U.S. patent number 3,786,344 [Application Number 05/185,939] was granted by the patent office on 1974-01-15 for voltage and current regulator with automatic switchover.
This patent grant is currently assigned to Motorola, Inc.. Invention is credited to William F. Davis, Thomas M. Frederiksen, Ernest L. Long, Ronald W. Russell.
United States Patent |
3,786,344 |
Davis , et al. |
January 15, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
VOLTAGE AND CURRENT REGULATOR WITH AUTOMATIC SWITCHOVER
Abstract
A system for energizing an inductive load includes a voltage
regulator for providing a constant voltage across the load until
the current builds up to a particular value, and a current
regulator which then takes over to provide a constant holding
current at a lower value. The voltage regulator may include a
closed loop for holding the voltage across the inductive load
constant or may respond to a regulated voltage value to control a
power stage for providing a constant voltage. The voltage across a
sensing resistor in the power stage controls the crossover from the
voltage regulation mode, to the current regulation mode and the
current regulator automatically resets the reference to control the
power stage to provide a constant current of a lower value through
the load. The system can be used to supply current to coils of
injector valves in a fuel injection system, and may include two
power stages for supplying current to two banks of coils. The
regulator system is switched from one power stage to the other
during successive 180.degree. rotary positions of the engine for
both stages.
Inventors: |
Davis; William F. (Tempe,
AZ), Russell; Ronald W. (Mesa, AZ), Frederiksen; Thomas
M. (Scottsdale, AZ), Long; Ernest L. (San Jose, CA) |
Assignee: |
Motorola, Inc. (Franklin Park,
IL)
|
Family
ID: |
22683018 |
Appl.
No.: |
05/185,939 |
Filed: |
October 4, 1971 |
Current U.S.
Class: |
323/267;
123/490 |
Current CPC
Class: |
H01F
7/1805 (20130101); H03K 17/64 (20130101); F02D
41/20 (20130101); F02D 2041/2031 (20130101); F02D
2041/2017 (20130101); F02D 2041/2058 (20130101) |
Current International
Class: |
H01F
7/08 (20060101); H03K 17/64 (20060101); F02D
41/20 (20060101); H03K 17/60 (20060101); H01F
7/18 (20060101); G05f 001/56 (); G05f 001/60 () |
Field of
Search: |
;315/29T,29M
;123/32EA,119R ;323/4,9,20,22T ;307/104 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Goldberg; Gerald
Attorney, Agent or Firm: Mueller; Foorman L.
Claims
We claim:
1. A circuit for supplying current from a power supply to an
inductive load, including in combination:
power stage means coupled to the power supply and having an input
terminal and an output terminal adapted to be connected to the
inductive load to supply current thereto, said power stage means
having output current sensing means;
voltage regulator means coupled to said input terminal for
controlling said power stage means to maintain a substantially
constant voltage at said output terminal thereof; and
current regulator means including a current regulator circuit
having an input and an output, means coupling said input of said
current regulator circuit to said output current sensing means, and
circuit means coupling said output of said current regulator
circuit to said input terminal for controlling the current supplied
by said power stage to the inductive load, said current regulator
circuit being rendered operative to control the output current in
response to a voltage across said output current sensing means
which indicates that the current in the load has reached a
predetermined value.
2. A circuit in accordance with claim 1 wherein said voltage
regulator means includes
a differential amplifier having a first input coupled to said
output terminal of said power stage means, a second input, and an
output,
reference voltage means providing a substantially fixed voltage
connected to said second input of said differential amplifier,
and
control means coupling said output of said differential amplifier
to said input terminal of said power stage means to control the
operation of said power stage means so that the voltage at said
output terminal remains substantially constant.
3. A circuit in accordance with claim 2 wherein said differential
amplifier and said control means cooperate to control said power
stage means so that the voltage at said output terminal thereof is
substantially the same as the reference voltage applied to said
second terminal of said differential amplifier.
4. A circuit in accordance with claim 3 wherein said control means
includes an emitter-follower circuit.
5. A circuit in accordance with claim 1 wherein said voltage
regulator means includes control means connected to said input
terminal of said power stage means for applying current thereto for
controlling the voltage at said output terminal thereof, and said
circuit means of said current regulator means is coupled to said
input terminal for controlling the current applied by said control
means to said input terminal of said power stage.
