Static Inverter Circuit Description - continued

TM 11-6125-259-30

capacitors, etc. In detail, when the nominal +37 V

charge reaches a high level, the positive

at capacitors C401A and C401B reaches a low limit

voltage at camparator Z703-C input pin 4

it is sensed and corrected as follows. The low voltage

overrides the input at pin 5 and sets com-

output at capacitor C401A and C401B goes across

parator Z703-C output to low. In addition, the

resistor divider network R731, R732, R733 and

total amount of choke L201 current flow

R734. This voltage is compared with zener diode

through transformer T201 winding 7-8 also

CR707 reference voltage by comparator Z703-B.

effects the charge-up of capacitor C705. The

The output of comparator Z703-B is positive and

more current flow, the more voltage induced

goes to input pin 5 of comparator Z703-C and when

into the secondary of T201 which adds to the

it is a higher positive amplitude than the positive

voltage sent to capacitor C705 thus the less

time choke L201 center tap is shorted to

amplitude from capacitor C705 at input pin 4 of

Z703-C (to be explained below), then Z703-C output

ground. Note that during the time needed to

is high. This high will set comparator Z703-D

charge capacitor C705, choke L201 center tap

output to high which results in the following:

is being shorted to ground and the choke is

storing up energy to later be fed to capacitors

q 2701 nand gate input pine 1 and 2 are high

C401A and C401B for the +37 vdc supply.

causing a low at output pin 3 which sets flip-

This low established at comparator Z703-C

flop Z702 output pins 12 and 13 to the opposite

output will cause a low at comparator Z703-D

states (i.e., if pin 12 was high and pin 13 low,

output which in turn will cause all power

then pin 12 is now low and pin 13 high). This

switch transistors Q206, Q207, Q208, Q306,

causes Z700 nand gate output pins 3, 6 and 8,

Q307 and Q308 to be turned off (described in

11 to switch to opposite states so that trans-

detail below) thus removing the center tap of

isitors Q701 and Q700 now go to opposite

both chokes L201 and L301 from ground.

states from the lst cycle in which one of them

Therefore, chokes L201 will no longer store

conducted. Note that in the cycle just before

this, when comparator Z703-D was low, both

energy but will discharge energy; and also, the

logic will now be set so that the opposite choke

transistors Q701 and Q700 were turned on

L301 will be the next to store energy during

causing both chokes L301 and L201 to lose

the next storage cycle. After each choke L201

their center tap ground path through the

or L301 has stored up a given amount of

power switch transistors. If in this case trans-

energy, the low at comparator Z703-C output

istor Q700 base was at low from Z700 nand

will occur and stop the charging up of that

gate output pins 3 and 6, then transistor Q700

choke. The capacitor C705 charging circuit in

would be turned off and transformer T201

general will provide that when the 37 vdc is

secondary winding 5-6 would generate bias

low, choke L201 or L301 will be shorted to

voltage in primary winding 1-2 and turn-on

ground (to store energy) for a short time and

power switch trnsistors Q206 through Q208.

then, after a total discharge cycle, the other

This would cause heavy current flow in choke

Choke via flip-flop Z702) will be shorted; thus

L201. At the same time transistor Q701 would

establishing a push-pull operation.

be turned on by a high at its base, which would

result in current flow through secondary

In the case when the +37 volt capacitors C401A

winding 4-3 of transformer T801. This would

and C401B are not low and are at the proper +37

continue the turned off condition of transistors

volts, then the voltage at comparator Z703-B input

Q306 through Q308 and choke L301 center tap

pin 10 is high with respect to zener diode CR707

would not be Shorted to ground; L601 would be

reference input pin 11. The high at pin 10 will set

discharging any remaining energy into

comparator Z703-B output to low which sets

capacitors C401A and C401B.

comparator Z703-C output low which sets com-

q The high at comparator Z70-D output also

p a r a t o r Z703-D output low. This has the

causes a high at Z701-8 nand gate output (pin

following results.

8) which turns on transistor Q704 for the short

q Nand gate Z701 input pins 1 and 2 are low

RC time needed to charge up capacitor C704.

causing a high at output pin 3 which has no

The momentary turn-on of transistor Q704,

effect on flip-flop Z702 outputs but prepares

discharges the positive voltage on capacitor

the flip-flop to be switched at the next low from

C705 but, as stated above, transistor Q700 (for

Z701, pin 3.

example) will now be turned off thus allowing

q The low at comparator Z709-D output sets

the +15 volt supply current through tran-

nand gate Z700 input pins 2, 5, 10 and 13 to

sformer T201 winding 3-6 to diode CR705A to

low which sets outpins 3, 6, 8, and 11 to high.

charge charge up capacitor C705 again. When the

This high turns on both transistors Q700 and

2-4