JP2006301069A - Power supply apparatus system and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply apparatus system capable of detecting more outputs at a satisfactory sampling cycle without increasing a circuit operation frequency (clock frequency), and to provide an image forming apparatus. <P>SOLUTION: The power supply apparatus system includes; a plurality of output detecting means for detecting the outputs of the plurality of power supply apparatuses; an order deciding means for deciding an order of selecting the detection outputs from the plurality of output detecting means in accordance with a timing signal generated by a timing signal generating means; a detection output selecting means for selecting a required detection output out of the detection outputs by the plurality of output detecting means; a difference calculating means for calculating a difference between the detection output selected by the detection output selecting means and a target value set by a target value setting means; a difference evaluation value calculating means for calculating the evaluation value of the difference; and a control means for controlling the plurality of power supply apparatuses based on the evaluation value calculated by the evaluation value calculating means. The sampling cycle is varied by the order deciding means in accordance with the object selected by the detection output selecting means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power supply system suitable for an image forming apparatus such as a copying machine or a printer using an electrophotographic system, and more particularly to sampling of power output in the power supply system.

  Due to rapid advances in digital technology and semiconductor integrated circuit technology in recent years, control of switching power supplies in copying machines and printers has been digitized to produce control chips and mount them in power supply devices (see Patent Document 1). .

  The outline will be described with reference to FIGS. 4, 5, and 6 (which are diagrams for explaining the first embodiment, but are used for explaining the background art).

Here, only one high-voltage output called high-voltage A will be described.
Reference numeral 1 denotes a high voltage generating means for forming an image forming process, and a high voltage output is supplied as A, for example, to a developing sleeve of an image forming process element.

  Connection of each component element and a series of operations will be described.

(1) DC high voltage generator In FIG. 4, a predetermined voltage is input as a B voltage to the primary side input of the transformer T1, and the other end of the transformer T1 is connected to the switching element Q4. A pulse signal (PWM signal) is input to the gate of the switching element Q4 from a digital PWM signal generation device 2-2 in a DC high voltage control device described later. The switching element Q4 performs a switching operation according to the PWM signal, thereby obtaining a turn ratio and a pulse output corresponding to the PWM signal on the secondary side of the transformer T1. The pulse output is rectified and smoothed by the diode 301 and the capacitor 201, and a DC high-voltage output is generated on the cathode side of the diode 301. T1, Q4, D301, and C201 are generally called flyback type (or on / off type) converters, and output higher voltages as the on-time ratio in the switching operation of the switching element Q4 is larger.

  A resistor R101 and a resistor R102 are connected to the DC high voltage output terminal, and a voltage stepped down by resistance division of each resistor, that is, a detection signal of a high voltage output is output.

(2) DC high voltage controller The high voltage output detection signal obtained by the resistors R101 and R102 in the high voltage generator 1 is input to the AD converter 2-3, and is sampled, held, and analog / digital converted (AD converted). . Sampling is performed after passing through an appropriate low-pass filter corresponding to the sampling frequency.

  The detection signal converted into digital data is input to one side of the comparison device 2-1. A DC high voltage target value is input to the other side of the comparison device 2-1, and a difference ΔV between the detected output value and the set target value is input to the digital PWM unit 2-2, where various arithmetic processes are performed. And a PWM signal is generated.

In the digital PWM unit 2-2, a difference evaluation value Z is first calculated. Here, the following values are used as the difference evaluation value Z.
Z = F1 * ΔV (k) Equation (1) where ΔV (k): difference between the detected output value at time k and the set target value, F1: constant According to the value of Z Thus, the fluctuation time of the pulse width (denoted as Δt) is determined. For example, if Δt = Z = 0100110 (binary) = 38 (decimal),
The ON pulse width of the PWM signal that is the switching element Q4 drive signal is increased by 38 pulses. Assuming that 20 MHz is used as the clock of the high-voltage control circuit, the 38 clock pulses are 1.9 μS, and the ON time width of the switching element Q4 is increased by Δt = 1.9 μS.

In the digital PWM unit 2-2, Δt is added to the current ON time T (k) of the switching element Q4, and T (K + 1) = T (K) + Δt is newly set as the ON time of the switching element Q4.

  By repeating the above operation, the high voltage output A is controlled to a predetermined value corresponding to the target value.

