JP2014161138A - Switching power supply, printing system and printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printing system that changes an output voltage of a switching power supply regardless of an input of a control signal via a signal line.SOLUTION: A printing system 1 includes an A/C adapter 2 (switching power supply) and a printer 3. The A/C adapter 2 has a current value monitoring circuit 24 for monitoring a current value of an output current while power is supplied to the printer 3, and a voltage switching circuit 25 for switching an output voltage between a first output voltage and a second output voltage every time the current value of the output current exceeds a threshold. The printer 3 includes a current consuming load generation circuit 17 capable of changing a current consumption value up to the threshold or higher. The printer 3 can change the current consumption value up to the threshold or higher to change the current value of the output current of the A/C adapter 2 and thereby switch the output voltage of the A/C adapter 2.

Description

  The present invention relates to a switching power supply such as an AC adapter, a printing system including a printer connected to the switching power supply, and a printer of the printing system.

  A printing system is known in which the output voltage of a switching power supply such as an AC adapter that supplies power to the printer during standby is lowered, thereby bringing the printer and the switching power supply into a power saving state with low power consumption. Patent Document 1 describes a switching power supply that can be used as a power supply for such a printing system. The switching power supply of Patent Document 1 reduces the output voltage based on a control signal input from an external device via a signal line. Therefore, the switching power supply includes a power supply line and a signal line in a cable connecting the power supply body and an external device.

JP 2010-206982 A

  Here, the cable including the power supply line and the signal line is more expensive than a cable including only the power supply line. Therefore, when the printing system is configured using the switching power supply disclosed in Patent Document 1, there is a problem that the cost of the printing system is increased. Further, if the signal line is included in the cable routed between the printer and the power supply main body, there is a problem that the electromagnetic non-interference and the durability of the printing system are lowered.

  In view of such a problem, an object of the present invention is to provide a switching voltage that can control a change in an output voltage without depending on an input of a control signal via a signal line. Another object of the present invention is to provide a printing system and a printer that control the output voltage of the switching power supply from the printer side.

  In order to solve the above-described problems, the present invention provides a switching power supply that can switch an output voltage between a first output voltage and a second output voltage that is lower than the first output voltage. A current value monitoring unit that monitors a value; and a voltage switching unit that switches the output voltage between the first output voltage and the second output voltage based on a change in the current value.

  According to the switching power supply of the present invention, the output voltage can be switched by changing the current value of the output current. Here, the current value of the output current of the switching power supply corresponds to the current consumption value of an external device to which power is supplied from the switching power supply. Therefore, by changing the current consumption value on the external device side, The output voltage of the switching power supply can be changed. Therefore, the output voltage can be changed without inputting a control signal to the switching power supply via the signal line.

  In the present invention, in order to change the output voltage, the voltage switching unit sets a resistance value of a reference resistor that creates a reference voltage for setting the output voltage based on a change in the current value. A changing configuration can be adopted.

  In this invention, the said voltage switching part shall switch the said output voltage, when the said electric current value becomes more than a predetermined threshold value. In this case, the threshold value is preferably set to a current value larger than the maximum current consumption during normal operation of an external device connected to the switching power supply. In this way, it becomes easy to distinguish between a change in the current consumption value during normal operation and a change in the current consumption value for switching the output voltage of the switching power supply, so that malfunction occurs in switching the output voltage. You can avoid that.

  In this invention, the said voltage switching part shall switch the said output voltage, when the time when the said current value became more than the predetermined threshold value exceeds the predetermined setting time. In this way, even when the threshold value is a current value smaller than the maximum current consumption during normal operation of an external device connected to the switching power supply, the change in the current consumption value during normal operation and the output voltage of the switching power supply Since it becomes easy to discriminate the change in the current consumption value for switching the output voltage, it is possible to avoid the occurrence of a malfunction in the switching of the output voltage.

  Next, a printing system of the present invention includes the above-described switching power supply and a printer that receives power supply from the switching power supply, and the printer can change a current consumption value to be equal to or greater than the threshold value. A current consumption load generator is provided.

