JP6330772B2 - Electrical equipment - Google Patents

Description

  The present invention relates to an electrical apparatus such as an MFP having a fixing device that thermally fixes a toner image onto a recording sheet.

  As shown in FIG. 4, the electrical apparatus 1 such as an image forming apparatus such as a copying machine, a facsimile machine, or a multifunction machine includes a power supply unit 3 that supplies power to a load 21 such as a motor provided in the main body 2.

  The power supply unit 3 is an AC / DC converter that converts electric power supplied from a commercial AC power supply AC into a DC voltage. Referring to FIG. 4, a rectifier circuit DB, smoothing capacitors C1, C2, a transformer T, a power supply A control IC 31, a rectifier diode D1, a switching element Q1, and a current detection resistor Rs are provided.

  A commercial AC power supply AC is connected to the AC input terminals ACL and ACN of the rectifier circuit DB having a diode bridge configuration, and the AC voltage input from the commercial AC power supply AC is full-wave rectified and output from the rectifier circuit DB. A smoothing capacitor C1 is connected between the rectified output positive terminal and the rectified output negative terminal of the rectifier circuit DB. Further, the rectified output negative terminal of the rectifier circuit DB is connected to the ground terminal. As a result, a DC voltage obtained by rectifying and smoothing the commercial AC power supply AC using the rectifier circuit DB and the smoothing capacitor C1 is obtained.

  The power supply control IC 31 incorporates a control circuit for performing on / off control of a switching element Q1 such as a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The power supply control IC 31 outputs a drive signal to the gate terminal of the switching element Q1, and controls the switching element Q1 on and off. The positive terminal of the rectified output of the rectifier circuit DB is connected to one end of the primary winding P of the transformer T, the other end of the primary winding P of the transformer T is connected to the drain terminal of the switching element Q1, and the switching element The source terminal of Q1 is connected to the ground terminal via the current detection resistor Rs. Thus, the power applied to the primary winding P of the transformer T is transmitted to the secondary winding S of the transformer T by performing on / off control of the switching element Q1. The current detection resistor Rs detects the current Id flowing through the switching element Q1 as a voltage signal. The voltage signal detected by the current detection resistor Rs is input to the power supply control IC 31. When the current Id reaches the overcurrent detection point, the power supply control IC 31 limits the power supplied to the main body unit 2.

  A smoothing capacitor C2 is connected between both terminals of the secondary winding S of the transformer T via a rectifier diode D1. The voltage induced in the secondary winding S of the transformer T is rectified and smoothed by the rectifying diode D1 and the smoothing capacitor C2. Then, the inter-terminal voltage of the smoothing capacitor C2 is output as the output voltage Vo from the power supply output terminals T3a and T3b, and is supplied to the load 21 via the power supply input terminals T2a and T2b of the main body 2 connected by a connector or the like.

JP-A-6-308785 JP 2006-296159 A JP 2014-154669 A

  In an image forming apparatus such as a copying machine, a facsimile machine, or a multifunction machine, a plurality of models having different printing speeds are prepared, and a common power supply unit 3 is used for the plurality of models in order to reduce component costs. In this case, since the load 21 is greatly different among a plurality of models, as shown in FIGS. 5A and 5B, the current Id flowing through the switching element Q1 varies depending on the model (when the load is model A <model B). The current Id is also model A <model B). Further, even in the same model, under a low temperature environment, the load 21 increases due to an increase in driving torque, and flows through the switching element Q1 depending on the temperature of the main body 2 as shown in FIGS. 5 (b) and 5 (c). The current Id is also different (low temperature> high temperature). Therefore, when the common power supply unit 3 is used, it is necessary to set the overcurrent detection point according to the highest condition as shown in FIG.

  The power supply unit 3 is also provided with a sleep mode in which the output voltage Vo is reduced from a normal voltage (for example, 24 V) to a sleep voltage (for example, 13 V) at light loads in consideration of energy saving and the like. When returning from the sleep mode, the output voltage returns to the normal voltage from the sleep voltage and starts driving.However, when the device is in a low-temperature environment, the current increases due to an increase in the motor torque and the inrush current increases. End up. When this inrush current is large, there is a problem that the life of the elements used in the main body such as a cutoff circuit is reduced.

