JP2008271662A - Charging device of capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent the eccentric magnetization of a transformer even if there is a difference between on-times at each half cycle of an inverter, in a charging system for charging a capacitor until its voltage reaches a charging target voltage by using an LC resonance current at each half cycle via the transformer by an output at each half cycle of the inverter. <P>SOLUTION: An on-time operation circuit 11 outputs a pulse having a width which corresponds to the on-time of an inverter switch according to the charging target voltage of the capacitor. A multiplying circuit 13 obtains an amount of positive or negative magnetic flux generated at the transformer according to the on-time by multiplying the on-time by a DC voltage of the inverter. An adder-subtractor 14 obtains a difference by adding and subtracting the amount of the positive or negative magnetic flux. A zero-comparison circuit 15 determines either positive polarity or negative polarity for an amount of the magnetic flux with a zero as a border. A state change permission circuit 16 latches a determination result of the zero comparison circuit. An on-switch selection circuit 17 selects the polarity of an on-output of the half cycle of the inverter according to a determination result of the state change permission circuit. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a charging device that repeatedly charges a power capacitor to a set voltage, and in particular, charges a capacitor to a charging target voltage with an LC resonance current for each half cycle through a transformer at an output for each half cycle of a single-phase inverter. The present invention relates to a charging device.

  This type of charging device is, for example, a charger for a pulse power source that initially charges a power capacitor at a high voltage and compresses a discharge pulse from the capacitor to a pulse such as a laser head at a high voltage and a large current. Provided.

  FIG. 3 is a main circuit configuration diagram of a charging device that charges a power capacitor with a single-phase inverter. The inverter unit 1 bridges four arms in which semiconductor switches S1 to S4 and diodes D1 to D4 are connected in antiparallel, and generates a single-phase AC output by complementary ON operations of the switches S1 and S4 and the switches S2 and S3. . The output transformer 2 obtains a secondary output obtained by boosting the output of the inverter unit 1. The rectifier circuit 3 bridges the diodes D5 to D8, full-wave rectifies the output of the transformer 2, and supplies a DC charging current to the power capacitor 4. The reactor 5 is inserted in series with the secondary output winding of the transformer 2, and generates an oscillating current having a half cycle with the capacitor 4 by the LC resonance operation with the capacitor 4, so that the capacitor 4 is charged.

The charge control circuit 6 alternately controls the switches S1, S4 on and the switches S3, S2 on among the semiconductor switches S1 to S4 of the inverter, and charges the capacitor 4 once with the half-cycle output of the inverter unit 1. . This charging operation is
(Mode 1) The charging operation is started by turning on the switches S1 and S4, and the charging operation is stopped by turning off the switches S1 and S4 when the charging voltage of the capacitor 4 reaches the target value. After this charging is completed, the capacitor 4 is discharged to the load side.

  (Mode 2) After the end of mode 1, the switches S3 and S2 are turned on to start the charging operation, and when the charging voltage of the capacitor 4 reaches the target value, the switches S3 and S2 are turned off to stop the charging operation. After this charging is completed, the capacitor 4 is discharged to the load side.

  In this charging operation, if there is a difference in the magnitude of the charging current between mode 1 and mode 2 or the charging period, a DC component of the voltage is applied to the transformer, and the iron core of the transformer is demagnetized. In the worst case, the transformer is magnetically saturated, and an excessive current flows through the inverter. Also, the predetermined charging operation is disabled.

As a circuit to prevent transformer magnetism, positive and negative primary currents flowing in the transformer are detected, and the ON period of the inverter (or push-pull circuit) arm (PWM waveform width, switch period) according to this positive / negative current difference There is a method of correcting (see, for example, Patent Document 1 and Patent Document 2).
JP 2004-15900 A JP-A-9-168278

  In the conventional anti-magnetization method that detects the transformer current and corrects the switch period according to the difference between the positive and negative currents, the output voltage (PWM waveform width, switch period) of the inverter or push-pull circuit is controlled. become.

  Here, in a charging device such as a charging device for a pulse power supply that charges a capacitor to a charging target voltage with an LC resonance current every half cycle with an output every half cycle of the inverter, the charging voltage target value of the capacitor, before charging starts Since the on-time of the switch is largely changed depending on the residual voltage of the capacitor and the DC voltage of the inverter, the conventional anti-bias method cannot make corrections following changes in these charging conditions.

