JP2712334B2 - AC power supply - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC corona generator required for a static elimination and separation process, which is one of electrophotographic image forming processes, such as an electronic copying machine and a laser beam printer, and an electric motor. Output frequency of uninterruptible power supply etc. is several K from commercial frequency of 50Hz / 60Hz
The present invention relates to an AC power supply that requires a low-frequency AC power supply of Hz.

Conventional technology As a means for supplying AC power, the conventional technology includes:
For example, there is a voltage resonance type DC-AC inverter as disclosed in Japanese Patent Publication No. Sho 62-16078. FIG. 35 shows a circuit diagram of the DC-AC inverter of the voltage resonance type, and FIG. 36 shows operation waveforms of each part. In FIG. 35, a DC power supply 14 is connected between the power supply terminals 12 and 13, and one power supply terminal 12 is connected to one of the inductances 5 having a reset winding.
Connected to the intermediate tap of the primary winding of the transformer 1 via the secondary winding. A resonance capacitor 11 is connected between both ends of the primary winding of the transformer 1 and commonly connected to the other power supply terminal 13 via the collector-emitters of a pair of switching transistors 2 and 3. A pulse signal having a constant frequency and a variable pulse width is supplied from the pulse width control oscillator 4 to the base of the power supply, and alternately turned on. One end of the secondary winding of the inductance 5 is connected in series with the diode 6 in the forward direction to one power supply. The other end is connected to the other power supply terminal 13. The transformer 1 is provided with an appropriate gap to adjust the inductance so that the resonance frequency in combination with the resonance capacitor 11 matches the oscillation frequency of the pulse width control oscillator 4. With the above configuration, the transistors 2 and 3 are alternately turned on by the output pulse of the pulse width control oscillator 4, so that a sine wave AC voltage can be obtained in the secondary winding of the transformer 1.

The pulse width control oscillator 4 includes an oscillation circuit 43, a pulse width modulation circuit 42, and a distribution circuit 41 as shown in FIG. Control. When this controlled output pulse, for example, a rectangular pulse as shown in FIGS. 36a and 36c is given to the bases of the transistors 2 and 3, respectively, the collector voltages of the transistors 2 and 3 are shown in FIGS. 36b and d, respectively. To change. That is, when the transistors 2 and 3 are turned off, the current in the primary winding of the inductance 5 is cut off, and an excessive voltage will be induced at both ends of the primary winding and the collectors of the transistors 2 and 3. However, the inductance 5 has a secondary winding, and Vid is induced at both ends of the secondary winding. When this voltage Vid exceeds the voltage Vdc of the DC power supply 14, the energy is transferred through the diode 6 to the energy of the DC power supply 14. And the peak values of the collector voltages of the transistors 2 and 3 are limited to a constant value. By varying the pulse width of the output of the pulse width control oscillator 4, the sine wave output voltage Vac obtained in the secondary winding of the transformer 1 can be arbitrarily varied.

However, in such a conventional configuration, resonance due to the inductance of the capacitor 11 and the transformer 1 is necessary, and the resonance current and the loss due to the DC resistance of the inductance element and the primary winding of the transformer 1 are reduced. The dielectric loss of the capacitor 11 having a large capacitance required to secure a certain Q and resonate becomes large, and this loss is a factor that deteriorates the power supply efficiency. Also, in order to keep a constant output waveform stable, stabilize the resonance frequency and improve the Q,
In order to tune the oscillation frequency and the resonance frequency, it is necessary to adjust the core gap of the transformer 1 and adjust the capacitor 11, resulting in a lack of productivity, and the presence of the gap reduces the efficiency of the transformer 1 and tends to further deteriorate the power supply efficiency. . In addition, because it is necessary to tune, the output frequency cannot be easily varied, and the μ and equivalent gap of the core change due to changes in temperature and aging. There were drawbacks to bring. Further, when the duty ratio changes to cope with fluctuations in input and load, when the duty ratio of the output pulse is small as shown in FIGS.
When the duty ratio of the output pulse is large as shown in FIGS.
There is a drawback that the crest factor is lowered, that is, the output crest factor fluctuates greatly due to input fluctuation and load fluctuation.

When used as an AC power supply for electrophotography, there are generally two types of output waveforms: a sine wave type and a rectangular wave type. However, in the conventional method, only a sine wave type is used because resonance is used. There are drawbacks that cannot be addressed. Further, since the switching frequency of the transistor is as low as the output frequency, it cannot be increased in frequency, requires a very large inductance, and cannot be provided in a small size and at low cost.

Means for Solving the Problems In order to solve the problems, the present invention can arbitrarily turn on and off the operation of current sources connected in series and in parallel to a waveform forming capacitor, and the current values of the current sources can be arbitrarily linked. The first and second current sources that can be changed by the operation, voltage detection means for detecting the voltage of the waveform forming capacitor, and the operation of the output of the voltage detection means are started, and the first time and the second time are determined. The time control means controls the end time of the operation of the first current source and the start time of the operation of the second current source, and the second current source is controlled by the voltage level of the waveform forming capacitor. And a switching element connected to the primary winding of the transformer, and a time ratio of each switching element to a trapezoidal wave with respect to time. And a regenerative diode inserted between the intermediate tap of the primary winding of the transformer and the DC input terminal, an inductance element having a reset winding, and the secondary winding of the transformer. This is a configuration in which an LC filter based on capacitance is provided.