  Patent Document 1 discloses a technique for setting an overcurrent detection point suitable for a standby state, an operation state, and a load current at the start of operation, and Patent Documents 2 and 3 describe an excessive current according to the temperature characteristics of the switching element. Although technologies for changing the current detection conditions are disclosed, they do not solve the above-described problems.

  An object of the present invention is to provide an electric device that solves the above-described problems and prevents an excessive inrush current that may occur when returning from a sleep mode.

An electrical device of the present invention is an electrical device having a power supply unit that generates an output voltage by on / off control of a switching element, and a main body that operates by the output voltage supplied from the power supply unit, and the power supply unit includes: On the basis of the control voltage generated by the control voltage generation circuit, a control voltage generation circuit that generates a control voltage according to on / off of the sleep signal input from the main body and the output voltage, the sleep signal is A control circuit that controls the output voltage to a normal voltage when off, and a control circuit that controls the output voltage to a sleep voltage lower than the normal voltage when the sleep signal is on, and the control generated by the control voltage generation circuit A unit-side control voltage adjustment terminal that accepts voltage adjustment, and the main body includes the unit-side control. When the sleep signal is switched from on to off, the control voltage is generated via the main body side control voltage adjustment terminal and the unit side control voltage adjustment terminal. A control voltage adjustment circuit that controls the output voltage to an intermediate voltage that is higher than the sleep voltage and lower than the normal voltage according to the in-machine temperature of the main body by adjusting the control voltage generated by a circuit It is characterized by comprising.
Furthermore, in the electric device of the present invention, the control voltage adjusting circuit of the main body may control the output voltage to the lower intermediate voltage as the in-machine temperature of the main body is lower.
Further, in the electric device according to the present invention, the control voltage generation circuit of the power supply unit divides the output voltage to generate the control voltage, and the control voltage adjustment circuit of the main body section adjusts the main body side control voltage adjustment The voltage dividing ratio of the output voltage by the control voltage generation circuit may be adjusted by a thermistor connected to the terminal.
Further, in the electric device according to the present invention, the control voltage adjustment circuit of the main unit controls the output voltage to the intermediate voltage for a preset adjustment period when the sleep signal is switched from on to off. Also good.

  According to the present invention, when returning from the sleep mode, it is possible to prevent an excessive inrush current and to prolong the life of a main body use element such as a cutoff circuit.

It is a figure which shows the structure of embodiment of the electric equipment which concerns on this invention. It is a graph which shows the relationship between the overcurrent point and the electric current which flows through a switching element in embodiment of the electric equipment which concerns on this invention. It is a graph which shows the intermediate voltage controlled by adjustment of the control voltage by the control voltage adjustment circuit shown in FIG. It is a figure which shows the structure of the conventional electric equipment. It is the graph which compared the electric current which flows through a switching element in a different model and different temperature. It is a graph which shows the relationship between the overcurrent point in the conventional electric equipment, and the electric current which flows through a switching element.

  Next, embodiments of the present invention will be specifically described with reference to the drawings.

  An electrical apparatus 10 according to the present embodiment is an image forming apparatus such as a copying machine, a facsimile machine, or a multifunction machine. Referring to FIG. 1, a main body unit 20 having various configurations for performing image formation, and a main body unit And a power supply unit 30 that supplies power to a load 21 such as a motor provided in the motor 20.

  The power supply unit 30 is an AC / DC converter that converts electric power supplied from a commercial AC power supply AC into a DC voltage. Referring to FIG. 4, a rectifier circuit DB, smoothing capacitors C1, C2, a transformer T, and a power supply A control IC 31, a rectifier diode D1, and a switching element Q1 are provided.

  A commercial AC power supply AC is connected to the AC input terminals ACL and ACN of the rectifier circuit DB having a diode bridge configuration, and the AC voltage input from the commercial AC power supply AC is full-wave rectified and output from the rectifier circuit DB. A smoothing capacitor C1 is connected between the rectified output positive terminal and the rectified output negative terminal of the rectifier circuit DB. Further, the rectified output negative terminal of the rectifier circuit DB is connected to the ground terminal. As a result, a DC voltage obtained by rectifying and smoothing the commercial AC power supply AC using the rectifier circuit DB and the smoothing capacitor C1 is obtained.

