VRef 16 VIN 15 Reference Regulator + 5 V to All Internal Circuitry +5V +5V RT 6 CT 7 3 Oscillator Output 12 CA FlipFlop NOR Oscillator 11 (Ramp) +5V 13 CA NOR Comparator 14 ES +5V Inv. Input 1 N.1. Input 2 Ground 8 (Substrate) +5V + Error Amp - 10 + 4 + Sense - 5 - Sense C. L. 9 1k Shutdown Compensation 10 k FIG 1 The block diagram of the first bipolar PWM controller chip SG1524. (Figure courtesy of Bob Mammano, from a 2007 APEC Plenary Talk.) surpassed SG1524 in volume sales, according to Mammano's article. In fact, Mammano said that "UC3842 became the most widely used and highly produced power-supply controller of its time. Second only to the TL431 reference circuit from TI." Contact: Web: www.mag-inc.com International Contact: Web: www.mag-inc.com.cn PWM Controllers and biCMOS While the bipolar process dominated power control circuits in the 1980s and early 1990s, the bipolar complementary metal-oxide-semiconductor (biCMOS) process entered the marketplace by the mid-1990s and drove Phone: +1 412 696 1333 Phone: +852 3102 9337 PWM controller ICs to the next level. According to Mammano, the biCMOS process made it easier to combine power devices on the same piece of silicon along with control circuitry. In addition, it enabled higher switching speeds, fewer parasitics, and lower Email: magnetics@spang.com Email: asiasales@spang.com September 2014 IEEE POWER ELECTRONICS MAGAZINE 11http://www.mag-inc.com http://www.mag-inc.com.cn