JP2007274750A - Capacitor charger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitor charger capable of charging a capacitor to a predetermined voltage in a predetermined time even when the capacitance varies from capacitor to capacitor. <P>SOLUTION: The capacitor charger is configured to control an inverter 9 to charge a capacitor 1 by a constant current. The charge includes: a current correction computation unit 8 that detects the charged voltage of the capacitor 1, determines the difference between it and a target voltage more than once during a charging period from the start of charging of the capacitor 1 to the completion of charging, and determines a current correction value based on this difference and the remaining time to the end of the charging period; a timer 10 that outputs timing signals indicating the timing of current correction computation; an error amplifier 7 that determines the difference between a current correction value determined by the current correction computation unit 8 and a detection value of charging current for the capacitor 1; and an inverter control unit 6 that controls the inverter 1 so that the difference from the error amplifier 7 is zeroed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a capacitor charging device that charges a capacitor to a predetermined voltage within a predetermined time.

  The capacitor is charged to a predetermined voltage, and the charging voltage of the capacitor is applied, and this is used for discharge emission of flash lamps, spot welding, generation of ultra-high frequency pulses by a magnetron, a klystron or the like. The charging voltage of the capacitor in that case varies depending on the application, but is about 500 V to 50,000 V. The charging power supply includes an inverter, a boosting transformer, and a rectifier circuit, and has a configuration for performing constant current charging control. It is common.

  FIG. 5 is an explanatory diagram of a conventional example, 51 is a capacitor, 52 is a rectifying and smoothing circuit, 53 is an insulating transformer, 54 is an inverter, 55 is a drive circuit, 56 is an inverter control unit, 57 is an error amplifier, and 58 is a voltage. A detection unit 59 is a rectifying / smoothing circuit for a commercial AC power source, and 60 is a flash lamp. The flash lamp 60 can be used for fixing toner in a printer, and can perform high-speed fixing processing by high-speed repeated discharge light emission.

  The rectifying / smoothing circuit 59 rectifies and smoothes the 100V or 200V AC voltage of the commercial AC power supply, and sets it as the input voltage of the inverter 54. The inverter 54 is switching-controlled by the drive circuit 55, boosts the output voltage by the insulating transformer 53, rectifies and smoothes the output voltage by the rectifying and smoothing circuit 52, and charges the capacitor 51. The charging voltage of the capacitor 51 is detected by the voltage detecting unit 58, and when the charging voltage of the capacitor 51 reaches the set voltage, the inverter control unit 56 is controlled so as to stop the operation of the inverter 54. Further, in order to charge the capacitor 51 at a constant current, the charging current is detected and compared with the current set value by the error amplifier 57. The inverter control unit 56 passes the driving circuit 55 through the drive circuit 55 so that the error becomes zero. To control the inverter 54. The charging voltage of the capacitor 51 is applied to the flash lamp 60, and the flash lamp 60 emits light.

When the capacitor 51 is discharged, the inverter 54 is operated again, and charging of the capacitor 51 is started. In this way, charging and discharging of the capacitor 51 are repeated, and the copied toner image is fixed by the discharge light emission of the flash lamp 60. In addition, a capacitor charging device that switches the current setting value during the charging process has been proposed so that the required power does not increase during constant current charging of the capacitor 51 (see, for example, Patent Document 1).
JP 2004-129345 A

  The above-described capacitor 51 desirably has a capacitance value as rated, but actually varies. Due to this variation in capacitance value, variation in the charging voltage when constant current charging is performed occurs, and a capacitor having a rated capacitance is used as the charging voltage when a predetermined time elapses from the start of charging. It will be different compared to the case. For example, FIG. 6 shows the constant current charging characteristics of a capacitor, where the horizontal axis represents time and the vertical axis represents the charging voltage, and the change in charging voltage with the passage of a predetermined time from the start of charging of the capacitor having the rated capacitance. And a change in voltage when charging is stopped and discharged are indicated by solid lines.