6. A circuit in accordance with claim 1 wherein said current
regulator circuit includes,
a differential amplifier having first and second inputs and an
output, said first input of said differential amplifier forming
said input of said current regulator circuit and said output of
said differential amplifier forming said output of said current
regulator circuit,
reference voltage means connected to said second input of said
differential amplifier; and
means coupling said circuit means to said reference voltage means
for changing the reference voltage applied to said second input of
said differential amplifier in response to a signal in said circuit
means produced in response to the voltage across said output
current sensing means, to control said power stage to reduce said
output current to a value less than said predetermined value.
7. A circuit of claim 6 wherein said reference voltage means
includes means having first and second branches with substantially
fixed current therein, and means for providing a reference voltage
which is related to the value of the currents in said first and
second branches.
8. A circuit in accordance with claim 7 wherein said reference
voltage means includes means for shunting said first branch so that
the reference voltage is related to the value of the current in
said branch alone.
9. A circuit in accordance with claim 6 wherein said reference
voltage means includes means responsive to decrease in the voltage
of the power supply means to modify the voltage applied to said
second input of said differential amplifier to modify the action
thereof to cause said power stage to apply increased current to the
load.
10. A circuit for supply current from a power supply to first and
second banks of coils of injector valves, including in
combination:
power stage means including first and second sections coupled to
the power supply and each having an input terminal and an output
terminal adapted to be connected to one bank of coils to supply
current thereto, said power stage means having output current
sensing means common to said first and second sections;
voltage regulator means adapted to provide a substantially constant
voltage;
current regulator means having an input and an output, means
coupling said input of said current regulator means to said output
current sensing means; and
circuit means including first and second sections each coupled to
said input terminal of one of said sections of said power stage
means, said circuit means being coupled to said voltage regulator
means and responsive to the voltage provided thereby to provide a
substantially constant voltage at said output terminals of said
sections of said power stage means, said circuit means being
coupled to said output of said current regulator means and
controlling said sections of said power stage means so that the
current supplied thereby to the bank of coils connected thereto is
maintained substantially constant;
said current regulator means being rendered operative to control
said sections of said power stage means in response to a voltage
across said output current sensing means which indicates that the
current in the coils has reached a predetermined value.
11. A circuit in accordance with claim 10 further including switch
means coupled to said circuit means for selectively rendering said
first and second sections thereof operative to control said
sections of said power stage means coupled thereto.
12. A circuit in accordance with claim 11 wherein said switch means
includes means for actuating the operative sections of said circuit
means to control the section of said power stage means connected
thereto to initiate the supply of current to the associated bank of
coils and to terminate such current supply.
13. A circuit in accordance with claim 10 wherein said current
regulator means includes,
a differential amplifier having first and second inputs and an
output, with said first input of said differential amplifier
forming said input of said current regulator means and said output
of said differential amplifier forming said output of said current
regulator means,
reference voltage means connected to said second input of said
differential amplifier,
said differential amplifier being rendered operative when the
voltage applied to said first input thereof from said output
current sensing means has a value equal to the voltage applied to
said second input of said differential amplifier to control said
circuit means and cause said sections of said power stage means to
supply substantially constant current to the associated bank of
coils.
14. A circuit in accordance with claim 13 wherein said reference
voltage means is coupled to said output of said differential
amplifier and includes means for changing the voltage applied to
said second input of said differential amplifier so that said
current regulator means controls said power stage means so that the
current supplied to the coils is maintained at a substantially
constant value below said predetermined value.
15. A circuit in accordance with claim 10 wherein each of said
sections of said circuit means includes first, second and third
transistors, with said first transistor having base, emitter and
first and second collector electrodes, and said second and third
transistors each having base, emitter and collector electrodes,
means connecting the path between said emitter and said first
collector of said first transistor in series with the path between
said emitter and said collector of said second transistor across
the power supply, and connecting the junction between said first
collector and said emitter of said second transistor to said input
of the section of said power stage means connected to such section
of said circuit means, resistor means connected in series with the
path between said emitter and said collector of said third
transistor across the power supply, the junction between said
resistor and said emitter of said third transistor being connected
to said base of said first transistor, and means connecting said
second collector of said first transistor to said base of said
third transistor and for controlling the current therein so that
the conductivity of said first transistor is controlled to thereby
control the current applied to said input of said connected section
of said power stage means.