A first and a second current source capable of arbitrarily turning on and off an operation of a current source connected in series and in parallel to the waveform forming capacitor and capable of arbitrarily changing the current value of the current source; A voltage detecting means for detecting a voltage of the forming capacitor; and a time controlling means for starting an operation by an output of the voltage detecting means and generating a first time and a second time. Control timing for controlling the end of operation of the current source and the start of operation for the second current source, and controlling the end of operation of the second current source based on the voltage level of the waveform forming capacitor. A switching element connected to a primary winding of a transformer, and applying a high-frequency pulse whose time ratio is modulated in a trapezoidal wave with respect to time to each switching element; Over-di-inductance and its 2
The configuration is such that an LC filter is provided with a capacitance provided on the next winding.

Operation With the above configuration, by adjusting the rising and falling slopes of the modulated trapezoidal wave, it is possible to easily output an arbitrary waveform of a rectangular wave, a trapezoidal wave, a pseudo sine wave, and a triangular wave, and an output waveform of an arbitrary rising and falling slope. It can be provided with a circuit configuration, high efficiency, small size and low cost.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit configuration of an AC power supply device according to an embodiment of the present invention.

In FIG. 1, a DC power supply 14 is connected between the power supply terminals 12 and 13, and one power supply terminal 12 is connected to an intermediate tap of the primary winding of the transformer 1 through a primary winding of an inductance 5 having a reset winding. Connect to Then, the primary winding of the transformer 1 is connected to the other power supply terminal 13 through the collector-emitter of the pair of switching elements, the transistors 2 and 3, and the pulse width control oscillator 4 is connected to the base of the transistors 2 and 3 A high-frequency pulse whose ratio is trapezoidally modulated with respect to time is applied to turn on alternately, and the inductance 5
One end of the next winding is connected to one power supply terminal 12 via the diode 6 in series in the forward direction, and the other end is connected to the other power supply terminal 13. A capacitor 15 is equivalently added to both ends of the secondary winding of the transformer 1. It goes without saying that the switching element may be an FET or the like other than a transistor.

The pulse width control oscillator 4 includes an amplitude control trapezoidal wave generation circuit 43, a high frequency oscillation circuit 45, a pulse width modulation circuit 42, and a distribution circuit 41 as shown in FIG.
As shown in FIG. 4, the trapezoidal wave output of the amplitude control trapezoidal wave generation circuit 43 and the high frequency output of the high frequency oscillation circuit 45 are converted by the trapezoidal wave as shown in FIG. A high frequency pulse having a modulated time ratio is obtained, and the high frequency pulse shown in FIGS. 2A and 2B is obtained by distributing the high frequency pulse every half cycle of the output cycle by the distribution circuit 41.

The high frequency pulse is applied to the bases of the transistors 2 and 3, respectively, so that the transistors 2 and 3 are alternately turned on, and the high frequency component is removed by an LC filter including the inductance 5 and the equivalent capacitor 15 of the secondary winding of the transformer 1. 7c to 7f, the trapezoidal output voltage Vac can be obtained in the secondary winding of the transformer 1. The output voltage Vac can be arbitrarily varied and feedback-controlled by varying the output amplitude of the high-frequency pulse amplitude control trapezoidal wave generation circuit 43 with the control signal 44. The trapezoidal wave generating circuit 43 shown in FIG. 3 for generating a trapezoidal wave generally has the following configuration.

FIG. 32 shows a block diagram, and FIGS. 33 and 34 show operation waveforms, which will be described below with reference to the drawings. 32 in Fig. 32
1 is a triangular wave generating circuit, 102 is a clamp circuit that clips the amplitude of the triangular wave obtained by the triangular wave generating circuit 101,
Reference numeral 103 denotes a limiter voltage source that determines the clipping point. With the above configuration, if the limiter voltage of the limiter voltage source 103 is changed to a-1, a-2, and a-3 while the amplitude of the triangular wave is constant as shown in FIG. As shown in the figure, the amplitude of the trapezoidal wave changes as b-1, b-2, b-3,
If the limiter voltage is constant and the amplitude of the triangular wave is changed to a-1, a-2, a-3 as shown in FIG.
B-1, b-2, b-3 and the rise of the trapezoidal wave as shown in FIG.
The fall was changing.

When a trapezoidal wave is used as the modulation signal of the pulse width modulation inverter, it is necessary to vary the amplitude in a waveform-similar manner. Amplitude must be accurately linked, which is very difficult, and if done, is complicated, expensive, and inaccurate.

The amplitude control trapezoidal wave generation circuit 43 of the present invention improves this point. FIG. 5 shows an amplitude control trapezoidal wave generation circuit 43 having a waveform similar to that of which the amplitude can be varied and the rising and falling slopes of the trapezoidal wave can be arbitrarily varied, and will be described below with reference to the operation waveforms of the respective parts in FIG. .

