JP2005245177A - High-voltage power unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize the compensation of breakdown strength under high voltage by arranging the constitution such that high-voltage generating circuits corresponding to each of positive polarity and negative polarity do not affect the circuits of mutually opposite polarity and that it gets off with the design of breakdown strength for the amount of boosting with each polarity. <P>SOLUTION: In the case of generating AC high voltage, using a Cockcroft-Walton circuit, usually input voltage is applied from one end of the Cockcroft-Walton circuit and boosted AC high voltage is output from the side of the other end, however, in this case the breakdown strength of voltage double the amplitude voltage to the positive electrode side and the negative electrode side becomes necessary in the case of generating AC high voltage oscillating to both sides of positive polarity and negative polarity, on the basis of reference voltage ( for example, 0V). So, the midpoint of the Cockcroft-Walton circuit is cut, and two pieces of capacitors 118 and 120 are connected in series between cut both ends, and a capacitive output end is taken out of the middle between these two pieces of capacitors 118 and 120. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a high voltage power supply device that drives an alternating high voltage by a Cockcroft-Walton circuit and applies the alternating high voltage to a capacitive load.

  Conventionally, as an electrophotographic image forming apparatus to which this type of power supply device is applied, the surface of the photosensitive drum is uniformly charged to a predetermined voltage by a primary charger, and then a light beam or the like is applied to the surface of the photosensitive drum. To form an electrostatic latent image, and the electrostatic latent image is developed by a toner developing device to obtain a toner image.

  The toner image is transferred to a recording sheet by a transfer unit and subjected to a fixing process, whereby image formation on the recording sheet is completed.

  When forming a full-color image, it is necessary to perform exposure and development of each color of CMYK for full-color images while the photosensitive drum rotates four times. For this reason, each developing device of the full-color image forming apparatus has A developing bias voltage composed of a DC voltage (DC) superimposed with an AC voltage (AC) for good development is applied to one developing device, while other developing devices that are not developing are applied. Therefore, a high voltage power supply device for applying a predetermined DC voltage that prevents unnecessary toner from adhering to the photosensitive drum is required.

  Here, in an image forming apparatus, when a high voltage is obtained by boosting an input voltage (DC 24 V) generated as a normal drive power supply, a transformer circuit is generally used, but the boost level (primary side and secondary side) If the voltage ratio is large, compensation of the transformer circuit becomes an important issue, and an inexpensive transformer circuit may not be used. For example, when the primary side voltage is 24V and the secondary side is required to be 1.0 KV, the voltage must be boosted 50 times by simple calculation.

  Further, in the transformer circuit, there is a limitation on the high frequency applied to the bias voltage of the developing device or the like, and it is difficult to cope with it.

  For this reason, an AC bias power supply device that obtains a high voltage signal by switching using resonance has been proposed (see Patent Document 1).

  In this Patent Document 1, an inductance that is connected in series to a capacitive load (developer, etc.) and forms an LC direct resonance circuit together with the capacitive load, and the LC series resonance circuit is energized in the positive and negative directions, respectively. And a pair of energizing circuits including a diode that regenerates series resonance energy after the energization by the switching circuit is completed, and controls the energizing time of the energizing circuit. Thus, the output voltage is controlled.

  However, in Patent Document 1, although a high frequency can be obtained, a transformer is used at the final stage for a required high voltage, and the above-described problems of the transformer circuit itself cannot be solved.

  As a high-voltage power supply circuit using resonance, Patent Document 2 includes a resonance circuit composed of an inductance and a capacitor, an oscillation transistor is connected to the resonance circuit, and a voltage doubler composed of a plurality of capacitors and diodes. A rectifier circuit (Cockcroft-Walton circuit) has been proposed for voltage doubler rectification.

  This high-voltage power supply circuit does not use a transformer, has a parallel fanatic circuit between the power supply and the transistor that is the switching element, and outputs a waveform touching positive and negative by resonance via the rectifier voltage doubler circuit. Thus, positive and negative DC voltages can be obtained.

  The Cockcrofton circuit is a circuit of a rectifier circuit system or a multi-stage rectifier system when manufacturing a high-voltage power supply, and the anode and cathode of the diode are connected to two base lines by using a staggered capacitor as a boundary. Are arranged in parallel so as to be staggered, thereby forming a so-called ladder structure in which a plurality of stages of rectifier circuits are configured. By setting the number of stages required for the voltage required for the input voltage, a high-voltage power supply device can be easily obtained.

