SupertexHV9861A21W通用AC输入高亮LED驱动方案

来源:电子技术应用发布时间:2013-01-22858浏览

The HV9861A is a patented, average-mode, constant current control LED driver IC operating in a constant off-time mode. Unlike the HV9910B, this control IC does not produce a peak-to-average error, and therefore greatly improves the accuracy, line and load regulation of the LED current without any need for loop compensation or highside current sensing. The output LED current accuracy is ±3%.

The IC is equipped with a current limit comparator for hiccup-mode output short circuit protection. Internal over-temperature protection is provided. The internally regulated voltage (VDD) for the HV9861A is 7.5V.

The IC can be powered from a 12 - 450V supply. A PWM dimming input is provided that accepts an external control TTL-compatible signal. The output current can be programmed by an internal 270mV reference, or controlled externally through a 0 - 1.5V dimming input.

The IC is pin-to-pin compatible with the Supertex HV9910B and HV9961, and can be used as a drop-in replacement for many applications to improve the LED current accuracy and regulation.

HV9861A主要特性:

►► Fast average current control

►► Programmable constant off-time switching

►► PWM / linear dimming input

►► Output short circuit protection with skip mode

►► Ambient operating temperature -40OC to +125OC

►► Pin-compatible with the HV9910B and HV9961

HV9861A应用:

►► DC/DC or AC/DC LED driver applications

►► LED backlight driver for LCD displays

►► General purpose constant current source

►► LED signage and displays

►► Architectural and decorative LED lighting

►► LED street lighting

图1.HV9861A方框图

图2.HV9861A应用电路图

21W通用AC输入电压LED驱动器

21-Watt, Universal, AC LED Driver Demoboard with Accurate Average-Mode, Constant Current Control

The HV9861ADB1 demoboard is a high-brightness LED driver employing the patented average-mode, constant current control scheme by Supertex Inc. The power conversion stage of the HV9861ADB1 consists of a diode bridge rectifier followed by a buck converter operating with fixed off-time of 20μs.

The HV9861ADB1 LED driver features tight regulation of the LED current within a few milliamps over the entire range of the input AC line and the output LED string voltage. The LED current accuracy is almost insensitive to the passive component tolerances, such as the output filter inductance or the timing resistor. The accuracy of the LED current is mainly determined by the internal 270mV ± 3% reference voltage of the HV9861A control IC and by the external current sense resistor tolerance.

(Note, that the linear dimming input of the HV9861A disables switching, when its voltage falls below a 200mV threshold. Expect the LED driver to shut off when the LED current falls below 50 ~ 55mA.)

PWM dimming can be achieved by applying a pulse-widthmodulated square wave signal between the PWMD and GND pins.

The HV9861ADB1 features protection from an output short circuit condition. Open LED protection is inherent, since the output filter capacitor can accept the full rated rectified AC line voltage.

Please, note that the demoboard is not CISPR15 compliant.An additional input EMI filter circuit is required to make the board meet conducted electro-magnetic emission limits.