A USB4 or Thunderbolt interface empty soldering test circuit

Abstract

The present invention discloses a USB4 or Thunderbolt interface empty soldering test circuit, which relates to the field of interface testing. The USB4 or Thunderbolt interface empty soldering test circuit includes a first diode, the cathode of the first diode is connected to the cathode of a button battery and one end of a first resistor, the anode of the button battery is connected to the S pole of a second switch tube, one end of a second resistor, and one end of a connector, the other end of the second resistor is connected to the D pole of the first switch tube and the G pole of the second switch tube, the S pole of the first switch tube is connected to the other end of the first resistor, and the D pole of the second switch tube is connected to the D pole of a third switch tube and one end of the third resistor. Compared with the prior art, the beneficial effect of the present invention is that when the USB4 or Thunderbolt interface has empty soldering, the present invention only needs to be inserted once to determine whether there is an empty soldering problem when checking for short circuit and empty soldering. If there is an empty soldering problem, the position of the empty soldering can be quickly located.

Description

Technical Field

[0001] The present invention relates to the field of interface testing, and in particular to a USB4 or Thunderbolt interface empty soldering test circuit. Background Art

[0002] USB has gone through many generations. There have been multiple specifications, including USB 1.0, USB 2.0, and USB 3.0. Interface shapes and designs have also evolved, including USB Type-A, USB Type-B, and the now-common USB Type-C. USB4 not only has faster transmission speeds but also offers greater compatibility (supporting backward compatibility with earlier versions), allowing it to more efficiently connect and charge nearly all devices.

[0003] Thunderbolt, commonly known as the Thunderbolt interface, combines PCI Express data transmission technology with DisplayPort display technology to transmit both data and video signals simultaneously, with each channel providing bidirectional 10Gbps bandwidth.

[0004] During the production process of USB4 or Thunderbolt interfaces, soldering and connector welding are prone to empty solder joints. To troubleshoot short circuits and empty solder joints, comprehensive testing is required. Test items include: 1. Connecting a Type-C docking station to a USB 3.0 device and a 4K 60Hz resolution monitor to measure the USB 3.0 device speed and monitor performance. Both sides of the Type-C docking station's Type-C connector must be tested. 2. Connecting a hard drive with a USB 4 / Thunderbolt 4 interface to test the hard drive's recognition. Both sides of the interface must be tested. USB4 or Thunderbolt interface testing is cumbersome and needs improvement. Summary of the Invention

[0005] The purpose of the present invention is to provide a USB4 or Thunderbolt interface empty soldering test circuit to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A USB4 or Thunderbolt interface empty soldering test circuit, the USB4 or Thunderbolt interface empty soldering test circuit comprising a first diode, the cathode of the first diode being connected to the cathode of a button battery and one end of a first resistor, the anode of the button battery being connected to the S electrode of a second switching tube, one end of a second resistor, and one end of a connector, the other end of the second resistor being connected to the D electrode of the first switching tube and the G electrode of the second switching tube, the S electrode of the first switching tube being connected to the other end of the first resistor, the D electrode of the second switching tube being connected to the D electrode of a third switching tube and one end of a third resistor, the S electrode of the third switching tube being connected to the G electrode of the first switching tube and the other end of the connector, and the other end of the third resistor being connected to the anode of the first diode; the third switching tube may be omitted from the USB4 or Thunderbolt interface empty soldering test circuit;

[0008] The USB4 or Thunderbolt interface empty soldering test circuit is set on a circuit board to form a test board. The test board tests the tested board where the USB4 or Thunderbolt interface is located by inserting a connector; a body diode and a ninth capacitor are present at the PIN pin of the USB4 or Thunderbolt interface;

[0009] When the PIN pins of the USB4 or Thunderbolt interface are not soldered, after the test board is inserted, the button battery, the body diode at the USB4 or Thunderbolt interface, the ninth capacitor, the third resistor, and the first diode form a first loop, charging the ninth capacitor and generating a patrol charging current. The current generates a voltage drop across the third resistor and the first diode, forming a voltage that acts on the G electrode of the first switch tube, turning on the first switch tube. After the first switch tube is turned on, the voltage of the button battery is divided by the second resistor and the first resistor, causing the second switch tube to turn on, forming a second loop of the button battery, the second switch tube, the third resistor, and the first diode, causing the first diode to emit light;

[0010] When the PIN pin of the USB4 or Thunderbolt interface is unsoldered, the first circuit is not formed and the first diode does not emit light. By judging whether the first diode emits light, it can be determined whether the corresponding PIN pin of the USB4 or Thunderbolt interface is unsoldered.

