JPH0815791B2 - Thermal head drive circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video printer for printing a video signal, and more particularly to a driving circuit for a thermal head suitable for high density gradation expression.

[Conventional technology]

In the conventional thermal head drive circuit for this type of printer, as described in Japanese Patent Application Laid-Open No. 55-69482, heat is generated for one dot, but heat is generated without a pause period until the end of energization. I am trying.

[Problems to be solved by the invention]

In the above-mentioned conventional technique, for example, when performing density recording of 64 gradations, 64 kinds of pulses having different lengths are generated according to the gradations to control the density.

When it is desired to generate N gradations of density on a certain line, one pulse corresponding to each line is used. When the energization time of the thermal head is controlled by the pulse, the temperature of the heating element continues to rise with the start of energization and at the end of energization,
That is, the maximum temperature is reached at the time corresponding to the trailing end of the pulse.

By the way, in order to reduce the time required for recording, it is conceivable to increase the electric power applied to the thermal head. In this case, with the start of energization, the temperature rises more rapidly than the previous example, reaches the color development temperature at an earlier time, the temperature of the heating element continues to rise, and similarly reaches the maximum temperature at the end of energization, but that temperature increases the applied power. In addition, there is a fear that the heat-sensitive head and the applied material are thermally destroyed due to the high temperature.

An object of the present invention is to provide a thermal head drive circuit that enables stable, high-quality and high-speed printing even when the electric power applied to the thermal head is set high.

[Means for solving problems]

The above object is achieved by using means for controlling the energization period per line of the thermal head and means for generating an energization suspension period during the heating period per line in the thermal head drive circuit.

For example, if the time per line is T _Line, the heating period per line is T _on , the cooling period per line is T _OF , the energization period of the Nth gradation, T _Non , the rest period of the Nth gradation, T _Noff As shown in FIG. Becomes

On the other hand, in the present invention, as shown in FIG. The energization is controlled so that

[Action]

The energization time control means controls the energization of the thermal head for a predetermined time (t _non ) for each gradation for expressing the density gradation.

The energization suspension control means controls the energization suspension of the thermal head for a predetermined time (t _noff ) for each gradation.

By alternately or continuously using the above-mentioned two means, the heating period for one dot of the thermal head can be constituted by repeating energization and de-energization. In the conventional example, the current continues to flow during the heating period (T _on ) for one dot, so when the applied power to the thermal head is increased for the purpose of speeding up printing, etc. The temperature becomes too high and the thermal head and the applied material are thermally destroyed. However, by providing multiple energization rest periods (t _noff ) during the heating period (T _on ), the head is cooled during the rest period t _noff , so it is possible to prevent overheating of the thermal head and increase the power applied to the thermal head. It enables high speed printing.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

First, the operation of the signal system of the video printer will be described with reference to FIG.

FIG. 4 is a block diagram for explaining the signal system of the video printer. 400 is an A / D converter, 401 is the main memory, and 402 is the main memory.
D / A converter, 403 decoder, 405 encoder, 1 system controller, 406 A / D converter, 408 matrix circuit, 409 complementary color conversion circuit, 411 line memory, 410
Is a data control circuit, 412 is an energization pulse control circuit, 7 is a thermal head, and 407 is a selector.

 The operation of the figure will be described.

A video signal is input to the A / D converter 400. A / D converter 400
The video signal is digitized by and sent to the main memory 401. The main memory 401 stores a video signal of one frame or one field according to a control signal from the system controller 1. The digital video signal is read again from the main memory 401 and sent to the D / A converter 402.
The D / A converter 402 again converts the digital video signal into an analog video signal and sends it to the decoder 403. Decoder 403
Generates a Y signal, a Y-R signal, and a Y-B signal from the video signal and sends them to the encoder 405 and the matrix circuit 408. Y
The signal, the Y-R signal, and the Y-B signal are converted into a composite video signal again by the encoder 405 and sent to the monitor.

