JP3257908B2 - DC high voltage generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC high voltage generator, particularly an output voltage of 2 kV to 20 kV and an output current of 5 mA to 2 mA.
The present invention relates to a small DC high voltage generator used for a laser tube of about 0 mA or the like.

[0002]

2. Description of the Related Art A helium-neon laser tube requires a DC high voltage of 2 kV to 20 kV and a current of 5 mA to 20 mA. In this case, a commercial power supply of AC 100 V is often used as an input power supply. Conventionally, as this type of DC high voltage generator, there is one proposed in Japanese Patent Publication No. 6-52988 by the same applicant as the present applicant.

[0003] This DC high voltage generator will be described below with reference to FIG. Rectifier circuit 6 for rectifying commercial AC
And the main current terminal of the switching element Q1 and the first winding n1 of the transformer 7 are respectively connected in series, and a positive feedback circuit is provided from the fourth winding n4 of the transformer 7 to the control electrode of the switching element Q1. Are connected to form a self-excited inverter, and the transformer 7
A rectifier circuit 9 is connected to the second winding n2 to constitute a DC high voltage generator for obtaining an output DC high voltage. In this DC high-voltage generator, the output terminal of the second switching element Q2 is connected in parallel to the control electrode of the switching element Q1, and the control terminal of the second switching element Q2 is synchronized with the control terminal of the second switching element Q2 via the insulating pulse transformer 21. The output signal of the control pulse generation circuit 22 is supplied. The configuration of the synchronous control pulse generation circuit 22 includes a capacitor C5, a series circuit of a resistor and a diode having one end connected to the third winding n3 of the transformer 7, a parallel circuit connected in parallel to the series circuit and having the opposite polarity. A second series circuit of the diode, the resistor, and the Zener diode, and the output DC high voltage setting signal are connected to the non-inverting input terminal of the comparator U1, and a constant potential is applied to the inverting input terminal of the comparator U1. Thus, there has been proposed a DC high voltage generator characterized by being configured to generate a synchronization control pulse signal from an output terminal of the comparator U1.

Since this DC high-voltage generator has a so-called self-excited inverter for ON operation, the switching element on the primary side always has a terminal voltage of zero regardless of fluctuations in load conditions and input conditions. Turn on near. Therefore, no excessive reactive current flows through the switching element on the primary side. In the off operation, an off-pulse is supplied until the switching element is reliably turned off by acting as a so-called separately excited inverter, and the control range can be widened.

[0005]

However, this DC high voltage generator has the following problems or requests. First, there is a problem of a problem at the time of transition from the trigger region to the constant current region. The constant voltage control is performed at the time of the trigger, and the constant current control is performed after the trigger is completed.

[0006] Second, it is necessary to increase stability in a range below the control range. At the lower limit of the control range, the voltage generated by the transformer decreases in proportion to the output, so that the control of the synchronous control pulse may deviate from the intended operation. We need to solve this problem.

Third, when the commercial AC input voltage is
It is required to share with 0V system. The commercial AC power supply is mainly 100V system in Japan, but there are many countries with 200V system in foreign countries, and it is strongly demanded that the same DC high voltage generator can be shared.

Fourth, since the inverter is a self-excited inverter, it is desired that the inverter be started even under the worst conditions because of the influence of temperature characteristics due to variations in the current amplification factor of the switching elements and changes in the environment.

Fifth, there is a problem of compatibility with a load tube.
The load bulb needs a trigger voltage several times higher than the steady voltage, for example, 10 kV. After the trigger is completed, a steady voltage, for example, 2 kV is required. It is required to prepare design conditions that can always provide a DC high-voltage generator that satisfies both conditions.

Sixth, it is required to switch the function of the delay safety circuit from outside after completion of the DC high voltage generator.

[0011]

In order to solve the first problem, a current detection circuit, a constant current control circuit which operates in response to this signal, a voltage detection circuit, and a constant voltage control circuit which operates in response to this signal And these two outputs are supplied to a synchronous control pulse generation circuit via an OR circuit.

