LED is recognized as the fourth generation green light source. It is a strong cold light source. It has the advantages of high efficiency, long service life, safety and environmental protection, small size, high reliability and fast response speed. At present, the same lighting effect has been achieved. The power consumption of LED is about 1/10 of incandescent lamp and 1/2 of fluorescent lamp. Many countries and regions have issued various policies to support the development of the LED industry, making the industry an important part of the country’s important industries, which has created enormous business opportunities. LED driver circuit is very important for LED, and LED dimming control can save energy. Driving and dimming of high brightness white LED is a hot topic in recent years.
LED Driver Introduction
The LED driver changes the power supply to a specific voltage and current to drive the LED voltage converter. Generally speaking, the input of LED driver includes high-voltage power frequency AC (i.e. city power), low-voltage DC, high-voltage DC, low-voltage and high-frequency AC (e.g. the output of electronic transformer). The output of LED driver power supply is mostly constant current source, which can change voltage with the change of forward voltage drop of LED. The core components of LED power supply include switch controller, inductor, switching element (MOSFET), feedback resistance, input filter, output filter, etc. According to the requirements of different occasions, there must be input over-voltage protection circuit, input under-voltage protection circuit and LED open-circuit protection.
LED Driver Power Supply Features
- High reliability – especially the driving power supply of LED street lamp installed in high altitude areas, inconvenient maintenance, maintenance costs are also high.
- High efficiency – LED is an energy-saving product with high driving efficiency. It is very important to install the power supply in the lamp. The utility model has the advantages of high power efficiency, low power consumption, small heat in lamps, and lower temperature rise of lamps. It is advantageous to delay the attenuation of LED.
- High power factor – power factor is the demand for load in power grid. Normally, electrical appliances below 70 watts have no mandatory indicators. Although the power factor of a single electrical appliance is low, it has little impact on the power grid, but at night, a large number of lighting and the concentration of the same load will seriously affect the power of the power grid. For 30-40 W LED drives, it is said that there may be some power factor requirements in the near future.
- Driving mode – There are two kinds of flow: one is a constant voltage source for multiple constant current sources, each constant current source is provided to each LED separately. In this way, the combination of flexible, all LED failures will not affect the work of other LEDs, but the cost will be slightly higher. The other is the DC constant current power supply, which is the driving mode of “Cocoa Huibao”, driven by the series or parallel operation of LED. It has the advantages of low cost, but poor flexibility. It can also solve the problems of LED without affecting other LED operation problems. These two forms coexist for a period of time. In terms of cost and performance, multi-channel constant current output power will be better. Perhaps this is the main direction for the future.
- Surge Protection – The ability of LED to resist surge is relatively poor, especially the ability to resist reverse voltage. It is also important to strengthen protection in this area. Some LED lights are outdoors, such as LED street lights. Due to load shedding and lightning induction, various surges will intrude from the grid, and some surges will lead to LED damage. Therefore, the analysis of driving power of “Zhongke Huibao” should be insufficient surge protection. As for frequent replacement of power supply and light bulbs, the LED driver should be able to suppress surges and protect the LED from damage.
- Protection function – In addition to conventional protection, it is better to add negative temperature feedback of LED in constant current output to prevent high temperature of LED and meet the requirements of safety and electromagnetic compatibility.
LED Driver Types
LED driver constant current – Common Market LED lamp driver is divided into two types according to the driving mode. One is constant current drive. The characteristic of constant current drive is that the output current is constant. The output voltage varies in a range. So we often see the drive case on the market marked (output: DC ** V – ** V * * * mA + – 5%). This means that the output voltage is one of the output voltages.
LED driver constant voltage – the other is constant voltage drive. The characteristic of constant voltage drive is that the output voltage is fixed. With the change of lamps, the current is in the maximum range. In this case, the housing usually indicates (output: DC ** V ** A) the voltage of the output fixed voltage and the maximum output current. Common market output is 5V, 12V, 24V and so on.
LED Driver Application
The application of LED drivers depends on the LED parameters to be driven. The two most important parameters are the input voltage and the input current. How to calculate the input voltage and current of LED lamp, the transmission lamp has a separate description. The following is just a description of the input of the LED lamp. People will see the original driving parameters (must identify some false driving targets!)!!!
After knowing the input voltage and current of the lamp board, we choose the corresponding LED driver to use. For example, if the input voltage of the lamp board is known to be 370-40V and the input current is 300 mA, the output voltage of the LED driver can be selected to include it, and the current is approximately the same. Formula surfaces that are higher or lower than all voltages must be included. Otherwise, there will be flicker. A small current will do.
Finally, we only need to press the positive and negative poles marked on the lamp board to weld the driving or connecting wires. It should be noted that red is the positive pole of the traditional LED drive output line. Black is the negative pole. If it is a grey line, then grey is the positive pole and white is the negative pole. Blue-brown line, blue line is negative, blue line is negative, etc.