JP2000102249A - High-voltage power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-voltage power supply, capable of always supplying power with stability to a load having large fluctuation of impedance. SOLUTION: When a constant-voltage control or constant-current control is exercised, based on the output voltage of a rectifying and smoothing circuit 18 detected through a voltage detection circuit 22 or the output current of the rectifying and smoothing circuit 18 detected through a current detection circuit 24, an input voltage variable circuit 14 is controlled, so that the value for voltage applied to the primary winding of a step-up transformer 16 from a direct-current power supply 26 is varied, according to the humidity detected by an environment detecting means 38.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high voltage power supply, and more particularly, to a digital control type high voltage power supply which can be used as a power supply for, for example, an electrophotographic printer or copier.

[0002]

2. Description of the Related Art Conventionally, a power supply has been developed for the purpose of stably making an output voltage or an output current of a power supply as described in JP-A-62-279366 consistent with a target value. As a configuration as shown in FIG.
The voltage monitor value V _mon indicated by the voltage monitor signal generated by the voltage detection circuit 22 or the current monitor value I _mon indicated by the current monitor signal generated by the current detection circuit 24
Is fed back to the CPU 30 through the A / D converter 36, and the pulse generator 3 is adjusted so that the value matches the target value.
4 generated by PWM (Pulse Width Modulation,
(Pulse width modulation) The duty of the signal PWM is controlled,
A so-called digital control type power supply that controls on / off of a switch element 20 for controlling application / non-application of a voltage generated by a DC power supply 26 to a step-up transformer 16 by a WM signal is widely known. I have.

However, such a digital control type power supply has the following problems.

In a power supply device of a digital control system as shown in FIG. 20A, an output is generated by repeatedly turning on / off a switching element 20, and its value is determined by the switching element 20.
On / off of the PWM signal. That is, the duty is increased when the output is to be increased, and the duty is decreased when the output is to be decreased.

The problem here is the variable width of the duty. In the conventional power supply device of the so-called analog control method as shown in FIG. 20B, the variable width of the duty of the PWM signal PWM can be said to be almost infinite, but FIG.
In the case of a digital control type power supply as shown in
Since the M signal PWM is generated by the pulse oscillator 34 under the control of the CPU 30, the duty can be changed only in a predetermined minimum bit unit.

That is, for example, when the frequency of the reference clock signal of the CPU 30 is 20 MHz, FIG.
As shown in (A), the period of one pulse is 50 ns. Here, 1 when the CPU 30 has an 8-bit configuration.
Since the cycle is 256 pulses, as shown in FIG. 21B, the time of one cycle is 12.8 μS, and the frequency in this case is about 80 kHz (= 20 MHz / 256 pulses).
And the resolution per bit in this case is about 0.39% (= 100% / 256 pulses).

On the other hand, when the CPU 30 has a 10-bit configuration, one cycle is 1024 pulses.
As shown in (C), the time of one cycle is 51.2 μS, and the frequency in this case is about 20 kHz (= 20 MHz /
1024 pulses), and the resolution per bit in this case is about 0.098% (= 100% / 1024 pulses).

That is, for example, as described above, the CPU 30
Of the reference clock signal is 20 MHz and the CP
When U30 has a 10-bit configuration, the duty of the PWM signal PWM is 0.098, as shown in FIG.
%, The output voltage can be changed only in a step shape as shown in FIG. 22 (B), so that the output voltage greatly deviates from the target value or the ripple increases. , There was a problem.

As a technique capable of solving this problem, in the technique described in Japanese Patent Application Laid-Open No. 9-149637, the constant of the primary side snubber circuit of the step-up transformer is devised, By devising the reactance component, the relationship between the duty and the output voltage / output current is directly proportional and gradual throughout the output range, and the output resolution is improved in the variable range (see FIG. 23). As a result, the fluctuation range of the output when the duty is changed by the minimum number of bits is reduced, and the above problem can be solved.

[0010]

However, the above-described technique for devising the constant of the primary-side snubber circuit of the step-up transformer and the reactance component of the step-up transformer has the following problems when the fluctuation of the load impedance is large. There was a point.

For example, a printer whose load is an electrophotographic system,
When a transfer roller is used for transferring an image in a copying machine or the like, the impedance of the transfer roller greatly varies depending on environmental conditions such as temperature and humidity. For example, the load impedance is 20 MΩ in a high-temperature and high-humidity state where the temperature is 25 ° C. or more and the humidity is 80% or more, and the load impedance is 200 MΩ in a low-temperature drying state where the temperature is 10 ° C. or less and the humidity is 25% or less. In this case, the impedance fluctuates about 10 times.

At this time, the duty-output voltage characteristic is:
As shown in FIG. 24, the voltage fluctuates greatly according to the impedance of the load. This is because when the load becomes lighter (in the above example, at 200 MΩ), the energy supplied from the primary side of the step-up transformer needs to be small, and the duty of the PWM signal for generating the same output voltage is This is because it may be small. For this reason, when each constant of the circuit is determined so as to obtain good output characteristics in a high-temperature and high-humidity state, the output resolution is about twice as high in a low-temperature drying state, and the output value largely deviates from a target value. Problems such as an increase in ripples and inability to obtain stable image quality occur.

As a technique that can solve this problem, FIG.
As shown in FIG. 5, there is a technique using a bleeder resistor Rt having a resistance value capable of absorbing a change in load impedance. That is, if the resistance value of the bleeder resistor Rt is 10 MΩ, the impedance of the load is 20 MΩ.
Even if the voltage fluctuates within the range from Ω to 200 MΩ, the fluctuation of the load viewed from the step-up transformer side is from about 6.7 MΩ to about 9.5.
The range is up to MΩ, and the deviation of the characteristics can be reduced.

However, if the same means is applied to a power supply device that outputs a high voltage, if the output voltage is 9 kV, the power consumption applied to the bleeder resistor Rt is 8.1 W
Since there is a problem that the bleeder resistance Rt itself needs to be increased and becomes expensive and a problem that the input current of the power supply device increases, the bleeder resistance Rt of the power supply device that performs high-voltage output is usually 200 MΩ or more. 300
A resistor having a resistance value of about MΩ is used, and this means can solve the above-mentioned problems, that is, a problem that the output value of the high-voltage power supply largely deviates from a target value or that the ripple increases. Can not.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a high-voltage power supply capable of always supplying stable power to a load having a large variation in impedance. The purpose is.

[0016]

According to another aspect of the present invention, there is provided a high-voltage power supply apparatus comprising: a step-up transformer; and a direct-current power supply for generating a direct-current voltage to be supplied to a primary winding of the step-up transformer. A power supply, signal generation means for generating a pulse width modulation signal having a variable duty, and switch means for intermittently switching a DC voltage supplied from the DC power supply to the primary winding according to the pulse width modulation signal. Output means connected to the secondary winding of the step-up transformer for supplying power to a load, detection means for detecting an output value of the output means, environment detection means for detecting an environmental state, and wherein the output value is While controlling the signal generation means to change the duty of the pulse width modulation signal so as to match a preset target value, according to the environmental state detected by the environment detection means Changing the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer, thinning out the pulse width modulation signal generated by the signal generation means, and the frequency of the pulse width modulation signal generated by the signal generation means And control means for controlling at least one of the changes.

According to the high voltage power supply device of the first aspect, the output value of the output means connected to the secondary winding of the step-up transformer and supplying power to the load is detected by the detection means, and the detected output value is detected by the detection means. The signal generation unit is controlled by the control unit so that the duty of the pulse width modulation signal is changed so as to match a preset target value.

At this time, a DC voltage is supplied from the DC power supply to the primary winding side of the step-up transformer, and the primary winding side is supplied in accordance with the pulse width modulation signal generated by the control by the control means. The DC voltage supplied to the switch is interrupted by the switch means.

That is, for example, when the output value controlled so as to match the target value is the value of the output voltage of the output means, the constant voltage control outputs the output value controlled so as to match the target value. In the case of the output current of the means, constant current control is performed by each control means.

