JP2021196465A - Power supply device and image forming apparatus - Google Patents

Abstract

To control the drive of a cooling fan to achieve quietness.SOLUTION: A power supply device comprises: a transformer that has primary winding and secondary winding; an input voltage detection unit that detects an input voltage output from a smoothing capacitor and applied to the primary winding of the transformer; a temperature detection unit that detects a temperature of the transformer; a cooling unit that cools the transformer; and a control unit 9 that controls the cooling unit based on results of detection performed by the temperature detection unit and the input voltage detection unit. The control unit 9 controls the cooling unit 8 (S108) based on a temperature increase rate (S107) in a period from a time t1 to a time t2 calculated based on a temperature T1 detected by the temperature detection unit at the time t1 and a temperature T2 detected by the temperature detection unit at the time t2, the temperature T2 (S106), and an input voltage (S101) detected by the input voltage detection unit 6.SELECTED DRAWING: Figure 4

Description

The present invention relates to a power supply device and an image forming apparatus including a power supply device.

An image forming device equipped with a power supply device or a power supply device detects the temperature of the transformer of the power supply device and drives a cooling fan according to the detected temperature of the transformer to cool the transformer and prevent the temperature of the transformer from rising. (For example, see Patent Document 1).

Japanese Unexamined Patent Publication No. 2014-106293

In the image forming apparatus, the temperature of the transformer is detected in order to determine whether or not it is necessary to drive the cooling fan to cool the transformer. As a method of detecting the temperature of the transformer, there are a method of directly detecting the temperature of the transformer by connecting a temperature sensor such as a thermistor to the transformer, and a simple method of indirectly detecting the temperature of a component near the transformer. However, in the method of directly detecting the temperature of the transformer, it is necessary to connect the transformer and the temperature sensor in consideration of insulation, so that the connection method and the configuration may be complicated. On the other hand, in the case of a method of indirectly detecting the temperature of a component near the transformer, even if the temperature detected by the temperature sensor is the same, for example, when the input voltage is low, the temperature rise rate of the transformer becomes large. , The temperature rise rate of the transformer differs depending on the input voltage of the transformer. Therefore, when the cooling fan is driven when the input voltage is low, the driving time of the cooling fan becomes long, and as a result, the time during which the wind noise of the cooling fan that is offensive to the ear is generated also becomes long. If the cooling fan is controlled based only on the temperature detected by the temperature sensor and the temperature rise rate, the cooling fan is driven even when it is not necessary to drive the cooling fan, and the wind noise of the cooling fan is generated. It may end up.

The present invention has been made under such circumstances, and an object of the present invention is to control the drive of a cooling fan to reduce noise.

In order to solve the above-mentioned problems, the present invention has the following configurations.

(1) A power supply device to which an AC voltage is input and outputs a DC voltage, which has a primary winding and a secondary winding, and is input from an AC power supply and a transformer in which the primary side and the secondary side are insulated. The rectifying and smoothing means for rectifying and smoothing the AC voltage, the voltage detecting means for detecting the input voltage output from the rectifying and smoothing means and applied to the primary winding of the transformer, and the temperature of the transformer. The temperature detecting means for detecting, a cooling means for cooling the transformer, the temperature detecting means, and a control means for controlling the cooling means based on the result detected by the voltage detecting means are provided. The control means includes a first temperature detected by the temperature detecting means in the first time, a second temperature detected by the temperature detecting means in the second time after detecting the first temperature, and the like. The cooling is based on the temperature rise rate during the period from the first time to the second time calculated based on the above, the second temperature, and the input voltage detected by the voltage detecting means. A power supply device characterized by controlling means.

(2) Control the image forming portion that forms an image by transferring the toner image to the sheet, the fixing portion that heats and pressurizes the toner image transferred onto the sheet to fix the image on the sheet, and the image forming portion. An image forming apparatus comprising: a control unit, the image forming unit, the fixing unit, and the power supply device according to (1), which supplies the DC voltage to the control unit.

According to the present invention, it is possible to control the drive of the cooling fan to reduce the noise.

Block diagram showing the configuration of the power supply device of the first embodiment A circuit diagram showing the configuration of the power supply device of the first embodiment. The figure explaining the input voltage of the transformer of the power supply apparatus of Examples 1 and 2, the temperature in the vicinity of a transformer, and the temperature rise rate. A flowchart showing a control sequence for acquiring drive control information of the cooling units of the first and second embodiments. A flowchart showing a control sequence of drive control of the cooling unit of the first and second embodiments. Sectional drawing which shows the structure of the image forming apparatus of Example 2. A block diagram showing the configuration of the image forming apparatus and the power supply apparatus of the second embodiment. A circuit diagram showing a configuration of a fixing portion of the power supply device and the image forming device of the second embodiment. The figure explaining the signal waveform of the fixing part of the image forming apparatus of Example 2. A flowchart showing a control sequence for acquiring the input voltage of the transformer of the second embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Overview of power supply]
FIG. 1 is a block diagram showing the configuration of the power supply device 100 of the first embodiment. In FIG. 1, the commercial AC power supply 1 is an AC power supply that supplies an AC voltage Vac to the power supply device 100. The power supply device 100 includes a rectifying unit 2, a smoothing unit 3, and a switching unit 4. The rectifying unit 2 is composed of a bridge diode that rectifies the AC voltage Vac input from the commercial AC power supply 1. The smoothing unit 3 is composed of a smoothing capacitor that smoothes the voltage rectified by the rectifying unit 2. The rectifying unit 2 and the smoothing unit 3 constitute a rectifying and smoothing means. The switching unit 4, which is a switching means, converts the DC voltage Vdc (hereinafter referred to as voltage Vdc) input from the smoothing unit 3 into a DC output voltage Vout by a switching operation. The load 5 is a unit to which an output voltage Vout is supplied from the power supply device 100, and is a unit that consumes power of an information processing device such as a computer or an image input / output device such as an image scanner or a printer. The input voltage detecting unit 6 which is a voltage detecting means detects the voltage Vdc input from the smoothing unit 3 to the switching unit 4. A thermistor is used in the temperature detecting unit 7 which is a temperature detecting means, and detects the temperature of the switching unit 4. In the following, the temperature detection unit 7 will be the thermistor 7. The cooling unit 8 which is a cooling means cools the switching unit 4 whose temperature rises due to heat generation due to the switching loss by blowing air.

