POWER SUPPLY CIRCUIT FOR LED ROADLAMP

摘要

PURPOSE: A power supply circuit for an LED streetlight is provided to prevent deterioration of the LED streetlight by controlling a duty ratio when a temperature of an LED streetlight is above a preset temperature. CONSTITUTION: An EMI(Electromagnetic Interference) filter(10) is arranged on an input terminal of a commercial AC power. A rectification and PFC(Power Factor Correction) switch circuit unit(20) rectifies the AC power passing through the EMI filter. An SMPS(Switching Mode Power Supply) switch circuit unit(30) converts the DC voltage from the rectification and PFC switch circuit unit into the high frequency AC voltage. A second rectification circuit unit(50) converts the high frequency AC voltage from the SMPS switch circuit unit into the DC voltage. A constant voltage feedback circuit unit(60) controls a duty ratio of a PWM(Pulse Width Modulation) control circuit unit(40). If the temperature of the LED is above the preset temperature, a heat sensing circuit outputs a heat sensing signal to the constant voltage feedback circuit unit.