A key multiplexing circuit and POS machine

Abstract

A key multiplexing circuit and a POS terminal, wherein a key in a key matrix array is connected to a power supply voltage according to user input to generate a DC voltage and a start trigger signal, a switch circuit generates a key trigger signal according to the DC voltage, a control circuit flips the level of an enable adjustment signal when the duration of the key trigger signal is greater than or equal to a preset duration, or obtains a function key value when the duration of the key trigger signal is less than the preset duration, a switch control circuit generates a voltage conversion enable signal according to the start trigger signal and the enable adjustment signal of the first level and stops generating the voltage conversion enable signal according to the termination of the enable adjustment signal of the second level, a step-down circuit generates a first voltage according to the power supply voltage and the voltage conversion enable signal and stops generating the first voltage according to the termination of the voltage conversion enable signal, thereby realizing the multiplexing of a general key in the key matrix array, with a simple circuit structure, low cost, saving the number of keys and space, and high practicality.

Description

Technical Field

[0001] The present application belongs to the technical field of key multiplexing, and in particular to a key multiplexing circuit and a POS machine. Background Art

[0002] The key switch mainly refers to the light-touch key switch, also called the light-touch switch. It has been widely used in electronic equipment and white appliances because of its advantages such as small contact resistance, precise operating force error, and diversified specifications. By inputting various commands and characters through the key switch, the device can be effectively controlled, such as the power on and off in electronic equipment. There can be multiple key switches in a device, but for small devices, due to insufficient space, only a limited number of key switches can be set on its panel. At this time, to realize all the functions of the device related to the key switch, it is necessary to reuse the key switch, that is, one key switch realizes multiple functions. At present, the traditional key multiplexing method is generally realized through the timing control of the controller, or the key function multiplexing is realized through the multiplexing end of the controller, and it is necessary to increase the control chip or occupy the pins of the original controller, which is costly and cannot realize the power on and off and key function multiplexing based on the original key array, which is not conducive to the optimization design of the product appearance and volume.

[0003] Therefore, the traditional technical solution has the problem that the key reuse circuit structure is complex and costly, and it cannot realize the power on / off and key function reuse based on the original key array, which is not conducive to optimizing the appearance and volume of the product. Summary of the invention

[0004] The purpose of the present application is to provide a key multiplexing circuit and a POS machine, aiming to solve the problems existing in traditional POS machines, such as complex key multiplexing circuit implementation and structure, high cost, inability to realize power on / off and key function multiplexing based on the original key array, and disadvantageous for optimizing the appearance and volume of the product.

[0005] A first aspect of an embodiment of the present application provides a key multiplexing circuit, the key multiplexing circuit comprising:

[0006] A key assembly, configured to connect a power supply voltage to generate a DC voltage and a start trigger signal according to a user input; the key assembly is a key in a key matrix array;

[0007] A switch circuit, connected to the key assembly, configured to generate a key trigger signal according to the DC voltage;

[0008] A control circuit connected to the switch circuit and the key assembly, configured to flip the level of the enable adjustment signal according to the key trigger signal when the duration of the key trigger signal is greater than or equal to the preset duration, and to obtain the function key value according to the key trigger signal when the duration of the key trigger signal is less than the preset duration;

[0009] a switch control circuit, connected to the switch circuit and the control circuit, configured to generate a voltage transformation enable signal according to the start trigger signal and the enable adjustment signal of the first level, and stop generating the voltage transformation enable signal according to the termination of the enable adjustment signal of the second level;

[0010] a step-down circuit, connected to the switch control circuit, configured to generate a first voltage according to the power supply voltage and the voltage transformation enable signal, and stop generating the first voltage according to termination of the voltage transformation enable signal;

[0011] A DC conversion circuit is connected to the step-down circuit, the switching circuit and the on / off control circuit, and is configured to perform voltage conversion on the first voltage to generate an operating voltage to power various functional circuits, and stop generating the operating voltage according to the termination of the first voltage.

