KR101998327B1 - Laser diode actuation circuit capable of generating short pulse and high constant current - Google Patents

Abstract

The present invention relates to a circuit to drive a laser diode and, more specifically, to a laser diode driving circuit capable of generating a short pulse and a high constant current which allows a laser diode driving circuit to include a charging unit, a driving unit, a switch transistor, and a current detection unit at proper positions to reduce the size of a driving transistor and the driving voltage of the driving transistor and improve the operating speed of the circuit. More specifically, the laser diode driving circuit capable of generating a short pulse and a high constant current comprises: a pulse input unit to apply a pulse having a low value and a high value; a switch transistor to receive the pulse; a charging unit connected to the switch transistor to charge charges when the pulse is at the low value; an amplifier to receive a reference voltage and a voltage applied to a current detection unit as input voltages; a driving unit connected to an output terminal of the amplifier to charge charges of a driving voltage of the amplifier when the pulse is at the high value; a driving transistor to receive a voltage charged in the driving unit as a driving voltage when the pulse is at the high value; and a laser diode driven by a constant current flowing by charges charged in the charging unit when the pulse is at the high value.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser diode driving circuit capable of generating a short pulse and a high constant current,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for driving a laser diode, and more particularly, a laser diode driving circuit includes a charging unit, a driving unit, a switch transistor, a current sensing unit, To a laser diode driving circuit capable of generating a short pulse and a high constant current that can improve the operation speed of a circuit.

The laser diode is a semiconductor device, which is also called a semiconductor laser. The laser diode has a small size of about several hundreds of micrometers and can directly modulate a laser beam by a current having a small driving power. It is possible to obtain the wavelength of visible light and the infrared light emitted from the infrared ray.

The laser diode is characterized in that the process of the induced emission is performed by a transition between a conduction band and a valence band or an impurity band, and the excitation method includes a light excitation (light), an electron beam excitation, (Injection), and the reflector constituting the Fabry-Perot resonator can be formed by using the cleavage plane of the crystal.

And the material of the laser diode is _{Ga, As 1 -x, P x} , Al x, Ga 1 - x As, In 1 - _x Ga _x As and around the like, Ⅲ-V compound is present a number of reasons.

Conventional laser diodes typically require short pulses (short pulses of short period) and high constant current. Conventional circuit configurations to satisfy devices or circuits that require short pulses and high constant current as well as laser diodes There are many problems.

First, when the constant current used for driving the driving transistor is very large, such as several tens of A, the voltage across the sensing resistor becomes a considerable level, so that the voltage of the source terminal of the NMOS used as the driving transistor becomes high, The output voltage of the amplifier must be further increased.

1, unlike the ideal current value I _DRV (Ideal) of the constant current, the actual current value I _DRV (Real) does not reach the target constant current 30A within the high value interval of the pulse, So that the desired result can not be obtained.

In order to cancel or minimize the above phenomenon, the size of the driving transistor must be very large and the driving voltage of the driving transistor is also increased.

Accordingly, in order to realize a short pulse and a high constant current for a laser diode, there are various problems to be overcome, and at the same time, there is a need for a new circuit structure to improve the above.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a circuit configuration capable of driving a short pulse and a high constant current without burdening the size of a driving transistor and the size of a driving voltage.

More specifically, the present invention provides a laser diode driving circuit capable of reducing the size and driving voltage of a driving transistor by providing a charging part, a driving part, a switch transistor, a current sensing part, .

The technical objects to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical subjects which are not mentioned can be clearly understood by those skilled in the art from the description of the present invention .

According to an aspect of the present invention, there is provided a plasma display apparatus comprising: a pulse input unit for applying a pulse having a low value and a high value; A switch transistor receiving the pulse; A charging unit coupled to the switch transistor to charge the charge when the pulse is at a low value; An amplifier receiving the reference voltage and a voltage across the current sensing unit as an input voltage; A driving unit connected to an output terminal of the amplifier to charge a charge equal to a driving voltage of the amplifier when the pulse is at a low value; A driving transistor for receiving a voltage charged in the driving unit when the pulse is at a high value, as a driving voltage; And a laser diode driven by a constant current flowing through the charge charged in the charging unit when the pulse is at a high value; And a laser diode drive circuit capable of generating a high constant current.

The present invention is characterized by a first switch located between an output terminal of the amplifier and a gate terminal of the driving transistor and turned off when a pulse is a low value and turned on when a pulse is a high value; And a second switch located between a gate terminal and a ground terminal of the driving transistor, the second switch being on when the pulse is a low value and being off when the pulse is on a high value; .

