A three-phase arc high-voltage discharge system for optical fiber fusion splicing machine

Abstract

A three-phase arc high-voltage discharge system for fiber optic fusion splicers is disclosed. The system boosts the power supply voltage through a primary boost circuit; after a flyback converter, the voltage is significantly increased, and then converted into a discharge DC voltage by a diode rectifier circuit. The final voltage of the primary boost circuit and two identical flyback converters are controlled by an adjustable duty cycle PWM wave and signals obtained from AD sampling to generate two sets of discharge DC voltages with a voltage difference of 1.5KV. The system collects the current in the primary boost circuit and flyback converter circuit during fiber optic fusion splicer operation to maintain power within a safe operating range and ensure power stability. Three-phase discharge electrodes are used to form a three-electrode discharge. This system possesses a large-area thermal radiation field, high heat generation power, and a wide controllable discharge power range, thus facilitating the splicing of large-diameter optical fibers. It features low splicing loss and fast splicing speed, shortening splicing time. Suitable for splicing both large-core and small-core optical fibers, it has a wide range of applications and enables workers to promptly repair optical cables.

Description

Technical Field

[0001] The invention relates to the field of optical cable supporting equipment, and in particular to a three-phase arc high-voltage discharge system for an optical fiber fusion splicer. Background Art

[0002] Fiber fusion splicers are needed for both laying and repairing optical cables. If the optical cable is interrupted and repaired in time, it will seriously endanger safety. Fiber fusion splicing is the key to laying and repairing optical cables, so fast and low-loss fiber fusion splicing is the only way to solve the problem. With the rapid development of contemporary communication technology, optical fiber communication, as the main pillar of modern communication, has also entered a stage of rapid development. The demand for high-end optical fiber fusion splicing equipment has greatly increased. At the same time, higher requirements have been put forward for optical fiber fusion splicing equipment.

[0003] The arc discharge welding circuit is the most important circuit in the fiber fusion splicer system. The entire fiber fusion splicer includes an optical path imaging module, a high-precision mobile platform module, an arc discharge welding module, and a human-computer interaction module. The optical fiber is first observed by the optical path imaging module and the high-precision mobile platform module is aligned by micro-movement in the way that the two end faces are aligned, and then the aligned optical fiber is welded through the thermal radiation field of the arc generated by the electrode needle discharge.

[0004] However, most of the arc discharge welding circuits of optical fiber welding machines currently use two-phase electrode needles. This method can only heat the middle high-temperature zone of the high-voltage spindle-shaped arc generated by the discharge of two electrode needles. The high-temperature zone is small in area and the heat generation power is relatively small, which is not conducive to welding large-diameter optical fibers. Summary of the invention

[0005] In view of the problems existing in the above-mentioned background technology, a three-phase arc discharge system for an optical fiber fusion splicer is proposed. The system has a large-area thermal radiation field, high heat generation power, and a wide controllable range of discharge power, which is conducive to the fusion of large-diameter optical fibers, and has lower fusion loss and faster fusion speed.

[0006] A three-phase arc discharge system for an optical fiber fusion splicer, wherein:

[0007] A boost circuit is used to form a primary boost circuit to increase the power supply voltage; after flyback conversion, the pulse power signal voltage is significantly increased, and then converted into a discharge DC voltage through a diode rectifier circuit; the final voltage of the primary boost is controlled by a PWM wave with adjustable duty cycle and the signal obtained by processing AD sampling, and two identical flyback conversions are controlled to obtain two sets of discharge DC voltages with a voltage difference of 1.5KV; the current of the primary boost circuit and the flyback conversion circuit is collected when the optical fiber fusion splicer is working, so that the power is kept in a safe working area during operation and the power is kept stable; a three-phase discharge electrode is used to form a three-pole discharge.

[0008] The system is mainly composed of a primary boost circuit, a flyback conversion circuit, an AD sampling circuit, an MCU main control circuit, and a three-phase discharge electrode circuit. The input DC voltage is 12V, and the primary boost circuit converts the 12V DC voltage into a 33V DC voltage; then the 33V DC voltage is converted into a 1500V AC voltage through a flyback conversion; then the 1500V AC voltage is converted into a 1500V DC voltage through a diode rectifier circuit; finally, two flyback conversion circuits with exactly the same structure are connected to the three-phase electrode pins to form a three-phase "T-type" discharge, and the radiation heat zone generated by the three-pole "T-type" discharge arc is used to weld the optical fiber. Among them, the MCU main control circuit is responsible for generating a PWM wave with a variable duty cycle to control the DC voltage amplitude of the primary boost and the AC voltage amplitude of the flyback conversion output. The sampling circuit collects the current of the primary boost circuit and the flyback conversion circuit when the optical fiber fusion splicer is working, and uses the PID algorithm to control the duty cycle of the PWM wave so that the power is kept in the safe working area and the power is stable during operation.