Further, according to the high voltage power supply device of the first aspect, the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer by the control means in accordance with the environmental state detected by the environment detecting means. , The pulse width modulation signal generated by the signal generation unit, and the frequency of the pulse width modulation signal generated by the signal generation unit are controlled to perform at least one of the following. The environmental state detected by the environment detecting means includes humidity, temperature, and the like.

Thus, according to the high voltage power supply device of the first aspect, the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer is changed in accordance with the environmental state detected by the environment detecting means. Since at least one of the thinning of the pulse width modulation signal generated by the signal generation means and the change of the frequency of the pulse width modulation signal generated by the signal generation means is performed, the load of the load is changed due to the change in the environmental condition. Changing the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer, and changing the pulse generated by the signal generation means so that the output characteristics of the high-voltage power supply do not change as much as possible even when the impedance fluctuates. By controlling at least one of thinning out the width modulation signal and changing the frequency of the pulse width modulation signal generated by the signal generation means, the impedance is controlled. It is possible to supply electric power constantly stable against variations in the large load.

The high-voltage power supply according to claim 2 is the high-voltage power supply according to claim 1, wherein the control means includes:
A process according to the environment state detected by the environment detection means is performed at the time of warm-up.

As described above, according to the high-voltage power supply device of the second aspect, the same effect as that of the first aspect of the invention can be obtained, and the processing according to the environmental state detected by the environment detecting means is warm. Since the processing is performed at the time of uploading, the time spent for the processing can be reduced as compared with the case where the processing is performed sequentially.

According to a third aspect of the present invention, there is provided a high voltage power supply according to the first or second aspect, wherein an output value detected by the detection means is any one of an output voltage and an output current of the output means. If the environmental condition detected by the environment detecting means is humidity, the control means controls the output voltage to be equal to a preset target value and controls the boosting transformer. When changing the voltage value of the DC voltage supplied to the primary winding side, the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer is increased as the humidity increases, and the output current is reduced. In the case where control is performed so as to match a preset target value and the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer is changed, the higher the humidity, the higher the primary voltage of the step-up transformer. In the case where the voltage value of the DC voltage supplied to the line side is reduced, the output voltage is controlled to match a preset target value, and the pulse width modulation signal generated by the signal generation unit is thinned out. The higher the humidity, the less the amount of thinning of the pulse width modulation signal, the more the output current is controlled to match a preset target value, and the pulse width modulation signal generated by the signal generation means. When performing the thinning, the amount of thinning of the pulse width modulation signal is increased as the humidity becomes higher, the output voltage is controlled so as to match a preset target value, and generated by the signal generating means. When changing the frequency of the pulse width modulation signal, the frequency is set to a smaller value as the humidity is higher, and the output current is controlled so as to match a preset target value, and When performing change of the frequency of the pulse width modulation signal generated by the serial signal generating means, it is preferable that a larger value of the frequency as the humidity is high.

According to a fourth aspect of the present invention, there is provided a high-voltage power supply apparatus, comprising: a step-up transformer; a DC power supply for generating a DC voltage to be supplied to a primary winding of the step-up transformer; A signal generating means for generating a signal, a switch means for intermittently supplying a DC voltage supplied from the DC power supply to the primary winding according to the pulse width modulation signal, and a secondary winding of the step-up transformer. Being said 2
Rectifying and smoothing means for rectifying and smoothing the alternating current induced in the next winding, voltage detecting means for detecting the output voltage of the rectifying and smoothing means, current detecting means for detecting the output current of the rectifying and smoothing means, Controlling the signal generating means to change the duty of the pulse width modulation signal so that one of the output voltage and the output current matches a preset target value; The primary winding side of the step-up transformer according to the voltage value of the output voltage and the value obtained based on the current value of the output current when the signal generation means is controlled to generate a width modulation signal. Changing the voltage value of the DC voltage supplied to the signal generator, thinning out the pulse width modulation signal generated by the signal generation unit, and changing the frequency of the pulse width modulation signal generated by the signal generation unit. Further in and and a control unit for controlling to perform at least one.

According to the high voltage power supply device of the fourth aspect, the output voltage of the rectifying / smoothing means which is connected to the secondary winding of the step-up transformer and rectifies and smoothes the alternating current induced in the secondary winding. The output current is detected by the voltage detection means and the current detection means, respectively, and the duty of the pulse width modulation signal is changed so that either one of the detected output voltage and the detected output current matches a preset target value. The signal generating means is controlled by the control means as described above.

At this time, a DC voltage is supplied from the DC power supply to the primary winding side of the step-up transformer, and the primary winding side is supplied according to the pulse width modulation signal generated by the control by the control means. The DC voltage supplied to the switch is interrupted by the switch means.

That is, when the value controlled to match the target value is the value of the output voltage of the rectifying and smoothing means, the constant voltage control is performed. In the case of the output current, constant current control is performed by the control means.

According to the high voltage power supply device of the fourth aspect, the signal generation means is controlled by the control means so as to generate a pulse width modulation signal having a predetermined duty, and the voltage value of the output voltage at this time is controlled. And changing the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer according to the value obtained based on the current value of the output current, and thinning out the pulse width modulation signal generated by the signal generation means. , And at least one of changing the frequency of the pulse width modulation signal generated by the signal generation means is controlled.

When a pulse width modulation signal having a predetermined duty is used, when the impedance of the load changes, at least one of the output voltage and the output current changes in accordance with the amount of change in the impedance. Therefore, the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer is changed in accordance with the amount of change in the value obtained based on the output voltage and the output current, and the pulse width modulation generated by the signal generating means is performed. By controlling to perform at least one of the thinning of the signal and the change of the frequency of the pulse width modulation signal generated by the signal generation unit, it is possible to suppress the fluctuation of the output characteristic.

Thus, according to the high voltage power supply device of the fourth aspect, the voltage value of the output voltage and the current value of the output current when the signal generation means is controlled to generate the pulse width modulation signal of the predetermined duty. Depending on the value obtained based on
Changing the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer, thinning out the pulse width modulation signal generated by the signal generation means, and changing the frequency of the pulse width modulation signal generated by the signal generation means Since the control is performed so as to perform at least one, even if the impedance of the load fluctuates, the DC voltage supplied to the primary winding side of the step-up transformer is controlled so that the output characteristics of the high-voltage power supply device do not change as much as possible. At least one of changing the voltage value of the voltage, thinning out the pulse width modulation signal generated by the signal generation means, and changing the frequency of the pulse width modulation signal generated by the signal generation means
By performing such control, stable power can always be supplied to a load having a large variation in impedance.

According to a fifth aspect of the present invention, in the high voltage power supply device according to the fourth aspect, the control means includes:
At the time of warm-up, a process corresponding to a value obtained based on a voltage value of the output voltage and a current value of the output current when the signal generation unit is controlled to generate a pulse width modulation signal having a predetermined duty is performed. It is characterized by the following.

Thus, according to the high voltage power supply device of the fifth aspect, the same effect as the invention of the fourth aspect can be obtained, and the signal generating means can generate a pulse width modulation signal of a predetermined duty. Since the processing according to the values obtained based on the voltage value of the output voltage and the current value of the output current at the time of controlling is performed at the time of warm-up, it is necessary to spend the processing in comparison with the case where the processing is performed sequentially. Time can be reduced.

The signal generating means is controlled so as to generate the pulse width modulation signal of the predetermined duty in the high voltage power supply according to the fourth or fifth aspect, as in the high voltage power supply according to the sixth aspect. When the value obtained based on the voltage value of the output voltage and the current value of the output current at the time is an impedance, the control unit controls the output voltage so as to match a preset target value. When controlling and changing the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer, the larger the impedance is, the more the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer is changed. When controlling the output current to be equal to a preset target value and changing the value of the DC voltage supplied to the primary winding side of the step-up transformer, As the impedance increases, the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer is increased, the output voltage is controlled to match a preset target value, and the output voltage is generated by the signal generation means. When performing the pulse width modulation signal thinning, the larger the impedance is, the larger the amount of the pulse width modulation signal thinning is, the output current is controlled to match a preset target value, and the signal is controlled. When thinning out the pulse width modulation signal generated by the generation means, the larger the impedance, the smaller the amount of the thinning out of the pulse width modulation signal, so that the output voltage matches a preset target value. When controlling and changing the frequency of the pulse width modulation signal generated by the signal generation means, the larger the impedance, the more the When the wave number is set to a large value and the output current is controlled to match a preset target value and the frequency of the pulse width modulation signal generated by the signal generation unit is changed, the larger the impedance is, Preferably, the frequency is set to a small value.

