JPS63186559A - Dc high voltage generator and controlling method - Google Patents

Abstract

PURPOSE:To prevent an excess reactive current from flowing by turning ON a switching element of primary side by the intrinsic oscillation of an electric oscillator with regard to a transformer, and driving it OFF by a synchronous control pulse generator within its half period. CONSTITUTION:A DC high voltage generator has a commercial AC voltage rectifier 3, a transformer 4, a rectifier 5, a stabilized controller 10, a voltage detector 11, an output current detector 12, a timer 13, and a synchronous control pulse generator 22, etc. Further, an output DC voltage is obtained by the third winding n3 of the transformer 4, and a second switching element Q2 is connected in parallel with the control electrode of a switching element Q1. The output of the generator 22 synchronized with the period of a self-excited inverter obtained from a fourth winding n4 is connected to the control electrode of the element Q2. Thus, the element Q1 of the primary side is always turned ON by its terminal voltage near zero irrespective of the oscillation in the load and input conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is directed to a DC high voltage generator, particularly a small DC high voltage generator used in a laser tube with an output voltage of 2 kV to 20 kV and an output current of approximately 5 mA to 20 mA. and its control method.

[Conventional technology]

The helium-neon laser tube has a DC voltage of 2 to 2.
It requires a high DC voltage of 0 kV and a current of 5 mA to 20 mA. In this case, the human power source is commercial power source AC 100
V or DC 12V is often used. As a conventional commercial voltage generator of this type, a DC high voltage generator having a configuration as shown in FIG. 5 is used. To explain Fig. 5 below, commercial AC power supply 100V is input from input terminal 1.2.
diodes D1-D4. The rectifier 3, which is composed of a resistor R1 and an electrolytic capacitor CI, has a DC voltage of 120
The voltage is converted to V and supplied to the series circuit of the first winding nl of the transformer 4 and the transistor Ql. The transistor Q1 is repeatedly turned on and off at approximately 50 kHz by the drive circuit 8. Approximately 240Vpp, 50kHz at both ends of winding nl
A waveform of z is generated. The second winding n2 of the transformer 4 is the first
There are 7 times as many turns as the winding nl, where 240VppX
7=1680V. This high voltage alternating current is double voltage rectified by the rectifier circuit 5 and an output of 3300 VDC is outputted to the high voltage output terminal 6.

In order to stabilize the output voltage, the voltage generated by the third winding n3 of the transformer 4 is detected by a voltage detection circuit 11 and connected to a stabilization control circuit 10'. On the other hand, the current of the laser tube is detected by the output current detection circuit 12, and the stabilization control circuit 10
connected to. The timer circuit 13 is added as required by the BRH standard, and generates a control signal for stopping output voltage generation for 3.5 seconds after input power is turned on. The signal from the stabilization control circuit 10' is insulated and transmitted by a photocoupler 9 and connected to the drive circuit 8.

The operation of this circuit is as follows: First, the power supply voltage is input to the input terminal 1. 2, the timer circuit 13 outputs a stop signal.

Upon receiving this signal, the stabilization control circuit "to" also outputs a stop signal and sends it to the drive circuit 8 via the photocoupler 9. Approximately 3.5
Seconds later, when the timer circuit 13 generates a starting signal, the output voltage set by the voltage detection circuit 11 and the stabilization control circuit IO'' is generated, and when it reaches the ignition level of the laser tube of the load and ignites, the laser tube Since a constant current characteristic is required, the output current is detected by the output current detection circuit 12, a constant current signal is generated by the stabilization control circuit 10', and constant current operation is performed.

[Problem that the invention seeks to solve]

However, since the turns ratio between the winding n1 and the winding n2 of the transformer 4 is 7 in this case, the impedance seen from the winding n1 is the impedance of the winding n2 plus the square of this turns ratio, that is, 4.
The value is multiplied by 9. And the stray capacitance Go in the winding n2
are added in parallel, and the inverter frequency is 50kHz.
A large reactive overcharging current flows through the transistor Ql due to charging at z. Due to the relationship between the on/off period of the drive circuit 8 and the natural frequency of the transformer 4, an even larger amount of reactive current flows through the transistor Q1. Conventionally, this was dealt with by increasing the current capacity of the transistor O1 or inserting an inductance in series with the winding n1 of the transformer 4, but this was uneconomical as it consumed unnecessary power and required a large number of components. This has the disadvantage that the device becomes complicated.

[Means for solving problems]

The invention has been described above. -To solve problems related to excessive current in the switching elements on the next side.

A synchronous control pulse generation circuit that turns on a switching element on the primary side by being energized by the natural vibration of an electric oscillation circuit formed in connection with the transformer, and generates an extinguishing pulse within a half period of the natural vibration. The switching element is turned off.

