CN106652161B

CN106652161B - Paper money recognition device and recognition method based on thermal printing head

Info

Publication number: CN106652161B
Application number: CN201710025049.6A
Authority: CN
Inventors: 赵哲; 远藤孝文
Original assignee: Shandong Hualing Electronics Co Ltd
Current assignee: Shandong Hualing Electronics Co Ltd
Priority date: 2017-01-13
Filing date: 2017-01-13
Publication date: 2022-06-07
Anticipated expiration: 2037-01-13
Also published as: JP7096655B2; JP2018113016A; CN106652161A

Abstract

The invention provides a paper money recognition device and a recognition method based on a thermal printing head, wherein the paper money recognition device comprises a base station, a conveying device and the thermal printing head are arranged on the base station, the resistance value of a heating resistor of the thermal printing head can reversibly change along with the temperature change caused by joule heat, and the thermal printing head is also connected with a control processing part; in the process of identifying the paper money, the potential between the heating resistor body and the reference resistor is detected, the potential is subjected to analog-to-digital conversion to form a digital signal, and the authenticity of the paper money or whether the paper money is repaired by an adhesive tape is judged according to the digital signal. The paper currency recognition device and the recognition method based on the thermal printing head utilize the thermal printing head with variable resistance value to recognize the paper currency, and simplify the structure of the recognition device on the premise of ensuring the recognition precision.

Description

Paper money recognition device and recognition method based on thermal printing head

Technical Field

The invention relates to the field of paper money identification, in particular to a paper money identification device and method based on a thermal printing head.

Background

In the using process of paper money, valuable securities or checks, the phenomena of unfilled corners, tearing and the like often occur, and people often adopt an adhesive tape to bond and repair the defected or torn paper money and the like so as to be used continuously.

For the problem of identifying the banknotes repaired by the adhesive tape, some solutions have been disclosed in the prior art, for example, chinese patent application CN101075363A discloses a banknote handling device, and the specific solution for detecting whether the banknotes are repaired by the adhesive tape is as follows: when the adhesive tape is adhered to the paper money, the rising amount of the inspection roller exceeds the reference amount at the position where the adhesive tape is adhered, so that the inspection roller reaches the displacement sensor, the displacement sensor detects the inspection roller, and information indicating the detection of the inspection roller is transmitted to the discriminating portion. However, the structure of the above-described banknote handling apparatus is excessively complicated.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a paper money recognition device and a recognition method based on a thermal printing head, which are simple in structure.

In order to achieve the above object, one aspect of the present invention provides a thermal print head-based paper money discriminating apparatus, including a base, a thermal print head disposed on an upper surface of the base, a resistance value of a heating resistor of the thermal print head being reversibly changeable with a temperature change caused by joule heat, and a conveying device disposed on the base for conveying paper money line by line through the heating resistor of the thermal print head in a conveying direction; the heating substrate of the thermal printing head is provided with a pressing part fixed on the base platform, and the thermal printing head is also connected with the control processing part.

Preferably, the control circuit of the banknote recognition apparatus is as follows: the printing power supply supplies power to the N heating resistors respectively, each heating resistor is grounded through a first driving circuit part of the driving IC, the first driving circuit part comprises N switches, each heating resistor is also led out of a lead wire and grounded through a second driving circuit part of the driving IC and a reference resistor, and the second driving circuit part also comprises N switches; the control circuit also comprises analog-to-digital converters, the number of the analog-to-digital converters corresponds to the number of the reference resistors, wires are respectively led out from the positions between the switches and the reference resistors of the second driving circuit part and correspondingly connected to one input end of the analog-to-digital converters, the other input end of the analog-to-digital converters is connected to the anode of a reference voltage source, and the cathode of the reference voltage source is grounded; the first driving loop part and the second driving loop part are controlled by the control processing part, and the output end of the analog-to-digital converter is connected to the control processing part.

The paper currency recognition device based on the thermal printing head has the advantages that the structure is simple, the thermal printing head with the variable resistance value is used for recognizing paper currency, and the structure of the recognition device is simplified on the premise of ensuring the recognition accuracy.

