In the one that publish before ” Static induction thyristor SITH Applied research ” In the article, we have studied the basic characteristic for producing SITH device in China, and developed four kinds of driving circuit. Driven by these four kinds of circuit, SITH device made the switch speed under 0.2 ms. Expand actual switching power supply, employ the circuit together driving circuit and the intersection of SITH and device further now, through testing, have received more advanced performance index. In this way, the applied research to SITH device is more overall, lay a sturdy foundation to its popularization and application.
2 circuit is studied
2.1 Employ the circuit 1
Application this one switching power supply in circuit, design and in view of following several points concerns: 1Employ the direction to high-power such as speed governing of the electrical machinery, temperature control, is confirmed to be AC-DC and varied, refer to and exchange the Voltage by One Phase 220V mains frequency electric wire netting for 50 weeks here AC; 2This power input must be above the high power factor 0.95, it also must be the low noise, accord with or is superior to the national standard; 3This power of efficiency demands to be above 90%; 4Can reflect the advantage of SITH tube, avoid its weakness.
Have adopted BOOST to vary the form Fig. 1 here . R1 in the picture: 1k; R2: 20; R3: 10k; R 4: 5k; R5: 5k; R6: 800k; R7: 10k ; R8: 20k; R9: 1M; R10: 0.2 ; R11: 50k; R12: 10k; C1: 0.01mf; C2: 200pf; C3: 0.1mf; C4: 50mf; C5: 100mf/400V; C6: 2mf/~250V; C7: 2000pf; D1: 12V/0.5W voltage stabilizing diode; D2: 3A soon extensive diode HER308; D3, D6: 2A/400V rectifier bridge; Q1, Q3: Npn triode 8050; Q2: Pnp triode 8550; Q4: VDMOS 10A/30V; L1: 2mH/ 1A high-frequency inductance; L2: 2mH/ 1A high-frequency inductance; IC: UC3852.
Detailed operating principle of UC3852 please consult relevant materials, Company of Texas Instruments. The one that should pointed out emphatically is, UC3852 is a kind of special control chip of switching power supply for improving the input power factor, its basic principle is to work under being far higher than the frequency of 50 weeks, control the gas switching tube to turn on an invariable time Ton, the inductance L2 bears and all exchanges the input voltage Vin while turning on. At the end of Ton, inductive current, only input current I in =Vin /L2 *Ton, so Iin is proportional to Vin. Then, UC3852 makes the gas switching tube shut off, L2 discharges to the load end, Iin presents linear attenuation, when UC3852 detects Iin decays to zero, control the gas switching tube to be turned on again, enter the next Ton, see Fig. 2.
In the picture, the upper portion is a drive waveform of UC3852, the high level drives the gas switching tube to be turned on, time Ton of the high level is invariable; The underpart is the input voltage Vin and inputs the wave form in the electric current Iin. Within Ton interval of time, Iin rises linearly, the anabatic speed is proportional to Vin value at that time, because start from scratch each time, the crest value of Iin is proportional to Vin. In fact, the operating frequency of UC3852 is much higher than the ones that showed in the picture, about 25kHz. So can be thought on each triangle sector Vin to be invariable, then the mean value of Iin is proportional to V in, low-pass through L1, C6 to strain the wave rear, the input current waveform keeps the same with input voltage, then the power factor must be very high. This is a simple operating principle of UC3852.
The circuit parameter of Fig. 1 forms one to export as the circuit of 100W, SITH tube is a main switch, adopt the driving circuit 1 Scheme,by Q1, Q2, Q3 and Q4 last SITH the driving circuits of the tubes; L2 is BOOST inductance; C5 is the Filtering capacitance of the output; R 6, R7, R8, R9 and C3 makes up the backfeed loop, for UC3852 to adopt, controls and exports the voltage stabilization; R12 and C7 are the time circuit of UC3852 operating frequency, are fixed on about 25kHz here; L1 and C6 are low-pass filters, prevent the high-frequency composition in Iin from passing the electric wire netting back; R 10 is that the electric current sample the resistance, provides the waveform of Iin for UC3852.
Can be found out from the waveform of Fig. 2, this is that a electric current is not the continuous mode, its advantage is that the gas switching tube always begins to be turned on from the zero-current, reach the double average current finally, thus make SITH tube avoid turning on the slow weakness and develop its advantage with good high-current characteristic. It makes the diode D2 not bear back pressure in the forward current until after zero again, has avoided the question lossed in backward recovery. The function of D2 is to prevent the electric capacity C5 of the output from discharging to L2 and SITH tube, it was load current that it flowed through forward, and that bore backward is 400V voltage. D2 use extensive diode soon of moderate speed test, temperature rise is very low. It is circuit job requirements consult the relevant materials of Texas Instruments Company that the output voltage fetches 400V ,Therefore is irreducible. SITH tube bears the back pressure of 400V too during shutoff, excess is relatively great for it, it is advantage too.
Measure its major indicator as follows: Input voltage: AC220V 50Hz; Input current: 0.58A; Input power: 111W; Power factor: 0.95; Output voltage: DC410V, the peak-to-peak value of the ripple: Vpp =20V; Export the load resistance: 1610; Output power: 104W; Efficiency: 0.94. In view of this, SITH device and driving circuit have met the demands, the result is satisfactory.
