TWI644493B - Laser diode drive system - Google Patents

Abstract

The invention relates to a laser diode driving system, which receives a current of a power source for driving a laser diode. The laser diode driving system comprises a control command unit, a digital control unit and a switch. DC-DC converter unit, a latch current control unit, a switch control unit, and a laser diode unit. The invention integrates power electronics and digital control technology to achieve high efficiency of laser diode driving. High stability, instant and fast planning (microsecond) switching and advanced control features such as precise latch current regulation required for the fast switching process described above.

Description

Laser diode drive system

The invention relates to the technical field of laser driving circuit architecture, in particular to a laser diode driving system.

In recent years, the technology of laser diodes has been widely used in human life, and it has been applied to different fields according to its power level. For example, most of the fields of medical, electronic products and communication systems are low. Power laser diodes, while medium or high power laser diodes are used in industrial and military fields.

Moreover, in the technical architecture of the laser diode, the driving power supply plays a very important role, and according to the technical characteristics of the laser diode driven by it, the technical characteristics of the driving power supply can be mainly simple regions. It is divided into the following two types: (1) Pulse/continuous laser driving power source: It can be switched to pulse wave laser output mode or continuous wave laser output mode according to user requirements, in the continuous wave laser output mode, The output power is constant, and in the pulsed laser output mode, the output power changes with time, and in the pulsed laser output mode, the output power at the peak is much larger than the same time axis. The output power of a continuous wave laser, however, its average power is less than the average power of a continuous wave laser. (2) High-power laser diode driving power supply: High-power laser systems are becoming more and more widely used, and the required excitation light source power is also increasing. The cost of a single high-power laser diode is high, and the continuous output power is very limited. In the laser diode structure with large continuous output power, the high-power laser diode module with parallel or array structure is used. How to improve the efficiency and regulation of the driving power supply while improving the laser power? Performance is an extremely important job.

On the other hand, in the circuit structure of the above-mentioned laser diode driving power source, it can be divided according to its driving mode: (1) Switch driving type: according to different circuit design and control command design manner, generally can be divided For both "fixed current" and "fixed power", the switch-driven drive power supply has higher system efficiency but slower response. (2) Linear drive type: The circuit structure is simple, the current control precision is high, and the control method is relatively direct, but the system efficiency is low and the device is bulky. Therefore, when the laser diode is operated in a high-power system application, the efficiency of the driving power system, the stability of the output power of the laser diode, the fast switching that can be planned, and the precise and precise control of the latch current are provided. The circuit and control method of the characteristic is extremely important.

In order to improve the shortcomings of the prior art, the present invention provides a laser diode driving system, which integrates power electronics and digital control technology to achieve high efficiency, high stability, and instant planning of laser diode driving. Microseconds) Switch and match the advanced control features such as precise latch current regulation required for the fast switching process described above.

The present invention provides a laser diode driving system that receives power from a power source to drive laser diode operation. The laser diode driving system includes: a control command a unit for generating a current control command; a digital control unit for connecting the control command unit, the digital control unit receiving the current control command to control operation of the laser diode driving system; The DC-DC converter unit is connected to the digital control unit, and the switching DC-DC converter unit is used for converting the power of the power supply; a latch current control unit is connected to the digital control unit and the switch a DC-DC converter unit, the latch current control unit receives power supply converted by the switching DC-DC converter unit, and generates a latch current command according to the current control command; a switch control unit, Connecting the digital control unit and the switching DC-DC converter unit, and the switch control unit receives the a DC-DC converter unit converted power supply power, and generating a switch control command according to the current control command; and a laser diode unit connecting the latch current control unit and the switch control unit, The laser diode unit adjusts its drive current according to the latch current command and the switch control command to change its optical power output.

In an embodiment of the present invention, the control command unit can input and adjust the content of the current control command through a control program, and the current control command content includes: controlling the output of the switching DC-DC converter unit operation. Power control command; controlling the driving power of the laser diode unit The flow value control command, the latch current value control command, and the switch control command for controlling the operation of the switch control unit.

In an embodiment of the invention, the control command unit is composed of a stylized software module and a hardware module.

