Electronic apparatus, image reading device, and recording device

Abstract

To provide an electronic apparatus capable of reducing consumption power.SOLUTION: An electronic apparatus includes: a power switch element capable of switching on and off power supply from an input power-source line to an output power-source line; a power-source supply controller for requesting an external device to supply power to the input power-source line when the connection with the external device is established; a power switch capable of switching on and off the power switch element through operation; and a control unit for operating itself with the power supplied to the output power-source line. The power-source supply controller includes an output unit for switching from a first state to a second state when the connection with the external device is established. The electronic apparatus includes a power controlling switch element between the power switch element and the output unit, the power controlling switch element keeping the power switch element off by remaining off until the power switch is operated when the output unit is in the second state and the power switch element is off.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electronic device, an image reading device, and a recording device that operate using power supplied from an external device. [Background technology]

[0002] A known type of electronic device is a power receiving device that operates on power supplied from an external device when connected to the external device via a Universal Serial Bus (USB) interface. Such a power receiving device is equipped with a PD (power delivery) controller that controls the connection with the external device. The PD controller performs a negotiation process to establish a connection with the external device via the USB interface, and starts receiving power when it determines that power can be supplied. For reference, Patent Document 1 discloses a storage device that operates using power supplied from an external device via a USB interface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-15752 Summary of the Invention [Problem to be solved by the invention]

[0004] When the PD controller determines that power can be supplied, it automatically starts receiving power, so power is consumed even if the receiving device is turned off. [Means for solving the problem]

[0005] The electronic device of the present invention is an electronic device that operates using power supplied to an input power line from a connected external device, a power switch element capable of switching on and off the supply of power from the input power line to the output power line; a power supply controller that requests the external device to supply power to the input power line when a connection with the external device is established; a power switch that can be operated to turn on and off the power switch element; a control unit that operates using power supplied to the output power line, the power supply controller includes an output unit that switches from a first state to a second state when a connection with the external device is established; The electronic device has an aspect in which a power control switch element is provided between the power switch element and the output unit, which keeps the power switch element off by remaining off until the power switch is operated when the output unit is in the second state and the power switch element is off.

[0006] The image reading device of the present invention is an image reading device that operates using power supplied to an input power line from a connected external device, a power switch element capable of switching on and off the supply of power from the input power line to the output power line; a power supply controller that requests the external device to supply power to the input power line when a connection with the external device is established; a power switch that can be operated to turn on and off the power switch element; a control unit that operates using power supplied to the output power line; a reading unit capable of reading a medium using power supplied to the output power line, the power supply controller includes an output unit that switches from a first state to a second state when a connection with the external device is established; The electronic device has an aspect in which a power control switch element is provided between the power switch element and the output unit, which keeps the power switch element off by remaining off until the power switch is operated when the output unit is in the second state and the power switch element is off.

[0007] The recording apparatus of the present invention is a recording apparatus that operates using power supplied to an input power line from a connected external device, a power switch element capable of switching on and off the supply of power from the input power line to the output power line; a power supply controller that requests the external device to supply power to the input power line when a connection with the external device is established; a power switch that can be operated to turn on and off the power switch element; a control unit that operates using power supplied to the output power line; a recording unit capable of recording an image on a medium using power supplied to the output power line, the power supply controller includes an output unit that switches from a first state to a second state when a connection with the external device is established; The electronic device has an aspect in which a power control switch element is provided between the power switch element and the output unit, which keeps the power switch element off by remaining off until the power switch is operated when the output unit is in the second state and the power switch element is off. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram schematically illustrating an example of the configuration of an electronic device. [Figure 2] FIG. 1 is a circuit diagram schematically illustrating an example of a main part of an electronic device. [Figure 3] 4 is a timing chart schematically illustrating the operation of an electronic device in a normal state. [Figure 4] 4 is a timing chart schematically illustrating the operation of an electronic device when an overvoltage occurs. [Figure 5] FIG. 10 is a circuit diagram schematically illustrating another example of a main part of an electronic device. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes embodiments of the present invention. Of course, the following embodiments are merely examples of the present invention, and not all of the features shown in the embodiments are necessarily essential to the solution of the invention.

