CN217606061U - Laser drive open circuit detection circuit - Google Patents
Laser drive open circuit detection circuit Download PDFInfo
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- CN217606061U CN217606061U CN202122958216.7U CN202122958216U CN217606061U CN 217606061 U CN217606061 U CN 217606061U CN 202122958216 U CN202122958216 U CN 202122958216U CN 217606061 U CN217606061 U CN 217606061U
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Abstract
The utility model discloses a laser drive detection circuitry that opens circuit, including laser drive circuit, laser instrument LD, resistance R T Resistor Rs, third constant current source I T And a comparator CP, a resistor R T And the third constant current source I T After being connected in series, the two ends of the resistor R are respectively connected between the positive end of the resistor Rt and the ground, and the resistor R T One end of the first constant current source is connected with the positive end of the resistor Rt, and the other end of the first constant current source is connected with the third constant current source I T One input end of the comparator CP is connected with the resistor R, one end of the resistor Rs is connected with the negative end of the resistor Rt, the other end of the resistor Rs is connected with the other input end of the comparator CP, and the resistor R is connected with the output end of the comparator CP T The other end voltage of the resistor Rs is a voltage Vref1, the other end voltage of the resistor Rs is a voltage Vout1, and the voltage Vref1 and the voltage Vout1 are comparedAnd judging whether the laser driving circuit and the laser LD are open or not. It has the following advantages: the laser drive open circuit detection is realized, the detection is easy to realize, power failure is not needed or an external detection tool is used, and the normal work of a laser drive circuit and a laser device is not influenced.
Description
Technical Field
The utility model relates to a detection circuitry especially relates to a laser drive detection circuitry that opens a way.
Background
In the production process of the laser driving module (especially in the packaging and routing process of the laser LD and the driving chip) or in the use stage of the laser driving module (due to external force factors or other factors), the routing disconnection between the driving chip and the laser LD occurs, so that the driving current cannot normally flow into the laser LD, and the laser LD does not emit light. Although the problem of open circuit of the wire bonding between the driving chip and the laser LD can be detected by powering off the driving module and using a third detection tool, the method obviously consumes time and resources. In order to reduce the time and cost for detecting the wire bonding open circuit, a detection circuit capable of automatically detecting the wire bonding open circuit of the laser LD and the driver chip package needs to be designed inside the driver chip.
As shown in fig. 1, a conventional open circuit detection scheme for driving a laser LD is schematically illustrated, in which a resistor RFAULT is connected in series between an output terminal of a driving circuit and the laser LD, and a voltage drop across the resistor RFAULT (actually detecting a current flowing through the resistor RFAULT, i.e., a current flowing into the laser LD) is detected, amplified by a DIFF _ AMP amplifier circuit, and compared with a threshold voltage VTH, so as to determine whether an open circuit exists between the driving chip and the laser LD.
The prior art has the following disadvantages:
1. the output end is connected with the laser LD in series to form a resistor, so that the modulation current of the laser LD can be reduced.
2. The output terminal and the laser LD are connected in series with a resistor to consume a certain voltage margin and generate unnecessary power consumption.
3. The output terminal and the laser LD are connected in series with a resistor which affects the performance (rise-fall time, amplitude, etc.) of the driving current.
4. The existence of parasitic capacitance at the input of the DIFF AMP amplifier also affects the bandwidth of the driver circuit, and thus the rise and fall times of the drive current.
SUMMERY OF THE UTILITY MODEL
The utility model provides a laser drive detection circuitry that opens a way, it has overcome in the background art the not enough of prior art.
