JP2013219894A - Power source device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately determine failure of a multistage voltage doubler rectifier circuit.SOLUTION: In a power source device, a controller 206 that controls a frequency of a pulse signal on the basis of a voltage value detected by an output voltage detection circuit detects a voltage by the output voltage detection circuit while changing a frequency of a pulse signal to be output for turning on and off a field effect transistor Q101, calculates a feature amount based on the frequency of the pulse signal and the detected voltage, and determines failure of a multistage voltage doubler rectifier circuit on the basis of the calculated feature amount.

Description

  The present invention relates to a power supply device that generates a high voltage and an image forming apparatus including the power supply device.

  In a conventionally known electrophotographic image forming apparatus, a semi-conductive or elastic roller having a dielectric layer on the surface is used as a developing roller, and a contact developing method in which development is performed while being pressed against the surface of a photoreceptor is often used. It is done. In such a contact development system, a DC voltage is used as a voltage applied to the developing member in order to carry the toner on the surface of the developing member. In order to perform good image formation, it is usually necessary to apply a DC voltage of about 300 V to 800 V to the developing member. In addition to a member such as a developing roller, a charging roller as a charging member for uniformly charging the surface of the photosensitive member or a transfer for transferring a toner image developed on the photosensitive member to a transfer member such as a recording paper or a belt. It is necessary to apply a high voltage to the member.

  In order to apply a high voltage, conventionally, a high voltage power supply device using a wound electromagnetic transformer or a piezoelectric transformer is used. As a method for performing output voltage control, in a circuit using an electromagnetic transformer, a method of changing a voltage supplied to the transformer is mainly used. Further, in a circuit using a piezoelectric transformer, a method of changing the frequency supplied to the primary side of the piezoelectric transformer is mainly used.

JP 2006-091757 A

  However, the use of a transformer in the high-voltage power supply device has the following problems. First, the ratio of transformer component costs to the cost of high-voltage circuits is large compared to other components. Also, in terms of space, the height and area are often larger than other parts. Furthermore, in terms of weight, particularly an electromagnetic transformer using ferrite or copper wire is heavier than other components. In particular, in a high-voltage power supply device used in a full-color image forming apparatus that requires a plurality of high-voltage circuits, the influence caused by using a transformer is large. As described above, cost reduction, size reduction, and weight reduction of high-voltage power supply devices using transformers are major issues.

  For this reason, it is conceivable that a multistage voltage doubler rectifier circuit is constituted by a plurality of capacitive elements and a plurality of rectifier elements to provide a power supply device capable of outputting a high voltage. However, there are the following problems in using the multistage voltage doubler rectifier circuit in the high-voltage power supply device. That is, when one element forming the multi-stage voltage doubler rectifier circuit fails, the output voltage of the high voltage output is slightly reduced, but the high voltage can continue to be output. Even when the load connected to the high-voltage power supply device becomes large, the output voltage of the high-voltage output is lowered. As described above, the conventional multi-stage voltage doubler rectifier circuit has a problem that it is difficult to distinguish whether the decrease in the output voltage is caused by a failure of the multi-stage voltage doubler rectifier circuit or a load change.

  The present invention has been made under such circumstances, and an object thereof is to accurately determine a failure of a multistage voltage doubler rectifier circuit.

  In order to solve the above-described problems, the present invention has the following configuration.

  (1) An inductive element for generating a voltage, a switching element for turning on and off a voltage applied to the inductive element, a plurality of capacitive elements and a plurality of rectifying elements, and boosting the voltage generated in the inductive element A boosting circuit; a detecting means for detecting a voltage output from the boosting circuit; and a control means for controlling a frequency of a pulse signal output for turning on and off the switching element based on a voltage value detected by the detecting means. The control means detects the voltage by the detection means while changing the frequency of the pulse signal, calculates the feature quantity based on the frequency of the pulse signal and the detected voltage, and calculates the calculated feature quantity. And determining a failure of the booster circuit based on the power supply device.

  (2) a photoconductor, a charging unit for charging the photoconductor, an exposure unit for forming an electrostatic latent image on the photoconductor charged by the charging unit, and an electrostatic latent image formed by the exposure unit An image forming apparatus comprising: a developing unit that develops toner with toner; and a transfer unit that transfers a toner image developed by the developing unit to an image carrier. The apparatus supplies an electric power to at least one of the charging unit, the developing unit, and the transfer unit.

  According to the present invention, it is possible to accurately determine the failure of the multistage voltage doubler rectifier circuit.

