ST公司的HVLED805是具有初级检测的离线LED驱动器,包括了高性能低压PWM控制器和800V耐雪崩击穿的功率MOSFET,可直接连接到火线整流电压,恒流LED输出电流精度5%,不需要光耦器件,准谐振(QR)零电压开关(ZVS)工作,内部HV起动电路,能对LED串的开路或短路进行管理,主要用在AC/DC LED驱动器,LED替代灯(如E27, GU10)等.本文介绍了HVLED80主要特性, 应用框图以及多种性能测试电路.
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应用:
■ AC-DC led driver applications
■ LED retrofit lamps (i.e. E27, GU10)
图1.HVLED80应用框图
图2.HVLED80关断态漏和源电流测试电路图
图3.HVLED80起动电流测试电路图
图4.HVLED80静态电流测试电路图
图5.HVLED80工作电流测试电路图
图6.HVLED80故障时静态电流测试电路图
