Driving circuit of microchip laser

Abstract

The invention discloses a driving circuit of a microchip laser. According to the driving circuit, an analog switch circuit controls on-off of a constant-current discharge circuit according to an externally input control signal; the constant-current discharge circuit simulates the switching circuit to control the constant-current discharge circuit to output a discharge signal to the voltage converter circuit after being turned on, and outputs the electric energy input by the capacitor energy storage circuit to the outside; the voltage converter circuit increases the voltage input range, performs voltage conversion on the discharge signal and outputs the discharge signal after voltage conversion to the error amplifier charging current limiting circuit; the error amplifier charging current-limiting circuit detects the magnitude of the current in the driving circuit, limits the current, and outputs a discharging signal after current limiting processing to the capacitor energy storage circuit; and the capacitance energy storage circuit stores electric energy and outputs the electric energy to the constant-current discharge circuit according to the discharge signal after current limiting processing. The charging efficiency is high, the input voltage range is wide, the equivalent resistance of the energy storage capacitor is small, the size is small, the adaptability to high and low temperature environments is good, and the low-temperature capacity cannot be greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of microchip laser control, and in particular relates to a driving circuit of a microchip laser. Background Art

[0002] As a semiconductor-pumped solid-state laser, microchip laser has the advantages of compact structure, good beam quality and high conversion efficiency. Microchip lasers are usually composed of a thin standard tool of gain material coated with a dielectric film on the surface and a semiconductor laser as a pump source, which produces high-intensity laser output through the stimulated emission amplification process. According to actual needs, the drive circuit of the microchip laser modulates the light intensity, frequency and pulse width of the laser diode by controlling the drive current of the laser diode. The drive circuit has the characteristics of low noise, high precision and fast response, ensuring the stability and reliability of the laser output.

[0003] At present, the driving current of the micro-chip laser driving circuit actually used in China does not exceed 20A under the condition of a certain pulse width. The converter is mostly built with imported lithium battery charging chips, and the energy storage capacitor is mostly supercapacitor or electrolytic capacitor. This technical solution has many problems such as low charging efficiency, narrow voltage range, large capacitor equivalent resistance, large size, and poor adaptability to high and low temperature environments. Summary of the invention

[0004] The purpose of the present invention is to provide a driving circuit for a microchip laser, which has high charging efficiency, wide input voltage range, small equivalent resistance of energy storage capacitor, small volume, good adaptability to high and low temperature environments, and low-temperature capacity will not be significantly reduced.

[0005] In order to solve the above technical problems, the technical solution of the present invention is: a driving circuit of a microchip laser, comprising: an analog switch circuit, a constant current discharge circuit, a voltage converter circuit, an error amplifier charging current limiting circuit and a capacitor energy storage circuit; wherein,

[0006] An analog switch circuit, used for controlling the opening and closing of the constant current discharge circuit according to an external input control signal;

[0007] A constant current discharge circuit, used for outputting a discharge signal to the voltage converter circuit after the analog switch circuit controls the circuit to turn on, and outputting the electric energy inputted by the capacitor energy storage circuit to the outside;

[0008] A voltage converter circuit is used to increase the voltage input range, perform voltage conversion on the discharge signal and output the voltage-converted discharge signal to the error amplifier charging current limiting circuit;

[0009] The error amplifier charging current limiting circuit is used to detect the current size inside the driving circuit and limit the current to protect the driving circuit, and output the discharge signal after the current limiting process to the capacitor energy storage circuit;

[0010] The capacitor energy storage circuit is used to store electric energy and output electric energy to the constant current discharge circuit according to the discharge signal after current limiting processing.

[0011] The chip model of the voltage converter circuit is selected as SGM61232, which has a voltage input range of 4 to 28V, a 0.8V internal reference and a switching frequency of 540Hz.

[0012] The chip model of the error amplifier charging current limiting circuit is MS321.

[0013] The capacitor energy storage circuit includes a number of identical tantalum chip capacitors connected in parallel, and the tantalum capacitor model is CAK55-H-10V-1500uF-K.

[0014] The chip model of the constant current discharge circuit is MS358.

