Laser diode driving circuit and driving method

Abstract

The present invention provides a driving circuit and driving method for a laser diode. The driving circuit includes n parallel switching tubes and n driving selection units, each switching tube corresponds to a driving selection unit, where n is an integer greater than 1; the first end of each switching tube is connected to the laser diode, and the second end of each switching tube is grounded or connected to a driving power supply; the control end of each switching tube is respectively connected to the output end of the corresponding driving selection unit; each driving selection unit is used to select one of different driving signals under the control of an independent driving control signal and transmit it to the control end of the corresponding switching tube to control the corresponding switching tube; the different driving signals include at least a first driving signal for controlling the rise time of the driving current, a second driving signal for controlling the pulse width of the driving current, and a shutdown signal for controlling the shutdown of the switching tube.

Description

Technical Field

[0001] The present invention relates to the field of driving circuits, and in particular to a driving circuit and a driving method for a laser diode. Background Art

[0002] A vertical-cavity surface-emitting laser (VCSEL) is a type of semiconductor laser diode. Typically, laser diode drivers use a bias FET in series with a switch driver transistor to limit current. The amplitude of the drive current pulse is controlled by controlling the gate voltage of the bias FET. While connecting the switch and bias FETs in series effectively controls the amplitude of the drive current pulse, this approach, in high-current drive applications, can significantly increase the driver area. This can also lead to excessive chip size if a drive array is required, placing pressure on manufacturing and costs.

[0003] Using a single-transistor structure with a single switching transistor as the main driver transistor offers advantages in terms of speed and area. However, the main problem with the single-transistor drive method is that the pulse current amplitude is difficult to control, and it is impossible to simultaneously control and improve the drive current pulse rise time and drive current pulse amplitude. Summary of the Invention

[0004] The present invention provides a driving circuit and a driving method for a laser diode, so as to solve the problems of improving the rise time of a driving pulse current and controlling the amplitude of the pulse current.

[0005] According to a first aspect of the present invention, a laser diode driving circuit is provided, comprising n parallel-connected switching tubes and n driving selection units, each switching tube corresponding to one driving selection unit, wherein n is an integer greater than 1;

[0006] The first end of each switch tube is connected to the laser diode, and the second end of each switch tube is grounded or connected to the driving power supply; the control end of each switch tube is respectively connected to the output end of the corresponding driving selection unit;

[0007] Each drive selection unit is used to select one of the different drive signals under the control of an independent drive control signal and transmit it to the control end of the corresponding switch tube to control the corresponding switch tube; the different drive signals include at least a first drive signal for controlling the rise time of the drive current, a second drive signal for controlling the pulse width of the drive current, and a shutdown signal for controlling the shutdown of the switch tube.

[0008] Optionally, the switch tube is a MOSFET;

[0009] The source or drain of each of the n parallel MOSFETs is connected to the cathode or anode of the laser diode, the drain or source of each MOSFET is grounded or connected to a driving power supply, and the gate of each MOSFET is respectively connected to the output end of the corresponding driving selection unit.

[0010] Optionally, the driving circuit further includes a control module; the control module is used to generate the first driving signal, the second driving signal, the shutdown signal and n driving control signals.

[0011] Optionally, the control module includes a first signal generating unit and a second signal generating unit;

[0012] The first signal generating unit is used to generate the first driving signal;

[0013] The second signal generating unit is used to generate the second driving signal;

[0014] The shutdown signal generating unit is configured to generate the shutdown signal.

[0015] Optionally, each drive selection unit includes a multiplexer; the output end of each multiplexer is connected to the control end of a corresponding switching tube, and is used to output one of the shutdown signal, the first drive signal, and the second drive signal to the corresponding switching tube under the control of the corresponding drive control signal.

[0016] Optionally, each multiplexer includes a first input terminal, a second input terminal and a third input terminal; the first input terminal is connected to the output terminal of the first signal generating unit; the second input terminal is connected to the output terminal of the second signal generating unit; and the third input terminal is connected to the output terminal of the shutdown signal generating unit.

[0017] Optionally, the control module also includes multiple buffer units; the input end of each buffer unit is connected to the output end of each multiplexer, and the output end of the buffer unit is connected to the control end of each switch tube; the buffer unit is used to enhance the output of each multiplexer and output it to each switch tube.

