JP2016129185A - Electronic apparatus, printing apparatus, and control method of electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a malfunction of a device to be controlled with a simple configuration.SOLUTION: The electronic apparatus includes: an nMOS 113 for controlling lighting of an LED 50, which is a device; and a CPU 120 for supplying a control voltage for controlling the nMOS 113. An open drain port 123 and an input and output port 122 of the CPU 120 are connected to a gate terminal of the nMOS 113. Depending on an output state of the open drain port 123, supply of a control voltage to the gate terminal is controlled.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an electronic device, a printing apparatus, and an electronic device control method.

  2. Description of the Related Art Conventionally, when a driving voltage for turning on an LED is different from an operating voltage of a CPU that controls the LED, a technique for preventing the LED driving voltage from being applied to the CPU by using a two-stage transistor is known. (For example, refer to Patent Document 1). The LED drive circuit of Patent Document 1 has a configuration in which a plurality of resistors, in which a resistor and a second switching element are connected in series, are connected in parallel between a first switching element that controls an LED energization current and a ground terminal. Prepare. Each of the plurality of second switching elements is individually turned on and off to finely adjust the energization current flowing through the LED.

JP 2008-192730 A

By the way, in an electronic device, there exists a request | requirement that the malfunctioning (error lighting) of LED etc. when CPU was reset was prevented. For example, if the output state of the CPU is changed for resetting the CPU before the drive voltage for lighting the LED is lowered, the LED may be erroneously lit.
The present invention has been made in view of the above circumstances, and provides an electronic device, a printing apparatus, and an electronic device control method for preventing malfunction of a device to be controlled, in particular, erroneous lighting of an LED, with a simple configuration. The purpose is to provide.

In order to achieve the above object, an electronic apparatus according to the present invention includes a switch that controls a device, and a CPU that supplies a control voltage for controlling the switch. The open drain port and the input / output port of the CPU include: The control voltage is connected to the control terminal of the switch, and the supply of the control voltage to the control terminal is controlled by the output state of the open drain port.
According to the present invention, malfunction of a device to be controlled can be prevented with a simple configuration.

According to the present invention, in the electronic device, the CPU performs PWM control on the control voltage supplied to the control terminal according to an output state of the open drain port.
According to the present invention, the control voltage supplied to the control terminal by the open drain port can be PWM-controlled. Therefore, dimming control of the LED can be performed.

According to the present invention, in the electronic device, the device is an LED that is lit by a drive current, and includes a power supply unit that supplies the drive current to the LED, and the CPU supplies the LED to the LED. The control voltage having a voltage lower than the voltage to be supplied is supplied.
According to the present invention, even if the forward voltage of the LED is higher than the operating voltage of the CPU, the LED can be controlled to be turned on by the CPU.

According to the present invention, in the electronic device, the CPU turns off the LED by controlling the output of the input / output port to low level or high impedance and controlling the open drain port to high impedance. It is characterized by making it.
According to the present invention, erroneous lighting of LEDs can be prevented.

In the electronic device according to the present invention, the switch includes a gate terminal as the control terminal connected to the open drain port of the CPU and the input / output port, and a drain terminal connected to the power supply unit. The n-channel MOSFET is connected, the source terminal is grounded, and the control terminal and the source terminal are connected via a resistor.
According to the present invention, lighting of an LED can be controlled with a simple configuration.

In addition, the printing apparatus of the present invention includes an operation unit that receives an operation, a display unit that includes an LED, a switch that controls lighting of the LED, and a control unit that includes a CPU that supplies a control voltage of the switch, The open drain port and the input / output port of the CPU are connected to the control terminal of the switch, and the supply of the control voltage to the control terminal is controlled by the output state of the open drain port. To do.
According to the present invention, malfunction of an LED to be controlled can be prevented with a simple configuration.

According to the present invention, in the printing apparatus, the control unit controls the output state of the open drain port and the input / output port to turn off the LED when the operation unit receives a power-off operation. It is characterized by making it.
According to the present invention, it is possible to prevent erroneous lighting of the LED after an operation for turning off the power is received by the operation unit.

