Key detection circuit and method

Abstract

The present invention discloses a key detection circuit and method, including an original car key circuit, a voltage input circuit, a first control switch circuit, a second control switch circuit, a resistance output circuit and a control signal output circuit; the method includes the steps of: when the key is not pressed, outputting a suspended resistance to the original car; when the first key is pressed, detecting and outputting the first key resistance to the original car, and when the second key is pressed, detecting and outputting the second key resistance to the original car; when the first key or the second key is pressed, outputting a level signal to the control circuit. The present invention is implemented, by outputting the key resistance to the original car and detecting the key resistance to output the key function signal, not only the control function of the key is retained, but also the key can be isolated, avoiding the influence of the unstable key output voltage waveform on the control circuit.

Description

Technical Field

[0001] The invention relates to the field of circuit design, and in particular to a button resistance detection circuit and method for an automobile. Background Art

[0002] In recent years, the automotive industry has become increasingly connected with smart technology. A variety of vehicle function buttons have appeared on cars, which has brought great convenience to our lives. Modification has become a trend today. Many young people are willing to accept new ideas, and the most popular one is the smart electric tailgate modification.

[0003] At present, some models have tailgate buttons, but no electric tailgate function. The electric tailgate function buttons of vehicles use positive trigger buttons, negative trigger buttons and differential pressure buttons. The button line in the positive trigger button is usually suspended, and the button is connected to a high level, such as 12V, 5V or 3.3V voltage when pressed; the button line in the negative trigger button is usually suspended, and the button is connected to a low level, such as grounding, when the button is pressed; the button line in the differential pressure button is usually connected to a high level, and the button is connected to a low level when the button is pressed, for example: the button line is connected to 4.7V when the button is not pressed, and the button line is connected to 2.3V after the button is pressed.

[0004] The original car's tailgate function button will also generate unstable voltage waveforms when not in operation. Since the button to be used controls the modified car electric tailgate, the original car circuit will also affect the newly added tailgate circuit, which may cause the tailgate to malfunction and pose a safety hazard. At present, it is urgent to establish a "safe zone" between the button and the tailgate circuit, which can not only ensure the safety of the original car and the tailgate, but also send a level signal to the car tailgate control circuit, so as to normally operate the unlocking and locking of the car tailgate. Summary of the invention

[0005] The purpose of the present invention is to provide a car electric button resistance change detection circuit, which establishes a "safety zone" between the original car button and the newly added function circuit, aiming to solve the potential safety hazard problem caused by the original car button adding a new function.

[0006] A key detection circuit includes an original car key circuit, a voltage input circuit, a first control switch circuit, a second control switch circuit, a resistance output circuit and a control signal output circuit, wherein the control signal output circuit includes a first signal switch circuit and a second signal switch circuit;

[0007] The original car key circuit is connected to the input ends of the first control switch circuit and the second control switch circuit respectively, and is used to input the divided voltage signal to the first control switch circuit and the second control switch circuit;

[0008] A voltage input circuit, used to input voltage to the first control switch circuit and the second control switch circuit respectively;

[0009] The output ends of the first control switch circuit and the second control switch circuit are connected to the input ends of the first signal switch circuit and the second signal switch circuit respectively, and are used to control the output resistance circuit and the on and off of the first signal switch circuit and the second signal switch circuit according to the voltage division signal;

[0010] A resistance output circuit, used for outputting corresponding key resistance according to the conduction status of the first control switch circuit and the second control switch circuit;

[0011] The first signal switch circuit and the second signal switch circuit are used to output control signals to the control circuit.

[0012] Preferably, the first control switch circuit and the second control switch circuit respectively include a first switch tube circuit and a second switch tube circuit; the output ends of the first switch tube circuit and the second switch tube circuit are respectively connected to the input ends of the first signal switch circuit and the second signal switch circuit.

[0013] Furthermore, the original car button circuit includes an original car button circuit input end, an original car button circuit output end, a current limiting unit and a filtering unit. The original car button circuit output end is set at the output end of the detection circuit. The filtering unit is a circuit of two capacitors in parallel. One end of the filtering unit is grounded. The output end of the original car button circuit input end is respectively connected to the input end of the first switch tube circuit, the input end of the second switch tube circuit and one end of the current limiting unit. The other end of the current limiting unit is connected to the non-grounded end of the filtering unit.

