Analog signal protection circuit, audio playing device and audio and video playing device

Abstract

The utility model provides an analog signal protection circuit, audio frequency playing equipment and audio -video playing equipment. Analog signal protection circuit includes: analog signal input end, analog signal output end, first switch unit, second switch unit, first protection circuit and second protection circuit. First switch unit is conducted when first signal is accessed in analog signal input end, and the passage of external power supply with analog signal output end is conducted, first protection circuit is conducted when the current value of first current flowing through first switch unit is greater than first setting, and the current of controlled end of first switch unit is shunted, second switch unit is conducted between the passage of analog signal output end and ground when second signal is accessed in analog signal input end, and second protection circuit is conducted when the current value of second current flowing through second switch unit is greater than second setting, and the current of controlled end of second switch unit is shunted.

Description

TECHNICAL FIELD

[0001] The utility model relates to analog signal protection technical field, especially relate to an analog signal protection circuit, audio frequency playing equipment and audio and video playing equipment. BACKGROUND

[0002] At present, in the music player equipment, in order to enrich the function, analog signal input will be increased, and the conventional practice is that analog signal application chip carries out analog signal protection detection, but the price of chip is relatively expensive, and the project cost will be increased invisibly. INVENTION CONTENTS

[0003] The utility model discloses a kind of analog signal protection circuits, to provide low-cost analog signal protection circuit.

[0004] To achieve the above object, the analog signal protection circuit provided by the utility model, the analog signal protection circuit includes:

[0005] Analog signal input end, analog signal output end, first switch unit, second switch unit, first protection circuit and second protection circuit;

[0006] The controlled end of the first switch unit and the controlled end of the second switch unit are connected with the analog signal input end;The input end of the first switch unit is connected with external power supply;The output end of the second switch unit is grounded;The second protection circuit is connected in parallel between the controlled end and the output end of the second switch unit;The first protection circuit is connected in parallel between the controlled end and the output end of the first switch unit;The output end of the first switch unit and the input end of the second switch unit are connected with the analog signal output end;

[0007] The first switch unit is used for turning on the passageway between the external power supply and the analog signal output end when the first signal is connected to the analog signal input end;

[0008] The first protection circuit is used for turning on when the current value of the first current flowing through the first switch unit is greater than the first set value, and shunting the current flowing into the controlled end of the first switch unit;

[0009] The second switch unit is used for turning on the passageway between the analog signal output end and the ground when the second signal is connected to the analog signal input end;

[0010] The second protection circuit is used for turning on when the current value of the second current flowing through the second switch unit is greater than the second set value, and shunting the current flowing out of the controlled end of the second switch unit.

[0011] The utility model discloses an audio frequency playing equipment, the audio frequency playing equipment includes the analog signal protection circuit.

[0012] The utility model discloses an audio frequency playing equipment, the audio frequency playing equipment includes the analog signal protection circuit. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to make the technical scheme of the embodiments of the utility model or the prior art clearer, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description, and obviously, the drawings in the following description are only some embodiments of the utility model, and for those skilled in the art, other drawings can be obtained according to the structure shown in these drawings without creative labor.

[0014] Figure 1 It is the structural schematic diagram of analog signal protection circuit one embodiment of the utility model,

[0015] Figure 2 It is the structural schematic diagram of analog signal protection circuit first embodiment of the utility model,

[0016] Figure 3 It is the structural schematic diagram of analog signal protection circuit second embodiment of the utility model,

[0017] Figure 4 It is the first structural schematic diagram of analog signal protection circuit third embodiment of the utility model,

[0018] Figure 5 It is the second structural schematic diagram of analog signal protection circuit third embodiment of the utility model,

[0019] Figure 6 It is the third structural schematic diagram of analog signal protection circuit third embodiment of the utility model.

[0020] EXPLANATION OF DRAWINGS:

[0021]

[0022] The utility model purposes realization, functional characteristics and advantages will be further explained by combining with the embodiment, and referring to the drawings. DETAILED DESCRIPTION

[0023] The technical scheme in the embodiments of the utility model will be clearly and completely described in the following by combining with the drawings in the embodiments of the utility model, and obviously, the described embodiments are only some embodiments of the utility model, not all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor belong to the range of the utility model protection.

[0024] It should be noted that all the directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative positional relationship, movement condition, etc. between the components in a certain specific posture (as shown in the drawings), and if the specific posture changes, the directional indications will also change accordingly.

