Reference Supply, O- to 500-Volt Dc

TM 11-6625 -537-14-1

5-4. Reference Supply, O- to 500-Volt Dc

p o r t i o n of the output with the voltage of a

standard cell. The reference range voltage divider

a. Block Diagram (fig. 5-4). The O- to 500-volt

uses resistor divider networks to obtain voltages

dc reference supply consists of a 500-volt dc

of 50, 5, and 0.5. These voltages are selected by

reference supply, a reference voltage range

the RAN GE switch and applied to the precision

divider and a precision voltage divider. The 500-

voltage divider which divides the input reference

volt dc reference supply is a conventional series

voltage into 500 equal steps.

r e g u l a t e d power supply with single stage

r e g u l a t i o n , It is calibrated by comparing a

Figure 5-4. 0- to 500- volt dc reference supply, block, diagram.

V101. Voltage divider R102 and R101 maintains

b. 500- Volt Dc Reference Supply (fig. FO-3].

Voltage from a 284 volt secondary winding of

the filaments of V101 and V105 at approximately

400 volts dc to prevent breakdown within the

p o w e r transformer T1 is converted to ap-

proximately 700 volts pulsating dc by a half-wave

tubes. The output of the power supply is set to

voltage doubler. During the positive half cycle,

500 volts by comparing a precise sample of the

CR101, CR102, and CR103 conduct to charge

o u t p u t voltage, o b t a i n e d from divider string

C 101 to the peak output voltage of the secondary.

R316, R317, REF CAL ADJ R318, and R319,

During the negative half-cycle, CR106 and CR107

w i t h the voltage of standard cell B1. In the

conduct to charge C102. Resistors R109 and R110

CALIBRATE position, levels A and B of

maintain equal voltages across C101 and C102 to

OPERATE-CALIBRATE switch S4 connect the

prevent dielectric breakdown. The voltage applied

dc vtvm to indicate the difference between the

to the plate of series passing tube V101 is the

standard cell voltage and the divider string. REF

total of the voltages across C101 and C102. The

CAL ADJ R318 allows the divider string to be

grid of series passing tube V 101 is controlled by

calibrated. When properly adjusted, the output of

differential amplifiers V104 and V105. Amplifier

the 500 -volt dc reference supply is 500 volt dc

V104 compares the voltage of reference tube V102

( +0.2). R e g u l a t i o n of the power supply is

with a sample of the output voltage obtained from

0.0025 percent for a 10-percent change in line

d i v i d e r string R123, C106, R124, R121 and

voltage.

c. Reference Voltage Range Divider (fig. 5-5).

C A L I B R A T E R2. The output voltage sample,

The reference voltage range divider consists of

along with the output of the power supply, is

resistance divider networks selected by RANGE

adjusted by CALIBRATE control R2. Capacitor

switch S2F and AC-de polarity switch S5G. For

C106 in the divider string decreases the sen-

t h e dc mode of operation, the output of the

s i t i v i t y of the regulator circuit to very rapid

changes in output voltage to prevent oscillation

reference voltage range divider is 500, 50, 5, or 0.5

within the supply. The outputs of V104 are ap-

volts as determined by the setting of the RANGE

switch. Level E of RANGE switch S2 connects

plied to a second differential amplifier V 105. Plate

the selected voltage divider resistor string to the

voltage for one-half of V 105 is obtained directly

output of the 500-volt dc reference supply and

from the output voltage of the power supply.

level F connects the selected divider string to the

Plate voltage for the other half of V 105 is ob-

precision voltage divider. When RANGE switch

tained from the unregulated dc through dropping

S2 is set to 500, the output of the 500-volt dc

resistors R114, R118, and R119. Capacitor C105

reference supply is directly connected to the

and resistor R 119 act as the plate load. Regulator

precision voltage divider and R322 is connected

V103 will conduct to prevent the entire

across the output of the power supply to maintain

unregulated dc voltage from being applied to

a minimum load on the power supply. Resistors

V105 if V101 ever fails. The output of V105 is

50 VDC ADJ R323, 5 VDC ADJ R326, and 0.5

applied to the control grid of series passing tube

5-7