The control unit 9 which is a control means controls the operation of the load 5, the output voltage Vout is input from the switching unit 4, and the voltage signal corresponding to the input voltage Vdc is input from the input voltage detection unit 6. The control unit 9 temporarily holds information in a central processing unit (hereinafter referred to as CPU) that controls the operation of the load 5, a non-volatile memory (hereinafter referred to as ROM) in which programs and data instructing operation procedures are stored, and information. It has a volatile memory (hereinafter referred to as RAM). The control unit 9 may be a one-chip microcomputer in which a CPU, ROM, and RAM are integrated. Further, the control unit 9 is provided with a terminal having an analog-to-digital conversion (hereinafter referred to as A / D conversion) function for converting an input analog signal into a digital signal. The storage unit 10 which is a storage means is a rewritable non-volatile memory, and stores information necessary for the operation of the control unit 9. As shown in FIG. 1, the storage unit 10 may be a part of a one-chip microcomputer arranged inside the control unit 9. Further, the information equivalent to the information stored inside the storage unit 10 may be stored in a ROM (not shown), and the storage unit 10 may not be provided inside the control unit 9.

[Power supply configuration]
FIG. 2 is a circuit diagram showing a circuit configuration of the power supply device 100 of FIG. In the switching unit 4, the switching element 11b repeats the conduction state and the non-conduction state to perform the switching operation of the transformer 12. As the switching element 11b, for example, a switching element such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is used. Further, the switching control IC 11a is an IC that controls the switching operation of the switching element 11b.

The switching transformer 12 (hereinafter referred to as a transformer 12) has a primary winding 12a, an auxiliary winding 12b, and secondary windings 12c and 12d connected in series, and the primary side and the secondary side are electrically connected to each other. It has an insulated structure. The AC voltage Vac input from the commercial AC power supply 1 is full-wave rectified by the bridge diode 2, input to the smoothing capacitor 3, and smoothed. The potential on the high potential side of the smoothing capacitor 3 is DCH, and the potential on the low potential side is DCL.

A DC voltage voltage Vdc is applied to the primary winding 12a from the smoothing capacitor 3 by the switching operation of the switching element 11b. Then, a DC voltage proportional to the number of turns of each winding is output to the auxiliary winding 12b of the transformer 12 and the secondary windings 12c and 12d. The rectifier circuit 13 is a circuit that rectifies the DC voltage output from the secondary windings 12c and 12d, and in this embodiment, a diode (hereinafter, also referred to as a diode 13) is used. The capacitor 14 smoothes the voltage rectified by the rectifier circuit 13, and the charging voltage of the capacitor 14 is supplied to the load 5 as an output voltage Vout. Further, the output voltage Vout is input to the power supply terminal VCC2 of the control unit 9 and is supplied as a power supply voltage for operating the control unit 9.

The input voltage detection unit 6 has a diode 60, a capacitor 61, and resistors 62 and 63. In the diode 60, the anode terminal is connected to a connection point to which one end of the secondary winding 12c and one end of the secondary winding 12d are connected, and the cathode terminal is connected to one end of the capacitor 61 and one end of the resistor 62. The other end of the capacitor 61 is connected to the anode terminal of the diode 13. One end of the resistor 62 is connected to the cathode terminal of the diode 60 and one end of the capacitor 61, and the other end is connected to one end of the resistor 63. The other end of the resistor 63 is connected to the other end of the capacitor 61, and the cathode terminal is connected to the anode terminal of the diode 13 connected to the secondary winding 12c. Further, the connection point to which the other end of the resistor 62 and one end of the resistor 63 are connected is connected to the ACDET terminal of the control unit 9.

The input voltage detection unit 6 rectifies the output voltage Vout charged in the capacitor 14 and the forward voltage output from the secondary winding 12d by the diode 60, and smoothes them by the capacitor 61. The charging voltage of the capacitor 61 is a voltage obtained by superimposing a voltage proportional to the voltage Vdc charged in the smoothing capacitor 3 applied to the primary winding 12a of the transformer 12 and an output voltage Vout. The voltage charged in the capacitor 61 is divided by the resistors 62 and 63, and the divided voltage is input to the ACDET terminal of the control unit 9. The control unit 9 A / D-converts the DC voltage (hereinafter referred to as ACDET voltage) input to the ACDET terminal and acquires it as voltage data.

The thermistor 7 is arranged in the vicinity of the rectifier circuit 13 provided on the secondary side of the transformer 12, and indirectly detects the temperature of the transformer 12 by detecting the temperature in the vicinity of the rectifier circuit 13. The position where the thermistor 7 is arranged is not limited to the vicinity of the rectifier circuit 13, and may be arranged, for example, in the vicinity of the switching element 11b or the transformer 12 to indirectly detect the temperature of the transformer 12. .. One end of the pull-up resistor 71 is connected to the output voltage Vout, and the other end is connected to the thermistor 7 and the TDET terminal of the control unit 9. A voltage obtained by dividing the output voltage Vout by the pull-up resistor 71 and the thermistor 7 is input to the TDET terminal of the control unit 9. The resistance value of the thermistor 7 changes as the temperature around the rectifier circuit 13 changes. Therefore, the temperature of the transformer 12 changes, and the temperature of the rectifier circuit 13 installed in the vicinity of the transformer 12 changes accordingly, so that the resistance value of the thermistor 7 changes, and as a result, the TDET terminal of the control unit 9 changes. The input voltage (hereinafter referred to as TDET voltage) also changes. The control unit 9 A / D-converts the TDET voltage and acquires it as the temperature data of the transformer 12.

