Multilayer Varistor - Thinking Electronics Industrial Co., Ltd.

Metal Oxide Varistor:
:
Application Note
IC Protection against Electro-static Discharge(ESD)
+VCC
Signal line
IC
Power supply
Fig.10
IC protection
Noise Suppression
SIG.1
SIG.2
SIG.3
SIG.4
Equipment
to be
protected.
Fig.11
Protection of signal
equipment
COM
THINKING ELECTRONIC INDUSTRIAL Co., LTD.
1
www.thinking.com.tw
2008.07
Metal Oxide Varistor:
:
Application Note
Equipment Protection against Line Transient Damage
The varistors have many advantages which make it ideal for use as a suppressor on AC or DC power line.
AC/DC
Equipment
to be
protected
Equipment
to be
protected
AC/DC
Fig.4
Absorption of line-line
and line-ground
surge in single-phase system
Fig.3
Absorption of line-line
surge in single-phase system
System.
AC220V
Equipment
to be
protected
Equipment
to be
protected
AC220V
Fig.6
Absorption of line-line and
line-ground
surge in three-phase system
Fig.5
Absorption of line-line
surge in three-phase system
Protection of Components Switching Inductive Load
The transistor in Fig.7 is to operate a solenoid, inductive load. The energy stored in inductor is dissipated in the reverse
bias conduction of the transistor and might cause transistor breakdown. A varistor can be connected, collector-to-base, to
dissipate the stored energy in the forward bias state without damaging the transistor.
V+
Fig.7
Solenoid circuit with
varistor protection.
THINKING ELECTRONIC INDUSTRIAL Co., LTD.
2
www.thinking.com.tw
2008.07
Metal Oxide Varistor:
:
Application Note
Transient Protection of Solid State Circuit
Modern electronic equipments and appliances contain solid state circuits that are susceptible to malfunction or damage
caused by transient voltage spikes.
Fig.8
Semiconductor protection
Extend the Life of Relay Contacts
When the current in inductive load is interrupted by mechanical contacts, the voltage across the contacts builds up and
cause arcing which is destructive to the contacts. Varistors can be applied to prevent initiation of the arc.
M
THINKING ELECTRONIC INDUSTRIAL Co., LTD.
3
Fig.9
Contact protection
www.thinking.com.tw
2008.07