JP2692132B2 - High voltage power supply for electrophotography - Google Patents

Description

Description: TECHNICAL FIELD The present invention takes at least two or more outputs from one output winding, controls at least one of the outputs with a constant current, and substantially constants the other outputs. The present invention relates to a high-voltage power supply device for electrophotography that controls a current.

2. Description of the Related Art Conventionally, the output side rectifier circuit of this type of electrophotographic high-voltage power supply device has a structure as shown in FIG. In FIG.
20 is the primary winding of the transformer 19, 21 is the output winding of the output 1, 22
Are output windings of outputs 2 and 3, 1, 2, 3, 4 are rectifying capacitors, 9 and 11 are discharge resistors for discharging the charges of the rectifying capacitors 1 to 4, 5, 6, 7, Reference numeral 8 is a diode, and the first Cockcroft-Walton rectifying circuit is composed of the rectifying capacitors 1 and 2 and the diodes 5 and 6 to form a rectifying capacitor.
A second Cockcroft-Walton rectifier circuit is composed of 3, 4 and diodes 7, 8. 10 is a current detector for detecting the current of the output 1, 13 is a control circuit, 14 is a DC-AC inverter,
L _1, L _2, L ₃ uses normal corotron load of each output.
That is, since the current detector 10 is connected in series between the output winding 21 and the ground,
When two or more outputs are taken out, the current flowing through the load of each output flows through the current detector 10, so that one of the currents cannot be detected, and the current detection is performed as shown in FIG. By making the output 1 to be performed and the output windings 22 of the other outputs 2 and 3 independent, it is possible to detect the current of the output 1. The voltage of the output 1 in this case is determined by the product of the impedance of the load L ₁ and the current flowing through the load, that is, the current i ₁ controlled by the control circuit 13, and the voltages of the outputs 2 and 3 are the same. Since it is taken out by the output winding in the magnetic circuit, assuming an ideal transformer 19, the voltage of the outputs ₂ and ₃ is determined by the turn ratio of the output windings N ₁ and N ₂ and N ₃ and the voltage of the output 1. It By this operation, the voltage of the outputs 2 and 3 that are not configured by the negative feedback loop is made to follow the change in the impedance of the corotron due to environmental changes, so that the load
The current flowing through L ₂ and L ₃ can be made a substantially constant current with respect to input fluctuations and environmental fluctuations, as in the case of the output 1 forming the negative feedback loop.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In such a conventional configuration, since two or more output windings 21 and 22 are required, the cost is increased and the transformer is increased.
There was a defect that 19 became large. Also, output winding 2
Since the coupling between 1 and 22 is less than 1, leakage inductance occurs between the output windings 21 and 22, and especially in a transformer that handles high frequencies, such as a switching power supply, the output 1 and the outputs 2 and 3 are not always There was also a drawback that the output was not proportional.

FIG. 6 shows an example of voltage-current characteristics of output 2 according to the conventional method. As shown in FIG. 6A, the output voltage does not change linearly with the load current. This is the primary winding 20 and the output winding
Leakage inductance between 21 and primary winding 20 and output winding 22
Since the leakage inductance between them is not the same, the stray capacitance of the winding and the resonance frequency generated by the leakage inductance differ between the former and the latter, and the relationship between the duty cycle and the output voltage is linear due to the effect of the resonance phenomenon. No, it is due to having a wavy characteristic. Also, transformer 19
Since the leakage inductance also changes due to variations in
As shown in FIGS. 6A and 6B, the voltage-current characteristics (output load characteristics) of the output 2 are greatly varied.

Means for Solving the Problem In order to solve the problem, the present invention focuses on that the value obtained by integrating the current flowing through the rectifier diode is equal to the sum of the current value flowing through the load and the current flowing through the discharge resistor. However, a current detector is connected in series between the low potential side of the diode connected to the place closest to the ground potential and the ground, and the current flowing through the discharge resistor is in the opposite direction to the current flowing through the current detector. In order to make it flow, the low potential side of the discharge resistance is connected to the connection point of the diode and the current detector. With the above circuit, the current flowing through the load and the integrated value of the current flowing through the current detector have the same value.

