LED DRIVER OPERATING FROM UNFILTERED MAINS ON A HALF-CYCLE BY HALF-CYCLE BASIS

摘要

An analog electronic circuit for driving a string of LEDs including input terminals for accepting connection to AC voltage, a current regulation circuit operatively coupled to receive an AC voltage from the input terminals and to provide an output for connection to drive the string of LEDs. Included is a current regulation circuit configured to limit the current flow through the string of LEDs on a half-cycle basis to a predetermined value. Also disclosed are an overvoltage circuit configured to switch off electrical connection between the AC voltage and the string of LEDs upon the AC reaching a predetermined high voltage value on a half-cycle basis in order to limit power. Overtemperature and power factor correction are also addressed. Also improving efficiency by shorting part of the LED string during the lower voltage phase of the input AC voltage.

主权项

1. An LED driver circuit for powering a string of LEDs directly from mains-level AC voltage comprising:
a constant current sink circuit, the current regulated through a power transistor to a predetermined current level where the current can be turned off by grounding a low voltage control point; an overvoltage detection circuit configured to detect the voltage across the string of LEDs plus the voltage across the current sink circuit, the overvoltage detection circuit configured to turn off the sink current via grounding the control point when the total voltage reaches a predetermined value;