Laser diode modulation driving circuit

Abstract

According to the laser diode modulation driving circuit provided by the utility model, after a power supply is switched on, the laser diode LD can emit modulation laser with specified frequency. According to the scheme, only one laser diode is used for emitting modulated laser, matching of light path elements is not needed, and use is convenient. According to the technical scheme, the Q2, the Q3, the C1 and the C2 form positive feedback connection, so that the Q1 can maintain stable on and off states, and the switching time of the on and off states is extremely short; and because the R3, the C1, the R4 and the C2 form two charging circuits for timing, the Q1 can maintain the current on or off state for a time determined by the resistance values and the capacitance values of the R3, the C1, the R4 and the C2 and then switch to the other state. Therefore, after the power supply is switched on, the Q1 continuously performs switching between the on state and the off state, and the laser diode LD can emit the modulation laser with the specified frequency, so that the technical problems mentioned in the background technology are solved.

Description

Technical Field

[0001] The utility model relates to the field of circuit design, in particular to a laser diode modulation drive circuit. Background Art

[0002] Laser diode is an electronic device that uses semiconductor pn junction to convert current into light energy and generate laser. Laser diode has excellent directivity and straightness. As a light source with easy energy control, it is widely used in optical communication, medical treatment, sensing, data storage and leisure and entertainment. Its basic principle is to use the light generated when electrons and holes recombine. There are many products with different wavelengths and output characteristics on the market.

[0003] When using a laser diode, it is easy to be interfered by sunlight or light because of the fixed wavelength it emits. Therefore, a modulation circuit must be added when using it so that the laser it emits has a specific frequency emitted by the modulation circuit. The receiving end can determine whether a signal is received by demodulating and identifying the specific frequency.

[0004] In the prior art:

[0005] CN 106451060 B records a laser driving circuit, including a power supply VCC, a first laser diode LD1, a second laser diode LD2, a first transistor T1, a second transistor T2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, an amplifier COP, a reference power supply VCC1, a capacitor C1, a capacitor C2, and a capacitor C3. When the driving voltage of the first laser diode LD1 suddenly increases and exceeds a certain value, LD2 will obtain driving current, and LD2 can only emit laser light of one band, and the laser light of this band is within the emission wavelength range of LD1. When the laser light of this band is incident on the resonant cavity of LD1, it will consume the carriers in LD1, thereby reducing the number of carriers participating in the excitation light of another band, thereby causing the laser beam energy of another band to decrease. The band emitted by LD2 in the mixed light of the two bands output by LD1 is reflected to other directions by the dichroic mirror, so that the energy of the obtained laser beam remains unchanged or decreases, thereby achieving stable output.

[0006] CN 106300007 A records a laser driving circuit with stable frequency and power output, including a power supply VCC, the power supply VCC is respectively connected to the anodes of a first laser diode LD1 and a second laser diode LD2, the cathode of the first laser diode LD1 is connected to the collector of a first transistor T1, the cathode of the second laser diode LD2 is connected to the collector of a second transistor T2, the base of the first transistor T1 is connected to a control end, the emitter of the first transistor is connected to one end of a first resistor R1 and one end of a second resistor R2, the other end of R1 is grounded, the other end of the second resistor R2 is connected to one end of a third resistor R3 and a fourth resistor R4, the other end of the third resistor R3 is connected to the base of a second transistor T2, the emitter of T2 is connected to one end of a fifth resistor R5, the other ends of R4 and R5 are both grounded, and C1 is connected in parallel with LD1, capacitor C2 is connected in parallel with LD2, and capacitor C3 is connected in parallel with R1.

[0007] In the above prior art, two laser diodes are used in combination, and the purpose of driving the laser diode is achieved by mixing the optical path. However, the modulation function cannot be achieved. Specific optical path components are also required, which is inconvenient to use. There is an urgent need for a laser diode modulation circuit that can work by connecting a power supply. Summary of the invention

[0008] In view of this, the technical problem to be solved by the utility model is to provide a laser diode modulation circuit.

[0009] The utility model solves the above technical problems through the following technical solutions:

[0010] A laser diode modulation circuit, comprising a laser diode LD, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a first capacitor C1, a second capacitor C2, a third capacitor C3, a first transistor Q1, a second transistor Q2, a third transistor Q3, a positive power supply VCC, and a negative power supply GND;

[0011] R1~R5 and R7 are all connected to VCC, and the emitters of Q1~Q3 are all connected to GND.