[0014] Furthermore, the resistance output circuit includes a first resistance output circuit, a second resistance output circuit and a third resistance output circuit, the input end of the first resistance output circuit is connected to the output end of the first control switch circuit, the input ends of the second resistance output circuit and the third resistance output circuit are connected to the output end of the second control switch circuit, and the output ends of the first resistance output circuit, the second resistance output circuit and the third resistance output circuit are connected.

[0015] Further, the first switch tube circuit and the second switch tube circuit respectively include a first transistor Q1, a second transistor Q6, base resistors R2, R15, emitter resistors R4, R14, emitter grounding resistors R6, R18 and collector grounding resistors R3, R16;

[0016] The first signal switch circuit includes a third switch tube circuit, a first MOS tube circuit and a filter unit, and the first MOS tube circuit is connected to the third switch tube circuit; the second signal switch circuit includes a fourth switch tube circuit and a second MOS tube circuit, and the second MOS tube circuit is connected to the fourth switch tube circuit;

[0017] The third switch tube circuit and the fourth switch tube circuit respectively include base resistors R5 and R17, collector resistors R7 and R19, a third triode Q2 and a fourth triode Q7; the first MOS tube circuit and the second MOS tube circuit respectively include gate resistors R8 and R20, a source current limiting unit 3 and R21, a first MOS tube Q3 and a second MOS tube Q8, the input ends of the base resistors R5 and R17 are directly connected to the collectors of the first triode Q1 and the second triode Q6 respectively, the input ends of the gate resistors R8 and R20 are directly connected to the collectors of the third triode Q2 and the fourth triode Q7 respectively, the source current limiting units 3 and R21 are commonly connected to the output end KEY2, the output end of the collector resistor R7, the drain of the first MOS tube Q3 and the non-grounded end of the filter unit are commonly connected to the first LED+ end, the output end of the collector current limiting unit 9 and the drain of the first MOS tube Q3 are commonly connected to the second LED+ end, and the emitters of the third triode Q2 and the fourth triode Q7 are respectively grounded.

[0018] Further, the first resistance output circuit and the second resistance output circuit respectively include gate resistors R9 and R11, drain resistors R10 and R12, a third MOS transistor Q4, and a fourth MOS transistor Q5. The third resistance output circuit includes resistors R24 and R12. The sources of the third MOS transistor Q4 and the fourth MOS transistor Q5 and one end of the resistor R24 ​​are commonly grounded. The output ends of the drain resistors R10 and R12 are commonly connected to the output end of the resistance output circuit. The input ends of the gate resistors R9 and R11 are respectively connected to the collectors of the first triode Q1 and the second triode Q6.

[0019] Preferably, the key detection circuit is arranged between the original vehicle key circuit and the tailgate control circuit, and is used to return the resistor to the original vehicle and output a control signal to the tailgate control circuit.

[0020] Preferably, the control signal output circuit is a single chip microcomputer circuit, which is connected to the first control switch circuit and the second control switch circuit respectively.

[0021] In a second aspect, a key detection method comprises the steps of:

[0022] S1, when the button circuit of the original car is not pressed, output the floating resistor to the original car;

[0023] S2: When the first button is pressed, detect and output the resistance of the first button to the original car or

[0024] When the second button is pressed, the resistance of the second button is detected and output to the original vehicle;

[0025] S3. When the first key or the second key is pressed, output a level signal to the control circuit.

[0026] Preferably, the step S3 comprises the sub-steps of:

[0027] When the resistance of the first key is detected, the first control switch circuit and the second control switch circuit are turned on, and when the resistance of the second key is detected, the second control switch circuit is turned on;

[0028] The first control switch circuit and the second control switch circuit control the signal output circuit to output a level to the control circuit.

