A bipolar transistor in series with the battery as the control element also in series with a zener diode and a resistor is used to maintain a predetermined voltage until the battery voltage decays to very nearly the predetermined voltage. A field effect transistor between the base of the bipolar transistor and a junction between the zener diode and resistor regulates base current of the bipolar transistor, thereby regulating the conductivity of the bipolar transistor for control of the output voltage

Black, J. M.

English

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United States Patent 1191 [111 4,151,456 
Black [451 Apr. 24, 1979 
[54] VOLTAGE REGULATOR FOR BA'ITERY 
POWER SOURCE 
[75] Inventor: 
[73] Assignee: 
[21] Appl. No.: 
[22] Filed: 
Jmea M. Black, Lancaster, Calif. 
The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
AdIUMShh 'on, Washington, D.C. 
885,049 
Mu. 9,1978 
[51] Int. Cl.2 ................................................ GOSF 1/56 
[52] US. CI. ................................................... 323/22 T 
[58] Field of Sevch ................... 307/296 R, 297, 304, 
323/16, 39, 19,22 R, 22 T 
[561 References Cited 
U.S. PATENT DOCUMENTS 
3,813,595 5/1974 Shag ................................ 323/22 R 
3,899,693 8/1975 Gaudreault .......................... 307/297 
4,005,353 VI977 Yokoyama ......................... 323/22 R 
Primary Examiner-A. D. Pellinen 
Attorney, Agent, or Firm-Monte F. Mott; John R. 
Manning; Paul F. McCaul 
A voltage regulator for a battery power source capable 
of maintaining a predetermined voltage until the battery 
voltage decays to very nearly the predetermined volt- 
age uses a bipolar transistor in series with the battery as 
the control element in series with a zener diode and a 
resistor. A field effect transistor between the base of the 
bipolar transistor and a junction between the zener 
diode and resistor regulates base current of the bipolar 
transistor, thereby to regulate the conductivity of the 
bipolar transistor for control of the output voltage. 
P I  ABSTRACT 
7 clnims, 3 Drawing Figures 
L20 
2 
EGULATED 
OUTPUT 
+VDC 
https://ntrs.nasa.gov/search.jsp?R=19790015174 2020-03-20T19:00:15+00:00Z
U.S. Patent Apr. 24,1979 Sheet 1 of 2 4,15 1,456 
w 
0 
I- 
-I 
a 
P 
s 
>. 
W 
I- 
a 
m 
- INITIAL (FRESH BATTERY) CHARGE 
VOL 
ILATED 
'UT 
rAGE 
TIME A -1 
NORMAL USABLE 
BATTERY LIFE 
TIME B- 
IMPROVED REGULATED 
BATTERY LIFE 
L 
TIME 
FIG. I 
U.S. Patent Apr. 24, 1979 Sheet 2 of 2 4,151,456 
4,lS 1,456 
A 1 I 
lated output voltage to a very small differential. The 
extent to which that differential may be reduced is es- 
sentially limited by only the voltage drop in the regulat- 
ing circuit between the voltage source and the output 
The invention described herein was made by an em- The novel features that are considered characteristic 
ployee of the United States Government and may be of this invention are set forth with particularityh the 
manufactured and used by and for the Government for appended claims. The invention will best be understood 
governmental purposes without the payment of any from the following description when read in connection 
royalties thereon or therefore. 
BACKGROUND OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS 
This invention relates to a voltage regulator, and FIG. 1 is a graph useful in understanding the objec- 
more particularly to a circuit for regulating battery tives and advantages of the present invention. 
voltage source. 15 FIG. 2 is a circuit diagram of the present invention. . 
In many applications, equipment with battery oper- FIG. 3 is a circuit diagram of a modification of the 
ated power regulation is requireij. A typical application present invention. 
DESCRIPTION OF PREFERRED EMBODIMENT 
is for airborne television using a battery operated minia- 
ture camera. The problem is to provide a circuit that 
regulates voltage with maximum utilization of available 20 Referring now to FIG. 2 of the drawings, an im- 
battery power, Le., with maximum efficiency. proved battery voltage regulator is comprised of a bipo- 
The prior art has not fully utilized available battery lar transistor Qi, having its emitter connected to a bat- 
power because the difference between the regulated tery 10 and its collector connected to an output terminal 
output voltage and the battery voltage had to be main- 12 for delivering a regulated output voltage, and a field- 
tained at one volt, or more. That is wasteful at the end 25 effect transistor (FET) connekting the base of the bipo- 