The cooling unit 8 has a cooling fan 81 and a transistor 82 that controls the drive of the cooling fan 81. The control unit 9 drives or stops the cooling fan 81 by setting the transistor 82 in the on state or the off state by the signal output from the FAN_DRV terminal. When the cooling fan 81 is driven, air is blown in the direction of the white arrow in the figure to cool the transformer 12 and other parts that are components of the power supply device 100.

The photocoupler 15 has a light emitting diode and a phototransistor that operates with light from the light emitting diode. A voltage obtained by dividing the output voltage Vout by the resistors 17 and 18 is input to the shunt regulator 16. The shunt regulator 16 compares the internal reference voltage with the input voltage, and sets a conduction or non-conduction state according to the comparison result. The light emitting diode of the photocoupler 15 is in a conductive state when the shunt regulator 16 is in a conductive state, and the phototransistor is also turned on. On the other hand, when the shunt regulator 16 is in the non-conducting state, the light emitting diode of the photocoupler 15 is in the non-conducting state, and the phototransistor is also in the off state. In this way, the photocoupler 15 feeds back the state of the output voltage Vout as an FB signal to the FB terminal of the switching control IC 11a. Then, the switching control IC 11a controls the switching operation of the switching element 11b according to the FB signal. The resistor 19 is a current limiting resistor.

A rectifying smoothing circuit composed of a diode 20 and a capacitor 21 is connected to the auxiliary winding 12b of the transformer 12, and the voltage induced in the auxiliary winding 12b is charged to the capacitor 21 as a power supply voltage Vfb. The capacitor 21 is connected to the power supply terminal VCC1 of the switching control IC 11a, and the power supply voltage Vfb is supplied as a voltage for operating the switching control IC 11a.

The resistors 22 and 23 are resistors for detecting the current flowing through the primary winding 12a of the transformer 12 when the switching element 11b is in a conductive state. The switching control IC 11a switches the switching element 11b based on the IS signal input to the IS terminal via the resistor 23 and the FB signal input to the FB terminal described above when the switching element 11b is in a conductive state. Control the operation. The switching control IC 11a compares the internal current detection threshold voltage with the voltage value of the IS signal, and if the voltage of the IS signal is lower than the threshold voltage, the switching element 11b is set to the conduction state. On the other hand, the switching control IC 11a controls the switching element 11b to be set to the non-conducting state when the voltage of the IS signal is equal to or higher than the threshold voltage. Immediately after the AC voltage Vac is supplied from the commercial AC power supply 1, the switching control IC 11a inputs the power supply voltage for operating the switching control IC 11a via the ST terminal connected to the smoothing capacitor 3. After that, the switching control IC 11a starts operation as the voltage of the voltage Vdc charged in the smoothing capacitor 3 rises.

The control unit 9 controls the load 5 to which the output voltage Vout is supplied from the power supply device 100 via the CTRL signal. For example, when the CTRL signal output from the control unit 9 is in the low level state, the load 5 is in the light load state in which the power consumption is extremely small. When the load 5 is in a light load state, the temperature rise of the transformer 12 and the rectifier circuit 13 is small even if the control unit 9 sets the cooling fan 81 of the cooling unit 8 to the stopped state. On the other hand, when the CTRL signal output from the control unit 9 is in a high level state, the load 5 is in a load state in which the amount of power consumption is large, and the temperatures of the transformer 12 and the rectifier circuit 13 rise. When the temperatures of the transformer 12 and the rectifier circuit 13 rise, it may be necessary to drive the cooling fan 81 of the cooling unit 8 to cool the power supply device 100 in order to prevent destruction due to heat. And. Although the control unit 9 is externally attached to the power supply device 100 in FIG. 2, it may be built in as a part of the power supply device 100.

[Temperature rise according to input voltage]
FIG. 3 shows the temperature change of the transformer 12 corresponding to the input voltage Vdc input from the smoothing capacitor 3 and the temperature change of the thermistor 7 in a state where the load 5 is consuming the electric power supplied from the power supply device 100. It is a graph. In FIG. 3, the graph shown by the thin solid line is a graph showing the temperature change of the thermistor 7. The graph shown by the thick solid line is a graph showing the temperature change of the transformer 12 when the input voltage Vdc is high. On the other hand, the graph shown by the alternate long and short dash line is a graph showing the temperature change of the transformer 12 when the input voltage Vdc is low. The vertical axis of FIG. 3 indicates the temperature, T0, T1 and T2 indicate the temperature of the transformer 12, and THmax indicates the maximum temperature (threshold value) of the thermistor 7. The horizontal axis of FIG. 3 indicates time, and t0, t1, t2, and tmax indicate time (timing).

When the load 5 consumes electric power, the temperature of the transformer 12 of the switching unit 4 of the power supply device 100 that supplies electric power to the load 5 rises. As shown in FIG. 3, even if the power consumption in the load 5 is the same, when the input voltage Vdc is low, the conduction state time of the switching element 11b becomes longer than when the input voltage Vdc is high. As a result, the power loss of the transformer 12 becomes large, and the temperature of the transformer 12 becomes high. Since the temperature of the thermistor 7 arranged in the vicinity of the rectifier circuit 13 has a constant output voltage Vout, it is assumed that the influence of the input voltage Vdc is small when the power consumption of the load 5 is the same.

