High-speed thermal printer driver chip and thermal printer

Abstract

The present invention provides a high-speed thermal printer driver chip, comprising: a multi-stage shift register that shifts the signal at the SI terminal to the SO terminal for output; a data latch that latches serially received data after LATX for output; an output driver transistor that controls an external heating resistor to leave a trace on thermal printing paper; an output enable control that controls whether the output driver transistor performs effective output; a buffer, one of which is used by each multi-stage shift register to enhance signal driving capability; and a group unit comprising a multi-stage shift register and a corresponding buffer. By grouping the buffers, the high-speed thermal printer driver chip reduces the total buffer delay and increases the clock speed, thereby accelerating printing.

Description

Technical Field

[0001] The invention belongs to the field of printer driving, and in particular relates to a high-speed thermal printer driving chip and a thermal printer. Background Art

[0002] The basic principle of thermal printing technology is to convert the data received by the printer into a dot matrix signal that controls the heating of the thermal unit, thereby developing the thermal coating on the thermal paper. Thermal printers have been widely used in POS terminals, banking systems, medical equipment, and other fields. Thermal printers can only use dedicated thermal paper. As the market expands, the demand for thermal printing speed is also increasing. On the one hand, a higher number of dots produces more detailed print results. On the other hand, a higher number of dots requires more data to be transmitted, resulting in slower printing speeds. At the same time, customers want to increase printing speed while maintaining good print clarity.

[0003] To increase printing speed with current thermal printer chips, two key factors are needed: 1. Increase data transmission speed, essentially the clock speed of the internal shift register; and 2. Increase the heating time of the print head resistor. For multi-point shift registers, using a conventional clock circuit, the clock speed cannot be too high. Testing has found that when the clock speed exceeds 10M, data cannot be accurately transmitted, resulting in abnormal data and undesirable printing results. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a high-speed thermal printer driver chip and a thermal printer, which can improve the printing speed of the thermal printer.

[0005] To achieve the above object, the present invention adopts the following scheme:

[0006] The present invention provides a high-speed thermal printer driver chip, comprising:

[0007] The multi-stage shift register includes several CELLs (shift register units) that shift the signal at the SI terminal (data input) and output it to the SO terminal (data output);

[0008] The data latch latches the serially received data into the latch after LATX (latch signal) for output;

[0009] Output driver tube, used to control the external heating resistor to leave marks on thermal printing paper;

[0010] Output enable control, used to control whether the output driver tube performs effective output;

[0011] Buffer, each of the CELLs uses one of the buffers to enhance signal driving capability;

[0012] The small group unit includes a CELL and a corresponding buffer, wherein the number of the small group units is X, and the X small group units are divided into A large groups of equal number, and each large group contains B small group units, wherein the small group units in each large group are connected in series, and the large groups are connected in parallel, so that the input of the first buffer in each large group is directly derived from the clock input signal, thereby shortening the total delay of the X buffers to the total delay of the B buffers, X=A×B, A and B are both positive integers, and A≥2.

[0013] In some embodiments, the present invention further includes the following technical features:

[0014] The output drive tube is manufactured by adopting a double-diffused metal oxide process, so that the operating voltage can be increased and the heating time of the heating resistor can be shortened.

[0015] Each of the CELLs includes a plurality of shift registers connected in series.

[0016] The output enable control includes control terminals STBL (output enable low) and STBH (output enable high). When STBL is at a low level or STBH is at a high level, the output driver tube is enabled. When STBL is at a high level and STBH is at a low level, the output driver tube is disabled.

[0017] The high-speed thermal printer driver chip has N outputs, DO1 to DOn.

[0018] The maximum withstand voltage of the output drive tube is 30V, the resistance when not conducting is greater than 10M ohms, and the resistance when conducting is less than 15 ohms.

[0019] In the multi-stage shift register, data is input from the SI terminal, and a clock signal is input from the clock input CLK terminal, wherein data is read in at the rising edge of the clock input CLK. There are N shift registers in a high-speed thermal printer driver chip, so the clock input is N CLK signals, and N clocks are input from the SI terminal at the same time, and then the data is output through the SO terminal.

[0020] The present invention also provides a thermal printer, which uses the high-speed thermal printer driver chip as a driver chip.

[0021] In some embodiments, there are at least two driver chips, and the driver chips are connected in series.

[0022] The beneficial effects of the present invention are:

[0023] The present invention provides a high-speed thermal printer driver chip, which includes a new shift register clock structure. By grouping, the total buffer delay is shortened, the clock speed is increased, and the printing speed is accelerated. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of a thermal printer chip in the prior art;

[0025] Figure 2 This is a pinout diagram of a thermal print head driver chip in the prior art;

[0026] Figure 3 This is a diagram of the clock driver structure of a thermal printer chip in the prior art;

[0027] Figure 4 This is the internal structure diagram of CELL;

[0028] Figure 5 This is a clock drive structure diagram of a high-speed thermal print head driver chip in an embodiment of the present invention;

[0029] Figure 6 This is a typical application circuit diagram of a high-speed thermal print head driver chip in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] To make the technical solutions and advantages of the present invention more clear, the following fully describes the technical solutions of the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0031] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0032] The present invention proposes a head driver chip for a thermal printer. A shift register and latch are internally provided. Data transmitted from the main control is received via the DI data input, and the parallel output drives the heating resistor. The heating resistor is controlled to be conductive by controlling whether each output tube is conductive. If conductive, the resistor generates heat, forming a black dot on the thermal paper. In conjunction with a stepper motor, the thermal paper printing effect can be achieved, producing the desired text and graphics. The present invention also proposes a novel chip clock structure that enables the chip to accept higher clock frequencies.