[0029] The key detection circuit and method described in the present invention are implemented. By adding a detection circuit between the key and the control circuit, not only can the key resistance be output to the original vehicle, but the key function signal can also be output by detecting the key resistance, thereby retaining the key control function, isolating the key, and avoiding the influence of the unstable key output voltage waveform on the vehicle control circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a logical connection diagram of a key detection circuit embodiment 1 of the present invention;

[0031] Figure 2 This is a schematic diagram of the logical connections of a key detection circuit according to Embodiment 1 of the present invention;

[0032] Figure 3 This is a logical connection diagram of a resistance output circuit of Embodiment 2 of a key detection circuit in the present invention;

[0033] Figure 4 This is a schematic diagram of electronic component connections of a key detection circuit according to Embodiment 3 of the present invention;

[0034] Figure 5 This is a schematic diagram of electronic component connections of a key detection circuit according to Embodiment 4 of the present invention;

[0035] Figure 6 This is a schematic diagram of electronic component connections of a key detection circuit according to Embodiment 5 of the present invention;

[0036] Figure 7 This is a schematic diagram of the steps of Example 1 of a key detection method in the present invention;

[0037] Figure 8 This is a schematic diagram of the steps of Example 2 of a key detection method in the present invention;

[0038] Explanation of the accompanying drawing numbers: 100 - original car button circuit, 110 - original car button circuit input end, 111 - current limiting unit, 120 - original car button circuit output end, 200 - detection circuit, 300 - tailgate control circuit, 201 - filtering unit, 210 - control switch circuit, 211 - first control switch circuit, 212 - second control switch circuit, 220 - voltage input circuit, 230 - resistance output circuit, 231 - first resistance output circuit, 232 - second resistance output circuit, 233 - third resistance output circuit, 240 - control signal output circuit, 241 - first signal switch circuit, 242 - second signal switch circuit, 250 - single-chip computer circuit. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention 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 invention and are not intended to limit the present invention.

[0040] The purpose of the present invention is to provide a key detection circuit 200 and method, which establishes a "safety zone" between the original vehicle key circuit 100 and the tailgate control circuit 300, aiming to solve the potential safety hazard problem caused by adding the electric function of the tailgate.

[0041] Embodiment 1, as Figure 1 , Figure 1 This is a logical connection diagram of Embodiment 1 of a key detection circuit 200 in the present invention, which provides a key detection circuit 200 arranged between an original vehicle key circuit 100 and a control circuit.

[0042] As an implementation method, the key detection circuit 200 is arranged between the original car key circuit 100 and the tailgate control circuit 300, and is used to return the resistance to the original car and output the control signal to the tailgate control circuit 300. Its function is to isolate the original car key circuit 100 from the tailgate control circuit 300, and can also output the control signal to control the opening and closing of the car tailgate.

[0043] As another implementation, the detection circuit 200 in the present application can also be arranged between the original vehicle button circuit 100 and other newly added function control circuits to isolate the original vehicle button circuit 100 and avoid the influence of the original vehicle button circuit 100 on the newly added function control circuit.

[0044] Embodiment 2, as Figure 2 , Figure 21 is a schematic diagram of the logical connection of the composition of Example 1 of a key detection circuit 200 in the present invention. In this embodiment, a key detection circuit 200 includes an original car key circuit 100, a voltage input circuit 220, a first control switch circuit 211, a second control switch circuit 212, a resistance output circuit 230 and a control signal output circuit 240. The control signal output circuit 240 includes a first signal switch circuit 241 and a second signal switch circuit 242; the original car key circuit 100 is respectively connected to the input ends of the first control switch circuit 211 and the second control switch circuit 212, and is used to input a voltage division signal to the first control switch circuit 211 and the second control switch circuit 212; the voltage The input circuit 220 is used to input voltage to the first control switch circuit 211 and the second control switch circuit 212 respectively; the output ends of the first control switch circuit 211 and the second control switch circuit 212 are respectively connected to the input ends of the first signal switch circuit 241 and the second signal switch circuit 242, and are used to control the output resistance circuit and the on-off of the first signal switch circuit 241 and the second signal switch circuit 242 according to the voltage division signal; the resistance output circuit 230 is used to output the corresponding key resistance according to the conduction status of the first control switch circuit 211 and the second control switch circuit 212; the first signal switch circuit 241 and the second signal switch circuit 242 are used to output the control signal to the control circuit.