In the present invention, it is preferable that an inverter is disposed between the second switch and the pulse input unit so that the second switch is turned on when the pulse is at a low value, and turned off when the pulse is at a high value.

In the present invention, the period of the high value of the pulse may be equal to or less than 100 kPa.

In the present invention, it is preferable that the switch transistor is formed of PMOS (P-channel Metal Oxide Semiconductor).

The present invention may further include a level shifter disposed between the pulse input unit and the switch transistor.

In the present invention, it is preferable that the driving transistor is composed of NMOS (P-channel Metal Oxide Semiconductor), and the source terminal of the driving transistor is connected to the ground terminal.

In the present invention, it is preferable that each of the charging unit and the driving unit comprises a capacitor.

In the present invention, the charging unit and the driving transistor may have the same capacitance.

In the present invention, the constant current may be 30 A or less.

The present invention has an effect that a short pulse and a high constant current can be driven without increasing the size of the driving transistor or improving the driving voltage of the driving transistor.

Accordingly, the present invention reduces the burden of increasing the size of the driving transistor and its driving voltage for driving a device such as a laser diode requiring a short pulse and a high constant current, and at the same time, So that the operation speed of the circuit is also improved.

1 is an exemplary view showing an ideal constant current and a substantially constant current according to a conventional circuit configuration;
2 is a configuration diagram of a laser diode driving circuit capable of generating a short pulse and a high constant current according to an embodiment of the present invention.
3 is a circuit diagram of a laser diode drive circuit capable of generating a short pulse and a high constant current according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating a pulse according to an exemplary embodiment of the present invention, a driving voltage of the driving transistor, a constant current, a voltage of a charging unit, and a voltage applied to the current sensing unit. FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present description and claims should not be construed as limited to ordinary or dictionary meanings, and the inventor should properly interpret the concepts of the terms in order to describe their invention in the best way. It should be interpreted in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the embodiments described in this specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention, and not all of the technical ideas of the present invention are described. Therefore, It is to be understood that equivalents and modifications are possible.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise.

In order to improve the operating speed of a circuit while reducing the size and driving voltage of a driving transistor in a laser diode driving circuit capable of generating a short pulse and a high constant current, a pulse having a low value and a high value is applied A switching transistor 200 receiving the pulse, a charger 300 coupled to the switch transistor to charge the charge when the pulse is a low value, a reference voltage and current detector 800, A driving unit 500 connected to an output terminal of the amplifier for charging a voltage corresponding to a driving voltage of the amplifier when the pulse is at a low value, A driving transistor 600 for receiving a voltage charged in the driving unit as a driving voltage, And a laser diode (700) driven by a constant current flowing by the charge charged in the charger.

2 is a block diagram of a laser diode driving circuit capable of generating a short pulse and a high constant current according to an embodiment of the present invention. In FIG. 3, And a laser diode driving circuit capable of generating a high constant current. FIG. 4 is a circuit diagram illustrating a pulse according to an embodiment of the present invention and a driving voltage, a constant current, a voltage of a charging unit, An illustrative view is shown.

First, the present invention provides a short pulse, that is, a pulse having a high value and a low value and having a high value period shorter than a general pulse, wherein the high value period is a short pulse of about 100 kV or less It says.

In order to apply the short pulse as described above, the present invention includes a pulse input unit 100, which is not limited to a specific configuration but is often generated by a mode-locked laser.

Mode synchronization is an operation for maintaining a constant phase relation among modes in a laser oscillating in a multi-mode, and is mainly used as a method of obtaining a high-speed optical pulse with a narrow time width. Passive mode using a saturable absorber, self-mode synchronous due to the nonlinear characteristics of the laser medium, forced mode synchronous with a modulator at the same frequency as the mode interval, and forced mode Synchronization is also referred to as active mode synchronization.

The pulse width, that is, the period of the high value is determined by the reciprocal of the spectral width of the oscillation line in the case of the ideal mode-locked laser, but in actual cases, the pulse width of the broader width due to other factors such as the fluorescence lifetime It is often implemented.

At present, it is possible to generate a short pulse up to about 0.1,, which is used to make a strong photoelectric field until the peak output is remarkably high, besides the observation of ultra fast phenomenon.

The switch transistor 200 receives a pulse applied by the pulse input unit 100 and is configured to enable a charging unit 300, which will be described later, to perform charging operation. The switch transistor includes a PMOS (P-channel) Metal Oxide Semiconductor).

The PMOS refers to a semiconductor in which an n-type substrate is used as a carrier in which a carrier flowing through a current path is a hole. Although the switching speed is slower than that of an NMOS, in the present invention, it is preferable to use PMOS because of the characteristics of circuit operation. It is easy to connect the circuit.

