Parallel Switch LED Driver Circuit for High Dimming Ratio
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Solution Overview
Problem
Existing LED driver circuits face limitations in achieving high dimming ratios and efficiency due to slow current changes and inefficient power management, particularly when using switching converters and series switches.
Innovation Solution
An LED driver circuit with a switching converter and a switch in parallel with the LED, where the switching element and inductor are connected in series, and a diode is connected in parallel, allowing for high dimming ratios and efficient power management by controlling the duty cycle and switch operation to adjust current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a switching converter is used to change LED current, then the LED can be dimmed, but the current changes are slow and the dimming ratio is limited
Solution Approach 1:
The patent divides the current control function into two separate switches: Switch 1 controls the main current path through the LED, while Switch 2 provides a parallel bypass path. This segmentation allows independent control of current magnitude and timing, enabling fast dimming response without being limited by inductor current ramp rates.
Solution Approach 2:
The patent employs periodic switching of Switch 2 in parallel with the LED at high frequency to rapidly modulate the LED current. This periodic action enables fast dimming transitions by periodically shunting current away from the LED, achieving high-speed brightness control that overcomes the slow current changes inherent in conventional switching converter approaches.
2Illumination intensity
If a switch is connected in series with the LED to change current, then the LED can be dimmed, but the switch is always in the current path which reduces efficiency
Solution Approach 1:
Instead of placing the dimming switch in series with the LED (conventional approach), the patent inverts the configuration by placing Switch 2 in parallel with the LED. This inversion allows the switch to control current by providing an alternative bypass path rather than directly interrupting the LED current, reducing power losses when the switch is in the ON state.
Solution Approach 2:
The patent extracts the dimming function from the main current path by using a separate parallel switch (Switch 2) that independently controls current shunting. This extraction allows the main series switch (Switch 1) to remain optimized for efficient current conduction while the parallel switch handles dimming control, separating the two functions to minimize overall power loss.
3Device complexity
If conventional LED driver circuits are used, then the circuit structure is simple, but the dimming ratio is limited and efficiency is reduced
Solution Approach 1:
The patent introduces dynamic control through two independently controllable switches that can operate in different modes. Switch 1 provides continuous current control while Switch 2 enables rapid dimming transitions through parallel switching. This dynamic configuration allows the circuit to adapt its operation mode based on dimming requirements, achieving high dimming ratios without proportionally increasing circuit complexity.
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 configuration enables fast and efficient control of LED brightness over a wide range, achieving high dimming ratios while minimizing power dissipation and maintaining efficiency across varying brightness levels.
Implementation Method 1
a switching element in series with an inductor and the LED
Implementation Method 2
with a switch connected in parallel with the LED
Data Source
AI summary
An LED driver circuit may include dimming circuitry. In particular, the LED driver circuit may include a switching converter, an LED and a switch. The LED may be electrically connected to the switching converter and the switch may be connected in parallel with the LED. The switching converter and/or the switch may be configured to be controlled to achieve dimming of the LED. Current may be supplied to the LED and the switch may be turned on and off to dim the LED. The switching converter coupled to the LED may include a switching element in series with an inductor and the LED. In such case, the switching element may be turned on to supply current to the LED and the inductor, and the switch may be turned on and off to dim the LED.