[0012] In one embodiment, the key multiplexing circuit further includes:

[0013] The power adapter circuit is connected to the step-down circuit and is configured to generate the power supply voltage according to an external power supply.

[0014] In one embodiment, the switch circuit includes: a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor and a first transistor;

[0015] The first end of the first resistor and the first end of the first capacitor together constitute a DC voltage input end of the switch circuit, the second end of the first resistor is connected to the first end of the third resistor and the first end of the second resistor, the second end of the third resistor is connected to the base of the first transistor, the second end of the second resistor and the second end of the first capacitor are connected to the power ground, and the collector of the first transistor is connected to the first end of the fourth resistor;

[0016] The second end of the fourth resistor is the first working voltage input end of the switch circuit;

[0017] The collector of the first transistor and the emitter of the first transistor together constitute the key trigger signal output end of the switch circuit.

[0018] In one embodiment, the power on / off control circuit includes: a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a second capacitor, a third capacitor, a first diode and a second diode;

[0019] The first end of the fifth resistor is the first working voltage input end of the switch control circuit, the second end of the fifth resistor is connected to the first end of the sixth resistor, the second end of the sixth resistor is connected to the first end of the second capacitor and the anode of the second diode, the cathode of the second diode is connected to the first end of the seventh resistor, the second end of the second capacitor is connected to the power ground, the second end of the seventh resistor is connected to the cathode of the first diode, the anode of the first diode is connected to the first end of the third capacitor and the first end of the eighth resistor, and the second end of the third capacitor is connected to the power ground;

[0020] The second end of the fifth resistor and the first end of the sixth resistor together constitute an enable regulation signal input end of the switch control circuit;

[0021] The second end of the seventh resistor and the cathode of the first diode together constitute a voltage conversion enable signal output end of the switch control circuit;

[0022] The second end of the eighth resistor is a start trigger signal input end of the power on / off control circuit.

[0023] In one embodiment, the step-down circuit includes: a step-down chip, a fourth capacitor, a fifth capacitor, a sixth capacitor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a third diode and a first inductor;

[0024] The first end of the tenth resistor is the power supply voltage input end of the buck circuit, the second end of the tenth resistor is connected to the first end of the fourth capacitor and the input end of the buck chip, the second end of the fourth capacitor and the ground end of the buck chip are connected to the power ground, the self-boosting end of the buck chip is connected to the first end of the fifth capacitor, the sensing end of the buck chip is connected to the second end of the fifth capacitor and the first end of the first inductor, the second end of the first inductor is connected to the first end of the eleventh resistor, the first end of the twelfth resistor and the first end of the sixth capacitor, the second end of the eleventh resistor, the second end of the twelfth resistor, the second end of the sixth capacitor and the feedback end of the buck chip are connected to the first end of the thirteenth resistor, the second end of the thirteenth resistor is connected to the power ground, the enable end of the buck chip is connected to the first end of the ninth resistor and the cathode of the third diode, and the second end of the ninth resistor and the anode of the third diode are connected to the power ground;

[0025] The enable terminal of the buck chip is the voltage conversion enable signal input terminal of the buck circuit;

[0026] The second end of the first inductor is a first voltage output end of the buck circuit.

[0027] In one embodiment, the control circuit includes: a microprocessor and a seventh capacitor;

[0028] The power supply terminal of the microprocessor is connected to the first terminal of the seventh capacitor, the second terminal of the seventh capacitor is connected to the power ground, and the ground terminal of the microprocessor is connected to the power ground;

[0029] The first data input / output terminal of the microprocessor and the second data input / output terminal of the microprocessor together constitute a key trigger signal input terminal of the control circuit;

[0030] The third data input and output terminal of the microprocessor is the enable adjustment signal output terminal of the control circuit;

[0031] The power supply terminal of the microprocessor is the first working voltage input terminal of the control circuit.

[0032] A second aspect of an embodiment of the present application provides a POS machine, which includes a key multiplexing circuit as described in any one of the above items.

