Design of High Power LED Constant Current Drive Circuit Based on DC/DC Regulator

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Overview:
In this paper, the general design method of high-efficiency constant-current regulated power supply based on DC/DC regulators commonly used in the market is described in the current high-speed and difficult-to-purchase DC/DC LED (light-emitting diode) dedicated constant current control chip. A design example based on the LM2596-ADJ switching regulator is given. Compared with the traditional constant voltage power supply, the circuit adds a sampling resistor with a small resistance value, a voltage feedback loop composed of a general-purpose operational amplifier, a current sampling and an amplification feedback loop, and an automatic switching circuit for voltage and current feedback loops. The circuit can automatically switch between constant voltage and constant current modes depending on the load. The experimental data shows that the LED constant current regulated power supply designed based on this method has high constant current precision, the error is less than 1%, the efficiency is over 87%, and the circuit works stably. The components are widely used and the price is low.

The current global energy shortage is increasing, restricting economic development, and energy conservation has become an important issue facing humanity. In the field of Lighting, LED lighting products known as the 4th generation of lighting sources or green light sources attract the attention of the world with energy saving, environmental protection, long life, small size and durability.

Due to the non-linearity of the volt-ampere characteristics of LEDs and the negative temperature coefficient of volt-ampere characteristics, as well as the difference in production process and production level, there are differences in the volt-ampere characteristics of high-power LEDs of the same power class produced by different manufacturers, even if they are the same. The same batch of LEDs produced by the manufacturer, there are some differences in the forward voltage drop between the individual, etc. In order to reduce the light decay of the LED and prolong the service life of the LED, the driving power supply of the LED uses a low-voltage DC constant current power supply. At present, world-renowned semiconductor device companies such as ON Semiconductor and TI have introduced DC/DC dedicated constant current control integrated circuits suitable for LED driving, such as NCP3066 and TPS40211DG. These integrated circuits have high conversion efficiency, but such integration The circuit price is relatively high and it is not easy to buy on the market. In response to this problem, this paper describes the general design method of constant current regulated power supply based on DC/DC switching regulator commonly used in the market, and gives relevant design examples and related test data.

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