Microchip Technology LR745
LR745 is a high input voltage SMPS start-up circuit. LR745 is ideally suited for use with industry standard low-voltage, Pulse-Width Modulation (PWM) ICs having start thresholds of 13.9 to 18.0V. It allows the PWM ICs to be operated from rectified 120 or 240VAC lines, and eliminates the use of power resistors often used for this purpose.FEATURES
● Accepts inputs from 35 to 450V● Output current limiting
● For PWM ICs with start-up threshold voltage of 13.9 - 18.0V
● Very low power consumption after start-up
APPLICATIONS
● Notebook and laptop computers● Telecommunication power supplies
● Battery chargers
● Motor controllers
DESCRIPTION
The internal circuitry of the LR745 allows the PWM ICs to operate at a VCC voltage below their start-threshold voltage after start-up. The auxiliary voltage can be less than the start-threshold voltage, which allows for improved efficiency. Current from the high voltage line is drawn only during t