A level shifter may be disposed between the switch transistor 200 and the pulse input unit 100 according to need, which corresponds to a configuration for adjusting the level of the power supply. This is because the level of the pulse applied by the pulse input unit is different from the level of the power supply for driving the switch transistor.

The level shifter may be a resistor, a junction diode, or a constant voltage diode. The voltage level of the input or output is adjusted by the voltage drop of the resistor, the junction diode, or the constant voltage diode.

It goes without saying that the level shifter may be omitted from the circuit configuration in some cases.

The charging unit 300 is connected to the switch transistor 200 serving as a switch in response to a pulse, and charges the charge when the pulse is at a low value.

More specifically, when the pulse applied by the pulse input unit 100 is a low value, the switch transistor 200 is turned on. Therefore, charges corresponding to VCC on the circuit are charged at this time, and when the pulse is at a high value, The driving transistor 600 is turned on, and the charged charge is supplied through the driving transistor in the form of a constant current.

At this time, the charging unit 300 may be implemented in various configurations to charge and supply electric charges, and it is generally preferable that the charging unit 300 includes a capacitor.

The amplifier 400 receives a reference voltage as a positive input and a voltage applied to the current sensing unit 800 as a negative input, and sets VDD in the drawing as a drive voltage.

Accordingly, the voltage applied to the current sensing unit 800 follows a reference voltage input to the amplifier 400 by virtually short, and the magnitude of the constant current to be described later is the resistance of the current sensing unit It is divided by the value.

Since the first switch of the present invention is in the OFF state when the pulse is at a low value, the output terminal of the amplifier 400 includes a driver 500 for charging a charge equivalent to VDD, which is a driving voltage of the amplifier, .

The driving unit 500 may also be implemented in various configurations that can charge and supply electric charges, and generally comprises a capacitor.

The driving transistor 600 according to the present invention has a configuration in which a gate terminal is connected to an output terminal of the amplifier 400 with a first switch interposed therebetween, and when the pulse is a low value, And operates when receiving a driving voltage from the driving unit when the pulse has a high value.

The driving transistor 600 is preferably formed of an NMOS (P-channel Metal Oxide Semiconductor), and its source terminal is connected to the ground terminal and is a channel through which a constant current flows from the drain terminal to the source terminal.

In the conventional circuit structure having the same purpose, a sensing resistor for determining the magnitude of the constant current is disposed at the source terminal of the driving transistor 600 composed of NMOS so that the voltage at the source terminal of the driving transistor rises, The driving voltage also increases. However, in the present invention, the source terminal of the driving transistor is directly connected to the ground terminal, thereby reducing the size of the driving transistor and the burden of the driving voltage.

Meanwhile, in the present invention, the current sensing unit 800 performs the function of the conventional sensing resistor, and the current sensing unit may include resistance components as shown in the drawing, but the present invention is not limited thereto.

Meanwhile, the laser diode 700 of the present invention is a diode for generating a laser by using a forward semiconductor junction as an active medium. When the applied pulse is at a high value, the laser diode 700 is driven by a constant current generated by the charge charged in the charging unit 300 And corresponds to a configuration in which short pulses are required, which is one of the main objects of the present invention.

In order to operate the above constructions, the present invention is characterized in that the first switch is located between the output terminal of the amplifier 400 and the gate terminal of the driving transistor 600, is off when the pulse is a low value, And a second switch located between a gate terminal and a ground terminal of the driving transistor, the second switch being on when the pulse is a low value and being off when the pulse is on a high value.

An inverter is disposed between the second switch and the pulse input unit 100 so that the operations of the first switch and the second switch can be reversed. same.

Default behavior

When the pulse applied by the pulse input unit 100 is a value low first switch (SW1) is off and the second switch (SW2) is turned on, at this time, the switching transistor (TR _SW) (200) is on the live parts (C _PP ) Is charged with the charge of VCC.

On the contrary, when the pulse is at a high value, the first switch SW1 is turned on, the second switch SW2 is turned off, and the switch transistor TR _SW 200 is also turned off.

Operation for speed up operation

When the pulse applied to a value low, a drive (C _CH) (500) is the electric charge of as VDD in the driving voltage of the amplifier 400 is filled with the first switch (SW1) is so turned off the driving transistor (TR _DRV) (600 ), the gate terminal voltage (V _G) is in the 0V.

In the initial stage when the pulse becomes a high value, the first switch SW1 is turned on, and the charge of the driving unit (C _CH ) 500 and the charge of the gate of the driving transistor (TR _DRV ) 600 are distributed to each other The voltage V _{G at the} gate terminal of the driving transistor rises very rapidly.