In an embodiment of the invention, the control command unit communicates with the digital control unit through an entity or a virtual communication interface.

In an embodiment of the invention, the switching DC-DC converter unit is a multi-phase interleaved conventional buck converter circuit, a multi-phase interleaved synchronous rectification buck converter circuit or any type of power Converter unit.

In an embodiment of the invention, the switch control unit is formed by connecting a power electronic switch and a diode in parallel.

In one embodiment of the invention, the laser diode unit is a laser diode or is composed of a plurality of laser diodes in a series, parallel or matrix arrangement.

The above summary, the following detailed description and the accompanying drawings are intended to further illustrate the manner, the Other objects and advantages of the present invention will be described in the following description and drawings.

11‧‧‧Control command unit

12‧‧‧Digital Control Unit

13‧‧‧Switching DC-DC Converter Unit

14‧‧‧Latch current control unit

15‧‧‧Toggle switch control unit

16‧‧‧Laser diode unit

1 is a block diagram of an embodiment of a laser diode driving system of the present invention.

2 is a temperature characteristic diagram of the laser diode latch current in the embodiment of the present invention.

3(a) to 3(c) are diagrams showing the correspondence relationship between the driving current of the laser diode and the latch current in the first state according to the embodiment of the present invention.

4(a) to 4(c) are diagrams showing the correspondence relationship between the driving current of the laser diode and the latch current in the second state according to the embodiment of the present invention.

FIG. 5 is a corresponding diagram of driving current chopping size of a laser diode in a second state according to an embodiment of the present invention.

FIG. 6 is a diagram showing the drop and rise time of the driving current of the laser diode according to the embodiment of the present invention.

The embodiments of the present invention are described below by way of specific examples, and those skilled in the art can readily appreciate other advantages and functions of the present invention from the disclosure herein.

The purpose of the present invention is to provide a latch current regulation mechanism by utilizing the characteristics of an operating current value of the laser diode itself, so that the laser diode is charged and maintained at a latch current value before starting operation (the latch The current value needs to be smaller than the driving current value of the laser diode, and then the digital control design provided by the invention performs fast switching control of the driving current of the laser diode, so that the laser diode can be Achieve the operational goals of fast start and switch, and instantly plan and change the output control mechanism (switching frequency, number of times, output power, etc.) of the laser diode to meet the needs of different occasions. begging.

The architecture diagram of the embodiment of the laser diode driving system of the present invention is shown in FIG. 1. In this embodiment, the power of a power source is received to drive the operation of the laser diode. The embodiment includes: a control command unit. 11, is used to generate a current control command; a digital control unit 12 is connected to the control command unit, the digital control unit receives the current control command to control the operation of the laser diode driving system; The switching DC-DC converter unit 13 is connected to the digital control unit 12, and the switching DC-DC converter unit 13 receives power of a power source (not shown) and powers the power supply according to the control command. Performing a conversion; a latch current control unit 14 is connected to the digital control unit 12 and the switching DC-DC converter unit 13, and the latch current control unit 14 receives the converted by the switching DC-DC converter unit 13 Power supply power, and according to the current control command, immediate planning and output of a latch current command; a switch control unit 15 is connected to the digital control unit 12 and the The off-type DC-DC converter unit 13 receives the power of the power converted by the switching DC-DC converter unit 13 and generates a laser diode according to the current control command. a switch control command; and a laser diode unit 16 connected to the latch current control unit 14 and the switch control unit 15, the laser diode unit 16 according to the latch current command and the switch The switch control command adjusts its output current to change the optical power output of the laser diode unit 16.

In an embodiment of the invention, the switching DC-DC conversion The unit 13 converts the power source power to the latch current control unit 14 and the switch control unit 15, and the latch current control unit 14 and the switch control unit 15 further control the command according to the latch current and the switch. The switch control command further controls the operation and optical power output of the laser diode unit 16 to achieve a quick start.

In an embodiment of the present invention, the user can input and adjust the content of the current control command of the control command unit 11 through a control program.