  In particular, the discharge from the capacitor to the pulse generation circuit or the discharge load serving as a load may cause the charge voltage target value to vary greatly, for example, from 50 to 100% for each half-cycle charge of the capacitor. In the correction, it becomes difficult to cope.

  An object of the present invention is that there is a difference in on-time for each half cycle of the inverter in a charging method in which a capacitor is charged to a charge target voltage with an LC resonance current for each half cycle via a transformer with an output for each half cycle of the inverter. Even in such a case, it is an object of the present invention to provide a capacitor charging device that can reliably prevent transformer magnetic demagnetization.

  In order to solve the above problems, the present invention obtains the difference between the amount of positive and negative magnetic flux generated in the transformer from the DC voltage of the inverter, the ON time of the inverter switch, and the positive / negative current polarity flowing in the transformer, and the inverter is determined according to the positive / negative of this difference. The next half-cycle output has a polarity in a direction that does not saturate the iron core of the transformer, and has the following configuration.

(1) The half-cycle output of a full-bridge single-phase inverter is controlled by the on-time of the inverter switch, and this output is supplied to the reactor and capacitor via the transformer to pass LC resonance current, charging the capacitor every half cycle. In a charging device that charges to a target voltage,
The difference in the amount of positive and negative magnetic flux generated in the transformer is determined from the DC voltage of the single-phase inverter, the inverter switch ON time, and the polarity of the positive and negative currents flowing in the transformer, and the next half-cycle output of the inverter is calculated based on the positive and negative of this difference. A charge control circuit is provided that sets the polarity so that the iron core does not saturate.

(2) The charge control circuit includes:
An on-time arithmetic circuit for obtaining an on-time of a half cycle of the inverter according to the charging target voltage of the capacitor and outputting a pulse having a width corresponding to the on-time;
Multiplying the on-time by a DC voltage of the inverter as a coefficient to obtain a positive or negative magnetic flux amount generated in the transformer according to the on-time of the half cycle of the inverter;
An addition / subtraction circuit for obtaining a difference between positive and negative magnetic flux amounts generated according to positive and negative current polarities flowing in the transformer by addition / subtraction of positive or negative magnetic flux amount;
A zero comparison circuit for determining whether the calculated magnetic flux amount of the addition / subtraction circuit is positive or negative with respect to zero;
A state change permission circuit that latches the determination result of the zero comparison circuit in an off period of the inverter;
An on-switch selection circuit that selects the polarity of the ON output of the half cycle of the inverter according to the determination result of the state change permission circuit;
It is provided with.

(3) The charge control circuit includes:
An on-time arithmetic circuit for obtaining an on-time of a half cycle of the inverter according to the charging target voltage of the capacitor and outputting a pulse having a width corresponding to the on-time;
An addition / subtraction circuit for obtaining a difference between positive and negative magnetic flux amounts generated according to positive and negative current polarities flowing in the transformer by adding and subtracting the DC voltage detection value of the inverter only during this signal period, with the ON time as an integration permission signal;
A zero comparison circuit for determining whether the calculated magnetic flux amount of the addition / subtraction circuit is positive or negative with respect to zero;
A state change permission circuit that latches the determination result of the zero comparison circuit in an off period of the inverter;
An on-switch selection circuit that selects the polarity of the ON output of the half cycle of the inverter according to the determination result of the state change permission circuit;
It is provided with.

  As described above, according to the present invention, the difference between the amount of positive and negative magnetic flux generated in the transformer is obtained from the DC voltage of the inverter, the ON time of the inverter switch, and the polarity of positive and negative currents flowing in the transformer, and the next time of the inverter according to the positive and negative of this difference. Since the polarity of the half-cycle output is such that the transformer core does not saturate, even if there is a difference in the on-time for each half-cycle of the inverter, the transformer can be reliably prevented from being magnetized.

  In addition, since the charge control circuit is composed of an arithmetic circuit based on the ON time (pulse width) of the inverter cycle, the circuit processing is simpler than when the inverter DC voltage and ON time arithmetic circuit output are digital quantities. And requires only a slight modification of the existing charge control circuit.

(Embodiment 1)
FIG. 1 is a block configuration diagram of a charge control circuit showing the present embodiment, which replaces the charge control circuit 6 of the inverter unit 1 of FIG.