[0010] (1) Summary of the aspects included in the present invention: First, an overview of the embodiments included in the present invention will be described with reference to the examples shown in Figures 1 to 5. Note that the figures in this application are diagrams showing schematic examples, and the magnification in each direction shown in these figures may differ, and the figures may not be consistent with each other. Of course, each element of this embodiment is not limited to the specific example indicated by the symbol. In the "Outline of the embodiments included in the present invention," the words in parentheses indicate supplementary explanations for the words immediately preceding them.

[0011] [Aspect 1] As illustrated in FIGS. 1 and 2, an electronic device 1 according to one embodiment operates using power supplied to an input power line (e.g., VBUS) from a connected external device 100, and includes a power switch element M1, a power supply controller (e.g., USB PD controller 10), a power switch (e.g., power tactile switch SW1), a control unit 20, and a power control switch element M2. The power switch element M1 can switch on and off the power supply from the input power line (VBUS) to the output power line (Vout). When a connection with the external device 100 is established, the power supply controller (10) requests the external device 100 to supply power to the input power line (VBUS). The power switch (SW1) can switch on and off the power switch element M1 by operation. The control unit 20 operates using the power supplied to the output power line (Vout). Here, the power supply controller (10) includes an output unit M3 that switches from a first state (e.g., off) to a second state (e.g., on) when a connection with the external device 100 is established. The power control switch element M2 is disposed between the power switch element M1 and the output unit M3, and when the output unit M3 is in the second state (on) and the power switch element M1 is off, the power control switch element M2 remains off until the power switch (SW1) is operated, thereby keeping the power switch element M1 off.

[0012] As a result, power is not supplied to the power receiving side until the power is turned on. Therefore, the above aspect can provide an electronic device that can reduce power consumption, thereby contributing to energy conservation of electronic devices.

[0013] There are various examples of the above-described aspects. The power switch element M1 may be a FET (field effect transistor), a PNP transistor, or the like. The power control switch element M2 may be an FET or an NPN transistor. The output section M3 of the power supply controller (10) may be an FET or an NPN transistor. In this application, the terms "first", "second", etc. are terms for distinguishing between elements among a plurality of elements having similarities, and do not imply any order. Of course, the above remarks also apply to the following aspects.

[0014] [Aspect 2] 2 and other examples, the electronic device 1 may further include a diode D4 having an anode connected between the power switch element M1 and the power control switch element M2. The power switch (SW1) may be disposed between the cathode of the diode D4 and ground. When the output section M3 is in the second state (ON) and the power switch element M1 is ON, the power control switch element M2 may be switched from ON to OFF when the power switch (SW1) is operated, thereby turning off the power switch element M1. In the above cases, when the power is turned off, power is not supplied to the power receiving side. Therefore, the above aspect can reduce power consumption when the electronic device is not in use, thereby contributing to energy conservation of the electronic device. Note that the connection of a first element and a second element means that these elements are connected so that a direct current flows from one element to the other. Therefore, the connection of a first element and a second element includes not only a direct connection between the first element and the second element, but also a connection between the first element and the second element via a resistor or the like. This statement also applies to the following aspects.

[0015] [Aspect 3] However, when an abnormality occurs in the power receiving electronic device and it is desired to stop the power reception, it is possible that the power receiving electronic device will not be able to send a correct signal to the external device because of the abnormality. Therefore, as illustrated in Figures 1 and 2, the electronic device 1 may further include an overvoltage detection unit 30 that detects an overvoltage applied to the electronic device 1. The electronic device 1 may also include a latch circuit 40 that switches off the power switch element M1 and keeps the power switch element M1 off when the overvoltage is detected. In the above cases, the power switch (SW1) does not function unless the user disconnects the electronic device 1 from the external device 100, so that power is not supplied to the power receiving side when an overvoltage occurs. Therefore, the above embodiment can protect the electronic device from an overvoltage.

[0016] [Aspect 4] 1, the electronic device 1 may further include a motor 52. The electronic device 1 may further include a motor driver 51 that can drive the motor 52 with power supplied to the output power line (Vout). The control unit 20 may control the operation of the motor driver 51. A large amount of power is required for the motor 52 and the motor driver 51. Therefore, the above embodiment can provide a preferable example for reducing power consumption.