An electronic device control method according to the present invention is a control method for an electronic device including a switch that controls lighting of an LED and a CPU that supplies a control voltage of the switch, the control voltage being applied to a control terminal included in the switch. Is controlled by the output states of the open drain port and the input / output port of the CPU connected to the control terminal of the switch.
According to the present invention, malfunction of an LED to be controlled can be prevented with a simple configuration.

1 is a system configuration diagram of a printing system. The block diagram of the electronic device which controls lighting of LED. The flowchart which shows the process sequence of CPU core. FIG. 11 illustrates a configuration of an electronic device of a comparative example. The figure which shows the voltage of 5V power supply and voltage source at the time of reset of the electronic device of a comparative example. The figure which shows the voltage of 5V power supply and input-output port at the time of reset of CPU.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a system configuration diagram of the printing system 1.
The printing system 1 includes a printing apparatus 10 and a host computer 30 that communicates with the printing apparatus 10 and causes the printing apparatus 10 to execute printing. The printing apparatus 10 and the host computer 30 are communicably connected via a network 20 such as Ethernet (registered trademark).
The host computer 30 includes an application for creating print data and a printer driver. The host computer 30 generates image and character information to be printed by the printing apparatus 10 using an operator instruction or the like as a trigger. The host computer 30 generates control data of a command system that can be interpreted by the printing apparatus 10 based on the generated image and character information. The host computer 30 transmits the generated control data to the printing apparatus 10 via the network 20. The printing apparatus 10 prints an image on printing paper based on control data received from the host computer 30.

  The printing apparatus 10 includes a control unit 11, a nonvolatile memory 12, a buffer memory 13, a display unit 14, an operation unit 15, a communication unit 16, and a printing unit 17.

  The control unit 11 controls the printing operation as a print engine and centrally controls each unit of the printing apparatus 10. The nonvolatile memory 12 stores programs executed by the control unit 11 and various data. The buffer memory 13 temporarily stores data received from the host computer 30.

The display unit 14 includes a display panel on which an image to be printed and a menu screen are displayed. Further, the display unit 14 includes a plurality of LED indicators (hereinafter referred to as LEDs) 50 (see FIG. 2). Under the control of the control unit 11, the LED 50 is turned on, turned off, or blinked to operate the printing apparatus 10. The status, the presence / absence of an error, and other information are reported.
The operation unit 15 includes a power switch for operating the power supply of the printing apparatus 10 and a selection switch for selecting and operating a desired selection item on the menu screen displayed on the display unit 14. The operator operates the operation unit 15 while confirming the display on the display unit 14 to open the print setting screen from the menu screen, and various printing conditions such as the type of the print medium, the size of the print medium, and the print quality. Can be set.

  The communication unit 16 performs data communication with the host computer 30 connected via the network 20 and receives control data from the host computer 30. The printing unit 17 includes hardware for printing on printing paper based on the control of the control unit 11.

FIG. 2 is a configuration diagram of the electronic device 100 that controls the lighting of the LED 50.
The electronic device 100 includes a driving unit 110 that drives the LED 50 as a device to be controlled, and a CPU 120 that controls the lighting of the LED 50 by controlling the driving unit 110. The CPU 120 is a CPU that is mounted on the control unit 11 and controls the printing apparatus 10. The drive unit 110 may be mounted on the display unit 14 together with the LED 50, but in the present embodiment, the drive unit 110 is mounted on the control unit 11 and constitutes the electronic device 100 together with the CPU 120.

  The drive unit 110 includes a 5V power supply 111, a p-channel MOSFET (hereinafter referred to as pMOS) 112, a resistor R1, a resistor R2, an n-channel MOSFET (hereinafter referred to as nMOS) 113, and a resistor R3. And a resistor R4.

  In the present embodiment, a 5V power supply 111 that supplies a voltage of 5V (first voltage) is used as a power supply for turning on the LED 50. For this reason, even if LED50 is LED with high forward voltage (VF), such as a blue light emitting diode, it can be used. The 5V power supply 111 is turned on / off by a power switch of the operation unit 15.

The anode terminal of the LED 50 is connected to the resistor R1, and the cathode terminal is grounded.
The source terminal of the pMOS 112 is connected to the 5V power source 111, and the drain terminal is connected to the resistor R1. The gate terminal of the pMOS 112 is connected to the 5V power source 111 via the resistor R2.