In an embodiment of the present invention, the digital control unit 12 is configured to receive a current control command generated by the control command unit 11 and convert the current control command into a digital control signal via signal processing, and then transmit the digital control signal to the switched DC. The DC converter unit 13, the latch current control unit 14 and the changeover switch control unit 15 cause the latch current control unit 14 to generate a latch current command, and the switch control unit 15 to generate a switch control command to control the laser diode The output optical power of the module unit 16. The content of the current control command includes: an output power control command for controlling operation of the switching DC-DC converter unit; a driving current numerical control command for controlling operation of the laser diode unit, and controlling operation of the latch current control unit The latch current value control command and the switch control command for controlling the operation of the switch control unit.

In an embodiment of the present invention, the control command unit 11 can be a stylized software module and a hardware circuit. The control command unit 11 can be connected to the digital control unit through a physical or virtual communication interface. Instant communication, the user can instantly plan and change the latch current command and the drive power The content of the on/off command is flowed, thereby changing the optical power output of the laser diode.

In an embodiment of the present invention, the digital control unit 12 is a digital control core of the laser diode driving system, and the operation, control and command execution of each unit in the system are performed by the digital control unit 12, The closed loop control of the system is also digitally controlled by the digital control unit 12, which means that the digital control unit can instantly detect and adjust the operational status of various components of the laser diode drive system. The digital control unit 12 is configured to digitally convert the control command of the control command unit 11 to generate a digital control signal, and then separately control the latch current control unit 14, the switch control unit 15, and the switching DC-DC conversion. The operation of the unit 13 further adjusts the driving current of the laser diode unit 16, and the optical power output by the laser diode unit 16 can be adjusted and controlled by the above method.

In an embodiment of the invention, the switching DC-DC converter unit 13 is configured to convert the power of the power source into a stable direct current suitable for use in a laser diode. The switching DC-DC converter unit 13 is modularized and supplemented by closed loop interleaving control to provide high current required for high power laser diodes and low output current ripple. Moreover, through the modular and closed-loop interleaved inductor current control design, it can meet the high reliability, high system efficiency, balanced phase current and system heat dissipation characteristics and advantages required for the laser diode driving power supply. .

In an embodiment of the present invention, the latch current control unit 14 is coupled to the switching DC-DC converter unit 13 through the control command. The current control command issued by the unit 11 and converted by the digital control unit 12 can immediately plan and produce the latch current command of the latch current control unit 14 to determine the magnitude of the latch current.

In an embodiment of the present invention, the switch control unit 15 is coupled to the switch DC-DC converter unit 13 and is controlled by the control command unit 11 to be converted by the digital control unit 12. The drive current on/off command signal of the changeover switch control unit 15 is planned and generated in real time to drive the switching operation of the laser diode unit 16. The switching DC-DC converter unit 13 is a multi-phase interleaved buck converter (Multi-phase Interleaved Buck Converter) circuit and a multi-phase interleaved synchronous buck converter (Multi-phase Interleaved Synchronous). Rectification Buck Converter) Circuit or any type of power converter unit.

In an embodiment of the invention, the switch control unit 15 is formed by connecting a power electronic switch and a diode in parallel. The laser diode unit is a laser diode or consists of a plurality of laser diodes in a series, parallel or matrix arrangement.

In an embodiment of the invention, the embodiment has a mechanism for receiving a laser diode on and off command signal for immediate planning and performing fast current switching. When the current control switch of the laser diode unit is turned OFF, the power electronic switch in the switch control unit 15 is also rapidly turned on, so that the current originally flowing through the laser diode passes through the switch. control One of the diodes in the unit 15 (which can be a fast diode module) is guided back to the input end of the power source, and the current flowing through the laser diode is a latch current value (less than the laser two) The polar body preset drive current), or zero (when the latch current control function is not activated). When the current control switch of the laser diode unit is turned ON, the power electronic switch will also synchronously turn on and off the current of the original cycle, and the latch current control mechanism provided by the present invention forces the flow through The current of the laser diode quickly reaches the preset driving command value, and the function of rapidly switching the driving current of the laser diode is completed. In the implementation of the invention, a plurality of power electronic switches and a plurality of diodes can be used in parallel in the switch control unit 15 to achieve the purpose of improving current switching capability, reducing circuit cost, and reducing circulating current energy loss.