[0017] [Aspect 5] 2, the power switch element M1 may be a field effect transistor. The source of the power switch element M1 may be connected to the input power supply line (VBUS). The drain of the power switch element M1 may be connected to the output power supply line (Vout). The gate of the power switch element M1 may be connected to the power control switch element M2 via a resistor R2. The above aspect can provide a suitable example for reducing the power consumption of an electronic device.

[0018] [Aspect 6] 5, the power switch element M1 may be a PNP transistor. The emitter of the power switch element M1 may be connected to the input power supply line (VBUS). The collector of the power switch element M1 may be connected to the output power supply line (Vout). The base of the power switch element M1 may be connected to the power control switch element M2 via a resistor R2. The above aspect can also provide a suitable example for reducing the power consumption of an electronic device.

[0019] [Aspect 7] 2, the power control switch element M2 may be a field effect transistor. The source of the power control switch element M2 may be connected to the output unit M3. The drain of the power control switch element M2 may be connected to the power switch element M1 via a resistor R2. A voltage signal v3 may be input from the control unit 20 to the gate of the power control switch element M2. The above aspect can also provide a suitable example for reducing the power consumption of an electronic device.

[0020] [Aspect 8] 5, the power control switch element M2 may be an NPN transistor. The emitter of the power control switch element M2 may be connected to the output unit M3. The collector of the power control switch element M2 may be connected to the power switch element M1 via a resistor R2. A voltage signal v3 may be input from the control unit 20 to the base of the power control switch element M2. The above aspect can also provide a suitable example for reducing the power consumption of an electronic device.

[0021] [Aspect 9] The image reading device 2 according to one embodiment is an image reading device 2 that operates using power supplied to an input power line (VBUS) from a connected external device 100, and includes the power switch element M1, the power supply controller (10), the power switch (SW1), the control unit 20, and a reading unit 60. The reading unit 60 is capable of reading a medium 80 using power supplied to the output power line (Vout). As a result, power is not supplied to the power receiving side, such as the reading unit 60, until the power is turned on. Therefore, the above aspect can provide an image reading device that can reduce power consumption, and can contribute to energy conservation of the image reading device.

[0022] [Aspect 10] Incidentally, the recording device 3 according to one embodiment is a recording device 3 that operates using power supplied to an input power line (VBUS) from a connected external device 100, and includes the power switch element M1, the power supply controller (10), the power switch (SW1), the control unit 20, and a recording unit 70. The recording unit 70 can record an image 81 on a medium 80 using power supplied to the output power line (Vout). As a result, power is not supplied to the power receiving side, such as the recording unit 70, until the power is turned on. Therefore, the above aspect can provide a recording device that can reduce power consumption, thereby contributing to energy conservation in recording devices.

[0023] (2) Examples of electronic devices: Fig. 1 is a block diagram that schematically illustrates an example of the configuration of an electronic device 1. Fig. 2 is a circuit diagram that schematically illustrates an example of the main parts of the electronic device 1. The electronic device 1 shown in FIG. 1 is a power-receiving device that operates using power supplied from a connected external device 100 to an input power line VBUS. The electronic device 1 may be an image reading device 2, a recording device 3, a digital camera, or the like. FIG. 1 shows both the case where the electronic device 1 is an image reading device 2 and the case where the electronic device 1 is a recording device 3. The image reading device 2 serving as the electronic device 1 includes a reading unit 60 capable of reading a medium 80 using power supplied to an output power line Vout. The reading unit 60 includes a line sensor (not shown) for reading an image 81 on the medium 80, a motor 52 for changing the relative positional relationship between the line sensor and the medium 80, a motor driver 51 capable of driving the motor 52 using power supplied to the output power line Vout, and the like. The recording device 3 serving as the electronic device 1 includes a recording unit 70 capable of recording an image 81 on the medium 80 using power supplied to the output power line Vout. The recording unit 70 includes a recording head (not shown) that forms an image 81 on a medium 80, a motor 52 that changes the relative positional relationship between the recording head and the medium 80, and a motor driver 51 that can drive the motor 52 with power supplied to an output power line Vout. The recording device 3 may be an inkjet printer or a thermal transfer printer. The image 81 may also include a group of characters, etc.