The matrix circuit 408 converts the Y signal, the Y-R signal, and the Y-B signal into R (red), G (green), and B (blue) signals of primary color signals, and sends them to the selector 407. The selector 407 first selects the B signal and sends it to the A / D converter 406. The A / D converter 406 converts the digital R signal into a Ye (yellow) signal via the complementary color conversion circuit 409 and sends it to the data control circuit 410. The data control circuit 410 temporarily stores one line of the input digital Ye signal in the line memory 411.

The data control circuit 410 reads the stored digital Ye data again, and sends head on / off data suitable for heat generation of the thermal head 7 to the thermal head 7 together with the clock CK necessary for data transfer.

When the data transfer to the thermal head 7 is completed, the energizing pulse control circuit 412 sends the energizing pulse corresponding to the gradation to the thermal head 7. The Inf paper of Ye and the printing paper are closely attached to the thermal head 7, and the dye of the ink paper is sublimated by the thermal energy of the heating element in the thermal head 7 and is adsorbed on the printing paper to express the density.

When printing of one line is completed, the line memory 411
Then, the line data is read and one line is printed in the same manner as above.

In the same way, if you print to the last line in sequence, the selector
408 selects G, and performs the above operation in the same manner as M which is a complementary color of G.
Print g (magenta).

Similarly, printing of Cy (cyan), which is the complementary color of R, is performed, and one printing is completed.

FIG. 1 is a block diagram showing a first embodiment of the present invention, in which 1 is a system controller, 2 is a gradation CK generation circuit,
Reference numeral 3 is a gradation counter, 4 is an energizing pulse generating circuit for generating an energizing period of each gradation, 5 is a quiescent period generating circuit for generating a quiescent period of each gradation, 6 is a strobe pulse generating circuit, 7 is a heat sensitive Head, 8 energization pulse control circuit, 100 1 line start signal, 101 gradation counter reset signal, 102 1 gradation end signal, 103 gradation CK, 104
Is gradation data, 105 is a strobe pulse, and 106 is a predetermined gradation end signal.

1 is a detailed view of the energizing pulse control circuit of FIG. 4 constructed according to the present invention.

 Next, the operation of FIG. 1 will be described.

First, the system controller 1 sends a gradation counter reset signal 101 to the gradation counter 3 to reset the gradation counter.

Then, the system controller 1 sends a 1-line start signal 100 to the gradation CK generation circuit 2.

The gradation CK generation circuit 2 converts the gradation CK103 into the gradation counter 3
To the energization pulse generation circuit 4. The gradation counter 3 sets the count value to 1 by the gradation CK103 and sends the gradation counter value of 1 to the energization pulse generating circuit 4 and the pause period generating circuit 5.

The energization pulse generation circuit 4 sends the strobe pulse 105 having a width suitable for the gradation count value from the gradation counter 3 to the thermal head 7 in synchronization with the gradation CK103. When the strobe pulse having a width suitable for the first gradation has been output, a control signal for ending energization is sent to the pause period generation circuit 5. The quiescent period generating circuit 5 generates a period suitable for a quiescent period of one gradation, and when the quiescent period ends, sends a quiescent period end control signal to the energization pulse generating circuit 4. The energization pulse generation circuit 4 receives the idle period control signal and prepares for input of the next gradation CK. At the same time, the strobe pulse generation circuit 6 sends a gradation end signal 102 to the gradation CK generation circuit 2.

 With the above operation, printing for one gradation is completed.

The gradation CK generation circuit 2 receives the gradation end signal 102 from the strobe pulse generation circuit 6 and sends the gradation CK 103 again to the gradation counter 3 and the energization pulse generation circuit 4. The gradation counter 3 increments the gradation count value by 1 by the gradation CK103,
Use gradation.

The gradation count value of two gradations is sent to the energization pulse generating circuit 4 to the pause period generating circuit 5 and the strobe pulse of the second gradation is sent to the thermal head 7 in the same manner as described above, and the pause period corresponding to the second gradation is set. Apply to the thermal head 7.

