DE3036378A1 - POWER DRIVER CIRCUIT FOR THERMAL PRINTER - Google Patents

Description

TISCHER ■ KERN & BREHM -Jf-

Albert-Rosshaupter-Strasse 65 D 8000 Munich 70 Telephone (089) 7605520 Telex 05-212284 palsd - Telegrams core patent Munich

GOULD INC. Sept. 26, 1980

10 Gould Center, Rolling Meadows, GD-36 Illinois 60008,
United States

Current driver circuit for thermal printer

Description:

The present invention relates to writing, printing or imaging apparatus employing thermal imaging; Such devices are hereinafter referred to as "thermal printers" designated. In particular, the invention relates to a current driver circuit which the heat generating Resistance elements or pens in such a thermal printer are supplied with energy.

There are thermally operating recording and reproducing devices known whose image-generating writing tips or

130016/0794

Pens are arranged in a linear array. Such devices typically have a variety of Writing pens, which are produced by applying electrically resistive material to an insulating substrate have been received; this plurality of individual pens are arranged in a single row. Any pen is specifically supplied or excited with electrical current by a driver circuit in order to generate Joule-like heat. When the pens are brought into contact with or in sufficient proximity to a thermosensitive recording material then each pen that is supplied with power creates a mark on the recording material. Typically, the incoming print data is in the form of a series and is generated using Shift registers converted into parallel print data. After the date has been inserted, the driver circuit will be released and the pen supplied with energy.

It is known to convert the incoming data from the serial form to a parallel form and then to convert the Enable driver circuit as described above. Such a circuit is for example in the US patent 3,813,513 to Vora et al. Here is a definite Amount of serial data is inserted into the shift register, which converts the serial print data into parallel print

130016/0794

convert data. The supply of print data must then be stopped. The driver circuit is used for a specific Duration released. After the cycle has been completed, new print data can be entered in the shift register be inserted. This starting and stopping the incoming Print data means that the cycle time or the time between the individual characters is quite long. Furthermore must wait before the next information can be printed out, the driver circuit enabling device until the next piece of information has been shifted into the shift register.

With this in mind, the object of this invention is to provide a current drive circuit for thermal imaging devices provide, which does not have the mentioned deficiencies. In particular, with the present invention a current drive circuit can be provided which reduces the print cycle time. After another The aim of the invention is to provide a simple current drive circuit for thermal imaging devices that can be easily incorporated into an integrated hybrid circuit. Finally, after another The aim of the invention is to provide a current driver circuit, which incoming data with random or alternating Picks up speed.

130016/079

Further objects, features and advantages of the invention result from the following description.

The inventive solution to this problem and objectives is a current driver circuit having the features specified in claim 1. Advantageous further developments of these according to the invention Current driver circuit results from the subclaims.

With this invention a current driver circuit is thus provided which is suitable for use in thermally operating Image generation, printing or reproduction devices is determined which circuit allows higher printing capacities because the print cycle time is reduced. An incoming digital sequence of serial print data is processed by a serial-to-parallel converter recorded. The number of parallel bits in the converter is preferably equal to the number of pens in the thermal writing arrangement. The incoming digital sequence of serial print data corresponds to a Line of data to be printed out by the linear writing array. The data sequence or data line has individual Data positions on; each position corresponds to a particular pen in the writing arrangement. After the full Line of data has been recorded, i.e. converted into parallel data, becomes one operatively connected to the transducer Hold circuit released instantly in order to

130016/0 7 94

to hold converted parallel data line interlocking. The next line of data can then be inserted into the converter without any time delay as the latch latches the previous line of data holds. After the first line of data has been converted and held, but before the next Data line is converted, the current driver device effectively connected to the hold circuit is enabled, to supply the pens with energy. The release of the driver device controls the clock ratio or the duration of excitation of the pens. After the next line of data has been completely converted, this is held and the cycle can run again.

The invention is described below on the basis of preferred embodiments explained with reference to Figures 1 and 2; it shows:

1 shows a schematic embodiment of the present invention on the basis of a block diagram; and

2 shows an embodiment of the present invention on the basis of a circuit diagram.