The figure which shows the multistage voltage doubler rectifier circuit of Example 1. FIG. 1 is a block diagram showing a high-voltage power supply device according to a first embodiment. The figure which shows operation | movement of the multistage voltage doubler rectifier circuit of Example 1. FIG. The figure which shows the multistage voltage doubler rectifier circuit of Example 1, the graph which shows a drive frequency-high voltage output voltage characteristic The graph which shows the feature-value detection method of Example 1, The graph which shows a high voltage | pressure load-feature-value characteristic A graph which shows the feature-value detection method of Example 2. The figure which shows the multistage voltage doubler rectifier circuit of Example 3, the graph which shows the feature-value detection method, The graph which shows a high voltage load-feature-value characteristic The figure which shows operation | movement of the multistage voltage doubler rectifier circuit of Example 4. FIG. 10 is a diagram illustrating a configuration of an image forming apparatus according to a fifth embodiment.

  The mode for carrying out the present invention will be described in detail below with reference to examples.

[Multi-stage voltage doubler rectifier circuit]
FIG. 1 shows a multi-stage voltage doubler rectifier circuit (boost circuit) of the high-voltage power supply device according to the first embodiment. In FIG. 1, an inductor L100 (inductive element) and a capacitor C100 constitute a voltage resonance circuit. The inductor L100 is an element connected between a switching element and a power supply voltage Vcc (+24 V or the like), and is an example of an element having an inductance component to which voltage is intermittently applied by driving the switching element. The capacitor C100 is grounded. The output of the voltage resonance circuit is rectified and smoothed to a positive voltage by a rectifying and smoothing circuit. The rectifying / smoothing circuit includes a diode D101 (rectifier element) that conducts current in the forward direction and a capacitor C101 (capacitor element) that is connected between the cathode terminal of the diode D101 and the power supply voltage Vcc and charges electric charges. The back voltage is taken out. Subsequently, a multi-stage rectifier circuit is formed by diodes D102, D103, D104, D105 (a plurality of rectifier elements) and capacitors C102, C103, C104, C105 (a plurality of capacitor elements). The output is grounded through the smoothing capacitor C106, and the output waveform is smoothed. Note that a required number of capacitors and diodes corresponding to a required output voltage are connected between the capacitor C104 and the diode D104, and the illustration is omitted.

  The output of the rectifying and smoothing circuit is connected to the output terminal 104 (Vout), and the output voltage is taken out. On the other hand, the voltage detection resistor R101, the voltage dividing resistors R102 and R103, and the noise removal capacitor C107 constitute an output voltage detection circuit. The output voltage is input to the output voltage detection circuit, and the output of the output voltage detection circuit is output from the output voltage detection terminal 102 to the controller 206 (see FIG. 2) as the detection voltage Vsense. The controller 206 can determine from the output voltage (detection voltage Vsense) input from the output voltage detection terminal 102 that the output voltage is a desired voltage. If the output voltage is not a desired voltage, the controller 206 controls the drive frequency output to the control frequency input terminal 103 (fcont).

  The control frequency input terminal 103 (fcont) is connected to the gate terminal of the field effect transistor Q101 via the limiting resistor R107. The field effect transistor Q101 is an example of a switching element that is driven by being turned on / off by a pulsed output signal (pulse signal) from the controller 206. The drain terminal of the field effect transistor Q101 is connected to the above-described voltage resonance circuit, is connected to the power supply voltage Vcc (for example, +24 V) via the inductor L100, and is grounded via the capacitor C100. The source terminal of the field effect transistor Q101 is grounded.

  In this way, the voltage amplified by the voltage resonance circuit composed of the inductor L100 and the capacitor C100 is directly rectified by the rectifier circuit, and the number of stages of the rectifier circuit is increased to increase the voltage to be output. Can do. The above is an example of the circuit configuration and circuit operation of this embodiment.

[Operation of high-voltage power supply]
Next, the operation of the high-voltage power supply device will be described with reference to the block diagram shown in FIG. The high voltage generator 202 is a block that includes the multistage voltage doubler rectifier circuit shown in FIG. The controller 206 includes a central processing unit 201, a feature amount calculation unit 203, an output voltage detection unit 204, and a nonvolatile memory 205.

  The detection voltage Vsense is output from the output voltage detection terminal 102 of the high voltage generator 202 to the controller 206. The detection voltage Vsense is input to the output voltage detection unit 204 of the controller 206, and the output voltage detection unit 204 performs analog-to-digital (AD) conversion from an analog value to a digital detection voltage 207 expressed by a digital value. The central processing unit 201 determines whether the digital detection voltage 207 AD-converted by the output voltage detection unit 204 is a target voltage, and changes the control frequency so as to be a target value. The signal of the control frequency fcont output from the central processing unit 201 is input to the control frequency input terminal 103 of the high voltage generator 202, and the high voltage generator 202 outputs a high voltage (Vout) corresponding to the control frequency fcont from the output terminal 104. Output.

