JP2006340435A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materialize the simplification of layout and the cost reduction by making a photocoupler for all abnormality detecting circuits consist of only one piece, in a power unit for a multiconverter. <P>SOLUTION: The power unit has a first AC-DC converter 103 which is equipped with an overcurrent detecting circuit or an overvoltage detecting circuit 201 which supplies a controller 106 with power, a second AC-DC converter 105 which is equipped with an overcurrent detecting circuit or an overvoltage detecting circuit 202 which supplies others than the controller 106 with power, and a switch means which switches on or switches off the power supply to the second AC-DC converter 105, interlocking with the first AC-DC converter 103. The power unit feeds back the detection results of the overcurrent detecting circuit or the overvoltage detecting circuit 202 of the second AC-DC converter to the primary side of the first AC-DC converter 103. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power supply unit, and more particularly to a power supply circuit having a plurality of AC-DC converter circuits.

  In order to realize both high power of the power supply unit and low power consumption during standby, the power supply unit may be configured as shown in FIG. That is, the power supply unit 300 is configured by a plurality of converters such as the high-power converter 2 and the low-power converter 1, and the converter 2 is used for power supply of a load that requires high power, and the control unit and the like are compared. The converter 1 is used to supply power to a load having a small dynamic power. Further, the converter 2 can be turned on / off by a control unit supplied with power by the converter 1 in accordance with a load connected to the power supply unit. By configuring the power supply unit in this way, a power supply unit that can supply a large amount of power and can consume low power at a light load is realized.

  Each converter includes an overcurrent detection circuit and an overvoltage detection circuit so that the power supply unit is stopped and protected when an abnormality occurs on the load side.

  An example of a conventional configuration of the overcurrent detection circuit and the overvoltage detection circuit will be described with reference to FIG. In the configuration of FIG. 4, only the basic configuration is described in order to emphasize the description of the overcurrent detection circuit and the overvoltage detection circuit.

  In FIG. 4, 401 is an insulation transformer for transmitting primary energy to the secondary side, and 402 is a rectifier diode for rectifying the voltage of the insulation transformer 401. The current output from the rectifier diode 402 corresponds to the output current of the generated power supply voltage, and this output current is detected by a resistor 403.

  Since the power supply voltage output side (right side in the figure) of the resistor 403 is adjusted to a constant voltage by a voltage adjustment circuit (not shown), the potential on the rectifier diode side (left side in the figure) of the resistor 403 increases as the output current increases. Get higher.

  Here, when the output current increases and the voltage across the resistor 403 increases, the PNP transistor 404 starts to enter the active region from a predetermined output current.

  When the voltage across the resistor 403 reaches about 0.7 V, the PNP transistor 404 enters the saturation region and is completely turned on.

  Reference numeral 405 denotes a resistor for limiting the current to the photocoupler 406, and the photocoupler 406 is driven according to the driving state of the PNP transistor 404.

  Therefore, the voltage drop of the resistor 403 is limited by Vbe of the PNP transistor 404. That is, the output current is limited by the resistor 403 and the PNP transistor 404.

  On the other hand, reference numeral 407 denotes a resistor for limiting the current flowing through the Zener diode 408 and the photocoupler 406, and reference numeral 409 blocks current from an overcurrent detection circuit including the resistor 403, the PNP transistor 404, and the resistor 405. It is a diode for.

  Here, by selecting the Zener voltage of the Zener diode 408 to be several V higher than the power supply voltage Vcc, the photocoupler 406 can be driven when the power supply voltage Vcc exceeds the Zener voltage, and the overvoltage detection circuit. Can be operated as

In this way, the overcurrent detection circuit and overvoltage detection circuit are controlled so that when an abnormality is detected on the secondary side, the primary side is notified via an insulating element such as a photocoupler and switching of the converter is stopped. is doing. The overcurrent detection circuit and the overvoltage detection circuit have the same configuration as the number of converters.
Japanese Patent No. 2829863

  However, in the case of the power unit of the above-described conventional example, photocouplers for detecting an abnormality are required by the number of converters. Since this photocoupler is a component that extends across the primary side and the secondary side, the mountable positions are limited on the board layout, which is a factor complicating the pattern layout. Moreover, it is necessary to enlarge the board area by forcibly drawing the pattern, which increases the cost of the board itself in addition to the cost of the parts.