As indicated, the invention is explained below with reference to preferred embodiments, but without referring to this

130016/0794

to be limited. In the drawings, the same reference numbers refer to the same elements in the different figures "or components.

In the context of these documents, the term "HIGH" is used in a known manner to designate a specific digital Voltage level used; Such a digital "HIGH" state can also be represented and denoted by the number "1" then the logic state 1. Correspondingly, the indication "LOW" is used to designate a different, lower one digital voltage level used; Such a digital "LOW" state can also be represented with the number "O" and then designates the logic state 0. The actual voltage values, which are assigned to the digital "HIGH" or 'ιLOW' state may correspond, depend on the type of used digital device. If e.g. a transistor-transistor logic (TTL) is used, has a digital LOW state typically a voltage value of 0.0 to 0.8 V DC; a digital HIGH state indicates accordingly has a voltage value of 2.0 to 5i5 V DC.

Using the block diagram according to FIG. 1, a schematic representation is made Embodiment of a device according to the invention explained. A serial-parallel converter A is provided which has a data input and a clock input. The serial, digital print data is transferred via the data input

130016/0794

gear recorded. The converter A converts the serial input data into parallel output data. A clock device generates clock pulses in order to clock the input of the converter A in order to locate and synchronize the incoming serial data with respect to the parallel output data. Each recorded clock pulse corresponds to a specific individual pen in the writing arrangement 512 clock pulses are provided in a sequence of serial data. The converter A then generates 512 parallel output signals If, for example, the incoming data line has HIGH states during clock pulses 21 to 50 and 176 to 200, the parallel output signals 21 to 50 and 176 to 200 will have a HIGH state after these 512 clock pulses have elapsed Include one end of a line of digital data. After the data is clocked into converter A and before another data sequence begins, a hold circuit B holds and maintains the parallel output data generated by converter A. It is apparent to those skilled in the art that a new data sequence can be clocked into converter A immediately thereafter. This means that the data flow in the converter A can run uninterrupted, while the hold circuit % d \ fc parallel data at the end

130016/0794

the data sequence holds locking. A current drive device C is operatively connected to the holding circuit B, which powers the pens of the thermal writing assembly. When data on the Hold circuit of the coming bits exist, then the current driver means C the corresponding pens supply with energy. According to the example given above, assuming that the latch circuit is HIGH in pos. 21 to 50 and 176 to 200, the current driver device C also becomes the pens 21 to 50 and 176 to 200 with energy.

With reference to FIG. 2, end a special one Embodiment of the invention explained. The general mode of action this circuit is the same as that of the general embodiment shown in FIG One method of performing the conversion of the serial data to parallel data is by a number of shift registers 1A to NA provided. Here N stands for an integer, which is preferably equal to the number of pens in the writing assembly. If 512 pens are provided are, N preferably has the value 512. With regard to the shift register, a dynamic two-phase shift register be used. Typically, a two-phase clock is required for a two-phase shift register. In this particular embodiment will be

130016/0794

the two phases of the clock are referred to as clock A and B. During & s typical two-phase shift register operation the incoming data is recorded during clock A and during the rising edge of cycle B to the output. The data remain at the output until the next clock pulse B. as will be apparent to those skilled in the art, a number of serially wired shift registers will be the incoming ones move serial data to parallel output data. The timing of bars A and B can be changed, so that the input data can be picked up at any given rate. Furthermore, a number of One-bit latch circuits shown as 1B through NB are designated; again, N preferably corresponds to the number of pens in the writing arrangement. In detail the holding circuit 1B is operatively linked to the shift register 1A; the hold circuit 2B is effective linked to the shift register 2A, etc .; finally, the hold circuit NB operates with the shift register NA linked. A hold circuit release control is provided, which is effectively linked to all of the hold circuits 1B to NB. After the line of data is added and has been shifted into the shift registers 1A to NA, the enable control of the hold circuit becomes its logic states change so that the converted parallel data are held by the holding circuits 1B to NB. Direct the next line of data can then be added

130016/0794

and it starts moving into the registers 1A to NA.

