Optical device multiplexing drive abnormality detection circuit

Abstract

The application relates to the technical field of optical device detection, and discloses a kind of optical device multipath drive abnormality detection circuit, MCU control unit outputs first voltage to constant current control unit, through the regulation and control of loop current feedback unit and constant current control unit, make the constant output of circuit corresponding with the current of first voltage;Pressure drop sampling unit is parallelly connected with laser, for collecting the second voltage at the two ends of laser;Loop current detection unit is connected with the negative electrode of laser, for collecting the third voltage of the negative electrode of laser;Abnormal analog switch group is connected with pressure drop sampling unit, for simulating the abnormal connection condition of laser;MCU control unit judges whether laser is abnormal according to first voltage and third voltage, and judges the abnormal type of laser according to second voltage and third voltage.The application not only realizes the detection whether laser is abnormal, but also can distinguish the abnormal type, is very favorable to the rapid positioning of abnormal laser in production process, saves the analysis and inspection time of problem.

Description

Technical Field

[0001] This invention relates to the field of optical device testing technology, and in particular to an optical device multi-channel drive anomaly detection circuit. Background Technology

[0002] During the manufacturing process of optical devices, multiple power-on performance tests are conducted at various stations, including tests for coupling, responsivity, and sensitivity. High-speed optical devices typically include multiple lasers (LDs) symmetrically distributed and connected to an external test circuit board via flexible printed circuit boards (FPCs) for performance testing. To ensure signal impedance integrity, the FPC is usually designed as a microstrip or stripline model with a signal ground (GSSG), meaning that a return ground (GND) is symmetrically designed on both sides of the positive and negative lines of the laser to ensure signal return. During production, the FPC is repeatedly plugged and unplugged from the external test circuit board. With increased use, the FPC and its connectors suffer damage such as bending and wear. Damage to the positioning terminal limit structure can also cause misalignment, leading to alignment deviations when the FPC is connected to the test circuit board. This can result in abnormal connections, such as the LD positive terminal being connected to GND or the LD negative terminal being connected to GND. These abnormalities will lead to inaccurate performance test data and may also cause soft damage to the lasers in the optical device. Although these damages may not manifest immediately, they can severely shorten the lifespan of optical devices and cause sudden malfunctions during use, seriously affecting the effectiveness of optical device products. Summary of the Invention

[0003] The technical problem this invention aims to solve is that, since the LDs of optical devices are multi-channel symmetrically distributed, necessary performance testing during the manufacturing process may lead to a momentary short circuit risk between the positive and negative terminals of the LD and GND. When the positive terminal of the LD is short-circuited to GND, different driving control methods may exhibit malfunctions or fail to be detected. When the negative terminal of the LD is short-circuited to GND, most driving schemes will not be detected until the final testing of the optical device. By this time, the manufacturing process of the optical device is basically completed, and rework will risk further damage to the optical device. To address this, an optical device multi-channel driving anomaly detection circuit is provided, which detects whether the positive and negative terminals of the LD are short-circuited and whether the optical device is broken down during the manufacturing process, thus avoiding shortened lifespan and sudden malfunctions caused by short circuits or open circuits of the LD.

[0004] To achieve the above-mentioned objectives, the embodiments of the present invention provide the following technical solutions:

[0005] An optical device multi-channel drive anomaly detection circuit for detecting whether a laser is abnormal includes: an MCU control unit, and a loop current feedback unit, a constant current control unit, a voltage drop sampling unit, a loop current detection unit, and an abnormality simulation switch group respectively connected to the MCU control unit;

[0006] The MCU control unit outputs a first voltage to the constant current control unit. Through the regulation of the loop current feedback unit and the constant current control unit, the circuit outputs a current corresponding to the first voltage at a constant rate.

[0007] The voltage drop sampling unit is connected in parallel with the laser to collect the second voltage across the laser and feed it back to the MCU control unit;

[0008] The loop current detection unit is connected to the negative terminal of the laser to collect the third voltage of the negative terminal of the laser and feed it back to the MCU control unit;

[0009] The abnormal simulation switch group is connected to the voltage drop sampling unit to simulate abnormal connection conditions of the laser;

[0010] The MCU control unit determines whether the laser is abnormal based on the first voltage and the third voltage, and determines the type of laser abnormality based on the second voltage and the third voltage.