[0015] The chip model of the analog switch circuit is SGM3157.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention provides a voltage converter circuit and a capacitor energy storage circuit formed by connecting a number of identical tantalum chip capacitors in parallel, so that the driving circuit has high charging efficiency, a wide input voltage range, a small equivalent resistance of the energy storage capacitor, a small volume, good adaptability to high and low temperature environments, and the low-temperature capacity will not be significantly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of a connection structure of an embodiment of the present invention;

[0019] Figure 2 is a circuit schematic diagram of a voltage converter circuit in an embodiment of the present invention;

[0020] Figure 3 1 is a circuit schematic diagram of an error amplifier charging current limiting circuit in an embodiment of the present invention;

[0021] Figure 4 is a circuit schematic diagram of a capacitor energy storage circuit in an embodiment of the present invention;

[0022] Figure 5 is a circuit schematic diagram of a constant current discharge circuit in an embodiment of the present invention;

[0023] Figure 6 is a circuit schematic diagram of an analog switch circuit in an embodiment of the present invention;

[0024] Figure 7 Schematic diagram of the internal structure of the analog switch circuit in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] The technical solution of the present invention is: a driving circuit of a microchip laser, such as Figure 1 The circuit shown includes: an analog switch circuit, a constant current discharge circuit, a voltage converter circuit, an error amplifier charging current limiting circuit and a capacitor energy storage circuit; wherein,

[0027] An analog switch circuit, used for controlling the opening and closing of the constant current discharge circuit according to an external input control signal;

[0028] A constant current discharge circuit, used for outputting a discharge signal to the voltage converter circuit after the analog switch circuit controls the circuit to turn on, and outputting the electric energy inputted by the capacitor energy storage circuit to the outside;

[0029] A voltage converter circuit is used to increase the voltage input range, perform voltage conversion on the discharge signal and output the voltage-converted discharge signal to the error amplifier charging current limiting circuit;

[0030] The error amplifier charging current limiting circuit is used to detect the current size inside the driving circuit and limit the current to protect the driving circuit, and output the discharge signal after the current limiting process to the capacitor energy storage circuit;

[0031] The capacitor energy storage circuit is used to store electric energy and output electric energy to the constant current discharge circuit according to the discharge signal after current limiting processing.

[0032] Furthermore, the voltage converter circuit is built with Shengbang Microchip SGM61232 as the core, and has a 4-28V voltage input range, 0.8V internal reference, 540kHz switching frequency, overvoltage and overheating protection characteristics. Figure 2In the chip, the chip 2 pin VIN is the power input. The resistors R2 and R5 divide the enable terminal EN, and the chip is in the enabled state. C26 is connected to the 4-pin SS terminal to set the soft start time. Capacitor C27 and resistor R9 are connected to the 6-pin COMP for frequency compensation. Resistors R4 and R8 are connected to the voltage divider feedback VSENSE. The freewheeling diode V4 is connected to the 8-pin SW, output through the inductor L1, and the bootstrap capacitor C2 is connected to the 1-pin BOOT. C24 and C25 are output filter capacitors, and the resistance values ​​of resistors R2 and R5 are reasonably selected to ensure that after power-on, the voltage of the enable terminal EN is greater than 1.25V and the chip is in the enabled state. C26 takes a value of 0.01uF to set the soft start time. Capacitor C27 and resistor R9 perform frequency compensation. Resistor R4 is 43k and R8 is 5.6k. Because VSENSE=0.8V, according to Ohm's law, the output voltage Vdd=6.9V. The freewheeling diode V4 is S0340 with a current of 3A, the inductor L1 is 100uH, and the bootstrap capacitor C2 is 0.1uF. These parameters are reasonably selected to provide good line and load transient response.

[0033] Furthermore, the error amplifier charging current limiting circuit is built with Ruimeng electronic chip MS321 as the core. Figure 3 , R3 is a sampling resistor of 0.1 ohm. According to the error amplifier formula: Vo = (Rf / R7)*(Vi+-Vi-), Vo is proportional to the difference between the two voltages. In the series circuit, when Rf = R12 and R6 = R7, the circuit also meets the requirement that the DC resistance of the two input terminals to the ground is equal. R12 is connected across the input and output terminals, and the resistor R10 is grounded. R11 and diode V5 are connected to the output to play a role in current limiting reverse protection. R12 takes a value of 7.5k and R6 takes a value of 1k. The signal is amplified 7.5 times. When the current on R3 exceeds 2A, Vo will be greater than 1.5V. Minus the 0.7V voltage drop on R5, VSENSE is greater than 0.8V, thereby achieving the purpose of current limiting.

