LEDs are current-driven devices whose brightness is proportional to forward current. A wide range of portable electronics require a backlight LED driver solution with the following features: DC control, high efficiency, PWM dimming, overvoltage protection, load disconnection, small size, and ease of use. This article explores each feature and how to implement it, and finally shows a typical circuit with each feature.
DC control
LEDs are current-driven devices whose brightness is proportional to forward current. There are two ways to control the forward current. The first method is to use the LED VI curve to determine the voltage that is required to be applied to the LED to produce the desired forward current.
The implementation method generally uses a voltage supply and a ballast resistor. Figure 1 illustrates this approach. As described below, this method has several shortcomings. Any change in the LED forward voltage will result in a change in the LED current. If the rated forward voltage is 3.6V, the current of the LED in Figure 1 is 20mA.
If the voltage becomes 4.0V, which is a specific pressure change caused by temperature or manufacturing changes, the forward current is reduced to 14 mA. A 11% change in forward voltage results in a larger forward current change of up to 30%. In addition, depending on the available input voltage, the ballast resistor's voltage drop and power dissipation can waste power and reduce battery life.
Figure 1: Voltage supply with ballast resistors results in reduced efficiency and forward current mismatch.
MOSO Public LED lighting Driver is a IP67,
constant current design for Public lighting application like street light,
tunnel light, Flood light, Stadium Light, etc. This Public LED lighting Driver
has brilliant waterproof design and universal input voltage range that ensure
this LED control gear to be suitable for all of outdoor application use.
The Public Lighting LED Driver got global safety certifications, including UL, CE, TUV, CB, ENEC,SAA, BIS, KC, PSE, etc. The LED Driver has universal input voltage, from 90~305Vac. It is a reliable product compatible with various application and different countries.
The high efficiency of these Public lighting LED Power Supply and compact metal case enable them to run cooler, significantly improving reliability and extend product lifetime to at least 50,000hours.
To ensure trouble-free operation, protection is provided against built-in Surge protection, output over voltage, short circuit, and over temperature.
MOSO grants the product with 5 years global warranty. Customer can refer to Warranty policy, find the closest MOSO distributors or sales representatives, to get a local replacement in case of any failure.
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Moso Electronics , https://www.mosoleddriver.com