Why someone didnot suggested, the use of auxillary full floating high side supply of 15VDC with reference to source of high side mosfet. Any problem associated with, i think is common mode filtering issues only.
Iyremenko said:
That would be also great solution, but in that case it needs to be placed near the high side mosfet to get lower EMI
Another simple solution that would not even have to be isolated would be a flyback converter consisting of a coil that is connected to the low-side driver supply with its first leg. The second leg is periodically pulsed low to the lower rail by a small FET and it's freewheeling current is "discharged" to the high-side bootstrap capacitor via a small and fast diode.
Regards
Charles
Regards
Charles
phase_accurate said:
How about using the clock[assume a forced clock design] itself in providing pulse for driving isolated transformer for floating supply need, just drive the clock into set of buffers powered from preamp +/-15V supplies and their outputs attached to the floating tranformer primary and you have 2 sets of isolated voltages in handy!!!
I would not even dare to use anything else than the amp's clock to do this ! 😎
An isolated supply has the disadvantage that it relies on isolation. This is not difficult to achieve from a DC point-of-view but rather tricky regarding the capacitive coupling between primary and secondary.
A non-isolated flyback circuit would not be susceptible to such problems.
Regards
Charles
An isolated supply has the disadvantage that it relies on isolation. This is not difficult to achieve from a DC point-of-view but rather tricky regarding the capacitive coupling between primary and secondary.
A non-isolated flyback circuit would not be susceptible to such problems.
Regards
Charles
phase_accurate said:
I was not referring to 250Khz clock for amp, but i was referring to the lower frequency sync clock generated from the same clock driver.......😉
Can you more ellaborate on capacitive coupling between pri-sec disadvantage in class-D......
Kanwar
Well - the coupling capacity of your transformer is acting like a capacitor between the switching output signal and ground. This might result in quite high current spikes.
Regards
Charles
Regards
Charles
Most probably into the signal ground of the control stages of your amp - since you want to feed this auxiliary PSU from the low voltage rails.
Regards
Charles
phase_accurate said:
Ok....thats very good point ........
So you are against contamination of signal ground😀
thanx
I think we can also power the flyback from the main rails and then use isolating DC-DC converter to get 2 X +15V for hi & lo sides respectively......without taking the ground in to play!!
phase_accurate said:
I have to disagree on it now.......after testing one of the reputed Class-D amps in real life with isolated gate driver voltages obtained from +15V preamp supplies......there is no trace of current spikes anywhere.....
The amp which was tested is from Powersoft
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