Similarly, a strobe pulse up to 64 gradations and a rest period are sent to the thermal head 7.

When the gradation counter 3 reaches 64, the 64 gradation end signal 106
To the gradation CK generation circuit 2. The gradation CK generation circuit 2 receives the 64 gradation end signal 106 and receives the strobe pulse generation circuit 6
Even if the gradation end signal 102 from is received, the gradation CK is not output. The heating period per line is completed when all 64 gradations have been energized, and the cooling period per line is until the next line starts.

By the above operation, the strobe pulse including the rest period of 1 to 64 gradations is sent to the thermal head 7 to complete the printing of one line.

FIG. 2 is a graph showing how the temperature of the heating element rises when the strobe pulse has no pause period, and FIG. 3 is a graph showing how the temperature of the heating element rises when the strobe pulse has a pause period.

2 and 3, 200 is the temperature at which the ink paper or the printing paper is destroyed by the temperature of the heating element, and 201 is the sublimation start temperature of the sublimable dye.

The print density shows a substantially proportional relationship with the shaded area in the figure.

In the case of FIG. 2 in which no strobe period is provided, if the voltage applied to the thermal head is increased to increase the printing speed, the maximum temperature of the heating element exceeds the ink paper / printing paper destruction temperature 200. According to the third case in which the pause period is provided, the temperature of the heat generating element is increased all the way to the destruction temperature of about 200, and then the temperature is raised and lowered for each gradation to maintain a substantially constant temperature. It is possible to develop the color of the density.

That is, if a rest period is provided during the heating period for one line, the thermal head applied voltage can be increased and the printing time can be shortened.

In this embodiment, Ye (yellow), Mg (magenta), Cy
Although the color printer using the three color inks of (cyan) has been described, it is needless to say that the present invention can be applied to a four color print in which BK (black) is further added and a monochrome printer.

Next, the embodiment of FIG. 1 will be described in more detail with reference to FIG.

Fig. 5 shows RO for the energization time and rest period for each gradation.
The configuration is such that the energizing pulse and the rest period are generated by the counter stored in M based on the data.

In the figure, 10 is an energization ROM, 11 is an energization pulse counter, 12 is a rest period ROM, 13 is a rest period counter, and 14 is S.
-R latches having the same reference numerals in FIG. 1 have the same function.

 FIG. 6 is an operation timing chart of FIG.

The energizing ROM 10, energizing pulse counter 11, and SR latch 14 in FIG. 5 form the energizing pulse generating circuit 4 in FIG. 1, and the rest period ROM 12 is a rest period counter and the rest period in FIG. The generation circuit 5 is formed.

 The operation of FIG. 5 will be described below with FIG.

First, as described with reference to FIG. 1, the gradation CK generation circuit 2 receives the 1-line start signal 100 from the syscon 1 and outputs the gradation CK103 to the gradation counter 3 and the SR latch 14.
To the energization pulse counter 11.

The SR latch 14 sets the Q output to "L" and sends the strobe pulse 105 to the thermal head 7. (In this embodiment,
The strobe pulse 105 is "L" active. At the same time, the gradation counter 3 receives the gradation CK103, sets the gradation count value to 1, and sends it to the energization ROM 10 and the rest period ROM 12.

The energization ROM 10 is suitable for energizing the first gradation. The energization ROM 10 sends energization time data suitable for energizing the first gradation to the energization pulse counter 11. On the other hand, the rest period ROM 12 sends rest period data suitable for the first gradation to the rest period counter 13. (Energization ROM1
0, the energization period data and the suspension period data suitable for each gradation are stored in advance in the suspension period ROM 12. The energization pulse counter 11 loads the energization time data from the energization ROM 10 with the gradation CK and starts counting.
When the counting for the energization time data is completed, the energization pulse counter 11 sends an energization end signal 111 to the S input of the SR latch 14 and the load input of the rest period counter 13.

The S-R latch 14 sets the O output to "H" by the S input,
Set the strobe 105 to "H" (no energization).