In another aspect of the present invention, a banknote recognition method based on the above banknote recognition apparatus is provided, the method including the following steps: step 1: conveying the Mth row of the paper money to a heating resistor of the thermal printing head through a conveying device; step 2: turning on the switches of the first drive circuit unit; and step 3: after a preset time period, enabling each switch of the first driving circuit part to be in a cut-off state; and 4, step 4: according to the number of the reference resistors, all switches of the second driving circuit part are simultaneously or sequentially in a conducting state, and the electric potential between the heating resistor body and the reference resistors is collected and converted into a digital signal of 8 bits through an analog-to-digital converter; and 5: storing the converted digital signal; step 6: repeating the steps 1-5, reading information from the (M +1) th row to the (M + g) th row of the paper money, and sequentially storing digital signals corresponding to the read information; and 7: judging whether digital signals of a continuous area are 200-255 digit in the stored digital signals; and 8: if yes, judging the paper money is repaired by the adhesive tape; and step 9: if not, selecting an anti-counterfeiting area in the stored digital signal array, and performing decrement processing on the digital signal in the area; step 10: carrying out binarization processing on the reduced digital signal; step 11: comparing the data after binarization processing with data after binarization processing formed by a true currency anti-counterfeiting area; step 12: if the two are consistent, the paper money is judged to be genuine.

Preferably, the following steps are further included between the step 4 and the step 5: step 41: comparing the converted digital signal with a digital threshold value through a digital comparison loop, and judging whether the converted digital signal is smaller than the digital threshold value; step 42: if all the converted digital signals are less than the digital threshold value, repeating the steps 2 to 41; step 43: and when one of the converted digital signals is equal to or greater than the digital threshold value, enabling the switch of the first driving circuit part to be in a cut-off state.

Drawings

Fig. 1 is a schematic plan view showing a banknote recognition apparatus according to the present invention.

Fig. 2 is a schematic cross-sectional view showing a banknote recognition apparatus according to the present invention.

Fig. 3 is a cross-sectional view of the periphery of a heating resistor of a thermal head according to the present invention.

Fig. 4 is a graph showing a temperature coefficient change of the heating resistor according to the present invention.

Fig. 5 is a graph showing the temperature-dependent change in the resistance value of the heating resistor according to the present invention.

Fig. 6 is a control circuit diagram of the banknote recognition apparatus according to the present invention.

Fig. 7 shows an action timing diagram of fig. 6.

Fig. 8 shows another action timing diagram of fig. 6.

Fig. 9 shows an operation timing chart of the increase in the heating rate of the bill identifying device according to the present invention.

FIG. 10 shows an illustrative graph of the digital signals output from different transmission areas of the note after passing through an analog-to-digital converter.

Fig. 11 shows a data processing diagram of the security area of a banknote.

FIG. 12 shows a schematic view of a taped banknote.

FIG. 13 is an explanatory diagram showing digital signals output from the paper money with the repair tape after passing through the A/D converter.

FIG. 14 is an explanatory diagram showing an output curve of a digital signal outputted after the tape repairing area of the bill passes through the A/D converter.

Reference numerals: 1-paper money, 1 a-transmission region, 1 b-breakage region, 2 a-paper feed side glue roller, 2 b-paper discharge side glue roller, 2 c-leading-in glue roller, 2 d-leading-out glue roller, 3-thermal print head, 3 a-heat-generating substrate, 3 b-signal processing substrate, 3 c-drive IC, 3 d-resin glue, 3 e-heat-radiating plate, 4-pressing part, 5 a-paper feed side storage box, 5 b-paper discharge side storage box, 5 c-fixing part, 5 d-base, 6-insulating substrate, 7-ground coat layer, 8-heat-generating resistor layer, 8 a-heat-generating resistor, 9 a-common electrode, 9 b-individual electrode, 10-protective layer, 11-reference resistor part, 12-analog-digital converter, 13-a first driving circuit part, 14-a reference voltage source, 15-a control processing part, 16-a repairing adhesive tape and 17-a second driving circuit part.

Detailed Description

The following further describes embodiments of the present invention with reference to the drawings.

The invention relates to a paper money identification device based on a thermal printing head, which is mainly used for judging the authenticity of reading media such as paper money, valuable securities or checks, or judging the existence of adhesive tape repairing on the reading media such as the paper money, the valuable securities or the checks.

