JPS6140075A - Charging circuit - Google Patents

Abstract

PURPOSE:To improve the charging efficiency and reduce the size and weight of a charging device, by providing a means for quickly discharging the electric charge accumulated in the capacitance between the gate and source of a MOSFET for high electric power at the same time as the switching pulse applised to the gate of the MOSFET shifts to an OFF state. CONSTITUTION:A DC water supply V is switched through a MOSFET2 for high electric power. The voltage V is boosted by a transformer 1 and supplied to an excitation charging circuit 100 through a diode D11. An accumulated charge dischargng circuit 16 has an astable multivibrator 161, an input resistor R162 and a transistor TR163 and carries out discharging of the electric charge accumulated in the capacitance between the gate and source electrodes of the FET2. The vibrator 161 performs free-running at a preset period and outputs timing pulses Q and inverted pulses Q', which are generated with opposite polarity. In consequence, the transistor TR163 is turned conductive at substantially the same timing as an OFF state of the gate voltage is started, so that the charge accumulated in the capacitance between the gate and the source of the FET2 is quickly discharged. Thus, it is possible to improve the charging efficiency and reduce the size and weight of the device.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a charging circuit, and particularly to a charging circuit that uses a large DC power source to charge a capacitor that supplies electrical energy to an excitation/discharge circuit that is an excitation means of a laser. A voltage obtained by switching using a power MOSFET is boosted and rectified to a charging circuit that generates a DC voltage for charging at a predetermined level.

[Prior Art] □ A normal excitation discharge circuit that uses a discharge tube as a laser excitation means excites a laser element or the like at the discharge repetition period of the excitation discharge tube to perform laser oscillation.

The excitation discharge tube used for this purpose is connected between the anode and the cathode every time it receives a trigger high voltage pulse from the trigger high voltage generator circuit via the trigger wire at the same repetition rate as the laser oscillation repetition frequency. The capacitor connected to the anode of the excitation discharge tube discharges electrical energy while receiving laser excitation, and the capacitor, which is connected to the anode of the excitation discharge tube and repeats discharge with each laser excitation, is constantly charged in response to the laser excitation and generates the electrical energy commensurate with the discharge. We must aim to accumulate the following. Charging circuits for this purpose generally use a transformer to boost the voltage obtained by switching a DC power supply, and then rectify it to obtain a DC voltage. Recently, high power MOSFETs have been increasingly used because of their ability to obtain relatively large currents.

FIG. 1 is a circuit diagram showing the basic configuration of a conventional charging circuit using a high-power MOSFET as a switching element.

The conventional charging circuit shown in Figure 1 has a transformer 1, a high power M
OSFET (hereinafter simply referred to as MOSFET) 2, clock circuit 3, NAND circuit 4, inverter, comparator 6, resistor 7, capacitor 8, variable resistor 9, Zener diode 10, diode 11, resistor 12.13, capacitor 14.15. In addition, an excitation discharge tube circuit 100 for excitation of a laser element is also shown.

Note that the excited discharge tube circuit 100 includes a choke coil 1001.
, a discharge tube 1002, a trigger wire 1003, and a trigger high-voltage pulse generation circuit 1004.

FIG. 2 is an operational waveform diagram of each main part of the conventional charging circuit shown in FIG. 1. The charging circuit shown in FIG. 1 will be explained below with reference to FIG.

The DC power supply V is connected to the MOSFE through the primary winding of the transformer.
It is applied between the drain D and source S of T2. M.O.
SFET2 becomes conductive only when a predetermined gate voltage is applied to the transformer G, and is switched so that a drain current 1d flows through the transformer 1.
becomes the primary current.

Now, the clock circuit 3 outputs a clock pulse (2), which is supplied to the rjNAND circuit 4 as a single power.

The output of the comparator 6 is supplied to the other input of the NAND circuit 4, but when the voltage applied to the compared voltage terminal is lower than the reference voltage applied to the reference voltage or less, the comparator 6 Comparator output of high level and low level when high is NAND circuit 4
supply to.

2 and 2 in FIG. 2 respectively indicate clock pulse and comparator outputs. As for the reference voltage of the comparator 6, the voltage of the DC power supply ■ is made into a constant voltage by a Zener diode 10, and this voltage is adjusted by a variable resistor 9 and a capacitor 8. The current voltage is adjusted to the voltage and applied through the voltage line 601, and the voltage applied through the universal voltage line 602 is charged until the charging capacitor 14 or 79r is fully charged. , ) A is set to a level below the reference voltage. Therefore, is the output of comparator 6 a capacitor? The I/I level is set to H until 14 reaches a predetermined voltage.

The NAND circuit 4 then outputs a negative pulse of a preset level only when receiving the clock pulse ■ and the comparator output high level H, and then the inverter 5 outputs a positive pulse gate pulse a L l −r 11 Eighth Q
D V +71 n Small 27 L 711tol
+n −J+ −/? The gate pulse ■ is the 21st
As shown in the figure, τ from the rising edge of clock pulse ■. It rises to a predetermined level with a delay, and τ from the falling point of the clock pulse ■. and t fall with an equal delay. The capacitance between the gate and drain electrodes of Fibao8pvr 2 with such a time delay (several 100 to 10009 it'
) is caused by

Now, every time the gate pulse ■ is input, the MOSFET
2 is switched to a conductive state, and a drain current Id■ is caused to flow.