[0033] The key multiplexing circuit and POS terminal provided by the embodiment of the present invention connect the power supply voltage to generate a DC voltage and a start trigger signal through a key in the key matrix array according to the user input, the switch circuit generates the key trigger signal according to the DC voltage, the control circuit flips the level of the enable adjustment signal when the duration of the key trigger signal is greater than or equal to the preset duration, or obtains the function key value when the duration of the key trigger signal is less than the preset duration, the switch control circuit generates a voltage conversion enable signal according to the start trigger signal and the enable adjustment signal of the first level and stops generating the voltage conversion enable signal according to the enable adjustment signal of the second level, and the step-down circuit generates the voltage conversion enable signal according to the power supply voltage and the voltage conversion The enable signal generates a first voltage and stops generating the first voltage according to the termination of the transformer enable signal. The DC conversion circuit performs voltage conversion on the first voltage to generate an operating voltage to power each functional circuit and stops generating the operating voltage according to the termination of the first voltage, thereby realizing the multiplexing of a key in a general digital or function key matrix array, so that one key can be used as both a power button and a general key. The circuit implementation and structure are simple and the cost is low. There is no need to consider the position of the power button separately, which saves the number of keys and space, facilitates the appearance design and makes the device or machine design more compact. The overall structural design is convenient, can support different power inputs, and is highly practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A structural schematic diagram of a key multiplexing circuit provided in an embodiment of the present application;

[0035] Figure 2 Another structural schematic diagram of a key multiplexing circuit provided in an embodiment of the present application;

[0036] Figure 3 for Figure 1 An example circuit schematic diagram of a key multiplexing circuit is shown;

[0037] Figure 4 for Figure 1 An example circuit schematic diagram of the control circuit in the key multiplexing circuit shown. DETAILED DESCRIPTION

[0038] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0039] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0040] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0041] Figure 1 An embodiment of the present application is shown ( Figure 1 FIG. 1 shows a schematic diagram of a key multiplexing circuit provided in the first embodiment of the present application. For the sake of convenience, only the part related to the present embodiment is shown, which is described in detail as follows:

[0042] A key multiplexing circuit includes: a key component 01, a switch circuit 11, a control circuit 12, a switch control circuit 13, a step-down circuit 14 and a DC conversion circuit 15.

[0043] The key component 01 is configured to connect the power supply voltage according to the user input to generate a DC voltage and a start trigger signal; the key component 01 is a key in the key matrix array 100; the switch circuit 11 is connected to the key component 01 and configured to generate a key trigger signal according to the DC voltage; the control circuit 12 is connected to the switch circuit 11 and the key component 01, and is configured to flip the level of the enable adjustment signal according to the key trigger signal when the duration of the key trigger signal is greater than or equal to the preset duration, and to obtain the function key value according to the key trigger signal when the duration of the key trigger signal is less than the preset duration; the power on / off control circuit 13 is connected to the switch circuit 11 and the control circuit 12. The circuit 12 is connected and configured to generate a voltage transformation enable signal according to a start trigger signal and an enable adjustment signal of a first level, and to stop generating the voltage transformation enable signal according to the termination of the enable adjustment signal of a second level; the step-down circuit 14 is connected to the switch control circuit 13 and configured to generate a first voltage according to the power supply voltage and the voltage transformation enable signal, and to stop generating the first voltage according to the termination of the voltage transformation enable signal; the DC conversion circuit 15 is connected to the step-down circuit 14, the switch circuit 11 and the switch control circuit 13, and configured to perform voltage conversion on the first voltage to generate an operating voltage to power various functional circuits, and to stop generating the operating voltage according to the termination of the first voltage.