In FIG. 5, reference numeral 431 denotes a waveform forming capacitor. 432
Is a first current source (hereinafter referred to as a charging current source) that is connected in series to the waveform forming capacitor 431, can be turned on and off arbitrarily, and can be set to an arbitrary current value. Reference numeral 433 denotes a second current source (hereinafter referred to as a discharging current source) which is connected in parallel to the waveform forming capacitor 431 and can be turned on and off arbitrarily and set to an arbitrary current value. The first current source 432 for charging and the second current source 433 for discharging are configured such that their current values can be changed in conjunction with each other by the control signal 44. 434 input terminal 438 by the comparator is connected to the discharge end time setting reference voltage source 435, connects the input terminal 437 to the waveform forming capacitor 431, the voltage of the discharge end timing setting reference voltage source 435 (hereinafter V _L to) and give to the output terminal 439 of the comparison output of the voltage (hereinafter referred to as V _CM) of the waveform forming the capacitor 431. Reference numeral 436 denotes time control means. TRIG is connected to the output terminal 439 of the comparator 434, generates a first timing at OUT1, and generates a second timing at OUT2, and generates the first and second current sources for charging and discharging. Performs ON / OFF control of 432,433. The block diagram configured as described above will be described below with reference to the operation waveform diagram of FIG. FIG. 6a shows the time control means 43.
OUT 1 of 6, b represents the waveform of OUT 2, c denotes the waveform of the V _CM. Time control means 436 which is triggered by t ₀ the output of the comparator 434 generates the waveform of Figure 6 a to OUT 1 a timer for generating a timing of t _1, t _2. OUT at t ₀
1 for charging at the first current source 432 constant current operation in the waveform forming capacitor 431 to start of charging to the L level, V _CM is OUT by linearly first time increases to the right up t ₁
1 goes to the H level to end the operation. First time
charging and past the t ₁ be discharged even V _CM is moved in parallel while maintaining because not performed. Next, the waveform of FIG. 6B is generated at OUT2. In the second period t ₂ OUT 2 is to start the operation of the second current source 433 for become discharged to L level, for discharging the corrugating capacitor 431 at constant current, V _CM linearly downward to the right down I do. The V _CM reaches the level of the V _L, becomes a point of t ₃ the OUT 1 gives again triggered to the time control means 436 output of the comparator 434 L, OUT
2 to terminate the operation of the second current source 433 for discharging the H level, and to return to the t ₀ resets the timer repeats the above operation, V _CM generates a trapezoidal wave continuously. V _CM is b-1 in Figure 7 b by optionally variably interlocking the current value of the second current source 433 for discharging the current of the first current source 432 for charging, b-2, As shown in b-3, the trapezoidal waveform has a similar shape and the amplitude can be varied. Also, the rise of a-1, a-2, a-3, a trapezoidal waveform as shown in a-4 of Figure 7 a by varying the first time t ₁ of the time control means 436, falling The slope can be arbitrarily changed, that is, a waveform from a rectangular wave to a trapezoidal wave and a triangular wave can be made continuously variable. Further, as described above, the trapezoidal wave forming means of the present invention is characterized in that the rising part (charging part) has a time of t ₁ -t ₀ , the flat part (non-charge / discharge part) has a time of t ₂ -t ₁ , Since the end time of the section (discharge section) is performed at the _VL level, the latter is the first and second current sources for charging and discharging compared to the case where the rising section, flat section, and falling section are all performed at the same time. 432,433 current or t ₁ −t ₀ and t ₃ −t
If there is a slight difference between the time difference and ₂ , the difference in current and time is accumulated as shown in FIGS. 8a and 8b, and the trapezoidal wave is shifted to obtain a waveform that maintains a stable level. On the other hand, the former (the present invention) can obtain a waveform that always maintains a stable level with a simple circuit configuration. In the latter case, when a trapezoidal wave as shown in FIG. 8A is used as a pulse width modulation waveform for the power supply shown in FIGS. 1 and 20, the level of the trapezoidal wave increases rapidly, so that the pulse width modulation is not performed. The high-frequency output (Fig. 4a), which is the comparison waveform, is completely exceeded, and the pulse duty ratio is always 100% or the maximum duty ratio if there is a limiting circuit with the maximum duty ratio. Becomes a rectangular wave, and the transformer 1 in which the magnetic flux density is set by the trapezoidal wave is saturated, an excessive current flows through the transistors 2 and 3, and the transistors 2 and 3 may be burned. When the trapezoidal wave voltage further rises and rises to the power supply voltage of the trapezoidal wave generation circuit, the trapezoidal wave becomes a DC level. The distribution circuit shown in FIG.
The trigger of 41 is the output 439 of the comparator 434 shown in FIG.
Although applied at the timing of t _0, the trigger is lost because the trapezoidal wave is at the DC level, the distribution circuit 41 does not operate, and the push-pull transistors 2 and 3
One of them is turned on continuously and burns out instantaneously. On the other hand, when a trapezoidal wave as shown in FIG. 8b is used as the pulse width modulation waveform for the power supply shown in FIGS. 1 and 20, the level of the trapezoidal wave decreases. However, there is a disadvantage that the high frequency output (FIG. 4a) is completely dropped, and the pulse ratio becomes 0%, and the output stops.

FIG. 9 shows a first timer and a second timer arranged in parallel as the time control means 436, the timer operation is started triggered by the output of the comparator 434, the first time is obtained by the first timer, Second by timer 2
And the waveform of FIG. 6a is obtained at OUT 1 and the sixth waveform is obtained at OUT 2.
This is the result of the waveform shown in FIG.

FIG. 10 shows a first timer and a second timer arranged in series as another time control means 436, and the first timer is triggered by the output of the comparator 434 to obtain a first timing. According to the timing, the second timer is triggered to obtain the second timing, the waveform of FIG. 6A is obtained at OUT1, and the waveform of FIG. 6B is obtained at OUT2.