  According to the present invention, the current value of the output current of the switching power supply can be changed by changing the current consumption value of the printer by the current consumption load generating unit, and the output voltage of the switching power supply is changed by changing the current value. can do. Therefore, the output voltage can be changed without inputting a control signal to the switching power supply via the signal line.

  In the present invention, the current consumption load generation unit includes a first load generation circuit that sets the current consumption value to be equal to or higher than the threshold when the first output voltage is supplied from the switching power supply, and the switching power supply It is desirable to include a second load generation circuit that sets the current consumption value to be equal to or higher than the threshold when the second output voltage is supplied. By doing this, the current value of the output current of the switching power supply changes to a threshold value or more regardless of whether the power supply voltage of the printer, that is, the output voltage of the switching power supply is the first output voltage or the second output voltage. Can be made.

  Next, the present invention can be a printer of the above printing system.

  According to the present invention, since the printer includes a load generation unit that changes its current consumption value, the current value of the output current of the switching power supply that supplies power to the printer is arbitrarily set from the printer side. Can be changed. Therefore, when the switching power supply has a function of switching the output voltage based on the change in the current value of the output current, the output voltage can be changed without inputting a control signal to the switching power supply via the signal line.

  According to the present invention, the switching power supply switches the output voltage based on a change in the current value of the output current. Therefore, the output voltage can be changed by changing the current value of the output current of the switching power supply by changing the current consumption value on the printer side to which power is supplied from the switching power supply. Therefore, the output voltage of the switching power supply can be changed without relying on the input of a control signal via an external signal line.

1 is a schematic block diagram of a printing system to which the present invention is applied. It is a circuit diagram of the secondary side of an A / C adapter. FIG. 3 is a circuit diagram of a current consumption load generation unit of a printer. 6 is a timing chart of an operation mode switching operation of the printing system. It is a timing chart of the operation mode switching operation | movement of the printing system of a modification.

  A printing system to which the present invention is applied will be described below with reference to the drawings.

(overall structure)
FIG. 1 is a schematic block diagram of a printing system to which the present invention is applied. The printing system 1 of this example includes an A / C adapter 2 and a printer 3 that receives power supply from the A / C adapter 2. The A / C adapter 2 is a switching power supply that can switch an output voltage between a first output voltage and a second output voltage lower than the first output voltage. The A / C adapter 2 is detachably connected to the printer 3.

  The printer 3 includes a printer control unit 10 including a CPU, a print head 11, a head driver 12, a carry motor 13, and a motor driver 14. The printer control unit 10 controls the printing operation, and the transport motor 13 is a drive source of a transport mechanism that transports the recording paper along a paper path passing through a printing position by the print head 11. The printer control unit 10 drives and controls the print head 11 via the head driver 12 and also drives and controls the transport motor 13 via the motor driver 14 to print the print data supplied to the printer 3.

  The printer 3 also includes a power control unit 15 and a DC / DC converter 16. The electric power from the A / C adapter 2 is supplied to the print head 11 and the transport motor 13 via the power control unit 15 and the drivers 12 and 14. The power from the A / C adapter 2 is supplied to the printer control unit 10 via the power supply control unit 15 and the DC / DC converter 16. The CPU drive voltage supplied to the printer control unit 10 via the DC / DC converter 16 is lower than the mechanical drive voltage supplied to the print head 11 and the carry motor 13.

  Here, the printing system 1 includes a normal operation mode and a power saving operation mode that consumes less power than the normal operation mode.

  The normal operation mode is an operation mode in which the power of the first output voltage that can drive the print head 11 and the transport motor 13 is supplied from the A / C adapter 2 to the printer 3. When print data is supplied to the printer 3 in a state where the printing system 1 is in the normal operation mode, the printer control unit 10 drives the print head 11 and the conveyance motor 13 to perform a print operation for printing the print data.

  The power saving operation mode is an operation mode in which the power of the second output voltage that is lower than the mechanical drive voltage and can drive the printer control unit 10 is supplied from the A / C adapter 2 to the printer 3. . For example, when the print data is not supplied to the printer 3 for a predetermined time or more, the printing system 1 shifts from the normal operation mode to the power saving operation mode. In the power saving operation mode, the power consumption of the printer control unit 10 decreases as the output voltage of the A / C adapter 2 (the power supply voltage of the printer 3) decreases. Accordingly, when the printing system shifts to the power saving operation mode, the power consumption of the printing system 1 as a whole is reduced.