2 is a temperature characteristic diagram of the laser diode latch current in the embodiment of the present invention. In an embodiment of the present invention, the latch current command content of the latch current control unit 14 includes a laser diode. The latch current value (as shown in the circle), which means the critical current value of the laser light output by the laser diode unit. Since the working condition of the laser diode varies with temperature and the physical condition of the laser diode itself, the value of the latch current varies. Therefore, the amount of fluctuation of the latch current will cause a time deviation of the output of the diode laser light. When the switching control is performed, the light output time point of the laser diode will be different under the same input current dynamic condition. Therefore, in the precise and fast optical power output regulation, it is necessary to control the instantaneous latch current to maintain the control precision of the original design.

In an embodiment of the invention, the latch current control unit can have a current controllable current source circuit, and the precision current source circuit can perform a precise latch current command tracking function, and when the precision latch current command tracking function is activated When the fast-responding controllable current source is synchronized with the control condition of the laser diode current, the current value of the laser diode is adjusted and maintained to achieve fast switching of the driving current of the laser diode. Features. In other words, when this precision latch current control command is activated, the controllable current source will start synchronously and maintain the laser diode through a predetermined current value (latch current) instead of zero. When the precision latch current command tracking function is not activated, the current value of the laser diode will drop to zero, and the output time deviation of the laser light caused by the change of the laser diode latch current will be unavoidable.

In an embodiment of the present invention, when the power source is operated in the continuous wave constant current driving mode, the switch control unit can receive the instantaneously planned laser diode driving current on/off command signal and perform current switching control. mechanism. When the current control switch of the laser diode is turned on (OFF) according to an operation command, the power electronic switch of the switch control unit is also rapidly turned on, so that the current originally flowing through the laser diode passes through a diode. (A fast diode module can be guided back to the input of the power supply, and the current flowing through the laser diode can be a latch current value (the latch current control function is activated) or zero (the latch current control) The function is not activated). When the above-mentioned laser diode current control switch is turned on (OFF), the circuit will form a low-energy inductor current maintaining loop. At this time, the switch control unit stops the high-frequency switching operation, and the power supply only provides the latch current. The minimum power required (when the latch current control function is activated) or zero (when the latch current control function is not activated). When the current control switch of the laser diode is closed (ON) according to the operation command, the power electronic switch will also open and close the current of the original cycle synchronously, and the laser current is forced to flow through the laser through the latch current control mechanism. The current of the polar body quickly reaches the preset driving command value. At this time, the power supply synchronously starts and completes the fast switching function of the driving current required for the laser diode, and the circuit returns to the constant current driving operation of the continuous wave laser diode. status.

3(a) to 3(c) are diagrams showing the correspondence relationship between the driving current of the laser diode and the latch current in the first state according to the embodiment of the present invention, which are shown in FIG. 3(a) to FIG. 3(c). In the middle, a high-power laser diode driving power supply (that is, the aforementioned power supply) is operated on a continuous wave (CW) 50A, the simulation time is set to 8 ms, and the current is stopped every 0.1 ms for 0.1 ms to restart, and the operation is performed 5 times in total. As shown in Fig. 3(a), when no latch current value I_th is set, the current value I_LD of the laser diode is reduced to 0 amps per switching operation; as shown in Fig. 3(b), When the latch current value I_th is set to 3 amps, the laser diode current value I_LD is reduced to about 3 amps per switching operation; as shown in Fig. 3(c), when the latch current value I_th is adjusted to 5 At ampere, the laser diode current value I_LD drops to approximately 5 amps per switch operation.

