JPS5855752B2 - High voltage generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high voltage generator that generates a high voltage pulse on the output side of a step-up transformer to obtain a high DC voltage by opening and closing an electric circuit including an inductive load such as a step-up transformer. .

Conventionally, a high voltage generator that obtains a DC high voltage using an inductive load, such as a step-up transformer, has a circuit configuration as shown in FIG.

In the figure, 1 and 2 are input terminals to which an AC voltage is applied, and the AC voltage applied to these input terminals 1 and 2 is converted into a DC voltage by a rectifier circuit composed of a diode 3 and a smoothing capacitor 4. .

5 is a step-up transformer around which a primary winding 6, a secondary winding 7 and a feedback winding 8 are wound;
, the connection polarity of the secondary winding 7 and the feedback winding 8 is as shown in FIG.

Reference numeral 9 denotes an NPN type transistor configured to form a closed circuit with the primary winding 6 of the step-up transformer 5, the diode 3, and a rectifier circuit made up of the smoothing capacitor 4 in series; It opens and closes a series circuit between the next winding 6 and the rectifier circuit.

10.11 is a bias resistor; this bias resistor 10.
Reference numeral 11 divides the rectified power supply voltage and applies it between the base and emitter of the transistor 9 via the feedback winding 8.

A diode 12 is connected between the emitter and the collector of the transistor 9, and this diode prevents the application of a power supply voltage between the collector and emitter of the transistor 9.

Reference numeral 13.14 is an output terminal for taking out high voltage DC, and from this output terminal 13.14, the voltage induced in the secondary winding 7 of the step-up transformer 5 is transferred to a diode 15 and a smoothing capacitor 16.
The rectified voltage is taken out by a rectifier circuit consisting of.

Note that 17 is a resonant capacitor connected to both ends of the secondary winding 7 of the step-up transformer 5;
It can be omitted when using the stray capacitance of

Further, it is not necessary when obtaining AC high voltage output.

Now, when an AC voltage is applied to the input terminals 1 and 2, it is rectified and smoothed by the diode 3 and the smoothing capacitor 4, divided by the bias resistor 10.11, and applied between the base and emitter of the transistor 9.
starts and begins to flow collector current.

The collector current increases depending on the time constant of the circuit, mainly the time constant of the primary winding 6, or at this time a positive feedback voltage is induced in the feedback winding 8, keeping the transistor 9 in a conductive state.

Thereafter, when the collector current reaches a value suppressed by the positive feedback voltage, the transistor 9 is rapidly cut off due to the reverse regeneration effect.

At this time, a large back electromotive force is generated in the primary winding 6, and a high voltage pulse is generated.

Note that this high voltage pulse starts to resonate due to the resonance capacitor 17 connected to both ends of the secondary winding 7 and the equivalent inductance seen from the secondary winding 7, but at this time, the transistor 9 of the primary winding 6 If the side terminal is positive, it is blocked by the transistor 9 and no current flows in the primary winding 6.

However, when the power supply side terminal of the primary winding 6 becomes positive, the energy stored in the step-up transformer 5 and the resonance Releases the energy stored in the circuit.

Further, by boosting the high voltage pulse generated in the primary winding 6 in the secondary winding 7, and rectifying and smoothing it in the diode 15 and smoothing capacitor 16, it is possible to obtain a DC high voltage from the output terminal 13.14. can.

Here, in this circuit, the base current of the transistor 9 is caused to flow through the base-emitter resistor 11 circuit of the transistor and the transistor 9 by the induced voltage of the feedback winding 8, and the transistor 9 is turned OFF to cause the circuit to oscillate. Thus, the feedback winding 8 must be provided in the step-up transformer 5, which has the disadvantage that not only does the step-up transformer 5 become large in size, but also its circuit becomes complicated.

The present invention was developed to eliminate such drawbacks, and will be described below with reference to FIG. 2, which shows one embodiment of the present invention.