As shown in fig. 1 and 2, the paper money discriminating device based on thermal printer according to the present invention comprises a metal base 5d, a paper feeding-side storage box 5a and a paper discharging-side storage box 5b are respectively provided at both ends of the upper surface of the base 5d, a thermal printer 3 is provided at the middle of the upper surface of the base 5d, a guiding rubber roller 2c is provided at the paper feeding-side storage box 5a, a discharging rubber roller 2d is provided at the paper discharging-side storage box 5b, a paper feeding-side rubber roller 2a is provided at the base 5d between the paper feeding-side storage box 5a and the thermal printer 3, a paper discharging-side rubber roller 2b is provided at the base 5d between the paper discharging-side storage box 5b and the thermal printer 3, and the paper feeding-side rubber roller 2a, the paper discharging-side rubber roller 2b, the guiding rubber roller 2c, and the discharging rubber roller conveying device 2d are respectively fixed to the base 5d via a fixing member 5c, and the paper feeding side rubber roller 2a, the paper discharging side rubber roller 2b, the leading-in rubber roller 2c and the leading-out rubber roller 2d are all driven by a motor (not shown in the figure). The thermal head 3 includes a heat radiation plate 3e, a heat generation substrate 3a and a signal processing substrate 3b each formed of a linear heat generation resistor perpendicular to the conveyance direction are arranged on the heat radiation plate 3e, a driver IC3c is arranged on the heat generation substrate 3a and the signal processing substrate 3b, and the driver IC3c is encapsulated and protected by a resin paste 3 d. The heating substrate 3a is provided with a pressing part 4, the pressing part 4 is composed of a rubber roller or an arc elastic part, the pressing part 4 is also fixed on the base platform 5d, and when the paper money 1 passes through the conveying channel, the pressing part 4 presses the paper money 1 on the heating substrate 3a, so that a good contact effect is achieved. The thermal head 3 is also connected to a control processing section 15 (not shown in the figure).

The resistance value of the heating resistor of the thermal print head 3 according to the present invention can be reversibly changed with the temperature change caused by joule heat, specifically, the cross-sectional view of the periphery of the heating resistor of the thermal print head 3 is shown in fig. 3, and the specific manufacturing process flow is as follows.

The method comprises the following steps: on an insulating substrate 6 such as ceramics, an amorphous glass is printed over the entire surface or a part thereof, and then sintered at 1200 to 1300 ℃ to form a ground coat layer 7.

Step two: a heating resistor layer 8 of a chromium-aluminum (Cr/Al) alloy having a film thickness of 50 to 300nm is formed on the surface of the ground coat layer 7 of the insulating substrate 6 by thin film sputtering.

Step three: the heating resistor layer 8 is subjected to heat treatment at 300 to 400 ℃ for about 10 to 20 minutes.

Step four: an aluminum conductor electrode layer is formed on the insulating substrate 6, the ground coat layer 7, and the heat-generating resistor layer 8 by thin film sputtering.

Step five: through a patterning etching process, a part of the aluminum conductor electrode layer on the heating resistor layer 8 is etched and removed to form a common electrode 9a and an individual electrode 9b, the heating resistor layer 8 is exposed, the exposed heating resistor layer 8 is etched to form an independent heating resistor 8a, one end of the heating resistor 8a is connected with the common electrode 9a, and the other end is connected with the individual electrode 9 b.

Step six: a protective layer 10 is formed on the heating resistor 8a, the common electrode 9a, and the individual electrode 9b by sputtering or CVD (chemical vapor deposition).

The heating resistor 8a is electrically connected to the driver IC3c of the thermal head 3 by gold wire bonding or flip chip bonding through the lead metal pattern of the individual electrode 9 b.

The heat treatment process for the heating resistor layer 8 can be divided into a first heat treatment process for adjusting the temperature coefficient of the heating resistor and a second heat treatment process for adjusting the resistance value of the heating resistor. As shown in fig. 4, the temperature coefficient change of the heating resistor according to the present invention is such that the Temperature Coefficient (TCR) of the heating resistor 8a is relatively small after the non-heat treatment or the low-temperature heat treatment at about 200 ℃, and the heating resistor 8a exhibits a relatively large negative temperature coefficient after the high-temperature heat treatment at about 300 ℃ to 400 ℃. Further, the temperature coefficient of the heating resistor 8a tends to increase negatively by the heat treatment at 300 ℃.