This paper proposes a control method for a DC high voltage generator.

More specifically, a DC power source obtained by receiving and rectifying a commercial alternating current, a switching element, and a first winding of a transformer having at least four sets of windings are each connected in series,
A device comprising a self-excited inverter configured by connecting a second winding of the transformer to a control electrode of the switching element in a positive feedback direction, wherein a rectifier circuit is connected to a third winding of the transformer. is connected to obtain an output DC high voltage, and the output terminal of the second switching element is connected in parallel to the control electrode of the switching element to obtain the above voltage obtained from the winding of the transformer 4. A DC high voltage generator is proposed, characterized in that the output of a synchronous control pulse generation circuit synchronized with the cycle of a self-excited inverter is connected to the control electrode of the switching element of ¥S2 via an isolation transformer. It is. Note that the above configuration is for the case where the commercial AC power supply is powered by human power, and in the case of DC input, the fourth winding of the transformer is used in common with the second winding, and an isolation transformer is not required.

[Effect]

Since the present invention is constructed as described above, the primary side switching element is always turned on when its terminal voltage is near zero, regardless of changes in load conditions and input conditions. Therefore, an excessive maneuvering current does not flow through the switching element on the negative side.

〔Example〕

FIG. 1 shows an embodiment of the present invention, and FIG. 1 will be described below. Commercial AC voltage 1 is applied to input terminal 1 and input terminal 2.
00v is connected to diodes D1 to D4 and resistor R1.
, a rectifier 3 consisting of an electrolytic capacitor C1 converts the DC voltage to 120V, and a resistor R2 connected in series with the first winding nl of the transformer 4 and a transistor 01 acting as a switching element is connected to a transistor Ql. This is a resistor that allows the starting current to flow. The fourth winding n4 of the transformer 4 is connected between the base and emitter of the transistor Ql via a resistor R3 and a diode D7. A slight base current 1b flows through the base of the transistor Ql via the resistor R2. The value obtained by multiplying the DC current amplification factor hFE corresponding to this base current 1b, the collector current 1
The first winding nl and the fourth winding n of the transformer 4, through which c flows
The mutual polarity of 4 is as shown in the figure, and the collector current 1c
The increase becomes an increase in the winding threshold voltage of the first winding IJfnl, and further becomes an increase in the base current 1b of the transistor Q1 via the resistor R3 and the diode D7. In this way, a slight oscillation occurs due to the positive feedback effect, and this increases until the transistor Ql is turned on to the saturation region.

The collector current 1c of the transistor Ql increases,
When Ic>hFE-1b, the transistor Q1 cannot maintain the saturated state, and conversely, the collector current 1c begins to decrease and is rapidly turned off due to positive feedback in the decreasing direction. When the transistor Ql is turned off, the voltage oscillates at the natural period of the electric oscillation circuit formed from the inductance of the second winding n2 of the transformer 4, the stray capacitance Go, and the load conditions, etc. When the transistor Ql is reversed, the transistor Ql is turned on again. return.

Here, the resistor R4 connected in parallel with the diode D7 operates to limit the reactive power of the resistor R3 when a reverse voltage is generated in the fourth winding of the transformer 4. Also capacitor C2
is for facilitating the growth of the minute oscillation.

Diode D5 is for collector-emitter reverse protection of transistor Q1.

The diode D6 is for discharging the excess base current of the transistor from the winding n4 as the collector current of the transistor Q1.

Setting and stabilizing the output voltage or output current to a predetermined value operates as follows. First, before the transistor Q1 turns off by itself, at the value of the collector current 1c corresponding to a predetermined output voltage or a predetermined output current.

Turn on the second transistor q2 and turn on the transistor 01
By shorting between the base and emitter of.

Turn off transistor Q1. That is, the transistor Q
The output voltage or output current is controlled by controlling the on-time of l. The base current of the transistor 02 is provided by an insulating pulse transformer 21.

The secondary circuit and the primary circuit commercial power line side are insulated.

