JP2826918B2 - High-voltage AC voltage generation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-voltage AC voltage generating circuit used for a means for uniformly charging a photosensitive member by bringing a charging roller into contact with the photosensitive member.

[0002]

2. Description of the Related Art As shown in FIG. 3A, a high-voltage AC voltage generating circuit used for a means for uniformly charging a photosensitive member by bringing a charging roller into contact with the photosensitive member is connected to a primary side of a high-voltage transformer 270 as shown in FIG. Energy was supplied to the high-voltage transformer as an AC voltage source so that the applied AC voltage became constant, and the secondary high-voltage AC voltage was kept constant.

In FIG. 3A, a Wien bridge oscillation circuit 210 includes resistors 211, 213, 215, capacitors 214, 212, and an operational amplifier 216, and oscillates a sine wave. The peak-to-peak voltage of this sine wave Vp-
p is controlled by the gain control circuit 220. The gain control circuit 220 includes resistors 221 and
23, 225, condenser 222 and junction F
When the gate voltage of the junction FET 224 constituted by the ET 224 rises, the gain of the operational amplifier 216 decreases and the sine wave Vp-p decreases. The gate voltage of the junction FET 224 is supplied to the rectifier circuit 230.
Is controlled by The rectifier circuit 230 includes a diode 233, a capacitor 231 and a resistor 232, and rectifies an output sine wave. However, the output sine wave Vp-p is always controlled to be constant. The operational amplifier 240 and the current booster circuit 250 supply energy from the sine wave output of the Wien bridge oscillation circuit 210 to the high-voltage transformer 270 as an AC voltage source. The current booster circuit 250 includes resistors 251, 253, and 2
54, 257, diodes 252, 256, and transistors 258, 259. Condenser 26
Reference numeral 0 denotes a capacitor for preventing the high-voltage transformer 270 from magnetizing. The secondary high-voltage output side of the high-voltage transformer 270 includes an equivalent circuit 291 of a photoconductor and a charging roller, a DC high-voltage power supply 290, and an AC bypass capacitor 281. The equivalent circuit 291 includes a resistor 293 and a capacitor 292. The AC bypass capacitor 281 is a capacitor having a sufficiently low impedance with respect to the frequency of the sine wave output from the Wien bridge oscillation circuit 210.

In the above circuit, an AC equivalent circuit viewed from the primary side of the high voltage transformer 270 is considered as shown in FIG. L (301) is the excitation inductance as viewed from the primary side of the high voltage transformer 270, and the capacitor 303 is a capacitor when the capacitor 292 is converted to the primary side. The resistance 304 is a resistance when the resistance 293 is converted to the primary side. This equivalent circuit constitutes a parallel resonance circuit. Therefore, when the frequency of the sine wave of the Wien bridge circuit 210 is higher than the resonance frequency of the resonance circuit, the current becomes a current that is earlier than the voltage, and when the frequency is lower, the current is a current that is later than the voltage. Wien Bridge Circuit 21
When the frequency of the sine wave of 0 is equal to the resonance frequency of the above-described resonance circuit, the current has the same phase as the voltage, and the photosensitive member can be uniformly charged efficiently.

[0005]

However, since the variation in the capacity between the photosensitive member and the charging roller considerably changes depending on the combination of the photosensitive member and the charging roller, the above-described frequency matching is performed between the photosensitive member and the charging roller of the cartridge type. This is extremely difficult and results in low efficiency charging.

In addition, a high-precision element is required to fix the frequency of an oscillator such as a Wien bridge circuit.

An object of the present invention is to provide a high-voltage AC voltage generating circuit capable of easily performing frequency matching.

[0008]

According to the present invention, in order to achieve the above object, a charging roller is brought into contact with a photoreceptor, and a high-voltage AC power is supplied to a high-voltage power supply used for a means for uniformly charging the photoreceptor. in generating circuit, variable frequency
Generating means for generating an alternating current;
A high-voltage transformer for generating high pressure upon input;
First detecting means for detecting the voltage on the primary side of the
Second detecting means for detecting the current on the primary side of the high voltage transformer
And the phase of the voltage detected by the first detecting means.
Difference from the phase of the current detected by the second detecting means
Frequency of the alternating current generated by the generating means so that
Frequency control means for controlling the frequency of the alternating current.
By controlling the wave number, the input of the high-voltage transformer is controlled.
The total inductance including the conductance component
The total capacity of the body and the charging roller including the capacity component
It is characterized by doing so.

[0009]

[0010]

[0011]

According to the present invention, the primary side of the high voltage transformer is resonated with the total inductance including the inductance component of the high voltage transformer and the total capacitance including the capacitance component of the photosensitive member and the charging roller. The frequency of the high-voltage AC is controlled by the frequency control means so that the applied voltage and the current on the primary side of the high-voltage transformer have the same phase.

[0012]

FIG. 1 shows a first embodiment of the present invention. FIG.
The same circuit parts as in (a) are given the same numbers, and the description is omitted here. The voltage-frequency conversion circuit (FV circuit) 110 includes an operational amplifier 115 and resistors 111, 112,
114, 117, capacitor 113 and transistor 1
At 18, a triangular wave is output. At this time, the oscillation frequency changes depending on the voltage at the connection point as the resistor 111. The triangular wave is converted into a rectangular wave by the comparator 124 through the resistor 116. The resistors 120, 121, and 122 are resistors that determine the slice level and the hysteresis. The resistor 123 is a pull-up resistor. The square wave is fed back to the inverting input of the operational amplifier 115 by the transformer 118. The FV circuit outputs a frequency proportional to the voltage.

