LED Driver Ripple Detection and DC Level Control
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Solution Overview
Problem
Power supply systems for LEDs face challenges in maintaining stable luminous output due to sensitivity to drive current changes, with output ripple affecting feedback loops and leading to inaccuracies in DC signal levels.
Innovation Solution
A secondary-side output correction circuit generates a feedback control signal to dynamically adjust the DC level of the output signal based on measured ripple, using a sense resistor, current sense circuit, operational amplifier, and reference generator to calculate correction factors and adjust the reference signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a feedback loop measures the output to implement ripple control, then output ripple is reduced, but the output signal DC level becomes inaccurate
Solution Approach 1:
The feedback signal is separated into AC ripple component and DC component. The AC component is used for ripple control while the DC component is used for DC level regulation, allowing independent optimization of both control objectives without interference
Solution Approach 2:
A capacitor is introduced as an intermediary element in the feedback path. The capacitor blocks the DC component while allowing the AC ripple component to pass through to the ripple controller, enabling selective ripple control without affecting DC level accuracy
2Stability of the object's composition
If LED is driven by constant current to maintain stable luminous output, then luminosity stability is improved, but sensitivity to drive current changes increases
Solution Approach 1:
A feedback loop continuously monitors the LED drive current and adjusts the current regulator to maintain constant current flow. This feedback mechanism compensates for any current variations, ensuring stable luminous output while reducing sensitivity to external disturbances
Solution Approach 2:
The system dynamically adjusts the drive current in real-time based on feedback from the current sensor. This dynamic control allows the system to maintain optimal current levels and stability while adapting to changing operating conditions
3Measurement precision
If output correction circuit dynamically adjusts DC level based on measured ripple, then DC level accuracy is improved, but circuit complexity increases
Solution Approach 1:
The ripple control function and DC level control function are merged into a single feedback system. By separating the feedback signal into AC and DC components and routing them through appropriate control paths, both functions achieve their objectives using a unified circuit architecture
Solution Approach 2:
The correction circuit uses the ripple measurement itself to generate the correction signal. The measured ripple information is processed and fed back to automatically adjust the DC level, enabling the system to self-correct without external intervention
Data Source
AI summary
According to some embodiments, there is provided a power supply system including a converter configured to generate an output signal based on a rectified input signal for driving a light source, an output correction circuit coupled to an output of the converter and configured to measure a ripple in the output signal and to generate a correction signal to dynamically control a DC-level of the output signal of the converter based on the measured ripple and a reference signal corresponding to a desired DC-level of the output signal.