[0025] In the present application, unless otherwise explicitly specified and limited, the terms "connection", "fixing", etc. should be understood in a broad sense, for example, "fixing" can be fixed connection, or detachable connection, or integral; can be mechanical connection, or electrical connection; can be direct connection, or indirect connection through intermediate medium; can be internal communication of two elements or interaction relationship between two elements, unless otherwise explicitly limited. For ordinary skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0026] In addition, in the present application, the description such as "first", "second", etc. is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that ordinary skilled in the art can realize it, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, and is not within the protection scope required by the present application.

[0027] The utility model provides a kind of analog signal protection circuit, referring to Figure 1 , the analog signal protection circuit includes:

[0028] analog signal input terminal 10, analog signal output end 60, first switch unit 40, second switch unit 50, first protection circuit 20 and second protection circuit 30;

[0029] The controlled end of the first switch unit 40 and the controlled end of the second switch unit 50 are connected to the analog signal input terminal 10;The input end of the first switch unit 40 is connected to external power supply;The output end of the second switch unit 50 is grounded;The second protection circuit 30 is connected in parallel between the controlled end and the output end of the second switch unit 50;The first protection circuit 20 is connected in parallel between the controlled end and the output end of the first switch unit 40;The output end of the first switch unit 40 and the input end of the second switch unit 50 are connected to the analog signal output end 60;

[0030] The first switch unit 40 is configured to turn on a path between the external power supply and the analog signal output end when the analog signal input end 10 is connected to the first signal.

[0031] The first protection circuit 20 is configured to turn on when the current value of the first current flowing through the first switch unit 40 is greater than the first set value, and to shunt the current flowing into the controlled end of the first switch unit 40.

[0032] The second switch unit 50 is configured to turn on a path between the analog signal output end and the ground when the analog signal input end 10 is connected to the second signal.

[0033] The second protection circuit 30 is configured to turn on when the current value of the second current flowing through the second switch unit 50 is greater than the second set value, and to shunt the current flowing out of the controlled end of the second switch unit 50.

[0034] It should be noted that the analog signal input end 10 is connected to an analog signal, which can be positive or negative, i.e. the first signal and the negative analog signal. The controlled end of the first switch unit 40 and the controlled end of the second switch unit 50 are connected to the analog signal input end 10. The first switch unit 40 is configured to turn on when the analog signal input end 10 is connected to the first signal. The second switch unit 50 is configured to turn on when the analog signal input end 10 is connected to the second signal.

[0035] It is easy to understand that the first signal can control the first switch unit 40 to turn on, so that the current output by the external power supply flows through the first switch unit 40 into the analog signal output end 60. The amplitude of the first signal can change the degree of conduction of the first switch unit 40, thereby changing the current value flowing through the first switch unit 40. The second switch unit 50 is turned off when the analog signal input end 10 is connected to the first signal, so that when the analog signal input end 10 is connected to the first signal, all the current flowing through the first switch unit 40 enters the analog signal output end 60.

[0036] If the first switch unit 40 includes a current-controlled device, the current value flowing into the controlled end of the first switch unit 40 directly determines the current value output by the external power supply to the analog signal output end 60 through the first switch unit 40. If the current value of the first current flowing through the first switch unit 40 is too large, it may damage the electronic device connected to the analog signal output end 60. The first protection circuit 20 detects the first current value flowing through the first switch unit 40, turns on when the first current value is greater than the first set value, and shunts the current flowing into the controlled end of the first switch unit 40, thereby reducing the current value flowing into the controlled end of the first switch unit 40, reducing the degree of conduction of the first switch unit 40, and reducing the current value of the first current.

[0037] If the first switch unit 40 comprises a voltage-type control device, the voltage value applied to the controlled end of the first switch unit 40 directly determines the current value outputted by the external power supply to the analog signal output end 60 through the first switch unit 40. The first protection circuit 20 detects the first current value flowing through the first switch unit 40, and turns on when the first current value is greater than the first set value, divides the voltage of the controlled end of the first switch unit 40, and reduces the voltage value at the controlled end of the first switch unit 40, thereby reducing the on degree of the first switch unit 40 and reducing the current value of the first current. It should be noted that the first switch unit 40 is used to control the opening and closing of the path between the external power supply and the analog signal output end 60. Specifically, the first switch unit 40 is used to switch or close through the electrical signal at the controlled end thereof. The analog signal input end 10 is connected to the controlled end of the first switch unit 40. The first switch unit 40 can comprise a switching device, and the controlled end of the first switch unit 40 is the control end of the switching device.

