Although the LED video screen is different, the voltage of DC power supply and independent equipment is low, so the conversion circuit is usually used when using city electric. The technical realization of LED power converter depends on the usage.
According to the power supply voltage, LED drivers can be divided into three categories: mainly used to drive portable electronic products, low power and medium power white LEDs. The second is power supply, such as step-down, adjustable DC (converter), or power supply greater than 5, which uses battery to work. Third, direct power supply to the main power supply (110V or 220V) or corresponding high-voltage DC (such as} 40 to 400V), mainly used for camel high output white LED, such as Buck DC / DC converter.
1. Battery power driver
Battery power supply voltage is usually used for low-power lighting equipment (such as 0.8 to 1.65v LED electronic screen), mainly used to drive medium power white LEDs, such as portable electronic products, low-power and LED flashlight, LED emergency lights, energy-saving lights, etc. Considering that it can work with No.5 battery or have the smallest volume, the best technology is not to use several drivers of LDO circuit, but to use charge pump boost converter such as boost DC converter (or boost (or lift) charge pump boost converter).
2. High voltage trunk and driver solutions
Low voltage power supply with voltage higher than 5 uses special power supply or battery power supply. The voltage value of LED power supply is always higher than the voltage drop of LED tube. In other words, 6V, 9V, 12V, 24V or higher are always greater than 5V. In this case, it is mainly powered by power supply or battery and used to drive indicator light. This kind of power supply scheme must solve the problem of low blood pressure, and typically use solar grass lamp, solar garden lighting, automobile lighting system, etc.
3. Program directly driven by main power or high voltage DC power
This solution directly from the main power supply (100V or 220V) or its high-voltage DC power supply, mainly used to drive high-power white LED lights. The main power driver is the most expensive way of power supply for LED electronic screen, which is the development direction of LED popular applications.
The LED driver solves the problems of power consumption and rectification, with high conversion efficiency, small size and low cost. In addition, we need to solve the problem of security isolation. Considering the impact on the power grid, electromagnetic interference and power factor problems should also be solved. For low and medium power LED, the best circuit structure is isolated single ended flyback converter. For high power applications, a bridge converter must be used. The main challenge of LED driver is the nonlinearity of LED display. This is mainly reflected in the led forward voltage changes with the current and temperature, different LED devices have differences in the forward voltage, led “color point” drift with the current and temperature, and the LED must work within the range of specifications to achieve reliable operation. The main function of LED driver is to limit the current under operating conditions, regardless of input conditions and changes in forward voltage.
For LED drive circuit, there are some main requirements besides constant current and normal current. For example, if LED dimming operation is required, PWM technology needs to be provided, and the typical PWM frequency used for LED dimming is 1 to 3kHz. In addition, the power handling capacity of LED driver circuit must be strong enough to withstand various fault conditions, and can be easily realized. It is worth noting that the indicator does not always drift at the optimum current.
In the selection of LED electronic screen driver, boost DC / DC with inductance was once considered. In recent years, the output current of charge pump driver has increased from several hundred Ma to 1.2 A, and the output of these two types of driver is close.
Cooling method of LED electronic screen
