Temperature control circuit of ultrafast laser seed pump laser diode

Abstract

The utility model relates to a temperature control circuit of an ultrafast laser seed pump laser diode. The normal phase input end of an operational amplifier I is connected to one end of a capacitor I, one end of a capacitor II and the output end of an operational amplifier III; the negative phase input end of the operational amplifier I is connected to the positive input end of the semiconductor cooler and the output end of the operational amplifier I; the non-inverting input end of the operational amplifier II is connected to one end of a resistor III; the negative-phase input end of the operational amplifier II is connected to one end of the resistor I; the output end of the operational amplifier II is connected to the negative input end of the semiconductor cooler; the positive input end of the third operational amplifier is connected to one ends of a sixth resistor and a seventh resistor, and the negative input end of the third operational amplifier is connected to one ends of a third resistor and a fourth resistor; the other end of the resistor III is connected with the other end of the capacitor I; the positive input end of the fourth operational amplifier is connected to one ends of the thermistor and the eighth resistor; the negative input end of the fourth operational amplifier is connected to one ends of a fifth resistor and a third capacitor; the output end of the fourth operational amplifier is connected to the other end of the fourth resistor, the other end of the fifth resistor and the other end of the third capacitor.

Description

Technical Field

[0001] The utility model relates to a temperature control circuit of an ultrafast laser seed pumping laser diode. Background Art

[0002] At present, industrial pulse lasers, especially ultrafast lasers such as picosecond lasers and femtosecond lasers, generally use single-mode laser diodes (LDs) as seed pump sources. The temperature change of the pump LD will directly affect the deviation of the output laser wavelength, so the LD needs to be temperature controlled.

[0003] Therefore, it is necessary to design a simple and effective temperature control circuit for quickly controlling the temperature of the pump LD. Utility Model Content

[0004] The utility model aims to overcome the shortcomings of the prior art and provide a temperature control circuit for an ultrafast laser seed pump laser diode.

[0005] The purpose of the utility model is achieved through the following technical solutions:

[0006] The temperature control circuit of the ultrafast laser seed pump laser diode is characterized by: comprising an operational amplifier 1, an operational amplifier 2, an operational amplifier 3 and a semiconductor refrigerator, the positive phase input terminal of the operational amplifier 1 is connected to one end of the capacitor 1 and the capacitor 2, and the output terminal of the operational amplifier 3; the negative phase input terminal of the operational amplifier 1 is connected to the positive input terminal of the semiconductor refrigerator, the output terminal of the operational amplifier 1, and connected to one end of the resistor 2; the positive phase input terminal of the operational amplifier 2 is connected to one end of the resistor 3; the other end of the resistor 3 is connected to a reference voltage; the negative phase input terminal of the operational amplifier 2 is connected to one end of the resistor 1 and is also connected to the other end of the resistor 2; the output terminal of the operational amplifier 2 is connected to the negative input terminal of the semiconductor refrigerator and is also connected to the other end of the resistor 1 ; The positive input terminal of operational amplifier three is connected to one end of resistor six and resistor seven, and is connected to the temperature setting signal terminal; the other end of resistor six is ​​connected to the reference voltage +2.5V; the other end of resistor seven is connected to the reference ground; the negative input terminal of operational amplifier three is connected to one end of resistor three and resistor four, and is connected to the other end of capacitor two; the other end of resistor three is connected to the other end of capacitor one; the positive input terminal of operational amplifier four is connected to one end of the thermistor and resistor eight; the other end of the thermistor is connected to the reference ground; the other end of resistor eight is connected to the reference voltage +2.5V; the negative input terminal of operational amplifier four is connected to one end of resistor five and capacitor three; the output terminal of operational amplifier four is connected to resistor four, resistor five and the other end of capacitor three, and is connected to the temperature feedback signal terminal.

[0007] Furthermore, in the temperature control circuit of the ultrafast laser seed pumped laser diode, operational amplifier 1 and operational amplifier 2 are power operational amplifiers powered by a single 5V power supply.

[0008] Furthermore, in the temperature control circuit of the ultrafast laser seed pumped laser diode, operational amplifier 1 is a voltage follower, and the positive phase input voltage output drives the positive end of the semiconductor refrigeration device; operational amplifier 2 is a voltage follower, and the output voltage is a constant voltage, namely, the reference voltage Vref, which drives the negative end of the semiconductor refrigeration device, and the reference voltage Vref is adjusted to limit the maximum operating voltage of the semiconductor refrigeration device.

