JP2017216822A - Converter, and image forming apparatus including converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source device that has a compact and simple configuration and has a protective function.SOLUTION: There is provided a converter comprising: a switching part that drives a primary side of a transformer; a temperature detection part that detects temperature on a secondary side of the transformer; an overcurrent detection part that detects an overcurrent on the secondary side of the transformer; a transmission part that transmits a signal from the secondary side of the transformer to the switching part; and a latch part that stops the switching performed by the switching part by stopping the transmission of the signal from the transmission part to the switching part according to an output from the temperature detection part or an output from the overcurrent detection part, and continues to stop the switching.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a power supply device having a protection function against an overcurrent state or an abnormal temperature state (overload state).

  It is necessary to stably operate the power supply device in response to fluctuations in the AC voltage input from the commercial power supply and fluctuations in the load supplied by the power supply apparatus that converts the AC voltage. Therefore, a power supply device having a protection function for providing a circuit for detecting an overcurrent or a circuit for detecting an abnormal temperature on the secondary side of the power supply device and stopping the operation of the power supply device by the output of each detection circuit is known. (See Patent Document 1). In addition, since fluctuations in voltage (current) and temperature are usually not monotonically increasing, if the output of the above detection circuit repeatedly detects an abnormal value and a normal value, the power supply device operates as a protection function. Non-operation is frequently repeated, and the output voltage becomes unstable. In order to avoid such an unstable operation, it is common to provide a latch function for holding the stopped state when the power supply device is stopped.

JP-A-11-215690

  However, in order to mount the latch function, it is necessary to add a latch circuit. It is also conceivable to provide a latch function as a function of the control IC that controls the switching operation of the power supply device instead of adding a latch circuit. However, in this case, a signal propagation path for a latch operation is added from the detection circuit on the secondary side of the power supply device to the control IC on the primary side separately from the start / stop signal. As described above, in either case, the circuit scale increases and the manufacturing cost may increase. Therefore, there is a demand for a power supply device that has a circuit scale that is reduced to downsize a board on which a power supply circuit is mounted, and that has an overcurrent detection, an abnormally high temperature detection, and a latch function in a simple (inexpensive) manner.

  The converter of the present invention for solving the above-described problems includes a transformer, switching means for driving the primary side of the transformer, temperature detection means for detecting temperature on the secondary side of the transformer, and a secondary side of the transformer. According to an overcurrent detection means for detecting an overcurrent, a transmission means for transmitting a signal from the secondary side of the transformer to the switching means, an output from the temperature detection means or an output from the overcurrent detection means And the latch means for stopping the switching of the switching means by stopping the transmission of the signal from the transmitting means to the switching means.

  The image forming apparatus of the present invention further includes an image forming unit for forming an image, and a converter for supplying power to the image forming apparatus. The converter includes a transformer and a primary of the transformer. Switching means for driving the side, temperature detecting means for detecting the temperature on the secondary side of the transformer, overcurrent detecting means for detecting an overcurrent on the secondary side of the transformer, and from the secondary side of the transformer The switching means by stopping transmission of the signal from the transmission means to the switching means in response to an output from the temperature detection means or an output from the overcurrent detection means; And latch means for stopping the switching of the means and continuing the stop of the switching.

  As described above, according to the present invention, it is possible to provide a power supply device having a circuit scale that is small, small and simple (inexpensive), having overcurrent detection, abnormal high temperature detection, and a latch function.

The figure explaining schematic structure of the power supply device of this invention Detailed circuit diagram of converter according to embodiment 1 Detailed circuit diagram of converter according to embodiment 2 Detailed circuit diagram of converter according to embodiment 3 The figure explaining the positional relationship between the heat sink and the feet of the heat sink and the thermistor 1 is a diagram illustrating an overall configuration of an image forming apparatus according to the present invention.