[0009] For the Boost circuit, the voltage across the capacitor and the current flowing through the capacitor have the following relationship, where i C is the voltage across the capacitor, C is the capacitance value, v C is the voltage across the capacitor, V C0 is the initial voltage across the capacitor:

[0010]

[0011] By using this characteristic, the capacitor can be equivalent to a voltage source when the capacity is large enough. At this time, the load will continuously draw energy from the capacitor, so semiconductor devices are required to continuously replenish the capacitor with energy. However, the moment the voltage source and the capacitor are forcibly connected through the switch, the capacitor is charged, which is equivalent to a short circuit, and a large impact current will be generated. This problem can be solved by connecting an NTC negative temperature coefficient thermistor in series between the power supply and the capacitor. This resistor has a large resistance (ten Ω level) when charging, and it generates heat when current passes through it, reducing its resistance and reducing power consumption. In addition, the current passing through the inductor cannot change suddenly. The voltage across the inductor and the current flowing through the inductor have the following relationship, where V L is the voltage across the inductor, I L0 is the initial voltage across the inductor:

[0012]

[0013] Therefore, by adding an inductor to the Buck circuit, the rate of change of the current can be controlled by the inductor. When the semiconductor device is turned off, a freewheeling path needs to be found for the inductor, otherwise a very high reverse voltage will be generated across the inductor, destroying the circuit, so a diode is added.

[0014] The beneficial effects achieved by the present invention are: 1. The three-phase discharge electrode needle used has a large-area thermal radiation field, high heat generation power, and a wide controllable range of discharge power, which is conducive to the welding of large-diameter optical fibers; 2. It has lower welding loss and faster welding speed, which greatly shortens the welding time; 3. It is suitable for the welding of large-core diameter and small-core diameter optical fibers at the same time, has a wide range of applications, and can enable workers to repair optical cables in time. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 4 is a circuit structure diagram of a primary boost circuit in an embodiment of the present invention.

[0016] Figure 2 4 is a circuit structure diagram of a flyback conversion circuit in an embodiment of the present invention.

[0017] Figure 3 It is a circuit structure diagram of the MCU main control circuit in an embodiment of the present invention.

[0018] Figure 4 is a circuit structure diagram of an AD sampling circuit in an embodiment of the present invention.

[0019] Figure 5 It is a structural diagram of a three-phase discharge electrode in an embodiment of the present invention.

[0020] Figure 6 It is a diagram showing the actual effect of the three-phase discharge electrode in the embodiment of the present invention.

[0021] Figure 7 It is a flow chart of the PID algorithm of the MCU main control circuit in the embodiment of the present invention.

[0022] Figure 8 It is a physical demonstration diagram of a three-phase arc high-voltage discharge system in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0024] like Figure 1 As shown, the primary boost circuit is a boost circuit. When the MOS tube is turned on, the following relationship exists:

[0025]

[0026] During the MOS tube off period, there is the following relationship:

[0027]

[0028] By Δi L+ +Δi L-=0, the relationship between the input and output voltage of the Boost circuit is as follows:

[0029]

[0030] In this circuit, a Boost circuit is used to increase the +12V power supply voltage to +33V. The U1 single-channel gate driver chip in the circuit plays the role of current amplification, so that the high-level 3.3V duty-cycle adjustable PWM wave can drive the semiconductor device switch; the boost output port is the same-name end interface of the transformer.

[0031] like Figure 2 As shown, when the switch is turned on, current flows through the primary coil N1 of the transformer T1, and the transformer stores energy in the form of a magnetic field. Since the primary and secondary coils are in different phases, when current flows through the primary coil, no current flows through the secondary coil N2. When the switch is turned off, the disappearing magnetic field reverses the polarity of the voltage in the primary and secondary coils, and the rectifier diode VD is turned on. The current flows to the load through VD, and the energy of the transformer is released to provide load voltage and current. The ratio of output to input voltage is:

[0032]

[0033] The input is a +33V pulse power signal (obtained by boosting the +12V power supply through the Boost circuit), and the output is a +1.5kV pulse power signal, which is then converted into a discharge DC voltage through the subsequent diode rectifier circuit.