[0033] The chip receives data and clock signals through its data input SI and clock input CLK. It can also shift the SI signal and output it to the data output SO, allowing multiple chips to be connected in series. When connected in series, more dots can be output per row, resulting in a higher pixel density. The chip also features high voltage resistance (up to 30V) and high clock speed (maximum CLK frequency of 25MHz).

[0034] The circuit structure principle of ordinary thermal printer chip is as shown in the attached Figure 1 As shown, Figure 1 The chip has 152 pins. DO1 to DO144 are data output pins that drive the heating resistors. The internal structure consists of 144 shift registers and 144 latches. There are also 144 AND gates and 144 output MOS transistors. Data input SI and clock input CLK send data to the master controller, with N shift registers in between. After N data transfers are completed, the data is latched into the N latch registers during the low period of the latch signal LATX. Output enable high (STBH) and output enable low (STBL) are output enable pins. When STBH is high or STBL is low, the output is valid. At this time, if the latched data is 1, the output transistor turns on, allowing the heating resistor to operate. If the data is 0, the output transistor turns off. This achieves the desired printing effect.

[0035] Figure 2 The pinout is as follows: the top row is DO1~DO144, the leftmost pad is SI, the following four pads are SI, STBH, STBL and VDD, the middle is 17 GND, the upper right is SO, and the following four pads are VDD, CLK, LATX and SO.

[0036] The reason why the clock speed of ordinary thermal printer chips cannot be too high is that for a long string of shift registers, the data signal needs to be from left to right, and to prevent the clock signal from being ahead of the data signal, the clock signal needs to be in the opposite direction of the data signal, that is, from right to left. At the same time, the signal cannot be driven too long, otherwise the signal will be deformed if it is too long, causing malfunction. Therefore, it is necessary to add a BUF at a certain distance to increase the signal strength of CLK. Generally, one level of BUF is required for every 8 shift registers, and 18 are required if there are 144 shift registers. Each level of BUF will have a little delay. After 18 BUFs, the total delay is longer. This total delay cannot be less than the period of the clock signal, so the frequency of the clock signal cannot be very high. This structure is like Figure 3 As shown, the clock line goes from right to left, and every 8 shift registers form a CELL. The CLK of each CELL uses a BUF to enhance the driving ability of the signal. Each cell is composed of 8 shift registers, such as Figure 4 shown.

[0037] The present invention provides a high-speed thermal printer driver chip, comprising:

[0038] A multi-stage shift register, including several CELLs, shifts the signal at the SI terminal (data input) and outputs it to the SO terminal (data output);

[0039] The data latch latches the serially received data into the latch after LATX (latch signal) for output;

[0040] Output driver tube, used to control the external heating resistor to leave marks on thermal printing paper;

[0041] Output enable control, used to control whether the output driver tube performs effective output;

[0042] Buffer, each of the CELLs uses one of the buffers to enhance signal driving capability;

[0043] The small group unit includes a CELL and a corresponding buffer, wherein the number of the small group units is X, and the X small group units are divided into A large groups of equal number, and each large group contains B small group units, wherein the small group units in each large group are connected in series, and the large groups are connected in parallel, so that the input of the first buffer in each large group is directly derived from the clock input signal, thereby shortening the total delay of the X buffers to the total delay of the B buffers, X=A×B, A and B are both positive integers, and A≥2.

[0044] In some embodiments, the present invention further includes the following technical features:

[0045] The output drive tube is manufactured by adopting a double-diffused metal oxide process, so that the operating voltage can be increased and the heating time of the heating resistor can be shortened.

[0046] Each of the CELLs includes a plurality of shift registers connected in series.

[0047] The output enable control includes control terminals STBL (output enable low) and STBH (output enable high). When STBL is at a low level or STBH is at a high level, the output driver tube is enabled. When STBL is at a high level and STBH is at a low level, the output driver tube is disabled.

[0048] The high-speed thermal printer driver chip has N outputs, DO1 to DOn.

[0049] The maximum withstand voltage of the output pin is 30V. The resistance when not conducting is greater than 10M, and the resistance when conducting is about 10 ohms.

[0050] In the multi-stage shift register, data is input from the SI terminal, and a clock signal is input from the clock input CLK terminal, wherein data is read in at the rising edge of the clock input CLK. There are N shift registers in a high-speed thermal printer driver chip, so the clock input is N CLK signals, and N data is input from the SI terminal at the same time, and then the data is output through the SO terminal.