[0024] The external device 100 may be any device capable of supplying power to the electronic device 1, such as an AC (Alternating Current) adapter, a computer such as a personal computer, or a mobile battery. In this specific example, the electronic device 1 operates in accordance with the USB (Universal Serial Bus) Type-C standard and the USB PD (Power Delivery) standard. Therefore, the electronic device 1 includes a receptacle 11 conforming to the USB Type-C standard and a USB PD controller 10 that operates in accordance with the USB PD standard. The USB PD controller 10 is an example of a power supply controller. When a connection with the external device 100 is established, the USB PD controller 10 requests the external device 100 to supply power to an input power line VBUS. Upon receiving the request, the external device 100 starts supplying power to the input power line VBUS. The USB PD controller 10 includes an output unit M3 that switches from off to on when a connection with the external device 100 is established. The off state of the output unit M3 as a switching element indicates a current interruption state, while the on state of the output unit M3 as a switching element indicates a current conduction state. The state in which output unit M3 is off is an example of a first state, and the state in which output unit M3 is on is an example of a second state. The on state of output unit M3 indicates that a connection with external device 100 has been established. External device 100 is equipped with a USB interface 101 that operates in accordance with the Type-C standard and the USB PD standard. A USB cable equipped with a plug 102 that complies with the Type-C standard is connected to USB interface 101. Plug 102 and receptacle 11 are matable with each other.

[0025] Power from the external device 100 is supplied from the receptacle 11 to the input power line VBUS. The USB interface 101 and the USB PD controller 10 communicate in accordance with the USB PD standard via the CC1 and CC2 lines. CC stands for Configuration Channel. Although not shown, the receptacle 11 also has a GND terminal connected to the ground of the electronic device 1.

[0026] The electronic device 1 shown in FIGS. 1 and 2 includes, in addition to the USB PD controller 10 described above, switching elements (M1, M2), a power tactile switch SW1, a control unit 20, an overvoltage detection unit 30, a latch circuit 40, a DC / DC converter 50, and other components. Note that "DC" stands for "Direct Current." The DC / DC converter 50 converts the DC current from the output power line Vout into a DC voltage for operating the control unit 20 and other components. The DC / DC converter 50 may output multiple levels of DC voltage. The control unit 20 operates on power supplied from the DC / DC converter 50. Therefore, the control unit 20 operates on power supplied to the output power line Vout via the DC / DC converter 50. The control unit 20 can be configured, for example, as a system on a chip (SoC) including a central processing unit (CPU) 21, which is a processor. The motor driver 51 shown in FIG. 1 receives power directly from the output power line Vout. The motor driver 51 may receive power from the DC / DC converter 50. The motor 52 may receive power directly from the output power line Vout. The control unit 20 controls the operation of the motor driver 51.

[0027] 2 includes switch elements (M1 to M3), transistors Q1 to Q3, diodes (D1 to D4), resistors R1 to R9, capacitors C1 to C4, etc. The switch elements (M1 to M3) and transistors Q1 to Q3 being off means that the current is cut off, and the switch elements (M1 to M3) and transistors Q1 to Q3 being on means that the current is conductive. The switch elements (M1 to M3) shown in Figure 2 are FETs (field effect transistors), specifically MOSFETs (metal oxide semiconductor field effect transistors). For convenience, the source is indicated by "S," the drain is indicated by "D," and the gate is indicated by "G." "G" is sometimes written as "G1."

[0028] The power switch element M1 shown in Figure 2 is a P-channel MOSFET. The source of the power switch element M1 is connected to the input power line VBUS. The drain of the power switch element M1 is connected to the output power line Vout. The gate of the power switch element M1 is connected to the drain of the power control switch element M2 via a resistor R2. The power switch element M1 can switch on and off the power supply from the input power line VBUS to the output power line Vout.

[0029] 2 is an N-channel MOSFET included in the USB PD controller 10. The source of the output unit M3 is connected to ground. The drain of the output unit M3 is connected to the source of the power control switch element M2.