In FIG. 3, when the power consumption in the load 5 starts from the time t0, the temperature of the transformer 12 rises and the temperature of the rectifier circuit 13 also rises, and the temperature of the thermistor 7 installed in the vicinity of the rectifier circuit 13 rises at the time t0. The temperature rises from T0 in. In FIG. 3, the temperature of the thermistor 7 is the temperature T1 which is the first temperature at the time t1 which is the first time, and the temperature T2 which is the second temperature at the time t2 which is the second time after which the time has elapsed. It shows that there is. Assuming that the temperature change rate of the thermistor 7 from the time t0 to the time t1 is ΔT1, the temperature change rate ΔT1 = (temperature T1-temperature T0) / (time t1-time t0). On the other hand, assuming that the temperature change rate of the thermistor 7 from the time t1 to the time t2 is ΔT2, the temperature change rate ΔT2 = (temperature T2-temperature T1) / (time t2-time t1). As shown in FIG. 3, the temperature change rate ΔT1 from the time t0 to the time t1 immediately after the start of power consumption in the load 5 is larger than the temperature change rate ΔT2 from the time t1 to the time t2 thereafter. The relationship (temperature change rate ΔT1> temperature change rate ΔT2). Regarding the temperature change of the transformer 12, similarly to the temperature change of the thermistor 7, the initial temperature change rate (temperature rise rate) at the start of power consumption in the load 5 is larger than the subsequent temperature change rate.

Further, as shown in FIG. 3, when the input voltage Vdc of the transformer 12 is low, the temperature and the temperature change rate of the transformer 12 are larger than those where the input voltage Vdc is high. If the transformer 12 exceeds the upper limit temperature defined by the safety standard, the insulation function of the transformer 12 may deteriorate. Therefore, before the temperature of the thermistor 7 reaches the upper limit temperature, it is necessary to drive the cooling fan 81 of the cooling unit 8 to cool the transformer 12. As shown in FIG. 3, when the input voltage Vdc of the transformer 12 is high, the temperature of the transformer 12 may not exceed the upper limit temperature of the transformer 12 even if the temperature of the thermistor 7 reaches the temperature THmax at the time tmax. be. In this case, the control unit 9 does not need to drive the cooling fan 81 of the cooling unit 8, it is possible to avoid the generation of the operating noise of the cooling fan 81, and it is possible to reduce the noise. Therefore, the control unit 9 needs to control the drive of the cooling fan 81 based not only on the temperature and the temperature rise rate of the transformer 12 but also on the input voltage Vdc of the transformer 12.

When the position of the thermistor 7 is closer to the transformer 12, the temperature change of the thermistor 7 in FIG. 3 is lower than the temperature change when the input voltage Vdc is high. In that case, the upper limit temperature (threshold value) of the thermistor 7 is a temperature lower than the upper limit temperature THmax in FIG. 3, and is set to a temperature lower than the temperature of the transformer 12 when the input voltage Vdc is high at the time tmax.

[Drive control of cooling fan of cooling unit]
FIG. 4 is a flowchart showing a control sequence for determining the drive control of the cooling fan 81 of the cooling unit 8 based on the input voltage Vdc of the transformer 12 and the temperature and the temperature change rate of the thermistor 7 that detects the temperature in the vicinity of the transformer 12. Is. The process shown in FIG. 4 is started when an AC voltage Vac is supplied from the commercial AC power supply 1 and starts operation of the power supply device 100, and is always executed by the control unit 9 while the power supply device 100 is operating. The storage unit 10 of the control unit 9 stores a table in which information corresponding to the TDET voltage input to the TDET terminal of the control unit 9 connected to the thermistor 7 and the temperature of the thermistor 7 is stored. ing. Further, the storage unit 10 of the control unit 9 stores an information table associating the input voltage Vdc of the transformer 12, the temperature and temperature change rate of the thermistor 7, and the control information for controlling the cooling unit 8. It is assumed that there is. The details of the information table will be described later.

In step 101 (hereinafter referred to as S) 101, the control unit 9 acquires the ACDET voltage input to the ACDET terminal from the input voltage detection unit 6. In S102, the control unit 9 acquires the TDET voltage input to the TDET terminal in order to detect the temperature of the rectifier circuit (diode 13) installed in the vicinity of the transformer 12 detected by the thermistor 7. In S103, the control unit 9 acquires the temperature of the thermistor 7 corresponding to the TDET voltage acquired in S102 from the table stored in the storage unit 10, and sets the acquired temperature of the thermistor 7 as the temperature T1. Then, the control unit 9 resets the timer and starts it.

In S104, the control unit 9 refers to the timer and determines whether or not the waiting time set in advance as the time tw has elapsed. The time tw is the time from the time t1 to the time t2 in FIG. 3 (time tw = time t2-time t1). The control unit 9 advances the process to S105 when it is determined that the waiting time tw has elapsed, and returns the process to S104 when it is determined that the waiting time tw has not elapsed. In S105, the control unit 9 acquires the TDET voltage input to the TDET terminal in order to detect the temperature of the rectifier circuit 13 detected by the thermistor 7.

In S106, the control unit 9 acquires the temperature of the thermistor 7 corresponding to the TDET voltage acquired in S105 from the table stored in the storage unit 10, and sets the acquired temperature of the thermistor 7 as the temperature T2. In S107, the control unit 9 calculates the temperature change rate ΔT of the thermistor 7 by using the temperatures T1 and T2 of the thermistor 7 acquired in S103 and S106. The control unit 9 calculates the temperature change rate ΔT using the equation ΔT = (temperature T2-temperature T1) / hour tw. In S108, the control unit 9 controls the temperature T2 of the thermistor 7 at time t2, the temperature change rate ΔT, and the control information of the cooling unit 8 corresponding to the ACDET voltage acquired in S101 from the information table stored in the storage unit 10. Acquires fc and ends the process.

FIG. 5 is a flowchart showing a control sequence for performing drive control (cooling control) of the cooling fan 81 provided in the cooling unit 8 according to the control information fc of the cooling unit 8 acquired in the process of FIG. The process of FIG. 5 is always executed by the control unit 9 while the power supply device 100 is operating.

