CN101924324A - Automatic power control circuit for controlling bias current of laser diode - Google Patents
Automatic power control circuit for controlling bias current of laser diode Download PDFInfo
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- CN101924324A CN101924324A CN 201010276950 CN201010276950A CN101924324A CN 101924324 A CN101924324 A CN 101924324A CN 201010276950 CN201010276950 CN 201010276950 CN 201010276950 A CN201010276950 A CN 201010276950A CN 101924324 A CN101924324 A CN 101924324A
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Abstract
The invention relates to an automatic power control circuit for controlling the bias current of a laser diode, which comprises a photodiode, wherein the photodiode is used for sensing the luminous intensity of the laser diode so as to generate a negative feedback current; one of rated currents is selected according to a control signal; the current difference between the selected rated current and the negative feedback current is converted into a load voltage; a comparison signal is generated by comprising a reference voltage with the load voltage; a counting valve adds the value, decreases the value or maintains the present value according to the comparison signal and the control signal; and a laser diode drive is used for receiving the adjusted counting value so as to generate a pair of bias currents to drive the laser diode to emit light. Therefore, the bias current of the laser diode is adjusted by negative feedback to be in an admissible range to enable a light source emitted by the laser diode to be maintained at a certain luminous intensity.
Description
Technical field
The present invention is relevant for a kind of automatic power control circuit of bias current in order to the control laser diode, and negative feedback is adjusted the bias current of laser diode to allowable range, remains on a fixing luminous intensity with the light source that makes laser diode send.
Background technology
Common light communication system transmits light signal by an optical fiber, carrying out the conduction of data communication, and generally uses the light emitting source of laser diode as light signal.In the light communication system, utilized an automatic power control circuit (Automatic Power Control in the past; APC) luminous intensity of monitoring laser diode reaches a load current value with the bias current of FEEDBACK CONTROL laser diode, and the light source that makes laser diode send can remain on a fixing luminous intensity.
As shown in Figure 1, for having the circuit structure diagram of digital automatic power control circuit now.As shown in the figure, automatic power control circuit 100 includes a photodiode 11, an amplifier 12, a sampling retainer 13, a comparator 14, a counter 15, a digital analog converter 16, a laser diode drive 17 and a laser diode 18.
Wherein, photodiode 11 receives the light source that laser diode 18 is sent, to change out a photosignal (IS).Amplifier 12 receives and amplifies this photosignal (IS), to produce an amplifying signal (AS).Sampling retainer 13 receives, takes a sample and keeps this amplifying signal (AS), to produce a sampling inhibit signal (SH).
Again, automatic power control circuit 100 provides reference voltage R1, R2, R3, the R4 of four groups of different sizes (R1＞R2＞R3＞R4), and be set with a desired value, this desired value can be the median ((R2+R3)/2) between R2 and R3.Comparator 14 receives sampling inhibit signal (SH), is compared to each reference voltage R1, R2, R3, R4 with the inhibit signal (SH) of will taking a sample, and produces the counting controling signal (C1, C2, C3, C4) of four digital states, provides to counter 15.
When sampling inhibit signal (SH) during greater than reference voltage R1, comparator 14 produces counting controling signals (C1C2C3C4=1100).When sampling inhibit signal (SH) drops between reference voltage R1, R2, comparator 14 produces counting controling signals (0100).When sampling inhibit signal (SH) drops between reference voltage R2, R3, comparator 14 produces counting controling signals (0000).When sampling inhibit signal (SH) drops between reference voltage R3, R4, comparator 14 produces counting controling signals (0010).When sampling inhibit signal (SH) during less than reference voltage R4, comparator 14 produces counting controling signals (0011).
The default count values (N) of counter 15, according to the counting controling signal (C1, C2, C3, C4) that receives,, down depreciation or keep present worth up value added to carry out for this count value (N), and after adjusting, export.During the counting controling signal (if 1100) that counter 15 is received, count value (N) is depreciation " 2 " down.When the counting controling signal that counter 15 received was (0100), count value (N) is depreciation " 1 " down.When the counting controling signal that counter 15 received was (0000), count value (N) remained unchanged.During the counting controling signal (if 0010) that counter 15 is received, count value (N) up value added " 1 ".When the counting controling signal that counter 15 received was (0011), count value (N) is value added " 2 " up.
Then, the count value (N) that digital analog converter 16 count pick up devices 15 adjusted are finished is converted to an analog signal (AN) with the count value (N) with digital form, and provides to laser diode drive 17.
Automatic power control circuit 100 is by the luminous intensity of photodiode 11 monitoring laser diodes 18, so that feedback signal (for example: inhibit signal SH takes a sample) is adjusted to desired value gradually, use the same load current value that equals of bias current (Ibias) that negative feedback control laser diode drive 17 is produced.Afterwards, the light source that laser diode 18 is sent can remain on a fixing luminous intensity, and makes light communication system can carry out the conduction of data communication exactly.
Though but the bias current (Ibias) of existing automatic power control circuit 100 negative feedbacks control laser diode 18 reaches a load current value, so, represent the sampling inhibit signal (SH) of laser diode 18 luminous intensities to compare with many groups reference voltage R1, R2, R3, R4 simultaneously, whether the bias current that just can learn laser diode equals a load current value, way like this, not only comparison program is too loaded down with trivial details, and make the circuit complexity of comparator 14 increase, and can therefore improve the power consumption of circuit, very unfavorable.
