STMicroelectronics, a joint venture between ST and France, has launched the "HVLED805", a driver IC for small LED bulbs. The IC is used on the primary side of a flyback-type isolated AC-DC converter, which integrates a PWM control IC and a +800V withstand voltage power MOSFET on one chip. The current flowing through the primary side can be detected without using a current detecting resistor, and the current supplied to the LED can be stabilized. Therefore, the current detecting resistor and the optical coupler which are usually used on the secondary side are not required. According to STMicroelectronics, not only can component costs be reduced, but reliability can also be improved.
The feedback circuit control mode of the PWM control IC uses a current mode. Zero voltage switching (ZVS) is achieved using quasi-resonant technology. As a result, the amount of radiation electromagnetic noise (EMI) can be significantly reduced while improving efficiency. The switching frequency is up to 166kHz. It also has a function to automatically reduce the switching frequency when the load is reduced to prevent the conversion efficiency from decreasing. Even if the switching frequency is reduced, the ZVS is guaranteed to work. The current error supplied to the LED is only 5%. The power supply voltage is +11.5~23V.
According to STMicroelectronics, the products that were released this time are equipped with a start-up circuit that uses the power introduced from the high-voltage power line to start the IC. Protection against LED short-circuit and open circuit is also available. The package is made of SO16N with a size of 10mm × 4mm × 1.75mm. The temperature of the working joint ranges from -40 to +150 °C. The unit price when purchasing 10,000 is $0.70. There are also special prices for large purchases.

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