Automatic voltage output circuit and test equipment

Abstract

The present invention discloses an automatic voltage output circuit and a test device. The automatic voltage output circuit includes a voltage output module, a reference voltage generating circuit and a comparison circuit. The input end of the voltage output module is connected to the test device, the output end is connected to the input end of the board to be tested, and the voltage output module is used to output the test voltage to the board to be tested. The input end of the reference voltage generating circuit is connected to the voltage output end of the test device, the output end is connected to the first input end of the comparison circuit, and the reference voltage generating circuit generates a reference voltage according to the voltage output by the test device. The second input end of the comparison circuit is connected to the board to be tested, the output end is connected to the controlled end of the voltage output module, and the comparison circuit is used to output a voltage signal. The voltage output module is also used to output a corresponding power supply voltage according to the voltage signal. The present invention solves the problem of a single test object of the test device, so that the same test device can test boards to be tested with multiple working voltages.

Description

Technical Field

[0001] The invention relates to PCBA testing, and in particular to an automatic voltage output circuit and testing equipment. Background Art

[0002] When testing a PCBA, the tester will put the PCBA that matches the output voltage of the test equipment into the test equipment for testing, so that the test equipment can only test PCBAs with the same working voltage as it. Therefore, different test equipment needs to be replaced to test PCBAs with different working voltages. If the PCBA is placed in the wrong place, there is a risk of damaging the PCBA. Replacing the test equipment affects work efficiency and increases testing costs. Summary of the invention

[0003] The main purpose of the present invention is to provide a voltage automatic output circuit and a test device, which are intended to select the voltage output by the test device to the board to be tested.

[0004] To achieve the above object, the present invention proposes an automatic voltage output circuit for automatically selecting a power supply voltage output by a test device to a board to be tested, wherein the automatic voltage output circuit comprises:

[0005] A voltage output module, wherein the input end of the voltage output module is used to connect to the voltage output end of the test equipment, the output end of the voltage output module is used to connect to the input end of the board to be tested, and the voltage output module is used to output a test voltage to the board to be tested;

[0006] a reference voltage generating circuit, wherein the input terminal of the reference voltage generating circuit is used to be connected to the voltage output terminal of the test equipment, the output terminal of the reference voltage generating circuit is connected to the first input terminal of the comparison circuit, and the reference voltage generating circuit is used to generate a reference voltage according to the voltage output by the test equipment; and

[0007] A comparison circuit, wherein a second input terminal of the comparison circuit is connected to a signal feedback terminal of the board to be tested, an output terminal of the comparison circuit is connected to a controlled terminal of the voltage output module, and the comparison circuit is used to compare the reference voltage with the feedback voltage and output a first voltage signal or a second voltage signal;

[0008] The voltage output module is further used to output a first supply voltage according to the first voltage signal; the voltage output module is further used to output a second supply voltage according to the second voltage signal, and the first supply voltage is greater than the second supply voltage.

[0009] In one embodiment, the reference voltage generating circuit includes a first resistor, a second resistor, a first capacitor and a first diode;

[0010] The input end of the first resistor is connected to the voltage output end of the test equipment, the second end of the first resistor is connected to the first end of the first capacitor, the first end of the second resistor and the cathode of the first diode, and then connected to the first input end of the comparison circuit, and the second end of the first capacitor, the second end of the second resistor and the anode of the first diode are all grounded.

[0011] In one embodiment, the comparison circuit includes a third resistor and a comparator;

[0012] The input end of the third resistor is used to be connected to the signal feedback end of the board to be tested, the output end of the third resistor is connected to the second input end of the comparator, and the output end of the comparator is connected to the input end of the voltage output module;

[0013] The comparator is used for comparing the reference voltage and the feedback voltage, and outputting a first voltage signal or a second voltage signal.

[0014] In one embodiment, the comparison circuit further includes a fourth resistor;

[0015] The input end of the fourth resistor is used to be connected to the voltage output end of the test equipment, and the output end of the fourth resistor is connected to the output end of the comparator and then connected to the controlled end of the voltage output module.

[0016] The present invention also provides a testing device, characterized in that it comprises the automatic voltage output circuit and the protection module as described above;

[0017] The input end of the protection module is used to connect to the power supply device, the output end of the protection module is connected to the input end of the automatic voltage output circuit, and the output end of the automatic voltage output circuit is used to connect to the input end of the board to be tested;

[0018] The protection module is used to disconnect the test equipment from the power supply device when the power supply voltage is greater than or equal to a preset voltage value.