Summary of the invention
Main purpose of the present invention, be to provide a kind of automatic power control circuit of the bias current in order to the control laser diode, it is the circuit framework that an innovation is simplified, but the luminous intensity of monitoring laser diode not only, the bias current of adjusting laser diode with negative feedback is to permissible rated range, and the light source that makes laser diode send remains on a fixing luminous intensity.
Secondary objective of the present invention, be to provide a kind of automatic power control circuit of the bias current in order to the control laser diode, set many group rated current, when negative feedback current surpasses the rated current of the upper limit, downgrade the bias current of laser diode, when negative feedback current surpasses the rated current of lower limit, increase the bias current of laser diode, be adjusted in the permissible rated range with bias current laser diode.
Another purpose of the present invention, be to provide a kind of automatic power control circuit of the bias current in order to the control laser diode, wherein the comparator in the automatic power control circuit is set with a number of comparisons, after repeatedly comparing, confirm negative feedback current all greater than upper limit rated current in or less than the lower limit rated current, just may increase or downgrade for bias current, constantly adjust for bias current in the short time with the factor of avoiding noise, and the stability of the driving power of reduction laser diode.
For this reason, for reaching above-mentioned purpose, the invention provides a kind of automatic power control circuit of bias current in order to the control laser diode, it includes: a laser diode receives a bias current, with driven for emitting lights; One photodiode in order to the luminous intensity of sensing laser diode, produces a negative feedback current, and connects a first node; One controller is in order to export a control signal; One switching selector, be arranged between first node and a plurality of rated current, include a plurality of derailing switches, each rated current is a corresponding derailing switch respectively, connect controller to receive control signal, select a wherein rated current according to control signal, and open the pairing derailing switch of selecting of rated current, the rated current of selecting with order connects first node; One transducer connects first node, and the difference between current between the rated current of reception negative feedback current and selection is changed out a load voltage; One comparator, connect transducer and controller, include a first input end and one second input, first input end connects a reference voltage, and second input receives load voltage, relatively load voltage and reference voltage, to produce a comparison signal, and comparison signal is sent to controller, and controller is according to the signal condition of comparison signal transformation control signal, with the rated current of decision selection; One counter writes down a count value, connects comparator and controller and receives comparison signal and control signal, according to comparison signal and the up value added count value of control signal, depreciation count value or keep count value originally down; And a laser diode drive, linkage counter and laser diode, the count pick up value is to produce corresponding bias current driving laser led lighting.
Described automatic power control circuitry, wherein, still include a digital analog converter between this counter and this laser diode drive, in order to receiving this count value of digital form, with this count value of changing out analog form and be sent to this laser diode drive.
Described automatic power control circuitry, wherein, this load voltage is during greater than this reference voltage, this comparison signal is a negative saturation signal, when this load voltage equals this reference voltage, this comparison signal is a signal value of zero, and this load voltage is during less than this reference voltage, and this comparison signal is a positive saturation signal.
Described automatic power control circuitry, wherein, this rated current includes one with reference to rated current, one upper limit rated current and once limit decide electric current, this control signal includes one first signal condition, one secondary signal state and one the 3rd signal condition, when this control signal is this first signal condition, select this to be connected to this first node with reference to rated current, when this control signal is this secondary signal state, select this upper limit rated current to be connected to this first node, when this control signal is the 3rd signal condition, select this lower limit rated current to be connected to this first node.
Described automatic power control circuitry, wherein, default this control signal of this controller is this first signal condition, this controller receive for the first time should be negative during saturation signal, this controller record at present this bias current greater than this with reference to rated current, if continue to receive this negative saturation signal, this control signal will continue to change between this first signal condition and this secondary signal state, receive the signal condition that this positive saturation signal stops to change this control signal up to this controller, otherwise, during this positive saturation signal that this controller receives for the first time, this controller record at present this bias current less than this with reference to rated current, if continue to receive this positive saturation signal, this control signal continues to change between this first signal condition and the 3rd signal condition, receives the signal condition that this negative saturation signal stops to change this control signal up to this controller.
Described automatic power control circuitry, wherein, receive this second status signal and should be negative during saturation signal, down this count value of depreciation simultaneously when this counter, when this counter receives this third state signal and this positive saturation signal simultaneously, up value added this count value.
Described automatic power control circuitry, wherein, this transducer receives a reset signal, when this reset signal is a high level state, this first input end of this comparator and this second input connect by this transducer conducting, are equal to this reference voltage to control this load voltage.
Described automatic power control circuitry, wherein, this transducer receives a reset signal, when this reset signal is a low level state, difference between current between the rated current of this negative feedback current and this selection flows to this transducer, changes out this load voltage with this second input at this comparator.
Described automatic power control circuitry, wherein, this transducer includes:
One the first transistor is a P type MOS (metal-oxide-semiconductor) transistor, and source terminal connects this first node, and drain electrode end connects second input of this comparator, and gate terminal receives a reset signal; And
One transistor seconds is a N type MOS (metal-oxide-semiconductor) transistor, and source terminal connects the first input end of this comparator, and drain electrode end connects second input of this comparator, and gate terminal receives this reset signal;
Wherein, when this reset signal was a high level state, this first transistor was a closed condition, this transistor seconds is a conducting state, when this reset signal was a low level state, this first transistor was a conducting state, and this transistor seconds is a closed condition.
Described automatic power control circuitry, wherein, this comparator is set with a number of comparisons, if this load voltage and this reference voltage are after this number of comparisons of process, this load voltage of each comparative result is all greater than this reference voltage or all less than this reference voltage, then this comparator produces and should bear saturation signal or this positive saturation signal, otherwise this comparator produces this signal value of zero.