[Example 1]
FIG. 6 is a schematic diagram of a laser beam printer as an example of the image forming apparatus 1 according to the present invention. When a print command is generated by receiving a print command transmitted from a computer (not shown), the scanner unit 21 constituting the image forming unit 3 emits a laser beam modulated according to image information. Then, a laser beam is scanned on the photoconductor 19 charged to a predetermined polarity by the charging roller 16 in the toner cartridge 15, and an electrostatic latent image is formed on the surface of the photoconductor 19. Toner is supplied from the developing unit 17 to the electrostatic latent image, and a toner image corresponding to image information is formed on the photoreceptor 19. On the other hand, recording materials (also referred to as recording paper) 10 loaded in a paper feeding cassette 11 serving as a paper feeding unit are fed one by one by a pickup roller 12 and conveyed toward a registration roller 14 by a conveying roller 13. . Further, the recording material 10 is conveyed by the registration roller 14 in accordance with the timing at which the toner image on the photoconductor 19 reaches the transfer nip formed by the photoconductor 19 and the transfer roller 20. While the recording material 10 passes through the transfer nip, the toner image on the photoconductor 19 is transferred to the recording material 10. Thereafter, the recording material 10 is heated by the heating device 2, and the toner image is heated and fixed on the recording material 10. The recording material 10 on which the toner image is fixed is discharged to a tray at the top of the printer by rollers 26 and 27 which are paper discharge units. The motor 30 rotates the photoconductor 19 and the heating device 2, and the motor 31 rotates the pickup roller 12, the transport roller 12, and the registration roller 14. Further, a high voltage is applied from the high voltage power source 32 to the charging roller 16, the developing device 17, and the transfer roller 20. The power supply device 32 supplies power to electric circuits such as the motors 30 and 31, the high voltage power supply 32, and the scanner unit 21.

  FIG. 1 is a schematic diagram of a power supply device 32 according to the first embodiment of the present invention. The AC voltage input from the commercial power supply 100 is connected to the primary smoothing capacitor 101 via a rectifier 103 (rectification bridge circuit). Insulating converter 104 and insulating converter 105 are connected in parallel with primary smoothing capacitor 101. A load 106 is connected to the insulating converter 104, and a load 109 is connected to the insulating converter 105. A load 106 is a signal system load such as a sensor or a CPU, and a load 109 is a power system load including an actuator such as a motor. Thus, the signal system converter and the power system converter can be configured separately, and the power system converter can be stopped in a state where the apparatus is not operating (during sleep) or the like to reduce power consumption. For example, when the insulation converter 105 is stopped, a start / stop signal is transmitted from the CPU 108 in the control unit 33 to the input terminal 112 to the insulation converter 105.

  FIG. 2 shows the detailed circuit of the converter 105 and the connection with the load 109. In FIG. 2, converter 105 has switching unit 201 on the primary side of transformer 615. In addition, the start / stop signal transmission unit 202 includes an abnormal temperature detection unit 203, an overcurrent detection unit 204, and a latch unit 205 on the secondary side of the transformer 615. First, the flow from when the Hi level signal is input to the input terminal 112 for the start / stop signal of the converter 105 until the converter 105 outputs a voltage to the load 109 will be described. The power source for the LLC control unit 606 is generated in the insulating converter 104 and charged to the capacitor 611 via the terminal 610.

  The start signal input from the CPU 108 of the control unit 33 to the input terminal 112 turns on the transistor 651 by a signal divided through the resistors 652 and 653 in the start / stop signal transmission unit 202. When the phototransistor side of the photocoupler 613 is turned on, a current flows through the resistor 612 and the resistor 630, and the transistor 608 is turned on. A voltage limited by the Zener diode 609 is supplied to the capacitor 607 and Vcc 605 which is a power supply line of the LLC control unit 606. The LLC control unit 606 that has obtained the power supply turns on and off the switch 601 with a signal from the output terminal 603 of the switching signal on the high side of the LLC control unit 606. In addition, the switch 602 is turned on / off by a signal from the output terminal 604 of the low-side switching signal, and power is propagated to the secondary side of the transformer 615 while current flows through the transformer 615 and the capacitors 616 and 631. When current flows from the transformer 615 in the direction of the capacitor 616, the current flows through the diode 617, and conversely, when current flows from the capacitor 616 in the direction of the transformer 615, current flows through the diode 618 to the capacitor 619 and is smoothed. Then, a current flows from the capacitor 619 through the resistor 665 to the load 109.

  Next, the flow until the output current to the load 109 becomes an overcurrent and the converter 105 is latched and stopped will be described. An output current to the load 109 is converted into a voltage by the resistor 665. The voltage across the resistor 665 is applied to the negative input of the comparator 210 via the resistor 664. On the other hand, a threshold voltage set by resistors 662 and 663 is applied to the + input. When the input voltage is compared by the comparison unit 210 and the input is larger, that is, when a current larger than the set threshold value flows through the resistor 665, the output of the comparison unit 210 is at a low level. When the output of the comparison unit 210 becomes a low level, the transistor 651 is turned off by drawing a current through the diode 654. When the transistor 651 is turned off, the current of the photocoupler 613 is also stopped, the switching operation by the LLC control unit 606 is stopped, and the output of the converter 105 is also stopped.