[0038] The negative analog signal can control the second switch unit 50 to turn on, so that the analog signal output end 60 outputs a current flowing through the second switch unit 50 to the ground. The amplitude of the second signal can change the on degree of the second switch unit 50, thereby changing the current value of the second current flowing through the second switch unit 50. The first switch unit 40 is turned off when the analog signal input end 10 is connected to the second signal, so that the current outputted by the analog signal output end 60 flows through the second switch unit 50 to the ground when the analog signal input end 10 is connected to the second signal.

[0039] If the second switch unit 50 comprises a current-type control device, the current value flowing out of the controlled end of the second switch unit 50 directly determines the current value outputted by the analog signal output end 60 to the ground through the second switch unit 50. If the current value of the second current flowing through the second switch unit 50 is too large, it may damage the equipment. In addition, due to the presence of the current-type control device, if the current value of the second current is large, the current value flowing out of the controlled end of the second switch unit 50 will also be large, which may damage the electronic equipment connected to the analog signal input end 10. It should be noted that the second switch unit 50 is used to control the opening and closing of the path between the analog signal output end 60 and the ground. Specifically, the second switch unit 50 is used to switch or close through the electrical signal at the controlled end thereof. The analog signal input end 10 is connected to the controlled end of the second switch unit 50. The second switch unit 50 can comprise a switching device, and the controlled end of the second switch unit 50 is the control end of the switching device.

[0040] The second protection circuit 30 detects the second current value flowing through the second switch unit 50, and turns on when the second current value is greater than the second set value, shunts the current flowing into the controlled end of the second switch unit 50, reduces the current value of the current flowing into the controlled end of the second switch unit 50, thereby reducing the on degree of the second switch unit 50 and reducing the current value of the second current.

[0041] If the second switch unit 50 includes a voltage type control device, the voltage value applied to the controlled end of the second switch unit 50 directly determines the current value of the current output from the analog signal output end 60 to the ground through the second switch unit 50. The second protection circuit 30 detects the second current value flowing through the second switch unit 50, and turns on when the second current value is greater than the second set value, shunts the voltage of the controlled end of the second switch unit 50, reduces the voltage value at the controlled end of the second switch unit 50, thereby reducing the on degree of the second switch unit 50 and reducing the current value of the second current.

[0042] It should be noted that the first set value and the second set value are determined by the researchers according to the circuit design parameters.

[0043] The first protection circuit 20 needs to detect the current value of the first current, and determine whether to shunt the current of the controlled end of the first switch unit 40 according to the comparison relationship between the first current value and the first set value. It is easy to understand that the present scheme aims to provide a low-cost analog signal protection circuit; the present scheme does not use a chip, but only uses simple components to complete the construction of the analog signal protection circuit, for example: a specific combination of resistors, capacitors, inductors and switching devices.

[0044] In an example, the first protection circuit 20 includes a control device, and the first switch unit 40 includes a switching device and a first load unit arranged in series; the first protection circuit 20 obtains the potential of the first load unit and inputs it into the controlled end of the control device; it is easy to understand that the potential of the first load unit is in a positive correlation with the current value of the first current flowing through the first switch unit 40; correspondingly, the potential difference between the control device will input the current of the controlled end to meet the control condition of the control device when the control device is a current type control device. It should be noted that the first set value is related to the on condition of the control device in the first protection circuit 20, and the current value of the first current corresponding to the on condition of the control device can be taken as the first set value.

[0045] Similarly, the second protection circuit 30 obtains the control voltage or control current from the second switch unit 50, so that it turns on when the current value of the second current flowing through the second switch unit 50 is greater than the second set value, and shunts the current flowing out of the controlled end of the second switch unit 50.