Description of drawings
Fig. 1 is the circuit structure diagram of existing digital automatic power control circuit;
Fig. 2 is the circuit structure diagram of the present invention in order to automatic power control circuit one preferred embodiment of the bias current of control laser diode;
Fig. 3 is the signal timing diagram of automatic power control circuit one embodiment of the present invention;
Fig. 4 is the signal timing diagram of the another embodiment of automatic power control circuit of the present invention.
Wherein, Reference numeral:
100 automatic power control circuits, 11 photodiodes
12 amplifiers, 13 sampling retainers
14 comparators, 15 counters
16 digital analog converters, 17 laser diode drives
18 laser diodes
300 automatic power control circuits, 301 first nodes
31 switching selectors, 311 derailing switches
313 derailing switches, 315 derailing switches
32 photodiodes, 33 transducers
331 the first transistors, 333 transistor secondses
34 comparators, 341 first input ends
342 second inputs, 35 counters
36 digital analog converters, 37 laser diode drives
38 laser diodes, 39 controllers
The magnitude of voltage of magnitude of voltage 552 load voltages of 551 load voltages
The magnitude of voltage of magnitude of voltage 554 load voltages of 553 load voltages
The magnitude of voltage of magnitude of voltage 556 load voltages of 555 load voltages
The magnitude of voltage of magnitude of voltage 558 load voltages of 557 load voltages
The current value of magnitude of voltage 561 negative feedback current of 559 load voltages
The magnitude of voltage of current value 571 load voltages of 562 negative feedback current
The magnitude of voltage of magnitude of voltage 573 load voltages of 572 load voltages
The magnitude of voltage of magnitude of voltage 575 load voltages of 574 load voltages
The magnitude of voltage of magnitude of voltage 577 load voltages of 576 load voltages
The magnitude of voltage of magnitude of voltage 579 load voltages of 578 load voltages
The current value of current value 582 negative feedback current of 581 negative feedback current
Embodiment
Describe the present invention below in conjunction with the drawings and specific embodiments, but not as a limitation of the invention.
At first, please refer to Fig. 2, be the circuit structure diagram of the present invention in order to automatic power control circuit one preferred embodiment of the bias current of control laser diode.As shown in the figure, automatic power control circuit 300 is applied to the adjustment of the luminous intensity of light signal in the light communication system, and it includes a switching selector 31, a photodiode 32, a transducer 33, a comparator 34, a counter 35, a laser diode drive 37, a laser diode 38 and a controller 39.
Wherein, laser diode 38 receives bias currents (Ibias), with driven for emitting lights as the light emitting source of light signal.The luminous intensity of photodiode 32 sensing laser diodes 38 is to produce a negative feedback current I
FB, negative feedback current I
FBAlso can equal bias current (Ibias), and photodiode 32 connects a first node 301, this first node 301 is the tie point of 31 of photodiode 32 and switching selectors.
Switching selector 31 is arranged on first node 301 and a plurality of rated current I
SET, I
UL_SET, I
LL_SETBetween, include a plurality of derailing switches 331,333,335, each rated current I
SET, I
UL_SET, I
LL_SETThe corresponding derailing switch 331,333,335 of difference.In addition, switching selector 31 still connects controller 39, to receive the control signal (CS) that controller 39 produces, selects a wherein rated current I according to control signal (CS)
SET/ I
UL_SET/ I
LL_SET, and open the rated current I that selects
SET/ I
UL_SET/ I
LL_SETPairing derailing switch 331/333/335 is to make selected rated current I
SET/ I
UL_SET/ I
LL_SETCan be electrically connected to first node 301, and on first node 301, export negative feedback current I
FBWith selected rated current I
SET/ I
UL_SET/ I
LL_SETBetween a difference between current I
D
Again, rated current includes one with reference to rated current I
SET, a upper limit rated current I
UL_SETAnd once limit is decided electric current I
LL_SET, upper limit rated current I
UL_SETCan be set at reference to rated current I
SET1.2 times or other is greater than 1 multiple, lower limit rated current I
LL_SETCan be set at reference to rated current I
SET0.8 times or other is less than 1 multiple.Control signal (CS) includes one first signal condition (00), a secondary signal state (01) and one the 3rd signal condition (10), when control signal (CS) is this first signal condition (00), opens derailing switch 311, to select with reference to rated current I
SETBe connected to first node 301, when control signal (CS) is secondary signal state (01), open derailing switch 313, to select upper limit rated current I
UL_SETBe connected to first node 301, when control signal (CS) is the 3rd signal condition (10), open derailing switch 315, select lower limit rated current I
LL_SETBe connected to first node 301.