  When the target voltage is reached and charging is stopped and discharged, if the capacitor with a large capacitance value is Ca and the capacitor with a small capacitance is Cb, the change in the charging voltage is the capacitance of the rated value indicated by the solid line. Compared to the case of a capacitor, this is indicated by a dotted line. That is, when a predetermined time elapses from the start of charging, the charging voltage of the capacitor Ca having a large capacitance value is Va, and the charging voltage of the capacitor Cb having a small capacitance value is Vb> Va as shown by Vb. Therefore, if the time from the start of charging to the stop of charging is defined, the charging voltage varies with respect to the target voltage due to the magnitude of the capacitance value, and if the charging voltage is the target voltage, the charging end time is different. In other words, there is a problem that the flash lamp cannot discharge and emit light at a predetermined cycle. Although it is conceivable to select a capacitor having a small variation in capacitance value, there is a problem that the capacitor becomes expensive and the cost is increased.

  The present invention solves the above-described problems, and an object thereof is to control charging so that variations in the capacitance value of a capacitor can be absorbed.

  The capacitor charging device according to the present invention is a capacitor charging device that controls an inverter to charge a capacitor at a constant current, and the capacitor charging device has a plurality of timings in a charging period from the start of charging of the capacitor to the completion of charging. A current correction calculation unit for obtaining a current correction value based on the difference and the remaining time in the charging period, and a current correction obtained by the current correction calculation unit And an inverter control unit that controls the inverter so that a difference between the value and the charge current detection value of the capacitor becomes zero.

  The current correction calculation unit starts when charging the capacitor, and outputs a timing signal for a plurality of times within a charging period until charging is completed until the target voltage is charged, and the charging voltage of the capacitor A subtraction circuit that detects a difference from a target voltage by calculating a current correction value based on the difference from the subtraction circuit and the remaining time in the charging period for each timing signal from the timer; It has the structure containing.

  There is a variation in the capacitance value by obtaining a current correction value for correcting the variation in the capacitance value of the capacitor and controlling the charging current of the capacitor at every multiple timings within the charging period. As with the case of using the rated value capacitor, the target voltage can be charged within a predetermined time.

  The capacitor charging device of the present invention will be described with reference to FIG. 1. In the capacitor charging device that controls the inverter 9 to charge the capacitor 1 at a constant current, the capacitor charging device within the charging period from the start of charging of the capacitor 1 to the completion of charging. A current correction calculation unit 8 for detecting a charging voltage of the capacitor 1 at a plurality of times in the time period to obtain a difference from the target voltage and obtaining a current correction value based on the difference and the remaining time in the charging period; A timer 10 for outputting a timing signal indicating the timing of the current correction calculation, an error amplifier 7 for determining a difference between the current correction value obtained by the current correction calculation unit 8 and the charge current detection value of the capacitor 1, and the error amplifier 7 And an inverter control unit 6 that controls the inverter 1 so that the error from the output becomes zero.

  FIG. 1 is an explanatory diagram of a main part of the first embodiment of the present invention, in which 1 is a capacitor, 2 is a rectifying and smoothing circuit, 3 is an insulating transformer, 4 is an inverter, 5 is a drive circuit, 6 is an inverter control unit, and 7 is An error amplifier, 8 is a current correction calculation unit, 9 is a rectifying / smoothing circuit, and 10 is a timer.

  The first embodiment corresponds to a configuration in which a current correction calculation unit 8 and a timer 10 are added as compared with the conventional example shown in FIG. Also, a flash lamp that applies a charging voltage of the capacitor 1 and emits light, for example, is not shown. The timer 10 receives a charge start / stop signal input to the inverter control unit 6 and performs a correction calculation in the current correction calculation unit 8 a plurality of times at a preset time interval within the time from the start of charge to the stop. Outputs a timing signal for performing The current correction calculation unit 8 receives the charging voltage of the capacitor 1 at the timing, the target charging voltage, and the remaining time until the target charging completion time by a plurality of timing signals in the charging period from the timer 10. Based on the time, a current correction value for correcting the charging current is calculated and input to the error amplifier 7. At the start of charging, a current setting value for constant current charging is input to the error amplifier 7 as an initial value.

