Opto-coupler test system

Abstract

The application discloses a photoelectric coupler testing system, which comprises a control unit and a testing current generating unit, wherein the control unit is adapted to output a control signal to the testing current generating unit; the testing current generating unit is adapted to receive the control signal, generate a testing current corresponding to the control signal and output to a photoelectric coupler to be tested; and the control signal is used for indicating a waveform and / or current amplitude of the testing current. The above scheme can realize the testing of the photoelectric coupler without input of an optical signal.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optoelectronic technology, and in particular to an optoelectronic coupler testing system. BACKGROUND

[0002] An optoelectronic coupler is generally composed of a light-emitting device, a photodetector, a signal receiving, amplifying and output control circuit, etc. The light-emitting device is generally an infrared light-emitting diode (IR LED), the photodetector is generally a photodiode, and the signal receiving, amplifying and output control circuit is generally composed of a transimpedance amplifier, a comparator and an output stage circuit. The light emitted by the light-emitting device irradiates on the photodiode, and the photodiode converts the light signal into an electric signal.

[0003] Generally, the photodetector, the signal receiving, amplifying and output control circuit are integrated on the same chip, and then integrated together with the light-emitting device through packaging, i.e. the packaged optoelectronic coupler contains the light-emitting device, but the light coupling chip in the optoelectronic coupler itself does not contain the light-emitting device.

[0004] Under the condition of no light-emitting device, i.e. under the condition of no light signal input, the testing of the optoelectronic coupler cannot be realized. SUMMARY

[0005] The present application embodiment solves how to realize the testing of the optoelectronic coupler under the condition of no light signal input.

[0006] To solve the above technical problem, the present application embodiment provides an optoelectronic coupler testing system, comprising: a control unit and a test current generating unit, wherein: the control unit is adapted to output a control signal to the test current generating unit; the test current generating unit is adapted to receive the control signal, generate a test current corresponding to the control signal and output to the optoelectronic coupler to be tested; and the control signal is used to indicate the waveform and / or current amplitude of the test current.

[0007] Optionally, the control signal comprises an enable signal and an amplitude adjustment signal; the test current generating unit comprises an amplitude input port and an enable port; wherein the enable port inputs the enable signal; the amplitude input port inputs the amplitude adjustment signal; and the current amplitude of the test current is determined by the amplitude adjustment signal.

[0008] Optionally, the optoelectronic coupler testing system further comprises a variable resistor, a first end of which is coupled with the amplitude input port, a second end of which is grounded, and a control end of which inputs the amplitude adjustment signal; and the current amplitude of the test current is related to the resistance value of the variable resistor.

[0009] Optionally, the optoelectronic coupler test system further comprises a waveform adjustment unit, a first end of the waveform adjustment unit is coupled to the enable port, a second end of the waveform adjustment unit is grounded, and a first end of the waveform adjustment unit outputs a waveform adjustment signal; and a waveform of the test current is related to the waveform adjustment signal.

[0010] Optionally, when the enable signal is a low-level signal, the test current generation unit stops working.

[0011] Optionally, the test current is a direct current or a pulse current.

[0012] Optionally, the optoelectronic coupler comprises a differential trans-impedance amplification unit, a first photodiode, and a second photodiode, wherein: a positive electrode of the first photodiode is coupled to a first input end of the differential trans-impedance amplification unit, and a negative electrode of the first photodiode is connected to a first power supply voltage; a positive electrode of the second photodiode is coupled to a second input end of the differential trans-impedance amplification unit, and a negative electrode of the second photodiode is connected to the first power supply voltage; a first output end of the differential trans-impedance amplification unit outputs a first current, and a second output end of the differential trans-impedance amplification unit outputs a second current; the first current is generated by the first photodiode, and the second current is generated by the second photodiode.

[0013] Optionally, the optoelectronic coupler test system further comprises a power supply test unit, which is adapted to test a first power supply voltage and a second power supply voltage output by a linear voltage stabilizer in the optoelectronic coupler to be tested.