  The drain terminal of the nMOS 113 is connected to the 5V power source 111 via the resistor R2, and the source terminal is grounded. The gate terminal of the nMOS 113 is connected to the open drain port 123 of the CPU 120. The gate terminal and the source terminal of the nMOS 113 are connected via a resistor R4.

The resistor R3 is connected in series to the resistor R4, and constitutes the voltage dividing circuit 115 together with the resistor R4.
One end of the resistor R3 is connected to the input / output port 122 of the CPU 120, and the other end is connected to the gate terminal of the nMOS 113. The resistor R4 is connected to the gate terminal of the nMOS 113 and the source terminal of the nMOS 113.

The CPU 120 includes a CPU core 121, an input / output port 122, and an open drain port 123.
The CPU core 121 is mounted with a logic circuit, a cache memory, and the like, performs arithmetic processing, and controls the printing apparatus 10.
The input / output port 122 is a general CMOS structure input / output port. The input / output port 122 takes three states of H (High) level, L (Low) level, and high impedance (Z) as voltage output states.
The open drain port 123 takes two states, a sink (Sink) and a high impedance (Z). When the open drain port 123 is in a sink state, a sink current flows through a pull-down resistor (not shown) included in the open drain port 123.

The CPU 120 outputs a control voltage (3.3 V) for controlling the nMOS 113 from the input / output port 122. When the output state of the input / output port 122 becomes H level, the output voltage of the input / output port 122 becomes 3.3V. The control voltage (3.3V) of the nMOS 113 supplied from the input / output port 122 is lower than that of the 5V power supply 111.
Further, the open drain port 123 of the CPU 120 is connected to a gate terminal which is a control terminal of the nMOS 113. The CPU core 121 controls application of the control voltage output from the input / output port 122 to the gate terminal of the nMOS 113 by controlling the output state of the open drain port 123.

FIG. 3 is a flowchart showing the processing procedure of the CPU core 121.
When turning on the LED 50 (step S1 / YES), the CPU core 121 sets the output state of the input / output port 122 to the H level, and sets the open drain port 123 to high impedance (step S2).
When the output state of the input / output port 122 is H level and the open drain port 123 is in a high impedance state, a voltage obtained by dividing the control voltage by the voltage dividing circuit 115 is applied to the gate terminal of the nMOS 113. As a result, the gate-source voltage, which is the voltage of the gate terminal with respect to the source terminal of the nMOS 113, becomes larger than the threshold voltage, and the nMOS 113 is turned on. When the nMOS 113 is turned on, the source-gate voltage that is the voltage of the source terminal with respect to the gate terminal of the pMOS 112 becomes larger than the threshold voltage, and the pMOS 112 is also turned on. When the pMOS 112 is turned on, a drive current flows from the 5V power supply 111 to the LED 50 via the resistor R1, and the LED 50 is lit.

The CPU core 121 sets the output state of the input / output port 122 to the H level and sets the open drain port to the sink state when the LED 50 is not turned on (step S1 / NO) but is turned off (step S3 / YES). (Step S4).
When the output state of the input / output port 122 is at the H level and the open drain port 123 is in the sink state, a sink current flows through the open drain port 123, the gate-source voltage of the nMOS 113 becomes smaller than the threshold value, and the nMOS 113 Turns off. When the nMOS 113 is turned off, the pMOS 112 is also turned off and the LED 50 is turned off.

  Further, when the open drain port 123 of the CPU 120 is a port that can support PWM control, the dimming control of the LED 50 can be performed by the PWM control by the open drain port 123. In this case, the CPU core 121 switches the state of the open drain port 123 to high impedance or sink according to the control pulse while maintaining the output state of the input / output port 122 at the H level. The control pulse is a pulse for PWM control of the LED 50. For example, when the LED 50 is turned on at 100%, the on-duty of the control pulse is 100%, and when the LED 50 is turned on at 50%, the on-duty of the control pulse is 50% and the off-duty is 50%.