As described above, at least two or more outputs are taken out from one output winding, and it is possible to detect the current of only one arbitrary DC output. Also, since two or more outputs are extracted from one output winding, the coupling between each output is 1, and the voltage ratio between the detected output and other outputs is proportional to the winding ratio of the output winding. The present invention enables a high voltage power supply device for electrophotography, which has good output voltage-current characteristics.

Action The present invention can take out two or more outputs from one output winding by using the above-mentioned configuration, make one output constant current, and make all other outputs substantially constant current. , The size of the transformer is reduced, the coupling is improved, and the constant current output is accurately proportional to the other output.
Moreover, it is possible to obtain a flat voltage-current characteristic of another output.

Embodiment FIG. 1 is an embodiment of the present invention. In FIG.
Reference numerals 1 and 2 are rectifying capacitors, 5 and 6 are diodes, which form a first Cockcroft-Walton rectifying circuit, 3 and 4 are rectifying capacitors, and 7 and 8 are diodes, which are a second Cockcroft-Walton rectifying circuit. 9, 11 is a discharge resistor, 10 is a current detector, 12 is a capacitor for integrating a detection signal, 13 is a control circuit, 14 is a DC-AC inverter, 19 is a transformer, 20 is a primary winding, 21 is an output winding. Lines, L ₁ , L ₂ and L ₃ are loads of each output.

In the circuit of FIG. 1, the output 1 current is as follows. First, the alternating current generated in the output winding 21 is charged in the rectifying capacitor 1 via the current detector 10 and the diode 5 when S ₂ is negative. Next, when S ₂ is positive, the current i ₁ flows through the rectifying capacitor 1 and the diode 6 and is smoothed by the rectifying capacitor 2. In this case, since it is AC coupling by the rectifying capacitor 1,
No DC current flows, and the integrated current i _N and integrated current i _P are the same. The current i ₁ flowing through the load is the difference between the integrated value of the current i _P and the current i _D flowing through the discharge resistor 9, and the integrated value of the current i _S flowing through the current detector 10 is the integrated value of the current i _N. And the current i _D. That is, the following equation holds for the integrated value of the current i ₁ flowing through the load and the current i _S flowing through the detection resistor.

i ₁ = i _P integral value −i _D i _S integral value = i _N integral value −i _D i _P integral value = i _N integral value ∴i ₁ = i _S integral value …… Formula 1 According to the above formula, the load current i ₁ and the current i _S flowing through the current detector 10 are integrated to have the same value, and the output 1 is subjected to constant current control.

The DC currents of the outputs 2 and 3 flow through the diode 7 and do not flow to the current detector 10, and the voltage is taken out from the same output winding. Therefore, the coupling is 1, which is completely proportional to the voltage of the output 1 and is the same. In the case of a winding, a current controlled by the output 1 and the same voltage as the output 1 generated by the load are generated. Also, S ₂
By changing the number of turns from S ₃ to S ₃ , the voltage ratio between output 1 and outputs 2 and 3 can be set arbitrarily.

FIG. 4 is an example of the voltage-current characteristic of the output 2 according to the present invention. Since the voltage of the output 2 is completely proportional to the output 1, the impedance of the rectifying capacitor 3 is sufficiently smaller than that of the load L _2. If it is made small, the voltage drop due to the current i _P can be almost ignored, and the load current i ₂
The characteristic is that there is no voltage change due to.

If the resistance value of the discharge resistor 9 is sufficiently larger than the impedance of the load L ₁ , that is, if the current i _D flowing through the discharge resistor 9 is much smaller than the load current i ₁ ,
It goes without saying that even if the low potential side of the discharge resistor 9 is grounded, the current i ₁ flowing through the load L ₁ becomes a substantially constant current.

As a result, in the electrophotography, the tendency of the environmental change of the load impedance is the same, so that the outputs 2 and 3 operate as a substantially constant current.