[0019] In one embodiment, the protection module includes:

[0020] a voltage surge protection circuit, wherein an input end of the voltage surge protection circuit is used to be connected to a power supply device, and the voltage surge protection circuit is used to disconnect the test equipment from the power supply device when triggered; and

[0021] A key protection circuit, wherein the input end of the key protection circuit is used to be connected to a power supply device, the output end of the key protection circuit is connected to the input end of the automatic voltage output circuit, and the key protection circuit is used to disconnect the power supply device from the test equipment when the positive and negative poles of the power supply device are reversely connected;

[0022] The key protection circuit is also used to control the connection status between the power supply device and the test equipment.

[0023] In one embodiment, the voltage surge protection circuit includes a fuse and a fifth resistor;

[0024] The input end of the fifth resistor is used to be connected to the positive electrode of the power supply device, the output end of the fifth resistor is connected to the first end of the fuse, and the second end of the fuse is used to be connected to the negative electrode of the power supply device.

[0025] In one embodiment, the voltage surge protection circuit further includes an electrostatic discharge circuit;

[0026] The first end of the electrostatic discharge circuit is used to be connected to the ground end of the power supply device, and the second end of the electrostatic discharge circuit is used to be connected to both the negative electrode of the power supply device and the second end of the fuse.

[0027] In one embodiment, the key protection circuit includes a switch key, a switch tube, a second diode, a third diode and a relay;

[0028] The first pin of the switch button is connected to the controlled end of the switch tube, the second pin of the switch button is used to connect to the positive electrode of the power supply device, and the third pin of the switch button is grounded;

[0029] The input end of the switch tube is connected to the anode of the second diode, and the output end of the switch tube is connected to both the anode of the third diode and the first output end of the relay;

[0030] The cathode of the second diode is used to be connected to the positive electrode of the power supply device, the first input end of the relay and the second input end of the relay;

[0031] The second output terminal of the relay is a voltage output terminal of the test equipment, connected to the input terminal of the automatic voltage output circuit, and the third output terminal of the relay is suspended;

[0032] A cathode of the third diode is grounded.

[0033] In one embodiment, the protection module further includes an indicator light;

[0034] The input end of the indicator light is used to be connected to the positive pole of the power supply device, the output end of the indicator light is grounded, and the indicator light is used to indicate the connection status of the test equipment and the power supply device.

[0035] The present invention compares a reference voltage and a feedback voltage through a comparison circuit, and outputs a first voltage signal or a second voltage signal, and controls a voltage output module to automatically output a voltage corresponding to the working voltage of a board to be tested, so as to test boards to be tested with different working voltages without replacing the test equipment, thereby avoiding damage to the test equipment or the board to be tested when the test equipment tests the board to be tested with a different working voltage, solving the problem of a single test object applicable to the test equipment, and enabling the same test equipment to test boards to be tested with a variety of working voltages. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0037] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention;

[0038] Figure 2 A schematic diagram of the structure of a reference voltage generating circuit and a comparison circuit according to an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of the structure of a protection module according to an embodiment of the present invention;

[0040] Figure 4 It is a schematic diagram of an embodiment of the present invention.

[0041] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0044] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0045] Reference Figure 1 The present invention provides an automatic voltage output circuit for selecting a voltage output from a test device to a board to be tested, comprising a voltage output module 100, a reference voltage generating circuit 200 and a comparison circuit 300.

[0046] The voltage output module 100 has an input end connected to a voltage output end of a test device, and an output end connected to an input end of a board to be tested. The voltage output module 100 is used to output a test voltage to the board to be tested.

[0047] The reference voltage generating circuit 200 has an input terminal connected to a voltage output terminal of a test device, and an output terminal of the reference voltage generating circuit 200 is connected to a first input terminal of a comparison circuit 300. The reference voltage generating circuit 200 is used to generate a reference voltage according to a voltage output by the test device.

[0048] The comparison circuit 300 has a second input terminal connected to a signal feedback terminal of the board to be tested, and an output terminal of the comparison circuit 300 is connected to a controlled terminal of the voltage output module 100. The comparison circuit 300 is used to compare a reference voltage and a feedback voltage, and output a first voltage signal and a second voltage signal.

[0049] The voltage output module 100 is further used to output a first supply voltage according to the first voltage signal; the voltage output module 100 is further used to output a second supply voltage according to the second voltage signal, and the first supply voltage is greater than the second supply voltage.

[0050] The comparison circuit 300 may be a comparison chip or a comparator.

