JP2010109962A - Image processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus for reducing power consumption by switching an output voltage of a power circuit between an operational mode and a power saving mode. <P>SOLUTION: The image processing apparatus includes: a power circuit which outputs either a first voltage or a second voltage lower than the first voltage in response to a mode switching signal; an electronic circuit to which power is applied from the power circuit to operate; a voltage transformer for transforming the first voltage output by the power circuit to a voltage completely or approximately equal to the second voltage and outputting the voltage to the electronic circuit; and a short-circuiting means for forming a route short-circuiting the voltage transformer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image processing apparatus. In particular, the present invention relates to an image processing apparatus capable of stopping power supply except for a part of the apparatus in the power saving mode.

  Conventionally, various proposals have been made on techniques for reducing the power consumption of an apparatus. For example, it is patent document 1. FIG.

JP-A-11-177731

  Patent Document 1 discloses a communication terminal device provided with a normal power mode in which a plurality of functions of the device can be used and a low power consumption mode in which each function is stopped to reduce power consumption when the function is not used Is disclosed. In the normal power mode, power is supplied to the entire device from the main power supply. In the low power consumption mode, the main power supply is used only for the detection circuit that detects the line call or operation that is an external trigger for returning to the normal power mode. Power is supplied. In the low power consumption mode, the power supplied to the entire apparatus is supplied only to the detection circuit, so that the power consumption in the apparatus is reduced.

  In the apparatus described in Patent Document 1, the main power supply itself supplies power in the same manner regardless of whether it is in the low power consumption mode or the normal power mode. The main power source needs to generate a large amount of power in order to operate the entire apparatus, and the main power source itself consumes that much power. In the low power consumption mode, only the detection circuit operates and the other circuits are stopped, but the power supply to the detection circuit is similarly performed by the main power supply. does not change. Therefore, there is a problem that even in the low power consumption mode, the power consumption cannot be sufficiently reduced.

  The present invention has been proposed in view of the above problems. An object of the present invention is to provide an image processing apparatus capable of reducing power consumption by switching an output voltage of a power supply circuit between an operation mode and a power saving mode.

  An image processing apparatus according to claim 1 of the present invention is an image processing apparatus that includes an operation mode and a power saving mode, and can stop power supply except for a part of the apparatus in the power saving mode. A power supply circuit that outputs either the first voltage or a second voltage lower than the first voltage in response to the mode switching signal, an electronic circuit that is powered by the power supply circuit, and a first voltage output from the power supply circuit. A voltage converter that converts the voltage to a voltage that is the same as or substantially equal to the second voltage and outputs the voltage to an electronic circuit; and a short-circuit unit that forms a path for short-circuiting the voltage converter.

  According to a second aspect of the present invention, in the image processing device according to the first aspect, the voltage converter stops the conversion operation in response to the mode switching signal.

  According to a third aspect of the present invention, there is provided the image processing device according to the first aspect, wherein the voltage converter is configured such that the output voltage of the power supply circuit is lower than a reference voltage which is equal to or lower than the first voltage and equal to or higher than the second voltage. Stop conversion operation.

  According to a fourth aspect of the present invention, there is provided the image processing apparatus according to any one of the first to third aspects, wherein the electronic circuit operates only when the power supply circuit outputs the first voltage, and the power supply circuit. Includes a second functional unit that operates when either the first voltage or the second voltage is output.

  An image processing apparatus according to a fifth aspect of the present invention is the image processing apparatus according to any one of the first to fourth aspects, further comprising a delay circuit that short-circuits or opens the short-circuit means in accordance with the mode switching signal.

  The image processing device according to claim 6 of the present invention is the image processing device according to claim 4, wherein the output voltage of the power supply circuit is short-circuited in a range that is not more than the maximum rated voltage of the second functional unit and not less than the reference voltage. Short-circuit control means for short-circuiting or opening the means is provided.

  According to a seventh aspect of the present invention, in the image processing apparatus according to the fourth to sixth aspects, the first functional unit includes a first voltage operating unit that operates at a first voltage output from the power supply circuit, and a voltage conversion unit. And a second voltage operating unit that operates at a voltage that is the same as or substantially equal to the second voltage output by the device.