[0030] The power tactile switch SW1 can be operated to switch the power switch element M1 on and off. The tactile switch has a momentary operation part that energizes when pressed and de-energizes when released. When the power of the electronic device 1 is off, the user can turn on the power of the electronic device 1 by pressing the power tactile switch SW1. When the power of the electronic device 1 is on, the user can turn off the power of the electronic device 1 by pressing the power tactile switch SW1.

[0031] The power control switch element M2 shown in Figure 2 is an N-channel MOSFET located between the power switch element M1 and the output section M3. The source of the power control switch element M2 is connected to the drain of the output section M3. The drain of the power control switch element M2 is connected to the gate of the power switch element M1 via resistor R2. Therefore, it can be said that the switch elements (M1 to M3) are indirectly connected in series. The gate of the power control switch element M2 is connected to the control section 20. A voltage signal v3 is input to the gate of the power control switch element M2 from the control section 20. When the output section M3 is on and the power switch element M1 is off, the power control switch element M2 remains off until the power tactile switch SW1 is operated, thereby keeping the power switch element M1 off.

[0032] A diode D4 is arranged between the power control switch element M2 and the power tactile switch SW1. The anode of the diode D4 is connected between the resistor R2 and the power control switch element M2. Therefore, it can be said that the anode of the diode D4 is connected between the power switch element M1 and the power control switch element M2. The power tactile switch SW1 is arranged between the cathode of the diode D4 and ground. When the power tactile switch SW1 is operated while the output section M3 is on and the power switch element M1 is on, the power control switch element M2 switches from on to off, thereby turning off the power switch element M1.

[0033] The overvoltage detection unit 30 includes a resistor R7 and a Zener diode D2. One end of the resistor R7 is connected to the anode of the Zener diode D2, and the other end of the resistor R7 is connected to ground via a resistor R4. The output of the DC / DC converter 50, for example, is input to the cathode of the Zener diode D2. The cathode of the Zener diode D2 may be connected to the output power line Vout. The Zener voltage of the Zener diode D2 is set higher than the normal voltage. When a voltage higher than the Zener voltage is applied to the Zener diode D2, a breakdown current flows through the Zener diode D2. Therefore, a voltage higher than the Zener voltage can be said to be an overvoltage applied to the electronic device 1. The overvoltage detection unit 30 detects an overvoltage applied to the electronic device 1.

[0034] The latch circuit 40 includes transistors Q1 to Q3, resistors R3 to R6, and a capacitor C3. For convenience, the emitters of the transistors Q1 to Q3 are indicated by "E," the collectors by "C," and the bases by "B." The transistor Q1 is a PNP transistor. The emitter of the transistor Q1 is connected to the input power line VBUS. The collector of the transistor Q1 is connected between the power switch element M1 and the resistor R2. The base of the transistor Q1 is connected between the resistors R3 and R6.

[0035] The transistor Q2 is an NPN transistor. The emitter of the transistor Q2 is connected to ground. The collector of the transistor Q2 is connected between the base of the transistor Q3 and the resistor R5. The base of the transistor Q2 is connected between the resistor R7 and the resistor R4. Transistor Q3 is an NPN transistor. The emitter of transistor Q3 is connected between resistors R6 and R5. The collector of transistor Q3 is connected between resistor R7 and the base of transistor Q2. The base of transistor Q3 is connected between resistor R5 and the collector of transistor Q2.

[0036] When an overvoltage causes current to flow from Zener diode D2 to ground through resistors R7 and R4, current flows through the base of transistor Q2, turning transistor Q2 on and pulling down the voltage at the collector of transistor Q2. This causes current to flow through the base of transistor Q3, turning transistor Q3 on and causing current to flow from the emitter to the collector. In this state, transistors Q2 and Q3 remain on. The emitter of transistor Q3 draws current from resistor R6, turning transistor Q1 on. This switches power switch element M1 from on to off. After that, transistors Q1 to Q3 remain on, so power switch element M1 remains on. In this way, when an overvoltage is detected, latch circuit 40 switches power switch element M1 off and keeps it off. Because latch circuit 40 is independent of control unit 20, power reception is reliably stopped in the event of an overvoltage.

