Constant-current drive system of LED string lights

Abstract

The invention discloses a constant-current drive system of LED string lights. The constant-current drive system comprises a voltage pre-regulating module, a high-voltage protection module and a low-temperature coefficient constant-current module. The voltage pre-regulating module is used for realizing step-down of input voltage and outputting direct-current voltage and generating reference voltage. The high-voltage protection module is used for converting the reference voltage into threshold voltage, comparing the input voltage to the throttle voltage to generate a control signal for controlling on and off of the LED string lights. The low-temperature coefficient constant current module generates PTAT(proportional to absolute temperature) current by taking the direct-current voltage as working voltage, performing temperature compensation and fine tuning to the PTAT current and then outputting constant current to the LED string lights under action of the control signal. The PTAT current is subjected to temperature compensation by the aid of thermistors RC1 and RC2 respectively having positive temperature coefficient and negative temperature coefficient; a current trimming circuit is used for trimming size of the PTAT current to guarantee high precision of the constant current; the high-voltage protection circuit controls on and off of the constant current on the over-voltage condition so as to guarantee system reliability.

Description

technical field [0001] The invention relates to the field of lighting LED drive, in particular to a constant current drive system for LED lamp strings. Background technique [0002] LED is a new type of light source, which has the characteristics of low energy consumption, high efficiency, and long life. It has been widely used in various fields, especially in lighting equipment. In order to keep the luminance of the LED stable, it is usually necessary to use a constant current power supply to drive the LED load. Moreover, the constant current source can prolong the service life of the LED, and multiple constant current sources can flexibly cooperate with appropriate control circuits to drive multiple LED arrays. [0003] In the conventional lighting LED constant current driving device, there are usually two methods to realize the constant current. One is to use a switching power supply to modulate the output current, including methods such as switching pulse width modulat...

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Problems solved by technology

[0007] In view of the above problems, the present invention provides a low temperature coefficient constant current drive system with high voltage protection, aiming to solve the problems of poor reliability and low precision existing in the prior art

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