P6SMB Series
TVS APPLICATION NOTES
Transient Voltage Suppressors may be used at various points in a circuit to provide various degrees of
protection. The following is a typical linear power supply with transient voltage suppressor units placed at
different points. All provide protection of the load.
LOAD
FIGURE 1
TVS1 provides the maximum protection. However, the system will probably also require replacement of the
line fuse (F) since it provides the major portion of the series impedance when a surge is encountered. We do
not recommend using the TVS diode in this way. Unless the electrical circuit impedance and the magnitude of
the surge are well understood, the TVS diode may be easily destroyed by the voltage surge.
TVS2 provides execllent protection of the circuitry with the exception of the transformer (T). However, since
the transformer represents a large part of the series impedance, the chance of the line fuse opening during the
surge condition is reduced.
TVS3 provides the load with complete protection. It uses a unidirectional TVS which is a cost advantage.
The series impedance now includes the line fuse, transformer, and bridge rectifier (B) so the chance of a failure
of the line fuse is further reduced. If only TVS3 is used, then the bridge rectifier is unprotected and requires a
higher voltage and current rating to prevent failure by transients.
Any combination of these three, or any single one of these applications, will prevent damage to the load. This
would require varying trade-offs in power supply protection versus maintenance (changing the fuse .
An additional method is to utilize the Transient Voltage Suppressor units as a controlled avalanche bridge.
This reduces the parts count and incorporates the protection within the bridge rectifier.
FIGURE 2
Information furnished by Silicon Standard Corporation is believed to be accurate and reliable. However, Silicon Standard Corporation makes no
guarantee or warranty, express or implied, as to the reliability, accuracy, timeliness or completeness of such information and assumes no
responsibility for its use, or for infringement of any patent or other intellectual property rights of third parties that may result from its
use. Silicon Standard reserves the right to make changes as it deems necessary to any products described herein for any reason, including
without limitation enhancement in reliability, functionality or design. No license is granted, whether expressly or by implication, in relation to
the use of any products described herein or to the use of any information provided herein, under any patent or other intellectual property rights of
Silicon Standard Corporation or any third parties.
11/26/2005 Rev.3.01
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