U208B

U208B Open Loop Phase Control Circuit Description The integrated circuit, U208B, is designed as a phase control circuit in bipolar technology with internal supply-voltage monitoring. As the voltage is built up, uncontrolled output pulses are avoided by internal monitoring. Furthermore, it has internal-current and voltage synchronisation. It is recommended as a low cost open-loop control. Features D Automatic retriggering D Triggering pulse typ. 125 mA D Voltage and current synchronisation D Internal supply voltage monitoring D Current requirement ≤ 2.5 mA Package: DIP8 Block Diagram BYT77 18 kW/ 2W R3 220 kW/ 0.5 W 7 Voltage detector 8 Current detector Automatic retriggering Output pulse 3 R7 180 W R4 470 kW/ 0.5 W D1 R1 M L 95 11224 TIC 236N VM = 230 V ~ 5 4 R2 180 kW R6 18 kW 100 kW R5 120 kW 6 10 nF C2 –VS C1 22 mF/ 25 V N Phase control unit ö = f (V6) 2 Supply voltage limitation Voltage monitoring 1 GND Figure 1. Block diagram for simple phase control system TELEFUNKEN Semiconductors Rev. A1, 28-May-96 1 (7) U208B Description Mains Supply The U208B is fitted with voltage limiting and can therefore be supplied directly from the mains. The supply voltage between Pin 1 (+ pol/ ) and Pin 2 builds up across D1 and R1 and is smoothed by C1. The value of the series resistance can be approximated using figure 1: When the potential on Pin 5 reaches the given value of Pin 6, then a trigger pulse is generated whose width tp is determined by the value of C2 (the value o...