Note: Descriptions are shown in the official language in which they were submitted.
97
DUAL RATE VOLTAGE REGULATOR
BACKGROUND OF THE INVENTION
This invention relates to voltage regulators for engine-
driven DC alternators or DC generators, and more particularly
to a voltage regulator which provides two levels of DC voltage
regulation.
Conventional voltage regulators control the DC voltage
output of a DC alternator or DC generator so as to produce a
predetermined rate of charge. This rate of charge is a com-
promise: If the voltage is adjusted so as to recharge the bat-
tery ideally, the battery gases and consumes water. If the
voltage is adjusted so as to avoid gasing and consumption of
water, the charge rate is so low that the battery does not ch-
arge properly.
The problem presented by this compromise is magnified
in the case of the new "maintenance free" batteries, since it
A is not possible to have a single regulator setting that will
maintain such batteries in short run applications and still not
overcharge a conventional battery on long distance runs.
SUMMARY OF THE INVENTION
In its basic concept, this invention provides a yoltage
regulator by which an engine-driven DC alternator or DC gene-
rator charges, on startup, at a sufficiently high level of vol-
tage regulation to afford quick charging of the engine battery
25 to a predetermined level and thereafter to continue charging
at said lower level of voltage regulation which is predeter-
mined to maintain the battery charge without siginificant gas-
ing and consumption of water.
It is by virtue of the foregoing basic concept that the
30 principal objective of this invention is achieved; namely, to
~11497
overcome the aforementioned disadvantages and limitations of
prior voltage regulators by providing a dual rate voltage reg-
ulator which is operable with all types of conventional DC
alternators and DC generators.
The dual rate voltage regulator of this invention is of
simplified construction for economical manufacture and is of
rugged design for maintenance free operation over a long
service life.
Other advantages of this invention will appear from the
following detailed description, taken in connection with the
accompanying drawing of a preferred embodiment.
BRIEF DESCRIPTION OF THE DRAWING
The single figure is a schematic electrical diagram of
a dual rate voltage regulator embodying the features of this
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The drawing illustrates a conventional DC generator or DC
alternator 10 which is provided with positive, negative and
field coil terminals 12, 14 and 16, respectively, and is driven
by a vehicle engine (not shown) by means of a conventional pull-
ey and beIt coupling 18. The vehicle battery 20 is connected
across the positive and negative terminals 12 and 14 of the
generator or alternator, as illustrated, and the voltage regu-
lator is electricall~ releasably connected to the generator or
alternator, as through a switch 22 which may be the ignition
switch of the vehicle engine.
The dual rate voltage regulator of this invention is an
integral unit which is provided with positive, negative and
- 3
.,
~1~14~7
field coil terminals 24, 26 and 28, respectively, which are con-
nected to the generating coils and the field coils respectively of
the generator or alternator. Conductors interconnect the corres-
ponding terminals, with the switch 22 interposed in the conductor
connecting the appropriate positive or negative terminals. In
the embodiment illustrated, the switch is interposed
- 3a -
97
in the conductor interconnecting the positive terminals.
The housing, indicated by the broken line 30, which mo-
unts the terminals, confines therein the electrical circuitry
making up the dual rate voltage regulator.
An electric switch is provided for interconnecting the
field coil terminal 28 and the appropriate one of the positive
or negative terminals, herein illustrated as the positive ter-
minal 24. In the embodiment illustrated, the switch comprises
the collector-emitter circuit of a transistor 32. The collec-
tor is connected to the field coil terminal 28 and the emitter
is connected through a diode 34 to the positive terminal 24.
The transistor is biased "on" by means of a resistor 36 which
interconnects the transistor base and the negative terminal 26,
and the diode 38 which interconnects the collector and negative
terminal.
The emitter-collector switch of transistor 32 is contr-
olled by a switch actuator which includes the base-emitter ci-
rcuit of the transistor. The base of transistor 32 is conn-
ected to the collector of a second transistor 40 the emitter
of which is connected through diode 34 to the emitter of tran-
sistor 32. Thus, upon activation of transistor 40 the emitt-
ter-collector thereof functions as a switch to connect the ba-
se and emitter of transistor 32 together, deactivating the la-
~ tter. The base-emitter of transistor 40 is in an electric
circuit which is connected across the positive and negative
terminals 24 and 26. Thus, the circuit extends from the pos-
itive terminal 24 through the emitter-base circuit of trans-
istor 40, through zener diode 42 and voltage divider resist-
ors 44, 46 and 48, thence through the silicon controlled rec-
tifier 50 to the negative terminal 26.
The zener diode 42 is chosen to fire at a predeterminedlower level of voltage which establishes the lower level of
voltage regulation. The firing voltage of the zener diode is
established by adjustment of the voltage divider potentiome-
ter resistor 46.
The silicon controlled rectifier 50 functions as a sw-
itch in the electric circuit of the actuator for the first sw-
itch transistor 32. The control electrode or gate of the si-
97
licon controlled rectifier functions as the actuator of the sw-
itch, and it is connected across the positive and negative ter-
minals 24 and 26 through a second zener diode 52. This zener
diode is chosen to fire at a predetermined higher voltage th-
an the zener diode 42, to establish a higher level of volt-
age regulation.
As an illustration, let it be assumed that the vehicle
battery 20 is a convention~ 12 volt type. Conventional single
rate voltage regulators presently in use are set at the com-
promise level of about 14.2 volts. As discussed hereinbefore,this level of voltage regulation provides adequate charging of
a 12 volt battery, but it does so with considerable gasing and
consumption of water.
