Power supply circuit, low-frequency reader and radio frequency identification assembly

Abstract

The utility model discloses a power supply circuit, a low-frequency reader and a radio frequency identification assembly. The power supply circuit is applied to the low-frequency reader and comprises a power input end, a power output end, a first filter circuit, a voltage conversion circuit and a second filter circuit. The first filter circuit can filter a first power supply voltage input by the power supply input end. The voltage conversion circuit can convert the first power supply voltage into a second power supply voltage for output. The second filter circuit can filter the second power supply voltage and then output the second power supply voltage to the power supply output end. The utility model aims to reduce the parasitic low-frequency power supply ripple of the second power supply voltage output by the power supply circuit, thereby reducing the transceiving interference of the low-frequency power supply ripple on the low-frequency radio-frequency signal of the low-frequency reader, and increasing the distance of the low-frequency reader for effectively sensing the RFID electronic tag.

Description

Technical Field

[0001] The utility model relates to the technical field of radio frequency identification, in particular to a power supply circuit, a low-frequency reader and a radio frequency identification component. Background Art

[0002] Low frequency readers are widely used in the fields of Internet of Things, supply chain management, security access control and animal identification. They are devices used to read RFID (Radio Frequency Identification) electronic tags in the low frequency range of 125kHz to 134.2kHz. The power supply circuit can convert the external power supply voltage into the power required by the low frequency reader and output it to the low frequency reader.

[0003] In the prior art, the power output by the power supply circuit has low-frequency power ripple, which greatly interferes with the transmission and reception of low-frequency radio frequency signals between the low-frequency reader and the RFID electronic tag, easily shortening the distance at which the low-frequency reader effectively senses the RFID electronic tag. Utility Model Content

[0004] The main purpose of the utility model is to provide a power supply circuit, aiming to increase the distance at which a low-frequency reader effectively senses an RFID electronic tag.

[0005] To achieve the above object, the power supply circuit proposed by the utility model is applied to a low-frequency reader, and the power supply circuit includes:

[0006] A power input terminal, used for inputting a first power voltage;

[0007] A power supply output terminal, used for outputting a second power supply voltage;

[0008] a first filter circuit, the first filter circuit being connected to the power input terminal; the first filter circuit being used for filtering the first power supply voltage and then outputting it;

[0009] A voltage conversion circuit, wherein an input end of the voltage conversion circuit is connected to the first filter circuit; the voltage conversion circuit is used to convert the first power supply voltage into the second power supply voltage for output;

[0010] The second filter circuit is connected to the output end of the voltage conversion circuit and the power supply output end respectively; the second filter circuit is used for filtering the second power supply voltage and then outputting it.

[0011] Optionally, the voltage conversion circuit includes an SCT2400 chip.

[0012] Optionally, the first filtering circuit includes a first capacitor, a second capacitor and a third capacitor; the input end of the first filtering circuit, one end of the first capacitor, one end of the second capacitor, and one end of the third capacitor are connected to the VIN pin of the SCT2400 chip; the other end of the first capacitor, the other end of the second capacitor, and the other end of the third capacitor are grounded.

[0013] Optionally, the second filtering circuit includes a fourth capacitor, a fifth capacitor, a sixth capacitor and a first inductor; one end of the fourth capacitor and one end of the first inductor are connected to the SW pin of the SCT2400 chip; the other end of the fourth capacitor is connected to the BST pin of the SCT2400 chip; the other end of the first inductor, one end of the fifth capacitor and one end of the sixth capacitor are connected to the output end of the second filtering circuit; the other end of the fifth capacitor and the other end of the sixth capacitor are grounded.

[0014] Optionally, the voltage conversion circuit also includes an enable input terminal, a first resistor, a first switch tube and a second resistor; one end of the first resistor is connected to the VIN pin of the SCT2400 chip; the other end of the first resistor, the EN pin of the SCT2400 chip and the first end of the first switch tube are connected; the second end of the first switch tube and one end of the second resistor are grounded; the other end of the second resistor, the controlled end of the first switch tube and the enable input terminal are connected.

[0015] Optionally, the voltage conversion circuit also includes a third resistor, a fourth resistor and a seventh capacitor; one end of the third resistor and one end of the seventh capacitor are connected to the other end of the first inductor; the other end of the third resistor, the other end of the seventh capacitor, and one end of the fourth resistor are connected to the FB pin of the SCT2400 chip; the other end of the fourth resistor is grounded.