Description
BACKGROUND OF THE INVENTION
Electronic fuel injection systems have injector valves with
inductive coils for opening and closing the valves in timed
relation. This timed relation requires rapid current buildup in the
coils to accurately time the opening of the injector valves.
Reduced current can then be applied to the coils to keep the valves
open for a specified length of time, with the valves being closed
at a precise time by cutting off the current in the coils. The
magnetic characteristics of inductive coils, whether used in fuel
injection systems for driving a magnetic valve, or in a mechanical
relay, or even in certain magnetic memories, are such that once the
magnetic field has been established by the buildup of current,
maintenance of the field requires much less current, with the
current needed varying in the range from one-half to one-tenth the
amount needed to originally energize the field. This is because the
energy necessary to pull in a valve or armature is greater than
that required to hold the same operated.
Separate voltage and current regulators have been utilized in the
past to energize coils, but no successful system has been designed
which can automatically crossover from voltage regulation to
precise current regulation, as is desired. In order to conserve
space, it is desirable to have a regulator system of the
aforementioned characteristics which can be incorporated into an
integrated circuit chip.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a system for
precisely controlling current buildup in an inductive load.
It is another object of the invention to provide an energizing
system for an inductive load which provides voltage controlled
current buildup therein, and maintains current regulation after a
predetermined current is reached.
It is a further object of the invention to provide a system for
energizing an inductive load which reduces the current in the
energized load to permit precise cutoff of the magnetic field of
the inductive load.
It is still another object of the invention to provide a voltage
and current regulator for an inductive load, with automatic
crossover from voltage regulation to current regulation.
It is yet a further object to provide a precise voltage and current
regulator with automatic crossover from voltage regulation to
current regulation for fuel injector coils, which regulator is
adapted to be incorporated in an integrated circuit chip.
A power stage which supplies a controlled current to an inductive
load formed by a bank of fuel injector coils is controlled by a
voltage regulator working together with a current regulator. In one
embodiment the voltage regulator includes a differential amplifier
operating in a closed loop to control the output of the power stage
to the injector valve coils, to limit the voltage of the power
stage output to a given value. A voltage regulator of other known
design can be used.
The power stage includes a current sensing resistor through which
the current supplied to the bank of injector coils flows. A control
voltage developed across the current sensing resistor is coupled to
a current regulator which includes a differential amplifier having
a first input for receiving the control voltage and a second input
to which a reference voltage is applied. When the current applied
to the injector coils reaches a designated value, the current
regulator is rendered operative and a feedback circuit acts to
change the reference voltage applied to the differential amplifier
and causes the same to act to provide reduced current through the
coils. This is accomplished by providing reduced drive to the power
stage to reduce the output current, and in turn reduce the voltage
across the current sensing resistor. With a reduction in the output
current, the differential amplifier becomes balanced and the
current output to the injector coils is maintained at a
predetermined value, lower than that necessary to originally
energize the bank of injector coils.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of one embodiment of the voltage and
current regulator circuit with automatic crossover, of the present
invention;
FIG. 2 is a curve illustrating the current buildup and holding
current in the coils; and
FIG. 3 is a schematic diagram of a second embodiment of the
invention.
DETAILED DESCRIPTION
The voltage and current regulator shown in the schematic diagram of
FIG. 1 precisely controls the current buildup and turn off in the
bank of injector coils 10. Four coils are shown which may
simultaneously provide fuel to four cylinders of an engine, and
which may be used with a second set of four coils for a V-8 engine.
To provide current buildup in the coils, current is applied thereto
from a voltage supply 38, which may be energized by a battery. The
voltage supplY may have a nominal value of 12 volts, and may vary
from 11 to 16 volts depending on the condition of charge of the
battery. Under starting conditions when heavy current is drawn from
the battery, the voltage may drop below 11 volts and can reach a
value of the order of 6 volts.
Current is applied from the supply 38 through a power amplifier 26
which includes transistors 46, 47 and 48 to terminal 32 connected
to the coils 10. The three transistors 46, 47 and 48 can be
considered equivalent to a single large NPN transistor which has a
very high beta. The current supplied by the amplifier 26 to the
coils 10 flows through resistor 50 which is used to measure the
output current, as will be explained. The current flowing through
resistor 50 is illustrated in FIG. 2.