[0034] like Figure 3 As shown in the figure, the MCU main control circuit uses a 32-bit single-chip microcomputer model STM32F103C6T6 to generate three PWM waves with adjustable duty cycles and process the signals obtained by AD sampling. The first PWM wave is used to control the final voltage of the primary boost, which must be guaranteed to be around 33V; the second and third PWM waves control two identical flyback conversions to obtain two sets of discharge DC voltages with a voltage difference of 1.5KV.

[0035] like Figure 4 As shown in the figure, the AD sampling circuit uses the ADS1256 analog-to-digital converter chip to form the main circuit. ADS1256 is a 24-bit high-precision, extremely low noise, low power consumption, four-way differential input or eight-way single-ended input, and a maximum sampling rate of 30KSPS A / D converter. It is mainly used to collect the current of the primary boost circuit and the flyback conversion circuit when the optical fiber fusion splicer is working, so that the power is kept in the safe working area and the power is stable during operation.

[0036] like Figure 5As shown in the figure, the two sets of discharge DC voltages obtained by flyback transformation with a voltage difference of 1.5 kV are connected to each other (the low-potential end of the first group is connected to the high-potential end of the second group), resulting in three ports. Then, the three ports are respectively connected to the "T-shaped" three-phase electrode needles designed by ourselves to obtain two sets of high voltage differences with a voltage difference of 1.5 kV and one set of high voltage differences with a voltage difference of 3 kV, constituting a three-stage discharge.

[0037] As Figure 6 shown in the figure, the STM32F103C6T6 single-chip microcomputer core board of the Cortex3 kernel series is used in this design. The Keil uvision5 programming software of Keil Software Company and the graphical software configuration tool STM32CUBEMX launched by STMicroelectronics are used. After installing the MDK corresponding to the single-chip microcomputer model, the single-chip microcomputer control program of the overall discharge module is written in C language.

[0038] In order to obtain a PWM wave with a stable waveform, the PWM1 mode in the general timer TIM2 of the 32 series microcontrollers (as long as TIMx_CNT < TIMx_CCRz, the channel z of timer x is in the effective state, otherwise it is in the invalid state) is used to generate the pulse width modulation wave.

[0039] Since two timers need to be enabled to generate two PWM waves with three different frequencies. Since the maximum crystal oscillator frequency of the single-chip microcomputer main frequency is 72 MHz, the count values (reload count values ARR) of TIM2 and TIM3 are respectively set to the corresponding count values required for the primary boost boost and flyback flyback transformation.

[0040] In the implementation of adjusting the PWM duty cycle, the TIM2->CCR1 and TIM3->CCR1 for setting the comparison value are directly called to set the duty cycle. The duty cycle value is

[0041] The PID algorithm is used. According to the voltage fed back by the INA282 current detection chip and then collected by AD1256 and transmitted to the single-chip microcomputer, the error, its integral term, and differential term are calculated and processed through the PID algorithm to control the increase and decrease of the PWM duty cycle, so that the current of the front-stage boost is stabilized. The discretization formula of the PID algorithm is as follows:

[0042]

[0043] Among them, Kp is the proportional coefficient, T / TI is the integral coefficient, and TD / T is the differential coefficient. Through appropriate ratios of these three adjustment terms, the discharge current can be quickly adjusted to the expected value.

[0044] Figure 8This is a physical picture of the three-phase arc high-voltage discharge system. The lower left corner of the picture is the boost primary boost circuit board, the upper left corner is the microcontroller core board, the two in the middle are the flyback secondary boost circuit boards, and the far right is the three-phase discharge electrode structure diagram.

[0045] The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Any equivalent modifications or changes made by ordinary technicians in this field based on the contents disclosed by the present invention should be included in the protection scope recorded in the claims.