In S201, the control unit 9 determines whether the control information fc of the cooling unit 8 acquired in S108 of FIG. 4 is 1 (driving the cooling fan 81). When the control unit 9 determines that the control information fc is 1, the control unit 9 advances the process to S202 in order to drive the cooling fan 81. On the other hand, when it is determined that the control information fc is not 1 (the control information fc is 0 (the cooling fan 81 is stopped)), the process proceeds to S203 in order to stop the cooling fan 81. In S202, the control unit 9 sets the transistor 82 to the ON state by the signal output from the FAN_DRV terminal, drives the cooling fan 81, and ends the process. In S203, the control unit 9 sets the transistor 82 to the off state by the signal output from the FAN_DRV terminal, stops the driving of the cooling fan 81, and ends the process.

[Control information table]
Table 1 is a table showing an example of the information table used in the process of S108 of FIG. Table 1 is a table for acquiring the control information fc of the cooling fan 81 of the cooling unit 8 based on the ACDET voltage, the temperature change rate ΔT, and the temperature of the thermistor 7 at the time t2 indicated by the TDET voltage. Is.

Table 1 shows the temperature (unit: ° C.) of the thermistor 7 indicated by the TDET voltage (unit: V), the temperature change rate of the thermistor 7 ΔT (unit: ° C./s), and the ACDET voltage (unit: V). It is composed of items of input voltage Vdc (unit: V) of the transformer 12.

In Table 1, the temperature column of the thermistor 7 is divided into 30 ° C., ..., 60 ° C., ..., 80 ° C., ..., 90 ° C., 95 ° C. or higher. The temperature of the thermistor 7 of 30 ° C., 60 ° C., 80 ° C., 90 ° C., 95 ° C. or higher corresponds to the case where the TDET voltage is 2.5V, 1.43V, 0.24V, 0.10V, 0.05V or less, respectively. .. Further, in the column of the temperature change rate of the thermistor 7, the temperature change rate is 0.0, 0.1, ..., 0.5, ..., 0.9, 1.0 for each temperature of the thermistor 7. It is divided into the above.

Further, the ACDET voltage is divided into less than 1.0 V, 1.0 V or more and less than 1.2 V, ... 1.8 V or more and less than 2.0 V, and 2.0 V or more, depending on the ACDET voltage. When the ACDET voltage is less than 1.0V, 1.0V or more and less than 1.2V, 1.8V or more and less than 2.0V, and 2.0V or more, the input voltage Vdc is less than 100V, 100V or more and less than 120V, and 180V or more, respectively. It corresponds to less than 200V and more than 200V. Then, the control information fc for the cooling unit 8 is set in the column corresponding to the items of the temperature of the thermistor 7 and the temperature change rate of the thermistor 7 in the column of ACDET voltage. In Table 1, "0" and "1" set as control information fc mean stopping the cooling fan 81 and driving the cooling fan 81, respectively.

For example, the ACDET voltage acquired by the control unit 9 by the process shown in FIG. 4 is 1.0 (V), the TDET voltage is 2.5 (V), and the calculated temperature change rate ΔT is 0.1 (° C./s). And. In Table 1, when the ACDET voltage is 1.0 (V), the corresponding input voltage Vdc is 100V. Similarly, if the TDET voltage is 2.5 (V), the temperature of the thermistor 7 will be 30 (° C.). In Table 1, the ACDET voltage is 1.0 (V) (input voltage Vdc is 100V), the TDET voltage is 2.5 (V) (thermistor 7 temperature is 30 (° C.)), and the temperature change rate ΔT is 0. The control information fc of the cooling unit 8 in the case of .1 (° C./s) is "0". Therefore, in this case, the control unit 9 stops the cooling fan of the cooling unit 8 by the process shown in FIG.

Further, the ACDET voltage acquired by the control unit 9 by the process shown in FIG. 4 is 0.9 (V), and the TDET voltage is 0.1 (V). In Table 1, when the ACDET voltage is 0.9 (V), the corresponding input voltage Vdc is less than 100V. Similarly, if the TDET voltage is 0.1 (V), the temperature of the thermistor 7 will be 90 (° C.). In Table 1, when the ACDET voltage is 0.9 (V) (input voltage Vdc is less than 100V) and the TDET voltage is 0.1 (V) (thermistor 7 temperature is 90 (° C.)), the temperature change rate. The control information fc of the cooling unit 8 is "1" regardless of the numerical value of ΔT. Therefore, in this case, the control unit 9 drives the cooling fan of the cooling unit 8 by the process shown in FIG.

表１に示すように、ＴＤＥＴ電圧が０．１（Ｖ）で、入力電圧Ｖｄｃが１００Ｖ未満の場合には、温度変化率△Ｔの数値に関係なく、冷却部８の制御情報ｆｃは「１」となっている。一方、ＴＤＥＴ電圧が同じ０．１（Ｖ）でも、入力電圧Ｖｄｃが２００Ｖ以上の場合には、サーミスタ７の温度変化率が１．０（℃／ｓ）の場合を除いて、冷却部８の制御情報ｆｃは「０」となっている。このように、サーミスタ７の温度が同じでも、入力電圧Ｖｄｃの電圧値により、冷却ファン８１を駆動させる場合や停止させる場合が存在し、冷却ファン８１の制御内容が異なる。表１に示された制御内容に基づいて冷却ファン８１の制御を行うことにより、冷却ファン８１の不要な駆動が回避され、静音化を実現することができる。

As shown in Table 1, when the TDET voltage is 0.1 (V) and the input voltage Vdc is less than 100V, the control information fc of the cooling unit 8 is "1" regardless of the numerical value of the temperature change rate ΔT. ". On the other hand, even if the TDET voltage is the same 0.1 (V), when the input voltage Vdc is 200 V or more, the cooling unit 8 is provided with the exception that the temperature change rate of the thermistor 7 is 1.0 (° C./s). The control information fc is "0". As described above, even if the temperature of the thermistor 7 is the same, the cooling fan 81 may be driven or stopped depending on the voltage value of the input voltage Vdc, and the control content of the cooling fan 81 is different. By controlling the cooling fan 81 based on the control contents shown in Table 1, unnecessary driving of the cooling fan 81 can be avoided, and noise reduction can be realized.