[0044] In a specific implementation, the key matrix array 100 is a universal key array, and a key in the universal key array is used as the key component 01. Optionally, the first level is a high level, and the second level is a low level. When the machine is turned on, the key component 01 is pressed to connect the power supply voltage to generate a DC voltage and a start trigger signal, the switch circuit 11 generates a key trigger signal according to the DC voltage, the switch control circuit 13 generates an effective voltage conversion enable signal (such as a high-level voltage conversion enable signal) according to the start trigger signal, the step-down circuit 14 generates a first voltage according to the power supply voltage and the high-level voltage conversion enable signal to power the control circuit 12, and the DC conversion circuit 15 converts the first voltage to generate a working voltage to power other functional circuits, such as the control circuit 12, and the working voltage includes the first working voltage; after the control circuit 12 is powered on, the control circuit 12 generates a high-level enable adjustment signal according to the key trigger signal, so that the voltage conversion enable signal remains at a high level, and then the step-down circuit 14 and the DC conversion circuit 15 maintain continuous and stable power supply to the control circuit 12 and other functional circuits, so as to realize the function of powering on.

[0045] During the normal operation of the control circuit 12, after the key component 01 is pressed again, a key trigger signal is generated through the switch circuit 11. The control circuit 12 receives and confirms the duration of the key trigger signal, that is, detects and confirms the duration of the key component 01 being pressed. When the duration of the key trigger signal is greater than or equal to the preset duration (for example, the preset duration is 2s), the control circuit 12 obtains the power-on / off key value information according to the key trigger signal, thereby flipping the level of the enable adjustment signal, that is, flipping the high-level enable adjustment signal to a low-level enable adjustment signal, and the power-on / off control circuit 13 stops generating according to the low-level enable adjustment signal. The step-down circuit 14 stops generating the first voltage according to the termination of the voltage transformation enable signal, and the DC conversion circuit 15 stops generating the working voltage according to the termination of the first voltage, thereby causing the control circuit 12 and other functional circuits to lose power and stop working, thereby realizing the shutdown function; when the duration of the key trigger signal is less than the preset duration (2s), the control circuit 12 obtains the function key value according to the key trigger signal, and performs the corresponding general key function according to the function key value. At this time, the voltage transformation circuit 14 and the DC conversion circuit 15 work normally, and continuously and stably supply power to the control circuit 12 and other functional circuits.

[0046] The embodiments of the present application can realize the reuse of a button in a general digital or function button matrix array, so that one button can be used as a power button and a general button. The circuit implementation and structure are simple and the cost is low. There is no need to consider the position of the power button separately, which saves the number of buttons and space, is convenient for appearance design, and makes the device or machine design more compact. The overall structure is convenient to design, can support different power inputs, and is highly practical.

[0047] See also Figure 2 In one embodiment, the key multiplexing circuit further includes: a power adapter circuit 16.

[0048] The power adapter circuit 16 is connected to the step-down circuit 14 and is configured to generate a power voltage according to an external power supply.

[0049] In a specific implementation, the power adapter circuit 16 can convert and stabilize the external input AC power, such as the mains power, to generate a power voltage, thereby realizing reliable power supply to the key multiplexing circuit.

[0050] See also Figure 3 The switch circuit 11 includes: a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first capacitor C1 and a first transistor Q1.

[0051] The first end of the first resistor R1 and the first end of the first capacitor C1 together constitute a DC voltage input end of the switch circuit 11, the second end of the first resistor R1 is connected to the first end of the third resistor R3 and the first end of the second resistor R2, the second end of the third resistor R3 is connected to the base of the first transistor Q1, the second end of the second resistor R2 and the second end of the first capacitor C1 are connected to the power ground, and the collector of the first transistor Q1 is connected to the first end of the fourth resistor R4.

[0052] The second end of the fourth resistor R4 is the first working voltage input end of the switch circuit 11 .

[0053] The collector of the first transistor Q1 and the emitter of the first transistor Q1 together constitute a key trigger signal output terminal of the switch circuit 11 .

[0054] See also Figure 3 In one embodiment, the on / off control circuit 13 includes: a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a second capacitor C2, a third capacitor C3, a first diode D1 and a second diode D2.

[0055] The first end of the fifth resistor R5 is the first working voltage input end of the switch control circuit 13, the second end of the fifth resistor R5 is connected to the first end of the sixth resistor R6, the second end of the sixth resistor R6 is connected to the first end of the second capacitor C2 and the anode of the second diode D2, the cathode of the second diode D2 is connected to the first end of the seventh resistor R7, the second end of the second capacitor C2 is connected to the power ground, the second end of the seventh resistor R7 is connected to the cathode of the first diode D1, the anode of the first diode D1 is connected to the first end of the third capacitor C3 and the first end of the eighth resistor R8, and the second end of the third capacitor C3 is connected to the power ground.