4(a) to 4(c) are diagrams showing the correspondence relationship between the driving current of the laser diode and the latch current in the second state according to the embodiment of the present invention, which are shown in FIG. 4(a) to FIG. 4(c). The high-power laser diode driving power supply operates on a continuous wave of 50A, and the time is set to 8ms, and the current is stopped every 0.2ms, 0.2ms, 0.4ms, 0.6ms, Start after 0.8ms and 1ms, and operate a total of 5 times. As shown in Fig. 4(a), when no latch current value I_th is set, the laser diode current value I_LD drops to 0 amps per switch operation; as shown in Fig. 4(b), When the latch current value I_th is set to 3 amps, the laser diode current value I_LD drops to about 3 amps every time the switch is turned off, as shown in Figure 4(c). When the latch current value I_th is 5 amps, the laser diode current value I_LD drops to about 5 amps per switching operation.

Please refer to FIG. 5 and FIG. 6. FIG. 5 is a diagram showing the magnitude of the driving current chopping of the laser diode in the second state according to the embodiment of the present invention, and FIG. 6 is a driving current of the laser diode according to the embodiment of the present invention. The decline and rise time chart. In the actual test, in the setting state of the above FIG. 4(b), when the latch current value I_th is set to 3 amps and the laser diode is operated at 50 amps, as shown in the indication of FIG. 5, By the design of the present invention, the peak-to-peak (pk-pk) system is small and its current continuous wave value (0.04%) is very stable, and as shown in the indication of FIG. 6, by the present invention The design, when the laser diode drive current is turned on and off, the reaction time is also very short (0.96μs and 0.97μs). It can be seen that the present invention has the advantages of stable driving current and fast switching of switching compared with the conventional technology.

In summary, the present invention provides a laser diode driving system. The purpose of the present invention is to provide a latch current regulation mechanism by using a diode having a working current value to allow a laser diode to be Charge before charging operation, maintain a latch current value, and then pass the digital controller A fast switching control of the driving current of the laser diode is performed. Compared with the conventional technology, the present invention has the following advantages: (1) high system efficiency and high reliability; (2) extremely low output current chopping range; (3) real-time adjustment of laser diode latch current value on the line Mechanism; (4) High-efficiency, ready-to-plan continuous wave laser diode current fast (microsecond level) on and off control mechanism.

The above-described embodiments are merely illustrative of the features and functions of the present invention, and are not intended to limit the scope of the technical scope of the present invention. Modifications and variations of the above-described embodiments can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be as set forth in the scope of the claims described below.

Claims (6)

A laser diode driving system receives power from a power source to drive a laser diode operating system, the laser diode driving system includes: a control command unit for generating a current control command; The digital control unit is connected to the control command unit, and the digital control unit receives the current control command to control the operation of the laser diode driving system; a switching DC-DC converter unit is connected to the digital position a control unit, the switching DC-DC converter unit is configured to convert power of the power source; a latch current control unit is connected to the digital control unit and the switching DC-DC converter unit, the latch current control The unit receives the power supply converted by the switching DC-DC converter unit, and generates a latch current command according to the current control command; a switch control unit is connected to the digital control unit and the switch DC a DC converter unit, the switch control unit receives the power converted by the switching DC-DC converter unit And generating a switch control command according to the current control command, wherein the switch control unit is connected by a power electronic switch and a diode; and a laser diode unit is connected to the latch current control unit and The switch control unit, the laser diode unit is electrically connected according to the latch The flow command and the switch control command adjust its drive current to change its optical power output. The laser diode driving system of claim 1, wherein the control command unit inputs and adjusts the content of the current control command through a control program, the control command content includes: controlling the switch mode The output power control command of the DC-DC converter unit operation; the drive current numerical control command for controlling the operation of the laser diode unit, the latch current value control command; and the switch control command for controlling the operation of the switch control unit. The laser diode driving system of claim 1, wherein the control command unit is composed of a stylized software module and a hardware module. The laser diode driving system of claim 1, wherein the control command unit communicates with the digital control unit through a physical or virtual communication interface. The laser diode driving system of claim 1, wherein the switching DC-DC converter unit is a multi-phase interleaved conventional buck converter circuit, and a multi-phase interleaved synchronous rectification Buck converter circuit or any type of power converter unit. The laser diode driving system of claim 1, wherein the laser diode unit is a laser diode or a plurality of laser diodes are connected in series, in parallel or in a matrix. The layout is composed.