Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2002-10-02
2004-05-18
Han, Jessica (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S225000, C320S166000, C307S109000
Reexamination Certificate
active
06737847
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resonant charging type capacitor charging apparatus in which an inductance device and an energy accumulating capacitor resonate to charge the energy accumulating capacitor. In particular, the invention relates to a capacitor charging method and charging apparatus that prevent with high accuracy, an energy accumulating capacitor from being overcharged by inertial current, which is caused by magnetic energy stored in an inductance device.
2. Description of the Related Art
In a pulse laser such as an excimer laser, the charge of a capacitor for accumulating energy, which has been charged to a high voltage of approximately several kV to several tens of kV, is discharged at high speed to a laser tube via a magnetic compressor or the like, thereby exciting laser light. In an apparatus using a pulse laser, the higher the number of laser light excitations, that is, the higher the number of repetitions of charging and discharging the energy accumulating capacitor, the greater its capability as a laser apparatus. Therefore in recent years there have been attempts to achieve a high repetition rate of several kHz.
Consequently, the charging apparatus of the energy accumulating capacitor must be capable of repeated high-speed charging operations to completely charge it in less than several hundred &mgr;s. Furthermore, excimer lasers require a highly accurate degree of voltage stability, detecting fluctuations in the output of laser light in each cycle and controlling the output of laser light in the subsequent cycle accordingly. Therefore, the charge voltage must be controlled in each cycle, making high-speed controllability an important feature.
FIG. 12
shows an example of a conventional resonant charging type capacitor charging apparatus. Reference numeral
1
represents a dc power supply obtained by rectifying ac power such as a commercial power supply. Reference numeral
4
represents a semiconductor switch such as an IGBT (Insulated Gate Bipolar Transistor) or the like, reference numeral
5
represents a resonant inductance device, reference numeral
7
represents a diode circuit, reference numeral
8
represents an energy accumulating capacitor, being a load, and these are connected to the dc power supply
1
equivalently, in series. Reference numerals
9
and
10
represent voltage detecting resistors. Reference numeral
3
represents a flywheel diode connected between the negative terminal of the dc power supply
1
and a node between the semiconductor switch
4
and the resonant inductance device
5
. Reference numeral
14
represents a control circuit, which controls such that the semiconductor switch
4
is switched on by a charge start signal
16
, and the semiconductor switch
4
is switched off when the voltage of the energy accumulating capacitor
8
reaches a target charge voltage VI supplied from a reference voltage power supply
15
.
The operation will be described using
FIG. 13. I
represents the current flowing through the resonant inductance device
5
, the white part is current flowing through the semiconductor switch
4
, and the diagonally hatched part is current in which inertial current, occurring due to magnetic energy stored in the resonant inductance device
5
, flows into the energy accumulating capacitor
8
through the flywheel diode
3
after the energy supply from the dc power supply
1
to the resonant inductance device
5
is stopped by switching off the semiconductor switch
4
.
When the semiconductor switch
4
is switched on by the control circuit
14
on receiving the charge start signal
16
at time t
0
, resonant current flows due to the resonant inductance device
5
and the energy accumulating capacitor
8
, and if no circuit loss occurs in components, wiring or the like by the flow of the charging current, the energy accumulating capacitor
8
is charged toward approximately twice the voltage value of the output voltage E of the dc power supply
1
. When the charge voltage Vc, obtained by dividing the charge voltage of the energy accumulating capacitor
8
using the voltage detecting resistors
9
and
10
, reaches the target charge voltage V
1
at time t
1
, the control circuit
14
switches off the semiconductor switch
4
. However, the flywheel diode
3
is switched on by inertial current due to the residual energy of the resonant inductance device
5
, and continues charging the energy accumulating capacitor
8
, which is overcharged by &Dgr;V.
Therefore, Japanese Unexamined Patent Application, First Publication No. Hei 8-9638 using a resonant charging scheme discloses a method in which power supply voltage is detected and added to a reference voltage out of phase, and the off timing of a semiconductor switch is adjusted such that variations of power supply voltage are compensated. However, the relationship between power supply voltage variation and excess charge amount is not linear, and in a real charger the final charge voltage always changes, so that it is not possible to improve the accuracy by only compensating for power supply voltage variation.
SUMMARY OF THE INVENTION
Accordingly, the present invention aims to provide a capacitor charging method and charging apparatus that can always charge an energy accumulating capacitor with highly accurate voltage stability, using a target charge voltage for the energy accumulating capacitor, and input voltage variation, even if the voltage of a dc power supply changes due to variations of a target charge voltage of the energy accumulating capacitor and an input voltage.
A capacitor charging method according to a first aspect of the present invention comprises the steps of: in a series connected circuit of a first semiconductor switch, a resonant inductance device, a diode circuit, and an energy accumulating capacitor, which are connected together in series to a dc power supply, starting charging of the energy accumulating capacitor due to the resonance of the resonant inductance device and the energy accumulating capacitor by switching on the first semiconductor switch; stopping energy supply from the dc power supply to the resonant inductance device by switching off the first semiconductor switch, when an equation Vc=&agr;((V
1
2
−Vo
2
)/(2E)+Vo) is satisfied, where V
1
is a target charge voltage of the energy accumulating capacitor, Vc is a charge voltage of the energy accumulating capacitor, Vo is an initial voltage of the energy accumulating capacitor, E is an output voltage of the dc power supply, and a is a circuit loss coefficient for compensating for power loss occurring in components and wiring due to the flow of charging current; and after the first semiconductor switch is switched off, charging the energy accumulating capacitor to the target charge voltage V
1
by the flow of inertial current caused by magnetic energy stored in the resonant inductance device, using a flywheel diode.
That is to say, charging is performed while calculating a forecast of the amount of added charge due to inertial current after the energy supply from the dc power supply to the resonant inductance device is stopped by the first semiconductor switch being switched off, and when it is determined by the calculation of the above equation that the energy accumulating capacitor can be charged to the target charge voltage by the inertial current, the first semiconductor switch is switched off, after which it is possible to charge to the target charge voltage with high accuracy using the inertial current.
A capacitor charging method according to a second aspect of the present invention comprises the steps of: in a series connected circuit of a first semiconductor switch, a resonant inductance device, a diode circuit, and an energy accumulating capacitor, which are connected together in series to a dc power supply, starting charging of the energy accumulating capacitor due to the resonance of the resonant inductance device and the energy accumulating capacitor by switching on the first semiconductor switc
Mimura Takayuki
Tomaki Teruo
Watanabe Kiyomi
Han Jessica
Hoffmann & Baron , LLP
Origin Electric Company Limited
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