  At this time, the comparison unit 210 also draws current through the diode 655. As a result, the voltage at the + input of the comparison unit 206 is lowered. By making the voltage of the + input lower than the threshold voltage set by the resistors 660 and 661 which are the −input of the comparison unit 206, the output of the comparison unit 206 becomes a low level. Since the output of the comparison unit 206 becomes low level, the current continues to be drawn through the diode 654 even if the output of the comparison unit 210 returns to Hi, that is, the overcurrent state is released. Will work. That is, the state where the output is stopped is continued.

  Next, the flow from when an abnormal temperature is detected until the converter 105 stops latching will be described. Resistors 657 and 658 are connected to a thermistor 659 as an element for detecting temperature. As the temperature rises, the resistance value of the thermistor 659 decreases, and the voltage at the + input of the comparison unit 206 decreases. On the other hand, a threshold voltage set by resistors 660 and 661 is applied to the − input. When the input voltage is compared by the comparison unit 206 and the input is larger, that is, when the thermistor temperature becomes higher than the set threshold value, the output of the comparison unit 206 becomes the low level. When the output of the comparison unit 206 becomes low level, the transistor 651 is turned off by drawing current through the diode 654. When the transistor 651 is turned off, the current of the photocoupler 613 is also stopped and the signal does not reach the switching unit 201. Therefore, the switching by the LLC control unit 606 is stopped and the output of the converter 105 is also stopped.

  At this time, the comparison unit 206 also draws a current through the diode 655 to further reduce the voltage of the + input of the comparison unit 206. Regardless of the temperature of the thermistor, by making the voltage sufficiently lower than the threshold voltage set by the resistors 660 and 661 that are the negative inputs of the comparator 206, the output of the comparator 206 continues to be Low. That is, even if the abnormal temperature state is released, the current continues to be drawn through the diode 654, so that the latch function works. That is, the state where the output is stopped is continued.

  In addition, there is a configuration in which a signal input to the input terminal 112 of the start / stop signal is also used as a signal for supplying power to the comparison units 206 and 210 and a configuration in which the signal is not shared. In the former case, after that, the signal to the input terminal 112 is turned off (low level) to return to the state before the signal is input to the input terminal 112. After that, when the signal to the input terminal 112 is turned on (becomes Hi level), the converter 105 is started according to the procedure described above.

  On the other hand, in the latter case (when not shared), the comparison unit 206 and 210 that output signals to the transmission unit 202 are supplied with the + input power source separately from the signal to the input terminal 112, and the comparison unit 206. The input power source is the same as the signal to the input terminal 112. Then, when the signal to the input terminal 112 is turned off (set to Low level), the low level output latch of the comparison units 206 and 210 is released, and becomes Hi output. Therefore, after that, if the signal to the input terminal 112 is turned on, the converter 105 is started according to the procedure described above.

  As described above, the signal to the input terminal 112 is turned off by being pulled in by the outputs of the comparison units 206 and 210, and the converter is stopped and the input voltage of the comparison unit 206 is changed. Thereby, it is possible to realize an overcurrent case, an abnormal temperature detection (overload detection), and a latch function at a small size and at low cost.

  In this embodiment, the insulating converter 105 has been described as an LLC converter (current resonance converter), but the present embodiment can also be applied to other types of converters (eg, a pseudo resonance converter).

  In addition, as described above, the signal input to the input terminal 112 is also used as the power source of the comparison units 206 and 210, so that the input signal to the converter 105 can be reduced. In this case, attention must be paid to the output impedance of the activation signal output from the control unit 33 and the output logic of the comparison units 206 and 210 during the transition. In the circuit in FIG. 2, it is possible to share the signal from the control unit 33 with part or all of the symbol Δ. The diode 654 can be omitted depending on the voltage of the activation signal, the resistance values of the resistors 652 and 653, and the voltage of the + input of the comparison unit 206.

