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CRM PFC controllers offer 'best' THD level

Posted: 20 Dec 2006 ?? ?Print Version ?Bookmark and Share

Keywords:critical conduction mode? power factor correction controller chip? power factor correction controller chips? controller? Fairchild?

Fairchild's CRM PFC controller

Fairchild Semiconductor has introduced critical conduction mode (CRM) power factor correction (PFC) controller ICs designed to meet stringent standby power and harmonic regulations affecting ballast, notebook adaptors, LCD TVs and LCD monitors.

The FAN7529 and FAN7530 use a patent-pending variable on-time control method to achieve total harmonic distortion (THD) performance of <10 percent at 25 percent load, 265Vac, for high system reliability. They also meet standby power regulations by reducing input-voltage sensing loss to approximately 100mW. These highly integrated PFC controllers help designers reduce part count and save system costs.

'Best' THD performance
"Fairchild's FAN7529 and FAN7530 PFC controllers offer designers the best THD performance on the market, an important consideration since government regulations specify that manufacturers must reduce harmful noise that can affect system reliability," said CJ Kim Fairchild's product manager, power conversion product line. "Fairchild uses a unique variable on-time control method based on ZCD winding voltage to achieve less than 10 percent THD at 25 percent of the full load. As a result, when designing four lamp ballasts, a designer can control THD to be less than 10 percent even if only one lamp is turned on. This low THD translates into excellent system performance and offers more flexibility to system designers."

Both the FAN7529 and FAN7530 use an internal voltage-mode PWM method compared with conventional current-mode controllers requiring rectified AC-line voltage information even when the PFC IC does not operate. As a result, these controllers reduce overall power loss by approximately 200mW. Moreover, they offer a disable function to further reduce power consumption during standby mode, and their current-type error amplifiers enable these devices to use a higher Rfb (output-voltage-sensing resistor) over 1 megaohm, resulting in reduced power loss (80mW, 2 megaohms).

System reliability
To increase system reliability, Fairchild's controllers feature open-feedback protection and a disable function (65?A), making Vcc shutdown circuitry unnecessary. They also offer adjustable-output overvoltage protection (OVP) of 2 percent. This type of voltage-sensing OVP is immune to noise. The devices also offer a 150?s internal startup timer, MOSFET overcurrent protection and undervoltage lockout with 3.5V hysteresis.

The FAN7529 and FAN7530 are offered separately as pin-out options for meeting specific requirements and design preferences. Both are available in DIP-8 and SOP-8 packages. These Pb-free products meet the requirements of the joint IPC/JEDEC standard J-STD-020C and are compliant with EU requirements now in effect.

Pricing for FAN7529 is 70 cents and 60 cents for FAN7530, both in 1,000-unit quantities. Samples and demo boards are available today. Delivery is 8 weeks ARO.




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