  An image processing apparatus according to an eighth aspect of the present invention is the image processing apparatus according to any one of the first to seventh aspects, wherein when the mode switching signal shifts from the operation mode to the power saving mode, the output voltage of the power supply circuit is the first voltage. When switching from the second voltage to the second voltage and returning from the power saving mode to the operation mode, the output voltage of the power supply circuit is switched from the second voltage to the first voltage.

  According to the image processing apparatus of the first aspect of the present invention, the power supply circuit outputs the first voltage or the second voltage lower than the first voltage in accordance with the mode switching signal. The short-circuit means forms a path for short-circuiting the voltage converter that converts the first voltage to a voltage that is the same as or substantially equal to the second voltage. Thereby, the 2nd voltage which a power supply circuit outputs can be supplied to an electronic circuit without going through a voltage converter. Only a necessary part of the electronic circuit can be operated with the second voltage, and the other parts can be stopped.

  In this case, since the power supply circuit only has to supply the second voltage to only a necessary part of the electronic circuit, the power consumption of the power supply circuit itself can be suppressed. Moreover, since the 2nd voltage which a power supply circuit outputs can be supplied via a short circuit means, not via a voltage converter, the power consumption in a voltage converter can also be reduced. Further, since power consumption can be reduced with a simple circuit configuration, the apparatus can be downsized.

  According to the image processing device of the second aspect of the present invention, the voltage converter stops the conversion operation in response to the mode switching signal. Thereby, the power consumption in a voltage converter can be reduced.

  According to the image processing apparatus of the third aspect of the present invention, the voltage converter stops the conversion operation when the output voltage of the power supply circuit falls below the reference voltage that is equal to or lower than the first voltage and equal to or higher than the second voltage. As a result, when the output voltage of the power supply circuit drops from the first voltage to the second voltage, the operation of the voltage converter is stopped when the output voltage falls below the reference voltage, and the power consumption in the voltage converter can be reduced. it can.

  According to the image processing apparatus of the fourth aspect of the present invention, the first functional unit of the electronic circuit operates only when the output voltage of the power supply circuit is the first voltage. Further, the second functional unit of the electronic circuit operates when the output voltage of the power supply circuit is the first voltage or the second voltage. Thereby, when the power supply circuit outputs the first voltage, both the first functional unit and the second functional unit of the electronic circuit can operate. In addition, when the power supply circuit outputs the second voltage, the first function unit of the electronic circuit is stopped, and only the second function unit can operate. Therefore, it is possible to reduce the power consumption by operating only the second functional unit of the electronic circuit and to suppress the power consumption of the power supply circuit itself.

  According to the image processing device of the fifth aspect of the present invention, the delay circuit short-circuits or opens the short-circuit means according to the mode switching signal. Thus, when the output voltage of the power supply circuit drops from the first voltage to the second voltage, the time until the output voltage of the power supply circuit becomes equal to or lower than the maximum rated voltage of the second function unit is delayed by the delay circuit and short-circuit means Can be short-circuited. In addition, when the output voltage of the power supply circuit rises from the second voltage to the first voltage, the time until the output voltage of the power supply circuit becomes equal to or higher than the reference voltage at which the voltage converter operates is delayed by the delay circuit and the short circuit means It can be opened. Therefore, the second functional unit can be always operated within the rated range.

  According to the image processing apparatus of the sixth aspect of the present invention, the short-circuit control means includes the short-circuit means in a range in which the output voltage of the power supply circuit is equal to or lower than the maximum rated voltage of the second functional unit and equal to or higher than the reference voltage. Short circuit or open. Thereby, based on the output voltage of a power supply circuit, a 2nd function part can be always operated within the range of a rating.

  According to the image processing apparatus of the seventh aspect of the present invention, the first voltage operating unit of the first function unit operates at the first voltage output from the power supply circuit, and the voltage converter outputs the second voltage operating unit. The second voltage is equal to or substantially equal to the second voltage. Therefore, by disposing a function that operates at the second voltage but is not necessary in the power saving mode in the second voltage operation unit, a configuration that operates at the second voltage in the operation mode and stops in the power saving mode can be obtained.

