KR910003596Y1 - Driving circuit of printer head - Google Patents

Abstract

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Description

Print circuit drive circuit

1 is a circuit diagram according to the present invention.

2a, b or waveform diagram of each part according to FIG.

3a-c is a waveform diagram of the current response of the print wire in each case.

The present invention relates to a driving circuit of the printhead, and more particularly to a driving circuit of the printhead with improved response characteristics when the printhead is driven at high speed.

In the past, the driving power and driving time of printing, ie, the low speed mode and the high speed mode, were fixed rather than variable in the driving speed of the printhead. .

First, calculate the maximum value of the power supply to be used to increase the power capacity. If the power capacity is large and the duty ratio to adjust the driving time is constant, the higher the head drive frequency is, the higher the head drive frequency is due to the inductance characteristics of the printhead. The response characteristic of the load inductance becomes worse.

In other words, as the frequency increases, the load inductance increases and the current flowing through the load inductance decreases, so that the current flowing through the head decreases. As a result, the force applied to the ribbon and paper of the printhead of the printhead is weakened. there was.

Accordingly, an object of the present invention is to provide a print head driving circuit which improves the current characteristics of load inductance by raising the driving power of the head for a certain period during high speed printing.

In order to achieve the object of the present invention as described above, the present invention has a predetermined time constant and a monostable multivibrator for maintaining a first output of the second logic level for a predetermined time constant period by a trigger signal of the first logic level; And a first voltage terminal supplied with a first supply voltage higher than the first output, a first node supplied with a first supply voltage through a first resistor, and the first output and the respective pin data. A printhead drive device comprising: a plurality of printhead drivers supplied to a printhead driver transistor; and a plurality of printhead parts connected between each printhead driver and a first node, wherein the first node and the stage are provided. The first supply voltage is transmitted to the first node when the first output is at the first logic level between the stable multivibrators, and the first supply voltage is supplied to the first node when the first output is at the second logic level.Characterized by a first means adapted to deliver a voltage as the sum of the first output voltage.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a detailed circuit diagram of an embodiment of a printhead driving circuit according to the present invention.

In the figure, reference numeral 10 denotes a 555 timer as a monostable multivibrator.

The trigger voltage Vt is applied to the terminal 2, the terminals 6 and 7 are connected to the power supply voltage Vcc through a resistor R1, and the power supply voltage Vcc is connected to the terminals 4 and 8, and the terminal 3 is connected. The output Vo is output, the resistor R2 is connected between the terminal 8 and the terminal 3, and the capacitor C1 connected in series with the resistor R1 determines the time constant of the 555 timer.

Reference numeral 20 is a first means for increasing the supply voltage applied to the print head in the high speed mode, and the output Vo is connected to the base of the PNP transistor Q2, which is a switching transistor, via the diode D2 and the resistor R3, and the resistor R2, It is connected to the emitter of transistor Q2 through diode D3 and resistor R5, resistor R4 is connected to the base of transistor Q2, the cathode of diode D4 is connected to the emitter of transistor Q2, and resistor R7 is connected through capacitor C2. It is connected to Va.

A frithead driving voltage Vs greater than the power supply voltage Vcc is connected to the node Va through a resistor R6.

Reference numerals (30a) and (30b) denote print head drivers, and the output Vo and the respective pin data PD1-PDn are connected to the base of the NPN transistor Q1, which is a driving transistor, through the AND gate G1.

Reference numerals 40a and 40b denote print heads, and a plurality of internal load inductances L1 and diodes D1 are connected in parallel between the plurality of print head drive transistors Q1 and the node Va.

2a-b are waveform diagrams of the output Vo and no Va according to FIG.

The operation of FIG. 1 will be described with reference to FIGS. 2A-B.

First, when a trigger voltage of 1/3 Vcc or less is applied to the trigger terminal 2 of the 555 timer 10, the output Vo, which was previously in the "low" state, is equal to the time constant of the resistor R1 and the capacitor C1 (t1-t2 in FIG. 2). Maintain a "high" state.