  The applicant can apply the power supply circuit configured as described above to output a high-frequency AC waveform and increase the ratio between the input voltage and the output voltage (24V → 1.0KV in the above). Has proposed a new power supply circuit (filed December 9, 2002).

By the way, the output side voltage may use both positive polarity and negative polarity. That is, when the voltage is boosted to 1.0 KV, the voltage is applied as ± 500 V with the middle as the reference.
Japanese Patent Laid-Open No. 6-197542 JP-A-7-107737

  However, when a voltage of 1.0 KV is required for each of positive polarity and negative polarity with respect to the reference voltage, the voltage to be boosted must be doubled, that is, 2.0 KV. That is, even if the instantaneous voltage (voltage of one polarity) is 1.0 KV, if it vibrates positively and negatively with respect to the reference voltage, twice the breakdown voltage is required.

  For this reason, it is necessary to further improve the breakdown voltage of the diodes and capacitors constituting the Cockcroft-Walton circuit and the peripheral elements (switching elements and the like), and the breakdown voltage compensation under high voltage becomes unstable.

  In consideration of the above facts, the present invention allows the high voltage generation circuit corresponding to each of the positive polarity and the negative polarity not to affect the circuits having opposite polarities, and is designed to withstand the boost voltage for each polarity. The object is to obtain a high-voltage power supply circuit capable of stabilizing withstand voltage compensation under a high voltage.

A first aspect of the present invention is a high voltage power supply device for driving a load by generating an alternating high voltage by a Cockcroft-Walton circuit and applying the alternating high voltage to a capacitive load. A positive AC voltage generating means for generating an AC voltage that vibrates on the positive electrode side with respect to a reference voltage using a clock signal having a predetermined frequency from a DC low voltage input from a positive AC voltage generating means; A first Cockcroft-Walton circuit that boosts an AC voltage as an input and generates a positive AC high voltage to be applied to the capacitive load; a DC low voltage input from a negative DC power supply; and the clock signal Is a negative AC voltage generating means for generating an AC voltage that vibrates on the negative electrode side with respect to a reference voltage using a clock signal having an opposite phase, and the negative AC voltage generator The second cockcroft Walton circuit that boosts the AC voltage generated in step 1 as an input and generates a negative AC high voltage to be applied to the capacitive load is connected in series with the output terminal of the first cockcroft Walton circuit. The first capacitor for charging / discharging the positive high voltage applied to the output terminal and the output terminal of the second cockcroft Walton circuit are connected in series to charge / discharge the negative high voltage applied to the output terminal. A second capacitor,
An output terminal connected to the capacitive load is provided between the first capacitor and the second capacitor.

  According to the first invention, in the positive AC voltage generating means, the AC voltage that vibrates to the positive side with respect to the reference voltage using a clock signal having a predetermined frequency from a DC low voltage input from a positive DC power supply. Is generated. In the first Cockcroft-Walton circuit, the AC voltage is boosted as an input, and a positive AC high voltage applied to the capacitive load is generated.

  On the other hand, the negative polarity AC voltage generating means generates an AC voltage that vibrates on the negative side with respect to the reference voltage using a clock signal having a phase opposite to that of the clock signal from a DC low voltage input from a negative polarity DC power source. Let In the second Cockcroft-Walton circuit, the AC voltage is boosted as an input, and a negative AC high voltage applied to the capacitive load is generated.

  The first and second cockcroft wonton circuits are connected to output terminals of the first and second capacitors via a first and second capacitor, and are connected to a capacitive load between the first and second capacitors. The end.

  As a result, the voltage boosted to the positive polarity side does not affect the negative polarity side, and conversely, the voltage boosted to the negative polarity side does not affect the negative polarity side. That's fine.

  That is, according to the first aspect of the invention, one unit having the first cockcroft Walton circuit on the positive polarity side and the other unit having the second cockcroft Walton circuit on the negative polarity side are connected to the first and second units. This is characterized in that the capacitor is connected in series with the capacitor and the output terminal is in the middle of the first and second capacitors.

  A second aspect of the present invention is a high-voltage power supply device that drives an AC high voltage generated by a Cockcroft Walton circuit and applies the AC high voltage to a capacitive load. A positive AC voltage generating means connected to one end side and generating an AC voltage oscillating to the positive side with respect to a reference voltage from a DC low voltage inputted from a positive DC power supply using a clock signal of a predetermined frequency; , Which is connected to the other end of the Cockcroft Walton circuit and vibrates to the negative side with respect to a reference voltage using a clock signal having a phase opposite to that of the clock signal from a DC low voltage input from a negative DC power source Negative voltage AC voltage generating means for generating an AC voltage, and is wired from the one end to the other end in the Cockcroft-Walton circuit. One of the pair of base lines is cut at an intermediate position of a diode connected in parallel so that the anode side and the cathode side are staggered with respect to the pair of base lines, and the positive high voltage is applied to the other base line A first capacitor for charging / discharging the capacitor and a second capacitor for charging / discharging the negative high voltage are connected in series, and the capacitive load is connected between the first capacitor and the second capacitor. The output terminal is connected to.