  The power supply control IC 31 incorporates a control circuit for performing on / off control of a switching element Q1 such as a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The power supply control IC 31 outputs a drive signal to the gate terminal of the switching element Q1, and controls the switching element Q1 on and off. The positive terminal of the rectified output of the rectifier circuit DB is connected to one end of the primary winding P of the transformer T, the other end of the primary winding P of the transformer T is connected to the drain terminal of the switching element Q1, and the switching element The source terminal of Q1 is connected to the current output terminal T3c.

  The current output terminal T3c of the power supply unit 30 is connected to the current input terminal T2c of the main body 20 by a connector or the like. Thereby, the current Id flowing through the switching element Q1 is output from the current output terminal T3c of the power supply unit 30 and input from the current input terminal T2c of the main body unit 20. In the main body 20, the current input terminal T2c is connected to the ground terminal through a parallel circuit including the thermistor TH1 and the current detection resistor Rs. A parallel circuit including the thermistor TH1 provided in the main body 20 and the current detection resistor Rs functions as the overcurrent detection circuit 22.

  By turning on / off the switching element Q1, the power applied to the primary winding P of the transformer T is transmitted to the secondary winding S of the transformer T. The overcurrent detection circuit 22 detects the current Id flowing through the switching element Q1, that is, the current Id input from the current input terminal T2c as a voltage signal. The voltage signal detected by the overcurrent detection circuit 22 is input to the power supply control IC 31 via the current input terminal T2c and the current output terminal T3c. When the current Id reaches the overcurrent detection point, the power supply control IC31 The power supplied to 20 is limited.

  A smoothing capacitor C2 is connected between both terminals of the secondary winding S of the transformer T via a rectifier diode D1. The voltage induced in the secondary winding S of the transformer T is rectified and smoothed by the rectifying diode D1 and the smoothing capacitor C2. The inter-terminal voltage of the smoothing capacitor C2 is output as the output voltage Vo from the power supply output terminals T3a and T3b, and is supplied to the load 21 via the power supply input terminals T2a and T2b of the main body 20 connected by a connector or the like.

  At the same temperature, the resistance of the overcurrent detection circuit 22, that is, the combined resistance of the thermistor TH1 and the current detection resistor Rs connected in parallel, is smaller in the model with the smaller load 21 than the model with the larger load 21. It is set to be large. Therefore, the voltage signal detected by the overcurrent detection circuit 22 is larger in the model A with the small load 21 than the model B with the large load 21 even if the current Id flowing through the switching element Q1 is the same. Become. Accordingly, when the overcurrent detection point to be compared with the voltage signal is constant, as shown in FIG. 2, the overcurrent detection point of the model A having the smaller load 21 is detected by the overcurrent detection point of the model B having the larger load 21. It looks smaller than the point. That is, the overcurrent detection point apparently fluctuates in conjunction with load fluctuations due to model differences, so even a model with a small load 21 can reliably detect a state such as a partial short circuit and can be used more safely. .

  The thermistor TH1 uses PTC (Positive Temperature Coefficient) having a positive temperature characteristic in which the resistance value increases as the temperature increases. Therefore, the voltage signal detected by the overcurrent detection circuit 22 is larger at a high temperature than at a low temperature even if the current Id flowing through the switching element Q1 is the same. Accordingly, when the overcurrent detection point to be compared with the voltage signal is constant, the high temperature overcurrent detection point is apparently smaller than the low temperature overcurrent detection point as shown in FIG. In other words, the overcurrent detection point apparently fluctuates in conjunction with load fluctuations due to temperature differences, so even when the temperature is high and the load 21 is small, it is possible to reliably detect a state such as a partial short circuit and use it more safely. it can.