Finally, a number of driver devices AC to KC are provided, N preferably again being the same is the number of pens in the writing assembly. In detail, the driver device 1C is effective with linked to the hold circuit 1B; the driver device 2C is effectively linked to the holding circuit 2B and like; finally, the driver device NC is effectively linked to the holding circuit NB. It's a release fcung provided for the driver devices, which are effective with all driver devices 1C until NC is linked. The outputs of the driver devices are operative with the pens of the writing arrangement linked (which is not shown in the figure). The purpose of the release control of the driver device is in controlling the duty cycle of the driver device. If, for example, a digital LOW state means "no release", then the driver device is enabled when the enable line for the driver devices a digital HIGH state is supplied. In this way the data in the holding circuits control which pen is driven. The duration of the pen excitement depends solely on the duration the digital HIGH state on the enable line for

130016/0794

the driver devices, controlled. Like that for professionals can be seen, the control of the clock ratio of the driver devices allows control of the overall temperature, which the thermal writing arrangement adopts. If there is a temperature sensor on the writing surface is appropriate, the duty cycle for the driving time can be reduced to prevent the Prevent writing pens.

The embodiments of current driver circuits according to the invention explained with reference to FIGS. 1 and 2 can be in the form of discrete, individual components can be realized, or these current driver circuits can be integrated in the form of an Hybrid circuit can be formed.

The application of the above current driver circuits is not applicable thermal devices with linear writing arrangement limited; rather, these circuits can be in any Recording and playback devices are used which record data lines or sequences in serial form and require parallel output data and have a driver device to the recording or reproducing device provide the necessary information.

As stated, the invention is based on preferred embodiments has been explained. Obviously, modifications and changes can be made without departing from the core

130016/0794 ORIGINAL BATHROOM

of the invention differ as it relates to the subject matter of Claims and their equivalents is outlined. Such modifications and alterations are therefore also allowed encompassed by the present invention.

1300-16 / 0794

Claims (1)

TISGHER ■ KERN & BREHM Aioert-Rosshaupter-Strasse 65 D 8000 Munich 70 · Telephone (089) 7605520 ■ T elex 05-212284 patsd ■ Telegrams core patent Munich GOULD INC. Sept. 26, 1980 10 Gould Center, Rolling Meadows, GD-36 Illinois 60008,
United States Current driver circuit for thermal printer Patent claims: 1.) Stroin driver circuit for thermal imaging devices (thermal printer) with a linear arrangement of the heat-generating resistance elements for generating characters on a heat-sensitive recording material during the printing or writing process,
marked by a converter for converting the incoming serial print data into parallel print data; 130016/0794 a hold circuit operatively connected to the transducer for lockingly holding the parallel print data generated by the transducer; and a current drive device operatively connected to the hold circuit to supply the heat-generating resistance elements with sufficient driving current. 2. Current driver circuit according to claim 1, characterized in that the converter comprises a number of one-bit shift registers connected in series having, the number of the shift registers being equal to the number of the heat-generating resistance elements is in the thermal image forming apparatus. 5. current driver circuit according to claim Λ or 2, characterized in that the hold circuit has an input for controlling the release of the hold state to control when the hold circuit forwards and when the hold circuit holds the parallel print data received from the converter. 4 ·. Current driver circuit according to Claim 3, characterized in that a logical HIGH state at the input of the release control the hold circuit causes the hold circuit to turn off 130016/0794 holds parallel print data obtained from the converter; and that a logical LOW state at the input of the release control of the hold circuit causes the hold circuit to forward the parallel print data received from the converter. 5. Current driver circuit according to one of claims 1 to 4 ·, characterized in that the current driver device has an input for enabling control of the driver device in order to set the duty cycle to control at the output of this current driver device. 6. Current driver circuit according to one of claims 1 to 5> characterized in that the converter, the holding circuit and the current driver device are incorporated into an integrated hybrid circuit. 130016/0794