JPH02303851A - Driving circuit of impact head - Google Patents

Abstract

PURPOSE:To improve stabilization of a current waveform of a driving coil at low cost because of quick absorption of counter electromotive force to be generated when electrification of the coil is ended by a method wherein a dummy coil having an electric time constant almost similar to that of an actual driving coil is provided in an impact head or on a control substrate. CONSTITUTION:One end of a dummy coil 6 is connected to an earthing wire of a power source wire via a driving NPN transistor 7 and a current detecting resistance 8, and the other end of the dummy coil 6 is connected to a power source wire of voltage V2 after stabilizing power source voltage via a current controlling PNP transistor 5. Further, the joint is connected to the earthing wire of the power source wire via a diode 11. The joint of the dummy coil 6 is connected to a power source wire of voltage V1 higher than the power source voltage V2 via a diode 12. For an actual driving coil, driving NPN transistor 15, 20 are respectively connected to actual driving coils 14, 19 in the same way as the circuitry of the dummy coil 6. A current controlling PNP transistor 13 is connected commonly to two actual driving coils, and the PMP transistor 13 is further connected to the power source wire of voltage V2 after stabilizing the power source voltage.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for driving high-response frequency multi-wire pins.
The present invention relates to a driving circuit for an impact head, which is quick and inexpensive to absorb back electromotive force generated at the end of energization of the coil, and has good stability of the current waveform of the driving coil.

[Conventional technology]

Among printers that print characters or bit images in a dot matrix, serial type printers that use wire pins in the print head are widely used because they can print 1M and have excellent cost performance. As an example of a conventional wire pin driving system, the circuit configuration shown in FIG.
L-1, 2, 3). In Figure 3, 1
0 is the actual drive coil, and fA of the current detection resistor 27?
-N voltage Vi is manually applied to the comparator 38, and the output signal controls the actual drive coil control transistor 36 to 0N10.
' FF, and a constant 11tli waveform Icoil shown in FIG. 4 is obtained. Figure 5 shows another conventional example of the patent Hiroyoshi Sho 59.
-45209, the driving transistor 22 is controlled by the signal rJ by the detection resistor R2 and the comparator 25 and the driving signal, and the driving transistor 23 is controlled by the adjustment pulse signal υ The control is 11 for constant current 2Ii control or flyback current Luli control.

[Problem to be solved by the invention]

In the conventional drive system as shown in Fig. 3, the drive switch's $
In order to generate the 111Jll 4M number, a control comparator is required for each actual drive coil, which has the disadvantage of increasing the 1llh rating of the drive circuit and increasing the board area of the drive circuit. Ta.

There is also a method of controlling the 1ltl control bow by the cut-off time using a timer without detecting the current, but in that case, fluctuation factors such as changes in electric circuit constants such as power supply voltage and changes in magnetic resistance of the magnetic circuit. The disadvantage is that the coil cannot be driven by correcting the current waveform, resulting in poor stability of the current waveform. Also,
In conventional drive circuits as shown in Figures 3 and 5, the back electromotive force that occurs when the coil is energized is not absorbed quickly, and when driving an impact dot head with a high response frequency multi-wire pin. , when the drive cycle becomes shorter, the number of times y3
Another drawback was that the configuration allowed current to flow when the coil was de-energized.

[Means to solve the problem]

In the impact head drive circuit of the present invention, a dummy coil having an electrical time constant almost similar to that of the actual drive coil is used as a drive circuit to control f111 the current flowing through the actual drive coil, which is the coil that actually drives the wire pin. In the head or i! The first feature is that the dummy coil is installed on the control board, and the first feature is that the dummy coil is used as the drive IL of the actual drive coil! The second feature is that it is driven by a drive circuit that is substantially similar to the circuit. Furthermore, the third feature is that the actual drive coil is driven by a drive selection fR number and a control fs number which is 10 by driving the dummy coil, and the dummy and real parts.

