LED Driver Dimming Circuit Frequency Management
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Solution Overview
Problem
Conventional LED driver power converters face low conversion efficiency during low or deep dimming applications, leading to increased noise when reducing operating frequency to achieve energy reduction, which is difficult to manage within noise test standards.
Innovation Solution
A dimming control circuit and method that adjusts the switching state of a power transistor in an LED driver using a PWM dimming signal, with a duty cycle threshold determination to avoid frequency reduction to audio ranges, incorporating an adjusting signal with a first duty cycle greater than the PWM dimming signal's duty cycle, and adaptive delay time correlation with the duty cycle to maintain efficiency and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the operating frequency is reduced to achieve energy reduction during deep dimming, then energy consumption is reduced, but noise increases to levels that fail noise test standards
Solution Approach 1:
The patent implements dynamic frequency adjustment where the operating frequency of the LED driver is adaptively changed based on the dimming depth. During deep dimming operations, the system dynamically selects from multiple frequency ranges (first frequency range for deep dimming, second frequency range for normal operation) to optimize both energy efficiency and noise performance. This dynamic adaptation allows the system to maintain low energy consumption while avoiding the audio-frequency noise range.
Solution Approach 2:
The patent changes the operating frequency parameter based on the dimming condition. By detecting the dimming depth and switching between different frequency ranges, the system modifies a key operational parameter (frequency) to simultaneously achieve energy reduction and noise avoidance. This parameter change strategy enables the LED driver to operate efficiently at non-audio frequencies during deep dimming while consuming minimal energy.
2Illumination intensity
If the duty cycle of PWM dimming signal is reduced to achieve deeper dimming, then illumination intensity is reduced, but conversion efficiency decreases
Solution Approach 1:
The patent employs dynamic frequency selection based on the PWM duty cycle and dimming depth. When deep dimming is detected (low duty cycle), the system dynamically switches to a first frequency range optimized for efficient energy conversion at low output levels. This dynamic adaptation prevents the conversion efficiency from deteriorating even when the illumination intensity is significantly reduced through PWM dimming.
Solution Approach 2:
The patent changes the operating frequency parameter in response to changes in PWM duty cycle. By detecting when the duty cycle indicates deep dimming conditions, the system adjusts the frequency parameter to a range that maintains high conversion efficiency. This parameter coupling ensures that energy loss is minimized while achieving the desired reduction in illumination intensity through PWM control.
3Use of energy by moving object
If the operating frequency is reduced to audio ranges for energy reduction, then energy consumption is reduced, but the system becomes difficult to manage within noise test standards
Solution Approach 1:
The patent implements a dynamic frequency management system that automatically adapts the operating frequency based on dimming conditions. During deep dimming, the system dynamically selects a first frequency range that is specifically chosen to be outside the audio noise range, thereby maintaining noise compliance. This dynamic frequency selection eliminates the need for manual noise testing and adjustment, making the system easy to manage while achieving energy efficiency.
Solution Approach 2:
The patent changes the frequency parameter to values that inherently satisfy noise test standards. By selecting operating frequencies from predefined ranges that exclude audio-frequency noise during deep dimming operations, the system automatically complies with noise requirements. This parameter optimization approach simplifies noise compliance management while maintaining low energy consumption.
Data Source
AI summary
A dimming control circuit for an LED driver, can include: an adjusting circuit configured to generate an adjusting signal in accordance with a PWM dimming signal; and where a switching state of a power transistor of the LED driver is adjusted in accordance with the adjusting signal and a constant current control signal. A dimming control method for an LED driver, can include: determining a first threshold in accordance with a frequency of the PWM dimming signal and a frequency range of audio noise; generating an adjusting signal having a first duty cycle when a duty cycle of a PWM dimming signal is not greater than the first threshold; and controlling, by the adjusting signal, a switching state of a power transistor in the LED driver, where the first duty cycle is greater than the duty cycle of the PWM dimming signal.