[0035]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[First Embodiment] As shown in FIG. 1, a high-voltage power supply unit 10 according to the first embodiment includes a high-voltage power supply unit 12 for generating high-voltage power to be supplied to a load 40; , A main control unit 28 that controls the operation of the entire apparatus, and an environment detecting unit 38 that detects an environmental state (humidity in the present embodiment) near the apparatus.

The high-voltage power supply section 12 includes a two-input one-output input voltage variable circuit 14, a step-up transformer 16, a one-input three-output rectifying / smoothing circuit 18, a switch element 20, and a voltage detection circuit 2.
2, and an output terminal of the input voltage variable circuit 14 is connected to one terminal of a primary winding of the step-up transformer 16. In addition, one of the step-up transformers 16
The output terminal of the switch element 20 is connected to the other terminal of the next winding, and the terminal of the secondary winding of the step-up transformer 16 is connected to the input terminal of the rectifying / smoothing circuit 18. Further, two input terminals of the three output terminals of the rectifying / smoothing circuit 18 are connected to respective input terminals of the voltage detection circuit 22 and the current detection circuit 24.

Further, the output terminal of the DC power supply 26 is connected to one input terminal of the input voltage variable circuit 14, to one input terminal of the input voltage variable circuit 14 to the DC voltage V _in generated by the DC power source 26 Can be applied.

On the other hand, the main control unit 28 includes a CPU 30, a pulse oscillator 34, and an analog / digital converter (hereinafter, referred to as an A / D converter) 36 with three inputs and one output. An output calculator 32 is provided.

One output terminal of the arithmetic unit 32 is connected to the other input terminal of the input voltage variable circuit 14, the other output terminal of the arithmetic unit 32 is set to the input terminal of the pulse oscillator 34, and the input terminal of the arithmetic unit 32 is set to A / The output terminal of the D converter 36 and the output terminal of the pulse oscillator 34 are connected to the input terminal of the switch element 20, respectively. Therefore, the trigger signal TRG generated by the calculator 32 can be input to the input voltage variable circuit 14, and the PWM signal PWM generated by the pulse oscillator 34 can be input to the switch element 20.

Further, the output terminals of the voltage detection circuit 22 and the current detection circuit 24 are connected to two of the three input terminals of the A / D converter 36, respectively.
The output terminal of the environment detecting means 38 is connected to the remaining input terminal of the D converter 36. Accordingly, the CPU 30 supplies the voltage monitor value V _mon indicated by the voltage monitor signal generated by the voltage detection circuit 22, the current monitor value I _mon indicated by the current monitor signal generated by the current detection circuit 24, and the monitor generated by the environment detection means 38. Monitor value M indicated by signal
_on can be input as a digital value.

The remaining output terminal of the rectifying / smoothing circuit 18 corresponds to an external load 40 and is connected to the load 40.

The input voltage variable circuit 14 and the main control unit 28 serve as control means of the present invention, the rectifying / smoothing circuit 18 serves as output means and rectifying / smoothing means of the present invention, and the switch element 20 serves as switch means of the present invention. The circuit 22 corresponds to the detecting means and the voltage detecting means of the present invention, the current detecting circuit 24 corresponds to the detecting means and the current detecting means of the present invention, and the pulse oscillator 34 corresponds to the signal generating means of the present invention.

FIG. 2 shows an example of a specific circuit configuration of the high-voltage power supply section 12 in the first embodiment shown in FIG.

As shown in FIG.
Has an FET 50 and a transistor 52, and FE
The gate terminal of T50 is connected to the transistor 5 via the resistor 54.
2 collector terminal. In addition, FET50
Are connected to the drain terminal via a resistor 56 and to the gate terminal of the FET 50 via a resistor 58, respectively.

The source terminal of the FET 50 is a resistor 62
It is also connected to the output terminals of the DC power supply 26 via a DC voltage V _in that is generated by the DC power source 26 is applied. The drain terminal of the FET 50 is connected to the step-up transformer 1.
6 is connected to one terminal of the primary winding.

On the other hand, the emitter terminal of the transistor 52 is connected to the base terminal of the transistor 52 via the resistor 60 and is grounded. The base terminal of the transistor 52 is connected to one output terminal of the computing unit 32 via a resistor 64, and receives the trigger signal TRG generated by the computing unit 32.

The input voltage variable circuit 1 configured as described above
4, the trigger signal TRG input from the arithmetic unit 32
Is high level, the transistor 52 is turned on, and the FET 50 is turned on. Thus, the DC voltage V _in applied from the DC power source 26 at this time is the voltage drop due to resistance 56 is applied to one terminal of the primary winding of the step-up transformer 16 without being made. When the trigger signal TRG input from the calculator 32 is at a low level, the transistor 52 is turned off and the FET 50 is turned off. Thus, the DC voltage V _in applied from the DC power source 26 at this time is applied to one terminal of the primary winding of the step-up transformer 16 after the voltage drop due to resistance 56 is made. That is, the voltage value applied to the step-up transformer 16 can be switched by the trigger signal TRG input to the input voltage variable circuit 14.

On the other hand, the rectifying and smoothing circuit 18 is
6 has one terminal connected to one terminal of the secondary winding, and the other terminal of the capacitor 66 has an anode terminal of the diode 68, a cathode terminal of the diode 70, and one terminal of the capacitor 72. The other terminal of the capacitor 72 is connected to the anode terminal of the diode 74.
Is connected to the anode terminal of the diode 70 and one terminal of the capacitor 76, and the other terminal of the capacitor 76 is connected to the cathode terminal of the diode 68 and the other terminal of the secondary winding of the step-up transformer 16. ing.

In the rectifying / smoothing circuit 18 configured as described above, the alternating current induced in the secondary winding of the step-up transformer 16 is rectified and smoothed by a combination of a capacitor and a diode.

The switch element 20 in the first embodiment is constituted by an FET 78,
The gate terminal 8 is connected to the output terminal of the pulse oscillator 34 via the resistor 80, and receives the PWM signal PWM generated by the pulse oscillator 34. Also, FET
The gate terminal 78 is also connected to one terminal of a resistor 82 whose other terminal is grounded.

On the other hand, the drain terminal of the FET 78 is connected to the cathode terminal of the diode 84, and the anode terminal of the diode 84 is connected to the other terminal of the primary winding of the step-up transformer 16. A resistor 86 is connected between one terminal of the primary winding of the step-up transformer 16 and the other terminal.
And the resistor 88 are connected in parallel to form a snubber circuit. The source terminal of the FET 78 is grounded.

In the switch element 20 configured as described above, the PWM signal PWM input from the pulse oscillator 34
Is high level, the FET 78 is turned on and PW
When the M signal PWM is at a low level, the FET 78 is turned off. Therefore, the FET 78 alternately repeats the ON / OFF state in a period corresponding to the duty of the PWM signal PWM. Therefore, the input from the input voltage variable circuit 14 to the primary winding of the step-up transformer 16 depends on the duty of the PWM signal PWM. Power application / non-application can be performed alternately.

On the other hand, the operational amplifier 9 is
0, the inverting input terminal of the operational amplifier 90 is connected to the output terminal of the rectifying / smoothing circuit 18 via a resistor 92, and the output terminal of the operational amplifier 90 is connected in parallel with a capacitor 94, a resistor 96 and a resistor 98. , And to the non-inverting input terminal of the operational amplifier 90 via the capacitor 102. The output terminal of the operational amplifier 90 is also connected to the input terminal of the A / D converter 36 via the resistor 100. The non-inverting input terminal of the operational amplifier 90 is grounded.

In the voltage detecting circuit 22 configured as described above, the voltage value of the output voltage of the rectifying / smoothing circuit 18 can be constantly output to the A / D converter 36 as the voltage monitor value V _mon .

