JPH0732620A - Serial printer - Google Patents

Abstract

PURPOSE:To prevent the breakdown of a head driver due to an overvoltage and the breakdown of a sensor element and the like due to the generation of discharge by providing a regenerative circuit for consuming a secondarily regenerative current from the head driver and a regenerative sub-circuit on a main control base plate portion and a head driver base plate portion, respectively. CONSTITUTION:A main body unit A1 of a serial printer has a main base plate portion 11, and a carriage unit A2 has a motor base plate portion 13, a printing head control signal base plate portion 14 and a printing head driver base plate portion 15. The main control base plate portion 11 is connected to the motor base plate portion 13 by a flexible cable 16. In this case, a regenerative circuit 59 consuming a secondarily regenerative current from a head driver 21 and consisting of the Zener diode Z1 and a power transistor 28 is provided on the main control base plate portion 11, and a regenerative sub-circuit 60 consisting of the Zener diode D2 and a reverse current-preventing diode 61 is provided on the head driver base plate portion 15 in parallel to the regenerative circuit 59, thereby preventing the breakdown of the head driver 21 due to an overvoltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a serial printer.

[0002]

2. Description of the Related Art Conventionally, a serial printer for printing with a dot type print head has a head drive circuit for driving the print head, and the head drive circuit is arranged in a carriage section. ing. FIG. 2 is a head drive circuit diagram of a conventional serial printer.

In the figure, A ₁ is the main body of the serial printer, and A ₂ is the carriage of the serial printer. The main body A ₁ has a platen (not shown) rotatably supported, and a carriage shaft (not shown) is installed in parallel with the platen. Also,
The carriage portion A ₂ has a carriage (not shown) movably supported along the carriage shaft,
A print head and an ink ribbon cassette (not shown) are mounted on the carriage.

The print head has an armature having a print wire fixed to the tip thereof, and the armature is swingably supported by the body of the print head by a leaf spring. On the other hand, a magnet is arranged so as to face the armature, and a permanent magnet generates a magnetic flux to attract the armature to the magnet against the elastic force of the leaf spring.

The magnet has a head coil 10, and a magnetic flux is generated by energizing the head coil 10 through a power supply line 50 to cancel the magnetic flux of the permanent magnet and release the armature. At this time, the print wire flies and collides with a print sheet (not shown) via the ink ribbon to print. By the way, the main body section A ₁ has a main control board section 11 for controlling the entire serial printer. On the other hand, the carriage A ₂
Is a motor board portion 13 for supporting a motor (not shown) for spacing, a print head control signal board portion 14 for generating a control signal corresponding to the operation of the print wire, and a print head driver board portion 15 for driving the print head. Have. The print head control signal board portion 14 and the print head driver board portion 15 are mounted on the print head.

The main control board 11 and the motor board 13 are connected by a flexible cable 16 having flexibility. The main control board unit 11 has a power supply unit 18, a circuit unit 24, and a regenerative circuit 26 for consuming the secondary live current from the head driver 21, and the CPU (not shown) of the circuit unit 24 is a carriage unit A. ₂
It controls the motor circuit unit 20, the head driver 21, and the like. The regenerative circuit 26 is composed of a Zener diode Z1 as a constant voltage element for setting a regenerative voltage, a power transistor 28, and a reverse current preventing diode 29.

Each signal line extending from the main control board portion 11 is connected to one end of the flexible cable 16 by a connecting means C ₁ such as a connector and pressure contact.
The other end of 6 is connected to the motor board 1 by the same connecting means C ₂ .
3 signal lines. The motor board portion 13 has a motor circuit portion 20 provided with a motor coil, a sensor and the like (not shown), and also has a bypass capacitor 32 connected to the power source portion 18 to absorb electric charges when the power source is turned on and off.

The motor board portion 13, the print head control signal board portion 14 and the print head driver board portion 1
A special connector member 33 having an integral structure is arranged between the five members 5, and the connector member 33 and the motor board portion 13 are provided.
The connector member 33 is connected to the print head control signal board portion 14 and the print head driver board portion 15 by a card edge connector.