[0012] R2 connects the collector of Q2,

[0013] R3 connects to the base of Q3,

[0014] R4 connects to the base of Q2,

[0015] R5 connects the collector of Q3,

[0016] R6 connects the base of Q1,

[0017] R7 connects R6 and C3,

[0018] C1 connects R2 and R3,

[0019] C2 connects R4 and R5,

[0020] C3 connects R5 and R6,

[0021] The positive electrode of LD is connected to R1, and the negative electrode of LD is connected to the collector of Q1.

[0022] Further: the resistance values ​​of R2 and R5 are equal, the resistance values ​​of R3 and R4 are equal, and the capacitance values ​​of C1 and C2 are equal.

[0023] This makes the circuit parameters symmetrical.

[0024] The laser diode emits a modulated laser with a duty cycle of half.

[0025] The circuit provided by the utility model, because Q2, Q3 and C1, C2 form a positive feedback connection, Q1 can maintain a stable on and off state, and the switching time between the on and off states is extremely short; and because R3, C1 and R4, C2 form two charging circuits for timing, Q1 can maintain the current on or off state for a time determined by the resistance and capacitance of R3, C1 and R4, C2 and then switch to another state. In this way, after the power is turned on, Q1 will continuously switch between the on and off states, and the laser diode LD can emit a modulated laser of a specified frequency. This solution can emit a modulated laser with only one laser diode, does not require the cooperation of optical path components, and is easy to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a circuit diagram of the utility model. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0028] See also Figure 1 : Figure 1 This is a circuit diagram of the utility model.

[0029] The specific parameter values ​​of the components are:

[0030] R1: 75R; R2: 300R; R3: 39K: R4: 39K; R5: 300R; R6: 100R; R7: 39K;

[0031] C1: 100pF; C2: 100pF; C3: 100nF;

[0032] Q1~Q3:S8050.

[0033] After the power is turned on, since R3R4 are the base bias resistors of transistors Q3 and Q2 respectively, the two transistors have a tendency to turn on under the action of the bias resistors. Due to the discrete type of the components, one of the two transistors always turns on first. Assuming Q2 turns on first, at this time, the collector of Q2 is at a low level, and this low level is coupled to the base of Q3 through C1, causing Q3 to tend to be cut off, and the collector potential of Q3 rises. This rising high level is coupled to the base of Q2 through C2, causing Q2 to be more conductive... Such positive feedback causes Q2 to quickly saturate and turn on, while Q3 quickly turns off. At this time, Q1 is cut off and the LD does not light up.

[0034] After Q2 is turned on, capacitor C1 is charged through R3, and the charging result causes C1 to be charged, so that the base potential of Q3 begins to rise. According to the reverse principle of the transistor, the collector potential of Q3 will drop, and the base potential of Q2 will also drop through the coupling of C2. The collector potential of Q2 rises and is added to the base of Q3 through C1, causing the collector potential of Q3 to drop further, thus forming a positive feedback, resulting in Q2 quickly entering the cut-off state, and Q3 quickly entering the saturated conduction state. At this time, Q1 is turned on and LD lights up.

[0035] From the above analysis, it can be seen that after the power is turned on, Q1 continuously alternates between the on and off states, so the laser diode LD also continuously alternates between lighting up and not lighting up, thereby forming a modulated laser.

[0036] The above is a preferred implementation of the utility model, and its description is relatively specific and detailed, but it cannot be understood as a limitation to the utility model. Any deformation and improvement made without departing from the concept of the utility model shall fall within the protection scope of the utility model.

Claims

1. A laser diode modulation drive circuit, characterized in that: Including laser diode LED1, resistors R1~R7, capacitors C1~C3, transistors Q1~Q3; R1~R5 and R7 are all connected to 5V, and the emitters of Q1~Q3 are all connected to GND. R2 connects the collector of Q2, R3 connects to the base of Q3, R4 connects to the base of Q2, R5 connects the collector of Q3, R6 connects the base of Q1, R7 connects R6 and C3, C1 connects R2 and R3, C2 connects R4 and R5, C3 connects R5 and R6, The positive terminal of LED1 is connected to R1, and the negative terminal is connected to the collector of Q1.

2. A laser diode modulation drive circuit according to claim 1, characterized in that: The resistance values ​​of R2 and R5 are equal, the resistance values ​​of R3 and R4 are equal, and the capacitance values ​​of C1 and C2 are equal.

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