The system of FIG. 1 includes a voltage regulator comprising a
differential amplifier 14 including transistors 16 and 18. A
reference voltage is applied to terminal 12, which is connected
through diode 15 to the base of transistor 16. The voltage across
the coils 10 is applied from terminal 32 through diode 30 to the
base of transistor 18. The emitters of transistor 16 and 18 are
connected through current source 19 to ground potential. The
collector of transistor 16 is connected through diode 20 to the
supply voltage line 38, and the collector of transistor 18 is
connected through the emitter-collector path of transistor 22 to
the line 38.
Transistor 22 and diode 20 form a turn around circuit for
controlling the output of the differential amplifier derived at
point 40 connected to the collector of transistor 18. The diode 20
and transistor 22 are constructed so that when transistors 16 and
18 conduct equal amounts, there is no current flow through point
40. However, when transistor 16 conducts the full current of the
source 19 and transistor 18 is nonconducting, current will flow
from the supply through transistor 22 to the point 40. On the other
hand when transistor 18 conducts the full current from the source
19 and transistor 16 conducts no current, so that there is no
current through diode 20, transistor 22 is cut off and the current
through transistor 18 is supplied from point 40. Accordingly, full
current can flow in opposite directions through point 40 as the
conductivity shifts from transistor 16 to transistor 18, and vice
versa.
The voltage at the terminal 32 during the current buildup in the
injector coils of bank 10 is controlled by the voltage regulator
loop comprising the differential amplifier 14, the power stage 26,
the feedback path through diode 30 to terminal 24 connected to the
base of transistor 18 of the differential amplifier 14, and the
emitter-follower circuit 42 connecting output 40 of the
differential amplifier to the input 44 of the power stage 26. This
acts to maintain the voltage at the output terminal 32 at the
reference voltage applied from terminal 12 through diode 15 to the
terminal 34 of the differential amplifier, during the current
buildup time which is indicated as A in FIG. 2.
When the potential at the output terminal 32 is greater than the
reference potential, transistor 18 conducts more than transistor
16, being turned on more as the voltage at terminal 32 is higher
than the reference voltage at terminal 12. Less current then flows
through the transistor 16 to reduce the current through diode 20 to
reduce the conductivity of transistor 22. As a consequence, the
current through transistor 18 is derived, at least in part, from
point 40, which causes the emitter-followers 42 to in effect
"steal" current from the current source 43 so that less current is
applied to the input terminal 44 of power stage 26, which is
connected to the base of transistor 46. This current "stealing"
from the base of transistor 46 continues, with the current being
shunted through emitter-followers 42 to the ground potential, until
the potential at terminal 32 is reduced to that of the reference
terminal 12. Transistor 46 decreases in conduction during this
period of time, with transistor 47 likewise decreasing its
conduction, and the output transistor 48 also decreasing its
conduction. This decrease in current through the coils causes the
potential at terminal 32 to decrease.
In the event that the potential at output terminal 32 is less than
the reference potential at terminal 12, transistor 16 conducts more
than transistor 18, drawing more current through diode 20. This
causes transistor 22 to conduct heavily and it can supply more
current than transistor 18 conducts. This acts to turn off the
emitter-followers 42 so that the full current from source 43 is
supplied to the base of transistor 46. This causes the power stage
26 to operate to increase the potential at output terminal 32.
The circuit of the invention crosses over to current control when
the current flowing through the coils 10, and which passes through
resistor 50, has increased to a predetermined value, such as 5
amps. This produces 0.5 volts across the 0.1 ohm resistor 50, and
activates the current regulator 82. The current regulator includes
a differential amplifier 52 which has one input 56 connected
through lead 54 to the resistor 50, and a second input 78 to which
a reference potential is applied from the voltage supply line 38
through resistor 77. The differential amplifier is formed by first
and second Darlington circuits having the common emitters connected
to ground through current source 59. The first Darlington circuit
is formed by transistor 58 and 60, and the second circuit is formed
by transistors 61 and 62. While the current is building up in the
coils 10, the voltage across resistor 50 is less than the voltage
across resistor 77, and as both resistors are connected to the
supply line 38, potential applied at input 56 is greater than the
potential applied at input 78, so that transistors 58 and 60
conduct heavily.
The voltage across resistor 77, which produces the reference
potential, is controlled by the current through this resistor,
which in turn is controlled by the conductivity of transistor 65.