  An object of this invention is to provide the power supply unit which can solve the subject which concerns.

  In order to achieve the above object, the power supply unit according to claim 1 of the present application includes an overcurrent detection circuit that supplies power to the control unit, or a first AC-DC converter including an overvoltage detection circuit, An overcurrent detection circuit that supplies power to other than the control unit, or a second AC-DC converter having an overvoltage detection circuit, and a second AC-DC converter in conjunction with the first AC-DC converter Switch means for turning on and off the power supply of the second AC-DC converter, and feedback-controls the detection result of the overcurrent detection circuit of the second AC-DC converter or the detection result of the overvoltage detection circuit to the primary side of the first AC-DC converter. It is characterized by that.

  The power supply unit according to claim 1 provided by the present invention includes an overcurrent detection circuit that supplies power to the control unit, or a first AC-DC converter that includes an overvoltage detection circuit, and power to other than the control unit. Overcurrent detection circuit to be supplied, or second AC-DC converter provided with an overvoltage detection circuit, and a switch for turning on / off power supply to the second AC-DC converter in conjunction with the first AC-DC converter And a feedback control of the detection result of the overcurrent detection circuit of the second AC-DC converter or the detection result of the overvoltage detection circuit to the primary side of the first AC-DC converter, and a pattern layout Simplification of the circuit board and reduction of the board bare board and component costs can be realized.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

  In FIG. 1, 100 is a power supply unit. An AC voltage 101 is connected to the power supply unit 100, and a voltage of 100V to 127V is input to the 100V system, and a voltage of 220V to 240V is input to the 200V system. The input AC voltage 101 is full-wave rectified by the diode bridge 102 and supplied to the converter 1 103. Converter 1 (103) converts the AC voltage into a DC voltage, and generates a predetermined voltage value Vcc1.

  On the other hand, the AC voltage 101 is also supplied to the other diode bridge 104, and the AC voltage 101 that is full-wave rectified by the diode bridge 104 is supplied to the converter 2 of 105. Converter 2 (105) also converts the AC voltage into a DC voltage, and generates Vcc2 different from Vcc1. Here, Vcc1 generated by the converter 1 (103) is used for a load such as the control unit 106 having relatively low power consumption, and Vcc2 generated by the converter 2 (105) is used for a load 108 having high power consumption. . Further, the control unit 106 to which the Vcc1 generated by the converter 1 (103) is connected is configured to be able to turn on and off the AC power supply to the converter 2 (105) by a switching element such as a relay 107. Therefore, unless Vcc1 is output, relay 107 is not driven and Vcc2 is not output. In other words, since relay 107 is not driven unless Vcc1 is output, Vcc2 is not output.

  Next, the overcurrent detection circuit and overvoltage detection circuit of converter 1 (103) and converter 2 (105) will be described with reference to the circuit diagram of FIG.

  In the figure, 201 is an overcurrent detection circuit and overvoltage detection circuit of the converter 1, and 202 is an overcurrent detection circuit and overvoltage detection circuit of the converter 2.

  The energy on the primary side is transmitted to the secondary side by the insulating transformer 203, and the output of the insulating transformer 203 is rectified by the rectifier diode 204.

  The current output from the rectifier diode 204 corresponds to the output current of the power supply voltage Vcc1, and this output current is detected by a resistor 205.

  Since the voltage output side (right side in the figure) of the resistor 205 is adjusted to a constant voltage by a voltage adjustment circuit (not shown), the potential on the rectifier diode side (left side in the figure) of the resistor 205 increases as the output current increases. Become.

  Here, when the output current increases and the voltage across the resistor 205 rises, the PNP transistor 206 begins to enter the active region. When the voltage across the resistor 205 reaches about 0.7 V, the PNP transistor 206 enters the saturation region and is completely turned on.