The utility model provides a technical scheme that its technical problem adopted is:
the laser driving open circuit detection circuit comprises a laser driving circuit and a laser LD, wherein the laser driving circuit comprises a main circuit and two branches which are branched by the main circuit and are connected in parallel, one common end of each branch is connected with the main circuit, the other common end of each branch is grounded, a first constant current source Ib and a resistor Rt are connected in series on the main circuit, one branch is connected in series with a second constant current source Im, the other branch is connected in series with the laser LD, and the laser LD is driven to work by the first constant current source Ib and the second constant current source Im;
also includes a resistor R T Resistance Rs the third constant current source I T And a comparator CP, wherein the end of the resistor Rt connected with the first constant current source Ib is set as a positive end, the other end of the resistor Rt is set as a negative end, and the resistor R T And the third constant current source I T After being connected in series, the two ends are respectively connected between the positive end of the resistor Rt and the ground, and the resistor R T One end of the first constant current source is connected with the positive end of the resistor Rt, and the other end is connected with the third constant current source I T One input end of the comparator CP is connected with the resistor R, one end of the resistor Rs is connected with the negative end of the resistor Rt, the other end of the resistor Rs is connected with the other input end of the comparator CP T The other end voltage of the resistor Rs is a voltage Vref1, the other end voltage of the resistor Rs is a voltage Vout1, and the comparator CP compares the voltage Vref1 with the voltage Vout1 to judge whether the voltage is zero or notWhether an open circuit exists between the laser driving circuit and the laser LD;
wherein, the resistance value of the resistor Rt is set as R term The resistance R T Has a resistance value of R term * N, N is greater than or equal to 1; let the output current of the second constant current source Im be
The third constant current source I T Has an output value of
I θ Is less than I th ，I th A threshold current is turned on for the laser LD.
In one embodiment: and a capacitor C S The capacitor C S A filter circuit formed by the resistor Rs and the capacitor C S One end of the resistor is connected with the other end of the resistor Rs, and the other end of the resistor is grounded.
In one embodiment: the resistance of the resistor Rs is much larger than that of the resistor Rt.
In one embodiment: the comparator CP is a hysteresis comparator.
The laser drive open circuit detection circuit comprises a laser drive circuit and a laser LD, wherein the laser drive circuit comprises a first triode and a second triode which can form a differential circuit, the control ends of the first triode and the second triode are respectively and correspondingly connected with a first input end VINP and a second input end VINN, one end of the first triode is connected with a load Z L The laser LD is connected to the output end of the second triode connected with the resistor Rt, and the other end of the laser LD is grounded;
also comprises a resistor R T Resistance Rs the third constant current source I T And a comparator CP, one end of the resistor Rt connected with the first constant current source Ib is set as a positive endThe other end of the resistor Rt is a negative terminal, and the resistor R is T And the third constant current source I T After being connected in series, the two ends are respectively connected between the positive end of the resistor Rt and the ground, and the resistor R T One end of the first constant current source is connected with the positive end of the resistor Rt, and the other end of the first constant current source is connected with the third constant current source I T One input end of the comparator CP is connected with the resistor Rs, one end of the resistor Rs is connected with the negative end of the resistor Rt, the other end of the resistor Rs is connected with the other input end of the comparator CP, and the resistor R is arranged T The other end voltage of the resistor Rs is voltage Vref1, the other end voltage of the resistor Rs is voltage Vout1, and the comparator CP compares the voltage Vref1 with the voltage Vout1 to judge whether the laser driving circuit and the laser LD are open-circuited;
wherein, the resistance value of the resistor Rt is set as R term The resistance R T Has a resistance of R term * N, N is greater than or equal to 1; let the output current of the second constant current source Im be I mod The third constant current source I T Has an output value of
I θ Is less than I th ，I th The threshold current is turned on for the laser LD.
In one embodiment: and a capacitor C S The capacitor C S A filter circuit formed by the resistor Rs and the capacitor C S One end of which is connected to the other end of the resistor Rs, and the other end of which is grounded.
In one embodiment: the resistor Rs and the capacitor C S The time constant is greater than the input duration of the input voltage of the first input terminal or the input voltage of the second input terminal.
In one embodiment: the resistance of the resistor Rs is much greater than the resistance of the resistor Rt.
In one embodiment: the comparator CP is a hysteresis comparator.
Compared with the background technology, the technical scheme has the following advantages:
1. the detection circuit does not affect the working performance of the original drive circuit and the laser LD.
2. The technical scheme skillfully applies the relation between current and voltage drop (ohm law), mathematical formula derivation and reasonable circuit design, and converts the comparison of the current magnitude into the comparison of the voltage magnitude, thereby judging whether the connection between the driving circuit and the laser LD is normal or not.
3. The circuit of the technical scheme is suitable for any external input signal frequency and amplitude, namely, whether the connection between the laser LD and the laser driving circuit is normal or not can be judged for any input signal frequency and amplitude.
4. The laser driving open circuit detection circuit designed by the technical scheme has a simple structure, is easy to realize, and does not need to be powered off or be assisted by an external detection tool.
Drawings
The present invention will be further explained with reference to the drawings and examples.
Fig. 1 is a schematic diagram of a conventional laser LD driving open circuit detection scheme.