[0011] In the above scheme, firstly, to ensure a constant output current I1 corresponding to the first voltage, a loop current feedback unit and a constant current control unit are introduced. When the current I1 fluctuates due to external factors, the loop will perform closed-loop regulation to stabilize the output current I1. Secondly, the MCU control unit adjusts the value of the first voltage, and the current I1 will change accordingly. Therefore, to adjust the current I1, the output first voltage can be adjusted. Then, by comparing the output first voltage with the collected third voltage value, it is possible to determine whether the laser is malfunctioning. Thirdly, after the MCU control unit fixes the output first voltage, when the laser's positive terminal is short-circuited to GND, the negative terminal is short-circuited to GND, the positive terminal is short-circuited to the negative terminal, or the positive terminal is open-circuited to the negative terminal, the second and third voltages collected by the MCU control unit will be different. Therefore, the type of malfunction of the laser can be determined by comparing the values ​​of the second and third voltages.

[0012] Furthermore, it also includes a drive control unit, which controls the external power supply VCC to supply power to the circuit according to the level output by the MCU control unit.

[0013] Furthermore, the drive control unit includes a transistor Q1, a capacitor C1, and a resistor R1. The transistor Q1 is a PMOS. The first terminal of the capacitor C1, the first terminal of the resistor R1, and the source of the transistor Q1 are all connected to the external power supply VCC. The second terminal of the capacitor C1 is grounded. The second terminal of the resistor R1 and the gate of the transistor Q1 are respectively connected to the PWR port of the MCU control unit. The drain of the transistor Q1 is connected to the loop current feedback unit.

[0014] In the above scheme, when the PWR port of the MCU control unit outputs a low level, transistor Q1 is turned on, and the external power supply VCC supplies power to the back-end circuit; when the PWR port of the MCU control unit outputs a high level, transistor Q1 is turned off, and the external power supply VDD is cut off from supplying power to the back-end circuit.

[0015] Furthermore, the loop current feedback unit includes an amplifier U1 and a resistor R2. The first end of the resistor R2 is connected to the positive input terminal of the amplifier U1 and the drain of the transistor Q1, respectively. The second end of the resistor R2 is connected to the negative input terminal of the amplifier U1 and the constant current control unit, respectively. The output terminal of the amplifier U1 is connected to the constant current control unit.

[0016] Furthermore, the constant current control unit includes an amplifier U2, resistors R3 and R4, capacitors C2, C3, and C4, and a transistor Q2. The output terminal of amplifier U1, the first terminal of capacitor C2, and the first terminal of capacitor C4 are respectively connected to the negative input terminal of amplifier U2, and the second terminal of capacitor C4 is grounded. The first terminal of resistor R3 is connected to the IDAC port of the MCU control unit, and the second terminal of resistor R3 is connected to the first terminal of capacitor C3 and the positive input terminal of amplifier U2, and the second terminal of capacitor C3 is grounded. The output terminal of amplifier U2 is connected to the second terminal of capacitor C2 and the first terminal of resistor R4, the second terminal of resistor R4 is connected to the base of transistor Q2, the collector of transistor Q2 is connected to the second terminal of resistor R2, and the emitter of transistor Q2 is connected to the positive terminal of the laser and the voltage drop sampling unit.

[0017] Furthermore, the voltage drop sampling unit includes an amplifier U3, a capacitor C5, and a resistor R5. The positive input terminal of the amplifier U3 is connected to the emitter of the transistor Q2 and the positive terminal of the laser, respectively. The output terminal of the amplifier U3 is connected to the first terminal of the resistor R5, and the second terminal of the resistor R5 is connected to the first terminal of the capacitor C5 and the VADC port of the MCU control unit, respectively. The negative input terminal of the amplifier U3 is connected to the negative terminal of the laser and the loop current detection unit, respectively.

[0018] Furthermore, the loop current detection unit includes an amplifier U4, a resistor R6, a resistor R7, and a capacitor C6. The positive input terminal of the amplifier U4 is connected to the first terminal of the resistor R7 and the negative input terminal of the amplifier U3, respectively. The negative input terminal of the amplifier U4 and the second terminal of the resistor R7 are both grounded. The output terminal of the amplifier U4 is connected to the first terminal of the resistor R6, and the second terminal of the resistor R6 is connected to the first terminal of the capacitor C6 and the IADC port of the MCU control unit, respectively.