  Reference numeral 207 denotes a resistor for limiting the current to the photocoupler 208, and the photocoupler 208 is driven according to the driving state of the PNP transistor 206. The photocoupler 208 is configured to stop switching of the primary side main circuit.

  Therefore, the voltage drop of the resistor 205 is limited by the Vbe of the PNP transistor 206.

  That is, the output current is limited by the resistor 205 and the PNP transistor 206, and the converter 1 (103) is stopped with the result.

  On the other hand, reference numeral 209 denotes a resistor for limiting the current flowing through the Zener diode 210 and the photocoupler 208, and reference numeral 211 blocks the current flowing from the overcurrent detection circuit including the resistor 205, the PNP transistor 206, and the resistor 207. It is a diode for.

  Here, by selecting the Zener voltage of the Zener diode 210 to be several V higher than the power supply voltage Vcc1, the photocoupler 208 can be driven when the power supply voltage Vcc1 exceeds the Zener voltage, and the overvoltage detection circuit. Can be operated as

  The overcurrent detection circuit and the overvoltage detection circuit 201 configured by the converter 1 have the same configuration in the overcurrent detection circuit and the overvoltage detection circuit 202 of the converter 2.

  Therefore, description of the operation of the overcurrent detection circuit and the overvoltage detection circuit 202 of the converter 2 is omitted. Note that the overcurrent detection circuits of converter 1 (103) and converter 2 (105), and overvoltage detection circuits 201 and 202 are connected by a diode 212 to share a photocoupler 208.

  Here, when the overcurrent detection circuit or the overvoltage detection circuit 201 of the converter 1 operates, the detection result is transmitted to the primary side of the converter 1 (103) by the photocoupler 208, and the converter 1 (103) stops. . Then, Vcc1, which is the power supply voltage of converter 1 (103), is also lowered, so that driving of relay 107 for supplying AC power to converter 2 (105) is cut off, and converter 2 (105) can be stopped. .

  On the other hand, the photocoupler 208 is also driven through the diode 212 when the overcurrent detection circuit or the overvoltage detection circuit 202 of the converter 2 operates. Also in this case, the converter 1 (105) can be stopped when the operation of the converter 1 is stopped and the power supply of the Vcc1 is reduced and the drive of the relay 107 is cut off.

Configuration diagram of the power supply unit according to the first embodiment Basic circuit diagram of overcurrent detection circuit and overvoltage detection circuit according to the first embodiment Configuration diagram of the power supply unit in the conventional example Basic circuit diagram of overcurrent detection circuit and overvoltage detection circuit in the conventional example

Explanation of symbols

100 power supply unit 101 AC power supply (AC voltage)
102 Diode bridge 103 Converter 1
104 Diode bridge 105 Converter 2
106 Control Unit 107 Relay 108 Load 201 Overcurrent Overvoltage Detection Circuit 202 Overcurrent Overvoltage Detection Circuit 203 Insulation Transformer 204 Rectifier Diode 205 Resistance 206 PNP Transistor 207 Resistance 208 Photocoupler 209 Resistance 210 Zener Diode 211 Diode 212 Diode 300 Power Supply Unit 301 Isolation Transformer 302 Rectifier diode 303 Resistor 304 PNP transistor 305 Resistor 306 Photocoupler 307 Resistor 308 Zener diode

Claims (2)

An overcurrent detection circuit for supplying power to the control unit, or a first AC-DC converter provided with an overvoltage detection circuit;
An overcurrent detection circuit for supplying power to other than the control unit, or a second AC-DC converter provided with an overvoltage detection circuit;
Switch means for turning on and off the power supply to the second AC-DC converter in conjunction with the first AC-DC converter,
A power supply unit that feedback-controls the detection result of the overcurrent detection circuit or the overvoltage detection circuit of the second AC-DC converter to the primary side of the first AC-DC converter.   2. The power supply unit according to claim 1, wherein the feedback control feeds back with one photocoupler.

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