  According to the image processing apparatus of the eighth aspect of the present invention, the mode switching signal switches the output voltage of the power supply circuit from the first voltage to the second voltage when shifting from the operation mode to the power saving mode. When returning from the mode to the operation mode, the output voltage of the power supply circuit is switched from the second voltage to the first voltage. Thereby, the operation mode and the power saving mode are switched by the mode switching signal, and in the power saving mode, the power supply circuit outputs the second voltage, and only the second function unit of the electronic circuit can be operated. Therefore, the power consumption of the device can be reduced while suppressing the power consumption of the power supply circuit itself.

1 is an external perspective view showing a multifunction peripheral as an example of an image processing apparatus of the present invention. It is a block diagram (operation mode) which shows an example about an electrical structure. It is a flowchart at the time of shifting from an operation mode to a power saving mode. It is behavior explanatory drawing at the time of shifting from an operation mode to a power saving mode. It is a block diagram (power saving mode) which shows an example about an electric configuration. It is a flowchart at the time of returning from a power saving mode to an operation mode. It is behavior explanatory drawing at the time of returning from a power saving mode to an operation mode. It is a block diagram which shows another example about an electrical structure.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is an external perspective view showing a multifunction peripheral device 100 as an example of the image processing apparatus of the present invention. The multifunction peripheral device 100 has a printer function, a copy function, a scanner function, and the like. In addition, the multifunction peripheral device 100 includes an operation mode and a power saving mode. In the power saving mode, power supply is stopped except for a part of the device.

  As shown in FIG. 1, the multifunction peripheral device 100 is covered with a main body case 101 made of synthetic resin. A paper feed cassette 102 is inserted in the front surface of the multifunction peripheral device 100. A paper discharge unit 103 is disposed above the paper feed cassette 102.

  A slot portion 104 is disposed at the upper front of the multifunction peripheral device 100. By loading various storage media such as a memory card into the slot unit 104, it is possible to print image data or the like stored in the storage medium.

  On the upper side of the multifunction peripheral device 100, an operation panel including various operation buttons 105, a liquid crystal display unit 106, and the like is provided.

  Further, inside the multi-functional peripheral device 100, a print carriage motor for driving a print carriage having a print head, a paper feed motor for conveying paper, and a scanner carriage having a scanner sensor are driven. A scanner carriage motor is provided.

  Next, the electrical configuration of the multifunction peripheral device 100 will be described. FIG. 2 is a block diagram illustrating an example of the electrical configuration of the multifunction peripheral device 100. Here, the block diagram of FIG. 2 corresponds to the operation mode.

  The power supply circuit 1 converts the input alternating current into direct current and outputs it to the main board 2. The main board 2 has a ground connected in common with the power supply circuit 1. The main board 2 includes a first function unit 3 and a second function unit 5 as an electronic circuit that operates by being supplied with power from the power supply circuit 1.

  The first function unit 3 includes a first voltage operation unit 31 and a second voltage operation unit 32. Here, the first voltage operating unit 31 operates at the first voltage V1, and the second voltage operating unit 32 operates at the second voltage V2. The output of the power supply circuit 1 is connected to the first voltage operation unit 31. Further, the output of the power supply circuit 1 is connected to the second voltage operating unit 32 via the voltage converter 4.

  The output of the power supply circuit 1 is connected to the second function unit 5 through a path passing through the voltage converter 4 and the diode D1 and a path passing through the short-circuit means 6 and the diode D2, and the regulator 7 is connected to these two paths. It is also connected via. A capacitor C1 is connected between the voltage supply line of the second functional unit 5 and the ground.

  The second function unit 5 outputs a mode switching signal PSDDOWN. The mode switching signal PSDDOWN is input to the power supply circuit 1 and also input to the short circuit means 6 via the delay circuit 8.