[0019] Furthermore, the abnormal simulation switch group includes switch ST1, switch ST2, and switch ST3. The first end of switch ST1 and the first end of switch ST2 are respectively connected to the positive input terminal of amplifier U3. The second end of switch ST2 and the first end of switch ST3 are respectively connected to the negative input terminal of amplifier U3. The second end of switch ST1 is grounded to GND, and the second end of switch ST3 is grounded to GND.

[0020] Furthermore, the IDAC port of the MCU control unit outputs the first voltage V_IDAC, and the IADC port of the MCU control unit acquires the third voltage V_IADC. If the difference between V_IADC and V_IDAC is equal to R7×K4×Ib, or the difference between V_IADC and V_IDAC is within the range [(R7×K4×Ib)-x, (R7×K4×Ib)+x], then the laser is determined to be normal. Here, R7 is the resistance value of resistor R7, K4 is the gain of amplifier U4, Ib is the base current of transistor Q2, and x is the set threshold.

[0021] Furthermore, if the second voltage V_VADC=0V and the third voltage V_IADC=0V, it indicates that the positive terminal of the laser is short-circuited to GND.

[0022] If the second voltage V_VADC meets the requirements of the volt-ampere characteristic curve and the third voltage V_IADC=0V, it indicates that the negative terminal of the laser is short-circuited with GND.

[0023] If the second voltage V_VADC=0V and the third voltage V_IADC meets the requirements of the volt-ampere characteristic curve, it indicates that the positive and negative terminals of the laser are short-circuited.

[0024] If the second voltage V_VADC=VCC and the third voltage V_IADC=0V, it indicates that the laser has broken down and is open-circuited.

[0025] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention is carried out in two stages. In the first stage, by changing the opening and closing state of the abnormal simulation switch group, five conditions are simulated: normal operation of the laser, short circuit between positive and GND, short circuit between negative and GND, short circuit between positive and negative, and breakdown open circuit. The voltage parameters V_VADC and V_IDAC received by the MCU control unit under each condition are obtained. In the second stage, the laser to be tested is connected to this circuit, and all switches in the abnormal simulation switch group are opened. The MCU control unit still outputs a voltage V_IDAC = 1V. Based on the received voltage values ​​V_VADC and V_IDAC, it can be determined whether the laser is abnormal and what type of abnormality it belongs to. The judgment process of this circuit not only realizes the detection of whether the laser is abnormal, but also distinguishes the type of abnormality, which is very beneficial for the rapid location of abnormal lasers in the production process and saves the analysis and inspection time. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram showing the alignment and connection between the flexible circuit board and the test circuit board.

[0028] Figure 2 This is a schematic diagram showing a misaligned connection between a flexible circuit board and a test circuit board.

[0029] Figure 3 This is another schematic diagram showing a misaligned connection between the flexible circuit board and the test circuit board.

[0030] Figure 4 This is the circuit schematic diagram of the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0032] It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance, or suggesting any such actual relationship or order between these entities or operations. Additionally, the terms "connected," "linked," etc., can refer to a direct connection between elements, components, modules, etc., or an indirect connection via other elements, components, modules, etc.

[0033] Example 1:

[0034] like Figure 1 As shown, the left side is the test circuit board, and the right side is the flexible circuit board for the optical device. Four symmetrical lasers (LD1, LD2, LD3, and LD4) are connected to the flexible circuit board. Each laser has positive and negative terminals; for example, LD1 has a positive terminal LD1+ and a negative terminal LD1-. Normally, the LDi+ terminal of the test circuit board is connected to the LDi+ terminal of the optical device, the LDi- terminal of the test circuit board is connected to the LDi- terminal of the optical device, and the GND terminal of the test circuit board is connected to the GND terminal of the optical device. However, in production practice, due to multiple factors, issues may arise such as… Figure 2 , Figure 3 An abnormal situation may cause one or more LDi+ channels of the optical device to connect to the GND of the test circuit board, or one or more LDi- channels of the optical device to the GND of the test circuit board. Such a short circuit abnormality may cause soft damage or permanent damage to the electronic components inside the optical device. i is the index of the i-th laser, i=1,2,...,n, and n is the number of laser channels in the optical device. In this embodiment, n=4.