Transducer 33 detailed circuit structures include a first transistor 331 and a transistor seconds 333.The first transistor 331 is a P type MOS (metal-oxide-semiconductor) transistor (PMOS), and source terminal (S) connects first node 301, and drain electrode end (D) connects second input 342 of comparator 34, and gate terminal (G) receives a reset signal RS.Transistor seconds 333 is a N type MOS (metal-oxide-semiconductor) transistor (NMOS), and source terminal (S) connects the first input end 341 of comparator 34, and drain electrode end (D) connects second input 342 of comparator, and gate terminal (G) receives reset signal RS.When reset signal RS is a high level state (H), the first transistor 331 is a closed condition, transistor seconds 333 is a conducting state, at this moment, the first input end 341 of comparator 34 and second input 342 directly connect via the transistor seconds 333 of transducer 33, with control load voltage V
LBe equal to reference voltage V
REFOtherwise when reset signal RS was a low level state (L), the first transistor 331 was a conducting state, and transistor seconds 333 is a closed condition, with reference to rated current I
SETWith negative feedback current I
FBBetween difference between current I
DThe first transistor 331 via transducer 33 flows to second input 342, to change out corresponding this load voltage V on second input 342 of this comparator 34
L
Moreover the comparison signal (C) that comparator 34 is produced can be sent to controller 39, and controller 39 is in the signal condition that changes control signal (CS) according to comparison signal (C), with the rated current I of decision desire selection
SET, I
UL_SETOr I
LL_SETAnd counter 35 is a digital counter, for example: ten digit counters, write down a count value (N), connect comparator 34 and controller 39, receiving comparison signal (C) and control signal (CS), according to comparison signal (C) and the up value added count value of control signal (CS) (N), depreciation count value (N) or keep count value (N) originally down.
From the above, content for controller 34 and counter 35 further specifies, when automatic power control circuitry 300 began to carry out the program of luminous intensity of monitoring laser diode 38, controller 39 default control signals (CS) were first signal condition (00), at first can select with reference to rated current I
SETWith negative feedback current I
FBCompare.
As negative feedback current I
FBGreater than reference rated current I
SETThe time, comparator 34 can be exported a negative saturation signal to counter 35 and controller 39.When counter 35 receives first signal condition (00) and negative saturation signal, can't be for count value (N
X) carry out any change, and behind the negative saturation signal of controller 39 receptions, learn negative feedback current I
FBGreater than reference rated current I
SET, control signal (CS) is changed into secondary signal state (01), select upper limit rated current I
UL_SETWith negative feedback current I
FBCompare.If negative feedback current (I
FB) still greater than upper limit rated current I
UL_SETThe time, comparator 34 also can be exported negative saturation signal to counter 35 and controller 39.When counter 35 receives secondary signal state (01) and negative saturation signal simultaneously, just can be for count value (N
X) depreciation down, and after controller 39 received negative saturation signal once more, it was first signal condition (00) that control signal (CS) is changeed back from secondary signal state (01), uses again with reference to rated current I
SETWith adjusted negative feedback current I
FBCompare.Continue above-mentioned flow process, up to negative feedback current (I
FB) less than upper limit rated current I
UL_SET, and making the just saturated comparison signal (C) of comparator 34 outputs, controller 39 will stop to change the signal condition of control signal (CS), to finish count value (N
X) the counting adjustment.
Opposite, as negative feedback current I
FBLess than reference rated current I
SETThe time, comparator 34 will be exported a positive saturation signal to counter 35 and controller 39.When counter 35 receives first signal condition (00) and positive saturation signal, can't be for count value (N
X) carry out any change, and behind the positive saturation signal of controller 39 receptions, learn negative feedback current I
FBLess than reference rated current I
SET, control signal (CS) is changed into the 3rd signal condition (10), select lower limit rated current I
LL_SETWith negative feedback current I
FBCompare.If negative feedback current I
FBStill less than lower limit rated current I
LL_SETThe time, comparator 34 also can be exported positive saturation signal to counter 35 and controller 39.When counter 35 receives the 3rd signal condition (10) and positive saturation signal simultaneously, just can be for count value (N
X) up value added, and after controller 39 received positive saturation signal once more, it was first signal condition (00) that control signal (CS) is changeed back from the 3rd signal condition (10), uses again with reference to rated current I
SETWith adjusted negative feedback current I
FBCompare.Continue above-mentioned flow process, up to negative feedback current I
FBGreater than lower limit rated current I
LL_SET, and making the negative saturated comparison signal (C) of comparator 34 outputs, controller 39 will stop to change the signal condition of control signal (CS), to finish count value (N
X) the counting adjustment.
Certainly, in the present embodiment, with the count value (N of digital form
X) directly control laser diode drive 37 generation bias currents (Ibias), perhaps, by the count value (N of a digital analog converter 36 with digital form
X) be converted to the count value (AN of analog form
X), produce bias current (Ibias) with simulated mode control laser diode drive 37.
By this, present embodiment automatic power control circuit 300 utilizes many group rated current and negative feedback current I
FBCompare, as negative feedback current I
FBThe rated current I that surpasses the upper limit
UL_SETThe time, downgrade the bias current (Ibias) of laser diode 38, as negative feedback current I
FBThe rated current I that surpasses lower limit
LL_SETThe time, increase the bias current (Ibias) of laser diode 38, be adjusted to gradually in the permissible rated range with bias current (Ibias), and the light source that makes laser diode 38 send remains on a fixing luminous intensity laser diode 38.
Again, comparator 34 of the present invention is set with a number of comparisons, for example: 16 times, after repeatedly comparing, load voltage V
LAll be greater than or less than reference voltage V
REFThe time, comparator 34 just can be exported negative saturation signal or positive saturation signal, in other words, repeatedly confirms negative feedback current I
FBAll greater than upper limit rated current I
UL_SETOr less than lower limit rated current I
LL_SETComparator 34 just can be exported negative saturation signal or positive saturation signal, afterwards, just may increase or downgrade for bias current (Ibias), constantly adjust for bias current (Ibias) in the short time with the factor of avoiding noise, and the stability of the driving power of reduction laser diode 38.