The current detection circuit 24 includes an operational amplifier 1
The inverting input terminal of the operational amplifier 104 is connected to the output terminal of the operational amplifier 104, and the non-inverting input terminal of the operational amplifier 104 is connected to one terminal of the capacitor 66 of the rectifying / smoothing circuit 18. The output terminal of the operational amplifier 104 is also connected to the input terminal of the A / D converter 36 via the resistor 106.

In the current detecting circuit 24 configured as described above, the current value of the current flowing through the rectifying and smoothing circuit 18 can be constantly output to the A / D converter 36 as the current monitor value I _mon .

Next, as the operation of the first embodiment, control performed by the CPU 30 of the main control unit 28 will be described. In the first embodiment, the case where the control is performed based _{on the} monitor value Mon input from the environment detecting means 38,
Two cases, that is, control based on the voltage monitor value V _mon and the current monitor value I _mon input from the voltage detection circuit 22 and the current detection circuit 24 will be described.

First, a case where control is performed based _{on the} monitor value Mon input from the environment detecting means 38 will be described with reference to FIG.

In step 200 of FIG.
It is determined whether or not 2 is in an operable state, and if not, it stands by until it becomes operable. When the high-voltage power supply unit 12 is in an operable state, the determination in step 200 is affirmed, and the process proceeds to step 202. In step 202, it is determined whether the present time is a warm-up time at the start of the job. The process proceeds to step 204, where the monitor value _Mon (a digital value indicating humidity in the present embodiment) is fetched from the environment detecting means 38 via the A / D converter 36, and the next step 206
Then, it is determined whether or not the monitor value _Mon is larger than a predetermined threshold value. If the monitor value _Mon is larger than the predetermined threshold value, the process proceeds to step 208, the trigger signal TRG is set to a high level, and then the process proceeds to step 250. To 25 after the trigger signal TRG is set to low level
Move to 0.

On the other hand, if it is determined in step 202 that it is not during warm-up, the processing of steps 204 to 210 is not performed and step 2
Move to 50.

[0062] At step 250, the constant voltage control based on the voltage monitor value V _{mo n} being input from the voltage detection circuit 22.

That is, the voltage monitor value V input from the voltage detection circuit 22 through the A / D converter 36
The duty of the PWM signal PWM is controlled so that _mon (digital value indicating the voltage value) matches the target value. Here, when increasing the output voltage value, the duty of the PWM signal PWM may be increased, and when decreasing the output voltage value, the duty of the PWM signal PWM may be decreased.
This PWM signal PWM is input to the switch element 20 and is switched according to the duty of the PWM signal PWM.
By repeating ON / OFF of 0, control is performed so that the value of the output voltage matches the target value.

In the next step 252, the high voltage power supply
Is determined to be in a state in which the high-voltage power supply unit 12 is stopped. If the state is not in a state in which the high-voltage power supply unit 12 stops. This control is ended when becomes.

Next, the voltage detection circuit 22 and the current detection circuit
Voltage monitor value V input from 24 _monAnd current monitor
Value I_monFIG. 4 shows the case where control is performed based on
It will be described in the light of the above. Note that the same processing as in FIG. 3 of FIG. 4 is performed.
Steps are assigned the same step numbers as in FIG.
Therefore, the description is omitted.

If it is determined in step 202 that the current time is at the time of warming up, the process proceeds to step 212 to control the pulse oscillator 34 so that the PWM signal PWM having a predetermined duty is output. In step 216, the current detection circuit 24
And the current monitor value I _mon and the voltage monitor value V _mon output from the voltage detection circuit 22 are sequentially acquired as digital values via the A / D converter 36, and the next step 218 is performed.
Then, the impedance A is calculated by the following equation (1).

A = V _mon / I _mon (1) In the next step 220, it is determined whether or not the impedance A is larger than a predetermined threshold. After the high level, the process proceeds to step 250. If it is determined that the trigger signal TRG is high, the trigger signal TRG is set to the low level in step 224, and the process proceeds to step 250.

As described above, the control shown in FIG.
Is performed, for example, when the humidity becomes high and the load 40 becomes heavy (for example, when the impedance of the load 40 is 20 MΩ), the trigger signal TRG output from the main control unit 28 becomes high level. Next FE
T50 turns on. At this time, the voltage applied to the primary winding of the step-up transformer 16 V _in, and the duty - output voltage characteristic is the characteristic 150A of FIG.

Here, when the humidity becomes low and the load 40 becomes light (for example, when the impedance of the load 40 becomes 200M).
When Omega), the characteristic values of the output voltage is as characteristic 150B or greatly deviated from the set value in a case where if if the input voltage V _in is applied as it is to the step-up transformer 16,
There is a problem that the ripple becomes large.

[0070] However, the monitored value M _on or current monitoring value I _mon and voltage monitor value V main control unit 28 entered the fluctuation information of the load based on the _{mo n,} the trigger signal TRG
Is set to low level to turn off the FET 50, and the input current I _{in at} this time passes through the resistor 56 and the boosting transformer 16
, The voltage applied to the primary winding of the step-up transformer 16 becomes (V _in -Ra × I _in ). Here, Ra is the resistance value of the resistor 56. The characteristic at this time is the characteristic 150C in FIG. 5, and the above problem can be improved.

[0071] That is, when performing the constant voltage control as described above, as the monitor value M _on is large, that increase the value of the voltage humidity is applied to the higher step-up transformer 16, boosting the higher the impedance A large The above problem can be improved by reducing the value of the voltage applied to the transformer 16.

As described in detail above, in the high-voltage power supply according to the first embodiment, the humidity detected by the environment detecting means, or the voltage value and the current value detected by the voltage detection circuit and the current detection circuit are used. Since the value of the voltage applied to the step-up transformer at the time of the constant voltage control based on the PWM signal is changed based on the PWM signal, it is possible to avoid a problem that the value of the output voltage greatly deviates from the set value or the ripple increases.

In the first embodiment, the case where the present invention is applied to the case where the constant voltage control is performed has been described.
The present invention is not limited to this, and the present invention can be applied to the case where constant current control is performed. in this case,
The affirmative / negative relationship of each determination in step 206 of FIG. 3 and step 220 of FIG. 4 is reversed.

That is, when the constant voltage control is performed, the energy should be reduced as the load impedance increases (the humidity decreases). In the case of the constant current control, the energy decreases as the load impedance increases. Need to be larger. Therefore, in the case of the constant current control, the voltage applied to the step-up transformer 16 needs to be increased as the load impedance increases. Therefore, the state of the trigger signal TRG needs to be reversed from that in the case of the constant voltage control.

When the constant current control is performed, the current monitor value I _mon (digital value indicating the current value) input from the current detection circuit 24 via the A / D converter 36 matches the target value. Thus, the duty of the PWM signal PWM is controlled. Here, PWM is used to increase the output current value.
To increase the duty of the signal PWM and decrease the output current value, the duty of the PWM signal PWM may be reduced. This PWM signal is input to the switch element 20, and the switch element 20 is repeatedly turned on / off in accordance with the duty of the PWM signal PWM, so that the output current value is controlled to match the target value.

In the first embodiment, the case where the value of the voltage applied to the step-up transformer 16 is changed in two steps has been described. However, the present invention is not limited to this, and may be changed in a plurality of steps. It is good also as a form. FIG. 6 shows an example of the circuit configuration of the input voltage variable circuit 14 in this case, in which a plurality of sets (n sets in FIG. 6) of combinations of resistors and transistors are connected in parallel. In this case, trigger signals TRG1, TRG2,..., TRGn input to the base terminal of each transistor
A plurality of total resistance values can be set by the combination of the above, and a plurality of voltage values can be applied to the primary winding of the step-up transformer 16.

Further, in the first embodiment, the case where the value of the voltage applied to the step-up transformer 16 is set only at the time of warming-up has been described. However, the present invention is not limited to this. It is needless to say that the mode may be set to.

Further, in the first embodiment, the input voltage variable circuit 14, the rectifying / smoothing circuit 18, the switch element 20, and the voltage detecting circuit 2 constituting the high voltage power supply section 12 shown in FIG.
2, and the circuit configuration of the current detection circuit 24 is merely an example, and any circuit configuration that can realize the functions of the above-described units can be applied.

