LED Power Supply Short-Circuit Circuit With Low-Loss Current Sensing
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Solution Overview
Problem
Existing LED power supply systems lack a simple, low energy consumption, and high stability load short-circuit protection circuit suitable for high power constant voltage power supplies, as existing methods either fail to detect short circuits promptly or suffer from high power losses and heating issues.
Innovation Solution
A load short-circuit protection circuit with a switching module, sampling resistor, signal amplification module comprising triodes and a constant current source, and a protection control module that quickly amplifies voltage changes across the sampling resistor to control the switching module, allowing for rapid disconnection in case of a short circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage detection method is used to detect short circuit, then the detection can be implemented, but when VCC power output is large or short circuit has resistance value, the voltage falls slowly or below detection threshold, causing protection failure
Solution Approach 1:
The patent introduces a sampling resistor as an intermediary element to convert the difficult-to-detect voltage changes into easily measurable voltage signals across the resistor. This mediator transforms the detection problem from direct voltage monitoring to current-induced voltage drop monitoring, solving the sensitivity issue in high-power scenarios
2Reliability
If current detection method with sampling resistor is used, then short circuit can be detected, but when power supply power is very high, the sampling resistor power is very high causing serious heating
Solution Approach 1:
The patent changes the detection parameter from direct current measurement to voltage measurement across the sampling resistor. By using the relationship U=IR, the system detects current through voltage changes, allowing the use of smaller sampling resistors that generate less heat while maintaining detection capability
Solution Approach 2:
The patent replaces direct power measurement with voltage measurement substitution. Instead of measuring current directly which requires high-power handling, the system measures the voltage drop across a small sampling resistor, substituting a high-power measurement problem with a low-power voltage measurement
3Measurement precision
If high value sampling resistor is used for detection, then detection signal is strong, but power loss and heating increase significantly
Solution Approach 1:
The patent changes the detection approach from direct current measurement to voltage drop measurement. This parameter change allows the use of small sampling resistors because the detection is based on voltage changes (which can be amplified) rather than direct current magnitude, reducing power loss while maintaining signal detectability
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
The solution enables quick detection and protection against short circuits with minimal power loss, high stability, and low cost, even at high power levels, by amplifying subtle voltage changes and using a small sampling resistor to reduce energy consumption.
Implementation Method 1
the voltage at both ends of R will increase. It is only necessary to detect the CHECK point voltage higher than a certain threshold
Implementation Method 2
a signal amplification module that collects the current change signal of the sample resistor
Data Source
AI summary
A load short-circuit protection circuit of LED power supply includes a power supply end, a load end, a switching module disposed between the power supply end and the load end, and a sampling resistor set in series with the load end, and further includes a signal amplification module that collects the current change signal of the sample resistor, and a protection control module that receives a amplification signal of the signal amplification module and controls the on-off of the switching module according to the signal. The circuit can quickly magnify the subtle voltage difference changes on the sampling resistor and output them to the protection control module. The resistance value of the sampling resistance can be set very small to reduce the loss. Meanwhile, the selected devices are simple, with very fast response speed, low cost and high stability.