Please refer to Fig. 3, be the signal timing diagram of automatic power control circuit one embodiment of the present invention, and consult Fig. 2 simultaneously.As shown in the figure, at first, before the luminous intensity of automatic power control circuit 300 monitoring laser diodes 38, can receive a high level state (H
1) reset signal RS, with control load voltage V
LMagnitude of voltage 551 be equal to reference voltage V
REF, and photodiode 32 can not sense any negative feedback current I for the luminous intensity of light-emitting diode 38
FBAfterwards, automatic power control circuit 300 receives a low level state (L
1) reset signal RS, the luminous intensity of photodiode 32 beginning sensing laser diodes 38, and the negative feedback current I that is relatively sensed
FBWith rated current I
SET, I
UL_SETOr I
LL_SETBetween size.
Before present embodiment automatic power control circuitry 300 began to carry out the luminous intensity of monitoring laser diode 38, controller 39 default control signals (CS) were first signal condition (00), at first select with reference to rated current I
SETWith negative feedback current I
FB Current value 561 compare.In the present embodiment, because negative feedback current I
FB Current value 561 greater than reference rated current I
SET, negative feedback current I
FB Current value 561 with reference to rated current I
SETBetween difference between current I
DTo make load voltage V
LMagnitude of voltage 552 up draw high load voltage V
LMagnitude of voltage 552 greater than reference voltage V
REF, comparator 24 outputs one negative saturation signal (C=-1).When counter 35 receives first signal condition (00) and negative saturation signal (C=-1), can't be for count value (N
X) carry out any change, and controller 39 receives when bearing saturation signal (C=-1) for the first time, learns negative feedback current I
FBCurrent value 561 (it is equal to bias current (Ibias)) greater than reference rated current I
SETSituation and note, and control signal (CS) is changed into secondary signal state (01), alternative is selected upper limit rated current I
UL_SETWith negative feedback current I
FB Current value 561 compare.
Automatic power control circuit 300 receives next high level state (H
2) reset signal RS, control load voltage V
LMagnitude of voltage 553 be equal to reference voltage V
REF, and photodiode 32 can not sense any negative feedback current I
FBAutomatic power control circuit 300 receives next low level state (L
2) reset signal RS, and utilize upper limit rated current I
UL_SETWith negative feedback current I
FBCurrent value 561 compare upper limit rated current I
UL_SETWith negative feedback current I
FBThe difference between current I of 561 of current values
D, will make load voltage V
LMagnitude of voltage 554 up draw high load voltage V
LMagnitude of voltage 554 greater than reference voltage V
REF, the negative saturation signal (C=-1) of comparator 34 outputs.At this moment, counter 35 receives the control signal (CS) and the negative saturation signal (C=-1) of secondary signal state (01) simultaneously, can be for count value (N
X) depreciation (N down
X=N-1).Laser diode drive 37 count pick up value (N
X=N-1), produce one corresponding to count value (N
X=N-1) bias current (Ibias), therefore the luminosity of laser diode 38 will downgrade, and then photodiode 32 senses the negative feedback current I of a reduced-current value 562
FB, the negative feedback current I of reduced-current value 562
FBCan drag down fractional load voltage V
LMagnitude of voltage 555.Moreover controller 39 receives negative saturation signal (C=-1) once more, learns the negative feedback current I of present reduced-current value 561
FBThrough adjusting, change back first signal condition (00) from secondary signal state (01) with control signal (CS).
Automatic power control circuit 300 receives next high level state (H
3) reset signal RS, control load voltage V
LMagnitude of voltage 556 be equal to reference voltage V
REF, and photodiode 32 can not sense any negative feedback current I
FBAutomatic power control circuit 300 receives next low level state (L
3) reset signal RS, and utilize with reference to rated current I
SETNegative feedback current I with reduced-current value 562
FBCompare, with reference to rated current I
SETNegative feedback current I with reduced-current value 562
FBBetween difference between current I
D, will make load voltage V
LMagnitude of voltage 557 up draw high load voltage V
LMagnitude of voltage 557 greater than reference voltage V
REF, comparator 34 outputs one negative saturation signal (C=-1).Counter 35 receives first signal condition (00) and negative saturation signal (C=-1), for count value (N
X=N-1) keep present situation, and after controller 39 receives negative saturation signal (C=-1), learn the negative feedback current I of reduced-current value 562
FBStill greater than reference rated current I
SET, control signal (CS) is changed into secondary signal state (01), alternative is selected upper limit rated current I
UL_SETNegative feedback current I with reduced-current value 562
FBCompare.
Automatic power control circuit 300 receives next high level state (H
4) reset signal RS, control load voltage V
LMagnitude of voltage 558 be equal to reference voltage V
REF, and photodiode 32 can not sense any negative feedback current I
FBAutomatic power control circuit 300 receives next low level state (L
4) reset signal RS, and utilize upper limit rated current I
UL_SETNegative feedback current I with reduced-current value 562
FBCompare, as a result upper limit rated current I
UL_SETNegative feedback current I greater than reduced-current value 562
FB, upper limit rated current I then
UL_SETNegative feedback current I with reduced-current value 562
FBBetween difference between current I
D, will make load voltage V
LMagnitude of voltage 559 toward drop-down falling, load voltage V
LMagnitude of voltage 559 will be less than reference voltage V
REF, and make comparator 35 export positive saturation signals (C=+1), then controller 39 stops to change the signal condition of control signal (CS), to finish count value (N
X) the counting adjustment, and this moment laser diode 38 bias current (Ibias) adjusted to the permissible rated range.
