Abstract: In order to raise the frequency, reduction switching loss duplicate EMI, the resonant converter obtained the widespread pressure to use. Analyzed under the perceptual load to build the bridge inversion current supply each working pattern, the selective analysis resonance equivalent circuit, and has carried on the corresponding simulation. According to the resonance theoretical analysis and the parameter choice, have designed one kind of new entire bridge inversion current supply, this current supply has the output sinusoidal waveform to be good, the resonant component voltage, the electric current stress suitable mansion load scope wide and so on characteristics, the simulation and the experimental result have confirmed the theoretical analysis.
Key word: Exchange current supply; Entire bridge inversion; Resonance; Switch stress
Chinese Library classification number: TM46 document code: A article serial number: 0219-271 3(2005)06-0007-05
O introduction
The high frequency transformation can effectively the throttle closure converter’s volume, the weight. But has also brought the voltage peak which, electromagnetic interference (EMI), the high frequency switching loss, the efficiency low status question the high switch stress, the high-frequency transformer leakage inductance causes. But the resonant transformation has the operating frequency to be high, the switching loss is small, the efficiency is high, the weight is light, the volume is small, EMI is small, the switch should
Strength low status characteristic, therefore recently obtains the extensive research.
The resonant converter has series connected and the parallel two fundamental types. The series resonance converter has can separate the direct component, avoid the transformer being saturated as well as the underloading efficiency is high, suits characteristics and so on high-pressured undercurrent output. The antiresonance converter load may lead the way, requests to the electric capacity pulsating current small as well as suits characteristics and so on low pressure big electric current output. According to the current supply electric circuit’s characteristic, the choice antiresonance way, and further designs two level of I/C resonance network.
Under this article first part of analysis perceptual load the current supply each working pattern, the second part is to the antiresonance way theoretical analysis, the simulation research and the experimental result, the third part is two level of I/C resonance network design which improves by the antiresonance. In order to be advantageous for the analysis, does not advance the resonant network in the current supply working pattern analysis.
l current supply working pattern
The main circuit is adds the entire bridge inversion electric circuit by the first-level Buck electric circuit to be composed, like chart l shows. The Buck electric circuit through outputs the big inductance to have the approximate constant constant current, turns the square-wave current supply again through the entire bridge inversion, takes two time side power source’s electric power supply.
The false switch component has not been the ideal component, the inductance and the electric capacity is the non-loss stored energy part, line other losses may neglect, the inductance electric current “the ripple is very small, when analyzes other current waveform may think the permanent value. Regarding the perceptual load, its active status divides into 8 stages, prime task profile as shown in Figure 2. Various stages’ equivalent circuit as shown in Figure 3.
1) stage l[t0-t1] t0 time, because the load current is opposite in the reference direction for negative, in switching valve S2 and S5 parasites the diode breakover for the load current after flow, D1 and the S1 breakover gives the inductance electric current after flow.
2) stage 2[t1-t2] load current commutation, switching valve S2 and S5 zero potential clear, t2 time, iD1=0, diode D1ling electric current shutdown.
3) the stage 3[t2-t3] voltage drop is zero, Buck inductance L and the load inductance series, the load current maintains invariable basically.
4) the stage 4[t3-t4] time, S1 shuts off, the inductance electric current through diode D2, switching valve S2 and the S5 breakover, the load current maintains invariable basically.
5) the stage 5[t4-t5] time, S2 and S5 shut off, load current relative reference direction still for positive, this time, S3 and the S4 parasitic diode gives the load current after flow. D1 and the D2 breakover gives the inductance electric current after flow, the inductance and the load voltage clamp is Vdc, the load current under the Vdc function the rapid drop, inductance electric current iL because of the induction reactance but greatly only then small drop. During, S3 and S4 have the breakover signal, but load current still for positive, was still S3 and the S4 parasitic diode breakover after flow.
6) stage 6[t5-t6] time, load current commutation, S3 and S4 zero potential breakover, when iD1=0, D1ling electric current shutdown.