FIG. 11 shows the first and second charge / discharge units in the above-described block configuration.
A third current source 17 interlocking with the second current sources 432 and 433 is connected, an impedance element 18 for flowing the current of the third current source 17 to generate a voltage drop is connected, and a voltage generated in the impedance element 18 is connected. Is connected to the waveform forming capacitor 431, and when the currents of the first and second current sources 432, 433 for charging and discharging fall below a certain set value, the V 19 By discharging the _CM , the amplitude of the trapezoidal wave is suppressed, and malfunction of the circuit when the control signal 44 becomes a small signal is prevented. Hereinafter the operation shown illustrating the voltage waveform of V _CM in FIG. 12. When the signal of the control signal 44 becomes minute and the current value of the charge / discharge current sources 432, 433 becomes minute in conjunction with the signal, V
The amplitude of the _CM becomes smaller as shown by b-2 in FIG. When the current values of the first and second current sources 432 and 433 for charging / discharging become small, the input bias current present at the input terminal 437 of the comparator 434 cannot be ignored and is greatly affected. That is, the waveform forming capacitor 43
When the input bias current 1 flows, V _CM is in Figure 12 b-
As shown in FIG. 1, since the discharge capability is canceled, the discharge capability rises to the upper right. When the waveform as shown in b-1 of FIG. 12 is used as the pulse width modulation waveform for the power supply shown in FIGS. 1 and 20, when the control signal 44 becomes very small, such as when it is desired to reduce the output, a trapezoidal shape is obtained. Since the level of the wave rises, it completely exceeds the high-frequency output (FIG. 4a), which is the comparison waveform of pulse width modulation, so that the pulse duty ratio is always 100% or if there is a limiting circuit with the maximum duty ratio, it is always Not only the maximum duty ratio becomes uncontrollable, but also the pulse duty ratio becomes a rectangular wave, and the transformer 1 in which the magnetic flux density is set by a trapezoidal wave is used.
Is saturated, an excessive current flows through the transistors 2 and 3, and the transistors 2 and 3 may be burned. When the trapezoidal wave voltage further rises and rises to the power supply voltage of the trapezoidal wave generation circuit, the trapezoidal wave becomes a DC level. Third triggering of distribution circuit 41 shown in FIG output 439 in distribution circuit 41 eliminates the trigger operation for but applied at the timing has trapezoidal wave with the DC level of t ₀ of the comparator 434 shown in FIG. 5 And one of the push-pull transistors 2 and 3 is turned on continuously, causing instantaneous burnout. Therefore, if the ratio between the third current source 17 and the first and second current sources 432 and 433 and the impedance of the impedance element 18 are set so that the amplitude is suppressed at a current value equal to or higher than the input bias current, As described above, malfunction of the circuit can be prevented.

FIG. 13 specifically shows a circuit configuration of the amplitude control trapezoidal wave generation circuit 43 in one embodiment of the present invention. In addition,
The same components as those in FIG. 5 are denoted by the same reference numerals, and the description of the configuration is omitted.

In FIG. 13, reference numeral 16 denotes a second comparator which is an input terminal 61.
Is connected to the time control capacitor 11, the input terminal 62 is connected to the reference voltage source 27 for setting the discharge start timing (second timing t ₂ ),
The comparison output is obtained at the output terminal 63.

Reference numeral 9 denotes a first comparator, an input terminal 91 is connected to the time control capacitor 11, and an input terminal 92 is connected to a charging end time (first
T ₁ ) Connect to the setting reference power supply 10 and obtain its comparison output at the output terminal 93. Reference numeral 8 denotes an RS flip-flop having two input terminals and two output terminals. One input terminal 81 is connected to the output terminal 439 of the comparator 434, and the other input terminal 82 is connected to the output terminal 63 of the comparator 16. The output terminal 83 is connected to the input terminals 52 and 51 of the OR circuit 25 together with the output terminal 93 of the first comparator 9, and the signal of the output terminal 53 of the OR circuit 25 is connected to the first terminal for charging. Of the current source 432 is turned on and off. Also the above RS
The output terminal 84 of the flip-flop 8 controls on / off of the second current source 433 for discharging. The time control capacitor 11 is charged by a charging unit 15 including a resistor 151 and a voltage source 152, is rapidly discharged by a reset unit including a switch element 12, and constitutes a charge / discharge circuit that is reset. The switch element 12 is turned on and off by a signal of an output terminal 83 of the RS flip-flop 8.

In the circuit configured as described above, FIG.
This will be described with reference to the operation waveform diagram of FIG.

Before t ₀ , the input condition of the comparator 4 is that the input terminal 437 <the input terminal 438, so that the output terminal 439 of the comparator 434 is at the L level. So t ₀
V _CM is lowered and become, input conditions of the comparator 434, the output for the input terminal 437> input terminal 438 terminal 439
Becomes H level as shown in FIG.
The signal 9 sets the input terminal 81 of the RS flip-flop 8. Then, the output terminal 83 of the RS flip-flop 8 is
Becomes L level as shown in FIG.
A current is supplied to the time control capacitor 11 by the charging means 15 to turn off the
The voltage generated at 11 (hereinafter referred to as _VCF ) rises exponentially to the upper right as shown in FIG. 14b. Output terminal 84 of the RS flip-flop 8 in addition t ₀ becomes H level as shown in FIG. 14 g, the second current source 433 for discharge is turned off, the input condition input terminal 91 of the comparator 9
<Because of the input terminal 92, the output terminal 93 of the comparator 9 becomes L level as shown in FIG.
Since the output terminal 83 of the RS flip-flop 8 is also at the L level, both of the input terminals 51 and 52 of the OR circuit 25 are at the L level. Therefore, the output terminal 53 of the OR circuit 25 is shown in FIG.
As shown in FIG. 7, the first current source 43 for charging is at the L level.
2 is turned on, to supply current to the waveform forming capacitor 431, V _CM increases linearly to the right upward as shown in Figure 14 a. Further becomes t ₁ to reach the voltage (hereinafter referred to as V _W) of the charging end timing setting reference power supply 10 as shown in FIG. 14 b the V _CF increases input conditions of the comparator 9 is an input terminal 91> Input Since the output terminal 93 becomes the terminal 92 in FIG.
As shown in the figure, the output terminal of the OR circuit 25
The signal 53 also goes high as shown in FIG. 14d, the first current source 432 for charging is turned off, and the supply of current to the waveform forming capacitor 431 is stopped. At this time the above RS
Because the state of the flip-flop 8 does not change, V _CM is the first
4 Translates while maintaining the voltage as shown in FIG.

