JP2009105360A - Laser diode driving circuit and method for driving it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser diode driving circuit which speeds up a current switch and reduces power consumption, and to provide a method for driving it. <P>SOLUTION: The circuit controls a semiconductor switch by a pulse amplitude adjustment controller. During a rise time, additional plus voltage pulse or additional minus voltage pulse is provided by the circuit, and a laser diode is driven. Thereby, the current switch time is reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a drive circuit, and more particularly to a laser-diode drive circuit and the same drive method.

  Laser diodes have several advantages such as small size, high performance, low power consumption, long life, and easy control of output power or operating frequency by current. Due to these advantages, laser diodes are widely applied in the fields of data processing, optical fiber communication, home appliances and accuracy measurement.

  If the injection current of the laser diode must be larger than the coastal circuit, the diode can irradiate the laser. The laser diode is characterized in that the intensity of the laser output can be controlled by the current through the laser diode.

  The PN junction of the laser diode is the same as that of a normal diode. The difference between a laser diode and a diode is that the laser diode has a pair of mirrors as a resonant cavity. Types of laser diodes depending on the junction structure include single heterostructures, double heterostructures, quantum well structures and vertical cavity surface emitting lasers.

  Depending on the wavelength and application, laser diodes are usually classified as shortwave lasers or longwave lasers. The wavelength of shortwave lasers in the range of 390 nm to 950 nm is mainly used for optical information processing and display device applications for optical disc drives, laser jets, barcode readers, scanners, and pointers. On the other hand, long wave lasers in the range of 980 nm to 1550 nm are usually applied to optical fiber communications.

  A laser diode driver (LDD) needs to drive a laser diode. The laser diode driving circuit is used for supplying a laser diode passing current for converting electric energy into light energy. With current technology, laser diode drivers often consume too much power. For this reason, power conversion efficiency deteriorates.

In a laser diode drive circuit, there are not only parasitic capacitors that come into contact with connectors and printed circuit boards, but each electronic component also has a stray capacitor. During current switching, an opposing electric force (ie, ΔV = L ^* Δi / Δt) is generated by the inductor.

  When high frequency and high power converters are supplied to the laser diode drive circuit, rapid current switching is required for rapid switching between rise and fall time cycles. In the current switching mechanism, the voltage drop due to the parasitic capacitor in the conduction path is large. In order to achieve the purpose of rapid current switching, it is necessary to increase the voltage supply to drive the laser diode. However, a very large amount of power is consumed by the stable additional voltage supply, and the power conversion efficiency can be deteriorated.

  Since these prior arts have such disadvantages, it is necessary to improve the power conversion efficiency.

  An object of the present invention is to provide a laser diode driving circuit to solve the above-mentioned problems.

  Another object of the present invention is to add a positive voltage pulse or a negative voltage pulse that accelerates the current switching speed when rising and simultaneously reduces power consumption.

  With respect to the foregoing, a first inductive path having a laser diode and a semiconductor switch utilized in accordance with the present invention so that the semiconductor switch can open and close the first conduction path. A first voltage is connected to the first conduction path to supply the first voltage to the first conduction path, and includes a power converter, a first inductor, and a first energy storage device, and the power converter causes the first voltage to be 1 First supply conduction path supplied to the energy storage device. A second supply conduction path coupled to the first conduction path and having a voltage pulse supplier, a second inductor, and a second energy storage device, wherein the voltage pulse supplier is coupled to the first energy storage apparatus. A laser diode drive circuit is disclosed that includes a semiconductor switch and a PWM (Pulse Amplitude Adjustment) controller coupled to a voltage pulse supply.

  Furthermore, the present invention also discloses a laser diode driving method including supplying a first voltage to the laser diode via a first capacitor and a power converter. A PWM controller is used to transmit the control signal to the semiconductor switch and the voltage pulse generator. A second voltage is supplied to the second capacitor in response to the control signal.

The above features and advantages of the present invention will be fully understood through the detailed description with reference to the accompanying drawings.

