Gate driving front-end circuit for isolating optocoupler

Abstract

The invention discloses a grid driving front-end circuit for isolating an optocoupler. The grid driving front-end circuit comprises a first photoelectric conversion branch, a second photoelectric conversion branch, a logic control circuit and an output driving circuit, the first photoelectric conversion branch and the second photoelectric conversion branch are respectively used for converting optical signals into photovoltage signals and comparing the photovoltage signals with different reference levels, and the logic control circuit is used for outputting corresponding control signals according to comparison results output by the first photoelectric conversion branch and the second photoelectric conversion branch. Therefore, the output driving circuit is turned on or turned off. According to the gate drive front-end circuit, two signal paths are adopted, the optical signals are converted into the optical voltage signals respectively, then the optical voltage signals are compared with different reference levels respectively, opening transmission delay and closing transmission delay of the gate drive front-end circuit are greatly shortened compared with those of the prior art, the response speed can be effectively increased, and transmission delay of the gate drive front-end circuit is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of integrated circuits, and particularly relates to a gate drive front-end circuit for isolating optocouplers. Background Art

[0002] Opto-coupled drive circuits generally use light-emitting diodes in the input unit to convert electrical signals into optical signals for transmission, and then use photosensitive elements in the output unit to restore the optical signals into electrical signals for driving. They have the advantages of good isolation, small size, simple circuit, high reliability, good switching performance, etc., so they are widely used in fields such as gate drive of high-power devices. For on-chip integrated photodiodes, usually their photocurrent signals are converted into photovoltage signals for processing, and their response speed with the analog front-end is an important part of the overall circuit transmission delay. Therefore, it is necessary to improve the structure of the analog front-end circuit for receiving and converting optical signals to reduce the circuit transmission delay. Summary of the Invention

[0003] Aiming at the deficiencies of the above-mentioned prior art, the technical problem to be solved by the present invention is: to provide a gate drive front-end circuit for isolating optocouplers.

[0004] To solve the above technical problem, the present invention provides the following technical solutions:

[0005] A gate drive front-end circuit for isolating optocouplers, comprising

[0006] A first opto-electric conversion branch, configured to convert an optical signal into a first photovoltage signal, compare it with a first reference level, and output a light-coming judgment signal to a first input end of a logic control circuit according to the comparison result;

[0007] A second opto-electric conversion branch, configured to convert an optical signal into a second photovoltage signal, compare it with a second reference level, and output a light-disappearing judgment signal to a second input end of the logic control circuit according to the comparison result;

[0008] A logic control circuit, configured to output corresponding logic control signals according to the light-coming judgment signal and the light-disappearing judgment signal; and

[0009] An output drive circuit, configured to output a gate drive signal under the control of the logic control signal.

[0010] Further, the first reference level is lower than the second reference level.

[0011] Further, when the logic control circuit detects that the light arrival judgment signal is valid, it outputs a first logic control signal to turn on the output driving circuit and output a gate driving signal; when the logic control circuit detects that the light disappearance judgment signal is valid, it outputs a second logic control signal to turn off the output driving circuit and stop outputting the gate driving signal.

[0012] Further, the first photoelectric conversion branch includes a first photodiode unit, a first transimpedance amplifier, and a first comparator. The first photodiode unit is used to convert an optical signal into a first photocurrent signal; the negative terminal of the first photodiode unit is connected to a power supply, and the positive terminal of the first photodiode unit is electrically connected to the input terminal of the first transimpedance amplifier. The first transimpedance amplifier is used to convert the first photocurrent signal into a first photovoltage signal; the output terminal of the first transimpedance amplifier is electrically connected to the first input terminal of the first comparator, and the second input terminal of the first comparator is connected to a first reference level; the first comparator is used to compare the first photovoltage signal with the first reference level and output a corresponding light arrival judgment signal according to the comparison result. The output terminal of the first comparator serves as the output terminal of the first photoelectric conversion branch and is electrically connected to the first input terminal of the logic control circuit.

