JPS626654Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive circuit for a printing device that absorbs the ripples at the rise and fall when the power is turned on and prints correctly.

When a solenoid is excited by a drive pulse signal to drive a hammer in a printing device, ripples occur at the rise and fall of the power when the power is turned on, resulting in malfunctions.

The present invention is designed to absorb such ripples at the rise and fall when the power is turned on to ensure printing.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

In Figure 1, 1 is supplied to the equipment.
This is a detection circuit that detects whether or not an abnormality has occurred in the voltage of the AC power supply.The detection terminal 2 of the unstable voltage that is supplied to the equipment of this detection circuit 1 is grounded via a Zener diode 3 and a resistor 4. The connection point is connected to the base of a transistor 6 via a resistor 5. The emitter of this transistor 6 is grounded, and the collector is connected to a stabilized battery power supply terminal (+V _B ) via a resistor 7 and a diode 8, and to these connection points, which will be described later.
It is connected to the power supply terminal 13 to the CMOSICs 9, 10, 11, and 12.

14 is NAND gate 1 made of CMOSIC
This is an RS flip-flop circuit formed by cross-coupling 0 and 11, and between the R input side of this flip-flop circuit 14 and the collector of the transistor 6,
An inverter circuit 9 made of CMOSIC is inserted. Q of the RS flip-flop circuit 14
On the output side, there is a power supply voltage down detection signal (PD
An output terminal 15 (referred to as a signal) is connected thereto, and a first delay circuit 16 is connected to the output side.
This first delay circuit 16 has a charging/discharging resistor 17 and a capacitor 18 connected in series, and a series circuit of a charging resistor 19 having a smaller value and a diode 20 is connected in parallel to this resistor 17. It will be done.

A reset signal (hereinafter referred to as "reset signal") is connected to the connection point B between the resistor 17 and the capacitor 18 of the first delay circuit 16 via an inverter circuit 12 made of a CMOSIC.
An output terminal 21 of the RST signal is connected thereto. A second delay circuit 24 consisting of a charging/discharging resistor 22 and a capacitor 23 is connected to the output terminal 21 of the RST signal, and a connection point A between the resistor 22 and the capacitor 23 is connected to the S of the RS flip-flop circuit 14. Connected to the input side.

Next, the input terminal (+B) of the stabilized power supply and the drive signal terminal 25 are connected at one point C through a resistor 26 and a diode 27, respectively, and the RST signal is connected from this point C through one diode 28. It is connected to the output terminal 21 and to the base of the transistor 30 via the other diode 29. The base of this transistor 30 is grounded via a resistor 31, the emitter is directly grounded, and the collector is connected via a resistor 32 to the base of a transistor 33 in the next stage.
The emitter of this transistor 33 is the power supply terminal (+
B), and its collector is connected to the drive pulse input terminal 34 to the next stage.

Next, the solenoid drive circuit 35 includes two Darlington-connected transistors 36, 37 and resistors 38, 39 connected between their bases and emitters.
and a common diode 40 connected between the collector and emitter. One end of the DC solenoid 41 is connected to the collector side of the transistors 36 and 37 of this solenoid drive circuit 35.
A power supply terminal 42 is connected to the other end, the emitter side of the transistors 36 and 37 is grounded via a current detection resistor 43, and the drive signal input terminal 34 is connected to the base side via a resistor 44. It is connected. Reference numeral 45 indicates two transistors 46 and 47 with similar characteristics, and these transistors 4.
This is a differential amplifier composed of emitters 6 and 47 and a common resistor 48 connected between ground. The base and collector of one transistor 46 of this differential amplifier 45 are connected to the emitter side and base side of the solenoid drive circuit 41, respectively, and the collector of the other transistor 47 is connected to the stabilized power supply terminal (+B). . This stabilized power supply terminal (+B) is grounded via voltage dividing resistors 49 and 50, and its connection point D is connected to the base of the other transistor 47 of the differential amplifier 45, and the terminal is connected to the base of the other transistor 47 of the differential amplifier 45. It is grounded via a variable resistor 51.

Next, the operation of the present invention will be explained.

At time _t1 in FIG. 2, the power supply voltage has not yet been applied to the device, so the voltage at the power supply voltage detection terminal 2 becomes 0V as shown in FIG. 2a, and the transistor 6 of the detection circuit 1 is off. Therefore, the R input of the RS flip-flop circuit 14 becomes "L",
Since the output becomes "H", the Q output, that is, the PD signal becomes "H" (in this case, the battery voltage V _B appears) as shown in FIG. 2d. Also, when the output is "H", the capacitor 18 is charged and the connection point B is "H" as shown in c of the figure, so the RST signal is inverted by the inverter circuit 12 and "L" as shown in e of the figure. ”. Further, the connection point A is also "L".

Next, when a predetermined power supply voltage is applied to the device at time t ₂ , the voltage at the power supply voltage detection terminal 2 also becomes higher than the predetermined level (for example, 5V) as shown in Figure 2a, and the transistor 6 is turned on. As a result, the R input of the RS flip-flop circuit 14 changes from "L" to "H". Therefore, the output becomes "L" and the PD signal maintains "H" (however, this voltage is the power supply voltage for operating the IC, which is 5V) as shown in d of the figure. On the other hand, when the output becomes "L", the power supply of the capacitor 18 of the first delay circuit 16 is switched to the resistor 17.
This capacitor 1
After the time constant _T1 determined by the resistor 8 and the resistor 17 has elapsed, the connection point B changes from "H" to "L" as shown in FIG. 2c. Immediately, the RST signal changes to "H" as shown in the figure e, and the reset is released.

