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What are the types of LED electronic display drivers?

2022-06-10

According to the level of supply voltage, LED drivers can be divided into three categories: one is powered by batteries, mainly used for portable electronic products, driving low-power and medium-power white LEDs; the other is power supply greater than 5, powered by regulated power supply or battery Power supply, such as step-down and buck-boost DC converters; the third is to directly supply power from mains (110V or 220V) or corresponding high-voltage direct current (such as 40~400V), mainly used for camel-driven high-power White LEDs, such as step-down DC/DC converters. 


1. Battery powered drive scheme

The battery supply voltage is generally 0.8~1.65V. For low-power lighting devices such as LED displays, this is a common use case. This method is mainly suitable for portable electronic products to drive low-power and medium-power white LEDs, such as LED flashlights, LED emergency lights, energy-saving desk lamps, etc. Considering that it is possible to work with a 5th battery and have the smallest volume, the best technical solution is a charge pump boost converter, such as a boost DC Zhuang (converter or boost (or Buck-boost (buck-boost) charge pump converters, a few of which are drivers using LDO circuits. 


2. High voltage and dry driving scheme

The low-voltage power supply scheme with a voltage higher than 5 uses a dedicated regulated power supply or battery power supply, and the voltage value of the LED power supply is always higher than the LED tube voltage drop, that is, always greater than 5V, such as 6V, 9V, 12V, 24V or higher. In this case, it is mainly powered by a regulated power supply or a battery to drive the LED lights. This power supply solution must solve the problem of power supply voltage reduction, and typical applications include solar lawn lights, solar garden lights, and lighting systems for motor vehicles. 


3. Drive solutions powered directly from mains or HVDC 

This solution is directly powered by mains (100V or 220V) or corresponding high-voltage DC, and is mainly used to drive high-power white LED lamps. Mains drive is a power supply method with the highest price ratio for LED electronic displays, and it is the development direction of the popularization and application of LED lighting. 


When driving LED with commercial power, it is necessary to solve the problem of step-down and rectification, and also have relatively high conversion efficiency, small size and low cost. Also, security isolation should be addressed. Considering the impact on the power grid, it is also necessary to solve the problems of electromagnetic interference and power factor. For medium and low power LEDs, the best circuit structure is an isolated single-ended flyback converter. For high power applications, bridge converter circuits should be used. 


For LED drivers, the main challenge is the nonlinearity of the LED display. This is mainly reflected in the forward voltage of the LED will change with current and temperature, the forward voltage of different LED devices will be different, the LED "color point" will drift with current and temperature, and the LED must be within the specifications required. range for reliable operation. The primary role of an LED driver is to limit current under operating conditions, regardless of changes in input conditions and forward voltage. For the LED electronic display drive circuit, in addition to constant current regulation, there are some other key requirements. For example, if LED dimming is required, PWM technology needs to be provided, and the typical PWM frequency for LED dimming is 1~3kHz. In addition, the power handling capability of the LED driver circuit must be sufficient, robust, able to withstand multiple fault conditions, and easy to implement. It is worth mentioning that, because the LED electronic display screen will not drift under the optimum current. 


In the selection of LED electronic display drive solutions, the boost DC/DC, which was considered to have inductance in the past, has been output by the charge pump driver from several hundred mA to about 1.2A in recent years. Therefore, these two The output of each type of runner is about the same.