Intelligent card swiping scanning and reading equipment protection circuit based on PPTC resettable fuse

Abstract

The utility model relates to the technical field of electronic circuits, in particular to an intelligent card swiping scanning and reading equipment protection circuit based on a PPTC resettable fuse. A voltage input end of the power conversion circuit is connected with a PPTC1 and a TVS1 which are connected in series during DC power supply, a voltage input end of the power conversion circuit is connected with a PPTC2 and a TVS2 which are connected in series during lithium battery power supply, a PPTC3 is connected between the MOS tube Q1 and the intelligent card induction and identification circuit, and a PPTC4 and a PPTC5 are connected between the power conversion circuit and the data read-write storage and transmission circuit. The card swiping device is small in size, low in cost and high in reliability, and can be applied to all card swiping related product equipment in various fields of buses, hospitals, shopping malls, supermarkets and the like.

Description

TECHNICAL FIELD

[0001] The utility model relates to electronic circuit technical field especially relates to a kind of intelligent card swiping reading equipment protection circuit based on PPTC self-restoring fuse. BACKGROUND

[0002] The existing card swiping machine is a single unit completed by a group of multi-element combination for each function circuit, the quality of component cannot be consistent, the layout of circuit cannot avoid the influence of distributed parameters to appear unpredictable abnormal situation, tin tip short circuit, copper film short circuit and pin bending short circuit may occur during production operation, etc., these problems and various abnormalities are the main factors affecting product safety and reliability.

[0003] In the traditional circuit protection scheme, the self-restoring fuse position is mostly protected by disposable glass fuse tube or 0Ω resistor, or replaced by a small piece of PCB copper film to complete the protection function, but it is used only once, and mostly the protection device will be burned out after short circuit, the first two types of fuses can be manually repaired and replaced, but after the PCB copper film is disconnected, the maintenance personnel may not know what to do, because it is difficult to determine the type of fuse to be used, and it is also difficult to analyze the reason for burning the fuse.

[0004] In the traditional design, each set of electronic circuit is used for detection and protection control, a small resistance resistor is used for current sampling, the sampling signal is sent to the amplification circuit for amplification, the amplified signal and the signal generated by the reference signal circuit are compared through the comparison circuit and the difference value or control signal is output, then the control signal is amplified to the driving amplitude through the amplification circuit, and the amplified driving signal is sent to the execution circuit to complete the switch control, which is mostly completed by non-contact MOS tube, and the on-off of relay is also designed and applied in the early stage, but the contact will be oxidized and stuck, which will cause hidden problems such as continuous burning of board and wire.

[0005] So far, manufacturers either use the above-mentioned circuit for control, or use simple circuit, or remove the protection and automatic control function circuit to save cost for market competition. Products using simple circuit will also have the same problems, resulting in premature failure of the product and becoming waste products. So far, there is no circuit with few components, high reliability, not easy to damage, overvoltage and overcurrent protection, which can effectively prolong the service life of the product equipment in the above-mentioned application field, to achieve the ideal protection circuit scheme. CONTENT OF THE UTILITY MODEL

[0006] The utility model discloses a kind of intelligent card scanning equipment protection circuits based on PPTC self-restoring fuse, to complete the above function with least component, not only small, low in cost, high reliability, can well solve and avoid the series hidden trouble problem above, let maintenance become more simple, market competition advantage will significantly improve, simultaneously also change the design thought of engineer.

[0007] In order to realize the above-mentioned purpose, the utility model adopts the following technical scheme: a kind of intelligent card scanning system control circuit based on PPTC self-restoring fuse, including lithium battery and the smart card induction and identification circuit, system control circuit, data read-write storage and transmission circuit, internal power supply circuit and power conversion circuit installed on same circuit board PCB, the voltage input end when DC power supply is connected with the series first self-restoring fuse PPTC1 and one-way TVS1 tube, the voltage input end when lithium battery power supply is connected with the series second self-restoring fuse PPTC2 and bidirectional TVS2 tube, MOS tube Q1 and the smart card induction and identification circuit between being connected with third self-restoring fuse PPTC3, power conversion circuit and data read-write storage and transmission circuit between being connected with fourth self-restoring fuse PPTC4 and fifth self-restoring fuse PPTC5.

[0008] Further, inductance L1 and capacitor C1 are connected between the system control circuit and the smart card induction and identification circuit in series, one end of capacitor C1 is connected to the node of the smart card induction and identification circuit and the third self-restoring fuse PPTC3.

[0009] Further, the system control circuit is connected with power indicator light LED1, power lamp LED2, LED nixie tube, buzzer, voice broadcast loudspeaker, KEY setting keyboard, data read-write storage and transmission circuit, two-dimensional code scanner, positioning radar and GSM card.

