The role of switching power supply transformers
Switching power supply transformer and switching tube together constitute a self-excited (or other excitation) type of intermittent oscillator, so that the input DC voltage modulation into a high-frequency pulse voltage.
Play the role of energy transfer and conversion. In the flyback circuit, when the switch is on, the transformer converts the electrical energy into magnetic field energy stored, when the switch is off then released. In a forward circuit, when the switch is on, the input voltage is supplied directly to the load and the energy is stored in the energy storage inductor. When the switch is switched off, the energy is transferred to the load by the storage inductor.
The input DC voltage is converted into the required low voltage.
Classification of switching power supply transformer
Switching power supply transformer is divided into single excitation switching power supply transformer and double excitation switching power supply transformer, two kinds of switching power supply transformer working principle and structure is not the same. The input voltage of single excitation switching power supply transformer is unipolar pulse, and it is also divided into forward and reverse excitation voltage output; while the input voltage of double excitation switching power supply transformer is bipolar pulse, generally bipolar pulse voltage output.
Characteristic parameters of switching power supply transformer
Voltage ratio: the ratio of the primary voltage to the secondary voltage of the transformer.
DC resistance: i.e. copper resistance.
Efficiency: that is, the output power / input power * 100 [%].
Insulation resistance: the transformer between the windings and the core of the insulation between the ability.
Resistance to electric strength: transformer in 1 second or 1 minute can withstand the degree of the specified voltage.
Switching power transformer composition
Switching power transformer main materials: magnetic materials, wire materials and insulation materials are the core of the switching transformer.
Magnetic materials: switching transformer magnetic materials used for soft magnetic ferrite, according to its composition and application frequency can be divided into two categories of MnZn system and NiZn system. The former has a high permeability and high saturation magnetic induction, in the mid-frequency and low-frequency range with low loss. There are many types of core shapes, such as EI type, E type, EC type, etc.
Wire materials - enamelled wire: generally used for winding small electronic transformers enamelled wire with high strength polyester enamelled wire (QZ) and polyurethane enamelled wire (QA) two kinds. According to the thickness of the paint layer is divided into 1 type (thin paint type) and 2 type (thick paint type) two kinds. The former insulating coating for polyester lacquer, with superior heat resistance, insulation resistance up to 60kv/mm; the latter insulating layer of polyurethane lacquer, with self-adhesive, self-welding properties (380 ℃), can be directly welded without going to the lacquer film.
Pressure-sensitive adhesive tape: insulating tape with high electrical strength, easy to use good mechanical properties, is widely used in switching transformer coils between layers, group insulation and outsourcing insulation. Must meet the following requirements: good adhesion, anti-peeling, with a certain tensile strength, good insulation, good pressure resistance, flame retardant and high temperature resistance.
Skeleton material: switching transformer skeleton and general transformer skeleton is different, in addition to the coil as insulation and support materials, but also assume the role of the entire transformer installation and positioning, so the production of skeleton materials in addition to meet the insulating requirements, there should be a considerable tensile strength, and at the same time, in order to withstand the pins of the resistance of the weld heat, the requirements of the skeleton material of the heat deformation temperature is higher than 200 ℃, the material must achieve Flame retardant, and should also be good processing, easy to process into a variety of shapes.