[0037] The control unit 20 is triggered by the start of power supply from the output power line Vout and outputs a voltage signal v3 to the gate of the power control switch element M2 to turn on the power control switch element M2. The control unit 20 is also capable of reading the potential state PSW of the anode of the diode D3. When the control unit 20 detects the operation of the power tactile switch SW1 by reading that the potential state PSW has switched from H to L, the control unit 20 performs a power-off process using the CPU 21 and outputs a voltage signal v3 to the gate of the power control switch element M2 to turn off the power control switch element M2.

[0038] (3) Operation of the specific electronic device: 3 is a timing chart schematically showing the normal operation of the electronic device 1. Normally, the latch circuit 40 is kept off. When the electronic device 1 and the external device 100 are connected to each other, for example by inserting the plug 102 into the receptacle 11, the USB PD controller 10 performs negotiation communication with the USB interface 101 in accordance with the USB PD standard. After establishing a connection with the external device 100, the USB PD controller 10 requests the external device 100 to supply power to the input power line VBUS and switches the output unit M3 from OFF to ON (timing t1). Upon receiving this request, the external device 100 begins supplying power to the input power line VBUS. If the power tactile switch SW1 is not operated, the voltage signal v3 that turns on the power control switch element M2 is not input to its gate, and therefore the power control switch element M2 remains OFF. Furthermore, the voltage that turns on the power switch element M1 is not input to its gate, and therefore the power switch element M1 remains OFF. In this way, when the output section M3 is on and the power switch element M1 is off, the power control switch element M2 remains off until the power tactile switch SW1 is operated, thereby keeping the power switch element M1 off. Operating the power tactile switch SW1 in this state turns on the power of the electronic device 1.

[0039] When the power tactile switch SW1 is operated to momentarily turn on, a voltage to turn on the power switch element M1 is input to the gate of the power switch element M1 via resistor R2 and diode D4, switching the power switch element M1 from off to on (timing t2). When the power switch element M1 turns on, power is supplied from the input power line VBUS to the output power line Vout, causing the voltage on the output power line Vout to rise from low (L) to high (H). This activates the DC / DC converter 50, which then activates the control unit 20 (e.g., an SoC), which outputs a voltage signal v3 to the gate of the power control switch element M2 to turn on the power control switch element M2. As a result, the power control switch element M2 switches from off to on. Because the power control switch element M2 is on, the power switch element M1 remains on even when the user releases the power tactile switch SW1. 3, from timing t1 to timing t2, the output power line Vout does not rise, and power is not supplied to the control unit 20, the motor driver 51, etc. In this way, even if the connection between the electronic device 1 and the external device 100 is established, power is not supplied to the power receiving side until the power tactile switch SW1 is operated. Therefore, power consumption from timing t1 to timing t2 is reduced.

[0040] Operation of the power tactile switch SW1 after the power control switch element M2 is turned on turns off the power of the electronic device 1. When the power tactile switch SW1 is momentarily turned on by being operated, the control unit 20 detects the operation of the power tactile switch SW1 by detecting that the potential state PSW of the anode of the diode D3 has dropped from H to L, and the CPU 21 performs power-off processing. At this time, the control unit 20 outputs a voltage signal v3 to the gate of the power control switch element M2 to turn off the power control switch element M2. As the power control switch element M2 switches from ON to OFF, a voltage to turn off the power switch element M1 is input to the gate of the power switch element M1, switching the power switch element M1 from ON to OFF. As a result, the output power line Vout drops from H to L, returning to the same state as between timing t1 and timing t2 (timing t3). In this way, when the power tactile switch SW1 is operated while the output section M3 is on and the power switch element M1 is on, the power control switch element M2 switches from on to off, thereby turning off the power switch element M1. 3, after timing t3, the output power line Vout remains at L, and no power is supplied to the control unit 20, motor driver 51, etc. In this way, when the power is turned off, no power is supplied to the power receiving side. Therefore, the power consumption until the power is turned on is reduced.

