Digital adjustable current limiting circuit for USB interface of POS machine base

Abstract

The utility model provides a digital adjustable current limiting circuit for a USB interface of a POS machine base, which is characterized in that the input end of a current limiting chip main circuit is connected with a power supply in the POS machine base, and the output end of the current limiting chip main circuit is connected with the USB interface of the POS machine base; the output ends of the first analog switch resistor access circuit, the second analog switch resistor access circuit and the third analog switch resistor access circuit are connected with the input end of the current limiting chip main circuit; the first analog switch resistor is connected to the input end of the circuit, the second analog switch resistor is connected to the input end of the circuit, and the third analog switch resistor is connected to the input end of the circuit and can receive control signals of external software. The utility model has the beneficial effects that the current limiting size of the USB interface of the POS machine base can be directly and digitally adjusted, and the use experience of a user is greatly improved.

Description

Technical Field

[0001] The utility model relates to the technical field of circuits, in particular to a digital adjustable current limiting circuit for a USB interface of a POS machine base. Background Art

[0002] A POS terminal is a multifunctional terminal installed at authorized merchants and credit card acceptance locations, connected to a computer network, enabling automatic electronic fund transfers. It supports purchases, pre-authorization, balance inquiries, and transfers, making it safe, fast, and reliable. A current limiting circuit limits the current within a conductive loop to protect electronic components or the conductive loop from burnout. It is typically connected in series between a rectifier bridge and a filter capacitor. A parallel circuit consisting of a current-limiting resistor and a short-circuit switch is called a current limiting circuit.

[0003] POS machine docks typically provide charging, USB connectivity, and network connectivity for POS machines. Their USB interfaces typically utilize current-limiting ICs to limit discharge current. This ensures compliance with USB interface requirements and ensures safety during use. Typically, current-limiting ICs in POS machine docks use a resistor to determine the current limit. However, this current limit is fixed, and the current output cannot be adjusted. If an adjustable resistor is used, real-time adjustments cannot be made via software after the POS machine dock is manufactured, resulting in significant inconvenience and a suboptimal user experience. Utility Model Content

[0004] In order to solve the problems in the prior art, the present invention provides a digitally adjustable current limiting circuit for the USB interface of a POS machine base. By arranging a current limiting chip main circuit, a first analog switch resistor access circuit, a second analog switch resistor access circuit and a third analog switch resistor access circuit that cooperate with each other in the digitally adjustable current limiting circuit for the USB interface of the POS machine base, the control signal of the external software can control the resistance size output by the first analog switch resistor access circuit, the second analog switch resistor access circuit and the third analog switch resistor access circuit to the current limiting chip main circuit, thereby adjusting the current limiting size ultimately output by the current limiting chip main circuit. This can realize direct digital adjustment of the current limiting size of the USB interface of the POS machine base, greatly improve the user experience, and solve the problems in the prior art that the current limiting size of the USB interface of the POS machine base cannot be adjusted and the current limiting size cannot be adjusted after the POS machine base is produced using an adjustable resistor.

[0005] The utility model provides a digitally adjustable current limiting circuit for a USB interface of a POS machine base, comprising a current limiting chip main circuit, a first analog switch resistor access circuit, a second analog switch resistor access circuit, and a third analog switch resistor access circuit. The input end of the current limiting chip main circuit is connected to a power supply in the POS machine base, and the output end of the current limiting chip main circuit is connected to the USB interface of the POS machine base. The first analog switch resistor access circuit, the second analog switch resistor access circuit, and the third analog switch resistor access circuit are connected in series with each other, and the output ends are connected to the input end of the current limiting chip main circuit. The input ends of the first analog switch resistor access circuit, the second analog switch resistor access circuit, and the third analog switch resistor access circuit can receive control signals from external software. The control signals from the external software can control the resistance output by the first analog switch resistor access circuit, the second analog switch resistor access circuit, and the third analog switch resistor access circuit to the current limiting chip main circuit, thereby adjusting the current limiting size ultimately output by the current limiting chip main circuit.

