Power Supply Current Compensation for LED Brightness Consistency
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Solution Overview
Problem
Conventional hysteretic power supply systems experience signal propagation delays, leading to time lags in switching states, which affect the inductor current and brightness of LEDs, resulting in varying average current and brightness with the number of emitting LEDs.
Innovation Solution
A power supply system with a current driver circuit, sensor circuit, control circuit, voltage generator circuit, and signal generator circuit, which adjusts the reference voltage based on the number of loads and generates threshold voltages to compensate for signal delays, ensuring a consistent average output current across different scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional hysteretic power supply system is used, then the system structure is simple, but the average inductor current varies with the number of emitting LEDs due to signal propagation delay
Solution Approach 1:
The patent applies preliminary action by predicting the required average current based on the detected number of emitting LEDs before the actual switching occurs. The controller pre-adjusts the switching duty cycle to compensate for the signal propagation delay, ensuring that the average current reaches the target value despite the time lag. This is achieved by detecting the number of emitting LEDs, calculating the required average current, and proactively adjusting the switching parameters before the delay effects manifest in the actual current waveform.
Solution Approach 2:
The patent implements feedback by continuously detecting the number of emitting LEDs and using this information to dynamically adjust the switching duty cycle. The system monitors the actual number of emitting LEDs, compares it with the target average current requirement, and automatically adjusts the switching parameters to maintain consistent average current. This closed-loop feedback mechanism eliminates the variation in average current that would otherwise occur due to signal propagation delays.
2Adaptability or versatility
If the number of emitting LEDs changes, then the brightness control flexibility is improved, but the inductor current average and waveform stability deteriorate
Solution Approach 1:
The patent applies dynamics by making the switching duty cycle adaptive and variable based on the detected number of emitting LEDs. Instead of using a fixed switching pattern, the system dynamically adjusts the duty cycle in real-time according to the actual operating conditions. When the number of emitting LEDs changes, the controller automatically modifies the switching parameters to maintain stable average current, transforming the system from static to dynamic operation.
Solution Approach 2:
The patent implements parameter changes by adjusting the switching duty cycle and frequency based on the detected number of emitting LEDs. The system changes the electrical parameters of the switching operation dynamically to compensate for the varying load conditions. By modifying these parameters in response to the number of emitting LEDs, the system maintains stable inductor current characteristics despite changes in the lighting configuration.
3Speed
If signal propagation delay is present, then the switching response time is reduced, but the threshold voltage comparison accuracy deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-calculating the appropriate threshold voltages and comparing them with the actual sensed voltages before the signal propagation delay fully affects the switching decision. The controller proactively determines the switching timing based on predicted values, compensating for the delay inherent in the voltage comparison process. This ensures that the switching occurs at the correct moment despite the finite time required for voltage sensing and comparison.
Data Source
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AI summary
A power supply system includes a current driver circuit (2), a sensor circuit (3), a control circuit (4), a voltage generator circuit (5) and a signal generator circuit (6). The current driver circuit (2) generates, based on a pulse signal (GATE), an output current (IL) for driving a load unit (100) that includes series connected loads (1). The sensor circuit (3) senses the output current (IL) to generate a sensed voltage (VSense). For each load (1), the control circuit (4) is operable, based on a control input, to allow or not to allow the output current (IL) to flow through the load (1). The voltage generator circuit (5) generates a reference voltage (VREF_COM) based on the control input. The signal generator circuit (6) generates the pulse signal (GATE) based on the reference voltage (VREF_COM) and the sensed voltage (VSense).