Functional Description - Main Outputs - TTI PL Series Service Manual

Functional Description – Main Outputs
The relationship between the major circuit elements is shown in the block diagram opposite.
The transformer incorporates two secondary windings, one which produces the main supply
powering the output, and another which produces an auxiliary supply powering the control and
metering circuits.
The series regulator is placed in the positive output of the main supply, but because of the way in
which the control and metering circuits operate, it is convenient to label the output of the series
regulator as 0 volts, and to regard the negative side of the main supply as being the controlled
output voltage (-V out).
The auxiliary supply provides stabilised symmetrical voltage outputs V+ and V- with the common
point connected to the +ve output.
The series regulator is controlled by the 'voltage control circuit' until the output current flowing
reaches the current limit setting, upon which the 'current control circuit' takes over. The voltage
control buffer amplifies and provides low output impedance from the voltage controls.
The input to the voltage control circuit is from the control buffer, or from the master output on the
slave side of PLQMD/PLQMT units.
The 12 bit A to D measures output voltage and either preset current or output current selected by
the multiplexer.
The micro-controller reads the output of the A to D and drives the appropriate display.
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