[0056] The second end of the fifth resistor R5 and the first end of the sixth resistor R6 together constitute an enable regulation signal input end of the on / off control circuit 13 .

[0057] The second end of the seventh resistor R7 and the cathode of the first diode D1 together constitute a voltage conversion enable signal output end of the on / off control circuit 13 .

[0058] The second end of the eighth resistor R8 is the start trigger signal input end of the on / off control circuit 13 .

[0059] See also Figure 3 In one embodiment, the buck circuit 14 includes: a buck chip U1, a fourth capacitor C4, a fifth capacitor C6, a sixth capacitor C7, a ninth resistor R12, a tenth resistor R13, an eleventh resistor R14, a twelfth resistor R15, a thirteenth resistor R16, a third diode D3 and a first inductor L1.

[0060] The first end of the tenth resistor R13 is the power supply voltage input end of the buck circuit 14, the second end of the tenth resistor R13 is connected to the first end of the fourth capacitor C4 and the input end IN of the buck chip U1, the second end of the fourth capacitor C4 and the ground end GND of the buck chip U1 are connected to the power ground, the self-boosting end BS of the buck chip U1 is connected to the first end of the fifth capacitor C6, the sensing end LX of the buck chip U1 is connected to the second end of the fifth capacitor C6 and the first end of the first inductor L1, the second end of the first inductor L1 is connected to the first end of the eleventh resistor R14 The first end of the ninth resistor R12 and the first end of the ninth diode D3 are connected to the power ground. The second end of the ninth resistor R12 and the anode of the third diode D3 are connected to the power ground.

[0061] The enable terminal EN of the buck chip U1 is the voltage conversion enable signal input terminal of the buck circuit 14 .

[0062] The second end of the first inductor L1 is a first voltage output end of the buck circuit 14 .

[0063] See also Figure 4 In one embodiment, the control circuit 12 includes: a microprocessor U2 and a seventh capacitor C8; wherein, the power supply terminal VDD of the microprocessor U2 is connected to the first end of the seventh capacitor C8, the second end of the seventh capacitor C8 is connected to the power ground, and the ground terminal GND of the microprocessor U2 is connected to the power ground; the first data input and output terminal GPIO1 of the microprocessor U2 and the third data input and output terminal GPIO2 of the microprocessor U2 together constitute the key trigger signal input terminal of the control circuit 12; the third data input and output terminal GPIO6 of the microprocessor U2 is the enable adjustment signal output terminal of the control circuit 12; the power supply terminal VDD of the microprocessor U2 is the first working voltage input terminal of the control circuit 12.

[0064] In a specific implementation, the optional power supply voltage is VIN, the DC voltage is equal to the power supply voltage, the first voltage is VCC, the first operating voltage is AON_3P3, and the voltage value of the first voltage and the voltage value of the first operating voltage may be equal or unequal. The key component 01 is a key K0, the first end of the key K0 is connected to the power supply voltage, and the second end of the key K0 is connected to the first end of the first resistor R1 of the switch circuit 11.

[0065] The following will be combined Figure 3 and Figure 4A brief description of the working principle of the key multiplexing circuit:

[0066] The power supply voltage VIN is connected at the moment when the button K0 is pressed to generate a DC voltage and a start trigger signal. The switch circuit 11 generates a button trigger signal according to the DC voltage and outputs it to the microprocessor U2. The start trigger signal is output to the first end of the eighth resistor R8 of the switch control circuit 13. The start trigger signal generates a high-level voltage transformation enable signal after passing through the eighth resistor R8 and the first diode D1 and is output to the enable end EN of the buck chip U1. The buck chip U1 generates a first voltage VCC according to the high-level voltage transformation enable signal and the power supply voltage VIN. The DC conversion circuit 15 performs voltage conversion on the first voltage VCC to generate a first working voltage AON_3P3, and the microprocessor U2 and other functional circuits are powered by the first voltage VCC and the first working voltage AON_3P3; after the microprocessor U2 is powered on, a high-level enable adjustment signal is generated according to the button trigger signal, thereby keeping the voltage transformation enable signal at a high level, so that the buck chip U1 and the DC conversion circuit 15 maintain continuous and stable power supply to the microprocessor U2 and other functional circuits, thereby realizing the power-on function.