[0051] When the automatic voltage output circuit is powered on, the test voltage is first sent to the board to be tested through the voltage output module 100, and the board to be tested outputs a feedback voltage to the comparison circuit 300 according to the test voltage. If the working voltage of the board to be tested is the first power supply voltage, the feedback voltage is a high voltage greater than the reference voltage, the comparison circuit 300 compares the reference voltage with the feedback voltage, outputs a high voltage signal to the voltage output module 100, and controls the voltage output module 100 to output the first power supply voltage to the board to be tested; if the working voltage of the board to be tested is the second power supply voltage, the feedback voltage is a low voltage less than the reference voltage, the comparison circuit 300 compares the reference voltage with the feedback voltage, outputs a low voltage signal to the voltage output module 100, and controls the voltage output module 100 to output the second power supply voltage to the board to be tested.

[0052] The present invention can select and output a corresponding voltage according to the feedback signal of the board to be tested. For boards to be tested with different working voltages, the corresponding voltage signal is output by the comparison circuit, and the voltage output module is controlled to output a corresponding power supply voltage, so as to avoid damaging the test equipment or the board to be tested when the test equipment tests the board to be tested with a different working voltage. Moreover, the same device can be compatible with boards to be tested with multiple working voltages, and there is no need to frequently replace the device, which solves the problem of a single test object applicable to the test equipment.

[0053] Reference Figure 2 In one embodiment, the reference voltage generating circuit 200 includes a first resistor R1, a second resistor R2, a first capacitor C1 and a first diode D1.

[0054] The input end of the first resistor R1 is connected to the voltage output end of the test equipment, the second end of the first resistor R1 is connected to the first end of the first capacitor C1, the first end of the second resistor R2 and the cathode of the first diode D1, and then connected to the first input end of the comparison circuit 300, and the second end of the first capacitor C1, the second end of the second resistor R2 and the anode of the first diode D1 are all grounded.

[0055] The first diode D1 is a voltage stabilizing diode, and the reference voltage generating circuit 200 generates a constant reference voltage through the first diode D1. If the first diode D1 fails, the reference voltage can also be generated by dividing the first resistor R1 and the second resistor R2. The first capacitor C1 is used to filter the supply voltage.

[0056] In one embodiment, the comparison circuit 300 includes a third resistor R3 and a comparator L1 .

[0057] The input end of the third resistor R3 is connected to the signal feedback end of the board to be tested, the output end of the third resistor R3 is connected to the second input end of the comparator L1, the output end of the comparator L1 is connected to the input end of the voltage output module 100, and the comparator L1 is used to compare the reference voltage and the feedback voltage, and output the first voltage signal and the second voltage signal.

[0058] If the feedback voltage value is greater than the reference voltage value, the comparator L1 flips and outputs a high voltage signal, and the control voltage output module 100 outputs the first power supply voltage to the board to be tested; if the feedback voltage value is less than the reference voltage value, the comparator L1 outputs a low voltage signal, and the control voltage output module 100 outputs the second power supply voltage to the board to be tested.

[0059] In one embodiment, the comparison circuit further includes a fourth resistor R4.

[0060] The input end of the fourth resistor R4 is connected to the voltage output end of the test equipment, and the output end of the fourth resistor R4 is connected to the output end of the comparator L1 and then connected to the controlled end of the voltage output module 100 .

[0061] Reference Figure 2 , the specific circuit principle of the voltage automatic output circuit is described in detail below:

[0062] For example, the output voltage of the test equipment is 24V and the reference voltage is 3.3V. After the voltage automatic output circuit is powered on, the test equipment first outputs a 12V test voltage to the board to be tested.

[0063] If the operating voltage of the board to be tested is 24V, the board to be tested outputs a 5V voltage to the second input terminal of the comparator L1 through the signal feedback terminal, the reference voltage value is less than the feedback voltage value, and the comparator L1 outputs a high voltage signal to the controlled end of the voltage output module 100. After receiving the high voltage signal, the voltage output module 100 outputs a 24V voltage to the board to be tested.

[0064] If the operating voltage of the board to be tested is 12V, there is no voltage output at the signal feedback end of the board to be tested, that is, the feedback voltage is 0V, the reference voltage value is greater than the feedback voltage value, and the comparator L1 outputs a low voltage signal to the controlled end of the voltage output module 100. After receiving the low voltage signal, the test equipment outputs a 12V voltage to the board to be tested.