[0016] Optionally, the power supply circuit also includes a fifth resistor, a sixth resistor and a seventh resistor; one end of the fifth resistor is connected to the power input terminal, and the other end of the fifth resistor is connected to one end of the third capacitor; one end of the sixth resistor is connected to the power output terminal, and the other end of the sixth resistor is connected to the other end of the first inductor; one end of the seventh resistor is connected to the controlled end of the first switch tube, and the other end of the seventh resistor is connected to the enable input terminal.

[0017] Optionally, the first switch tube is a transistor; the base of the transistor is connected to the other end of the second resistor, the collector of the transistor is connected to the EN pin of the SCT2400 chip, and the emitter of the transistor is grounded.

[0018] The utility model also provides a low-frequency reader, and the low-frequency reader comprises the power supply circuit as described above.

[0019] The utility model also provides a radio frequency identification component, which includes an RFID electronic tag and the low frequency reader as described above.

[0020] The technical solution of the utility model adopts a power supply circuit, which is applied to a low-frequency reader. The power supply circuit includes a power input terminal, a power output terminal, a first filtering circuit, a voltage conversion circuit and a second filtering circuit. Among them, the first power supply voltage is filtered by the first filtering circuit. The first filtering circuit can filter out the noise and ripple of the first power supply voltage, ensuring that the voltage input to the voltage conversion circuit has a high quality, so as to provide a relatively stable and clean power supply. The voltage conversion circuit can convert the first power supply voltage into a second power supply voltage output. The voltage conversion circuit can be designed with a switching power supply whose switching frequency is much higher than the frequency range of the low-frequency radio frequency signal to reduce the output of the low-frequency power supply ripple. The second filtering circuit can filter the second power supply voltage and output it to the power output terminal. The second filtering circuit can effectively filter out the ripple of the second power supply voltage, so that the power output terminal obtains a more stable and clean second power supply voltage. In this way, the utility model provides power supply through the voltage conversion circuit, which can reduce the generation of low-frequency power supply ripple, and the parasitic ripple of the second power supply voltage is filtered out by the second filtering circuit, thereby reducing the transmission and reception interference caused by the low-frequency power supply ripple to the low-frequency radio frequency signal of the low-frequency reader, and increasing the distance at which the low-frequency reader effectively senses the RFID electronic tag. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0022] Figure 1 This is a schematic diagram of the structure of an embodiment of a power supply circuit of the utility model;

[0023] Figure 2 This is an electronic circuit diagram of an embodiment of the power supply circuit of the utility model.

[0024] Description of Figure Numbers:

[0025]

[0026]

[0027] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0029] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back...) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0030] In addition, the descriptions of "first", "second", etc. in the present utility model are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present utility model.

[0031] In the prior art, the power output by the power supply circuit has low-frequency power ripple, which greatly interferes with the transmission and reception of low-frequency radio frequency signals between the low-frequency reader and the RFID electronic tag, easily shortening the distance at which the low-frequency reader effectively senses the RFID electronic tag.

[0032] In order to solve the above problems, the utility model provides a power supply circuit.

[0033] In one embodiment of the present invention, Figure 1 As shown, the power supply circuit is applied to a low frequency reader, comprising:

[0034] A power input terminal, used for inputting a first power voltage;

[0035] A power supply output terminal, used for outputting a second power supply voltage;

[0036] A first filter circuit 01, the first filter circuit 01 is connected to the power input terminal; the first filter circuit 01 is used to filter the first power supply voltage and then output it;

[0037] A voltage conversion circuit 02, the input end of the voltage conversion circuit 02 is connected to the first filter circuit 01; the voltage conversion circuit 02 is used to convert the first power supply voltage into a second power supply voltage for output;

[0038] The second filtering circuit 03 is connected to the output end of the voltage conversion circuit 02 and the power supply output end respectively; the second filtering circuit 03 is used for filtering the second power supply voltage and then outputting it.

[0039] It should be noted that the power supply circuit of the existing low-frequency reader generally performs voltage conversion and power supply through a switching power supply circuit. Among them, the switching frequency of the power supply circuit of the existing low-frequency reader is relatively low, close to the radio frequency frequency of the low-frequency reader. For example, when the switching frequency is 150kHz, the power supply circuit is prone to generate low-frequency power ripple. Since the radio frequency signal between the low-frequency reader and the RFID electronic tag is also a low-frequency signal, with a frequency range of 125kHz to 134.2kHz, when the low-frequency reader is working, the low-frequency power ripple is prone to interfere with the low-frequency radio frequency signal, resulting in impure low-frequency radio frequency signals. Especially when the RFID electronic tag is far away from the low-frequency reader, the low-frequency radio frequency signal is extremely weak, and affected by the low-frequency power ripple, the low-frequency reader cannot effectively sense the information of the RFID electronic tag.