  When the printing system 1 is in the power saving operation mode, the printer control unit 10 cannot drive the print head 11 and the transport motor 13 due to insufficient power. Accordingly, when print data is supplied to the printer 3 while the printing system 1 is in the power saving operation mode, the printing system 1 returns from the power saving operation mode to the normal operation mode, and then performs the printing operation. .

  Here, the A / C adapter 2 is configured to switch the output voltage between the first output voltage and the second output voltage based on a change in the current value of its own output current. Therefore, when the operation mode of the printing system is switched, the current consumption value of the printer 3 is changed on the printer 3 side to change the current value of the output current of the A / C adapter 2, thereby the A / C adapter. Switch the output voltage of 2. The printer 3 includes a current consumption load generation circuit (current consumption load generation unit) 17 that changes its current consumption value based on a control signal from the printer control unit 10 in the power supply control unit 15. Details of the current consumption load generation circuit 17 will be described later.

(A / C adapter)
FIG. 2 is a circuit diagram of the secondary side circuit of the A / C adapter 2. As shown in FIG. 2, the secondary circuit 21 on the output side of the high-frequency transformer 20 in the A / C adapter 2 includes a rectifier circuit 22 inserted in the power supply line Vc, a power supply line Vc, and a power supply line GND. An electrolytic capacitor 23 is provided between them. The secondary side circuit 21 includes a current value monitoring circuit (current value monitoring unit) 24 and a voltage switching circuit (voltage switching unit) 25. The current value monitoring circuit 24 monitors the current value of the output current while the A / C adapter 2 supplies power to the printer 3. The voltage switching circuit 25 switches the output voltage between the first output voltage and the second output voltage based on the change in the current value of the output current. Here, the current value of the output current of the A / C adapter 2 corresponds to the current consumption value of the printer 3, and these are the same value.

  The current value monitoring circuit 24 outputs a resistor Rx inserted in the power supply line GND, an amplifier Ap that amplifies an output current appearing at both ends of the resistor Rx, and an amplified current of the output current output from the amplifier Ap. A toggle flip-flop T-FF that switches a signal between High and Low is provided. The toggle flip-flop T-FF switches the output signal between High and Low every time the current value of the output current exceeds a predetermined threshold (each time the current value of the amplified current exceeds a predetermined value). In this example, the threshold value of the output current is slightly lower than 2A.

  The voltage switching circuit 25 includes a transistor Tr, resistors R1, R2, and R3, an integrated circuit IC for voltage control, and a photocoupler Pc. The transistor Tr is a PNP transistor, and the output signal of the toggle flip-flop T-FF of the current value monitoring circuit 24 is input to the base. The transistor Tr is turned off when the output signal of the toggle flip-flop T-FF is High and turned on when the output signal is Low.

  The resistors R1, R2, and R3 are reference resistors that create a reference voltage for setting an output voltage. The resistors R1 and R2 are connected in series and inserted between the power supply line Vc and the power supply line GND. A reference voltage is output from the middle point P of the resistors R1 and R2. The resistor R3 is inserted between the power supply line Vc and the emitter of the transistor Tr, and the collector of the transistor Tr1 is connected to the midpoint position P. Accordingly, when the transistor Tr1 is turned on, the resistor R3 is connected in parallel to the resistor R1. In this example, the resistance value of the resistor R1 is 86 kΩ, the resistance value of the resistor R2 is 10 kΩ, and the resistance value of the resistor R3 is 86 kΩ.

  The reference voltage is input to the integrated circuit IC for voltage control. The integrated circuit IC for voltage control becomes active when the reference voltage changes due to the disconnection of the parallel connection of the resistor R3 with respect to the resistor R1, and passes a current corresponding to the change to the photocoupler Pc. Thereby, the integrated circuit IC for voltage control adjusts the output voltage by feedback controlling the primary side circuit 28 (see FIG. 1) on the input side of the high frequency transformer 20 via the photocoupler Pc. In this example, the voltage value of the reference voltage is 2.5V.