  The invention will be described in more detail with reference to preferred embodiments of the invention and the accompanying drawings. However, it should be recognized that the preferred embodiment of the present invention is for illustrative purposes only. In addition to the preferred embodiments referred to herein, the present invention can be practiced in a wide variety of other embodiments than those explicitly described, and the scope of the present invention is explicitly limited thereto. None, as defined in the appended claims.

  The present invention relates to a laser diode (LD) drive circuit. At the time of the rise, in addition to the drive voltage, an excessive plus voltage pulse or a minus voltage pulse is added to the drive circuit of the present invention, and the LD is driven for quick switching of the current. In steady state. Excess voltage pulses are not supplied and power consumption is reduced from the excess drive voltage. The drive circuit of the present invention can improve the power conversion efficiency of a power converter applied to an LD or LED (light emitting diode) having various characteristics of low pressure, high frequency, high current and high power (over 500 mW). .

  At the time of current switching rise, no excess voltage is introduced, and another low impedance conduction path is provided by the drive circuit of the present invention, while at the same time the inductor has a higher voltage to increase the rate of current rise. . When the drive current reaches the desired level, the low impedance conduction path is opened and the current is maintained at the normal level. As a result, the purpose of accelerating the current rise rate can be achieved.

FIG. 1 is an explanatory diagram of a drive circuit 10 for LD according to a preferred embodiment of the present invention. The drive circuit 10 includes a second transfer circuit 14 having a first conductive circuit 12 and MOSFET switch _{Q 2} having a MOSFET switch _{Q 1} is. The impedance of the first conduction path 12 is greater than that of the second conduction path 14. When a low impedance conduction path 14 is provided, the rising high voltage can be obtained by an inductor L that increases the rate of current rise.

The input voltage terminal Vin is connected to the input inductor. The parallel Lin is shown in FIG. The input capacitor Cin is connected to the end of the input inductor and the anode of the LD. The other end of the input impedance Cin is grounded. One end of the inductor L is connected to the cathode of the LD, and the other end is connected between the first conduction path 12 and the second conduction path 14. The current through the LD is equal to the sum of the currents provided in the first conduction path 12 and the second conduction path 14. (Ie i (t) = I _Q1 + I _Q2 )

The first conductive path 12 includes a resistor _{R 1} and MOSFET switches _{Q 1,} the second conducting path 14 includes a resistor _{R 2} and the MOSFET switches _{Q 2.} Greater resistance of the resistor _{R 1} is one of a resistor _{R 2.} The gates of the switches _{Q 1} and _{Q 2,} is a control signal transmitted from the external PWM (pulse amplitude adjustment) control unit 16 each receive, frequency and duty cycle of the switch _{Q 1, Q 2} (duty circle) is processed .

となる。 Referring to FIGS. 2A-2C, these show a time sequence diagram illustrating the operation of the drive circuit 10 shown in FIG. When t = a 0-T1 period, respectively, a PWM controller 16 control signal transmitted to the gate of the switch Q ₁ and Q _2, since these switches, the current through the LD is

It becomes.

tが3(L/R)を越える場合には該方程式は次のように単純化される。

tがT2周期以上の時は、Ｑ_１およびＱ_２両スイッチともオフであるので、第１伝導経路１２と第２伝導経路は開いている。 when it is t = T1-T2 period, switch Q ₂ is switch Q ₁ and at the same time is off is still on. Since the current only passes through the first conduction path 12, the following equation is obtained at this time.

When t exceeds 3 (L / R), the equation is simplified as follows.

When t is greater than or equal T2 cycle, since it is Q ₁ and Q ₂ both switches both off, and the first conduction path 12 and the second conduction path is open.

  Regarding the above point, when t = 0-T1 period, the second conduction path 14 having the smaller impedance can increase the current speed when the current increases because the current increase speed is accelerated. In the present invention, the LD current rise time is 20-30% less than the prior art time.

  FIG. 3 is an illustration of a drive circuit 30 according to another preferred embodiment of the present invention. Referring to FIGS. 3 and 4, the drive circuit 30 includes a first electric supply path 31 and a second electric supply path 33. The first supply conduction path 31 and the second supply conduction path 33 are respectively connected to a first conduction path 35 formed from an LD, resistors, inductors, and a semiconductor switch.