[Second Embodiment] Next, a second embodiment of the present invention will be described. In the second embodiment, an embodiment in which the input voltage variable circuit in the first embodiment has another circuit configuration will be described. Therefore, the second
The configuration other than the circuit configuration of the input voltage variable circuit according to the embodiment is the same as that of the first embodiment, and a description thereof will be omitted.

First, the circuit configuration of the input voltage variable circuit 14 'in the second embodiment will be described with reference to FIG. Note that the same reference numerals in FIG. 7 as those in FIG. 2 denote the same parts, and a description thereof will be omitted.

The input voltage variable circuit 14 ′ according to the second embodiment includes a three-terminal regulator 110. The output terminal (O terminal) and the input terminal (IN terminal) of the three-terminal regulator 110 are connected to a diode 112. Connected through. The three input terminals of the terminal regulator 110 is also connected to the output terminals of the DC power supply 26 via the resistor 62, the DC voltage V _in that is generated by the DC power source 26 is applied. Further, the input terminal of the three-terminal regulator 110 is grounded via the capacitor 114.

The ADJ of the three-terminal regulator 110
The terminal is connected to the output terminal of the three-terminal regulator 110 via the resistor 122, and the ADJ terminal is further connected to the resistor 12
3 and grounded via a transistor 52 connected in series with a resistor 54. The output terminal of the three-terminal regulator 110 is connected to one terminal of the primary winding of the step-up transformer 16 and is grounded via a capacitor 116, and is also grounded via a diode 118 and a capacitor 120. .

Next, as the operation of the second embodiment, control performed by the CPU 30 of the main control unit 28 will be described. In the second embodiment, similarly to the first embodiment, the control is performed based _{on the} monitor value Mon input from the environment detecting unit 38, and the control is performed based _{on the} input from the voltage detection circuit 22 and the current detection circuit 24. The following two cases will be described: a case where the control is performed based on the voltage monitor value V _mon and the current monitor value I _mon .

First, the case where control is performed based _{on the} monitor value Mon input from the environment detecting means 38 will be described with reference to FIG. Steps for performing the same processing as in FIG. 3 in FIG. 8 are assigned the same step numbers as in FIG. 3, and descriptions thereof are omitted.

In step 206 ′, step 20
Preparative incorporated a monitor value M _on the 4 determines whether greater than a predetermined threshold value, the greater the process proceeds to step 250 after the trigger signal TRG to a high level and then proceeds to step 208 ', not greater Step 21 in case
After shifting to 0 'and setting the trigger signal TRG to low level, the process shifts to step 250.

Next, the voltage detection circuit 22 and the current detection circuit
Voltage monitor value V input from 24 _monAnd current monitor
Value I_monFIG. 9 shows a case where control is performed based on
It will be described in the light of the above. Note that the same processing as in FIG. 4 of FIG. 9 is performed.
Steps are assigned the same step numbers as in FIG.
Therefore, the description is omitted.

In step 220 ′, step 21
It is determined whether or not the value of the impedance A calculated in Step 8 is greater than a predetermined threshold. If it is not, the process proceeds to Step 222 ′, where the trigger signal TRG is set to a high level, and then the process proceeds to Step 250. If it is determined that the trigger signal TRG is at the low level, the process proceeds to step 224 '.

That is, in the high-voltage power supply 10 including the input voltage variable circuit 14 ′ configured as shown in FIG. 7, the output voltage of the three-terminal regulator 110, that is, the output voltage applied to the primary winding of the step-up transformer 16. The voltage is determined as follows from the characteristics of the semiconductor.

The voltage V _out1 when the trigger signal TRG is at a low level is: V _out1 = (1 + Ra / Rb) × V _ref (2) The voltage V _out2 when the trigger signal TRG is at a high level is V _out2 = (1 + Ra) / ((Rb × Rc) / (Rb + Rc))) × V _ref (3) where Ra is the resistance of the resistor 122 and Rb is the resistance of the resistor 12.
3, Rc is the resistance value of the resistor 54, and _Vref is 3
The reference voltage (the voltage of the ADJ terminal) of the terminal regulator 110 is shown.

Based _on the monitor value _Mon , the current monitor value _Imon, and the voltage monitor value _Vmon , for example, it was determined that the humidity became high and the load 40 became heavy (for example, the impedance of the load 40 was 20 MΩ). When the main control unit 2
8, the trigger signal TRG becomes high level, and the transistor 52 is turned on. At this time, the step-up transformer 16
Is _Vout2 , and the duty-output voltage characteristic is, for example, a characteristic 152A in FIG.

Here, when the humidity becomes low and the load 40 becomes lighter (for example, when the impedance of the load 40 becomes 200M).
Omega) is monitored value M _on or current monitoring value I _mon and the main control unit 28 that inputs the load variation information based on the voltage monitor value V _mon, because turning off the transistor 52 a trigger signal TRG as a low level, At this time, the voltage applied to the primary winding of the step-up transformer 16 becomes _Vout1 , and the duty-output voltage characteristic becomes as shown at 152B, so that substantially the same characteristic as before the load change is obtained.

As described in detail above, in the high-voltage power supply according to the second embodiment, the humidity detected by the environment detecting means, or the voltage value and the current value detected by the voltage detection circuit and the current detection circuit are used. Since the value of the voltage applied to the step-up transformer at the time of the constant voltage control by the PWM signal is changed based on the PWM signal, as in the first embodiment,
Problems such as a large deviation of the output voltage from the set value and an increase in ripples can be avoided.

In the second embodiment, the case where the present invention is applied to the case where constant voltage control is performed has been described.
The present invention is not limited to this, and the present invention can be applied to the case where constant current control is performed. in this case,
The affirmative / negative relationship of each determination in step 206 ′ of FIG. 8 and step 220 ′ of FIG. 9 is reversed.

In the second embodiment, the case where the value of the voltage applied to the step-up transformer 16 is changed in two stages has been described. However, the present invention is not limited to this. It is possible to adopt a form of changing in multiple stages by adding.

Further, in the second embodiment, the case where the value of the voltage applied to the step-up transformer 16 is set only at the time of warming up has been described. However, the present invention is not limited to this. It goes without saying that, similarly to the embodiment, the mode may be set at predetermined time intervals.

The circuit configuration of the input voltage variable circuit 14 'shown in FIG. 7 in the second embodiment is merely an example, and any circuit configuration capable of realizing the same function can be applied. Can be.

In the first and second embodiments, both the voltage detection circuit 22 and the current detection circuit 24 and the environment detection means 38 are provided. The case where the value of the voltage applied to the step-up transformer 16 is controlled based on the value obtained by any one of the environment detecting means 38 has been described, but the present invention is not limited to this. Only when the humidity obtained by 38 is a value that needs to change the value of the voltage applied to the step-up transformer 16, the step-up transformer 16 is set based on the values output from the voltage detection circuit 22 and the current detection circuit 24. It is also possible to control the value of the voltage applied to the.

[Third Embodiment] Next, a third embodiment of the present invention will be described. First, the configuration of the high-voltage power supply device 10 'according to the third embodiment will be described with reference to FIG. The same parts as those in FIG. 1 of FIG. 11 are denoted by the same reference numerals, and description thereof will be omitted.

High voltage power supply 1 according to the third embodiment
0 ′ indicates that the high-voltage power supply unit 12 does not include the input voltage variable circuit 14 and that the high-voltage power supply unit 12 ′ includes the switch circuit 25, as compared with the high-voltage power supply device 10 according to the first and second embodiments. And the main control unit 28 does not include the pulse oscillator 34 and the first pulse oscillator 3
Main control unit 2 including 4 ′ and second pulse oscillator 34 ″
8 'is different.

As shown in FIG. 11, the output terminal of the DC power supply 26 in the third embodiment is directly connected to the terminal of the primary winding of the step-up transformer 16. One output terminal of the arithmetic unit 32 of the main control unit 28 is connected to the input terminal of the switch element 20 via the first pulse oscillator 34 ', and the other output terminal of the arithmetic unit 32 is connected to the second pulse oscillator 34''. The output terminal of the switch circuit 25 is connected to the input terminal of the switch element 20. First pulse oscillator 34 'and second pulse oscillator 3
4 ″ is a first PWM signal PWM1 and a second PWM signal PWM having a duty based on the calculation result of the calculator 32.
M2 are generated and output to the switch element 20 and the switch circuit 25, respectively.