The current flowing through the moving coil! As a drive circuit that controls I+,
One end of the coil is connected to one of the power lines via drive switch A, the other end of the coil is connected to the power line of voltage v2 after the power supply voltage has been stabilized via drive switch B, and drive switch B is connected to one end of the coil. A unidirectional element is further connected to the connection C5t between the drive switch A and the coil, and the connection point between the drive switch A and the coil is connected to the power supply smoothing circuit via the unidirectional element. The fourth feature is that the power supply voltage stabilized +1iJ outputted from the power supply voltage (2) is connected to the power supply line of the voltage Vl of the rli voltage.

[Effect]

As described above, according to the impact head drive circuit of the present invention, when driving a high-response frequency multi-wire pin, the back electromotive force generated at the end of energization to the coil can be absorbed quickly and inexpensively, and the current waveform of the drive coil can be changed. It is possible to drive an impact head with good stability (IP).

become.

(Embodiments) Hereinafter, the present invention will be described in accordance with embodiments in which the present invention is implemented in a head drive circuit of an impact dot printer.

FIG. 1 is a drive circuit diagram. One end of the dummy coil 6 is connected to the ground line of the power supply line via a drive NPNI-Rangistaft and a current detection resistor 8, and the other end of the dummy coil 6 is connected to the ground line of the power supply line via a current control PNP transistor 5 after the power supply voltage is stabilized. It is connected to the power line of voltage v2, and the connection point is further connected to the ground line of the power line via a diode 11. The connection point between the drive NPN transistor 7 and the dummy coil 6 is the voltage output from the power supply smoothing circuit via the diode 12. From the source voltage Ii, H'B; is connected to the power supply line of the voltage Vl. Similar to the circuit configuration of the dummy coil 6, the actual drive coil has a drive N for each of the actual drive coils 14 and 19.
PN) transistors 15 and 20 are connected, and in the case of the embodiment shown in FIG. 1, a PNP) transistor 13 for current control is commonly connected to the two actual drive coils.
) The transistor 13 is further connected to the power line of the voltage v2 after the power supply voltage has been stabilized. Further, a diode 16 for the current υ11JI is also commonly connected to the two actual drive coils, and the other end of the diode is connected to the ground line of the power supply. The PNP transistor 13 and the diode 16 for controlling the electric current i+fE may be provided one by one for each of the plurality of actual coils or for each actual drive coil within the range permitted by the rating of the element.

FIG. 2 shows the drive timing and the drive currents flowing through the dummy coil 6 and the actual drive coils 14 and 19.

The dummy coil is energized in accordance with the selection signal or maximum response frequency of the actual drive coil.

and 3D signals. The driving PNP transistor 5 and the NPN transistor 7 connected to the dummy coil 6 are simultaneously turned ON by the above two signals, and the current begins to flow, and as shown in the current waveform 1d in Fig. 2, the dummy coil 6 and the current detection resistor 8 and the time constant of the drive circuit.

When the terminal voltage of the current detection resistor 8 reaches the preset comparison voltage Vrefl of the comparator 9, the output of the comparator 9 changes and the signal output (
The PNP transistor 5 is inverted as shown in cp).
is turned off. After that, the current flowing through the dummy coil 5 circulates through the PNP transistor 8 and the diode 11 and gradually decreases, and when the terminal voltage of the current detection resistor 8 falls below the comparison voltage Vrefl, the output of the comparator 9 changes again. As shown in the signal output (cp) of FIG. 2, the signal is inverted and the PNP transistor 5 is turned on. This 0
The chopping signal of N10FF is generated during the period when the SO and SD double signals are ON, and the current flowing through the dummy coil changes as shown in iD. When the SO and SD double signals are turned off, a back electromotive force is generated, and the back electromotive force is applied to the power supply line Vl of lli voltage from the power supply voltage v2 before the power supply voltage stabilization, which is output from the power supply smoothing circuit via the diode 12. diode 11
It is quickly absorbed by flowing through the water. As shown in the circuit configuration of FIG. 1, the output signal of the comparator 9 is inputted to the actual drive circuit as a control signal for the actual drive coil as well as the dummy coil, and a PNP l-transistor 13 for controlling the current υ is input. 0N10FF.