The print head control signal board portion 14 is also provided.
Has a control circuit 35 and a sensor 36. The control circuit 35 receives print data and a print control command from the main control board unit 11, generates a control signal, and sends the control signal to the print head driver board unit 15. In this case, the operation of the print wire for each pin of the print head is detected by the sensor 36, and an optimum control signal corresponding to the operation of the print wire is generated.

The control signal is transmitted via the connector member 33 to the pair of head drivers 2 of the print head driver board portion 15.
Output for 1. The head driver 21 supplies a current so that each head coil 10 is driven for a required drive time. Reference numeral 38 denotes a regenerative current line for passing a secondary regenerative current, and the secondary regenerative current passes through the connector member 33, the motor board portion 13, the connecting means C ₂ , the flexible cable 16 and the connecting means C _1. The regenerative circuit 2
6 and is consumed in the regenerative circuit 26.

Next, the operation of the head driver 21 will be described. FIG. 3 is a circuit diagram of a head driver in the conventional serial printer, and FIG. 4 is a waveform diagram of the head driver in the conventional serial printer. As shown in the figure, the head driver 21 has a control circuit 43, a main switching element 45, a primary-use switching element 46, and diodes 47 and 48. The control circuit 43 is connected to the print head control signal board section 14 (FIG. 2) via a signal line 44, and receives a control signal from the print head control signal board section 14 to turn on / off the signals EN1 and EN2.
Then, when the signal EN1 is turned on, the main switching element 45 is turned on, and when the signal EN2 is turned on, the primary switching element 46 is turned on.

The diode 47 is connected to the power line 5
0 is connected between 0 and the main switching element 45 to prevent the reverse flow of the primary current live current i _F , and the diode 48 is connected between the head coil 10 and the regenerative circuit 26 so that the secondary current live current i _Z flows backward. Prevent from doing. In the head driver 21 having the above structure, the control circuit 43 receives the control signal from the print head control signal board unit 14 and outputs the signal EN.
1 and EN2 are turned on, the main switching element 45 and the primary-use switching element 46 are turned on, and the current i _{A in the} head coil 10 is changed to the main switching element 4
A current i flows through 5 to drive a magnet (not shown).
At this time, the coil output terminal voltage V _A drops from the power supply voltage E to almost zero. Next, when the signal EN1 is switched from on to off, the main switching element 45 is turned off and the current i becomes 0, and the current i _A flowing in the head coil 10 passes through the primary-use switching element 46 and the diode 47. As a result, the next-time raw current i _F is supplied to the head coil 10 again via the power supply line 50. In addition, the coil output terminal voltage V _A decreases and the power supply voltage E
Is equal to

By the way, a print head armor (not shown)
Chua mugs the signal EN1 from ON to OFF.
Released from the net, flying the print wire (not shown)
Collide with the printing paper (not shown) through the ink ribbon.
It When the print wire collides with print paper,
Alternatively, the signal EN2 is turned on and off before and after that time.
Then, the primary switching element 46 is turned off.
And the next time the raw current i _FBecomes 0. In addition,
The surplus energy in IL 10 is the secondary current i_ZWhen
Through the diode 48 and the regenerative current line 38,
It flows to the raw circuit 26 and is consumed. This second carp at the time of birth
Output terminal voltage V_AAnd secondary voltage V_ZIs the power supply voltage
Zener of Zener diode Z1 in regenerative circuit 26 to E
-Voltage E_ZIt becomes the value which added. And the secondary current i
_ZBecomes 0, the coil output terminal voltage V_AAnd second time student
Voltage V_ZGradually decreases and becomes equal to the power supply voltage E. This
Like this, the armature is attracted to the magnet,
A series of operations ends. In addition, 18 is a power supply part.

[0014]

However, the above-mentioned
In the conventional serial printer, the flexible cable 16
When the wire breaks due to fatigue, the head coil 10
The counter-electromotive force is generated by the inductance in proportion to the current change rate.
And coil output terminal voltage V_AAnd secondary voltage V _ZIs the pole
It will be expensive.