  More recently, electrophotographic apparatuses have performed more complex high voltage control for further higher image quality. For example, in developing bias high voltage for applying toner to an electrostatic latent image, toner is obtained by superimposing a desired alternating high voltage (hereinafter referred to as AC component) on a direct current high voltage (hereinafter referred to as DC component). There is an example of controlling the behavior of Examples of the configuration are shown in FIGS. In an electrophotographic image forming apparatus, development is generally performed by causing a developing sleeve (developer carrying member) carrying a developer of a developing device to correspond to an image carrier carrying an electrostatic latent image. A developing bias is applied to the developing sleeve to form a developing electric field between the image carrier and the developing sleeve.

  As this developing bias, a DC component in which an AC component is superimposed has been used. Conventionally, a rectangular wave as an AC component has a frequency of about 2 kHz (1/2 period = 250 μsec) and a peak-to-peak voltage ( Vpp) of about 2 kV was used, a high voltage of about 300 to 800 was used as the DC component, and a good developed image was obtained.

In addition, in the charging bias high voltage applied to the charging roller, the charger, etc. for uniformly charging the photosensitive drum for forming the electrostatic latent image, the desired high AC voltage is superimposed on the high DC voltage, so that the drum There is an example of realizing a uniform electric potential distribution. As an AC component used in this case, a sine wave having a frequency of about 500 Hz to 2 KHz and a peak-to-peak voltage (Vpp) of about 1 kV is used, and a high voltage of about 300 to 1500 V is used as a DC component.
JP 09-197916 A

  As described above, since a complex high voltage is used, the high voltage control circuit needs to detect more outputs. Conventionally, each high voltage output is detected in a time-sharing manner using a multiplexer or the like. However, in order to ensure the same sampling period as before, it is necessary to increase the number of control circuits or to increase the operating frequency. However, both increase costs. In general, a sufficiently short sampling period is necessary to perform high-speed and stable control. In other words, a stable response cannot be obtained faster than the sampling period.

  In the high voltage output used in the electrophotographic apparatus, the influence of the output voltage accuracy on the image quality is not uniform. For example, the sensitivity of the DC component of the charging output and the DC component of the developing bias output with respect to the image is very high, followed by the transfer output, the AC component of the charging output, the AC component of the developing bias output, and other toner transfer to the fixing device. In addition, there are sufficient accuracy such as a fixing bias high voltage to prevent abnormal charging.

  The present invention has been made under such circumstances, and provides a power supply system and an image forming apparatus that can detect more outputs with a sufficient sampling period without increasing the circuit operating frequency (clock frequency). It is an object to do.

  In order to solve the above-described problems, in the present invention, a power supply system is configured as described in (1) below.

  (1) A plurality of power supply apparatuses, a plurality of output detection means for detecting outputs from the plurality of power supply apparatuses, and a timing signal generation means for generating a timing signal for determining timing for sampling the detection outputs of the plurality of output detection means And an order determining means for determining an order of selecting the detection outputs from the plurality of output detecting means according to the timing signal generated by the timing signal generating means, and the plurality of the order determining means based on the outputs of the order determining means. A detection output selection means for selecting a required detection output from the detection outputs of the output detection means; an A / D conversion means for converting the detection output selected by the detection output selection means into a digital value; and Target value setting means for setting the output target value with a digital signal, output from the A / D conversion means, and setting with the target value setting means A difference calculation means for calculating a difference from the target value, a difference evaluation value calculation means for calculating an evaluation value of the difference using the difference calculated by the difference calculation means, and an evaluation value calculated by the evaluation value calculation means A power supply system comprising control means for controlling the plurality of power supply devices based on the above.

  According to the present invention, more outputs can be detected with a sufficient sampling period without increasing the circuit operating frequency (clock frequency).

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described in detail below with reference to embodiments.

[Embodiment 1]
FIG. 1 is a diagram showing a main configuration of a “high-voltage power supply system” for forming an image forming process according to the first embodiment. 2 is a configuration example of the sampling device 11 in FIG. 1, and FIG. 3 is a block diagram showing the internal configuration of the arithmetic device 16 in FIG. 4 and 5 are diagrams detailing the configuration of the DC high voltage generator and the AC high voltage generator. 7 and 9 are tables showing selection patterns based on the detection output selection signal.

  First, each component will be described. In FIG. 4, T1 boosts and converts a voltage input to the primary side in accordance with a primary-secondary winding ratio and an on / off time ratio of the PWM signal to provide a predetermined voltage on the secondary side. The output inverter transformer Q4 is a switching element for driving the inverter transformer T1.