Claims

1. A three-phase arc high-voltage discharge system for an optical fiber fusion splicer, characterized in that: The system includes a primary boost circuit, a flyback conversion circuit, an AD sampling circuit, an MCU main control circuit, and a three-phase discharge electrode circuit; The primary boost circuit is based on the boost circuit. When the MOS tube is turned on, there is the following relationship, where V S is the input voltage, V O is the output voltage, L is the self-inductance coefficient, t is the time, i L is the current flowing through the inductor, T off T is the time when the MOS tube is turned off. on is the time when the MOS tube is turned on, and D is the duty cycle of the input pulse wave: During the MOS tube off period, there is the following relationship: By Δi L+ +Δi L- =0, the relationship between the input and output voltage of the Boost circuit is as follows: The primary boost circuit boosts the input DC voltage; the boosted DC voltage is converted into AC voltage through flyback conversion, and then the AC voltage is converted into DC voltage through a diode rectifier circuit; finally, two flyback conversion circuits with exactly the same structure are connected to the three-phase pole needles to form a three-phase T-type discharge, and the radiation heat zone generated by the three-pole T-type discharge arc is used to weld the optical fiber; The MCU main control circuit generates a PWM wave with a variable duty cycle to control the DC voltage amplitude of the primary boost and the AC voltage amplitude of the flyback conversion output; the AD sampling circuit collects the current of the primary boost circuit and the flyback conversion circuit when the optical fiber fusion splicer is working, and uses the PID algorithm to control the duty cycle of the PWM wave to keep the power in the safe working area and maintain the power stability during operation.

2. A three-phase arc high-voltage discharge system for an optical fiber fusion splicer according to claim 1, characterized in that: In the primary boost circuit, a Boost circuit is used to increase the +12V input DC voltage to +33V. The U1 single-channel gate driver chip in the circuit plays the role of current amplification, so that the high-level 3.3V duty-cycle adjustable PWM wave drives the semiconductor device switch. The boost output port is the same-name end interface of the transformer.

3. A three-phase arc high-voltage discharge system for an optical fiber fusion splicer according to claim 1, characterized in that: In the flyback converter circuit, the ratio of the output voltage to the input voltage is: Among them, N1 is the number of turns of the primary coil, and N2 is the number of turns of the secondary coil.

4. A three-phase arc high-voltage discharge system for an optical fiber fusion splicer according to claim 3, characterized in that: The input is a +33V DC voltage, and the output is a +1.5kV AC voltage, which is then converted into a discharge DC voltage through a subsequent diode rectifier circuit.

5. A three-phase arc high-voltage discharge system for an optical fiber fusion splicer according to claim 4, characterized in that: The two groups of discharge DC voltages with a voltage difference of 1.5KV obtained by the flyback conversion are connected to each other, that is, the low potential end of the first group is connected to the high potential end of the second group, to obtain three ports; the three ports are respectively connected to the T-type three-phase electrode needles to obtain two groups of high voltage differences with a voltage difference of 1.5kV and one group of high voltage difference with a voltage difference of 3kV, forming a three-stage discharge.

6. A three-phase arc high-voltage discharge system for an optical fiber fusion splicer according to claim 1, characterized in that: The AD sampling circuit uses the INA282 current detection chip and the ADS1256 analog-to-digital converter chip to collect the current of the primary boost circuit and the flyback conversion circuit when the optical fiber fusion splicer is working, so that the power is kept in the safe working area and the power is stable during operation.

7. A three-phase arc high-voltage discharge system for an optical fiber fusion splicer according to claim 1, characterized in that: The MCU main control circuit uses the STM32F103C6T6 single-chip core board of the Cortex3 core series to generate three PWM waves with adjustable duty cycles and process the signals obtained by AD sampling.

8. A three-phase arc high-voltage discharge system for an optical fiber fusion splicer according to claim 7, characterized in that: Among the three PWM waves with adjustable duty cycles, the first PWM wave is used to control the final voltage of the primary boost, which must be ensured to be around 33V; the second and third PWM waves control two identical flyback conversions to obtain two sets of discharge DC voltages with a voltage difference of 1.5KV.

9. A three-phase arc high-voltage discharge system for an optical fiber fusion splicer according to claim 7, characterized in that: In the MCU main control circuit, the voltage fed back by the AD sampling circuit is processed by the PID algorithm to calculate the error and its integral and differential terms to adjust the increase and decrease of the PWM duty cycle, so that the previous stage boost current is stabilized to the discretization formula of the PID algorithm as follows: Among them, K p is the proportionality factor, T / T I is the integration coefficient, T D / T is the differential coefficient. These three adjustment items quickly adjust the discharge current to the expected value through appropriate proportions; e() is the deviation signal, and u0 is the reference value of the control quantity.

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