[0018] Optionally, each buffer unit includes a plurality of cascaded inverters.

[0019] Optionally, the pulse width of the first driving signal is smaller than the pulse width of the second driving signal.

[0020] According to a second aspect of the present invention, a method for driving a laser diode is provided. The laser diode is driven by the laser diode driving circuit described in the first aspect of the present invention. The method comprises:

[0021] Forming independent drive control signals and different drive signals;

[0022] Under the control of the independent drive control signal, each drive selection unit transmits one of the different drive signals to the control terminal of the corresponding switch tube to control the corresponding switch tube, thereby achieving control of the drive current of the laser diode;

[0023] The different driving signals at least include a first driving signal for controlling a rising time of a driving current, a second driving signal for controlling a pulse width of a driving current, and a shutdown signal for controlling the shutdown of a switch tube.

[0024] The laser diode drive circuit provided by the present invention employs a parallel drive architecture, comprising n parallel-connected switching transistors and n drive selection units. The control terminal of each switching transistor is connected to the output terminal of a corresponding drive selection unit. Under the control of an independent drive control signal, each drive selection unit selects one of different drive signals and transmits it to the control terminal of the corresponding switching transistor to control the corresponding switching transistor, thereby controlling the drive current of the laser diode. The different drive signals include at least a first drive signal for controlling the rise time of the drive current, a second drive signal for controlling the pulse width of the drive current, and a shutdown signal for controlling the shutdown of the switching transistor.

[0025] Each switch can be turned off or driven by either the first or second drive signal under the control of an independent drive control signal. The entire drive circuit can be divided into different branches based on the drive signals, with different drive signals controlling the switching timing of each branch. Adjusting the first drive signal can adjust the rise rate of the drive current, adjusting the pulse width of the second drive signal can adjust the pulse width of the drive current, and adjusting the number of switches controlled by the second drive signal can control the amplitude of the drive current.

[0026] The driving circuit provided by the present invention can not only have the advantages of a single-tube structure in speed and area, but also achieves improvement in the driving current rise speed and control of the driving current amplitude, while greatly reducing the chip area of ​​the laser diode (laser diode) driver. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 is a schematic diagram of a circuit structure of a laser diode driving circuit provided in an exemplary embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of a circuit structure of a switch tube driving a common cathode laser tube provided in an exemplary embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of a circuit structure of a switch tube driving a common anode laser tube provided in an exemplary embodiment of the present invention;

[0031] Figure 4 is a schematic diagram of an equivalent circuit structure of a laser diode driving circuit provided in an exemplary embodiment of the present invention;

[0032] Figure 5 is another schematic diagram of an equivalent circuit structure of a laser diode driving circuit provided in an exemplary embodiment of the present invention;

[0033] Figure 6 is a waveform diagram of a first driving signal and a second driving signal in a driving circuit provided in an exemplary embodiment of the present invention;

[0034] Figure 7 This is a schematic diagram of the structure of a control module in a laser diode driving circuit provided in an exemplary embodiment of the present invention.

[0035] Figure 8 It is a flowchart of a laser diode driving method provided in an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] The terms "first," "second," "third," "fourth," and so on (if any) in the description and claims of the present invention and in the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in orders other than those illustrated or described herein. In addition, the terms "including" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus that includes a series of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, product, or apparatus.

[0038] The following specific embodiments are used to describe the technical solution of the present invention in detail. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0039] Figure 1 : is a schematic diagram of the circuit structure of the laser diode driving circuit provided by the present invention, wherein the laser diode driving circuit includes n parallel switching tubes 1X and n driving selection units 2X, each switching tube 1X corresponds to one driving selection unit 2X, wherein n is an integer greater than 1; wherein X is any integer from 1 to n;

[0040] The first end of each switch tube 1X is connected to the laser diode, and the second end of each switch tube 1X is grounded or connected to the driving power supply; the control end of each switch tube 1X is respectively connected to the output end of the corresponding drive selection unit 2X;

[0041] In one embodiment of the present invention, the first end of each switch tube is connected to the cathode of the laser diode, and the second end of each switch tube is grounded. This embodiment corresponds to the following Figure 3 The common anode drive architecture shown in Figure 1 is not limited to this connection method. Figure 2 As shown, in the common cathode driving architecture, the first end of the switch tube is connected to the positive electrode of the laser diode, and the second end of each switch tube is connected to the driving power supply.