  The digital detection voltage 207 output from the output voltage detection unit 204 is also input to the feature amount calculation unit 203. For example, when the power supply device is in the self-diagnosis mode, the feature amount calculation unit 203 measures the input / output characteristics of the high voltage generation unit 202 by detecting the voltage of the high voltage generation unit 202 while sweeping the control frequency fcont. Calculate the feature quantity of the input / output characteristics. That is, the feature amount calculation unit 203 outputs a pulse signal having a certain drive frequency to the control frequency input terminal 103 of the high voltage generation unit 202. Then, the output voltage output from the high voltage generator 202 in accordance with the drive frequency is input to the feature amount calculator 203 as the digital detection voltage 207 via the output voltage detector 204. The feature amount calculation unit 203 repeats the above processing while changing the control frequency output to the control frequency input terminal 103 of the high voltage generation unit 202 (while performing the sweep operation). In this way, the feature amount calculation unit 203 can obtain a correspondence relationship (that is, input / output characteristics) between the drive frequency (input frequency) and the high-voltage output voltage corresponding to the drive frequency. The feature amount calculation unit 203 outputs information on the feature amount calculated from the input / output characteristics to the central processing unit 201.

  The feature amount output from the feature amount calculation unit 203 and input to the central processing unit 201 is compared with a threshold value, which will be described later, recorded in advance in the nonvolatile memory 205, and the central processing unit 201 has failed in the high voltage generation unit 202. Used for detection.

  A pulse signal having a control frequency fcont is input to the control frequency input terminal 103 of the high voltage generation unit 202 from the central processing unit 201 or the feature amount calculation unit 203. For example, when the high-voltage power supply device starts operating in the self-diagnosis mode, the input to the control frequency input terminal 103 is switched from the feature amount calculation unit 203. A portion indicated by a white circle in the controller 206 in FIG. 2 is, for example, a selector and performs the above-described switching. The frequency (fcont) of the signal (pulse signal) input from the central processing unit 201 or the feature amount calculation unit 203 to the control frequency input terminal 103 is hereinafter referred to as a control frequency, a drive frequency, an input frequency, or the like.

[Operation of multi-stage voltage doubler rectifier circuit]
FIG. 3 is an operation waveform of each part shown in FIG. Here, 3A is a voltage waveform (gate voltage waveform) applied from the controller 206 to the gate of the field effect transistor Q101, which is a pulse signal as shown in the figure. The waveform of the signal output at the control frequency fcont from the central processing unit 201 or the feature amount calculation unit 203 is also substantially equivalent to 3A. When field effect transistor Q101 is turned on, a current flows from power supply voltage Vcc to inductor L100. The waveform (drain current waveform) representing the drain current flowing through the field effect transistor Q101 at this time is 3B. That is, energy is stored in the inductor L100 in accordance with the current flowing time.

  Next, when the field effect transistor Q101 is turned off, voltage resonance occurs between the capacitor C100 and the inductor L100. The drain voltage waveform of the field effect transistor Q101 at this time is 3C. This voltage waveform is generally called a flyback voltage. Due to the voltage resonance, the maximum value V1a of the flyback voltage of the resonance circuit becomes a voltage value several times the power supply voltage Vcc. Further, by setting the resonance voltage to be 0 V or less so that the next on-time of the field effect transistor Q101 starts, it is possible to efficiently supply the voltage to the subsequent circuit without performing hard switching. The voltage generated by this resonance circuit is boosted by the number of rectification stages in the subsequent rectification circuit. The voltage waveform (anode voltage waveform) of the anode terminal of the diode D105 arranged at the final stage of the rectifier circuit is 3D. The voltage waveform is the maximum voltage value V1b, and ideally the flyback voltage V1a is superimposed on it. The voltage at the cathode terminal of the diode D105 is a constant voltage V1b (one-dot chain line), which is smoothed and stabilized by the smoothing capacitor C106, and is represented by 3E (high voltage output) at the output terminal 104 (Vout). Voltage waveform.

  Next, the operation of the rectifier circuit will be described in detail. When field effect transistor Q101 is turned off, a positive flyback voltage is generated by the resonant circuit of inductor L100 and capacitor C100. The generated flyback voltage is held at the maximum voltage Vmax1 by charging C101 through the diode D101. Next, when the field effect transistor Q101 is turned on, a counter electromotive voltage is generated in the inductor L100. This time, the charge moves through the diode D102, and the capacitor C102 is charged. As a result, the flyback voltage Vmax1 is applied to the capacitor C102 based on the maximum voltage Vmax1 at the capacitor C101, and is amplified to the maximum voltage Vmax2 (≈2 × Vmax1). Furthermore, when the field effect transistor Q101 is turned off, the charge charged in the capacitor C102 moves through the diode D103, and the capacitor C103 is charged. As a result, the capacitor C103 is held at the maximum voltage Vmax2. Similarly, the voltage is amplified by repeating the voltage hold by the capacitor and the voltage addition for the flyback voltage by the number of rectification stages.

  Actually, loss due to the capacity of the capacitor or the diode is unavoidable, so the flyback voltage of the resonance circuit cannot be amplified by the number of rectification stages. The voltage generated at the connection between the cathode of the diode D105 and the capacitor C105, which is the final stage of the rectifier circuit, is smoothed by the smoothing capacitor C106, and is output as a stable voltage from the output terminal 104 (Vout).