[0009] Furthermore, in the temperature control circuit of the ultrafast laser seed pumped laser diode, resistor five, capacitor three and operational amplifier four form a follower, the output voltage of operational amplifier four is equal to the input voltage of the positive input pin, that is, the voltage on the thermistor; the resistance value of resistor five is 1k~2k, which is used for current limiting, and the capacitance value of capacitor three is 10nF, which is used for filtering.

[0010] Furthermore, in the temperature control circuit of the ultrafast laser seed pumped laser diode, operational amplifier three, resistor three, resistor four, capacitor one and capacitor two constitute an error amplifier controlled by a PI regulator, and the temperature is controlled by outputting a corresponding voltage after comparing the positive input terminal voltage of operational amplifier three with the actual current temperature feedback voltage. Operational amplifier three and operational amplifier four are powered by a single 5V power supply with a bandwidth of 5MhZ.

[0011] Furthermore, in the temperature control circuit of the above-mentioned ultrafast laser seed pump laser diode, the resistance of resistor six and resistor seven is equal, and the resistance is 10k. When the external temperature setting voltage signal is disconnected, resistor six and resistor seven divide the 2.5V reference voltage to form a temperature setting voltage of 1.25V, so that the seed pump LD is controlled at 25°C to prevent damage to the device; the capacitance value of capacitor one is 4.7uF, the capacitance value of capacitor two is 0.1uF, the resistance value of resistor three is 10k, and the resistance value of resistor four is 5k.

[0012] Compared with the prior art, the present invention has significant advantages and beneficial effects, which are specifically embodied in the following aspects:

[0013] ① The utility model realizes rapid control of the pump LD temperature with a simple and effective temperature control circuit, uses a power operational amplifier to drive the semiconductor refrigerator in the seed laser diode, and realizes the temperature control of cooling and heating through a PI regulator built by the operational amplifier. At the same time, the maximum operating voltage of the semiconductor refrigerator can be flexibly adjusted, which simplifies the circuit structure, has good reliability, fast response and low cost;

[0014] ② The power amplifier drives the semiconductor cooler, replacing the half-bridge or full-bridge drive semiconductor cooler TEC composed of metal-oxide-semiconductor field-effect transistors; the circuit realizes bidirectional control of cooling and heating under single power supply, and can limit the maximum operating voltage of TEC;

[0015] ③ No dedicated TEC temperature control chip or microcontroller is required. The PI regulator built with operational amplifier is used for control, which has a fast response speed.

[0016] Other features and advantages of the utility model will be described in the following description, and partly become apparent from the description, or understood by implementing the specific implementation of the utility model. The purpose and other advantages of the utility model can be achieved and obtained by the structures specifically pointed out in the written description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the utility model and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 : Schematic diagram of the circuit structure of the utility model. DETAILED DESCRIPTION

[0019] The technical scheme in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is only a part of the embodiment of the utility model, rather than all the embodiments. The components of the embodiment of the utility model generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiment of the utility model provided in the drawings is not intended to limit the scope of the utility model claimed for protection, but merely represents the selected embodiment of the utility model. Based on the embodiment of the utility model, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the utility model.

[0020] It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. At the same time, in the description of the utility model, directional terms and order terms are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0021] like Figure 1As shown, the temperature control circuit of the ultrafast laser seed pump laser diode includes an operational amplifier U1, an operational amplifier U2, an operational amplifier U3 and a semiconductor cooler TEC, wherein the positive phase input terminal of the operational amplifier U1 is connected to the capacitor C1 and one end of the capacitor C2, and the output terminal of the operational amplifier U3; the negative phase input terminal of the operational amplifier U1 is connected to the positive input terminal of the semiconductor cooler TEC, the output terminal of the operational amplifier U1, and one end of the resistor R2; the positive phase input terminal of the operational amplifier U2 is connected to one end of the resistor R3; the other end of the resistor R3 is connected to the reference voltage +Vref; the negative phase input terminal of the operational amplifier U2 is connected to one end of the resistor R1, and is also connected to the other end of the resistor R2; the output terminal of the operational amplifier U2 is connected to the negative input terminal of the semiconductor cooler TEC, and is also connected to the other end of the resistor R1. one end; the positive input end of the operational amplifier U3 is connected to one end of the resistor R6 and the resistor R7, and is connected to the temperature setting signal end; the other end of the resistor R6 is connected to the reference voltage +2.5V; the other end of the resistor R7 is connected to the reference ground; the negative input end of the operational amplifier U3 is connected to one end of the resistor R3 and the resistor R4, and is connected to the other end of the capacitor C2; the other end of the resistor R3 is connected to the other end of the capacitor C1; the positive input end of the operational amplifier U4 is connected to one end of the thermistor Rt and the resistor R8; the other end of the thermistor Rt is connected to the reference ground; the other end of the resistor R8 is connected to the reference voltage +2.5V; the negative input end of the operational amplifier U4 is connected to one end of the resistor R5 and the capacitor C3; the output end of the operational amplifier U4 is connected to the resistor R4, the resistor R5 and the other end of the capacitor C3, and is connected to the temperature feedback signal end.