However, SITH tube probably has about 3.5W of tubes that dawdle while working, it is the only device to have obvious temperature rise in the circuit. SITH tube used in the circuit is that TO-220 capsulate, adds 50mm * 60mm air-cooling fin at first, starting up is 50 of Damien of temperature rise of interior surface of 5 minutes, the input power has increased 3W. Later, use with fan the intersection of CPU and heat sink instead, the intersection of fan and the intersection of power and 1W, after the 15 minutes such as starting up, the surface is not yet far over 5 of temperature rise, the input power is about 111W all the time. Therefore can be thought, SITH tube, like other electric devices, the switching loss is raised and increased with the temperature. If does not dispel the heat well, will form the vicious circle. The frequent high temperature difference change will also make flux embrittle too early, makes weld quality deteriorate. It is to guarantee reliability, guarantee the efficient most effective and most important means so dispel the heat well. Because SITH tube has stronger flowing capacity, under dispelling the heat well, needn’t adopt and ” lower the capacity to use ” Classic method,it is all right device when it is equal to working rated value in current rating since it choose, do not influence reliability in order to lower costs.
2.2 Employ the circuit 2
Employ the circuit 1 Output voltage fixed direct-flow 400V,can’t flexible to change, be with inputting and isolating, often need to add the circuit of final-stage. Circuit of this application 2 It is on the circuit 1 Unless change in foundation, it is isolate to export,can regulator voltage,last 3 Fig.s. In the picture: R1: 1k; R2: 20; R 3: 10k; R4: 5k; R5: 5k; R6: 800k; R7: 10k; R8: 20k; R9: 1M; R10: 0.2; R11: 50k; R12: 10k ; R13: 20k / 3W; R14: 40 / 10W; C 1: 0.01mf; C2: 200pf; C3: 0.1mf; C 4: 50mf; C5: 2000pf / 400V; C6: 2mf / ~250V; C7: 2000pf; C8: 0.1mf / 600V; C9: 3000mf / 50V; C10: 2mf / 400V; D1: 12V / 0.5W voltage stabilizing diode; D2, D7, D8, D9: 3A soon extensive diode HER308; D3, D4, D5, D6: 2A/400V rectifier bridge; D10: 46V / 1W rice presses the diode; Q1, Q3: Npn triode 8050; Q2: Pnp triode 8550; Q4: VDMOS 10A/30V; L1: 2mH/ 1A high-frequency inductance; L2: 2mH/ 1A high-frequency inductance; L3: 500mH/ 2A high-frequency inductance; Tr: High-frequency voltage transformer; Turns ratio: 2:1* 2; IC1: UC3852; IC2: Photosensitive resister 521-1.
This circuit parameter is the direct current power supply that 48V/100W exports. Its operating principle and circuit 1 Similarly, but it becomes directly that exchange the rectangular wave that the output leaks SITH tube the polar direct-flow rectangular wave and cuts with electric capacity C 10, the ones that sent to the voltage transformer Tr are elementary, then has coupled to the second order and changed the voltage, and then filter exporting through commutating. The second order is divided into two coils, pass different filtering links of rectification separately, this is because through the exchange rectangular wave of C10, it is not symmetric, actually inductance L2 discharge on some forward directions, it is the current source, commutate with the first half of the secondary; Some negative-going actually C10 discharge, it is the voltage source, commutate with the latter half of the secondary.
The turns ratio which changes Tr can get the required output voltage, isolate with inputting the electric wire netting too. The photosensitive resister 521-1 is the isolation element of the negative feedback. D2, C5, C8, R13, R14 make up the absorbing circuit of overshoot, because of the reason of leakage inductance, when the voltage transformer is accepting the pulse of current source, overshoot is very strong, very unfavorable to the device, still cause the high-frequency noise greatly at the same time, must dampen it. The absorbing circuit can dampen overshoot effectively, but show by a large number of tests, such damped energy consumption is quite large, regard reducing efficiency as cost. Should consume about 6W of power to absorb links in this test, overshoot still accounts for 25% of the dominant wave, make efficiency drop from 91% to 84%, there is an obvious heat source on the breadboard. So before solving the high-efficient absorption problem, this circuit should consider in low-powered application.
2.3 Employ the circuit 3
This is an AC switch, transferring the load of 1000W, it is very wide to employ. The original document is made up with the silicon controlled rectifier or bidirectional thyrister, is replaced with SITH tube now. It has a function shut off in opening and zero crossing, in order to reduce the impact to electric wire netting, can shut off immediately too while needing. Because of using SITH tube, just forces to shut off, namely the function that shuts off fast. This can not be made of silicon controlled rectifier or bidirectional thyrister, it can use with one-chip computer. Only offer some schematic diagrams Fig. 4 of heavy current here . In the picture: R1, R2: 1k; R3: 10k; R4: 200; R5, R6, R7: 5.1k; C1: 300mF /16V ; D1, D2: 10A/400V kenotron; D3, D4, D5: 1N4001; Q1, Q2: VDMOS Ron =0.05W : IC1: LM393 one pair of comparators; IC2: CD4013 D flip-flop; IC3, IC4: Photosensitive resister 521; Tr1: Power transformer 220V/9V * 2- 3W.
In the picture, SITH tube connects in series instead, and each connect with a diode in parallel instead, SITH tube shoot-through or shutting off at the same time, formed the AC switch. IC1 comparator has produced a pulse signal, as the clock signal of IC2 D flip-flop, so IC2 can only change the output during zero crossing of the alternating current voltage. A pair of complementary output of it controls grid pouring into and VDMOS tube of SITH tube separately, just controls the zero crossing of the AC switch to be turned on and shut off. R forcing to shut off signals and directly control the D flip-flop resets the end, shuts off the AC switch immediately. The control signal is input through the photosensitive resister, this is for preventing the interference.