Further input condition of the V _CF When becomes t ₂ to reach the elevated 14th discharge start timing voltage setting reference power source 27 as shown in FIG b (hereinafter referred to as V _F) the comparator 16 is an input terminal
Since 62 <input terminal 61, the output terminal 63 goes high as shown in FIG. 14e, resetting the input terminal 82 of the RS flip-flop 8. Then, the RS flip-flop 8 is inverted, and the output terminal 83 becomes H level as shown in FIG.
Level, and resets the time control capacitor 11 is quickly discharged to indicate the V _CF to turn on the switch element 12 in FIG. 14 b. The output terminal 84 of the RS flip-flop 8 in t ₂ becomes the L level as shown in FIG. 14 g, the V _CM for that the second current source 433 for the discharge in the ON state Figure 14 a As shown in (1), the discharge is performed linearly downward to the right. When C _CM is t ₃ when the following V _L as shown in FIG. 14 a continued discharge the comparator 434
Again sets the RS flip-flop 8, repeat the above operation for terminating the operation of the second current source 433 for the discharge, V _CM generates a trapezoidal wave in succession.

In the embodiment shown in FIGS. 9 and 10, since two timers are used as time control means, a time constant is required for each of them, and the number of parts increases and the circuit of the present invention is integrated. The number of pins of the IC increases, which leads to an increase in chip area and an increase in external components, resulting in an increase in cost. In addition, in order to vary the frequency of the trapezoidal wave with a constant waveform, it is necessary to vary the time constants of the two timers in conjunction with each other while maintaining the relative ratio with high precision, and it is very difficult to realize. Here, if the embodiment of FIG. 13 of the present invention is used, the time constant of the time control means may be one,
Since the number of parts can be reduced and the number of pins when IC is used can be reduced, the cost can be reduced, and one time constant can be changed (the resistance of the charging means 15 is a variable resistance), and the waveform is constant and simple. The frequency of the trapezoidal wave can be varied.

FIG. 15 shows another embodiment of the amplitude control trapezoidal wave generation circuit of the present invention, in which the time control circuit 436 of FIG. 13 is introduced into the amplitude suppression means shown in FIG.

FIGS. 16 and 17 show an embodiment of the charging means 15, the time control capacitor 11, and the switch element 12 of the time control circuit shown in FIG. 13, respectively. The operation waveform is shown and described.

Reference numeral 21 in FIG. 16 is a reset means for the time control capacitor, which is composed of the switch element 12 and the power supply 211.
Is discharging means corresponding to the charging means 15 in FIG. 13, and is constituted by a resistor.

V _CF because the voltage applied to the time control capacitor 11 if the switch element 12 is turned on rises rapidly as shown in FIG. 18. Next, when the switch element 12 is turned off, the time control capacitor 11 discharges through the discharging means (resistor) 22 to have an exponentially lower right waveform as shown in FIG. The on / off control of the switch element 12 is performed by the signal of the RS flip-flop 8 to realize the eighteenth operation.
A continuous time control waveform as shown in the figure can be obtained.

In FIG. 17, reference numeral 15 denotes a charging means provided in place of the charging means 15 of FIG. 13, which is constituted by a current source 153.The current source 153 is connected in series to the time control capacitor 11, and the switch element 12 is the time control capacitor 11
When the switch element 12 is off, a current source is supplied to the time control capacitor 11,
As shown in Fig. 19, V _CF rises linearly to the upper right. Next, when the switch element 12 is turned on, V _CF is short-circuited, so that a rapid discharge occurs as shown in FIG. By performing the on / off control of the switch element 12 by the signal of the RS flip-flop 8, a continuous time control waveform as shown in FIG. 19 can be obtained. In addition, FIG.
By comparing the time control waveform shown in FIG. 19 with the levels of V _L and V _W , the first timing, as in the circuit of FIG.
A second time can be obtained.

The output voltage V _ac by applying an RF pulse which is pulse width modulated by the above-described V _CM to transistors 2 and 3 of FIG. 1 FIG. 7 c, d, e, is obtained as shown in f, 7 Figure c
As shown in c-1, c-2, and c-3, the output waveform can be similar and the amplitude can be varied. That is, a waveform having no change in waveform depending on the magnitude of the output amplitude is obtained.

