Electric power conversion systems – Current conversion – Using semiconductor-type converter
Reexamination Certificate
1999-01-26
2002-07-16
Berhane, Adolf Deneke (Department: 2838)
Electric power conversion systems
Current conversion
Using semiconductor-type converter
Reexamination Certificate
active
06421261
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a power supply apparatus which can be incorporated in arm-worn type or other type of portable electronic equipment and which is provided with a power generating device of such a type as the one that is capable of converting the kinetic energy of a human body into alternating current by making use of the motion of a rotary weight.
RELATED ART
Portable electronic equipment has been devised and put to practical use which makes it possible to obviate the need for replacing a battery or to eliminate the battery itself by incorporating a power generating device in small electronic equipment suited for carrying such as a wristwatch device.
FIG. 11
shows the schematic configuration of a wristwatch device
10
incorporating a power generating unit
1
as an example. The portable electronic equipment (wristwatch device)
10
is provided with a rotary weight
13
which swings in the case of the wristwatch device, a wheel device
11
which transmits the rotary motion of the rotary weight
13
to an electromagnetic power generator, and a rotor
14
and a stator
15
making up the electromagnetic power generator
12
; when the rotor
14
which has been magnetized to have two poles rotates, an electromotive force is generated in an output coil
16
of the stator
15
, and an AC output can be taken out. Further, a power supply apparatus
20
of the portable electronic equipment is equipped with a rectifier circuit
24
which rectifies the alternating current output from the power generating unit
1
and supplies it to a large-capacity capacitor
5
and a processing unit
9
; connected to the output side thereof are the large-capacity capacitor
5
, which serves as a charging unit, and the processing unit
9
. Hence, the processing unit
9
connected to the power supply apparatus
20
is able to operate a mounted timing function
7
, etc. by the power of the power generating unit
1
or the power that the large-capacity capacitor
5
has discharged. Therefore, the portable electronic equipment is able to continuously operate the processing unit
9
even in the absence of a battery, thus implementing electronic equipment that permits the use of the processing unit at any place whenever required and that is also capable of solving the problems involved in discarding batteries.
In the electronic equipment shown in
FIG. 11
, since the power supplied from the built-in power generating unit
1
is of alternating current, it is rectified through the rectifier circuit
24
of the power supply apparatus
20
before it is charged in the large-capacity capacitor
5
, and it turns into the operating power of the processing unit
9
equipped with an IC, etc. The power supply apparatus
20
shown in
FIG. 11
employs the rectifier circuit
24
which temporarily charges the power, which has been half-wave rectified using two diodes
25
and
26
, in an auxiliary capacitor
27
to perform boosting and rectification. For these diodes
25
and
26
, silicon diodes are employed; as shown in
FIG. 12
, they have a forward voltage Vf of about 0.5 V to about 0.6 V with respect to a forward current If. Hence, power W
1
obtained by rectifying power W
0
supplied from the power generating unit
1
through the rectifier circuit
24
will be as shown below because there is a loss attributable to the forward voltage Vf of the diodes making up the rectifier circuit
24
:
W
1
=&eegr;
c×W
0
(1)
&eegr;
c
=V
1
/(V
1
+2
×Vf
) (2)
where &eegr;c denotes the rectifying efficiency at the time of charging, and V
1
indicates the output voltage from the rectifier circuit and it corresponds to the charging voltage of the large-capacity capacitor
5
in the circuit shown in
FIG. 11
Regarding the operating voltage of the processing unit
9
of the portable electronic equipment such as a wristwatch device, ICs or the like are increasingly driven at lower voltage to decrease power consumption; the processing unit may be started, for example, at about 0.9 V to about 1.0 V. Hence, the voltage of the large-capacity capacitor
5
is set to about 1.5 V to about 2 V; when the forward voltage Vf of about 0.5 V to about 0.6 V is considered, the rectifying efficiency &eegr;c undesirably takes a value of approximately 0.6. Therefore, it is desirable that the forward voltage Vf is low in order to improve the rectifying efficiency &eegr;c.
Further, as the power generating unit which can be built in the portable electronic equipment, there are, for example, a device which employs a rotary weight to catch the movement of a human body or the like and rotates a rotor so as to convert it to AC power, a device which employs a spiral spring to accumulate energy and converts it to AC power, a device which vibrates a piezoelectric element by the movement of a human body or the like in order to obtain AC power, and a device which employs a thermoelectric element or a solar battery to obtain DC power. Among these devices, in the power generating units which provide AC power, the kinetic energy obtained for power generation from the movement of a human body or the like is small, and the electromotive force is also small because the power generator itself is extremely miniaturized to build it in portable electric equipment; and further, the electromotive force greatly varies depending on the movement of a human body or the like and power, therefore, is not always obtained. Thus, the input voltage of the rectifier circuit is low and varies at a voltage in the vicinity of the forward voltage Vf; it reaches only a few times as high as the forward voltage Vf at the maximum. This means that the power feeding efficiency is markedly improved by lowering the forward voltage Vf.
In a power supply apparatus using a power generating unit such as a solar battery which generates DC power, the electromotive force also varies greatly depending on illuminance or the like. Hence, it is possible to effectively use the power, which has been generated, by lowering the forward voltage Vf of a backflow preventing diode even if the illuminance is low and the electromotive force is small. Thus, it is a significant challenge to lower the forward voltage Vf used in the supply circuit in order to effectively use the power supplied from the power generating unit which can be incorporated in portable electronic equipment for which the development is being pursued in recent years.
It is, therefore, an object of the present invention to provide a power supply apparatus with high power feeding efficiency, which power supply apparatus employs a unidirectional unit capable of lowering the forward voltage Vf in place of the diodes to markedly improve the rectifying efficiency &eegr;c of the power supply apparatus for portable electronic equipment. And, it is another object of the invention to provide portable electronic equipment which can be used at any place whenever necessary without the need for replacing a battery by providing itself with the power generating unit with high efficiency and a processing unit.
DISCLOSURE OF THE INVENTION
To these ends, in a power supply apparatus which can be built in portable electronic equipment in accordance with the present invention, a unidirectional unit equipped with a diode, a bypass switch connected in parallel to the diode, and a controller which turns ON the bypass switch when a forward voltage appears in the diode is employed for the supply unit that supplies power from a power generating unit to a charging device or a processing unit. In the unidirectional unit, if current flows in the forward direction of the diode and a forward voltage appears, then the bypass switch is turned ON, so that the loss caused by the forward voltage can be prevented. Moreover, if the flowing direction of current is opposite from that of the diode, then a voltage of an opposite polarity from the forward voltage appears; therefore, the bypass switch is not turned ON and backflow can be prevented by the diode.
As a popular unidirectional unit mentioned above
Fujisawa Teruhiko
Kadowaki Tadao
Shinkawa Osamu
Yabe Hiroshi
Berhane Adolf Deneke
Seiko Epson Corporation
Stroock & Stroock & Lavan LLP
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