Note that the same parts as those in the conventional circuit shown in FIG. 1 are given the same numbers, and the explanation will be omitted.

In the figure, a diode 21 serves as an impedance element inserted and connected between the emitter and base of the transistor 9, and this diode 21 is connected to the smoothing capacitor 4, the diode 21. The transistor 9 is inserted and connected in such a direction that it discharges through its base and collector.

22 and 23 are capacitors for activating the transistor 9, and the capacitors 22 and 23 are connected in series and connected in parallel to the smoothing capacitor 4.

Reference numeral 24 denotes a bidirectional diode as a trigger element that exhibits negative resistance at a constant voltage, and this bidirectional diode 24 is inserted and connected between the connection point of the capacitors 22 and 23 and the base of the transistor 9.

Moreover, this bidirectional diode 24 and the capacitor 2
2.23 constitutes a drive circuit for activating the transistor 9.

In this circuit, when an AC voltage is applied to input terminals 1 and 2, it is rectified and smoothed by a diode 3 and a smoothing capacitor 4, and the rectified and smoothed voltage is transferred to a capacitor 22.
．． 23 and capacitors 22.23 begin charging.

The terminal voltage of the capacitor 23 is the bidirectional diode 24
When the operating voltage is reached, the bidirectional diode 24 becomes conductive, thereby causing the capacitor 23 to discharge the stored charge through the base-emitter of the transistor.

As the charge on capacitor 23 discharges through the base-emitter of transistor 9, transistor 9 becomes conductive and the collector current of transistor 9 increases due to the time constant of the circuit.

Then, the capacitor 23 discharges the charge, and the capacitor 2
When the terminal voltage of 3 drops to a voltage at which the bidirectional diode 24 becomes non-conductive, the base current no longer flows to the transistor 9, and after an accumulation time, the transistor 9 becomes non-conductive, and at the same time, the primary winding of the step-up transformer 5 A high voltage is generated across 5.

Also, the accumulated energy accumulated in the step-up transformer 5 during this period is transferred to the smoothing capacitor 4, the diode 21 . Discharge passes through the base and collector of the transistor 9, and at this time, the transistor 9 operates as if it were a reverse transistor, with the collector acting as an emitter and the emitter acting as a collector.

Further, at this time, since the impedance of the discharge circuit for the stored energy of the step-up transformer 5 is low, a sufficient discharge current flows and a sufficient reverse base current flows through the transistor 9, so that the stored charge remains in the transistor 9.

Then, when the discharge of the stored energy in the step-up transformer 5 is finished, the transistor 9 discharges the remaining stored charge,
As a result, current flows from the collector toward the base, and since no discharge can occur from the base, current flows from the base to the emitter.

This base current makes transistor 9 conductive again.

At this time, the transistor 9 is in a conductive state until the accumulated charge is released, and becomes non-conductive when the accumulated charge is exhausted.

Then, a high voltage pulse is generated again in the primary winding 6, and thereafter the above operation is repeated and oscillation continues.

In addition, in this state, if the output terminals 13 and 14 are short-circuited, the energy stored in the step-up transformer 5 is released in the secondary winding 7, so the reverse current flowing through the transistor 9 is drastically reduced, and oscillation stops. .

In addition, the energy stored in the step-up transformer 5 is also drastically reduced, so that the step-up transformer 5 completely oscillates or stops.

In this way, a high voltage pulse is generated across the primary winding 6 of the step-up transformer 5, and the voltage is further increased from the output terminals 13 and 14, and the voltage is further increased through the diode 15 and the smoothing capacitor 1.
6, a rectified and smoothed DC high voltage is taken out.

As is clear from the above description, in the high voltage generator of this embodiment, a diode 21 is inserted and connected between the emitter and base of the transistor 9 that constitutes a series circuit with the step-up transformer 5. Energy is transferred to diode 21. The transistor 9 is configured to be discharged by the base-collector circuit, and once the transistor 9 is made conductive, the accumulated charge accumulated in the transistor 9 due to the discharge of the accumulated energy of the step-up transformer 5, The transistor 9 can be turned ON and OFF, eliminating the need to provide the feedback winding 8 in the step-up transformer 9 as in the past, simplifying the circuit, and providing a highly reliable high voltage generator with extremely low power consumption. be able to.

