JPH01129714A - Power interruption detecting circuit - Google Patents

Abstract

PURPOSE:To eliminate erroneous detection of source voltage drop except in case of power interruption, by judging power interruption with high or low level respectively for turning ON or OFF of an incorporated printer. CONSTITUTION:When a motor is driving, an output(b) from a first Zener diode ZD1 set with a lowest voltage level, as a Zener voltage, of a head in an incorporated printer is fed as a power interruption detecting level to an integrated circuit IC1 for an inverter. If source voltage level (a) is lower than a lowest operating level at this time, power interruption is detected and printing operation is stopped. When the motor is stopped, an output (c) of a second Zener diode ZD2 set with a Zener voltage lower than the Zener voltage when the motor is driving is fed as a power interruption detecting level to the integrated circuit IC1 for inverter. Even if the source voltage level (a) drops due to an optional machine and the like, power interruption is not detected so long as the droppage is within the output voltage level (c).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power outage detection circuit used in electronic equipment having a built-in printer, such as an electronic cash register.

[Prior Art 1] Generally, electronic equipment has a built-in power failure detection circuit, and the power failure detection level has conventionally been fixed at a constant level. This also applies to electronic devices such as electronic cash registers that include a built-in printer, such as a dot printer. However, in the case of a dot printer, a high voltage of, for example, 20 volts is required as the head voltage, and if it is lower than this, problems such as printed characters becoming thinner occur.

Therefore, in this type of electronic equipment, it is necessary to set a certain power failure detection level to a relatively high level in order to ensure the head voltage of the built-in printer.

[Problems to be Solved by the Invention] 'However, when the power failure detection level is set to a high level, a drop in the power supply voltage level other than a power failure that occurs when the built-in printer is turned off may be regarded as a power failure. In particular, when an optional device such as a printer other than the built-in printer is externally connected to this type of electronic device, there is a risk that the drop in the N'm voltage level that occurs when the M power source of the optional device is turned on may be regarded as a power outage. .

Therefore, the present invention provides a highly reliable and highly practical power failure detection circuit that can sufficiently ensure power failure detection accuracy for the head voltage of a built-in printer and is free from the risk of erroneously detecting a drop in power supply voltage level other than a power failure. This is what I am trying to do.

[Means for Solving the Problems] The present invention provides a power outage detection circuit for a Yoiko meter with a built-in printer, including a first setting section for setting a first power outage detection level, and a first setting section for setting a first power outage detection level. a second setting section for setting a second power failure detection level lower than the power failure detection level; and a level for selecting the first power failure detection level when the built-in printer is turned on and selecting the second power failure detection level when the built-in printer is turned off. It consists of a selection section and a power outage determination section that makes a power outage determination based on the power outage detection level selected by the selection section.

[Operation] By taking such measures, a power failure determination is made at a relatively high level when the built-in printer is turned on, and the head voltage of the printer is sufficiently guaranteed. When the built-in printer is turned off, a power failure determination is made at a relatively low level, and there is no possibility of erroneously detecting a drop in the power supply voltage level other than a power failure.

[Embodiment] Hereinafter, an embodiment in which the present invention is applied to an electronic device with a built-in dot printer, such as an electronic cash register, will be described with reference to the drawings.

FIG. 1 is a circuit configuration diagram of this embodiment, and FIG. 2 is a signal waveform diagram at points (a) to (f) in FIG. 1. 1st
In the figure, 11 is an IR power input terminal, and this terminal 11
The cathodes of a first Zener diode ZD1 and a second Zener diode ZD2 are connected in parallel. The first Zener diode ZD1 has a Zener voltage V1 of the lowest operating level of the head voltage of the built-in printer, for example 20.
Volt is set and its anode is connected to the input terminal of the inverter integrated circuit ICI.

The second Zener diode ZD2 uses the Zener voltage ■1 of the first Zener diode ZDI as the Zener voltage ■2.
12 volts, for example, and its anode is connected to the emitter of the first PNP transistor Q1.

There is a resistor R between the emitter and base of the transistor Q1.
1 is interposed, and the base is NPN via resistor R2.
Q2 is connected to the collector of the second transistor Q2 of type Q2. Further, the input terminal of the inverter integrated circuit ICI is connected to the collector of the first transistor Q1.

12 is an input terminal for a motor drive signal of the built-in printer, and this terminal I2 is connected to a second inverter integrated circuit IC2.
input terminal is connected. The output terminal of the inverter integrated circuit IC2 is connected to the base of the second transistor Q2 via a resistor R3. The emitter of the second transistor Q2 is grounded, and the base
A resistor R4 is interposed between the emitters.

A threshold level SH determined by eight values of a resistor R5 and a capacitor C is set in the first inverter integrated circuit IC1, and its output terminal is connected to an output terminal PF of a power failure detection signal.