[0040] In this embodiment, the first power supply voltage is filtered by the first filtering circuit 01. The first filtering circuit 01 can filter out the noise and ripple of the first power supply voltage, ensure that the voltage input by the voltage conversion circuit 02 has a high quality, and help provide a relatively stable and clean power supply. The voltage conversion circuit 02 can convert the first power supply voltage into a second power supply voltage output. It should be noted that the voltage conversion circuit 02 can be designed with a switching power supply whose switching frequency is much higher than the frequency range of the low-frequency RF signal, such as a switching power supply circuit with a switching frequency of 2MHz, so as to avoid outputting low-frequency power supply ripple. The second filtering circuit 03 can filter the second power supply voltage and output it to the power supply output terminal. The second filtering circuit 03 can effectively filter out the parasitic ripple and high-frequency noise of the second power supply voltage, so that the power supply output terminal obtains a more stable and clean second power supply voltage. In this way, this embodiment provides power supply through the voltage conversion circuit 02, which can reduce the generation of low-frequency power supply ripple, and the parasitic ripple of the second power supply voltage is filtered out by the second filtering circuit 03, thereby reducing the transmission and reception interference caused by the low-frequency power supply ripple to the low-frequency radio frequency signal of the low-frequency reader, and increasing the distance at which the low-frequency reader effectively senses the RFID electronic tag.

[0041] In the utility model, the first power supply voltage is filtered by the first filter circuit 01. The first filter circuit 01 can filter out the noise and ripple of the first power supply voltage, ensure that the voltage input by the voltage conversion circuit 02 has a high quality, and help provide a relatively stable and clean power supply. The voltage conversion circuit 02 can convert the first power supply voltage into a second power supply voltage output. It should be noted that the voltage conversion circuit 02 can be designed with a switching power supply whose switching frequency is much higher than the frequency range of the low-frequency radio frequency signal, such as a switching power supply circuit with a switching frequency of 2Mhz, so as to avoid outputting low-frequency power supply ripple. The second filter circuit 03 can filter the second power supply voltage and output it to the power supply output end. The second filter circuit 03 can effectively filter out the parasitic ripple and high-frequency noise of the second power supply voltage, so that the power supply output end obtains a more stable and clean second power supply voltage. In this way, the utility model provides power supply through the voltage conversion circuit 02, which can reduce the generation of low-frequency power supply ripple, and the parasitic ripple of the second power supply voltage is filtered out by the second filtering circuit 03, thereby reducing the transmission and reception interference caused by the low-frequency power supply ripple to the low-frequency radio frequency signal of the low-frequency reader, and increasing the distance at which the low-frequency reader effectively senses the RFID electronic tag.

[0042] Further, in an embodiment of the present invention, if Figure 2 As shown, the voltage conversion circuit 02 includes an SCT2400 chip U1.

[0043] It should be noted that the power supply circuit of the existing low-frequency reader generally uses the LM2596R-12 chip as the voltage conversion chip. Among them, the switching frequency of the LM2596R-12 chip is 150khz (close to the RF frequency of the low-frequency reader 134.2kHz). Due to the close frequency, the parasitic ripple on the output power of the existing power supply circuit is easy to interfere with the purity of the RF signal of the low-frequency reader, thereby affecting the sensing distance.

[0044] In this embodiment, the first power supply voltage can be 24V, and the second power supply voltage can be 12V. The SCT2400 chip U1 can be used to convert 24V into 12V output. When the output voltage of the SCT2400 chip U1 is 12V, the ripple of the output voltage can be reduced to less than 0.1% of the output. Among them, the switching frequency of the SCT2400 chip U1 is 2MHz, which is far away from the radio frequency frequency of the low-frequency reader 134.2kHz. Due to the great difference in frequency, the radio frequency signal of the low-frequency reader is not easily interfered by the parasitic ripple of the output power supply of the SCT2400 chip U1. In this way, this embodiment can reduce the interference of the output ripple on the operation of the low-frequency reader and increase the distance of the low-frequency reader to effectively sense the RFID electronic tag. In this embodiment, the use of the SCT2400 chip can enhance the effective sensing distance of the low-frequency reader from 30cm to a stable 45cm compared to the LM2596R-12 chip.