Further, since the regenerative current line 38 is connected by the connector member 33 and the connecting means C ₁ and C ₂ , contact failure is likely to occur, and when contact failure occurs, the coil output terminal voltage V _A and the secondary voltage. The raw voltage V _Z becomes extremely high. FIG. 5 is a waveform diagram of the coil output terminal voltage and the secondary secondary voltage when a contact failure occurs.

When a contact failure occurs in the regenerative current line 38 (FIG. 2), the coil output terminal voltage V _A and the secondary regenerative voltage V _Z become extremely high as shown in the figure. When the coil output terminal voltage V _A and the secondary secondary voltage V _Z exceed the element withstand voltage of the head driver 21, the head driver 21 is destroyed by overvoltage. In addition, discharge may occur between the patterns having a short separation distance and a low withstand voltage, and a small signal system circuit such as the control circuit 43 or an element in the sensor 36 may be destroyed.

The present invention solves the problems of the conventional serial printer described above, and when the flexible cable is broken or a contact failure occurs in the regenerative current line connecting the regenerative circuit and the head driver, the coil There is no possibility that the output voltage of the output terminal or the secondary voltage increases and the head driver is damaged by overvoltage, or discharge occurs between patterns with low withstand voltage, and the circuit of small signal system or the element of the sensor is not damaged. The purpose is to provide a printer.

[0018]

To this end, in the serial printer of the present invention, a head driver for driving the head coil of the print head, which is provided in the main control board portion provided in the main body portion and in the carriage portion. Along with
And a head driver board portion connected to the main control board portion via a flexible cable.

The main control board unit includes a regenerative circuit that consumes the secondary regenerative current of the head driver, and the head driver board unit includes a sub regenerative circuit that consumes the secondary regenerative current of the head driver. Prepare In another serial printer of the present invention, a main control board portion arranged in a main body portion, a board portion connected to the main control board portion via a flexible cable, and a carriage portion are arranged in a print head. And a head driver board portion connected to the board portion.

The main control board section includes a regenerative circuit that consumes the secondary regenerative current of the head driver, and the board section includes a sub regenerative circuit that consumes the secondary regenerative current of the head driver. In still another serial printer of the present invention, the regenerative circuit and the sub regenerative circuit include constant voltage elements. Then, the secondary regenerative voltage set by the constant voltage element of the regenerative circuit is made higher than the secondary regenerative voltage set by the constant voltage element of the sub regenerative circuit.

[0021]

According to the present invention, as described above, the serial printer is provided with the main control board portion arranged in the main body portion and the head driver arranged in the carriage portion for driving the head coil of the print head. At the same time, it has a head driver board portion connected to the main control board portion via a flexible cable.

The main control board portion includes a regenerative circuit that consumes the secondary regenerative current of the head driver, and the head driver board portion includes a sub regenerative circuit that consumes the secondary regenerative current of the head driver. Prepare In this case, if the flexible cable is broken due to fatigue or contact failure occurs in the connecting means between the main control board portion and the flexible cable or the connector between the head driver board portion and the flexible cable, the print head A counter electromotive voltage proportional to the current change rate is generated by the inductance of the head coil.

However, since the sub-regeneration circuit is provided, it is possible to prevent the secondary regenerative current from flowing through the sub-regeneration circuit and increasing the output terminal voltage of the head driver and the secondary regenerative voltage. In another serial printer of the present invention, a main control board portion arranged in a main body portion, a board portion connected to the main control board portion via a flexible cable, and a carriage portion are arranged in a print head. And a head driver board portion connected to the board portion.

The main control board section includes a regenerative circuit that consumes the secondary regenerative current of the head driver, and the board section includes a sub regenerative circuit that consumes the secondary regenerative current of the head driver. In this case, if the flexible cable is broken due to fatigue, or if contact failure occurs in the connection means between the main control board and the flexible cable, the back electromotive force proportional to the current change rate is caused by the inductance of the head coil of the print head. Voltage is generated.