When the power switch provided in the operation unit 15 of the printing apparatus 10 is turned off, the CPU core 121 performs a reset process of the CPU 120 and stops its operation. When performing the reset process of the CPU 120 (step S5 / YES), the CPU core 121 sets the output state of the input / output port 122 to L level or high impedance, and sets the open drain port 123 to high impedance (step S6). . That is, even if the open drain port 123 is set to high impedance, the control voltage is not applied to the gate terminal of the nMOS 113 and the nMOS 113 and pMOS 112 are turned on by setting the input / output port 122 to L level or high impedance. There is nothing to do. Therefore, after the operator turns off the power switch of the operation unit 15, the LED 50 of the display unit 14 is not lit.
The CPU core 121 sets the input / output port 122 and the open drain port 123 to a high impedance state during the initialization process. This prevents the LED 50 from being unnecessarily lit during the initialization process.

  FIG. 4 shows a configuration of an electronic apparatus of a comparative example. The electronic device of the comparative example shows a case where the voltage source 130 supplies a control voltage of 3.3 V to the gate terminal of the nMOS 113 instead of the CPU 120. The voltage source 130 is turned on / off by a power switch of the operation unit 15. FIG. 5 shows voltage changes between the 5 V power supply 111 and the voltage source 130 when the electronic device of the comparative example shown in FIG. 4 is reset. When the power switch of the operation unit 15 is turned off, the 5V power supply 111 and the voltage source 130 are turned off, the reset signal input to the CPU 120 falls to the L level, and the CPU core 121 performs the reset process of the CPU 120. In the case of supplying a 3.3V control voltage from the voltage source 130, the voltage of the 5V power supply 111 and the voltage source 130 decreases even if the power switch of the operation unit 15 is turned off and the reset signal falls to the L level. It takes time to do. For this reason, if the open drain port 123 is set to high impedance before the voltage between the 5V power source 111 and the voltage source 130 is lowered, the nMOS 113 and the pMOS 112 may be turned on. For this reason, the LED 50 is erroneously turned on.

FIG. 6 shows the 5V power supply 111 and the output voltage of the input / output port 122 during the reset process of the CPU 120 of this embodiment.
In this embodiment, since the control voltage supplied to the gate terminal of the nMOS 113 is supplied from the input / output port 122 of the CPU 120, when the reset signal falls to the L level, the output of the input / output port 122 also becomes the L level (or high level).・ Fall to (impedance). Therefore, even if the open drain port 123 becomes high impedance before the voltage of the 5V power supply 111 drops, the control voltage is not supplied to the gate terminal of the nMOS 113. Therefore, erroneous lighting of the LED 50 at the time of resetting can be prevented.
Further, if the open drain port 123 is used as a sink, even if the output state of the input / output port 122 becomes H level by mistake, the nMOS 113 will not be turned on.

  As described above, the electronic apparatus 100 according to this embodiment includes the nMOS 113 that controls lighting of the LED 50 as a device and the CPU 120 that supplies a control voltage for controlling the nMOS 113. The open drain port 123 and the input / output port 122 of the CPU 120 are connected to the gate terminal of the nMOS 113, and the supply of the control voltage to the gate terminal is controlled by the output state of the open drain port 123. Therefore, erroneous lighting of the LED 50 can be prevented with a simple configuration.

  Further, the CPU 120 performs PWM control on the control voltage supplied to the gate terminal according to the output state of the open drain port 123. Accordingly, the control voltage supplied to the gate terminal by the open drain port 123 can be PWM-controlled. For this reason, dimming control of the LED can be performed.

  The drive unit 110 includes a 5V power supply 111 that supplies a drive current to the LED 50. The CPU 120 supplies a control voltage that is lower than the voltage that the 5V power supply 111 supplies to the LED 50. Therefore, even when the forward voltage of the LED 50 is higher than the operating voltage of the CPU, the CPU 50 can control the lighting of the LED 50.

  The CPU 120 controls the output level of the input / output port 122 to low level or high impedance, and controls the open drain port 123 to high impedance, thereby turning off the LED 50. Therefore, erroneous lighting of the LED 50 can be prevented.