In addition, if the output terminals 13 and 14 are short-circuited, that is, the load circuit is short-circuited, the transistor 9 is turned OFF, that is, the oscillation of the circuit is stopped, and there is no abnormal heat generation or fire in the load, and an emergency occurs. It is highly safe.

In this embodiment, the power supply voltage is divided by the capacitors 22 and 23, and the voltage of the capacitor 23 connected between the base and emitter of the transistor 9 is higher than the operating voltage of the bidirectional diode 24 connected to the base of the transistor 9. As a result, the electric charge in the capacitor 23 is discharged, a base current flows through the transistor 9, and the capacitor 23 starts charging again after a predetermined time.
Due to the charge remaining in the capacitor 23, the charging of the capacitor 23 is stopped before the bidirectional diode 24 is charged to the voltage at which the bidirectional diode 24 operates.
2.23 stops charging and discharging after starting the transistor 9, and as a result, the terminal voltage also stops at a constant voltage, and the transistor 9
Base current no longer flows through.

That is, only the base current for starting up the transistor 9 flows for the first time, but does not flow thereafter.

Note that if the capacitances of the capacitors 22 and 23 are appropriately selected, the capacitor 23 can be repeatedly charged and discharged several times, and the transistor 9 can be activated reliably.

In the circuit shown in FIG. 2, the storage time of the transistor 9 cannot be adjusted, so variations in the characteristics of the transistor 9 result in variations in the characteristics of the device.

Therefore, as shown in FIG.
By inserting and connecting the transistor 9 between the base and emitter of the transistor 9, the accumulated charge of the transistor 9 is shunted from the base to the emitter side through the resistor 25, so that the accumulation time of the transistor 9 can be adjusted.

In addition, when a resistor 25 is inserted and connected between the base and emitter of the transistor 9 in order to adjust the accumulation time of the transistor 9, the diode 21 that was inserted and connected between the base and emitter is omitted as shown in Fig. 4. You can also do that.

This means that the energy stored in the step-up transformer 5 is
, begins to flow through the base and collector of transistor 9, transistor 9 acts as a reverse transistor as described above, and transfers the energy stored in step-up transformer 5 to the emitter.
This is because discharge can occur in the collector circuit.

Similar results can be obtained even when the resistor 25 is inserted and connected between the base and emitter of the transistor 9 in this way.

Furthermore, as shown in FIG. 5, the bidirectional diode 24 is connected to a unijunction transistor 26 and resistors 27 and 28.
Even if it is replaced with , the same effect as in FIG. 2 can be obtained.

In addition, the method of adjusting the storage time of the transistor 9 is not limited to the fixed resistor 25 as described above, but as shown in FIG.
Thyristor 29 between the base and emitter of transistor 9
The thyristor 29 is connected to a delay circuit consisting of a resistor 30 and a capacitor 31, and a bidirectional diode 32, which fires the thyristor 29 at regular intervals to short-circuit the base and emitter of the transistor 9. It may be configured to do so.

That is, this short circuit can instantly release the accumulated charge and turn off the transistor 9.

Such means can also change the impedance between the base and emitter of the transistor 9, and the charge accumulation time can be adjusted.

In particular, the charge accumulation time of the transistor 9 is unstable and tends to fluctuate significantly due to many fluctuation factors such as temperature and the energy release current of the step-up transformer 5. The base of transistor 9
Maintaining a constant value by short-circuiting the emitters is a very effective means from the standpoint of device stability.

Note that, as shown in FIG. 7, the same effect can be obtained even when the thyristor 29 is replaced with an NPN type transistor 33.