The base of transistor 65 is connected to a circuit including
current sources 66 and 67 connected to the supply voltage line 38,
and diodes 68 and 69. Source 67 is connected in series with diode
68, and the currents through the sources 66 and 67 flow through
diode 69. Diode 69 is constructed with areas matched to the
transistor 65 so that the same amount of current which flows
through diode 69 will flow through transistor 65 to thereby control
the current through resistor 77. The voltage drop across resistor
77 controls the reference voltage applied to the base of transistor
62.
When the current through resistor 50 increases to drop the voltage
applied to the base of transistor 58, this transistor, as well as
the transistor 60 will conduct less. This causes transistors 61 and
62 to increase in conductivity. Transistor 60 has its collector
connected through diode 64 to the voltage of supply line 38, and
transistor 61 has its collector connected through transistor 63 to
the line 38. Transistor 63 and diode 64 form a turn around circuit
as described above in connection with differential amplifier 14.
The output of the differential amplifier 52, at the collector of
transistor 61, is connected to the base of transistor 68, which is
a lateral PNP transistor having first and second collector
electrodes. When transistor 61 increases its conduction, the
current through transistor 63 will be reduced so that current will
be drawn through diode 73 connected to the base of transistor 68.
This causes transistor 68 to conduct.
Collector 74 of transistor 68 is coupled to transistor 76, which is
connected to shunt the current of the current source 67 to ground.
This reduces the current through diode 69 and the current through
transistor 65 to reduce the current through resistor 77. This acts
to reduce the voltage drop across resistor 77 and causes the
reference potential input 78 of the differential amplifier 52 to
rise. This acts in the manner described, to increase the
conductivity of transistor 68. Collector 75 of transistor 68 is
connected to the base of transistor 70, and causes transistor 70 to
conduct through diode 72 and "steal" current applied from the
source 43 to the base of transistor 46. Thus the current control
takes over from the voltage control. This reduces the output
current of power stage 26 which is applied through output terminal
32 to the injector coils 10. This reduction in current through the
coils occurs at a point in time after the magnetic field of the
injector coils 10 has built up to open the injector valves at a
specific time. The reduced current, illustrated by the part of FIG.
2 indicated as B, is sufficient to maintain the valves in the open
position, since the magnetic field from the coils to hold the
valves open requires less current than that required to open up the
valves.
As previously stated, the voltage on the supply line 38 may drop to
a very low voltage, such as 6 volts, under certain conditions, as
when the internal combustion engine is being cranked. In order to
insure that sufficient current is applied to the coils under such
conditions, a low voltage compensating circuit is provided. This
includes a terminal 80 adapted to be connected to a regulated
voltage, to which a voltage divider string is connected including
resistor 81, zener diode 82 and resistor 83. This string is
normally conducting to provide a voltage across resistor 83 which
holds transistor 85 conducting, and this brings the base of
transistor 86 near ground, so that this transistor is cut off.
Transistor 86 is connected in series with resistor 88 across the
transistor 65. When the voltage at point 80 drops to a low value,
as for example 6 volts, the zener diode 82, which may be selected
to conduct at 7 volts, is rendered nonconducting so that the
voltage divider is open circuited and transistor 85 is turned off.
The voltage from terminal 80 is therefore applied through resistor
87 to the base of transistor 86, and renders transistor 86
conducting. This pulls current through resistor 88 and reference
resistor 77, to drop the voltage applied to input terminal 78 of
the differential amplifier. This voltage which is applied to the
base of transistor 62 causes the differential amplifier 52 to act
through transistors 68 and 70 to increase the current supplied to
the injector coils 10. When the supply voltage rises to its normal
value, in the range from 11 to 16 volts, the zener diode 82 will
again conduct so that the low voltage compensating circuit is
rendered inactive.
In FIG. 3 there is illustrated a second embodiment of the invention
which includes a power amplifier for supplying current to injector
coils for an internal combustion engine, which is controlled by a
regulator which provides constant voltage across the coils during
the initial part of the cycle, and constant current through the
coils during the final part of the cycle. In FIG. 3, two sets of
injector coils are provided, set 10 as in FIG. 1, and a second set
110. As previously stated, each set includes four coils for the
injector valves which provides fuel to half of the eight cylinders
of a V-8 engine. The four coils in the set 10 are energized
simultaneously during one 180.degree. portion of rotation of the
engine and the coils of set 110 are energized during the other
180.degree. portion. Separate power amplifiers are provided for
supplying the current to the two sets of coils, with amplifier 112
supplying current to the coils 10, and amplifier 114 supplying
current to the coils 110. The currents for both amplifiers are
drawn through resistor 115 which is connected to the voltage supply
line 116.
