LED Driving Circuit with Automatic Current Mirror Switching
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Solution Overview
Problem
Existing LED driving circuits for AC power supply face challenges in efficiently controlling LED light emission due to nonlinear LED characteristics, leading to increased size, cost, and power consumption, as well as inefficiencies in light-emission timing and power usage, particularly when trying to extend the light-emission period or increase the number of LED blocks.
Innovation Solution
The proposed LED driving circuit includes a rectifier with a positive and negative output, a first LED array connected to the rectifier, a current detection unit, and a current limiting unit that automatically switches the connection of LED arrays based on the rectifier's output voltage, eliminating the need for a switch circuit and allowing for efficient timing of LED block connections without digital control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a switch circuit is added to control LED block connections, then the light-emission period can be extended, but the device complexity and power consumption increase
Solution Approach 1:
The patent employs a current mirror circuit that automatically detects and responds to voltage changes across LED blocks. When the voltage across a LED block reaches its forward voltage, the current mirror inherently switches the connection mode without external control signals, making the circuit self-regulating and eliminating the need for complex switch control logic
Solution Approach 2:
The current mirror circuit provides automatic feedback control by monitoring the voltage across each LED block. When the voltage reaches the forward voltage threshold, the current mirror automatically adjusts the connection configuration, creating a closed-loop system that adapts to changing conditions without external intervention
2Duration of action of moving object
If the number of LED blocks is increased to extend light-emission period, then the duration improves, but the number of switch circuits required increases
Solution Approach 1:
The current mirror circuit serves multiple functions simultaneously: it acts as a current source, a voltage detector, a switch controller, and a connection manager. This single multi-functional circuit replaces what would otherwise require multiple separate switch circuits, one for each LED block, thereby scaling efficiently as more LED blocks are added
3Ease of operation
If switching timing is set based on predicted Vf values, then the control can be simplified, but the actual switching timing may be inaccurate
Solution Approach 1:
The patent replaces predictive timing control with real-time electrical detection. Instead of using timers or microcontrollers to predict when switching should occur, the system uses the inherent electrical characteristics of the LED blocks (forward voltage) to trigger switching automatically through the current mirror mechanism, achieving both simplicity and precision
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
This solution simplifies the circuit configuration, reduces costs, and enables efficient power usage by automatically determining the optimal timing for LED block connections, allowing for a larger number of LED blocks with reduced power consumption and improved light-emission efficiency.
Implementation Method 1
AC power supplied from a commercial power supply is full-wave rectified by a diode bridge
Implementation Method 2
the rectified output voltage is applied across a plurality of series-connected LEDs, causing the plurality of LEDs to emit light
Data Source
AI summary
The invention is directed to the provision of an LED driving circuit that switches the connection of LED blocks in accordance with the supply voltage and the Vf's specific to individual LEDs contained in each LED block. The LED driving circuit includes a rectifier; a first circuit, a first current detection unit for detecting current flowing from the first LED array to the negative output of the rectifier, and a first current limiting unit for limiting the current flowing from the first LED array to the negative output of the rectifier in accordance with the current detected by the first current detection unit, and a second circuit which includes a second LED array and a current path passing through the second LED array and leading to the negative output of the rectifier, and wherein a current path in which only the first LED array is connected to the rectifier and a current path are formed in accordance with an output voltage of the rectifier, and the first current detection unit, upon detecting current flowing through the first and second LED arrays, operates the first current limiting unit to perform current path switching.