On the other hand, the rest period counter 13 receives the energization end signal 111, loads the rest period data of one gradation from the rest period ROM 12, and starts counting. When the counting of the pause period data is completed, the pause period end signal 112 is sent to the energization pulse counter 11 to reset the energization pulse counter 11.

 At the same time, the gradation end signal 102 is sent to the gradation CK generation circuit 2.

 With the above, printing for one gradation is completed.

The gradation CK generation circuit 2 receives the gradation end signal 102 and receives the gradation C.
Outputs K103.

In the same manner, the printing for the 2nd to 64th gradations is completed.

When the gradation counter reaches 64 gradations, 1 line end signal
106 is sent to the gradation CK generation circuit 2, and the output of the gradation CK103 is stopped.

 With the above, printing of one line is completed.

In the present embodiment, since the energization time can be arbitrarily changed in the rest period, the strobe pulse shown in FIG. 3 can be easily generated.

Next, a second embodiment of the present invention will be described with reference to FIGS. 7 and 8.

FIG. 7 is a block diagram showing a second embodiment of the present invention. In order to generate a strobe quiescent period, means for generating a width of one gradation including the quiescent period and energizing time are generated. Means are provided and a value obtained by subtracting the energization time from one gradation width is used as the pause period.

In the figure, 20 is a gradation width ROM, 21 is a gradation width counter, and those denoted by the same reference numerals as in FIG. 5 have the same functions.

 FIG. 8 is an operation timing chart of FIG.

 Hereinafter, the operation of FIG. 7 will be described together with FIG.

The operations of the gradation CK generation circuit 2 and the gradation counter 3 are the same as in FIG.

The gradation CK is generated from the gradation CK generating circuit 2 by the gradation counter 3 and S
-Send to the R latch 14, the gradation width counter 21, and the energization pulse width counter 11.

The SR latch 14 receives the R input and receives the strobe pulse 10
Set 5 to “L” and send to thermal head 7.

The gradation counter 3 sets the gradation count value 1 to the gradation width ROM20.
And sends it to the energization pulse ROM10. The gradation width ROM sends one gradation width data including the pause period to the gradation width counter 21, and the energization pulse ROM 10 supplies the energization time data to the energization pulse counter 1.
Send to 1.

The gradation width counter 21 and energization pulse counter 11 are gradation CK
By 103, the gradation width data and the energization time data are loaded respectively, and counting is started. The energization pulse counter outputs the energization end signal with the count value for the energization time data.
-Send it to the S input of R latch 14 and set the strobe to "H" (not energized).

Next, when the count for the gradation width data is completed, the gradation width counter 21 outputs the gradation width end signal 120 to the gradation CK generation circuit 2.
Send to Here, the gradation width and the energization time are set to satisfy the relationship of gradation width ≧ energization time, and the period in which the energization time is subtracted from the gradation width is the strobe pause period.

 With the above operation, the operation for one gradation is completed.

By the same operation, energization of 2 to 64 gradations is performed, and the printing of one line is completed.

Also in this embodiment, since the energization time and the rest period can be arbitrarily changed, the strobe pulse shown in FIG. 3 can be easily generated.

 Next, a third embodiment of the present invention will be described.

FIG. 9 is a block diagram showing a third embodiment of the present invention, and FIG.
The figure is an operation timing chart of FIG.

In this embodiment, the change point of the strobe is stored in the ROM in advance, the ROM is read and the change point is input as CK to the toggle FF to generate the strobe passage time and the rest period.

In FIG. 9, 30 is an address counter and 31 is a change point.
ROM, 32 are D-FFs, 33 is an AND gate, and those denoted by the same reference numerals as in FIG. 5 have the same function.

 The operation of FIG. 9 will be described below with reference to FIG.

The address counter 30 is reset by the 1-line start signal 100 from the system controller 1 and then C
Start counting by K134. The address counter 30 sends the address 130 to the change point ROM. “1” is stored in the change point ROM only for the strobe ON / OFF change points.

