Dimming Driver Circuit Digital PWM Control for LED Current Precision
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Solution Overview
Problem
Conventional dimming driver circuits face challenges in precision and dimming range, particularly with analog dimming technology, which results in unsatisfactory output current control and limited dimming range, failing to meet the requirements of wide dimming ranges needed for applications like scene or building lighting where LEDs produce different color light beams.
Innovation Solution
A dimming driver circuit and control method that utilizes a power converting unit with a switch element, alternately turned on or off in switching cycles, and a control method that adjusts the initial control signal based on detecting signals and dimming current thresholds to generate a real control signal, allowing for precise control of output current and expanding the dimming range by adjusting pulse width or chopping pulse number.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog dimming technology is used to control output current, then the circuit structure is simple, but the precision of output current control is unsatisfactory due to tolerance, deviation and delay
Solution Approach 1:
The patent replaces the analog dimming technology with digital pulse width modulation (PWM) technology. The control unit generates PWM signals to control the switching element, and uses digital processing to detect inductor current through voltage signals from the detecting resistor. This substitution of analog system with digital system resolves the precision issues caused by tolerance and deviation while maintaining manageable circuit complexity through integrated digital control.
2Adaptability or versatility
If conventional analog dimming technology is used, then the dimming range is limited between 10% and 100%, but the circuit structure is simple
Solution Approach 1:
The patent implements a dynamic control method that adapts the switching element's on-time based on real-time inductor current detection. The control unit adjusts the PWM duty cycle dynamically to achieve dimming ranges from 0.1% to 100% or even 0.01% to 100%. This dynamic adjustment capability expands the dimming range significantly while the integrated control unit manages the complexity through automated digital processing.
Solution Approach 2:
The patent incorporates a feedback mechanism where the control unit detects the inductor current through the detecting resistor and uses this information to adjust the PWM signal accordingly. This closed-loop feedback control enables precise current regulation and expanded dimming range, with the control unit automatically processing the feedback signals to maintain optimal operation across the full dimming range.
3Measurement precision
If a current detection resistor is used to detect output current, then the circuit structure is simple, but the precision is reduced due to tolerance and deviation
Solution Approach 1:
The patent uses the detecting resistor as an intermediary element to convert inductor current into a detectable voltage signal. The control unit then processes this voltage signal digitally to determine the actual inductor current. This intermediary approach allows for simple circuit implementation while achieving high precision through digital signal processing, as the voltage signal from the resistor is amplified and processed with high accuracy by the control unit's analog-to-digital converter and processing algorithms.
Data Source
AI summary
A control method for a dimming driver circuit is provided. Firstly, a detecting signal is generated according to a result of detecting a parameter of a power converting unit. Then, the dimming current is compared with a preset current threshold value. If the dimming current is higher than the preset current threshold value, a status information of a switch element of the power converting unit is determined according to the detecting signal, and a first setting is defined. If the dimming current is lower than or equal to the preset current threshold value, the status is determined according to the detecting signal, a pulse ratio in a chopping cycle is calculated, and a second setting is defined. According to the first setting or the second setting, an initial control signal is adjusted to a real control signal to control the switch element.