As described above, the control unit 9 drives the cooling fan 81 that cools the transformer 12 based on the input voltage Vdc and the temperature detected by the thermistor 7 of the rectifier circuit arranged in the vicinity of the transformer 12 and the temperature change rate. The outage can be controlled appropriately. As a result, the control unit 9 drives the cooling fan 81 only when the transformer 12 of the power supply device 100 needs to be cooled, thereby shortening the time during which the wind noise of the cooling fan is generated and reducing the noise of the power supply device 100. Can be planned.

As described above, according to the present embodiment, it is possible to control the drive of the cooling fan to reduce the noise.

In the second embodiment, an example in which the power supply device described in the first embodiment is applied to the image forming apparatus will be described. Further, in the first embodiment, the input voltage was calculated based on the voltage detected inside the power supply device. In this embodiment, an example in which the input voltage is calculated based on the current value supplied from the commercial AC power supply to the fixing portion of the image forming apparatus will be described.

[Image forming device]
FIG. 6 is a cross-sectional view showing the configuration of an image forming apparatus 200 including the power supply apparatus 100 of this embodiment. The image formation control unit 201 is a control unit (CPU) that controls the image formation device 200, and temporarily holds information and a ROM in which procedures and data for controlling the image formation operation of the image formation device 200 are stored. Has RAM. The image formation control unit 201 may be configured by connecting a one-chip microcomputer in which a CPU, ROM, and RAM are integrated, or circuits having the same functions individually. The sheet 202 is a recording medium such as paper on which an image is formed. The pickup roller 203 feeds the sheet 202 when forming an image on the sheet 202, and the resist roller 204 aligns the tips of the fed sheet 202. The image forming unit 205 forms an image on the sheet 202 (on the sheet) conveyed by a known electrophotographic process. The exposure unit 205a irradiates the photoconductor 205b with a light beam to form an electrostatic latent image of an image in an electrophotographic process. The developing unit 205c adheres toner to the electrostatic latent image formed on the photoconductor 205b to form a toner image. The transfer member 205d transfers the toner image formed on the photoconductor 205b to the sheet 202.

The fixing unit 300, which is an image heating means, heats and pressurizes the toner image transferred onto the sheet 202 to fix the toner image on the sheet 202. The heater 301, which is a heating member, generates heat by being supplied with an AC voltage from the commercial AC power supply 1. The fixing film 300a, which is a film member, transfers the heat of the heater 301 to the sheet 202. The pressure roller 300b, which is a pressure member, forms a nip portion together with the fixing film 300a. The sheet 202 conveyed to the nip portion is heated by the heat from the heater 301 by the fixing film 300a, and the sheet 202 and the toner image are pressed by the pressure roller 300b, and the toner image is fixed to the sheet 202. .. The fixing storage unit 310 is a rewritable non-volatile memory arranged in the fixing unit 300, and stores resistance value R and the like which are characteristic information of the heater 301.

The discharge roller 206 discharges the sheet 202 to the discharge tray 207 provided on the upper part of the image forming apparatus 200. The sheet 208 represents a state in which the image-formed sheet 202 is discharged to the discharge tray 207 and loaded. The current detection unit 311 detects the current effective value of the current flowing from the commercial AC power supply 1 to the fixing unit 300. The motor 210 is supplied with electric power from the power supply device 100 and drives the pickup roller 203, the resist roller 204, and the image forming unit 205 that convey the sheet 202. On the other hand, the motor 211 is supplied with electric power from the power supply device 100 to drive the fixing unit 300. The pickup roller 203, the resist roller 204, the discharge roller 206, and the motors 210 and 211 constitute a transport system for transporting the sheet 202.

[Power supply configuration]
FIG. 7 is a block diagram illustrating a control relationship between the power supply device 100 provided in the image forming apparatus 200 and the fixing portion 300 of the image forming apparatus 200. The power supply device 100 shown in FIG. 7 is different from FIG. 1 of the first embodiment in that the input voltage detecting unit 6 provided inside the switching unit 4 is deleted. Further, the connection between the control unit 9, the load 5, and the cooling unit 8 is the same as in the first embodiment, and the output voltage Vout is supplied from the power supply device 100 to each device in the image forming device 200 which is the load 5. Further, in this embodiment, the control unit 9 acquires information for calculating the input voltage Vdc from the current detection unit 311. Further, in the present embodiment, the control unit 9 controls the fixing unit 300 based on the instruction from the image formation control unit 201, and the information of the fixing unit 300 from the fixing storage unit 310 provided in the fixing unit 300. To get.

[Circuit configuration of power supply]
FIG. 8 is a circuit diagram showing a circuit configuration of the power supply device 100, the current detection unit 311 and the fixing unit 300 shown in FIG. 7. As described above, the control unit 9 of the second embodiment acquires information for calculating the input voltage Vac from the current detection unit 311. Therefore, the circuit of the input voltage detection unit 6 and the secondary winding 12d of the transformer 12 are deleted from the switching unit 4 of the power supply device 100 shown in FIG. 8, and the ACDET terminal of the control unit 9 is also deleted accordingly. There is. The other circuit configurations of the power supply device 100 and the circuit configurations of the cooling unit 8 are the same as those in FIG. 2 of the first embodiment, and the description thereof will be omitted here.

The fixing unit 300 has a triac 302 which is a switch for connecting or disconnecting a current path from the commercial AC power supply 1 to the heater 301. When the triac 302 becomes conductive, the heater 301 of the fixing portion 300 is supplied with an AC voltage Vac from the commercial AC power supply 1 and generates heat. The phototriac coupler 303 sets the triac 302 to a conductive state or a non-conducting state according to a control signal output from the FSR_DRV terminal by the control unit 9 via the resistor 304. The resistors 305 and 306 are current limiting resistors that limit the current of the phototriac coupler 303 and the triac 302.