Next, the second
The operation of the circuit of this embodiment will be explained when a power supply voltage and a motor drive signal that change over time as shown in (a) and (d) in the figure are supplied.In other words, the power supply voltage is input at time to, and the The voltage level of the first and second Zener diodes ZD1.ZD2f)') is set to the voltage V1.
．． V2, each diode ZD1. Voltages with waveforms shown in (b) and (c) in the figure are output to the cathode of ZD2. Note that the voltage level v4 of the above output (b) is [V3
-V1], and the output (c) (7) electric JI level V5 becomes [V3-V2]. When the power supply voltage is input, the motor drive signal is at a LOW level (stop command), so the second transistor Q2 is on, and thereby the first transistor Q1 is also on. Therefore, the output (C) of the second Zener diode ZD2 is selected;
) becomes the input (e) to the inverter integrated circuit IC1. As a result, at time t1, the input (e) is at the threshold level SH of the inverter integrated circuit IC1.
When the output of this circuit ICI is inverted, it becomes a power failure detection waveform (f) of LOW level.

In this state, when the motor drive signal (d) becomes HIGH level (drive command) at time t2, the second transistor Q2 is turned off, and therefore the first transistor Q1 is also turned off. Therefore, the output (b) of the first Zener diode ZD1 is selected, and this output (b) becomes the input (e) to the inverter integrated circuit ICI.

Thereafter, when the motor drive signal becomes LOW level at time t3, the first . Second transistor Q1. When Q2 is turned off, the output of the second Zener diode ZD2 (C
) is selected.

From time t4 to time t5, a case is shown in which the power supply voltage level (a) drops due to activation of an optional device such as a printer externally connected to the electronic device of this embodiment when the built-in printer is stopped.

Then, at time t6, the power is turned off, and at time t7, the input (e) of the inverter integrated circuit 1c1 reaches the threshold level SH of the inverter integrated circuit IC1.
When the output (f) of this circuit ICI is inverted and reversed. At this time, the input of the inverter integrated circuit ICI (e
), the motor drive signal is at a LOW level, so the output (C) of the Zener diode ZD2 is selected.

As described above, in this embodiment, when the motor is driven, that is, when the motor drive signal (d) is at the HIGH level, the output of the first Zener diode zD1 is set as the Zener voltage V1 to the lowest operating level of the head of the built-in printer. (
b) is selected as the power failure detection level and supplied to the inverter integrated circuit ICI. Therefore, at this time a
! When the power supply voltage level a) falls below the minimum operating level (1), a power failure is detected and the printing operation of the printer is stopped. As a result, sufficient head voltage of the printer can be ensured, and stable printing operation becomes possible.

On the other hand, when the motor is stopped, that is, the motor drive signal (d) is L.
In the case of the OW level, the output (C) of the second Zener diode ZD2, in which a voltage level lower than the Zener voltage v1 of the first Zener diode ZD1 is set as the Zener voltage v2, is selected as the power failure detection level, and the voltage level for the inverter is It is supplied to the integrated circuit IC1. Therefore, even if the power supply voltage level (a) drops due to activation of an optional device, etc. at this time, the drop will be at voltage level V5-V3-V2.
If it is within the range, power outage detection will not occur. However, if the output (b) of the first Zener diode zD1 with the head voltage adjusted is selected as the power failure detection level, there is a possibility that a power failure will be detected even if the drop is within the range of V5. As a result, when the built-in printer is stopped, there is no risk of malfunction due to a drop in voltage level other than a power outage, improving reliability and increasing practicality.

Additionally, in the past, it was possible to reduce malfunctions by expanding the power supply capacity in order to suppress the drop in voltage level due to activation of optional equipment, etc., but by applying this embodiment, this is no longer necessary. .

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to sufficiently ensure power failure detection accuracy for the head voltage of the built-in printer, and there is no risk of erroneously detecting a drop in the power supply voltage level other than a power failure. A highly reliable and highly practical power failure detection circuit can be provided.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of this embodiment, and FIG. 2 is a signal waveform diagram of the main parts of the circuit in the same embodiment. ZDl, ZD2... Zener diode, Ql. Q2...Transistor, IC1, 1C2...Inverter integrated circuit. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] In the power failure detection circuit of electronic equipment with a built-in printer,
a first setting unit for setting a first power failure detection level; a second setting unit for setting a second power failure detection level lower than the first power failure detection level; and a second setting unit for setting a second power failure detection level lower than the first power failure detection level; a level selection section that selects a first power outage detection level and selects a second power outage detection level when the built-in printer is turned off; and a power outage determination section that makes a power outage determination based on the power outage detection level selected by the selection section. A power outage detection circuit comprising: