原标题：PowerInt LYT4324E PAR38 LED灯高效电源方案(DER-396)

　　powerint公司的LYTSwitch-4系列产品LYT4324E把控制器和高压大功率FET组合在同以封装中,控制 器提供高的功率因素和恒流输出,具有优于±5%的恒流性能,TRIAC调光,全亮度的起动时间小于250ms,功率因素大于0.9,高达92%的效率,开关频率132kHz可使用较小的磁性材料.主要用在大功率LED驱动.本文介绍LYTSwitch-4系列产品主要特性,框图和典型电路,以及可替代 PAR38灯的采用LYT4324E的20W高效TRIAC调光LED驱动器主要特性,电路图,材料清单和PCB元件布局图.

　　A LYTSwitch-4 device monolithically combines a controller and high-voltage power FET into one package. The controller provides both high power factor and constant current output in a single-stage. The LYTSwitch-4 controller consists of an oscillator, feedback (sense and logic) circuit, 5.9 V regulator, hysteretic over-temperature protection, frequency jittering, cycle-by-cycle current limit, auto-restart, inductance correction, power factor and constant current control.

　　LYTSwitch-4主要特性:

　　Better than ±5% CC regulation

　　TRIAC dimmable to less than 5% output

　　Fast start-up <250 ms at full brightness

　　<1s at 10% brightness

　　High power factor >0.9

　　Easily meets EN61000-3-2 Less than 10% THD in optimized designs

　　Up to 92% efficient

　　132 kHz switching frequency for small magnetics

　　High Performance, Combined Driver, Controller, Switch

　　The LYTSwitch-4 family enables off-line LED drivers with high power factor which easily meet international requirements for THD and harmonics. Output current is tightly regulated with better than ±5% CC tolerance1. Efficiency of up to 92% is easily achieved in typical applications. Supports a Wide Selection of TRIAC Dimmers

　　The LYTSwitch-4 family provides excellent turn-on characteristics for leading-edge and trailing-edge TRIAC dimming applications. This results in drivers with a wide dimming range and fast start-up, even when turning-on from a low conduction angle. Large dimming ratio and low “pop-on” current. Low Solution Cost and Long Lifetime

　　LYTSwitch-4 ICs are highly integrated and employ a primary-side control technique that eliminates the optoisolator and reduces component count. This allows the use of low-cost single-sided printed circuit boards. Combining PFC and CC functions into a single-stage also helps reduce cost and increase efficiency. The 132 kHz switching frequency permits the use of small, low-cost magnetics.

　　LED drivers using the LYTSwitch-4 family do not use primary-side aluminum electrolytic bulk capacitors. This means greatly extended driver lifetime, especially in bulb and other high temperature applications.

　　图1. LYTSwitch-4方框图

　　图2. LYTSwitch-4典型应用电路

　　采用LYT4324E的20W高效TRIAC调光LED驱动器,效率大于85%,可用于PAR38灯

　　This document is an engineering report describing an isolated power factor dimmable LED driver (power supply) utilizing a LYT4324E from the LYTSwitch-4 High Line Family of devices.

　　The DER-396 provides a single 20 W (36 VTYPICAL) dimmable 550 mA constant current output across an input voltage range of 185 to 265 VAC.

　　The key design goals were high efficiency to maximize efficacy and small size. This allowed the driver to fit into PAR38 sized lamps and be as close to a production ready design as possible.

　　LYTSwitch-4 ICs allow the implementation of cost effective, low component count LED drivers which meet both power factor and harmonics limits. The LYTSwitch-4 driver IC, combines the PFC function and secondary output constant current control circuitry into a single switching stage.

　　The topology used is an isolated flyback operating in continuous conduction mode. Output current regulation is achieved entirely from the primary side, eliminating the need for secondary feedback components. No external current sensing is required on the primary side as this is performed inside the IC, further reducing component costs and improving efficiency. The internal controller adjusts the power MOSFET duty cycle to maintain a sinusoidal input current with high power factor and low harmonic current control.

　　The LYT4324E also provides a sophisticated range of protection features including autorestart for open control loop and output short-circuit conditions. Line overvoltage provides extended line fault and surge withstand, output overvoltage protects the supply should the load be disconnected and accurate hysteretic thermal shutdown ensures safe average PCB temperatures under all conditions.

　　In any LED luminaire the driver determines many of the performance attributes experienced by the end user including startup time, dimming performance and unit to unit consistency. This design was optimized to ensure operation with a wide range of dimmers and as well as a wide dimming range.

　　The document contains the power supply specification, schematic, bill of materials, transformer documentation, printed circuit layout, design spreadsheet and performance data.

　　20W高效TRIAC调光LED驱动器主要特性:

　　 Single-stage power factor corrected with accurate constant current (CC) output (+5%)

　　 PF >0.9 at 230 VAC

　　 %A THD <20% at 230 VAC

　　 Consistent dimming performance across production and over temperature range

　　 Low cost, low component count and small PCB footprint design

　　 Highly energy efficient, >86 % at 230 VAC input

　　 Fast start-up time (<250 ms) – no perceptible delay

　　 Clean monotonic start-up – no output blinking

　　 Integrated protection and reliability features

　　 No-load protection, short-circuit protected

　　 Auto-recovering thermal shutdown with large hysteresis protects both components and PCB

　　 No damage during line brown-out conditions

　　 Meets IEC 2.5 kV ring wave, 500 V differential line surge and EN55015 conducted EMI

　　图3. 20W高效TRIAC调光LED驱动器外形图

　　20W高效TRIAC调光LED驱动器主要指标:

　　图4. 20W高效TRIAC调光LED驱动器电路图:36V 550mA

　　20W高效TRIAC调光LED驱动器材料清单:

　　图5.变压器电路图