[0046] The utility model provides a kind of analog signal protection circuit, the analog signal protection circuit includes: analog signal input end 10, analog signal output end 60, first switch unit 40, second switch unit 50, first protection circuit 20 and second protection circuit 30;The controlled end of the analog signal input end 10 is connected with the controlled end of the first switch unit 40 and the second switch unit 50;The input end of the first switch unit 40 is connected with external power supply;The output end of the second switch unit 50 is grounded;Second protection circuit 30 is arranged between the controlled end and the output end of the second switch unit 50 in parallel;The first protection circuit 20 is arranged between the controlled end and the output end of the first switch unit 40 in parallel;The output end of the first switch unit 40 and the input end of the second switch unit 50 are connected with the analog signal output end 60;The first switch unit 40 is used to turn on the passageway between the external power supply and the analog signal output end when the first signal is connected to the analog signal input end 10;The first protection circuit 20 is used to turn on when the current value of the first current flowing through the first switch unit 40 is greater than first set value, and the current flowing into the controlled end of the first switch unit 40 is shunted;The second switch unit 50 is used to turn on the passageway between the analog signal output end and ground when the second signal is connected to the analog signal input end 10;Second protection circuit 30 is used to turn on when the current value of the second current flowing through the second switch unit 50 is greater than second set value, and the current flowing out of the controlled end of the second switch unit 50 is shunted.The utility model uses first protection circuit 20 and second protection circuit 30, respectively when the first current is greater than the first set value and the second current is greater than the second set value, the controlled end current of corresponding switch unit is shunted, and the protection of circuit when input analog signal is oversize is satisfied.

[0047] Refer to Figure 2 In the first embodiment of the utility model, the first switch unit 40 includes:

[0048] First NPN triode and first resistance R1;

[0049] The first NPN triode and first resistance R1 are arranged in series between the external power supply and the analog signal output end 60;The controlled end of the first NPN triode is connected with the analog signal input end 10;The collector of the first NPN triode is connected with the external power supply;

[0050] The first protection circuit 20 includes: second NPN triode;

[0051] The controlled end of the second NPN triode is connected with the end of the first resistance R1 and the first NPN triode, the collector is connected with the base of the first NPN triode, and the emitter is connected with the analog signal output end 60.

[0052] It should be noted that the collector of the first NPN transistor is connected to an external power supply, and the emitter is connected to the first terminal of the first resistor R1; the second terminal of the first resistor R1 is connected to the analog signal output terminal 60. For example... Figure 2 As shown, the base of the second NPN transistor is connected to the first terminal of the first resistor R1, and the emitter is connected to the second terminal of the first resistor R1. The first current flowing through the first NPN transistor creates a voltage difference across the first resistor R1, meaning there is a voltage between the base and emitter of the second NPN transistor. If this voltage is greater than the turn-on voltage of the second NPN transistor, the second NPN transistor turns on, shunting the current at the base of the first NPN transistor, thus protecting the circuit when the first signal is too large. When the output current of the first NPN transistor is small, the voltage drop across the first resistor R1 is less than the turn-on voltage, and the second NPN transistor turns off, not affecting the operation of the circuit.

[0053] In other examples, the second NPN transistor can be replaced with a MOSFET, whose drain is connected to the base of the first NPN transistor, whose source is connected to the analog signal output terminal 60, and whose gate is connected to the first end of the first resistor R1.

[0054] However, it should be noted that, compared to MOSFETs, the second NPN transistor used in this solution, after being turned on, has a multiple relationship between the current between the base and emitter and the current between the collector and emitter, making it easier to determine the resistance value of the first resistor R1 based on the transistor's on-state voltage.

[0055] The second switching unit 50 includes:

[0056] First PNP transistor and second resistor R2;

[0057] The second resistor R2 is connected in series between the emitter of the first PNP transistor and the analog signal output terminal 60; the collector of the first PNP transistor is grounded, and the base is connected to the analog signal input terminal 10;

[0058] The second protection circuit 30 includes: a third NPN transistor, a fourth NPN transistor, and a third resistor R3;

[0059] The collector of the third NPN transistor is connected to the base of the first PNP transistor, the base is connected to the analog signal input terminal 10, and the emitter is connected to the first end of the third resistor R3; the collector of the fourth NPN transistor is connected to the analog signal input terminal 10, the base is connected to the first end of the third resistor R3, and the emitter is connected to the second end of the third resistor R3 and grounded.

[0060] It is to be noted that the emitter of the first PNP triode is connected to the second resistor R2; the first PNP triode is turned on when the voltage difference between the base and the emitter thereof is less than the turn-on voltage, that is, when the voltage amplitude of the negative analog signal inputted by the analog signal input end 10 is less than the turn-on voltage of the first PNP triode, the first PNP triode is turned on. After being turned on, the current outputted by the analog signal output end 60, part of which flows out from the collector of the first PNP triode through the base, and the other part of which flows out from the collector through the emitter; wherein the current flowing out from the emitter and the current flowing out from the base are in a multiple relationship.