[0013] Further, the second photoelectric conversion branch includes a second photodiode unit, a second transimpedance amplifier, and a second comparator. The second photodiode unit is used to convert an optical signal into a second photocurrent signal; the negative terminal of the second photodiode unit is connected to a power supply, and the positive terminal of the second photodiode unit is electrically connected to the input terminal of the second transimpedance amplifier. The second transimpedance amplifier is used to convert the second photocurrent signal into a second photovoltage signal; the output terminal of the second transimpedance amplifier is electrically connected to the first input terminal of the second comparator, and the second input terminal of the second comparator is connected to a second reference level; the second comparator is used to compare the second photovoltage signal with the second reference level and output a corresponding light disappearance judgment signal according to the comparison result. The output terminal of the second comparator serves as the output terminal of the second photoelectric conversion branch and is electrically connected to the second input terminal of the logic control circuit.

[0014] Further, the first input terminal of the first comparator is its non-inverting input terminal, and the second input terminal of the first comparator is its inverting input terminal; when the logic control circuit detects that the light arrival judgment signal flips upward, it determines that the light arrival judgment signal is valid.

[0015] Further, the first input terminal of the second comparator is its non-inverting input terminal, and the second input terminal of the second comparator is its inverting input terminal; when the logic control circuit detects that the light disappearance judgment signal flips downward, it determines that the light disappearance judgment signal is valid.

[0016] Further, the first photodiode unit includes a plurality of first photodiodes connected in parallel, and the second photodiode unit includes a plurality of second photodiodes connected in parallel; the first photodiodes and the second photodiodes correspond to each other one by one and have the same parameters, and the plurality of first photodiodes and the plurality of second photodiodes are arranged alternately and evenly.

[0017] Further, adjust the parameters of the photodiodes in the first photodiode unit and the second photodiode unit according to the required switching speed and the corresponding detection threshold.

[0018] Further, the photodiode parameters include the area of the photodiode.

[0019] In the present invention, two signal paths are adopted. After converting the optical signal into two optical voltage signals respectively, they are compared with different detection thresholds respectively. Among them, the rising edge of the optical voltage signal is compared with a lower detection threshold to determine whether the optical signal comes; the falling edge of the optical voltage signal is compared with a higher detection threshold to determine whether the optical signal disappears; thus, both the turn-on transmission delay and the turn-off transmission delay are greatly shortened compared with the current technology. Therefore, the response speed can be effectively improved and the transmission delay of the gate drive front-end circuit can be reduced. Description of the Drawings

[0020] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0021] Figure 1 It is a structural block diagram of an embodiment of the gate drive front-end circuit for an isolation optocoupler of the present invention.

[0022] Figure 2 It is a layout diagram when the first photodiodes and the second photodiodes are arranged alternately and evenly.

[0023] Figure 3 It is a timing diagram of the gate drive front-end circuit in the prior art during the optical signal conversion process.

[0024] Figure 4 It is a timing diagram of the gate drive front-end circuit for an isolation optocoupler of this embodiment during the optical signal conversion process.

[0025] The reference numerals in the specification are as follows:

[0026] The first optoelectronic conversion branch - 110; the second optoelectronic conversion branch - 120; the logic control circuit - 200; the output driving circuit - 300; the first photodiode unit - PD1; the first photodiodes - PD11, PD12, PD13, PD14; the first transimpedance amplifier - TIA1; the first comparator - CMP1; the second photodiode unit - PD2; the second photodiodes - PD21, PD22, PD23, PD24; the second transimpedance amplifier - TIA2; the second comparator - CMP2; the first reference level - V REF1 ; the second reference level - V REF2 。The first optical voltage signal - I pulse1 ; the second optical voltage signal - I pulse2 ; the light arrival judgment signal - CMP out1 ; the light disappearance judgment signal - CMP out2 。 Detailed implementation manners