  The output voltage Vo (voltage across the smoothing capacitor C2) includes resistors R1 to R6, a PNP transistor Q2, a shunt regulator Z, a capacitor C3, a secondary side feedback circuit 32 including a light emitting diode PCD constituting the photocoupler PC, and a photocoupler. The error signal is fed back to the power supply control IC 31 by the light receiving transistor PCTR constituting the PC and the primary side feedback circuit 33 including the resistor R7.

  A resistor R1, a light emitting diode PCD, and a shunt regulator Z are connected in series between both terminals of the smoothing capacitor C2, that is, between the power supply line and the GND line. The resistor R1 is a current limiting resistor that limits the current flowing through the light emitting diode PCD and the shunt regulator Z. A voltage dividing resistor R2 and a resistor R3 are connected in series between the power supply line and the GND line, and a connection point A between the resistors R2 and R3 is connected to a control terminal of the shunt regulator Z. Further, a series circuit including a resistor R4, a PNP transistor Q2, and a resistor R5 is connected in parallel with the resistor R2. The base of the PNP transistor Q2 is connected to the sleep signal input terminal T3d, and the sleep signal input terminal T3d is connected to the sleep signal output terminal T2d of the main body 20 by a connector or the like. As a result, the PNP transistor Q2 is on / off controlled in accordance with the on / off state of the sleep signal output from the main body unit 20. The sleep signal is a voltage switching signal that switches the output voltage Vo between a normal voltage and a sleep voltage lower than the normal voltage. When the output voltage Vo is switched to the normal voltage, the sleep signal is turned off, the PNP transistor Q2 is turned off, and the voltage at the connection point A is a value obtained by dividing the output voltage Vo by the resistor R2 and the resistor R3. When the output voltage Vo is switched between sleep voltage and voltage, the sleep signal is turned on, the PNP transistor Q2 is turned on, and the voltage at the connection point A is a combined resistance of the resistor R2 and the resistors R4 and R5 connected in parallel. The output voltage Vo is divided by the resistor R3. The capacitor C3 and the resistor R6 connected between the connection point A and the cathode of the shunt regulator Z1 are a negative feedback circuit for the shunt regulator Z.

  The voltage at the connection point A is input to the control terminal of the shunt regulator Z as a control voltage. That is, the secondary feedback circuit 32 functions as a control voltage generation circuit that generates a control voltage controlled by the shunt regulator Z. The shunt regulator Z compares the input control voltage with the internal reference voltage, and passes a current corresponding to the error voltage to the light emitting diode PCD, and this current is output as an error signal from the light emitting diode PCD to the light receiving transistor PCTR. . The collector terminal of the light receiving transistor PCTR is connected to the feedback terminal of the power supply control IC 31 via the resistor R7, and the emitter terminal of the light receiving transistor PCTR is connected to the ground terminal. In the light receiving transistor PCTR, when an error signal from the light emitting diode PCD is received, a current corresponding to the received error signal flows, and the error signal is transmitted to the power supply control IC 31. As a result, the power supply control IC 31 generates a PWM signal having a pulse width corresponding to the error signal, thereby PWM-controlling the switching element Q1, and maintaining the output voltage Vo at the normal voltage or the sleep voltage.

  The connection point A is connected to the control voltage adjustment circuit 23 of the main body 20 via the unit side control voltage adjustment terminal T3e and the main body side control voltage adjustment terminal T2e connected to the unit side control voltage adjustment terminal T3e by a connector or the like. It is connected. The control voltage adjustment circuit 23 controls the output voltage Vo to an intermediate voltage Va that is higher than the sleep voltage and lower than the normal voltage according to the internal temperature of the main unit during a preset period when switching from the sleep voltage to the normal voltage. Circuit.

  The control voltage adjustment circuit 23 includes a thermistor TH2, a one-shot circuit 24, and a switch 25. The power input terminal T2a, that is, the power line, the thermistor TH2, and the switch 25 are connected in series. The one-shot circuit 24 outputs a one-shot pulse signal having a preset width at the timing when the sleep signal switches from on to off, and the switch 25 outputs the one-shot pulse signal from the one-shot circuit 24. Turns on during the adjustment period T1.