[0065] The present invention compares the reference voltage and the feedback voltage through a comparison circuit and outputs a first voltage signal or a second voltage signal, and controls the voltage output module to automatically select the power supply voltage output to the board to be tested, thereby avoiding damage to the test equipment or the board to be tested when the test equipment tests the board to be tested with a working voltage different from that of the test equipment. The present invention is compatible with boards to be tested with multiple working voltages, does not require frequent replacement of the test equipment, is convenient for testing, and solves the problem of a single test object applicable to the test equipment.

[0066] Reference Figure 3 and Figure 4 The present invention also provides a test device, comprising the above-mentioned automatic voltage output circuit 500 and a protection module 400. The input end of the protection module 400 is connected to the power supply device, the output end of the protection module 400 is connected to the input end of the automatic voltage output circuit 500, the output end of the protection module 400 is also used to connect to other subsequent circuits, and the output end of the automatic voltage output circuit 500 is connected to the input end of the board to be tested. The protection module 400 is used to disconnect the test device from the power supply device when the power supply voltage is too large to prevent the abnormal voltage from damaging the test device.

[0067] The detailed structure of the automatic voltage output circuit 500 can be referred to the above-mentioned embodiment, which will not be repeated here; it can be understood that since the above-mentioned automatic voltage output circuit 500 is used in the test equipment of the present invention, the embodiment of the test equipment of the present invention includes all technical solutions of all embodiments of the above-mentioned automatic voltage output circuit 500, and the technical effects achieved are also exactly the same, which will not be repeated here.

[0068] The protection module 400 includes a voltage surge protection circuit 410 and a key protection circuit 420 .

[0069] An input end of the voltage surge protection circuit 410 is connected to the power supply device, and the voltage surge protection circuit 410 is used to disconnect the test equipment from the power supply device when the power supply voltage surges.

[0070] The input end of the key protection circuit 420 is connected to the power supply device, the output end of the key protection circuit 420 is connected to the input end of the automatic voltage output circuit 500, the output end of the key protection circuit 420 is also used to connect to other subsequent circuits, and the key protection circuit 420 is used to disconnect the power supply device from the test equipment when the positive and negative poles of the power supply device are reversed.

[0071] The key protection circuit 420 is also used to control the connection status between the power supply device and the test equipment.

[0072] When the test equipment is working, if the supply voltage is greater than the preset voltage value or the supply voltage growth rate is greater than the preset voltage growth rate within a certain period of time, the voltage surge circuit is triggered to automatically disconnect the circuit connection between the test equipment and the power supply device to achieve power-off protection; if the voltage of the test equipment is abnormal but does not reach the triggering condition of the voltage surge protection circuit 410, the circuit connection between the test equipment and the power supply device can also be manually disconnected through the button protection circuit 420 to achieve power-off protection.

[0073] The present invention realizes double protection by automatically cutting off the power when overvoltage occurs through the voltage surge protection circuit 410 and manually cutting off the power when voltage is abnormal through the key protection circuit 420, making the use of electricity by the test equipment safer. The key protection circuit 420 can also disconnect the connection between the test equipment and the automatic voltage output circuit when the positive and negative poles of the circuit are reversely connected to the positive and negative poles of the power supply device, thereby preventing the circuit from being damaged by reverse connection of the positive and negative poles.

[0074] In one embodiment, the voltage surge protection circuit 410 includes a fuse F1 and a fifth resistor R5 .

[0075] An input end of the fifth resistor R5 is connected to the positive electrode of the power supply device, an output end of the fifth resistor R5 is connected to a first end of the fuse F1, and a second end of the fuse F1 is connected to a negative electrode of the power supply device.

[0076] In the above embodiment, the fifth resistor R5 is a varistor.

[0077] When the test equipment is working, if the power supply voltage is greater than the preset voltage value, the resistance of the fifth resistor R5 becomes smaller, the current passing through the fuse F1 is too large, the fuse F1 itself generates heat to melt the fuse, disconnecting the circuit connection between the test equipment and the power supply device, and realizing power-off protection.

[0078] The present invention realizes automatic power off due to overvoltage through the fuse F1, has a fast response speed, and can effectively avoid circuit damage due to overvoltage.

[0079] In one embodiment, the voltage surge protection circuit 410 further includes an electrostatic discharge circuit 411 .

[0080] The first end of the electrostatic discharge circuit 411 is connected to the ground of the power supply device, and the second end of the electrostatic discharge circuit 411 is connected to the negative electrode of the power supply device and the second end of the fuse F1. The ground of the power supply device is connected to the housing of the test equipment or is grounded.

