JP2826262B2 - Capacitor charging circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a capacitor charging circuit, and more particularly to a capacitor charging circuit suitable for charging a large-capacity capacitor for a solid-state laser.

[0002]

2. Description of the Related Art In general, a condenser for excitation is connected to a flash lamp used for exciting a solid-state laser such as a YAG laser. Discharge the amount at once and apply more than 500V to the flash lamp .
High of an applied excitation voltage is to emit light.

A conventional capacitor charging circuit for charging such a large-capacity capacitor is one of charging transformers.
The energization state to the next side is controlled by a switching circuit,
It is formed so as to charge a capacitor connected to the secondary side of the charging transformer after rectification.

[0004] Actual charging is performed as follows.
That is, charging is performed by gradually increasing the charging voltage until the charging voltage reaches the charging set voltage Vs of about 500 V for the capacitor having the potential of 0. After the charging voltage of the capacitor reaches the charging set voltage Vs, supplementary charging is performed at predetermined time intervals to maintain the charging voltage of the capacitor at the charging set voltage Vs. After discharging to excite the flash lamp, the charging voltage is 500
The charging is performed by gradually increasing the charging voltage until the charging set voltage Vs of about V is reached, and then the supplementary charging is performed.

[0005]

However, in the prior art, the switching of the switching circuit is performed from the initial stage of charging the capacitor until the charging voltage reaches the charging set voltage Vs, and at any time during the supplementary charging timing. The following inconveniences have occurred because charging is performed by supplying a constant current to the element.

That is, as shown in FIG. 4A, as shown in FIG. 4A, the switching elements of the switching circuit are switched from the initial stage of charging shown in FIG. 4C until the charging voltage reaches the charging set voltage Vs and over the subsequent supplementary charging timing. As shown in FIG. 2B, a very large inrush voltage is applied to the switching element at the beginning of charging as shown in FIG. Electric current flows. This occurs due to a delay in detecting the current of the circuit and a delay in the operation of the control circuit. Therefore, a large-capacity switching element that can withstand this large inrush current is required, and the cost is high. Also, at the time of the replenishment charge, as shown in FIGS.
Since a high peak current also flows through each switching element, a large current flows through the charging transformer every predetermined time,
As a result, there is a disadvantage that a loud noise is generated from the charging transformer.

[0007] The present invention has been made in view of these points, the current flowing through the switching element at the initial stage of charging can be suppressed low, a small capacity switching element can be used, and the cost can be reduced. It is another object of the present invention to provide a capacitor charging circuit capable of achieving a very low level of noise generated at the time of supplementary charging.

[0008]

According to a first aspect of the present invention, there is provided a capacitor charging circuit according to the first aspect of the present invention, wherein a power supply state to a primary side of a charging transformer is controlled by a switching circuit. In a capacitor charging circuit for charging a capacitor for supplying energy to a laser excitation lamp connected after rectification to a secondary side of a charging transformer, the capacitor is charged at an initial stage of charging the capacitor.
Until the charging voltage of the sensor reaches a predetermined value, the switch
As a constant current reference voltage for supplying a constant current to the
Apply a voltage lower than the voltage applied during normal charging, and then
The charging voltage of the capacitor is changed from the predetermined value to the charging set voltage.
Until the switching circuit reaches the constant current reference voltage
Is formed so as to apply the voltage during the steady charging.
A current setting circuit.

According to a second aspect of the present invention, there is provided a capacitor charging circuit according to the present invention, in which a primary side of a charging transformer is energized.
Is controlled by a switching circuit to control the charging transformer.
After rectifying the secondary side,
Capacitor charging to charge the capacitor that supplies energy
In the power supply circuit, in the early stage of charging the capacitor,
Until the charging voltage of the capacitor reaches the predetermined value.
A constant current reference for supplying a constant current to the switching circuit
Starting from a voltage lower than the voltage applied during steady-state charging
Voltage to gradually increase to the voltage at the time of steady charging
And then charge the capacitor
Until the charge setting voltage is reached from the specified value, the switch
The constant current reference voltage is supplied to the
Having a current setting circuit formed to apply pressure.
And features.

According to a third aspect of the present invention, there is provided a capacitor charging circuit according to the present invention, in which a primary side of a charging transformer is energized.
Is controlled by a switching circuit to control the charging transformer.
After rectifying the secondary side,
Capacitor charging to charge the capacitor that supplies energy
In the power supply circuit, the charging voltage of the capacitor is a charging setting.
After reaching the constant voltage, a constant current is supplied to the switching circuit.
Assigned as a constant current reference voltage for flowing during steady charging
It is configured to perform supplementary charging by applying a voltage lower than the voltage.
It has a current setting circuit formed.

[0011]

[0012]

According to the present invention, the capacitor is charged by controlling the current flowing through the switching circuit in accordance with the magnitude of the charging voltage of the capacitor.
The current flowing through the switching element in the initial stage of charging can be suppressed low, so that a small-capacity switching element can be used, the cost can be reduced, and the sound generated at the time of replenishment charging can be extremely reduced. Can be smaller.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows an embodiment of a capacitor charging circuit according to the present invention.

