JPH08308101A - Power unit for printer - Google Patents

Abstract

PURPOSE: To reduce the ability of the external power supplying section to be made to correspond to a printer which requires largely different currents at standby time and at printing time. CONSTITUTION: At standby time, a current which is supplied from the outside and limited by a current limiting circuit 7 is supplied to a printer 4 and, when the charged voltage of a battery 8 is low, the current is also supplied to a charging circuit 9 for charging the battery 8. At printing time, the current supplied to the printer 4 through the circuit 7 becomes insufficient, because the printer 4 requires a larger current as compared with the standby time, and the insufficient amount is supplied through the discharging operation of the battery 8 connected to a power line 11 so that the printer 4 can perform printing operation. Therefore, the power supply section 10 which supplies the current from the outside is not required to supply a current larger than that required by the printer 4 at the standby time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer power supply unit incorporated in a printer unit for driving the printer with a direct current.

[0002]

2. Description of the Related Art Conventionally, when a printer such as a receipt / journal printer for printing on receipt paper or journal paper in a POS system (point-of-sale information management system) is considered, it becomes one load factor in the system. The necessary drive current is distributed from an external power supply unit for the entire system.

In this case, for example, a receipt / journal printer configured as a thermal printer is provided with a drive unit such as a thermal head or a stepping motor for feeding paper. In such a printer, a large current is usually required during an actual printing operation in which a thermal head or a stepping motor operates, while a small current is usually required during standby. And, even during printing operation, the actual print contents (print data
Depending on the print speed, the print width (range), etc., the required current also increases or decreases.

[0004]

Therefore, under such circumstances, a power supply unit having a capacity (capacity) capable of covering the maximum current required during the printing operation is required. Here, since the cost and the external shape of the power supply increase in proportion to the capacity, the conventional method that requires a power supply unit with a large capacity wastes cost and mounting space for the external power supply side. Further, it is necessary to take measures such as inserting a capacitor in the power supply line in order to suppress the peak current in consideration of the increase / decrease in current depending on the print content during the actual printing operation. Further, as printers, there are small printers, large printers, etc. that are specified by the size of printing paper, etc., and the required currents differ, but the specifications on the power supply side must be changed for each printer according to the difference. Will also be required.

[0005]

SUMMARY OF THE INVENTION A printer power supply device of the present invention is a current limiting circuit for limiting the value of a supply current supplied from the outside to a fixed value or less set based on a current value required during printer standby. And a storage battery which is connected to a power supply line for the printer of the current limiting circuit and discharges and outputs to the printer an undercurrent during printer printing operation,
And a charging circuit for selectively charging the storage battery with a supply current supplied from the outside via the current limiting circuit.

[0006]

According to the present invention, the current limiting circuit is supplied to the printer while the current supplied from the outside and limited by the current limiting circuit is supplied to the printer during standby when the required current value is small. It is charged through the charging circuit by the current supplied therethrough. On the other hand, during printer printing operation, a larger current is required than when the printer is in standby, and the current supplied via the current limiting circuit is insufficient, but this insufficient current is supplied by the discharging operation of the storage battery connected to that power supply line. By doing so, the printer executes the original printing operation. Therefore, the power supply unit that supplies current from the outside may be any unit that can supply a constant amount of current set assuming the current value required during printer standby, during printer printing operation. Even when the printer is on standby, a small-capacity external power supply is sufficient as long as it supplies a large current. Conversely, as a power supply unit that supplies current from the outside, the current limiting circuit limits the supply current even when used as a power source for devices other than the printer. Therefore, a large amount of current is not consumed, and the current distribution is excellent.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. The printer power supply device according to the present embodiment is applied to, for example, the thermal printer power supply device 1. The thermal printer power supply device 1 is integrated with a thermal printer 4 including a thermal head 2 and a stepping motor 3 for feeding paper, and a drive circuit 5 for driving the thermal printer 4 to form a printer unit 6. are doing.

Here, the power supply unit 1 for the thermal head
Is composed of a current limiting circuit 7, a storage battery 8 and a charging circuit 9. The current limiting circuit 7 is provided on the power supply line 11 connecting the thermal head 2 and the power supply unit 10 located outside the printer unit 6, and is supplied from the power supply unit 10. It has a current limiting function to limit the current value to a preset value or less. The storage battery 8 is branched and connected to the output side of the current limiting circuit 7 via the charging circuit 9, and is connected to the power line 11 (the position downstream of the charging circuit 9) for the thermal printer 4. And a diode 12 for preventing backflow. The charging circuit 9 controls the charging operation for the storage battery 8, and simply,
It is composed of a resistor for limiting the charging current.