[0011] As a further solution of the present invention: when the third switch tube is present, the USB4 or Thunderbolt interface empty soldering test circuit further includes:

[0012] The button start module is used to start through the button switch. After the button switch is pressed, the continuous output voltage is supplied to the delay module;

[0013] The delay module is used to supply voltage to the signal indication module after a delay after voltage input, and to supply voltage to the self-recovery module after a further delay;

[0014] The signal indicator module is used to illuminate and indicate that the third switch tube is cut off during operation, and the test board does not form a loop with the tested board where the USB4 or Thunderbolt interface is located through the connector;

[0015] The self-recovery module is used to control the key start module to stop supplying power after the voltage is input, so that the key start module, delay module, signal indication module and self-recovery module are restored to their initial states;

[0016] The output end of the key start module is connected to the input end of the delay module, the output end of the delay module is connected to the input end of the signal indication module and the input end of the self-recovery module, and the output end of the self-recovery module is connected to the input end of the key start module.

[0017] As a further solution of the present invention: the key start module includes a key switch, a fourth resistor, a fourth transistor, a fifth transistor, a fifth resistor, and a sixth switch tube. One end of the key switch is connected to the positive electrode of the button battery, one end of the fifth resistor, and the S pole of the sixth switch tube. The other end of the key switch is connected to one end of the fourth resistor, the collector of the fifth transistor, the input end of the delay module, and the D pole of the second switch tube. The other end of the fourth resistor is connected to the base of the fourth transistor, the emitter of the fourth transistor is grounded, the collector of the fourth transistor is connected to the other end of the fifth resistor and the base of the fifth transistor, the emitter of the fifth transistor is connected to the D pole of the sixth switch tube, and the G pole of the sixth switch tube is connected to the output end of the self-recovery module.

[0018] As a further solution of the present invention: the delay module includes a third diode, a sixth resistor, a first potentiometer, and a tenth capacitor. The positive pole of the third diode is connected to the output end of the key start module, the negative pole of the third diode is connected to one end of the sixth resistor, the other end of the sixth resistor is connected to one end of the first potentiometer, the other end of the first potentiometer is connected to one end of the tenth capacitor, the input end of the signal indication module, and the input end of the self-recovery module, and the other end of the tenth capacitor is grounded.

[0019] As a further solution of the present invention: the signal indication module includes a seventh resistor and a second diode, one end of the fourth resistor is connected to the output end of the delay module, the other end of the fourth resistor is connected to the positive electrode of the second diode, and the negative electrode of the second diode is connected to the G pole of the third switching tube.

[0020] As a further solution of the present invention: the self-recovery module includes a fourth diode and an eighth resistor, the cathode of the fourth diode is connected to the output end of the delay module, the anode of the fourth diode is connected to one end of the eighth resistor, and the other end of the eighth resistor is connected to the input end of the key start module.

[0021] Compared with the prior art, the beneficial effect of the present invention is that when a USB4 or Thunderbolt interface has a hollow solder joint, the present invention only needs to be inserted once to determine whether there is a hollow solder joint problem. If there is a hollow solder joint, the position of the hollow solder joint can be quickly located. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the equivalent circuit diagram of the reverse-connected diode to ground at the chip pin.

[0023] Figure 2 This is the schematic diagram of the interface empty soldering test circuit.

[0024] Figure 3 This is a schematic diagram of a USB4 or Thunderbolt interface empty soldering test circuit.

[0025] Figure 4 A schematic diagram of a USB4 or Thunderbolt interface empty soldering test circuit that can be added to the module.

[0026] Figure 5 A circuit diagram of a USB4 or Thunderbolt interface empty soldering test circuit can be added to the module.