[0006] The present utility model is further improved. The main circuit of the current limiting chip is provided with a current limiting chip U1 and a capacitor C1, wherein the current limiting chip U1 is provided with 5 pins, the 1st pin of the current limiting chip U1 is connected to the USB interface of the POS machine base, the 3rd pin of the current limiting chip U1 is connected to the output end of the first analog switch resistor access circuit, the 4th pin of the current limiting chip U1 is connected to the 5th pin of the current limiting chip U1, one end of the capacitor C1, and the power supply in the POS machine base, and the 2nd pin of the current limiting chip U1 and the other end of the capacitor C1 are grounded.

[0007] The present utility model is further improved, wherein the first analog switch resistor access circuit is provided with an analog switch chip U2 and a resistor R1, wherein the analog switch chip U2 is provided with 10 pins, the 8th pin of the analog switch chip U2 is connected to one end of the resistor R1, the 9th pin of the analog switch chip U2 is connected to the other end of the resistor R1, the 2nd pin of the analog switch chip U2 can receive a control signal from external software, the 3rd pin of the analog switch chip U2 is connected to the 3rd pin of the current limiting chip U1, and the 4th pin of the analog switch chip U2 is connected to the output end of the second analog switch resistor access circuit.

[0008] The present invention is further improved, the second analog switch resistor access circuit is provided with an analog switch chip U3 and a resistor R2, wherein the analog switch chip U3 is provided with 10 pins, the 8th pin of the analog switch chip U3 is connected to one end of the resistor R2, the 9th pin of the analog switch chip U3 is connected to the other end of the resistor R2, the 2nd pin of the analog switch chip U3 can receive a control signal from external software, the 3rd pin of the analog switch chip U3 is connected to the 4th pin of the analog switch chip U2, and the 4th pin of the analog switch chip U3 is connected to the output end of the third analog switch resistor access circuit.

[0009] The present utility model is further improved, the third analog switch resistor access circuit is provided with an analog switch chip U4 and a resistor R3, wherein the analog switch chip U4 is provided with 10 pins, the 8th pin of the analog switch chip U4 is connected to one end of the resistor R3, the 9th pin of the analog switch chip U4 is connected to the other end of the resistor R3, the 2nd pin of the analog switch chip U4 can receive the control signal of the external software, the 3rd pin of the analog switch chip U4 is connected to the 4th pin of the analog switch chip U3, and the 4th pin of the analog switch chip U4 is grounded.

[0010] The present invention is further improved, and the model of the current limiting chip U1 is KT9700.

[0011] The present invention is further improved in that the model of the analog switch chip U2 is SGM7227_MSOP10, and the resistance value of the resistor R1 is 4.99KΩ.

[0012] The present invention is further improved in that the model of the analog switch chip U3 is SGM7227_MSOP10, and the resistance value of the resistor R2 is 10KΩ.

[0013] The present invention is further improved in that the model of the analog switch chip U4 is SGM7227_MSOP10, and the resistance value of the resistor R3 is 20KΩ.

[0014] Compared with the prior art, the beneficial effects of the present invention are: providing a digitally adjustable current limiting circuit for the USB interface of a POS machine base, by setting a current limiting chip main circuit, a first analog switch resistor access circuit, a second analog switch resistor access circuit and a third analog switch resistor access circuit that cooperate with each other in the digitally adjustable current limiting circuit for the USB interface of the POS machine base, the control signal of the external software can control the resistance size output by the first analog switch resistor access circuit, the second analog switch resistor access circuit and the third analog switch resistor access circuit to the current limiting chip main circuit, thereby adjusting the current limiting size ultimately output by the current limiting chip main circuit, and realizing direct digital adjustment of the current limiting size of the USB interface of the POS machine base, greatly improving the user experience, and solving the problem in the prior art that the current limiting size of the USB interface of the POS machine base cannot be adjusted and the current limiting size cannot be adjusted after the POS machine base is produced using an adjustable resistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the solutions in the present invention or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0016] Figure 1 The utility model is a circuit diagram of a digital adjustable current limiting circuit for a USB interface of a POS machine base. DETAILED DESCRIPTION

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which this utility model belongs. The terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this utility model. The terms "including" and "having" and any variations thereof in the specification and claims of this utility model and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this utility model or the above-mentioned drawings are used to distinguish different objects, not to describe a specific order.

