationship between series-connected LEDs. By introducing monitoring and control elements (transistors Q1-Q4, sampling resistor R6), the circuit can isolate individual LED failures from affecting other devices, maintaining voltage distribution stability while preventing cascading damage
3Device complexity
If traditional protection methods are used, then simple structure is maintained, but control functionality is insufficient leading to frequent failures
Solution Approach 1:
The protection circuit achieves multi-functionality by combining overcurrent protection, overload protection, and short-circuit protection in a single integrated circuit design. The same transistor-switching mechanism (Q1-Q4) and sampling resistor (R6) handle multiple protection scenarios, providing comprehensive protection without requiring separate complex circuits for each function
Data Source
AI summary
An overcurrent and overload protection circuit of an LED light string includes an LED light string control circuit 20 connecting to a protection circuit 10 and a wireless receiving circuit 30 respectively. The protection circuit 10 includes a first, a second, and a fourth switch transistors Q1, Q2, and Q4 connected in parallel to an input terminal of a power supply, and a third switch transistor Q3 connected in parallel with the first and the fourth switch transistor Q1, Q4 respectively. The LED light string control circuit 20 comprises an LED light string forward and reverse output circuit 21, a step-down voltage stabilization circuit 22 and a main control chip U2 connected to the LED light string forward and reverse output circuit 21. When the LED light string is overloaded or short-circuited, the circuit can be cut off by promptly disconnecting the switch transistor of the control circuit.