[0035] To solve the above problems, the present invention provides a multi-channel drive anomaly detection circuit for optical devices, which detects any one of the laser LDs (the detection is the same for each laser, so this embodiment only shows any one of them). Figure 4 As shown, it includes an MCU control unit, and a drive control unit, a loop current feedback unit, a constant current control unit, a voltage drop sampling unit, a loop current detection unit, and an abnormal simulation switch group, all connected to the MCU control unit.

[0036] The MCU control unit outputs a first voltage V_IDAC to the constant current control unit. Through the regulation of the loop current feedback unit and the constant current control unit, the circuit outputs a constant current I1 corresponding to the first voltage V_IDAC.

[0037] The voltage drop sampling unit is connected in parallel with the laser LD to acquire the second voltage V_VADC across the laser LD and feed it back to the MCU control unit;

[0038] The loop current detection unit is connected to the negative terminal of the laser LD to collect the third voltage V_IADC of the negative terminal of the laser LD and feed it back to the MCU control unit.

[0039] The abnormal simulation switch group is connected to the voltage drop sampling unit to simulate abnormal connection conditions of the laser LD;

[0040] The MCU control unit determines whether the laser LD is abnormal based on the first voltage V_IDAC and the third voltage V_IADC, and determines the type of abnormality of the laser LD based on the second voltage V_VADC and the third voltage V_IADC.

[0041] In detail, the drive control unit includes a transistor Q1, a capacitor C1, and a resistor R1. The transistor Q1 is a PMOS. The first terminal of the capacitor C1, the first terminal of the resistor R1, and the source of the transistor Q1 are all connected to the external power supply VCC. The second terminal of the capacitor C1 is grounded. The second terminal of the resistor R1 and the gate of the transistor Q1 are respectively connected to the PWR port of the MCU control unit. The drain of the transistor Q1 is connected to the loop current feedback unit.

[0042] The loop current feedback unit includes an amplifier U1 (current sampling chip) and a resistor R2. The first end of the resistor R2 is connected to the positive input terminal of the amplifier U1 and the drain of the transistor Q1, respectively. The second end of the resistor R2 is connected to the negative input terminal of the amplifier U1 and the constant current control unit, respectively. The output terminal of the amplifier U1 is connected to the constant current control unit.

[0043] The constant current control unit includes amplifier U2, resistors R3 and R4, capacitors C2, C3, and C4, and transistor Q2. The output terminal of amplifier U2, the first terminal of capacitor C2, and the first terminal of capacitor C4 are connected to the negative input terminal of amplifier U2, and the second terminal of capacitor C4 is grounded. The first terminal of resistor R3 is connected to the IDAC port of the MCU control unit, and the second terminal of resistor R3 is connected to the first terminal of capacitor C3 and the positive input terminal of amplifier U2, and the second terminal of capacitor C3 is grounded. The output terminal of amplifier U2 is connected to the second terminal of capacitor C2 and the first terminal of resistor R4, the second terminal of resistor R4 is connected to the base of transistor Q2, the collector of transistor Q2 is connected to the second terminal of resistor R2, and the emitter of transistor Q2 is connected to the positive terminal of laser LD and the voltage drop sampling unit.

[0044] The voltage drop sampling unit includes an amplifier U3, a capacitor C5, and a resistor R5. The positive input terminal of the amplifier U3 is connected to the emitter of the transistor Q2 and the positive terminal of the laser LD. The output terminal of the amplifier U3 is connected to the first terminal of the resistor R5, and the second terminal of the resistor R5 is connected to the first terminal of the capacitor C5 and the VADC port of the MCU control unit. The negative input terminal of the amplifier U3 is connected to the negative terminal of the laser LD and the loop current detection unit.

[0045] The loop current detection unit includes amplifier U4 (current sampling chip), resistor R6, resistor R7, and capacitor C6. The positive input terminal of amplifier U4 is connected to the first terminal of resistor R7 and the negative input terminal of amplifier U3, respectively. The negative input terminal of amplifier U4 and the second terminal of resistor R7 are both grounded. The output terminal of amplifier U4 is connected to the first terminal of resistor R6, and the second terminal of resistor R6 is connected to the first terminal of capacitor C6 and the IADC port of MCU control unit, respectively.