[Control of output voltage by control frequency]
Next, an operation when the control frequency fcont input from the controller 206 to the gate terminal of the field effect transistor Q101 is variably controlled will be described. Here, the duty ratio between on (ON) and off (OFF) of the control frequency is fixed. The output voltage control by frequency can be performed by lowering the control frequency when increasing the output voltage, and by increasing the control frequency when decreasing the output voltage. More specifically, when the control frequency is lowered, energy is stored in the inductor L100 as the on-time ton of the field effect transistor Q101 becomes longer, and the maximum value of the flyback voltage waveform of the resonance circuit is increased. Also gets higher. That is, the voltage output from the output terminal 104 increases. Conversely, as the control frequency increases, the energy stored in the inductor L100 decreases as the ON time ton of the field effect transistor Q101 decreases, and the maximum value of the flyback voltage waveform of the resonant circuit also decreases. That is, the voltage output from the output terminal 104 (Vout) becomes low. In this way, the output voltage can be controlled by changing the control frequency fcont.

[Causes of output voltage drop of multi-stage voltage doubler rectifier]
-Failure of multi-stage voltage doubler rectifier circuit Here, consider the case where the above-mentioned multi-stage voltage doubler rectifier circuit fails. FIG. 4A shows a circuit diagram when the capacitor C103 in the rectifier circuit has an open failure. This can be seen from the absence of the capacitor C103 when comparing FIG. 1 and FIG. 4 (a). In this case, the charge charged in the capacitor C102 charges the capacitor C105 via the capacitor C104 and the diode D105. Since the capacitor C103 does not exist, the number of capacitors to be charged decreases, and the output voltage output from the output terminal 104 (Vout) also decreases by Vmax1.

-Load fluctuation Even if the rectifier circuit is normal, when the load connected to the output terminal 104 (Vout) increases, the output voltage to be output also decreases.

  FIG. 4B shows the drive frequency-high voltage output voltage characteristics when the load is heavy (heavy load) during normal operation (solid line) and when the load is light (light load) during failure (broken line). Here, the output voltage drop due to load fluctuations and the output voltage drop due to a failure are substantially equal. Here, comparing the failure time with the normal time, the output voltage obtained when driving at the same control frequency is increased by the smaller number of capacitors, and the efficiency of the output voltage obtained is higher at the time of failure. Become.

  There is a leakage current in an actual capacitor. Therefore, when the drive frequency is high and the flyback voltage is low, the amount of charge stored in the capacitor is small and the ratio of leakage current to the charge is large, and the high-voltage output voltage is higher in the case of a failure with a small number of capacitors. On the other hand, when the drive frequency is low and the flyback voltage is high, the number of capacitors that charge the flyback voltage is large, so that the high-voltage output voltage is higher under normal conditions. Thus, at the time of failure, the drive frequency-high voltage output voltage characteristics tend to be gentle as shown by the curve shown in FIG. 4B, compared to when normal (heavy load).

[Separation between normal and failure]
Next, with reference to FIG. 5A, how the controller 206 distinguishes between a normal time and a failure time will be described. First, the feature quantity calculation unit 203 measures input / output characteristics by detecting the high voltage output voltage of the high voltage generation unit 202 while sweeping the input frequency. The frequency range for sweeping the input frequency (control frequency fcont) is not particularly limited. For example, it may be determined according to the standard of the field effect transistor Q101 to be used. For example, the lower limit of the limiting frequency fcont is determined by the drain current (3B in FIG. 3) of the field effect transistor Q101 used, and the upper limit is determined by the drain voltage (3C in FIG. 3) of the field effect transistor Q101 used.

The feature amount calculation unit 203 calculates a reference line (6D) obtained by interpolating, for example, with an arithmetic sequence between the output voltage (6A) at the start frequency and the output voltage (6B) at the end frequency. Here, the input frequency at the _{start of} the sweep is x _start , and the output voltage output according to the input frequency x _start at the _{start of} the sweep is y _start . Also, the input frequency at the _{end of} the sweep is x _end , and the output voltage output according to the input frequency x _end at the _{end of} the sweep is y _end . Further, with respect to the measurement data between the start and end of the sweep, the input frequencies are x ₁ , x ₂ ,..., X _n and the output voltages output according to the respective input frequencies are y ₁ , y ₂ ,. ..., and _{y n.} Then, the feature amount calculation unit 203 adds the divergence amount (6C) between the measured input / output characteristic and the reference line (6D) in the entire measurement point to obtain the divergence feature amount Ec. Incidentally, the deviation amount (6C) is for example the n-th measurement data, the value obtained when substituting x _n to the reference straight line (6D) which is a function of the input frequency, which is output according to the input frequency x _n is the difference between the output voltage y _n.

