LED Driver Analog Dimming Voltage Reduces Transistor Stress
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Solution Overview
Problem
Existing LED drivers face voltage stress issues when using PWM dimming, leading to potential deterioration of the light source and increased costs due to high-rated voltage and power consumption in current regulators.
Innovation Solution
The proposed LED driver incorporates a current regulator with bipolar junction transistors and an analog dimming voltage generating unit, which adjusts the dimming voltage to allow a micro current to flow during PWM dimming off, reducing voltage stress by controlling the voltage between the collector and emitter terminals of the transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If PWM dimming control is used to control LED brightness, then brightness control is achieved, but voltage stress occurs on the current regulator
Solution Approach 1:
The patent introduces an analog dimming voltage generating unit as an intermediary component between the PWM dimming pulse generating unit and the current regulator. This unit generates a dimming voltage based on the PWM signal and feeds it to the current regulator, allowing the regulator to operate at lower voltage stress levels while still achieving effective brightness control through the combined action of PWM and analog dimming.
2Reliability
If current regulator is designed with high rated voltage to handle PWM dimming voltage stress, then reliability is improved, but power consumption increases
Solution Approach 1:
The patent changes the operating parameters of the current regulator by introducing an analog dimming voltage that operates at lower voltage levels compared to traditional PWM-only operation. The analog dimming voltage generating unit processes the PWM signal to create a voltage signal that reduces the voltage stress on the current regulator, allowing the regulator to operate with lower rated voltage requirements and consequently lower power consumption while maintaining reliability.
3Stress or pressure
If PWM dimming is turned off completely to prevent voltage stress, then current regulator is protected, but LED characteristics may deteriorate
Solution Approach 1:
The patent ensures continuous useful action by maintaining a micro current flow through the LED even when PWM dimming is turned off. The analog dimming voltage generating unit continues to operate and provide a dimming voltage signal that keeps the current regulator active at low current levels. This continuous operation prevents LED characteristic deterioration by maintaining minimal current flow, while the reduced voltage stress protects the current regulator from damage.
Data Source
AI summary
A light emitting diode (LED) driver is provided that includes a light emitting diode, a converter connected to the light emitting diode, wherein the converter receives an input voltage and converts the input voltage to a basic voltage for driving the light emitting diode, a current regulator connected to the light emitting diode, a first operational amplifier connected to the current regulator, an analog dimming voltage generating unit including a second operational amplifier, a first resistor, a second resistor, and a third resistor, wherein a first terminal of the first resistor, a first terminal of the second resistor, and a first terminal of the third resistor are connected to a non-inversion terminal of the second operational amplifier, and connected to the first operational amplifier, and a pulse-width-modulation dimming pulse generating unit connected to a second terminal of the third resistor.