The power amplifiers 112 and 114 are generally similar to the
amplifier stage 26 in the circuit of FIG. 1. The amplifier 112
includes NPN transistor 118 which drives PNP transistor 120, which
in turn drives the final NPN transistor 122. All three transistors
contribute to the current supplied to the coils 10, with the
transistor 122 supplying the largest portion of the current.
Resistor 123 and the series combination of capacitor 124 and
resistor 127, connected between the base and emitter of transistor
120, act to prevent spurious oscillations in the power amplifier
112. The power amplifier 114 can be identical to the power
amplifier 112.
A voltage regulator 125 is provided for controlling the power
amplifier to provide a constant voltage over the first part of the
cycle. The voltage regulator 125 may be of known construction and
can provide a regulated output voltage of about 9.5 volts from the
voltage supplied applied at terminal 126. This voltage may be from
a battery having a nominal voltage of 12 volts, and which varies
from about 11 to 16 volts under various conditions of charge. The
regulated voltage is applied to the base of PNP transistor 128, the
emitter of which is connected to one collector of transistor 130,
and the collector of which may be connected to ground. Transistor
130 is a multiple collector lateral transistor, with collector 130a
being of a size to provide three times as much current as collector
130b. The transistor 130 is normally conducting to complete a path
through collector 130a for transistor 128. The voltage at the
emitter of transistor 128 is above the reference voltage applied to
the base thereof by the base-emitter drop of transistor 128. With
the reference voltage being at 9.5 volts, a voltage of
approximately 10.2 volts is applied to the base of input transistor
118 of amplifier 112. The voltage at the emitter of transistor 118,
which is applied to the coils 10, is reduced by the base-emitter
drop to about 9.5 volts, and is therefore substantially the same as
the reference voltage.
In the event that the voltage across the injector coils 10 rises
above the reference voltage, transistor 118 will start to be biased
off to reduce the conductivity of transistor 120, which will in
turn reduce the conductivity of transistor 122. This will reduce
the current flow in the coils 10, and thereby reduce the voltage
across the injector coils. Sufficient current is applied to the
base of transistor 118 by transistor 130 so that the required
current is applied to the injector coils 10. The voltage regulator
action then starts, as has been described, to hold the voltage
across the coils constant.
As in the system of FIG. 1, the current regulating circuit comes in
effect when the voltage across resistor 115 reaches a predetermined
value. Resistor 115 is in the circuit for both power amplifiers 112
and 114, but only one of these amplifiers will be operative at any
given time. Accordingly, the current through resistor 115 will be
only the current supplied to the bank of regulator coils 10, or the
bank of regulator coils 110. As described in connection with the
circuit of FIG. 1, the system will automatically cross over from
the constant voltage condition to the constant current condition
when the current through resistor 115 reaches five amperes. This
will provide a voltage of one half volt cross the 0.1 ohm resistor
115.
The current control circuit includes differential amplifier 132
formed by two Darlington connected transistor pairs, the first
including transistor 134 and 135, and the second including
transistors 137 and 138. The voltage across resistor 115 is applied
to the base of transistor 135, and a reference voltage is applied
to the base of transistor 138. The differential amplifier 132
includes a current source formed by transistor 184 and resistor
185, and is similar to the differential amplifier 52 in the circuit
of FIG. 1.
The reference voltage applied to the base of transistor 138 is
produced across resistor 140 which is connected to the voltage
supply line, and in series with transistor 142 to ground. The
current through resistor 140 is regulated by the conduction of
transistor 142, which is in turn controlled by the conductivity of
diode 144 connected between the base of transistor 142 and the
emitter thereof. Connected in series between the regulated voltage
applied to terminal 148 and diode 144 is a first path including
resistor 146 and a second path including resistor 150 and diode
151. The regulated voltage at terminal 148 may be provided by the
voltage regulator 125. The sum of the currents through resistors
146 and 150 flows through diode 144, and the characteristics of
this diode and transistor 142 are matched so that substantially the
same value of current which flows through diode 144 will also flow
through the emitter-collector path of transistor 142. Accordingly,
the current through diode 144 will also flow through the reference
resistor 140. It will be apparent that the current relation does
not need to be that described as the components can be constructed
to provide a ratio of currents other than a unity ratio.