The change point ROM 31 uses the address 130 to change the change point data 131.
To D-FF32. Toggle D-FF and change point RO
When the data from M31 is 1, the output Q is inverted and the polarity of the strobe pulse 105 is inverted.

When the address counter 30 counts the time for one line, the one-line end signal 133 is sent to the AND gate 33 and C
Gate K and stop CK.

 The above operation ends the energization of one line.

According to the present embodiment, it is possible to arbitrarily generate the energization time and the suspension period without using a counter for generating the suspension period. Therefore, there is an advantage that the number of parts used can be reduced.

 Next, a fourth embodiment of the present invention will be described.

FIG. 11 is a block diagram showing a fourth embodiment of the present invention, and FIG.
The figure is an operation timing chart of FIG.

In this embodiment, an energization time with a long gradation is first created separately by providing a mono-multi.

In FIG. 11, reference numeral 40 denotes a monomulti, and those designated by the same reference numerals as those in FIG. 5 have the same functions.

The part of FIG. 11 that operates differently from FIG. 5 will be described.

The mono-multi 40 operates by using the 1-line start signal from the system controller 1 as CK and generates a pulse of the energization time of the first gradation-α minutes, and the energization pulse counter 11
Send to

The energization pulse counter 11 receives the pulse from the monomulti 40 as a load signal, loads the energization time data from the energization ROM 10, and starts counting.

As the data of the first gradation of the energization ROM 10, the energization time required for the first gradation-the time of the pulse generated in mono-multi is stored.

When the energization pulse counter counts a predetermined pulse, the energization end signal is sent to the S-R latch 14 for the rest period counter.
Send to 13.

Thereafter, similarly to the operation of FIG. 5, 2 to 64 gradations are energized, and the printing of one line is completed.

According to this embodiment, since the first long energization time is separately created, the number of bits of the energization ROM 10 and the energization pulse counter 11 can be reduced.

 Next, a fifth embodiment of the present invention will be described.

FIG. 13 is a block diagram showing a fifth embodiment of the present invention. In this embodiment, the temperature of the thermal head substrate is read by a temperature sensor, the rest period of the strobe is varied according to the temperature, and the temperature of the heating element is kept constant. It is something to keep.

In the figure, 50 is a thermistor, 51 is a current conversion circuit,
Reference numeral 52 is an A / D converter, and those designated by the same reference numerals as those in FIG. 5 have the same functions.

The operation of the part different from FIG. 5 will be described below.

The thermistor 50 detects the substrate temperature of the thermal head 7 and sends a resistance value change to the current conversion circuit 51.

The current conversion circuit converts the resistance value from the thermistor 50 into a current and sends the current value to the A / D converter 52.

The A / D converter 52 digitizes the current value and outputs digital temperature data for the temperature of the thermal head substrate during the rest period RO
Send to M12.

In this embodiment, the rest period ROM 12 stores rest period data corresponding to the head substrate temperature.

Rest period ROM12 receives digital temperature data,
With respect to the temperature of the thermal head substrate, the rest period data for keeping the temperature of the heat generation rest constant during the energization time is selected and sent to the rest period counter 13.

Further, the energization time may be selected in the energization ROM 10.

In the following, the operation shown in FIG. 5 is similarly energized and printed.

The temperature detection may be performed immediately before the start of one-line printing, immediately before the start of single-color printing, or immediately before the start of single-sheet printing.

According to this embodiment, the energization time or the rest period can be changed according to the temperature of the thermal head substrate.
Regardless of the temperature of the thermal head substrate, the temperature of the heating element can be kept substantially constant when the heating element heats up, and there is an effect such that the density becomes low and ink paper or printing paper is not destroyed.

 Next, a sixth embodiment of the present invention will be described.

FIG. 14 is a block diagram showing a sixth embodiment of the present invention,
The figure is an operation timing chart of FIG.

In this embodiment, energization for each gradation is performed in the same cycle over all gradations, the number of parts is reduced, and the cost is reduced.

