Introduction to inverter switching power supplies forrepairinginverters
The so-called soldiers and horses have not moved, food and fodder first. Switching power supply circuit to provide inverter machine control power, is a prerequisite for the normal operation of the inverter. The switching power supply circuit applied in the frequency converter is a direct-analogue inverter circuit, which is a kind of voltage and power converter, and converts DC voltage and power into pulse voltage, and then rectifies it to become another kind of DC voltage. The input and output voltages are isolated from each other by a switching transformer, which plays the role of power transfer and voltage/current conversion. The switching transformer is a step-down transformer. The characteristics of switching power supply are as follows:
1)The oscillation and voltage regulation of switching power supply is to use the change of pulse width or period to adjust the output voltage, known as time-proportional control, which is also divided into two control modes: PWM (width-modulation) and PFM (frequency-modulation).
2) From the energy conversion characteristics of the circuit, can be divided into two types of forward and flyback mode of operation. When the switching tube is saturated, the rectifier connected to the secondary winding is cut off by the reverse bias voltage, and the primary winding of the switching transformer flows into the current and stores energy (electromagnetic conversion). When the switching tube cuts off, the secondary winding releases electrical energy through the load circuit (magneto-electric conversion). Forward mode is the opposite of this, not many practical applications.
3) From the primary circuit structure of the switching transformer, there are discrete components and integrated oscillator chip composed of two circuit forms. Thus, from the source of the oscillation signal, and is divided into self-excited (discrete parts) and other excitation (IC circuit) switching power supply. Both circuit structures have applications.
4) Switching tube has the use of bipolar devices and the use of field effect transistors.
5) small power inverter using single-ended positive excitation circuit, large and medium power inverter often use double-ended positive excitation circuit. General inverter switching power supply, often provide the following types of voltage output: CPU and ancillary circuits, control circuits, operation display panel +5V power supply; current, voltage, temperature and other fault detection circuits, control circuits, ± 15V power supply; control terminals, the work of the relay coil 24V power supply. Four mutually isolated about 22V drive circuit power supply, the four power supply is often processed by the voltage regulator circuit into +15V, -7.5V positive and negative power supply for the drive circuit, for the IGBT inverter output circuit to provide excitation current.
Any electronic equipment, the failure rate of the power supply circuit is always quite high because it has to provide the power supply of the machine, the heaviest burden. Inverter switching power supply circuit, the form is relatively single, the structure is relatively simple. But simple circuits may also produce difficult failures. Switching power supply maintenance is not as intuitive as linear power supply, any small part of the circuit an oscillation, voltage regulation, protection, load and other anomalies, will make the circuit a variety of fault phenomena.
No reaction after power on, no display on the operation display panel, the inverter seems to be not powered on. Measure the control voltage of the control terminal and 10V frequency adjustment voltage are 0, measure the inverter main terminal resistance is normal, then generally can be concluded that the problem is in the switching power supply circuit.