  FIG. 5 shows an example of a pattern diagram on a circuit board to which this embodiment can be applied. The thermistor 659 as a temperature detection element is installed in the vicinity of a component whose temperature may increase when the load of the converter 105 is abnormal or when the component is abnormal. The thermistor 659 is an example of an element whose resistance value changes according to the temperature of the element. For example, if a component whose temperature is likely to rise is connected to the heat sink, connecting the feet of the heat sink to the same pattern on the circuit to which the thermistor is connected will enable a very good thermal conductivity to be detected from the temperature detection target. Can be connected to a thermistor. This makes it possible to detect the temperature with good reaction. In this embodiment, the diodes 617 and 618 are joined to the heat sink 811, and the heat sink leg 812 is connected to the cathode pattern of the capacitor 619. The thermistor 659 is arranged in the vicinity of the heat sink leg.

[Example 2]
FIG. 3 shows a detailed circuit of the converter 105 used in this embodiment. The switching part etc. which are the same as those of the first embodiment are omitted. Note that the configuration and output operation of the image forming apparatus and the converter in this embodiment are the same as those in the first embodiment, and thus the description of the same parts is omitted. Hereinafter, connection and operation of the abnormal temperature detection unit 203 and the overcurrent detection unit 204 in the present embodiment will be described in detail.

  Based on FIG. 3, the flow until the output current to the load 109 becomes an overcurrent and the converter 105 stops latching will be described. An output current to the load 109 is converted into a voltage by the resistor 665. The voltage across the resistor 665 is applied to the negative input of the comparator 210 via the resistor 664. On the other hand, a threshold voltage set by resistors 662 and 663 is applied to the + input. When both input voltages are compared and the input is larger, that is, when a current larger than the set threshold value is flowing through the resistor 665, the output of the comparison unit 210 becomes a low level, and current is drawn through the diode 654. Thus, the transistor 651 is turned off. When the transistor 651 is turned off, the current of the photocoupler 613 is also stopped, the switching by the LLC control unit 606 is stopped, and the output of the converter 105 is also stopped.

  At this time, the comparison unit 210 draws a current through the resistor 702, so that the transistor 703 is turned on and the voltage at the negative input of the comparison unit 206 increases. By making this voltage higher than the both-ends voltage of the thermistor 659 which is the + input of the comparison unit 206, the output of the comparison unit 206 becomes low level. When the output of the comparison unit 206 becomes a low level, current is drawn through the resistor 705, the transistor 706 is turned on, and the voltage at the negative input of the comparison unit 210 increases. The voltage of the −input is made higher than the threshold voltage set by the resistors 662 and 663 that are the + inputs of the comparison unit 210, so that the diode 654 is activated regardless of the voltage across the resistor 665, that is, even if the overcurrent state is released. As a result, the current continues to be drawn, and the latch function works. That is, the state where the output is stopped is continued.

  Next, the flow from when an abnormal temperature is detected until the converter 105 stops latching will be described. When the temperature of the thermistor 659 increases, the resistance value decreases and the voltage at the + input of the comparison unit 206 decreases. On the other hand, a threshold voltage set by resistors 660 and 661 is applied to the − input. When the input voltage is compared by the comparison unit 206 and the input is larger, that is, when the thermistor temperature becomes higher than the set threshold value, the output of the comparison unit 206 becomes the low level. Then, current is drawn through the resistor 705, the transistor 706 is turned on, and the voltage at the negative input of the comparator 210 increases. By making this negative input voltage higher than the threshold voltage set by the resistors 662 and 663 that are the positive inputs of the comparator 210, the output of the comparator 210 becomes low regardless of the voltage across the resistor 665.

  As described above, in this embodiment, the latch unit 205 includes a circuit including the transistor 703 and the resistors 701 and 702, and the logic adjustment unit 301 includes a circuit including the transistor 706 and the resistors 704, 705, and 706. The latch unit 205 and the logic adjustment unit 301 stop the signal output to the transmission unit 202 and continue the latched state.

  The output of the comparison unit 210 turns off the transistor 651 by drawing current through the diode 654. When the transistor 651 is turned off, the current of the photocoupler 613 is also stopped and the start signal does not reach the switching unit, so that the switching is stopped and the output of the converter 105 is also stopped.

  At the same time, the output of the comparison unit 210 draws a current through the resistor 702, whereby the transistor 703 is turned on and the voltage at the negative input of the comparison unit 206 is increased. Regardless of the temperature of the thermistor, this negative input voltage is made higher than the voltage across the thermistor 659, which is the positive input of the comparator 206, so that the Low output of the comparator 206 is maintained and the latch function works. That is, the state where the output is stopped is continued.