[0067] During the normal operation of the microprocessor U2, the button K0 is pressed again, and the button trigger signal is output through the switch circuit 11. The microprocessor U2 receives and confirms the duration of the button trigger signal. When the duration of the button trigger signal is greater than or equal to the preset duration (for example, 2s), the microprocessor U2 flips the level of the enable adjustment signal according to the button trigger signal, and flips the high-level enable adjustment signal to a low-level enable adjustment signal. The low-level enable adjustment signal stops generating a valid voltage transformation enable signal through the fifth resistor R5, the sixth resistor R6 and the second diode D2. The buck chip U1 stops generating a valid voltage transformation enable signal according to the terminal of the valid voltage transformation enable signal. The first voltage VCC is stopped from being generated, and the DC conversion circuit 15 stops generating the first working voltage AON_3P3 according to the termination of the first voltage VCC, so that the microprocessor U2 and other functional circuits are powered off and do not work, thereby realizing the shutdown function; when the duration of the key trigger signal is less than the preset duration (for example, 2s), the microprocessor U2 obtains the function key value according to the key trigger signal, and performs the corresponding key function according to the function key value. At this time, the step-down chip U1 and the DC conversion circuit 15 work normally, maintain stable power supply to the microprocessor U2 and other functional circuits, and realize the general key function of the key K0.

[0068] A second aspect of an embodiment of the present application provides a POS machine, the POS machine comprising a key multiplexing circuit as described in any one of the above items.

[0069] The embodiments of the present application can realize the multiplexing of a button in a general digital or function button matrix array, so that one button can be used as a power button and a general button. The circuit implementation and structure are simple and the cost is low. There is no need to consider the position of the power button separately, which saves the number of buttons and space, is convenient for appearance design, and makes the device or machine design more compact. The overall design of the POS product structure is convenient, can support different power inputs, and is highly practical.

[0070] Those skilled in the art can clearly understand that, for the convenience and simplicity of description, only the division of the above-mentioned functional circuits, units, and modules is used as an example for illustration. In actual applications, the above-mentioned functions can be assigned to different functional circuits, units, and modules as needed, that is, the internal structure of the device is divided into different functional circuits or units or modules to complete all or part of the functions described above. In addition, the specific names of the functional circuits, units, and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application.

[0071] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0072] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A key multiplexing circuit, characterized in that: The key multiplexing circuit comprises: A key assembly, configured to connect a power supply voltage to generate a DC voltage and a start trigger signal according to a user input; the key assembly is a key in a key matrix array; A switch circuit, connected to the key assembly, configured to generate a key trigger signal according to the DC voltage; A control circuit connected to the switch circuit and the key assembly, configured to flip the level of the enable adjustment signal according to the key trigger signal when the duration of the key trigger signal is greater than or equal to the preset duration, and to obtain the function key value according to the key trigger signal when the duration of the key trigger signal is less than the preset duration; a switch control circuit, connected to the switch circuit and the control circuit, configured to generate a voltage transformation enable signal according to the start trigger signal and the enable adjustment signal of the first level, and stop generating the voltage transformation enable signal according to the termination of the enable adjustment signal of the second level; a step-down circuit, connected to the switch control circuit, configured to generate a first voltage according to the power supply voltage and the voltage transformation enable signal, and stop generating the first voltage according to termination of the voltage transformation enable signal; A DC conversion circuit is connected to the step-down circuit, the switching circuit and the on / off control circuit, and is configured to perform voltage conversion on the first voltage to generate an operating voltage to power various functional circuits, and stop generating the operating voltage according to the termination of the first voltage.