[0045] Preferably, the first control switch circuit 211 and the second control switch circuit 212 include a first switch tube circuit and a second switch tube circuit respectively; the output ends of the first switch tube circuit and the second switch tube circuit are respectively connected to the input ends of the first signal switch circuit 241 and the second signal switch circuit 242.

[0046] Furthermore, the original car button circuit 100 includes an original car button circuit input terminal 110, an original car button circuit output terminal 120, a current limiting unit and a filtering unit 201. The original car button circuit output terminal 120 is set at the output end of the detection circuit 200. The filtering unit 201 is a circuit of two capacitors in parallel. One end of the filtering unit 201 is grounded. The output end of the original car button circuit input terminal 110 is respectively connected to the input ends of the first switch tube circuit, the second switch tube circuit and one end of the current limiting unit. The other end of the current limiting unit is connected to the non-grounded end of the filtering unit 201.

[0047] In one implementation, the current limiting unit may be a resistor R1 , and current limiting and voltage division are performed through the resistor R1 .

[0048] Furthermore, if Figure 3 , Figure 3This is a logical connection diagram of the resistance output circuit 230 of Example 2 of a key detection circuit 200 in the present invention. The resistance output circuit 230 includes a first resistance output circuit 231, a second resistance output circuit 232 and a third resistance output circuit 233. The input end of the first resistance output circuit 231 is connected to the output end of the first control switch circuit 211, the input ends of the second resistance output circuit 232 and the third resistance output circuit 233 are connected to the output end of the second control switch circuit 212, and the output ends of the first resistance output circuit 231, the second resistance output circuit 232 and the third resistance output circuit 233 are connected.

[0049] Embodiment 3, as Figure 4 , Figure 4 1 is a schematic diagram of electronic component connection of embodiment 3 of a key detection circuit 200 in the present invention, wherein the first switch tube circuit and the second switch tube circuit respectively include a first triode Q1, a second triode Q6, base resistors R2, R15, emitter resistors R4, R14, emitter grounding resistors R6, R18 and collector grounding resistors R3, R16; the first signal switch circuit 241 includes a third switch tube circuit, a first MOS tube circuit and a filter unit 201, and the first MOS tube circuit is connected to the third switch tube circuit; the second signal switch circuit 242 includes a fourth switch tube circuit and a second MOS tube circuit, and the second MOS tube circuit is connected to the fourth switch tube circuit; the third switch tube circuit and the fourth switch tube circuit respectively include base resistors R5, R17, collector resistors R7, R19, the third triode Q2, the fourth triode transistor Q7; the first MOS transistor circuit and the second MOS transistor circuit respectively include gate resistors R8 and R20, source limiting current units 3 and R21, the first MOS transistor Q3, the second MOS transistor Q8, the input ends of the base resistors R5 and R17 are directly connected to the collectors of the first transistor Q1 and the second transistor Q6 respectively, the input ends of the gate resistors R8 and R20 are directly connected to the collectors of the third transistor Q2 and the fourth transistor Q7 respectively, the source limiting current units 3 and R21 are commonly connected to the output end KEY2, the output end of the collector resistor R7, the drain of the first MOS transistor Q3, and the non-grounded end of the filter unit 201 are commonly connected to the first LED+ end, the output end of the collector limiting current unit 9 and the drain of the first MOS transistor Q3 are commonly connected to the second LED+ end, and the emitters of the third transistor Q2 and the fourth transistor Q7 are respectively grounded.

[0050] In this embodiment, when there is no key input at the original car key circuit input terminal 110KEY_SIGIN, the original car key circuit input terminal 110KEY_SIGIN and the level signal output terminal KEY2 are suspended. At this time, the third MOS tube Q4 and the fourth MOS tube Q5 are not turned on, and the input resistance of the original car key circuit input terminal 110KEY_SIGIN to ground is R24+R12.

