Welch Allyn PneumoCheck 61000, Service Manual

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32 Pneumocheck Handle and Printer/Charger Service Manual 610132 Rev. E
The 24 volt output is fed into a divider network made up
of R27 and R28. The output of the divider network is
then fed into the error amplifier, ERR1. The 5 volt
reference voltage is reduced through a divider made up
of R37, R38, and R39 to 2 volts, and also fed into ERR1.
The difference voltage is then used to correct the 24 volt
output voltage.
The output current is limited to 2.5A by comparing the
voltage across R29 and to the 0.5 volt output of the
reference divider network.
A soft start circuit made up of C18, R31, and R38
causes the regulator to wait about 50 clock cycles
before the transistor control pulse width is increased to
its normal duration.
Section 3 - Theory of Operation