[0042] Each drive selection unit 2X is used to select one of the different drive signals under the control of an independent drive control signal and transmit it to the control end of the corresponding switch tube 1X to control the corresponding switch tube 1X; the different drive signals include at least a first drive signal for controlling the rise time of the drive current, a second drive signal for controlling the pulse width of the drive current, and a shutdown signal for controlling the shutdown of the switch tube.

[0043] In one embodiment, the switch tube is a MOSFET; the gate of each of the n parallel MOSFETs is respectively connected to the output terminal of the corresponding drive selection unit. In practical applications, the switch tube is not limited to MOSFET, and the same function can be achieved by using bipolar transistors or other switch tubes based on integrated processes. In one embodiment of the present invention, an N-type MOSFET is used as an example for illustration and description. The drain of each MOSFET is connected to the cathode of the laser diode, the source of each MOSFET is grounded, and the gate of each MOSFET is respectively connected to the output terminal of the corresponding drive selection unit.

[0044] In practical applications, if a MOSFET with a width-to-length ratio of W / L is designed, it is usually implemented using a large number of basic units (fingers) with the same width-to-length ratio. Each of these basic units is a MOSFET, and the gates, sources, and drains of all these unit MOSFETs are short-circuited together. For example, a MOSFET with a total width-to-length ratio of 50,000 / 1 can be implemented by connecting 1,000 basic units (fingers) with a width-to-length ratio of 50 / 1 in parallel. In this embodiment, the source and drain of each MOSFET are connected together, but the gate can be selectively connected to a different drive signal, so each MOSFET can be regarded as a basic unit (fingers). Therefore, the n MOSFETs in the laser diode drive circuit provided by the present invention can be divided into different parallel drive branches according to the drive signal, and the number of MOSFETs in each drive branch can be adjusted. Each drive branch is driven by a different drive signal. By changing the drive signal, the switching timing of the corresponding branch can be adjusted. The switch tube receiving the shutdown signal remains closed during the driving process. The rise rate of the drive current can be adjusted by adjusting the first drive signal, and the pulse width of the drive current can be adjusted by adjusting the pulse width of the second drive signal. The amplitude of the drive current is determined by the width-to-length ratio of the MOSFET driven by the drive branch, that is, it is related to the number of basic units (fingers) in the drive branch. In the drive circuit provided by the present invention, the number of switching transistors in the branches driven by different drive signals is also adjustable, thereby achieving control of the drive current amplitude.

[0045] In one embodiment, the drive circuit further includes a control module 30; the control module 30 is configured to generate the first drive signal, the second drive signal, the shutdown signal, and n drive control signals. Based on the n drive control signals generated by the control module 30, the control terminal of each switch tube can be selectively controlled by one of the three drive control signals: the first drive signal, the second drive signal, and the shutdown signal. The switch tube controlled by the shutdown signal is in an off state in the drive circuit.

[0046] The control module 30 includes a first signal generating unit 31, a second signal generating unit 32 and a shutdown signal generating unit 33; the first signal generating unit 31 is used to generate the first driving signal Ton1;

[0047] The second signal generating unit 32 is used to generate the second driving signal Ton2;

[0048] The shutdown signal generating unit is configured to generate the shutdown signal.

[0049] In one embodiment, each drive selection unit 2X includes a multiplexer 2X1; the output of each multiplexer is connected to the control terminal of a corresponding switch transistor 1X, and is configured to output one of the shutdown signal, the first drive signal Ton1, and the second drive signal Ton2 to the corresponding switch transistor 1X under the control of the corresponding drive control signal. Each multiplexer 2X1 includes a first input terminal, a second input terminal, and a third input terminal; the first input terminal is connected to the output terminal of the first signal generating unit 31; the second input terminal is connected to the output terminal of the second signal generating unit 32; and the third input terminal is connected to the output terminal of the shutdown signal generating unit.