[0022] The seed pump LD is packaged with an integrated TEC and a negative temperature coefficient thermistor. The semiconductor cooler TEC and the thermistor Rt are integrated inside the LD and lead out the corresponding input and output pins to connect with the external circuit. Operational amplifier U1 and operational amplifier U2 are power operational amplifiers, using TI's OPA569, 5V single power supply, and a driving capacity of 2A. At present, a bridge circuit composed of MOS tubes is usually used to switch the MOS tube output current to control the TEC to achieve temperature control through a pulse width modulation signal PWM. The utility model uses a power operational amplifier to directly drive the semiconductor cooler (TEC) for cooling and heating, eliminating the complex peripheral circuits.

[0023] Operational amplifier U1 is a voltage follower, and the positive input voltage output drives the positive end of the semiconductor refrigeration device TEC; Operational amplifier U2 is a voltage follower, and the output voltage is a constant voltage, namely the reference voltage Vref, which directly drives the negative end of the semiconductor refrigeration device TEC. The reference voltage Vref is adjusted to limit the maximum working voltage of the semiconductor refrigeration device TEC to prevent the semiconductor refrigeration device TEC from being damaged. The maximum working voltage of the TEC inside the seed LD is 2.5V, then the power supply voltage of the operational amplifier is 5V, and the reference voltage Vref is 2.5V. When the output voltage of operational amplifier U1 is greater than the output voltage of operational amplifier U2, namely Vref, the semiconductor refrigeration device TEC is in a cooling state, otherwise it is in a heating state; when the output voltage of operational amplifier U1 is equivalent to the output voltage of operational amplifier U2, the temperature control reaches stability, that is, it is in a balanced state; the role of resistor R1 and resistor R3 is to limit the current to prevent damage to operational amplifier U2, and the value is 1k. After the temperature control is stable, it is a dynamic balance process, and resistor R2 can play a role in stabilizing the dynamic balance, and the value is 2k.

[0024] The thermistor in LD has a negative temperature coefficient. At 25°C, for example, the resistance is 10k or 20k. If it is 10k, the value of resistor R8 is 10k. If it is 20k, the value of resistor R8 is 20k. Resistor R5, capacitor C3 and operational amplifier U4 form a follower. The output voltage of operational amplifier U4 is equal to the input voltage of the positive input pin, which is the voltage on the thermistor Rt. The resistance of resistor R5 is 1k~2k, which is used for current limiting. The capacitance of capacitor C3 is 10nF, which is used for filtering.

[0025] When the LD temperature is detected to be 25℃, the voltage divided on the thermistor Rt is 1.25V. When the LD temperature is greater than 25℃, the voltage divided on the thermistor Rt is less than 1.25V. When the LD temperature is less than 25℃, the voltage divided on the thermistor Rt is greater than 1.25V. The voltage on the thermistor Rt is input to the positive input terminal of the operational amplifier U4. Let the voltage signal be Ur. The voltage output after the follower is also Ur, which is the temperature feedback signal. During measurement, the voltage signal Ur is collected and the resistance value Rt of the thermistor is calculated. Using the formula (2.5-Ur) / R8=Ur / Rt, Rt=Ur / R8(2.5-Ur) is calculated to calculate the resistance value of the thermistor. The current temperature is converted according to the table lookup method or the thermistor coefficient value of LD.

[0026] Operational amplifier U3, resistor R3, resistor R4, capacitor C1 and capacitor C2 constitute an error amplifier controlled by a PI regulator. The positive input voltage of operational amplifier U3 (i.e., the temperature setting voltage) is compared with the actual current temperature feedback voltage (i.e., the voltage Ur output by the follower) and then the corresponding voltage is output for temperature control. Operational amplifier U3 and operational amplifier U4 (U4) are powered by a single power supply and have a moderate bandwidth to ensure the response speed of temperature control regulation, such as TI's OPA2340, which is powered by 5V and has a bandwidth of 5MhZ.