FIG. 12 shows an example of a specific circuit configuration of the high-voltage power supply section 12 'in the third embodiment shown in FIG. 12 that are the same as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

The gate terminal of the FET 78 of the switch element 20 is connected to the output terminal of the pulse oscillator 34 'via the resistor 80, and receives the first PWM signal PWM1 output from the pulse oscillator 34'.

The switch circuit 25 includes an FET 130. The gate terminal of the FET 130 is connected to the output terminal of the pulse oscillator 34 '' via the resistor 132, and the second terminal output from the pulse oscillator 34 '' PWM
Signal PWM2 is input. The gate terminal of the FET 130 is also connected to one terminal of a resistor 134 whose other terminal is grounded. Further, the drain terminal of the FET 130 is connected to the gate terminal of the FET 78, and the source terminal is grounded.

The high-voltage power supply device 10 'thus constructed
Then, the FET 130 repeats on / off according to the duty of the second PWM signal PWM2.

Next, as the operation of the third embodiment, control performed by the CPU 30 of the main control unit 28 will be described. In the third embodiment, similarly to the first and second embodiments, the control is performed based _{on the} monitor value Mon input from the environment detecting means 38, and the voltage detection circuit 22 and the current Two cases, that is, the case where control is performed based on the voltage monitor value V _mon and the current monitor value I _mon input from the detection circuit 24, will be described.

First, a case where control is performed based _{on the} monitor value Mon input from the environment detecting means 38 will be described with reference to FIG.
This will be described with reference to FIG. Steps in FIG. 13 that perform the same processing as in FIG. 3 are assigned the same step numbers as in FIG. 3, and descriptions thereof are omitted.

In step 230, step 204
Based _{on the} monitor value Mon taken in at the following (4)
The duty D of the second PWM signal PWM2 is calculated by the equation.

D = K1 / M _on (4) Here, K 1 is a coefficient determined according to the configuration of the high-voltage power supply 10 ′, and is substituted into the above equation (4) to obtain the load impedance. Is a value obtained by an experiment or the like in advance as a value capable of obtaining the duty D that can minimize the fluctuation of the output characteristic due to the fluctuation of the output characteristic. (4) The larger the monitor value M _on the equation, i.e. the duty D of the second PWM signal PWM2 more humid is small.

In the next step 232, the second PWM signal PWM2 is output to the switch circuit 25 by controlling the second pulse oscillator ″ so as to generate the second PWM signal PWM2 having the calculated duty D. I do.

Next, the voltage detection circuit 22 and the current detection circuit
Voltage monitor value V input from 24 _monAnd current monitor
Value I_monFIG. 14 shows the case where control is performed based on
It will be described with reference to FIG. Note that the same processing as in FIG.
The steps to be performed are given the same step numbers as in FIG.
The description is omitted.

In step 234, step 218 is performed.
The duty D of the second PWM signal PWM2 is calculated by the following equation (5) using the value of the impedance A calculated by the following equation (5).

D = K2 × A (5) Here, K2 is a coefficient determined according to the configuration and the like of the high-voltage power supply 10 ′, and is substituted into the above equation (5) to obtain the impedance of the load. This is a value previously obtained by an experiment or the like as a value capable of obtaining the duty D that can minimize the fluctuation of the output characteristic due to the fluctuation. According to the equation (5), the duty D of the second PWM signal PWM2 increases as the impedance A increases.

In the next step 236, the pulse generator 34 '' is controlled so that the second PWM signal PWM2 having the calculated duty D is generated.
The WM signal PWM2 is output to the switch circuit 25.

The environment detecting means 38 or the current monitor value I
For example, when it is determined that the humidity is high and the load 40 is heavy (for example, the impedance of the load 40 is 20 MΩ) based on the _mon and the voltage monitor value V _mon , the second output from the main control unit 28 is performed. Of the PWM signal PWM2 becomes a value close to 0%, and the FET 130 is always turned off. At this time, the duty-output voltage characteristic becomes, for example, a characteristic 154A in FIG.

[0115] Here, when the load humidity lower lightened (e.g. impedance of the load 40 is 200 M.OMEGA) is judged that if tentatively characteristic when the input voltage V _in is applied as it is to the step-up transformer 16 As shown by the characteristic 154B, problems such as a large deviation of the output voltage from the set value and a large ripple occur.

[0116] However, the monitored value M _on or current monitoring value I _mon and voltage monitor value V _{mo n} main control unit 28 entered the variation information based load, the duty D determined in advance with respect to the fluctuation information The second PWM signal P having
Generate WM2. In response, FET 130 is turned on /
The first PWM signal PWM1 is thinned out while repeating the OFF operation.

FIG. 16A shows that the first PWM signal PWM1 of 19.55 kHz has a frequency of 100 Hz and a duty of 1.
FIG. 1 shows a state where the second PWM signal PWM2 is thinned out.
6 (B) is a first PWM signal PWM of 19.55 kHz.
1 is the second PW with 100 Hz and the duty is 18%
The states decimated by the M signal PWM2 are shown. 16 (A) and (B), the first PWM signal PWM
M1 is the waveform after thinning, that is, the switching element 2
The waveform input to 0 is shown. As shown in FIG. 16, as the duty of the second PWM signal PWM2 is larger, the amount of thinning out the first PWM signal PWM1 is larger.

As a result, according to the duty of the second PWM signal PWM2, the duty-output voltage characteristic becomes, for example, as shown by a characteristic 154C and a characteristic 154D, and the above problem can be solved.

As described above in detail, in the high-voltage power supply according to the third embodiment, the humidity detected by the environment detecting means, or the voltage value and the current value detected by the voltage detection circuit and the current detection circuit are used. Input to the switch element at the time of constant voltage control based on the PWM signal
Since the M signal is thinned out, it is possible to avoid the problem that the value of the output voltage greatly deviates from the set value or the ripple increases.

In the third embodiment, the case where the present invention is applied to the case where the constant voltage control is performed has been described.
The present invention is not limited to this, and the present invention can be applied to the case where constant current control is performed. in this case,
It is necessary to change equation (4) used in step 230 of FIG. 13 to the following equation (6), and to change equation (5) used in step 234 of FIG. 14 to the following equation (7).

[0121] _{D = K1 × M on (6} ) D = K2 / A (7) Thus, in the case of the constant current control, the larger the monitor value M _on, that is, as the humidity is higher second PWM signal PW
The duty D of M2 is increased, and the duty D of the second PWM signal PWM2 is reduced as the impedance A increases.

In the third embodiment, the case where the duty D of the second PWM signal PWM2 is set only at the time of warm-up has been described. However, the present invention is not limited to this, and the present invention is not limited to this. It is needless to say that the mode may be set to.

In the third embodiment, the circuit configuration of each unit shown in FIG. 12 is an example, and any circuit configuration that can realize the function of each unit can be applied.

In the third embodiment, both the voltage detecting circuit 22 and the current detecting circuit 24 and the environment detecting means 38 are provided, and the voltage detecting circuit 22 and the current detecting circuit 24 are provided.
And the case where the PWM signal input to the switch element 20 is thinned out based on the value obtained by any one of the environment detecting means 38, the present invention is not limited to this. The switch element 20 based on the values output from the voltage detection circuit 22 and the current detection circuit 24 only when the humidity obtained by 38 is a value that needs to change the value of the voltage applied to the step-up transformer 16. May be controlled so as to thin out the PWM signal input to the.

[Fourth Embodiment] Next, a fourth embodiment of the present invention will be described. First, the configuration of the high-voltage power supply 10 ″ according to the fourth embodiment will be described with reference to FIG. Note that the same reference numerals as in FIG. 1 in FIG. 17 denote the same parts, and a description thereof will be omitted.

High voltage power supply 1 according to the third embodiment
0 ″ is different from the high-voltage power supply device 10 in the first and second embodiments in that the high-voltage power supply unit 12 is a high-voltage power supply unit 12 ″ without the input voltage variable circuit 14. Are different.

As shown in FIG. 17, the output terminal of the DC power supply 26 in the fourth embodiment is directly connected to the terminal of the primary winding of the step-up transformer 16.

