Protection circuit of semiconductor laser diode
By combining an active control loop with a passive current limiting circuit and utilizing an operational amplifier and a solid-state relay to protect the laser diode, the problem of insufficient reliability in the prior art is solved and efficient protection of the laser diode is achieved.
Patent Information
- Application Number
- CN202422890490.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-26
- Publication Date
- 2025-10-14
- Estimated Expiration
- 2034-11-26
AI Technical Summary
Existing semiconductor laser diode protection solutions have reliability issues, especially the insufficient reliability of passive protection solutions. Active protection solutions are prone to damage when the initial state of the system is unclear, and switch performance affects the protection effect.
The active control loop circuit and the passive current limiting circuit are combined, the operational amplifier is used to detect the laser diode current, the laser diode current is controlled by the MOS tube and the solid-state relay, and the forward and reverse diodes are combined to limit the current to form double protection.
It significantly improves the protection reliability of the laser diode, avoids damage caused by current pulses and noise, and improves the overall reliability of the laser.
Smart Images
Figure CN223436804U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of semiconductor lasers, in particular to a protection circuit for a semiconductor laser diode. Background Art
[0002] Semiconductor laser diodes, due to their small size, high efficiency, ability to be driven by current injection, and ease of light modulation, have important applications in cold atom physics, quantum precision measurement, and quantum information. Commonly used laser diodes include DFB (distributed feedback), ECDL (external cavity), and DBR (distributed Bragg reflector), all of which exhibit excellent monochromaticity. However, a key characteristic of laser diodes is their high cost. Like many chips, they are electrostatically sensitive devices, requiring an operating current exceeding the threshold current and below the maximum allowable current. Laser diodes are susceptible to irreversible damage due to transient current pulses, current reversal, and other conditions. Therefore, the laser diode drive current must be strictly controlled to prevent abnormalities.
[0003] Most existing laser diode protection solutions are passive, employing combinations of passive components such as resistors, capacitors, and diodes to limit the current at the laser diode's input. Because these components are typically discrete, they present reliability issues. A smaller number of active protection solutions utilize monitoring methods to collect the laser diode's current and compare it with the limit value, thereby controlling the on / off switching of a switch to connect or disconnect the laser diode's current. However, these solutions can easily damage the laser tube in the event of program errors or unclear initial system states. Furthermore, the switching performance of these solutions significantly impacts the effectiveness of the protection. Currently, switches with contacts, such as polarized relays, are commonly used, but these switches suffer from issues such as slow switching speeds and reliability issues caused by contact aging. Utility Model Content
[0004] The purpose of the present utility model is to provide a protection circuit for a semiconductor laser diode to solve the problems raised in the above background technology.
[0005] To achieve the above-mentioned object, the present utility model provides the following technical solutions: a protection circuit for a semiconductor laser diode, comprising an active control loop circuit and a passive current limiting circuit;
[0006] The active control loop circuit includes operational amplifiers U1, U2, and MOS transistor Q1. The non-inverting input of operational amplifier U1 is connected to the laser diode current setting signal Vcset, the inverting input of operational amplifier U1 is connected to the source of MOS transistor Q1, and the output of operational amplifier U1 is connected to the gate of MOS transistor Q1. One end of resistor R1 is connected to the source of MOS transistor Q1, and the other end is connected to ground. The non-inverting input of operational amplifier U2 is connected to the source of MOS transistor Q1, the inverting input of operational amplifier U2 is connected to the output of operational amplifier U2, and the output of operational amplifier U2 is connected to the laser diode current monitoring signal Vcmon.
[0007] The passive current limiting circuit includes a forward diode D1, a forward diode D2, a forward diode D3 and a forward diode D4 which are connected in series in a forward direction. The anode of the forward diode D1 is connected to the positive input terminal LD+ of the laser diode, and the cathode of the forward diode D4 is connected to the negative input terminal LD- of the laser diode.