[0061] The current flowing out from the base of the first PNP triode flows through the third NPN triode and the third resistor R3 to the ground; wherein the base of the third NPN triode is connected to the analog signal input end 10, that is, the value of the current flowing between the collector and the emitter of the third NPN triode is determined by the negative analog signal inputted by the analog signal input end 10. The negative analog signal can change the current flowing out from the base of the first PNP triode by controlling the current flowing between the collector and the emitter of the third NPN triode, and further change the value of the current outputted by the analog signal input end 10, that is, change the size of the negative current at the analog signal output end 60.

[0062] The base of the fourth NPN triode is connected to the first end of the third resistor R3, and the third resistor R3 is connected in series with the third NPN triode. Since the current flowing through the emitter of the first PNP triode and the current flowing into the collector of the third NPN triode are in a multiple relationship, and the current flowing through the third NPN triode is controlled by the negative analog signal, when the current value of the second current flowing through the first PNP triode is greater than the second set value, the voltage drop generated by the current flowing through the third NPN triode on the third resistor R3 is greater than the turn-on voltage of the fourth NPN triode, so that the fourth NPN triode shunts the current value at the base of the third NPN triode, causing the current value of the second current to decrease, thereby completing the protection circuit when the amplitude of the negative analog signal is too large.

[0063] It is easy to understand that the switching devices in the first switching unit 40 and the second switching unit 50 all have turn-on voltages; and the amplitude of the voltage inputted by the analog signal input end 10 can be insufficient to turn on the first switching unit 40 and the second switching unit 50, thereby causing the current at the analog signal output end 60 to appear crossover distortion phenomenon.

[0064] To solve this problem, the second embodiment of the utility model is provided, and the analog signal protection circuit further comprises a bias circuit 70.

[0065] The first end of the bias circuit 70 is connected to an external power supply and the controlled end of the first switch unit 40, and the second end is connected to the controlled end of the second switch unit 50.

[0066] The bias circuit 70 is used to provide the first switch unit 40 and the second switch unit 50 with first bias and second bias respectively, so as to reduce the on-voltage of the first switch unit and the second switch unit.

[0067] It should be noted that the bias circuit 70 applies a certain forward bias to the controlled end of the first switch unit 40 and the second switch unit 50, specifically, the first switch unit is provided with the first bias, and the second switch unit is provided with the second bias, so that the first switch unit 40 and the second switch unit 50 are slightly turned on in the static state; thereby avoiding the situation that the first switch unit 40 and the second switch unit 50 are not turned on under the action of the analog signal, and the crossover distortion phenomenon of the current at the analog signal output end 60 can be avoided.

[0068] The bias circuit 70 comprises:

[0069] The fourth resistor R4, the fifth resistor R5 and the fifth NPN transistor;

[0070] The collector of the fifth NPN transistor is connected to the external power supply and the controlled end of the first switch unit 40, and the emitter is connected to the controlled end of the second switch unit 50; the fourth resistor R4 and the fifth resistor R5 are connected in series between the collector and the emitter of the fifth NPN transistor; the base of the fifth NPN transistor is connected to one end of the fourth resistor R4 and the fifth resistor R5.

[0071] As shown in Figure 3 The fourth resistor R4 and the fifth resistor R5 form a resistance voltage dividing circuit; the base of the fifth NPN transistor is connected to the first end of the fifth resistor R5, and the emitter is connected to the second end of the fifth resistor R5. Because there is a voltage difference in the fifth resistor R5, and the value of the voltage difference is equal to the voltage difference between the base and the emitter of the fifth NPN transistor; the value of the fourth resistor R4 and the fifth resistor R5 can be set to change the voltage difference, so that the fifth NPN transistor maintains the on state.

[0072] The collector of the fifth NPN triode is connected with the external power supply and the controlled end of the first switch unit 40, and the emitter is connected with the controlled end of the second switch unit 50. It should be noted that when the potential of the emitter changes, the voltage and current of the external power supply to the base of the fifth NPN triode change, and the current value flowing through the collector of the fifth NPN triode and the current value output to the controlled end of the first switch unit 40 are adjusted accordingly. For example, if the potential of the emitter rises, the voltage difference across the fifth resistor R5 becomes smaller, and the current flowing through the collector of the fifth NPN triode decreases, thereby increasing the current value output by the external power supply to the controlled end of the first switch unit 40.

