Electronic transformer manufacturers and wholesalers

A power electronic transformer is a power transmission and distribution device that combines power electronic transformers (rectifiers, inverters) and high-frequency transformers to realize the basic functions of electrical conversion, energy transmission and system isolation of traditional power transformers. Since the power equipment currently applied to the power system is lower than the transmission system in terms of capacity and withstand voltage level, it is expected that the power electronic transformer will be firstly used in the power distribution field.

The power electronic converter (rectifier, inverter) of the power electronic transformer shall include the main circuit and the control circuit. For the transformer of the distribution system, in order to be consistent with the traditional power transformer, the power electronic transformer connected to the power supply side and its corresponding high-frequency transformer are defined as the primary side; the power electronic transformer connected to the load side and its corresponding high-frequency transformer are defined as the primary side; A frequency transformer is defined as the secondary side. The two are connected through a high frequency transformer.

The working principle is as follows: on the primary side, the high voltage of the industrial frequency bus is transformed into a high-frequency AC square wave through the power electronic converter, that is, the primary side increases the voltage frequency to realize up-frequency. Since the volume of the transformer is related to the saturation flux density of the core material and the maximum allowable temperature rise of the winding, a transformer with a large saturation flux density is also large. The saturation magnetic flux density of the core material is inversely proportional to the operating frequency of the transformer. Therefore, the up-frequency effect of the primary-side power electronic converter can improve the utilization rate of the iron core material, reduce the volume of the transformer, and save the space of the transformer. This is also a major advantage of power electronic transformers compared to conventional power transformers.

features

The input is an electronic transformer AC220V, the output is AC12V, and the power can reach 50W-300W. It is mainly a transformer circuit developed on the basis of high-frequency electronic ballast circuits. It has stable performance, small size and high power, and overcomes the shortcomings of traditional silicon steel plate transformers, such as large body, heavy weight and high price.

An electronic transformer is an unregulated switching power supply, which is actually an inverter. First, convert the AC current to DC. Then use electronic components to form a high-frequency oscillator, convert the direct current into high-frequency alternating current, output the required voltage through the switching transformer, and then use it in the secondary rectifier. Switching power supply is small in size, light in weight and low in price, and is widely used in various electrical appliances.

According to the different driving modes of the high-frequency switching tube, it can be divided into self-excited oscillation type and other excited type.

electronic transformer

as the picture shows. The working principle of the electronic transformer is similar to that of the switching power supply. VD1~VD4 is composed of a rectifier bridge composed of an oscillating transformer to convert the mains power into a direct current T1. Transformer T2 steps down the high-frequency high-voltage pulse to obtain the required voltage and power. R1. Current limiting resistor. Resistor R2, capacitor C and diode bidirectionally trigger VD to form a start-up trigger circuit. Transistor VT1, VT2 select S13005, and its B is 15-20 times. C3093 and other BUceo>=35OV high-power transistors can also be used. The trigger diode VD5 selects DB3 or VR60 of about 32V. The oscillating transformer can be self-made, and the audio wire is used to wind the H7 X 10 X 6 magnetic ring. TIa, T1b around 3 turns, Tc around 1 turn. Transformer output ferrite T2. The magnetic core also needs to be self-made, EI type ferrite with a side length of 27mm, a width of 20mm, and a thickness of 10mm. T2a is wound with 100 turns of high-strength enameled wire with a diameter of 0.45mm, and T2b is wound with 8 turns of high-strength enameled wire with a diameter of 1.25mm. Diodes VD1-VD4 use 4007-type bidirectional trigger diode DB3 for use as IN, and capacitors C1-C3 use polypropylene polyester capacitors with a withstand voltage of 250V.

When the circuit is working, the operating voltage at point A is about 12V; point B is about 25V; point C is about 105V; point D is about 10V. If the voltage does not meet the above values, or the circuit does not oscillate, check the circuit for wrong, missing or virtual soldering. Then check whether VT1 and VT2 are in good condition, and whether the phases of T1a and T1b are correct. After the whole circuit is successfully installed, it can be put into a small box made of metal material, which is conducive to shielding and heat dissipation, but attention must be paid to the insulation of the circuit and the shell. In addition, changing the number of turns of T2 a and b coils can change the output high-frequency voltage.

He stimulated

After the bridge rectifier is connected to the power frequency mains, the Rs current flows into the IC pin VCC except the start-up current, and most of the rest of the current charges the capacitor CVCC1. When the voltage on the IC pin VCC reaches the startup threshold (11.8 V), the IC starts to work. Once the IC starts, the charge pump circuit composed of CSNUB, DCP1 and DCP is the IC pin VCC feed current. The bootstrap diode DB and capacitor CB power the IC's high-side drive circuit. The zener diode DZ is used as a shunt IC to prevent IC from being damaged by excess current.

The resistance of the halogen filament has a positive temperature coefficient, and the cold resistance at room temperature is much smaller than the thermal resistance when the lamp is working. When the lamp is started, a large surge current will be generated, which will affect the service life of the lamp. But IR provides soft-start operation to avoid inrush current. When the lamp starts, the IR2161 outputs a high frequency of 125 kHz. The output T primary leakage inductance of the high-frequency transformer in the system is fixed, and presents a higher impedance at a higher frequency, and the voltage on the primary winding is lower. The output voltage of the transformer is low, and the lamp current is small to avoid triggering the protection circuit. The circuit runs at a lower frequency for about 1 s. During this process, the voltage on the external capacitor CSD of IC pin 3 increases from OV to 5V.

When no load, VCSD = OV, the frequency of the oscillator is about 60kHz. At maximum load, VCSD=5V, the frequency of the oscillator is about 30kHz. When the output is short-circuited, a large current flows through the half-bridge, and RCS senses it. As long as the voltage on IC pin 4 (CS) exceeds the threshold level of 1V for 50ms, the system will shut down at the above time. If the load exceeds 50% of the maximum load, the voltage on IC pin 4 will exceed the O 5 V threshold voltage, and after 0.5S, the system will shut down. Both short circuit protection and overload protection can be reset automatically. IR2161 also provides thermal shutdown function. When the chip junction temperature exceeds 135°C, when the temperature limit value is too high, the half-bridge switch will stop working to avoid MOSFET burnout.

use

Electronic transformers are widely used in traditional lighting fixtures, such as fluorescent lamps, table lamps, energy-saving lamps, advertising lamps, etc. The electronic transformer is almost usable, and after using the electronic transformer, the starter can be omitted. In terms of LED lighting, most new products also use electronic transformers. In terms of voltage transformation function, the electronic transformer has high efficiency, low cost, saving iron and copper materials, small structure and light weight. The disadvantage is that the voltage resistance and high current impact resistance are worse than those of iron transformers.

Applied to power technology

Electronic transformers in power supply units generally use electronic transformers (soft magnetic components) made of soft magnetic cores. Although air-core electronic transformers and piezoelectric ceramic transformers do not have soft magnetic cores, until the beginning of the 21st century, most electronic transformers in power supply units still use soft magnetic cores.