The DC to DC converter 32 is connected to the inductor L ₁ and supplies a DC voltage with an amplitude V _dc1 to the first conduction path 35. Capacitor C ₁ is charged by DC to DC converter 32. Current, when the diode _{D 2} conducts forwardly through the diode _{D 2,} a parasitic capacitor _{L pr1} and LD. Therefore, the capacitor voltage C ₁ is approximately equal to the forward voltage V _FD2 of the diode D ₂ and the node A voltage V _A.

The PWM controller 34 is connected to the MOSFET switch Q ₁ and the gate of the voltage pulse generator 36. The PWM controller transmits a fresh control signal to the MOSFET switch Q ₁ and the voltage pulse generator 36. MOSFET switches _{Q 1} is perform on-off function in response to a control signal from the PWM control unit 34. The voltage pulse generator 36 is connected to one end of the inductor L _2. Another inductor _{L 2} is connected to the capacitor _{C 3} and resistor _{R CS2.} Supplying a voltage pulse to the capacitor C ₃ in accordance voltage pulse generator 36 to a control signal from the PWM control unit 34. Capacitor C ₃ is charged with voltage V _DC2 by voltage pulse generator 36 when the control signal is off duty. Voltage pulse generator 36 is supplied to the condenser C ₃ and the inductor L ₂ of the voltage when the duty cycle of the control signal is stopped.

但し、Ｒ_Ｑ１ＯＮはスイッチＱ_１のオン時抵抗である。 MOSFET switches _{Q 1} is adjusting the operation period and the switch frequency in response to a control signal from the PWM control unit 34. Current _{I OUT} from the condenser _{C 3} flows resistor _{R CS2, R CS1,} the parasitic inductor _{L pr1, L pr2, L pr3} , LD and MOSFET switches _{Q 1} to ground. Capacitor _{C 2} is charged. The slope of the current I _OUT is determined by the voltage drop across the parasitic inductor and capacitor. The equation for maximum current I _OUT is given by:

_{However, R Q1ON} is on-time resistance of the switch _{Q 1.}

The capacitor C ₃ is discharged until the capacitor C ₁ is discharged after the voltage V _C becomes lower than the voltage (V _DC1 −V _FD2 ). Thus, the maximum current I ′ _OUT is as follows.

Condenser _{C 2} is the switch _{Q 1} is discharged to turn off through a path of the resistor _{R 2, R CS1,} and the diode _{D 2.} For the above points, the voltage pulse generator 36 is the drive circuit 30 to charge the capacitor C ₃ again provide a voltage pulse and the above-described operation is repeated. From Figure 4, it is understandable that reduce the power loss P _LOSS by the drive circuit of the present invention when the switch Q ₁ is turned on.

A drive circuit 40 for an LD according to another preferred embodiment of the present invention is illustrated as shown in FIG. Since the structure of the drive circuit 40 is similar to that of the drive circuit 30, the same details are not shown. In the drive circuit 40, a negative voltage pulse generator 42 is used in place of the voltage pulse generator 36 that generates a negative pulse for accelerating the current switching speed. Further, power loss of the diode D ₂ which is turned on is reduced since the diode D ₂ is omitted, and further delay of the switching current is also improved.

The present invention also discloses a method for driving a high power laser diode or LED. Initially, a DC to DC converter provides a first voltage V _DC1 to a first capacitor and a laser diode load. The control signal is transmitted by an external PWM controller that controls the semiconductor switch connected to the voltage pulse generator and the LD load. The voltage pulse generator supplies the second voltage V _DC2 to the second capacitor according to the control signal after receiving the signal. When the control signal is off-duty, the voltage is supplied to the second capacitor through a voltage pulse generator. After receiving the signal, the semiconductor switch is turned on when the control signal has a duty cycle.

The current supplied from the second capacitor flows through a conduction path including a resistor, an inductor, an LD, and a semiconductor, thereby driving the LD when the semiconductor switch is turned on. When the LD drive current I _OUT is between the first current A ₁ and the second current A ₂ shown in FIG. 4, the second current V _DC2 is supplied by the second capacitor to drive the LD.