FIG. 20 shows that the function as a filter is improved by connecting a capacitor 15 when the stray capacitance of the winding of the transformer 1 is small as the capacitor for the LC filter of the above-described embodiment. Although the filter capacitor 15 is connected to the secondary winding in the embodiment shown in FIG. 20, the same effect can be obtained by connecting it to the primary winding.

FIG. 21 shows the LC filter capacitor of the above-described embodiment, which utilizes the stray capacitance of the winding of the transformer 1.
As shown in FIG. 22, a foil-wound transformer having an increased opposing area between the windings and a stray capacitance is used.

FIG. 23 shows a case where a high-voltage generating transformer used for electrophotography or the like is used as the transformer 1 of the above-described embodiment, and the stray capacitance of the secondary winding of the transformer 1 is used as a capacitor for an LC filter. is there. In general, a high-voltage generating transformer boosts the voltage applied to the primary winding and outputs it as a high voltage to the secondary winding, so that the turns ratio between the primary winding and the secondary winding is set to a large value. Is the number of primary windings / the number of secondary windings. The stray capacitance of the secondary winding with many windings
It was used as an LC filter capacitor. Although the stray capacitance obtained in the embodiment shown in FIGS. 21 and 23 is not so large, the present invention can sufficiently obtain the effect as a filter even with a small stray capacitance because the switching frequency is high. FIG. 24 shows the voltage / current characteristics of an AC corona generator as a load for use as an AC power supply device for electrophotography.
FIGS. 25a, 25b and 25c show voltage waveforms and current waveforms when each output waveform is applied to the AC corona generator, and will be described below with reference to the drawings. In general, an AC corona generator is used in a charge removing and separating portion of an electrophotographic process, and it is necessary to increase a charge removing efficiency in order to improve a charge removing property of a photoreceptor and a separating performance of a photoreceptor and copy paper. For that purpose, it is necessary to increase the effective corona discharge current. No.
In Fig. 24, points a and b are the corona starting voltages on the plus side and the minus side, respectively. From point 0 onward, current does not flow even if the voltage is increased. Has the property of starting to flow. However, the current flowing through the stray capacitance of the corona generator flows even if it does not exceed the points a and b. When the output voltage is a sine wave as shown in FIG.
Since the ratio of the time during which the half cycle of the waveform is equal to or higher than the corona start voltage is small (the conduction angle is small), a large effective corona discharge current cannot be obtained and the charge removal efficiency does not increase. In addition, when the output voltage is increased to increase the effective corona discharge current, it is necessary to strengthen the insulation relation and increase the size of the transformer. When the output voltage is a rectangular wave as shown in Fig. 25b, a large effective corona discharge current can be obtained, but since the output waveform contains a high frequency, the current flowing into the stray capacitance of the AC corona generator and high voltage wiring has a large peak value. Becomes Although this peak current is a reactive current and does not contribute to the static elimination efficiency, the capacity of the switching element is required to be large, which is inefficient and cannot be provided at low cost. In addition, since the current flows in a spike shape, it causes noise and has a great possibility of affecting other circuits and devices. Further, since the rise and fall of the waveform are sharp, overshoot occurs in the output voltage. Because of this overshoot, the peak voltage becomes high, and it is necessary to strengthen the insulating relationship.

Therefore, the output voltage is set to a trapezoidal wave as shown in Fig. 25c, and the rising and falling slopes of the trapezoidal wave are arbitrarily varied to optimize the output peak voltage (insulation relation), effective current and noise generation. It can be easily set, simplifying and minimizing the insulation of the corona generator,
Insulation of the power supply can be simplified and downsized, and the static elimination efficiency can be maximized, and the static elimination performance and the separation performance can be improved.

FIG. 26 shows a circuit configuration of an AC power supply device according to another embodiment of the present invention.

In FIG. 26, a DC power supply 14 is connected between the power supply terminals 12 and 13, and one power supply terminal 12 is connected to an intermediate tap of the primary winding of the transformer 1. Then, the primary winding of the transformer 1 is connected to the other power supply terminal 13 through the collector-emitter of the pair of switching elements, the transistors 2 and 3, and the regenerative diode 7 is connected in the reverse direction from the collector of the transistors 2 and 3 to the emitter. , 8 are connected to the bases of the transistors 2 and 3, and high-frequency pulses whose time ratios are modulated in a trapezoidal manner with respect to time are applied from the pulse width control oscillator 4 to the bases of the transistors 2 and 3 so as to be turned on alternately. Capacitors 15 are equivalently added to both ends of the secondary winding of the transformer 1.

As shown in FIG. 29, the equivalent circuit of the transformer 1 is composed of an ideal transformer 10, a secondary side inductance 601, a secondary side converted leakage inductance 501 (hereinafter referred to as a leakage inductance), and a stray capacitance 9. The high-frequency pulse is applied to the bases of the transistors 2 and 3, respectively, and the transistors 2 and 3 are turned on alternately,
The high frequency component is removed by the LC filter by the leakage inductance 501 and the stray capacitance 9, so that the output voltage V of the trapezoidal wave shown in FIGS.
You can get _ac .