[0046] The abnormal simulation switch group includes switch ST1, switch ST2, and switch ST3. The first end of switch ST1 and the first end of switch ST2 are respectively connected to the positive input terminal of amplifier U3. The second end of switch ST2 and the first end of switch ST3 are respectively connected to the negative input terminal of amplifier U3. The second end of switch ST1 is grounded to GND, and the second end of switch ST3 is grounded to GND.

[0047] Based on the above circuit and connection relationships, the functional principle of the circuit will be introduced in two stages: The first stage involves connecting the abnormal simulation switch group and the laser LD to the circuit. By controlling the state of the abnormal simulation switch group, the abnormal conditions of the laser LD—positive short circuit to GND, negative short circuit to GND, positive short circuit to negative, and breakdown open circuit—are simulated. These four abnormal conditions and the voltage parameters received by the MCU control unit under normal conditions are obtained. The second stage involves connecting the laser LD under test to the circuit, while the abnormal simulation switch group is not connected. The voltage parameters received by the MCU control unit are used to determine whether the laser LD exhibits any of the abnormal conditions of positive short circuit to GND, negative short circuit to GND, positive short circuit to negative, or breakdown open circuit.

[0048] (a) The first stage.

[0049] When the MCU control unit outputs a low level through the PWR port, and the source voltage of transistor Q1 is greater than its gate voltage, the external power supply VCC powers the entire downstream circuit through the source and drain of transistor Q1, thus starting the circuit. When the MCU control unit outputs a high level through the PWR port, and the gate voltage of transistor Q1 is greater than its source voltage, the source and drain of transistor Q1 are not connected, thereby turning off the external power supply VCC from powering the entire downstream circuit and stopping the circuit.

[0050] Based on the circuit and connections, the voltage at the positive input terminal of amplifier U1 is V2, the voltage at the negative input terminal is V3, and the voltage at the output terminal is V4. The current amplification gain of amplifier U1 is K1, so V4 = (V2 - V3) × K1. The current through resistor R2 is I1, and the collector current of transistor Q2 is Ic, so I1 = Ic. Since V2 - V3 = I1 × R2, then V4 = I1 × R2 × K1. The base current of transistor Q2 is Ib, and the amplification factor of transistor Q2 is β, so Ic = Ib × β. The voltage at the positive input terminal of amplifier U5 is V1, the voltage at the negative input terminal is V4, and the voltage at the output terminal is V5. The gain of amplifier U2 is K2, and the voltage output from the IDAC port of the MCU control unit, V_IDAC = V1, so V5 = (V1 - V4) × K2 = (V_IDAC - V4) / (V1 ... The emitter voltage of transistor Q2 is V6, so Ib = (V5 - V6) / R4; the current flowing through resistor R7 is I2, so I2 = Ic + Ib; the positive input voltage of amplifier U3 is V6, the negative input voltage is V7, the output voltage is V8, the gain of amplifier U3 is K3, so V8 = (V6 - V7) × K3, V7 = I2 × R7; the voltage input to the VADC port of the MCU control unit is V_VADC = V8; the positive input voltage of amplifier U4 is V7, the negative input voltage is 0V, the output voltage is V9, the current amplification factor of amplifier U4 is K4, so V9 = (V7 - 0) × K4, since V7 = I2 × R7, V9 = I2 × R7 × K4; the voltage input to the IADC port of the MCU control unit is V_IADC = V9.