Further, the drive circuit 5 is connected to a power supply line 11 to output a strobe signal STB for printing operation to the thermal head 2 or to the stepping motor 3 as shown in FIG. Transistor Q _A for sequentially supplying current to four-phase field coils φA to φD
A CPU 13 having an IC configuration for controlling ON / OFF of Q _D by drive signals A to D is provided. Here this CP
A voltage monitoring circuit 14 for converting the power supply capacity of the storage battery 8 into the voltage of the power supply line 11 and monitoring it is interposed between the U13 and the power supply line 11. The voltage monitoring circuit 14 is mainly formed by an IC-configured comparator 15, and the reference input is connected to the connection midpoint of the voltage dividing resistors R ₁ and R ₂ connected to the power supply line 11, and the reference input is connected to the reference input. The connection midpoints of the voltage dividing resistors R ₃ and R ₄ connected to the power source Vcc = 5V are connected.
That is, when the voltage of the power supply line 11 and a _{V M, V M · R 1} / the reference input of the comparator 15 (R ₁ + R ₂₎ becomes a divided voltage is applied, the reference input 5 · R ₃ / (R ₃ + R ₄ )
When the reference voltage is given and (reference input voltage) <(reference input voltage), the output of the comparator 15 is set to L level.

In such a structure, as a concrete example, the current limiting circuit 7 has a current limit of 1 [A], the storage battery 8 has a capacity of 2 [Ah], and the thermal printer 4 and the drive circuit 5 are in a standby state. The operation will be described on the assumption that the current consumption is 0.5 [A] and the maximum current consumption during the printer printing operation is 4 [A]. The storage battery 8 is assumed to be fully charged.

First, while the printer is on standby, a current of 0.5 [A] flows through the output portion a on the power supply line 11 in order to supply the necessary current consumption to the thermal printer 4 and the drive circuit 5. On the other hand, since the storage battery 8 is fully charged,
Since the charging circuit 9 limits the charging operation for the storage battery 8, no current flows in the portion b on the branch line. Therefore, in this case, the printer unit 6 is supplied from the external power supply unit 10.
Therefore, a current of only 0.5 [A] will be supplied.

On the other hand, at the time of the printer printing operation in which the strobe signal STB is given to the thermal head 2 and the printing operation is actually executed, it is necessary to supply a maximum current of 4 [A] to the thermal printer 4 side. . At this time, since the current supplied from the power supply unit 10 side is limited to 1 [A] or less by the current limiting circuit 7, the power supply unit 1
When the current is supplied from 0, the current of 3 [A] is insufficient. In order to compensate for such an insufficient current, a current of 3 [A] is supplied from the storage battery 8 to the power supply line 11 connected through the diode 12 by the discharging operation. As a result, on the thermal printer 4 side, the
When the current [A] is supplied, the printing operation is performed normally.
When the printing operation is performed for 10 minutes in such a current supply state, the capacity of the storage battery 8 is 3 [A] × 1/6.
[H] = 0.5 [Ah] is consumed.

After that, when the printer returns to standby mode,
A current of 0.5 A is supplied to the thermal blinter 4 and the drive circuit 5 at the output portion a of the power supply line 11, while it is supplied from the power supply unit 10 and limited to 1 [A] by the current limiting circuit 7. [A] of the current of [] that flows to the output part a
0.5 [A], excluding the amount, flows to the portion b side on the branch line. As a result, the charging current flows to the storage battery 8 via the charging circuit 9, and the storage battery 8 is charged. If the charging efficiency in this case is 50%, the storage battery 8 returns to the fully charged state by performing the charging operation for 20 minutes.

Therefore, according to this embodiment, since the printer unit 6 is provided with the thermal printer power supply device 1 including the current limiting circuit 7 and the storage battery 8, the required current consumption is about 0.5 [A] or less. Even when the printer standby operation and the printer printing operation, which are largely different in the width up to about 4 [A], are taken into consideration, the shortage of the current during the printer printing operation is equivalent to
Since it is compensated by the discharge current of the
0 is 1 [A] limited by the current limiting circuit 7.
It suffices to supply the following currents, and the current values supplied from the power supply unit 10 are time-sequentially averaged. Therefore, the power supply of the power supply unit 10 may have a small capacity, and the cost and mounting space can be reduced. Conversely, as the external power supply unit 10, P
Even when the OS system is used as a power source for other devices (load elements) other than the thermal printer 4, the current limiting circuit 7 limits the supply current, so that a large current is generated on the thermal printer 4 side. The current can be favorably distributed in the entire POS system without being consumed. In particular, according to this embodiment, the current limiting circuit 7 controls the current supplied from the external power supply unit 10.
On the other hand, the shortage is compensated by the storage battery 8 built in the printer unit 6 of its own, so that the specifications of the power supply unit 10 side are not changed regardless of whether the printer is a small printer or a large printer. , Can be applied, and can be versatile.

By the way, if the printer standby time is at least twice as long as the printer printing operation time, the storage battery 8 will not be sufficiently charged under the condition that the charging efficiency is 50% as described above. Absent. However, when the printer standby time is less than twice the printer printing operation time, the capacity of the storage battery 8 may decrease, and the charging voltage may decrease below a certain value. For example, storage battery 8
3, which shows the change of the charging voltage in a time series, the time point t ₁ represents the time point when the charging voltage drops below a certain value. If the printer printing operation is continued normally in such a situation, the current required for the printing operation cannot be secured. Therefore, in this embodiment, the CPU 13 in the drive circuit 5 shows the interrupt processing flowchart of FIG. The control for reducing the printing speed is executed.

