Electricity: single generator systems – Automatic control of generator or driving means – Current output
Reexamination Certificate
2001-08-07
2004-08-24
Dougherty, Thomas M. (Department: 2834)
Electricity: single generator systems
Automatic control of generator or driving means
Current output
C322S017000, C322S028000
Reexamination Certificate
active
06781350
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an electronic control circuit for controlling generator output, which is accommodated in a vehicle-mounted A.C. generator, and is in the form of a monolithic IC chip on a ceramic substrate.
BACKGROUND ART
Heretofore, as a controller, for an A.C. generator in a vehicle in which discrete components are employed as circuit elements to be mounted onto a wiring board, a controller is known which has a circuit configuration shown in FIG.
3
. This controller includes: an A.C. generator
1
having an armature coil
101
for driving an engine and for starting the generating operation of electrical energy, and a field coil
102
; a rectifier
2
for taking out an output of generating electrical energy from the armature coil
101
to rectify the output, which is supplied to batteries
4
or to an electrical load (not shown); and a controller
3
having a voltage regulator
3
a
for detecting the voltage developed across the terminals of the batteries
4
to adjust the output voltage of the A.C. generator
1
on the basis of the voltage thus detected and a field current restricting unit
3
b
for detecting the field current caused to flow through the field coil
102
to restrict the field current on the basis of the detected current.
Reference numeral
5
indicates a key switch for starting the engine. This key switch
5
is turned ON so that the current flows through the field coil
102
from the batteries
4
to carry out the initial excitation.
The voltage regulator
3
a
is configured in such a way as to include: a constant voltage circuit in which an operating resistor
301
and a Zener diode
302
are electrically connected in series between the positive electrode of the batteries
4
and the earth through the key switch
5
to fetch a constant voltage A, which is determined on the basis of the breakdown voltage of the Zener diode
302
, from a connection point P between the operating resistor
301
and the Zener diode
302
; a voltage dividing circuit having voltage dividing resistors
303
and
304
, which are electrically connected in series between an output terminal
201
of a positive electrode and an output terminal
202
of a negative electrode of the rectifier
2
to divide the output voltage of the rectifier
2
; a first comparator
307
for applying a divided voltage Vd from the voltage dividing circuit to an input terminal (−) of the negative side and for applying a fixed reference voltage V
REF1
to an input terminal (+) of the positive side to make H or L the logical level at the output terminal in accordance with the magnitude relationship between the divided voltage Vd and the reference voltage V
REF1
; an output transistor
311
which is turned ON at the time when the logical level at the output terminal of the first comparator
307
has become H to cause the field current to flow through the field coil
102
from the batteries
4
; a suppression diode
310
which is electrically connected in reverse between a positive side line and a collector of the output transistor
311
to suppress a surge current which occurs at the time when shutting off the field current; and a base resistor
309
which is electrically connected between the output side of the key switch
5
and the base of the output transistor
311
to restrict a base current which is caused to flow through the base of the output transistor
311
at the time when carrying out the initial excitation of the field coil
102
.
The field current restricting unit
3
b
includes: a voltage dividing circuit having voltage dividing resistors
305
and
306
for dividing a constant voltage A at a predetermined resistance ratio to generate a predetermined reference voltage V
REF2
; a field current detecting resistor
312
connected between an emitter of the output transistor
311
and the earth for converting the field current flowing through the emitter into a voltage V
1
to detect the voltage V
1
thus obtained; and a second comparator
308
for applying the reference voltage V
REF2
to an input terminal (+) of the positive side and for applying the voltage V
1
to an input terminal (−) of the negative side to make L the logical level at the output terminal at the time when the voltage V
1
has become higher than the reference voltage V
REF2
.
Now, the description hereinbelow will be given with respect to the outline of the operation in the conventional controller for an A.C. generator for a vehicle.
After having started the engine, the divided voltage Vd as a criterion of the terminal voltage of the batteries
4
rises above the reference voltage V
REF1
to provide the over-charging state, the logical level at the output terminal of the first comparator
307
goes to L to turn OFF the output transistor
311
so that the field current to the field coil
102
is shut off, which reduces the output of the electrical energy generation.
When the terminal voltage of the batteries
4
has been reduced and also the divided voltage Vd has become lower than the reference voltage V
REF1
, the logical level at the output terminal of the first comparator
307
goes to H to turn ON the output transistor
311
. As a result, the current flowing loop consisting of the batteries
4
, the field coil
102
, the output transistor
311
, the field current detecting resistor
312
, and the earth is formed so that the field current is caused to flow from the batteries
4
to the field coil
102
to carry out the generation of electrical energy, and also the output of the generation of electrical energy is rectified through the rectifier
2
to be supplied to the batteries
4
which are in turn charged with the fixed voltage 14.5 V for example.
In this way, the output transistor
311
is turned repeatedly ON/OFF in accordance with the drop and the rise of the voltage developed across the terminals of the batteries
4
to intermittently control the field current to so that the terminal voltage is maintained at a fixed value.
The surge current which is generated through the field coil
102
along with the interruption of the field current is suppressed by the suppression diode
310
to mitigate the influence thereof exerted on the electronic circuit.
However, if the line through which the terminal voltage of the batteries
4
is detected is cut in the voltage regulator
3
a
so that the divided voltage Vd becomes zero, for example, then the logical level of the output of the first comparator
307
continues to be H, and hence the A.C. generator
1
starts to cause to flow the excessive field current through the output transistor
311
in order to make the divided voltage Vd the reference voltage V
REF1
.
At this time, the field current is caused to flow through the field current detecting resistor
312
to generate the voltage drop of the voltage V
1
. Then, the voltage V
1
is applied to the negative side input terminal (−) of the second comparator
308
. The reference voltage V
REF2
which is used to judge the excessive field current is applied to the positive side input terminal (+) of the second comparator
308
. At the time when the voltage V
1
has become higher than the reference voltage V
REF2
, the logical level at the output terminal of the second comparator
308
goes to L.
For this reason, the output at the logical level H of the first comparator
307
is absorbed by the output terminal of the second comparator
308
, whereby the base current of the output transistor
311
is shut off, and the field current is also shut off to stop the generation of electrical energy to prevent the burning of the A.C. generator.
If the discrete components such as resistors, capacitors and semiconductor devices are mounted onto the printed board as in the method of mounting the electronic apparatus in the conventional controller, then a large mounting area is required and the scale of the whole controller becomes large.
In addition thereto, since the high accuracy is required for the output control of the vehicle A.C. generator along with the promotion of the elect
Iwatani Shiro
Kouwa Tatsuki
Watanabe Hirofumi
Cuevas Pedro J
Dougherty Thomas M.
Mitsubishi Denki & Kabushiki Kaisha
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