Fig. 5 shows a graph of the resistance of the heating resistor 8a according to the present invention, in which the resistance of the heating resistor 8a is relatively low after the heat treatment or the heat treatment at a low temperature of about 200 ℃, and the resistance of the heating resistor 8a is relatively high after the heat treatment at a high temperature of about 300 ℃ to 400 ℃, and in addition, the resistance of the heating resistor 8a is increased by the heat treatment at 300 ℃ for a plurality of times.

After the heating resistor 8a is subjected to the heat treatment at the temperature of 300-400 ℃, a relatively large Temperature Coefficient (TCR) can be formed, and when the heating temperature of the heating resistor 8a rises, the resistance of the heating resistor 8a tends to rise, so that the banknote 1 can be identified by detecting the change of the resistance of the heating resistor 8a in real time.

Fig. 6 is a control circuit diagram of the banknote recognition apparatus according to the present invention. The printing power supply VTH supplies power to each of the heating resistors 8a, assuming that the number of the heating resistors 8a is N (N is a positive integer), each of the heating resistors 8a is correspondingly connected to the first driving circuit section 13 of the driving IC3c, the first driving circuit section 13 includes N NMOS tubes, each of the heating resistors 8a is connected to the drain of a corresponding NMOS tube, the source thereof is connected to the ground GND, the drain of each NMOS tube is further connected to the second driving circuit section 17 by a lead wire, the second driving circuit section 17 also includes N NMOS tubes, the drain of each NMOS tube of the first driving circuit section 13 is further connected to the drain of each NMOS tube of the second driving circuit section 17 by a lead wire, the source of each NMOS tube of the second driving circuit section 17 is connected to the reference resistor section 11, the reference resistor section 11 may include one reference resistor or N reference resistors, in this embodiment, it is assumed that the reference resistance portion 11 includes N reference resistances, and therefore the sources of the NMOS transistors of the second driving circuit portion 17 are also grounded to GND through the reference resistances. The control circuit further comprises analog-to-digital converters 12, the number of the analog-to-digital converters 12 corresponds to the number of the reference resistors, lead wires are further led out from the source electrodes of the NMOS transistors of the second driving circuit portion 17 and correspondingly connected to one input end of each analog-to-digital converter 12, the other input end of each analog-to-digital converter 12 is connected to the anode of a reference voltage source 14, and the cathode of the reference voltage source 14 is grounded GND. The gate of each NMOS transistor and the output of each analog-to-digital converter 12 are connected to a control processing unit 15, the control processing unit 15 is configured to control on/off of the first driving circuit unit 13 and the second driving circuit unit 17, and process the signal from each analog-to-digital converter 12, where the processing includes comparing the digital signal from the analog-to-digital converter 12 with a digital threshold; and storing, reducing, binarizing, comparing with reference information and the like on the digital signal. The control processing unit 15 may use a general-purpose FPGA (Field-Programmable Gate Array) chip, and may use an FPGA of EP3C25F324C8N, for example, to implement the above functions.

Fig. 7 shows an action timing diagram of fig. 6. As shown in fig. 6 and 7, the control processing unit 15 may be provided with N and gates, output terminals of the and gates are respectively connected to gates of NMOS transistors of the first driving circuit unit 13, input signals of each and gate include DATA signals (DATA 1-N), STOP indication signals (STOP 1-N), and an alternate pulse Signal (SCLK), and when each signal is at a high level, each NMOS transistor of the first driving circuit unit 13 is in an Open (ON) state.

The invention relates to a paper money identification method based on a thermal printing head, which comprises the following steps:

step 1: the mth (M is a positive integer) line of the bill 1 is conveyed to the heating resistor 8a of the thermal head 3 via the conveyance device.

Step 2: each NMOS transistor of the first drive circuit unit 13 is turned ON (ON).

When the alternating pulse signal SCLK is in the high level section and the data signal DATAn and the stop instruction signal STOPn are also in the high level, the NMOS transistors of the first drive circuit unit 13 are in the Open (ON) state, and at this time, the printing power supply VTH and the ground GND are turned ON by the heat resistor 8a, and the heat resistor 8a generates heat and the temperature rises.

And step 3: after a predetermined period of time, the NMOS transistors of the first driving circuit unit 13 are turned OFF (OFF). When the alternating pulse signal SCLK is in the low level section, each NMOS transistor of the first driving circuit portion 13 is in an OFF state.