[0073] Referring to Figure 3 In the third embodiment of the utility model, the collector of the fifth NPN triode is connected with the external power supply and the base of the first NPN triode, and the emitter is connected with the base of the first PNP triode and the collector of the fourth NPN triode. The emitter of the fourth NPN triode is grounded through the third resistor R3, and the base is connected with the analog signal input end 10.

[0074] The external power supply provides a forward bias voltage for the first NPN triode and the first PNP triode through the bias circuit 70, so that they operate at an appropriate operating point, thereby avoiding signal distortion and performance degradation.

[0075] When the amplitude of the first signal input to the analog signal input end 10 becomes larger, the current flowing through the third resistor R3 increases, and the voltage at the fifth resistor R5 rises, so that the voltage difference across the fifth resistor R5 decreases, thereby reducing the current value of the output current of the external power supply flowing through the collector of the fifth NPN triode, and correspondingly increasing the current value output to the base of the first NPN triode.

[0076] The process is similar when the amplitude of the second signal becomes larger.

[0077] It should be noted that the analog signal input end 10 inputs an external analog signal, and the amplitude of the external analog signal may be small and the driving ability may be weak, so that the first switch unit 40 and the second switch unit 50 cannot be successfully controlled to turn on and turn off.

[0078] Referring to Figure 4 In the third embodiment of the utility model, the analog signal protection circuit further comprises a driving circuit 80.

[0079] The input end of the driving circuit 80 is connected with the analog signal input end 10, and the output end of the driving circuit 80 is connected with the output end of the bias circuit 70 and the controlled end of the second switch unit 50.

[0080] The driving circuit 80 is configured to amplify the analog current of the analog signal input end 10 and output the amplified analog current.

[0081] Specifically, the driving circuit 80 can be a current amplification driving circuit 80, or a thyristor control driving circuit 80, a relay control driving circuit 80, and a MOS tube control driving circuit 80, and the like power amplification driving circuit 80.

[0082] The current amplification driving circuit 80 can convert the input small current signal into an output large current signal by using the current amplification characteristics of the transistor and the like electronic elements. In the process of amplifying the power, the power amplification driving circuit 80 is accompanied by the amplification of the current; because the power is the product of voltage and current, when the output power is increased, the output of the current often needs to be increased accordingly.

[0083] It is easy to understand that the present scheme needs to provide a low-cost analog signal protection circuit, and under this goal, the current amplification driving circuit 80 is more in line with the needs of the present scheme.

[0084] The current amplification circuit can use NPN triode or PNP triode for current signal amplification.

[0085] In an example, the driving circuit 80 includes a Darlington tube.

[0086] The base of the Darlington tube is connected to the analog signal input end 10, the collector is connected to the second end of the bias circuit 70 and the controlled end of the second switch unit 50, and the emitter is connected to the second protection circuit 30.

[0087] It is easy to understand that the working principle of the Darlington tube is to connect the bases, collectors and emitters of multiple triodes according to certain rules to form an equivalent new triode. The amplification factor of this equivalent triode is the product of the amplification factors of the original multiple triodes, so its amplification factor is very high. Specifically, the collector of the front triode is connected to the collector of the rear triode, and the emitter of the front triode is connected to the base of the rear triode. After such connection, the output current of the front triode directly serves as the input current of the rear triode, thereby realizing current amplification.

[0088] The Darlington tube can amplify a small electrical signal and output a large electrical signal to drive the first switch unit 40 and the second switch unit 50. It should be noted that the amplification factor of the Darlington tube depends on the number of transistors and the amplification factor of a single transistor. The researchers can determine the range of the output current of the Darlington tube according to the first switch unit 40 and the second switch unit 50, and then determine the amplification factor of the Darlington tube in combination with the output current value of the analog signal, and the number of transistors and the amplification factor of the Darlington tube.

[0089] The Darlington tube can include two transistors, and the Darlington tube includes a sixth NPN transistor and a seventh NPN transistor.

[0090] The base of the sixth NPN transistor is connected to the analog signal input end 10, the collector of the sixth NPN transistor is connected to the second end of the bias circuit 70, the controlled end of the second switch unit 50 and the collector of the seventh NPN transistor, and the emitter of the seventh NPN transistor is connected to the second protection circuit 30.

