Key Points of electronic transformer knowledge

1.What is an electronic transformer
Electronic transformer, with the alternating voltage of the power supply converted to DC and then through semiconductor switching devices and electronic components and high-frequency transformer winding constitute a high frequency AC voltage output electronic devices, is also described in the electronics theory of an AC-dc inverter circuit. To put it simply, it is mainly composed of high-frequency transformer magnetic core (iron core) and two or more coils, they do not change the position of each other, from one or more than two electrical circuits, through ac power with the help of electromagnetic induction, into AC voltage and current. At the output end of the high-frequency transformer, different voltage levels of high-frequency AC or DC are supplied to one or more electrical circuits.

A simple transformer is composed of a closed magnetic conductor and two windings, one of which is connected to the AC power supply and is called the primary winding Np, the other winding can be connected to the load and is called the secondary winding Ns.

If the primary winding is connected to the power supply of THE AC voltage Ui, the transformer is in no-load, and the alternating power Io is generated in the primary winding, Io is called no-load current. This current establishes an alternating flux that is closed along the magnetic circuit of the magnetic core. The flux passes through the primary winding and the secondary winding at the same time and generates a self-induced electromotive force E1 in the primary winding and a mutual induced electromotive force E2 in the secondary winding. Then E1: E2=Np: Ns. Np is the number of turns of primary winding, Ns is the number of turns of secondary winding.

Transformers play the roles of boost, step-down, isolation, rectifier, inverter, invert phase, impedance matching, inverter, energy storage, filtering and so on in electronic circuits.

2. Classification of transformers
A. Classified by working frequency:
Power frequency transformer: operating frequency is 50Hz or 60Hz
Intermediate frequency transformer: operating frequency is 400Hz or 1KHz
Audio transformer: operating frequency is 20Hz or 20KHz
Super audio transformer: above 20KHz, not exceeding 100KHz
High frequency transformer: the operating frequency is usually from upper KHz to over hundreds of KHz.
B. By purpose:
Power transformer: A transformer used to supply the power needed for electronic equipment
Audio transformer: A transformer used in audio amplifier circuits and audio equipment
Pulse transformer: A transformer operating in a pulse circuit whose waveform is generally a unipolar rectangular pulse wave
Special transformer: A transformer with a special function, such as a parametric transformer, a stabilizing transformer, a super isolating transformer, a transmission line transformer, a leakage transformer
Switching power transformer: Transformer used in switching power supply circuits
Communication transformer: a transformer used for starting and filtering in communication networks

3.Common materials for transformers
Electronic transformer materials mainly include:
Bobbin, Base, Case
FerriteCore, SI - Steel Lamination
Copper Foil
Safety tape, also called Margin Tape
Chemicals: SolderBar, Varnish,Glue, Thinner, flux, Ink.

4 Main technological process
1) Pre-processing, such as copper foil, skeleton and other pre-processing; (before hand process)
2) winding; (winding coil)
3) Termianl lead wire;
4) Solder 1; (dipsolder 1)
5) Combined magnetic core, including adhesive dots and wrapping tape; (assembly)
6) Test 1; (test1)
7) baked glue; (bakeglue)
8) including leaching; (dipvarnished or vacuumed varnish)
9) Baking fresh water; (bake varnish)
10) Solder 2; (dipsolder 2)
11) Test 2; (test2)
12) Appearance inspection and cleaning; (inspection&cleaning)
13) Packaging of finished products; (packing)

5. Performance index
A. Inductance (Inductance)
B. Leakage Inductance
C. Dc resistors 
D. Winding number ratio (Turn Radio)
E. pressure - POT (Hi)
F. Insulation Resistance
G. Mechanical Dimension
H. Layer Insulation.
I. Online Test (InCircuit Test)