In order to solve the second problem, as a power supply for the synchronous control pulse generation circuit, a power supply which is half-wave rectified from the winding of the transformer and is not smoothed is used. Even if the average output value of the transformer winding voltage decreases by this means,
Since the instantaneous value is used as the power supply for the synchronous control pulse generation circuit, a stable operation can be performed.

In order to solve the third problem, a first rectifier circuit is constituted by forming a diode bridge and connecting two sets of symmetrical series-connected smoothing capacitors to its output terminal. The connection point of these two sets of smoothing capacitors is the AC input terminal 3, and the connection point of this series capacitor is the connection point of the starting resistor at the same time. For 100V input, double voltage rectification is used. For 200V input, bridge rectification is used.

In order to solve the fourth problem, a positive feedback circuit is provided by providing a first tap on a fourth winding of a transformer, and a series circuit of a resistor and a diode is provided from the first tap. And a second tap having a larger number of turns than the first tap is provided on the fourth winding of the transformer, and the resistance of the resistor is connected from the second tap to the fourth winding of the transformer. The switching element is connected to a control electrode of the switching element via a resistor having a higher resistance value.

[0015] In order to solve the fifth problem, regarding the configuration of the second rectifier circuit, a first tap is provided in the second winding of the transformer, and a first multi-stage voltage doubler rectifier circuit is connected thereto. And
A second tap having a larger number of turns than the first tap is provided in the second winding of the transformer, a second multi-stage voltage doubler rectifier circuit is connected to the second tap, and a first multi-stage voltage doubler is provided. It is superimposed on the output of the rectifier circuit.

Sixth, the output side power supply line of the comparator constituting the timer circuit is formed into a loop and drawn out of the DC high voltage generator. Therefore, the presence or absence of the function of the delay safety circuit can be externally switched after the completion of the DC high voltage generator.

[0017]

FIG. 1 shows an embodiment of the present invention. Input terminals 1, 2, and 3 receive 100 V or 200 V of a commercial AC power supply. Reference numeral 6 denotes a rectifier circuit for rectifying the commercial AC. Reference numeral 7 denotes a transformer, which generates a high-frequency high voltage in the secondary winding of the transformer 7 by switching the transistor Q1 as a switching element at a high frequency. The multi-stage voltage doubler rectifier circuit 9 constitutes a multi-stage voltage doubler rectifier circuit for applying a high trigger voltage when the load tube is activated. The high-voltage rectifier circuit 8 is for supplying a steady-state current to the load tube. Reference numeral 11 denotes a voltage detection circuit. Upon receiving the detection signal, a constant voltage control circuit 14 generates a control signal to make the high voltage for trigger substantially constant. Reference numeral 12 denotes an output current detection circuit. Upon receiving the detection signal, the constant current control circuit 10 generates a control signal so as to keep the output current in a steady state constant. The constant voltage control signal and the constant current control signal are used as control pulses by a synchronous control pulse generation circuit 22, and the transistors are transmitted through a pulse transformer 21.
Apply to the base of Q2. When the transistor Q2 turns on, the transistor Q1 turns off. The timer circuit 13 is a safety device that starts its operation after a predetermined delay from the time when the input power supply of the DC high voltage generator is connected. This DC high-voltage generator can be roughly classified into a rectifier circuit 6, a switching element Q1, a primary circuit 101 including windings n1, n3 of a transformer 7, etc., a winding n2 of a transformer 7, a high-voltage rectifier circuit 8, and the like. A secondary high voltage circuit 202 including a multi-stage voltage doubler rectifier circuit 9; a synchronous control pulse generating circuit 22 which operates by receiving power and a signal from a winding n3 of the transformer 7; a constant current control circuit 10; The control circuit 303 includes a voltage detection circuit 14, a voltage detection circuit 11, and an output current detection circuit 12. The entire DC high-voltage generator having such a circuit configuration is insulated and molded with synthetic resin to complete it.