portion of the discharge cycle because the final one volt lar transistor to the junction between the zener diode 18 
of battery voltage above the regulated voltage can not and the bias resistor 16. A resistor 20 shown in series 
be utilized. with the battery and the collector of the bipolar transis- 
The graph of FIG. 1 is useful in understanding this tor represents the internal resistance of the battery and 
problem. A voltage regulator maintains a constant volt- 30 any external resistance that may be added, as will be 
age output at some predetermined level substantially described hereinafter. 
below the initial (fresh charge) voltage. When the bat- The voltage drop between the emitter and collector 
tery voltage has decayed to a level within a difference of the bipolar transistor is regulated by its base current, 
AV that must by maintained between the regulated which is in turn controlled by the FET. This control is 
output voltage and the battery voltage, the battery is no 35 established through the use of the zener diode 18 and 
longer weable. the bias resistors 14 and 16. Assuming the regulated 
The useful life of a battery could be extended signifi- output voltage +VDC is to be 12 volts, the FET is 
cantly from time A to time B in the graph of FIG. 1 if biased by resistors 14 and 16 to control the base current 
its regulated output voltage could be maintained with a for the bipolar transistor such that the voltage drop 
difference AV that is substantially zero. The importance 40 across it will reduce the initial battery voltage, such as 
in thus extending the life of a battery can be appreciated +22 V or + 15 V, to the desired regulated + 12 V. The 
by considering that if a battery We of time B is required, zener diode 18 and small resistor 16 (typically a 1 watt 
and the regulated output voltage can be maintained resistor of 390 ohms for an 11-volts zener diode) estab- 
with a difference AV of almost zero from the battery lish the bias voltage for the FET which has its gate 
voltage, a smaller battery may be used. The weight 45 connected to circuit ground by the large resistor 14 
saved with a smaller battery is an important consider- (typically a 4 watt resistor of 10 K ohms) to provide the 
ation in any battery operated equipment and may be regulated +I2 VDC. 
critical in aircraft and space vehicles. If the regulated output becomes less than 12 volts, as 
the battery voltage decays from its initial value, the 
50 regulated output voltage becomes less and will decrease SUMMARY OF THE INVENTION 
In accordance with the present invention, a circuit the gate-source voltage of the FET and increase its 
for regulating the output voltage delivered from a DC drain current. Note that gate voltage of Qzis essentially 
source is comprised of a bipolar transistor having its ground and source voltage is regulated output voltage 
emitter electrode connected to the source and its collec- minus the zener voltage. That in turn increases the base 
tor electrode connected to a voltage output terminal, 55 current of the bipolar transistor causing it to conduct 
and a field-effect transistor connected to the base elec- more, thereby causing the voltage drop across the emit- 
trode of the bipolar transistor and connected to both the ter and collector to decrease. That will return the out- 
collector electrode of the bipolar transistor by a zener put voltage to 12 VDC. In that manner the FET is used 
diode and to circuit ground by a small resistor. The gate to control the base current of the bipolar transistor to 
electrode of the field effect transistor is connected to 60 maintain the output voltage constant as the emitter 
@ circuit ground by a large resistor. If the source voltage voltage decreases from some voltage significantly 
decreases, the output voltage tends to decrease, but the greater than the regulated output voltage. The output 
field-effect transistor then tends to increase its conduc- voltage can be maintained until the voltage source ap- 
tivity proportionately, thereby increasing the base cur- proaches very nearly the level of the output voltage 
rent of the bipolar transistor to increase its conductivity 65 that is to be maintained. 
and increase the output voltage proportionately. Regu- In the exemplary embodiment of FIG. 2 the voltage 
lation will be maintained until the source voltage de- output is positive. Consequently the bipolar transistor is 
