HVLED807PF

Device description

Doc ID 023464 Rev 5

15/36

4

Device description

The HVLED807PF is a high-voltage primary switcher intended for operating directly from the

rectified mains with minimum external parts to provide high power factor (> 0.90) and an

efficient, compact and cost effective solution for LED driving. It combines a high-

performance low-voltage PWM controller chip and an 800 V, avalanche-rugged Power

MOSFET, in the same package.

The PWM is a current-mode controller IC specifically designed for ZVS (Zero Voltage

Switching) flyback LED drivers, with constant output current (CC) regulation using primary

sensing feedback (PSR). This eliminates the need for the optocoupler, the secondary

voltage reference, as well as the current sense on the secondary side, while still maintaining

a good LED current accuracy. Moreover, it guarantees a safe operation when short-circuit of

one or more LEDs occurs.

The device can also provide a constant output voltage regulation (CV): it allows the

application to be able to work safely when the LED string opens due to a failure.

In addition, the device offers the shorted secondary rectifier (i.e. LED string shorted due to a

failure) or transformer saturation detection.

Quasi-resonant operation is achieved by means of a transformer demagnetization sensing

input that triggers MOSFET 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 feedforward).

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 startup 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 flyback voltage generated by the winding drops.

4.1

Application information

The device is an off-line led driver with all-primary sensing, based on quasi-resonant flyback

topology, with high power factor capability. In particular, using different application schematic

the device is able to provide a compact, efficient and cost-effective led driver solution with

high power factor (PF>0.9 - see application schematic on

Figure 1) or with standard power

factor (PF>0.5/0.6 - see application schematic on

Figure 2), based on the specific

application requirements.

Referring to the application schematic on

Figure 1, the IC modulates the input current in

according to the input voltage providing the high power factor capability (PF>0.9) keeping a

good line regulation. This application schematic is intended for a single range input voltage.

For wide range application a different reference schematic can be used; refer to the

dedicated application note for further details.

Moreover, the device is able to work in different modes depending on the LED's driver load

condition (see

Figure 11):