Quote:
Originally Posted by Matt L
The stock regulator has a power transistor that controls a partial load by imposing a constant restriction to the current. That is, the transistor runs at a partial conductance at all times.
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Check out this thread
http://www.peachparts.com/shopforum/showthread.php?t=76998
We disected a MB regulator both mechanically and simulation wise.
Quote:
Originally Posted by Matt L
Computer power supplies have a similar circuit to control the voltage to the system . . . they use what is called a "switching" supply, which runs the transistors with either zero or full conductance. When you quickly switch a MOSFET to control the power (with PWM, for example), the only time the MOSFET actually uses any power is during the switch itself, and that switch is very, very fast.
If you never have partial conductance, you aren't doing any work and you don't have to release heat. Computer power supplies went this way to save power. Of course, since the MOSFETs aren't perfect and do actually have a (small) switching time, there is some heat released. But that heat is minimal compared to a similar circuit using a bipolar transistor in partial-saturation mode.
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The difference is that a SPS starts with "AC", not DC. It's a whole different ballgame b/c you need an inverter. They are tough on power, ie not very efficient and so you require more power than would a standard regulator.
Power is power and it has to be the same amount that's delivered to the load. You may save some 'heat' via switching but 'eat' power b/c of the inverter. So heat
is generated. Since they are recalling the devices, they are NOT 'heat-less'!
We tried one at my tech's shop and came to the same conclusion; it was replaced w/ the latest version MB regulator.