[0081] In one embodiment, the electrostatic release circuit 411 includes a sixth resistor R6 and a second capacitor C2, the sixth resistor R6 and the second capacitor C2 are connected in parallel, the first ends of the sixth resistor R6 and the sixth capacitor are connected to the ground end of the power supply device, and the second ends of the sixth resistor R6 and the sixth capacitor are connected to the negative electrode of the power supply device and the second end of the fuse F1.

[0082] In one embodiment, the key protection circuit 420 includes a switch key W1 , a switch tube Q1 , a second diode D2 , a third diode D3 and a relay J1 .

[0083] The switch tube Q1 can be an NPN transistor or an N-channel MOS tube. In this embodiment, the switch tube Q1 is an NPN transistor.

[0084] The first pin of the switch button W1 is controllably connected to the switch tube Q1 , the second pin of the switch button W1 is connected to the positive electrode of the power supply device, and the third pin of the switch button W1 is grounded.

[0085] The input end of the switch tube Q1 is connected to the anode of the second diode D2 , and the output end of the switch tube Q1 is connected to both the anode of the third diode D3 and the first output end of the relay J1 .

[0086] The cathode of the second diode D2 is connected to the positive electrode of the power supply device, the first input end of the relay J1 and the second input end of the relay J1.

[0087] The second output terminal of the relay J1 is the voltage output terminal of the test equipment, connected to the input terminal of the automatic voltage output circuit 500. The second output terminal of the relay J1 is also used to connect to other subsequent circuits. The third output terminal of the relay J1 is suspended.

[0088] The cathode of the third diode D3 is grounded.

[0089] When the test equipment is powered on and the key switch is in the initial state, the second output terminal of the relay J1 is connected to the third output terminal, and the first and second pins of the key switch are connected. The path between the input and output terminals of the switch tube Q1 is connected, the positive electrode of the power supply device is grounded through the switch tube Q1, and the key protection circuit 420 outputs no voltage to the voltage automatic output circuit 500.

[0090] After pressing the push switch, the first and third pins of the push switch are connected, the path between the input and output ends of the switch tube Q1 is connected, current flows through the relay J1, and the second input end of the relay J1 is connected to the second output end due to magnetic attraction, and the power supply device supplies power to the automatic voltage output circuit 500.

[0091] If an abnormal voltage appears in the test equipment, the tester can manually press the switch button W1 to disconnect the circuit connection between the power supply device and the automatic voltage output circuit 500 to achieve power-off protection.

[0092] When the positive and negative poles of the input terminal of the key protection circuit 420 are reversely connected to the positive and negative poles of the power supply device, the cathode of the third diode is a high voltage, the first pin of the key switch W1 is always at a low level, the switch tube Q1 is disconnected, no current passes through the relay J1, and the key protection circuit 420 has no voltage output to the voltage automatic output circuit 500.

[0093] In one embodiment, the protection module 400 further includes an indicator light D4.

[0094] The input end of the indicator light D4 is used to be connected to the positive pole of the power supply device, and the output end of the indicator light D4 is grounded. The indicator light D4 is used to indicate the connection status between the test equipment and the power supply device.

[0095] If the power supply device supplies power to the test equipment normally, the indicator light D4 will light up; if the power supply device supplies power to the test equipment abnormally, the indicator light D4 will go out, and the test personnel can promptly discover the power supply abnormality and troubleshoot the problem.

[0096] The present invention automatically selects and outputs the voltage that matches the board to be tested through the automatic voltage output circuit, and does not require manual operation to frequently replace the equipment, thereby improving the test efficiency and solving the problem of the single test object of the test equipment. The voltage surge protection circuit automatically cuts off the power when overvoltage occurs, and the key protection circuit manually cuts off the power when the voltage is abnormal, thereby achieving double protection and making the test equipment safer in using electricity. The key protection circuit can also disconnect the test equipment from the automatic voltage output circuit when the positive and negative poles of the circuit are reversely connected to the positive and negative poles of the power supply device, thereby preventing the positive and negative poles from being reversely connected and damaging the circuit.

