TRIAC Dimmer LED Driver Using Adaptive Reference Voltage
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Solution Overview
Problem
Conventional lighting systems with TRIAC dimmers struggle to provide effective dimming control for LEDs without requiring additional feedback lines or dimming logic, leading to flickering issues when replacing halogen bulbs with LED systems.
Innovation Solution
An electronic device configured with a control loop using a phase cut voltage from a TRIAC dimmer, where an error amplifier adjusts the duty cycle of a switched voltage converter to maintain a constant drive current to LEDs, eliminating the need for additional feedback lines and dimming logic by using a reference voltage that varies proportionally with the input voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional LED driver with fixed reference voltage is used in a TRIAC dimmer system, then the LED driver can operate with simple circuitry, but the LED brightness cannot be properly dimmed and flickering occurs
Solution Approach 1:
The patent applies parameter changes by making the reference voltage dynamic instead of fixed. The reference voltage is scaled proportionally to the input voltage level, allowing the LED driver to maintain proper dimming control across different TRIAC dimmer positions. This resolves the contradiction by changing the voltage parameter from static to adaptive, enabling reliable dimming without increasing circuit complexity
Solution Approach 2:
The patent implements feedback by using the input voltage level information to adjust the reference voltage. The error amplifier compares the feedback voltage from the LED current sensing with the scaled reference voltage, creating a closed-loop control system that automatically adapts to different dimmer settings. This feedback mechanism ensures reliable dimming control while maintaining simple circuit architecture
2Reliability
If additional feedback lines and dimming logic are added to enable LED dimming control, then proper dimming functionality is achieved, but device complexity increases
Solution Approach 1:
The patent applies universality by making the existing error amplifier and reference voltage circuit serve dual purposes: both LED current regulation and dimming control. The same circuit components that regulate LED current also handle dimming functionality by adapting the reference voltage to input voltage levels, eliminating the need for separate dimming logic and feedback lines
Solution Approach 2:
The patent implements self-service by allowing the LED driver to automatically adapt to TRIAC dimmer settings without external dimming signals. The system uses the input voltage level itself as the dimming control mechanism, where the driver self-adjusts its operation based on the reduced input voltage from the TRIAC, eliminating the need for additional external dimming control circuitry
3Ease of manufacture
If the reference voltage is fixed in the LED driver, then the circuit is simple to implement, but the LED brightness cannot be dimmed smoothly across different input voltage levels
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the reference voltage based on input voltage levels. The reference voltage is scaled proportionally to the input voltage, enabling smooth LED brightness control across the entire dimming range. This resolves the contradiction by changing the reference voltage from a fixed parameter to an adaptive one, achieving full brightness control while maintaining circuit simplicity
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
Enables smooth dimming of LEDs without flickering, maintaining constant brightness and reducing the need for additional circuitry, making it suitable for replacing halogen bulbs with LED systems in existing TRIAC dimmer setups.
Implementation Method 1
The control loop comprises an error amplifier that is coupled to receive a sense voltage that is indicative to a current through the light emitting semiconductor device. The error amplifier is configured to provide a feedback signal to a pulse width modulation logic
Implementation Method 2
The error amplifier is coupled to receive a reference voltage that is a function of the input voltage. The pulse width modulation logic is configured to control the duty cycle of the switched voltage converter so as to provide a constant drive current
Implementation Method 3
The TRIAC dimmer 6 cuts the leading or the trailing edge (depending on the type of the transformer) of the sinusoidal mains voltage as illustrated by the inset a) and b) in FIG. 1. Consequently, the RMS input voltage at the transformer 4 is reduced.
Implementation Method 4
A rectifier comprising diodes D1, D2, D5 and D6 rectifies this voltage
Data Source
AI summary
An electronic device for a lighting system, comprising a TRIAC dimmer configured to receive a mains supply voltage and provide a phase cut voltage to the electronic device and having a control loop configured to control a duty cycle of a switched voltage converter that receives the rectified input voltage and provides drive current to a light emitting semiconductor device. The control loop has an error amplifier that is coupled to receive a sense voltage that is indicative of a current through the light emitting semiconductor device, the error amplifier is configured to provide a feedback signal to a pulse width modulation logic configured to control the duty cycle of the switched voltage converter to provide a constant drive current to the light emitting semiconductor device in response to the sense voltage, the error amplifier being coupled to receive a reference voltage that is a function of the input voltage.