Next, the configuration and function of each section will be described in detail in order. A commercial AC voltage of 200 V is connected to the input terminals 1 and 2 and rectified to a DC voltage of about 240 V by a rectifier circuit 6 composed of diodes D1 to D4, resistors R1, R2 and electrolytic capacitors C1, C2. When the input voltage is 100 V, a commercial AC voltage of 100 V is connected to the input terminals 1 and 3 and voltage rectification is performed, and a DC voltage of about 240 V appears at both ends of the electrolytic capacitors C1 and C2. In this way, the DC 24
0V is obtained. The resistors R1 and R2 are used to limit the inrush current when the input power supply is connected, and have low resistance. The resistor R4 connected to the positive terminal of the capacitor C2 is a resistor for supplying a small current for starting to the base of the transistor Q1, and a high resistance value is suitable. A resistor R3 having the same resistance value as the resistor R4 is connected in parallel to the capacitor C1, and adjustment is performed so that the terminal voltages of these two capacitors C1 and C2 become substantially equal.

Next, a portion for generating a high frequency will be described. A first winding n1 of the transformer 7 and a transistor Q1 acting as a switching element are connected in series. The tap of the fourth winding n4 of the transformer 7 is connected to the resistor R6 and the diode D7.
Is connected between the base and the emitter of the transistor Q1. The base current Ib slightly flows through the base of the transistor Q1 via the resistor R4. The value obtained by multiplying the DC current gain hFE by the base current Ib, the collector current
Ic flows. The mutual polarity of the first winding n1 and the fourth winding n4 of the transformer 7 is as shown, and the increase in the collector current Ic is the increase in the inter-winding voltage of the first winding n1, Further, the current increases through the resistor R6 and the diode D7 to increase the base current Ib of the transistor Q1. As described above, a minute oscillation is generated due to the positive feedback action, and the oscillation is increased. Eventually, the transistor Q1 is turned on to the saturation region. When the collector current Ic of the transistor Q1 increases and becomes Ic> hFE × Ib, the transistor Q1 cannot maintain the saturated state, and conversely, the collector current Ic starts to decrease, and rapidly turns off due to the positive feedback action in the decreasing direction. I do. When the transistor Q1 is turned off, the voltage oscillates at the natural period of the electric oscillation circuit formed by the inductance of the second winding n2 of the transformer 7, the stray capacitance Co, the load condition, and the like. When the transistor Q1 is inverted, the transistor Q1 is turned on again. Return. For the base drive signal of transistor Q1, the winding
Since the polarity relationship between n1 and winding n4 is turned on starting from the time when the mark starts to become positive, the zero voltage switching operation is automatically performed.

Here, the resistor R5 connected between the tap of the fourth winding n4 of the transformer 7 and the base of the transistor Q1 increases the gain at the time of starting the inverter while increasing the fourth winding of the transformer 7. Operates to limit the reactive power when the reverse voltage is generated. The capacitor C3 is for facilitating the growth of the micro oscillation. Diode D5 is transistor Q1
For reverse protection between collector and emitter. The diode D6 discharges an excess of the base current of the transistor Q1 from the winding n4 as the collector current of the transistor Q1.

The circuit of the resistor R36, the capacitors C29, C36 and the diode D29 connected near the collector of the transistor Q1 is a circuit provided for protecting the transistor Q1 from overvoltage.

The high-frequency high-voltage generated in the second winding n2 of the transformer 7 is connected to the high-voltage rectifier circuit 8 between the transformer and the tap. The high voltage rectifier circuit 8 includes capacitors C14, C15, C16,
A one and a half stage voltage doubler rectifier circuit composed of C17 and diodes D19, D20 and D21 generates a DC high voltage which is about three times the input high frequency voltage. This high-voltage rectifier circuit 8 is a rectifier circuit for supplying a steady current of the load tube. Next, a multistage voltage doubler rectifier 9 is connected between the cathode of the diode D21, which is the output terminal of the high voltage rectifier 8, and the tap of the transformer 7. The multi-stage voltage doubler rectifier circuit 9 includes capacitors C23 to C2.
8 and diodes D23 to D28, a three-stage voltage doubler rectifier circuit for generating a DC high voltage approximately 6 times the voltage between the taps of the transformer 7 and a high voltage rectifier circuit 8 And outputs the sum with the generated voltage. This voltage acts as a trigger voltage for the load tube. The values of the capacitors C23 to C28 in the multi-stage voltage doubler rectifier circuit 9 are extremely small and have a voltage generating capability. Instead, the current mainly from the high-voltage rectifier circuit 8 flows bypassing the resistor R32 and the diode D22. The number of turns between the tap of the second winding n2 of the transformer 7 and the number of stages of the high voltage rectifier circuit 8 and the multi-stage voltage doubler rectifier circuit 9 are selected in accordance with the ratio between the trigger voltage of the load tube and the steady voltage. Can be designed more efficiently and economically. Note that resistor R34,
R35 is for instantaneous current limiting. Also capacitor C18
~ C22 is for smoothing.