[0014] Optionally, the power supply test unit comprises a second follower, a second inverter, a NAND gate circuit, an OR gate circuit, a level shift circuit, a first switch unit, and a second switch unit, wherein: an input end of the second follower inputs an enable signal, and an output end of the second follower is coupled to a first input end of the NAND gate circuit; an input end of the second inverter inputs the enable signal, and an output end of the second inverter is coupled to a first input end of the OR gate circuit; a second input end of the NAND gate circuit inputs a power supply test signal, and an output end of the NAND gate circuit outputs a first test enable signal; a second input end of the OR gate circuit inputs the power supply test signal, and an output end of the OR gate circuit is coupled to an input end of the level shift circuit; an output end of the level shift circuit outputs a second test enable signal; a first end of the first switch unit inputs the first power supply voltage, a control end of the first switch unit inputs the first test enable signal, and a second end of the first switch unit is coupled to an output end of the power supply test unit; a first end of the second switch unit inputs the second power supply voltage, a control end of the second switch unit inputs the second test enable signal, and a second end of the second switch unit is coupled to the output end of the power supply test unit.

[0015] Compared with the prior art, the technical scheme of the embodiment of the present application has the following beneficial effects:

[0016] The control unit generates and outputs a control signal, and the test current generating unit generates a corresponding test current according to the received control signal, and tests the photoelectric coupler to be tested by the test current. The waveform and / or current amplitude of the test current are indicated by the control signal, simulating the current generated in the working process of the photodetector, which can effectively solve the problem of being unable to test without light signal input, and the circuit structure is simple.

[0017] Further, the photoelectric coupler test system further comprises a power supply test unit for testing the power supply output by the linear voltage stabilizing source of the photoelectric coupler, so as to realize the power supply reliability test of the photoelectric coupler. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a partial circuit structure schematic diagram of a photoelectric coupler in an embodiment of the present application;

[0019] Figure 2 is a structure schematic diagram of a photoelectric coupler test system in an embodiment of the present application;

[0020] Figure 3 is a circuit structure schematic diagram of a test current generating unit in an embodiment of the present application;

[0021] Figure 4 is a circuit structure schematic diagram of a power supply test unit in an embodiment of the present application. DETAILED DESCRIPTION

[0022] Under the condition of no light-emitting device, that is, under the condition of no light signal input, the photoelectric coupler cannot be tested.

[0023] In the embodiment of the present application, the control unit generates and outputs a control signal, and the test current generating unit generates a corresponding test current according to the received control signal, and tests the photoelectric coupler to be tested by the test current. The waveform and / or current amplitude of the test current are indicated by the control signal, simulating the current generated in the working process of the photodetector, which can effectively solve the problem of being unable to test without light signal input, and the circuit structure is simple.

[0024] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the drawings.

[0025] The embodiment of the present application provides a photoelectric coupler test system for testing a photoelectric coupler. Referring to Figure 1 , a partial circuit structure schematic diagram of a photoelectric coupler in an embodiment of the present application is given. The above-mentioned partial circuit structure refers to Figure 1 The circuit structure shown is only a part of the circuit structure of the photoelectric coupler.

[0026] In some embodiments, the opto-coupler can include a differential trans-impedance amplification unit, a first photodiode PD-D, and a second photodiode PD-L, wherein:

[0027] The positive electrode of the first photodiode PD-D is coupled to the first input terminal of the differential trans-impedance amplifier, and the negative electrode of the first photodiode PD-D is coupled to the first power supply voltage VDD_L.

[0028] The positive electrode of the second photodiode PD-L is coupled to the first input terminal of the differential trans-impedance amplifier, and the negative electrode of the second photodiode PD-L is coupled to the first power supply voltage VDD_L.

[0029] The positive electrode of the first photodiode PD-D is coupled to the first input terminal of the differential trans-impedance amplifier, and the negative electrode of the first photodiode PD-D is coupled to the first power supply voltage VDD_L.

[0030] In some embodiments, when the opto-coupler is in use, if the second photodiode PD-L is irradiated by the light emitted by the light-emitting device (such as an infrared LED), the second current generated by the second photodiode PD-L includes a photo current and a second dark current.

[0031] The first photodiode PD-D is a light-receiving photodiode, which cannot receive the light emitted by the light-emitting device, and thus cannot generate a photo current. Therefore, the current generated by the first photodiode PD-D is a first dark current.

[0032] In some embodiments, the first photodiode PD-D can be sealed in a light-tight structure. For example, the top of the first photodiode PD-D can be covered with thick aluminum. It can be understood that the specific arrangement of the first photodiode PD-D is not limited to the above-mentioned example of "covered with thick aluminum on the top". Other arrangements of the first photodiode PD-D can also exist, which are not described here.