In FIG. 1, a switching circuit 2 is connected to a primary side of a charging transformer 1, and a large-capacity capacitor C2 to be charged is connected to a secondary side of the charging transformer 1 by a diode. Connected after rectification. IGB for discharging control is connected to this capacitor C2.
A lamp (not shown ) that excites the laser medium via a switch such as T, GTO, or transistor is connected.
The switching circuit 2 according to the present embodiment is formed by connecting in parallel a set of two transistors Q1 and Q2 and a set of transistors Q3 and Q4 in series, which serve as switching elements. Each pair is connected to both ends of a primary coil of the charging transformer 1, and each set is connected in parallel to a capacitor C1 for applying an operating voltage.
The switching circuit 2 includes a F
ET, IGBT, etc. may be used. The capacitor C2 is provided between the diode 3 or 4 and the coil 5 between each end of the secondary coil of the charging transformer 1 and the intermediate portion.
And are connected in series to form a closed circuit. The charging voltage VC2 of the capacitor C2 is detected by the voltage detection circuit 6. The voltage detection circuit 6 is formed so as to output a signal SVC2 indicating the detected charging voltage VC2 to the current setting circuit 7 and the switching control circuit 8. Also, the charge set voltage V of the capacitor C2
From the voltage setting circuit 9 for setting S, the charge setting voltage V
The signal SVS indicating S is output to the current setting circuit 7 and the switching control circuit 8. The current setting circuit 7 calculates the charging voltage V of the capacitor C2.
A command SVB for controlling the current supplied to the switching circuit 2 according to the magnitude of C2 is issued to the switching control circuit 8. The current flowing through the switching circuit 2 is detected by the ammeter 10 and input to the switching control circuit 8, and the charging current to the capacitor C2 is detected by the ammeter 11 and input to the switching control circuit 8 in the same manner. Is formed. A drive signal is applied to the base of each of the transistors Q1 to Q4 of the switching circuit 2 from the driver circuit 12, and the driver circuit 12 is turned on and off of the transistors Q1 to Q4 from the switching control circuit 8. The operation control signal having the content for controlling the operation is output.

An example of the command SVB of the current setting circuit 7 in this embodiment will be described with reference to FIGS.

First, as shown in FIG. 2, in the initial stage of charging the capacitor C2, the charge voltage VC2
Until the voltage reaches a predetermined value V1, a voltage VL lower than the voltage VH at the time of steady charging is applied as a constant current reference voltage VB for flowing a constant current to the switching circuit 2. Thereafter, the charging voltage VC2 of the capacitor C2 becomes the predetermined value. Until the charge setting voltage VS is reached from V1, a command SVB is output to the switching circuit 2 so as to apply the voltage VH during steady-state charging as the constant current reference voltage VB.

As another example in the early stage of charging the capacitor C2, as shown in FIG.
Until the charging voltage VC2 of the switching circuit 2 reaches the predetermined value V1, the constant current reference voltage VB for flowing the constant current to the switching circuit 2
As a voltage VL lower than the voltage VH applied during steady charging
, And outputs a command SVB having a content that is given by changing the voltage so as to gradually increase to the voltage VH during the steady charging.

After the charging voltage VC2 of the capacitor C2 reaches the charging set voltage VS, a voltage VL lower than the voltage VH applied at the time of steady charging is set as a constant current reference voltage VB for flowing a constant current to the switching circuit 2. It outputs a command SVB having a content for performing supplementary charging with the addition.

Next, the operation of this embodiment will be described with reference to FIGS.

First, according to FIG. 2, in the initial stage of charging the capacitor C2, the charging voltage VC2 of the capacitor C2 during the time t0 to t1 reaches a predetermined value V1 (see FIG. 2C).
Is a constant current reference voltage VB for flowing a constant current through the switching circuit 2, and is a voltage V
The current setting circuit 7 outputs a command SVB having a content to give L (see FIG. 4A) to the switching control circuit 8. As a result, a low voltage VL is applied to the switching circuit 2.
Is applied, the peak current flowing through each of the transistors Q1 to Q4 can be suppressed low as shown in FIG.
In particular, as compared with the conventional example of FIG. 4B, the rush current immediately after the start of charging is reduced to about 1/2 or less, and thereafter converges to a low current value corresponding to the low voltage VL.

Thereafter, from time t1 to t2, until the charging voltage VC2 of the capacitor C2 reaches the charging set voltage VS from the predetermined value V1, the switching circuit 2 sets the constant current reference voltage VB as the constant-current voltage VH ( A command SVB having a content to give the current setting circuit 7
To the switching control circuit 8. As a result, a high voltage VH is applied to the switching circuit 2, so that the peak current flowing through each of the transistors Q1 to Q4 is kept constant as shown in FIG. Thus, the charging voltage VC2 of the capacitor C2 gradually increases from the predetermined value V1 to the charging set voltage VS.

