IR采用IRS2540的IRPLLED1高压LED驱动方案

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IR采用IRS2540的IRPLLED1高压LED驱动方案

作者：时间：2009-12-18 14:06 来源：

IR公司的IRS254(0,1)是高压(200 V (IRS2540)和600 V (IRS2541))高频降压恒流LED电流调整控制器,采用连续模式时延滞后降压稳压器,直接控制负载平均电流.起动电流小于500uA,140ns死区,片内基准电压±2%,频率高达500kHz.本文介绍了IRS254(0,1)的主要特性,方框图以及采用单个和两个MOSFET的IRS2540应用电路.同时还介绍了采用IRS2540的350mA 到1.5A高压LED驱动器IRPLLED1的电路图和所用材料清单.

The IRS254(0,1) are high voltage, high frequency buck control ICs for constant LED current regulation. They incorporate a continuous mode time-delayed hysteretic buck regulator to directly control the average load current, using an accurate on-chip bandgap voltage reference.

The application is inherently protected against short circuit conditions, with the ability to easily add opencircuit protection. An external high-side bootstrap circuit drives the buck switching element at high frequencies. A low-side driver is also provided for synchronous rectifier designs. All functions are realized within a simple 8 pin DIP or SOIC package.

IRS2540主要特性:

200 V (IRS2540) and 600 V (IRS2541) half bridge driver

Micropower startup (<500 μA)

±2% voltage reference

140 ns deadtime

15.6 V zener clamp on VCC

Frequency up to 500 kHz

Auto restart, non-latched shutdown

PWM dimmable

Small 8-Lead DIP/8-Lead SOIC packages

图1.IRS2540方框图

图2.IRS2540应用电路

图3. 采用单个MOSFET的IRS2540应用电路

采用IRS2540的IRPLLED1 350mA 到1.5A高压LED驱动器

IRPLLED1 350mA to 1.5A High Voltage LED Driver using IRS2540

As the industry becomes more power conscious to compensate for increasing energy costs and to meet governmental regulations, new innovative ways of conserving energy are being developed. For the lighting industry one of these outlets has been LEDs. Due to their longevity, robust design, low maintenance and high efficiency, they have proven a viable alternative to less efficient light sources. With their long term projected falling cost and further increased efficiency, the industry has eagerly embraced LEDs, putting them largely in demand. LEDs require drivers that have specific features such as constant current control over the temperature and manufacturing variations of LEDs, dimming and appropriate fault protections. The IRS2540/1 is specifically designed to address these requirements The IRPLLED1evaluation board is a high voltage LED driver designed to operate from a DC input voltage of 50V to 170V and produce an output voltage of 16V-24V to supply a programmable load current of 350mA, 700mA, 1A, or 1.5A. It uses the IRS2540/1, a high voltage, high frequency Buck control IC for constant LED current regulation.

The IRS2540/1 controls the average load current by a continuous mode time-delayed hysteretic method using an accurate on chip band gap voltage reference. The 8-pin, 200V/600V rated IRS2540/1 inherently provides shortcircuit protection with open-circuit protection incorporated by a simple external circuit and has dimming capability.

The IRS2540/1 allows scalable designs to accommodate series and parallel onfigurations of LEDs, for today’s production LEDs as well as new generation higher current LEDs, and provides high current control accuracy over input and output voltage.

The evaluation board documentation will briefly describe the functionality of IRS2540/1, discuss the selection of the output stage, switching components and surrounding circuitry. This board was tested with a single Lumileds flood board for the 350mA and 700mA settings using two Lumileds flood boards in parallel to provide test loads for the 1A and 1.5A settings. Lumileds flood boards are available through Future Electronics and have a maximum nominal current rating of 700mA with a breakdown voltage between 16 and 24V. The IRPLLED1 evaluation board can operate from a 120V AC rectified line with the addition of a bridge rectifier and smoothing capacitor at the front end. It is non-isolated and therefore although the output voltage is low an electric shock hazard still exists!

The IRS2540/1 is a time-delayed hysteretic Buck controller. During normal operating conditions the output current is regulated via the IFB pin voltage to a nominal value of 500mV. This feedback signal is compared to an internal high precision band gap voltage reference. An on-board dV/dt filter has also been used to prevent erroneous transitioning. This is necessary since the IFB pin is sensitive to noise.

Once the VCC supply to the IR2540 reaches VCCUV+ the LO output is held high and the HO output low for a predetermined period of time. This initiates charging of the bootstrap capacitor establishing the VBS floating supply for the high side output. The chip then begins toggling HO and LO outputs as needed to regulate the load current. monitored and fed back through RCS shown in fig 1 The deadtimes of approximately 140ns between the LO and HO gate drive signals prevent “shoot through” and reduce switching losses, particularly at higher frequencies.