  In FIG. 5, T2 is an AC high-voltage generating transformer that boosts and converts the voltage input to the primary side according to the primary-secondary winding ratio and outputs a predetermined voltage to the secondary side, Q3- Reference numerals 1 and 3-2 denote switching elements for driving the AC high-voltage generating transformer T2.

  In FIG. 1, 11 is a sampling circuit that takes in a detection signal of the output voltage of the high voltage generator, 12 is an A / D converter that converts an analog signal into a digital signal, and 13 is a signal from a high voltage sequence controller (not shown). A device for setting a target value of the output of the high pressure generator, 14 is a device for calculating the difference between the output of the A / D converter 12 and the output of the target value setting device 13, and 15 is for holding the output of the difference calculator 14 A device 16 is a device that calculates a difference evaluation value Z between the target value and the detected output value using the value of the holding device 15. Reference numerals 20 to 22 denote output control circuits, each of which includes a PWM signal generation device or an amplitude control signal generation device. For example, in DC high voltage control, a pulse width variation ΔT is determined, and a time T = T + ΔT for turning on the switching element Q4 is output. In order to perform multi-output control, a multi-output detection / PWM signal generation is performed using a time division device.

  Next, connection of each component element and a series of operations will be described.

<DC high voltage generator>
In FIG. 4, a predetermined voltage is inputted as a B voltage to the primary side input of the transformer T1, and the other end of the transformer T1 is connected to the switching element Q4. A pulse signal (PWM signal) is input to the gate of the switching element Q4 from a PWM signal generation device 21 in the high-voltage control device described later, and the switching element Q4 performs a switching operation according to the PWM signal, so that the transformer A pulse output corresponding to the turn ratio and the PWM signal is obtained on the secondary side of T1. The pulse output is rectified and smoothed by the diode 301 and the capacitor C201, and a DC high voltage output is generated on the cathode side of the diode D301. T1, Q4, D301, and C201 are generally called flyback type (or on / off type) converters, and output higher voltages as the on-time ratio in the switching operation of the switching element Q4 is larger.

  A resistor R101 and a resistor R102 are connected to the DC high-voltage output, and a voltage stepped down by resistance division of each resistor, that is, a detection signal of a high-voltage output is output.

<AC high pressure generator>
In FIG. 5, the intermediate side tap is provided in the primary side winding of the transformer T2, and is connected to the power supply voltage Vcc through the amplitude control transistor Q3-3. Both ends of the transformer T2 primary winding are connected to switching elements Q3-1 and Q3-2. The gates of the switching elements Q3-1 and Q3-2 are connected to the drive signal generator 3-6. The drive signal generator 3-6 generates two rectangular wave signals having opposite polarities according to the input drive signal. Further, a “dead time” in which both the switching elements Q3-1 and Q3-2 are turned off may be provided as necessary.

  On the secondary side of the transformer T2, the turn ratio of the primary / secondary winding, the peak voltage corresponding to the output voltage of the switching element Q3-3, and the on / off time of the switching elements Q3-1 and Q3-2 A rectangular wave with a corresponding pulse width is output. One of the secondary windings of the transformer T2 is connected to a DC high voltage VHdc that is an output of the DC high voltage generator, and the other is supplied with power to the developing sleeve of the image forming process element.

  T2, Q3-1, and Q3-2 are generally referred to as push-pull inverters.

  As described above, the high-voltage output composed of (DC high voltage + AC high voltage) is cut into a DC component by C301, divided into an AC component by resistors R301 and R302, and full-wave rectified by an amplitude detector 3-5. The full-wave rectified signal is output to the high voltage control device as an AC amplitude detection signal.

<High pressure control device>
In FIG. 1, the DC high voltage output detection signal obtained by the resistors R101 and R102 in the DC high voltage generator 1 is input to the sampling device 11. Sampling is performed after passing through an appropriate low-pass filter corresponding to the sampling frequency. When controlling multiple outputs, the detection signal of each output is sequentially sampled using a multiplexer or the like as a sampling device.

  The sampled high-voltage output detection signal is input to the A / D converter 12, converted into digital data, and input to one of the input terminals of the difference calculation device 14.

  A sequence control unit (not shown) that controls the high-voltage unit outputs digital data corresponding to an output set value (target value) of the DC high-voltage output, and the target value passes through the target value setting device 13 and the difference calculation device. 14 to the other input terminal. The difference calculation device 14 calculates a difference ΔV between the detected output value and the set target value, and temporarily holds it in the holding device 15.