While the current is building up through the injector coils 10, the
reference voltage applied to the base of transistor 138 causes
transistors 134 and 135 of the differential amplifier 132 to be
conducting and transistors 137 and 138 to be nonconducting. When
the voltage across resistor 115 reaches the desired level, such as
that produced by 5 amps, the conduction of transistors 134 and 135
will decrease and the conduction of transistors 137 and 138 will
increase. Connected to the transistors 134 and 137 is a turn around
circuit including the multiple collector transistor 133 which
provides the same action as transistor 22 and diode 20 in the
differential amplifier 14 of FIG. 1. The output point 136 of the
differential amplifier 132 is at the connection between the
collector of transistor 134 and one of the collectors of transistor
133. The point 136 is connected to the base electrodes of
transistors 154 and 155 which are individually connected with
transistors 156 and 157 in separate branches of a differentially
operating circuit. The common emitters of transistors 156 and 157
are connected through transistor 158 and resistor 159 to the
reference potential, and the common collectors of transistors 154
and 155 are connected through one collector of multiple collector
transistor 160 to the voltage supply line 116.
This differential circuit is operated by a voltage applied to
terminal 162 connected to the base electrode of transistor 157 to
render this transistor conducting during 180.degree. of the
rotation of the engine and nonconducting during the other
180.degree.. A reference potential is applied to the base electrode
of transistor 156, as will be described, to provide the
differential action so that when transistor 157 is conducting,
transistor 156 is cut off, and when transistor 157 is cut off,
transistor 156 is conducting. In the following description it is
assumed that transistor 157 is conducting so that transistor 155 is
operative. Transistor 158 is rendered conducting by switch
transistor 180 which causes current flow through diodes 181 and
182. The drop across the diodes 181 and 182 renders transistor 158
conducting and provides a voltage equal to one diode drop across
resistor 159. Assuming that the switch transistor 180 is
conducting, and that transistor 158 is thereby conducting, current
having a value of about 1 mil will flow through the resistor 159
and through transistor 157 (or transistor 156). A path for this
current is normally provided through the collector electrode 130b
of transistor 130.
When transistors 134 and 135 of differential amplifier 132 reduce
conduction as the current through resistor 115 increases,
transistor 155 will be rendered conducting so that the current
through resistor 159 will be diverted from transistor 130 to
transistor 155. Transistor 164 is connected to control transistor
130, with the emitter of transistor 164 connected to the base of
transistor 130, and the base of transistor 164 connected to the
collector 130b of transistor 130. When current flows through the
collector 139b of transistor 130, current will also flow in
parallel through the base and emitter of transistor 164. When this
current reduces, the voltage drop across resistor 165 will likewise
reduce to cause the voltage at the base of transistor 130 to rise
to reduce the current flow therethrough. As previously stated, the
current through collector 130a is three times that through
collector 130b. The reduction in current at collector 130a is
amplified by the power amplifier 112 to greatly reduce the current
applied to the coils 10.
Transistor 160 which has one collector 160a thereof connected to
the collectors of transistors 154 and 155 has a second collector
160b, and is constructed so that the current through 160b is about
three times that through collector 160a. When transistors 154 and
155 are turned on by the differential amplifier 132, this will
cause the transistor 160 to conduct so that current from collector
160b will provide a voltage across resistor 168 to render
transistor 169 conducting. Transistor 169 shunts the current
through resistor 150 so that it does not flow through the diode
144. The current through resistor 150 is about twice the current
through resistor 146, so that this shunting action reduces the
current through diode 144 to about one-third its prior value. This
controls the reference voltage across resistor 140 so that it
reduces to about one-third its prior value, so that the voltage
applied to the base of transistor 138 is reduced to about
one-third.
The differential amplifier will act as described above to reduce
the current supplied to the amplifier 112 so that the current
through resistor 115 is only about one-third of its prior value.