[0027] The following uses specific examples to illustrate the implementation manners of the present invention. The diagrams provided in the following embodiments only illustrate the basic concept of the present invention schematically. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0028] Please refer to Figure 1 , Figure 1 which is a structural block diagram of an embodiment of the gate drive front-end circuit for an isolated optocoupler of the present invention. The gate drive front-end circuit for an isolated optocoupler in this embodiment is used for receiving and converting optical signals, and includes a first optoelectronic conversion branch 110, a second optoelectronic conversion branch 120, a logic control circuit 200, and an output driving circuit 300. The first optoelectronic conversion branch 110 is used to convert an optical signal into a first optical voltage signal I pulse1 ,and compare it with the first reference level V REF1 , and output the light arrival judgment signal CMP out1 to the first input end of the logic control circuit 200 according to the comparison result. The second optoelectronic conversion branch 120 is used to convert an optical signal into a second optical voltage signal I pulse2 ,and compare it with the second reference level V REF2 , and output the light disappearance judgment signal CMP out2 to the second input end of the logic control circuit 200 according to the comparison result. The logic control circuit 200 is used to output a corresponding logic control signal according to the light arrival judgment signal CMP out1 and the light disappearance judgment signal CMP out2 . The output driving circuit 300 is used to output a gate drive signal under the control of the logic control signal.

[0029] The first reference level VREF1 below the second reference level V REF2 Generally, the first reference level V REF1 is set to have a level value slightly higher than the low level value, and the second reference level V REF2 is set to have a level value slightly lower than the high level value.

[0030] In this embodiment, the first optoelectronic conversion branch 110 includes a first photodiode unit PD1, a first transimpedance amplifier TIA1, and a first comparator CMP1. The first photodiode unit PD1 is configured to convert an optical signal into a first photocurrent signal. The negative terminal of the first photodiode unit PD1 is connected to the power supply VDD, and the positive terminal of the first photodiode unit PD1 is electrically connected to the input terminal of the first transimpedance amplifier TIA1. The first transimpedance amplifier TIA1 is configured to convert the first photocurrent signal into a first photovoltage signal I pulse1 The output terminal of the first transimpedance amplifier TIA1 is electrically connected to the first input terminal of the first comparator CMP1, and the second input terminal of the first comparator CMP1 is connected to the first reference level V REF1 ; The first comparator CMP1 is configured to compare the first photovoltage signal I pulse1 with the first reference level V REF1 and output a corresponding light arrival determination signal CMP out1 according to the comparison result. The output terminal of the first comparator CMP1 serves as the output terminal of the first optoelectronic conversion branch 110 and is electrically connected to the first input terminal of the logic control circuit 200.

[0031] In this embodiment, the first input terminal of the first comparator CMP1 is its non-inverting input terminal, and the second input terminal of the first comparator CMP1 is its inverting input terminal. When the logic control circuit 200 detects that the light arrival determination signal CMP out1 flips upward (i.e., detects the rising edge of the light arrival determination signal CMP out1 ), it is determined that the light arrival determination signal CMP out1 is valid. Of course, it is also possible to make the first input terminal of the first comparator CMP1 its inverting input terminal and the second input terminal of the first comparator CMP1 its non-inverting input terminal. At this time, when the logic control circuit 200 detects that the light arrival determination signal CMP out1 flips downward (i.e., detects the falling edge of the light arrival determination signal CMP out1 ), it is determined that the light arrival determination signal CMP out1 is valid.

[0032] The second optoelectronic conversion branch 120 includes a second photodiode unit PD2, a second transimpedance amplifier TIA2, and a second comparator CMP2. The second photodiode unit PD2 is configured to convert an optical signal into a second photocurrent signal. The negative terminal of the second photodiode unit PD2 is connected to a power supply VDD, and the positive terminal of the second photodiode unit PD2 is electrically connected to the input terminal of the second transimpedance amplifier TIA2. The second transimpedance amplifier TIA2 is configured to convert the second photocurrent signal into a second photovoltage signal I pulse2 . The output terminal of the second transimpedance amplifier TIA2 is electrically connected to the first input terminal of the second comparator CMP2, and the second input terminal of the second comparator CMP2 is connected to a second reference level V REF2 ; The second comparator CMP2 is configured to compare the second photovoltage signal I pulse2 with the second reference level V REF2 , and output a corresponding light disappearance judgment signal CMP out2 according to the comparison result. The output terminal of the second comparator CMP2 serves as the output terminal of the second optoelectronic conversion branch 120 and is electrically connected to the second input terminal of the logic control circuit 200.

