Signs of the Times - July 2013 - (Page 26)
By Marcus Thielen
Marcus Thielen is a physicist and lighting-industry
consultant from Duisburg, Germany.
Electronic Neon Power Supplies
They’re not as simple as one might suspect.
dead. However, neon-glass shops
are reporting increasing work.
Sign customers probably recognize
neon as unique in its beauty, with
long-time endurance in outdoor
In contrast, in many new (outdoor)
installations, I do see electronic
neon power supplies (EPS) being
used instead of magnetic, core-andcoil transformers. But EPS use can
produce some trapdoors, so I’ve
compiled some technical facts on
the electronic powering of neon.
EPS isn’t an invention of the
semiconductor age (Fig. 1), and
gas-discharge lamps advantageously
powered by high-frequency electrical
currents date back to Nicola Tesla.
Neon tubes were even used to
detect radio waves long before the
vacuum electronic tube was invented
(Fig. 2). Powering neon tubes with
high frequency offers the benefit of
a lower starting voltage, compared
to a main’s frequency.
In the past two decades, modern
semiconductor electronics have
produced a generation of smaller
and cheaper, high-frequency, electrical
Photo credit: Krypton Neon, LIC, NY
Some voices to see)pronounced
(or would like
Fig. 1: EPS (flow effect) using vacuum tubes built in the early 1960s
currents, i.e., competition for standard
As I recently stated (see ST, March
2013, page 30), the higher the
frequency, the smaller the inductors
become for an equal power level.
But here, the problem with high
voltage, and, thus, neon supplies,
Fig. 2: A neon tube as a sensitive detector for high-frequency currents (left), right:
discharge with high frequency in said tube (top), without high frequency (bottom). Patent
by Zenneck (1892), taken from: Augusto Righi: Telegraphy Without Wires, 1903
26 SIGNS OF THE TIMES / JULY 2013 / www.signweb.com
Dielectric strength (the resistance
against electrical breakthrough, i.e.,
arcing) is reduced at higher frequencies, thus larger spacings and thicker
insulation are required for the same
voltage - so getting smaller in size
has limited value, unless new insulation materials are employed. Many
early EPS manufacturers learned
this the hard way.
EPS’ major technical problem is
that neon tubes require a constantcurrent power source (see ST, May
2012, page 30). The current can be
limited by several means, but, to
avoid losses in neon transformers,
the current is usually limited by
the inductance of the secondary
windings and a magnetic shunt in
the core (see ST, June 2006, p. 28).
However, with inductively limited
currents, any capacitance in the highvoltage circuit neutralizes its function.
In the worst case, coil inductance
and external-circuit capacitance
resonate on the operating frequency,
which immediately destroys the
power supply and the neon tube
Table of Contents for the Digital Edition of Signs of the Times - July 2013
Signs of the Times - July 2013
The Moving Message
Vehicle Graphics Contest Entry Form
Public Displays of Affection
Electric-Sign Company 1 on 1’s
Screenprinting for Signmakers
A Century of Going Places
Signs of the Times - July 2013