JP2009142134A - Capacitor-charging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the accuracy of a charging voltage of a capacitor by making sure the operation of finely adjusted charging time even when charging is repeated at high frequency. <P>SOLUTION: This charging device charges a power capacitor 8 rapidly in a rapid charging circuit (1-6) up to a value close to a charging voltage command value and afterward charges the capacitor in a finely adjusted charging circuit (10-15) with a constant current up to the charging voltage command value. In this device, a control circuit 9 obtains and controls a finely adjusted charging time ΔT of the finely adjusted charging circuit from a charging voltage detection value V of the capacitor charged rapidly by the rapid charging circuit, the charging voltage command value V<SP>*</SP>, capacitance C of the capacitor, and a constant current value I'. A digital control circuit obtains the current capacitance of the capacitor when operating the finely adjusted charging time and adjusts the finely adjusted charging time again according to the change of the capacitance of the capacitor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a capacitor charging device that repeatedly charges a capacitor to a set voltage with high accuracy in a pulse power source that uses a power capacitor as a DC power source to generate a pulse of high voltage and large current, and particularly relates to fine adjustment control of a charging voltage. .

  Applications of this type of pulse power source include an excimer laser and an ozonizer, and the charging accuracy with respect to the set value of the charging voltage is required to be particularly high (for example, accuracy of 0.1% or less). The charging device charges the load capacitor to a voltage given by the charging voltage command value within a predetermined time. This operation is repeated 4000 times per second, for example.

  FIG. 3 shows a circuit example of a conventional capacitor charging device. In order to obtain a high-speed and high-precision charging accuracy with respect to a charging voltage command value, a quick charging time and a fine adjustment period are provided in one charging time. The load capacitor is rapidly charged to a voltage (target voltage) several percent lower than the command value during the charging time, and then further charged to the voltage command value during the fine adjustment period. In this additional charging, it is difficult to perform high-accuracy charging with respect to the command value only with the quick charging circuit, so the load capacitor is charged slightly lower than the target value with the quick charging circuit, and high-accuracy charging is realized by adding the fine adjustment circuit. (For example, refer to Patent Document 1). The circuit configuration and operation will be described below (see FIG. 4 for waveforms).

<Operation of quick charge time>
In FIG. 3, the rapid charging circuit is configured as a DC chopper type using a DC power source 1 as a power source, and includes a semiconductor switch 2, a reactor 3, a semiconductor switch 7 and flywheel diodes 4 and 6, and the load capacitor 8 is rapidly supplied with the output current. Charge.

  The voltage control circuit 9 that performs digital calculation first turns on the switch 2 and the switch 7 at the same time, passes a current through the circuit along the path indicated by the arrow A, and stores energy in the reactor 3. Next, the switch 2 and the switch 7 are simultaneously controlled to be turned off, and a current is passed through the circuit along the path indicated by the arrow B, so that all the energy stored in the reactor 3 is transferred to the capacitor 8 and the capacitor 8 is charged. The charging voltage at this time is obtained by multiplying the charging voltage command by a coefficient (less than 1) as the voltage command value of the control circuit 9, and the calculation result of the control circuit 9 based on this voltage command value is the result of the switches 2 and 7 Find the off timing.

  In this calculation, the reactor value of the reactor 3 is L, the capacitor capacity of the capacitor 8 is C, the current (arrow A) when the switch 2 and the switch 7 are turned off is I, and the capacitor 8 when the current of the arrow B finishes flowing. If V is V (hereinafter referred to as coarse charge voltage), the law of conservation of energy

Holds. In the quick charge, the capacitor 8 is charged to a target voltage (voltage lower than the command value by several percent) V based on the above equation. That is, the current i of the reactor 3 is always detected, and the following equation:

When the above is established, the switch 2 and the switch 7 are turned off.

<Operation during the fine adjustment period>
In FIG. 3, the fine adjustment charging circuit obtains an AC voltage by an inverter 10 using a DC power source 1 as a power source, boosts this by a pulse transformer 11, and includes a rectifier circuit 12, a DC reactor 13, a semiconductor switch 14, and a diode 15. The fine adjustment charging current of the capacitor 8 is output by the constant current circuit. The constant current control circuit 16 always keeps the switch 14 turned on, and the operation of the inverter 10 causes a current (a constant direct current) set by a constant current command to flow through the path of the rectifier circuit 12, the reactor 13, and the switch 14. Keep it. Next, the switch 14 is controlled to be turned off, and the charging current continues to flow through the capacitor 8 to finely charge the capacitor 8.