In FIG. 14, reference numeral 60 denotes a constant pulse generating circuit,
The same reference numerals in the drawings have the same functions.

 The operation of FIG. 14 will be described below with reference to FIG.

The constant pulse generation circuit 60 receives the 1-line start signal from the system controller 1 and outputs the gradation CK160 of a constant cycle.
Is sent to the SR latch 14, the energization pulse counter 11 and the gradation counter 3.

The gradation CK160 from the constant pulse generation circuit 60 is output in a constant cycle as shown in FIG. 15, and only the energization time is set in the one cycle. Therefore, the remaining time of one cycle can be used as a rest period.

According to the present embodiment, since the ROM 3 and the counter for the idle period are not used, there is an effect that the circuit can be configured easily and at low cost.

FIG. 16 is a block diagram showing a seventh embodiment of the present invention, in which this embodiment uses a data transfer counter instead of the constant pulse generation circuit 60 of the embodiment described in FIG. This is a time period in which the head on / off signal sent to the thermal head is transferred at a constant cycle for the number of dots of the head for each gradation.

In the figure, reference numeral 70 is a data transfer counter, and those designated by the same reference numerals as those in FIG. 14 have the same functions.

 The operation of the figure will be described below.

The data transfer counter 70 is reset by the 1-line start signal 100 from the system controller 1, counts the CK (not shown) synchronized with the head on / off data to the thermal head 7, and transfers the data for the number of heating elements. When finished, the gradation CK is generated.

Thereafter, the energizing operation is performed in the same manner as the operation of FIG. 14, and printing is performed.

According to this embodiment, the data transfer counter can be used without a circuit for outputting the gradation CK for each gradation.
Further, the circuit can be constructed at a low cost.

FIG. 17 is a block diagram showing an eighth embodiment of the present invention,
The figure is an operation timing chart of FIG. 17, in which a plurality of energization times and rest periods are provided for each gradation to keep the head heating element temperature during energization more constant.
A ROM and an energization pulse counter are provided.

In FIG. 17, reference numeral 80 is an energization width ROM, 81 is an energization pulse number counter, 82 is an OR gate, 83 is an SR latch, and those denoted by the same reference numerals as those in FIG. 5 have the same function.

 The operation of FIG. 17 will be described below with FIG.

The gradation CK generation circuit 2 compares the gradation CK103 with the gradation counter 3 and S.
-Send the R latch 83 to the energization pulse counter 11.

The SR latch 83 is set in the initial state, and the gradation
CK is input, the Q output is set to "L", and the OR gate 82 is opened.

On the other hand, the energization pulse counter 11 and the rest period counter 13 output energization pulses a plurality of times during one gradation, and the S-R latch 14 sends them to the OR gate 82 and the energization pulse number counter 81.

The OR gate 82 sends strobes a plurality of times during one gradation.

On the other hand, the energization pulse number counter 81 counts the number of energization pulses from the S-R latch 14, and when the energization data from the energization width ROM 80 is counted, the energization pulse number count end signal is sent to the S-R latch 83 and the gradation. Send to CK generation circuit 2.

The SR latch 83 sets the Q output to "H", and the OR gate 82
The OR gate 82 for sending to the
The energization pulse from the R latch 14 is stopped and the energization for one gradation is completed.

The gradation CK generation circuit 2 receives the energization pulse number count end signal from the energization pulse number counter 81 and outputs the gradation CK again.

The gradation counter 3 outputs two gradations, and in response to this, the energization width ROM 80, the energization ROM 10 and the rest period ROM 12 send appropriate prestored data to the respective counters for the second gradation.

 Thereafter, the strobe is output similarly to the first gradation.

According to this embodiment, since the strobe can be controlled to be turned on / off a plurality of times during one gradation, there is an effect that the temperature of the heating element during color development can be kept more constant.

FIG. 19 is a block diagram showing the ninth embodiment of the present invention, and FIG.
The figure is a flow chart for explaining the operation of FIG.