[0051] Assuming switches ST1, ST2, and ST3 are all open, and the laser LD is normally connected (i.e., under normal conditions, the positive terminal of the laser LD has no short circuit, the negative terminal has no short circuit, and there is no breakdown open circuit), since the amplification factor β of transistor Q2 is fixed, as long as Ib remains unchanged, Ic will remain unchanged. Assuming resistors R2 and R7 are both 1Ω, the current amplification gain K1 of amplifier U1 is 10, and the current amplification gain K4 of amplifier U4 is 10, if the current I1 flowing through resistor R2 is 100mA, then V4 = I1 × R2 × K1 = 0.1 × 1 × 10 = 1V. Based on the "virtual short" principle of the positive and negative input terminals of amplifier U2, only when V1 = V4 = 1V, that is, when the output voltage V_IDAC of the IDAC port of the MCU control unit is 1V, can the current I1 flowing through resistor R2 be 100mA. Since I2 = Ic + Ib = I1 + Ib, when some factor causes the current I1 to decrease, i.e., the current Ic decreases, then V4 will also decrease, while V1 remains unchanged. At this time, the voltage V1 at the positive input terminal of amplifier U2 is greater than the voltage V4 at the negative input terminal. Since V5 = (V1 - V4) × K2, if K2 is set large enough, V5 will increase. Because Ib = (V5 - V6) / R4, Ib will also increase. Because Ic = Ib × β, Ic will also increase, i.e., I1 will increase. The feedback response speed of this hardware circuit is extremely fast, enabling the circuit to maintain a constant output current I1 = 100mA. Since I2 = I1 + Ib, then V_IADC = V9 = I2 × R7 × K4 = I2 × 1 × 10 = 10I1 + 10Ib; after the stable output current I1 = 100mA, V1 = V4, so V_IDAC = V4 = I1 × R2 × K1 = 10I1. Therefore, V_IADC - V_IDAC = 10Ib, and the current Ib is usually in the μA range. Therefore, the MCU control unit repeatedly samples the voltages of the IADC and IDAC ports and calculates the difference. If the difference is equal to 10Ib, or within the range [10Ib - x, 10Ib + x], it indicates that the laser LD is normal, where x is a set threshold, and the PWR port continuously outputs a low level.

[0052] Assuming switch ST1 is closed and switches ST2 and ST3 are open, simulating a short circuit between the positive terminal of the laser LD and GND, the output voltage V_IDAC of the MCU control unit's IDAC port is 1V. As mentioned earlier, the circuit will output a constant current I1 = 100mA. Since the positive terminal of the laser LD is connected to GND through switch ST1, V6 = 0V, V7 = 0V, I2 = 0mA, therefore V_VADC = 0V, V_IDAC = 0V. Theoretically, I1 should increase due to V6 = 0V, but because V4 increases and V5 decreases, I1 will decrease. Therefore, the loop current feedback unit and the constant current control unit will not be damaged due to overload, and the laser LD will not be damaged because no current flows through it. Therefore, when the MCU control unit outputs a normal voltage V_IDAC=1V, if V_VADC=0V and V_IADC=0V are detected, it indicates that the positive terminal of the laser LD is short-circuited with GND. Then, the PWR port outputs a high level, cutting off the external power supply VCC to power the back-end circuit, and the circuit ultimately has no current output.

[0053] Assuming switch ST3 is closed and switches ST1 and ST2 are open, simulating a short circuit between the negative terminal of the laser LD and GND, the output voltage V_IDAC of the MCU control unit's IDAC port is 1V. As mentioned earlier, the circuit will output a constant current I1 = 100mA. Since the negative terminal of the laser LD is connected to GND through switch ST3, V7 = 0V and I2 = 0mA at this time. Therefore, V_VADC = V6, meaning V_VADC is the voltage drop across the laser LD. The voltage drop V_VADC across the laser LD and the current I1 will form a voltage-current characteristic curve. Using a method similar to looking up a table, we can determine what value of V_VADC is normal when the current I1 is 100mA. Since V7=0V, V_IADC=0V. Therefore, when the MCU control unit outputs a normal voltage V_IDAC=1V, if V_VADC is detected to be normal but V_IADC=0V, it indicates that the negative terminal of the laser LD is short-circuited with GND. Then, the PWR port outputs a high level, cutting off the external power supply VCC to power the back-end circuit, and the circuit ultimately has no current output.

[0054] Assuming switch ST2 is closed and switches ST1 and ST3 are open, simulating a short circuit between the positive and negative terminals of the laser LD, the IDAC port of the MCU control unit outputs a voltage V_IDAC = 1V. As mentioned earlier, the circuit will output a constant current I1 = 100mA. Since the positive terminal of the laser LD is connected to the negative terminal through switch ST2, but this does not affect V_IADC, the voltage V_IADC and current I1 will form a volt-ampere characteristic curve. Using a lookup table-like method, we can determine the normal value of V_IADC when the current I1 is 100mA. Since V6-V7 = 0V, V_VADC = 0V. Therefore, when the MCU control unit normally outputs a voltage V_IDAC = 1V, if V_VADC = 0V but V_IADC is normal, it indicates a short circuit between the positive and negative terminals of the laser LD. Then, the PWR port outputs a high level, cutting off the external power supply VCC to power the downstream circuit, and the circuit ultimately has no current output.