[0033] In some embodiments, when the opto-coupler is in use, the first output terminal of the differential trans-impedance amplification unit outputs a first dark current, and the second output terminal outputs a second dark current and a photo current. The two output terminals of the differential trans-impedance amplification unit can be coupled to the two input terminals of a differential amplifier, and the first dark current can be used to eliminate the second dark current in the second current through the differential amplifier. The specific working principle of the opto-coupler can be known by those skilled in the art according to the prior art, and the specific working principle of the opto-coupler is not described here.

[0034] In a specific implementation, when testing the optocoupler, the light emitting device is in an off state. To achieve the testing of the optocoupler, a test current (such as Figure 1 TIA Test) is input to the second input end of the differential transimpedance amplification unit to simulate the photoelectric current signal generated by the second photoelectric diode PD-L when in an on state.

[0035] In a specific implementation, the differential transimpedance operational amplification unit can be composed of resistors, NPN triodes, current sources, capacitors, and the like.

[0036] Specifically, as shown in Figure 1 , the differential transimpedance operational amplification unit can include resistors R1, R2, R3, R4, triodes N1, N2, N3, N4, N5, N6, current sources I1, I2, I3, I4, and the like. The differential transimpedance operational amplification unit can also include two gain resistors R5 and R6. In addition, the differential transimpedance operational amplification unit also includes capacitors C1 and C2, which play a compensating role for loop stability.

[0037] Specifically, the circuit structure of each component in the differential transimpedance operational amplification unit can refer to Figure 1 .

[0038] Those skilled in the art can understand that the circuit structure of the transimpedance operational amplification unit shown in Figure 1 is only one specific implementation, which is used as an exemplary description in the embodiments of the present application. In actual applications, there can also be transimpedance operational amplification units with other circuit structures. The optocoupler in the embodiments of the present application can also use transimpedance operational amplification units with other circuit structures.

[0039] That is, the specific circuit structure of the transimpedance operational amplification unit does not affect the protection of the embodiments of the present application.

[0040] In the embodiments of the present application, the optocoupler testing system can include a control unit 11 and a test current generation unit 12. Referring to Figure 2 , a structure diagram of an optocoupler testing system in the embodiments of the present application is given. The following is described in combination with Figure 1 and Figure 2 .

[0041] In a specific implementation, the control unit 11 can be adapted to output a control signal to the test current generation unit 12;

[0042] The test current generation unit 12 is adapted to receive control signals, generate test currents corresponding to the control signals, and output them to the optocoupler under test.

[0043] In this embodiment of the invention, the waveform of the test current, or the amplitude of the test current, or both the waveform and the amplitude of the test current can be controlled by a control signal.

[0044] In a specific implementation, the control signal may include an enable signal and an amplitude adjustment signal, which can be two independent signals. Correspondingly, the test current generation unit 12 may include two input ports: an amplitude input port and an enable port, wherein the amplitude input port can input the amplitude adjustment signal, and the enable port can input the enable signal. The current amplitude of the test current can be determined by the amplitude adjustment signal.

[0045] Specifically, the optocoupler testing system may include a variable resistor. The first terminal of the variable resistor can be coupled to the amplitude input port of the test current generation unit 12, the second terminal of the variable resistor is grounded, and the control terminal of the variable resistor receives an amplitude adjustment signal. The resistance value of the variable resistor is adjusted using the amplitude adjustment signal, thereby adjusting the amplitude of the test current.

[0046] In practice, the variable resistor can be a sliding rheostat or other device capable of changing its resistance value.

[0047] The optocoupler testing system may also include an ammeter A. Ammeter A displays the amplitude of the test current corresponding to the adjustment of the variable resistor's resistance value.

[0048] In a specific implementation, the optocoupler testing system may also include a waveform adjustment unit 13. The first terminal of the waveform adjustment unit 13 is coupled to the enable port of the test current generation unit 12, outputting a waveform adjustment signal; the second terminal of the waveform adjustment unit 13 is grounded. The waveform of the test current is related to the waveform adjustment signal.

