LED drive power

by:MOSO     2019-12-09
? (1) Constant current a. The output current of the constant current drive circuit is constant, but the output DC voltage changes within a certain range with the size of the load resistance. The smaller the load resistance, the lower the output voltage. The higher the voltage; b. The constant current circuit is not afraid of short circuit of the load, but it is strictly prohibited that the load is completely open. c. Constant current drive circuit is ideal for driving LED, but the price is relatively high. d. Pay attention to the maximum current and voltage used, which limits the number of LEDs used; (2) Regulated type: a. After the parameters of the voltage stabilization circuit are determined, the output voltage is fixed, but the output current changes as the load increases or decreases; b. The voltage stabilization circuit is not afraid of the open circuit of the load, but it is strictly forbidden that the load is completely short-circuited. c. Drive the LEDs with a voltage-stabilized driving circuit. Each string needs to be added with a suitable resistor to make each string of LEDs display an average brightness; d. Brightness will be affected by voltage changes from rectification. (3) Pulse drive Many LED applications require dimming capabilities, such as LED backlighting or architectural lighting dimming. Dimming can be achieved by adjusting the brightness and contrast of the LED. Simply reducing the current of the device may be able to adjust the LED light emission, but letting the LED work below the rated current will cause many adverse consequences, such as color difference problems. An alternative to simple current regulation is to integrate a pulse width modulation (PWM) controller in the LED driver. The PWM signal is not directly used to control the LED, but instead controls a switch, such as a MOSFET, to provide the required current to the LED. PWM controllers usually work at a fixed frequency and adjust the pulse width to match the required duty cycle. At present, most LED chips use PWM to control LED lighting. In order to ensure that people do not feel obvious flicker, the frequency of PWM pulse must be greater than 100HZ. The main advantage of PWM control is that the dimming current through PWM is more accurate, which minimizes the color difference when LEDs emit light. [1] (4) AC drive The AC driver can also be divided into three types: buck type, boost type and converter according to different applications. The difference between an AC driver and a DC driver, in addition to the need to rectify and filter the input AC channel, from the perspective of safety, there are still problems of isolation and non-isolation. AC input drivers are mainly used for retrofit lamps: For ten PAR (Parabolic Aluminum Reflector, a common luminaire on professional stage) lamps, standard bulbs, etc., they are AC at 100V, 120V or 230V It operates under input; for MR16 lamp, it needs to work under 12V AC input. Due to certain complex issues, such as the dimming capability of standard triacs or leading-edge trailing edge dimmers, and compatibility with electronic transformers (generating 12V AC from MR16 lamps when operating from AC line voltage) (Ie flicker-free operation), compared to DC input drivers, AC input drivers are more complex. [1] AC power supply (commercial power drive) is applied to LED drive.Generally, it needs to go through steps such as step-down, rectification, filtering, voltage stabilization (or steady current) to convert AC power to DC power. Working current, it must also have high conversion efficiency, smaller size and lower cost, while solving the problem of safety isolation. Considering the impact on the power grid, the problems of electromagnetic interference and power factor must be solved. For small and medium power LEDs, the best circuit structure is an isolated single-ended flyback converter circuit; for high power applications, a bridge converter circuit should be used
Custom message
Chat Online 编辑模式下无法使用
Chat Online inputting...
Dear friend,thanks for your inquiry. Please leave your company E-mail and phone number, we will contact you asap. Have a good day!Contact E-mail:Niki.li@mosopower.com TEl: +86-755-27657000