[0034] Furthermore, the capacitor energy storage circuit adopts a parallel connection of twenty tantalum chip capacitors, such as Figure 4 , C4~C23 models are CAK55-H-10V-1500uF-K tantalum capacitors. This has high capacity, low equivalent series resistance, and small capacity change in low temperature environment.

[0035] According to the formula: U = Q / C, Q = I × △T

[0036] I×△T=△U×C

[0037] Where: I——discharge current, 30A in this embodiment;

[0038] △T——discharge time, which is 3ms in this embodiment;

[0039] △U——voltage drop of energy storage capacitor, in this embodiment, it is 3V (capacitor full voltage is 6.9V);

[0040] Calculate C = 30000uF;

[0041] In this embodiment, 20 1500uF / 10V capacitors are connected in parallel.

[0042] Furthermore, the constant current discharge circuit is built with Ruimeng Electronics chip MS358 and Xi'an Xinpai NMOS tube as the core. Figure 5 , current sampling resistor R33 = 35mΩ, when I = 30A, voltage V is about 1V, so when Vcon is set to 1V, the laser drive current can reach 30A. Figure 5 The 8-pin +Vs of the chip is connected to the +12V power supply, the 4-pin -Vs is grounded, the 3-pin +INA is the positive input terminal connected to the resistor R20, the 2-pin -INA is the reverse feedback terminal, connected to the capacitor C37 and the resistors R27 and R28, and the output terminal 1-pin OUTA is connected to R24; the D terminal of the MOS tube is connected to the negative terminal of the laser V3, the S terminal is connected to the sampling resistor R33, and the G terminal is connected to the resistor R23; the positive terminal of V3 is connected to the Vc of the energy storage capacitor.

[0043] Furthermore, the analog switch circuit is built with Shengbang microchip SGM3157 as the core. Figure 6 When LAS_con = 1, the output pin 4 of N3 is connected to the pin 1, and when LAS_con = 0, the output pin 4 of N3 is connected to the pin 3. Figure 7 , that is, the Vcon potential is equal to the potential of the 4th pin of N3. The potential of the 1st pin is set to 1V through a resistor divider, and the 3rd pin is grounded, so that the constant current circuit can be turned on and off. Figure 6 , the chip's 5-pin V+ is connected to +5V, 2-pin GND is grounded, 1-pin NO is connected through resistors R14, R16, and R19 for voltage division, 3-pin NC is grounded through resistor R25, 6-pin IN is connected to the control terminal LAS_con through resistor R21, and 4-pin COM is the selected output.

[0044] Furthermore, a summary table of electronic components is shown in Table 1.

[0045] Table 1

[0046]

[0047]

[0048] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A driving circuit for a microchip laser, characterized in that: include: Analog switch circuit, constant current discharge circuit, voltage converter circuit, error amplifier charging current limiting circuit and capacitor energy storage circuit; wherein, An analog switch circuit, used for controlling the opening and closing of the constant current discharge circuit according to an external input control signal; A constant current discharge circuit, used for outputting a discharge signal to the voltage converter circuit after the analog switch circuit controls the circuit to turn on, and outputting the electric energy inputted by the capacitor energy storage circuit to the outside; A voltage converter circuit is used to increase the voltage input range, perform voltage conversion on the discharge signal and output the voltage-converted discharge signal to the error amplifier charging current limiting circuit; The error amplifier charging current limiting circuit is used to detect the current size inside the driving circuit and limit the current to protect the driving circuit, and output the discharge signal after the current limiting process to the capacitor energy storage circuit; The capacitor energy storage circuit is used to store electric energy and output electric energy to the constant current discharge circuit according to the discharge signal after current limiting processing.

2. The driving circuit of a microchip laser according to claim 1, characterized in that: The chip model of the voltage converter circuit is selected as SGM61232, which has a voltage input range of 4 to 28V, a 0.8V internal reference and a switching frequency of 540Hz.

3. The driving circuit of a microchip laser according to claim 1, characterized in that: The chip model of the error amplifier charging current limiting circuit is MS321.

4. The driving circuit of a microchip laser according to claim 1, characterized in that: The capacitor energy storage circuit includes a number of identical tantalum chip capacitors connected in parallel, and the tantalum capacitor model is CAK55-H-10V-1500uF-K.

5. The driving circuit of a microchip laser according to claim 1, characterized in that: The chip model of the constant current discharge circuit is MS358.

6. The driving circuit of a microchip laser according to claim 1, characterized in that: The chip model of the analog switch circuit is SGM3157.

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