[0051] When the input terminal 110KEY_SIGIN of the original car key circuit has a 0.5K key input, that is, the first key is pressed, the input voltage of the voltage input unit, the first switch tube circuit, the second switch tube circuit, the third switch tube circuit, the fourth switch tube circuit, the first MOS tube circuit, the second MOS tube circuit, the third MOS tube circuit, and the fourth MOS tube circuit are set so that the above circuits are turned on in sequence, and the output resistance of the output terminal 120KEY_SIGOUT of the original car key circuit is R10·R12 / (R10+R12), so that the resistance output value is 0.5K, and the level signal output terminal KEY2 outputs a 12V high level signal. When applied to the tailgate, and then closed manually, the tailgate will automatically lock.

[0052] When the input terminal 110KEY_SIGIN of the original car key circuit has a KEY1K key input, that is, the second key is pressed, the input voltage of the voltage input unit, the first switch tube circuit, the second switch tube circuit, the third switch tube circuit, the fourth switch tube circuit, the first MOS tube circuit, the second MOS tube circuit, the third MOS tube circuit, and the fourth MOS tube circuit are set, so that the second switch tube circuit, the fourth switch tube circuit, and the fourth MOS tube circuit are turned on in sequence, and the output resistor of the original car key circuit output terminal 120KEY_SIGOUT is R12, so that the resistance output value is 1K, and the level signal output terminal KEY2 outputs a 12V high level signal. When applied to the tailgate, the tailgate is only closed at this time, and will not be locked.

[0053] The resistance of the original car key circuit 100 is output to the original car, and the function signal of the key can be output by detecting the resistance of the original car key circuit 100, thereby retaining the control function of the original car key circuit 100, isolating the original car key circuit 100, and avoiding the influence of the unstable output voltage waveform of the original car key circuit on the car control circuit.

[0054] Embodiment 5, as Figure 6 , Figure 6 This is a schematic diagram of electronic component connection of Example 6 of a key detection circuit 200 in the present invention. The first resistor output circuit 231 and the second resistor output circuit 232 respectively include gate resistors R9 and R11, drain resistors R10 and R12, a third MOS transistor Q4 and a fourth MOS transistor Q5. The third resistor output circuit 233 includes resistors R24 and R12. The sources of the third MOS transistor Q4 and the fourth MOS transistor Q5 and one end of the resistor R24 ​​are commonly grounded. The output ends of the drain resistors R10 and R12 are commonly connected to the output end of the resistor output circuit 230. The input ends of the gate resistors R9 and R11 are respectively connected to the collectors of the first transistor Q1 and the second transistor Q6.

[0055] Embodiment 4, as Figure 5 , Figure 5 This is a schematic diagram of electronic component connections of Example 5 of a key detection circuit 200 in the present invention. The difference from Example 4 is that the control signal output circuit 240 of this embodiment is a single-chip microcomputer circuit 250, which is connected to the first control switch circuit 211 and the second control switch circuit 212 respectively.

[0056] Method embodiment 1, as Figure 7 , Figure 7 The figure is a schematic diagram of the steps of Example 1 of a detection method of an original car key circuit 100 in the present invention. The detection method of an original car key circuit 100 comprises the steps of:

[0057] S1. When the original car button circuit 100 is not pressed, a floating resistor is output to the original car; S2. When the first button is pressed, the resistance of the first button is detected and output to the original car; when the second button is pressed, the resistance of the second button is detected and output to the original car; S3. When the first button or the second button is pressed, a level signal is output to the control circuit.

[0058] When there is no key input at the input terminal 110KEY_SIGIN of the original car key circuit, the level signal output terminal KEY2 is suspended. At this time, the third MOS tube Q4 and the fourth MOS tube Q5 are not turned on, and the input resistance of the original car key circuit input terminal 110KEY_SIGIN to ground is R24+R12.