  FIG. 5 (b) shows the high-voltage load-feature value characteristics during normal operation and failure. As shown in FIG. 5B, a threshold value (7A: one-dot chain line) can be provided between the normal feature value (7B: solid line) and the failure feature value (7C: broken line). The central processing unit 201 compares the deviation feature quantity Ec (7B or 7C) input from the feature quantity calculation unit 203 with a threshold value (7A) predetermined in the nonvolatile memory 205, and the deviation feature quantity Ec is determined. If it is smaller than the threshold value, it is determined that the high pressure generator 202 is in failure.

  When the central processing unit 201 determines that the high voltage generation unit 202 is in failure, the central processing unit 201 displays a warning that a failure may occur in the operation unit (not shown). In addition, the operation is continued while the high voltage power supply device can output the set high voltage. As a result, the user can request repair from the manufacturer after confirming the warning displayed on the operation unit. Until the repair by the manufacturer is started, if the necessary high voltage can be output, the high-voltage power supply device can operate, so that downtime due to failure can be limited to a minimum.

  As described above, in this embodiment, there is an effect that it is possible to accurately discriminate between a decrease in output voltage due to an increase in a high voltage load and a decrease in output voltage due to a failure, which could not be determined in a conventional multistage voltage doubler rectifier circuit. is there. And when it is a failure of a multistage voltage doubler rectifier circuit, the user can be notified appropriately. In this embodiment, since a multi-stage voltage doubler rectifier circuit is used, it is possible to eliminate a transformer that occupied a high proportion of cost, space, and weight, and the high-voltage power supply device can be made low-cost, small, and lightweight. In the present embodiment, the circuit configuration, the operation waveform, the circuit operation, and the failure detection method of the high-voltage power supply device have been described. As described above, in this embodiment, it is possible to configure a high voltage power supply device capable of detecting a failure by a simple method.

  As described above, according to this embodiment, it is possible to accurately determine the failure of the multistage voltage doubler rectifier circuit.

  In the second embodiment, the basic configuration other than the feature amount detection method performed by the feature amount calculation unit 203 is the same as that in the first embodiment, and thus detailed description regarding the basic configuration is omitted. The present embodiment is different from the first embodiment in that the curvature of the input / output characteristic is used as the feature amount detection method.

ここでａを曲率特徴量とする。前述のように故障時には駆動周波数−高圧出力電圧特性はなだらかになるため、曲率特徴量は小さくなる。また正常時では曲率特徴量は大きくなる。本実施例では、中央演算装置２０１は、曲率特徴量ａが予め不揮発メモリ２０５に記憶されたしきい値より小さい場合に、多段倍電圧整流回路の故障であると判断する。 [Calculation of features]
First, the features of this embodiment will be described with reference to FIG. In the circuit configuration of the present embodiment, since the flyback voltage generated by voltage resonance is connected to the multistage rectifier circuit, the drive frequency (input frequency) -high voltage output voltage characteristic is a curve as shown in the figure. This curve can be approximated by, for example, the following quadratic function (Formula 2-1).

Here, a is a curvature feature amount. As described above, since the drive frequency-high voltage output voltage characteristic becomes gentle at the time of failure, the curvature feature amount becomes small. In addition, the curvature feature amount is large at normal times. In the present embodiment, the central processing unit 201 determines that the multistage voltage doubler rectifier circuit has failed when the curvature feature amount a is smaller than the threshold value stored in the nonvolatile memory 205 in advance.

Next, a method for generating an approximate quadratic function from the input / output characteristics obtained by the feature amount calculation unit 203 by detecting the high-voltage output voltage of the high-voltage generation unit 202 while sweeping the input frequency will be described. In this embodiment, for example, the least square method is used. When the approximate expression is the above-described expression 2-1, all the measurement points ((x _start , y _start ), (x ₁ , y ₁ ), (x ₂ , y ₂ ), ..., (x _n , (y _n ),..., (x _end , y _end )) are substituted into the following equation (Equation 2-1). Then, a combination of a, b, and c that minimizes T is obtained.

で与えられるため、全ての測定点に対する誤差が最小となるａ，ｂ，ｃを求め、曲線を算出すると、駆動周波数−高圧出力電圧特性に近似する曲線を求めることができる。実施例１と同様に、中央演算装置２０１は、特徴量算出部２０３が求めた曲率特徴量ａを不揮発メモリ２０５に保存してあるしきい値と比較し、曲率特徴量ａがしきい値より小さければ、高圧発生部２０２が故障であると判断する。 The error at a measurement point is

Therefore, when a, b, and c that minimize the error for all measurement points are obtained and the curve is calculated, a curve that approximates the drive frequency-high voltage output voltage characteristic can be obtained. Similar to the first embodiment, the central processing unit 201 compares the curvature feature quantity a obtained by the feature quantity calculation unit 203 with a threshold value stored in the nonvolatile memory 205, and the curvature feature quantity a is greater than the threshold value. If it is smaller, it is determined that the high pressure generator 202 is out of order.