[0050] like Figure 4 As shown, based on the type of drive signal that controls each switch, the entire drive circuit can be considered to be composed of two parallel drive branches, where the first drive signal Ton1 controls the first drive branch, and the second drive signal Ton2 controls the second drive branch. In each parallel drive branch, the source and drain of each MOSFET are connected together, but the gate can be selected to receive different drive signals. Therefore, each MOSFET can be considered a basic unit (finger), and all MOSFETs in a parallel drive branch can be considered as a whole MOSFET. The number of basic units in each branch determines the width-to-length ratio of the MOSFET. Figure 5 As shown, the first driving signal Ton1 and the second driving signal Ton2 respectively control the MOSFETs in the corresponding driving branches.

[0051] like Figure 6In the waveform diagram of the drive signal shown, the first drive signal Ton1 has a short pulse width, typically within 1 ns. The first drive branch is only turned on during the rising edge of the first drive signal Ton1 pulse, and its function is to improve the rise time of the drive current Ivcsel. The second drive branch is controlled by the second drive signal Ton2. The second drive signal Ton2 has a longer pulse width and is used to control the pulse width of the drive current Ivcsel. In this embodiment, the starting time of the rising edge of the second drive signal Ton2 is the same as that of the first drive signal Ton1. The MOSFETs in the first drive branch and the second drive branch are turned on simultaneously, which helps to speed up the rising edge speed of the drive current Ivcsel pulse. In this way, the rise time of the drive current Ivcsel can be jointly controlled by the first drive signal Ton1 and the second drive signal Ton2, and the pulse width of the drive current Ivcsel can be controlled by the second drive signal Ton2. On the other hand, through the drive control signal, the control terminal of each switch can be selectively controlled by one of the three drive control signals: the first drive signal, the second drive signal, and the shutdown signal. This ensures dynamic adjustment of the number of switches in the first drive branch controlled by the first drive signal Ton1 and the second drive branch controlled by the second drive signal Ton2. The amplitude of the drive current is related to the number of switches in the drive branch. Therefore, by adjusting the number of switches controlled by the second drive signal Ton2 through the drive control signal, the amplitude of the drive current can be adjusted.

[0052] In this embodiment, the rising edge starting points of the first drive signal Ton1 and the second drive signal Ton2 are the same. However, in actual applications, in terms of the order in which the switch tubes are driven to be turned on, the switch tubes in different branches can be turned on sequentially, that is, the rising edge starting points of the first drive signal Ton1 and the second drive signal Ton2 are not limited to the same time point.

[0053] In this embodiment, the entire drive circuit is regarded as consisting of two parallel drive branches according to the first drive signal Ton1 and the second drive signal Ton2. In practical applications, the control module is not limited to generating only the first drive signal for controlling the rising speed of the drive current, the second drive signal for controlling the pulse width of the drive current, and the shutdown signal. If it is necessary to make a more detailed adjustment to the waveform of the drive current Ivcsel, such as to eliminate the following Figure 6As shown in the figure, the overshoot after the driving current Ivcsel waveform rises can be generated by the control module to generate more driving signals. According to the multiple driving signals, the driving tube is divided into more branches (the number of branches is greater than 2). A larger number of branches will correspond to more complex timing control. During the operation of the driving circuit, the switch tubes of different branches are controlled to turn on at the same time (turn-on), and then turned off in sequence as needed, thereby achieving further adjustment of the driving current Ivcsel waveform.

[0054] In practical applications, the first driving signal Ton1 and the second driving signal Ton2 are connected to the gates of the corresponding MOSFET basic units after passing through a buffer circuit to increase the driving capability. Figure 7 As shown,

[0055] The driving circuit also includes multiple buffer units 4X; the input end of each buffer unit is connected to the output end of each multiplexer, and the output end of the buffer unit is connected to the control end of each switch tube; the buffer unit is used to enhance the output of each multiplexer 2X and output it to each switch tube 1X.

[0056] In one embodiment, each buffer unit comprises a plurality of cascaded inverters. Generally, a circuit comprising several stages of inverters or a similar structure with progressively larger device sizes is employed to optimize the power consumption-delay product while achieving the desired resistance drive capability. The buffer unit is intended to enhance the drive capability of the first drive signal Ton1 and the second drive signal Ton2. In practical applications, the buffer circuit structure is not limited to a buffer circuit structure consisting of a plurality of cascaded inverters.

