Electricity: battery or capacitor charging or discharging – Capacitor charging or discharging
Reexamination Certificate
2002-07-30
2003-12-09
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Capacitor charging or discharging
Reexamination Certificate
active
06661205
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resonant type capacitor charger that charges a load capacitor to a preset voltage cyclically, at high speed, and with high accuracy.
2. Description of the Related Art
Capacitor chargers are used for charging first stage capacitors of driving pulse power sources for driving pulse lasers such as a copper vapor laser, an excimer laser or the like, at high speed, repeatedly.
A capacitor charger is constructed such that an output of an inverter section IV is connected to a rectifier RE as shown in FIG.
10
.
That is, the capacitor charger controls the power output from a dc voltage source DC, converts a direct current supplied from the dc voltage source DC into an alternating current (square wave ac voltage) using the inverter section IV, rectifies the alternating current boosted by a transformer H using the rectifier RE, and charges a load capacitor C
D
using this rectified current.
Then, a control section
100
controls the charging of the load capacitor C
D
, being a charged object, by measuring a measured voltage V
10
, which is proportional to a charging voltage value V
1
of the load capacitor C
D
, using a voltage divider M
1
, and comparing the measured voltage V
10
detected with a preset voltage V
2
that indicates a target value of charging voltage of the load capacitor C
D
.
That is, the control section
100
determines whether the measured voltage V
10
from the voltage divider M
1
exceeds the internal preset voltage V
2
or not. If exceeding, it stops the inverter section IV at this point of time and stops charging the load capacitor C
D
.
However, in a conventional capacitor charger, since it is necessary to satisfy the high speed required for a driving pulse laser, repeated charging at high speed is required, and hence it is necessary to increase the charging current to the load capacitor C
D
during a half cycle corresponding to one driving pulse driving the inverter section IV.
Therefore, there are problems in a conventional capacitor charger that since the charging voltage charged by the charging current in each half cycle becomes high, even if the inverter section IV is stopped at the time that the charging voltage of the load capacitor C
D
reaches the target value, it can easily overshoot, so control cannot be performed with high accuracy, and the output of the driving pulse laser is inconsistent.
On the other hand, in the above-described capacitor charger, if the number of driving pulses for driving the inverter section IV during the charge period is increased, and the charging voltage value V
1
of the load capacitor C
D
and the preset voltage V
2
are compared accurately, in order to perform a charging process with high accuracy, it is necessary to limit the charging voltage in one driving pulse.
By so doing, even if the accuracy of charging can be increased in the conventional capacitor charger, there is a disadvantage that the high speed charging required for a driving pulse laser cannot be satisfied.
SUMMARY OF THE INVENTION
The present invention takes this background into consideration with an object of providing a capacitor charger that can control charging voltage with high accuracy, and repeat a process of raising it to a target charging voltage at high speed.
A capacitor charging method according to a first aspect of the present invention is a capacitor charging method in which a resonant type inverter section is operated by driving pulses at a fixed frequency to generate an ac voltage, the ac voltage is converted to a dc voltage, and a capacitor is charged using the dc voltage, comprising the steps of: a first step where a first type of driving pulse of the driving pulses has a fixed driving pulse width W
1
determined in advance, which charges the capacitor by a boost voltage &Dgr;Vn (n is a natural number, step up voltages &Dgr;V
1
, &Dgr;V
2
, . . . that gradually decrease as a load capacitor C
D
is charged) at each input of the first type of driving pulse; and a second step which charges the capacitor by a single or a plurality of a second type of driving pulse having a controlled driving pulse width W
2
(W
1
>W
2
) as required to increase the voltage of the capacitor by a voltage [V
2
−V
1
] when a charging voltage V
1
of the capacitor reaches a value that satisfies [V
2
>V
1
>V
2
−V
1
<&Dgr;Vn] for a target voltage value V
2
.
A capacitor charging method according to a second aspect of the present invention is a capacitor charging method in which a resonant type inverter section is operated by driving pulses at a fixed frequency to generate an ac voltage, the ac voltage is converted to a dc voltage, and a capacitor is charged using the dc voltage, comprising the steps of: a first step where a first type of driving pulse of the driving pulses has a fixed driving pulse width W
1
determined in advance, which charges the capacitor by a boost voltage &Dgr;Vn (n is a natural number, &Dgr;V
1
, &Dgr;V
2
, . . . ) at each input of the first type of driving pulse; and a second step which charges the capacitor by a plurality of a second type of driving pulse having a fixed driving pulse width W
3
(W
1
>W
3
) in order to boost the voltage by [V
2
−V
1
] when a relationship between a charging voltage V
1
of the capacitor and a target voltage value V
2
is [V
2
−V
1
<&Dgr;Vk+ . . . +&Dgr;Vn (k is a natural number, and k<n), or [V
2
−V
1
<&Dgr;Vn].
In the capacitor charging method according to the second aspect of the present invention, only the last driving pulse among a plurality of the second type of driving pulses in the second step may have a controlled driving pulse width.
A capacitor charging method according to a third aspect of the present invention is a capacitor charging method in which a resonant type inverter section is operated by driving pulses at a fixed frequency to generate an ac voltage, the ac voltage is converted to a dc voltage, and a capacitor is charged using the dc voltage, comprising the steps of: a first step where a first type of driving pulse of the driving pulses has a fixed driving pulse width W
1
determined in advance, which charges the capacitor by a boost voltage &Dgr;Vn (n is a natural number, step up voltages &Dgr;V
1
, &Dgr;V
2
, . . . that gradually decrease as a load capacitor C
D
is charged) at each input of the first type of driving pulse; a second step which when a charging voltage V
1
of the capacitor is a midpoint preset voltage value V
3
that is lower than a target voltage value V
2
, charges by a boost voltage &Dgr;Vm (m is a natural number), by using a second type of driving pulse with a new, fixed driving pulse width W
4
obtained with consideration of a change of input voltage to the resonant type inverter section; and a third step which charges by a third type of driving pulse having a controlled driving pulse width W
5
(W
5
<W
4
) as required to boost the voltage by [V
2
−V
1
<&Dgr;Vm].
In the capacitor charging methods according to the present invention, at the start of charging of the first step, the capacitor may be charged by a fixed driving pulse width smaller than the fixed driving pulse width W
1
, or a soft start driving pulse with a gradually increasing driving pulse width.
A capacitor charger according to a first aspect of the present invention is a capacitor charger in which a resonant type inverter section is switched by driving pulses at a fixed frequency to generate an ac voltage, the ac voltage is converted to a dc voltage by a rectifier, and a capacitor is charged using the dc voltage, comprising: a control section that controls such that the voltage of the capacitor is increased by a boost voltage &Dgr;Vn (n is a natural number, step up voltages &Dgr;V
1
, &Dgr;V
2
, . . . that gradually decrease as a load capacitor C
D
is charged) at each input to the resonant type inverter section of a first type of driving pulse with a predetermined, fixed driving pulse w
Honma Yuji
Muraki Saori
Shinohara Shinichi
Yamamoto Makoto
Hoffmann & Baron , LLP
Origin Electric Company Limited
Tso Edward H.
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