  As described above, in the conventional single-phase inverter, the switches S1 and S4 are turned on and the switches S3 and S2 are turned on alternately and repeatedly. In contrast, in this embodiment, the difference between the amount of positive and negative magnetic flux generated in the transformer is obtained from the DC voltage of the inverter, the ON time of the inverter switch, and the polarity of positive and negative currents flowing through the transformer, and the next time the inverter is operated according to the positive and negative of this difference. The switches S1 and S4 are turned on and the switches S3 and S2 are turned on so that the half-cycle output has a polarity in a direction that does not saturate the iron core of the transformer.

  The on-time arithmetic circuit 11 obtains the on-time required for the switches S1 and S4 or the switches S3 and S2 according to the charging target voltage (target value) of the capacitor 4, and outputs a pulse having a width corresponding to the on-time. To do. The inverter DC voltage detection circuit 12 detects the DC voltage of the inverter unit 1 and detects it as a coefficient for correcting the magnetic flux fluctuation of the transformer due to the fluctuation of the DC voltage.

  The multiplication circuit 13 multiplies the on-time from the on-time arithmetic circuit 11 by the output (coefficient) of the voltage detection circuit 12 to obtain the amount of positive or negative magnetic flux generated in the transformer 2 according to the on-time of the switch. That is, the amount of positive or negative magnetic flux generated in the transformer 2 is calculated by inverter DC voltage × switch ON time. In charging the capacitor, if the charge / discharge cycle is short (the repetition frequency is high), the ON time of the inverter is also short. For example, the inverter on time when the repetition frequency is 10 kHz is about 50 μsec. In this case, the amount of positive or negative magnetic flux generated in the transformer 2 can almost ignore the change in the inverter DC voltage.

  The addition / subtraction circuit (integration circuit) 14 adds the calculated output of the multiplication circuit 13 when the switches S1 and S4 are on, and subtracts when the switches S3 and S2 are on. Find the difference between the amount of positive and negative magnetic flux generated.

  The zero comparison circuit 15 determines whether the calculated magnetic flux amount of the addition / subtraction circuit 14 is positive or negative with respect to zero. The state change permission circuit (latch circuit) 16 latches the determination result (polarity) of the zero comparison circuit 15 during the off period of the switches S1 and S4 or the off period of the switches S3 and S2.

  The on-switch selection circuit 17 turns on the switches S1 and S4 or the switches S3 and S2 with the on-time output (pulse output) of the on-time arithmetic circuit 11 according to the determination result of the state change permission circuit (latch circuit) 16. Switch.

  An operation of preventing the bias of the transformer having the above configuration will be described. The detection circuit 12 detects the inverter DC voltage, and the amount of magnetic flux generated in the transformer by the half-cycle current flowing through the transformer in the multiplier circuit 13 is determined based on the switch ON time determined by the ON time calculation circuit 11. That is, the integrated value of the voltage for one operation of the inverter (change in magnetic flux) is obtained. This is added / subtracted by the addition / subtraction circuit 14 to the value up to the previous operation. The addition and subtraction are, for example, addition when the switches S1 and S4 are on, and subtraction when the switches S3 and S2 are on. Based on this result, the zero comparison circuit 15 determines whether the amount of magnetic flux is positive or negative at zero.

  After the switches S1 and S4 or the switches S3 and S2 are turned off, the state change permission circuit (latch circuit) 16 latches the determination result of the zero comparison circuit 15, and the on-switch selection circuit 17 switches the switches S1 and S4 according to the latch state. Is turned on or the switches S3 and S2 are turned on, and the selected switch is turned on.

  As described above, the half-cycle output of a single-phase inverter with a full bridge configuration is controlled by the on-time of the inverter switch, and this output is supplied to the reactor and the capacitor via the transformer, and the LC resonance current is supplied to the capacitor every half cycle. In a charging device that charges to the target voltage, even if the on-time for each half cycle of the inverter changes due to the target value of the capacitor charging voltage, the residual voltage of the capacitor before the start of charging, and the inverter DC voltage, the transformer magnetic flux is biased. By selecting the switch in the non-directional direction, it is possible to reliably prevent the transformer from being demagnetized.