If the capacitance of the driving unit (C _CH ) (500) is equal to the capacitance of the driving transistor (TR _DRV ) (600), the voltage (V _G ) of the gate terminal of the driving transistor Becomes VDD / 2. Otherwise, the voltage at the gate terminal of the driving transistor will be determined according to the ratio of the mutual capacitances.

Then, the output of the amplifier 400 reaches a proper level for generating a constant current through the virtual re-short and is stabilized.

Operation for efficient high constant current drive

When the pulse applied to the pulse input unit 100 is a low value, the charging unit (C _PP ) 300 is charged with the charge of VCC. When the pulse is at the high value, the charging unit generates the constant current (I _DRV ) .

At this time, since the amount of charge charged in the charging part (C _PP ) 300 is limited, a voltage drop occurs in the charging part, and the voltage drop is as shown in the following formula.

In this case, the constant current I _DRV flows to the red path shown in FIG. 3. The voltage applied to the current sensing unit R _SEN 800 becomes R _SEN * I _DRV , and thus the negative input of the amplifier 400 VREF becomes equal to R _SEN * I _DRV , so that it is possible to drive a high constant current.

This is because the source terminal of the driving transistor TR _DRV 600 is not connected to the current sensing part 800 having the sensing resistance or resistance component, but is connected to the ground terminal, unlike the conventional circuit operation for short pulse and constant current driving So that the burden of the drive voltage for driving the driving transistor is alleviated. Accordingly, the driving voltage of the amplifier 400, which is the power supply source of the driving unit 500, can be formed to be relatively smaller than the conventional one.

In addition, the driving transistor (TR _DRV ) 600 may have a small size.

As a result, the present invention is advantageous in that it can drive a short pulse and a high constant current without increasing the size of the driving transistor or improving the driving voltage of the driving transistor and the amplifier.

Accordingly, it is an object of the present invention to alleviate the burden of increasing the size and driving voltage of a driving transistor in order to drive a device such as a laser diode requiring a short pulse and a high constant current, and at the same time, So that the operation speed of the circuit is also improved.

While the present invention has been described with reference to the specific embodiments, it is to be understood that the invention is not limited thereto. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents. Various modifications and variations are possible.

100: Pulse input section
200: switch transistor
300:
400: Amplifier
500:
600: Driving transistor
700: laser diode
800: Current sensing unit

Claims (10)

A pulse input section for applying a pulse having a low value and a high value;
A switch transistor receiving the pulse;
A charging unit coupled to the switch transistor to charge the charge when the pulse is at a low value;
An amplifier receiving the reference voltage and a voltage across the current sensing unit as an input voltage;
A driving unit connected to an output terminal of the amplifier to charge a charge equal to a driving voltage of the amplifier when the pulse is at a low value;
A driving transistor for receiving a voltage charged in the driving unit when the pulse is at a high value, as a driving voltage; And
A laser diode driven by a constant current flowing by the charge charged in the charging unit when the pulse is at a high value; And a laser diode drive circuit capable of generating a high constant current.
The method according to claim 1,
A first switch located between the output terminal of the amplifier and the gate terminal of the driving transistor and turned off when the pulse is a low value and turned on when the pulse is a high value; And
A second switch located between a gate terminal and a ground terminal of the driving transistor, the second switch being on when the pulse is a low value and being off when the pulse is on a high value; And a laser diode drive circuit capable of generating a high constant current.
3. The method of claim 2,
And an inverter is disposed between the second switch and the pulse input unit. The second switch is turned on when the pulse is at a low value, and turned off when the pulse is at a high value. The laser diode driving circuit .
The method according to claim 1,
Wherein a period of a high value of the pulse is equal to or less than 100 cd / m < 2 >. A laser diode drive circuit capable of generating a short pulse and a high constant current.
The method according to claim 1,
Wherein the switch transistor is formed of PMOS (P-channel Metal Oxide Semiconductor).
The method according to claim 1,
And a level shifter disposed between the pulse input unit and the switch transistor. The laser diode driving circuit according to claim 1,
The method according to claim 1,
Wherein the driving transistor is composed of NMOS (P-channel Metal Oxide Semiconductor), and a source terminal of the driving transistor is connected to a ground terminal.
The method according to claim 1,
Wherein the charging unit and the driving unit are constituted by capacitors, respectively, and the laser diode driving circuit is capable of generating short pulses and high constant currents.
The method according to claim 1,
Wherein the driving unit and the driving transistor have the same capacitance. A laser diode driving circuit capable of generating a short pulse and a high constant current.
The method according to claim 1,
And the constant current is 30 A or less. A laser diode drive circuit capable of generating a short pulse and a high constant current.

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