[0097] The above are only optional embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A voltage automatic output circuit for automatically selecting the supply voltage output by a test device to a board to be tested, characterized in that: The automatic voltage output circuit comprises: A voltage output module, wherein the input end of the voltage output module is used to connect to the voltage output end of the test equipment, the output end of the voltage output module is used to connect to the input end of the board to be tested, and the voltage output module is used to output a test voltage to the board to be tested; a reference voltage generating circuit, wherein the input terminal of the reference voltage generating circuit is used to be connected to the voltage output terminal of the test device, the output terminal of the reference voltage generating circuit is connected to the first input terminal of the comparison circuit, and the reference voltage generating circuit is used to generate a reference voltage according to the voltage output by the test device; and A comparison circuit, wherein a second input terminal of the comparison circuit is connected to a signal feedback terminal of the board to be tested, an output terminal of the comparison circuit is connected to a controlled terminal of the voltage output module, and the comparison circuit is used to compare the reference voltage and the feedback voltage, and output a first voltage signal or a second voltage signal; The voltage output module is further used to output a first supply voltage according to the first voltage signal; the voltage output module is further used to output a second supply voltage according to the second voltage signal, and the first supply voltage is greater than the second supply voltage; The reference voltage generating circuit comprises a first resistor, a second resistor, a first capacitor and a first diode; The input end of the first resistor is connected to the voltage output end of the test equipment, the second end of the first resistor is connected to the first end of the first capacitor, the first end of the second resistor and the cathode of the first diode, and then connected to the first input end of the comparison circuit, and the second end of the first capacitor, the second end of the second resistor and the anode of the first diode are grounded; The comparison circuit includes a third resistor and a comparator; The input end of the third resistor is used to be connected to the signal feedback end of the board to be tested, the output end of the third resistor is connected to the second input end of the comparator, and the output end of the comparator is connected to the input end of the voltage output module; The comparator is used for comparing the reference voltage and the feedback voltage, and outputting a first voltage signal or a second voltage signal.

2. The automatic voltage output circuit according to claim 1, characterized in that: The comparison circuit further includes a fourth resistor; The input end of the fourth resistor is used to be connected to the voltage output end of the test equipment, and the output end of the fourth resistor is connected to the output end of the comparator and then connected to the controlled end of the voltage output module.

3. A testing device, characterized in that: It comprises the automatic voltage output circuit and the protection module as claimed in any one of claims 1 to 2; The input end of the protection module is used to connect to the power supply device, the output end of the protection module is connected to the input end of the automatic voltage output circuit, and the output end of the automatic voltage output circuit is used to connect to the input end of the board to be tested; The protection module is used to disconnect the test equipment from the power supply device when the power supply voltage is greater than or equal to a preset voltage value.

4. The testing device according to claim 3, characterized in that The protection module comprises: a voltage surge protection circuit, wherein an input end of the voltage surge protection circuit is used to be connected to a power supply device, and the voltage surge protection circuit is used to disconnect the test equipment from the power supply device when triggered; and A key protection circuit, wherein the input end of the key protection circuit is used to be connected to a power supply device, the output end of the key protection circuit is connected to the input end of the automatic voltage output circuit, and the key protection circuit is used to disconnect the power supply device from the test equipment when the positive and negative poles of the power supply device are reversely connected; The key protection circuit is also used to control the connection status between the power supply device and the test equipment.

5. The test device according to claim 4, characterized in that The voltage surge protection circuit includes a fuse and a fifth resistor; The input end of the fifth resistor is used to be connected to the positive electrode of the power supply device, the output end of the fifth resistor is connected to the first end of the fuse, and the second end of the fuse is used to be connected to the negative electrode of the power supply device.

6. The test device according to claim 5, characterized in that The voltage surge protection circuit also includes an electrostatic discharge circuit; The first end of the electrostatic discharge circuit is used to be connected to the ground end of the power supply device, and the second end of the electrostatic discharge circuit is used to be connected to both the negative electrode of the power supply device and the second end of the fuse.

7. The testing device according to claim 4, characterized in that The key protection circuit includes a switch key, a switch tube, a second diode, a third diode and a relay; The first pin of the switch button is connected to the controlled end of the switch tube, the second pin of the switch button is used to connect to the positive electrode of the power supply device, and the third pin of the switch button is grounded; The input end of the switch tube is connected to the anode of the second diode, and the output end of the switch tube is connected to both the anode of the third diode and the first output end of the relay; The cathode of the second diode is used to be connected to the positive electrode of the power supply device, the first input end of the relay and the second input end of the relay; The second output terminal of the relay is a voltage output terminal, connected to the input terminal of the automatic voltage output circuit, and the third output terminal of the relay is suspended; A cathode of the third diode is grounded.

8. The testing device according to claim 4, characterized in that The protection module also includes an indicator light; The input end of the indicator light is used to be connected to the positive pole of the power supply device, the output end of the indicator light is grounded, and the indicator light is used to indicate the connection status of the test equipment and the power supply device.

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