[0091] Referring to Figure 4 , the base of the sixth NPN transistor is connected to the analog signal input end 10; the collector of the sixth NPN transistor and the collector of the seventh NPN transistor are connected, the emitter of the sixth NPN transistor is connected to the base of the seventh NPN transistor; the output current of the sixth NPN transistor serves as the input current value of the seventh NPN transistor, thereby realizing the amplification of the current of the analog signal input end 10.

[0092] The Darlington tube can also include a sixth resistor R6, the first end of the sixth resistor R6 is connected to the emitter of the sixth NPN transistor, and the second end is grounded. It is easy to understand that the seventh NPN transistor is grounded through the second protection circuit 30; the amplification factor of the Darlington tube can be changed by adjusting the resistance value of the sixth resistor R6; in addition, the sixth resistor R6 is also used to shunt the output circuit of the sixth NPN transistor to avoid damage to the seventh NPN transistor.

[0093] Referring to Figure 5 , in an example, the second protection circuit 30 includes a second NPN transistor, a fourth NPN transistor and a third resistor R3. In combination with the Darlington tube including a sixth NPN transistor, a seventh NPN transistor and a sixth resistor R6; it is easy to integrate the third NPN transistor into the Darlington tube, and use one NPN transistor to complete the current amplification and protection function, that is, use the third NPN transistor instead of the seventh NPN transistor. The integrated circuit connection relationship is as follows:

[0094] The collector of the third NPN triode is connected with the collector of the sixth NPN triode, the base of the first PNP triode and the emitter of the fifth NPN triode; the base of the third NPN triode is connected with the emitter of the sixth NPN triode and the first end of the sixth resistor R6, and the emitter is connected with the first end of the third resistor R3; the second end of the third resistor R3 and the second end of the sixth resistor R6 are grounded; the collector of the fourth NPN triode is connected with the analog signal input end 10 and the base of the sixth NPN triode.

[0095] The current output by the analog signal output end 60 is partially led to the ground through the first PNP triode and partially led to the ground through the third NPN triode and the third resistor R3; wherein the current value of the third NPN triode is controlled by the output current value of the sixth NPN triode, and the output current value of the sixth NPN triode is controlled by the first signal input by the analog signal input end 10. The first signal controls the output current of the third NPN triode by controlling the output current of the sixth NPN triode, so as to adjust the output current value of the first PNP triode and change the output current value of the analog signal output end 60. If the output current value of the first PNP triode is too large, specifically, when the second current flowing through the first PNP triode is greater than a second set value, the output current value of the second PNP triode is large, and the third resistor R3 outputs a voltage value to the fourth NPN triode under the action of the output current, so as to make the fourth NPN triode conductive, reduce the current value output by the sixth NPN triode to the third NPN triode, and thus reduce the output current value of the third NPN triode. When the output current value of the third NPN triode is reduced, the second current flowing through the first PNP triode is reduced, which leads to the reduction of the current value of the analog signal output end 60.

[0096] The analog signal protection circuit is constructed by using resistors and triodes, so that the circuit cost is reduced, and a low-cost analog signal protection circuit is provided.

[0097] The utility model discloses still propose a kind of audio playing equipment, and the audio playing equipment includes the analog signal protection circuit of the described.

[0098] The audio playing equipment can be a sound box, earphones and an audio player. In particular, the sound box includes a Bluetooth sound box and a WiFi wireless sound box, and the audio player includes an MP3 and an MP4.

[0099] The utility model discloses still propose a kind of audio and video playing equipment, and the audio and video playing equipment includes the analog signal protection circuit of the described.

[0100] The audio-video playing device can include a television, a DVD machine, a tablet computer, a notebook computer, a projector, and the like, which can display a picture and play audio.

[0101] The specific structure of the analog signal protection circuit refers to the above-mentioned embodiments, and since the audio playing device and the audio-video playing device adopt all the technical solutions of the above-mentioned embodiments, at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments are possessed, which will not be described one by one here.

[0102] The above-mentioned is only the optional embodiment of the present application, and does not limit the patent range of the present application, and any equivalent structural transformation made by using the content of the present application specification and drawings, or direct / indirect application in other related technical fields under the inventive concept of the present application is included in the patent protection range of the present application.