  The correction calculation in the current correction calculation unit 8 is that the capacitance of the capacitor 1 is C, the current correction value is I, the remaining charge voltage up to the target voltage is ΔV, and the remaining charge time until the target charge completion time is ΔT. Then, the current correction value I is obtained by I = C × ΔV / ΔT. The error amplifier 7 obtains the difference between the detected charging current of the capacitor 1 and the current correction value and inputs the difference to the inverter control unit 6. The inverter control unit 6 controls the inverter 4 via the drive circuit 5 in such a direction that the difference becomes zero. In the charging process of the capacitor 1, the variation in the capacitance value of the capacitor 1 can be absorbed by the correction calculation by the current correction calculation unit 8.

  In FIG. 2, the horizontal axis represents time (msec), the vertical axis represents the charging voltage (V), the charging voltage characteristic curve e of the capacitor having the rated capacitance, and −10% of the rated value When a current correction calculation is performed 50 times using a capacitor b, curve b indicates the case where the current correction is performed 10 times, curve c indicates the case where the current correction calculation is performed 4 times, and curve d indicates that the current correction calculation is not performed That is, the case of no compensation is indicated by a curve a.

  The charging voltage at the time when 100 msec has elapsed from the start of charging of the capacitor having the rated capacitance is 1,000 V as shown by the curve e, but a capacitor having a capacitance of -10% less than the rated value is used. When used, if no compensation is made, the charging voltage when 100 msec has elapsed since the start of charging is approximately 1,100 V, as shown by the curve a, which is a + 10% higher charging voltage. However, by performing the correction calculation in the first embodiment of the present invention described above, the charging voltage when 100 msec has elapsed since the start of charging is set to a voltage that is substantially the same as that when a capacitor having a rated capacitance is used. I was able to. In particular, when the correction calculation was executed about 50 times within the charging period of 100 msec, as shown by the curve b, the charging voltage was such that the error could be ignored.

  FIG. 3 is an explanatory diagram of the first embodiment of the present invention. The same reference numerals as those in FIG. 1 denote the same parts, 11 is a subtracting circuit, 12 is a current detection unit, 13 is a charge start / stop control unit, and C is voltage holding. Capacitors, R1 to R6 are resistors, and SW1 to SW5 are switches. 1 shows a case where the current correction calculation unit 8 is realized by a configuration including a subtraction circuit 11, switches SW1 to SW5, and resistors R1 to R6.

  Further, the timer 10 outputs signals 1 to 5 with a configuration such as a clock signal count start (not shown) or an analog signal integration start (not shown) by a charge start signal from the charge start / stop control unit 13. For example, in a counter configuration that counts clock signals, counting is started by a charge start signal, signals 1 to 5 are output in response to the count value, and the count value is reset by a charge stop signal. The switches SW1 to SW5 are turned on by the signals 1 to 5. These switches SW1 to SW5 can be constituted by semiconductor elements such as transistors.

  Signals 1 to 5 from the timer 10 are output, for example, at timings t1 to t4 shown in FIG. The charging voltage indicates the charging voltage of the capacitor 1 from the start of charging. The signal 1 is output at the timing t1 of the charge start signal from the charge start / stop control unit 13, the switch 1 is turned on by this signal 1, and the current initial value is held by the voltage holding capacitor C and input to the error amplifier 7. Is done. In response to the charge start signal, the inverter control unit 6 controls the inverter 9 via the drive circuit 5, boosts the voltage by the insulating transformer 4, and applies the high voltage DC voltage rectified and smoothed by the rectifying and smoothing circuit 2 to the capacitor 1. To charge.

