SCR Dimming Circuit Eliminates Holding Resistor for LED Efficiency
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Solution Overview
Problem
Conventional SCR dimming circuits for LED loads face inefficiencies and poor dimming performance, especially when the external voltage supply is low, leading to increased power loss and flicker due to the need for a holding resistor to maintain SCR conduction.
Innovation Solution
An SCR dimming circuit that includes an SCR rectifying circuit, a rectifier bridge, a filter capacitor, a conduction phase angle signal generator, and a dimming signal generator, which converts AC power to a lack-phase DC voltage and generates a dimming signal based on a slope reference signal to control the conduction phase angle of the SCR element, eliminating the need for a holding resistor by limiting current flow to a specific phase angle range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a holding resistor is added to maintain SCR conduction when external voltage supply is low, then SCR conduction is maintained, but power loss increases and operation efficiency decreases
Solution Approach 1:
The invention extracts and eliminates the holding resistor from the circuit by using a different approach - a capacitor-connected trigger electrode configuration that generates the necessary trigger current through capacitive coupling during the AC cycle, removing the continuous power-consuming resistive element while maintaining SCR conduction reliability
Solution Approach 2:
The invention changes the electrical parameters by using capacitive coupling instead of resistive coupling for the trigger signal generation. The capacitor allows the trigger electrode to receive sufficient current during specific phases of the AC cycle without requiring a continuous power draw, thereby reducing overall power loss while maintaining reliable SCR operation
2Reliability
If a holding resistor is added to maintain SCR conduction when external voltage supply is low, then SCR conduction is maintained, but operation efficiency decreases
Solution Approach 1:
The holding resistor is extracted and replaced with a capacitor-based trigger mechanism that provides the necessary trigger current without continuous power consumption, thereby improving operation efficiency while maintaining SCR conduction
Solution Approach 2:
The capacitor-connected trigger electrode utilizes periodic action by charging during specific phases of the AC cycle and discharging to provide trigger current, eliminating the need for continuous resistive power consumption while maintaining reliable SCR operation throughout the cycle
3Reliability
If conventional SCR dimming circuit is used with holding resistor, then SCR conduction is maintained, but dimming performance becomes poorer
Solution Approach 1:
By removing the holding resistor and using capacitor-connected trigger electrodes, the invention achieves better dimming performance through more precise control of the trigger timing and conduction angle, allowing for smoother and more accurate dimming operation
Solution Approach 2:
The capacitor-connected trigger electrode configuration provides improved feedback characteristics that enable better control of the SCR conduction angle, resulting in enhanced dimming performance and more accurate luminance control
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 enhances efficiency and dimming performance by avoiding the use of a holding resistor, reducing power loss and flicker, while allowing for precise control of LED luminance from maximum to minimum through a linear dimming phase angle range.
Implementation Method 1
the lack-phase DC voltage is configured to be filtered through a filter capacitor to generate a smooth DC voltage
Implementation Method 2
an SCR element configured to receive an AC power supply, and to generate a lack-phase AC voltage
Data Source
AI summary
The present invention relates to a silicon-controlled rectifier (SCR) dimming circuit and method for regulating the luminance of a light-emitting diode (LED) load. In one embodiment, an SCR dimming circuit can include: an SCR rectifying circuit having an SCR element that receives an AC power supply, and generates a lack-phase AC voltage; a rectifier bridge that converts the lack-phase AC voltage to a lack-phase DC voltage, where the lack-phase DC voltage is filtered through a filter capacitor to generate a smooth DC voltage; a conduction phase angle signal generator that receives the lack-phase DC voltage and generates a controlling signal indicating a conduction phase angle range of the SCR element; and a dimming signal generator that compares the controlling signal and a slope reference signal to output a dimming signal to control the luminance of the LED load.