  According to the second invention, in the Cockcroft-Walton circuit, the diodes are connected in parallel so that the anode side and the cathode side are staggered with respect to the pair of base lines.

  A first capacitor that cuts one of the pair of base lines and charges and discharges the positive high voltage to the other base line and a second capacitor that charges and discharges the negative high voltage at the middle position of the diode. A capacitor was connected in series, and an output terminal connected to the capacitive load was provided between the first capacitor and the second capacitor.

  As a result, the boosted parts on both sides of the cut are not affected by each other. That is, the voltage boosted to the positive polarity side does not affect the negative polarity side, and conversely, the voltage boosted to the negative polarity side does not affect the negative polarity side. Good.

  That is, the second invention is a configuration in which a single Cockcroft-Walton circuit is separated in the middle, connected in series by the first and second capacitors, and the middle of the first and second capacitors is the output end. Is a feature.

  In the first invention or the second invention, the first capacitor and the second capacitor are connected in parallel to each other, and the discharge of the charges stored in the first capacitor and the second capacitor is promoted. It is characterized by further having resistance for.

  That is, by facilitating the discharge of the first and second capacitors, charging / discharging can be performed quickly and high frequency can be handled.

  As described above, in the present invention, the high voltage generation circuit corresponding to each of the positive polarity and the negative polarity does not affect the circuits having the opposite polarities, and the withstand voltage design for the boost in each polarity is sufficient. And, it has an excellent effect that the withstand voltage compensation under a high voltage can be stabilized.

  FIG. 1 shows a high-voltage power supply device 100 according to the present embodiment.

  The high-voltage power supply device 100 is configured to generate an AC high voltage (1.0 KV) in two stages with respect to the DC power supply 102 (24 V). The AC voltage generator 104 </ b> A and the second AC voltage generator 104 </ b> B that swings to the negative electrode side are input.

  A clock signal having a predetermined frequency is input from the AC generation signal output unit 106 to the first AC voltage generation unit 104A and the second AC voltage generation unit 104B. The AC generation signal output unit 106 receives a clock signal having a predetermined frequency from the clock generation unit 108. The AC generation signal output unit 106 has different phases (opposite phases from each other) 2 based on this clock signal. Different types of signals (hereinafter, one is called “clock signal” and the other is called “inverter clock signal”), the clock signal is output to the first AC voltage generator 104A, and the inverter clock signal is generated as the second AC voltage. The data is output to the unit 104B.

  The first and second AC voltage generators 104A and 104B can be applied with a circuit as shown in FIG. 2, for example, and has a function of amplifying the voltage by a parallel resonance circuit.

  In other words, due to the effect of the parallel resonance circuit, it becomes about twice (± VDD ′) of the DC power supply voltage VDD (24V) output from the DC power supply 102 (note that this step-up rate depends on the sharpness Q).

  As shown in FIG. 1, the first AC voltage generation unit 104 </ b> A is connected to one end of the high voltage conversion unit 110. The second AC voltage generation unit 104B is connected to the other end of the high voltage conversion unit 110.

  That is, the voltage (approximately ± 50 V) generated in the first and second AC voltage generation units 104A and 104B is input to both ends of the high voltage conversion unit 108 as an input voltage.

  Here, the high voltage converter 110 includes a positive booster 112 and a negative booster 114, and two capacitors 118 and 120 are connected in series to a signal line 116 connecting between them. Yes. A branch line 122 is connected between the two capacitors 118 and 120, and is connected to a capacitive load via the capacitor 124. That is, the positive booster 112 and the negative booster 114 are connected by a capacitor group connected in a T-type, and the branch line 122 serves as an output terminal 126 to the capacitive load.

(High voltage converter 110)
A well-known Cockcroft-Walton circuit can be applied as the positive booster 112 and the negative booster 114 constituting the high voltage converter 110 (see FIG. 3).

  The circuit configuration will be briefly described. As shown in FIG. 2, the positive voltage boosting unit 112 is connected at both ends of the diode 128 so as to be stretched over the two base lines 130 and 132 which are parallel lines. Has been. At this time, the anodes and cathodes of the diodes 128 are alternately connected to the adjacent diodes 128. Further, capacitors 134 are interposed in a staggered manner between the connection ends of the respective diodes 128 to the base lines 130 and 132.

