Function or use of inverter
Inverter is to convert direct current energy (batteries, storage batteries) into alternating current (generally 220v50HZ sine wave or square wave).
Emergency power supplies usually convert DC batteries into 220 volts AC. Generally speaking, an inverter is a device that converts direct current (DC) into alternating current (AC).
It consists of inverter bridge, control logic and filter circuit. 400W high-power voltage-stabilizing inverter circuit composed of TL494. In the excitation conversion part, a current drive circuit is composed of TL494, VT 1, VT2, VD3 and VD4 to drive two 60V/30A MOS FET switches.
If it is necessary to increase the output power, 3~4 switches can be connected in parallel in each channel, and the circuit remains unchanged. The application method of TL494 in this inverter is as follows: 1 and 2 pins form a stable sampling and error amplification system. The positive input terminal 1 pin inputs the rectified 15V DC voltage of the inverter secondary sampling winding, which is divided by R 1 and R2, so that the 1 pin is nearly 4.7 when the inverter works normally.
Input a 5V reference voltage at pin 2 of the inverting input terminal (output through pin 14). When the output voltage decreases, the voltage at pin 1 decreases, and the error amplifier outputs a low level, thus increasing the output voltage through the PWM circuit.
Under normal circumstances, the voltage of 1 pin is 5.4V, the voltage of 2 pins is 5V, and the voltage of 3 pins is 0.06V At this time, the output AC voltage is 235V (square wave voltage).
The fourth pin is externally connected with R6, R4 and C2 to set the dead time. The normal voltage value is 0.01v.
The 5th and 6th pins are externally connected with CT and RT, and the frequency of triangular wave of oscillator is set to 100Hz. Under normal circumstances, the voltage value of the 5th pin is 1.75v, and the voltage value of the 6th pin is 3.73V.
The seventh foot is * * *. The 8th and 1 1 pins are the collectors of internal drive output transistors, and the 12 pin is the front-stage power supply terminal of TL494. These three terminals control the start/stop of TL494 through switch S as an inverter control switch.
When S 1 is turned off, TL494 has no output pulse, so switches VT4~VT6 have no current. When S 1 is turned on, this three-pin voltage value is the positive voltage of the battery.
Pins 9 and 10 are emitters of internal driver transistors, which output two positive pulses with different timing. The normal voltage is1.8v.
13, 14 and 15 pins, wherein 14 pin outputs 5V reference voltage, so that 13 pin has 5V high level, and the gate circuit is controlled, and the trigger outputs two driving pulses to the push-pull switch circuit. Pin 15 is externally connected with a voltage of 5V to form the inverting input reference voltage of the error amplifier, so that pin 16 of the noninverting input terminal forms a high-level protection input terminal.
In this regard, when the high level of 16 pin is more than 5V, the protection can be realized by stabilizing the voltage to reduce the output voltage or turning off the driving pulse. There is almost no possibility of output overvoltage in the other-excited inverter, so the 16 pin in this circuit is not used, and it is grounded through the resistor R8.
The inverter adopts a power frequency transformer with a capacity of 400VA, and the iron core adopts 45*60mm2 silicon steel sheets. The primary winding adopts enameled wire with a diameter of 1.2mm, and the two wires are wound in parallel for 2*20 turns.
The secondary sampling winding adopts 0.4 1mm 36 turn center tapped enameled wire. The secondary winding is calculated as 230V, and 400 turns are covered with 0.8mm enameled wire.
Switching transistors VT4~VT6 can be replaced by any type of 60V/30N channel MOS field effect transistors. VD7 can use 1N400X series common diodes.
The circuit can work normally without debugging. When the terminal voltage of C9 anode is 12V, R 1 can be selected between 3.6-4.7kω, or adjusted with10kΩ potentiometer to make the output voltage the rated value.
If the output power of this inverter is increased to nearly 600W, in order to avoid excessive primary current and increase resistance loss, the battery should be changed to 24V, and the switching tube can be a high-current MOS field effect tube with VDS of100V ... It should be noted that the switching tube with IDS greater than 50A is better to choose multiple tubes in parallel, because it is expensive and difficult to drive.