[0010] Further, resistance R1 and resistance R2 are connected between the system control circuit and the smart card induction and identification circuit in series.

[0011] Further, the intelligent card scanning system control circuit exchanges data with remote monitoring collective access equipment through RS485 serial port and read-write storage.

[0012] Further, the DC power supply is 12V power supply.

[0013] The utility model not only small, low in cost, high reliability, but also can adapt to be applied to bus, hospital, shopping mall, supermarket and all kinds of fields of various fields of card-related product equipment, it is a kind of use component few, more stable, safe, high reliability, low in cost, application simple, not easy to damage, prevent overvoltage and overcurrent, can effectively prolong the product equipment life of various application fields circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the circuit structure of the utility model. DETAILED DESCRIPTION

[0015] To facilitate understanding of the present invention, a more comprehensive description of the present invention will be provided below with reference to the accompanying drawings. The drawings illustrate preferred embodiments of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to facilitate a more thorough and comprehensive understanding of the disclosure of the present invention.

[0016] It should be noted that when an element is referred to as being “fixed to” another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or there may be an intermediate element.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0018] See also Figure 1 A protection circuit for a smart card swiping and scanning device based on a PPTC resettable fuse includes a lithium battery and a smart card sensing and identification circuit, a system control circuit, a data read, write, storage and transmission circuit, an internal power supply circuit and a power conversion circuit installed on the same circuit board PCB. When powered by DC, the voltage input end is connected to a first resettable fuse PPTC1 and a unidirectional TVS1 tube in series. When powered by a lithium battery, the voltage input end is connected to a second resettable fuse PPTC2 and a bidirectional TVS2 tube in series. A third resettable fuse PPTC3 is connected between the MOS tube Q1 and the smart card sensing and identification circuit. A fourth resettable fuse PPTC4 and a fifth resettable fuse PPTC5 are connected between the power conversion circuit and the data read, write, storage and transmission circuit.

[0019] There are inductance L1 and capacitance C1 in series between the system control circuit and the smart card induction and identification circuit, one end of the capacitance C1 is connected to the node of the smart card induction and identification circuit and the third self-resetting fuse PPTC3. The system control circuit is connected to the power indicator light LED1, the power light LED2, the LED digital tube, the buzzer, the voice broadcast speaker, the KEY setting keyboard, the data read-write storage and transmission circuit, the two-dimensional code scanning reader, the positioning radar and the GSM card. There are resistance R1 and resistance R2 in series between the system control circuit and the smart card induction and identification circuit.

[0020] The smart card scanning system control circuit exchanges data with the remote monitoring and data access equipment through the RS485 serial port. The DC power supply is 12V.

[0021] Working principle: the DC 12V input voltage is supplied to the smart card scanning system equipment through the first self-resetting fuse PPTC1 and the one-way TVS1 tube. When the smart card scanning system control equipment circuit is powered on, the power indicator light LED1 is lit to indicate that the power is on. The power light LED2 is lit to indicate that the system is ready after the internal self-checking of the card scanning system control circuit. The system sends a weak high-frequency signal to the induction coil AT through the MOS tube Q1 and the third self-resetting fuse PPTC3. When a card is placed in the smart card induction area, it will absorb the high-frequency magnetic energy of the coil, reducing the signal current of the coil. At this time, the reduced change is sent back to the system control circuit by the capacitance C1 and the inductance L1 for amplification, identification, transceiver, read-write, verification, and conversion control, etc. At the same time, the power light LED2 is lit red, and the voice broadcast speaker Y1 issues a voice report of the result of the work completion. If it is an invalid card, it will issue a beep alarm through the buzzer after identification, and the voice broadcast speaker Y1 will prompt invalid or illegal card. Similarly, the resistances R1 and R2 complete synchronous sampling to confirm the current strength of the induction coil, so that the internal circuit automatically adjusts the required current strength to enable the scanning system to accurately identify the card ID and related information read-write. The setting keyboard in the system can set and define the function and purpose of the smart card scanning device, identify the magnetic card category, and identify the signal strength and sensitivity. At the same time, the smart card scanning device will exchange data with the remote upper-level remote monitoring and data access equipment through the RS485 serial port, and the local TF card will also store the data for local call at any time.