In order to set and stabilize the output voltage or output current to a predetermined value, the following operation is performed. First, before the transistor Q1 is turned off by itself, the second transistor Q2 is turned on with the value of the collector current Ic corresponding to the predetermined output voltage or the predetermined output current, and the base and the emitter of the transistor Q1 are short-circuited. Turn off Q1. That is, the output voltage or the output current is controlled by controlling the ON time width of the transistor Q1. The base current of the transistor Q2 is provided by the insulating pulse transformer 21 and insulates the secondary circuit from the primary circuit commercial power line.

The synchronizing control pulse generating circuit 22 includes a capacitor C5
And the terminal voltage of the Zener diode DZ1 is generated by comparing with the comparator U1. The operation power supply of the comparator U1 is supplied with a DC voltage which is obtained by rectifying the third winding n3 of the transformer 7 and being completely smoothed. On the other hand, the output voltage terminal of the comparator U1 and the power supply to the transistor Q3 are not completely DC, and the third winding n3 of the transformer 7 is connected to the diode D1.
A pulsating voltage that is only half-wave rectified at 0 is supplied. When this DC high-voltage generator narrows down the output, the output voltage terminal of the comparator U1 and the power supply to the transistor Q3 that generates the pulse have more pulse generation capability in the pulsating flow than in the complete smoothing. Can be supplied stably.

Here, the constant current control circuit 10 and the constant voltage control circuit
A state where there is no charging current to the capacitor C5 due to the 14 output signal will be described. As shown in Fig. 2 (a)
At time t2 when the terminal voltage of C5 is charged through the resistor R5 and the diode D10 and exceeds the terminal voltage of the Zener diode DZ1, a synchronous control pulse is generated by the comparator U1 as shown in FIG. 2 (b). I do. This synchronization control pulse is sent between the base and the emitter of the transistor Q2 via the transistor Q3 and the insulating pulse transformer 21.
As shown at time t2, the collector and the emitter of the transistor Q2 are short-circuited. Immediately thereafter, as shown at time t2 in FIG. 2 (e), the collector current of the transistor Q1 rapidly turns off and completely turns off at time t3. At this time, the collector-emitter voltage of the transistor Q1 rises as shown in FIG. The peak value of the collector-emitter voltage of the transistor Q1 increases or decreases in accordance with the peak value of the collector current of the transistor Q1. As shown in FIG. 2F, the voltage of the first winding n1 of the transformer 7 is substantially positive during the period from the time t1 when the transistor Q1 is turned on to the time t2.
Edc = 240V is applied, but transistor Q1 is at time t3
When it is turned off, it swings to the negative side up to Er. At this time, the voltage of the third winding n3 of the transformer 7 also swings to the negative side, so that the terminal voltage of the capacitor C5 in the synchronous control pulse generation circuit 22 is a diode.
Discharged through D11, diode D12, resistor R11 and zener diode DZ2, the voltage becomes almost 0V at time t4. Transistor Q1 is turned on again, and 0V is applied until time t5 when the polarity of each winding voltage of transformer 7 becomes positive. maintain. That is, the transistor Q1 starts to turn off at time t2 and turns off completely at time t3, but until this time t3, an off pulse is supplied.
At time t4, the off-pulse ends. In the above, the state where there is no charging current to the capacitor C5 by the output signals of the constant current control circuit 10 and the constant voltage control circuit 14, that is, the maximum output state of τ1 shown in FIG.

