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Old 15th July 2009, 08:09 PM   #1
81bas is offline 81bas  Germany
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Default topology similar to BCA

Hi!

Simulated the following schematics (in attachment) in LTspice. It is very similar to BCA topology in first look, but works others. Mosfets are switched in antiphase - similar to usual class d output stage (had no spice model for IR2110, so had to build own driver ). Output inductors are on the _same_ core. There is no dead time at all. Even little bias required to avoid distortions. Advantage is that body diode does not limits the dV/dt of opposite mosfet. Also, usual halfbridge driver can be used here. I have not built it yet, but simulation does not shows any problems. Don't know, where I have seen this.
Any thoughts?
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Old 15th July 2009, 10:25 PM   #2
Pafi is offline Pafi  Hungary
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Hi!

I'd say this is BCA topology yet, only different modulation. Output inductors can be on the same core, but they have to be coupled weakly. I've built this some years ago, it works fine.

In reality I had a little trouble with dead-time, because I used IR2110 to drive 140 nC gate-charge with Vcc=12V, and it could switch the mosfets on almost immediately, but gate discharge needed much more time, so I had to make a little dead-time, wich was not so easy since I haven't prepared the PCB for this.
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Old 21st July 2009, 03:20 PM   #3
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What happen if the inductors are separated / not on the same core?

What is the purpose of R1=100ohm?
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Old 22nd July 2009, 09:08 PM   #4
81bas is offline 81bas  Germany
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Hi!

Sorry for the long silence... had no possibility to simulate and investigate this more precisely...

Now I have tried various configurations with this schematics. There is no practical purpose of R1, as I found from simulations. Also, when L1/L2 are not on the same core, then opposite side periodically goes into free wheeling state (i.e. has no any current). This causes a big distortions then. In attached image the blue line is the input signal (corrected in phase) and yellow is output signal from NOT coupled variant.
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Old 10th September 2014, 09:37 AM   #5
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Have you taken into consideration the circulated currents in the freewheeling diodes with this topology?
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