LED Driver Store Circuit PWM Voltage Decay
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Solution Overview
Problem
Existing LED driver systems experience voltage decay across the output capacitance element during PWM OFF periods due to internal leakage and external circuit leakage, leading to a recovery delay when the PWM signal is turned back ON, which can affect the desired color temperature and intensity of the LED load.
Innovation Solution
The LED driver system incorporates a store circuit and error amplifier to store the voltage level across the output capacitance element before the PWM signal turns OFF, maintaining this voltage level during the OFF period, thereby reducing or eliminating recovery time when the PWM signal is turned back ON.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the PWM OFF duration is increased to save power, then energy consumption is reduced, but the output capacitance voltage decays more significantly due to leakage, causing longer recovery time and affecting LED color temperature and intensity
Solution Approach 1:
The patent stores the voltage level across the output capacitance element before the PWM signal turns OFF in a store circuit. This preliminary action captures the voltage information in advance, allowing the system to quickly restore the voltage during PWM OFF periods without waiting for natural recharge, thereby reducing recovery time while maintaining power savings
Solution Approach 2:
The patent employs an error amplifier that compares the stored voltage level with the actual output capacitance voltage during PWM OFF periods. This feedback mechanism detects voltage decay and generates an error signal to drive the LED driver, ensuring the output capacitance voltage is restored to the correct level, thus eliminating recovery delay and maintaining LED color temperature and intensity
2Stability of the object's composition
If the output capacitance element size is increased to reduce voltage decay, then voltage stability is improved, but the circuit complexity and component size increase
Solution Approach 1:
The patent introduces a store circuit as an intermediary element that holds the voltage level information during PWM OFF periods. This intermediary component allows the system to maintain voltage stability without requiring a larger output capacitance element, as the stored voltage reference guides the restoration process through the error amplifier, thereby achieving voltage stability with the original capacitance size
Solution Approach 2:
The patent replaces the physical approach of increasing capacitance size with an electronic control approach using a store circuit and error amplifier. Instead of relying on a larger capacitor to naturally maintain voltage, the system uses electronic storage and feedback control to actively restore and maintain the voltage level, reducing component size and circuit complexity
3Reliability
If the PWM ON time is extended to include recovery delay, then LED color temperature and intensity are maintained, but power consumption increases
Solution Approach 1:
The store circuit captures the voltage level information before PWM turns OFF, preparing the system in advance. When PWM turns back ON, the stored information is immediately available to the error amplifier, allowing the system to maintain LED color temperature and intensity without requiring extended ON time for recovery, thus reducing overall power consumption while maintaining reliability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures that the LED driver quickly returns to the desired current and voltage levels without a recovery delay, even after long PWM OFF periods, maintaining the desired color temperature and intensity of the LED load.
Implementation Method 1
an output capacitance element 217 coupled between the first and second outputs of the driver 219. The output capacitance element 217 is configured to smooth out the signal across the LED load 215
Implementation Method 2
A first feedback path has a store circuit 241 that is configured to store an information indicative of a voltage level across the output capacitance element 217
Data Source
AI summary
A method and system of driving an LED load. A driver is configured to deliver a level of current indicated by a control signal to the LED load when a PWM signal is ON and stop delivering the level of current when the PWM signal is OFF. An output capacitance element is coupled across a differential output of the LED driver. A feedback path, having a store circuit, is configured to store an information indicative of a first voltage level across the output capacitance element as a stored feedback reference signal just after the PWM signal is turned OFF. The feedback path causes the voltage across the output capacitance element to be at the first voltage level just before the PWM signal is turned ON.