[0033] In this embodiment, the first input terminal of the second comparator CMP2 is its non-inverting input terminal, and the second input terminal of the second comparator CMP2 is its inverting input terminal; when the logic control circuit 200 detects that the light disappearance judgment signal CMP out2 flips downward (i.e., detects the falling edge of the light disappearance judgment signal CMP out2 ), it determines that the light disappearance judgment signal CMP out2 is valid. Of course, it is also possible to make the first input terminal of the second comparator CMP2 its inverting input terminal and the second input terminal of the second comparator CMP2 its non-inverting input terminal. At this time, when the logic control circuit 200 detects that the light disappearance judgment signal CMP out2 flips upward (i.e., detects the rising edge of the light disappearance judgment signal CMP out2 ), it determines that the light arrival judgment signal CMP out1 is valid.

[0034] When the logic control circuit 200 detects that the light arrival judgment signal CMP out1 is valid, it determines that light has arrived, outputs a corresponding first logic control signal, enables the output driving circuit 300 to be turned on, and outputs a gate driving signal to drive a high-power device. When the logic control circuit 200 detects that the light disappearance judgment signal CMP out2 is valid, it determines that the light has disappeared, turns off the output driving circuit 300, and stops the output of the gate driving signal.

[0035] To better ensure the lighting uniformity and reduce the process error, the first photodiode unit PD1 may further include a plurality of first photodiodes connected in parallel. The second photodiode unit PD2 includes a plurality of second photodiodes connected in parallel. The first photodiodes and the second photodiodes correspond to each other one by one and have the same parameters. Both the first photodiodes and the second photodiodes are on-chip integrated photodiodes, and the plurality of first photodiodes and the plurality of second photodiodes are arranged evenly and staggered with each other.

[0036] As Figure 2 shown, it is a layout schematic diagram of eight on-chip integrated photodiodes when the first photodiode unit PD1 and the second photodiode unit PD2 each include four on-chip integrated photodiodes (wherein, the first photodiode unit PD1 includes a first photodiode PD11, a first photodiode PD12, a first photodiode PD13, and a first photodiode PD14, and the second photodiode unit PD2 includes a second photodiode PD21, a second photodiode PD22, a second photodiode PD23, and a second photodiode PD24). The parameters of the first photodiode PD11, the first photodiode PD12, the first photodiode PD13, the first photodiode PD14, the second photodiode PD21, the second photodiode PD22, the second photodiode PD23, and the second photodiode PD24 may be the same.

[0037] Since the process error of on-chip integrated photodiodes may gradually change in a certain direction during actual production and manufacturing, if the first photodiode unit PD1 and the second photodiode unit PD2 each only include one on-chip integrated photodiode, then if the two on-chip integrated photodiodes are arranged side by side, there may be certain performance differences between the first photodiode unit PD1 and the second photodiode unit PD2. By adopting the above-mentioned finger-shaped symmetric arrangement of a plurality of on-chip integrated photodiodes (that is, arranging the first photodiodes and the second photodiodes at intervals and staggering them, and making the distances between adjacent two photodiodes equal), the error caused by the process can be reduced.

[0038] In addition, the parameters of the on-chip integrated photodiodes in the first photodiode unit PD1 and the second photodiode unit PD2 can also be adjusted according to the actual application. In this embodiment, since the first photodiode unit PD1 detects the arrival of light through the rising edge, a large amplitude and fast speed of the rising edge of the current waveform are required; the second photodiode unit PD2 detects the disappearance of light through the falling edge, and a rapid decrease in the photocurrent is required. Therefore, according to actual needs, parameters such as the area of the on-chip integrated photodiodes in the first photodiode unit PD1 and the second photodiode unit PD2 can be adjusted, and then the rising edge / falling edge waveforms can be adjusted to better match the detection threshold (i.e., the voltage values of the first reference level V REF1 and the second reference level V REF2 . That is, when adjusting the magnitudes of the first reference level V REF1 and the second reference level V REF2 , the parameters such as the area of the on-chip integrated photodiodes in the first photodiode unit PD1 and the second photodiode unit PD2 can be adjusted at the same time, so that the first photodiode unit PD1 and the second photodiode unit PD2 can be no longer symmetrically the same, and the response photocurrent waveforms can also be different, so as to change the waveform of the photocurrent pulse to better cooperate with the detection threshold and respond faster), thereby optimizing the transmission delay on both sides and achieving the required switching speed.

