PWM Current Regulator with Instant Duty-Cycle Adjustment
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Solution Overview
Problem
Existing current regulation systems for high-intensity LEDs experience slow transient response and settling times due to the low bandwidth of feedback loops, especially when digital dimming signals are applied, leading to inefficiencies in controlling brightness and maintaining constant current flow.
Innovation Solution
A current regulator circuit that includes a PWM controller and a digital dimming error circuit, which rapidly adjusts the duty-cycle of the switching signal by adding an error term to the feedback loop, allowing for instantaneous changes in current flow through a current-path shunt, thereby reducing transient settling times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a feedback loop is used to regulate current through high-intensity LEDs, then current regulation is achieved, but the transient response and settling times become slow due to low bandwidth
Solution Approach 1:
The patent applies preliminary action by predicting the required duty-cycle adjustment in advance of the actual current disturbance. When a digital dimming signal is detected, the system proactively calculates and applies the necessary error term to the PWM duty cycle before the current can deviate significantly, thereby preempting the transient response issue rather than reacting to it after it occurs.
Solution Approach 2:
The system provides beforehand cushioning by introducing a feedforward error term that compensates for anticipated current disturbances caused by digital dimming signals. This error term acts as a cushion that prevents large current transients from occurring in the first place, reducing the burden on the feedback loop and thereby maintaining fast transient response while preserving current regulation stability.
2Adaptability or versatility
If digital dimming signals are applied to control LED brightness, then brightness control is achieved, but transient settling times increase due to feedback loop bandwidth limitations
Solution Approach 1:
The patent introduces an intermediary error term that mediates between the digital dimming signal and the PWM duty cycle. This error term serves as a bridge that translates the dimming command into appropriate current adjustments, allowing brightness control to be achieved without directly disrupting the current feedback loop and thereby minimizing transient settling time.
Solution Approach 2:
The system applies parameter changes by dynamically adjusting the PWM duty cycle parameter in response to digital dimming signals. By changing the duty cycle parameter proactively based on the dimming command, the system achieves brightness control while maintaining fast transient response, avoiding the slow settling that would occur if only feedback-based parameter adjustment were used.
3Speed
If the feedback loop bandwidth is increased to reduce transient settling time, then transient response improves, but system stability and current regulation accuracy may deteriorate
Solution Approach 1:
By taking preliminary action through feedforward control, the system addresses current disturbances before they fully develop, reducing the need for high-bandwidth feedback correction. This allows the feedback loop to maintain lower bandwidth settings that preserve stability and accuracy while still achieving fast transient response through the proactive error term adjustment.
Data Source
AI summary
One embodiment of the present invention includes a current regulator circuit. The circuit includes at least one switch configured to periodically couple and decouple a respective at least one voltage rail to an inductor to maintain a current through the inductor. The circuit also includes a pulse-width modulation (PWM) controller configured to set a duty-cycle associated with a switching signal to control the at least one switch based on a feedback signal that is associated with a magnitude of the current. The circuit also includes a switch-controlled current path configured to shunt the current from a load in response to a control signal. The circuit further includes an error circuit configured to provide an error term to the PWM controller upon activating the control signal to adjust the duty-cycle substantially instantaneously in response to the control signal.