  The charging voltage of the capacitor 1 is divided by the resistors R1 and R2, and the difference ΔV from the target voltage is obtained by the subtracting circuit 11. The charging current is detected by the current detector 12 and input to the error amplifier 7. The error amplifier 7 inputs the difference between the current initial value held in the voltage holding capacitor C and the charging current value detected by the current detection unit 12 to the inverter control unit 6, and the inverter control unit 6 uses the error amplifier 7. The switching cycle of the inverter 9 or the switching ON period is controlled in the direction in which the difference becomes zero.

  At the next timing t2, signals 2 and 3 are output, and the switches SW2 and SW3 are turned on. A difference ΔV between the target voltage and the charging voltage from the subtraction circuit 11 is divided by the resistors R6 and R3, and is held by the voltage holding capacitor C via the switch SW2. That is, the values of the resistors R6 and R3 are selected so as to indicate the ratio C / ΔT of the correction current value I = C × ΔV / ΔT at time t2. In this case, the capacitance C is a rated value. Therefore, after time t2, the inverter 9 is controlled so that the difference between the correction current value held in the voltage holding capacitor C and the charging current detected by the current detection unit 12 becomes zero.

  At the next time t3, the signal 2 and the signal 4 are output from the timer 10, the switches SW2 and SW4 are turned on, and the current correction value I is set based on the difference ΔV from the subtraction circuit 11 by the resistors R6 and R4. The inverter 9 is controlled so that the difference between the detected charging current value and the current correction value is zero. At the next time t4, in a similar manner, the signals 2 and 5 are output from the timer 10, the switches SW2 and SW5 are turned on, and current correction is performed based on the difference ΔV from the subtraction circuit 11 by the resistors R6 and R5. The value I is obtained and held by the voltage holding capacitor C. At time t5, the charging voltage of the capacitor 1 becomes the target voltage, and the flash lamp discharges light.

  The calculation of the current correction value in FIG. 4 is performed three times during the charging period, and can be set to 4, 10, 50, etc. as in the charging characteristics shown in FIG. Thus, as the number of times is increased, the target voltage can be charged at a desired time even when the variation in the capacitance of the capacitor 1 is large. As the number of current correction value calculations within the charging period is increased, the number of signals output from the timer 10 increases, and a large number of switches and resistors are required. 8 (see FIG. 1) can be realized by using the arithmetic processing function of the microprocessor. Therefore, a configuration in which the current correction value is calculated as many as 50 times can be easily realized.

It is principal part explanatory drawing of Example 1 of this invention. It is explanatory drawing of the effect of Example 1 of this invention. It is explanatory drawing of Example 1 of this invention. It is explanatory drawing of the electric current correction timing of Example 1 of this invention. It is explanatory drawing of a prior art example. It is explanatory drawing of the charging voltage of a capacitor | condenser.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor 2 Rectification smoothing circuit 3 Insulation transformer 4 Inverter 5 Drive circuit 6 Inverter control part 7 Error amplifier 8 Current correction calculating part 9 Rectification smoothing circuit 10 Timer

Claims (2)

In the capacitor charger that controls the inverter and charges the capacitor with constant current,
At a plurality of times in the charging period from the start of charging of the capacitor to the completion of charging, the charging voltage of the capacitor is detected to obtain a difference from the target voltage, and the difference and the remaining time in the charging period A current correction calculation unit for obtaining a current correction value based on
A capacitor charging apparatus comprising: an inverter control unit that controls the inverter so that a difference between a current correction value obtained by the current correction calculation unit and a charging current detection value of the capacitor becomes zero.   The current correction calculation unit starts with charging of the capacitor, and outputs a timing signal for a plurality of times in a charging period until charging is completed until the target voltage is charged, and a charging voltage of the capacitor. A subtraction circuit that detects a difference from the target voltage and a calculation unit that calculates a current correction value based on the difference from the subtraction circuit and the remaining time in the charging period for each timing signal from the timer. The capacitor charging device according to claim 1, further comprising a configuration including the capacitor charging device.

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