Note that the circuit configuration of the high-voltage power supply section 12 ″ in the fourth embodiment can be, for example, the configuration shown in FIG. 2 with the input voltage variable circuit 14 removed.

Next, as the operation of the fourth embodiment, control performed by the CPU 30 of the main control unit ″ will be described. In the fourth embodiment, similarly to the first to third embodiments, the control is performed based _{on the} monitor value Mon input from the environment detecting unit 38, and the voltage detection circuit 22 and the current Two cases, that is, the case where control is performed based on the voltage monitor value V _mon and the current monitor value I _mon input from the detection circuit 24, will be described.

First, a case where control is performed based _{on the} monitor value Mon input from the environment detecting means 38 will be described with reference to FIG.
This will be described with reference to FIG. Steps in FIG. 18 that perform the same processing as in FIG. 3 are assigned the same step numbers as in FIG. 3, and descriptions thereof are omitted.

In step 240, the above-mentioned step 204
Based _{on the} monitor value Mon taken in at the following (8)
The frequency f of the PWM signal PWM is calculated by the equation.

F = K3 / M _on (8) Here, K3 is a coefficient determined according to the configuration of the high-voltage power supply device 10 ″, etc., and is substituted into the above equation (8) to obtain the load. This is a value previously obtained by an experiment or the like as a value capable of obtaining a frequency f capable of minimizing a change in output characteristics due to a change in impedance. By (8), the larger the monitor value M _on, that is, as the humidity is high PWM signal of frequency f is set to a small value.

In the next step 242, the PW of the frequency f
By controlling the pulse oscillator 34 to generate the M signal PWM, the switching device 20
The signal PWM is output.

Next, the voltage detection circuit 22 and the current detection circuit
Voltage monitor value V input from 24 _monAnd current monitor
Value I_monFIG. 19 shows the case where control is performed based on
It will be described with reference to FIG. Note that the same processing as in FIG.
The steps to be performed are given the same step numbers as in FIG.
The description is omitted.

In step 244, step 218 is performed.
The frequency f of the PWM signal PWM is calculated by the following equation (9) using the value of the impedance A calculated by the following.

F = K4 × A (9) Here, K4 is a coefficient determined according to the configuration and the like of the high-voltage power supply 10 ″, and is substituted into the above equation (9) to obtain the impedance of the load. Is a value previously obtained by an experiment or the like as a value capable of obtaining a frequency f capable of minimizing a change in the output characteristic caused by the change in the output characteristic. According to the equation (9), the larger the impedance A, the greater the PWM signal PWM.
Is a large value.

In the next step 246, the PW of the frequency f
By controlling the pulse oscillator 34 so that the M signal PWM is generated, a PWM signal PWM having a frequency f is output to the switch element 20.

As described in detail above, in the high-voltage power supply according to the fourth embodiment, the humidity detected by the environment detecting means, or the voltage value and the current value detected by the voltage detection circuit and the current detection circuit are used. Input to the switch element at the time of constant voltage control based on the PWM signal
Since the frequency of the M signal is changed, it is possible to avoid the problem that the value of the output voltage greatly deviates from the set value or the ripple increases.

In the fourth embodiment, the case where the present invention is applied to the case where constant voltage control is performed has been described.
The present invention is not limited to this, and the present invention can be applied to the case where constant current control is performed. in this case,
Expression (8) used in step 240 in FIG. 18 needs to be changed to the following expression (10), and expression (9) used in step 244 in FIG. 19 needs to be changed to the following expression (11).

[0140] _{f = K3 × M on (10} ) f = K4 / A (11) Thus, in the case of the constant current control, monitor value as M is larger _on, that is, as the humidity is high PWM signal of frequency f And the value of the frequency f of the PWM signal PWM decreases as the impedance A increases.

In the fourth embodiment, the case where the frequency f of the PWM signal PWM is set only at the time of warming-up has been described. However, the present invention is not limited to this, and the setting is performed every predetermined time. Needless to say, the form may be used.

Further, in the fourth embodiment, the circuit configuration of each unit shown in FIG. 17 is an example, and any circuit configuration that can realize the function of each unit can be applied.

In the fourth embodiment, both the voltage detecting circuit 22 and the current detecting circuit 24 and the environment detecting means 38 are provided, and the voltage detecting circuit 22 and the current detecting circuit 24 are provided.
And the case where the frequency of the PWM signal input to the switch element 20 is changed based on the value obtained by any one of the environment detecting means 38, but the present invention is not limited to this. Only when the humidity obtained by the environment detecting means 38 is a value that requires changing the value of the voltage applied to the step-up transformer 16, based on the values output from the voltage detecting circuit 22 and the current detecting circuit 24. The control may be such that the frequency of the PWM signal input to the switch element 20 is changed.

The equations (Equations (4) to (11)) used in the third and fourth embodiments are merely examples, and the present invention is not limited to these equations.

Further, in each of the above embodiments, the case where both the voltage detecting circuit 22 and the current detecting circuit 24 and the environment detecting means 38 are provided has been described. However, the present invention is not limited to this. performing voltage either of the detection circuit 22 and the current detection circuit 24 can be omitted, control based on the voltage monitor value V _mon and the current monitor value I _mon when performing, for example, control based on the monitored value M _on In this case, the environment detecting means 38 can be omitted. In any case, the cost of the apparatus can be reduced as compared with the above embodiments.

In the above embodiments, the case where the humidity is detected by the environment detecting means 38 has been described.
The present invention is not limited to this, and may be, for example, a mode for detecting temperature, or a mode for detecting both humidity and temperature.

[0147]

According to the high voltage power supply device of the first to third aspects, the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer according to the environmental state detected by the environment detecting means. At least one of the following: changing the frequency of the pulse width modulation signal generated by the signal generation means, and reducing the frequency of the pulse width modulation signal generated by the signal generation means. Therefore, even if the impedance of the load fluctuates, the output characteristics of the step-up
At least one of changing the voltage value of the DC voltage supplied to the next winding side, thinning out the pulse width modulation signal generated by the signal generation means, and changing the frequency of the pulse width modulation signal generated by the signal generation means By performing such control, it is possible to obtain an effect that stable power can always be supplied to a load having a large variation in impedance.

According to the high voltage power supply device of the fourth to sixth aspects, the voltage value of the output voltage and the output current when the signal generation means is controlled to generate a pulse width modulation signal of a predetermined duty. Changing the value of the DC voltage supplied to the primary winding side of the step-up transformer in accordance with the value obtained based on the current value, thinning out the pulse width modulation signal generated by the signal generation means, and signal generation means Is controlled so as to perform at least one of the changes of the frequency of the pulse width modulation signal generated by the above, so that even when the impedance of the load fluctuates, the output characteristics of the high-voltage power supply device do not change as much as possible. Changing the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer, thinning out the pulse width modulation signal generated by the signal generating means, and changing the power generated by the signal generating means. By controlling to perform at least one of the frequency change of the width modulation signal, can supply power to constantly stable against variations in impedance is large load, the effect is obtained that.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a high-voltage power supply device according to a first embodiment and a second embodiment.

FIG. 2 is a circuit diagram illustrating an example of a circuit configuration of a high-voltage power supply unit of the high-voltage power supply device according to the first embodiment.

FIG. 3 is a flowchart illustrating an operation of the high-voltage power supply device according to the first embodiment.

FIG. 4 is a flowchart illustrating another operation of the high-voltage power supply device according to the first embodiment.

FIG. 5 is a graph showing an example of a duty-output voltage characteristic of the high-voltage power supply according to the first embodiment.

FIG. 6 is a circuit diagram illustrating another configuration example of the input voltage variable circuit according to the first embodiment.

FIG. 7 is a circuit diagram illustrating an example of a circuit configuration of a high-voltage power supply unit of a high-voltage power supply device according to a second embodiment.

FIG. 8 is a flowchart illustrating an operation of the high-voltage power supply device according to the second embodiment.

FIG. 9 is a flowchart illustrating another operation of the high-voltage power supply device according to the second embodiment.

FIG. 10 is a graph illustrating an example of a duty-output voltage characteristic of the high-voltage power supply device according to the second embodiment.

