Gate driving circuit applied to optocoupler
By optimizing the design of the optocouple isolation gate driving circuit, the use of digital logic function modules and PMOS/NMOS tubes with large width and length ratios is used to solve the problems of high power consumption, long delay and undervoltage locking of the existing optocouple isolation gate driving circuits, and realize the optocouple isolation gate driving circuit with low power consumption, fast response and high reliability.
Patent Information
- Application Number
- CN202510276227.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-10
- Publication Date
- 2025-07-01
AI Technical Summary
The existing optocouple isolation gate driving circuits have problems such as high power consumption, large transmission delay, slow response speed and insufficient noise resistance. They are particularly outstanding in high-frequency switching applications, and the lack of undervoltage locking function affects system reliability.
The circuit design is adopted including photodiode module, TIA module, comparator and digital logic function module. Through the digital logic function module and the optimized driver circuit output submodule, combined with Zener diode and PMOS/NMOS tube with large width and length ratio, the rapid signal processing and low power output are achieved.
It significantly reduces the static and dynamic power consumption of the circuit, reduces signal transmission delay, improves response speed, enhances noise immunity, and has hysteresis function and undervoltage locking protection, improving the reliability and safety of the system.
Smart Images
Figure CN120238117A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of optocoupler isolation, and relates to a gate drive circuit applied to an optocoupler. Background Art
[0002] Optocoupler isolation technology is a technology that realizes electrical isolation through optical signals and is widely used in fields such as power electronics, communication, and industrial control. An optocoupler isolator usually consists of a light-emitting diode (LED), a photodetector, and a signal processing circuit. Its working principle is: when a voltage is applied to the input terminal, the light-emitting diode emits light, the photodetector receives the optical signal and generates a photocurrent, and then outputs a corresponding electrical signal through the signal processing circuit. Since the transmission of optical signals is not affected by electromagnetic interference, optocoupler isolators have high anti-interference ability and electrical isolation performance, so they are widely used in high-voltage and high-noise environments.
[0003] In the field of power electronics, optocoupler isolators are often used to drive high-voltage power devices such as IGBTs (Insulated Gate Bipolar Transistors) and VDMOSs (Vertical Double-Diffused Metal Oxide Semiconductors). These power devices usually require relatively high gate drive voltage and current, and optocoupler isolators can provide electrical isolation to ensure safe isolation between the control circuit and the power circuit. However, there are some technical bottlenecks in the existing optocoupler isolation gate drive circuits in practical applications, mainly including the following aspects:
[0004] 1. The existing optocoupler isolation gate drive circuits usually adopt traditional analog circuit designs. The photodetector and signal processing circuit in the circuit will generate a large static current during operation, resulting in relatively high overall power consumption. Especially in high-frequency switching applications, the dynamic power consumption of the circuit will also increase significantly, which not only increases the heat dissipation burden of the system but also limits its use in low-power applications.
[0005] 2. The signal transmission path of the optocoupler isolation gate drive circuit is relatively long and usually includes multiple links such as photoelectric conversion, current-voltage conversion, signal amplification, and logic processing. Each link will introduce a certain delay. Especially in high-frequency switching applications, these delays will accumulate, resulting in a decrease in the overall response speed. For application scenarios that require fast response (such as high-frequency switching power supplies, motor drives, etc.), the existing optocoupler isolation gate drive circuits often cannot meet the requirements.
[0006] 3. The existing optocoupler isolation gate drive circuits usually adopt analog signal processing methods. The photocurrent generated by the photodetector is amplified and filtered, and then processed through a comparator or logic circuit. Although this processing method can realize signal isolation and transmission, due to the bandwidth limitation of analog circuits, the overall response speed is relatively slow. In addition, the noise and interference in analog circuits will also affect the accuracy and stability of signals, further reducing the response speed of the circuit.
[0007] 4. In practical applications, the optocoupler isolation gate drive circuit may be affected by external factors such as optical noise and electromagnetic interference, resulting in false opening and closing phenomena. Especially in a high-noise environment, the photodetector may receive unexpected optical signals, leading to unstable output signals. Existing optocoupler isolation gate drive circuits usually lack effective noise suppression and false opening and closing protection mechanisms, resulting in a decrease in the reliability of the system.
[0008] 5. In some high-voltage applications, the power supply voltage may fluctuate or be undervoltage. Existing optocoupler isolation gate drive circuits usually lack undervoltage lockout function. When the power supply voltage is lower than a certain threshold, the circuit may not work properly, resulting in misoperation or damage of the power device. The lack of undervoltage lockout function not only affects the reliability of the system but also increases the maintenance cost of the system.
[0009] In view of the above problems, existing technical solutions mainly focus on optimizing the sensitivity of the photodetector, improving the bandwidth and noise suppression ability of the signal processing circuit, etc. However, these solutions can only achieve limited improvements in one aspect and cannot fundamentally solve problems such as high power consumption, large transmission delay, and slow response speed. Therefore, there is an urgent need for a new type of optocoupler isolation gate drive circuit that can significantly reduce power consumption, reduce transmission delay, and improve response speed while ensuring electrical isolation performance. Summary of the Invention
[0010] In view of this, the purpose of the present invention is to provide a gate drive circuit applied to an optocoupler, which reduces the transmission delay after receiving a signal and improves the overall response speed.
[0011] To achieve the above purpose, the present invention provides the following technical solutions:
[0012] A gate drive circuit applied to an optocoupler, which includes a photodiode module, a TIA module, a comparator, and a digital logic function module.