However, since the sub regenerative circuit is provided, it is possible to prevent the secondary regenerative current from flowing through the sub regenerative circuit and increasing the output terminal voltage of the head driver and the secondary regenerative voltage. In still another serial printer of the present invention, the regenerative circuit and the sub regenerative circuit include constant voltage elements. Then, the secondary regenerative voltage set by the constant voltage element of the regenerative circuit is made higher than the secondary regenerative voltage set by the constant voltage element of the sub regenerative circuit. In this case, the output terminal voltage and the secondary regenerated voltage of the head driver can be a value obtained by adding the constant voltage by the constant voltage element of the sub regeneration circuit to the power supply voltage.

[0026]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a head drive circuit diagram of a serial printer showing a first embodiment of the invention, and FIG. 7 is a circuit diagram of a head driver in a serial printer showing the first embodiment of the invention.

In the figure, A ₁ is the main body of the serial printer, and A ₂ is the carriage of the serial printer. The main body A ₁ has a platen (not shown) rotatably supported, and a carriage shaft (not shown) is installed in parallel with the platen. Also,
The carriage portion A ₂ has a carriage (not shown) movably supported along the carriage shaft,
A print head and an ink ribbon cassette (not shown) are mounted on the carriage.

The print head has an armature having a print wire fixed to the tip thereof, and the armature is swingably supported by the body of the print head by a leaf spring. On the other hand, a magnet is arranged so as to face the armature, and a permanent magnet generates a magnetic flux to attract the armature to the magnet against the elastic force of the leaf spring.

The magnet has a head coil 10, and a magnetic flux is generated by energizing the head coil 10 through a power supply line 50 to cancel the magnetic flux of the permanent magnet and release the armature. At this time, the print wire flies and collides with a print sheet (not shown) via the ink ribbon to print. By the way, the main body section A ₁ has a main control board section 11 for controlling the entire serial printer. On the other hand, the carriage A ₂
Is a motor board portion 13 for supporting a motor (not shown) for spacing, a print head control signal board portion 14 for generating a control signal corresponding to the operation of the print wire, and a print head driver board portion 15 for driving the print head. Have. The print head control signal board portion 14 and the print head driver board portion 15 are mounted on the print head.

The main control board 11 and the motor board 13 are connected by a flexible cable 16 having flexibility. The main control board unit 11 includes a power supply unit 18,
It has a circuit section 24 and a regenerative circuit 59 for consuming the second-order raw current i _Z from the head driver 21, and the CPU (not shown) of the circuit section 24 includes a motor circuit section 20 of the carriage section A ₂ and a head driver. 21 and the like are controlled. The regenerative circuit 59 is composed of a Zener diode Z1 as a constant voltage element for setting a regenerative voltage and a power transistor 28.

Each signal line extending from the main control board portion 11 is connected to one end of the flexible cable 16 by a connecting means C ₁ such as a connector or pressure contact.
The other end of 6 is connected to the motor board 1 by the same connecting means C ₂ .
3 signal lines. The motor board portion 13 has a motor circuit portion 20 provided with a motor coil, a sensor and the like (not shown), and also has a bypass capacitor 32 connected to the power source portion 18 to absorb electric charges when the power source is turned on and off.

The motor board portion 13, the print head control signal board portion 14 and the print head driver board portion 1
A special connector member 33 having an integral structure is arranged between the five members 5, and the connector member 33 and the motor board portion 13 are provided.
The connector member 33 is connected to the print head control signal board portion 14 and the print head driver board portion 15 by a card edge connector.

The print head control signal board portion 14 is also provided.
Has a control circuit 35 and a sensor 36. The control circuit 35 receives print data and a print control command from the main control board unit 11, generates a control signal, and sends the control signal to the print head driver board unit 15. In this case, the operation of the print wire for each pin of the print head is detected by the sensor 36, and an optimum control signal corresponding to the operation of the print wire is generated.

The control signal is transmitted via the connector member 33 to the pair of head drivers 2 of the print head driver board portion 15.
Output for 1. The head driver 21 supplies a current so that each head coil 10 is driven for a required drive time. Further, 38 is a regenerative current line for passing the secondary regenerative current i _Z , and the secondary regenerative current i _Z is the connector member 33, the motor board portion 13, the connecting means C ₂ , the flexible cable 16 and the connecting means C. It flows to the regeneration circuit 59 through ₁ and is consumed in the regeneration circuit 59.