[0027] Figure 6 This is a schematic diagram of the connector NER23-AK5V20. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] See also Figure 3A USB4 or Thunderbolt interface empty soldering test circuit includes a first diode D1, the cathode of the first diode D1 is connected to the cathode of a button battery E1 and one end of a first resistor R1, the anode of the button battery E1 is connected to the S electrode of a second switching tube V2 (PMOS), one end of a second resistor R2, and one end of a connector, the other end of the second resistor R2 is connected to the D electrode of a first switching tube V1 (NMOS) and the G electrode of the second switching tube V2, the S electrode of the first switching tube V1 is connected to the other end of the first resistor R1, the D electrode of the second switching tube V2 is connected to the D electrode of a third switching tube V3 (PMOS) and one end of a third resistor R3, the S electrode of the third switching tube V3 is connected to the G electrode of the first switching tube V1 and the other end of the connector, and the other end of the third resistor R3 is connected to the anode of the first diode D1; the third switching tube V3 can be omitted from the USB4 or Thunderbolt interface empty soldering test circuit;

[0030] The USB4 or Thunderbolt interface empty soldering test circuit is set on a circuit board to form a test board. The test board tests the tested board where the USB4 or Thunderbolt interface is located by inserting a connector; a body diode and a ninth capacitor C9 are present at the PIN pin of the USB4 or Thunderbolt interface;

[0031] When the PIN pins of the USB4 or Thunderbolt interface are not soldered, after the test board is inserted, the button battery E1, the body diode at the USB4 or Thunderbolt interface, the ninth capacitor C9, the third resistor R3, and the first diode D1 form a first loop, charging the ninth capacitor C9 and generating a patrol charging current. The current generates a voltage drop across the third resistor R3 and the first diode D1, forming a voltage that acts on the G electrode of the first switch tube V1, turning on the first switch tube V1. After the first switch tube V1 is turned on, the voltage of the button battery E1 is divided by the second resistor R2 and the first resistor R1, causing the second switch tube V2 to turn on, forming a second loop of the button battery E1, the second switch tube V2, the third resistor R3, and the first diode D1, causing the first diode D1 to emit light;

[0032] When the PIN pin of the USB4 or Thunderbolt interface is unsoldered, the first circuit is not formed and the first diode D1 does not emit light. Whether the corresponding PIN pin of the USB4 or Thunderbolt interface is unsoldered can be determined by judging whether the first diode D1 emits light.

[0033] In the specific embodiment: see Figure 1 、 Figure 2 、 Figure 3 and Figure 6 The present invention mainly refers to the use of the chip pin's reverse diode to ground. In modern integrated circuit technology, each pin has a reverse body diode to ground. For a simple equivalent circuit, please refer to Figure 1The forward conduction voltage of the chip's body diode is generally between 0.2V and 0.7V. Using this feature, we design the circuit as follows: the battery EX1 can provide a power supply of about 3V (the positive pole is grounded and the negative pole is -3V), and the resistor RX1 provides current limiting for the circuit. Through the connector, the chip's body diode, the current limiting resistor RX1, and the light-emitting diode DX1 form a power-on loop. When the loop connection is correct, the light-emitting diode DX1 will be lit. If the connector is unsoldered, the light-emitting diode DX1 will not light up, so we can determine whether there is a loose solder joint.

[0034] The USB4 / Thunderbolt interface includes 4 differential signals: VBUS, USB2.0, SBU1 / SBU2, CC1 / CC2. Without considering the connector, the VBUS, USB2.0, SBU1 / SBU2, CC1 / CC2 signals are directly connected to the CPU PIN pins. The detection circuit is referenced Figure 2 Design. The four groups of differential signals require capacitors in series between the chip PIN pins and the connector (first capacitor C1, second capacitor C2, third capacitor C3, fourth capacitor C4, fifth capacitor C5, sixth capacitor C6, seventh capacitor C7, eighth capacitor C8, as shown in Figure 2). Figure 6 shown), use Figure 2 The design cannot form a current loop and the circuit needs to be modified, such as Figure 3 Finally, by judging whether the first diode D1 is emitting light, it is determined whether the corresponding PIN pin of the USB4 or Thunderbolt interface is unsoldered.

[0035] In this example: See Figure 4 When the third switch tube V3 is present, the USB4 or Thunderbolt interface empty soldering test circuit further includes:

[0036] The button start module 1 is used to start through the button switch S1. After the button switch S1 is pressed, the continuous output voltage is supplied to the delay module 2;

[0037] Delay module 2 is used to supply voltage to signal indication module 3 after voltage input and to supply voltage to self-recovery module 4 after further delay;

[0038] The signal indicator module 3 is used to illuminate and indicate that the third switch tube V3 is turned off during operation, and the test board does not form a loop with the tested board where the USB4 or Thunderbolt interface is located through the connector;

[0039] The self-recovery module 4 is used to control the key start module 1 to stop supplying power after the voltage is input, so that the key start module 1, the delay module 2, the signal indication module 3, and the self-recovery module 4 are restored to their initial states;

[0040] The output end of the key start module 1 is connected to the input end of the delay module 2, the output end of the delay module 2 is connected to the input end of the signal indication module 3 and the input end of the self-recovery module 4, and the output end of the self-recovery module 4 is connected to the input end of the key start module 1.

[0041] The third switch V3 works in conjunction with the key-start module 1, delay module 2, signal indicator module 3, and self-recovery module 4. If these modules are not needed for detection, they can be omitted. The key-start module 1, delay module 2, signal indicator module 3, and self-recovery module 4 are provided to detect circuit anomalies at the first diode D1, preventing potential unsoldered USB4 / Thunderbolt ports from being detected.

[0042] In this example: See Figure 5 The key start module 1 includes a key switch S1, a fourth resistor R4, a fourth transistor V4, a fifth transistor V5, a fifth resistor R5, and a sixth switch tube V6. One end of the key switch S1 is connected to the positive electrode of the button battery, one end of the fifth resistor R5, and the S electrode of the sixth switch tube V6. The other end of the key switch S1 is connected to one end of the fourth resistor R4, the collector of the fifth transistor V5, the input end of the delay module 2, and the D electrode of the second switch tube V2. The other end of the fourth resistor R4 is connected to the base of the fourth transistor V4. The emitter of the fourth transistor V4 is grounded. The collector of the fourth transistor V4 is connected to the other end of the fifth resistor R5 and the base of the fifth transistor V5. The emitter of the fifth transistor V5 is connected to the D electrode of the sixth switch tube V6. The G electrode of the sixth switch tube V6 is connected to the output end of the self-recovery module 4.

[0043] To detect whether the circuit at the first diode D1 is abnormal, the push-button switch S1 is pressed. After the push-button switch S1 is pressed, the base of the fourth transistor V4 (NPN transistor) is at a high level, turning on the fourth transistor V4, which pulls down the base voltage of the fifth transistor V5 (PNP transistor), turning on the fifth transistor V5. Initially, the sixth switch V6 (PMOS) is in the on state. Therefore, the voltage of the button battery E1 (common point A) is output through the sixth switch V6 and the fifth transistor V5 to the fourth resistor R4, maintaining the fourth transistor V4 and the fifth transistor V5 on. The voltage is output to the delay module 2, prompting the subsequent circuit to operate. The voltage is output to the common point B (the third resistor R3). When the circuit at the first diode D1 is intact, the first diode D1 illuminates to indicate that the circuit is normal.

[0044] In another embodiment, the push-button switch S1 may also be a common switch, which only needs to be manually disconnected after the test is completed.

[0045] In this example: See Figure 5 The delay module 2 includes a third diode D3, a sixth resistor R6, a first potentiometer RP1, and a tenth capacitor C10. The anode of the third diode D3 is connected to the output end of the key start module 1, the cathode of the third diode D3 is connected to one end of the sixth resistor R6, the other end of the sixth resistor R6 is connected to one end of the first potentiometer RP1, the other end of the first potentiometer RP1 is connected to one end of the tenth capacitor C10, the input end of the signal indication module 3, and the input end of the self-recovery module 4, and the other end of the tenth capacitor C10 is grounded.