The fixing thermistor 307 is arranged in the vicinity of the heater 301 and detects the temperature of the heater 301. One end of the pull-up resistor 308 is connected to the output voltage Vout, and the other end is connected to the fixing thermistor 307 and the FSR_TH terminal of the control unit 9. A voltage obtained by dividing the output voltage Vout by a pull-up resistor 308 and a fixing thermistor 307 is input to the FSR_TH terminal of the control unit 9. The resistance value of the fixing thermistor 307 also changes as the temperature of the heater 301 changes. Therefore, as the temperature of the heater 301 changes, the resistance value of the fixing thermistor 307 also changes, and as a result, the voltage input to the FSR_TH terminal of the control unit 9 (hereinafter referred to as FSR_TH voltage) also changes. The control unit 9 A / D-converts the FSR_TH voltage, acquires it as the temperature data of the heater 301, outputs a control signal from the FSR_DRV terminal based on the acquired temperature data of the heater 301, controls the triac 302, and controls the heater. The temperature of 301 is controlled.

The zero-cross detection unit 309 detects the zero-cross timing of the voltage 0V at which the positive / negative of the AC voltage Vac input from the commercial AC power supply 1 is switched, and outputs a ZRX signal (zero-cross signal) indicating the zero-cross timing to the ZRX terminal of the control unit 9. do. The fixing storage unit 310 provided in the fixing unit 300 is connected to the COM terminal of the control unit 9 by a signal line, and the control unit 9 accesses the fixing storage unit 310 via the COM terminal to store the fixing in advance. The resistance value R of the heater 301 stored in the unit 310 is acquired.

The current detection unit 311 has a current detection circuit 312 and a current detection transformer 313. The current detection circuit 312 outputs a voltage corresponding to the current effective value Irms of the heater 301 when the triac 302 is in a conductive state to the IDET terminal of the control unit 9. The control unit 9 A / D-converts the voltage input to the IDET terminal and acquires the voltage video. The control unit 9 calculates the current effective value Irms of the fixing unit 300 by multiplying the acquired voltage video by the coefficient α (current effective value Irms = coefficient α × voltage video).

[Fixed part, signal waveform of current detection circuit]
FIG. 9 is a diagram showing signal waveforms of the fixing unit 300 and the current detection circuit 312 when an AC voltage is supplied from the commercial AC power supply 1 to the heater 301 of the fixing unit 300 of the image forming apparatus 200. In FIG. 9, (a) the commercial AC power supply voltage Vac shows the voltage waveform of the AC voltage Vac input from the commercial AC power supply 1. (B) The zero-cross signal ZRX is a signal waveform of a zero-cross signal output from the zero-cross detection unit 309 of the fixing unit 300 to the ZRX terminal of the control unit 9. The zero-cross signal ZRX is a signal that switches between high level and low each time the AC voltage of the commercial AC power supply 1 shown in (a) becomes 0V. (C) The drive signal FSR_DRV of the triac 302 is a signal output from the FSR_DRV terminal of the control unit 9 to the phototriac coupler 303, and controls the phototriac coupler 303 that controls the conduction state and the non-conduction state of the triac 302. The phototriac coupler 303 sets the triac 302 to the conductive state when the drive signal FSR_DRV is ON, and sets the Triac 302 to the non-conducting state when the drive signal FSR_DRV is OFF. (D) The current effective value of the heater 301 is a waveform indicating the effective current value Irms flowing through the heater 301 detected by the current detection unit 311. The control unit 9 inputs the voltage corresponding to the current effective value Irms from the current detection circuit 312 to the IDET terminal, and acquires the voltage video. Further, the horizontal axis of FIG. 9 indicates time, and t10 to t16 indicate timing (time).

When the control unit 9 detects that the zero cross signal ZRX has changed from the high level to the low level at the time t10, the control unit 9 sets the FSR_DRV signal output from the FSR_DRV terminal to the on state from the time t10 to the time t11. As a result, the triac 302 is set to the conduction state, and the continuity state of the triac 302 is continued until the time t12 when the AC voltage Vac input from the commercial AC power supply 1 becomes 0V. As a result, the power supply from the commercial AC power supply 1 to the heater 301 of the fixing unit 300 is continued from the commercial AC power supply 1 to the heater 301 via the current detection unit 311 from the time t10 to the time t12. The current detection circuit 312 outputs a voltage corresponding to the current effective value Irms flowing from the commercial AC power supply 1 to the heater 301 of the fixing unit 300 to the IDET terminal of the control unit 9.

Next, at the time t12, when the control unit 9 detects that the zero cross signal ZRX has changed from the low level to the high level, the control unit 9 sets the FSR_DRV signal output from the FSR_DRV terminal to the ON state from the time t12 to the time t14. As a result, the triac 302 is set to the conduction state, and the continuity state of the triac 302 is continued until the time t15 when the AC voltage Vac input from the commercial AC power supply 1 becomes 0V. The current detection circuit 312 is the effective current value flowing from the commercial AC power supply 1 to the heater 301 for outputting to the IDET terminal of the control unit 9 during the period from time t12 to time t13 during the period when the zero cross signal ZRX is at a high level. It holds the voltage corresponding to Irms. The control unit 9 A / D-converts the voltage input to the IDET terminal to acquire the voltage video. The current flowing from the commercial AC power supply 1 to the heater 301 has the opposite direction in the period of time t12 to time t15 and the period of time t10 to time t12. Therefore, in the period from time t12 to time t15, the voltage corresponding to the current effective value Irms is not output.

At the time t15, the above-mentioned operations of the control unit 9, the fixing unit 300, and the current detection unit 311 at the time t10 are performed. Similarly, at the time t16, the control unit 9, the fixing unit 300, and the current detection unit at the time t12 are performed. The above-mentioned operation of 311 is repeated.