The synchronous control pulse generation circuit 22 generates a pulse by comparing the terminal voltage of the capacitor C6 and the terminal voltage of the Zener diode DZ2 using a comparator III. When the terminal voltage of capacitor C6 is charged through resistor R5 and diode 010 and rises as shown in Fig. 2(a), and exceeds the terminal voltage of Zener diode DZ2, as shown in Fig. 2(b). A synchronous control pulse is generated from comparator IJI. This synchronization pulse is sent between the base and emitter of the transistor Q2 via the transistor 3 and the insulating pulse transformer 21, and the collector and emitter of the transistor Q2 are short-circuited as shown in FIG. 2(C). Immediately after this time, the collector current of the transistor 1 is rapidly turned off as shown in FIG. 2(e). At this time transistor Q
The collector-emitter voltage of No. 1 rises as shown in FIG. 2(d). The peak value of the collector-emitter voltage of this transistor Q1 increases or decreases in accordance with the peak value of the collector current of the transistor Q1. As shown in FIG. 2(f), the voltage of the first winding n1 of the transformer 4 is approximately Edc on the positive side during the period when the transistor Q1 is on.
= 120ν is applied, but when the transistor Ql is turned off, it swings to the negative side up to Er. At this time, the third
Since the voltage of the winding n3 also swings to the negative side, the terminal voltage of the capacitor C6 in the synchronous control pulse generation circuit 22 is discharged through the diode D8, the diode D9, the resistor R6, and the Zener diode Dzl, and becomes approximately Ov. Ov is maintained until the transistor O1 is turned on again and the polarity of each winding voltage of the transformer 4 becomes positive.

The third winding n3 of transformer 4 to stabilize the output voltage
A voltage proportional to the output voltage is extracted through the voltage detection circuit 11, compared with a reference voltage in the stabilization control circuit 10, and the error voltage is amplified.

The output voltage is sent to one end of the capacitor C6 in the synchronous control pulse generation circuit 22, and if the output voltage is higher than the predetermined output voltage, the charging of the capacitor C6 is accelerated and the conduction time of the transistor Ql is shortened, as shown in section (1) of FIG. Make it shorter. Further, when the output voltage is lower than a predetermined voltage, the stabilization control circuit 1O acts in the opposite way, and the capacitor C6 of the synchronous control pulse generation circuit 22
The charging of the transistor Ql is slowed down to lengthen the conduction time of the transistor Ql.

The output of the timer 13 circuit is connected to the capacitor C6 of the synchronous control pulse generation circuit 22, and the timer circuit 13 remains active for about 3.5 seconds after the human power is applied between the input terminals 1 and 2.
is an output on the high potential side, which accelerates the charging speed of the capacitor C6 and extremely shortens the conduction time of the transistor Ql. At this time, the discharge path of capacitor C6, diode D8.
A Zener diode DZI connected in series with D9 and resistor R6 operates to set the lower limit of the discharge voltage.

By selecting an appropriate voltage for the Zener diode DZ2, the timer circuit 13 and the synchronous control pulse generation circuit 22 can be perfectly linked.

FIG. 3 shows another embodiment of the present invention. It receives 2V from the input terminal 1.2 and generates a DC high voltage of 10kV from the high voltage output terminal 6°Ov terminal 7. The difference from the device shown in FIG. 1 is that the device shown in FIG. 3 has a rectifier circuit 3. Insulated pulse transformer 21. Timer circuit 1
3 is omitted, and the fourth winding n4 of transformer 4
is common to the third winding. The other components are the same as those of the device shown in FIG. 1 and have the same functions, so their explanation will be omitted.

FIG. 1 shows still another embodiment of the present invention, in which 12 V DC is received from the input terminal 1.2, and the high voltage output terminal 6, Ov
This is a device that generates a DC high voltage output of 10kV 3mA from the terminal. The difference from the device shown in FIG. 1 is that a relatively high power DC high voltage output is generated with a low DC input voltage. Therefore, the collector current of the transistor Ql becomes large and its base current also becomes thick (it is necessary to insert and connect the primary winding of the current transformer ST2 into the collector current path of the transistor 01, and connect the secondary winding of the current transformer T2 with a resistor. The transistor R41 is connected in parallel to supply the base current to the transistor Q1 through the diode 041.The base current of the transistor Q1 is equal to the value obtained by multiplying the reciprocal of the turns ratio of the current transformer T2 by the collector current of the transistor 01. The current flowing from the fourth winding n4 of the transformer 4 to the transistor Ql via the resistor l?3 is only a very small current that acts for the slight oscillation at startup, and the gl of the resistor R3
loss can be reduced. The other components are the same as those of the device shown in FIG. 1 and have the same functions, so their explanation will be omitted.

Note that the transistors Ql, Q2. Similar operation is possible for Q3 with other switching elements such as FE'r.

〔Effect of the invention〕

Since the present invention is configured as described above, the primary side switching element is always turned on when its terminal voltage is near zero, regardless of variations in load conditions, input conditions, inverter operating frequency, etc. Therefore, no excessive reactive current flows through the negative side switching element, and this characteristic is always maintained in a self-exciting manner. The circuit configuration for obtaining this characteristic is simple, does not require any configuration, and is economical. Reducing the power loss of the entire device also has economic and safety effects.

Since the control signal is sent in the form of a pulse wave, the pulse transformer has a simple structure for insulating the primary and secondary components, and its signal transmission characteristics do not change over time unlike a photocoupler.

