Abstract: Proposed one kind of novel active clamp ZVS-Boost converter. Through uses an auxiliary pipe and a clamp electric capacity, may, in does not need to add in any magnetic elements’ situation, causes the manager and the auxiliary pipe realizes ZVS. In order to eliminate the rectification diode’s voltage ringing, increased a diode. Trial produced a 50tlW/193 kHz prototype to confirm the theoretical analysis. When inputs 90 V full loads the efficiency is higher than 94%.
Key word: Active clamp; ZVS; Boost
Chinese Library classification number: TM46 document code: A article serial number: 0219 2713(2005)06-0012-05
0 introductions
In high efficiency domain, to realize the high power factor, low input current THD, applies the broadest electric circuit analysis situs is the Boost analysis situs. But this kind of technology’s biggest shortcoming is the rectification diode restores the question reverse. The diode restored reverse has prevented the turn-on frequency, the power density and the efficiency enhancement. In order to raise the efficiency and the power density, in recent years proposed this technical [1][2][3][4][5][6] improves this kind of situation. Used two coupling input inductance [1], the rectification diode restores reverse was improved, moreover the electric circuit was quite simple. But the switching loss was still high, and on diode’s voltage ringing is big. Uses auxiliary quality is guaranteed or the item will be replaced class electric circuit [2], although the manager may realize ZVS, but the auxiliary pipe is the hard switch. In literature [3], although the manager and the auxiliary pipe may realize ZVS, but as a result of the rectification diode’s parasitic capacity, enables the rectification two to move the tube withstanding voltage ringing. Uses auxiliary clamping diode [4], the voltage ringing may eliminate. Uses the active clamp, all switches can realize ZVS[3][6], but the manager and the auxiliary pipe serially connect in together, on switching valve’s breakover loses big [5], but in literature [6], the active clamping circuit is too complex, the primary device number which uses are relatively many. This simultaneously will increase the cost and the breakover loss. To simultaneously reduce auxiliary circuit’s primary device quantity and the breakover loses, this article proposed one kind novel comes based on active clamp ZVS-Boost converter’s single-phase power factor adjuster (PFC) to improve the above question effectively. In does not need to add in any magnetic elements’ situation, causes the manager and the auxiliary pipe realizes ZVS, eliminated the rectification diode’s voltage ringing, raised the efficiency and the power density.
1 electric circuit key job principle
Electric circuit schematic diagram like chart l shows. Two input coupling inductance may use in common a ferrites magnetic core, the coupling inductance leakage inductance indicated with Lik that this leakage inductance uses for to reduce Boost diode Dt the reverse restoration. Coupling inductance’s ratio-turn may ≥l. Electric capacity Cc is uses for in a switching period for the leakage inductance Lk charging and discharging, therefore the Cc value is big, and on the Cc voltage maintains a constant. Electric capacity Cs1, CDc, Csa, CD1 is the switch and diode’s parasitic capacity. Auxiliary pipe Sa and the clamp second-level manage D1 to use for to eliminate Boost rectification diode D1 the ringing. In order to simplify the analysis, on supposition clamp electric capacity Cc voltage Vc maintains invariable in one cycle, simultaneously neglects Lin1 and the Lin2 ripple electric current, and takes N1:N2=1 to analyze this electric circuit’s principle of work.
The electric circuit may divide into 8 different working patterns in one cycle, profile as shown in Figure 2. Figure 3 gave has been opposite in Figure 2 the profile equivalent circuit. Below does to each working pattern explained specifically.
Pattern l[t0-t1] in the t0 time, is in charge of the S1 breakover, input potential source Vin gives the inductance Lin2 charge. This time electric current i2 was equal to that the iin energy storage in inductance Lin2, saves on inductance Lin2 the energy in the t0 time section as a result of the coupling, transmits inductance Lin1 completely. This time, does not consider the ringing influence, D1 and on the auxiliary pipe Sa voltage is (Vo Vc). This stage when t1 time S1 shutdown finished.
Pattern 2[t1~t2] in the t1 time, S1 shuts off, all parasitic capacity starts the charging and discharging in this period of time. When S1 parasitic capacity Cs1 sufficient voltage vCs1 achieves [Vo Vc], this stage ended. The Vc voltage may through type (1) computation.
In the formula: fs is the turn-on frequency;
D is a dutyfactor.
Pattern 3[t2~t3] when t2 the time vcs1 voltage imitates to (Vo Vc). D1 and Sa body diode breakover. Realizes Sa ZVS. In the t2 time, the parial currents wind through clamping diode Dc, this time iDc=iin×CD1/(CD1 Cs1 Csa). Because CDc compared to other parasitic capacity small many, therefore may ignore. In this stage, electric current iDc reduces by slope - Vc/Lik, simultaneously i2 also by reduces with the iDc similar slope. When iDc drops the zero hour, this stage ended.
Pattern 4[t3~t4] reduces the zero hour in t3 time iDc, clamping diode Dc shuts off, i2 continues by slope - Vc/Lik to reduce, when i2 reduces to - Iin, this stage ended, this time i1=2Iin.
Pattern 5[t4~t5] in the t4 time, Sa shuts off, this time parasitic capacity Csa and Cs1 charge separately and the electric discharge. When the vsa voltage achieves (Vo Vc), the S1 body diode breakover, this stage ended.
Pattern 6[t5~t6] is in charge of S1 in the t5 time the body diode breakover. Realizes S1 ZVS. Meanwhile in the t5 time. D1 and S1 trade the class to start, when the iD1 electric current reduces the zero hour, this stage ended.
Pattern 7[t6~t7] in t6 time iD1=0 this time parasitic capacity Cd1 with the leakage inductance Lik resonance, when on D1 voltage vCD1 is a zero hour, this stage ended.
Pattern 8[t7~t8] in t7 time vCD1=0, the resonant time finished, this time, Dc breakover. Then as a result of the resonance, Iin and the i2 differential value electric current winds through Dc, and by the slope - Vcs/Lik reduction. When iDc=0, this stage ended.
Here only introduced that one cyclical the working condition, the next cycle is similar to this cycle circulates equally, does not give redundant showing in here.
2 experimental results
In order to confirm the above principle of work and the theoretical analysis, made an input to direct current 90~150V, output to direct current 350V, power 500W, the frequency 193 kHz DC/DC converter prototypes. In this electric circuit uses parameter like table l arranges in order, what all parameters and in the Figure I main circuit labels is corresponds. Figure 4 and Figure 5 has given the responsible and auxiliary pipe’s ZVS work process, from the chart may discover that was in charge of S1 and auxiliary pipe Sa has realized ZVS, and they leaked a source voltage clip about DC 440V. Figure 6 has given the rectification diode D1 voltage waveform, might see on diode’s voltage ringing from the chart to eliminate by clamping diode Dc. Figure 7 has given in the full load situation, winds through Lin2 the electric current. Figure 8 has given the auxiliary pipe sa current waveform. Figure 9 gave has been in charge of S1 the current waveform. These profiles with the above theoretical analysis basic consistent. Figure 10 has given the efficiency curve, when inputs 90V, the efficiency is highest about 375W, but when the 150V input, efficiency when 475W is highest.
3 conclusions
This article proposed one kind of new ZVS-Boost the DC/DC converter, the experiment came out well has confirmed the theoretical analysis. Uses a simple active clamping circuit, all switches have realized zvs, has realized the high efficiency under high frequency. This kind of converter may also apply in the power factor adjustment aspect, is opposite adjusts in the traditional hard switch CCMBoost power field number, it has a high power item of number, high efficiency and low cost merit.