[0022] If the code scanning needs to be applied to complete the payment function, there will be a voice broadcast code scanning result when the code scanning is completed. If the code scanning is invalid, there will be a voice report code scanning error or code scanning invalidity, etc. The completion prompt function, when the code scanning is valid, the result data will be stored in the local (local) TF memory, and at the same time, the data conversion will be completed and transmitted to the upper remote monitoring and data access equipment through RS485 to exchange and read and write data storage, etc. When offline work (no external power supply, no RS485 connection) is needed, GSM card and positioning radar are needed to complete the positioning and remote transmission of the above data. At this time, the intelligent card swiping system equipment becomes a mobile terminal, that is, an Internet of Things equipment. At this time, the power supply will be converted to internal lithium battery power supply.

[0023] The above functions can be completed after setting the keyboard settings. The working voltage of each function circuit is 5V and 3.3V, and the voltage of the lithium battery is 3V-4.2V. This requires that the 12V voltage input from the outside and the 3V-4.2V voltage of the lithium battery need to be converted to stable 5V and 3.3V to enable the intelligent card swiping system equipment to work normally.

[0024] When the external input 12V voltage (such as vehicle power supply) is connected to 36V or 48V, 60V or higher voltage, the internal power supply of the intelligent card system device may be burned out due to too high voltage, so overvoltage protection and overcurrent protection need to be designed at the input end, and here an innovative design is applied to complete it with a first self-resetting fuse PPTC1 and a one-way TVS1 tube, wherein the one-way TVS1 tube is used for overvoltage protection, and when the input voltage is higher than 12V, the one-way TVS1 tube is triggered to conduct to make the voltage short to ground to generate a large current, and at the same time when the TVS1 is turned on and short-circuited, the DC 12V output of the power supply is also forced to short-circuit parameters large current and superimposed through the TVS1 tube, so that the current of the TVS1 tube is greatly increased, but the one-way TVS1 tube belongs to uS level transient working device, and once the voltage is connected, it is continuous voltage and current, which will soon burn out the one-way TVS1 tube and continue to burn out the internal circuit of the device, resulting in device scrap, but here the first self-resetting fuse PPTC1 is connected, which will be suddenly changed from low resistance to high resistance close to open circuit under the action of the large current generated by the one-way TVS1 tube in the short-circuit state, so as to limit the current in time, thereby protecting the one-way TVS1 tube, and also protecting the load circuit system behind and the power supply circuit in front. Under normal input voltage, the load circuit behind may also be short-circuited due to PCB short-circuit in production, soldering tin short-circuit, quality problem of components, etc., which may burn out the front-end power supply, and the first self-resetting fuse PPTC1 can suddenly change from low resistance to high resistance under large current to limit the current and protect the power supply in front, and if there is no such protection, the load circuit, connection line and front-end power supply may be burned out or cause fire and other major problems.

[0025] The various signal conversion and control circuits or digital circuits in the intelligent card swiping system device are low-voltage and small-current circuits, but the output execution circuit works in a large-current and high-power state. For example, MOS tube Q1 is easily burned out due to self-excited oscillation caused by the superposition of distributed parameters and environmental signal interference to generate a large current. Here, the third self-resetting fuse PPTC3 has a low-resistance mutation to high-resistance current limiting at a large current to achieve the protection effect of MOS tube Q1 and the system circuit. When the inductively sensed magnetic card itself is short-circuited, the MOS tube Q1 can also generate a large current and can be burned out. It can be seen that when the third self-resetting fuse PPTC3 exists, Q1 and the internal circuit can be effectively protected from being burned out. In the state of lithium battery power supply, the load circuit of the lithium battery, including Q1 and other circuits, must also work normally. Therefore, the above-mentioned situation also exists. If the components of the control board are short-circuited, not only will the related circuits continue to be burned out, but also the lithium battery can be burned out due to a large current, and more seriously, the lithium battery can be exploded. It is an indisputable fact that the lithium battery is used. At this time, the fourth self-resetting fuse PPTC4 is used to effectively protect the lithium battery and its load circuit by using the design of the resistance value mutation from a resistance value to a high resistance value at a large current, so that the load circuit is not continuously damaged and the lithium battery is not exploded.

[0026] As can be seen from the above, in the system device scheme of this type, there are places where overcurrent protection and short-circuit protection are needed. PPTC self-resetting fuse elements are designed and used, and a single element can complete the function. Compared with the traditional MCU, which needs a series of circuit components such as sampling, amplification, reference circuit, comparison of amplified signals, amplification of comparison results, sending of control execution circuit, and driving of MOS tube switch working state conversion, the use of a single PPTC self-resetting fuse element is one hundredth of the size of the large circuit component, and it can complete the same function. The current resistance of the PPTC can reach more than 100A, and the current resistance of all the components of the above-mentioned traditional circuit component system cannot reach this 100A requirement, which is an indisputable fact. In the same protection function composed of a large number of components, not all components can be reliable, so the reliability of the PPTC self-resetting fuse is the highest level at present. Not only is the number of components small (one component completes the function of multiple components), but also the procurement cost, research and development production cost, sales service cost, PCB area occupied, and component installation space are all advanced and reliable. The advancement and reliability are actually tested and are incomparable.