Claims

1. An analog signal protection circuit, characterized by, The analog signal protection circuit comprises: an analog signal input end, an analog signal output end, a first switch unit, a second switch unit, a first protection circuit and a second protection circuit; the analog signal input end is connected to the controlled end of the first switch unit and the controlled end of the second switch unit; the input end of the first switch unit is connected to an external power supply; the output end of the second switch unit is grounded; the second protection circuit is arranged in parallel between the controlled end and the output end of the second switch unit; the first protection circuit is arranged in parallel between the controlled end and the output end of the first switch unit; the output end of the first switch unit and the input end of the second switch unit are connected to the analog signal output end; the first switch unit is configured to turn on the path between the external power supply and the analog signal output end when the analog signal input end is connected to a first signal; the first protection circuit is configured to turn on when the current value of a first current flowing through the first switch unit is greater than a first set value, and to shunt the current flowing into the controlled end of the first switch unit; the second switch unit is configured to turn on the path between the analog signal output end and the ground when the analog signal input end is connected to a second signal; the second protection circuit is configured to turn on when the current value of a second current flowing through the second switch unit is greater than a second set value, and to shunt the current flowing out of the controlled end of the second switch unit.

2. The analog signal protection circuit of claim 1, wherein, The first switch unit comprises: a first NPN transistor and a first resistor; the first NPN transistor and the first resistor are arranged in series between the external power supply and the analog signal output end; the controlled end of the first NPN transistor is connected to the analog signal input end; the collector of the first NPN transistor is connected to the external power supply; the first protection circuit comprises a second NPN transistor; the controlled end of the second NPN transistor is connected to one end of the first resistor and the first NPN transistor, the collector is connected to the base of the first NPN transistor, and the emitter is connected to the analog signal output end.

3. The analog signal protection circuit of claim 2, wherein, The second switch unit comprises: a first PNP transistor and a second resistor; the second resistor is arranged in series between the emitter of the first PNP transistor and the analog signal output end; the collector of the first PNP transistor is grounded, and the base is connected to the analog signal input end; the second protection circuit comprises a third NPN transistor, a fourth NPN transistor and a third resistor; the collector of the third NPN transistor is connected to the base of the first PNP transistor, the base is connected to the analog signal input end, and the emitter is connected to the first end of the third resistor; the collector of the fourth NPN transistor is connected to the analog signal input end, the base is connected to the first end of the third resistor, and the emitter is connected to the second end of the third resistor and grounded.

4. The analog signal protection circuit of claim 1, wherein, The analog signal protection circuit further comprises a bias circuit; the first end of the bias circuit is connected to the controlled end of the first switch unit, and the second end is connected to the controlled end of the second switch unit. The bias circuit is configured to provide a first bias and a second bias for the first switch unit and the second switch unit respectively, so as to reduce the on-voltage of the first switch unit and the second switch unit.

5. The analog signal protection circuit of claim 4, wherein, The bias circuit comprises: a fourth resistor, a fifth resistor and a fifth NPN transistor; a collector of the fifth NPN transistor is connected to the external power supply and a control end of the first switch unit, an emitter of the fifth NPN transistor is connected to a control end of the second switch unit, the fourth resistor and the fifth resistor are connected in series between the collector and the emitter of the fifth NPN transistor, and a base of the fifth NPN transistor is connected to one end of the fourth resistor and the fifth resistor.

6. An analog signal protection circuit as claimed in claim 4 or claim 5, characterized in that, The analog signal protection circuit further comprises a driving circuit. An input end of the driving circuit is connected to the analog signal input end, and an output end of the driving circuit is connected to an output end of the bias circuit and a control end of the second switch unit. The driving circuit is configured to amplify an analog current of the analog signal input end and output the amplified analog current.

7. The analog signal protection circuit of claim 6, wherein, The driving circuit comprises a Darlington tube. A base of the Darlington tube is connected to the analog signal input end, a collector of the Darlington tube is connected to the second end of the bias circuit and the control end of the second switch unit, and an emitter of the Darlington tube is connected to the second protection circuit.

8. The analog signal protection circuit of claim 7, wherein, The Darlington tube comprises a sixth NPN transistor and a seventh NPN transistor. A base of the sixth NPN transistor is connected to the analog signal input end, a collector of the sixth NPN transistor is connected to the second end of the bias circuit, the control end of the second switch unit and a collector of the seventh NPN transistor, and an emitter of the seventh NPN transistor is connected to the second protection circuit.

9. An audio playback device, comprising: The audio playing device comprises the analog signal protection circuit according to any one of claims 1 to 8.

10. An audio-video playing device, characterized in that, The audio and video playing device comprises the analog signal protection circuit according to any one of claims 1 to 8.

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