I just ran across an unusual (maybe oddball) Class D design that uses two TDA8927 in a parallel/bridge configuration. On paper, this thing cranks out around 250 W. I am somewhat skeptical about actually making this thing work. I've attached a schematic of one side. The other side is identical, but obviously runs out of phase to get the bridge mode. But looking at this half, there are a couple things that make me queasy. First is the summing of the two outputs through some chokes in the LP filter. Usually I like to see a 0.1-Ohm resistor in series with each output to keep the amps from fighting each other. But assuming the chokes have at least 0.1-Ohms resistance, my next concern is the feedback loop to the controller. Instead of summing the two outputs through a resistor network, only one output is fed back. Seems like this design assumes the two amps are absolutely identical. We all know this is never the case. Bottom line, I think this design is just asking for trouble. Any opinions?
As always, thanks in advance.
As always, thanks in advance.
An externally hosted image should be here but it was not working when we last tested it.
Consider that output transistors are 0.2ohm typ. MOSFET working as switches and with some dead time.
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