[0051] The present invention also provides a thermal printer, which uses the high-speed thermal printer driver chip as a driver chip.

[0052] The technical solution of the present invention is described below with reference to a specific embodiment. In this embodiment, X is 18, A is 3, and B is 6.

[0053] Figure 5 To adjust the clock signal structure, the 18 BUFs and cells were divided into three groups, each with 6 cells. Each group was connected in series and the other groups were connected in parallel. Therefore, the input of the first BUF in the first group was from the CLK signal, and the first BUFs in the second and third groups were also from the CLK signal. In this way, the maximum delay of the CLK signal was reduced from the original delay of 18 BUFs to the delay of 6 BUFs. This greatly reduced the longest signal delay time and the total delay of CLK from the last stage to the first stage, which greatly improved the clock signal of the chip.

[0054] After testing and simulation, the delay of each BUF is 4ns. The maximum delay is about 72ns when not grouped, which can be reduced to 24ns after grouping. The maximum frequency can be increased from 10MHz to 25MHz.

[0055] Figure 6 This is a typical application circuit for a thermal print head driver chip. IC1 through ICn are the driver chips for the thermal print head. They can be connected in cascades. In this cascade, IC1's SI pin connects to an external input signal, IC1's SO pin connects to IC2's SI pin, IC2's SO pin connects to IC3's SI pin, and so on. The other CLK, LATX, STBH, and STBL signals are all connected together, connected to the external input signal. The output is connected to a heating resistor.

[0056] The present invention has the advantage of improving the clock speed by proposing a new shift register clock structure, increasing the clock speed from the previous 10 MHz to a maximum of 25 MHz, an increase of approximately 150%. Simultaneously, the output driver transistor is upgraded from a conventional complementary metal oxide semiconductor (CMOS) process to a double diffused metal oxide (DMOS) process, raising the withstand voltage from 8V to 30V. This also increases the operating voltage from 8V to 24V, shortening the resistor heating time during printing by 66%. These two advantages work together to increase the printing speed of the finished thermal printer.

[0057] In this specification, reference to terms such as "one embodiment" and "example" means that a specific feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the exemplary description of the above terms does not necessarily mean that they are appropriately combined in the corresponding embodiment or example.

[0058] It must be pointed out that the description of the above embodiments is not intended to be limiting but only to help understand the core idea of ​​the present invention. For ordinary technicians in this technical field, any improvements to the present invention and alternatives equivalent to this product, without departing from the principles of the present invention, also fall within the scope of protection of the claims of the present invention.

Claims

1. A high-speed thermal printer driver chip, characterized in that: include: A multi-stage shift register, comprising a plurality of cells, shifts the signal at the SI terminal to the SO terminal for output, wherein each cell comprises a plurality of shift registers connected in series; Data latch, latches the serially received data into the latch after LATX for output; An output driver tube is used to control an external heating resistor to leave a mark on the thermal printing paper. The output driver tube is made using a double-diffused metal oxide process, which increases the operating voltage and shortens the heating time of the heating resistor. Output enable control, used to control whether the output driver tube performs effective output; Buffer, each of the CELLs uses one of the buffers to enhance signal driving capability; The small group unit includes a CELL and a corresponding buffer, wherein the number of the small group units is X, and the X small group units are divided into A large groups of equal number, and each large group contains B small group units, wherein the small group units in each large group are connected in series, and the large groups are connected in parallel, so that the input of the first buffer in each large group is directly derived from the clock input signal, thereby shortening the total delay of the X buffers to the total delay of the B buffers, X=A×B, A and B are both positive integers, and A≥2.

2. The high-speed thermal printer driver chip according to claim 1, characterized in that: The output enable control includes control terminals of STBL and STBH. When STBL is at a low level or STBH is at a high level, the output drive tube is enabled. When STBL is at a high level and STBH is at a low level, the output drive tube is disabled.

3. The high-speed thermal printer driver chip according to claim 1, characterized in that: The high-speed thermal printer driver chip has N outputs, DO1 to DOn.

4. The high-speed thermal printer driver chip according to claim 3, characterized in that: The maximum withstand voltage of the output pin of the output driving tube is 30V, the resistance when not conducting is greater than 10M ohms, and the resistance when conducting is less than 15 ohms.

5. The high-speed thermal printer driver chip according to claim 3, characterized in that: In the multi-stage shift register, data is input from the SI terminal, and a clock signal is input from the clock input CLK terminal, wherein data is read in at the rising edge of the clock input CLK. There are N shift registers in a high-speed thermal printer driver chip, so N clocks are input as the clock input, and N data are input from the SI terminal at the same time, and then the data is output through the SO terminal.

6. A thermal printer, characterized in that: A high-speed thermal printer driver chip according to any one of claims 1 to 5 is used as the driver chip.

7. The thermal printer according to claim 6, wherein: There are at least two driving chips, and the driving chips are connected in series.

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