Fig. 2 is a schematic diagram of a laser driving circuit according to the first embodiment.
Fig. 3 is a schematic diagram of a laser driving open circuit detection circuit according to the first embodiment.
Fig. 4 is a schematic diagram of a laser driving open circuit detection circuit according to the second embodiment.
Detailed Description
In the first embodiment, please refer to fig. 2 and fig. 3:
the laser drive open circuit detection circuit comprises a laser drive circuit and a laser LD, please refer to fig. 2, wherein the laser drive circuit comprises a first triode and a second triode which can form a differential circuit, the control ends of the first triode and the second triode are respectively and correspondingly connected with a first input end and a second input end, and one end of the first triode is connected with a load Z L The laser LD is connected with one end of the second triode connected with the resistor Rt, and the other end is connected with the input end of the second constant current source Im which is groundedA ground; as shown in fig. 2.
When the laser LD is normally connected with the laser driving circuit, the output current Ib of the first constant current source Ib and the current I of the second constant current source Im are reasonably conducted mod The laser driving circuit and the laser LD can work normally. Defining the average current flowing through the resistor Rt as I term The resistance value of the resistor Rt is R term . As can be seen from the figure, the average current I flowing into the laser LD out Equal to the difference between the average current through the resistor Rt and the average current into the second transistor Q2, i.e.
I out ＝I term -I C2 (1)
In the equilibrium state (VINP = VINN),
i.e. the average current through the second transistor Q2 is
The output current of the second constant current source Im is I mod (ii) a Under normal working condition of laser LD
When the laser LD and the laser driving circuit are disconnected, the average current flowing through the resistor Rt is equal to the average current flowing into the second transistor Q2.
We can compare the average value of the current Iterm with
The size is used for judging whether the laser LD is normally connected with the laser driving circuit.
When the laser LD is normally connected to the laser driving circuit,
there are then the following guide columns:
due to the fact that
Therefore, it is not only easy to use
Wherein, V P For the voltage of node P in the graph, take I θ ＜I th In which I th Starting threshold voltage for laser LD, N is greater than or equal to 1, and when laser LD is in normal operation, I θ ＜I out Is then provided with
Order to
R T ＝N*R term
Therefore, when the laser LD is normally connected to the laser driving circuit,
when the laser LD is disconnected from the laser driving circuit, I out ＝0，
The discrimination actually uses the voltage V OUT1 And V ref1 The magnitude of the voltage drop with respect to node P without the need to accurately calculate V OUT1 And V ref1 The magnitude of the voltage value. To V OUT1 And V ref1 The requirement on the accuracy of the voltage value is not high, so that the complexity of circuit design is greatly reduced.
The laser drive open circuit detection circuit is designed by inequalities (2) and (3), as shown in fig. 3. The laser drive open circuit detection circuit also comprises a resistor R T Resistance Rs the third constant current source I T And a comparator CP, wherein the end of the resistor Rt connected with the first constant current source Ib is set as a positive end, the other end of the resistor Rt is set as a negative end, and the resistor R T And the third constant current source I T After being connected in series, the two ends are respectively connected between the positive end of the resistor Rt and the ground, and the resistor R T One end of the first constant current source is connected with the positive end of the resistor Rt, and the other end is connected with the third constant current source I T One input end of the comparator CP is connected with the resistor R, one end of the resistor Rs is connected with the negative end of the resistor Rt, the other end of the resistor Rs is connected with the other input end of the comparator CP T The voltage at the other end of the resistor Rs is voltage Vref1, the voltage at the other end of the resistor Rs is voltage Vout1, and the comparator CP compares the voltage Vref1 with the voltage Vout1 to judge whether the laser driving circuit and the laser LD are open-circuited;
wherein the resistor R T Has a resistance value of R term * N, N is greater than or equal to 1; the third constant current source I T Has an output value of
I θ Is less than I th ，I th The threshold current is turned on for the laser LD.
And a capacitor C S The capacitor C S A filter circuit formed by the resistor Rs and the capacitor C S One end of which is connected to the other end of the resistor Rs, and the other end of which is grounded. The resistor Rs and the capacitor C S The time constant is larger than the input duration of the input voltage of the first input end or the input voltage of the second input end.