  As described so far, according to the present embodiment, it is possible to determine the failure of the high-voltage output unit by using the curvature feature amount that approximates the drive frequency-high-voltage output voltage characteristic to a quadratic function.

  As the feature amount, the deviation feature amount Ec is calculated in the first embodiment, and the curvature feature amount a is calculated in the present embodiment. Each is an amount obtained from the input / output characteristics (FIG. 4B or FIG. 6) of the control frequency fcont output by the feature amount calculation unit 203 and the output voltage output in accordance with the control frequency fcont. This is the amount that can be separated from normal and failure. Therefore, the feature quantity is not limited to the divergence feature quantity Ec or the curvature feature quantity a, but an amount that can extract the characteristic of the input / output characteristic at the time of failure that has changed due to the failure from the normal input / output characteristic. If it is.

  As described above, according to this embodiment, it is possible to accurately determine the failure of the multistage voltage doubler rectifier circuit.

  In the third embodiment, the basic configuration other than the circuit configuration is the same as that of the first embodiment, and thus detailed description regarding the basic configuration is omitted. The present embodiment is different from the first embodiment in that the circuit configuration for outputting a negative voltage is such that the polarity of the diodes constituting the multistage voltage doubler rectifier circuit is reversed.

  The circuit configuration of the high-voltage power supply device that can output a negative voltage can be easily configured as shown in FIG. The main difference from the circuit configuration in the first embodiment capable of outputting a positive voltage is that the diodes of the rectifier circuit are connected so as to invert the polarity. Apart from this, the output voltage detection circuit and the controller 206 also need to have circuit constants and specifications corresponding to the negative voltage. Further, when the rectifier circuit is multistage, it is necessary to invert the polarities of all the diodes. This can also be seen from a comparison of FIG. 1 and FIG. 7A that the diodes D101, D102, D103, D104, and D105 are inverted. By configuring the multi-stage voltage doubler rectifier circuit in this way, it is possible to extract a negative stable voltage at the output terminal 104 (Vout).

  As shown in FIGS. 7B and 7C, also in this embodiment, the central processing unit 201 uses the divergence feature amount Ec described in the first embodiment to cause the high-voltage generator 202 to fail. Judgment can be made. Even when the high-voltage output voltage is a negative voltage as in this embodiment, the curve indicating the drive frequency-high-voltage output voltage characteristic at the time of failure tends to be gentler than when it is normal. That is, in the present embodiment, a graph is shown in which the vertical axis of FIG. Since the high-voltage output voltage is a negative voltage, the deviation feature amount Ec is also a negative number as shown in FIG.

  FIG. 7C shows the high-voltage load-feature quantity characteristics in normal and failure conditions. As shown in FIG. 7C, a threshold value (11A: one-dot chain line) can be provided between the normal feature quantity (11B: solid line) and the fault feature quantity (11C: broken line). The controller 206 compares the deviation feature amount Ec (11B or 11C) output from the feature amount calculation unit 203 with a predetermined threshold value (11A: one-dot chain line). If the central processing unit 201 determines that the deviation feature amount Ec is greater than the threshold value, the central processing unit 201 determines that the high voltage generation unit 202 is in failure. Also in the present embodiment, the curvature feature amount a of the second embodiment can be used as the feature amount. As described above, according to the present embodiment, even if the high voltage output unit has a circuit configuration that outputs a negative voltage, it is possible to determine a failure of the high voltage output unit.

  As described above, according to this embodiment, it is possible to accurately determine the failure of the multistage voltage doubler rectifier circuit.

  Example 4 will be described with reference to FIG. However, the description of the same contents as those in the first embodiment is omitted. The circuit of the present embodiment is the same as the circuit diagram of the first embodiment shown in FIG. The main difference from the first embodiment is that, as a method of output voltage control, the off time toff of the pulse signal of the control frequency input to the gate terminal of the field effect transistor Q101 is fixed and only the on time ton is variable. It is.

  FIG. 8 is an operation waveform of each part shown in FIG. 1, and is an operation waveform of the present embodiment. A low voltage output (upper part of the figure) and a high voltage output (lower part of the figure) are separately illustrated. First, 12A and 12E are voltage waveforms (gate voltage waveforms) applied from the controller 206 to the gate of the field effect transistor Q101. When field effect transistor Q101 is turned on, a current flows from power supply voltage Vcc to inductor L100. Waveforms (drain currents) representing the drain current flowing through the field effect transistor Q101 at this time are 12B and 12F. That is, energy is stored in the inductor L100 in accordance with the current flowing time. Next, when the field effect transistor Q101 is turned off, voltage resonance occurs between the capacitor C100 and the inductor L100. The drain voltage waveforms of the field effect transistor Q101 at this time are 12C and 12G. Due to the voltage resonance, the maximum value V2a or V2c of the flyback voltage of the resonance circuit becomes a voltage value several times the power supply voltage Vcc. Further, by setting the resonance voltage to be 0 V or less so that the next on-time of the field effect transistor Q101 starts, it is possible to efficiently supply the voltage to the subsequent circuit without performing hard switching. The voltage generated by this resonance circuit is boosted by the number of rectification stages in the subsequent rectification circuit. The voltage waveform that has passed through the rectifier circuit and is smoothed and stabilized by the smoothing capacitor C106 becomes a voltage waveform (waveform of high voltage output) represented by 12D and 12H at the output terminal 104 (Vout), and the voltage V2b or V2d is Is output.

