The HV9805 driver IC is targeted at general LED lighting products, such as LED lamps and LED lighting fixtures with a maximum power rating of about 25W at 120VAC and about 50W at 230VAC.
A two-stage topology provides true constant current drive for the LED load while drawing mains power with high power factor. The first stage, a boundary conduction mode boost converter, transfers power from the AC line to a second stage with high power factor and high efficiency. The second stage, a linear regulator arranged for operation with low overhead voltage, transfers power from the first stage to the LED load with true constant current and protects the LED load from overvoltage that may pass from mains to the output of the first stage.
The IC is particularly geared to drive a high voltage LED load. An LED load arranged as a high voltage load is capable of offering cost advantages in terms of heat management and optics.                                
The boost converter employs a cascode switch for high-speed switching and convenient generation of the VDD supply. The control device of the cascode switch is an integral part of the HV9805 and is rated at 700 mA. Current for powering the VDD supply is derived by way of an internal connection to the cascode switch.      
Applications with  low output  voltage can be accommodated by the SEPIC topology.                   

  Provides True DC Light and protects load from line voltage transients

  Driver topology includes:

  Boundary Conduction Mode (BCM) Boost Converter with Power Factor Correction

  High Power Factor(98%+)

  High Efficiency (90%+)

  Linear Post-Regulator with Low Overhead Voltage

  Zero LED Current/Brightness Ripple

  Overvoltage Protection for LEDs

  High Efficiency

  ±4% Reference over Temperature

  Simple VDD Supply:

  No Auxiliary Winding Required

  Boost Converter Cascode Switch:

  Internal Switch rated at 700 mA peak

  Supports up to 25W at 120VAC

  Supports up to 50W at 230VAC

  Compatibility with SEPIC Topology for Low Output Voltage Applications