creases to a level which approaches the desired regu- a PNP type and the tield-effect transistor is an N type to 
VOLTAGE REGULATOR FOR BATI’ERY POWER, 
SOURCE 
5 terminal. ORIGIN OF INVENTION 7 
10 with the accompanying drawings. 
4,15 1,456 
3 4 
achieve an increase of output voltage when it is too low, reference potential, said circuit comprising: a bipolar 
and a decrease in output voltage when it is too high. Use transistor having a collector electrode, an emitter elec- 
of a P-type field-effect transistor would accomplish the trode, and a base electrode, said collector electrode 
reverse, and would thus be self defeating. However, if being connected to a voltage output terminal and said 
the output voltage is to be negative, the bipolar transis- 5 emitter electrode being connected to said voltage 
tor would be chosen to be of the NPN type and the source; a zener diode; a first resistor; a second resistor; 
field-affect transistor of the p type as shown FIG. 3 a field-effect transistor having a source electrode, a 
Where transistors Q 1  and 42 are Shown to be Of the drain electrode and a gate electrode, said gate electrode 
opposite conductivity type, and the zener diode 18 is being connected to said source of ground reference 
reversed in polarity. In either case, the field effect tran- 10 and 
mode MoS drain electrode being connected to said base electrode 
a silicon transistor or a germanium transistor. The mini- and drain electrodes being connected to both said 
mum difference between the Output and the source of reference potential by said second resistor and 
source voltage is limited by the saturation resistance of 15 to =id collector electrode of said bipolar transistor by 
the bipolar transistor in the circuit. Therefore the said zener diode with a polarity to said diode to be choice of bipolar transistor to be made is one having a reverse-biased in the circuit. very low saturation resistance. Some silicon transistors 2. A circuit as defined in claim 1 wherein said output 
by said first resistor, one of said 
may be Of the mode Or 
type, or a junction type. The transistor may be of said bipolar transistor, and the other of said Source 
have a saturation resistance of 55 milliohms or less. 
Another modification to the present invention is the 
inclusion of an external resistance between the battery 
source and the emitter of the bipolar transistor. Such a 
resistor is useful only when the initial battery voltage is 
much greater than that which the regulator has been 
designed to accommodate. Since such a resistor will 
have a substantial voltage drop, the extent to which the 
battery voltage may decrease while the circuit main- 
tains the output voltage constant is decreased. Conse- 
quently, it is preferred that no external resistor be used, 
and that the resistor 20 be limited to the internal resis- 
tance of the battery. The entire regulator circuit con- 
sists of two transistors, two resistors and a zener diode. 
Although particular embodiments of the invention 
have been described and illustrated herein, it is recog- 
nized that modifications and variations may readily 
occur to those skilled in the art. It is therefore intended 
that the claims be interpreted to cover such modifica- 
tions and variations. 
I claim: 
1. A circuit for regulating the output voltage deliv- 
ered from a source with respect to a source of ground 
2o voltage is positive and said bipolar transistor is a P&JP 
type and said field-effect transistor is an N type. 
3. A circuit as defined in claim 2 where said source is 
a battery having its negative terminal connected to said 
source of ground reference potential, and its positive 
25 terminal connected to said emitter electrode of said 
bipolar transistor. 
4. A circuit as defined in claim 3 including a resistor 
in series between said positive terminal and said emitter 
electrode. ’ 
5. A circuit as defined in claim 1 wherein said output 
voltage is negative and said bipolar transistor is an NPN 
type and said field-effect transistor is a P type. 
6. A circuit as defined in claim 5 wherein said source 
is a battery having its positive terminal connected to 
35 said source of ground reference potential, and its nega- 
tive terminal connected to said emitter electrode of said 
bipolar transistor. 
7. A circuit as defined in claim 6 including a resistor 
in series between said negative terminal and said emitter 
30 
40 electrode. * * * * *  
45 
50 
55 
60 
65 


Voltage regulator for battery power source

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