This embodiment is characterized in that the energization pulse control circuit 8 in FIG. 1 is replaced by a microcomputer.

In FIG. 19, 90 is a microcomputer, and the system controller 1 and the thermal head 7 have the same functions as in FIG.

The operation of FIG. 19 is as follows:
Upon receiving the 1-line start signal from the system controller 1, the strobe 105 including the pause period is sent to the thermal head 7.

Next, the operation of the microcomputer 90 will be described with reference to the flowchart of FIG.

In FIG. 20, 301 is initial setting, 302 is 1-line start signal input determination, 303 is gradation count up, 304 is strobe “L”, 305 is energization data load, 306 is timer count, 307 is strobe “H”. Reference numeral 308 is data for rest period data, 309 is a timer count, and 301 is predetermined gradation determination.

First, an initial setting 301 is performed, and operations such as boat setting and strobe "H" are performed.

Next, the procedure proceeds to 1 line start signal input determination 302. If the 1-line start signal is not input here, the branch 311 again determines whether to input the 1-line start signal 302
Return and wait for input of 1-line start signal.

When the 1-line start signal is input here, the process proceeds to the gradation count-up 303, and 1 is added to the value of the register in the microcomputer that counts the gradation.

Next, go to strobe "L" 304 and turn strobe "L".
(On).

Next, the process proceeds to the energization data load 305, and the energization data suitable for the first gradation is loaded into the output conveyor register of the hard timer in the microcomputer.

Next, the process proceeds to the timer count 306, and counts until the hard timer matches the value of the output compare register.

When the timer count 306 ends, the strobe “H” 307 is proceeded to, and the strobe is turned “H” (OFF).

Next, the process proceeds to a rest period data load 308 to load the rest period data suitable for the first gradation into the output compare register of the hard timer.

Next, the process proceeds to timer count 309, and continues counting until the hard timer matches the pause period data.

When the count value of the hard timer and the value of the pause period data in the output compare register match, the predetermined gradation determination 310 is performed.

Here, since the predetermined gradation is set to 64 gradations, at the first gradation, the process proceeds to the gradation count-up 303 by the branch 312.

Similarly, repeat the energization and rest for 2 to 64 gradations,
When the predetermined gradation judgment 310 is reached at the 64th gradation, the branch 313 advances to the 1-line start signal input judgment 302 to end the energization of 1 line.

According to the present embodiment, since the energization pulse control circuit can be configured by a one-chip microcomputer, there are effects that the cost can be reduced and the configuration can be changed by software.

〔The invention's effect〕

As described above, according to the present invention, it is possible to increase the electric power applied to the thermal head without thermally destroying the printing material such as ink paper and image receiving paper, so that the printing time can be shortened, and in particular, When used in a thermal transfer full-color printer using a sublimation dye, high-quality and high-quality prints can be obtained in a short time. Further, it is possible to provide a thermal head drive circuit having excellent functions except for the above-mentioned drawbacks of the prior art, such as reducing unnecessary heat radiation and improving energy efficiency with respect to color density by shortening the thermal head energization time.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention, FIG. 2 is a graph showing a temperature change of a heating element according to a conventional method, FIG. 3 is a graph showing a temperature change of a heating element according to the present invention, and FIG. FIG. 5 is a block diagram showing the entire signal system of the video printer, FIG. 5 is a block diagram showing details of the embodiment of the present invention shown in FIG. 1, FIG. 6 is an operation timing chart of FIG. 5, and FIG. FIG. 8 is a block diagram showing a second embodiment of the invention, and FIG.
FIG. 9 is an operation timing chart, FIG. 9 is a block diagram showing a third embodiment of the present invention, FIG. 10 is an operation timing chart of FIG. 9, and FIG. 11 is a block diagram showing a fourth embodiment of the present invention. FIG. 12 is an operation timing chart of FIG. 11, FIG.
FIG. 14 is a block diagram showing fifth and sixth embodiments of the present invention, FIG. 15 is an operation timing chart of FIG. 14, and FIG.
FIG. 17 is a block diagram showing a seventh embodiment of the present invention, FIG. 17 is a block diagram showing an eighth embodiment of the present invention, FIG. 18 is an operation timing chart of FIG. 17, and FIG. A block diagram showing a ninth embodiment, and FIG. 20 is a float chart for explaining the operation of FIG. 4 ... energization pulse generation circuit, 5 ... rest period generation circuit,
10 ... energization ROM, 11 ... energization pulse counter, 12 ... rest period ROM, 13 ... rest period counter, 14 ... SR latch.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuru Kudo 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside the Home Appliance Research Laboratory, Hitachi, Ltd. (56) Reference JP-A-61-54959 (JP, A) JP JP-A-58-151267 (JP, A) JP-A-63-242658 (JP, A) JP-A-63-5967 (JP, A) JP-A-61-263772 (JP, A)