(Embodiment 2)
FIG. 2 is a block diagram of the control circuit showing this embodiment, and the same parts as those in FIG.

  The addition / subtraction circuit (integration circuit) 14A adds the DC voltage detection value of the inverter when the switches S1 and S4 are on, and subtracts when the switches S3 and S2 are on. By executing the integration permission signal during the pulse period, the amount of change in the amount of magnetic flux generated in the transformer 2 due to the fluctuation of the inverter DC voltage is obtained. As a result, the integrated value of the voltage (change in magnetic flux) for one operation of the inverter is obtained.

  In the demagnetization prevention operation according to the present embodiment, the change in magnetic flux obtained by the addition / subtraction circuit 14A is zero-compared by the zero comparison circuit 15 to determine whether the magnetic flux is positive or negative, and after the switch is turned off, the state change permission circuit (latch circuit) 16 is turned on. Operate, switch switch selection, select switch for next inverter operation.

  As described above, in the charging method in which the capacitor is charged every half cycle through the transformer at the output of every half cycle of the inverter, the half of the inverter is determined based on the target charging voltage value of the capacitor, the residual voltage of the capacitor before starting charging, and the inverter DC voltage. Even when the on-time for each cycle changes, the bias of the transformer can be reliably prevented by the on-control of the switch in the direction in which the magnetic flux of the transformer does not deviate.

The block block diagram of the charge control circuit which shows embodiment of this invention. The block block diagram of the charge control circuit which shows other embodiment of this invention. The main circuit block diagram of a charging device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inverter part 2 Output transformer 4 Capacitor 5 Reactor 6 Charge control circuit 11 ON time arithmetic circuit 12 Inverter DC voltage detection circuit 13 Multiplication circuit 14 Addition / subtraction circuit 15 Zero comparison circuit 16 State change permission circuit 17 On switch selection circuit

Claims (3)

The output of the full-bridge single-phase inverter every half cycle is controlled by the on-time of the inverter switch, and this output is passed through the transformer to the reactor and the capacitor through the LC resonance current, and the capacitor reaches the target charging voltage every half cycle. In a charging device for charging,
The difference in the amount of positive and negative magnetic flux generated in the transformer is determined from the DC voltage of the single-phase inverter, the inverter switch ON time, and the polarity of the positive and negative currents flowing in the transformer, and the next half-cycle output of the inverter is calculated based on the positive and negative of this difference. A capacitor charging device comprising a charge control circuit for setting the polarity so that the iron core does not saturate. The charge control circuit includes:
An on-time arithmetic circuit for obtaining an on-time of a half cycle of the inverter according to the charging target voltage of the capacitor and outputting a pulse having a width corresponding to the on-time;
Multiplying the on-time by a DC voltage of the inverter as a coefficient to obtain a positive or negative magnetic flux amount generated in the transformer according to the on-time of the half cycle of the inverter;
An addition / subtraction circuit for obtaining a difference between positive and negative magnetic flux amounts generated according to positive and negative current polarities flowing in the transformer by addition / subtraction of positive or negative magnetic flux amount;
A zero comparison circuit for determining whether the calculated magnetic flux amount of the addition / subtraction circuit is positive or negative with respect to zero;
A state change permission circuit that latches the determination result of the zero comparison circuit in an off period of the inverter;
An on-switch selection circuit that selects the polarity of the ON output of the half cycle of the inverter according to the determination result of the state change permission circuit;
The capacitor charging device according to claim 1, further comprising: The charge control circuit includes:
An on-time arithmetic circuit for obtaining an on-time of a half cycle of the inverter according to the charging target voltage of the capacitor and outputting a pulse having a width corresponding to the on-time;
An addition / subtraction circuit for obtaining a difference between positive and negative magnetic flux amounts generated according to positive and negative current polarities flowing in the transformer by adding and subtracting the DC voltage detection value of the inverter only during this signal period, with the ON time as an integration permission signal;
A zero comparison circuit for determining whether the calculated magnetic flux amount of the addition / subtraction circuit is positive or negative with respect to zero;
A state change permission circuit that latches the determination result of the zero comparison circuit in an off period of the inverter;
An on-switch selection circuit that selects the polarity of the ON output of the half cycle of the inverter according to the determination result of the state change permission circuit;
The capacitor charging device according to claim 1, further comprising:

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