BY PETER STONARD
It’s fun to collect
and experiment with
But, you’ll need a
stable high voltage
power supply to get
electronics, vacuum tubes
were used for everything — from high volume consumer radios and
televisions to exotic one-of-a kind military and scientific applications.
A lot of the old and interesting glass is still around to be found at
hamfests, estate sales, and online auction sites.
Ineeded a couple of hundred volts to operate some
Nixie tubes (see the sidebar to find out why), so I
created a circuit. The prototype was so handy that I
reworked it into a self-contained high voltage power
supply unit (HVPSU) that I’m presenting here (Figure 1).
The HVPSU can be built into other projects as a
module with a 0.1 inch grid and 0.1 inch pitch header,
and can be connected with a wiring harness or mounted
directly on perfboard for those projects not ready for a
PCB (printed circuit board) commitment. The DC power
Anyone attempting to construct and use this module
should be aware of high voltage safety. Although the
energy is limited, there are high voltages on the PCB,
components, and connectors. Capacitors may store
some energy after the power is removed. Remember,
high voltage circuits bite fools!
jack mates with a wall-wart brick, and an LED power on
and neon high voltage active indicators complete the
design. Table 1 is the target specification and Table 2
shows the performance measured.
Look at Figure 2. To better understand the operation
of the flyback circuit, see the sidebar on Flyback Theory
of Operation and also Figures A and B.
The low voltage section provides a 5V DC output
from a linear regulator, IC1. LED, D1 is a power on
indicator fed from the 5V supply via R2. IC1 — a TO-220
type — does not require a heatsink for power dissipation
of one watt or less. With a 12V DC, input we are limited
to 140 mA, and the spec was arbitrarily set for 100 mA
max (IC1 dissipates about 700 m W).
The project uses a mix of through-hole (TH) power
components and SMT to conserve PCB space, but I