However, from t ₂ to t ₃ just before the reset is released,
When the RST signal is zero, switching diode 28
is on, so even if a drive signal is input to the drive signal terminal 25, it flows into the inverter circuit 12 via the diode 28, so the point C does not become "H". Therefore, the drive pulse signal is not sent to the other diode 29 side, and the solenoid drive circuit 35
is not affected by power supply start-up ripple.

Next, after ₃ o'clock when the influence of the ripple on the rise of the voltage has disappeared, the drive signal terminal 25 is connected to the
When a pulsed drive signal like the one shown in is input,
t Since one diode 28 is off after ₃ o'clock,
This pulsed drive signal is sent through the other diode 29. This pulse signal turns transistors 30 and 31 on and off in sequence, and sends a pulsed drive signal to the drive signal input terminal 34 for driving the printing hammer. This pulse-like drive signal adjusts the printing pressure of the printing hammer according to the characters and symbols printed by the printer, so when printing complex characters or multiple sheets, the pulse width can be adjusted as shown in Figure 2 f. When printing simple characters or symbols, a signal with a narrow pulse width is applied to control the printing pressure of the printing hammer, as shown in FIG. In response to these pulsed drive signals with various pulse widths, a drive current Ic having a sharp rise characteristic as shown by the solid line in g in the figure flows through the DC solenoid 41. This solenoid 41
The current Ic flowing through the current detection resistor 43,
A voltage is generated across the resistor 43, that is, at point E,
That voltage is applied to the base of one transistor 46 of differential amplifier 45. On the other hand, the base of the other transistor 47 of the differential amplifier 45, that is, D
Since a preset reference voltage Vs is applied to the point, the voltage at the point E is equal to the reference voltage Vs at the point D.
increases until it is equal to . In this way, the differential amplifier 45 consisting of the transistors 46, 47 and the resistor 48 is activated to control the voltage at point F in FIG. 1, thereby controlling the solenoid drive circuit 35. Therefore, the DC solenoid 41 is controlled so that a constant current flows therethrough. This means that the differential amplifier 45
The amount of feedback from the collector (point F) of one transistor 46 to the solenoid drive circuit 35 changes compared to the base voltages of transistors 46 and 47. That is, the differential amplifier 45 is stabilized at the point where the voltage generated across the resistor 43 (voltage at point E) becomes substantially equal to the reference voltage Vs (voltage at point D). Therefore, the current flowing through the resistor 43, that is, the solenoid drive current Ic, is determined by the reference voltage Vs (which can be arbitrarily set by the resistor 51), and becomes the set value current Ic.

Next, at t ₄ o'clock, it is assumed that the power to the equipment is interrupted or reduced. Then, the voltage at terminal 2 becomes
Transistor 6 turns off before the voltage drops to 5V, and RS
The R input of the flip-flop circuit 14 changes to "L", the output changes to "H", and the PD signal is immediately inverted to "L". At this point, since the output has changed to "H", the capacitor 18 of the first delay circuit 16
, the capacitor 18 is charged via the resistors 17, 19 and the diode 20 earlier than the time T ₁ during which it is discharged, and is delayed by the time constant T ₂ determined by these resistors 17, 19 and the capacitor 18 at t ₅ Sometimes RST
The signal changes from "H" to "L" as shown in FIG. 2e. At this point, the electric charge in the capacitor 23 of the second delay circuit 24 is discharged via the resistor 22, so that the connection point A is connected to the capacitor 23 after the time constant T ₃ determined by the capacitor 23 and the resistor 22 has elapsed, as shown in FIG. t Change to "L" at ₆ o'clock. The reason why the PD signal voltage is changed to "L" during period T ₃ in this way is that if the power is turned on again to the device during period T ₃ , the device may become unstable due to ripples caused by the power supply falling. This is because the device is controlled so that it does not operate during the period _T3 , since there are problems such as startup and malfunction.

Then, at time _T3 , the PD signal becomes "H" (V _B level) again as shown in d in the same figure.
The state will be the same as at time T ₁ . In this way, after time _t7 , the device returns to its initial state and enters a normal operating state.

As mentioned above, this invention stops the power supply for a certain period of time after the power is turned on and off.
The printing hammer does not malfunction due to ripples at the rise and fall of the power supply.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing an embodiment of a driving circuit of a printing device according to the present invention, and FIG. 2 is an output waveform diagram of each part. 12...Inverter, 16...Delay circuit, 1
7, 19...Resistor, 18...Capacitor, 20...
...Diode, 25...Drive signal input terminal, 28
... Switching diode, 35 ... Solenoid drive circuit, 41 ... Solenoid.

Claims (1)

[Claims for Utility Model Registration] (1) In a device in which a solenoid connected to a solenoid drive circuit is actuated by a pulsed drive signal to drive a printing hammer, a drive signal input terminal of the solenoid drive circuit, A driving circuit for a printing device, comprising a switching diode branched from the middle and connected, and a delay circuit that opens and closes the switching diode after a certain period of time after switching on and off of a power supply. (2) The delay circuit consists of a charging/discharging circuit of a resistor and a capacitor, and an inverter that inverts the output of this charging/discharging circuit. After a predetermined time after the power supply is switched on and off, the inverter output is reversed and the switching diode is opened and closed. A driving circuit for a printing device according to claim 1 of the utility model registration claim.