Further, the print head driver substrate portion 1
5, a sub-regenerative circuit 60 is arranged in parallel with the regenerative circuit 59. The sub-regenerative circuit 60 is composed of a Zener diode Z2 as a constant voltage element that connects the regenerative current line 38 and the power supply line 50, and a reverse current preventing diode 61 disposed on the regenerative current line 38. The anode of the diode 61 is connected to the diode 4 of the head driver 21.
The cathode of the diode 61 is connected to the cathode of the Zener diode Z2. The value of the Zener voltage E _Z2 of the Zener diode Z2 is made larger than the value of the Zener voltage E _Z of the Zener diode Z1 of the regenerative circuit 59.

The diode 6 is added to the sub regeneration circuit 60.
1, the diode is unnecessary in the regenerative circuit 59. Further, the head driver 21 has a control circuit 43, a main switching element 45, a primary switching element 46 and diodes 47 and 48. The control circuit 43 is connected to the print head control signal board unit 14 via a signal line 44, receives a control signal from the print head control signal board unit 14, and turns on signals EN1 and EN2.
Turn off. Then, when the signal EN1 is turned on, the main switching element 45 is turned on, and when the signal EN2 is turned on, the primary switching element 46 is turned on.

The diode 47 is connected to the power supply line 5
0 is connected between 0 and the main switching element 45 to prevent the primary current i _F from flowing backward, and the diode 48 is connected between the head coil 10 and the regenerative circuit 59 so that the secondary current i _Z flows backward. Prevent from doing. Next, the operation of the head driver 21 will be described with reference to FIG.

FIG. 6 is a waveform diagram of the head driver in the serial printer showing the embodiment of the present invention. Since the normal operation of the head driver 21 is the same as the conventional one, FIG. 4 is referred to. When the control circuit 43 receives a control signal from the print head control signal board section 14 and turns on the signals EN1 and EN2, the main switching element 4
5 and the primary switching element 46 is turned on,
_A current i _A flows through the head coil 10 and a current i flows through the main switching element 45 to drive a magnet (not shown). At this time, the coil output terminal voltage V _A drops from the power supply voltage E to almost zero. Next, when the signal EN1 is turned off from on, the main switching element 45 is turned off and the current i becomes 0, and the current i _A flowing in the head coil 10 is changed to the primary switching element 46 for the first time.
Then, it passes through the diode 47 and becomes the primary current i _F, and flows to the head coil 10 again via the power supply line 50. Further, the coil output terminal voltage V _A drops and becomes substantially equal to the power supply voltage E.

By the way, the armature of the print head is released from the magnet when the signal EN1 is turned from ON to OFF, and the print wire is caused to fly to collide with the print paper via the ink ribbon. Then, when the signal EN2 is turned off from before or after the time when the print wire collides with the printing paper, the first-time live switching element 46 is turned off, and the first-time live current i _F is 0.
become. In addition, the remaining energy in the head coil 10 becomes the secondary current I _z , which flows through the diode 48 and the regenerative current line 38 to the regenerative circuit 59 and is consumed. The coil output terminal voltage V _A and the secondary power voltage V _Z at the time of the secondary power generation have a value obtained by adding the Zener voltage E _Z of the Zener diode Z1 in the regenerative circuit 59 to the power supply voltage E. Then, when the secondary raw current i _Z becomes 0, the coil output terminal voltage V _A and the secondary raw voltage V _Z gradually decrease and become equal to the power supply voltage E. In this way, the armature is attracted to the magnet, ending the series of operations.

By the way, in the regenerative current line 38,
Second time raw current i_ZIs the connector member 33, the motor substrate
Part 13, connecting means C₂, Flexible cable 16 and connecting hand
Step C ₁To the regeneration circuit 59. And h
The cable 16 is not broken, and the connector
Material 33, connecting means C₁, C₂Contact failure occurs in
If not, Zener of Zener diode Z1
Voltage E_ZAnd the Zener voltage E of the Zener diode Z2
_Z2But E_Z<E_Z2 Therefore, the secondary current i_ZIs the regenerative circuit 5
9 and is consumed in the regenerative circuit 59.

Here, if the flexible cable 16 having the above-mentioned configuration is broken due to fatigue or contact failure occurs in the connector member 33, the connecting means C ₁ , C _2, etc., the inductance of the head coil 10 causes a change in the current change rate. A proportional back electromotive force is generated. However, since the secondary regenerative circuit 60 is arranged in parallel with the regenerative circuit 59 to form the secondary regenerative circuit, the secondary regenerated current i _Z flows through the Zener diode Z2, and the coil output terminal voltage V _A and the secondary output current i _Z. The next-generation raw voltage V _Z becomes a value obtained by adding the Zener voltage E _Z2 of the Zener diode Z2 of the sub-regeneration circuit 60 to the power supply voltage E, and does not become higher than that.

Here, the Zener voltage E _Z2 is slightly higher than the Zener voltage E _Z. Therefore, the flexible cable 1
Even if 6 is disconnected due to fatigue or contact failure occurs in the connector member 33, the connecting means C ₁ , C _2, etc., the coil output terminal voltage V _A and the secondary voltage V _Z are set to the power supply voltage E zener. It can be a value to which the voltage E _Z2 is added.

Therefore, the head driver 21 will not be destroyed by overvoltage, or discharge will occur between the patterns having a low withstand voltage, so that the small signal system circuit such as the control circuit 43 and the elements in the sensor 36 will not be destroyed. Next, a second embodiment of the present invention will be described. FIG. 8 is a head drive circuit diagram of a serial printer showing a second embodiment of the present invention. Incidentally, in the present embodiment, description of matters common to the first embodiment will be omitted.

In this case, a sub-regenerative circuit 70 is arranged on the motor board portion 13 in parallel with the regenerative circuit 59. The sub-regeneration circuit 70 is composed of a Zener diode Z2 as a constant voltage element connecting the regenerative current line 38 and the power supply line 50, and a backflow prevention diode 71 arranged on the regenerative current line 38. Then, the anode of the diode 71 is connected to the cathode of the diode 48 (FIG. 7) of the head driver 21, and the cathode of the diode 71 is connected to the cathode of the Zener diode Z2. The value of the Zener voltage E _Z2 of the Zener diode Z2 is made larger than the value of the Zener voltage E _Z of the Zener diode Z1 of the regenerative circuit 59.

The diode 7 is added to the sub regeneration circuit 70.
1, the diode is unnecessary in the regenerative circuit 59. Therefore, even if the flexible cable 16 is broken due to fatigue or contact failure occurs in the connecting means C ₁ , C _2, etc., the coil output terminal voltage V _A
And the secondary voltage V _Z to the power supply voltage E and the Zener voltage E _Z2
Can be added.

The present invention is not limited to the above-mentioned embodiments, but various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention.

[0047]

As described above in detail, according to the present invention, in the serial printer, the main control board portion arranged in the main body portion and the carriage portion are arranged to drive the head coil of the print head. And a head driver board portion connected to the main control board portion via a flexible cable.

The main control board section includes a regenerative circuit that consumes the secondary regenerative current of the head driver, and the head driver board section includes a sub regenerative circuit that consumes the secondary regenerative current of the head driver. Prepare In this case, if the flexible cable is broken due to fatigue or contact failure occurs in the connecting means between the main control board portion and the flexible cable or the connector between the head driver board portion and the flexible cable, the print head A counter electromotive voltage proportional to the current change rate is generated by the inductance of the head coil.

However, since the sub regenerative circuit is provided, it is possible to prevent the secondary regenerative current from flowing through the sub regenerative circuit and increasing the output terminal voltage of the head driver and the secondary regenerative voltage. Therefore, the head driver is not damaged by overvoltage, or discharge is generated between the patterns having a low withstand voltage, so that the circuit in the small signal system or the element in the sensor is not damaged.