Here, since the transistor Tr1 is turned off when the output signal of the toggle flip-flop T-FF is High, the resistance value of the reference resistor for creating the reference voltage is defined by the resistor R1 and the resistor R2. In this case, the output voltage of the A / C adapter (first output voltage Vout1) is as follows, assuming that the voltage value of the reference voltage is Vref, and the resistance values of the resistors R1, R2, and R3 are R1, R2, and R3, respectively. It is represented by the formula (1).
Vout1 = Vref × (R1 + R2) / R2 (1)
In this example, the first output voltage Vout1 is 24V.

On the other hand, since the transistor Tr1 is turned on when the output signal of the toggle flip-flop T-FF is Low, the resistance values of the reference resistors for creating the reference voltage are the resistance values of the resistors R1, R2, and R3. It is prescribed from. In this case, the output voltage (second output voltage Vout2) of the A / C adapter is expressed by the following equation (2).
Vout2 = Vref × ((R1 · R3 / (R1 + R3)) + R2) / R2 (2)
In this example, the second output voltage Vout2 is 13.25V.

(Current consumption load generation circuit)
FIG. 3 is a circuit diagram of the current consumption load generation circuit 17 configured in the power supply control unit 15 of the printer 3. The current consumption load generation circuit 17 includes a first load generation circuit 31 that sets the current consumption value of the printer 3 to a threshold value or more when the first output voltage (24 V) is supplied from the A / C adapter 2, and A / C When the second output voltage (13.25 V) is supplied from the C adapter 2, a second load generation circuit 32 is provided that sets the current consumption value of the printer 3 to a threshold value or more.

  The first load generation circuit 31 includes a transistor Tr1 and a resistor R10 inserted between the power supply line Vc and the power supply line GND. The transistor Tr1 is an NPN transistor, the collector is connected to the power supply line Vc via the resistor R10, and the emitter is connected to the power supply line GND. A high or low control signal is input from the printer control unit 10 to the base of the transistor Tr1. In this example, the resistance value of the resistor R10 is 12Ω.

  The second load generation circuit 32 includes a first load generation circuit 31 and a third load generation circuit 33 configured in parallel with the resistor R10 of the first load generation circuit 31. The third load generation circuit 33 includes a transistor Tr2 and a resistor R20. The transistor Tr2 is a PNP transistor, the emitter is connected to the power supply line Vc, and the collector is connected to the collector of the transistor Tr1 via the resistor R20. A high or low control signal is input from the printer control unit 10 to the base of the transistor Tr2. In this example, the resistance value of the resistor R20 is 12Ω.

  When the printing system 1 is shifted from the normal operation mode to the power saving operation mode, a high control signal is input from the printer control unit 10 to the transistor Tr1 of the first load generation circuit 31, and the transistor of the third load generation circuit 32 is input. A high control signal is input to Tr2. As a result, the transistor Tr1 is turned on and the transistor Tr2 is turned off, so that the first load generating circuit 31 operates. Here, in the normal operation mode, since the power supply voltage of the printer 3 (output voltage of the A / C adapter 2) is 24V, the current consumption value of the printer 3 can be increased to 2A by the operation of the first load generation circuit 31. it can. That is, when the printing system 1 is shifted from the normal operation mode to the power saving operation mode, the printer control unit 10 operates the first load generation circuit 31, thereby the current value of the output current of the A / C adapter 2. Is raised above the threshold at which the toggle flip-flop T-FF operates.

  When the printing system 1 is shifted from the power saving operation mode to the normal operation mode, a high control signal is input from the printer control unit 10 to the transistor Tr1 of the first load generation circuit 31, and the transistor of the third load generation circuit 33 is input. A low control signal is input to Tr2. As a result, both the transistor Tr1 and the transistor Tr2 are turned on, and the second load generating circuit 32 operates. In the second load generation circuit 32, since the resistor R1 and the resistor R2 are connected in parallel, the resistance value thereof is 6Ω. Here, in the power saving operation mode, the power supply voltage of the printer 3 (the output voltage of the A / C adapter 2) is about 13.25 V, so that the current consumption value of the printer 3 is reduced from 2A by the operation of the second load generation circuit 32. Can also be raised to higher values. That is, when the printing system 1 is shifted from the power saving operation mode to the normal operation mode, the printer control unit 10 operates the second load generation circuit 32, and thereby the current value of the output current of the A / C adapter 2. Is raised above the threshold at which the toggle flip-flop T-FF operates.