  Therefore, when the sleep signal is switched from on to off, the PNP transistor Q2 is turned off and the switch 25 is turned on, so that the voltage at the connection point A is a combination of the resistor R2 and the thermistor TH2 connected in parallel. The voltage is divided by the resistor and the resistor R3. The thermistor TH2 is a main body temperature measuring means for measuring the main body temperature of the main body section 20, and PTC (Positive Temperature Coefficient) having a positive temperature characteristic in which the resistance value increases as the temperature increases is used. In addition, the resistance value of the thermistor TH2 and the lowest possible temperature are set to a value larger than the combined resistance of the resistor 4 and the resistor R5 connected in series.

  Therefore, as shown in FIG. 3, when the sleep signal is turned off at time t1 for switching from the sleep voltage to the normal voltage, the output voltage Vo is higher than the sleep voltage and lower than the normal voltage. The intermediate voltage Va is controlled according to the in-machine temperature. As described above, when the sleep signal is turned off, the output voltage Vo rises from the sleep voltage to the intermediate voltage Va corresponding to the temperature inside the main unit. The intermediate voltage Va becomes lower as the temperature inside the main unit decreases, that is, as the load 21 becomes larger and the current flowing through the load 21 is assumed to increase significantly. Therefore, an increase in inrush current due to load fluctuations can be efficiently prevented, and the life of the elements used in the main body such as a cutoff circuit can be extended.

  Then, in the adjustment period T1 in which the switch 25 is turned on, when the temperature inside the main body rises due to the drive of the load 21, the resistance value of the thermistor TH2 increases, so that the intermediate voltage Va also rises as the temperature inside the main body rises. . That is, as the internal temperature of the main body 20 increases, the load 21 decreases and the current flowing through the load 21 decreases, the intermediate voltage Va is increased. Thereby, switching from the intermediate voltage Va to the normal voltage can be performed smoothly.

  When the adjustment period T1 elapses and the switch 25 is turned off, the voltage at the connection point A becomes a value obtained by dividing the output voltage Vo by the resistors R2 and R3, and the output voltage Vo is maintained at the normal voltage.

As described above, the present embodiment is an electric apparatus having the power supply unit 30 that generates the output voltage Vo by the on / off control of the switching element Q1 and the main body 20 that operates by the output voltage Vo supplied from the power supply unit 30. 10, the power supply unit 30 includes a control voltage generation circuit (secondary feedback circuit 32) that generates a control voltage according to on / off of the sleep signal input from the main body unit 20 and the output voltage Vo, Based on the control voltage generated by the generation circuit, the control circuit controls the output voltage Vo to a normal voltage when the sleep signal is off, and controls the output voltage Vo to a sleep voltage lower than the normal voltage when the sleep signal is on. (Power supply control IC 31, primary side feedback circuit 32, primary side feedback circuit 33) and control A unit-side control voltage adjustment terminal T3e that receives adjustment of the control voltage generated by the pressure generation circuit, and the main body unit 20 includes a body-side control voltage adjustment terminal T2e connected to the unit-side control voltage adjustment terminal T3e; When the sleep signal is switched from on to off, the control voltage generated by the control voltage generation circuit is adjusted via the main body side control voltage adjustment terminal T2e and the unit side control voltage adjustment terminal T3e, so that A control voltage adjustment circuit 23 that controls the output voltage Vo to an intermediate voltage Va that is higher and lower than the normal voltage and that corresponds to the internal temperature of the main body 20 is provided.
With this configuration, it is possible to prevent an excessive inrush current when returning from the sleep mode, and it is possible to extend the life of the elements used in the main body such as a cutoff circuit. Further, since the output voltage Vo is controlled to the intermediate voltage Va by adjusting the control voltage by the control voltage adjustment circuit 23 of the main body unit 20, the suitable intermediate voltage Va for each model is set on the main body unit 20 side. The power supply unit 30 can be shared.

Further, in the present embodiment, the control voltage adjustment circuit 23 of the main body unit 20 controls the output voltage Vo to a lower intermediate voltage Va as the in-machine temperature of the main body unit 20 is lower.
With this configuration, the intermediate voltage Va becomes lower as the temperature inside the main body decreases, that is, as the load 21 becomes larger and the current flowing through the load 21 is assumed to increase significantly. Therefore, an increase in inrush current due to load fluctuations can be efficiently prevented, and the life of the elements used in the main body such as a cutoff circuit can be extended.