[0049] The waveform adjustment signal can be a DC signal, and correspondingly, the test current can be a DC current, meaning the waveform of the test current is a DC waveform. Alternatively, the waveform adjustment signal can be a pulse signal, and correspondingly, the test current can be a pulse current, meaning the waveform of the test current is a pulse waveform.

[0050] In practice, when the enable signal is low, the test current generation unit 12 can be turned off and enter a low-power mode with almost no static current consumption.

[0051] The working principle of the optocoupler testing system is explained below.

[0052] During testing, the control unit 11 can be coupled to the test current generation unit 12 via two test pads (PADs): Test PAD1 and Test PAD2. Test PAD1 is externally connected to a sliding rheostat. The sliding rheostat is connected in series with ammeter A, thus enabling the acquisition of the desired current amplitude.

[0053] When Test PAD2 is not in test mode, it is at a low level (that is, the enable signal is at a low level or there is no enable signal), which allows the test current generation unit 12 to be turned off and enter a low power mode with almost no static current consumption.

[0054] When Test PAD2 is at a high level (i.e., the enable signal is high), the test current generation unit 12 is enabled. The amplitude of the test current is adjusted by regulating the sliding rheostat through the amplitude adjustment signal.

[0055] When the signal output by the waveform adjustment unit 13 is a DC signal and the Test PAD2 is at a high level (i.e., the power signal is at a high level), the amplitude of the test current is adjusted by adjusting the resistance of the sliding rheostat, thereby realizing the testing of the internal operational characteristics of the optocoupler, including the input current threshold and the input current hysteresis characteristics.

[0056] When the signal output by the waveform adjustment unit 13 is a pulse signal, the enable signal is modulated into a pulse signal. Correspondingly, the test current generated by the test current generation unit 12 is a pulse signal of the same frequency, which can be used to test and verify the dynamic characteristics of the optocoupler, including the input and output response time, output rise time (tr), and output fall time (tf).

[0057] In specific implementation, refer to Figure 3 The present invention provides a schematic diagram of the circuit structure of a test current generation unit 12 in an embodiment of the present invention.

[0058] Figure 3 In the test current generation unit 12, the first follower FO1, the first inverter INV1, the seventh resistor R7, the eighth resistor R8, and MOS transistors M1 to M11, wherein MOS transistors M1 to M6 are PMOS transistors and MOS transistors M7 to M11 are NMOS transistors.

[0059] Specifically, the connection relationships between the various components can be referred to accordingly. Figure 3 .

[0060] In summary, by generating and outputting control signals through the control unit, the test current generation unit 12 generates corresponding test currents based on the received control signals, and the optocoupler under test is tested using these test currents. By indicating the waveform and / or amplitude of the test current through the control signals, the current generated during the operation of the photodetector is simulated, effectively solving the problem of being unable to test without an optical signal input. Furthermore, the circuit structure is simple.

[0061] In practical implementation, the optocoupler testing system can also test the linear voltage regulator inside the optocoupler to test whether the linear voltage regulator inside the optocoupler can output the corresponding voltage value normally.

[0062] In practical applications, it is known that the linear voltage regulator inside the optocoupler can output a first power supply voltage and a second power supply voltage, which are not equal. Specifically, the first power supply voltage can be the voltage difference relative to ground, typically represented by VDD_L; the second power supply voltage can be the voltage difference relative to the power supply voltage supplying the optocoupler, typically represented by VDD_H.

[0063] In practical implementation, the optocoupler testing system can test both the first power supply voltage and the second power supply voltage.

[0064] Reference Figure 4 A circuit diagram of a power supply test unit according to an embodiment of the present invention is provided. The power supply test unit includes a second follower FO2, a second inverter INV2, a NAND gate, an OR gate, a level shifter 40, a first switching unit, and a second switching unit, wherein:

[0065] The input terminal of the second follower FO2 can be connected to an enable signal, and the output terminal of the second follower FO2 can be coupled to the first input terminal of the NAND gate circuit.

[0066] The input terminal of the second inverter INV2 can be used to input an enable signal, and the output terminal of the second inverter INV2 can be coupled to the first input terminal of the OR gate circuit.

[0067] The first input terminal of the NAND gate circuit receives an enable signal, the second input terminal of the NAND gate circuit receives a power test signal, and the output terminal of the NAND gate circuit outputs the first test enable signal VDD_L_EN.