  The nMOS 113 has a gate terminal connected to the open drain port 123 and the input / output port 122 of the CPU 120, a drain terminal connected to the 5V power supply 111, a source terminal grounded, and a gate terminal and a source terminal connected to each other. They are connected via a resistor R4. Therefore, the CPU 120 can turn on / off the LED 50 by controlling the nMOS 113. For this reason, lighting of LED50 is controllable with a simple structure.

  The printing apparatus 10 includes an operation unit 15 that receives an operation, a display unit 14 that includes an LED 50, an nMOS 113 that controls lighting of the LED 50, and a control unit 11 that includes a CPU 120 that supplies a control voltage of the nMOS 113. The open drain port 123 and the input / output port 122 of the CPU 120 are connected to the gate terminal of the nMOS 113, and the supply of the control voltage to the gate terminal is controlled by the output state of the open drain port 123. Therefore, it is possible to prevent malfunction of the LED to be controlled with a simple configuration.

The above-described embodiment is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention. For example, in the above-described embodiment, the case where the lighting control of the LED 50 is controlled has been described as an example, but the target of the lighting control is not limited to the LED. For example, it may be an EL element (Organic Light Emitting Diode) or an inorganic EL element. Furthermore, it is applicable not only to lighting control but also to other control objects.
Moreover, although embodiment mentioned above demonstrated as an example the case where lighting of 1 LED was controlled and light extinction, it is not limited to this. For example, a configuration in which a plurality of LEDs are connected in series may be used, or a configuration in which a plurality of LED groups in which a plurality of LEDs are connected in series may be connected in parallel.
Further, the FET (113) that supplies the control voltage is an n-channel type, and the transistor (112) that drives the LED 50 is a p-channel type. However, the conductivity type of the channel formation region of the transistor is not limited thereto.

  DESCRIPTION OF SYMBOLS 1 ... Printing system, 10 ... Printing apparatus, 11 ... Control part, 12 ... Non-volatile memory, 13 ... Buffer memory, 14 ... Display part, 15 ... Operation part, 16 ... Communication part, 17 ... Printing part, 20 ... Network, DESCRIPTION OF SYMBOLS 30 ... Host computer, 50 ... LED (device), 100 ... Electronic device, 110 ... Drive part, 111 ... 5V power supply (power supply part), 112 ... pMOS, 113 ... nMOS (switch), 115 ... Voltage divider circuit, 120 ... CPU, 121 ... CPU core, 122 ... input / output port, 123 ... open drain port.

Claims (8)

A switch to control the device;
A CPU for supplying a control voltage for controlling the switch,
An open drain port and an input / output port of the CPU are connected to a control terminal of the switch, and supply of the control voltage to the control terminal is controlled by an output state of the open drain port. machine.   The electronic device according to claim 1, wherein the CPU performs PWM control on the control voltage supplied to the control terminal according to an output state of the open drain port. The device is an LED that is lit by a drive current,
A power supply unit for supplying the LED with the driving current;
The electronic device according to claim 1, wherein the CPU supplies the control voltage that is lower than a voltage supplied to the LED by the power supply unit.   4. The CPU according to claim 3, wherein the CPU turns off the LED by controlling the output of the input / output port to a low level or high impedance and controlling the open drain port to high impedance. Electronics.   In the switch, a gate terminal as the control terminal is connected to the open drain port and the input / output port of the CPU, a drain terminal is connected to the power supply unit, a source terminal is grounded, and the control 5. The electronic apparatus according to claim 3, wherein the electronic device is an n-channel MOSFET in which a terminal and the source terminal are connected via a resistor. An operation unit for receiving an operation;
A display unit having an LED;
A switch for controlling lighting of the LED;
A control unit having a CPU for supplying a control voltage of the switch,
An open drain port and an input / output port of the CPU are connected to a control terminal of the switch, and supply of a control voltage to the control terminal is controlled by an output state of the open drain port. .   The said control part controls the output state of the said open drain port and an input / output port, and makes the said LED light-extinguish, when the operation of power-off is received by the said operation part. Printing device. An electronic device control method comprising a switch that controls lighting of an LED and a CPU that supplies a control voltage of the switch,
The control voltage supply to the control terminal of the switch is controlled by the output state of the open drain port and the input / output port of the CPU connected to the control terminal of the switch,
A method for controlling an electronic device.

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