Next, the control operation of the output voltage will be described. The third winding n3 of the transformer 7 is rectified by diodes D8 and D9 and capacitors C12 and C13, and this voltage is
The pressure is divided by R29, R30 and R31. A voltage proportional to the output voltage is taken out through the voltage detection circuit 11, is compared with a reference voltage by a zener diode ZD6 by a constant voltage control circuit 14, and its error voltage is amplified by a transistor Q4 to generate a synchronous control pulse. Feed to one end of capacitor C5 in circuit 22. When the output voltage is higher than the predetermined output voltage, as shown after time t5 in FIG. 2A, charging of the capacitor C5 is accelerated to shorten the conduction time of the transistor Q1 (section τ2 in FIG. 2E).
When the output voltage is lower than the predetermined voltage, the constant voltage control circuit 10 acts in the opposite manner, delaying the charging of the capacitor C5 of the synchronous control pulse generation circuit 22, and extending the conduction time of the transistor Q1.

The operation of controlling the output current will be described. A voltage proportional to the output current is extracted through an output current detection circuit 12 including a resistor R24 and a variable resistor RV1 inserted in a path through which the output current flows. This current detection signal is compared with the reference voltage by the Zener diode ZD4 by the constant current control circuit 10, and the error voltage is amplified by the operational amplifier U3.
It is sent to one end of the capacitor C5 in the synchronous control pulse generation circuit 22, and is operated in the same manner as the above-described constant voltage control.

The output voltage control signal and the output current control signal are supplied to a capacitor C5 of a synchronous control pulse generation circuit via an OR circuit of diodes D17 and D16, respectively. Regarding the cooperative relationship between the two, at first, since the output current does not flow before the load tube is triggered, the output voltage control signal is activated to generate a substantially set DC high voltage. Then, when the laser tube of the load tube is turned on, current starts to flow and the output current control signal is activated. Once the laser tube is lit, a holding current or higher current must be applied. However, until the operational amplifier U3 enters the stable region at the beginning of the operation as the constant current control, sometimes a sag occurs as shown by a broken line in FIG. Therefore, it is safe to follow a path slightly overshooted as shown by the solid line in FIG. It has an operational amplifier U3
The desired characteristics can be obtained by selecting the relationship between the values of the resistors R20 and R23 having the negative feedback constant and the capacitor C7.

The timer circuit 13 comprises a comparator U2, diodes D13, D14, D15, a capacitor C6, and resistors R15, R16, R17. The power line and the resistor of this timer circuit 13
The line connecting R15 is drawn as a delay function selection line 5 in a loop outside the DC high voltage generator. When the delay function selection line 5 is closed as shown in FIG. 1, the timer circuit 13 functions, and when the delay function selection line 5 is opened, the function of the timer circuit 13 stops. The output of the timer circuit 13 is connected to the capacitor C5 of the synchronous control pulse generation circuit 22. For about 3.5 seconds after the input power is applied between the input terminals 1 and 2, the timer circuit 13 outputs the high-potential output. Yes, the charging time of the capacitor C5 is increased to make the conduction time of the transistor Q1 extremely short. At this time, the discharge path of the capacitor C5, the diode D11,
Zener diode DZ2 connected in series with D12 and resistor R11 operates to set the lower limit of the discharge voltage. By selecting the voltage of the Zener diode DZ2 to an appropriate value, the cooperation between the timer circuit 13 and the synchronization control pulse generation circuit 22 can be completed.

The transistors Q1, Q2, Q3, Q4 are, for example, F
The same operation can be performed with other switching elements such as ET.

[0031]

Since the present invention is constructed as described above, the switching element on the primary side is always turned on when its terminal voltage is near zero irrespective of changes in load conditions, input conditions, inverter operating frequency and the like. The OFF condition is maintained until the OFF state is ensured. Therefore, no excessive reactive current flows through the primary side switching element, and this characteristic is always maintained automatically. Furthermore, the start of the inverter is more reliable, the adaptation to the load tube is easier, the stability at the lower limit of the control range is improved, and the characteristics when shifting from the trigger area to the constant current area are more stable. It also has an effect.

