In the design process of the LED
In the design process of the LED switching power supply, engineers need to select the most appropriate driving method for the new product according to the design requirements. At present, there are four commonly used LED switching power supply driving modes, namely low voltage driving, transient low voltage driving, high voltage driving and commercial power driving. This article will briefly analyze and introduce the driving methods of these four LED switching power supplies.
Low voltage drive
Low-voltage drive is a common driving method for LED switching power supply design. Its specific meaning refers to the voltage drive lower than the LED forward voltage drop. In actual operation, the low voltage drive needs to raise the voltage to a voltage sufficient to turn the LED on and stable. Portable device lighting applications such as cell phone backlights, LED flashlights, etc. Since battery capacity limitation generally does not require a large amount of power, it requires low cost, small size, and high conversion efficiency. The charge pump boost converter in these applications is the best topology choice.
2. Transition voltage drive
The transition voltage drive is another optional drive mode for the LED switching power supply. It means that the power supply voltage value changes around the LED tube voltage drop, which may be high and low. The transition voltage drive not only solves the boosting problem but also solves the step-down problem. It also needs to be as small as possible and low in cost. The reverse polarity charge pump converter is the most cost-effective.
3. High voltage drive
High-voltage drive is more common in some current high-power LED switching power supply applications. It refers to drives that are higher than the tube voltage drop, such as 12V, 24V batteries. High-voltage driving needs to solve the step-down problem. Since the high-voltage driving is generally powered by an ordinary battery, a relatively large power is used, and the optimal circuit structure of the converter is a series switching step-down circuit.
4. Mains drive
The mains drive is currently the most valuable power supply in the field of LED switching power supply, especially in the field of LED lighting. This is also a problem that must be solved in the popular application of semiconductor lighting. The mains drive LED needs to solve the buck and rectification problems, but also has a relatively high conversion efficiency. In addition, the problem of safety isolation should be solved. Considering the impact on the power grid, it is also necessary to solve the problem of electromagnetic interference and power factor. For small and medium power LEDs, isolated single-ended flyback converters are a good circuit structure. For high power applications, this bridge conversion circuit is used.