  In the operation mode, the mode switching signal PSDDOWN is in the OFF state and maintains the L level. When the mode switching signal PSDDOWN is OFF (L level), the power supply circuit 1 outputs the first voltage V1. Therefore, the first voltage operating unit 31 operates by the first voltage V1 output from the power supply circuit 1. The voltage converter 4 converts the first voltage V1 output from the power supply circuit 1 into a second voltage V2 lower than the first voltage V1 and outputs the second voltage V2. The second voltage operating unit 32 is operated by the second voltage V2 output from the voltage converter 4. The second voltage V2 output from the voltage converter 4 may include a normal error (for example, ± 1%).

  On the other hand, when the mode switching signal PSDDOWN is OFF (L level), the switch SW1 provided in the short-circuit means 6 is open. Therefore, the first voltage V1 output from the power supply circuit 1 is converted into the second voltage V2 and input to the second function unit 5 through the voltage converter 4 and the diode D1. Further, the regulator 7 outputs a constant voltage lower than the input second voltage V <b> 2 to the second function unit 5. Therefore, the second functional unit 5 operates by receiving the second voltage V2 and the output of the regulator 7.

  Next, the transition from the operation mode to the power saving mode will be described. FIG. 3 is a flowchart when shifting from the operation mode to the power saving mode. In S11, it is determined whether or not a condition for shifting to the power saving mode has occurred. The conditions for shifting to the power saving mode include, for example, a user request from the operation button 105 of the multi-function peripheral device 100, or a software request in response to a non-operation state continuing for a certain period of time. is there. When the power saving mode transition condition occurs (S11: YES), the process proceeds to S12. On the other hand, when the power saving mode transition condition has not occurred (S11: NO), the process returns to S11 again. That is, the process waits in S11 until the power saving mode transition condition occurs.

  In S12, the mode switching signal PSDDOWN is turned ON (H level). When the mode switching signal PSDDOWN is turned on (H level), the output voltage of the power supply circuit 1 drops from the first voltage V1 to the second voltage V2 (S13), the switch SW1 provided in the short circuit means 6 is closed and the short circuit means 6 is closed. Is short-circuited (S14), and the voltage converter 4 stops the conversion operation (S15).

  The behavior of S13 to S15 will be described in detail with reference to FIG. FIG. 4 is a diagram illustrating the behavior when shifting from the operation mode to the power saving mode. The horizontal axis represents time, and the vertical axis represents the output voltage of the power supply circuit 1. Va indicates the maximum rated voltage of the second functional unit 5, and Vth indicates a reference voltage at which the voltage converter 4 stops the conversion operation when less than that.

  At time T1, the output voltage of the power supply circuit 1 starts to drop from the first voltage V1 as the mode switching signal PSDDOWN is turned ON (H level). At time T2, the output voltage of the power supply circuit 1 becomes equal to the maximum rated voltage Va of the second function unit 5. At time T3, the output voltage of the power supply circuit 1 becomes equal to the reference voltage Vth, and thereafter, the voltage converter 4 stops the conversion operation.

  During this time, the delay circuit 8 closes the switch SW1 included in the short-circuit means 6 and short-circuits the short-circuit means 6 with a delay of a predetermined time x after the mode switching signal PSDDOWN is turned ON. Here, the predetermined time x is T2-T1 <x <T3-T1. Accordingly, the switch SW1 is closed and the short-circuit means 6 is short-circuited during the period from time T2 to time T3. That is, the short-circuit means 6 is short-circuited at a timing when the output voltage of the power supply circuit 1 is equal to or lower than the maximum rated voltage Va of the second functional unit 5 and equal to or higher than the reference voltage Vth. Therefore, as shown in the flowchart of FIG. 3, the short-circuit means 6 is short-circuited (S14), and then the voltage converter 4 stops the conversion operation (S15). The second function unit 5 is continuously supplied with a voltage within the rated range.