[0046] After the voltage is input, the tenth capacitor C10 is charged through the third diode D3, the sixth resistor R6 and the first potentiometer RP1. After a delay, the signal indication module 3 is powered to enable it to work; after a further delay, the self-recovery module 4 is triggered to work.

[0047] In another embodiment, the first potentiometer RP1 may be replaced with a common resistor, but the charging time of the tenth capacitor C10 cannot be adjusted.

[0048] In this example: See Figure 5 The signal indication module 3 includes a seventh resistor R7 and a second diode D2. One end of the fourth resistor R4 is connected to the output end of the delay module 2, the other end of the fourth resistor R4 is connected to the anode of the second diode D2, and the cathode of the second diode D2 is connected to the G pole of the third switch tube V3.

[0049] Because the second diode D2 itself requires a voltage to conduct, when voltage is input, it takes a while for the tenth capacitor C10 to charge before triggering the second diode D2 to conduct and emit light. The cathode of the second diode D2 outputs a high level to the G pole (common point C) of the third switch V3, which in turn turns off the third switch V3 and disconnects the USB4 or Thunderbolt interface soldering test circuit and connector, preventing any impact during the test. At this time, by observing the brightness of the first diode D1 and the second diode D2, it can be determined whether there is a circuit abnormality at the first diode D1.

[0050] In another embodiment, the seventh resistor R7 may be omitted, and the seventh resistor R7 is used for current limiting.

[0051] In this example: See Figure 5 The self-recovery module 4 includes a fourth diode D4 and an eighth resistor R8. The cathode of the fourth diode D4 is connected to the output end of the delay module 2, the anode of the fourth diode D4 is connected to one end of the eighth resistor R8, and the other end of the eighth resistor R8 is connected to the input end of the key start module 1.

[0052] After determining whether the circuit at the first diode D1 is abnormal, as the tenth capacitor C10 further charges, the voltage across the tenth capacitor C10 is sufficient to turn on the fourth diode D4 (Zener diode), providing a high level to the G terminal of the sixth switch tube V6 via the eighth resistor R8. The sixth switch tube V6 is turned off, and the common point B becomes low. The key start module 1 returns to its initial state. After the current in the tenth capacitor C10 has completely drained away, the delay module 2, signal indication module 3, and self-recovery module 4 return to their initial states, facilitating the next test.

[0053] In another embodiment, the self-recovery is delayed by the fourth diode D4, or by a comparator or the like.

[0054] See also Figure 6 The connector model is NER23-AK5V20. There is no restriction on the connector model. The NER23-AK5V20 connector is used as an example here. In actual use, other connectors that comply with USB4 or Thunderbolt interface welding can also be selected.

[0055] When a USB4 or Thunderbolt interface has a short circuit or empty solder joint, the present invention only needs to be inserted once to determine whether there is an empty solder joint. If an empty solder joint is found, the location of the empty solder joint can be quickly located. The key start module 1, delay module 2, signal indication module 3, and self-recovery module 4 are provided to detect whether the circuit at the first diode D1 is abnormal, thereby avoiding the final detection of an empty solder joint error of the USB4 / Thunderbolt interface due to circuit abnormality.

[0056] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be considered in all respects as exemplary and non-restrictive.