  As in the first embodiment, there is a configuration in which a signal input to the input terminal 112 of the start / stop signal is also used as a signal for supplying power to the comparison units 206 and 210 and is not used in combination. . In the former case, after that, the signal to the input terminal 112 is turned off (low level) to return to the state before the signal is input to the input terminal 112. After that, when the signal to the input terminal 112 is turned on (becomes Hi level), the converter 105 is started according to the procedure described above. On the other hand, in the latter case, the + input power source of the comparison unit 206 is input separately from the + input power source of the comparison units 206 and 210 that output signals to the transmission unit 202. Same as signal to terminal 112. Then, when the signal to the input terminal 112 is turned off (set to Low level), the low level output latch of the comparison units 206 and 210 is released, and becomes Hi output. Therefore, after that, if the signal to the input terminal 112 is turned on, the converter 105 is started according to the procedure described above.

  As described above, the signal to the input terminal 112 is turned off by being pulled in by the output of the comparison unit 210, the converter is stopped, and the input voltage of the comparison unit 206 is changed. Thereby, it is possible to realize an overcurrent case, an abnormal temperature detection (overload detection), and a latch function at a small size and at low cost.

[Example 3]
FIG. 4 shows a detailed circuit of the converter 105 used in this embodiment. The switching unit and the like that are the same as those in the first embodiment save the description. Since the configuration and output operation of the image forming apparatus and the converter in the present embodiment are the same as those in the first embodiment, description thereof is omitted, and connection and operation of the abnormal temperature detection unit 203 and the overcurrent detection unit 204 will be described. In this embodiment, unlike the second embodiment, the logic adjustment is not required, and the logic adjustment unit 301 is a simple connection circuit of input = output.

  First, the flow until the output current to the load 109 becomes an overcurrent and the converter 105 stops latching will be described. An output current to the load 109 is converted into a voltage by the resistor 665. The voltage across the resistor 665 is applied to the negative input of the comparator 210 via the resistor 664. On the other hand, a threshold voltage set by resistors 662 and 663 is applied to the + input. When the input voltage is compared by the comparison unit 210 and the input is larger, that is, when a current larger than the set threshold value is flowing through the resistor 665, the output of the comparison unit 210 is at the low level, and the + input of the comparison unit 206 is Reduce. By making the voltage of the + input lower than the threshold voltage set by the resistors 660 and 661 which are the −input of the comparison unit 206, the output of the comparison unit 206 becomes a low level. The output of the comparison unit 206 becomes Low, and the transistor 651 is turned off by drawing a current through the diode 654. When the transistor 651 is turned off, the current of the photocoupler 613 is also stopped, the switching by the LLC control unit 606 is stopped, and the output of the converter 105 is also stopped.

  At this time, the comparison unit 206 draws a current through the resistor 702, so that the transistor 703 is turned on and the voltage at the negative input of the comparison unit 206 is increased. By making this voltage higher than the both-ends voltage of the thermistor 659 which is the + input of the comparison unit 206, the output of the comparison unit 206 becomes low level. Even when the overcurrent state is released and the output of the comparison unit 210 becomes Hi level, the latch function works by setting the negative input voltage of the comparison unit 206 to be higher than the positive input voltage of the comparison unit 206. It becomes. That is, the state where the output is stopped is continued.

  Next, the flow until the abnormal temperature detection is activated and the converter 105 stops latching will be described. When the temperature of the thermistor 659 increases, the resistance value decreases and the voltage at the + input of the comparison unit 206 decreases. On the other hand, a threshold voltage set by resistors 660 and 661 is applied to the − input. When the input voltage is compared by the comparison unit 206-when the input is larger, that is, when the thermistor temperature becomes higher than the set threshold value, the output of the comparison unit 206 becomes a low level and current is drawn through the diode 654. Thus, the transistor 651 is turned off. When the transistor 651 is turned off, the current of the photocoupler 613 is also stopped and the start signal does not reach the switching unit, so that the switching is stopped and the output of the converter 105 is also stopped.

  As described above, in this embodiment, the signal output from the overcurrent detection unit 204 is connected to the thermistor 659 of the temperature detection unit 203 (corresponding to the logic adjustment unit 301), so that the signal to the transmission unit 202 is transmitted. The latched state is continued by stopping.

