- 636 -

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.

FIGURE 1

Transient Voltage Suppressors 1 provides maximum protection. However, the system will probably require

replacement of the line fuse(F) since it provides a dominant portion of the series impedance when a surge is

encountered.

However, we do not recommend to use the TVS diode here, unless we can know the electric circuit

impedance and the magnitude of surge rushed into the circuit. Otherwise the TVS diode is easy to be

destroyed by voltage surge.

Transient Voltage Suppressor 2 provides execllent protection of circuitry excluding the transformer(T).

However, since the transformer is a large part of the series impedance, the chance of the line fuse opening

during the surge condition is reduced.

Transient Voltage Suppressor 3 provides the load with complete protection. It uses a unidirectional

Transient Voltage Suppressor, which is a cost advantage. The series impedance now includes the line fuse,

transformer, and bridge rectifier(B) so failure of the line fuse is further reduced. If only Transient Voltage

Suppressor 3 is in use, then the bridge rectifier is unprotected and would require a higher voltage and current

rating to prevent failure by transients.

Any combination of these three, or any one of these applications, will prevent damage to the load. This would

require varying trade-offs in power supply protection versus maintenance(changing the time 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