[0045] Further, in an embodiment of the present invention, if Figure 2 As shown, the first filter circuit 01 includes a first capacitor C1, a second capacitor C2 and a third capacitor C3; the input end of the first filter circuit 01, one end of the first capacitor C1, one end of the second capacitor C2, and one end of the third capacitor C3 are connected to the VIN pin of the SCT2400 chip U1; the other end of the first capacitor C1, the other end of the second capacitor C2 and the other end of the third capacitor C3 are grounded.

[0046] In this embodiment, the filter circuit formed by the first capacitor C1, the second capacitor C2 and the third capacitor C3 can effectively filter out the noise and ripple of the first power supply voltage, which is conducive to providing a more stable and clean power supply to the SCT2400 chip U1.

[0047] Further, in an embodiment of the present invention, if Figure 2 As shown, the second filtering circuit 03 includes a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6 and a first inductor L1; one end of the fourth capacitor C4 and one end of the first inductor L1 are connected to the SW pin of the SCT2400 chip U1; the other end of the fourth capacitor C4 is connected to the BST pin of the SCT2400 chip U1; the other end of the first inductor L1, one end of the fifth capacitor C5, and one end of the sixth capacitor C6 are connected to the output end of the second filtering circuit 03; the other end of the fifth capacitor C5 and the other end of the sixth capacitor C6 are grounded.

[0048] In this embodiment, the filter circuit formed by the fourth capacitor C4, the fifth capacitor C5, the sixth capacitor C6 and the first inductor L1 can effectively filter out the noise and ripple of the second power supply voltage, which is conducive to the SCT2400 chip U1 outputting a more stable and clean power supply.

[0049] Further, in an embodiment of the present invention, if Figure 2 As shown, the voltage conversion circuit 02 also includes an enable input terminal, a first resistor R1, a first switch tube Q1 and a second resistor R2; one end of the first resistor R1 is connected to the VIN pin of the SCT2400 chip U1; the other end of the first resistor R1 and the EN pin of the SCT2400 chip U1 are connected to the first end of the first switch tube Q1; the second end of the first switch tube Q1 and one end of the second resistor R2 are grounded; the other end of the second resistor R2 and the controlled end of the first switch tube Q1 are connected to the enable input terminal.

[0050] In this embodiment, the SCT2400 chip U1 can be controlled to work or stop working by inputting a high level or a low level at the enable input terminal. When a high level is input to the enable input terminal, the first switch tube Q1 is turned on, and the SCT2400 chip U1 has no input and stops working. When a high level is input to the enable input terminal, the first switch tube Q1 is turned off, and the SCT2400 chip U1 has input and works. Among them, the SCT2400 chip U1 can convert a 24V power supply into a 12V power supply, and the high level input to the enable input terminal can be a 12V power supply. In this way, this embodiment can control the SCT2400 chip U1 through the input level of the enable input terminal, which is beneficial to the safe use of the circuit.

[0051] Further, in an embodiment of the present invention, if Figure 2 As shown, the voltage conversion circuit 02 also includes a third resistor R3, a fourth resistor R4 and a seventh capacitor C7; one end of the third resistor R3, one end of the seventh capacitor C7 are connected to the other end of the first inductor L1; the other end of the third resistor R3, the other end of the seventh capacitor C7, and one end of the fourth resistor R4 are connected to the FB pin of the SCT2400 chip U1; the other end of the fourth resistor R4 is grounded.

[0052] In this embodiment, the negative feedback circuit formed by the third resistor R3, the fourth resistor R4 and the seventh capacitor C7 can reduce the output voltage when the SCT2400 chip U1 detects through the FB pin that the output voltage is greater than the preset voltage, and can increase the output voltage when the output voltage is detected to be less than the preset voltage. In this way, when the preset voltage is 12V, this embodiment can stably output a power supply voltage of 12V.

[0053] Further, in an embodiment of the present invention, if Figure 2 As shown, the power supply circuit also includes a fifth resistor R5, a sixth resistor R6 and a seventh resistor R7; one end of the fifth resistor R5 is connected to the power input end, and the other end of the fifth resistor R5 is connected to one end of the third capacitor C3; one end of the sixth resistor R6 is connected to the power output end, and the other end of the sixth resistor R6 is connected to the other end of the first inductor L1; one end of the seventh resistor R7 is connected to the controlled end of the first switch tube Q1, and the other end of the seventh resistor R7 is connected to the enable input end.

[0054] In this embodiment, the fifth resistor R5, the sixth resistor R6 and the seventh resistor R7 can play the role of current limiting and protection.