[0039] Please refer to Figure 3 . For the timing diagram of the gate drive front-end circuit in the optical signal conversion and processing process in the current technology. In the figure, I pulse is the optical voltage signal converted from the current pulse, V REF is the comparator reference voltage, and CMP out is the comparator output result. When the reference voltage V REF is low, its turn-on transmission delay tPLH is small, while its turn-off transmission delay tPHL is large; when the reference voltage V REF is high, its turn-off transmission delay tPHL is small, while its turn-on transmission delay tPLH is large. And no matter how the value of the reference voltage V REF is adjusted, the transmission delays on both sides always change in the opposite direction and cannot be reduced simultaneously. Especially under the process conditions where the performance of the photodiode is poor (such as weak response, large junction capacitance, etc.), the rising of the current pulse is slow, which will cause extremely high transmission delays.

[0040] The working principle of this embodiment is as follows:

[0041] Please refer to Figure 4, after the input unit of the optical coupling drive circuit (not shown in the figure) converts the input electrical signal into an optical signal using a light-emitting diode, the light simultaneously irradiates the first photodiode unit PD1 and the second photodiode unit PD2, thereby generating almost the same photocurrent on two signal paths of the first photoelectric conversion branch 110 and the second photoelectric conversion branch 120. Among them, the photocurrent generated by the first photodiode unit PD1 is converted into a first optical voltage signal I by the first transimpedance amplifier TIA1 pulse1 , the photocurrent generated by the second photodiode unit PD2 is converted into a second optical voltage signal I by the second transimpedance amplifier TIA2 pulse2 . Since the first reference level V REF1 is less than the second reference level V REF2 , when the value of the first optical voltage signal I pulse1 is greater than the value of the first reference level V REF1 , the first comparator CMP1 flips first (in this embodiment, the light arrival judgment signal CMP out1 flips upward), and the logic control circuit 200 determines that the light arrival judgment signal CMP out1 is valid, outputs a first logic control signal, enables the output drive circuit 300 to turn on, and outputs a gate drive signal to drive the high-power device.

[0042] When the light signal disappears, since the second reference level V REF2 is greater than the first reference level V REF1 , the second comparator CMP2 flips first (in this embodiment, the light disappearance judgment signal CMP out2 flips downward), and the logic control circuit 200 determines that the light disappearance judgment signal CMP out2 is valid, outputs a second logic control signal, enables the output drive circuit 300 to turn off, and stops the output of the gate drive signal. It can be seen from Figure 4 that in this embodiment, after two signal paths are respectively compared with two different detection thresholds, both the turn-on propagation delay tPLH and the turn-off propagation delay tPHL are greatly shortened compared with the current technology. Therefore, the response speed can be effectively improved, and the propagation delay of the gate drive front-end circuit can be reduced.

[0043] In this embodiment, two signal paths are adopted to respectively convert the optical signal into an optical voltage signal (i.e., the first optical voltage signal I pulse1 and the second optical voltage signal I pulse2 ) and then compare them with different detection thresholds respectively. Among them, the rising edge of the optical voltage signal is compared with the lower detection threshold (i.e., the value of the first reference level V REF1 ), and the flipping of the first comparator CMP1 indicates the arrival of the optical signal. The falling edge of the optical voltage signal is compared with the higher detection threshold (i.e., the second reference level V REF2Compared with the value), the inversion of the second comparator CMP2 indicates the disappearance of the optical signal. Its turn-on propagation delay tPLH and turn-off propagation delay tPHL are both greatly shortened compared with the current technology. Therefore, the response speed can be effectively improved, and the propagation delay of the gate drive front-end circuit can be reduced.

[0044] The above embodiments only express the preferred embodiments of the present invention, and the description is relatively specific and detailed. However, it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A gate drive front-end circuit for isolating an optocoupler, characterized in that: include A first photoelectric conversion branch, used for converting the optical signal into a first photovoltage signal, and comparing it with a first reference level, and outputting a light coming judgment signal to a first input terminal of the logic control circuit according to the comparison result; A second photoelectric conversion branch is used to convert the optical signal into a second photovoltage signal, and compare it with a second reference level, and output a light disappearance judgment signal to a second input end of the logic control circuit according to the comparison result; A logic control circuit, used for outputting corresponding logic control signals according to the light coming judgment signal and the light disappearance judgment signal; as well as The output drive circuit is used to output a gate drive signal under the control of a logic control signal.