[Calculation of input voltage Vac]
FIG. 10 is a flowchart showing a control sequence in which the control unit 9 of the present embodiment calculates the input voltage Vdc based on the current effective value Irms detected by the current detection unit 311. It is executed by the part 9. In the first embodiment, the control unit 9 calculates the input voltage Vdc from Table 1 using the ACDET voltage output from the input voltage detection unit 6 provided in the switching unit 4 of the power supply device 100 and input to the ACDET terminal. Was. On the other hand, in this embodiment, the control unit 9 calculates the input voltage Vdc using the current effective value Irms detected by the current detection unit 311 and the resistance value of the heater 301 through which the current supplied from the commercial AC power supply 1 flows. do.

In S301, the control unit 9 reads the resistance value R of the heater 301 from the fixing storage unit 310 of the fixing unit 300 via the COM terminal. In S302, power is supplied from the commercial AC power supply 1 to the heater 301 of the fixing unit 300 in the same manner as in the period of time t10 to time t12 of FIG. In S303, the control unit 9 acquires a voltage video corresponding to the current effective value Irms flowing through the heater 301, which is output from the current detection circuit 312 of the current detection unit 311 to the IDET terminal. In S304, the control unit 9 calculates the current effective value Irms by using the formula obtained by multiplying the voltage video acquired in S303 by the coefficient α, the current effective value Irms = coefficient α × voltage video. In S305, the control unit 9 uses the input voltage Vdc as an equation using the current effective value Irms of the heater 301 calculated in S304 and the resistance value R of the heater 301 acquired in S301, input voltage Vdc = √2 × current effective. Calculated by the value Irms × resistance value R.

The control unit 9 is stored in the storage unit 10 based on the input voltage Vac calculated by the process shown in FIG. 10 and the temperature and temperature change rate of the thermistors 7 acquired in S102 to S107 shown in FIG. 4 of Example 1. From Table 1, the control information fc of the cooling unit 8 can be acquired. In Table 1 described in Example 1, the ACDET voltage is used instead of the input voltage Vdc. Therefore, it is assumed that Table 1 used in Example 2 uses the input voltage Vdc corresponding to the ACDET voltage of Example 1 instead of the ACDET voltage.

As described above, also in the image forming apparatus 200 such as a laser beam printer, the control unit 9 calculates the input voltage Vdc from the current effective value of the heater 301 of the fixing unit 300 and the resistance value R of the heater 301. , The control information fc of the cooling unit 8 can be acquired. As a result, the control unit 9 drives the cooling fan 81 only when the power supply device 100 in the image forming apparatus 200 needs to be cooled, and shortens the period during which the wind noise is generated to reduce the noise of the image forming apparatus 200. Can be planned.

As described above, according to the present embodiment, it is possible to control the drive of the cooling fan to reduce the noise.

3 Smoothing unit 6 Input voltage detection unit 7 Temperature detection unit 8 Cooling unit 9 Control unit 12 Transformer

Claims (10)

A power supply unit that inputs AC voltage and outputs DC voltage.
A transformer that has a primary winding and a secondary winding, and the primary side and the secondary side are insulated.
A rectifying and smoothing means that rectifies and smoothes the AC voltage input from the AC power supply,
A voltage detecting means for detecting an input voltage output from the rectifying and smoothing means and applied to the primary winding of the transformer.
A temperature detecting means for detecting the temperature of the transformer and
A cooling means for cooling the transformer and
A control means for controlling the cooling means based on the temperature detecting means and the result detected by the voltage detecting means.
Equipped with
The control means includes a first temperature detected by the temperature detecting means in the first time and a second temperature detected by the temperature detecting means in the second time after detecting the first temperature. , The temperature rise rate during the period from the first time to the second time calculated based on, the second temperature, and the input voltage detected by the voltage detecting means. A power supply device characterized by controlling cooling means. The cooling means has a cooling fan for cooling the transformer.
The power supply device according to claim 1, wherein the control means drives or stops the cooling fan. The temperature detecting means is a thermistor.
The power supply device according to claim 2, wherein the thermistor is arranged in the vicinity of the transformer. The power supply device according to claim 3, wherein the voltage detecting means detects a voltage corresponding to a voltage generated in the secondary winding by the input voltage applied to the primary winding of the transformer. The control means stores storage information in which the second temperature, the temperature rise rate, and the voltage detected by the voltage detecting means are associated with control information for driving or stopping the cooling fan. Have,
The power supply device according to claim 4, wherein the cooling fan is controlled based on the control information of the cooling fan acquired from the storage means. An image forming unit that forms an image by transferring a toner image to a sheet,
A fixing part that heats and pressurizes the toner image transferred on the sheet to fix it on the sheet,
A control unit that controls the image forming unit and
The power supply device according to claim 3, wherein the DC voltage is supplied to the image forming unit, the fixing unit, and the control unit.
An image forming apparatus comprising. The fixing portion has a heater for heating the toner image.
A current detecting means for detecting a current flowing from the AC power supply to the fixing portion is provided.
The voltage detecting means calculates the input voltage applied to the primary winding of the transformer based on the current value of the current detected by the current detecting means and the resistance value of the heater. The image forming apparatus according to claim 6. The fixing unit has a storage unit that stores the resistance value of the heater.
The image forming apparatus according to claim 7, wherein the control means acquires the resistance value of the heater from the storage unit. The control means stores information in which the second temperature, the temperature rise rate, and the input voltage calculated by the voltage detecting means are associated with control information for driving or stopping the cooling fan. Have a means,
The image forming apparatus according to claim 8, wherein the cooling fan is controlled based on the control information of the cooling fan acquired from the storage means. The fixing portion has a switch for connecting or disconnecting a current path between the AC power supply and the heater, and a thermistor for detecting the temperature of the heater.
The image forming apparatus according to claim 9, wherein the control means controls the temperature of the heater by controlling the switch based on the temperature of the heater detected by the thermistor.

Images