And 4, step 4: each NMOS transistor of the second drive circuit unit 17 is turned ON, and the analog-to-digital converter 12 collects and converts the potential between the heating resistor 8a and the reference resistor into an 8bit (256-level) digital signal.

When the reference resistance portion 11 includes a reference resistance, a time-sharing sampling control manner is adopted, that is, the control processing portion 15 controls each NMOS transistor of the second driving circuit portion 17 to be in an Open (ON) state in sequence, and further the analog-to-digital converter 12 collects and converts the potential between the heating resistor 8a and the reference resistance into an 8-bit (256-level) digital signal.

And 5: and storing the converted digital signal.

In order to improve the accuracy of identification, the following steps can be further included between step 4 and step 5:

step 41: and comparing the converted digital signal with a digital threshold value through a digital comparison loop, and judging whether the converted digital signal is smaller than the digital threshold value.

Step 42: if all of the converted digital signals are less than the digital threshold, steps 2 to 41 are repeated.

Step 43: when one of the converted digital signals is equal to or greater than the digital threshold, each NMOS transistor of the first drive circuit unit 13 is turned OFF (OFF), and the stop instruction signal STOPn is at a low level.

When the digital comparison circuit compares the converted digital signal with the digital threshold, the comparison process may be performed in two ways, and the first way compares the digital signal obtained by converting the potential between the heating resistor 8a and the reference resistor with the digital threshold every time, as shown in fig. 7. In the second embodiment, as shown in fig. 8, digital signals obtained by converting the potential between the heating resistor 8a and the reference resistor are accumulated one at a time, and the accumulated value is compared with a digital threshold value.

The thermal print head-based paper money discriminating apparatus according to the present invention only needs to detect a change in the resistance value of the heating resistor 8a when reading information from the paper money 1, and therefore the data signal DATAn is normally set to a high level. In order to increase the heating speed, as shown in fig. 9, the duty ratio of the alternating pulse signal SCLK may be adjusted, because the low level interval of the alternating pulse signal SCLK is only used for the purpose of sampling the potential between the heating resistor 8a and the reference resistor, and thus the heating speed of the heating resistor 8a may be effectively increased.

Step 6: and repeating the steps 1 to 5, reading the information from the (M +1) th row to the (M + g) th row of the paper money 1, and sequentially storing the digital signals corresponding to the read information.

Since the unevenness (concavity and convexity) of the different transmission regions 1a of the bill 1 varies, the temperature of the heating resistor 8a in contact with the bill 1 varies due to the concavity and convexity, and the resistance value of the heating resistor 8a varies. The banknote 1 has various printed patterns and characters, and the printed patterns, film thickness, unevenness, and other reactions to heat in different regions are different, so that different regions of the banknote 1 can be detected by different difference changes, and authentication or repair can be identified.

As shown in fig. 10, when the bill 1 is in contact with the heating resistor 8a, the digital signal into which the potential between the heating resistor 8a in contact with the different-color transmissive region 1a and the reference resistor is converted differs, and for example, the digital signal into which the potential between the heating resistor 8a in contact with the white transmissive region and the reference resistor is converted is about 50digit or less, and the digital signal into which the potential between the heating resistor 8a in contact with the black transmissive region of the bill 1 and the reference resistor is converted is about 80digit or more.

And 7: and judging whether the digital signals of the continuous area are 200-255 digit in the stored digital signals.

As shown in fig. 12 and 13, the taped banknote 1 is usually repaired in the broken region 1b with a repair tape 16. When the heat generating resistor 8a generates heat, if the banknote 1 has a tape repair region, the local thickness and surface undulations (irregularities) of the repair region change, and such irregularities cause a change in the temperature of the heat generating resistor 8a in contact with the banknote 1, thereby causing a change in the resistance. The potential between the heating resistor 8a and the reference resistor, which are in contact with the tape repair area of the bill 1, is converted into a digital signal of 200 to 255digit (denoted as OV: Over in FIG. 13). As shown in fig. 14, after a certain time of temperature accumulation, the potential between the heating resistor 8a in contact with the tape repairing region of the bill 1 and the reference resistor is converted into a digital signal of 200digit or more.

And 8: if yes, the banknote 1 is judged to be a banknote repaired by the adhesive tape.