[0059] When the input terminal 110KEY_SIGIN of the original car key circuit has a 0.5K key input, that is, the first key is pressed, the input voltage of the voltage input unit, the first switch tube circuit, the second switch tube circuit, the third switch tube circuit, the fourth switch tube circuit, the first MOS tube circuit, the second MOS tube circuit, the third MOS tube circuit, and the fourth MOS tube circuit are set so that the above circuits are turned on in sequence, and the output resistance of the output terminal 120KEY_SIGOUT of the original car key circuit is R10·R12 / (R10+R12), so that the resistance output value is 0.5K, and the level signal output terminal KEY2 outputs a 12V high level signal. When applied to the tailgate, and then closed manually, the tailgate will automatically lock.

[0060] When the input terminal 110KEY_SIGIN of the original car key circuit has a KEY1K key input, that is, the second key is pressed, the input voltage of the voltage input unit, the first switch tube circuit, the second switch tube circuit, the third switch tube circuit, the fourth switch tube circuit, the first MOS tube circuit, the second MOS tube circuit, the third MOS tube circuit, and the fourth MOS tube circuit are set, so that the second switch tube circuit, the fourth switch tube circuit, and the fourth MOS tube circuit are turned on in sequence, and the output resistor of the original car key circuit output terminal 120KEY_SIGOUT is R12, so that the resistance output value is 1K, and the level signal output terminal KEY2 outputs a 12V high level signal. When applied to the tailgate, the tailgate is only closed at this time, and will not be locked.

[0061] The key resistance is output to the original car, and the function signal of the key can be output by detecting the resistance of the original car key circuit 100, thereby retaining the control function of the original car key circuit 100, isolating the original car key circuit 100, and avoiding the influence of the unstable output voltage waveform of the original car key circuit on the car control circuit.

[0062] Method embodiment 2, as Figure 8 , Figure 8 This is a schematic diagram of the steps of Example 2 of a key detection method in the present invention, where step S3 includes sub-steps:

[0063] When the resistance of the first key is detected, the first control switch circuit 211 and the second control switch circuit 212 are turned on; when the resistance of the second key is detected, the second control switch circuit 212 is turned on;

[0064] The first control switch circuit 211 and the second control switch circuit 212 control the signal output circuit 240 to output a level to the control circuit.

