Cross Loop Control Circuit for Fast LED Backlight Load Regulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Single power stage multiple outputs topology in LED backlighting systems experiences slow dynamic response and poor load regulation due to slow feedback loops, particularly when sudden load changes occur.
Innovation Solution
A cross loop control circuit is introduced, comprising error amplifiers, saturation detecting circuits, and current source circuits to rapidly adjust power distribution between outputs, enhancing the dynamic response by using saturation indicating signals to charge and discharge error amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single power stage multiple outputs topology is used to provide multiple outputs, then the driver can provide currents to LED strings and voltages to other circuits, but the feedback loop with power conversion control responds slowly when load changes occur
Solution Approach 1:
The patent divides the control system into two independent feedback loops: a fast voltage feedback loop for the first output and a slow power conversion feedback loop for the second output. By segmenting the control functions, the voltage feedback loop can respond quickly to load changes without being constrained by the slower power conversion loop, thus resolving the contradiction between providing multiple outputs and maintaining fast dynamic response.
Solution Approach 2:
The patent introduces a current transfer mechanism as an intermediary between the two feedback loops. When the first output experiences a load change, the voltage feedback loop detects it and adjusts the current through the transfer mechanism, which then quickly adjusts the second output. This intermediary allows fast response to be transmitted from one loop to another without waiting for the slow power conversion loop.
2Reliability
If the feedback loop with power conversion control is used to control power conversion, then power conversion is controlled, but the load regulation is slow when sudden load changes occur
Solution Approach 1:
The patent implements preliminary action by having the fast voltage feedback loop continuously monitor and prepare to respond to load changes before they affect the power conversion loop. When a load change occurs, the voltage feedback loop immediately detects it and takes corrective action through the current transfer mechanism, preventing the slower power conversion loop from having to react to large deviations, thus reducing response time while maintaining reliable power conversion control.
Data Source
AI summary
A control circuit of a power converter providing at least a first output voltage and a second output voltage, having: a first loop control circuit, configured to provide a first error amplifying signal based on the first output voltage and a first reference voltage; a second loop control circuit, configured to provide a second error amplifying signal based on the second output voltage and a second reference voltage; a saturation detecting circuit, configured to provide a saturation indicating signal based on the first error amplifying signal and a saturation reference signal; and a first current source circuit, configured to charge an output terminal of the second error amplifier based on the saturation indicating signal.