  In this fine adjustment period control, the analog voltage obtained by converting the charging voltage command value (digital value) by the D / A converter 17 and the voltage of the capacitor 8 are always compared by the comparator 18, and the voltage of the capacitor 8 is set to the charging voltage command value. The switch 14 is turned off until it matches.

As another example of the charging circuit, there is one that supplies a quick charging circuit as an LC oscillation current (see, for example, Patent Document 2). In this LC resonance type quick charging circuit, pulses of positive and negative polarity are alternately generated in a pulse generating circuit of an inverter configuration, and a half-cycle oscillating current is supplied to a capacitor through a reactor for each pulse generation. The capacitor is charged to the target voltage for each occurrence.
Japanese Patent Laying-Open No. 2005-086970 JP 2005-108910 A

In the conventional device, in the fine adjustment period, the detection voltage Vc of the capacitor 8 and the output of the D / A converter 17 obtained by analog conversion of the charge voltage command (digital value) are compared by a comparison circuit (comparator) 18;
When the voltage Vc <D / A converter 17 output, the switch 14 is turned off. When the voltage Vc> = the D / A converter 17 output, the switch 14 is turned on.

  Here, the D / A converter has a settling time period from data input to output stabilization. The charge voltage command is determined before the start of charging, and the data is input to the D / A converter 17, but the output of the D / A converter 17 must be stable before the fine adjustment period. However, if the interval from the determination of the charging voltage command to the fine adjustment period becomes short due to an increase in the number of charge repetitions, the output of the D / A converter 17 becomes unstable before the fine adjustment period due to the effect of the settling time, and the capacitor There is a problem that the accuracy of the charging voltage is reduced.

  An object of the present invention is to provide a capacitor charging device that ensures calculation of a fine adjustment charging time even when charging is repeated at a high frequency, and that increases the charging voltage accuracy of the capacitor.

  In order to solve the above problems, the present invention obtains the fine adjustment charging time by digital calculation, controls the fine adjustment charging switch at this time, and further obtains the current capacitor capacity when calculating the fine adjustment charging time. The fine adjustment charging time is readjusted according to the capacitance change of the capacitor, and has the following configuration.

(1) A quick charging circuit that rapidly charges a power capacitor to a value close to a charging voltage command value, and a fine adjustment that charges the capacitor with a constant current after the rapid charging and charges the charging voltage to the charging voltage command value In a capacitor charging device comprising a charging circuit,
From the charging voltage detection value V of the capacitor rapidly charged by the quick charging circuit, the charging voltage command value V ^* , the capacitance C of the capacitor, and the constant current value I ′,

And a digital control circuit for obtaining a fine adjustment charging time ΔT of the fine adjustment charging circuit by the digital calculation and controlling the charging time of the fine adjustment charging circuit by this time ΔT.

  (2) The digital control circuit controls the charging operation of the fine adjustment charging circuit for a time ΔTc shorter than the fine adjustment charging time ΔT, and the capacitor charging voltage V ′ after this control and the quick charging circuit From the charging voltage detection value V of the rapidly charged capacitor and the constant current value I ′,

The capacitance C ′ of the capacitor is obtained by digital calculation of the following, and from the capacitance C ′ of the capacitor and the charge voltage command value V ^* , the following equation:

This is characterized in that fine adjustment charging time ΔT ′ is obtained by digital calculation of and fine adjustment charging control is performed only for time (ΔT′−ΔTc).

  As described above, according to the present invention, since the fine adjustment charging time is obtained by digital calculation and the fine adjustment charging switch is controlled by this time, the output of the conventional D / A converter 17 is stabilized before the fine adjustment period. In addition, the D / A converter 17 and the comparison circuit (comparator) 18 can be eliminated, and high charging accuracy can be secured even for high repeated charging.

  Further, the present invention obtains the current capacitor capacity when calculating the fine adjustment charging time, and readjusts the fine adjustment charging time according to the change in the capacitance of the capacitor, so that the capacitor capacity changes due to the influence of temperature or the like. Even in this case, it is possible to charge with high accuracy with respect to the charge voltage command value.

