Glossary of Terms Switching Transformer

Blocking Oscillator:

A blocking oscillator circuit is a self excited flyback circuit.

Circuit Topology:

A generic term used to reference the different types of circuit configurations that may be implemented in a switch mode power supply.

Flyback Circuit Topology:

Common circuit design for low power (<100 Watts) switch mode power supply.

Feed Forward:

Used in higher powered supplies were a pulse transformer and filter choke are used to convert the input voltage.


Maximum isolation voltage from winding to winding or winding to core / ground.

Hipot Duration:

Length of time in seconds to test device at the hipot voltage.

Input Voltage:

The voltage applied to the primary winding.


The method used to mount the component to the circuit board.

Number of Secondaries:

The number of secondaries required in the transformer.

Operating Frequency:

Frequency at which transformer will operate.

Operating Temperature:

The operating temperature is expected maximum temperature the transformer is expected to operate at expressed in degrees Celsius.

Peak Input Current:

Maximum peak current flowing through the primary winding.

Power Rating:

Maximum power transformer is expected to process.

Primary Inductance:

Inductance of the primary winding.

Pulse Duration:

Length of time energizing current pulse is applied through primary.

Pulse Repetition Rate:

Time from start of a pulse to the start of the next pulse.

Secondary Current:

Output current expected to flow through secondary winding(s) under fully loaded conditions.

Secondary Voltage:

Output voltage expected from secondary winding(s) under fully loaded conditions.

SMT Mounting:

Components manufactured with solder feet that are soldered to pads on the circuit board providing the mounting and connection to the circuit. Electrical connection is made through soldering the component to these solder pads.

Thru Hole Mounting:

Component is manufactured with pins that mount the device through holes in the circuit board which are soldered.

Turns Ratio:

The ratio of the number of primary turns to the number of secondary turns expressed as Np:Ns.

Voltage Range:

Range of input voltage that is expected across primary winding.