7) the stage 7[t6-t7]V1 voltage drop is zero, Buck inductance L and the load inductance series, the load current maintains invariable basically.
the stage 8[t7-t8]t7 time, the S1 breakover, S3 and S4 continue the breakover, Buck inductance L and the load inductance series, the load current maintain invariable basically.
2 antiresonance designs
Supposition inversion bridge output current for ‰ resonant inductance electric current iL resonance charging current iC, load current iR, then equivalent circuit model as shown in Figure 4, ip is the square-wave current supply.
In the formula ω=2πf;
ωi=iω, i=1,3,5…n.
Supposes the LC resonance angular frequency for Omega, then
Regarding turn-on frequency’s k subharmonic, the LC resistance value is as follows.
Takes ω0=ω, namely the resonance frequency is equal to the turn-on frequency, may know by type (6),|Zab|→∝,|Zab| is in reverse proportion with Q, namely the Q value is bigger,|Zab| is smaller, the filter effect is better, but on the resonant inductance, the electric capacity the electric current is also simultaneously bigger, considered in the big electric current situation, the resonant inductance, the electric capacity are not easy to design, actual electric circuit value Q≈3.
Used the PSPICE simulation software to carry on the simulation confirmation. The simulation parameter is as follows: Direct-current power supply voltage 300V, turn-on frequency l00kHz, prime factor Q=3, the loaded impedance 50Ω, the resonant inductance, the electric capacity respectively are 15.9μH, 159nF, in the simulation profile looked from Figure 5, the load current approximate is the sine wave, the harmonic component is small.
According to the above data, we have carried on the experiment to the current supply main circuit, obtains has not added the resonant network with to add the resonant network load current profile distinction like chart 6(a) and shown in Figure 6(b).
Contrast chart 6(a), chart 6(b) obviously. Added the resonant network load current profile to be improved, basically assumed the sine wave it is noteworthy that the above simulation and the experiment were do in the heavy load situation, when the load was very light, might know by type (6), the Q value was small, the resonant network effect was not obvious,
3 two level of LC resonance network design
Two level of LC resonance type electric circuit as shown in Figure 7. C1 and L1 mainly use in filtering the switch burr as well as the limit load maximum current, G2 and L2 are the main resonant networks, mainly uses in improving the load current profile, causes it tends the sine wave, reduces the electric current higher harmonic component. The current supply in satisfies the output request in the situation, selects the mean value feedback method. The sample electric current is on the filter inductance L electric current, neglects the ripple electric current.
May know by the electric circuit,
Therefore leaks from the filter electric capacity the electric current size may express is
From type (9) may understand that to regarding same assigns the output current, in the load output current is not definite, but with the load, the output frequency and the filter parameter has the close relationship. Considered the actual installment isolation actuation load is the small determination, to guarantee under any load the output current basic fixed, enlarges output inductance L, reduces output capacity C, may cause the load current close inductance the electric current, causes the load tends the anti- perceptual load, guaranteed that the load current is in some scope.
According to the above analysis, has carried on the experimental verification. The experiment parameter is as follows: Direct-current power supply voltage 300V, inversion and Buck turn-on frequency for 100kHz, C1=2.2nF, L1=115μH, C2=1OnF, L2=lOOμH. Figure 8 is the experiment obtained profile, before the heavy load and the underloading closed loop, the profile good sine, the work stable reliable, after underloading closed loop, the load and the resonant network approximate are the pure perception, the load current profile are triangular waves.
4 conclusions
This article mainly introduced the Buck electric circuit and the entire bridge electric circuit resonance current supply’s working pattern, and turns according to the resonant theory the square-wave electric current signal the good sinusoidal current signal, thus reduced EMI and raised the efficiency. To antiresonance underloading situation in resonant effect not obvious flaw, also has further designed two level of LC resonance network. The simulation and the experiment effect indicated that this resonant current supply can achieve the good results under the different load. As has the good sinusoidal waveform high frequency current mode exchange bus bar, flourishes more and more daily today in the distributional electrical power system, will demonstrate its broad application prospect more and more.
