A pulse transformer is a special type of transformer that is specially designed and optimized to transmit voltage pulses from windings to the load. It’s also known as gate drive, signal, trigger or wide-band transformer. The transformer can be used to transmit signals/ galvanic isolation, as a component of high power supply (switch mode) and as a component of low powered circuit control.

Essentially, it’s any transformer that can transmit voltage pulses with sufficient signal fidelity. Conditions such as high permeability core, little interwinding capacitance and low leakage inductance are fairly common for transformers in varying switched mode supplies. For these reasons, the term pulse transformer usually refers to a transformer with very high power rating.

The main similarity between pulse transformers and other types of transformers is that both categories can simultaneously make use of multiple functionalities such as pulse fidelity, Direct Current isolation, voltage-level transformation, galvanic isolation and impedance matching, among others.

Classification

Pulse transformers can be classified into two broad categories: signal transformers and power transformers.

The former are transformers that make use of electromagnetic induction for information transmission from circuit A to circuit B. They are commonly used to decrease or enhance voltage from one part to another.

On the other hand, the latter is used in the conversion of power voltages between different phase configurations.

Power Rating

Pulse transformers are designed with varying power ratings, ranging from megawatt devices to on-chip transformers incorporated into integrated circuits. The cost is directly proportional to power rating- the higher the rating, the greater the cost.

Most of the low powered devices are primarily designed for signal transmission rather than power transformation. Therefore, don’t be surprised if you come across devices with 50 A and 3Volt rating.

Equivalent Circuit

The transmission quality in pulse transformers is determined by the following: resistive losses, winding self-capacitance, leakage inductance as well as interwinding capacitance.

Engineers can design the equivalent circuit to suit different performance parameters requisite for given applications.

Uses

Power transformers have a wide range of applications. They include:

  1. As components for Alternating Current coupling parts of circuits
  2. Provision of galvanic saturation in circuits
  3. Enables variation of pulses’ amplitude
  4. Transmission of digital pulses
  5. Enables variation of impedance level for purposes of impedance matching and other objectives
  6. Allows coupling of amplifiers
  7. Enhancement of pulse transmission
  8. Differentiation of pulses
  9. Reversal of pulse polarity
  10. Separation of Direct Current between circuit components
  11. Simultaneous provision of negative and positive pulses

There are other applications of pulse transformers. They are used as components of mono-stable blocking oscillators, high power transmission of voltage and pulses from modulators to klystron, as components of multiple thyristors, wide-band signals transmission, galvanic isolation of gates and drivers found in power transistors and components of galvanic-separated lower power supplies.

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