The resistance of the resistor Rs is much greater than the resistance of the resistor Rt. The open circuit detection circuit thus designed has no influence on the performance of the laser driving circuit and the laser LD, and under the condition that the current sources of the laser driving circuit are reasonably configured, for a differential signal pair (the first input end VINP and the second input end VINN) with any input rate and amplitude, the voltage values of the voltage Vout1 and the voltage Vref1 have only very small ripples, and the output state of the comparator CP is only related to the connection state of the laser LD and the laser driving circuit and is not related to the input signal.
In this embodiment, the comparator CP is a hysteresis comparator. When the laser LD is normally connected with the laser driving circuit, V OUT1 ＜V ref1 The comparator CP outputs a low level; when the laser LD is disconnected from the laser driving circuit, V OUT1 ＞V ref1 The comparator CP circuit outputs a high level. The output state of the comparator CP can judge whether the laser LD is normally connected with the driving circuit.
In the second embodiment, please refer to fig. 4:
the laser driving open circuit detection circuit comprises a laser driving circuit and a laser LD, wherein the laser driving circuit comprises a main circuit and two branches which are branched by the main circuit and are connected in parallel, one common end of each branch is connected with the main circuit, the other common end of each branch is grounded, a first constant current source Ib and a resistor Rt are connected in series on the main circuit, one branch is connected in series with a second constant current source Im, the other branch is connected in series with the laser LD, and the laser LD is driven to work by the first constant current source Ib and the second constant current source Im.
According to the same detection principle as the first embodiment, an open circuit detection circuit is designed for the laser driving circuit of the second embodiment, and the open circuit detection circuit further comprises a resistor R T Resistance Rs the third constant current source I T And a comparator CP provided with the resistor Rt and a first constant current source Ib is connected with the other end of the resistor Rt as a positive end and the other end of the resistor R as a negative end T And the third constant current source I T After being connected in series, the two ends are respectively connected between the positive end of the resistor Rt and the ground, and the resistor R T One end of the first constant current source is connected with the positive end of the resistor Rt, and the other end of the first constant current source is connected with the third constant current source I T One input end of the comparator CP is connected with the resistor R, one end of the resistor Rs is connected with the negative end of the resistor Rt, the other end of the resistor Rs is connected with the other input end of the comparator CP T The other end voltage of the resistor Rs is voltage Vref1, the other end voltage of the resistor Rs is voltage Vout1, and the comparator CP compares the voltage Vref1 with the voltage Vout1 to judge whether the laser driving circuit and the laser LD are open-circuited;
wherein, the resistance value of the resistor Rt is set as R term The resistance R T Has a resistance value of R term * N, N is greater than or equal to 1; setting a branch of the current as
The third constant current source I T Has an output value of
I θ Is less than I th ，I th The threshold current is turned on for the laser LD.
Further comprises a capacitor C S The capacitor C S A filter circuit formed by the resistor Rs and the capacitor C S One end of which is connected to the other end of the resistor Rs, and the other end of which is grounded.
The resistance of the resistor Rs is much greater than the resistance of the resistor Rt. The open circuit detection circuit has no influence on the performance of the laser drive circuit and the laser LD, and the output state of the comparator CP is related only to the connection state of the laser LD and the laser drive circuit and is not related to the input signal.
The comparator CP is a hysteresis comparator. When the laser LD is normally connected with the laser driving circuit, V OUT1 ＜V ref1 The comparator CP outputs a low level; when the laser LD is disconnected from the laser driving circuit, V OUT1 ＞V ref1 Comparator CP circuitAnd outputting a high level. The output state of the comparator CP can determine whether the laser LD and the driving circuit are normally connected.
The above description is only a preferred embodiment of the present invention, and therefore the scope of the present invention should not be limited by this description, and all equivalent changes and modifications made within the scope and the specification of the present invention should be covered by the present invention.