Figure 27 d is a waveform obtained by enlarging the time axis of the waveform shown in a, C is the collector in the case of applying the waveform a 'in the base of the transistor - (abbreviated hereinafter V _CE) emitter voltage shows a waveform. Here good binding of the primary winding P ₁ and P ₂ of the transformer 1, assuming a forward voltage drop of the regeneration diode 8 and OV, transistors 2 and 3 is half of the output by the high-frequency pulse ratio modulated when It is assumed that switching is performed alternately in each cycle. Now, assuming that the transistor 3 is off in a half cycle and the transistor 2 performs an on / off operation in a half cycle, the veggie inductance of the transistor 2 is the winding width and winding position between the primary winding and the secondary winding. , Depending on the winding method. Generally, as shown in FIG. 28, the transformer 1 has the same winding width and winding position of the primary winding 61 and the secondary winding 62, and is wound in close contact with the same place (telescope winding).
Although the leakage inductance is devised to be relatively small, the leakage inductance is somewhat large when used as an inductance of an LC filter for removing a high-frequency component of a waveform modulated at a high frequency as in the present invention. In this case, the frequency (switching frequency) of the high-frequency oscillation circuit can be reduced and the efficiency can be increased. Therefore, as shown in FIG.
Change the winding width of the next winding 62 and shift the winding position, or
As shown in the figure, the coupling between the primary winding 61 and the secondary winding 62 is adjusted by separating and winding the primary winding 61 and the secondary winding 62, and the value of the leakage inductance is changed to the switching frequency. On the other hand, by setting the optimum point, it can be used as the inductance of the LC filter. However, the switching speed of the switching element can be increased,
If the switching frequency of the high-frequency pulse can be sufficiently increased, it goes without saying that even in a transformer having a relatively small leakage inductance as shown in FIG. 28, the leakage inductance has a sufficient effect as the inductance of the LC filter.

Advantageous Effects of the Invention As described above, according to the present invention, (1) a resonance circuit is not required, a loss due to a DC resistance component of a resonance current and an inductance is reduced, and a resonance capacitor becomes a small-capacity filter capacitor, so that a dielectric material is used. Since the loss is extremely small, high efficiency is achieved. Also,
It is not necessary to tune by adjusting the transformer core gap and the resonance capacitor in order to obtain a stable output waveform stably, which is excellent in productivity.The μ of the transformer core due to a temperature change, the change in the equivalent gap, and the The output waveform and output amplitude do not fluctuate. Further, since the core gap of the transformer is not required, the efficiency can be further improved.

(2) The output frequency can be easily varied by adjusting the period of the trapezoidal wave generation circuit. Since the amplitude control trapezoidal wave generation circuit has one time constant, the frequency can be varied while keeping the waveform constant. It can be easily changed with a single resistor as a charging / discharging means.

(3) The waveform obtained by the amplitude control trapezoidal wave generation circuit has a constant ratio between the rise time and the fall time and the time of the flat portion, and the amplitude can be varied in a similar manner. There is no change in the waveform and crest factor due to the magnitude of, and a stable output waveform can be obtained.

(4) Since no resonance current flows through the winding of the transformer, the copper wire diameter of the winding can be reduced, and the transformer can be reduced in size, and a switching element having a small capacity can be used, resulting in high efficiency and low cost. Becomes

(5) Since switching is performed at a high frequency, the LC filter L
In the embodiment shown in FIG. 1, the (inductance element) can be reduced in size. In FIG. 26, the leakage inductance of the transformer can be used, so that it becomes unnecessary. Will be cheaper.

(6) The rising and falling slopes of the waveform obtained by the amplitude control trapezoidal wave generation circuit can be arbitrarily varied, that is, the waveform from a rectangular wave to a trapezoidal wave and a triangular wave can be continuously varied, and the variable is V _W The output waveforms are rectangular, trapezoidal,
It is possible to provide an AC power supply device that can be set to an arbitrary one such as a pseudo sine wave and a triangular wave, and that can also set the rising and falling slopes arbitrarily.

(7) Since the waveform obtained by the amplitude control trapezoidal wave generation circuit controls the discharge end time by the voltage, a waveform having a stable voltage level can be always obtained, and the output of the AC power supply device also has a stable output. be able to.

(8) When the control signal becomes very small, malfunction of the circuit can be prevented by a simple circuit added to the amplitude control trapezoidal wave generation circuit, and the AC power supply device can be protected.

(9) The amplitude control trapezoidal wave generation circuit needs only one time constant.
Since the number of parts is small and the number of pins when integrated is small, low cost can be realized.

(10) When used as an AC power supply for electrophotography,
The rising and falling slopes of the trapezoidal wave can be set to the optimum points for the corona generator, the power supply insulation, and the static elimination efficiency, and the peak current of the switching element can be reduced. Can be maximized, the static elimination and separation performance can be improved, and the size and noise of the corona generator and the AC power supply can be reduced.