The arithmetic unit 16 calculates the difference evaluation value Z using the held difference. Here, the following values are used as the difference evaluation value Z.
Z = F1 * ΔV (k) + F2 * {ΔV (k) −ΔV (k−1)} (2) where ΔV (k): the detected output value at time k and the set target ΔV (k−1): difference between the output value detected once at the sampling time k−1 past the time k and the set target value F1, F2: constants In the equation (2) The first half part: F1 * ΔV (k) is an evaluation value of the current difference, and the second half part: F2 * {ΔV (k) −ΔV (k−1)} is the difference increasing or decreasing. It is a value that evaluates the fluctuation of the difference of whether or not.

  The PWM signal generation device 21 determines a pulse width fluctuation time (Δt) according to the value of Z. For example, as Δt = 2 * Z = 2 * 38 (D), the ON pulse width of the PWM signal that is the Q4 drive signal is increased by 76 pulses. Assuming that 20 MHz is used as the clock of the high voltage control circuit, the 76 clock pulses are 3.8 μS, and the ON time width of Q4 is increased by Δt = 3.8 μS.

In the PWM signal generation device 21, Δt is added to the current ON time T (k) of the switching element Q4 using the Δt, and T (K + 1) = T (K) + Δt is newly set as the ON time of the switching element Q4. .
In this way, the DC high voltage output is controlled.

  An AC detection signal obtained from the AC high voltage generator is input to the sampling device 11. Sampling is performed after passing through an appropriate low-pass filter corresponding to the sampling frequency. When controlling multiple outputs, the detection signal of each output is sequentially sampled using a multiplexer or the like as a sampling device.

  The sampled high-voltage output detection signal is input to the A / D converter 12, converted into digital data, and input to one of the input terminals of the difference calculation device 14.

  A sequence control unit (not shown) that controls the high voltage unit outputs digital data corresponding to the amplitude output set value (target value) of the AC high voltage output, and the target value passes through the target value setting device 13 to calculate the difference. The signal is input to the other input terminal of the device 14. The difference calculation device 14 calculates a difference ΔV between the detected output value and the set target value, and temporarily holds it in the holding device 15.

The arithmetic unit 16 calculates the difference evaluation value Z using the held difference. Here, the following values are used as the difference evaluation value Z.
Z = F1 * ΔV (k) + F2 * {ΔV (k) −ΔV (k−1)} (2) where ΔV (k): the detected output value at time k and the set target ΔV (k−1): difference between the output value detected once at the sampling time k−1 past the time k and the set target value, F1, F2: in constant (2) The first half part: F1 * ΔV (k) is an evaluation value of the current difference, and the second half part: F2 * {ΔV (k) −ΔV (k−1)} is the difference increasing or decreasing. It is a value that evaluates the fluctuation of the difference of whether or not.

  Up to this point, the control is the same as the DC high voltage control, and the same block is used in the control circuit in a time division manner.

  In the amplitude control signal generation device 20, a voltage variation (Δv) of the amplitude control signal is determined according to the value of Z. For example, Δv = 10 * Z = 1 * 380 (D), and the voltage of the amplitude control signal is increased by 380 mV.

In the amplitude control signal generating device 20, Δv is added to the current amplitude control signal V (k) using the Δv, and V (K + 1) = V (K) + Δv is newly set as the amplitude control signal.
In this way, the amplitude value of the AC high voltage output is controlled.

  Next, the operation of the sampling apparatus 11 when there are a plurality of high-voltage outputs described above will be described with reference to FIGS.

  The sampling device 11 includes a multiplexer 11-1, a memory reading device 11-2, a multiplexer selection signal pattern memory 11-3, and a sampling clock generator 11-4.

  The multiplexer selection signal pattern memory 11-3 stores the detection output selection signal pattern shown in FIG. This detection output selection signal pattern is sequentially read out by the memory reading device 11-2 in synchronization with the clock signal of the sampling clock generator 11-4, and the SEL. 0-SEL. 2, the order of signals selected by the multiplexer 11-1 is determined. In the example of FIG. It is selected in the order of 0 to 1 to 3 to 0 to 1 to 4 to 5 to 0 to 1 to 3 to 0 to 1 to 6 to 7.

  In this case, CH. 0, CH. 1 is selected at a cycle of once every four sampling clocks 11-4.