Also, in order to generate a constant high-voltage pulse in the primary winding 6, is it necessary to keep the amount of change in the forward current flowing through the primary winding 6 constant?In this case, if it is configured as shown in FIG. good.

In FIG. 8, 34 is a resistor connected in series to the emitter of the transistor 9, 35 is a capacitor connected in parallel with the resistor 34, 36 is a bidirectional diode, and 3T is a silice.

With this circuit configuration, when the emitter current of the transistor 9, that is, the current flowing through the primary winding 6, exceeds a certain value, the bidirectional diode 36 operates, making the thyristor 37 conductive and discharging the accumulated charge of the transistor 9. OF
Make it F.

That is, since the transistor 9 is turned off at a constant winding current value, a constant output can always be obtained.

In this way, the impedance between the base and emitter of the transistor 9 is changed during the operation of the circuit, and the transistor 9
By controlling the charge accumulation time, the voltage value of the high voltage pulse generated across the primary winding 6 can be kept constant.

Similar results can be obtained using the circuit shown in FIG.

In the circuit shown in FIG. 9, a series circuit consisting of a constant voltage diode 38 and a diode 39 is inserted and connected between the other end of a resistor 34 connected in series to the emitter of transistor 9 and the base of transistor 9. .

Note that the cathode of the constant voltage diode 38 is connected to the base of the transistor 9, the anode to the anode of the diode 39, and the cathode of the diode 39 to the resistor 34.

This circuit utilizes the Zener effect of the constant voltage diode 38, and therefore, when the current flowing through the transistor 9 exceeds a predetermined value, the transistor 9 is turned off.

In other words, the same effect as the circuit shown in FIG. 8 can be obtained.

As is clear from the above embodiments, the high voltage generator of the present invention has a diode 21 inserted and connected between the base and emitter of the transistor 9 forming a series circuit with the step-up transformer 5, and the energy stored in the step-up transformer 5 is transferred to the diode. 21
, is discharged in the base and collector circuit of the transistor 9, and the transistor 9 is operated as an inverse transistor.If the transistor 9 is activated for the first time, the energy stored in the step-up transformer 5 is discharged, and the transistor 9 is then activated. The accumulated charges can cause the transistor 9 to perform an ON-OFF operation, eliminating the need to provide the feedback winding 8 in the step-up transformer 5 as in the conventional case, and making the step-up transformer 5 smaller.・As the number of terminals of lance 5 decreases,
Misconnections can also be reduced.

Moreover, when the output terminals 13 and 14 are short-circuited, that is, when the load circuit is short-circuited, the 0N-
Since the OFF operation, that is, the oscillation of the circuit stops, abnormal heat generation of the load, fire, etc. do not occur, and the safety is extremely high.

Furthermore, conventionally, the energy stored in the step-up transformer 5 was discharged by the diode 12 connected between the collector and emitter of the transistor 9. The diode 21 used in the circuit of the present invention needs to be able to withstand pulses, but the diode 21 used in the circuit of the present invention only needs to have a withstand voltage higher than the forward voltage between the base and emitter of the transistor 9, and the circuit can be constructed at low cost. At the same time, since the number of parts to which high voltage is applied is reduced, the reliability of the circuit can be improved.

Moreover, in the high voltage generator of the present invention, the diode 21
By connecting a resistor 25 in parallel with the resistor 25, the storage time of the transistor 9 can be adjusted, and variations in the characteristics of the transistor 9 can be compensated for.

Furthermore, the same effect as when connecting the diode 21 can be obtained by using only the resistor 25, and in this case as well,
This allows the storage time of transistor 9 to be adjusted.

Further, the same effect can be obtained by using a transistor instead of the diode 21.

In other words, a diode 21 .is connected between the base and emitter of the transistor 9 . Any impedance element such as the resistor 25 or a transistor may be used.

In addition, since the accumulated charge of the transistor 9 is used for the ON-OFF operation of the transistor 9, it is better to use a low frequency transistor with a large amount of accumulated charge as the transistor 9 than to use a high frequency transistor. This is advantageous when adjusting the accumulation time using the resistor 25 to compensate for variations in the characteristics of the transistor 9 as described above.

