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CN-115832865-B - Self-adaptive control method and control circuit for laser driver

CN115832865BCN 115832865 BCN115832865 BCN 115832865BCN-115832865-B

Abstract

The invention discloses a self-adaptive control method and a control circuit for a laser driver, wherein a feedback control loop is arranged between a current source I drv of a front-stage differential amplifier A V and a modulation current I modset , the feedback control loop comprises a feedback transconductance amplifier G m2 , the feedback transconductance amplifier G m2 and a rear-stage transconductance amplifier G m1 in a main channel have the same circuit structure, the feedback transconductance amplifier G m2 works in a critical limiting state, the feedback control loop controls the output differential voltage amplitude of the front-stage differential amplifier A V , so that the rear-stage transconductance amplifier G m1 also works in the self-adaptive critical limiting state, the self-adaptive matching of the driving voltage amplitude and the output current of the laser driver is realized, the nonlinear matching of the driving voltage and the laser modulation current is improved through the design of an optimized circuit, the consistency and the stability of performance parameters when different types of lasers are driven are improved, and the self-adaptive control method is suitable for large-scale application.

Inventors

  • WANG HUAN

Assignees

  • 瑞韬电子科技(无锡)有限公司

Dates

Publication Date
20260512
Application Date
20221213

Claims (9)