Claims (9)
1. The laser driving open circuit detection circuit comprises a laser driving circuit and a laser LD, wherein the laser driving circuit comprises a main circuit and two branches which are branched by the main circuit and are connected in parallel, one common end of each branch is connected with the main circuit, the other common end of each branch is grounded, a first constant current source Ib and a resistor Rt are connected in series on the main circuit, one branch is connected in series with a second constant current source Im, the other branch is connected in series with the laser LD, and the laser LD is driven to work by the first constant current source Ib and the second constant current source Im;
the method is characterized in that: also includes a resistor R T Resistor Rs, third constant current source I T And a comparator CP, wherein the end of the resistor Rt connected with the first constant current source Ib is set as a positive end, the other end of the resistor Rt is set as a negative end, and the resistor R T And the third constant current source I T After being connected in series, the two ends are respectively connected between the positive end of the resistor Rt and the ground, and the resistor R T One end of the first constant current source is connected with the positive end of the resistor Rt, and the other end of the first constant current source is connected with the third constant current source I T One input end of the comparator CP is connected with the resistor R, one end of the resistor Rs is connected with the negative end of the resistor Rt, the other end of the resistor Rs is connected with the other input end of the comparator CP T The other end voltage of the resistor Rs is a voltage Vref1, the other end voltage of the resistor Rs is a voltage Vout1, and the comparator CP compares the voltage Vref1 with the voltage Vout1 to determine whether the laser driving circuit and the laser LD are open-circuited.
2. The laser drive open circuit detection circuit of claim 1, characterized in that: and a capacitor C S The capacitor C S A filter circuit formed by the resistor Rs and the capacitor C S Is connected with the other end of the resistor RsAnd the other end is grounded.
3. The laser drive open circuit detection circuit according to claim 1 or 2, characterized in that: the resistance of the resistor Rs is much larger than that of the resistor Rt.
4. The laser drive open circuit detection circuit of claim 1, characterized in that: the comparator CP is a hysteresis comparator.
5. The laser drive open circuit detection circuit comprises a laser drive circuit and a laser LD, wherein the laser drive circuit comprises a first triode and a second triode which can form a differential circuit, the control ends of the first triode and the second triode are respectively and correspondingly connected with a first input end VINP and a second input end VINN, one end of the first triode is connected with a load Z L The laser LD is connected to the output end of the second triode connected with the resistor Rt, and the other end of the laser LD is grounded;
the method is characterized in that: also includes a resistor R T Resistance Rs the third constant current source I T And a comparator CP, wherein the end of the resistor Rt connected with the first constant current source Ib is set as a positive end, the other end of the resistor Rt is set as a negative end, and the resistor R T And the third constant current source I T After being connected in series, the two ends are respectively connected between the positive end of the resistor Rt and the ground, and the resistor R T One end of the first constant current source is connected with the positive end of the resistor Rt, and the other end of the first constant current source is connected with the third constant current source I T One input end of the comparator CP is connected with the resistor Rs, one end of the resistor Rs is connected with the negative end of the resistor Rt, the other end of the resistor Rs is connected with the other input end of the comparator CP, and the resistor R is arranged T The other end voltage of the resistor Rs is a voltage Vref1, the other end voltage of the resistor Rs is a voltage Vout1, and the comparator CP compares the voltage Vref1 with the voltage Vout1 to determine the laser driving circuit andwhether there is an open circuit between the lasers LD.
6. The laser drive open circuit detection circuit of claim 5, wherein: and a capacitor C S The capacitor C S A filter circuit formed by the resistor Rs and the capacitor C S One end of which is connected to the other end of the resistor Rs, and the other end of which is grounded.
7. The laser drive open circuit detection circuit of claim 6, wherein: the resistor Rs and the capacitor C S The time constant is larger than the input duration of the input voltage of the first input end or the input voltage of the second input end.
8. The laser drive open circuit detection circuit according to claim 5 or 6, characterized in that: the resistance of the resistor Rs is much greater than the resistance of the resistor Rt.
9. The laser drive open circuit detection circuit of claim 5, wherein: the comparator CP is a hysteresis comparator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202122958216.7U CN217606061U (en) | 2021-11-29 | 2021-11-29 | Laser drive open circuit detection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202122958216.7U CN217606061U (en) | 2021-11-29 | 2021-11-29 | Laser drive open circuit detection circuit |
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| Publication Number | Publication Date |
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| CN217606061U true CN217606061U (en) | 2022-10-18 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202122958216.7U Active CN217606061U (en) | 2021-11-29 | 2021-11-29 | Laser drive open circuit detection circuit |
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- 2021-11-29 CN CN202122958216.7U patent/CN217606061U/en active Active
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Address after: 361000 402, No. 52, guanri Road, phase II, software park, Xiamen, Fujian Patentee after: Xiamen Youxun Chip Co.,Ltd. Country or region after: China Address before: 361000 402, No. 52, guanri Road, phase II, software park, Xiamen, Fujian Patentee before: XIAMEN UX HIGH-SPEED IC Co.,Ltd. Country or region before: China |