What Is a Pulse Transformer?
Pulse Transformers are transformers that are not intended to transmit power, but rather AC signals on a pulse waveform.
It is mainly installed in communication circuits within electronic equipment. Pulse Transformers consist of a magnetic core and windings, with two windings, a primary winding and a secondary winding, wound around the magnetic core. Pulse Transformers have few moving parts or aging element parts, making them high-life and highly reliable electronic components.
It is used to transmit signals while ensuring insulation between the input signal source and the output signal. A transformer ratio of 1:1 is mostly used. Pulse Transformers, like Power Transformers, are not used for the purpose of transmitting power, so the components can be made smaller.
Uses of Pulse Transformers
Pulse Transformers are used in communication circuits within electronic equipment as transmission media for sending and receiving communication signals. They are mainly used in communication circuits in electronic equipment that use long-distance cables for communication, such as LAN and Ethernet communication.
When long-distance cables are used for communication, they are easily affected by external noise, so Pulse Transformers are used to insulate the input and output sides of communication.
In many cases, Pulse Transformers are built into communication connectors because they are miniaturizable components. However, when using a single Pulse Transformer that is not built into a communication connector, the Pulse Transformer should be placed near the communication connector on the board.
Principle of Pulse Transformers
Pulse Transformers are roughly similar to transformers used to convert voltage. It has coils on the primary and secondary sides, and the primary and secondary coils are wound around a single ring-shaped iron core.
When the signal, or current, input to the Pulse Transformer flows through the primary coil, a magnetic field is generated in the iron core by electromagnetic induction. The magnetic field propagates through the iron core to the secondary side, causing electromagnetic induction in the secondary side and outputting current from the secondary side.
A transformer for transforming voltage generally has a 4-terminal configuration with a Vin and GND terminal on the primary side and a Vout and GND terminal on the secondary side, but in the case of Pulse Transformers, 4 or more terminals are often used. Communication involves both transmitting and receiving, and it is necessary to send signals from the primary side to the secondary side or from the secondary side to the primary side.
Since it is impossible to transmit both signals in a single transformer, some Pulse Transformers have a transmitter terminal and a receiver terminal. In practice, this configuration has a transformer for transmitting and a transformer for receiving within a single element.
Other Information on Pulse Transformers
1. Noise Suppression
Since Pulse Transformers are insulated at the signal input and output sides, when external noise gets on the communication signal sent from the output side, the Pulse Transformer intercepts the external noise and transmits only the signal necessary for communication to the input side. Pulse Transformers transmit pulse signals and, at the same time, protect the inside of electronic equipment by reducing the effects of static electricity and external noise.
2. Protection in the Event of Communication Circuit Failure
If a communication circuit in an electronic device, malfunctions, and an abnormal voltage leaves the communication circuit, the Pulse Transformer also prevents the abnormal voltage from flowing into the destination communication device. The use of Pulse Transformers isolates the communication circuit of each electronic device, thus reducing the possibility of failure of other electronic devices in the event of a failure of one electronic device.
3. Precautions for Use
The disadvantage of using a Pulse Transformer is that, depending on the winding material and characteristics, distortion of the pulse signal waveform may result in poor signal quality or attenuation of the pulse signal waveform voltage. When using a Pulse Transformer, the actual pulse signal waveform should be observed with an oscilloscope or other measuring instrument, and the waveform should be evaluated to confirm that it is consistent with the communication specifications adopted by the electronic equipment and the electrical specifications of the communication IC to be used.