The switching DC power transformer is a DC power transformer with a switch tube. When designing a DC power supply circuit, in addition to the DC voltage conversion function of an ordinary transformer, it also has the function of insulation and power transmission, which is often used in switching DC power supplies and high-frequency DC power equipment.
The DC power transformer, the switching DC transformer and the switch tube together form a self-excited (or other) intermittent oscillator, which modulates the input DC voltage into a high-frequency pulsed DC voltage. Role in energy transmission and conversion In the construction of flyback DC circuits, the transformer converts electrical energy into magnetic field energy, stores it when the switching tube is turned on, and releases it when the switching tube is turned off. In the design of the forward DC power supply circuit, when the switch tube is turned on, the input DC power supply voltage is directly provided to the load, and the energy is stored in the energy storage inductor.
When the switch tube is turned off, the energy storage inductor will carry out freewheeling transmission to the load. The input DC-DC power supply voltage is converted into various low voltages required.
The basic configuration of a DC switching transformer is the main material of the DC switching transformer, and magnetic materials, wire materials and insulating materials are the core of the switching transformer.
Magnetic material: The magnetic material used in the switching transformer is soft ferrite, which can be divided into two categories according to its composition and applicable frequency: MnZn and NiZn. The former has high permeability and high saturation magnetic induction at low and medium levels, and has a loss effect in the low frequency range. The magnetic core has various shapes, such as EI type, E type, EC type and other wire materials. Enameled wire: usually used to wind small electronic transformers. Enameled wire includes high-strength polyester enameled wire (QZ) and polyurethane enameled wire (QA).
According to the thickness of the coating, it can be divided into Type 1 (thin coating type) and Type 2 (thick coating type). The former insulation coating is a heat-resistant polyurethane coating up to 60kV/mm, and the latter insulation layer is a polyurethane coating with strong self-adhesive and self-welding properties (380°C). The pressure-sensitive tape can be welded directly without peeling off the paint film, and the insulating tape has high electrical strength.
Due to its ease of use and excellent mechanical properties, it is widely used for switching transformer coils, isolation between groups and outsourcing isolation. The following requirements must be met: excellent adhesion, peel strength, specific tensile strength, excellent insulation performance and excellent pressure resistance, flame resistance and heat resistance. Frame material: The frame of a switching transformer is different from that of a general transformer.
It is not only the insulation and support material of the coil, but also plays a role in the installation, fastening and positioning of the entire transformer. Therefore, it not only needs to meet the insulation requirements, but also must have considerable tensile strength. At the same time, the welding heat requires the heat distortion temperature of the frame material to be higher than 200°C. The material has flame retardancy, excellent workability and easy processing. Various shapes.
Classification and parameters of switching DC power transformers Switching DC power transformers are divided into single excitation switching DC power transformers and double excitation switching DC power transformers. The functional principle and structure of the two switching DC transformers are different. The DC transformer input DC power supply voltage is a unipolar pulse, divided into forward and reverse DC power supply voltage output. On the other hand, the DC input voltage of a DC transformer with two excitation switches is a bipolar pulse, usually bipolar. Pulse DC power supply output voltage.