  Next, the operation when the control frequency input from the controller 206 to the gate terminal of the field effect transistor Q101 is variably controlled will be described. The output voltage control by frequency can be performed by lowering the control frequency when increasing the output voltage, and by increasing the control frequency when decreasing the output voltage. More specifically, when the control frequency is lowered, energy is stored in the inductor L100 as the on-time ton of the field effect transistor Q101 becomes longer, and the maximum value of the flyback voltage waveform of the resonance circuit is increased. Also gets higher. That is, the voltage output from the output terminal 104 increases. Conversely, as the control frequency increases, the energy stored in the inductor L100 decreases as the ON time ton of the field effect transistor Q101 decreases, and the maximum value of the flyback voltage waveform of the resonant circuit also decreases. That is, the voltage output from the output terminal 104 becomes low. In this way, it is possible to control the output voltage by changing the control frequency.

  At this time, when the control frequency is increased while the duty ratio of the control frequency on (ON) and off (OFF) is fixed, the on-time ton and the off-time toff of the field effect transistor Q101 are similarly shortened. For this reason, when the frequency increases to a certain region, the drain voltage of the field effect transistor Q101 is turned on with a potential, and hard switching occurs. Thus, when hard switching occurs with a high drain voltage, a loss increases due to a current flowing between the drain and source at the moment of turning on.

Therefore, in this embodiment, as shown in FIG. 8, the off time toff when the flyback voltage is generated is fixed, and only the on time ton is set so that the flyback voltage is turned on after the flyback voltage drops to 0 V or less. Variable control is used. The off time toff is set to be longer than the time width of the flyback voltage waveform determined by the resonance frequency of the voltage resonance circuit constituted by the inductor L100 and the capacitor C100. The relationship between the on time ton1 at the time of low voltage output and the on time ton2 at the time of high voltage output is as follows:
ton1 <ton2
Control to be

  As a result, the occurrence of hard switching can be prevented in the frequency range in which the output voltage can be controlled, so that safe and stable output voltage control with reduced circuit loss is possible. In the present embodiment, the ON time ton of the control frequency fcont output to the control frequency input terminal 103 is also variable when performing the failure detection process of the multistage voltage doubler rectifier circuit. The feature amount calculation unit 203 sweeps the control frequency with the on-time ton variable, and calculates the deviation feature amount Ec described in the first embodiment and the curvature feature amount a described in the second embodiment as the feature amount. Then, the central processing unit 201 determines whether or not there is a failure in the multistage voltage doubler rectifier circuit based on the feature amount and the threshold value.

  As described so far, according to the present embodiment, even when the control frequency OFF time toff applied to the high voltage output unit is fixed and only the ON time ton is variable, the failure of the high voltage generation unit 202 is determined. can do. This embodiment can also be applied to the circuit configuration for outputting the negative voltage of the third embodiment.

  As described above, according to this embodiment, it is possible to accurately determine the failure of the multistage voltage doubler rectifier circuit.

  The high-voltage power supply apparatus described in the first to fourth embodiments can be applied to, for example, a high-voltage power supply apparatus for an image forming apparatus (electrophotographic system). In this case, the high-voltage power supply device supplies power to a charging member, a developing member, a transfer member, and the like as a high voltage output target (load). The configuration of the image forming apparatus to which the high-voltage power supply device according to the first to fourth embodiments is applied will be described below.

[Configuration of Image Forming Apparatus]
A laser beam printer will be described as an example of the image forming apparatus. FIG. 9 shows a schematic configuration of a laser beam printer which is an example of an electrophotographic printer. The laser beam printer 300 includes a photosensitive drum 311 as a photosensitive member on which an electrostatic latent image is formed by an exposure device 313 (exposure unit), and a charging unit 317 (charging unit) that uniformly charges the photosensitive drum 311. . The laser beam printer 300 includes a developing unit 312 (developing unit) that develops the electrostatic latent image formed on the photosensitive drum 311 with toner. The toner image developed on the photosensitive drum 311 is transferred to a sheet (not shown) as a recording material (image carrier) supplied from the cassette 316 by a transfer unit 318 (transfer means), and transferred to the sheet. The image is fixed by the fixing device 314 and discharged to the tray 315. The photosensitive drum 311, the charging unit 317, the developing unit 312, and the transfer unit 318 are image forming units. The laser beam printer 300 includes a power supply device (not shown in FIG. 9) described in the first to fourth embodiments. Note that the image forming apparatus to which the high-voltage power supply apparatus according to the first to fourth embodiments can be applied is not limited to the one illustrated in FIG. 9, and may be an image forming apparatus including a plurality of image forming units, for example. Further, the image includes a primary transfer portion that transfers the toner image on the photosensitive drum 311 to an intermediate transfer belt (image carrier) and a secondary transfer portion that transfers the toner image on the intermediate transfer belt to a sheet (image carrier). It may be a forming device.

