Well, I have designed and made a 4kW full-bridge SMPS with SG3525, with voltage control - no current control yet. Before you jump on me, remind that this is my very first SMPS project, so I am not that skilled in this stuff.
The DC output is 2x60V and it is pretty nice regulated. I use this supply to feed two 1500W tripath bridged amp modules.
And my problem is. After power-up, everything works fine. No EMI or RFI propagation. But, after a minute or so, the supply starts to produce VERY nasty and strong hi-frequency EMI into mains.
I am only using 1uF capacitors at mains - in front of the bridge and second 1uF is after the bridge.
I think it is easiest to say that I have to get some more EMI filtration on mains. Definitely I am going to. But why the noise is not propagating the first minute after power-up? I though it has sometning to do with the temperature, but it does not. Because when that EMI starts propagating and I shut the supply down even only for a second or so, it still takes about a minute to start interfering.
I think this may have something to do with transformer's saturation. Because there is a full-bridge switching, the transformer can easily come into saturation when switches are not symmetrical. I have read that this can be solved with a capacitor, connected in series with the primary winding, but I do not know the required capacitance for my supply.
Could somebody please help me and tell me if this EMI problem is caused by the transformer saturation or maybe something else?
P.S. the supply is behaving very good at normal cirstumcanses, the tripath modules hooked on have driven two 1000W woofers a lots of times before... but there is still that problem with EMI.
The DC output is 2x60V and it is pretty nice regulated. I use this supply to feed two 1500W tripath bridged amp modules.
And my problem is. After power-up, everything works fine. No EMI or RFI propagation. But, after a minute or so, the supply starts to produce VERY nasty and strong hi-frequency EMI into mains.
I am only using 1uF capacitors at mains - in front of the bridge and second 1uF is after the bridge.
I think it is easiest to say that I have to get some more EMI filtration on mains. Definitely I am going to. But why the noise is not propagating the first minute after power-up? I though it has sometning to do with the temperature, but it does not. Because when that EMI starts propagating and I shut the supply down even only for a second or so, it still takes about a minute to start interfering.
I think this may have something to do with transformer's saturation. Because there is a full-bridge switching, the transformer can easily come into saturation when switches are not symmetrical. I have read that this can be solved with a capacitor, connected in series with the primary winding, but I do not know the required capacitance for my supply.
Could somebody please help me and tell me if this EMI problem is caused by the transformer saturation or maybe something else?
P.S. the supply is behaving very good at normal cirstumcanses, the tripath modules hooked on have driven two 1000W woofers a lots of times before... but there is still that problem with EMI.