Electric power conversion systems – Current conversion – Using semiconductor-type converter
Reexamination Certificate
2000-08-01
2001-11-27
Wong, Peter S. (Department: 2838)
Electric power conversion systems
Current conversion
Using semiconductor-type converter
C363S089000
Reexamination Certificate
active
06324084
ABSTRACT:
DESCRIPTION
1. Technical Field
The present invention relates to a power supplying device and a power supplying method for efficiently rectifying generated alternating power and for supplying the rectified voltage as power, and portable electronic equipment and an electronic timepiece, each incorporating the power supplying device.
2. Background Art
With a generator built in, small portable electronic equipment, such as a wristwatch, is always ready to be operative, requiring no troublesome battery replacement. If the power generated by the generator is an alternating-current power, the use of a diode bridge circuit as a rectifier circuit is contemplated. However, since the diode bridge circuit creates a loss due to a voltage drop through two diodes, the diode bridge circuit is not appropriate for use with the generator for the compact portable electronic equipment, i.e., not appropriate as a rectifier for use with the generator that generates a small-amplitude alternating-current voltage.
To cope with this problem, a rectifier circuit has been proposed having, instead of the four diodes, four uni-direction units, each permitting a current to flow in one direction only (Japanese Unexamined Patent Application Publication No. 9-131064).
The uni-direction unit has two terminals so that a current flows from one terminal to the other terminal when the voltage at one terminal rises above the voltage at the other terminal and that no current flows when the voltage at the one terminal drops below the voltage at the other terminal.
In this case, each uni-direction unit includes a comparator and a P-channel or an N-channel field-effect transistor.
A current, rectified through a rectifier circuit, charges a power storage unit such as a capacitor, and power is supplied to a load. In this arrangement, an alternating current generated across output terminals of a generator is full-wave rectified, and because of the use of active elements, there occurs no loss due to a voltage drop in full-wave rectification. Even if a generator
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generates a small-amplitude alternating current, the load is driven by the charged power source (capacitor) or directly by the rectified current.
The uni-direction unit allows a current to flow in one direction depending on the voltage across both terminals, and the comparator for comparing the terminal voltages suffers from a response delay time from the magnitude inversion of the terminal voltages to the reflection of the result of the transition in the output signal thereof.
The response delay time of the comparator, typically constructed of a MOS transistor, is proportional to “Cg/Iop”, where Cg represents a gate capacitance of the output transistor, and Iop represents an operating current of the comparator. In other words, the response delay time and the current consumption are mutually inversely proportional. In an electronic timepiece, operated from power from a built-in generator, no large generated power is obtained because the size of the generator is limited by the space availability of an electronic timepiece. To meet available power, low power consumption design is implemented in the circuit of the electronic timepiece.
In the comparator constituting the above-referenced uni-direction unit, low current consumption design is implemented, and the operating current Iop needs to be minimized, and the response delay time of the comparator tends to increase.
For this reason, a rectifying transistor is turned on while the rectifying transistor should be turned off, allowing a current to reversely flow.
A surge current flows out of a capacitor in response to the reverse flow of current, and damages the capacitor.
Since the reverse flow of current adds impulsive noise to power source voltage, the load operated from the supply of the power source voltage is subject to erratic operations.
If the response delay time of the comparator is too long, the timing of charging the capacitor by controlling the uni-direction unit is delayed from the timing the generated voltage of the generator in the phase of the generated voltage.
As a result, the capacitor is charged for only a duration throughout which the amplitude of the generated voltage of the generator is greater than the voltage difference between a high potential voltage and a low potential voltage, and a chargeable duration is shortened, and rectification efficiency drops.
If the operating current of the comparator constituting the uni-direction unit is increased, the response delay time is shortened. But this raises a new problem that power is consumed by the comparator itself, lowering the efficiency of the power supplying device.
It is a first object of the present invention to provide a power supplying device and a power supplying method for preventing a reverse flow of current due to a delay time of a uni-direction unit, and portable electronic equipment and an electronic timepiece, each incorporating the power supplying device.
It is a second object of the present invention to provide a power supplying device and a power supplying method for efficiently rectifying generated alternating current power and supplying the rectified power, and portable electronic equipment and an electronic timepiece, each incorporating the power supplying device.
DISCLOSURE OF THE INVENTION
The present invention in a first aspect lies in a power supplying device for rectifying an alternating current voltage to supply power to a first power source line and a second power source line, including a uni-direction unit including two terminals, a comparator for comparing terminal voltages at the two terminals, and a switching unit that is controlled for an on-and-off operation in response to the comparison result provided by the comparator, the uni-direction unit allowing a current to flow from one terminal to the other terminal through the switching unit, the power supplying device including a storage unit for storing power, arranged between the first power source line and the second power source line, wherein the uni-direction unit starts an operation for turning off the switching unit with a duration in advance, corresponding to a response delay time.
In the present invention in a second aspect, in the power supplying device in accordance with the first aspect, the uni-direction unit turns off the switching unit when the voltage level at the one terminal drops below a voltage level which is the sum of the voltage at the other terminal and a predetermined voltage.
The present invention in a third aspect lies in a power supplying device for rectifying an alternating current voltage to supply power to a first power source line and a second power source line, including a plurality of uni-direction units, each uni-direction unit including two terminals, a comparator for comparing terminal voltages at the two terminals, and a switching unit that is controlled for an on-and-off operation in response to the comparison result provided by the comparator, the uni-direction unit allowing a current to flow from one terminal to the other terminal through the switching unit, and a storage unit for storing power, arranged between the first power source line and the second power source line, wherein one terminal of a first uni-direction unit is connected to a first input terminal to which the alternating current voltage is supplied, the other terminal of the first uni-direction unit is connected to the first power source line, one terminal of a second uni-direction unit is connected to a second input terminal to which the alternating current voltage is supplied, the other terminal of the second uni-direction unit is connected to the first power source line, one terminal of a third uni-direction unit is connected to the second power source line, the other terminal of the third uni-direction unit is connected to the first input terminal, one terminal of a fourth uni-direction unit is connected to the second power source line, the other terminal of the fourth uni-direction unit is connected to the second input terminal, and at least two of the fou
Seiko Epson Corporation
Vu Bao Q.
Wong Peter S.
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