led quick start circuit

Abstract

The invention discloses an LED (light-emitting diode) quick start-up circuit which comprises a feedback loop, a power tube, a start-up detection resistor connected with a load LED in series, a start-up detection amplifier for detecting a voltage drop on the start-up detection resistor, a power-on detection circuit used for detecting power of the circuit, a current detection resistor connected with the power tube in series, and a current detection comparator of which the input end is connected with the two ends of the current detection circuit, wherein the output ends of the start-up detection amplifier and the power-on detection circuit are connected with the input end and the reset end of a trigger; the start-up detection resistor is connected between an output voltage end and the load LED; the output end of an alternative gating switch is connected with the input end of a PWM (Pulse Width Modulation) comparator. The LED quick start-up circuit continuously runs with large duty ratio during the start-up period until the conducting conditions of the load LED are met, so that the increment speed of the output voltage is increased and the start-up time is shortened; by current feedback control, the loop response speed is further increased.

Description

technical field [0001] The invention belongs to the field of integrated circuit design and relates to a switching power supply, in particular to an LED quick start circuit. Background technique [0002] A type of semiconductor diode that converts electrical energy into light energy. Like ordinary diodes, light-emitting diodes are composed of a PN junction and also have unidirectional conductivity. When a forward voltage is applied to the light-emitting diode, holes are injected from the P region to the N region and electrons are injected from the N region to the P region. [0003] LED can only be turned on (energized) in one direction, which is called forward bias (forward bias). When the current flows, electrons and holes recombine in it to emit monochromatic light, which is called electroluminescence effect. Compared with incandescent bulbs and neon lamps, light-emitting diodes are characterized by: very low operating voltage (some are only a few volts); working current ...

AI Technical Summary

Problems solved by technology

If the soft-start control inside the chip is not added, the output voltage overshoot will easily occur during startup, causing the LED to have a high startup transient current.

Adding soft-start control inside the chip will increase the start-up time from when the switch is turned on to when the LED is fully lit, and it is difficult to meet the start-up time requirement of <0.5S

Images