Moreover, since low frequency transistors are easier to manufacture as high voltage and large current transistors than high frequency transistors, when trying to obtain high voltage pulses as in the present invention, it is necessary to replace transistor 9 with a low frequency transistor. It is easier to obtain a low-cost and highly reliable high voltage generator by using the above method.

Furthermore, as shown in FIGS. 6 and 7, by short-circuiting the base and emitter of the transistor 9 at regular intervals,
By changing the impedance between the base and emitter of the transistor 9 and adjusting the storage time of the transistor 9, the storage time of the transistor 9 will always be constant, improving the stability of the device.

Furthermore, as shown in FIGS. 8 and 9, when the current flowing through the primary winding 6 of the step-up transformer 5 exceeds a predetermined value, the impedance between the base and emitter of the transistor 9 is changed, and the accumulation time of the transistor 9 is changed. By adjusting , the current flowing through the primary winding 6 of the step-up transformer 5 can be kept constant, and the voltage value of the high voltage pulse can be kept constant.

As described above, in the high voltage generator of the present invention, an impedance element is connected between the base and emitter of the transistor forming a series circuit with the step-up transformer, and energy stored in the step-up transformer is transferred to the impedance element, the base of the transistor, and the emitter of the transistor. It is released through a collector,
As a result, the step-up transformer can be made smaller and the circuit can be made simpler, which makes it extremely superior in that it is inexpensive, consumes extremely little power, and has high reliability and safety.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram of a conventional high voltage generator, and FIG. 2 is an electric circuit diagram of a high voltage generator according to an embodiment of the present invention.
3 to 9 are electrical circuit diagrams of high voltage generators according to other embodiments of the present invention. 5...Step-up transformer, 6...Primary winding, 7...Secondary winding, 9,33...Transistor, 21.25... ... Impedance element (diode, resistor), 22.23, 31.35...
...Capacitor, 24°26.36...Trigger element (bidirectional diode, unijunction transistor, bidirectional diode), 30,34...
...Resistance, 29.37 ... Cyrisk, 38
... Constant voltage diode, 39... Diode.

Claims (1)

[Claims] 1. A step-up transformer having a primary winding and a secondary winding for taking out an output voltage. forming a closed circuit with a capacitor, and connecting an impedance element between the emitter and base of the transistor,
Furthermore, a trigger element is connected between the base of the transistor and the connection point of the plurality of series-connected capacitors. 2. The high voltage generator according to claim 1, wherein the impedance element is a diode. 3. The high voltage generator according to claim 1, wherein the impedance element is a parallel element of a diode and a resistor. 4. The high voltage generator according to claim 1, wherein the impedance element is a resistor. 5. The high voltage generator according to claim 1, wherein the base and emitter of the transistor are short-circuited at regular intervals. 6. The high voltage generator according to claim 5, wherein a sirisk or a transistor is connected between the base and emitter of the transistor, and the sirisk or transistor is driven by a delay circuit including a resistor and a capacitor. 7. The high voltage generator according to claim 1, wherein the current flowing through the primary winding of the step-up transformer short-circuits the base and emitter of the transistor. 8. A cyrisk is connected between the base and emitter of a transistor, and the cyrisk is driven by a parallel circuit consisting of a resistor and a capacitor that detects the current flowing through the transistor, and a trigger element operated by the terminal voltage of the capacitor of this parallel circuit. A high voltage generator according to claim 1. 9 Connect one end of a resistor to the emitter of the transistor, and connect a series circuit of a constant voltage diode and a diode between the base of the transistor and the other end of the resistor, and change the impedance between the base and emitter of the transistor by the current flowing through the transistor. The high voltage generator according to claim 7, wherein the high voltage generator is configured to reduce the voltage. 10. The high voltage generator according to claim 1, wherein the transistor 10 is a low frequency transistor.