  As a result, the mode shifts to the power saving mode. FIG. 5 is a block diagram corresponding to the power saving mode. In the power saving mode, the mode switching signal PSDDOWN is in the ON state and maintains the H level. When the mode switching signal PSDDOWN is ON (H level), the power supply circuit 1 outputs the second voltage V2. Accordingly, the first voltage operation unit 31 stops. Further, as described above, since the voltage converter 4 stops the conversion operation, the second voltage operation unit 32 also stops.

  On the other hand, when the mode switching signal PSDDOWN is ON (H level), the switch SW1 provided in the short-circuit means 6 is closed. Therefore, the second voltage V2 output from the power supply circuit 1 is input to the second function unit 5 through a path through the short-circuit unit 6 and the diode D2. Further, the regulator 7 outputs a constant voltage lower than the input second voltage V <b> 2 to the second function unit 5. Therefore, the second function unit 5 operates in the power saving mode by inputting the second voltage V2 and the output of the regulator 7 as in the operation mode.

  Next, the return from the power saving mode to the operation mode will be described. FIG. 6 is a flowchart when returning from the power saving mode to the operation mode. In S21, it is determined whether or not a condition for returning to the operation mode has occurred. The conditions for returning to the operation mode include, for example, a user request from the operation button 105 of the multi-function peripheral device 100 and a software request. When the operation mode return condition occurs (S21: YES), the process proceeds to S22. On the other hand, when the operation mode return condition has not occurred (S21: NO), the process returns to S21 again. That is, the process waits in S21 until an operation mode return condition is generated.

  In S22, the mode switching signal PSDDOWN is turned OFF (L level). When the mode switching signal PSDDOWN is turned OFF (L level), the output voltage of the power supply circuit 1 rises from the second voltage V2 to the first voltage V1 (S23), and the voltage converter 4 starts the conversion operation (S24). Then, the switch SW1 provided in the short-circuit means 6 is opened and the short-circuit means 6 is opened (S25).

  The behavior of S23 to S25 will be described in detail with reference to FIG. FIG. 7 is a diagram illustrating the behavior when returning from the power saving mode to the operation mode. As in FIG. 4, the horizontal axis represents time, the vertical axis represents the output voltage of the power supply circuit 1, Va represents the maximum rated voltage of the second functional unit 5, and Vth falls below that, the voltage converter 4 The reference voltage for stopping the conversion operation is shown.

  At time T4, as the mode switching signal PSDDOWN turns OFF (L level), the output voltage of the power supply circuit 1 starts to rise from the second voltage V2. At time T5, the output voltage of the power supply circuit 1 becomes equal to the reference voltage Vth, and thereafter, the voltage converter 4 performs a conversion operation. At time T <b> 6, the output voltage of the power supply circuit 1 becomes equal to the maximum rated voltage Va of the second function unit 5.

  During this time, the delay circuit 8 opens the switch SW1 included in the short-circuit means 6 and opens the short-circuit means 6 with a delay of a predetermined time y after the mode switching signal PSDDOWN is turned OFF. Here, the predetermined time y is set to T5-T4 <y <T6-T4. Accordingly, the switch SW1 is opened during the period from the time T5 to the time T6, and the short circuit means 6 is opened. That is, the short-circuit means 6 is opened at a timing when the output voltage of the power supply circuit 1 is not less than the reference voltage Vth and not more than the maximum rated voltage Va of the second function unit 5. Therefore, as shown in the flowchart of FIG. 6, the voltage converter 4 starts the conversion operation (S24), and then the short circuit means 6 is opened (S25). The second function unit 5 is continuously supplied with a voltage within the rated range.

  As a result, the operation mode is restored. As described with reference to FIG. 2, the power supply circuit 1 outputs the first voltage V1, and the first voltage operation unit 31 operates. The second voltage operating unit 32 is operated by the second voltage V2 output from the voltage converter 4. Further, the first voltage V1 output from the power supply circuit 1 is converted into the second voltage V2 and input to the second function unit 5 through a path via the voltage converter 4 and the diode D1. The second function unit 5 operates by receiving the second voltage V2 and the output of the regulator 7.

