Classification of Switching Power Transformers
A switch power transformer is a power transformer that incorporates a switch transistor. In the circuit, in addition to the voltage conversion function of a regular transformer, the switch power transformer also has insulation isolation and power transmission functions. Switching power transformers are generally used in situations involving high-frequency circuits such as switching power supplies.
The Function of Switching Power Transformer
The switch power transformer and switch tube together form a self excited (or self excited) intermittent oscillator, thereby modulating the input DC voltage into a high-frequency pulse voltage
It plays a role in energy transfer and conversion. In a flyback circuit, when the switch is turned on, the transformer converts electrical energy into magnetic field energy for storage. When the switch is turned off, it is released. In a forward circuit, when the switch is turned on, the input voltage is directly supplied to the load and energy is stored in the energy storage inductor. When the switch is turned off, the energy storage inductor continues to transfer to the load
Convert the input DC voltage into various required low voltages
Classification of Switching Power Transformers
Switching power transformers are divided into single excitation switching power transformers and double excitation switching power transformers, and the working principles and structures of the two types of switching power transformers are not the same. The input voltage of a single excitation switching power transformer is a unipolar pulse, and it also outputs forward and backward voltage; The input voltage of the dual excitation switching power supply transformer is a bipolar pulse, which is generally a bipolar pulse voltage output.
Composition of Switching Power Transformer
The main materials of switch power transformers are magnetic materials, wire materials, and insulation materials, which are the core of switch transformers
Magnetic materials: The magnetic materials used in switch transformers are soft magnetic ferrite, which can be divided into MnZn series and NiZn series according to their composition and application frequency. The former has high permeability and high saturation magnetic induction, and has low losses in the mid and low frequency ranges. The magnetic core has many shapes, such as EI type, E type, EC type, etc
Wire Material - Enamelled Wire: Generally used for winding small electronic transformers, there are two types of enameled wire: high-strength polyester enameled wire (QZ) and polyurethane enameled wire (QA). According to the thickness of the paint layer, they are divided into Type 1 (thin paint type) and Type 2 (thick paint type). The insulation coating of the former is polyester paint, which has excellent heat resistance, and the insulation resistance and electrical strength can reach 60kv/mm; The latter insulation layer is polyurethane paint, which has strong self-adhesiveness and self soldering performance (380 ℃), and can be directly welded without removing the paint film
Pressure sensitive tape: Insulating tape has high electrical strength, is easy to use, and has good mechanical properties. It is widely used in interlayer, inter group, and external insulation of switch transformer coils. It must meet the following requirements: good adhesion, anti stripping, has a certain tensile strength, good insulation performance, good voltage resistance, flame retardancy, and high temperature resistance.
Skeleton material: The switch transformer skeleton is different from the general transformer skeleton. In addition to serving as the insulation and support material for the coil, it also serves as the installation, fixation, and positioning of the entire transformer. Therefore, the material used to make the skeleton should not only meet the insulation requirements, but also have considerable tensile strength. At the same time, in order to withstand the welding heat resistance of the pins, the thermal deformation temperature of the skeleton material is required to be higher than 200 ℃. The material must be flame retardant and have good processability, Easy to machine into various shapes