[0008] Preferably, the active control loop circuit also includes a solid-state relay U3 and a resistor R1. Pin 3 of the solid-state controller U3 on the controlled side is connected to the power supply signal Vcc, and pin 4 on the controlled side is connected to the drain of the MOS transistor Q1. Using a solid-state relay instead of a switch with contacts, such as a polarized relay, increases switching speed and avoids reliability issues caused by contact aging.
[0009] Preferably, the passive current limiting circuit also includes a reverse diode D5, a resistor R2 and a capacitor C1, the two ends of the capacitor C1 are respectively connected to the two ends of the laser diode, the cathode of the reverse diode D5 is connected to the positive input terminal LD+ of the laser diode, and the anode of the reverse diode D5 is connected to the negative input terminal LD- of the laser diode.
[0010] Preferably, one end of the resistor R2 is connected to the power supply Vcc, and the other end is connected to the positive input terminal LD+ of the laser diode.
[0011] Compared with the existing technology, the beneficial effect of the present invention is that the present invention detects whether the current value of the laser diode is abnormal through an operational amplifier, actively controls it, and adds a passive current limiting circuit, thus forming a double insurance, which can significantly improve the protection reliability of the laser diode. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Figure 1 This is a circuit schematic diagram of the utility model. DETAILED DESCRIPTION
[0013] 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 embodiments described 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 making creative efforts are within the scope of protection of the present invention.
[0014] like Figure 1 As shown, the present invention provides a technical solution: a semiconductor laser diode protection circuit comprising an active control loop circuit and a passive current limiting circuit. The active control loop circuit includes operational amplifiers U1 and U2, a MOSFET Q1, a solid-state relay U3, and a resistor R1. The passive current limiting circuit includes forward diodes D1, D2, D3, and D4, a reverse diode D5, a resistor R2, and a capacitor C1. The non-inverting input of operational amplifier U1 is connected to the laser diode current setting signal Vcset, the inverting input of operational amplifier U1 is connected to the source of MOSFET Q1, and the output of operational amplifier U1 is connected to the gate of MOSFET Q1. One end of resistor R1 is connected to the source of MOSFET Q1, and the other end is connected to ground. The non-inverting input of operational amplifier U2 is connected to the source of MOSFET Q1, the inverting input of operational amplifier U2 is connected to the output of operational amplifier U2, and the output of operational amplifier U2 is connected to the laser diode current monitoring signal Vcmon. Control side pin 1 of solid-state relay U3 is connected to the switch control signal Vswitch, and control side pin 2 is connected to ground. The controlled-side pin 3 of solid-state controller U3 is connected to the power supply signal Vcc, and the controlled-side pin 4 is connected to the drain of MOS transistor Q1. Resistor R2 of the passive current limiting circuit has one end connected to the power supply Vcc and the other end connected to the positive input terminal LD+ of the laser diode. Forward diodes D1, D2, D3, and D4 are connected in series in a forward direction. The anode of forward diode D1 is connected to the positive input terminal LD+ of the laser diode, and the cathode of forward diode D4 is connected to the negative input terminal LD- of the laser diode. The two ends of capacitor C are connected to the two ends of the laser diode, respectively. The cathode of reverse diode D5 is connected to the positive input terminal LD+ of the laser diode, and the anode of reverse diode D5 is connected to the negative input terminal LD- of the laser diode.
[0015] The operational amplifier U1 , MOS transistor Q1 and resistor R1 are used to set the current value of the laser diode.
[0016] Operational amplifier U2 is configured as a voltage follower to monitor the laser diode's current. Solid-state relay U3 acts as a switch, turning the laser diode on and off according to a control signal. The four cascaded forward diodes conduct when the laser diode voltage exceeds four times its forward diode breakover voltage, limiting the laser diode's current. Reverse diode D5 conducts when the polarity is reversed, protecting the laser diode. Capacitor C1 filters out pulse current spikes and, combined with resistor R3, forms a low-pass filter to remove high-frequency noise.