[0018] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0019] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0020] like Figure 1 As shown, the present invention provides a digitally adjustable current limiting circuit for a POS machine base USB interface, comprising a current limiting chip main circuit, a first analog switch resistor access circuit, a second analog switch resistor access circuit, and a third analog switch resistor access circuit. The input end of the current limiting chip main circuit is connected to the power supply in the POS machine base, the output end of the current limiting chip main circuit is connected to the POS machine base USB interface, the first analog switch resistor access circuit, the second analog switch resistor access circuit, and the third analog switch resistor access circuit are connected in series with each other, and the output end is connected to the input end of the current limiting chip main circuit. The input end of the first analog switch resistor access circuit, the input end of the second analog switch resistor access circuit, and the input end of the third analog switch resistor access circuit can receive control signals from external software. In this embodiment, the control signal from the external software can control the resistance output of the first analog switch resistor access circuit, the second analog switch resistor access circuit, and the third analog switch resistor access circuit to the current limiting chip main circuit, thereby adjusting the current limiting value ultimately output by the current limiting chip main circuit. This can achieve direct digital adjustment of the current limiting value of the POS machine base USB interface, significantly improving the user experience.

[0021] like Figure 1 As shown, the current limiting chip main circuit is provided with a current limiting chip U1 and a capacitor C1. The model of the current limiting chip U1 is KT9700. The current limiting chip U1 has 5 pins. The first pin of the current limiting chip U1 is connected to the USB interface of the POS machine base. The third pin of the current limiting chip U1 is connected to the output end of the first analog switch resistor access circuit. The fourth pin of the current limiting chip U1 is connected to the fifth pin of the current limiting chip U1, one end of the capacitor C1, and the power supply in the POS machine base. The second pin of the current limiting chip U1 and the other end of the capacitor C1 are grounded. In this embodiment, the current limiting chip main circuit is used to limit the final output current of the USB interface of the POS machine base. The current limiting chip U1 limits the output current from 5V to 5V_OUT. The current magnitude is I = 10K / R (A), where R is the resistance between the third pin of the current limiting chip U1 and ground, that is, the final resistance after the first analog switch resistor access circuit, the second analog switch resistor access circuit, and the third analog switch resistor access circuit are connected in series.

