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What is a LED Driver Used For?

The LED driver changes the power supply to a specific voltage and current to drive the LED voltage converter. The output of LED driver power supply is mostly constant current source, which can change the voltage with the change of led forward voltage drop. The core components of LED power supply include switch controller, inductor, MOSFET, feedback resistor, input filter device, output filter, etc

LED Driver Introduction

The LED driver changes the power supply to a specific voltage and current to drive the LED voltage converter. Generally, 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. output of electronic transformer)). The output of LED driver power supply is mostly constant current source, which can change the voltage with the change of led forward voltage drop. The core components of LED power supply include switch controller, inductor, MOSFET, feedback resistor, input filter device, 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.

Characteristics of LED driver power supply

  • high reliability
  • high efficiency
  • high power factors
  • driving mode
  • surge protection
  • protection function

Types of LED Driver

  1. LED Driver Constant Current–The constant current driver is specially designed for LED lamps that need fixed output current and a certain range of output voltage. This type of driver will have a specified output current in amperes and its voltage range will vary depending on the rated power of the LED. Using a higher amperage will turn the LED on. However, it will eventually over drive the LEDs, resulting in shorter life and premature failure. Because constant current drivers maintain consistent brightness, they are often used for signage, backlighting and commercial LED displays.
  2. Constant voltage LED driver–The constant voltage driver is designed for LEDs that require a fixed output voltage and maximum output current. LED lamps working with constant voltage drivers need stable output voltage, usually 12V DC or 24VDC. This type of driver receives a standard voltage of approximately 120-277 volts in the form of an alternating current (VAC), which is converted to a low DC voltage (VDC). These drives will maintain a constant voltage as long as the current remains below its maximum amperage setting. Constant pressure applications include cabinet lights, stair lights, strip lights, and rope lights. The LED drivers we selected also include AC LED drivers designed for LEDs requiring AC voltage input, programmable LED drivers, dimmable LED drivers, and drivers recognized for outdoor use. When choosing the right LED driver for your application, verify that it operates at a constant current or voltage to avoid damaging your led. If you have questions about which type of replacement LED drive you need, please contact our customer service team at 1-972-525-0501.

Application of LED driver

The application of LED driver depends on the LED parameters we want to drive. The two most important parameters are input voltage and input current. How to calculate the input voltage and current of LED lamp, the propagation lamp is equipped with separate instructions. This is just a description of the LED input. People will see the original driving parameters (be sure to identify some wrong driving targets!!!!!

After knowing the input voltage and current of the light panel, we choose the corresponding LED driver to use. For example, given that the input voltage of the light board is 37-40v and the input current is 300mA, the output voltage of the LED driver can be selected to include it, and the current is about the same. Formula surfaces above or below all voltages must be included. Otherwise, it will flash. A small current will do.

Finally, we only need to press the positive and negative marked on the lamp board to weld the driver or connecting wire. It should be noted that the traditional LED driver output line, red is positive. Black is the negative pole… If it is a gray wire, then gray is the positive pole, white is the negative pole… Blue brown wire, blue wire is the negative pole, blue wire is the negative pole, etc

LED Driver Circuit Design

The actual feedback control of the switching power supply is the output voltage. The output current control is not easy to be accurate. When the control of the switching power supply is biased, the LED light is easy to be damaged. The efficiency of linear circuit is not high. Based on the above reasons, a novel LED driving circuit is designed. The single ended flyback switching power supply is used as the front control and the linear pressure control constant current source is used as the back control. After the single ended flyback power supply is converted, the DC voltage output can be used as the input of the post voltage controlled constant current source. Since the input voltage of the constant current source is controlled by an efficient single flyback switching power supply, the pressure controlled constant current source can accurately control the LED and change the input voltage of the constant current source in a large range, so the efficiency and accuracy are guaranteed, and the power supply can be powered by the city.

LED driver circuit
LED driver circuit

The system circuit is shown in Figure 2. Transformer T1, switch tube Q1, diode D1 and capacitor C1 form a single ended flyback switching power supply, and operational amplifiers U1, U2 and power transistors Q2 form a pressure control constant. The current source, and single-chip STC89C51 is the core control equipment. When the gray value changes, the microcontroller generates the corresponding brightness control voltage based on the obtained gray value. The brightness control voltage is applied to the in-phase input of U1. The reverse input of U1 is the LED current signal obtained by U2, and R12 is the current detection resistance. The output voltage of U1 is the control voltage of MOS Q2, which is known by the concept of operational amplifier deficiency.

According to the gray value, the single chip computer generates the corresponding brightness control voltage and PWM signal. The PWM signal intersects the TL431 signal to control the switch of Q1. Then, the MCU changes the duty cycle of PWM signal and the output voltage of switching power supply according to the obtained LED current signal, i.e. changes the constant. The input voltage of the flow source reduces the voltage on the power tube Q2, so when the output current is constant, it works in or near the adjustable resistance area to improve efficiency.

TL431 is a three terminal adjustable parallel reference. When the light is good, MCU controls the output of brightness control voltage according to the gray value obtained, so that the output current of constant current source is relatively small, which can achieve the effect of energy saving. In Figure 2, the output voltage of the microcontroller is controlled by D / A to provide a constant current source. Figure 2 does not show part D / A.

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