Claims (9)

[Claims] 1. A drive circuit for a thermal head of a video printer, which prints input data using the thermal head,
The strobe pulse generating circuit of the thermal head is composed of an energizing pulse generating circuit for controlling the energizing on time and a rest period generating circuit for controlling the energizing off time connected to the energizing pulse generating circuit. A drive circuit for a thermal head, characterized in that a period is set for each gradation so that the energization time to the thermal head can be shortened. 2. The thermal head drive circuit according to claim 1, wherein the energizing pulse generating circuit is energized RO.
A drive circuit for a thermal head, characterized by comprising an M and an energizing pulse counter connected to this energizing ROM, and said rest period generating circuit comprising an rest period ROM and a rest period counter. 3. The thermal head drive circuit according to claim 1, wherein a rest period generation circuit in the strobe pulse generation circuit includes a step including a turn-on period and a turn-off period for one gradation. Gradation width RO that stores adjustment width data
A drive circuit for a thermal head, comprising M and a gradation width counter connected to the gradation width ROM. 4. The thermal head drive circuit according to claim 1, wherein the strobe pulse generating circuit stores a change point RO storing a strobe on / off change point.
M, an address counter connected to this change point ROM,
A drive circuit for a thermal head, comprising: a change-point information connected to the change-point ROM, and means for converting the change-on information into energization on / off information, and a rest period is provided during a heating period. 5. The thermal head drive circuit according to claim 1, wherein the energizing pulse generating circuit outputs an energizing pulse having an initial gradation, which is longer than other gradations, to the energizing pulse generating circuit. The drive circuit of the thermal head, which is characterized by adding the. 6. A drive circuit for a thermal head according to claim 1, wherein the temperature detection means is attached to the thermal head, and the temperature detection means is connected to the rest period generation circuit or energization pulse generation circuit. And a temperature data conversion means for controlling the energization time or the rest period according to the temperature of the thermal head to keep the temperature of the heating element constant. 7. The drive circuit for a thermal head according to claim 1, wherein the strobe pulse generating circuit comprises the energizing ROM, an energizing pulse counter connected to the energizing ROM, and the energizing pulse counter. A driving circuit for a thermal head, comprising a constant pulse generating circuit for generating a start pulse for each gradation by a latch means connected to the constant pulse generating circuit. 8. The drive circuit for a thermal head according to claim 7, wherein the constant pulse generation circuit comprises a data transfer counter for counting ON / OFF data of the thermal head. Thermal head drive circuit. 9. The drive circuit for a thermal head according to claim 1, wherein the strobe pulse generating circuit includes a conduction width ROM, a conduction pulse number counter connected to the conduction width ROM, and a conduction ROM. An energization pulse counter connected to the energization ROM, a rest period ROM, a rest period counter connected to the rest period ROM, latch means connected to the energization pulse number counter, and the energization pulse number counter. A latch means connected to the energization pulse counter and the rest period counter, and a gate circuit connected to the two latch means, and a strobe pulse for one gradation is constituted by a plurality of energization on / off signals. Thermal head drive circuit characterized by.