Power Control via Frequency Spreading for LED Dimming
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Solution Overview
Problem
Existing power control methods for devices like LEDs and incandescent lamps using pulse width modulation (PWM) often produce harmonics that cause interference with the radio frequency spectrum, necessitating a solution that controls power output without generating such interference.
Innovation Solution
A method employing a pseudo random code to control energy delivery to devices, where a binary pseudo random code sequence determines the duration of power supply, ensuring no flicker is perceived by the human eye while minimizing radio frequency interference by spreading power application over the entire cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulse width modulation (PWM) is used to control power output, then power control precision is improved, but radio frequency interference increases
Solution Approach 1:
The invention segments the power delivery into multiple smaller pulses distributed throughout the cycle according to a pseudo-random code, rather than using a single continuous pulse. This segmentation spreads the energy delivery across time, reducing the amplitude of individual pulses and their harmonic content, thereby minimizing radio frequency interference while maintaining precise power control through the statistical properties of the pseudo-random sequence.
Solution Approach 2:
The invention employs a dynamic pseudo-random code sequence that changes over time to control power delivery. Unlike fixed PWM duty cycles, the pseudo-random sequence provides time-varying pulse patterns that spread spectral energy across a broader frequency range, reducing concentrated harmonic interference while maintaining average power control precision through the known statistical characteristics of the code.
2Stability of the object's composition
If PWM frequency is increased to eliminate flicker, then visual perception stability is improved, but radio frequency interference increases
Solution Approach 1:
The invention divides the power delivery into many small segmented pulses distributed throughout the cycle according to pseudo-random code, rather than using fewer larger pulses. This segmentation allows the system to achieve visual stability through high temporal distribution of energy while keeping individual pulse amplitudes low, thereby reducing harmonic content and radio frequency interference even at frequencies that eliminate flicker.
3Power
If duty cycle is increased to boost power output, then power delivery is improved, but radio frequency harmonics increase
Solution Approach 1:
The invention segments total power delivery into multiple smaller pulses distributed throughout the cycle according to pseudo-random code. This allows the system to deliver the required average power while keeping individual pulse amplitudes reduced, which minimizes the generation of radio frequency harmonics. The segmentation distributes energy in time, maintaining power delivery effectiveness while reducing spectral interference.
Solution Approach 2:
The invention uses dynamic pseudo-random code sequences to modulate power delivery timing and distribution. This dynamic approach spreads power delivery across varying time intervals, preventing concentrated energy bursts that generate strong harmonics. The statistical properties of the pseudo-random code ensure that average power delivery meets requirements while instantaneous power levels remain low, reducing harmonic content.
Data Source
AI summary
A method and apparatus for providing a selected amount of power from a power source to a load produce a pseudo random code sequence of different type bits, in which one type of the different type bits is used to control application of power from the source to the load so that the power applied to the load corresponds to the total of the number of the bits of one type applied to the load in a given time period. A plurality of code sequences is provided, with each corresponding to a different power level, and a sequence can be selected to provide a selected power level to the load.