In another serial printer of the present invention, a main control board section provided in the main body section, a board section connected to the main control board section via a flexible cable, and a carriage section are provided. A head driver for driving a head coil of the print head is provided, and a head driver substrate portion connected to the substrate portion is provided. And
The main control board unit includes a regenerative circuit that consumes the secondary regenerative current of the head driver, and the board unit includes a sub regenerative circuit that consumes the secondary regenerative current of the head driver.

In this case, when the flexible cable is broken due to fatigue or a contact failure occurs in the connecting means between the main control board and the flexible cable, the inductance of the head coil of the print head is proportional to the current change rate. A back electromotive force is generated. However, since the sub-regeneration circuit is provided, it is possible to prevent the secondary regenerative current from flowing through the sub-regeneration circuit and increasing the output terminal voltage of the head driver and the secondary regenerative voltage.

Therefore, the head driver will not be destroyed by overvoltage, or discharge will occur between the patterns having a low withstand voltage, so that the circuit in the small signal system or the element in the sensor will not be destroyed. In still another serial printer of the present invention, the regenerative circuit and the sub regenerative circuit include constant voltage elements. Then, the secondary regenerative voltage set by the constant voltage element of the regenerative circuit is made higher than the secondary regenerative voltage set by the constant voltage element of the sub regenerative circuit. In this case, the output terminal voltage and the secondary regenerated voltage of the head driver can be a value obtained by adding the constant voltage by the constant voltage element of the sub regeneration circuit to the power supply voltage.

Therefore, the head driver is not damaged by overvoltage, or discharge is generated between the patterns having a low withstand voltage, so that the circuit in the small signal system or the element in the sensor is not damaged.

[Brief description of drawings]

FIG. 1 is a head drive circuit diagram of a serial printer showing a first embodiment of the present invention.

FIG. 2 is a head drive circuit diagram of a conventional serial printer.

FIG. 3 is a circuit diagram of a head driver in a conventional serial printer.

FIG. 4 is a waveform diagram of a head driver in a conventional serial printer.

FIG. 5 is a waveform diagram of a coil output terminal voltage and a secondary regenerated voltage when a contact failure occurs.

FIG. 6 is a waveform diagram of a head driver in the serial printer showing the embodiment of the present invention.

FIG. 7 is a circuit diagram of a head driver in the serial printer showing the first embodiment of the present invention.

FIG. 8 is a head drive circuit diagram of a serial printer showing a second embodiment of the present invention.

[Explanation of symbols]

10 head coil 11 main control board section 13 motor board section 14 print head control signal board section 15 print head driver board section 16 flex cable 21 head driver 59 regenerative circuit 60, 70 sub regenerative circuit A ₁ main body section A ₂ carriage section E _Z , E _Z2 Zener voltage i _F Primary live current i _Z Secondary live current V _A Coil output terminal voltage V _Z Secondary live voltage Z1, Z2 Zener diode

Claims (3)

[Claims] 1. A main control board portion disposed on a main body portion, and a head driver disposed on a carriage portion for driving a head coil of a print head.
A head driver board portion connected to the main control board portion via a flexible cable; and (c) the main control board portion includes a regenerative circuit that consumes a secondary current of the head driver. d) A serial printer characterized in that the head driver board portion is provided with a sub-regeneration circuit that consumes a secondary current of the head driver. 2. A main control board portion arranged in (a) a main body portion, (b) a board portion connected to said main control board portion via a flexible cable, and (c) arranged in a carriage portion. Is
A head driver for driving a head coil of a print head is provided, and a head driver substrate unit connected to the substrate unit is provided, and (d) the main control substrate unit consumes a secondary current of the head driver. (E) The substrate unit includes a sub-regeneration circuit that consumes a secondary regenerated current of the head driver. 3. The regenerative circuit and the sub-regenerative circuit are provided with a constant voltage element, and the secondary regenerative voltage set by the constant voltage element of the regenerative circuit is regenerated by the secondary voltage set by the constant voltage element of the sub regenerative circuit. The serial printer according to claim 1, wherein the serial printer has a voltage higher than the voltage.