  The high-voltage power supply devices described in Embodiments 1 to 4 supply power to the charging unit 317, the developing unit 312 and the transfer unit 318. That is, the charging unit 317, the developing unit 312, and the transfer unit 318 are connected as loads to the output terminals 104 of the first to fourth embodiments.

[Failure determination processing in image forming apparatus]
The controller 206 described in FIG. 2 according to the first exemplary embodiment corresponds to, for example, an engine controller in the image forming apparatus. The detection voltage output from the output voltage detection terminal 102 of the high voltage generation unit 202 of the high voltage power supply device is converted into a digital detection voltage 207 by the output voltage detection unit 204 and output to the feature amount calculation unit 203. The feature amount calculation unit 203 detects the output voltage while sweeping the control frequency, calculates the feature amount, for example, the divergence feature amount Ec described in the first embodiment or the curvature feature amount a described in the second embodiment, Output to the central processing unit 201. The central processing unit 201 determines whether or not there is a failure in the multistage voltage doubler rectifier circuit based on the feature amount and the threshold value stored in advance in the nonvolatile memory 205.

  Some image forming apparatuses have a self-diagnosis mode in which various checks are performed after power is turned on. In such an image forming apparatus, the process for determining whether or not the multi-stage voltage doubler rectifier circuit is faulty executed by the engine controller is performed, for example, in the self-diagnosis mode. As a result, it is possible to determine whether or not the multi-stage voltage doubler rectifier circuit of the power supply device is faulty at a stage after the image forming apparatus is powered on. Further, the determination process of whether or not the multi-stage voltage doubler rectifier circuit has failed may be performed before the image forming operation is performed. As a result, it is possible to determine whether or not the multi-stage voltage doubler rectifier circuit of the power supply device is out of order before performing the image forming operation.

  As described above, according to this embodiment, it is possible to accurately determine the failure of the multistage voltage doubler rectifier circuit of the power supply device mounted on the image forming apparatus.

206 Controllers C101 to C105 Capacitors D101 to D105 Diode L100 Inductor Q101 Field-effect transistor R101 Voltage detection resistor

Claims (7)

An inductive element for generating a voltage;
A switching element for turning on and off a voltage applied to the inductive element;
A booster circuit having a plurality of capacitive elements and a plurality of rectifying elements, and boosting a voltage generated in the inductive element;
Detecting means for detecting a voltage output from the booster circuit;
Control means for controlling the frequency of a pulse signal output for turning on and off the switching element based on the voltage value detected by the detection means;
With
The control means detects the voltage by the detection means while changing the frequency of the pulse signal, calculates a feature amount based on the frequency of the pulse signal and the detected voltage, and the boost circuit based on the calculated feature amount A power supply apparatus characterized by determining a failure of the power supply.   The control means measures the input / output characteristic that is a correspondence relationship between the frequency and the voltage when the voltage is detected by the detection means by performing the change of the frequency of the pulse signal, and sets the frequency when the change is started. A straight line that passes through the voltage output in response to the voltage output in accordance with the frequency when the change is completed is calculated, and the feature value is calculated based on the amount of deviation between the input / output characteristics and the straight line The power supply device according to claim 1.   The control means measures an input / output characteristic corresponding to a frequency and a voltage when the voltage is detected by the detection means by performing the change of the frequency of the pulse signal, and calculates the curvature of the input / output characteristic as a feature amount. The power supply device according to claim 1, wherein:   4. The power supply device according to claim 1, wherein the booster circuit outputs a positive voltage. 5.   4. The power supply device according to claim 1, wherein the booster circuit outputs a negative voltage. 5.   The power supply apparatus according to claim 1, wherein the control unit makes the ON time of the pulse signal variable. A photoreceptor,
Charging means for charging the photoreceptor;
An exposure unit that forms an electrostatic latent image on the photoreceptor charged by the charging unit;
Developing means for developing the electrostatic latent image formed by the exposure means with toner;
Transfer means for transferring the toner image developed by the developing means to an image carrier;
An image forming apparatus comprising:
A power supply device according to any one of claims 1 to 6, comprising:
The image forming apparatus, wherein the power supply device supplies power to at least one of the charging unit, the developing unit, and the transfer unit.

Images