Using circuit diagram below can be built a voltage converter, able to convert a 70-260V AC to a 180-350V DC voltage.
For this, a rectifier contained in a MC34161 is used, as a voltage doubler for low input voltages and as rectifier for high standard input voltage.
A variation of four times of the input voltage is reflected in a variation of not more than two times in output voltage.
MC34161 has included a reference voltage source which supplies a voltage of 2.54 V to pin 1. The signal applied to pin 2 is compared with internal voltage of 1.27 V.
R2-R3 voltage divider provides change state of internal comparator which grow output input voltage over 135 V (pin 5 passes in 1 state). The potential at pin 2 is less than 1.27 V. Triac is blocked and disconnects median connection between the two output capacitors, C2 and C3, such that doubling output voltage can not be produced
- When the input voltage is less than 135 V, pin 2 is maintained above the potential value of 1.27 V
- Diodes D2 and D3 and capacitors C2 and C3 will function as voltage doubler.
- Zener diode D5, together with R1 and C4, integrated circuit provides power to a stable source of 12 V. The time required passing standard rectifier circuit of the voltage doubler is determined by R4-C1.
- Operating voltage of capacitors C2 and C3 must be> 250 V.