Up to this point, the electrical configuration and operation of the multifunction peripheral device 100 which is an example of the embodiment of the present invention have been described. Next, the effect will be described.
According to the present embodiment, the operation mode and the power saving mode are switched by the mode switching signal PSDDOWN. In the operation mode, the power supply circuit 1 outputs the first voltage V1, and both the first function unit 3 and the second function unit 5 operate. In the power saving mode, the power supply circuit 1 outputs the second voltage V2, and only the second function unit 5 operates. The first functional unit 3 includes a first voltage operating unit 31 that operates at the first voltage V1 and a second voltage operating unit 32 that operates at the second voltage V2.

  Therefore, for example, a drive circuit for each motor such as a print carriage motor is arranged in the first voltage operation unit 31, and a control circuit for the slot unit 104 and the liquid crystal display unit 106 is arranged in the second voltage operation unit 32. The detection circuit of the operation button 105 can be arranged in the input part of the unit 5 not through the regulator 7, and the RTC (REAL TIME CLOCK) or CPU can be arranged in the input part of the second function unit 5 through the regulator 7. .

  As a result, in the power saving mode, the drive circuit of each motor is stopped, and only the minimum necessary operation button 105 detection circuit, RTC, CPU, and the like are operated to reduce power consumption. In addition, the second voltage operating unit 32 is provided with functions that operate at the second voltage V2 but are not necessary in the power saving mode, such as the control circuit of the slot unit 104 and the liquid crystal display unit 106, in the operation mode. It can be operated at two voltages V2 and stopped in the power saving mode.

  In the power saving mode, the power supply circuit 1 needs to supply the second voltage V2 only to the second function unit 5, and thus the power consumption of the power supply circuit 1 itself can be suppressed. Further, since the second voltage V2 output from the power supply circuit 1 can be supplied via the short-circuit means 6 without passing through the voltage converter 4, the power consumption in the voltage converter 4 can also be reduced. . In addition, since the power consumption can be reduced with a simple circuit configuration, the multifunction peripheral device 100 can be reduced in size.

  When shifting from the operation mode to the power saving mode, the delay circuit 8 short-circuits the short-circuit means 6 at a timing when the output voltage of the power supply circuit 1 is equal to or lower than the maximum rated voltage Va of the second function unit 5 and equal to or higher than the reference voltage Vth. When returning from the power saving mode to the operation mode, the delay circuit 8 opens the short-circuit means 6 at a timing when the output voltage of the power supply circuit 1 is equal to or higher than the reference voltage Vth and equal to or lower than the maximum rated voltage Va of the second functional unit 5. Let Therefore, the voltage supply path for the second function unit 5 is switched between a path that passes through the voltage converter 4 and the diode D1 and a path that passes through the short-circuit means 6 and the diode D2, so that the second function unit 5 is within the rated range. Can be operated at all times.

  Further, the backflow when the output voltage of the power supply circuit 1 is switched can be prevented by the diodes D1 and D2 inserted in the voltage supply path of the second function unit 5. Further, the first function unit 3 to be stopped and the second function unit 5 to be operated can be separated in the power saving mode.

The short-circuiting / opening of the short-circuit means 6 may be controlled based on the output voltage of the power supply circuit 1 using an element that is turned on / off according to the voltage, in addition to being controlled by the delay circuit 8 in time. An example will be described with reference to FIG.
FIG. 8 is a block diagram illustrating another example of the electrical configuration of the multi-function peripheral device 100. Here, description of the same points as in FIG. 2 will be omitted, and different points will be mainly described.

