H-Bridge Buck-Boost LED Driver for Sub-Microsecond PWM Pulses
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Solution Overview
Problem
Existing LED driver systems face challenges in achieving very short pulse widths while maintaining a continuous inductor current, as shunt dimming methods often result in output capacitor discharge, which negates the benefits of continuous current flow and increases complexity and cost.
Innovation Solution
The proposed solution involves an H-bridge buck-boost LED driver circuit that uses average current mode control and a simplified topology without a dedicated shunting switch, allowing for continuous inductor current without discharging the output capacitor, achieved by integrating the functions of FETs and switches to maintain current flow and regulate pulse widths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If shunt dimming methods are used to achieve narrow pulse widths, then pulse width can be reduced, but output capacitor discharges which negates continuous current benefits and increases complexity
Solution Approach 1:
The patent removes the dedicated shunting switch component from the circuit topology. Instead of using a separate shunting switch to achieve narrow pulse widths, the invention extracts this function and integrates it into the existing H-bridge buck-boost converter switches, thereby eliminating the need for additional components while maintaining the ability to generate narrow pulses without discharging the output capacitor
Solution Approach 2:
The patent merges the shunting function with the existing H-bridge switches. By controlling the existing switches in a specific sequence and manner, the circuit achieves both the buck-boost conversion and the shunting dimming functions using the same components, thus reducing device complexity while enabling narrow pulse width operation
2Duration of action of moving object
If shunt dimming is used to achieve narrow pulse widths, then pulse duration can be shortened, but output capacitor discharge occurs increasing cost
Solution Approach 1:
The patent eliminates the need for a dedicated shunting switch by extracting its function and implementing it through control logic of existing switches. This reduction in component count directly lowers manufacturing cost while maintaining the ability to achieve narrow pulse durations without output capacitor discharge
Solution Approach 2:
The existing H-bridge switches are made multi-functional, serving both as power switches for buck-boost conversion and as shunting switches for dimming control. This universality reduces the total component count and manufacturing cost while achieving the desired narrow pulse width performance
3Device complexity
If conventional PWM dimming is used, then circuit simplicity is maintained, but very narrow pulse widths cannot be achieved while maintaining high LED current
Solution Approach 1:
The patent implements dynamic control of the H-bridge switches to achieve variable pulse widths. By dynamically adjusting the switching sequences and durations of the existing switches, the circuit can adapt to different pulse width requirements while maintaining circuit simplicity and avoiding the need for additional dedicated shunting components
Solution Approach 2:
The patent maintains continuous inductor current flow while achieving narrow output pulses. The control strategy ensures that the inductor current continues to flow continuously through proper switching sequences, while the LED current is pulsed narrowly through controlled switching intervals, thus maintaining both circuit simplicity and narrow pulse width capability
Data Source
AI summary
Described herein are systems and methods for generating short load current pulses using an H-bridge. In various embodiments, this is accomplished by controlling, in a shunting mode, a low-side switch of the H-bridge to drive a first average current and controlling, in a non-shunting mode, a high-side switch of the H-bridge to drive a second average current such that the first and second average currents are substantially the same and reduce a current pulse width of the load current.