  On the other hand, as shown in FIG. 2, both ends of the diode 140 are connected to the negative booster unit 114 so as to span between two base lines 136 and 138 that are parallel lines. At this time, the anodes and cathodes of the diodes 140 are alternately connected to the adjacent diodes 140. Capacitors 142 are interposed in a staggered manner between the connection ends of the respective diodes 140 to the base lines 136 and 138.

  The above is a simple circuit configuration, but the Cockcroft-Walton circuit is not limited to the circuit shown in FIG. 2 because the number of stages of the diode 114 varies depending on the required step-up rate and current.

  As shown in FIG. 1, the alternating voltage (± 1.0 KV) boosted by the positive booster 112 and the negative booster 114 of the high voltage converter 108 is applied to the capacitive load, and the load operates. .

  Here, the high voltage conversion unit 108 of the present embodiment has a configuration in which a pair of cockcroft Walton circuits are connected via capacitors 118 and 120. It can also be said that the positive booster 112 and the negative booster 114 are configured separately.

  Here, for example, when an AC voltage generated by the first AC voltage generator 104A is applied to one end, a voltage of +2.0 KV is applied to the other end. Conversely, when an AC voltage generated by the second AC voltage generator 104B is applied to the other end, a voltage of -2.0 KV is applied to one end. That is, when the output terminal to the capacitive load is simply branched from the midpoint of the Cockcroft-Walton circuit, a withstand voltage twice as high as the required voltage is required.

  Therefore, in the present embodiment, the middle of the one-unit Cockcroft Walton circuit is separated and two capacitors 118 and 120 are connected in series.

  As a result, charging / discharging is repeated at a predetermined voltage (± 1.0 KV), and a desired voltage (± 1...) Is applied between the pair of capacitors 118 and 120 (that is, the output terminal) without affecting each other. AC high voltage with an amplitude of 0 KV) can be generated.

  Here, in the capacitors 118 and 120, depending on the frequency, before the discharge of the charged electric charge is completed, the next charging is performed, and a stable AC waveform may not be obtained, which may be saturated. is there.

  Therefore, resistances 144 and 146 for promoting discharge are connected in parallel to the two capacitors 118 and 120, respectively. The resistors 144 and 146 have a role of promoting discharge of electric charges of the capacitors 118 and 120, and a stable AC waveform can be obtained.

  The operation of this embodiment will be described below.

  A clock signal (5 V) having a predetermined frequency (2 MHz in this embodiment) is sent from the clock generation unit 108 to the AC generation signal output unit 106.

  The AC generation signal output unit 106 generates an inverter clock signal having an opposite phase from the input clock signal.

  The AC generation signal output unit 106 transmits the clock signal to the first AC voltage generation unit 104A, and transmits the inverter clock signal to the second AC voltage generation unit 104B.

  In the first AC voltage generation unit 104A, based on the input clock signal, the DC voltage 24V received from the DC power source 102 is intermittently amplified, and the pulse waveform generated by the intermittent operation is amplified by a parallel resonance circuit. A positive AC voltage with an amplitude of +50 V is generated.

  On the other hand, in the second AC voltage generator 104B, the DC voltage 24V received from the DC power supply 102 is intermittently based on the input inverter clock signal, and the pulse waveform generated by the intermittent is amplified by the parallel resonance circuit. , A negative AC voltage having an amplitude of 0V to −50V is generated.

  The positive AC voltage generated by the first AC voltage generator 104A is input to one end of the positive booster 112 (first Cockcroft Walton circuit) of the high voltage converter 110. The positive voltage booster 112 boosts the input voltage (0 V to +50 V) (0 V to +1.0 KV) and applies it to the capacitive load by charging and discharging the capacitor 118.

  On the other hand, the negative AC voltage generated by the second AC voltage generator 104B is input to one end of the negative booster 114 (second Cockcroft Walton circuit) of the high voltage converter 110. The negative voltage booster 114 boosts the input voltage (0 V to −50 V) (0 V to −1.0 KV) and applies it to the capacitive load by charging and discharging the capacitor 120.

  Note that the voltage boosted by the positive voltage booster 112 and the negative voltage booster 114 is such that the base clock signal and the inverter clock signal are in opposite phases, so the voltage applied to the capacitive load is as shown in FIG. As shown in FIG. 4, the waveform alternately alternates between positive and negative, and can be applied as an AC voltage superimposed on a DC voltage, for example, in an image forming apparatus.