[0065] The present invention implements an original vehicle key circuit 100 detection circuit 200 and method. By adding the detection circuit 200 between the original vehicle key circuit 100 and the control circuit, not only can the resistance of the original vehicle key circuit 100 be output to the original vehicle, but also the function signal of the key can be output by detecting the resistance of the original vehicle key circuit 100, thereby retaining the control function of the original vehicle key circuit 100, isolating the original vehicle key circuit, and avoiding the influence of the unstable output voltage waveform of the original vehicle key circuit on the vehicle control circuit.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A key detection circuit, characterized in that: It includes an original car button circuit, a voltage input circuit, a first control switch circuit, a second control switch circuit, a resistance output circuit and a control signal output circuit, wherein the control signal output circuit includes a first signal switch circuit and a second signal switch circuit; The original car key circuit is connected to the input ends of the first control switch circuit and the second control switch circuit respectively, and is used to input the divided voltage signal to the first control switch circuit and the second control switch circuit; A voltage input circuit, used to input voltage to the first control switch circuit and the second control switch circuit respectively; The output ends of the first control switch circuit and the second control switch circuit are connected to the input ends of the first signal switch circuit and the second signal switch circuit respectively, and are used to control the output resistance circuit and the on and off of the first signal switch circuit and the second signal switch circuit according to the voltage division signal; A resistance output circuit, used for outputting corresponding key resistance according to the conduction status of the first control switch circuit and the second control switch circuit; The first signal switch circuit and the second signal switch circuit are used to output control signals to the control circuit; The first control switch circuit and the second control switch circuit respectively include a first switch tube circuit and a second switch tube circuit; the output ends of the first switch tube circuit and the second switch tube circuit are respectively connected to the input ends of the first signal switch circuit and the second signal switch circuit; The resistance output circuit comprises a first resistance output circuit, a second resistance output circuit and a third resistance output circuit, the input end of the first resistance output circuit is connected to the output end of the first control switch circuit, the input ends of the second resistance output circuit and the third resistance output circuit are connected to the output end of the second control switch circuit, and the output ends of the first resistance output circuit, the second resistance output circuit and the third resistance output circuit are connected; The first switch tube circuit and the second switch tube circuit respectively include a first transistor Q1, a second transistor Q6, base resistors R2, R15, emitter resistors R4, R14, emitter grounding resistors R6, R18 and collector grounding resistors R3, R16; The first signal switch circuit includes a third switch tube circuit, a first MOS tube circuit and a filter unit, and the first MOS tube circuit is connected to the third switch tube circuit; the second signal switch circuit includes a fourth switch tube circuit and a second MOS tube circuit, and the second MOS tube circuit is connected to the fourth switch tube circuit; The third switch tube circuit and the fourth switch tube circuit respectively include base resistors R5 and R17, collector resistors R7 and R19, a third transistor Q2 and a fourth transistor Q7; the first MOS tube circuit and the second MOS tube circuit respectively include gate resistors R8 and R20, a source current limiting unit 3 and R21, a first MOS tube Q3 and a second MOS tube Q8, the input ends of the base resistors R5 and R17 are directly connected to the collectors of the first transistor Q1 and the second transistor Q6 respectively, the input ends of the gate resistors R8 and R20 are directly connected to the collectors of the third transistor Q2 and the fourth transistor Q7 respectively, the source current limiting units 3 and R21 are commonly connected to the output end KEY2, the output end of the collector resistor R7, the drain of the first MOS tube Q3 and the non-grounded end of the filter unit are commonly connected to the first LED+ end, the output end of the collector current limiting unit 9 and the drain of the first MOS tube Q3 are commonly connected to the second LED+ end, the third transistor Q2 , and the emitter of the fourth transistor Q7 are grounded respectively; The first resistance output circuit and the second resistance output circuit respectively include gate resistors R9 and R11, drain resistors R10 and R12, a third MOS transistor Q4 and a fourth MOS transistor Q5. The third resistance output circuit includes resistors R24 and R12. The sources of the third MOS transistor Q4 and the fourth MOS transistor Q5 and one end of the resistor R24 ​​are commonly grounded. The output ends of the drain resistors R10 and R12 are commonly connected to the output end of the resistance output circuit. The input ends of the gate resistors R9 and R11 are respectively connected to the collectors of the first triode Q1 and the second triode Q6.

2. The key detection circuit according to claim 1, characterized in that: The original car button circuit includes an original car button circuit input end, an original car button circuit output end, a current limiting unit and a filtering unit. The original car button circuit output end is set at the output end of the detection circuit. The filtering unit is a circuit of two capacitors in parallel. One end of the filtering unit is grounded. The output end of the original car button circuit input end is respectively connected to the input end of the first switch tube circuit, the input end of the second switch tube circuit and one end of the current limiting unit. The other end of the current limiting unit is connected to the non-grounded end of the filtering unit.

3. The key detection circuit according to any one of claims 1 to 2, characterized in that: The key detection circuit is arranged between the original vehicle key circuit and the tailgate control circuit, and is used for returning the resistance to the original vehicle and outputting a control signal to the tailgate control circuit.

4. The key detection circuit as claimed in claim 3, characterized in that: The control signal output circuit is a single chip microcomputer circuit, which is connected to the first control switch circuit and the second control switch circuit respectively.

5. A key detection method, using the key detection circuit according to any one of claims 1 to 4, characterized in that: Includes steps: S1, when the button circuit of the original car is not pressed, output the floating resistor to the original car; S2: When the first button is pressed, detect and output the resistance of the first button to the original car or When the second button is pressed, the resistance of the second button is detected and output to the original vehicle; S3, when the first key or the second key is pressed, outputting a level signal to the control circuit; Wherein, the first button is a 0.5K button at the input end of the original car button circuit; The second button is the 1K button at the input end of the original car button circuit.

6. The key detection method according to claim 5, characterized in that: The step S3 comprises the following sub-steps: When the resistance of the first key is detected, the first control switch circuit and the second control switch circuit are turned on, and when the resistance of the second key is detected, the second control switch circuit is turned on; The first control switch circuit and the second control switch circuit control the signal output circuit to output a level to the control circuit.

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