Hold embodiment content schematic illustration, when automatic power control circuit 300 carried out monitoring program for the luminous intensity of light-emitting diode 38, controller 39 can default control signal (CS) be first signal condition (00), to utilize with reference to rated current I
SET(it is equal to negative feedback current I to carry out luminous bias current (Ibias) with driving laser diode 38
FB) compare.Relatively,, promptly represent bias current (Ibias) greater than reference rated current I if controller 39 receives negative saturation signal (C=-1)
SET, controller 39 conversion control signals (CS) are secondary signal state (01), decide electric current I in order to using limit
UL_SET(Ibias) compares with bias current.Relatively,, promptly represent bias current (Ibias) still greater than upper limit rated current I if controller 39 still receives negative saturation signal (C=-1)
UL_SET, automatic power control circuit 300 downgrades bias current (Ibias), and controller 39 signal condition that changes control signals (CS) to change back from secondary signal state (01) be first signal condition (00).Follow-up, if controller 39 constantly receives negative saturation signal (C=-1), can this control signal of control (CS) between first signal condition (00) and secondary signal state (01), continue conversion, and when each control signal (CS) was secondary signal state (01), automatic power control circuit 300 downgraded the bias current (Ibias) of laser diode 38.Repeat above-mentioned action, up to bias current (Ibias) less than upper limit rated current I
UL_SETOr make controller 39 receive positive saturation signal (C=+1) with reference to rated current (Ibias), will the stop transformation signal condition of control signal (CS) of controller 39.At this moment, bias current (Ibias) adjusted to the permissible rated range, then the bias current (Ibias) finished of adjusted but the light source that driving laser diode 38 is sent can be remained on a suitable luminous intensity.
Please refer to Fig. 4, be the signal timing diagram of automatic power control circuit one embodiment of the present invention, and consult Fig. 2 simultaneously.As shown in the figure, automatic power control circuit 300 at first can receive a high level state (H
1) reset signal RS, with control load voltage V
LMagnitude of voltage 571 be equal to reference voltage V
REF, and photodiode 32 can not sense any negative feedback current I for the luminous intensity of laser diode 38
FBAfterwards, automatic power control circuit 300 receives a low level state (L
1) reset signal RS, the luminous intensity of photodiode 32 beginning sensing laser diodes 38, and the negative feedback current I that is relatively sensed
FBWith rated current I
SET, I
UL_SETOr I
LL_SETBetween size.
Before present embodiment automatic power control circuitry 300 began to carry out the luminous intensity of monitoring laser diode 38, controller 39 default control signals (CS) were first signal condition (00), at first select with reference to rated current I
SETWith negative feedback current I
FBCurrent value 581 compare.In the present embodiment, because negative feedback current I
FBCurrent value 581 less than reference rated current I
SET, negative feedback current I
FBCurrent value 581 with reference to rated current I
SETBetween difference between current I
DTo make load voltage V
LMagnitude of voltage 572 toward drop-down falling, load voltage V
LMagnitude of voltage 572 less than reference voltage V
REF, comparator 24 output positive saturation signals (C=+1).When counter 35 receives first signal condition (00) and positive saturation signal (C=+1), can't be for count value (N
X) carry out any change, and controller 39 is learnt negative feedback current I when receiving positive saturation signal (C=+1) for the first time
FBCurrent value 581 (its be equal to relatively electric current (Ibias)) less than reference rated current I
SETSituation and note, and control signal (CS) is changed into the 3rd signal condition (10), select lower limit rated current I
LL_SETWith negative feedback current I
FBCurrent value 581 compare.
Automatic power control circuit 300 receives next high level state (H
2) reset signal RS, control load voltage V
LMagnitude of voltage 573 be equal to reference voltage V
REF, and photodiode 32 can not sense any negative feedback current I
FBAutomatic power control circuit 300 receives next low level state (L
2) reset signal RS, and utilize lower limit rated current I
LL_SETWith negative feedback current I
FBCurrent value 581 compare lower limit rated current I
LL_SETWith negative feedback current I
FBThe difference between current I of 581 of current values
D, will make load voltage V
LMagnitude of voltage 574 toward drop-down falling, load voltage V
LMagnitude of voltage 574 less than reference voltage V
REF, comparator 34 output positive saturation signals (C=+1).At this moment, counter 35 receives the control signal (CS) and the positive saturation signal (C=+1) of the 3rd signal condition (10) simultaneously, can be for count value (N
X) up value added (N
X=N+1).Laser diode drive 37 count pick up value (N
X=N+1), produce one corresponding to count value (N
X=N+1) bias current (Ibias), therefore the luminosity of laser diode 38 will increase, and then photodiode 32 senses the negative feedback current I of a high current value 582
FB, the negative feedback current I of high current value 582
FBCan draw high fractional load voltage V
LMagnitude of voltage 575.Moreover controller 39 receives positive saturation signal (C=+1) once more, learns the negative feedback current I of present high current value 582
FBThrough adjusting, change back first signal condition (00) from the 3rd signal condition (01) with control signal (CS).
Automatic power control circuit 300 receives next high level state (H
3) reset signal RS, control load voltage V
LMagnitude of voltage 576 be equal to reference voltage V
REF, and photodiode 32 can not sense any negative feedback current I
FBAutomatic power control circuit 300 receives next low level state (L
3) reset signal RS, and utilize with reference to rated current I
SETNegative feedback current I with high current value 582
FBCompare, with reference to rated current I
SETNegative feedback current I with high current value 582
FBBetween difference between current I
D, will make load voltage V
LMagnitude of voltage 557 toward drop-down falling, load voltage V
LMagnitude of voltage 557 less than reference voltage V
REF, comparator 34 output positive saturation signals (C=+1).Counter 35 receives first signal condition (00) and positive saturation signal (C=+1), for count value (N
X=N+1) keep present situation, and after controller 39 receives positive saturation signals (C=+1), learn the negative feedback current I of high current value 582
FBStill less than reference rated current I
SET, control signal (CS) is changed into the 3rd signal condition (10), select lower limit rated current I
LL_SETNegative feedback current I with high current value 582
FBCompare.