[0027] The PI regulator automatically adjusts the cooling and heating of the semiconductor refrigeration device TEC, eliminating the need for additional dedicated temperature control chips or microcontroller algorithm execution processes, improving response speed, simplifying circuits and reducing the complexity of the temperature control system; resistor six R6 and resistor seven R7 have equal resistance values ​​of 10k. When the external temperature setting voltage signal is disconnected, resistor six R6 and resistor seven R7 divide the 2.5V reference voltage to form a 1.25V temperature setting voltage, ensuring that the control temperature of the temperature control system is at 25°C without damaging the LD; capacitor one C1, capacitor two C2, resistor three R3 , the value of resistor R4 depends on the thermal load characteristics of LD itself. For seed LD, capacitor C1 takes 4.7uF, capacitor C2 takes 0.1uF, resistor R3 takes 10k, and resistor R4 takes 5k; setting the temperature means setting the corresponding voltage value, which is the final voltage value Ur on the thermistor Rt after the temperature control is stable. Using the formula (2.5-Ur) / R8=Ur / Rt, calculate Ur=2.5Rt / (R8+Rt), convert the Rt value according to the table lookup method or the thermistor coefficient, and get the voltage value corresponding to the set temperature.

[0028] In specific applications, when the temperature control system is in a stable state, that is, the temperature reaches the set value, the voltage value on the thermistor Rt is equal to the temperature setting voltage, the positive and negative input voltages input to the error comparator composed of the operational amplifier U3 are equal, and the output voltage of the error comparator, that is, the input voltage input to the operational amplifier U1 and the output voltage of the operational amplifier U2 are nearly equal, to ensure that the system maintains heating or cooling; when the set temperature value is lower than the existing temperature value, since the thermistor Rt is a negative temperature coefficient, the temperature setting voltage is greater than the voltage value on the thermistor Rt, the positive input voltage of the error comparator composed of the operational amplifier U3 is greater than the negative input voltage, the error comparator outputs the full-scale voltage value of the operational amplifier U3, and at the same time, the output of the operational amplifier U1 is consistent with the output of the operational amplifier U3, and the output voltage is greater than the output voltage of the operational amplifier U2, and the positive input voltage of the semiconductor refrigerator TEC is greater than the negative input voltage, which is used for cooling; cooling After that, the voltage value on the thermistor Rt gradually increases, and the negative input voltage of the operational amplifier U3 gradually increases. Under the action of the PI regulator, the output voltage of the operational amplifier U3 gradually decreases, which is equivalent to the output of the operational amplifier U2, and reaches a balance; when the set temperature value is higher than the existing temperature value, the temperature setting voltage is less than the voltage value on the thermistor Rt, the positive input voltage of the error comparator formed by the operational amplifier U3 is less than the negative input voltage, the output voltage of the error comparator is 0V, the output of the operational amplifier U1 is also 0V, and the negative input voltage of the semiconductor cooler TEC is greater than the positive input voltage, which is used for heating; after heating, the voltage value on the thermistor Rt gradually decreases, and the negative input voltage of the operational amplifier U3 gradually decreases. Under the action of the PI regulator, the output voltage of the operational amplifier U3 gradually increases, which is equivalent to the output of the operational amplifier U2, and reaches a new balance again; under the condition of single power supply, bidirectional control of cooling and heating is realized.

[0029] In summary, the simple and effective temperature control circuit of the utility model realizes rapid control of the temperature of the pump LD, adopts a power operational amplifier (referred to as power op amp) to drive the semiconductor refrigerator in the seed laser diode to work, and realizes cooling and heating temperature control through a PI regulator built by the op amp. At the same time, the maximum operating voltage of the semiconductor refrigerator can be flexibly adjusted, which simplifies the circuit structure, has good reliability, fast response and low cost.

[0030] The power operational amplifier drives the Thermoelectric cooler (TEC) to replace the half-bridge or full-bridge TEC composed of metal-oxide-semiconductor field effect transistors (MOS transistors). The circuit realizes bidirectional control of cooling and heating under a single power supply, and can limit the maximum operating voltage of the TEC.

[0031] No dedicated TEC temperature control chip or microcontroller is required. The PI (Proportional Integral) regulator built with an operational amplifier is used for control, which has a fast response speed.

[0032] The above description is only a preferred embodiment of the utility model and is not intended to limit the utility model. For those skilled in the art, the utility model may have various modifications and changes. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the utility model should be included in the protection scope of the utility model. It should be noted that similar numbers and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0033] The above is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention.