Further, in the present embodiment, the control voltage generation circuit of the power supply unit 30 divides the output voltage Vo to generate a control voltage, and the control voltage adjustment circuit 23 of the main body unit 20 is connected to the main body side control voltage adjustment terminal T2e. The voltage dividing ratio of the output voltage Vo by the control voltage generation circuit is adjusted by the connected thermistor TH2.
With this configuration, the thermistor TH2 can easily control the intermediate voltage Va corresponding to the in-machine temperature of the main body 20.

Furthermore, in the present embodiment, when the sleep signal is switched from on to off, the control voltage adjustment circuit 23 of the main body 20 controls the output voltage Vo to the preset adjustment period T1 and the intermediate voltage.
With this configuration, the intermediate voltage Va increases as the in-machine temperature of the main body 20 increases during the adjustment period T1, the load 21 decreases, and the current flowing through the load 21 decreases. Thereby, switching from the intermediate voltage Va to the normal voltage can be performed smoothly.

  Note that the present invention is not limited to the above-described embodiments, and it is obvious that the embodiments can be appropriately changed within the scope of the technical idea of the present invention. In addition, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiment, and can be set to a suitable number, position, shape, and the like in practicing the present invention. In each figure, the same numerals are given to the same component.

DESCRIPTION OF SYMBOLS 1, 10 Electric equipment 2, 20 Main-body part 3, 30 Power supply unit 21 Load 22 Overcurrent detection circuit 23 Control voltage adjustment circuit 24 One shot circuit 25 Switch 31 Power supply control IC
32 Secondary side feedback circuit 33 Primary side feedback circuit AC Commercial AC power supply C1, C2 Smoothing capacitor C3 Capacitor D1 Rectifier diode DB Rectifier circuit PCD Light emitting diode PCTR Light receiving transistor Q1 Switching element Q2 PNP transistor Rs Current detection resistors R1 to R7 Resistance T Transformers T2a, T2b Power input terminal T2c Current input terminal T2d Sleep signal output terminal T2e Main body side control voltage adjustment terminal T3a, T3b Power supply output terminal T3c Current output terminal T3d Sleep signal input terminal T3e Unit side control voltage adjustment terminal TH1, TH2 Thermistor Z Shunt regulator

Claims (4)

An electric device having a power supply unit that generates an output voltage by on / off control of a switching element, and a main body that operates by the output voltage supplied from the power supply unit,
The power supply unit is
A control voltage generation circuit for generating a control voltage according to on / off of a sleep signal input from the main body and the output voltage;
Based on the control voltage generated by the control voltage generation circuit, the output voltage is controlled to a normal voltage when the sleep signal is off, and the output voltage is lower than the normal voltage when the sleep signal is on. A control circuit for controlling the sleep voltage;
A unit-side control voltage adjustment terminal that receives adjustment of the control voltage generated by the control voltage generation circuit;
The main body is
A main body side control voltage adjustment terminal connected to the unit side control voltage adjustment terminal;
When the sleep signal is switched from on to off, the control voltage generated by the control voltage generation circuit is adjusted via the main body side control voltage adjustment terminal and the unit side control voltage adjustment terminal, An electrical apparatus comprising: a control voltage adjusting circuit that controls the output voltage to an intermediate voltage that is higher than a sleep voltage and lower than the normal voltage and corresponding to an in-machine temperature of the main body.   2. The electric device according to claim 1, wherein the control voltage adjustment circuit of the main body controls the output voltage to the lower intermediate voltage as the in-machine temperature of the main body is lower. The control voltage generation circuit of the power supply unit divides the output voltage to generate the control voltage,
3. The control voltage adjustment circuit of the main body section adjusts a voltage dividing ratio of the output voltage by the control voltage generation circuit by a thermistor connected to the main body side control voltage adjustment terminal. Electrical equipment.   4. The control voltage adjustment circuit of the main unit controls the output voltage to the intermediate voltage for a preset adjustment period when the sleep signal is switched from on to off. Electrical equipment in any one of.

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