2. The gate drive front-end circuit for isolating an optocoupler according to claim 1, characterized in that: The first reference level is lower than the second reference level.

3. The gate drive front-end circuit for isolating an optocoupler according to claim 1, characterized in that: The logic control circuit outputs a first logic control signal when detecting that the light is coming and the judgment signal is valid, so that the output drive circuit is turned on and the gate drive signal is output; the logic control circuit outputs a second logic control signal when detecting that the light is disappearing and the judgment signal is valid, so that the output drive circuit is turned off and the gate drive signal is stopped.

4. The gate drive front-end circuit for isolating an optical coupler according to any one of claims 1 to 3, characterized in that: The first photoelectric conversion branch includes a first photodiode unit, a first transimpedance amplifier and a first comparator, wherein the first photodiode unit is used to convert the optical signal into a first photocurrent signal; the negative end of the first photodiode unit is connected to a power supply, the positive end of the first photodiode unit is electrically connected to the input end of the first transimpedance amplifier, and the first transimpedance amplifier is used to convert the first photocurrent signal into a first photovoltage signal; the output end of the first transimpedance amplifier is electrically connected to the first input end of the first comparator, and the second input end of the first comparator is connected to a first reference level; The first comparator is used to compare the first photovoltage signal with the first reference level, and output a corresponding light arrival judgment signal according to the comparison result. The output end of the first comparator is electrically connected to the first input end of the logic control circuit as the output end of the first photoelectric conversion branch.

5. The gate drive front-end circuit for isolating an optical coupler according to claim 4, characterized in that: The second photoelectric conversion branch includes a second photodiode unit, a second transimpedance amplifier and a second comparator, wherein the second photodiode unit is used to convert the optical signal into a second photocurrent signal; the negative end of the second photodiode unit is connected to a power supply, the positive end of the second photodiode unit is electrically connected to the input end of the second transimpedance amplifier, and the second transimpedance amplifier is used to convert the second photocurrent signal into a second photovoltage signal; the output end of the second transimpedance amplifier is electrically connected to the first input end of the second comparator, and the second input end of the second comparator is connected to a second reference level; The second comparator is used to compare the second photovoltage signal with the second reference level, and output a corresponding light disappearance judgment signal according to the comparison result. The output end of the second comparator is electrically connected to the second input end of the logic control circuit as the output end of the second photoelectric conversion branch.

6. The gate drive front-end circuit for isolating an optical coupler according to claim 5, characterized in that: The first input terminal of the first comparator is its in-phase input terminal, and the second input terminal of the first comparator is its inverting input terminal; when the logic control circuit detects that the light coming judgment signal flips upward, it determines that the light coming judgment signal is valid.

7. The gate drive front-end circuit for isolating an optical coupler according to claim 5, characterized in that: The first input terminal of the second comparator is its in-phase input terminal, and the second input terminal of the second comparator is its inverting input terminal; when the logic control circuit detects that the light disappearance judgment signal flips downward, it determines that the light disappearance judgment signal is valid.

8. The gate drive front-end circuit for isolating an optical coupler according to claim 5, characterized in that: The first photodiode unit includes a plurality of first photodiodes connected in parallel, and the second photodiode unit includes a plurality of second photodiodes connected in parallel; the first photodiodes and the second photodiodes correspond one to one and have the same parameters, and the plurality of first photodiodes and the plurality of second photodiodes are arranged uniformly and staggered with each other.

9. The gate drive front-end circuit for isolating an optical coupler according to claim 5, characterized in that: Photodiode parameters in the first photodiode unit and the second photodiode unit are adjusted according to the required switching speed and the corresponding detection threshold.

10. The gate drive front-end circuit for isolating an optocoupler according to claim 9, characterized in that: The photodiode parameters include the area of ​​the photodiode.

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