2. The key multiplexing circuit according to claim 1, characterized in that: The key multiplexing circuit also includes: The power adapter circuit is connected to the step-down circuit and is configured to generate the power voltage according to an external power supply.

3. The key multiplexing circuit according to claim 1, characterized in that: The switch circuit comprises: a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor and a first transistor; The first end of the first resistor and the first end of the first capacitor together constitute a DC voltage input end of the switch circuit, the second end of the first resistor is connected to the first end of the third resistor and the first end of the second resistor, the second end of the third resistor is connected to the base of the first transistor, the second end of the second resistor and the second end of the first capacitor are connected to the power ground, and the collector of the first transistor is connected to the first end of the fourth resistor; The second end of the fourth resistor is the first working voltage input end of the switch circuit; The collector of the first transistor and the emitter of the first transistor together constitute the key trigger signal output end of the switch circuit.

4. The key multiplexing circuit according to claim 1, characterized in that: The switch control circuit includes: a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a second capacitor, a third capacitor, a first diode and a second diode; The first end of the fifth resistor is the first working voltage input end of the switch control circuit, the second end of the fifth resistor is connected to the first end of the sixth resistor, the second end of the sixth resistor is connected to the first end of the second capacitor and the anode of the second diode, the cathode of the second diode is connected to the first end of the seventh resistor, the second end of the second capacitor is connected to the power ground, the second end of the seventh resistor is connected to the cathode of the first diode, the anode of the first diode is connected to the first end of the third capacitor and the first end of the eighth resistor, and the second end of the third capacitor is connected to the power ground; The second end of the fifth resistor and the first end of the sixth resistor together constitute an enable regulation signal input end of the switch control circuit; The second end of the seventh resistor and the cathode of the first diode together constitute a voltage conversion enable signal output end of the switch control circuit; The second end of the eighth resistor is a start trigger signal input end of the power on / off control circuit.

5. The key multiplexing circuit according to claim 1, characterized in that: The step-down circuit includes: a step-down chip, a fourth capacitor, a fifth capacitor, a sixth capacitor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a third diode and a first inductor; The first end of the tenth resistor is the power supply voltage input end of the buck circuit, the second end of the tenth resistor is connected to the first end of the fourth capacitor and the input end of the buck chip, the second end of the fourth capacitor and the ground end of the buck chip are connected to the power ground, the self-boosting end of the buck chip is connected to the first end of the fifth capacitor, the sensing end of the buck chip is connected to the second end of the fifth capacitor and the first end of the first inductor, the second end of the first inductor is connected to the first end of the eleventh resistor, the first end of the twelfth resistor and the first end of the sixth capacitor, the second end of the eleventh resistor, the second end of the twelfth resistor, the second end of the sixth capacitor and the feedback end of the buck chip are connected to the first end of the thirteenth resistor, the second end of the thirteenth resistor is connected to the power ground, the enable end of the buck chip is connected to the first end of the ninth resistor and the cathode of the third diode, and the second end of the ninth resistor and the anode of the third diode are connected to the power ground; The enable terminal of the buck chip is the voltage conversion enable signal input terminal of the buck circuit; The second end of the first inductor is a first voltage output end of the buck circuit.

6. The key multiplexing circuit according to claim 1, characterized in that: The control circuit comprises: a microprocessor and a seventh capacitor; The power supply terminal of the microprocessor is connected to the first terminal of the seventh capacitor, the second terminal of the seventh capacitor is connected to the power ground, and the ground terminal of the microprocessor is connected to the power ground; The first data input / output terminal of the microprocessor and the second data input / output terminal of the microprocessor together constitute a key trigger signal input terminal of the control circuit; The third data input and output terminal of the microprocessor is the enable adjustment signal output terminal of the control circuit; The power supply terminal of the microprocessor is the first working voltage input terminal of the control circuit.

7. A POS machine, characterized in that: The POS machine comprises the key multiplexing circuit as described in any one of claims 1 to 6.

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