(Embodiment 1)
FIG. 1 is a circuit diagram showing an embodiment of the present invention. The difference from FIG. 3 is that the D / A converter 17 and the comparison circuit (comparator) 18 are removed, and the OFF time (fine adjustment period) of the switch 14 is controlled. 9 is obtained by digital calculation according to 9.

The calculation of the fine adjustment period by the control circuit 9 is made by adjusting the coarse charge voltage (rapid charge voltage) detected by the A / D converter 17 to V, the charge voltage command value V ^* , and the capacitor capacity of the capacitor 8 to C. If the constant current value for finely adjusting and charging the capacitor 8 during the period is I ′, the OFF time ΔT of the switch 14 required until the capacitor voltage V becomes V ^* is

Than,

The capacitor charging voltage that matches the charging voltage command value is obtained by turning off the switch 14 for ΔT time.

  Therefore, according to the present embodiment, the problem that the output of the D / A converter 17 becomes unstable before the fine adjustment period and the calculation of the fine adjustment charging time becomes unstable can be solved. Further, the D / A converter 17 and the comparison circuit (comparator) 18 are eliminated, thereby simplifying the hardware configuration.

(Embodiment 2)
In the first embodiment, the fine adjustment period (ΔT) is obtained by calculating the equation (4) using the control circuit 9. However, the capacitor capacity of the capacitor 8 may change due to the influence of temperature or the like. For example, when the capacitor capacity of the capacitor 8 changes from C to C ′, the charging voltage is

Therefore, for the charge voltage command value V ^* ,

There is a problem that causes an error.

  In the present embodiment, charging voltage compensation is performed when the capacitance of the capacitor changes, and charging voltage accuracy is ensured. In the present embodiment, in the configuration of FIG. 1, the control circuit 9 controls the fine adjustment period to turn off the switch 14 for a time ΔTc shorter than the time ΔT obtained by the above equation (4). At this time, the A / D converter When the charging voltage measured in 17 is V ′, the capacitor capacity C ′ of the capacitor 6 is

Than,

Ask for. Thereafter, the control circuit 9 substitutes the capacitor capacitance C ′ into the equation (4).

ΔT ′ is obtained, and the switch 14 is turned off again by this (ΔT′−ΔTc). A waveform diagram at this time is shown in FIG.

  Therefore, according to the present embodiment, in addition to the function and effect of the first embodiment, even when the capacitor capacity of the capacitor 8 changes due to the influence of temperature or the like, the charge voltage command value can be charged with high accuracy.

1 is a circuit diagram of a capacitor charging device showing Embodiment 1 of the present invention. FIG. 6 is a voltage / current waveform diagram according to the second embodiment. The example of a circuit of the conventional capacitor | condenser charging device. The conventional voltage / current waveform diagram.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC power supply 2, 7 Semiconductor switch 8 Capacitor 9 Voltage control circuit 14 Semiconductor switch 16 Constant current control circuit 17 A / D converter

Claims (2)

A quick charging circuit that rapidly charges the power capacitor to a value close to a charging voltage command value; and a fine adjustment charging circuit that charges the capacitor with a constant current after the rapid charging and charges the charging voltage to the charging voltage command value. In the capacitor charging device with
From the charging voltage detection value V of the capacitor rapidly charged by the quick charging circuit, the charging voltage command value V ^* , the capacitance C of the capacitor, and the constant current value I ′,

A capacitor charging apparatus comprising: a digital control circuit that obtains a fine adjustment charging time ΔT of the fine adjustment charging circuit by the digital calculation and controls the charging time of the fine adjustment charging circuit by this time ΔT. The digital control circuit controls the charging operation of the fine adjustment charging circuit for a time ΔTc shorter than the fine adjustment charging time ΔT, and is quickly charged by the capacitor charging voltage V ′ after the control and the quick charging circuit. From the charging voltage detection value V of the capacitor and the constant current value I ′,

The capacitance C ′ of the capacitor is obtained by digital calculation of the following, and from the capacitance C ′ of the capacitor and the charge voltage command value V ^* , the following equation:

2. The capacitor charging device according to claim 1, wherein the fine adjustment charging time ΔT ′ is obtained by digital calculation of and the fine adjustment charging control is performed only for a time (ΔT′−ΔTc).

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