FIG. 2 shows a circuit in which an AC output is taken out from the output winding 21. In FIG. 2, 1 and 2 are rectifying capacitors and 5, 6
Are diodes to form a first Cockcroft-Walton rectifier circuit, 3 and 4 are rectifying capacitors, and 7 and 8 are diodes to form a second Cockcroft-Walton rectifier circuit. Reference numerals 9 and 11 are discharge resistors, 10 is a current detector, 12 is an integrating capacitor, 15 is a bypass capacitor, 16 is a DC power supply, 20 is a primary winding, and 21 is an output winding. The difference from FIG. 1 is that the AC output is taken out to the output, the bypass capacitor 15 is connected to the low potential side S ₁ of the output winding, and the DC power supply 16 is applied to S ₁ . In this case, as described in FIG. 1, the rectifying capacitors 1 and 3 are connected to the output 1 and the output 2 by AC coupling, and no DC current flows. That is, the potential of the DC power supply 16 is applied only to the output 3 of the AC output. With this configuration, output 1 is a constant current and output 2 is a substantially constant current D.
The C and the output 3 are outputs with a substantially constant current AC and a DC bias superimposed. If DC bias is not required, S ₁ should be grounded.

FIG. 3 shows a rectifier circuit for extracting an output, which is a multiple voltage Cockcroft-Walton circuit. In FIG. 3, 1 and 2 are rectifying capacitors, and 5 and 6 are diodes.
Comprising a multiple pressure cockcroft Walton rectifier circuit,
Reference numerals 3 and 4 are rectifying capacitors, and 7 and 8 are diodes, which form a second multiple voltage Cockcroft-Walton rectifier circuit. 9,11
Is a discharge resistor, 10 is a current detector, 12 is an integrating capacitor, 20
Is a primary winding and 21 is an output winding.

In the operation of FIG. 3, the voltage of the output 1 and the output 2 can be generated higher than the voltage generated in the output winding 21 by the multiple voltage Cockcroft-Walton circuit, and the number of stages of the rectification circuit can be output. By changing between 1 and output 2,
It is possible to change the voltage ratio.

EFFECTS OF THE INVENTION As described above, according to the present invention, (1) By reducing the number of output windings from two or more to one, it is possible to reduce the size and cost.

(2) Conventionally, the output winding (Fig. 5 21) and the output winding (5th)
22) Insulation was required between the two, but since there is only one output winding, insulation is not required, resulting in downsizing and cost reduction.

(3) By extracting the output through the same output winding, since the coupling is 1, the output 1 of the constant current output and the output 2 and the output 3 of the other outputs are completely proportional. or,
Since the voltage ratio is proportional to the turns ratio, the output voltage can be easily set.

(4) The voltage-current characteristics (load fluctuation characteristics) of the outputs 2 and 3 are very good, variations in the voltage-current characteristics due to variations in the transformer are eliminated, and voltage accuracy is greatly improved.

(5) When it is desired to obtain a large output voltage or to reduce the number of secondary turns, a multiple pressure Cockcroft-Walton circuit may be used. In that case, the same effect can be obtained with a similar circuit. it can. Further, the voltage ratio between the outputs can be changed by changing the number of stages of the rectifier circuit.

It has the above effects and is of great industrial value.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of one embodiment of a high voltage power supply apparatus for electrophotography of the present invention, FIGS. 2 and 3 are circuit diagrams of other embodiments of the present invention, and FIG. 4 is an output 2 of FIG. 5 is a circuit diagram of a conventional example, and FIG. 6 is a characteristic diagram of output 2 of the conventional example. 1,2,3,4 …… Rectifying capacitors, 5,6,7,8 …… Diodes, 9,11 …… Discharge resistances, 10 …… Current detectors, 12 …… Integrating capacitors, 13 …… Control circuits , 14 …… DC-AC inverter, 19 …… transformer, 20 …… primary winding, 21 …… output winding.

Claims (1)

(57) [Claims] 1. A high-voltage power supply device for electrophotography which extracts at least two or more outputs from one continuously wound output winding of a transformer, wherein one end of the output winding is connected to ground. One end of the first capacitor is connected to the other end of the output winding or its intermediate tap, one end of the first diode is connected to the other end of the first capacitor, and the other end of the first diode is connected to the other end. One end of the second capacitor is connected and the other end of the second capacitor is connected to ground, and one end of the second diode is connected to the connection point between the first capacitor and the first diode At least one Cockcroft-Walton rectifier circuit whose other end is connected to ground and whose output is taken out from the connection point of the first diode and the second capacitor is provided, and one of the rectifier circuits has a second A current detector connected in series with the said current detector into a signal of the integral value transformer input side negative feedback is so configured and the electrophotographic high-voltage power supply apparatus to the control circuit of the generated between the diode and ground.