And step 9: if not, selecting an anti-counterfeiting area in the stored digital signal array, and performing decrement processing on the digital signal in the area. As shown in fig. 11 (a) and 11 (b), in the present embodiment, 50digit is used as a decrement criterion.

Step 10: and carrying out binarization processing on the reduced digital signal. As shown in fig. 11 (c), in the present embodiment, 30digit is used as the threshold value for binarization.

Step 11: and comparing the data after the binarization processing with the data after the binarization processing formed in the true currency anti-counterfeiting area.

Step 12: if they match, the banknote 1 is judged to be a genuine banknote.

The invention relates to a paper money identification method, which is characterized in that according to the fluctuation (concave-convex) difference of paper money or the difference of heat transfer effect of a white transmission area and a black transmission area, the paper money is contacted with a thermal printing head with a larger thermal Temperature Coefficient (TCR) to cause the resistance value of a heating resistor 8a to change, and then the detected image information is identified. After the truth of the paper money is identified and whether the paper money is repaired by the adhesive tape or not, a separating device can be arranged to automatically separate the identified paper money. The structure of the separation device is the prior art and is not described herein.

Claims

1. A paper money recognition device based on a thermal printing head is characterized in that: the paper money conveying device comprises a base station, wherein a thermal printing head is arranged on the upper surface of the base station, the resistance value of a heating resistor of the thermal printing head can be reversibly changed along with the temperature change caused by joule heat, and a conveying device used for enabling paper money to pass through the heating resistor of the thermal printing head line by line along the conveying direction is further arranged on the base station; a pressing part fixed on the base station is arranged at the heating substrate of the thermal printing head, and the thermal printing head is also connected with the control processing part; the control loop of the paper money recognition device is as follows: the printing power supply supplies power to the N heating resistors respectively, each heating resistor is grounded through a first driving circuit part of the driving IC, the first driving circuit part comprises N switches, each heating resistor is also led out of a lead wire and grounded through a second driving circuit part of the driving IC and a reference resistor, and the second driving circuit part also comprises N switches; the control circuit also comprises analog-to-digital converters, the number of the analog-to-digital converters corresponds to the number of the reference resistors, wires are respectively led out from the positions between the switches and the reference resistors of the second driving circuit part and correspondingly connected to one input end of the analog-to-digital converters, the other input end of the analog-to-digital converters is connected to the anode of a reference voltage source, and the cathode of the reference voltage source is grounded; the first driving loop part and the second driving loop part are controlled by the control processing part, and the output end of the analog-to-digital converter is connected to the control processing part.

2. A paper money discriminating method based on the thermal print head-based paper money discriminating apparatus of claim 1, characterized in that: the method comprises the following steps: step 1: conveying the Mth row of the paper money to a heating resistor of the thermal printing head through a conveying device; step 2: turning on the switches of the first drive circuit unit; and step 3: after a preset time period, enabling each switch of the first driving circuit part to be in a cut-off state; and 4, step 4: according to the number of the reference resistors, all switches of the second driving circuit part are simultaneously or sequentially in a conducting state, and the electric potential between the heating resistor body and the reference resistors is collected and converted into a digital signal of 8 bits through an analog-to-digital converter; and 5: storing the converted digital signal; step 6: repeating the steps 1-5, reading information from the (M +1) th row to the (M + g) th row of the paper money, and sequentially storing digital signals corresponding to the read information; and 7: judging whether digital signals of a continuous area are 200-255 digit in the stored digital signals; and 8: if yes, judging the paper money is repaired by the adhesive tape; and step 9: if not, selecting an anti-counterfeiting area in the stored digital signal array, and performing decrement processing on the digital signal in the area; step 10: carrying out binarization processing on the reduced digital signal; step 11: comparing the data after binarization processing with data after binarization processing formed by a true currency anti-counterfeiting area; step 12: if the two are consistent, the paper money is judged to be genuine.

3. The banknote recognition method according to claim 2, wherein: the method also comprises the following steps between the step 4 and the step 5: step 41: comparing the converted digital signal with a digital threshold value through a digital comparison loop, and judging whether the converted digital signal is smaller than the digital threshold value; step 42: if all the converted digital signals are less than the digital threshold value, repeating the steps 2 to 41; step 43: and when one of the converted digital signals is equal to or greater than a digital threshold value, enabling the switch of the first driving loop part to be in a cut-off state.