  1. 1. A self-adaptive control method for a laser driver is characterized in that a front-stage differential amplifier A V and a rear-stage transconductance amplifier G m1 are adopted in a main channel to amplify signals, a current source I mod of a rear-stage transconductance amplifier G m1 is controlled by a modulation current I modset , a feedback control loop is arranged between a current source I drv of a front-stage differential amplifier A V and the modulation current I modset , the feedback control loop comprises a feedback transconductance amplifier G m2 , the feedback transconductance amplifier G m2 and the rear-stage transconductance amplifier G m1 in the main channel have the same circuit structure, the value k 1 I modset of the current source I 2 of the feedback transconductance amplifier G m2 and the modulation current I modset are in a proportional relation, the output current I 4 of the feedback transconductance amplifier G m2 is amplified to obtain a feedback current I 1 , the value of the feedback current I 1 is k 2 I modset ,k 2 I modset <k 1 I modset , the feedback current I 1 is converted into voltage and then is output to the feedback transconductance amplifier G2 in one path, and the feedback transconductance amplifier G m2 is enabled to work in a limiting state, and the amplitude of the feedback transconductance amplifier G m2 is enabled to be controlled in a limiting state, and the amplitude of the other transconductance amplifier G m2 is also enabled to be in a limiting state.
  2. 2. An adaptive control circuit for laser driver is composed of a primary channel consisting of a front-stage differential amplifier A V with input end connected to data signal V data and output end connected to input end of said rear-stage transconductance amplifier G m1 , and a rear-stage transconductance amplifier G m1 with output end for driving current I out , and a feedback control loop consisting of converter I-V, The feedback transconductance amplifier G m2 and the current error amplifier A I are connected with the modulation current I modset , the output current I 4 output by the feedback transconductance amplifier G m2 is connected with the current input end of the current error amplifier A I , the feedback current I 1 output by the current error amplifier A I is connected with the input end of the converter I-V, the output end of the converter I-V is divided into two paths, one path is a feedback voltage output end connected with the input end of the feedback transconductance amplifier G m2 , and the other path is a control voltage output end connected with the preceding differential amplifier A V .
  3. 3. The adaptive control circuit for a laser driver according to claim 2, further comprising a transistor MOS 1 , a transistor MOS 2 , a transistor MOS 3 , The transistor MOS 4 and the transistor MOS 5 , the D electrode of the transistor MOS 2 is connected with the current source I mod of the post-stage transconductance amplifier G m1 , the G electrode is connected with the G electrode of the transistor MOS 1 in a common mode and then connected with the junction of the D electrode of the transistor MOS 1 and the modulation current I modset , the S electrode of the transistor MOS 1 is grounded, the G electrode of the transistor MOS 4 is connected with the G electrode of the transistor MOS 5 in a common mode and then connected with the junction of the D electrode of the transistor MOS 1 and the modulation current I modset , the D electrode of the transistor MOS 4 is connected with the current source I 3 of the current error amplifier A I , the S electrode of the transistor MOS 5 is connected with the current source I 2 of the feedback transconductance amplifier G m2 , the S electrode of the transistor MOS 3 is grounded, the D electrode of the transistor MOS 3 is connected with the current source I drv of the preceding stage differential amplifier A V , and the G electrode of the transistor MOS is connected with the control voltage output terminal of the converter.
  4. 4. An adaptive control circuit for a laser driver as claimed in claim 3, wherein the feedback transconductance amplifier G m2 comprises a transistor MOS 6 , a transistor MOS 7 , a transistor MOS 8 , The transistor MOS comprises a transistor MOS 9 and a transistor MOS 10 , wherein the S electrode of the transistor MOS 10 is connected with a power supply V DD , the G electrode is connected with the D electrode of the transistor MOS 9 , the G electrode of the transistor MOS 9 is connected with the G electrode of the transistor MOS 8 and then is connected with a bias voltage V B1 , the S electrode is connected with the D electrode of the transistor MOS 7 , the G electrode of the transistor MOS 7 is connected with the converter I-V, the D electrode of the transistor MOS 8 is connected with the current error amplifier A I , the S electrode is connected with the D electrode of the transistor MOS 6 , the G electrode of the transistor MOS 6 is connected with the converter I-V, and the S electrode of the transistor MOS 6 is connected with the S electrode of the transistor MOS 7 and then is connected with the D electrode of the transistor MOS 5 .
  5. 5. The adaptive control circuit for a laser driver according to claim 4, wherein the current error amplifier A I comprises a transistor MOS 11 , a transistor MOS 12 , a transistor MOS 13 , Transistor MOS 14 , transistor MOS 15 , The capacitor comprises a capacitor C and a current source I 5 , wherein the S electrode of the transistor MOS 11 is connected with the S electrode of the transistor MOS 12 and then connected with the power supply V DD , the G electrode of the transistor MOS 11 is connected with the G electrode of the transistor MOS 12 and then connected with the junction of the D electrode of the transistor MOS 11 and the D electrode of the transistor MOS 8 , the D electrode of the transistor MOS 12 is divided into two paths, one path is connected with the D electrode of the transistor MOS 4 and the other path is connected with the G electrode of the transistor MOS 13 , the S electrode of the transistor MOS 13 is connected with the power supply V DD and the D electrode is connected with the positive electrode of the current source I 5 , one end of the capacitor C is connected with the junction of the G electrode of the transistor MOS 12 and the G electrode of the transistor MOS 13 , the negative electrode of the transistor MOS 14 is grounded, the S electrode of the transistor MOS 14 is connected with the S electrode of the transistor MOS 15 and then connected with the junction of the transistor MOS 14 , and the D electrode of the transistor MOS 14 is connected with the junction of the transistor 14 .
  6. 6. The adaptive control circuit for a laser driver as recited in claim 5, wherein the converter I-V comprises a transistor MOS 16 , a transistor MOS 17 , The load resistor R 1 and the load resistor R 2 are connected in series, the other end of the load resistor R 1 and the load resistor R 2 are connected with the power supply V DD , the other end of the load resistor R 2 is connected with the D electrode of the transistor MOS 17 , the S electrode of the transistor MOS 17 is grounded, the D electrode of the transistor MOS 16 is connected with the D electrode of the transistor MOS 15 , the S electrode is grounded, the G electrode of the transistor MOS 3 is connected with the ground, The G-pole of transistor MOS 16 and the G-pole of transistor MOS 17 are connected to each other and then connected to the junction of the D-pole of transistor MOS 16 and the D-pole of transistor MOS 15 .
  7. 7. An adaptive control circuit for a laser driver according to claim 3, wherein said pre-stage differential amplifier A V comprises a transistor MOS 18 , a transistor MOS 19 , a transistor MOS 20 , transistor MOS 21 , The load resistor R and the load resistor R are connected in parallel, one end of the load resistor R is connected with a power supply V, the other end of the load resistor R is connected with the D pole of the transistor MOS, the S pole of the transistor MOS is connected with the D pole of the transistor MOS, the other end of the load resistor R is connected with the D pole of the transistor MOS, the G pole of the transistor MOS is connected with the G pole of the transistor MOS and then is connected with a bias voltage V, the S pole of the transistor MOS is connected with the S pole of the transistor MOS and then is connected with the positive pole of the current source I, the negative pole of the current source I is grounded, the G pole of the transistor MOS is connected with the positive pole V of the data signal V, the G pole of the transistor MOS is connected with the negative pole V of the data signal V, the junction of the G pole of the transistor MOS is the positive pole of the amplifier A, and the junction of the load resistor R is the positive pole of the amplifier A.
  8. 8. The adaptive control circuit for a laser driver according to claim 7, wherein the post-stage transconductance amplifier G m1 comprises a transistor MOS 22 , a transistor MOS 23 , The MOS comprises a transistor MOS 24 and a transistor MOS 25 , wherein the D electrode of the transistor MOS 24 is the positive electrode I out+ of the output end of the post-stage transconductance amplifier G m1 , the D electrode of the transistor MOS 25 is the negative electrode I out- of the output end of the post-stage transconductance amplifier G m1 , the positive input end V in+ of the G electrode of the transistor MOS 22 is the positive output end V out+ of the pre-stage differential amplifier A V , the negative input end V out+ of the G electrode of the transistor MOS out+ is the negative output end V out+ of the pre-stage differential amplifier A out+ , the G electrode of the transistor MOS out+ is connected with the G electrode of the transistor MOS out+ and then is connected with the bias voltage V2, the S electrode of the transistor MOS out+ is connected with the D out+ electrode of the transistor MOS out+ , the S electrode of the transistor MOS out+ is connected with the negative electrode S out+ of the transistor MOS out+ and then is connected with the positive electrode I out+ of the current source.
  9. 9. An adaptive control circuit for a laser driver according to any one of claims 2 to 8, characterized in that the components constituting the adaptive control circuit according to any one of claims 2 to 8 are packaged in the same integrated block.