It is suggested to select 100V/32A 2SK564, or select three 2SK906 for parallel application. At the same time, the cross section of transformer core needs to reach 50cm2, and the number of turns and wire diameter can be calculated according to the calculation method of ordinary power transformer, or it can be replaced by the transformer in waste UPS-600.
If you power the refrigerator and electric fan, don't forget to add LC low-pass filter. 1. Q: What is an inverter and what does it do? A: Simply put, an inverter is an electronic device that converts low-voltage (12 or 24 volts or 48 volts) DC into 220 volts AC.
Because we generally use 220 volts alternating current to rectify into direct current, and the inverter has the opposite effect, so it is named. We are in a "mobile" era, mobile office, mobile communication and mobile entertainment.
In the mobile state, people not only need low-voltage DC powered by batteries or storage batteries, but also need 220 volts AC which is indispensable in our daily environment. Inverter can meet this demand. 2. Q: According to the output waveform, how many types of inverters are there? A: There are two main types, one is sine wave inverter and the other is square wave inverter.
Sine wave inverter outputs the same or even better sine wave alternating current as the power grid we use every day, because it has no electromagnetic pollution in the power grid. The output of square-wave inverter is a square-wave alternating current with poor quality, and its positive maximum value and negative maximum value are generated almost at the same time, which has a serious unstable impact on the load and the inverter itself.
At the same time, its load capacity is poor, only 40-60% of the rated load, and it can't carry inductive load (see the next chapter for details). If the load is too large, the third harmonic component contained in the square wave current will increase the capacitive current flowing into the load and seriously damage the power filter capacitor of the load.
In view of the above shortcomings, quasi-sine wave (or improved sine wave, modified sine wave, analog sine wave, etc. Inverters have appeared in recent years. There is a time interval between the positive maximum and the negative maximum, and the use effect is improved. However, the quasi-sine wave is still composed of broken lines, which belongs to the category of square wave and has poor continuity. In a word, sine wave inverter provides high-quality alternating current, which can drive any kind of load, but the technical requirements and cost are high.
Quasi-sine wave inverter can meet most of our electricity demand because of its high efficiency, low noise and moderate price, so it has become the mainstream product in the market. Square wave inverter is made of simple multivibrator, and its technology belongs to the level of 50' s, and will gradually withdraw from the market.
3. Q: What is "perceived load"? A: In layman's terms.
What is the inverter for?
The function of inverter: convert direct current energy (batteries, livestock batteries) into alternating current.
Inverter consists of inverter bridge, control logic and filter circuit.
Extension of knowledge points:
A complete inverter circuit includes control circuit, input circuit, output circuit, auxiliary circuit and protection circuit besides the main inverter circuit.
The main functions of each part of the circuit are as follows:
(1) input circuit: provides DC voltage for the main inverter circuit to ensure its normal operation.
(2) Output circuit: quality of alternating current (including waveform, frequency, amplitude and phase of voltage and current, etc. The output of the main inverter circuit is corrected, compensated and adjusted to meet the requirements of users.
(3) Control circuit: provide a series of control pulses for the main inverter circuit, control the on and off of the inverter switch tube, and cooperate with the main inverter circuit to complete the inverter function. In inverter circuit, the control circuit is as important as the main inverter circuit.
(4) Auxiliary circuit: convert the input voltage into DC voltage suitable for the control circuit. Include various detection circuits.
(5) protection circuit: input overvoltage and undervoltage protection; Output overvoltage and undervoltage protection; Overload protection; Overcurrent and short circuit protection; Overheating protection, etc.
(6) Main inverter circuit: a conversion circuit composed of semiconductor switching devices, which is divided into two categories: isolated type and non-isolated type. Such as frequency converter, energy feedback, etc. Are non-isolated; UPS, communication basic switching current, etc. It is an isolated inverter circuit.