As shown in FIG. 8, the short-circuit means 6 includes a pnp transistor Tr1. The input of the short-circuit means 6 is connected to the emitter of the transistor Tr1, and the output of the short-circuit means 6 is connected to the collector of the transistor Tr1. The base of the transistor Tr1 is connected to the collector of the npn transistor Tr2 via the resistor R3. The base of the transistor Tr2 is connected to the input of the short-circuit means 6 in common with the emitter of the transistor Tr1 via the resistor R2 and to the collector of the npn transistor Tr3. The base of the transistor Tr3 is connected to the anode of the Zener diode ZD1. The cathode of the Zener diode ZD1 is connected to the input of the short circuit means 6 in common with the emitter of the transistor Tr1 via the resistor R1. The emitters of the transistors Tr2 and Tr3 are connected to the ground.
Further, the Zener voltage of the Zener diode ZD1 is set to be equal to or lower than the maximum rated voltage Va of the second functional unit 5 and equal to or higher than the operation reference voltage Vth of the voltage converter 4.
Next, the circuit operation when the output voltage of the power supply circuit 1 changes from the first voltage V1 to the second voltage V2 to the first voltage V1 will be described.
(1) When the output voltage of the power supply circuit 1 is the first voltage V1 Since the first voltage V1 that is higher than the Zener voltage is input, the Zener diode ZD1 is turned on. Therefore, the base current flows through the transistor Tr3 and is turned on. When the transistor Tr3 is turned on, the base of the transistor Tr2 becomes the ground level and is turned off. When the transistor Tr2 is turned off, the transistor Tr1 is turned off because no base current flows.
(2) When the output voltage of the power supply circuit 1 drops from the first voltage V1 to the second voltage V2 The output voltage of the power supply circuit 1 drops to be equal to or lower than the maximum rated voltage Va of the second function unit 5 and a voltage converter When the voltage drops below a Zener voltage that is equal to or higher than the operation reference voltage Vth of 4, the Zener diode ZD1 is turned off. Therefore, the base current does not flow in the transistor Tr3 and it is turned off. When the transistor Tr3 is turned off, a base current flows through the transistor Tr2, and the transistor Tr2 is turned on. When the transistor Tr2 is turned on, a base current flows through the transistor Tr1, and the transistor Tr1 is turned on.
(3) When the output voltage of the power supply circuit 1 is the second voltage V2 Since the Zener diode ZD1 is turned off, the transistor Tr1 is turned on as in (2) above.
(4) When the output voltage of the power supply circuit 1 rises from the second voltage V2 to the first voltage V1 The output voltage of the power supply circuit 1 rises and is less than or equal to the maximum rated voltage Va of the second function unit 5 and a voltage converter When the voltage exceeds a Zener voltage that is equal to or higher than the operation reference voltage Vth of 4, the Zener diode ZD1 is turned on. Therefore, the transistor Tr1 is turned off as in the case (1).

  As already described, in the example shown in FIG. 2, the short circuit 6 is controlled to be shorted and opened by the delay circuit 8. In the example shown in FIG. 8, with the configuration as described above, the output voltage of the power supply circuit 1 is monitored using the Zener diode ZD1 that is turned on and off according to the output voltage of the power supply circuit 1, and the transistor Tr1 is turned on and off. The short circuit and the open circuit of the short circuit means 6 are controlled. That is, the transistors Tr1, Tr2, Tr3, resistors R1, R2, R3, and zener diode ZD1 constituting the short-circuit means 6 function as a short-circuit control means. Thus, the short-circuit means is used in a range where the output voltage of the power supply circuit 1 is not more than the maximum rated voltage Va of the second function unit 5 and not less than the operation reference voltage Vth of the voltage converter 4 without using the delay circuit 8. 6 can be short-circuited or opened. Therefore, the second functional unit 5 can be always operated within the rated range. Compared with the example shown in FIG. 2, the delay circuit 8 is unnecessary, and there is no need to input the mode switching signal PSDDOWN. Therefore, there is an effect that the control is simplified.

  As described above in detail, according to the embodiment of the present invention, the operation mode and the power saving mode are switched by the mode switching signal PSDDOWN. In the operation mode, the power supply circuit 1 outputs the first voltage V1, and both the first function unit 3 and the second function unit 5 operate. On the other hand, in the power saving mode, the power supply circuit 1 outputs the second voltage V2 and only the second function unit 5 operates, so that power consumption can be reduced. In this case, since the power supply circuit 1 has only to supply the second voltage V2 only to the second function unit 5, the power consumption of the power supply circuit 1 itself can be suppressed. In addition, since the voltage converter 4 is stopped and power can be supplied through the short-circuit means 6, the power consumption in the voltage converter 4 can be reduced. In addition, since the power consumption can be reduced with a simple circuit configuration, the multifunction peripheral device 100 can be reduced in size.