[0022] like Figure 1As shown, the first analog switch resistor access circuit is provided with an analog switch chip U2 and a resistor R1, wherein the model of the analog switch chip U2 is SGM7227_MSOP10, the resistance of the resistor R1 is 4.99KΩ, the analog switch chip U2 is provided with 10 pins, the 8th pin of the analog switch chip U2 is connected to one end of the resistor R1, the 9th pin of the analog switch chip U2 is connected to the other end of the resistor R1, the 2nd pin of the analog switch chip U2 can receive the control signal of the external software, the 3rd pin of the analog switch chip U2 is connected to the 3rd pin of the current limiting chip U1, and the 4th pin of the analog switch chip U2 is connected to the output end of the second analog switch resistor access circuit; the second analog switch resistor access circuit is provided with an analog switch chip U3 and a resistor R2, wherein the model of the analog switch chip U3 is SGM7227_MSOP10, the resistance of the resistor R2 is 10KΩ, the analog switch chip U3 is provided with 10 pins, the 8th pin of the analog switch chip U3 is connected to the resistor One end of the analog switch chip U2 is connected, the 9th pin of the analog switch chip U3 is connected to the other end of the resistor R2, the 2nd pin of the analog switch chip U3 can receive the control signal of the external software, the 3rd pin of the analog switch chip U3 is connected to the 4th pin of the analog switch chip U2, and the 4th pin of the analog switch chip U3 is connected to the output end of the third analog switch resistor access circuit; the third analog switch resistor access circuit is provided with an analog switch chip U4 and a resistor R3, wherein the model of the analog switch chip U4 is SGM7227_MSOP10, the resistance of the resistor R3 is 20KΩ, the analog switch chip U4 is provided with 10 pins, the 8th pin of the analog switch chip U4 is connected to one end of the resistor R3, the 9th pin of the analog switch chip U4 is connected to the other end of the resistor R3, the 2nd pin of the analog switch chip U4 can receive the control signal of the external software, the 3rd pin of the analog switch chip U4 is connected to the 4th pin of the analog switch chip U3, and the 4th pin of the analog switch chip U4 is grounded.In this embodiment, the first analog switch resistor access circuit, the second analog switch resistor access circuit, and the third analog switch resistor access circuit are connected in series and output the final resistance to the third pin of the current limiting chip U1. The two interfaces of the first analog switch resistor access circuit, the second analog switch resistor access circuit, and the third analog switch resistor access circuit are respectively a specified resistance and a short circuit; when the second pin access signal SET_0 of the analog switch chip U2 is 0, the analog switch chip U2 is short-circuited, and the first analog switch resistor access circuit is equivalent to a resistance of 0. When the second pin access signal SET_0 of the analog switch chip U2 is 1, the first analog switch resistor access circuit is equivalent to a resistance of 0. The input circuit is equivalent to a 5K resistor. When the SET_1 signal connected to the second pin of analog switch chip U3 is 0, analog switch chip U3 is short-circuited, and the second analog switch resistor access circuit is equivalent to a resistance of 0. When the SET_1 signal connected to the second pin of analog switch chip U3 is 1, the second analog switch resistor access circuit is equivalent to a 10K resistor. When the SET_2 signal connected to the second pin of analog switch chip U4 is 0, analog switch chip U4 is short-circuited, and the third analog switch resistor access circuit is equivalent to a resistance of 0. When the SET_2 signal connected to the second pin of analog switch chip U4 is 1, the third analog switch resistor access circuit is equivalent to a 10K resistor. By controlling the states of SET_0, SET_1, and SET_2 to 0 or 1 through external software, the final resistance value of the first, second, and third analog switch resistor access circuits output in series to the current limiting chip U1 can be achieved, thereby achieving direct digital adjustment of the current limiting value of the USB interface on the POS terminal base.

[0023] From the above, it can be seen that the utility model provides a digitally adjustable current limiting circuit for the USB interface of the POS machine base. By setting a current limiting chip main circuit, a first analog switch resistor access circuit, a second analog switch resistor access circuit and a third analog switch resistor access circuit that cooperate with each other in the digitally adjustable current limiting circuit for the USB interface of the POS machine base, the control signal of the external software can control the resistance size output by the first analog switch resistor access circuit, the second analog switch resistor access circuit and the third analog switch resistor access circuit to the current limiting chip main circuit, thereby adjusting the current limiting size finally output by the current limiting chip main circuit. The current limiting size of the USB interface of the POS machine base can be directly digitally adjusted, which greatly improves the user experience and solves the problem in the prior art that the current limiting size of the USB interface of the POS machine base cannot be adjusted and the current limiting size cannot be adjusted after the POS machine base is produced using an adjustable resistor.

[0024] The specific implementation methods described above are preferred implementation methods of the present invention, and are not intended to limit the specific implementation scope of the present invention. The scope of the present invention includes but is not limited to the specific implementation methods. All equivalent changes made in accordance with the present invention are within the protection scope of the present invention.

Claims

1. A digitally adjustable current limiting circuit for a USB port on a POS machine base, characterized by: It includes a current limiting chip main circuit, a first analog switch resistor access circuit, a second analog switch resistor access circuit and a third analog switch resistor access circuit. The input end of the current limiting chip main circuit is connected to the power supply in the POS machine base, and the output end of the current limiting chip main circuit is connected to the USB interface of the POS machine base. The first analog switch resistor access circuit, the second analog switch resistor access circuit and the third analog switch resistor access circuit are connected in series with each other and the output ends are connected to the input end of the current limiting chip main circuit. The input end of the first analog switch resistor access circuit, the input end of the second analog switch resistor access circuit and the input end of the third analog switch resistor access circuit can receive control signals from external software. The control signals from external software can control the resistance output by the first analog switch resistor access circuit, the second analog switch resistor access circuit and the third analog switch resistor access circuit to the current limiting chip main circuit, thereby adjusting the current limiting size finally output by the current limiting chip main circuit.

