Ultra-Low Dropout Current Regulator for Vehicle Light Head
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing light head systems using linear voltage regulators can only power a maximum of three high-power LEDs in series due to significant voltage drops across the current regulator circuitry, limiting the number of LEDs that can be powered efficiently and resulting in wasted voltage as heat.
Innovation Solution
The implementation of ultra-low dropout (LDO) current regulator circuitry with a passive sense component, pass transistor, and feedback drive circuitry, which minimizes voltage drop across the current regulator, allowing for a negligible voltage drop and enabling the powering of at least four high-power LEDs in series by maintaining a control signal that adjusts the current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If linear voltage regulators are used to power high-power LEDs in series, then current regulation is achieved, but significant voltage drops occur across the regulator circuitry limiting the number of LEDs that can be powered
Solution Approach 1:
The patent changes the operational parameters of the pass transistor by maintaining it in the saturation region rather than the linear/triode region. This parameter change reduces the transistor's on-resistance and minimizes voltage drop across the regulator, enabling higher LED串的 voltage headroom while maintaining current regulation through feedback control
2Illumination intensity
If more high-power LEDs are connected in series to maximize light output, then illumination intensity increases, but the voltage headroom available for current regulator circuitry decreases
Solution Approach 1:
By changing the pass transistor operating region to saturation, the regulator requires minimal voltage headroom (ultra-low dropout), allowing the system to accommodate more series-connected LEDs within the same supply voltage while maintaining proper current regulation
Solution Approach 2:
The feedback mechanism continuously monitors the LED current and adjusts the pass transistor gate voltage accordingly, ensuring stable current regulation even as the number of series LEDs increases and voltage headroom becomes limited
3Reliability
If the pass transistor is maintained in the linear/triode region to regulate current, then current control is achieved, but additional voltage is lost across the regulator circuitry
Solution Approach 1:
The patent fundamentally changes the pass transistor operating region from linear/triode to saturation, transforming it from a variable resistor mode to a low-resistance switch mode. This parameter change dramatically reduces voltage loss across the regulator while feedback control maintains precise current regulation
Solution Approach 2:
Instead of using the conventional approach of operating the pass transistor in the linear region as a variable resistor, the patent inverts the approach by operating it in the saturation region as a low-resistance switch, thereby minimizing voltage loss while achieving current control through feedback
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 solution allows for a significant increase in the number of high-power LEDs that can be powered in series, maximizing light output while minimizing power dissipation as heat, thereby reducing the number of required current regulator components and lowering overall power consumption.
Implementation Method 1
a pass transistor, the pass transistor includes a first terminal coupled to receive current supplied by the battery-based voltage system
Implementation Method 2
the feedback drive circuitry having first and second input terminals to detect a difference between the reference and feedback voltages applied to, respectively, the first and second input terminals
Implementation Method 3
a passive sense component... providing a feedback voltage representing the current that passes through the series-connected set
Implementation Method 4
a series-connected set of high-power light-emitting diodes (HP LEDs) and current regulator circuitry electrically connected to, and facilitating light emission from, the HP LEDs
Data Source
AI summary
In connection with a ground transportation vehicle light head (86) powered by a battery-based voltage source (20) supplying positive (76) and reference (i.e., ground) (78) voltages that define a voltage difference (22) applied across a number of multiple series-connected high-power light-emitting diodes (HP LEDs) (12) and current regulator circuitry (80) electrically connected to them, ultra-low dropout circuit techniques are disclosed for increasing a portion of the voltage difference available from the battery-based voltage source to forward bias and thereby maximize the number of the multiple series-connected HP LEDs emitting light by maintaining a low voltage drop (82) across the current regulator circuitry. By maintaining the low voltage drop and making available from the battery-based voltage source an increased portion of the voltage difference, at least one additional HP LED is capable of being forward biased to thereby maximize the number of multiple series-connected HP LEDs emitting light from the light head.