[0055] Further, in an embodiment of the present invention, if Figure 2 As shown, the first switch tube Q1 is a triode; the base of the triode is connected to the other end of the second resistor R2, the collector of the triode is connected to the EN pin of the SCT2400 chip U1, and the emitter of the triode is grounded.

[0056] In this embodiment, the triode used as the first switch tube Q1 has the advantages of being easy to drive, having good stability and fast response.

[0057] The utility model also proposes a low-frequency reader, which includes a power supply circuit. The specific structure of the power supply circuit refers to the above embodiment. Since the low-frequency reader adopts all the technical solutions of all the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0058] The utility model also proposes a radio frequency identification component, which includes an RFID electronic tag and a low-frequency reader. The specific structure of the low-frequency reader refers to the above embodiment. Since the radio frequency identification component adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here one by one.

[0059] The above description is only an optional embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A power supply circuit, characterized in that: Applied to a low frequency reader, the power supply circuit comprises: A power input terminal, used for inputting a first power voltage; A power supply output terminal, used for outputting a second power supply voltage; a first filter circuit, the first filter circuit being connected to the power input terminal; the first filter circuit being used for filtering the first power supply voltage and then outputting it; A voltage conversion circuit, wherein an input end of the voltage conversion circuit is connected to the first filter circuit; the voltage conversion circuit is used to convert the first power supply voltage into the second power supply voltage for output; The second filter circuit is connected to the output end of the voltage conversion circuit and the power supply output end respectively; the second filter circuit is used for filtering the second power supply voltage and then outputting it.

2. The power supply circuit according to claim 1, characterized in that: The voltage conversion circuit includes an SCT2400 chip.

3. The power supply circuit according to claim 2, characterized in that: The first filtering circuit includes a first capacitor, a second capacitor and a third capacitor; the input end of the first filtering circuit, one end of the first capacitor, one end of the second capacitor, and one end of the third capacitor are connected to the VIN pin of the SCT2400 chip; the other end of the first capacitor, the other end of the second capacitor, and the other end of the third capacitor are grounded.

4. The power supply circuit according to claim 3, characterized in that: The second filtering circuit includes a fourth capacitor, a fifth capacitor, a sixth capacitor and a first inductor; one end of the fourth capacitor and one end of the first inductor are connected to the SW pin of the SCT2400 chip; the other end of the fourth capacitor is connected to the BST pin of the SCT2400 chip; the other end of the first inductor, one end of the fifth capacitor, and one end of the sixth capacitor are connected to the output end of the second filtering circuit; the other end of the fifth capacitor and the other end of the sixth capacitor are grounded.

5. The power supply circuit according to claim 4, characterized in that: The voltage conversion circuit also includes an enable input terminal, a first resistor, a first switch tube and a second resistor; one end of the first resistor is connected to the VIN pin of the SCT2400 chip; the other end of the first resistor, the EN pin of the SCT2400 chip and the first end of the first switch tube are connected; the second end of the first switch tube and one end of the second resistor are grounded; the other end of the second resistor, the controlled end of the first switch tube and the enable input terminal are connected.

6. The power supply circuit according to claim 5, characterized in that: The voltage conversion circuit also includes a third resistor, a fourth resistor and a seventh capacitor; one end of the third resistor and one end of the seventh capacitor are connected to the other end of the first inductor; the other end of the third resistor, the other end of the seventh capacitor and one end of the fourth resistor are connected to the FB pin of the SCT2400 chip; the other end of the fourth resistor is grounded.

7. The power supply circuit according to claim 6, characterized in that: The power supply circuit also includes a fifth resistor, a sixth resistor and a seventh resistor; one end of the fifth resistor is connected to the power input end, and the other end of the fifth resistor is connected to one end of the third capacitor; one end of the sixth resistor is connected to the power output end, and the other end of the sixth resistor is connected to the other end of the first inductor; one end of the seventh resistor is connected to the controlled end of the first switch tube, and the other end of the seventh resistor is connected to the enable input end.

8. The power supply circuit according to claim 5, characterized in that: The first switch tube is a triode; the base of the triode is connected to the other end of the second resistor, the collector of the triode is connected to the EN pin of the SCT2400 chip, and the emitter of the triode is grounded.

9. A low frequency reader, characterized in that: The low frequency reader comprises the power supply circuit according to any one of claims 1 to 8.

10. A radio frequency identification component, characterized in that: The radio frequency identification component includes an RFID electronic tag and the low frequency reader as claimed in claim 9.

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