[0055] Assuming switches ST1, ST2, and ST3 are all open and the laser LD is open-circuited, this is used to simulate a breakdown and open circuit in the laser LD. Since there is no return path in the circuit, V6 is approximately equal to VCC, and therefore V_VADC is also approximately equal to VCC. At this time, V_IADC=0V. Therefore, when the MCU control unit normally outputs a voltage V_IDAC=1V, if it detects that V_VADC≈VCC and V_IADC=0V, it indicates that the laser LD has broken down and opened circuit. Then, the PWR port outputs a high level, cutting off the external power supply VCC to power the back-end circuit, and the circuit ultimately has no current output.

[0056] In the first stage, by changing the opening and closing states of the abnormal simulation switch group, five scenarios were simulated for the laser LD: normal operation, short circuit between positive and GND, short circuit between negative and GND, short circuit between positive and negative, and breakdown / open circuit. The voltage parameters V_VADC and V_IDAC received by the MCU control unit under each scenario were obtained. In the second stage, the laser LD under test was connected to this circuit, and all switches in the abnormal simulation switch group were opened. The MCU control unit still outputs a voltage V_IDAC = 1V. Based on the received values ​​of V_VADC and V_IDAC, it is possible to determine whether the laser LD is abnormal and, if so, which type of abnormality it is.

[0057] (ii) Second stage.

[0058] Connect the positive terminal of the laser LD under test to the positive input terminal of amplifier U3, and connect the negative terminal of the laser LD under test to the negative input terminal of amplifier U3. The output voltage V_IDAC of the IDAC port of the MCU control unit is 1V.

[0059] If V_IADC-V_IDAC=10Ib, or V_IADC-V_IDAC is within the range [10Ib-x, 10Ib+x], then the laser LD is normal.

[0060] If V_VADC=0V and V_IADC=0V, it means that the positive terminal of the laser LD is short-circuited with GND.

[0061] If V_VADC is normal and V_IADC=0V, it means that the negative terminal of the laser LD is short-circuited with GND.

[0062] If V_VADC=0V and V_IADC is normal, it indicates that the positive and negative terminals of the laser LD are short-circuited.

[0063] If V_VADC≈VCC and V_IADC=0V, it indicates that the laser LD has broken down and is open-circuited.

[0064] The judgment process of this circuit not only realizes whether the laser is abnormal, but also distinguishes the type of abnormality. This is very helpful for quickly locating abnormal lasers in the production process and saving time for problem analysis and inspection.

[0065] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A multi-channel drive anomaly detection circuit for optical devices, used to detect whether a laser is malfunctioning, characterized in that, include: The MCU control unit, and the loop current feedback unit, constant current control unit, voltage drop sampling unit, loop current detection unit, and abnormal simulation switch group respectively connected to the MCU control unit; The MCU control unit outputs a first voltage to the constant current control unit. Through the regulation of the loop current feedback unit and the constant current control unit, the circuit outputs a current corresponding to the first voltage at a constant rate. The voltage drop sampling unit is connected in parallel with the laser to collect the second voltage across the laser and feed it back to the MCU control unit; The loop current detection unit is connected to the negative terminal of the laser to collect the third voltage of the negative terminal of the laser and feed it back to the MCU control unit; The loop current feedback unit includes an amplifier U1 and a resistor R2. The first end of the resistor R2 is connected to the positive input terminal of the amplifier U1 and the drive control unit, respectively. The second end of the resistor R2 is connected to the negative input terminal of the amplifier U1 and the constant current control unit, respectively. The constant current control unit includes amplifier U2, resistors R3 and R4, capacitors C2, C3, and C4, and transistor Q2. The output terminal of amplifier U2, the first terminal of capacitor C2, and the first terminal of capacitor C4 are connected to the negative input terminal of amplifier U2, and the second terminal of capacitor C4 is grounded. The first terminal of resistor R3 is connected to the IDAC port of the MCU control unit, and the second terminal of resistor R3 is connected to the first terminal of capacitor C3 and the positive input terminal of amplifier U2, and the second terminal of capacitor C3 is grounded. The output terminal of amplifier U2 is connected to the second terminal of capacitor C2 and the first terminal of resistor R4, the second terminal of resistor R4 is connected to the base of transistor Q2, the collector of transistor Q2 is connected to the second terminal of resistor R2, and the emitter of transistor Q2 is connected to the positive terminal of the laser and the voltage drop sampling unit. The loop current detection unit includes amplifier U4, resistor R6, resistor R7, and capacitor C6. The positive input terminal of amplifier U4 is connected to the first terminal of resistor R7 and the step-down sampling unit, respectively. The negative input terminal of amplifier U4 and the second terminal of resistor R7 are both grounded. The output terminal of amplifier U4 is connected to the first terminal of resistor R6, and the second terminal of resistor R6 is connected to the first terminal of capacitor C6 and the IADC port of MCU control unit. The abnormal simulation switch group is connected to the voltage drop sampling unit to simulate abnormal connection conditions of the laser; The MCU control unit determines whether the laser is abnormal based on the first voltage and the third voltage, and determines the type of laser abnormality based on the second voltage and the third voltage.