During the period from time t2 to time t3 after the charging of the capacitor C2 to the charging set voltage VS, a constant current reference voltage VB for supplying a constant current to the switching circuit 2 is provided at the time of steady charging. The current setting circuit 7 outputs to the switching control circuit 8 a command SVB that gives a voltage VL lower than the voltage VH (see FIG. 7A) to perform supplementary charging. As a result, a low voltage VL pulse voltage is applied to the switching circuit 2 every predetermined time, so that the peak current flowing through each of the transistors Q1 to Q4 is suppressed low as shown in FIG. Therefore, the current flowing through the charging transformer 1 can be suppressed to a low level, so that the sound emitted from the charging transformer 1 at the time of the supplementary charging is extremely small.

When the capacitor C2 is discharged from the capacitor C2 at time t3 to excite the solid-state laser, the charging voltage VC2 of the capacitor C2 becomes the charging set voltage VS from time t3 to t4.
, Charging is performed in the same manner as in times t1 to t2, and then supplementary charging is performed in the same manner as described above.

Next, in another example shown in FIG. 3, in the initial stage of charging the capacitor C2, until the charging voltage VC2 of the capacitor C2 from time t0 to t1 reaches a predetermined value V1 (see FIG. 3C). From the voltage VL lower than the voltage VH applied at the time of steady charging as the constant current reference voltage VB for flowing a constant current to the switching circuit 2 to the voltage V at the time of the steady charging.
The current setting circuit 7 outputs to the switching control circuit 8 a command SVB that changes the voltage so as to gradually increase to H. As a result, the switching circuit 2 switches from the low voltage VL to the voltage VH during the steady charging.
Since the voltage gradually increasing is applied, the peak current flowing through each of the transistors Q1 to Q4 is suppressed low as shown in FIG. In particular, as compared with the conventional example of FIG. 4B, the rush current immediately after the start of charging is reduced to about 以下 or less, and then converges to a current value corresponding to the voltage VH at the time of steady charging.

As described above, according to the present invention, the capacitor C
2, the capacitor C2 is charged by controlling the current flowing through the switching circuit 2 in accordance with the magnitude of the charging voltage VC2 of the second transistor. The flowing current can be suppressed low, so that a small-capacity switching element can be used, the cost can be reduced, and the noise generated at the time of replenishment charging can be extremely reduced.

It should be noted that the present invention is not limited to the above-described embodiment, but can be modified as needed.

[0028]

As described above, since the capacitor charging circuit according to the present invention is constructed and operates, the current flowing through the switching element in the initial stage of charging can be suppressed low, and a small-capacity switching element can be used. Can,
It is possible to reduce the cost and to make the sound generated at the time of the replenishment charge extremely small.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a capacitor charging circuit according to the present invention.

FIGS. 2A, 2B, and 2C are diagrams showing temporal changes in a voltage applied to a switching circuit, a peak current of each transistor, and a charging voltage of a capacitor, respectively, in the present invention.

FIG. 3 is a view similar to FIG. 2 showing another example of the present invention.

FIG. 4 is a view similar to FIG. 2 showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charging transformer 2 Switching circuit 7 Current setting circuit

Claims (3)

(57) [Claims] A switching circuit controls an energization state of a primary side of a charging transformer to control the state of the charging transformer.
In a capacitor charging circuit for charging a capacitor that supplies energy to a laser excitation lamp connected after rectification to the next side, in the initial stage of charging the capacitor, the capacitor is charged.
Until the charging voltage reaches a predetermined value, the switching circuit
Steady-state charging as a constant current reference voltage for flowing a constant current to the road
At a lower voltage than the voltage applied at the time, and then the charging voltage of the capacitor is set from the predetermined value.
Until the voltage is reached, a constant current
The voltage at the time of the steady charging is applied as the reference voltage.
A circuit for charging a capacitor, comprising a current setting circuit thus formed. 2. The state of energizing the primary side of the charging transformer
Controlled by a switching circuit, the charging transformer 2
After rectifying the secondary side,
Capacitor charging that charges the capacitor that supplies lugi
In the circuit for use, in the initial stage of charging the capacitor,
Until the charging voltage reaches a predetermined value, the switching circuit
Steady-state charging as a constant current reference voltage for flowing a constant current to the road
From the voltage lower than the voltage applied during
Applying by changing the voltage so that it gradually rises to the pressure
And, thereafter charging set from the charging voltage is the predetermined value of the capacitor
Until the voltage is reached, a constant current
The voltage at the time of the steady charging is applied as the reference voltage.
Characterized in that it has a current setting circuit
Sensor charging circuit. 3. The state of energizing the primary side of the charging transformer
Controlled by a switching circuit, the charging transformer 2
After rectifying the secondary side,
Capacitor charging that charges the capacitor that supplies lugi
Circuit, after the charging voltage of the capacitor reaches the charging set voltage.
A constant current for supplying a constant current to the switching circuitry
Voltage lower than the voltage applied during normal charging as the reference voltage
Current set to perform supplementary charging by applying
A circuit for charging a capacitor, comprising a circuit.