Low-dropout current regulator for light head

For a vehicle light head powered by a battery-based voltage system supplying upper and lower voltages that define a voltage difference applied across 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 of the series-connected set, a method of maximizing a number of HP LEDs in the series-connected set that are capable of emitting light, the method comprising:

• providing low-dropout (LDO) current regulator circuitry of which the current regulator circuitry, voltage reference circuitry, and feedback drive circuitry are parts;
• the current regulator circuitry including a passive sense component and a pass transistor, the pass transistor includes a first terminal coupled to receive current supplied by the battery-based voltage system, a second terminal coupled to deliver the current to the passive sense component providing a feedback voltage representing the current that passes through the series-connected set, and a control terminal by which an amount of the current is controllable;
• the voltage reference circuitry providing a reference voltage;
• 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, and an output terminal to generate a control signal upon amplification of the difference;
• and
• the control signal having a magnitude that rapidly adjusts between the upper and lower voltages for application to the control terminal of the pass transistor that, in response to the magnitude of the control signal, regulates the amount of the current that flows through the series-connected set while maintaining, as the voltage difference approaches a sum of minimum forward voltages of the HP LEDs, a negligible voltage drop across the current regulator circuitry such that substantially all of the voltage difference remains available for forward biasing the HP LEDs.