[0057] Please refer to Figure 8 , provides a method for driving a laser diode, using the laser diode driving circuit described in the first aspect of the present invention to drive the laser diode, the method comprising:

[0058] S1: forming independent drive control signals and different drive signals;

[0059] S2: Under the control of the independent drive control signal, each drive selection unit transmits one of the different drive signals to the control terminal of the corresponding switch tube to control the corresponding switch tube to achieve control of the drive current of the laser diode;

[0060] The different driving signals at least include a first driving signal for controlling a rising time of a driving current, a second driving signal for controlling a pulse width of a driving current, and a shutdown signal.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laser diode driving circuit, characterized in that: The system comprises n parallel-connected switching tubes and n drive selection units, wherein each switching tube corresponds to one drive selection unit, where n is an integer greater than 1; The first end of each switch tube is connected to the laser diode, and the second end of each switch tube is grounded or connected to the driving power supply; the control end of each switch tube is respectively connected to the output end of the corresponding driving selection unit; Each drive selection unit is used to select one of the different drive signals under the control of an independent drive control signal and transmit it to the control end of the corresponding switching tube to control the corresponding switching tube, so that the drive circuit is divided into different parallel drive branches, and each drive branch is driven by a different drive signal; the different drive signals include at least a first drive signal for controlling the rise time of the drive current, a second drive signal for controlling the pulse width of the drive current, and a shutdown signal for controlling the shutdown of the switching tube. The various drive signals jointly achieve the adjustment of the drive current waveform.

2. The laser diode driving circuit according to claim 1, wherein: The switch tube is a MOSFET; The source or drain of each of the n parallel MOSFETs is connected to the cathode or anode of the laser diode, the drain or source of each MOSFET is grounded or connected to a driving power supply, and the gate of each MOSFET is respectively connected to the output end of the corresponding driving selection unit.

3. The laser diode driving circuit according to claim 1, wherein: The driving circuit further includes a control module; the control module is used to generate the first driving signal, the second driving signal, the shutdown signal and n driving control signals.

4. The laser diode driving circuit according to claim 3, wherein: The control module includes a first signal generating unit, a second signal generating unit and a shutdown signal generating unit; The first signal generating unit is used to generate the first driving signal; The second signal generating unit is used to generate the second driving signal; The shutdown signal generating unit is configured to generate the shutdown signal.

5. The laser diode driving circuit according to claim 4, wherein: Each drive selection unit includes a multiplexer; the output end of each multiplexer is connected to the control end of a corresponding switching tube, and is used to output one of the shutdown signal, the first drive signal, and the second drive signal to the corresponding switching tube under the control of the corresponding drive control signal.

6. The laser diode driving circuit according to claim 5, wherein: Each multiplexer includes a first input terminal, a second input terminal and a third input terminal; the first input terminal is connected to the output terminal of the first signal generating unit; the second input terminal is connected to the output terminal of the second signal generating unit; and the third input terminal is connected to the output terminal of the shutdown signal generating unit.

7. The laser diode driving circuit according to claim 6, wherein: The control module also includes multiple buffer units; the input end of each buffer unit is connected to the output end of each multiplexer, and the output end of the buffer unit is connected to the control end of each switch tube; the buffer unit is used to enhance the output of each multiplexer and output it to each switch tube.

8. The laser diode driving circuit according to claim 7, wherein: Each buffer unit includes a plurality of cascaded inverters.

9. The laser diode driving circuit according to any one of claims 1 to 8, characterized in that: A pulse width of the first driving signal is smaller than a pulse width of the second driving signal.

10. A method for driving a laser diode, characterized in that: The laser diode is driven by the laser diode driving circuit according to any one of claims 1 to 9, the method comprising: Forming independent drive control signals and different drive signals; Under the control of the independent drive control signal, each drive selection unit transmits one of the different drive signals to the control terminal of the corresponding switch tube to control the corresponding switch tube, thereby achieving control of the drive current of the laser diode; The different driving signals at least include a first driving signal for controlling a rising time of a driving current, a second driving signal for controlling a pulse width of a driving current, and a shutdown signal for controlling the shutdown of a switch tube.

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