  At this time, the comparison unit 206 draws a current through the resistor 702, whereby the transistor 703 is turned on and the voltage of the negative input of the comparison unit 206 is raised. Regardless of the temperature of the thermistor, this negative input voltage is made higher than the voltage across the thermistor 659, which is the positive input of the comparator 206, so that the Low output of the comparator 206 is maintained and the latch function works. That is, the state where the output is stopped is continued.

  As in the first embodiment, there is a configuration in which a signal input to the input terminal 112 of the start / stop signal is also used as a signal for supplying power to the comparison units 206 and 210 and is not used in combination. . In the former case, after that, the signal to the input terminal 112 is turned off (low level) to return to the state before the signal is input to the input terminal 112. After that, when the signal to the input terminal 112 is turned on (becomes Hi level), the converter 105 is started according to the procedure described above. On the other hand, in the latter case, the + input power source of the comparison unit 206 is input separately from the + input power source of the comparison units 206 and 210 that output signals to the transmission unit 202. Same as signal to terminal 112. Then, when the signal to the input terminal 112 is turned off (set to Low level), the low level output latch of the comparison units 206 and 210 is released, and becomes Hi output. Therefore, after that, if the signal to the input terminal 112 is turned on, the converter 105 is started according to the procedure described above.

  As described above, the signal to the input terminal 112 is turned off by being pulled in by the output of the comparison unit 210, the converter is stopped, and the input voltage of the comparison unit 206 is changed. Thereby, it is possible to realize an overcurrent case, an abnormal temperature detection (overload detection), and a latch function at a small size and at low cost.

32 Power supply device 33 Control unit 104 Insulating converter 105 Insulating converter 108 CPU
202 Start / stop signal transmission unit 203 Abnormal temperature detection unit 204 Overcurrent detection unit 205 Latch unit 301 Logic adjustment unit

Claims (10)

With a transformer,
Switching means for driving the primary side of the transformer;
Temperature detecting means for detecting the temperature on the secondary side of the transformer;
Overcurrent detection means for detecting overcurrent on the secondary side of the transformer;
Transmitting means for transmitting a signal from the secondary side of the transformer to the switching means;
The switching of the switching unit is stopped by stopping the transmission of the signal from the transmission unit to the switching unit in accordance with the output from the temperature detection unit or the output from the overcurrent detection unit, and the switching is stopped. Latch means to continue,
The converter characterized by having.   The temperature detection means includes comparison means for comparing a voltage corresponding to the detected temperature with a threshold voltage, and the latch means controls a signal output from the comparison means to the transmission means. The converter according to Item 1. The overcurrent detection means has a comparison means for comparing a threshold voltage with a voltage corresponding to the detected current,
The converter according to claim 1, wherein the latch unit controls a signal output from the comparison unit to the transmission unit. The transmission means has an input terminal to which a signal is input,
4. The converter according to claim 1, wherein the stop of the switching is canceled by inputting a signal to the input terminal in a state where the stop of the switching is continued by the latch means. 5. .   The temperature detection means includes an element whose temperature changes according to the output current of the converter, and further includes a heat sink attached to the element, and the temperature detection means, the heat sink, and the same pattern on the substrate The converter according to claim 1, wherein the converter is connected to the converter.   6. The converter according to claim 5, wherein the temperature detecting means is an element whose resistance value changes according to the temperature of the element.   The transmission means divides the signal from the temperature detection means or the overcurrent detection means to generate a second signal, and stops the switching when the level of the second signal is changed. The converter according to claim 1, wherein the converter is characterized in that In an image forming apparatus for forming an image on a recording material,
An image forming means for forming an image;
A converter for supplying power to the image forming apparatus,
The converter is
With a transformer,
Switching means for driving the primary side of the transformer;
Temperature detecting means for detecting the temperature on the secondary side of the transformer;
Overcurrent detection means for detecting overcurrent on the secondary side of the transformer;
Transmitting means for transmitting a signal from the secondary side of the transformer to the switching means;
The switching of the switching unit is stopped by stopping the transmission of the signal from the transmission unit to the switching unit in accordance with the output from the temperature detection unit or the output from the overcurrent detection unit, and the switching is stopped. Latch means to continue,
An image forming apparatus comprising: Drive means for driving the image forming means;
The image forming apparatus according to claim 8, wherein the converter supplies power to the driving unit. A control unit for controlling the operation of the image forming unit;
10. The image forming apparatus according to claim 8, wherein a signal output from the control unit is input to the transmission unit to release the state where the switching is stopped. 11.

Images