Pulse Transformers

Pulse Transformers

Pulse transformers operate in a direct current (DC) mode, meaning that the flux density may meet but does not cross zero. A common application for pulse transformers is the coupling of a load resistance to a source of pulsed power. An example of this application would be radar transmitters, which typically employ an output power tube like a magnetron that requires high voltages and high impedance, or electric resistance, levels. Small versions of pulse transformers create the electrical surges that are often used in telecommunication and detail logic applications such as camera flashes, radar equipment and particle acceleration. Medium-sized versions of pulse transformers are used in electronic circuit applications. Pulse transformers are used for the digitization of computers, measuring devices and pulse communication. Large versions of pulse transformers are used in the electrical power distribution industry in order to create a common boundary between low-voltage control circuitry and high-voltage gates of power semiconductors.

Pulse transformers are used to interface a pulse forming network (PFN) and a load. They ensure that the electrical resistance of the load is matched to the PFN in order to maximize power-transfer efficiency. Pulse forming networks (PFNs) work by collecting electrical energy over a rather long period of time and then discharge this stored energy rapidly as a short-duration, relatively-square pulse. Typically consisting of an input winding, an output winding and a core structure made from ferromagnetic materials, pulse transformers transfer electrical energy in the form of pulses from the PFN through the input winding to the output winding and into the load. Power transformers generally operate at high frequencies that require low loss cores made from ferromagnetic material. There are two main types of pulse transformers: power and signal. Power pulse transformers are turned on and off using a switching device at an operational frequency and pulse duration that ensures the pulse transformer receives the required amount of power. As a result of controlling the power, the temperature of the pulse transformer is also controlled. Additionally, the pulse transformer provides electrical insulation between the input winding and the output winding. Signal pulse transformers handle relatively low amounts of power and deliver a series of pulses, or signals. This type of pulse transformer mainly concentrates on the delivery of a signal at the output winding. Also, a signal pulse transformer can use its turns ratio to adjust signal amplitude and provide electrical resistance between the source and the load.