2. The digital adjustable current limiting circuit for a POS machine base USB interface according to claim 1, characterized in that: The main circuit of the current limiting chip is provided with a current limiting chip U1 and a capacitor C1, wherein the current limiting chip U1 is provided with 5 pins, the 1st pin of the current limiting chip U1 is connected to the USB interface of the POS machine base, the 3rd pin of the current limiting chip U1 is connected to the output end of the first analog switch resistor access circuit, the 4th pin of the current limiting chip U1 is connected to the 5th pin of the current limiting chip U1, one end of the capacitor C1, and the power supply in the POS machine base, and the 2nd pin of the current limiting chip U1 and the other end of the capacitor C1 are grounded.

3. The digital adjustable current limiting circuit for a POS machine base USB interface according to claim 2, characterized in that: The first analog switch resistor access circuit is provided with an analog switch chip U2 and a resistor R1, wherein the analog switch chip U2 is provided with 10 pins, the 8th pin of the analog switch chip U2 is connected to one end of the resistor R1, the 9th pin of the analog switch chip U2 is connected to the other end of the resistor R1, the 2nd pin of the analog switch chip U2 can receive a control signal from external software, the 3rd pin of the analog switch chip U2 is connected to the 3rd pin of the current limiting chip U1, and the 4th pin of the analog switch chip U2 is connected to the output end of the second analog switch resistor access circuit.

4. The digital adjustable current limiting circuit for a USB interface of a POS machine base according to claim 3, characterized in that: The second analog switch resistor access circuit is provided with an analog switch chip U3 and a resistor R2, wherein the analog switch chip U3 is provided with 10 pins, the 8th pin of the analog switch chip U3 is connected to one end of the resistor R2, the 9th pin of the analog switch chip U3 is connected to the other end of the resistor R2, the 2nd pin of the analog switch chip U3 can receive a control signal from external software, the 3rd pin of the analog switch chip U3 is connected to the 4th pin of the analog switch chip U2, and the 4th pin of the analog switch chip U3 is connected to the output end of the third analog switch resistor access circuit.

5. The digital adjustable current limiting circuit for the USB interface of a POS machine base according to claim 4, characterized in that: The third analog switch resistor access circuit is provided with an analog switch chip U4 and a resistor R3, wherein the analog switch chip U4 is provided with 10 pins, the 8th pin of the analog switch chip U4 is connected to one end of the resistor R3, the 9th pin of the analog switch chip U4 is connected to the other end of the resistor R3, the 2nd pin of the analog switch chip U4 can receive a control signal from external software, the 3rd pin of the analog switch chip U4 is connected to the 4th pin of the analog switch chip U3, and the 4th pin of the analog switch chip U4 is grounded.

6. The digital adjustable current limiting circuit for a USB interface of a POS machine base according to claim 5, characterized in that: The model of the current limiting chip U1 is KT9700.

7. The digital adjustable current limiting circuit for a USB interface of a POS machine base according to claim 6, characterized in that: The model of the analog switch chip U2 is SGM7227_MSOP10, and the resistance of the resistor R1 is 4.99KΩ.

8. The digital adjustable current limiting circuit for a USB interface of a POS machine base according to claim 7, characterized in that: The model of the analog switch chip U3 is SGM7227_MSOP10, and the resistance value of the resistor R2 is 10KΩ.

9. The digital adjustable current limiting circuit for a USB interface of a POS machine base according to claim 8, characterized in that: The model of the analog switch chip U4 is SGM7227_MSOP10, and the resistance of the resistor R3 is 20KΩ.

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