Electricity: power supply or regulation systems – Self-regulating – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
1995-10-17
2001-03-13
Wong, Peter S. (Department: 2838)
Electricity: power supply or regulation systems
Self-regulating
Using a three or more terminal semiconductive device as the...
C327S540000
Reexamination Certificate
active
06201381
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reference voltage generator in a charging device.
2. Description of Related Art
Charging devices for charging batteries generally comprise an internal reference voltage generator for comparing the battery voltage with the reference voltage output by the reference voltage generating circuit, and controlling battery charging according to the detected voltage difference. Because the optimum charging voltage of the battery varies according to the temperature, the reference voltage generating circuit is built with output temperature characteristics matching the battery characteristics to achieve optimum control in charging devices that maintain a constant correlation between the ambient temperature and battery.
An example of a reference voltage generating circuit known in the prior art is shown in FIG.
1
. This reference voltage generating circuit comprises resistors R
51
and R
52
, n (where n is an integer) diodes D
1
~D
n
, and resistors R
53
connected in series in this order between the constant-voltage power supply
1
, which outputs a voltage with little temperature-dependent variation, and ground, and outputs the reference voltage V
0
from between the ground and the output terminal
3
connected to the junction point between resistor R
51
and resistor R
52
.
The reference voltage V
0
can be expressed by Equation (1) where the voltage of the constant-voltage power supply
1
is V
cc
, the forward voltage of diodes D
1
~D
n
is V
F
, and the current flowing through resistors R
51
and R
52
, n (where n is an integer) diodes D
1
~D
n
, and resistor R
53
is I
50
.
V
0
=V
cc
−I
50
×R
51
=(R
52
+R
53
)V
cc
/(R
51
+R
52
+R
53
)+n R
51
V
F
/(R
51
+R
52
+R
53
)[V] (1)
The temperature characteristic ∂V
0
/∂T of the reference voltage V
0
to the absolute temperature T can be expressed by Equation (2) derived from Equation (1) if it is assumed that the voltage V
cc
of the constant-voltage power supply
1
has no temperature dependence.
∂V
0
/∂T=n R
51
/(R
51
+R
52
+R
53
)×∂V
F
/∂T[V/° C.] (2)
From Equation (2), it is known that the temperature characteristic (∂V
0
/∂T) of the reference voltage V
0
is determined by the n diodes D
1
~D
n
, resistors R
51
, R
52
, and R
53
, and (∂V
F
/∂T). From Equation (2), it is therefore possible to obtain various combinations of n diodes D
1
~D
n
and resistors R
51
, R
52
, and R
53
if voltage V
cc
is fixed and the value of the reference voltage V
0
is determined, and the temperature characteristic (∂V
0
/∂T) can be achieved for this number of combinations.
The number n of diodes D
1
~D
n
, however, is a discrete integer value. As a result, it is not possible to set any desired temperature characteristic (∂V
0
/∂T) by means of the reference voltage generating circuit described above.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a reference voltage generator circuit for generating a reference voltage that has a desired temperature characteristic and varies linearly relative to the temperature.
A further object of the present invention is to provide a reference voltage generating circuit for generating a reference voltage having a negative temperature coefficient.
A further object of the present invention is to provide a reference voltage generating circuit for generating a reference voltage having a positive temperature coefficient.
A further object of the present invention is to provide a reference voltage generating circuit for generating plural reference voltages each having a desired temperature characteristic and varying linearly relative to the temperature.
A further object of the present invention is to provide a reference voltage generating circuit for generating, in addition to a reference voltage that has a desired temperature characteristic and varies linearly relative to the temperature, a look-up voltage of which the temperature characteristic is zero.
A further object of the present invention is to provide a reference voltage generating circuit which can generate, by means of combination with an operational amplifier, plural reference voltages having a desired temperature characteristic and varying linearly relative to the temperature.
In a reference voltage generating circuit according to the present invention, a constant-current source of which the current level flowing into or out of a voltage divider junction varies linearly with a desired temperature coefficient is connected to the voltage divider junction of the voltage dividing circuit connected between the output terminals of a constant-voltage power supply outputting a constant voltage, thereby outputting the reference voltage from the voltage divider junction.
Preferably, the reference voltage is controlled to vary linearly with a negative temperature coefficient to the temperature.
Preferably, the constant-current source is made as an integrated circuit.
Preferably, it further comprises a current mirror circuit which controls the current flowing through the first current path and the current flowing through the second current path to be equal, a first transistor and a second transistor are respectively connected to the first current path and the second current path of the current mirror circuit, and a current inversely proportional to the value of the resistor connected to the emitter of the first transistor and proportional to the temperature is output from the voltage divider junction of the voltage dividing circuit.
Preferably, the reference voltage is controlled to vary linearly with a positive temperature coefficient to the temperature.
Preferably, it further comprises a current mirror circuit which controls the current flowing through the first current path and the current flowing through the second current path to be equal, a first transistor and a second transistor are respectively connected to the first current path and the second current path of the current mirror circuit, and a current inversely proportional to the value of the resistor connected to the emitter of the second transistor and proportional to the temperature is input to the voltage divider junction of the voltage divider circuit.
A reference voltage generating circuit according to the present invention may comprise a plurality of voltage divider circuits; a current mirror circuit controlling the current flowing through the first current path and the current flowing through the second current path to be equal; a first transistor of which the emitter is connected to the other output terminal of the constant-voltage power supply; a second transistor of which the base is connected to the base and collector of the first transistor; a first resistor connected between the emitter of the second transistor and the other output terminal of the constant-voltage power supply; a third and a fourth transistor; a fifth transistor of which the base is connected to the collector of the fourth transistor, the emitter is connected to the base of the third transistor, and the collector is connected to one of the output terminals of the constant-voltage power supply; and current extracting transistors of which each base is connected to the emitter of the fifth transistor, and each collector is connected to each voltage divider junction of the voltage divider circuits; such that a current inversely proportional to the value of the first resistor and proportional to the temperature is obtained from the voltage divider junction.
Preferably, the reference voltage generating circuit may obtain a standard voltage of which the temperature characteristic is zero from the emitter of the fifth transistor.
Preferably, the reference voltage generating circuit may connect the constant-current source and the plural sets of voltage divider circuits to the output of an operational amplifier, and connect the standard po
Leydig Voit & Mayer Ltd
Mitsubishi Denki & Kabushiki Kaisha
Vu Bao Q.
Wong Peter S.
LandOfFree
Reference voltage generating circuit with controllable... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reference voltage generating circuit with controllable..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reference voltage generating circuit with controllable... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2472112