LED Driver Circuit Combining DC and PWM Current Control
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Solution Overview
Problem
Existing light emitting device driver circuits face issues with low frequency flicker, audio noise, and color drift due to limitations in dimming resolution and methods, particularly in digital and analog dimming techniques.
Innovation Solution
A light emitting device driver circuit that combines a switching power supply circuit with a multi-level DC current control circuit and a switching current control circuit, using both DC and PWM signals to adjust brightness, ensuring high resolution and minimizing flicker and noise by summing DC and PWM currents to achieve precise control over output current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital dimming with PWM is used to adjust brightness, then brightness control resolution is improved, but low frequency flicker and audio noise are generated
Solution Approach 1:
The patent segments the brightness control into two independent parts: coarse adjustment via multi-level DC current control and fine adjustment via PWM dimming. This segmentation allows each part to operate at optimal parameters, with DC control handling bulk brightness changes and PWM handling precise adjustments, thereby maintaining high resolution while avoiding flicker and noise issues
Solution Approach 2:
The patent merges DC current control and PWM dimming into a unified control system that operates simultaneously. The multi-level DC current control circuit and switching current control circuit work together to sum their outputs, creating a composite current signal that achieves both high resolution and elimination of harmful flicker and noise effects
2Ease of operation
If analog dimming is used to adjust output current level, then brightness adjustment is achieved, but color drift occurs
Solution Approach 1:
The patent replaces continuous analog current adjustment with a hybrid system combining discrete DC current levels and PWM switching. This substitution maintains ease of brightness adjustment while preventing color drift by avoiding continuous modulation of the LED drive current, instead using stepwise DC levels combined with duty-cycle based PWM control
3Speed
If output current is increased to improve conduction speed, then response time is reduced, but dimming resolution decreases
Solution Approach 1:
The patent segments the current control into DC component (for speed) and PWM component (for resolution). The DC current supply circuits provide fast conduction response, while the PWM switching provides precise dimming control. By separating these functions, the system achieves both high speed and high resolution simultaneously
Data Source
AI summary
A light emitting device driver circuit drives a light emitting circuit. The light emitting device driver circuit includes a switching power supply circuit and a current regulator circuit. The current regulator circuit includes a multi-level DC current control circuit, which individually determines whether plural DC current supply circuits are conducted or not conducted according to a DC dimmer signal to supply a DC current to the light emitting circuit; and a switching current control circuit, which operates a PWM switch according to a PWM dimmer signal to supply a PWM current to the light emitting device circuit. The DC current and the PWM current are summed together to form a total current flowing through the light emitting device circuit so that the brightness of the light emitting device circuit is adjustable according to the DC dimmer signal and the PWM dimmer signal.