inverter technology experienced nearly a decade of development, gradually replaced by backward-frequency thyristor rectifier technology into the era of high frequency conversion. The high frequency conversion technology process gone through its initial stage of that hard-switching PWM stages in recent years to enter its second phase, the soft switching PWM stages.
hard switching PWM converter topology. Mature technology suitable for mass production. Its main chip such as TL494, UC3525 and so more stable and reliable, which are hard-switching PWM inverter welding machine power converter is still the main reason to be widely used.
so-called hard-switching PWM (pulse width modulation), refers to the electronic switch in the power conversion process in the working conditions of the high-current or high voltage turn-on and turn-off instant, so the workpiece poor reliability , low efficiency, and electromagnetic interference is extremely serious.
so-called soft-switch technology, the device turned off at the main switch and turned on the moment, to achieve zero voltage across or current technology in power conversion technology. Is the terminology often said the ZVS (zero-voltage switching) and ZCS (zero flow switch) switching technology. Soft switching PWM power converter technology enough relative to the hard switching PWM technology is a revolutionary development, it does improve power reliability, efficiency, and electromagnetic interference (EMI) three basic performance to a considerable extent. Domestic counterparts, the development of high-power switching power supply is mostly hard-switching PWM control mode, only a small amount of soft-switching PWM, most of its soft-switching PWM phase shift control mode, the control chip, such as the UC3875 UC3879 UCC3895 , etc., using a phase shift control technique of power switching devices stress decrease the switching loss is reduced, thereby improving the overall efficiency. However, this soft switch also has many deficiencies and regret, such as:
(1) this high-power phase-shift control soft open Ge achieve soft switching is not full range;
(2) due to the presence of the circulation, switch conduction losses, light load efficiency is low, especially in the duty cycle is small, the loss is more serious,Grid tie inverter,power inverter;
(3) presence of parasitic oscillation output rectifier diode;
(4) in order to achieve the lagging leg ZVS, must be connected in series in the circuit inductance, which causes attributable reduce output capacity than the loss of space, increases the primary side current rating.
and phase shift control itself, there is a difficult to overcome the shortcomings, the deadtime bad adjust. When the load is heavy, due to the large circulation, the capacitor in parallel with the leading leg tube discharge faster, thus achieving zero voltage turn-on is relatively easy, but when the load is light, leading leg switch parallel capacitance discharge very slow , after leading leg switch must delay a long time to achieve ZVS conduction conduction.
defect of development and, to this end we absorb the traditional hard-switching PWM power converter topology, can wither the whole point is less reliable; while absorbing the shift easy to implement phase controlled soft switching PWM power converter overloaded ZVS, ZCS advantage of; launch new high-power full-bridge soft switch (FB-ZVZCS) technology to make super forearm for constant frequency width modulated control to achieve ZVS, lag arm for constant frequency constant width control to achieve ZCS. In order to achieve the super forearm the lagging arm umbrella range soft switch (FB-ZVZCS) of greatly improving the three indicators of the great merit prison switching power supply reliability, efficiency, and electromagnetic interference (EMI). Prove this control method is very good, said a revolution in the traditional hard-switching high-power switching power supply. http://www.gridtieinverter.de/
full bridge soft switching
l (FB-ZVZCS) inverter
the
shape of the system board of the high-power pulse inverter welder lemon schematic diagram shown in Figure l. The circuit board of leads 18 feet, is independently developed by the combination of analog and digital circuitry within the circuit board, this circuit is capable of forming a soft switching the desired drive pulse.
inverter control board
1.1
full-bridge soft switch (FB-ZVZCS) of the control panel internal diagram shown in Figure 2. The pin functions are described below.
pin 1 connected to the work of the power supply (UDD = 12V or 15V); the
foot 2 pick working power ground;
pin 3 is a reference power source (UREF = 5V);
foot 4 to the inverting input terminal of the voltage error amplifier; the the
foot 5 for voltage error amplifier same to the input terminal; the
pin 6, pin ll connected to the timing capacitor (CT1 = CT2); the
pin 7, pin 12 connected to the timing resistor (RT1 of < RT2);
pin 8, the feet 13, respectively to the collector of the oscillator of the discharge tube, the pin 8, pin 6 is connected a resistor,power inverter, the feet 13 on the foot 11 is connected to a resistor. Two resistor values should be equal, and change the resistor size super dead zone and hysteresis of the forearm arm can adjust the size of the dead zone; the
foot to ground by a capacitor, the capacitance from the soft-start ; the
foot 10 to the error amplifier output terminal;
feet 14 Close feet from feet can enter a 0.7V level about 4 group output are turned off; the the
pin 15 pin 16 width modulated pulse output, control soft switching full bridge (FB-ZVZCS) ahead of leg;
; feet 17 feet 18 for a fixed pulse width pulse output end the control soft switching full bridge (FB-ZVZCS) lagging leg.
1.2 inverter main circuit
full bridge soft switch inverter welding machine the primary circuit diagram shown in Figure 3. The welder input power for the three-phase power frequency AC voltage,Grid tie inverter.
works
2 inverter and waveform
waveform diagram shown in Figure 4, left arm leading leg, a constant frequency pulse width modulated excitation signal switch up and down two, right arm for the lagging leg, the upper and lower two switch excitation signal for the constant frequency pulse of constant width. Here we achieve soft switching for a brief analysis.
S1 and S4 are turned
of 2.1 primary Condition (t1 and t2), the inverter output energy to the secondary load, and then the working state and our usual way of working of hard-switching PWM .
2.2 Condition 2 (t2, t3)
S1 off, S4 to maintain conduction, because the S1 and S3
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