When the system is set up so that the current regulator switches in
when the current through resistor 115 is about 5 amps, the current
provided after the current regulator is operating will drop to
about 1.6 amps. This operation is shown by FIG. 2, and is generally
the same as previously described.
A low voltage sensing circuit 170 is coupled to transistor 142 in
the voltage reference circuit, which may be generally the same as
the low voltage sensing circuit described in connection with FIG.
1. This includes resistor 171 connected in series with zener diode
172 and resistor 173 between terminal 148 and the ground potential.
Resistor 173 provides a bias to transistor 175 to normally hold the
same conducting, with the collector of transistor 175 being
connected by resistors 176 and 177 to resistor 171. The junction
between resistors 176 and 177 provides the reference voltage to the
base of transistor 156 to control the differential action, as
previously described. Transistor 178 is connected in series with
resistor 179 across transistor 142 to provide additional current
through resistor 140 when transistor 175 is rendered nonconducting.
This further drops the reference voltage applied to the base of
transistor 138 so that adequate current is insured in the injector
coils when the supply voltage drops to a very low value, as has
been previously described.
As has been stated, the transistors 156 and 157 are alternately
conducting, each during one 180.degree. period of rotation of the
engine with which the fuel injector system is utilized. The
transistor 158 connected in series with transistors 156 and 157 is
rendered conducting by a switch circuit including transistor 180,
which provides a voltage drop across diodes 181 and 182. Transistor
184, which is in the emitter circuit of differential amplifier
circuit 132, is also rendered conductive by the switch transistor
180. When transistor 158 is not conducting, there is no current
path to the base of transistor 164 and this transistor is
nonconducting so that the voltage across resistor 165 renders
transistor 130 nonconducting. This in turn cuts off transistor 128
so that there is no drive for the amplifier 112, and no current
flows through the injector coils 10.
A positive turn on potential is applied to terminal 186 and coupled
through resistor 187 to the base of transistor 180. This voltage is
greater than the base-to-emitter drop of transistor 180 and the
drops across diodes 181 and 182 to cause turn on of transistor 180.
The voltage across diodes 181 and 182 causes the turn on of
transistor 158 and 184 so that drive is applied to power amplifier
112. This causes current to flow through coils 10, as shown by the
rising part of the curve in FIG. 2, indicated as A. As previously
stated, this current continues to rise as the voltage is maintained
across the injector coils until the combined current through the
four coils reaches a value of about 5 amps.
Since transistor 184 is also turned on by the switch transistor
180, differential amplifier 132 is operative to provide control
action when the current through resistor 115 reaches the 5 ampere
level. This action, which was previously described, acts to cut
down the output current to a value of about 1.6 amps, as shown by B
in FIG. 2. The output current continues at this low level until
switch transistor 180 is turned off, when the current in the coils
terminates as shown at point C in FIG. 2. The reduced current
through the coils is adequate to retain the injector valves open,
and the use of reduced current makes it possible to turn off the
current and allow the valves to close more precisely at the desired
time.
When the signal applied to terminal 162 changes at the 180.degree.
rotation points of the engine to cut off transistor 157 and turn on
transistor 156, the action of the differential amplifier 132 will
transfer from transistor 155 to transistor 154, and will effect the
operation of the transistors 190 and 192. The transistor 190 is of
the same construction, and operates in the same manner, which has
been described for transistor 130, and cooperates with transistor
194 to control the second power amplifier 114. Transistor 192 acts
in the manner described for transistor 164 to control the action of
transistor 190. Power amplifier 114 acts to provide current through
the bank of injector coils 110, in the same manner that amplifier
112 controls the current in the injector coils of bank 10. The
switch transistor 180 is turned on for a portion of the time during
which each transistor 156 or 157 is enabled, to control amplifier
112 or amplifier 114.
Each of the banks of injector coils is coupled through a diode 195
to zener diode 196, so that the energy in the coils when the
current is turned off is dissipated in the zener diode. For
preventing parasitic oscillations when current is applied to and
terminated in the injector coils, a circuit including resistor 198
and capacitor 199 is connected across each of the banks of
coils.
The circuit of the invention has been found to be highly effective
in controlling the operation of the coils of injector valves, to
thereby precisely control the opening and closing of the valves and
in turn control the amount of fuel fed to the cylinders of the
engine. Substantially all of the components of the control circuit
can be formed as an integrated circuit to provide a compact
inexpensive unit.
* * * * *