Switching Power Converter LED Current Control
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Solution Overview
Problem
Conventional PFC converters face challenges in maintaining a stable LED current while achieving a high power factor, leading to reduced LED life and low power factor due to the sinusoidal nature of the inductor current, which results in high peak-to-average ratio (PAR) of the LED current.
Innovation Solution
A switching power converter with a control method that adjusts the power switch to maintain a proportional relationship between the amplitude of the input voltage and the average current in specific time periods, reducing the peak-to-average ratio and enhancing the power factor by controlling the power switch based on signals generated from input and output voltage and current signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a large output capacitor is used to stabilize the output voltage, then the output voltage stability is improved, but the cost increases and the capacitor is more susceptible to damage
Solution Approach 1:
The patent changes the control parameters of the power switch to regulate the inductor current waveform, transforming it from a sinusoidal shape to a shape that compensates for LED nonlinearity. This parameter change in current waveform control allows the use of smaller output capacitors while maintaining stable output voltage, thereby reducing cost and improving reliability.
2Power
If the inductor current follows a sinusoidal waveform for power factor correction, then the power factor is improved, but the LED current peak-to-average ratio increases reducing LED life
Solution Approach 1:
The patent dynamically adjusts the inductor current waveform shape based on the operating conditions and LED nonlinearity characteristics. By making the current waveform dynamic rather than fixed sinusoidal, the system maintains high power factor while shaping the current to reduce peak-to-average ratio, thereby extending LED life.
Solution Approach 2:
The patent employs feedback control mechanisms that monitor the LED current and adjust the power switch control signals accordingly. This feedback loop ensures that the inductor current waveform is continuously optimized to maintain both high power factor and acceptable peak-to-average ratio, protecting LED longevity.
3Ease of manufacture
If a smaller output capacitor is used to reduce cost, then the cost is reduced, but the output voltage ripple increases
Solution Approach 1:
The patent changes the control parameters of the power switch to regulate the inductor current waveform, transforming it from a sinusoidal shape to a shape that compensates LED nonlinearity. This parameter change in current waveform control allows the use of smaller output capacitors while maintaining stable output voltage, thereby reducing cost and improving reliability.
Data Source
AI summary
A switching power converter with an input terminal configured to receive a first input voltage; an output terminal configured to provide an output current to a load, wherein the output current has a peak value and an average value; a power switch; a first loop coupled to the input terminal, wherein the first loop configured to generate a first output signal based on the first input voltage; a second loop configured to generate a second output signal based on the output current; a multiplier configured to generate a multiplying signal based on multiplying the first output signal with the second output signal; and a driving circuit configured to generate a driving signal based on the multiplying signal to control the power switch, so as to reduce the ratio between the peak value and the average value of the output current.