  CH. 2, CH. 3 is selected at a cycle of once every eight sampling clocks 11-4.

  CH. 4, CH. 5, CH. 6, CH. 7 is selected at a cycle of once every 16 sampling clocks 11-4.

  Therefore, as shown in FIG. 8, in order to shorten the detection cycle of the high-voltage output that has a great influence on the image quality, CH. 0, CH. A development DC and a charging DC are assigned to 1. Development AC and charging AC output with relatively low sensitivity to image quality are set to CH. 4, CH. 6 is assigned.

  Many other examples of such detection output selection signal patterns are conceivable, but another example is shown in FIG.

  In the example of FIG. 0, CH. 1, CH. 2, CH. 3 is selected at a cycle of once every five sampling clocks 11-4.

  CH. 4, CH. 5, CH. 6, CH. 7 is selected at a cycle of once every 20 sampling clocks 11-4.

As described above, according to the present embodiment, as shown in FIG. 8, the detection period of the high voltage output having a large influence on the image quality is shortened, and the detection period of the high voltage output having a small influence on the image quality is lengthened. As a result, more high-voltage outputs can be detected with a sufficient sampling period without increasing the circuit operating frequency (clock frequency) [Embodiment 2]
FIG. 10 is a diagram showing a main configuration of a “high-voltage power supply system” for forming an image forming process, which is the second embodiment.
In this example, six outputs are switched and detected using an 8-channel multiplexer.

  The development DC detection signal is connected to the 0th and 4th channels of the multiplexer, and the charged DC detection output is connected to the 1st and 5th channels. In the present embodiment, the detection output selection signal generation device is configured as a counter.

  In this way, the sampling cycle of the development DC output and the charging DC output can be doubled as compared with other outputs.

FIG. 2 is a block diagram showing a schematic configuration of the first embodiment. FIG. 2 is a block diagram illustrating a configuration of a sampling device according to Embodiment 1. The figure which shows the internal structure of the arithmetic unit in Embodiment 1. The figure which shows the structure of the DC high voltage generator in Embodiment 1. The figure which shows the structure of the alternating current high voltage generator in Embodiment 1. The block diagram which shows the structure of the direct current | flow and alternating current high voltage generator in Embodiment 1, and its control apparatus The figure which shows the detection output selection pattern example 1 in Embodiment 1. FIG. The figure which shows the example of detection output allocation in Embodiment 1. The figure which shows the detection output selection pattern example 2 in Embodiment 1. Block diagram showing a configuration of a sampling apparatus according to Embodiment 2

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High voltage direct current generator 2 High voltage controller 3 High voltage alternating current generator 11 Sampling device 13 Target value setting device 14 Difference calculating device 16 Computing device

Claims (5)

Multiple power supplies;
A plurality of output detection means for detecting outputs in the plurality of power supply devices;
Timing signal generation means for generating a timing signal for determining timing for sampling the detection outputs of the plurality of output detection means;
Order determining means for determining the order of selecting the detection outputs from the plurality of output detection means according to the timing signal generated by the timing signal generating means;
Detection output selection means for selecting a required detection output from detection outputs of the plurality of output detection means based on the output of the order determination means;
A / D conversion means for converting the detection output selected by the detection output selection means into a digital value;
Target value setting means for setting a target value of an output of the plurality of power supply devices by a digital signal;
Difference calculating means for calculating a difference between an output from the A / D conversion means and a target value set by the target value setting means;
Difference evaluation value calculation means for calculating an evaluation value of the difference using the difference calculated by the difference calculation means;
Control means for controlling the plurality of power supply devices based on the evaluation values calculated by the evaluation value calculation means;
And the order determination means varies the sampling period according to the object selected by the detection output selection means. The power supply system according to claim 1,
The power supply system according to claim 1, wherein the order determining means determines the order based on a selection order written in advance in the storage means. The power supply system according to claim 1 or 2,
A power supply apparatus system using a multiplexer as the detection output selection means and supplying the same detection output to a plurality of input terminals of the multiplexer. In the power supply system according to any one of claims 1 to 3,
A power supply apparatus system using a multiplexer as the detection output selection means and supplying the same detection output to a plurality of input terminals of the multiplexer. The image forming apparatus according to claim 4.
The image forming apparatus according to claim 1, wherein the order determining unit determines an order of selecting the detection output so that a detection cycle of the development DC and the charging DC is shorter than a detection cycle of the development AC and the charging AC.

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