The drain current fd of MO5FET2 is the gate pulse
The drain current in period τ1 of this flowing wL flow is consumed by MO8FE'I''2 as an invalid current.

Figure 2 ■ shows the drain voltage of the drain D of MOSFET 2, which is initially held at the level of the DC power supply ■, but at the same time as the drain current 1a starts flowing, it drops to 0 level. Corresponding to the rise′) Z, ll
- The drain current Id increases gradually through the primary winding of the lance 1, and at time τ when the drain current Id■ turns off, it suddenly tries to rise to level V again and the drain current Id at time τ1 Due to the effect of The corresponding drain voltage product is wasted in MOSFET 2 when the switching operation is off. Note that the primary and secondary sides of the transformer 1 are wound using a winding method so that the induced voltages are in opposite phases to each other, and the signals shown in the black circles in Figure 1 are from the beginning of each winding. Therefore, the effects of the voltages induced on the secondary side on the primary side operate so as to be added in phase.

Next, with such drain voltage ■, transformer 1
Based on the above-mentioned winding method, on the secondary side of the diode 11, only the voltage induced in the drain voltage during the period τ, corresponding to the drain voltage during the period τ, acts as a positive direction voltage for the diode 11. Therefore, a rectified current flows through the diode 11, which is the charging current Isφ in FIG.

This charging current 1. As soon as the capacitor 14 is charged and reaches a predetermined discharge starting voltage VN, the excitation discharge circuit 1
Capacitor 14 via choke coil 1001 of 00
An excitation discharge tube 1002 filled with xenon gas to which a voltage of . The choke coil 1001 is used to limit the maximum discharge current.

The charging voltage during excitation discharge by this excitation discharge circuit 100 is divided by a voltage dividing circuit including resistors 12, 13 and capacitor 15, and is constantly applied to comparator 6 via input line 602.
The reference voltage supplied via #1 is set equal to the voltage to be compared when the charging voltage ■ is the discharge starting voltage VN, and the output ■ of the comparator 6 is set equal to the voltage to be compared when the charging voltage ■ reaches the discharge starting voltage VN. Then, the high level H is set to the zero level low level L, and MOSFET 2 repeats on and off switching in this way.As is clear from the above explanation, the conventional charging circuit of this type is the M08F.
The falling time of the gate pulse that switches the FiT, the so-called off-time, becomes longer due to the influence of the capacitance between the gate and source electrodes, and the power loss generated in the MOSFET during this off-time increases, resulting in an increase in the size of the MOSFET, including the heat dissipation structure. is unavoidable, and this condition increases in proportion to the switching repetition frequency, resulting in an unavoidable decrease in charging efficiency.゛In addition, in order to reduce the above-mentioned drawbacks and shorten the switching off time of the MOSFET gate, the conventional charging circuit uses M08F.
The gate parallel resistance of E'l', in the case of Fig. 1, the - of resistor 7 is made small in order to reduce the capacitance between the gate and the source and the time constant formed by this resistance, but for this reason, the MO8FBT value s Low impedance input circuit 1 = -
A disadvantage is that dedicated drive power is required to compensate for this effect.

[Purpose of the invention]

' The object of the present invention is to eliminate the above-mentioned drawbacks, and to replace the DC power source with a MOSFET in a charging circuit that supplies electrical energy to an excitation/discharge circuit that is an excitation means for a laser probe.
When the voltage obtained by switching is boosted and rectified to obtain a charging DC voltage at a predetermined level, the MO
By providing means for rapidly discharging the charge accumulated in the gate-source capacitance of the 8FB'r at the same time as the switching pulse applied to the gate of the MOSFET is turned off, the charging efficiency is significantly improved. M
It is an object of the present invention to provide a charging circuit that can significantly reduce the size and weight of the O8FBT itself and its heat dissipation structure.

[Invention composition]

The circuit of the present invention boosts and rectifies a voltage obtained by switching a DC power supply through a high-power MOSFET to obtain a DC voltage at a predetermined level, and also uses a laser excitation means (
In the charging circuit that supplies electrical energy for charging necessary for all excitation and discharge circuits, a transistor is arranged between the gate and source of the high-power MO8FMT, and the on- and off-periods of the gate voltage corresponding to the switching operation are controlled. The transistor is configured to include an accumulated charge discharging means for rapidly discharging the charge accumulated during the ON period of the gate voltage to the capacitance between the gate and the source through the transistor which is turned on at approximately the same timing as the start of the OFF state. .

〔Example〕

Next, the present invention will be described in detail with reference to the drawings.

FIG. 3 is a circuit diagram showing the configuration of an embodiment of the charging circuit according to the present invention.