FIG. 11 is a block diagram illustrating a schematic configuration of a high-voltage power supply device according to a third embodiment.

FIG. 12 is a circuit diagram illustrating an example of a circuit configuration of a high-voltage power supply unit of the high-voltage power supply device according to the third embodiment.

FIG. 13 is a flowchart illustrating an operation of the high-voltage power supply device according to the third embodiment.

FIG. 14 is a flowchart illustrating another operation of the high-voltage power supply device according to the third embodiment.

FIG. 15 is a graph illustrating an example of a duty-output voltage characteristic of the high-voltage power supply device according to the third embodiment.

FIGS. 16A and 16B show a first PWM signal and a second PWM signal generated in the high-voltage power supply device according to the third embodiment;
FIG. 3 is a diagram showing an example of a waveform of a PWM signal of FIG.

FIG. 17 is a block diagram illustrating a schematic configuration of a high-voltage power supply device according to a fourth embodiment.

FIG. 18 is a flowchart illustrating an operation of the high-voltage power supply device according to the fourth embodiment.

FIG. 19 is a flowchart illustrating another operation of the high-voltage power supply device according to the fourth embodiment.

FIG. 20 is a diagram showing a schematic configuration of a conventional power supply device;
(A) shows a configuration example of a digital control type power supply device,
3B is a block diagram illustrating a configuration example of an analog control type power supply device.

21A shows the state of a reference clock signal of the CPU, FIG. 21B shows the state of one cycle and the resolution per bit when the CPU has an 8-bit configuration, and FIG.
7 is a time chart showing the state of one cycle and the resolution per bit in a case where is a 10-bit configuration.

FIG. 22A is a diagram illustrating a reference clock signal of a CPU and PWM.
It is a time chart which shows the relationship with a signal, (B) is P
5 is a graph illustrating a relationship between a duty of a WM signal and an output voltage.

FIG. 23 is a graph of a duty-output voltage characteristic used for describing a problem of the related art.

FIG. 24 is a graph of a duty-output voltage characteristic used for explaining another problem of the related art.

FIG. 25 is a circuit diagram showing an example of a circuit configuration of a conventional technique.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 high-voltage power supply device 12 high-voltage power supply unit 14 input voltage variable circuit (control means) 16 step-up transformer 18 rectification smoothing circuit (output means, rectification smoothing means) 20 switch element (switch means) 22 voltage detection circuit (detection means, voltage detection means) 24) current detection circuit (detection means, current detection means) 25 switch circuit 26 DC power supply 28 main control unit (control means) 30 CPU 32 arithmetic unit 34 pulse oscillator (signal generation means) 34 'first pulse oscillator (signal generation means) ) 34 '' second pulse oscillator (control means) 36 A / D converter 38 environment detecting means 40 load

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2H027 DA01 DA11 DA14 ED03 ED09 ED24 EF04 ZA01 ZA09 5H410 BB01 BB04 BB05 CC02 CC08 DD02 DD10 EA11 EA16 EA39 EB01 EB09 EB12 EB15 EB16 EB17 AS04 FF25 AS04 FF05 AS04 FF05 BB23 BB57 BB96 CC28 DD04 DD41 EE06 FD01 FD31 FD61 FF09 FG05 FG07 FG21

Claims (6)

[Claims] A step-up transformer; a DC power supply for generating a DC voltage to be supplied to a primary winding side of the step-up transformer; a signal generating means for generating a pulse width modulation signal having a variable duty; The DC power supply outputs the 1
Switch means for interrupting a DC voltage supplied to the next winding side; output means connected to the secondary winding of the step-up transformer for supplying power to a load; and detection means for detecting an output value of the output means Environment detection means for detecting an environment state; and controlling the signal generation means to change the duty of the pulse width modulation signal so that the output value matches a preset target value; Changing the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer in accordance with the environmental state detected by the detection means, thinning out the pulse width modulation signal generated by the signal generation means, and Control means for controlling at least one of the frequency changes of the pulse width modulation signal generated by the generation means. 2. The high-voltage power supply device according to claim 1, wherein the control unit performs a process according to an environment state detected by the environment detection unit at the time of warm-up. 3. An output value detected by the detection means is one of an output voltage and an output current of the output means, and an environmental state detected by the environment detection means is humidity. When controlling the output voltage to be equal to a preset target value and changing the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer, the higher the humidity, the higher the step-up voltage. The voltage value of the DC voltage supplied to the primary winding side of the transformer is increased, the output current is controlled to match a preset target value, and the DC voltage supplied to the primary winding side of the step-up transformer is increased. When changing the voltage value of the voltage, the higher the humidity is, the smaller the DC voltage value supplied to the primary winding side of the step-up transformer is, and the output voltage matches a preset target value. Yo When performing the thinning of the pulse width modulation signal generated by the signal generation unit, the amount of the thinning of the pulse width modulation signal is reduced as the humidity increases, and the output current is set to a predetermined target. When controlling to match the value and thinning out the pulse width modulation signal generated by the signal generation means, the amount of thinning out the pulse width modulation signal increases as the humidity increases, and the output voltage is When performing control to match a preset target value and changing the frequency of the pulse width modulation signal generated by the signal generation unit, the higher the humidity, the smaller the frequency, the lower the output current. Is controlled to match a preset target value, and when the frequency of the pulse width modulation signal generated by the signal generation unit is changed, the humidity is high. The high-voltage power supply device according to claim 1, wherein the higher the frequency, the larger the value. 4. A step-up transformer, a DC power supply for generating a DC voltage to be supplied to a primary winding side of the step-up transformer, a signal generating means for generating a pulse width modulation signal having a variable duty, The DC power supply outputs the 1
Switch means for interrupting a DC voltage supplied to the next winding side; rectifying and smoothing means connected to a secondary winding of the step-up transformer for rectifying and smoothing an alternating current induced in the secondary winding; Voltage detecting means for detecting an output voltage of the rectifying / smoothing means; current detecting means for detecting an output current of the rectifying / smoothing means; and a target in which one of the output voltage and the output current is set in advance. Controlling the signal generation means so as to change the duty of the pulse width modulation signal so as to match the value, and controlling the output when the signal generation means is controlled to generate a pulse width modulation signal having a predetermined duty. Changing the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer in accordance with the voltage value of the voltage and the value obtained based on the current value of the output current; A high-voltage power supply device comprising: control means for performing at least one of thinning out the generated pulse width modulation signal and changing the frequency of the pulse width modulation signal generated by the signal generation means. 5. The control means is obtained based on a voltage value of the output voltage and a current value of the output current when the signal generation means is controlled to generate a pulse width modulation signal having a predetermined duty. 5. The high-voltage power supply according to claim 4, wherein the processing according to the value is performed at the time of warm-up. 6. A value obtained based on a voltage value of the output voltage and a current value of the output current when the signal generation unit is controlled to generate the pulse width modulation signal of the predetermined duty is an impedance. The control means controls the output voltage to be equal to a preset target value, and when changing a voltage value of a DC voltage supplied to a primary winding side of the step-up transformer, As the impedance increases, the voltage value of the DC voltage supplied to the primary winding side of the step-up transformer is reduced, the output current is controlled to match a preset target value, and the primary winding of the step-up transformer is controlled. When changing the voltage value of the DC voltage supplied to the line side, the larger the impedance is, the larger the DC voltage value supplied to the primary winding side of the step-up transformer is, When controlling the output voltage to be equal to a preset target value and thinning out the pulse width modulation signal generated by the signal generation means, the amount of the thinning out of the pulse width modulation signal increases as the impedance increases. In the case where the output current is controlled to be equal to a preset target value and the pulse width modulation signal generated by the signal generation unit is thinned out, the pulse width modulation becomes larger as the impedance becomes larger. Reducing the amount of signal thinning, controlling the output voltage to match a preset target value, and changing the frequency of the pulse width modulation signal generated by the signal generating means, Is larger, the frequency is set to a larger value, the output current is controlled to match a preset target value, and the signal generation is controlled. 6. The high-voltage power supply device according to claim 4, wherein when changing the frequency of the pulse width modulation signal generated by the generating unit, the frequency is set to a smaller value as the impedance increases.