Automatic power control circuit 300 receives next high level state (H
4) reset signal RS, control load voltage V
LMagnitude of voltage 578 be equal to reference voltage V
REF, and photodiode 32 can not sense any negative feedback current I
FBAutomatic power control circuit 300 receives next low level state (L
4) reset signal RS, and utilize lower limit rated current I
LL_SETNegative feedback current I with high current value 582
FBCompare, as a result lower limit rated current I
LL_SETNegative feedback current I less than high current value 582
FB, lower limit rated current I then
LL_SETNegative feedback current I with high current value 582
FBBetween difference between current I
D, will make load voltage V
LMagnitude of voltage 579 up draw high load voltage V
LMagnitude of voltage 579 will be greater than reference voltage V
REF, and making comparator 35 outputs bear saturation signal (C=-1), controller 39 stops to change the signal condition of control signal (CS), to finish count value (N
X) the counting adjustment, and this moment laser diode 38 bias current (Ibias) adjusted to the permissible rated range.
Hold embodiment content schematic illustration, when automatic power control circuit 300 carried out monitoring program for the luminous intensity of laser diode 38, controller 39 can default control signal (CS) be first signal condition (00), to utilize with reference to rated current I
SET(it is equal to negative feedback current I to carry out luminous bias current (Ibias) with driving laser diode 38
FB) compare.Relatively,, promptly represent bias current (Ibias) less than reference rated current I if controller 39 receives positive saturation signal (C=+1)
SET, controller 39 conversion control signals (CS) are the 3rd signal condition (10), to utilize lower limit rated current I
LL_SET(Ibias) compares with bias current.Relatively,, promptly represent bias current (Ibias) still less than lower limit rated current I if controller 39 still receives positive saturation signal (C=+1)
LL_SET, automatic power control circuit 300 increases bias current (Ibias), and controller 39 signal condition that changes control signals (CS) to change back from the 3rd signal condition (10) be first signal condition (00).Follow-up, if controller 39 constantly receives positive saturation signal (C=+1), can this control signal of control (CS) between first signal condition (00) and the 3rd signal condition (10), continue conversion, and when each control signal (CS) was the 3rd signal condition (10), automatic power control circuit 300 increased the bias current (Ibias) of laser diode 38.Repeat above-mentioned action, up to bias current (Ibias) greater than lower limit rated current I
LL_SETOr make controller 39 receive negative saturation signal (C=-1) with reference to rated current (Ibias), to the stop transformation signal condition of control signal (CS) of controller 39, at this moment, bias current (Ibias) adjusted to the permissible rated range, then the bias current (Ibias) finished of adjusted but the light source that driving laser diode 38 is sent can be remained on a suitable luminous intensity.
Certainly; the present invention also can have other various embodiments; under the situation that does not deviate from spirit of the present invention and essence thereof; those of ordinary skill in the art work as can make various corresponding changes and distortion according to the present invention, but these corresponding changes and distortion all should belong to the protection range of the appended claim of the present invention.
Claims (10)
1. the automatic power control circuit in order to the bias current of control laser diode is characterized in that, includes:
One laser diode receives a bias current, with driven for emitting lights;
One photodiode in order to the luminous intensity of this laser diode of sensing, produces a negative feedback current, and connects a first node;
One controller is in order to export a control signal;
One switching selector, be arranged between this first node and a plurality of rated current, include a plurality of derailing switches, each rated current is a corresponding derailing switch respectively, connect this controller to receive this control signal, select a wherein rated current according to this control signal, and open pairing this derailing switch of rated current of this selection, connect this first node with the rated current that makes this selection;
One transducer connects this first node, receives the difference between current between the rated current of this negative feedback current and this selection, changes out a load voltage;
One comparator, connect this transducer and this controller, include a first input end and one second input, this first input end connects a reference voltage, and this second input receives this load voltage, relatively this load voltage and this reference voltage, to produce a comparison signal, and this comparison signal is sent to this controller, and this controller changes the signal condition of this control signal according to this comparison signal, to determine the rated current of this selection;
One counter writes down a count value, connects this comparator and this controller, receives this comparison signal and this control signal, according to this comparison signal and up value added this count value of this control signal, this count value of depreciation or keep this count value originally down; And
One laser diode drive connects this counter and this laser diode, receives this count value, and it is luminous to drive this laser diode with this bias current that produces correspondence.
2. automatic power control circuitry as claimed in claim 1, it is characterized in that, still include a digital analog converter between this counter and this laser diode drive, in order to receiving this count value of digital form, with this count value of changing out analog form and be sent to this laser diode drive.
3. automatic power control circuitry as claimed in claim 1, it is characterized in that, this load voltage is during greater than this reference voltage, this comparison signal is a negative saturation signal, when this load voltage equals this reference voltage, this comparison signal is a signal value of zero, and this load voltage is during less than this reference voltage, and this comparison signal is a positive saturation signal.
4. automatic power control circuitry as claimed in claim 3, it is characterized in that, this rated current includes one with reference to rated current, one upper limit rated current and once limit decide electric current, this control signal includes one first signal condition, one secondary signal state and one the 3rd signal condition, when this control signal is this first signal condition, select this to be connected to this first node with reference to rated current, when this control signal is this secondary signal state, select this upper limit rated current to be connected to this first node, when this control signal is the 3rd signal condition, select this lower limit rated current to be connected to this first node.