[0041] FIG. 4 is a timing chart showing the operation of the electronic device 1 when an overvoltage occurs. The operation is as shown in Figure 3 until the power control switch element M2 switches from off to on. When an overvoltage occurs, current flows from Zener diode D2 to ground via resistors R7 and R4, and current flows to the base of transistor Q2, switching transistor Q2 from off to on. When transistor Q2 switches on, transistor Q3 switches from off to on, maintaining transistors Q2 and Q3 on. When transistor Q3 switches on, transistor Q1 switches from off to on. In this way, the latch circuit 40 switches from off to on when an overvoltage is detected. When transistor Q1 switches on, power switch element M1 switches from on to off (timing t4), and the output power line Vout drops from high to low. Because transistors Q2 and Q3 remain on, power switch element M1 remains off even when power tactile switch SW1 is operated, unless the user disconnects the electronic device 1 from the external device 100. In other words, the power tactile switch SW1 does not function. In this way, when an overvoltage is detected, the latch circuit 40 switches the power switch element M1 off and keeps the power switch element M1 off. Therefore, when an overvoltage occurs, power is not supplied to the power receiving side, and the electronic device is protected from the overvoltage.

[0042] As described above, even if the connection between the electronic device 1 and the external device 100 is established, power is not supplied to the power receiving side until the power tactile switch SW1 is operated, and when the power is turned off, power is not supplied to the power receiving side. Therefore, this specific example can reduce the power consumption of the electronic device 1, contributing to energy conservation of the electronic device 1 and protecting the electronic device 1 from overvoltage.

[0043] (4) Variation: The present invention can be embodied in various modifications. For example, at least some of the switch elements (M1 to M3) may be replaced with transistors other than FETs.

[0044] Fig. 5 is a circuit diagram showing another example of the main parts of the electronic device 1. Compared to the circuit shown in Fig. 2, the circuit shown in Fig. 5 has the switch elements (M1 to M3) replaced with transistors rather than FETs, and resistors R10 and R11 added.

[0045] As shown in Fig. 5, the power switch element M1 may be a PNP transistor. The emitter of the power switch element M1 shown in Fig. 5 is connected to the input power supply line VBUS. The collector of the power switch element M1 shown in Fig. 5 is connected to the output power supply line Vout. The base of the power switch element M1 shown in Fig. 5 is connected to the collector of the power control switch element M2 via a resistor R2. As described above, the power switch element M1 can switch on and off the power supply from the input power line VBUS to the output power line Vout.

[0046] As shown in Fig. 5, the output section M3 may be an NPN transistor. The emitter of the output section M3 shown in Fig. 5 is connected to ground. The collector of the output section M3 shown in Fig. 5 is connected to the emitter of the power control switch element M2.

[0047] As shown in FIG. 5, the power control switch element M2 may be an NPN transistor. The emitter of the power control switch element M2 shown in FIG. 5 is connected to the collector of the output section M3. The collector of the power control switch element M2 shown in FIG. 5 is connected to the base of the power switch element M1 via a resistor R2. The base of the power control switch element M2 shown in FIG. 5 is connected to the control section 20 via a resistor R10. A voltage signal v3 is input to the base of the power control switch element M2 from the control section 20. When the output section M3 is on and the power switch element M1 is off, the power control switch element M2 remains off until the power tactile switch SW1 is operated, thereby keeping the power switch element M1 off. When the output section M3 is on and the power switch element M1 is on, the power control switch element M2 switches from on to off, thereby turning off the power switch element M1 when the power tactile switch SW1 is operated.

[0048] The electronic device 1 having the circuit shown in Fig. 5 also operates as shown in Fig. 3 and 4. Therefore, the electronic device 1 in which the switch elements (M1 to M3) are replaced with transistors other than FETs can also reduce the power consumption of the electronic device 1, contributing to energy conservation of the electronic device 1 and protecting the electronic device 1 from overvoltage. Even if some of the switch elements (M1 to M3) are FETs and the rest are transistors other than FETs, the electronic device 1 operates as shown in FIGS.