The configuration of the embodiment shown in FIG.
62 and a transistor 163, and the addition of the accumulated charge discharging circuit 16 and the deletion of the resistor 7 are the first steps.
Unlike the configuration in the figure, other identical symbols have the same contents, so detailed explanations regarding these will be omitted.

Moreover, FIG. 4 is an operation waveform diagram of each main part in the embodiment of FIG. 3. Except for the symbols and corresponding parts of the main parts shown in FIG. 4, all the parts shown in FIG. 3 are the same as those shown in FIG. The embodiment shown in FIG. 3 will be described below with reference to FIG. 4.

The accumulated charge discharge circuit 16 includes an astable multivibrator 161, an input resistor 162, and a transistor 163.
The accumulated charge is discharged by the capacitance between the gate and source electrodes of MOSFET 2 as follows.

The bus stable I multi-by-plane brake 161 performs 7 re-runnings at a repetition period that is preset in consideration of conditions such as the laser oscillation repetition frequency, and outputs timing pulses Q and Q output terminals that occur with mutually opposite polarities. These are shown in FIG. 4 as J and ωb multivibrator outputs, respectively.

The multi-by-break output fog is caused by the comparator output (2) from the comparator 6, which is delayed by the starting voltage vN, as described above with reference to FIG.
Then, the current is continued and the gate loss (2) as the output of the impark 5 is supplied after a rise time τG.

On the other hand, multi-pipe rake output - 1 human resistance 1627,
The multivibrator output ω is supplied to the gate of the C transistor 163, but has the opposite polarity to the multivibrator output C, and when the multivibrator output ↓ is in the off state, it assumes a one-on state M. Therefore, when the multivibrator output C is on, MOSFET 2
A drain current Is flows and a drain voltage ■ is generated.
Obtaining the charging voltage ■ by the discharging current Is■ is shown in Fig. 1. When the vibrator output J is in the off state, the multivibrator output ■5 is in the on state, and at most 10 r
Transistor 16 in a time of about llsEic (+1 second)
3 is in a conductive state, and the gauge star 163 of MOSFET 2 is turned on.
is rapidly discharged through the

As a result, the off time of the gate pulse (2) becomes significantly shorter than τ1 of the conventional example shown in FIG. The 41st gate pulse {circle around (2)} shows a gate pulse whose off time is thus significantly shortened. Corresponding to the shortening of the off-time, the period during which the drain voltage t pressure is generated to induce a positive force applied to the diode 11 on the secondary side of the transformer 1, that is, the charging current I
The βiL delay period τ of s■ will also be shortened AFj.

In this way, by shortening the off time of the gate pulse (2), the power loss generated in the MOSFET 2 is significantly reduced, and charging that basically does not require drive power becomes possible.

In addition, in the embodiment shown in FIG. 3, the multivibrator output C and the astable multipipe lake L are determined. It is clear that the problem can be solved in the same way by replacing it with a set of clock circuits that output pulses of opposite polarity. [Effects of the Invention] As explained above, according to the present invention, the excitation of the laser In a charging circuit that supplies electrical energy to an excitation/discharge circuit that is a means, when a voltage obtained by switching a DC power supply through a MOSFET is boosted and rectified to obtain a charging DC voltage at a predetermined level, the MOSFET is The M
A charging circuit that basically eliminates the need for OSFET drive power, dramatically increases the number of charging operation repetitions, significantly improves charging efficiency, and significantly reduces the size and weight of the MOSFET itself and its heat dissipation structure. The effect is that it can be realized.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing the basic configuration of a conventional charging circuit using a high-power MOSFET as a switching element, Figure 2 is an operational waveform diagram of each main part of the conventional charging circuit shown in Figure 1, and Figure 3 is A circuit diagram showing an embodiment of a charging circuit according to the present invention,
FIG. 4 is an operational waveform diagram of each main part in the embodiment of the charging circuit of the present invention shown in FIG. 1...Transformer, 2...MOSFET
, 3...Clock circuit, 4...NAN
D circuit, 5... Inverter, 6... Comparator, 7... Resistor, 8... Capacitor, 9... Variable resistor, 10 ...Zener diode, 11...Diode, 12
．． 13... Resistor, 14... Capacitor, 16... Accumulated charge, discharge circuit, 100...
... Excited discharge tube circuit, 161 ... Astable multivibrator, 162 ... Resistor, 16
3...Transistor, 1001...
Choke coil, 1002...Discharge tube, 100
3...Trigger wire, 1004...
Trigger high voltage pulse generation circuit. 2nd figure r----1---------Ko Iwa 41),

Claims (1)

[Claims] The voltage obtained by switching a DC power supply via a high-power MOSFET is boosted and rectified to obtain a DC voltage at a predetermined level, and then supplies the electric energy for charging necessary to the excitation/discharge circuit as a laser excitation means. In the charging circuit, a transistor is disposed between the gate and source of the high power MOSFET, and the transistor is brought into conduction at approximately the same timing as the start of the off state during the on and off periods of the gate voltage corresponding to the switching operation. 1. A charging circuit comprising an accumulated charge discharging means for rapidly discharging charges accumulated in a capacitance between a gate and a source during a period when a gate voltage is on.