TM 5-6675-316-14
(2) High current +5 V supply. The main high power supply provides +5 V at 24
amps with overvoltage protection and current limiting. The +5 V regulator gets the
unregulated dc voltages from pins 5 and 7 for the high-current section and pin 2 for
regulator U1.
(a) Regulator U1 compares the main +5 V output voltage with a reference
voltage and drives pass transistor Q1 through emitter-follower Q4 so that the two
Regulator U1 is referenced to both the +5 V output and the
voltages are equal.
ground (grid) sense terminals. These are tied directly to the load and bypass any
losses in the winding.
(b) Pin 6 on regulator U1 provides a +7.15 reference voltage which is
divided by R7-R9. Trimmer R8 allows an adjustment range from +4.6 to +5.4 V on
regulator Ul, pin 5. Regulator U1 drives the output so that the voltage on pin 4
equals that of pin 5. Since pin 4 is tied to the +5 V sense lines, and in turn to
the LOAD, then the load voltage will equal the voltage set on pin 5.
(c) Regulator U1 is also used in the current-seeking mode. Pin 11 seeks a
current proportional to the output demand. This current is sensed by the base of
pass transistor Q1, and its collector current drives the bases of emitter-followers
Q2, Q3 and Q4. The emitters of these transistors are tied together through 0.04 ohm
resistors to ensure current sharing.
2-71