[0049] (5) Conclusion: As described above, the present invention provides various configurations of electronic devices that can reduce power consumption. Of course, even in an embodiment that includes only the features of the independent claims, the basic functions and effects described above can be achieved. Furthermore, it is possible to implement configurations in which the components disclosed in the above examples are substituted with each other or the combination is changed, or configurations in which the components disclosed in the publicly known techniques and the above examples are substituted with each other or the combination is changed, etc. The present invention also includes these configurations. [Explanation of symbols]

[0050] 1...electronic device, 2...image reading device, 3...recording device, 10...USB PD controller, 20...control unit, 21...CPU, 30...overvoltage detection unit, 40...latch circuit, 50...DC / DC converter, 51...motor driver, 52...motor, 60...reading unit, 70...recording unit, 80...medium, 81...image, 100...external device, 101...USB interface, D4...diode, M1...power switch element, M2...power control switch element, M3...output unit, Q1 to Q3...transistor, R2...resistor, SW1...power tactile switch.

Claims

1. An electronic device that operates using power supplied to an input power line from a connected external device, a power switch element capable of switching on and off the supply of power from the input power line to the output power line; a power supply controller that requests the external device to supply power to the input power line when a connection with the external device is established; a power switch that can be operated to turn on and off the power switch element; a control unit that operates using power supplied to the output power line, the power supply controller includes an output unit that switches from a first state to a second state when a connection with the external device is established; The electronic device includes, between the power switch element and the output unit, a power control switch element that keeps the power switch element off by being off until the power switch is operated when the output unit is in the second state and the power switch element is off.

2. a diode having an anode connected between the power switch element and the power control switch element; the power switch is disposed between the cathode of the diode and ground; 2. The electronic device according to claim 1, wherein when the power switch is operated while the output section is in the second state and the power switch element is on, the power control switch element switches from on to off, thereby turning off the power switch element.

3. an overvoltage detection unit that detects an overvoltage applied to the electronic device; 3. The electronic device according to claim 1, further comprising: a latch circuit that switches off the power switch element when the overvoltage is detected, and keeps the power switch element off.

4. A motor and a motor driver capable of driving the motor with power supplied to the output power line, The electronic device according to claim 1 , wherein the control unit controls an operation of the motor driver.

5. the power switching element is a field effect transistor; a source of the power switch element connected to the input power line; the drain of the power switch element is connected to the output power line; 3. The electronic device according to claim 1, wherein a gate of the power switch element is connected to the power control switch element via a resistor.

6. the power switch element is a PNP transistor; an emitter of the power switch element connected to the input power line; a collector of the power switch element connected to the output power line; 3. The electronic device according to claim 1, wherein the base of the power switch element is connected to the power control switch element via a resistor.

7. the power control switch element is a field effect transistor, the source of the power control switch element is connected to the output section; the drain of the power control switch element is connected to the power switch element via a resistor; 3. The electronic device according to claim 1, wherein a voltage signal is input from the control unit to a gate of the power control switch element.

8. the power control switch element is an NPN transistor, the emitter of the power control switch element is connected to the output section, a collector of the power control switch element is connected to the power switch element via a resistor; 3. The electronic device according to claim 1, wherein a voltage signal is input from the control unit to a base of the power control switch element.

9. An image reading device that operates using power supplied to an input power line from a connected external device, a power switch element capable of switching on and off the supply of power from the input power line to the output power line; a power supply controller that requests the external device to supply power to the input power line when a connection with the external device is established; a power switch that can be operated to turn on and off the power switch element; a control unit that operates using power supplied to the output power line; a reading unit capable of reading a medium using power supplied to the output power line, the power supply controller includes an output unit that switches from a first state to a second state when a connection with the external device is established; The image reading device includes a power control switch element between the power switch element and the output unit, which keeps the power switch element off by remaining off until the power switch is operated when the output unit is in the second state and the power switch element is off.

10. A recording device that operates using power supplied to an input power line from a connected external device, a power switch element capable of switching on and off the supply of power from the input power line to the output power line; a power supply controller that requests the external device to supply power to the input power line when a connection with the external device is established; a power switch that can be operated to turn on and off the power switch element; a control unit that operates using power supplied to the output power line; a recording unit capable of recording an image on a medium using power supplied to the output power line, the power supply controller includes an output unit that switches from a first state to a second state when a connection with the external device is established; The recording device further includes a power control switch element between the power switch element and the output unit, which keeps the power switch element off by remaining off until the power switch is operated when the output unit is in the second state and the power switch element is off.

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