Step 8: Protection module
While comparing our amplifier setup procedure with the purchase of a car (where this procedure is generally accepted), we also have to mention the safety.
Of course we are not talking about seat belts, airbags, crash zones, etc. but checking if your amplifieer is working correctly or overloaded somehow.
We are a small company, developing our audio- and power supply modules in an extremely fast rate. Simply because they all (and more) are in our designer's head already for years. But, transferring these idea's into your head by writing costs a lot of time unfortunatelly. In former chapters you probably read a lot already.
One of those things we believe has to come as well, but last is a safety module checking if your amplifier is working correcty and if not, switching it off in a safe manner. We are working on a module like this and all our designs are already equipped with a connector where it will fit! Instead of the disconnecting device there is standard a fuse now and any amplifier will also work without this protection module. We simply need more time to find out if it's working with all kinds of combinations properly.
In about all protection circuits, a relay is disconnecting the speaker from the faulty amplifier. Error detection is mostly very simple and NOT controlling all possible faults! Our protection module checks following faults:
Distorted output (input and output signal are compared). LED indication
Overload / broken Mosfet error ( Currents of max. 4 Mosfet pairs, all 8 sepertely are checked). LED indication.
Over temperature is checked, both heatsink and interior. LED indication
If one or more errors occur, a master error LED will flash as well in a mixed rate, so you can leave out the other three. We use this master error indication in our High-End amps to blink a red circle around the on/off switch. In PA-amplifiers we also use the other three, so the technician can decide what to do, before the amp will shut down itself. F.e. lowering volume, giving it more ventilation, etc. For truly high power purposes you also can (dis)activate an external relay circuit taking away the power and/or disconnecting the speaker in any way you design it.
We are NOT disconnecting the speaker by use of a distorting relay contact, but seperate the amplifier module structure from the Power supply part by use of Hexfets. The possible supply capacitors on the amplifier module itself is at the same time discharges very fast, yet controlled. It is done that fast, that a connected speaker will not break down, even if the amplifier has a burned power transistor causing the full supply voltage at the output. More about our Protection module soon, but we are working on it:
Preliminary PCB drawing, still in development phase. But you have an idea….