ElectronicStage
Locomotive Controllers    --   The Power

The technical exposure of Locomotive Electronic Speed Controllers

The following diagram shows a typical Darlington pair power stage -
this is the standard power stage used by most British Locomotive Electronic Speed Controllers Manufacturers. It is the standard found in just about
every book written on Electronics for Model Railways. It is often shown
in Roger Amos's --  Complete Book of Model Railway Electronics.

This is very obsolete technology -- for motor speed control.

This is a fully integrated power IC -- a one chip complex performance Power Stage.
It replaces the two transistor darlington power stage -- shown above.
This IC contains 25 transistors, 4 zenner diodes, 3 on chip capacitors,
and 27 resistors.
It has multi functions:-
1. It regulates the output voltage to 0.1%.
2. It limits the output voltage to a adjusted 0.1%. Important for Z and N
3. It has  many internal voltage,  current, and phase control loops.
4. Due to the multi tailed transistor configuration -- very low output impedance.
5. It produces a excellent controlled voltage/current  transference ratio.
This will give excellent slow speed locomotive control. Performance a darlington
power stage cannot possible  match.
6. It will handle 1.5 Amps as a load to a 35 volt limit.
7. With external power devices -- and subtle electronic design it will control
a 100 Amps if needed.
8. It is a smart chip-- it will monitor its  voltages, current and internal
temperature -- should it see a short circuit on the track it will shut down electronically
very fast. It will also shut down on over voltage and over temperature.
This provides a bullet proof electronic system.