For use with the exemplified 12 volt battery, the dual ra-
te voltage regulator of this invention is adjusted to provide,for example, a lower level voltage regulation of about 13.2
volts, set by the zener diode 42, and a higher level voltage
regulation of about 14.8 volts, set by the zener diode 52, The
higher level of voltage regulation is chosen to quickly rechar-
ge the battery after cranking, to replace the ampere-hours ut-
ilzed during cranking. The lower level voltage regulation is
chosen for continuing the recharging of the battery at a level
which maintains the load demand, without any significant bat-
tery gasing or water consumption. This minimizes battery ma-
intenance and prevents premature plate damage, resulting insignificantly increased battery life.
It will be appreciated that the lower and higher levels
of voltage regulation may be set to various values other th-
an those exemplified, to accommodate a wide variety of bat-
tery capacities and uses.
The operation of the dual rate voltage regulator descr-
ibed hereinbefore is as follows: Let it be assumed, for il-
lustration, that the DC alternator or generator is driven by
the internal combustion engine of a boat, truck, passenger car,
or other vehicle and that the vehicle battery is of the 12 vo-
lt type and that the switch 22 represents the ignition switch
of the vehicle engine.
Upon closure of the switch 22, preparatory to starting
the engine through an electrical starter (not shown), the em-
-~" 111149t7
itter-collector switch of transistor 32 is activated to its
normally "on" condition by the bias provided by resistor 36
and diode 38. Accordingly, the field coil terminal 28 is co-
nnected to the positive battery terminal 24 through the nor-
mally closed emitter-collector switch of transistor 32 and the
diode 34.
With the engine now activated, the DC generator or alter-
nator causes voltage to rise progressively as the ampere-hours
used for cranking are replaced in the battery 20. Depending
upon the extent of cranking, this replacement charging varies
in time, for example from about 5 seconds to about a minute.
Completion of the replacement charging results in the vol-
tage rising to the higher level set by the zener diode 52, ca-
using the latter to fire. This completes the electric cir-
cuit of the control gate of the silicon controlled rectifi-
er 50, whereupon activation of the latter functions as a se-
cond switch to complete the electric circuit through the zen-
er diode 42 and the base-emitter of transistor 40.
Completion of the electric circuit just described, results
in activation of the zener diode 42 at the lower voltage lev-
el of 13.2 volts in accordance with this example. The tran-
sistor 4~t~us is turned "on", whereupon the transistor 32 is
turned '~9~' and the associated emitter-collector switch is
- opened.
Opening of the emitter-collector switch of transistor 32
results in deenergization of the field coil of the generator
or alternator 10, thereby reducing the voltage output to a
level which reestablishes the blocking Osf ~te of zener diode
42. The transistor 40 thus is turned ~ , turning "on" the
transistor 32 and closing its switch to reenergize the field
coil.
Since the silicon controlled rectifier 50 stays latched
"on" as long as DC voltage appears across the voltage divider
resistances and the silicon controlled rectifier, the zener
diode 42 fires intermittently as the voltage rises to the ex-
exemplified lower level of 13.2 volts and then falls again.
This provides continued regulation at the lower voltage level,
maintaining sufficient charging of the battery to maintain the
11497
- load demand without any siginificant battery gasing or water
consumption.
When the engine is shut down ~ opening the ignition
switch 22, the regulator isshut and the silicon con-
trolled rectifier 50 is unlatched. The regulating cycle thenis repeated upon closure of the ignition switch and restart-
ing of the engine.
In the preferred embodiment illustrated, a resistance 54
of predetermined value is connected across the silicon con-
trolled rectifier 50 so that the zener diode 42 fires whenthe voltage reaches a level slightly higher than the level
ofthe exemplified 14.8 volts which causes the zener diode 52
to fire. This protects against the development of excess-
ively high and therefore damaging voltage at the generator
or alternator 10 in the event of malfunctioning of the sili-
con controlled rectifier 50.
Resistor 56 and capacitors 58 and 60 serve to smooth out
the operation of the regulator, and capacitor 62 serves to
prevent premature turn-on of the silicon controlled recti-
fier 50.
There may be special circumstances of heavy battery usewithout simultaneous charging, as when the vehicle engine is
-~ turned off, that it may be desirable to continue charging the
. battery at the higher voltage levèl. For this purpose a ti-
mer 64 may be associated with the second switch actuator ze-
ner diode 52, either in series, or in parallel, to maintain
the diode inactive for a predetermined time after the alter-
nator or generator lO has been energized. A variety of ty-
pes of timers may be utilized. Exemplary of one such type
is the integrated circ~uit Model No. SE-555 manufactured by
Signetics Corporation.
. ~
: From the foregoing it will be appreciated that the vol-
tage regulator of the present invention provides a regula-
ted higher voltage level which functions to recharge a batt-
ery quickly, following engine cranking, to replace the am-
pere-hours used for cranking, and therea$ter to reduce the
voltage to a regulated lower level for continued charging of
the battery at a level which maintains the load demand with-
out any significant battery gasing or water consumption. Th-
1111497
is mode of operation eliminates battery sulfaction which or-
dinarily results from undercharging, eliminates premature
plate damage which ordinarily results from battery gasing,
and significantly increases battery life while simultaneo-
usly minimizing the necessity of battery maintenance. Thebattery is maintained in proper charge at all times, whether
it is being used in short or long run applications.
It will be apparent to those skilled in the art that va-
rious changes may be made in the type of components and cir-
cuit arrangement described hereinbefore, without departingfrom the spirit of this invention.