Description

Self-adaptive control method and control circuit for laser driver Technical Field The invention relates to a laser driver, belonging to the technical field of optical communication integrated circuit design. Background In an optical communication data transmission link, a high-speed data signal typically passes through a differential-form laser driver to drive a laser to emit light. In the laser driver, the data signal is amplified to a certain amplitude by the pre-stage differential voltage amplifier and then drives the final stage differential transconductance amplifier, the voltage signal is converted into a current signal, namely, a modulation current, and the current flows into an external laser to excite the laser to emit light, so that the electric-optical conversion is realized. The modulation current comes from the current source of the last stage differential transconductance amplifier. The magnitude of the modulation current output by the laser driver needs to be set according to the characteristics of the laser, so that the laser driver needs to adapt to different modulation currents, the output stage of the laser driver is generally of a differential structure, the magnitude of the voltage signal output by the front stage is equal to the product of the current source and the load resistor of the voltage signal, the amplitude of the voltage signal is matched with the magnitude of the modulation current of the rear stage, the rear stage is enabled to work in a limiting state, but the amplitude of the voltage signal cannot be too large, overshoot, pulse width distortion and the like of the output modulation current can be guaranteed to be minimum, and then the eye pattern quality of an optical signal output by the laser is guaranteed. In order to realize the matching of the two, the current source of the front-stage differential amplifier is designed to be in a certain proportion relation with the modulation current of the rear stage, so that the amplitude of the voltage driving signal output by the front stage is related to the modulation current, the modulation current is large, the amplitude of the voltage driving signal is also large, and vice versa, the correlation brought by the method is linear, namely, the amplitude of the voltage driving signal is linearly changed along with the change of the modulation current, but the square law relation is formed between the output current of the output-stage differential amplifier and the required amplitude of the voltage driving signal, and the correlation is nonlinear. It is clear that such linear correlation can only improve the eye quality of the output signal to some extent, but is difficult to adapt to the nonlinear matching requirement, so that the eye quality of the output optical signal is difficult to ensure when the laser driver drives lasers with different modulation currents, and the consistency is poor. Disclosure of Invention In order to overcome the defects in the prior art, the invention provides a self-adaptive control method and a control circuit for a laser driver, which are used for improving the matching of driving voltage and laser modulation current and improving the quality of an output optical eye diagram by optimizing circuit design. The technical scheme adopted for solving the technical problems is as follows: A self-adaptive control method for a laser driver comprises the steps of amplifying signals in a main channel by adopting a front-stage differential amplifier A V and a rear-stage transconductance amplifier G m1, wherein a current source I mod of the rear-stage transconductance amplifier G m1 is controlled by a modulation current I modset, a feedback control loop is arranged between a current source I drv of the front-stage differential amplifier A V and the modulation current I modset, the feedback control loop comprises a feedback transconductance amplifier G m2, the feedback transconductance amplifier G m2 and the rear-stage transconductance amplifier G m1 in the main channel have the same circuit structure and similar limiting characteristics, a value k 1Imodset of a current source I 2 of the feedback transconductance amplifier G m2 and the modulation current I modset are in a proportional relation, an output current I 4 of the feedback amplifier G8238 is obtained after being amplified, a value of the feedback current I3735 is k 2Imodset,k2Imodset<k1Imodset, the feedback current I 1 is converted into voltage and then is output to the feedback transconductance amplifier G2, the feedback transconductance amplifier G m2 has the same circuit structure and similar limiting characteristics with the same amplitude when the same-stage differential amplifier G m2 is driven, and the amplitude of the amplitude is not suitable for driving the same, and the amplitude of the amplitude is suitable for the laser driver to be in a critical amplitude of the differential amplifier G m2. The self-adaptive control circuit for laser dr