Then, the actual drive coil selection signal Sl and NP by 82
When the coil is driven by the N transistors 15 and 20 (7) ONloFF, actual drive coil currents as shown in il and i2 in FIG. 2 flow. Current waveforms id and il in Figure 2
, i2 are waveforms in the case of a conventional drive circuit.To explain the operation using the case of the actual drive coil 14 as an example, the PNP transistor 13 and the NPN transistor 15
When the actual drive coil 19 that shares the transistor 13 (PNP) is driven, the back electromotive force remaining in the actual drive coil 14 causes the actual drive coil 19 to be driven. When the actual drive coil 14 is not driven, a current as shown by the broken line flows through the actual drive coil 14, making the response of the coil unstable.

However, according to the circuit configuration of the present invention, the generated back electromotive force quickly flows through the actual driving coil and is absorbed as a back electromotive current that circulates the high voltage Vl of the power supply circuit, so that it is stable even when the wire pin is driven at high speed. Operate.

〔Effect of the invention〕

As described below, according to the impact head drive circuit of the present invention, when driving a high response frequency multi-wire pin,
It becomes possible to drive an impact head in which the back electromotive force generated at the end of energization of the coil is quickly absorbed, is inexpensive, and the current waveform of the drive coil is stable.

[Brief explanation of drawings]

Figure 1 is a drive circuit diagram of the impact head of the present invention, Figure 2 is a drive circuit diagram of the impact head of the present invention.
The figure is an explanatory diagram of the drive timing signal in Figure 1, Figure 3 is a drive circuit diagram of a conventional impact head, and Figure 4 is a diagram showing the timing (No. 8) of Figure 3. Figure m5 is an illustration of the drive timing signal of a conventional impact head. Drive circuit diagram. l...Power supply smoothing circuit 2...Power supply stabilization circuit 3.4...Capacitor 5.13...Drive switch A 6...Dummy coil?, 15.20... Drive switch B8...Current detection resistor 9...Comparator 10...Reference power supply 11.12, 16, 17.22...Unidirectional element 14.19...Actual drive coil or more Applicant Seiko Epson Corporation Representative Patent Attorney Kisanbe Suzuki and 1 other person So Wabi

Claims (4)

[Claims] (1) In a dot matrix printer where wire pins are selectively driven by a print command to print characters or bit images, the actual drive circuit is used as a drive circuit that controls the current flowing through the actual drive coil, which is the coil that actually drives the wire pins. An impact head drive circuit characterized in that a dummy coil having an electrical time constant substantially similar to that of the coil is installed inside the impact head or on a control board. (2) The impact head drive circuit according to claim 1, wherein the dummy coil is driven by a drive circuit that is substantially similar to a drive circuit for the actual drive coil. (3) The impact head drive circuit according to claim 1, wherein the actual drive coil is driven by a drive selection signal for selecting during printing and a control signal obtained by driving the dummy coil. (4) As a drive circuit that controls the current flowing through the dummy and actual drive coils, one end of the coil is connected to a drive switch A.
The other end of the coil is connected to the voltage V2 power line after stabilizing the power supply voltage through the drive switch B, and the connection point between the drive switch B and the coil is Furthermore, a unidirectional element is connected to the power supply line to which drive switch A is connected, and the connection point between drive switch A and the coil is connected to the power supply voltage output from the power supply smoothing circuit via the unidirectional element. 2. The impact head drive circuit according to claim 1, wherein the impact head drive circuit is connected to a power supply line having a voltage V1 higher than the power supply voltage V2 before stabilization.