5. automatic power control circuitry as claimed in claim 4, it is characterized in that, default this control signal of this controller is this first signal condition, this controller receive for the first time should be negative during saturation signal, this controller record at present this bias current greater than this with reference to rated current, if continue to receive this negative saturation signal, this control signal will continue to change between this first signal condition and this secondary signal state, receive the signal condition that this positive saturation signal stops to change this control signal up to this controller, otherwise, during this positive saturation signal that this controller receives for the first time, this controller record at present this bias current less than this with reference to rated current, if continue to receive this positive saturation signal, this control signal continues to change between this first signal condition and the 3rd signal condition, receives the signal condition that this negative saturation signal stops to change this control signal up to this controller.
6. automatic power control circuitry as claimed in claim 4, it is characterized in that, when this counter receives this second status signal simultaneously and should bear saturation signal, this count value of depreciation down, when this counter receives this third state signal and this positive saturation signal simultaneously, up value added this count value.
7. automatic power control circuitry as claimed in claim 1, it is characterized in that, this transducer receives a reset signal, when this reset signal is a high level state, this first input end of this comparator and this second input connect by this transducer conducting, are equal to this reference voltage to control this load voltage.
8. automatic power control circuitry as claimed in claim 1, it is characterized in that, this transducer receives a reset signal, when this reset signal is a low level state, difference between current between the rated current of this negative feedback current and this selection flows to this transducer, changes out this load voltage with this second input at this comparator.
9. automatic power control circuitry as claimed in claim 1 is characterized in that, this transducer includes:
One the first transistor is a P type MOS (metal-oxide-semiconductor) transistor, and source terminal connects this first node, and drain electrode end connects second input of this comparator, and gate terminal receives a reset signal; And
One transistor seconds is a N type MOS (metal-oxide-semiconductor) transistor, and source terminal connects the first input end of this comparator, and drain electrode end connects second input of this comparator, and gate terminal receives this reset signal;
Wherein, when this reset signal was a high level state, this first transistor was a closed condition, this transistor seconds is a conducting state, when this reset signal was a low level state, this first transistor was a conducting state, and this transistor seconds is a closed condition.
10. automatic power control circuitry as claimed in claim 3, it is characterized in that, this comparator is set with a number of comparisons, if this load voltage and this reference voltage are after this number of comparisons of process, this load voltage of each comparative result is all greater than this reference voltage or all less than this reference voltage, then this comparator produces and should bear saturation signal or this positive saturation signal, otherwise this comparator produces this signal value of zero.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2010102769509A CN101924324B (en) | 2010-09-07 | 2010-09-07 | Automatic power control circuit for controlling bias current of laser diode |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2010102769509A CN101924324B (en) | 2010-09-07 | 2010-09-07 | Automatic power control circuit for controlling bias current of laser diode |
Publications (2)
| Publication Number | Publication Date |
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| CN101924324A true CN101924324A (en) | 2010-12-22 |
| CN101924324B CN101924324B (en) | 2012-05-23 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2010102769509A Expired - Fee Related CN101924324B (en) | 2010-09-07 | 2010-09-07 | Automatic power control circuit for controlling bias current of laser diode |
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| Country | Link |
|---|---|
| CN (1) | CN101924324B (en) |
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| CN102437507A (en) * | 2011-12-02 | 2012-05-02 | 烽火通信科技股份有限公司 | Automatic power control circuit for driving optical communication laser |
| CN102549946A (en) * | 2011-12-12 | 2012-07-04 | 华为技术有限公司 | Modulator circuit of optical time domain reflectometer test signal, passive optical network and device |
| CN102570296A (en) * | 2011-02-25 | 2012-07-11 | 北京国科世纪激光技术有限公司 | Drive circuit of laser diode |
| CN103682980A (en) * | 2013-12-17 | 2014-03-26 | 昂纳信息技术（深圳）有限公司 | Output control method for laser signals |
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| CN102570296A (en) * | 2011-02-25 | 2012-07-11 | 北京国科世纪激光技术有限公司 | Drive circuit of laser diode |
| CN102570296B (en) * | 2011-02-25 | 2014-08-06 | 北京国科世纪激光技术有限公司 | Drive circuit of laser diode |
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| WO2013086674A1 (en) * | 2011-12-12 | 2013-06-20 | 华为技术有限公司 | Circuit for modulating optical time domain reflectometer test signal, and passive optical network system and device |
| US8780340B2 (en) | 2011-12-12 | 2014-07-15 | Huawei Technologies Co., Ltd. | Optical time domain reflectometer test signal modulation circuit, and passive optical network system and apparatus using same |
| CN102549946B (en) * | 2011-12-12 | 2014-11-05 | 华为技术有限公司 | Modulator circuit of optical time domain reflectometer test signal, passive optical network and device |
| CN103682980A (en) * | 2013-12-17 | 2014-03-26 | 昂纳信息技术（深圳）有限公司 | Output control method for laser signals |
| CN106464821A (en) * | 2014-06-25 | 2017-02-22 | 索尼公司 | Imaging element and imaging-element drive method, electronic device, and program |
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| CN109142333A (en) * | 2018-08-16 | 2019-01-04 | 北京乐普医疗科技有限责任公司 | A kind of detection system to fail for reflector on chemical illumination immunity analysis instrument |
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