LED brightness control system for a wide-range of luminance control

A head-up display (HUD) system, comprising:

• a HUD computer for providing control and data signals;
• an overhead unit (OHU), comprising:
• a communication interface for receiving said control and data signals and providing desired communication with other portions of said HUD system;
• an LED brightness control system, comprising:
• a brightness control module for providing a pulse width modulation (PWM) control signal and a peak current control signal from said control and data signals received from said communication interface;
• a pulse width modulation (PWM) converter circuit for receiving said PWM control signal and converting it to a PWM signal;
• a multiplier for receiving said PWM signal and said peak current control signal from said brightness control module and for multiplying the same to provide a light emitting diode (LED) current control signal with a variable “on” time as well as variable “on” level;
• a voltage-controlled current source for utilizing said LED current control signal and an LED current feedback signal for providing an LED current;
• an LED illuminator array for receiving said LED current;
• and,
• a current sensing element connected to said LED illuminator array for providing an LED current feedback signal representing LED peak current,
• wherein said voltage-controlled current source controls a drive voltage to the LED illuminator array at a commanded level;
• and,
• an LCD driver for receiving display signals from said communication interface and for providing an LCD drive signal;
• an LCD for generating a display image in response to said LCD drive signal;
• and,
• a power source for providing power to said communication interface;
• LED brightness control system, LCD driver, and LCD;
• and,
• a combiner including an ambient light sensor (ALS) that detects ambient light and sends an ambient light signal, brightness and contrast control signals to said OHU for processing.

A method for providing a wide range of luminance control of an LED illuminator array, comprising the steps of:

• providing a pulse width modulation (PWM) control signal and a peak current control signal;
• receiving said PWM control signal and converting it to a PWM signal;
• multiplying said PWM signal and said peak current control signal to provide a light emitting diode (LED) current control signal with a variable “on” time as well as variable “on” level;
• utilizing said LED current control signal and an LED current feedback signal with a voltage-controlled current source for providing an LED current;
• receiving said LED current with an LED illuminator array;
• and,
• utilizing a current sensing element connected to said LED illuminator array for providing an LED current feedback signal representing LED peak current,
• wherein said voltage-controlled current source controls a drive voltage to the LED illuminator array at a commanded level.