[0034] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

Claims

1. Temperature control circuit for ultrafast laser seed pump laser diode, characterized by: The invention comprises an operational amplifier 1 (U1), an operational amplifier 2 (U2), an operational amplifier 3 (U3) and a semiconductor cooler (TEC), wherein the positive phase input terminal of the operational amplifier 1 (U1) is connected to one end of the capacitor 1 (C1) and the capacitor 2 (C2), and the output terminal of the operational amplifier 3 (U3); the negative phase input terminal of the operational amplifier 1 (U1) is connected to the positive input terminal of the semiconductor cooler (TEC), the output terminal of the operational amplifier 1 (U1), and is connected to one end of the resistor 2 (R2); the positive phase input terminal of the operational amplifier 2 (U2) is connected to one end of the resistor 3 (R3); the other end of the resistor 3 (R3) is connected to a reference voltage (+Vref); the negative phase input terminal of the operational amplifier 2 (U2) is connected to one end of the resistor 1 (R1), and is also connected to the other end of the resistor 2 (R2); the output terminal of the operational amplifier 2 (U2) is connected to the negative input terminal of the semiconductor cooler (TEC), and is also connected to the other end of the resistor 1 (R1); the operational amplifier 3 (U3) The positive input terminal of the operational amplifier U3 is connected to one end of the resistor six (R6) and the resistor seven (R7), and is connected to the temperature setting signal terminal; the other end of the resistor six (R6) is connected to the reference voltage +2.5V; the other end of the resistor seven (R7) is connected to the reference ground; the negative input terminal of the operational amplifier U3 is connected to one end of the resistor three (R3) and the resistor four (R4), and is connected to the other end of the capacitor two (C2); the other end of the resistor three (R3) is connected to the other end of the capacitor one (C1); the positive input terminal of the operational amplifier U4 is connected to one end of the thermistor (Rt) and the resistor eight (R8); the other end of the thermistor (Rt) is connected to the reference ground; the other end of the resistor eight (R8) is connected to the reference voltage +2.5V; the negative input terminal of the operational amplifier U4 is connected to one end of the resistor five (R5) and the capacitor three (C3); the output terminal of the operational amplifier U4 is connected to the resistor four (R4), the resistor five (R5) and the other end of the capacitor three (C3), and is connected to the temperature feedback signal terminal.

2. The temperature control circuit of the ultrafast laser seed pump laser diode according to claim 1, characterized in that: Operational amplifier one (U1) and operational amplifier two (U2) are power operational amplifiers, which are powered by a single 5V power supply.

3. The temperature control circuit of the ultrafast laser seed pump laser diode according to claim 1, characterized in that: Operational amplifier 1 (U1) is a voltage follower, and the positive-phase input voltage output drives the positive end of the semiconductor refrigeration device (TEC); Operational amplifier 2 (U2) is a voltage follower, and the output voltage is a constant voltage, namely, the reference voltage Vref, which drives the negative end of the semiconductor refrigeration device (TEC), and the maximum operating voltage of the semiconductor refrigeration device (TEC) is limited by adjusting the reference voltage Vref.

4. The temperature control circuit of the ultrafast laser seed pump laser diode according to claim 1, characterized in that: Resistor five (R5), capacitor three (C3) and operational amplifier four (U4) form a follower. The output voltage of operational amplifier four (U4) is equal to the input voltage of the positive input pin, which is the voltage on the thermistor (Rt). The resistance value of resistor five (R5) is 1k~2k, which is used for current limiting. The capacitance value of capacitor three (C3) is 10nF, which is used for filtering.

5. The temperature control circuit of the ultrafast laser seed pump laser diode according to claim 1, characterized in that: Operational amplifier three (U3), resistor three (R3), resistor four (R4), capacitor one (C1) and capacitor two (C2) constitute an error amplifier controlled by a PI regulator. The temperature is controlled by outputting a corresponding voltage after comparing the positive input voltage of operational amplifier three (U3) with the actual current temperature feedback voltage. Operational amplifier three (U3) and operational amplifier four (U4) are powered by a single 5V power supply with a bandwidth of 5MhZ.

6. The temperature control circuit of the ultrafast laser seed pump laser diode according to claim 1, characterized in that: Resistor six (R6) and resistor seven (R7) have equal resistance values, 10k. When the external temperature setting voltage signal is disconnected, resistor six (R6) and resistor seven (R7) divide the 2.5V reference voltage to form a 1.25V temperature setting voltage, so that the seed pump LD is controlled at 25°C to prevent damage to the device; capacitor one (C1) has a capacitance value of 4.7uF, capacitor two (C2) has a capacitance value of 0.1uF, resistor three (R3) has a resistance value of 10k, and resistor four (R4) has a resistance value of 5k.

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