Primary Side Current Regulation for LED Drivers
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Solution Overview
Problem
Conventional switching power converters for LED drivers face challenges in achieving high power factor due to increased system complexity and cost associated with using high-speed analog-to-digital converters (ADCs) for primary side current sensing, which complicates cycle-by-cycle constant current control.
Innovation Solution
A method for a switching power converter that regulates average output current by using a regulation voltage based on peak primary side current, allowing output current to vary switching-cycle by switching-cycle, while maintaining a constant average output current over time, without relying on high-speed ADCs for primary side current sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-speed ADC is used for primary side current sensing, then output current regulation precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the high-speed ADC component from the system and replaces it with a simpler voltage sensing approach. By taking out the complex current sensing hardware and using only voltage measurements combined with mathematical estimation, the system achieves current regulation without the complexity and cost of high-speed ADCs.
Solution Approach 2:
The patent creates a mathematical model (copy) of the primary current waveform based on voltage measurements and circuit parameters. Instead of directly measuring the complex current signal, the system copies the current information through estimation algorithms that reconstruct the current waveform from simpler voltage measurements, achieving the same regulatory function with less hardware complexity.
2Measurement precision
If high-speed ADC is used for primary side current sampling, then output current regulation is improved, but system cost increases
Solution Approach 1:
The patent replaces the expensive high-speed ADC with cheaper, lower-speed voltage sensing components and digital signal processing. By using standard microcontroller ADCs to sample voltage at lower speeds and computing the current information through algorithms, the system achieves the same functional result at significantly reduced component cost.
Solution Approach 2:
The patent substitutes the direct electrical measurement mechanism (high-speed current ADC) with a computational approach. Instead of using hardware to directly measure and process high-speed current signals, the system uses mathematical algorithms running on a microcontroller to estimate current from voltage measurements, replacing complex electrical measurement hardware with software-based computation.
3Stability of the object's composition
If cycle-by-cycle constant current control is implemented, then output current stability is improved, but power factor deteriorates
Solution Approach 1:
The patent implements dynamic control that adapts the current regulation strategy based on the operating phase. During the conduction phase, the system maintains constant current for LED stability, while during the non-conduction phase, it allows current to follow the voltage waveform to improve power factor. This dynamic switching between control modes resolves the contradiction between current stability and power factor.
Solution Approach 2:
The patent applies periodic control actions that alternate between constant current regulation and power factor correction modes within each AC cycle. By using periodic duty cycle modulation and alternating between different control strategies in different time intervals, the system achieves both stable LED current and high power factor, converting the harmful contradiction into a coordinated periodic operation.
Data Source
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AI summary
The embodiments disclosed herein describe a method of a controller to maintain a substantially constant average output current at the output of a switching power converter. In one embodiment, the controller uses a regulation voltage that corresponds to the primary peak current regulation level to regulate the average output current.