[0027] The mechanism of the PPTC playing the overcurrent protection role is: when a large current passes through the PPTC self-resetting fuse, the internal heating temperature of the PPTC is increased, and in the set temperature range (-40 DEG C to +85 DEG C), the resistance value of the PPTC changes in a small range without affecting the normal work of the circuit; when the internal heating and the external temperature of the PPTC are superposed, the PPTC produces thermal expansion, most of the conductive links in the PPTC are disconnected, the resistance value of the PPTC is suddenly increased, and after the power is disconnected, the temperature of the PPTC is decreased, the cold contraction is generated, the original disconnected conductive links are reconnected to restore the initial low resistance value state and can be reused. Therefore, the PPTC is also called a self-resetting fuse. However, compared with the TVS trigger conduction (similar to short circuit), the resistance value of the PPTC is several times, dozens of times or even hundreds of times of the resistance value of the TVS, and the resistance value of the PPTC is increased to limit the current, so that the continuous large current does not cause the TVS to be short-circuited and burned or exploded, thereby protecting the TVS, and the purpose of protecting the system circuit is achieved through the protection of the TVS. Ultimately, the service life of the device is greatly prolonged. As a result: not only can the overvoltage protection of the TVS for a long time and repeatedly be completed, but also the artificial and non-artificial short circuit protection in the production process can be completed. When the short circuit occurs in the circuit system, the circuit components are not burned due to the short circuit and component damage, and a serious fire situation is not caused.

[0028] The design and use of the advanced PPTC self-resetting fuse not only simplify the overall circuit design, but also solve the current limiting protection of component damage and short circuit, and can complete the artificial and non-artificial short circuit protection of the above-mentioned circuit system to avoid the circuit from being burned due to the short circuit and a serious fire situation. At the same time, the problems in the design work of the related equipment manufacturers and engineers are solved, the use of components is minimized, the occupied space is small, the cost is low, the reliability is high, the product is safer, the design is simpler and easier, the related equipment has a real safety guarantee, and the market competitive advantage of the production manufacturer is directly improved.

[0029] The above-mentioned embodiments only express several implementation manners of the utility model, the description is more specific and detailed, but it cannot be understood as the limitation of the utility model patent range. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the utility model, a number of modifications and improvements can be made, which belong to the protection range of the utility model. Therefore, the protection range of the utility model patent should be subject to the appended claims.

Claims

1. A protection circuit for smart card scanning and reading devices based on a PPTC resettable fuse, characterized by: The system includes lithium battery, smart card induction and identification circuit, system control circuit, data read-write storage and transmission circuit, internal power supply circuit and power conversion circuit mounted on the same PCB. The voltage input end of the DC power supply is connected with series-connected first self-recovery fuse PPTC1 and unidirectional TVS1 tube. The voltage input end of the lithium battery power supply is connected with series-connected second self-recovery fuse PPTC2 and bidirectional TVS2 tube. The third self-recovery fuse PPTC3 is connected between MOS tube Q1 and the smart card induction and identification circuit. The fourth self-recovery fuse PPTC4 and the fifth self-recovery fuse PPTC5 are connected between the power conversion circuit and the data read-write storage and transmission circuit.

2. The PPTC self-recovery fuse based smart card swipe reading device protection circuit according to claim 1, characterized in that: The inductance L1 and the capacitance C1 are connected in series between the system control circuit and the smart card induction and identification circuit. One end of the capacitance C1 is connected to the node of the smart card induction and identification circuit and the third self-recovery fuse PPTC3.

3. The PPTC self-recovery fuse based smart card swipe reading device protection circuit according to claim 1, characterized in that: The system control circuit is connected with power indicator light LED1, power light LED2, LED nixie tube, buzzer, voice broadcast speaker, KEY setting keyboard, data read-write storage and transmission circuit, two-dimensional code scanning reader, positioning radar and GSM card.

4. The PPTC self-recovery fuse based smart card swipe reader protection circuit of claim 1, wherein: The resistance R1 and the resistance R2 are connected in series between the system control circuit and the smart card induction and identification circuit.

5. The PPTC self-restoration fuse based smart card swipe reading device protection circuit according to claim 1, characterized in that: The smart card scanning system control circuit exchanges data and read-write storage with the remote monitoring centralized access equipment through the RS485 serial port.

6. The PPTC self-restoring fuse based smart card swipe reader protection circuit according to claim 1, characterized in that: The DC power supply is 12V power supply.

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