LED Driver Precharge and Track-Hold Voltage Regulation
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Solution Overview
Problem
Conventional LED drivers face inefficiencies due to variations in bias voltages across LED strings and transient voltage droops in PWM-based systems, leading to increased power consumption and potential instability in current regulation.
Innovation Solution
The implementation of a feedback controller with precharge and track/hold schemes that dynamically adjusts the output voltage based on the minimum tail voltage of LED strings, incorporating short-term and long-term precharging mechanisms to counteract transient voltage droops and thermal changes, ensuring consistent current regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed voltage sufficiently higher than worst-case bias drop and transient voltage droop is provided, then proper operation of each LED string is ensured, but power consumption by the LED driver is unnecessarily increased
Solution Approach 1:
The patent implements dynamic voltage adjustment by transitioning from a fixed voltage approach to a dynamic voltage regulation system that adapts to real-time conditions. The feedback controller continuously monitors tail voltages and adjusts the output voltage accordingly, allowing the system to maintain reliable LED string operation while minimizing power consumption by only providing the necessary voltage headroom rather than a consistently excessive fixed voltage
Solution Approach 2:
The patent employs feedback control mechanisms where the feedback controller monitors the tail voltages of LED strings and uses this information to regulate the output voltage. This closed-loop feedback system enables the LED driver to maintain proper operation of all LED strings by dynamically adjusting the output voltage to compensate for forward voltage variations and transient droop, while avoiding the power waste associated with fixed excessive voltage provisioning
2Stability of the object's composition
If the output voltage is increased to account for forward voltage variations and transient droop, then current regulation stability is improved, but power consumption increases
Solution Approach 1:
The patent implements precharge circuits that proactively compensate for transient voltage droop before it occurs during PWM transitions. By anticipating the voltage droop that occurs when LED strings are activated and applying a preliminary voltage boost, the system maintains stable current regulation without needing to continuously operate at an excessively high output voltage, thereby reducing overall power consumption while preserving regulation stability
Solution Approach 2:
The patent dynamically changes the output voltage parameter based on operating conditions, LED string activation states, and measured tail voltages. Rather than maintaining a constantly high output voltage to ensure stability, the system adjusts the voltage parameter in real-time to match actual requirements, achieving stable current regulation only when necessary and reducing power consumption during periods when full voltage headroom is not needed
Data Source
AI summary
A power source provides an output voltage to drive a plurality of light emitting diode (LED) strings. A feedback controller monitors the tail voltages of the LED strings to identify the minimum tail voltage and adjusts the output voltage based on a relationship between the minimum tail voltage and a reference voltage. The feedback controller implements precharging of the output voltage, including one or both of short-term precharging or long-term precharging. Further, the feedback controller incorporates a track/hold circuit that tracks the minimum tail voltage while the LED strings are active and holds the minimum tail voltage at the last tracked minimum tail voltage while the LED strings are inactive and uses the held minimum tail voltage for controlling the output voltage while the LED strings are inactive so as to permit the power source to supply an appropriate output voltage when the LED strings are subsequently activated again.