The rectangular wave output from the FV circuit 110 is input to a secondary low-pass filter circuit 150. The low-pass filter circuit 150 includes an operational amplifier 156 and a resistor 1
51, 154, 155 and capacitors 152, 153 constitute a positive feedback type active filter. The low-pass filter circuit 150 converts the rectangular wave into a sine wave. Gain control circuit 220 and rectifier circuit 230
Controls the gain of the operational amplifier 156 to keep the output voltage constant as described above. The comparator 166 detects the voltage, and the comparator 167 detects the zero cross point of the current detected by the resistor 168. The diodes 162 and 163 and the resistors 164 and 165 are elements for clamping to ground. Resistance 160, 16
1 is pulled up to the power supply voltage of the PLL IC 108. PLL circuit (phase lock loop circuit) 100
Are connected to a PLL IC 108 (e.g., corresponding to MC4044) and resistors 101, 106, 107, 104, 10
5, a capacitor 102, and an operational amplifier 103, and outputs a voltage proportional to the phase difference between the comparator 166 and the comparator 167. However, the oscillation frequency is controlled so that the applied voltage on the primary side of the high voltage transformer 270 and the current on the primary side of the high voltage transformer have the same phase. Here, the PLL circuit 100 and the resistor 16
0, 161, 164, 165, diodes 162, 16
3. The comparators 166 and 167 constitute frequency control means C.

FIG. 2 shows a second embodiment of the present invention. First
Since the same circuit parts as in the embodiment of FIG.
Here, the description is omitted. As in the first embodiment, the voltage and current phase on the primary side of the high voltage transformer 270 are output from the comparators 166 and 167. This output is input to the EXOR circuit 420. Then, a pulse corresponding to the phase shift is output from the EXOR circuit 420. This is input to an integrating circuit 460 including an operational amplifier 430, a capacitor 440, and a resistor 450, and is used as a DC voltage. The CPU 410 takes in this voltage value from an analog input. Also CPU
410 outputs a 50% duty clock from the port P1 and inputs it to the bandpass filter 400. The bandpass filter 400 includes an operational amplifier 408 and a resistor 402,
403, 404, 406 and capacitors 405, 40
1, 407 constitute a simulated induct and a tank circuit of a condenser. Rectifier circuit 23
0 and Vp-p of the output sine wave are kept constant by the gain control circuit 220. In such a circuit configuration, the CPU 410 changes the frequency of the clock output from the port P1 so that the voltage of the analog input becomes 0V. Here, the CPU 410, the integration circuit 460,
EXOR circuit 420, resistors 160, 161, 164, 1
65, diodes 162, 163, comparator 16
Reference numerals 6 and 167 constitute frequency control means C.

[0015]

As described above, the total inductance including the inductance component of the high-voltage transformer and the voltage applied to the primary side of the high-voltage transformer so as to resonate with the total capacitance including the capacitance components of the photosensitive member and the charging roller are used. The frequency of the high-voltage alternating current is controlled by frequency control means so that the primary-side current of the high-voltage transformer has the same phase, and resonance occurs , so that
Even if the contact charging method reduces the Q of the
The change in capacity due to the combination of the light body and the charging roller
The resonance frequency can be easily matched,
Highly efficient charging is possible, and the photoconductor is charged uniformly
It became possible. Also, the primary side of the high voltage transformer
It became easy to convert the road into logic.

Further, since the frequency is controlled by the capacitance, a high-precision element is not required, and the frequency matching can be stably performed even when the temperature changes.

[Brief description of the drawings]

FIG. 1 is a diagram showing a high-voltage AC voltage generation circuit according to a first example of the present invention.

FIG. 2 is a diagram illustrating a high-voltage AC voltage generation circuit according to a second embodiment of the present invention.

FIG. 3 (a) is a diagram showing a conventional high-voltage AC voltage generation circuit,
(b) is a diagram showing an equivalent circuit of the same circuit.

[Explanation of symbols]

 270 High-voltage transformer C frequency control means

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hidenobu Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-62-52876 (JP, A) (58 ) Surveyed field (Int.Cl. ⁶ , DB name) G03G 15/02 102

Claims (1)

(57) [Claims] 1. A high-voltage AC generation circuit in a high-voltage power supply used for a unit for uniformly charging the photoconductor by bringing a charging roller into contact with the photoconductor, a generation unit for generating an AC having a variable frequency, and the generation unit. High pressure to generate high pressure by inputting AC from
Transformer and first detection for detecting a voltage on a primary side of the high-voltage transformer
Means for detecting a current on a primary side of the high voltage transformer
Means, a phase of the voltage detected by the first detecting means,
The difference between the phase of the current detected by the second detecting means and the phase of the current is detected.
Frequency of the alternating current generated from the generating means so that
Frequency control means for controlling the frequency of the alternating current,
The total inductance including the inductance component of the high-voltage transformer
And the capacitance component of the photoconductor and the charging roller.
A high-voltage AC voltage generating circuit characterized by resonating with a total capacity including the voltage.