Power factor correction boost controller achieves 0.99 PF

February 23, 2015 // By Graham Prophet
LT8312 is a power factor correction (PFC) boost controller that can achieve a power factor of greater than 0.99 by actively modulating the input current, allowing compliance with most harmonic current emission requirements.

This device operates with current mode control and critical conduction mode, which is a variable frequency switching scheme that returns the current to zero in the inductor with every cycle. This switching behaviour is similar to zero voltage switching, which minimises the electromagnetic interference and energy lost in the power switch, improving efficiency as much as 5%.

The LT8312 is suitable for universal AC (90-265VAC) input and higher ranges, depending on the choice of external components. The LT8312 uses hysteretic start-up, eliminating the need for a bias power supply. After start-up the device is powered by a bootstrap winding off of the inductor. With a 1.9A gate driver, the LT8312 drives most high voltage MOSFETs. The 102 mV current sense threshold facilitates the use of small value shunt resistors, which increase efficiency.

The LT8312 is available in a 16-lead MSOP package. Four temperature grades are available, with operation from -40 to 125°C for the extended and industrial grades, a high temp automotive grade of -40°C to 150°C and a military grade of -55°C to 150°C. Pricing starts at $2.25 (1000).

Linear Technology; www.linear.com/product/LT8312