Principle of inverter
Popular, the inverter is a direct current (DC) into alternating current (AC) of the device. It consists of inverter bridge, control logic and filter circuit.
400W high power voltage stabilizing inverter circuit composed of TL494. The, VT1, VT2, VD4, VD3 and TL494 are used to form the driving circuit of the current drive, which drives the two MOS FET 60V/30A switches. If the output power is increased, each circuit can be used in parallel with 4 to 3 switching tubes, and the circuit is not changed. The application method of TL494 in the inverter is as follows:
First, 2 foot voltage sampling, error amplifier, positive input terminal 1 15V DC voltage pin input inverter secondary winding rectifier output sampling, by R1, the partial pressure of R2, the first foot nearly 4.7 ~ 5.6V sampling voltage in the inverter during normal operation. Inverting input pin 2 pin input 5V reference voltage (output by 14 pin). When the output voltage is reduced, the 1 pin voltage is reduced, the output voltage of the error amplifier is low, and the output voltage is increased by the PWM circuit. The normal voltage value of the 1 pin is 5.4V, 2 pin voltage value is 5V, the 3 foot voltage value is 0.06V. At this point the output AC voltage is 235V (square wave voltage). Fourth pin external R6, R4, C2 set the dead time. Normal voltage value is 0.01V. Fifth, 6 pin external CT, RT set oscillator triangle wave frequency is 100Hz. The normal voltage value of the 5 pin is 1.75V, and the voltage value of the 6 foot is 3.73V. Seventh feet for the common ground. Eighth, 11 pin for the internal drive output transistor collector, Twelfth feet for the TL494 front stage power supply side, the three end through the switch S control TL494 start / stop, as the inverter control switch. When the S1 off, TL494 no output pulse, so the switch tube VT4 ~ VT6 without any current. S1 is switched on, the voltage value is three positive voltage battery. Ninth, 10 pin for the internal drive level of the emitter, the output of the timing of the different timing of the positive pulse. Normal voltage value is 1.8V. Thirteenth, 14, 15 feet 14 feet 5V output reference voltage, the 13 foot 5V high level control gate circuit, trigger pulse output two push-pull switching circuit for driving. Fifteenth pin external 5V voltage, constitute the error amplifier inverting input reference voltage, in order to make the 16 feet of the input side of the same phase constitute the high level protection input. In this connection, when the sixteenth pin input is greater than 5V, the output voltage can be reduced by stabilizing the voltage, or the off drive pulse can be protected. There is almost no possibility of the output voltage in the inverter, so the circuit is not used in the circuit of sixteenth feet, which is grounded by the resistance R8.
The inverter adopts the power frequency transformer with the capacity of 400VA, and the iron core is made of 45 * 60mm2 silicon steel sheet. The primary winding uses a diameter of 1.2mm of the enamel wire, two and 2 x 20 turns around. The secondary sampling winding is wound around the 36 turn with a 0.41mm paint package. The secondary winding is calculated by 0.8mm, and the 230V coating wire is wound around the 400 turn. Switch tube VT4 ~ VT6 available N any model of the 60V/30A channel FET MOS tube instead. VD7 available 1N400X series of ordinary diodes. The circuit can work normally without debugging. When the C9 is at an extreme voltage of 12V, the R1 can be selected between 3.6 ~ 4.7K, or with a 10k potentiometer to adjust the output voltage to the rated value. If the output power of the inverter is increased to nearly 600W, in order to avoid the primary current is too large, increasing the resistive loss, the battery should be switched to 24V, the switch can be used VDS for MOS FET 100V tube current. It must be noted that the selection of multiple parallel rather not only, use the switch IDS is greater than 50A, the reason is that a higher price, the two is too difficult to drive. Recommended selection of 2SK564 100V/32A, or choose three 2SK906 parallel applications. At the same time, the transformer core section to reach 50cm2, according to the ordinary power transformer calculation method to calculate the number of turns and wire diameter, or the use of waste UPS-600 transformer replacement. For the refrigerator, electric fan power supply, do not forget to join the LC low pass filter.
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