Abstract: A system for backlighting a display uses an open or closed loop and small components that are well suited to high-frequency applications. The system includes multiple LED strings, a high-voltage source, and a low-voltage regulator that has a polarity opposite to that of the high-voltage source. The high-voltage source and the low-voltage regulator provide voltage differences across the LED strings to illuminate them. In one embodiment, the high-voltage source is about 200 VDC, and the low-voltage regulator produces voltages between ?2 VDC and ?30 VDC. Many types of displays, such as those used on LCD televisions and LCD personal computers, can be backlit in accordance with the embodiments.

Abstract: A power circuit includes a voltage limited charge circuit and a linear regulator to supply high current pulses to a load while maintaining a regulated output and not discharging the battery below a predetermined level. The voltage limited charge circuit includes a low impedance transistor and an operational amplifier that are together configured as an active loop. The transistor functions as a switch, and the operational amplifier provides an adjustable control voltage that adjusts the impedance of the transistor according to current battery voltage and a minimum threshold voltage. Adjusting the impedance of the transistor enables the storage capacitor to charge very fast when the battery impedance is low, or very slow when the battery impedance is high.

Abstract: A power circuit includes a voltage limited charge circuit and a linear regulator to supply high current pulses to a load while maintaining a regulated output and not discharging the battery below a predetermined level. The voltage limited charge circuit includes a low impedance transistor and an operational amplifier that are together configured as an active loop. The transistor functions as a switch, and the operational amplifier provides an adjustable control voltage that adjusts the impedance of the transistor according to current battery voltage and a minimum threshold voltage. Adjusting the impedance of the transistor enables the storage capacitor to charge very fast when the battery impedance is low, or very slow when the battery impedance is high.

Abstract: A system for backlighting a display uses an open or closed loop and small components that are well suited to high-frequency applications. The system includes multiple LED strings, a high-voltage source, and a low-voltage regulator that has a polarity opposite to that of the high-voltage source. The high-voltage source and the low-voltage regulator provide voltage differences across the LED strings to illuminate them. In one embodiment, the high-voltage source is about 200 VDC, and the low-voltage regulator produces voltages between ?2 VDC and ?30 VDC. Many types of displays, such as those used on LCD televisions and LCD personal computers, can be backlit in accordance with the embodiments.