[0068] An enable signal is input to the first input terminal of the OR gate circuit, a power supply test signal is input to the second input terminal of the OR gate circuit, and the output terminal of the OR gate circuit is coupled to the input terminal of the level shifting circuit 40.

[0069] The output terminal of the level shifting circuit 40 outputs a second test enable signal VDD_H_EN; the level shifting circuit 40 performs level shifting on the signal output terminal of the OR gate circuit OR.

[0070] The first terminal of the first switching unit is input to the first power supply voltage VDD_L, the control terminal of the first switching unit is input to the first test enable signal VDD_L_EN, and the second terminal of the first switching unit is coupled to the output terminal of the power supply test unit.

[0071] The first terminal of the second switching unit receives the second power supply voltage VDD_H, the control terminal of the second switching unit receives the second test enable signal VDD_H_EN, and the second terminal of the second switching unit is coupled to the output terminal of the power supply test unit.

[0072] In a specific implementation, the second follower FO2, the second inverter INV2, the NAND gate, and the OR gate can be powered by the first power supply voltage.

[0073] In practical implementation, a test PAD for inputting an enable signal can be set up in the optocoupler test system. This test PAD is coupled to the input terminal of the second follower FO2 and the input terminal of the second inverter INV2, such as... Figure 4 Test PAD3 in the middle.

[0074] In the optocoupler testing system, another test PAD is set up to input the power supply test signal. This test PAD can be coupled to both the second input of an OR gate and the second input of a NAND gate, such as... Figure 4 V_Test PAD4 in the example.

[0075] The NAND gate outputs a first test enable signal VDD_L_EN, and the level shifter 40 outputs a second test enable signal VDD_H_EN. The level shifter 40 raises the output voltage of the OR gate from the first power supply voltage VDD_L to the second power supply voltage VDD_H.

[0076] The first switching unit can be a PMOS transistor MP1, wherein: the source of the PMOS transistor MP1 is input to the first power supply voltage VDD_L, the control terminal of the PMOS transistor MP1 can input the first test enable signal VDD_L_EN, and the drain of the PMOS transistor MP1 is coupled to the output terminal of the power supply test unit.

[0077] The second switching unit can also be a PMOS transistor MP2, wherein: the source of the PMOS transistor MP2 is input to the second power supply voltage VDD_H, the control terminal of the PMOS transistor MP2 can input the second test enable signal VDD_H_EN, and the drain of the PMOS transistor MP2 is coupled to the output terminal of the power supply test unit.

[0078] In practical implementation, the optocoupler test unit can also be equipped with a test PAD to receive the test signal output from the power supply test unit. Specifically, this PAD can be... Figure 4 The V_Test PAD shown.

[0079] In practical applications, the voltage on V_Test PAD will change under the combined effect of the enable signal and the power supply test signal. If the linear regulated source of the optocoupler is working normally, the voltage on V_Test PAD will switch between the first power supply voltage and the second power supply voltage.

[0080] In practice, a current-limiting resistor can be set between the power supply test unit and the V_Test PAD. The current-limiting resistor mainly serves to protect the port of the V_Test PAD.

[0081] The working principle of the power supply test unit provided in the above embodiments of the present invention will be explained below.

[0082] When Test PAD3 is floating or when a low-level signal is input to Test PAD3 (i.e., the enable signal is low), the power supply test unit's test function is disabled. Typically, a pull-down resistor can be added between Test PAD3 and ground to ensure a low-level signal is input to Test PAD3 by default. When a high-level signal is input to Test PAD3 (i.e., the enable signal is high), the power supply test unit's test function is enabled.

[0083] When both Test PAD3 and Test PAD4 input a high-level signal (i.e., the power supply test signal is high), the first test enable signal VDD_L_EN is low, and the second test enable signal VDD_H_EN is high. At this time, PMOS transistor M1 is turned on, and the signal output on V_Test PAD is the first power supply voltage VDD_L. Using instruments such as a voltmeter, measure whether the voltage value of the first power supply voltage VDD_L is equal to the first theoretical voltage value (e.g., 5V). If the measured voltage value of the first power supply voltage VDD_L differs significantly from the first theoretical voltage value, then the linear regulator of the optocoupler is faulty.