[0057] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A USB4 or Thunderbolt interface empty soldering test circuit, characterized in that: The USB4 or Thunderbolt interface empty soldering test circuit includes a first diode, the cathode of the first diode is connected to the cathode of the button battery and one end of the first resistor, the anode of the button battery is connected to the S electrode of the second switch tube, one end of the second resistor, and one end of the connector, the other end of the second resistor is connected to the D electrode of the first switch tube and the G electrode of the second switch tube, the S electrode of the first switch tube is connected to the other end of the first resistor, the D electrode of the second switch tube is connected to the D electrode of the third switch tube and one end of the third resistor, the S electrode of the third switch tube is connected to the G electrode of the first switch tube and the other end of the connector, and the other end of the third resistor is connected to the anode of the first diode; the USB4 or Thunderbolt interface empty soldering test circuit can omit the third switch tube; The USB4 or Thunderbolt interface empty soldering test circuit is arranged on a circuit board to form a test board, and the test board tests the tested board where the USB4 or Thunderbolt interface is located by inserting a connector; There is a body diode and a ninth capacitor at the PIN pin of the USB4 or Thunderbolt interface; When the PIN pins of the USB4 or Thunderbolt interface are not soldered, after the test board is inserted, the button battery, the body diode at the USB4 or Thunderbolt interface, the ninth capacitor, the third resistor, and the first diode form a first loop, charging the ninth capacitor and generating a patrol charging current. The current generates a voltage drop across the third resistor and the first diode, forming a voltage that acts on the G electrode of the first switch tube, turning on the first switch tube. After the first switch tube is turned on, the voltage of the button battery is divided by the second resistor and the first resistor, causing the second switch tube to turn on, forming a second loop of the button battery, the second switch tube, the third resistor, and the first diode, causing the first diode to emit light; When the PIN pin of the USB4 or Thunderbolt interface is unsoldered, the first circuit is not formed and the first diode does not emit light. Whether the corresponding PIN pin of the USB4 or Thunderbolt interface is unsoldered can be determined by judging whether the first diode emits light. When the third switch tube exists, the USB4 or Thunderbolt interface empty soldering test circuit further includes: The button start module is used to start through the button switch. After the button switch is pressed, the continuous output voltage is supplied to the delay module; The delay module is used to supply voltage to the signal indication module after a delay after voltage input, and to supply voltage to the self-recovery module after a further delay; The signal indicator module is used to illuminate and indicate that the third switch tube is cut off during operation, and the test board does not form a loop with the tested board where the USB4 or Thunderbolt interface is located through the connector; The self-recovery module is used to control the key start module to stop supplying power after the voltage is input, so that the key start module, delay module, signal indication module and self-recovery module are restored to their initial states; The output end of the key start module is connected to the input end of the delay module, the output end of the delay module is connected to the input end of the signal indication module and the input end of the self-recovery module, and the output end of the self-recovery module is connected to the input end of the key start module.

2. The USB4 or Thunderbolt interface empty soldering test circuit according to claim 1, characterized in that: The key start module includes a key switch, a fourth resistor, a fourth transistor, a fifth transistor, a fifth resistor, and a sixth switch tube. One end of the key switch is connected to the positive electrode of the button battery, one end of the fifth resistor, and the S pole of the sixth switch tube. The other end of the key switch is connected to one end of the fourth resistor, the collector of the fifth transistor, the input end of the delay module, and the D pole of the second switch tube. The other end of the fourth resistor is connected to the base of the fourth transistor, the emitter of the fourth transistor is grounded, the collector of the fourth transistor is connected to the other end of the fifth resistor and the base of the fifth transistor, the emitter of the fifth transistor is connected to the D pole of the sixth switch tube, and the G pole of the sixth switch tube is connected to the output end of the self-recovery module.

3. The USB4 or Thunderbolt interface empty soldering test circuit according to claim 1, characterized in that: The delay module includes a third diode, a sixth resistor, a first potentiometer, and a tenth capacitor. The positive pole of the third diode is connected to the output end of the key start module, the negative pole of the third diode is connected to one end of the sixth resistor, the other end of the sixth resistor is connected to one end of the first potentiometer, the other end of the first potentiometer is connected to one end of the tenth capacitor, the input end of the signal indication module, and the input end of the self-recovery module, and the other end of the tenth capacitor is grounded.

4. The USB4 or Thunderbolt interface empty soldering test circuit according to claim 1, characterized in that: The signal indication module includes a seventh resistor and a second diode. One end of the fourth resistor is connected to the output end of the delay module, the other end of the fourth resistor is connected to the anode of the second diode, and the cathode of the second diode is connected to the G pole of the third switch tube.

5. The USB4 or Thunderbolt interface empty soldering test circuit according to claim 1, characterized in that: The self-recovery module includes a fourth diode and an eighth resistor. The cathode of the fourth diode is connected to the output end of the delay module, the anode of the fourth diode is connected to one end of the eighth resistor, and the other end of the eighth resistor is connected to the input end of the key start module.

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