[0017] The active control loop circuit actively monitors the laser diode for overcurrent. The microcontroller sets the laser diode current setpoint, Vcset. Operational amplifier U1 is configured for negative feedback. The imaginary short circuit indicates that the voltage across resistor R1 equals Vcset, and the laser diode current is Icset = Vcset / R1.
[0018] Operational amplifier U2 is configured as a voltage follower, so the laser diode's real-time current value, Ic, equals Vcmon / R1. When the real-time current value exceeds the maximum allowable output current, the microcontroller sets the switch control signal, Vswitch, to a high level. This turns on pins 3 and 4 of the solid-state relay, preventing current from flowing to the laser diode, thus providing protection.
[0019] The passive current limiting circuit passively limits overcurrent in the laser diode. This circuit can serve multiple purposes. First, the cathode of reverse diode D5 is connected to the laser diode's positive input terminal, LD+, and the anode of reverse diode D5 is connected to the laser diode's negative input terminal, LD-. Reverse diode D5 conducts when the polarity is reversed, protecting the laser diode from reverse breakdown. Second, the four forward diodes D1, D2, D3, and D4 are cascaded together. They conduct when the laser diode voltage exceeds four times the forward diode's conduction voltage, eliminating current flow through the laser diode. Current limiting is achieved by controlling the laser diode's overvoltage. Third, capacitor C1 filters out pulse spikes generated when the switch is turned on and off. Combined with resistor R3, it forms a low-pass filter to filter out high-frequency noise.
[0020] After applying this circuit in actual laser products, the reliability of the laser has been greatly improved: (1) The noise and current pulses generated by normal operations such as turning the laser power on and off and adjusting the laser tube current will not cause damage to the laser tube; (2) Most human errors and wiring errors are unlikely to cause damage to the laser diode.
[0021] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A protection circuit for a semiconductor laser diode, characterized in that: Including active control loop circuit and passive current limiting circuit; The active control loop circuit includes an operational amplifier U1, an operational amplifier U2, and a MOS transistor Q1. The non-inverting input of the operational amplifier U1 is connected to the laser diode current setting signal Vcset, the inverting input of the operational amplifier U1 is connected to the source of the MOS transistor Q1, the output of the operational amplifier U1 is connected to the gate of the MOS transistor Q1, one end of the resistor R1 is connected to the source of the MOS transistor Q1, and the other end is connected to ground. The non-inverting input of the operational amplifier U2 is connected to the source of the MOS transistor Q1, the inverting input of the operational amplifier U2 is connected to the output of the operational amplifier U2, and the output of the operational amplifier U2 is connected to the laser diode current monitoring signal Vcmon. The passive current limiting circuit includes a forward diode D1, a forward diode D2, a forward diode D3 and a forward diode D4 which are connected in series in a forward direction. The anode of the forward diode D1 is connected to the positive input terminal LD+ of the laser diode, and the cathode of the forward diode D4 is connected to the negative input terminal LD- of the laser diode.
2. The semiconductor laser diode protection circuit according to claim 1, wherein: The active control loop circuit also includes a solid-state relay U3 and a resistor R1. The controlled side pin 3 of the solid-state controller U3 is connected to the power signal Vcc, and the controlled side pin 4 is connected to the drain of the MOS tube Q1.
3. The semiconductor laser diode protection circuit according to claim 2, wherein: The passive current limiting circuit also includes a reverse diode D5, a resistor R2 and a capacitor C1. The two ends of the capacitor C1 are respectively connected to the two ends of the laser diode, the cathode of the reverse diode D5 is connected to the positive input terminal LD+ of the laser diode, and the anode of the reverse diode D5 is connected to the negative input terminal LD- of the laser diode.
4. The semiconductor laser diode protection circuit according to claim 3, wherein: One end of the resistor R2 is connected to the power supply Vcc, and the other end is connected to the positive input terminal LD+ of the laser diode.