[0084] When a high-level signal is input to Test PAD3 and a low-level signal is input to Test PAD4 (i.e., the power supply test signal is low), the first test enable signal VDD_L_EN is high, and the second test enable signal VDD_H_EN is low. At this time, PMOS transistor M2 is turned on, and the signal output on V_Test PAD is the second power supply voltage VDD_D. Using instruments such as a voltmeter, measure whether the voltage value of the second power supply voltage VDD_D is equal to the second theoretical voltage value (e.g., 12V). If the measured voltage value of the second power supply voltage VDD_D differs significantly from the second theoretical voltage value, then the linear regulator of the optocoupler is faulty.

[0085] It is understood that the specific values ​​of the first theoretical voltage and the second theoretical voltage mentioned above are only illustrative examples. For different optocouplers, the corresponding first theoretical voltage and second theoretical voltage values ​​can be other values.

[0086] Therefore, the power supply test unit provided in the above embodiments of the present invention can be used to test the linear voltage regulator inside the optocoupler.

[0087] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A test system for an optocoupler, characterized in that, include: The control unit and the test current generation unit, wherein: The control unit is adapted to output a control signal to the test current generation unit; The test current generation unit is adapted to receive the control signal, generate a test current corresponding to the control signal, and output it to the optocoupler under test; the control signal is used to indicate the waveform and / or current amplitude of the test current. The optocoupler includes: a differential transimpedance amplifier unit, a first photodiode, and a second photodiode, wherein: the positive terminal of the first photodiode is coupled to the first input terminal of the differential transimpedance amplifier unit, and its negative terminal is connected to a first power supply voltage; the positive terminal of the second photodiode is coupled to the second input terminal of the differential transimpedance amplifier unit, and its negative terminal is connected to the first power supply voltage; the differential transimpedance amplifier unit outputs a first current at its first output terminal and a second current at its second output terminal; the first current is generated by the first photodiode, and the second current is generated by the second photodiode.

2. The optocoupler testing system as described in claim 1, characterized in that, The control signals include: an enable signal and an amplitude adjustment signal; The test current generation unit includes an amplitude input port and an enable port; wherein the enable port receives the enable signal, the amplitude input port receives the amplitude adjustment signal, and the current amplitude of the test current is determined by the amplitude adjustment signal.

3. The optocoupler testing system as described in claim 2, characterized in that, Also includes: A variable resistor, the first end of which is coupled to the amplitude input port, the second end of which is grounded, and the control terminal of which receives the amplitude adjustment signal; The magnitude of the test current is related to the resistance value of the variable resistor.

4. The optocoupler testing system as described in claim 2, characterized in that, Also includes: The waveform adjustment unit has a first terminal coupled to the enable port, a second terminal grounded, and a waveform adjustment signal output from its first terminal; the waveform of the test current is related to the waveform adjustment signal.

5. The optocoupler testing system as described in claim 2, characterized in that, When the enable signal is a low-level signal, the test current generation unit stops working.

6. The optocoupler testing system as described in claim 1, characterized in that, The test current is either a direct current or a pulse current.

7. The optocoupler testing system as described in claim 1, characterized in that, The test current is input to the second input terminal of the differential transimpedance amplifier unit.

8. The optocoupler testing system as described in claim 1, characterized in that, Also includes: The power supply test unit is adapted to test the first power supply voltage and the second power supply voltage output by the linear regulated source in the optocoupler under test.

9. The optocoupler testing system as described in claim 8, characterized in that, The power supply test unit includes: a second follower, a second inverter, a NAND gate, an OR gate, a level shifter, a first switching unit, and a second switching unit, wherein: The second follower has an enable signal input at its input terminal and its output terminal coupled to the first input terminal of the NAND gate circuit. The second inverter receives the enable signal at its input terminal and its output terminal is coupled to the first input terminal of the OR gate circuit. The NAND gate circuit has a power supply test signal input at its second input terminal and a first test enable signal output at its output terminal. The OR gate circuit has the power test signal input at its second input terminal and its output terminal coupled to the input terminal of the level shifting circuit. The level shifting circuit outputs a second test enable signal at its output terminal; The first switching unit has the first power supply voltage input at its first terminal, the first test enable signal input at its control terminal, and its second terminal coupled to the output terminal of the power supply test unit. The second switching unit has the second power supply voltage input at its first terminal, the second test enable signal input at its control terminal, and its second terminal coupled to the output terminal of the power supply test unit.

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