That is, the comparator 15 in the power supply monitoring circuit 14 constantly monitors the charging voltage of the storage battery 8 using the voltage V _M at the output portion a of the power supply line 11, and at time t ₁
In such a situation, the divided voltage of V _M · R ₁ / (R ₁ + R ₂ ) becomes lower than the reference voltage of 5 · R ₃ / (R ₃ + R ₄ ), so that the voltage drop L A level signal is output from the comparator 15 to the CPU 13. Therefore,
The CPU 13 causes the comparator 13 to perform the interrupt processing shown in FIG.
When the change to the L level is detected (Y in step S1), the thermal printer 4 side is stopped or the operation control is performed so as to delay the printing operation (S).
2). A method for slowing the operation will be described later. In any case, the current supplied to the thermal printer 4 side at the output portion a of the power supply line 11 is 1 by this operation control.
[A] Make the following. Under these circumstances,
There is also a shunt current on the part b side of the branch line, and the charging circuit 9
A charging current flows through the storage battery 8 via the. As a result, the voltage of the storage battery 8 is restored as shown at time t ₂ in FIG. Such voltage recovery is also monitored by the voltage monitoring circuit 14. Here, when the CPU 13 knows that the output of the comparator 15 has changed to the H level and the voltage has returned (Y in S3), in reality, there is a possibility that the storage battery 8 has a small capacity. The recovery time is counted by a predetermined value (S4, S5), and the operation control of step S2 is continued during this period. Through such a process, the capacity of the storage battery 8 is completely recovered as shown at time t ₃ in FIG. 3 (fully charged state). At such a stage, the CPU 13
Returns the thermal printer 4 side to the control for normal printing.

By the way, when performing the operation control such that the operation shown in step S2 is delayed, the CPU 1
3 increases the pulse width of the drive signals A to D for each phase to be supplied to the stepping motor 3 from the normal time to reduce the printer speed, and at the same time, the strobe signal ST that defines the energizing pulse to the thermal head 2
It suffices to extend the cycle of B. At this time, since the energization width for the thermal head 2 is constant, the required current consumption tends to decrease. FIG. 5 shows pulse waveforms of the drive signals A to D and the strobe signal STB at the normal time, and FIG. 6 shows pulse waveforms of the drive signals A to D and the strobe signal STB at the low speed drive. According to these figures, the pulse widths of the drive signals A to D at the low speed are wider than those at the normal time, and the pulse width (cycle) T ₂ of the strobe signal STB at the low speed is smaller than the pulse width T ₁ at the normal time. You can see that it is spreading.

In this embodiment, the thermal printer 4
However, the printer is not limited to a thermal printer, and may be a printer such as a dot impact printer or an inkjet printer.

[0019]

According to the present invention, a current limiting circuit for limiting the value of the supply current supplied from the outside to a fixed value or less set based on the current value required during printer standby, and the current limiting circuit. A storage battery which is connected to a power supply line for the printer and discharges and outputs an undercurrent during the printer printing operation to the printer, and a storage battery which is externally supplied through the current limiting circuit to selectively charge the storage battery. Since it is equipped with a charging circuit, for printers in which the required currents during standby and during printing differ greatly,
Since the insufficient current during printing operation can be compensated for by the discharge current from the storage battery, the power supply unit that supplies current from the outside supplies a current of a fixed value set assuming the current value required during printer standby. Therefore, it is sufficient to supply a current that does not make a large difference even during printer printing operation or printer standby. A small capacity external power supply advantageous in terms of cost and mounting space is sufficient. Conversely, as a power supply unit that supplies current from the outside, the current limiting circuit limits the supply current even when it is used together as a power source for devices other than the printer. , The printer side does not consume a large current, and the current distribution can be performed well.
Furthermore, while the current supplied from the outside is limited by the current limiting circuit, the shortage is compensated by the built-in storage battery, so whether the printer is a small printer or a large printer, the external power supply side It can be applied without changing the specifications of, and it can also have versatility.

[Brief description of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a partial block diagram mainly showing the drive circuit.

FIG. 3 is a waveform diagram showing how the charging voltage of the storage battery changes with time.

FIG. 4 is a flowchart showing operation control in a drive circuit.

FIG. 5 is a time chart showing an operation during normal operation.

FIG. 6 is a time chart showing an operation at low speed.

[Explanation of symbols]

 4 Printer 7 Current limiting circuit 8 Storage battery 9 Charging circuit 11 Power line

Claims (1)

[Claims] 1. A current limiting circuit for limiting a value of a supply current supplied from the outside to a certain value or less set based on a current value required during printer standby, and a power supply line for the printer of the current limiting circuit. And a charging circuit for selectively charging the storage battery with a supply current supplied from the outside via the current limiting circuit. A power supply device for a printer characterized by the above.