  When the operation mode of the printing system 1 is maintained in either the normal operation mode or the power saving operation mode, the printer control unit 10 inputs a low control signal to the transistor Tr1 of the first load generation circuit 31. . When a low control signal is input from the printer control unit 10 to the transistor Tr1, the first load generation circuit 31 and the second load generation circuit 32 are maintained in an inoperative state.

  Here, the threshold value is higher than the maximum current consumption value during normal operation of the printer 3. In other words, the maximum current consumption value in the printer 3 is lower than the threshold value even during the printing operation. The current consumption value of the printer 3 is equal to or greater than the threshold only when the first load generation circuit 31 or the second load generation circuit 32 is driven by the printer control unit 10 in order to switch the operation mode of the printing system 1. is there.

(Operation mode switching operation)
FIG. 4 is a timing chart of the operation mode switching operation in the printing system 1. The upper chart shows the current consumption value of the printer 3 (current value of output current of the A / C adapter 2), and the lower chart shows the output voltage value of the A / C adapter 2 (power supply voltage value of the printer 3). . In the example shown in FIG. 4, the printing system 1 is initially in a normal operation mode in which the output voltage of the A / C adapter 2 is the first output voltage (24V).

  In the normal operation mode, a printing operation is performed by supplying print data. The current consumption value of the printer 3 increases during the printing operation, but does not exceed the threshold value. Accordingly, the operation mode of the printing system 1 is not switched.

  Here, when the print data is not supplied to the printer 3 for a predetermined time or longer, the printer control unit 10 operates the first load generation circuit 31 of the current consumption load generation circuit 17 to set the current consumption value of the printer 3 to the threshold value. Over 2A. As a result, the toggle flip-flop T-FF operates in the current value monitoring circuit 24 of the A / C adapter 2, and the control signal to the transistor Tr of the voltage switching circuit 25 is switched from High to Low. As a result, the transistor Tr1 is turned on, and the resistance value of the reference resistor for creating the reference voltage is determined from the resistance values of the resistors R1, R2, and R3. Accordingly, the second output voltage (13.25V) is output from the A / C adapter 2, and the printing system 1 shifts to the power saving operation mode. When the printing system 1 shifts to the power saving operation mode, the printer control unit 10 inputs a Low control signal to the transistor Tr1 of the current consumption load generation circuit 17 and maintains the operation mode.

  Thereafter, when print data is supplied to the printer 3, the printer control unit 10 operates the second load generation circuit 32 of the current consumption load generation circuit 17, and sets the current consumption value of the printer 3 to a value of 2A or more exceeding the threshold value. And As a result, the toggle flip-flop T-FF operates in the current value monitoring circuit 24 of the A / C adapter 2, and the control signal to the transistor Tr of the voltage switching circuit 25 is switched from Low to High. As a result, the transistor Tr1 is turned off, and the resistance value of the reference resistor for creating the reference voltage is determined from the resistance values of the resistors R1 and R2. Accordingly, the first output voltage (24V) is output from the A / C adapter 2, and the printing system 1 returns to the normal operation mode.

  When the printing system 1 returns to the normal operation mode, the printer control unit 10 inputs a Low control signal to the transistor Tr1 of the current consumption load generation circuit 17 and maintains the operation mode. As a result, a printing operation is possible, and the printer control unit 10 drives the print head 11 and the transport motor 13 to print the print data.

(Function and effect)
According to this example, the output voltage of the A / C adapter 2 can be changed by changing the current consumption value on the printer 3 side. Therefore, the output voltage of the A / C adapter 2 can be changed without inputting a control signal to the A / C adapter 2 via the signal line.

  In this example, the threshold for switching the output voltage of the A / C adapter 2 is set to a value larger than the maximum current consumption value during the printing operation (during normal operation) of the printer 3 connected to the A / C adapter 2. Yes. This makes it easy to discriminate between changes in the current consumption during normal operation and changes in the current consumption for switching the output voltage of the A / C adapter 2, thus causing a malfunction in switching the output voltage. Can be avoided.

  In the above example, the resistance value of the resistor Rx inserted into the power supply line GND for detecting the output current is set to be small in consideration of efficiency. For this reason, the amplifier Ap amplifies the output current appearing at both ends of the resistor Rx and inputs the amplified current to the toggle flip-flop T-FF. May be omitted.

(Modification)
In the above example, the output voltage of the A / C adapter 2 is switched when the current consumption value of the printer 3 (current value of the output current of the A / C adapter 2) exceeds the threshold. The output voltage may be switched when the time during which the current consumption value of the printer 3 is equal to or greater than the threshold exceeds a predetermined set time.

  In this case, a timer IC is mounted on the current value monitoring circuit 24 of the A / C adapter 2, and the time during which the current value of the output current is equal to or greater than the threshold is counted using the timer IC. Then, when the time during which the current value of the output current is equal to or greater than the threshold value exceeds the set time, the current value monitoring circuit 24 is set so that the output signal from the toggle flip-flop T-FF is switched between High and Low. Configure. Further, the threshold value is set to a current value smaller than the maximum current consumption value during the printing operation (normal operation) of the printer 3.

  On the other hand, on the printer 3 side, the operation time during which the printer control unit 10 operates the first load generation circuit 31 or the second load generation circuit 32 is set to be a set time or more. Further, by changing the resistance values of the resistor R10 and the resistor R20, the current consumption value of the printer 3 when the first load generation circuit 31 or the second load generation circuit 32 is operated exceeds the threshold value. The value is smaller than the maximum current consumption value during printing operation (during normal operation).

  FIG. 5 is a timing chart of the operation mode switching operation in the modified printing system. The upper chart shows the current consumption value of the printer 3 (current value of output current of the A / C adapter 2), and the lower chart shows the output voltage value of the A / C adapter 2 (power supply voltage value of the printer 3). . In the example shown in FIG. 5, the printing system 1 is initially in a normal operation mode in which the output voltage of the A / C adapter 2 is the first output voltage (24V).

  In the normal operation mode, a printing operation is performed by supplying print data. In this example, the current consumption value of the printer 3 increases during the printing operation and becomes equal to or greater than the threshold value. However, the state in which the current consumption value exceeds the threshold due to the printing operation does not continue for the set time or longer. Accordingly, the operation mode of the printing system 1 is not switched.

  Here, when the print data is not supplied to the printer 3 for a predetermined time or more, the printer control unit 10 operates the first load generation circuit 31 of the current consumption load generation circuit 17 for the set time or more, and the current consumption value of the printer 3 Continues for more than the set time. As a result, in the current value monitoring circuit 24 of the A / C adapter 2, the toggle flip-flop T-FF operates, and the control signal to the transistor Tr is switched from High to Low. As a result, the second output voltage (13.25V) is output from the A / C adapter 2, and the printing system 1 shifts to the power saving operation mode. When the printing system 1 shifts to the power saving operation mode, the printer control unit 10 inputs a Low control signal to the transistor Tr1 of the current consumption load generation circuit 17 and maintains the operation mode.

  Thereafter, when print data is supplied to the printer 3, the printer control unit 10 operates the second load generation circuit 32 of the current consumption load generation circuit 17 for a set time or more, and the current consumption value of the printer 3 exceeds the threshold value. The state is continued for the set time or longer. As a result, the toggle flip-flop T-FF operates in the current value monitoring circuit 24 of the A / C adapter 2 and the control signal to the transistor Tr is switched from Low to High. As a result, the first output voltage (24V) is output from the A / C adapter 2, and the printing system 1 returns to the normal operation mode. When the printing system 1 returns to the normal operation mode, the printer control unit 10 inputs a Low control signal to the transistor Tr1 of the current consumption load generation circuit 17 and maintains the operation mode. As a result, a printing operation is possible, and the printer control unit 10 drives the print head 11 and the transport motor 13 to print the print data.

  Also in this example, the output voltage of the A / C adapter 2 can be changed by changing the current consumption value on the printer 3 side. Therefore, the output voltage of the A / C adapter 2 can be changed without inputting a control signal to the A / C adapter 2 via the signal line.

  In this example, the output voltage is switched when the current consumption value of the printer 3 (the current value of the output current of the A / C adapter) exceeds the threshold for a set time or longer. Even when the current value is smaller than the maximum current consumption value during printing operation (during normal operation), the change in current consumption value during normal operation and the current consumption value for switching the output voltage of the A / C adapter 2 It is possible to discriminate from the change of. Therefore, even when the threshold value is set to a small value, it is possible to avoid a malfunction in switching the output voltage.

(Other embodiments)
In the above example, the current consumption load generation circuit 17 is used to change the current consumption value of the printer 3. However, when the printer control unit 10 drives the transport motor 13 via the motor driver 14, The current consumption value may be varied. That is, the motor driver 14 and the transport motor 13 may be a current consumption load generation circuit.

  Here, the printer control unit 10 drives the transport motor 13 via the motor driver 14, thereby determining the current consumption value of the printer 3 regardless of the power supply voltage of the printer 3 (output voltage of the A / C adapter 2). It can be varied to any value. Further, the printer control unit 10 can change the current consumption value to a threshold value or more without rotating the transport motor 13 by simultaneously energizing each phase of the transport motor 13 via the motor driver 14.

  As described above, if the motor driver 14 and the transport motor 13 are current consumption load generation circuits, a special circuit such as the current consumption load generation circuit 17 is not mounted as a circuit for changing the current consumption value of the printer 3. The output voltage of the A / C adapter 2 can be switched by changing the current consumption value of the printer 3 (current value of the output current of the A / C adapter 2) to an arbitrary value.

1 .... Printing system, 2 .... A / C adapter (switching power supply), 3 .... Printer, 10 .... Printer controller, 11 .... Print head, 12 .... Head driver, 13 .... Conveyance motor, 14 ....・ Motor driver, 15 ・ ・ Power control unit, 16 ・ ・ DC / DC converter, 17 ・ ・ Current consumption load generation circuit (current consumption load generation unit), 20 ・ ・ High frequency transformer, 21 ・ ・ Secondary side circuit, 22 ..Rectifier circuit, 23 ... Electrolytic capacitor, 24 ... Current value monitoring circuit (current value monitoring unit), 25 ... Voltage switching circuit (voltage switching unit), 28 ... Primary side circuit, 31 ... Load generating circuit, 32 ... second load generating circuit, 33 ... third load generating circuit, Ap ... amplifier, GND ... power supply line, IC ... integrated circuit, P ... middle position, Pc ... Photo coupler , R1 · R2 · R3 · R10 · R20 · Rx ·· resistance, T-FF ·· toggle flip-flop, Tr · Tr1 · Tr2 ·· transistor, Vc ·· power supply line

Claims (7)

A switching power supply capable of switching an output voltage between a first output voltage and a second output voltage lower than the first output voltage,
A current value monitoring unit for monitoring the current value of the output current;
A switching power supply comprising: a voltage switching unit that switches the output voltage between the first output voltage and the second output voltage based on a change in the current value. In claim 1,
The switching power supply, wherein the voltage switching unit changes a resistance value of a reference resistor that creates a reference voltage for setting the output voltage based on a change in the current value. In claim 1,
The switching power supply, wherein the voltage switching unit switches the output voltage when the current value is equal to or greater than a predetermined threshold. In claim 1,
The switching power supply, wherein the voltage switching unit switches the output voltage when a time when the current value is equal to or greater than a predetermined threshold exceeds a predetermined set time. A switching power supply according to claim 3 or 4,
A printer that receives power from the switching power supply,
The printer includes a current consumption load generation unit capable of changing a current consumption value to be equal to or greater than the threshold value. In claim 5,
The current consumption load generation unit includes: a first load generation circuit that sets the current consumption value to be equal to or greater than the threshold value when the first output voltage is supplied from the switching power supply; and the second output voltage from the switching power supply. And a second load generation circuit that sets the current consumption value to be equal to or greater than the threshold value when the printer is supplied.   The printer of the printing system according to claim 5 or 6.

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