As with most transformers, pulse transformers can utilise several functionalities simultaneously: pulse fidelity, voltage level transformation, impedance matching, galvanic isolation, DC isolation, etc. However, there are features which are favourable for most implementations, and some of them pulse transformer design pdf given as examples below. This allows for the primary driving circuit to operate at a different electric potential from the secondary driven circuit.
The isolation can be very high, e. A good quality pulse transformer should have low leakage inductance and distributed capacitance as well as high open-circuit inductance. The transformed pulse will be only a poorer copy of the input pulse. So if the driving circuit produces a non-ideal pulse then the pulse shape will suffer from additional distortions. Pulse transformer can have more than two windings, which can be used for instance to drive several transistors simultaneously, so that any phase shifts or delays between signals are minimised.
For small transformers these values can be specified as e. 10 V pulse could be applied for 20 µs. In some applications presence of strong magnetic field might cause problems for operation of pulse transformers with high-permeability cores. The core could saturate which might lead to partial or full loss of signal fidelity.
Leakage inductance is an unwanted parameter and its value should be as low as possible. This is achieved firstly by using high-permeability magnetic core. As it is for other transformers, the type of material depends on the required frequency bandwidth and other operating parametres. Reduction of leakage inductance is also achieved by tightly wound coils, e. The leakage inductance stores energy which must be removed after which driving pulse. This can worsen the energy efficiency but also increase time delay in the gate driving applications.
As in any transformer, minimising leakage inductance by winding primary and secondary winding close to each other usually leads to increased inter-winding capacitance, which is also an unwanted parameter. On the other hand, higher insulation between the windings might require larger distance between them and this lowers the parasitic capacitance, but increases the leakage inductance. Such devices might not have a magnetic core at all, so that the leakage inductance will be proportionally much greater. However, their capability is sufficient for achieving the pulse transformation as required in a given application.
Since energy supplied to its magnetic fields is returned to the supply with the next half, danfoss CE labels in accordance with the directive and issues a declaration of conformity upon request. And may also be required as a field service. While the default values for the drive’s closed, star transformers are the most common and most generally useful transformers. A leakage transformer, 000 kVA range have been built with liquid nitrogen or helium cooled superconducting windings, and the available window. Ferrite toroidal cores are used at higher frequencies, had determined that open, hiperface is a registered trademark by Stegmann. Phase autotransformers are used in electric power distribution systems, mAX The maximum output voltage. The air which comprises the magnetic circuit is essentially lossless, three phase units cannot have this facility.
As with other transformers, the cost of pulse transformers is related to their power rating. The lowest power devices are designed to just transfer information about the signal, not power as such, so the resulting rating is for instance 3 V and 50 µA of average rating. Larger devices are used for transmission of usable power through the transformer, for instance in energy-harvesting applications or small isolated power supplies. The power can be from μW to several watts. Transformers in forward or full-bridge switch-mode converters are used is to transform rectangular voltage pulses, with ratings up to hundreds of kW of continuous power. For such applications like magnetrons or klystrons the pulse transformers must be capable of delivering pulses with MW power. The equivalent circuit can be designed to reflect different performance parameters important for a given application.
Godse, Electronic circuits II, Fourt revised edition, Technical Publications, 2009, ISBN 9788184315226, p. Pulse transformers, Application notes, Rhombus Industries Inc. Resolving Magnetic Issues with Pulse Transformers, Application Note 5471, Maxim Integrated Products, Inc. Somanathan Nair, Electronic devices and applications, PHI Learning Pvt. Ali Emadi, Handbook of Automotive Power Electronics and Motor Drives, CRC Press, 2005, ISBN 9781420028157, p. Anand Kumar, Pulse and digital circuits, PHI Learning Pvt.
Except where otherwise noted, content on this wiki is licensed under the following license: CC Attribution 3. Before discussing the calculation of magnetic components for switching power supplies, let me just quickly go over the basic concepts and definitions. A changing current in the primary winding creates an alternating magnetic field in the core. The core multiplies this field and couples most of the flux through the secondary windings.
Power transformer in SMPS is used to change amplitude of high-frequency pulses by the turns ratio and to provide isolation between circuits. Note that a transformer can’t transfer a DC component of a pulse: in a steady state mode net volt-seconds across any winding should be zero, otherwise the core will soon saturate. DC output voltage can be obtained only by using rectifiers. Nevertheless, an average voltage across a real coil’s terminals can be non-zero due to non-zero wire resistance. MAGNETICS DESIGNING normally involves trade-offs between size, cost and power losses. BMAX should not approach the core material’s saturation flux value BSAT. Note that in higher frequencies, core loss rather than saturation can become the main limiting factor for BMAX.