In a high voltage generator, safety and moisture resistance can be increased by molding the entire device with insulating resin, but in this case, internal heat loss is reduced and the capacity of the switching element is reduced, as in this device.

The absence of a current-limiting inductance for the switching element reduces mold resin material and reduces stress on the mold due to heat generation, which is economical and has the effect of extending life.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the present invention, FIG. 2 is a voltage and current waveform diagram of each part of the device shown in FIG. 1, FIG. 3 is a diagram showing another embodiment of the present invention, and FIG. The figure shows still another embodiment of the present invention, and FIG. 5 shows a conventional device. 1.2... Input terminal 3... Rectifier 4... Transformer 5... Rectifier 6... High voltage output terminal 7... Ov terminal 8... Drive circuit 9
... Photocoupler 10 ... Stabilization control circuit 11
... Voltage detection circuit 12 ... Output current detection circuit 13
...Timer circuit 10'...Stabilization control circuit 21.
... Insulation pulse transformer 22 ... Synchronous control pulse generation circuit 01, D2. D3. D4.05. D6. D7,08.
D9,010,041...Diode

Claims (1)

[Scope of Claims] 1. A DC high voltage generator comprising an input DC power source, a switching element that repeats on/off, a transformer, and a rectifier circuit connected to the secondary winding of the transformer, The switching element is turned on by being energized by the natural vibration of an electric oscillation circuit formed in connection with the transformer, and the synchronous control pulse generation circuit generates an extinguishing pulse within a half period of the natural vibration. A method for controlling a DC high voltage generator, characterized by turning off a switching element. 2. The first part of the transformer, which has a DC power source that receives and rectifies commercial AC, a switching element, and at least four sets of windings.
The windings are connected in series, and the second
In a device comprising a self-excited inverter in which the winding is connected to the control electrode of the switching element in a positive feedback direction, a rectifier circuit is connected to the third winding of the transformer to increase the output DC. A voltage is obtained, the output terminal of a second switching element is connected in parallel to the control electrode of the switching element, and synchronous control pulses are generated in synchronization with the period of the self-excited inverter obtained from the fourth winding of the transformer. A direct current high voltage generator characterized in that the output of the circuit is connected to the control electrode of the second switching element via an isolation transformer. 3. A DC power supply, a switching element, and the first winding of a transformer having at least three sets of windings are connected in series, and the second winding of the transformer provides positive feedback to the control electrode of the switching element. In a device comprising a self-excited inverter connected in a direction, a rectifier circuit is connected to the third winding of the transformer to obtain an output DC high voltage, and a control electrode of the switching element has a rectifier circuit connected to the third winding of the transformer. The output terminals of the second switching element are connected in parallel, and the output of the synchronous control pulse generation circuit synchronized with the period of the self-excited inverter obtained from the second winding of the transformer is applied to the control electrode of the second switching element. A DC high voltage generator characterized by being connected to. 4. In the DC high voltage generator according to claim 2, the synchronous control pulse generation circuit charges a capacitor from the fourth winding of the transformer through a series circuit of a resistor and a diode, and A second series circuit of a diode and a resistor of opposite polarity is used to discharge the voltage, inject a setting signal for the output DC high voltage, and connect these to the non-inverting input terminal of the comparator. A direct current high voltage generator, characterized in that a potential is applied and obtained from the output terminal of the comparator. 5. In the DC high voltage generator according to claim 3, the synchronous control pulse generation circuit charges a capacitor from the second winding of the transformer through a series circuit of a resistor and a diode, and A second series circuit of a diode and a resistor of opposite polarity is used to discharge the voltage, inject a setting signal for the output DC high voltage, and connect these to the non-inverting input terminal of the comparator. A direct current high voltage generator, characterized in that a potential is applied and obtained from the output terminal of the comparator. 6. In the DC high voltage generator according to claim 2, the synchronous control pulse generation circuit charges a capacitor from the fourth winding of the transformer through a series circuit of a resistor and a diode, and Discharged by a second series circuit of a Zener diode and a resistor of the same polarity,
A setting signal for the output DC high voltage is injected, these signals are connected to a non-inverting input terminal of a comparator, and a constant potential is applied to the inverting input terminal of the comparator, so that the signal is obtained from the output terminal of the comparator. DC high voltage generator. 7. In the DC high voltage generator according to claim 2, the synchronous control pulse generation circuit charges a capacitor from the fourth winding of the transformer through a series circuit of a resistor and a diode, and Discharged by a second series circuit of a Zener diode and a resistor of the same polarity,
The output DC high voltage setting signal and the timer circuit output signal are injected and connected to the non-inverting input terminal of the comparator, and a constant potential is applied to the inverting input terminal of the comparator. A DC high voltage generator characterized by: