ST HVLED805離線(xiàn)反激LED驅(qū)動(dòng)解決方案

作者：時(shí)間：2011-05-27 來(lái)源：網(wǎng)絡(luò)

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ST公司的HVLED805是具有初級(jí)檢測(cè)的離線(xiàn)LED驅(qū)動(dòng)器,包括了高性能低壓PWM控制器和800V耐雪崩擊穿的功率MOSFET,可直接連接到火線(xiàn)整流電壓,恒流LED輸出電流精度5%,不需要光耦器件,準(zhǔn)諧振(QR)零電壓開(kāi)關(guān)(ZVS)工作,內(nèi)部HV起動(dòng)電路,能對(duì)LED串的開(kāi)路或短路進(jìn)行管理,主要用在AC/DC LED驅(qū)動(dòng)器,LED替代燈(如E27, GU10)等.本文介紹了HVLED80主要特性, 應(yīng)用框圖以及多種性能測(cè)試電路.

HVLED805: Off-line LED driver with primary-sensing

The HVLED805 is a high-voltage primary switcher intended for operating directly from the rectified mains with minimum external parts to provide an efficient, compact and cost effective solution for LED driving. It combines a high-performance low-voltage PWM controller chip and an 800V, avalanche-rugged power MOSFET, in the same package.

The PWM is a current-mode controller IC specifically designed for ZVS (zero voltage switching) fly-back LED drivers, with constant output current (CC) regulation using primarysensing feedback. This eliminates the need for the opto-coupler, the secondary voltage reference, as well as the current sense on the secondary side, still maintaining a good LED current accuracy. Moreover it guarantees a safe operation when short circuit of one or more LEDs occurs.

In addition, the device can also provide a constant output voltage regulation (CV): it makes the application able to work safely when the LED string opens due to a failure.Quasi-resonant operation is achieved by means of a transformer demagnetization sensing input that triggers MOSFET’s turn-on. This input serves also as both output voltage monitor, to perform CV regulation, and input voltage monitor, to achieve mains-independent CC regulation (line voltage feed forward).

The maximum switching frequency is top-limited below 166 kHz, so that at medium-light load a special function automatically lowers the operating frequency still maintaining the operation as close to ZVS as possible. At very light load, the device enters a controlled burst-mode operation that, along with the built-in high-voltage start-up circuit and the low operating current of the device, helps minimize the residual input consumption. Although an auxiliary winding is required in the transformer to correctly perform CV/CC regulation, the chip is able to power itself directly from the rectified mains. This is useful especially during CC regulation, where the fly-back voltage generated by the winding drops.

In addition to these functions that optimize power handling under different operating conditions, the device offers protection features that considerably increase end-product’s safety and reliability: auxiliary winding disconnection or brownout detection and shorted secondary rectifier or transformer’s saturation detection. All of them are auto restart mode.

HVLED80主要特性:

■ 800 V, avalanche rugged internal power MOSFET

■ 5% accuracy on constant LED output current with primary control

■ Optocoupler not needed

■ Quasi-resonant (QR) zero voltage switching (ZVS) operation

■ Internal HV start-up circuit

■ Open or short LED string management

■ Automatic self supply

■ Input voltage feed-forward for mains independent cc regulation

HVLED80應(yīng)用:

■ AC-DC led driver applications

■ LED retrofit lamps (i.e. E27, GU10)