2. The optical device multi-channel drive anomaly detection circuit according to claim 1, characterized in that, It also includes a drive control unit, which controls the external power supply VCC to supply power to the circuit according to the level output by the MCU control unit.

3. The optical device multi-channel drive anomaly detection circuit according to claim 2, characterized in that, The drive control unit includes a transistor Q1, a capacitor C1, and a resistor R1. The transistor Q1 is a PMOS. The first terminal of the capacitor C1, the first terminal of the resistor R1, and the source of the transistor Q1 are all connected to the external power supply VCC. The second terminal of the capacitor C1 is grounded. The second terminal of the resistor R1 and the gate of the transistor Q1 are respectively connected to the PWR port of the MCU control unit. The drain of the transistor Q1 is connected to the first terminal of the resistor R2.

4. The optical device multi-channel drive anomaly detection circuit according to claim 1, characterized in that, The voltage drop sampling unit includes amplifier U3, capacitor C5, and resistor R5. The positive input terminal of amplifier U3 is connected to the emitter of transistor Q2 and the positive terminal of the laser, respectively. The output terminal of amplifier U3 is connected to the first terminal of resistor R5, and the second terminal of resistor R5 is connected to the first terminal of capacitor C5 and the VADC port of MCU control unit, respectively. The negative input terminal of amplifier U3 is connected to the negative terminal of laser and the positive input terminal of amplifier U4, respectively.

5. The optical device multi-channel drive anomaly detection circuit according to claim 4, characterized in that, The abnormal simulation switch group includes switch ST1, switch ST2, and switch ST3. The first end of switch ST1 and the first end of switch ST2 are respectively connected to the positive input terminal of amplifier U3. The second end of switch ST2 and the first end of switch ST3 are respectively connected to the negative input terminal of amplifier U3. The second end of switch ST1 is grounded to GND, and the second end of switch ST3 is grounded to GND.

6. The optical device multi-channel drive anomaly detection circuit according to claim 4, characterized in that, The MCU control unit's IDAC port outputs the first voltage V_IDAC, and the MCU control unit's IADC port acquires the third voltage V_IADC. If the difference between V_IADC and V_IDAC is equal to R7×K4×Ib, or if the difference between V_IADC and V_IDAC is within the range [(R7×K4×Ib)-x, (R7×K4×Ib)+x], then the laser is determined to be normal. Here, R7 is the resistance value of resistor R7, K4 is the gain of amplifier U4, Ib is the base current of transistor Q2, and x is the set threshold.

7. The optical device multi-channel drive anomaly detection circuit according to claim 4, characterized in that, If the second voltage V_VADC=0V and the third voltage V_IADC=0V, it means that the positive terminal of the laser is short-circuited to GND. If the second voltage V_VADC meets the requirements of the volt-ampere characteristic curve and the third voltage V_IADC=0V, it indicates that the negative terminal of the laser is short-circuited with GND. If the second voltage V_VADC=0V and the third voltage V_IADC meets the requirements of the volt-ampere characteristic curve, it indicates that the positive and negative terminals of the laser are short-circuited. If the second voltage V_VADC=VCC and the third voltage V_IADC=0V, it indicates that the laser has broken down and is open-circuited.

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