LED Driver Store and Hold Circuit for PWM Voltage Recovery
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Solution Overview
Problem
Traditional LED driver circuits experience voltage decay across the operating point capacitance element during PWM OFF periods due to internal leakage, leading to a recovery delay when the PWM signal is turned back ON, which is problematic for maintaining immediate color temperature and intensity of LEDs.
Innovation Solution
The implementation of a store and hold circuit that preserves the operating point voltage across the operating point capacitance element during PWM OFF times, using either digital or analog methods to maintain the voltage level, ensuring quick recovery and stable current delivery when the PWM signal is turned back ON.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If PWM OFF duration is increased to save energy or control average brightness, then power consumption is reduced and average brightness is controlled, but voltage decay across operating point capacitance increases causing longer recovery delay
Solution Approach 1:
The patent applies preliminary action by storing the operating point voltage value in a register or memory element before the PWM OFF period begins. This stored value is then used to quickly restore the operating point capacitance voltage at the start of the next PWM ON period, eliminating the need to wait for natural recharge during the OFF period. The operating point information is preserved in advance and applied proactively when needed.
2Stability of the object's composition
If operating point capacitance value is increased to maintain voltage stability, then voltage stability is improved, but circuit complexity and leakage effects are worsened
Solution Approach 1:
The patent introduces an intermediary element (register or memory storage element) that mediates between the PWM control signal and the operating point capacitance. This intermediary stores the operating point voltage information and provides it to the capacitance when needed, allowing the capacitance to remain small while still achieving voltage stability through the stored reference value rather than relying on the capacitance's natural charge-holding ability.
3Stability of the object's composition
If PWM duty cycle is increased to maintain operating point voltage, then voltage stability is maintained, but average brightness control flexibility is reduced
Solution Approach 1:
The patent segments the brightness control function into two independent parts: (1) PWM duty cycle control for average brightness adjustment, and (2) operating point voltage restoration for circuit stability. By separating these functions, the PWM duty cycle can be freely adjusted for brightness control without compromising operating point stability, which is independently maintained through the stored voltage value applied to the capacitance at the start of each ON period.
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 significantly reduces or eliminates the recovery time of the LED driver circuit, maintaining the desired operating point voltage even after long PWM OFF periods, thus ensuring immediate and consistent LED performance.
Implementation Method 1
an operating point capacitance element (213) and an optional output capacitance element (217)
Data Source
AI summary
A method and system of driving an LED load. There is a power stage that 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. There is a feedback circuit that is configured to generate the operating point signal, which causes the power stage to deliver a level of current indicated by the control signal, when the PWM signal is ON. A store and hold circuit is configured to store an information indicative of a level of the operating point signal just after the PWM signal is turned OFF and cause the operating point signal to be at that level just before the PWM signal is turned ON.