  Further, at the time of mode switching, the delay circuit 8 controls the short circuit and the short circuit of the short circuit means 6. In another example, the transistors Tr1, Tr2, Tr3, the resistors R1, R2, R3, and the Zener diode ZD1 control the short circuit and the open circuit of the short circuit means 6 as the short circuit control means. Thereby, the 2nd function part 5 can be always operated within the range of a rating.

Note that the present invention is not limited to the above-described embodiment, and it goes without saying that various improvements and modifications can be made without departing from the spirit of the present invention.
For example, the mode switching signal PSDDOWN may be input to the voltage converter 4 so that the voltage converter 4 stops the conversion operation according to the mode switching signal PSDDOWN.

  4 and 7, the maximum rated voltage Va of the second functional unit 5 has been described as being larger than the operation reference voltage Vth of the voltage converter 4, but the present invention is not limited to this. When the operation reference voltage Vth of the voltage converter 4 is larger than the maximum rated voltage Va of the second function unit 5, a period in which the stop of the voltage converter 4 and the opening of the short-circuit means 6 overlap occurs, but the second function unit 5 The capacitor C1 connected between the voltage supply line and the ground functions as a temporary voltage supply source.

  In addition to the above-described example, the short-circuiting / opening control of the short-circuit unit 6 may be performed using a comparator, for example.

DESCRIPTION OF SYMBOLS 1 Power supply circuit 2 Main board 3 1st function part 4 Voltage converter 5 2nd function part 6 Short-circuit means (short-circuit control means)
7 regulator 8 delay circuit 31 first voltage operation unit 32 second voltage operation unit 100 multifunction peripheral device PSDDOWN mode switching signal V1 first voltage V2 second voltage Va maximum rated voltage Vth of second function unit reference voltage

Claims (8)

An image processing apparatus having an operation mode and a power saving mode, wherein in the power saving mode, power supply can be stopped except for a part of the apparatus,
A power supply circuit that outputs either a first voltage or a second voltage lower than the first voltage in response to a mode switching signal;
An electronic circuit that is powered by the power supply circuit and operates;
A voltage converter that converts the first voltage output from the power supply circuit to a voltage that is the same as or substantially equal to the second voltage, and outputs the voltage to the electronic circuit;
Short-circuiting means for forming a path for short-circuiting the voltage converter.   The image processing apparatus according to claim 1, wherein the voltage converter stops a conversion operation in accordance with the mode switching signal.   2. The image according to claim 1, wherein the voltage converter stops a conversion operation when an output voltage of the power supply circuit falls below a reference voltage that is equal to or lower than the first voltage and equal to or higher than the second voltage. Processing equipment. The electronic circuit is
A first functional unit that operates only when the power supply circuit outputs the first voltage;
The image processing apparatus according to claim 1, further comprising: a second function unit that operates when the power supply circuit outputs either the first voltage or the second voltage.   The image processing apparatus according to claim 1, further comprising a delay circuit that short-circuits or opens the short-circuit unit according to the mode switching signal.   The power supply circuit includes a short-circuit control unit that short-circuits or opens the short-circuit unit in a range where the output voltage of the second functional unit is equal to or lower than the maximum rated voltage of the second functional unit and equal to or higher than the reference voltage. Item 5. The image processing apparatus according to Item 4. The first function unit includes:
A first voltage operating unit that operates at a first voltage output by the power supply circuit;
The image processing apparatus according to claim 4, further comprising: a second voltage operation unit that operates at a voltage that is the same as or substantially equal to the second voltage output by the voltage converter. The mode switching signal is
When shifting from the operation mode to the power saving mode, the output voltage of the power supply circuit is switched from the first voltage to the second voltage,
8. The image processing apparatus according to claim 1, wherein when returning from the power saving mode to the operation mode, the output voltage of the power supply circuit is switched from the second voltage to the first voltage. 9.

Images