(11) The regenerative diode also functions as an element for preventing the application of a reverse voltage to the switching element. Further, when a MOS field-effect transistor is used as the switching element, a parasitic diode can be used as the diode. A diode for preventing voltage application can be eliminated.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the AC power supply device of the present invention, FIGS. 2a and 2b are waveform diagrams illustrating the operation of the circuit shown in FIG. 1, and FIG. 3 is a diagram shown in FIG. FIG. 4 is a block diagram of the pulse width control oscillator, FIG. 4 is a waveform diagram illustrating the operation of the block shown in FIG. 3, FIG. 5 is a circuit diagram of the amplitude control trapezoidal wave generation circuit shown in FIG. 3, and FIG. FIGS. 7A and 7B are waveform diagrams illustrating the operation of the circuit shown in FIG. 5, and FIGS. 7A and 7B are waveform diagrams illustrating changes in the operation of the block shown in FIG. 3, and FIGS. FIG. 8 is a waveform diagram for explaining a change in the operation when the operation is performed at all times as the waveform formation detecting means;
9 is a block diagram showing an example of the configuration of the time control means shown in FIG. 5, FIG. 10 is a block diagram showing another example of the configuration of the time control means shown in FIG. 5, and FIG. FIG. 12 is a circuit diagram showing an application example of the trapezoidal wave generation circuit shown in FIG. 12, FIG. 12 is a waveform diagram illustrating the operation of the circuit shown in FIG. 11, and FIG. 13 is an embodiment showing the amplitude control trapezoidal wave generation circuit in detail. FIG. 14 is a circuit diagram of FIG.
FIG. 15 is a waveform diagram for explaining the operation of the circuit shown in FIG. 15, FIG. 15 is a circuit diagram of another embodiment showing the amplitude control trapezoidal wave generation circuit in detail, and FIGS. 16 and 17 are charging and discharging of the time control circuit. 18 and 19 are circuit diagrams showing other embodiments of the unit, respectively.
17 is an operation waveform diagram, FIG. 20 is a circuit diagram showing one embodiment of the AC power supply device of the present invention, FIG. 21 is a circuit diagram showing another embodiment of the AC power supply device of the present invention, FIG. Is a perspective view showing the structure of the winding of the transformer shown in FIG. 21, FIG. 23 is a circuit diagram showing another embodiment of the AC power supply device of the present invention, and FIG. 24 is an AC corona generator for electrophotography. 25a, b, and c are plots of FIG.
FIG. 26 shows a comparison of changes in output voltage and current waveforms when an electrophotographic AC corona generator is used as a load in the AC power supply shown in FIG. 26, and FIG. 26 shows another embodiment of the AC power supply of the present invention. 27, a, b, c, and d are waveform diagrams for explaining the operation of the circuit shown in FIG. 26, FIG. 28 is a cross-sectional view showing the structure of the transformer, and FIG. 29 is an equivalent circuit diagram of the transformer. FIG. 30 and FIG. 31 are cross-sectional views showing the structure of a transformer, FIG. 32 is a circuit diagram showing an example of a general trapezoidal wave generating circuit, and FIGS. 33 and 34 are circuit diagrams of the circuit shown in FIG. FIG. 35 is a waveform diagram for explaining the operation, FIG. 35 is a circuit diagram showing an example of a conventional voltage resonance type DC-AC inverter, and FIG.
FIG. 35 is a waveform diagram for explaining the operation of the circuit shown in FIG. 35, FIG. 37 is a block diagram of the conventional pulse width control oscillator shown in FIG. 35, and FIGS. 38 a, b, c, and d are FIG. FIG. 6 is a waveform chart comparing the operation of the circuit shown in FIG. 1 ... Transformer, 2,3 ... Transistor, 4 ... Pulse width control oscillator, 5 ... Inductance, 501 ... Leakage inductance, 6 ... Diode, 601 ... Secondary inductance, 7,8 ... Regeneration diode , 9 ... stray capacitance, 12, 13 ... power supply terminal, 14 ... DC power supply, 15 ... capacitor.

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-16078 (JP, A) JP-A-1-278267 (JP, A) JP-A-1-3111874 (JP, A)

Claims (3)

(57) [Claims] A first and a second current source that can arbitrarily turn on and off the operation of a current source connected in series and parallel to a waveform forming capacitor, and that can variably change the current value of the current source. A voltage detecting means for detecting a voltage of the waveform forming capacitor; and a time controlling means for starting operation by an output of the voltage detecting means and generating a first time and a second time. Amplitude control configured to control the operation end time of the first current source and the operation start time of the second current source, and to control the operation end time of the second current source by the voltage level of the waveform forming capacitor. A trapezoidal wave generating circuit, a pair of switching elements connected in series to both ends of a primary winding of a transformer, and a direct current between an interconnection point of the pair of switching elements and an intermediate tap of the primary winding. Power and times An inductance element having a reset winding to which a diode is connected is connected in series, and a high-frequency pulse whose time ratio is modulated by a trapezoidal wave obtained by the amplitude control trapezoidal wave generation circuit is used as the pair of the high-frequency pulses every half cycle of the output cycle. An AC power supply device in which a winding of the transformer has a filter capacity by alternately applying the voltage to a switching element. A first and a second current source capable of arbitrarily turning on and off an operation of a current source connected in series and in parallel to a waveform forming capacitor, and a current value of the current source being arbitrarily variable in conjunction with the current source; A voltage detecting means for detecting a voltage of the waveform forming capacitor; and a time controlling means for starting operation by an output of the voltage detecting means and generating a first time and a second time. Amplitude control configured to control the operation end time of the first current source and the operation start time of the second current source, and to control the operation end time of the second current source by the voltage level of the waveform forming capacitor. A trapezoidal wave generating circuit, a pair of switching elements connected in series to both ends of a primary winding of a transformer, and a direct current between an interconnection point of the pair of switching elements and an intermediate tap of the primary winding. Power supply A regenerative diode is connected in parallel to the pair of switching elements, and a high-frequency pulse whose time ratio is modulated by a trapezoidal wave obtained by the amplitude control trapezoidal wave generating circuit is connected to the pair of switching elements every half cycle of the output cycle. An AC power supply device comprising an LC filter constituted by alternately applying the switching elements to the switching element and forming a leakage inductance of the transformer and a capacitance of the winding of the transformer. 3. The AC power supply according to claim 1, further comprising a high-voltage generating winding as a transformer.