LED driver solution for MR16 and similar retrofit lamps

来源：作者：发布时间：2015-01-24 09:46:56 浏览量：

Active PFC does not require large value (i.e., electrolytic) input capacitors. This is an advantage of the design. In this solution the input capacitor (C2) is a small value and ceramic. This solution works without electrolytic capacitors, which considerably extends the lamp lifetime.

LEDs dissipate most of the power provided to them by conduction. Meanwhile, MR16 LED lamps have little space for heatsinks because of their small size. Consequently, they often run at high temperatures in the +80°C to +1绕线型电感器00°C range. At those temperatures, even the lifetime of high-grade electrolytic capacitors is limited to little more than 10,000 hours, which is too few hours for an LED lamp.

Active PFC in this solution shapes the input current as a square wave, as in Figure 2.

Figure 2. Input current for the LED driver.

Shaping the input current as a square is the best solution for control: it keeps its value (i.e., the transformer and dimmer load current) above the required minimum for the whole c工字电感器ycle of the line voltage.

This control is obtained using components R8 (sense resistor), R7, and C9. R7 and C9 provide the average MOSFET current, which is the same as the average input current; the MAX16834 maintains this value constant throughout each cycle of the input voltage.

Since this solution does not include electrolytic capacitors, the LED current is a rectified sinusoid (without dimmer) or a rectified sinusoid cut for a part of the angle (with dimmer), because energy is not stored between one cycle of the AC voltage and the following (Figure 3).

Figure 3. LED current is a rectified sinusoid, with frequency equal to twice the line voltage frequency.

The MAX16834 features output overvoltage protection (OVP). With OVP, if the LEDs are disconnected or open the driver turns off and the driver is not damaged.

Test results

This reference design board was tested under thes大功率电感贴片电感器e conditions:

Electronic transformer: Lightech LET-60
Input voltage of the electronic transformer: 120VAC, 60Hz
Input voltage of the driver circuit: 12VAC, 60Hz modulated at 40kHz
Output: 4 series LEDs

We measured (wit功率电感器hout dimmer):

LED power: 4.2W
Efficiency: 77%
Input power factor: 0.943

This design is compatible with these electronic transformers.

请教个DC-DC开关电源问题请问各位大侠们：1.直流转直流开关电源的变压器参数怎么确定？2.变压器线圈匝数比怎么计算的？尤其变压器有没什么书籍专门讲开关电源变压器的介绍介绍3.开关电源输入的电压范围怎么确定，是带负载测还是空载测？（安全和极限电压范围）满意回复+20liukunming2007 查看完整内容变压器与电感器设计手册（第三版）作者（美）麦克莱

UOUT=1V的DC/DC变换器发展趋势1简介为了以更低的功耗获得更高的速度和更佳的性能，半导体器件正在向1V工作电压发展，这也对DC/DC变换器提出了更高的要求。由于便携产品将率先采用1V工作电压，因而对电源效率和功率密度的挑战显得更为严

TOPswicth芯片的频率问题大家好，请教一个问题：用PI的开关电源芯片topswitch271，芯片引脚设置的频率是132K，但是测试Vds的时候发现频率大概为33K，这是为啥呢轻载下的测试的吧，开关频率占空比接近0了谢谢，已

2/3 首页上一页 1 2 3 下一页尾页

推荐产品

LED driver solution for MR16 and similar retrofit lamps

Test results