This signal saturates the drive transistor Q1 by the input pin data PD1-PDn and the logical product gate G1 of the printhead drivers 30a-30n, so that a current flows through the printhead windings to force the print wire. The ink is transferred to the ribbon and the paper, and dots are generated in the delivered area.

However, when the trigger voltage Vt is "high", the output Vo is "low", so the collector of transistor Q2 is almost 0 volts, and the driving voltage Vs is charged to capacitor C2, and the voltage of capacitor C2 is almost the same level as the driving voltage Vs. The voltage of is being charged.

Diodes D2 and D3 take almost a drive voltage Vs higher than the supply voltage to the diodes of diodes D2 and D3 when there is no initial charge on capacitor C2. This is to prevent the devices and the timer 555 from being destroyed because they cannot withstand the internal pressure.

When the output Vo goes “high” by the trigger voltage Vt at time t1, the transistor Q2 is turned off and the emitter of the transistor rises to almost 5 volts. Thus, the potential of the node Va is increased between the voltages Vs and 5 volts of the capacitor C2. It is expressed as the sum of 2b.

3a-c is a waveform diagram of the current response of the printed wire, Figure 3a is a waveform diagram of the current response in the conventional low-speed printing, Figure 3b is a waveform diagram of the current response waveform in the conventional high-speed printing, Figure 3c is a present invention Shows waveforms of current response in high-speed mode printing.

First, as shown in the 3a diagram, when the frequency of the trigger signal is low, the current iL flowing through the print wire L1 to the collector of the transistor Q1 rises to the level il. However, as shown in FIG. 3B, the load inductance increases when the frequency of the high speed mode, i.e., the trigger increases, so the current iL rises to i2 level lower than the current il in the low speed mode.

In the structure of the present invention, even though the frequency increases in the high speed mode, the voltage of Vs + Vo higher than the driving voltage Vs is applied to the print wire Li, so that the current iL rises to the level of the current ia as shown in 3c. This is improved. The electric charge charged in the capacitor C2 discharges, and the voltage across the capacitor C2 starts to decrease. At this time, as shown in FIG. 2B, the print wire is driven at the driving voltage Vs.

In the above, the voltage of 5 volts is used as the supply voltage of the 555 timer, but it may be configured using a voltage higher than that. In this case, the voltage of the node Va may be increased by the supply voltage of the 555 timer than the driving voltage Vs. It is also possible to use switching transistors as NPN transistors instead of PNP transistors.

It will also be readily understood by one of ordinary skill in the art that a conventional monostable multivibrator circuit can be used in place of the 555 timer.

As described above, the present invention improves the current response characteristics by driving the load inductance at a voltage higher than the driving power supplied by the operation of the internal circuit while the externally applied driving power is fixed, thus increasing the frequency during high-speed mode printing. There is an advantage that can prevent the printing is blurred.

Claims (2)

A monostable multivibrator having a predetermined time constant and holding a first output of a second logic level for a predetermined time constant period by a trigger signal of a first logic level, and a first supply voltage higher than the first output is supplied. A first node supplied with a first voltage terminal, a first node supplied with a first resistor, and a plurality of print head drivers supplied to a print head driving transistor by multiplying each pin data with the first output; A printhead drive device having a plurality of printhead parts connected between each printhead drive unit and a first node, wherein the first output is at a first logic level between the first node and the monostable mulberry vibrator. A first means for delivering a first supply voltage to a first node and transferring a voltage equal to the sum of the first supply voltage and the first output voltage to the first node when the first output is at a second logic level. phrase Characterized in that. The method of claim 1, wherein the first means is the second node 100, and when the first output is the first logic level, the second node is zero volts when the first output is the second logic level. And switching means for switching the second node to the first output, a capacitor and a resistor connected in series between the first node and the second node.