The output voltage V _OUT maintains the first voltage of the V _DC1 level when the LD drive current I _OUT reaches the second current A ₂ , and at the same time, the second capacitor V _DC2 is supplied from the first capacitor. It is discharged until it becomes less than the first voltage V _DC1 supplied.

When the semiconductor switch is turned on rapidly, the reverse electric force _VL is generated from the parasitic capacitor. In order to solve this problem, an excessive second voltage V _DC2 is added at the time of rising, and the LD is driven to achieve the purpose of acceleration of the current switching speed. Thereby, the power conversion efficiency of the power converter can be improved, and at the same time, the power consumption can be reduced.

  When rising, a positive voltage pulse or a negative voltage pulse is added to the drive circuit of the present invention to accelerate the current switching speed and simultaneously reduce power consumption.

  The drive circuit of the present invention is applicable to laser diodes or high power LEDs. Thereby, switching of a large current (200 A / us (microsecond)) and high power conversion efficiency can be achieved.

  While preferred embodiments of the present invention have been described above, it will be understood by those skilled in the art that the present invention should not be limited to the described preferred embodiments. Rather, various changes and modifications can be made within the spirit and scope of the invention as defined by the following claims.

FIG. 2 is an explanatory diagram of a laser diode driving circuit according to a preferred embodiment of the present invention. FIG. 2 is a time sequence diagram illustrating the operation of the drive circuit of FIG. 1. FIG. 2 is a time sequence diagram illustrating the operation of the drive circuit of FIG. 1. FIG. 2 is a time sequence diagram illustrating the operation of the drive circuit of FIG. 1. FIG. 3 is an explanatory diagram of a laser diode driving circuit according to another preferred embodiment of the present invention. FIG. 4 is a time sequence diagram illustrating the operation of the drive circuit of FIG. 3. FIG. 6 is an explanatory diagram of a laser diode driving circuit according to still another preferred embodiment of the present invention.

Claims (5)

The first conduction path comprises a laser diode semiconductor switch, the semiconductor switch being utilized to allow opening and closing of the first conduction path;
A first supply conduction path is coupled to the first conduction path for supplying a first voltage to the first conduction path, and the first supply conduction path includes a power converter, a first inductor, and A first energy storage device, wherein the power converter supplies the first voltage to the first energy storage device;
The second supply conduction path is connected to the first conduction path and includes a voltage pulse supplier, a second inductor, and a second energy storage device, and the voltage pulse supplier is connected to the first energy storage device. And a PWM (pulse amplitude adjustment) controller connected to the semiconductor switch and the voltage pulse supply.   The first energy storage device and the second energy device include a capacitor, the semiconductor switch includes a MOSFET switch, the voltage pulse supplier includes a voltage pulse generator or a negative voltage pulse generator, and The drive circuit according to claim 1, wherein the power converter includes a DC-to-DC converter. When the voltage pulse supplier receives a control signal from the PWM controller and the control signal has a non-duty cycle, the first voltage pulse is supplied to the second energy storage device, and the control signal The drive circuit according to claim 1, wherein the semiconductor switch is switched on after receiving the control signal at a duty cycle of the first cycle. Supply to the laser diode by a first capacitor of a first voltage and a power converter;
A laser diode driving device characterized by using a PWM control device for transmitting a control signal to a semiconductor switch and a voltage pulse generator; and supplying a second voltage to a second capacitor in response to the control signal. Input voltage terminal;
A laser diode coupled to the input voltage terminal;
An inductor connected to the cathode of the laser diode;
A first conduction path connected to the inductor and having a first semiconductor switch as well as a first resistor, the first semiconductor switch being utilized to allow opening and closing of the first conduction path; A first conduction path;
A second conduction path connected to the inductor and having a second semiconductor switch as well as a second resistor, the second semiconductor switch being utilized to allow opening and closing of the second conduction path; A laser diode driving circuit comprising: a second conduction path; and a PWM controller connected to the first semiconductor switch and the second semiconductor switch.

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