In a high-voltage generator, safety and moisture resistance can be increased by molding the entire device with an insulating resin. In this case, however, reducing internal heat loss as in the present device requires less molding resin material. There is a reduction in the stress of the mold due to heat generation, which is economical and has the effect of extending the life. Regarding the correspondence of input voltage, even after molding, it can support both 100V system and 200V system. Also, the operation of the timer circuit can be easily switched from outside even after molding.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing the voltage of each part of the DC high voltage generator shown in FIG.
It is a current waveform diagram.

FIG. 3 is an output current waveform at the time of startup of the DC high-voltage generator shown in FIG. 1;

FIG. 4 is an example of a configuration of a conventional DC high voltage generator.

[Explanation of symbols]

1, 2, 3 ... input terminal 4 ... ground terminal 5 ... delay function selection line 6 ... rectifier circuit 7 ... transformer 8 ... high voltage rectifier circuit 9 ... multi-stage voltage doubler rectifier circuit 10 ... constant current control circuit 11 ... voltage detection circuit 12 ... Output current detection circuit 13 ... Timer circuit 14 ... Constant voltage control circuit 15 ... High voltage output terminal 16 ... 0 V terminal 21 ... Pulse transformer 22 ... Synchronous control pulse generation circuit 101 ... Primary circuit 202 ... Secondary high voltage circuit 30
3… Control circuit Q1, Q2, Q3, Q4… Transistor U1, U2… Comparator
U3, U4: operational amplifier C0: stray capacitance of secondary winding of transformer 4

Claims (5)

(57) [Claims] 1. A first switching element having a pair of main current terminals and a control terminal at a pair of rectification output terminals of a first rectifier circuit having a pair of commercial AC input terminals and a pair of rectification output terminals. A pair of main current terminals, a first winding and a second
Of a transformer having a third winding, a third winding and a fourth winding
And a positive feedback circuit is connected to the control electrode of the first switching element from the fourth winding of the transformer to form a self-excited inverter. In a DC high voltage generator for obtaining an output DC high voltage by connecting a second rectifier circuit to a second winding, a control electrode of the first switching element and one main current terminal are provided with a pair of main currents. Second having a terminal and a control terminal
A pair of main current terminals of the switching element are connected to each other, and an output signal of a synchronous control pulse generating circuit is supplied to a control terminal of the second switching element via an insulating pulse transformer. As a power supply for the circuit, a power supply that performs half-wave rectification and is not smoothed from the third winding of the transformer is used. The synchronization control pulse generating circuit includes a synchronization signal obtained from the third winding of the transformer. And a constant current control signal from the constant current control circuit or a constant voltage control signal from the constant voltage control circuit are 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 generating device configured to generate a synchronization control pulse signal from an output terminal of a comparator. 2. The configuration of the first rectifier circuit is as follows.
A diode bridge is formed, and two sets of smoothing capacitors connected in series to each other symmetrically are connected to the output terminal thereof,
The connection point of these two sets of smoothing capacitors should be the AC input terminal 3, the connection point of this series capacitor should be the connection point of the starting resistor at the same time, 100V input should be double voltage rectification, and 200V input should be bridge rectification. The DC high voltage generator according to claim 1 or 2, wherein 3. The configuration of the positive feedback circuit, wherein a first tap is provided in a fourth winding of the transformer,
From the tap to the switching element control electrode via a series circuit of a resistor and a diode, and a fourth tap of the transformer is provided with a second tap having a larger number of turns than the first tap. 3. The direct current as claimed in claim 1, wherein the second tap is connected to a control electrode of the switching element via a resistor having a resistance higher than the resistance of the resistor. High voltage generator. 4. The configuration of the second rectifier circuit is as follows.
A first tap is provided in a second winding of the transformer, to which a first multi-stage voltage doubler rectifier circuit is connected, and a second winding of the transformer has more turns than the first tap. 2. A multi-stage voltage doubler rectifier circuit comprising: a second tap connected to a second multi-stage voltage doubler rectifier circuit and superimposed on an output of the first multi-stage voltage doubler rectifier circuit. Or claim 3
The direct-current high-voltage generator according to any one of the above. 5. The circuit according to claim 1, wherein an output of a timer circuit is connected to a non-inverting input terminal of the comparator, and a power supply line of the timer circuit is drawn out in a loop. The DC high-voltage generator according to any one of the above.