  At this time, since the resistors 144 and 146 are connected in parallel to the capacitors 118 and 120, discharge is promoted and a stable AC waveform can be obtained.

  As described above, in the present embodiment, when an AC high voltage is generated using a Cockcroft-Walton circuit, normally, an input voltage is applied from one end of the Cockcroft-Walton circuit, and an AC high voltage boosted from the other end is applied. In this case, in the case of generating an AC high voltage that has both a positive polarity and a negative polarity with reference to a reference voltage (for example, 0 V), it is twice the amplitude voltage to the positive side and the negative side. The withstand voltage of the voltage of is required.

  Therefore, the intermediate point of the Cockcroft-Walton circuit is disconnected, and two capacitors 118 and 120 are connected in series at both ends, and the output terminal from the middle of the two capacitors 118 and 120 to the capacitive load. I took out.

  As a result, the Cockcroft-Walton circuit is only applied with a unipolar voltage (positive polarity and negative polarity), so that the withstand voltage compensation can be relaxed.

  In addition, resistors 144 and 146 are connected in parallel to improve the charge / discharge response by the two capacitors 118 and 120, respectively. Thereby, a stable alternating current waveform can be obtained.

It is a block diagram which shows the outline of the high voltage power supply device which concerns on this Embodiment. It is a circuit diagram which shows an example of the high voltage power supply device which concerns on this Embodiment. It is an output characteristic figure of the high voltage power supply device concerning this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 High voltage power supply device 102 DC power supply 104A 1st alternating current voltage generation part 104B 2nd alternating current voltage generation part 106 AC generation signal output part 108 Clock generation part 110 High voltage conversion part 112 Positive voltage | pressure boost part 114 Negative voltage | pressure boost part 116 Signal Line 118, 120 Capacitor 122 Branch line 124 Capacitor 126 Output 130, 132 Base line 128 Diode 134 Capacitor 136, 138 Base line 140 Diode 142 Capacitor 144, 146 Resistance

Claims (3)

A high voltage power supply device that generates a high voltage by the Cockcroft Walton circuit and drives the load by applying the high voltage to a capacitive load,
A positive AC voltage generating means for generating an AC voltage that vibrates to the positive side with respect to a reference voltage using a clock signal of a predetermined frequency from a DC low voltage input from a positive DC power supply;
A first Cockcroft Walton circuit that boosts an AC voltage generated by the positive AC voltage generating means as an input and generates a positive AC high voltage to be applied to the capacitive load;
A negative AC voltage generating means for generating an AC voltage that vibrates on the negative electrode side with respect to a reference voltage using a clock signal having a phase opposite to that of the clock signal from a DC low voltage input from a negative DC power supply;
A second Cockcroft-Walton circuit for boosting an AC voltage generated by the negative AC voltage generating means as an input and generating a negative AC high voltage applied to the capacitive load;
A first capacitor connected in series to the output terminal of the first cockcroft Walton circuit and charging / discharging a positive high voltage applied to the output terminal;
A second capacitor connected in series to the output terminal of the second cockcroft Walton circuit and charging and discharging a negative high voltage applied to the output terminal;
A high-voltage power supply apparatus characterized in that an output terminal connected to the capacitive load is provided between the first capacitor and the second capacitor. An AC high voltage is generated by a Cockcroft-Walton circuit, and the AC high voltage is applied to a capacitive load to drive the load.
Positive polarity connected to one end of the Cockcroft Walton circuit and generating an alternating voltage that vibrates to the positive side with respect to a reference voltage using a clock signal of a predetermined frequency from a direct current low voltage input from a positive polarity direct current power supply AC voltage generating means,
AC connected to the other end of the Cockcroft-Walton circuit and oscillating to the negative side with respect to a reference voltage using a clock signal having a phase opposite to that of the clock signal from a DC low voltage input from a negative DC power supply A negative AC voltage generating means for generating a voltage,
One of the pair of base lines at an intermediate position of a diode connected in parallel so that the anode side and the cathode side are staggered with respect to the pair of base lines wired from the one end to the other end in the Cockcroft Walton circuit. A first capacitor that charges and discharges the positive high voltage to the other base line, and a second capacitor that charges and discharges the negative high voltage in series,
A high-voltage power supply apparatus characterized in that an output terminal connected to the capacitive load is provided between the first capacitor and the second capacitor.   2. The apparatus according to claim 1, further comprising a resistor connected in parallel to each of the first capacitor and the second capacitor, and for promoting discharge of charges stored in the first capacitor and the second capacitor. The high voltage power supply device according to any one of claims 1 and 2.

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