[0013] Among them, the photodiode module includes two photodiodes formed on the same substrate; one of the photodiodes is subjected to light shielding treatment, and the photodiode subjected to light shielding treatment only generates dark current. The photodiode subjected to light shielding treatment is connected to the negative input terminal of the TIA module, and the photodiode not subjected to light shielding treatment is connected to the positive input terminal of the TIA module.
[0014] The photodiode without light shielding receives the optical signal to generate a photocurrent, and the photocurrent is transmitted to the positive input terminal of the TIA module; the TIA module converts the current signal into a voltage signal and outputs it to the two input terminals of the comparator through two output terminals; the comparator compares the voltages at the two input terminals and outputs the comparison result to the digital logic function module; the digital logic function module outputs a driving signal of high level or low level according to the comparison result of the comparator. Among them, when the photocurrent generated by the photodiode without light shielding makes the voltage at the positive output terminal of the TIA module higher than the voltage at the negative output terminal, the output of the comparator will flip.
[0015] Further, both photodiodes are connected in reverse bias, that is, the cathode of the photodiode is connected to the high potential and the anode is connected to the low potential.
[0016] Further, the gate driving circuit further includes a reference circuit module, and the reference circuit module provides reference voltages for the TIA module, the comparator and the digital logic function module respectively.
[0017] Further, the digital logic function module includes a digital function sub-module and a driving circuit output sub-module. The digital function sub-module obtains a control signal of high level or low level according to the reference voltage provided by the reference circuit module and the voltage output by the comparator; the driving circuit output sub-module outputs a driving signal of high level or low level according to the control signal.
[0018] Further, the digital function sub-module includes Zener diodes D1 and D2, resistors R1 and R2, and an AND gate. The negative electrode of the Zener diode D1 is connected to the power supply voltage, and the positive electrode is grounded through the series-connected resistors R1 and R2; a voltage V1 is led out at the connection point of the resistors R1 and R2, the negative electrode of the Zener diode D2 is connected to the voltage V1, and the positive electrode is grounded; the first input terminal of the AND gate is connected to the voltage V1, the second input terminal is connected to the voltage V2 output by the comparator, and outputs a control signal VO of high level or low level.
[0019] In the digital function sub-module, by adjusting the ratio of the two resistors R1 and R2, the undervoltage lockout threshold of the entire circuit can also be adjusted, so that the circuit has an undervoltage lockout function.
[0020] Further, according to the control signal VO output by the digital function sub-module, two sets of voltages Vn and Vp with different ranges are generated through the reference voltage module and the voltage conversion module, where the voltage Vn is less than the voltage Vp; the voltages Vn and Vp are transmitted to the driving circuit output sub-module, and the driving circuit output sub-module outputs a driving signal of high level or low level according to the values of the voltages Vn and Vp.
[0021] Further, the driving circuit output sub-module includes a PMOS transistor and an NMOS transistor. The source of the PMOS transistor is connected to the power supply voltage, the drain is connected to the drain of the NMOS transistor, and the source of the NMOS transistor is grounded; the gate of the PMOS transistor is connected to the voltage Vp, and the gate of the NMOS transistor is connected to the voltage Vn. According to the values of the voltages Vn and Vp, a driving signal is output by either the PMOS transistor or the NMOS transistor. When the driving signal is output by the PMOS transistor, the driving signal is at a high level; when the driving signal is output by the NMOS transistor, the driving signal is at a low level.
[0022] The beneficial effects of the present invention are as follows:
[0023] (1) By adopting a digital logic function module and an optimized driving circuit output sub-module, the present invention significantly reduces the static and dynamic power consumption of the circuit. The Zener diode and resistor network in the digital logic function module can effectively control the power consumption of the circuit, and the PMOS and NMOS transistors in the driving circuit output sub-module are designed with a large aspect ratio, further reducing the power consumption of the circuit.
[0024] (2) By optimizing the signal transmission path, the present invention reduces the signal processing links and significantly reduces the transmission delay. The photocurrent generated by the photodiode module is directly transmitted to the TIA module, and after being processed by the comparator and the digital logic function module, a driving signal is quickly output. This simplified signal transmission path effectively reduces the delay and improves the response speed of the circuit.
[0025] (3) By adopting a high-speed comparator and a digital logic function module, the present invention significantly improves the response speed of the circuit. The comparator can quickly judge the magnitude of the input voltage and output a corresponding logic signal, and the digital logic function module can quickly generate a driving signal according to the output signal of the comparator. This design enables the circuit to achieve a fast response in high-frequency switching applications.
[0026] (4) By introducing a hysteresis function, the present invention effectively reduces the occurrence of false turn-off phenomena. The Zener diode and resistor network in the digital logic function module can form a circuit with a hysteresis function. When there is noise or interference in the input signal, the circuit can maintain a stable output state, avoiding the occurrence of false turn-off phenomena.
[0027] (5) By adjusting the resistance ratio in the digital logic function module, the present invention realizes an under-voltage lockout function. When the power supply voltage is lower than a certain threshold, the circuit can automatically lock the output state to avoid misoperation or damage of the power devices. This under-voltage lockout function improves the reliability and safety of the system.
[0028] In summary, through innovative circuit design and structural optimization, the present invention significantly improves the performance of the gate drive circuit applied to the optocoupler, and has characteristics such as reducing power consumption, reducing transmission delay, increasing response speed, malfunction protection, and undervoltage lockout function.
[0029] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be learned from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following specification. Brief Description of the Drawings
[0030] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:
[0031] Figure 1 It is a schematic structural diagram of a gate drive circuit applied to an optocoupler provided by an embodiment of the present invention;
[0032] Figure 2 It is a schematic structural diagram of a photodiode;
[0033] Figure 3 It is a schematic structural diagram of a digital function module;
[0034] Figure 4 It is a schematic diagram of a drive circuit output module. Detailed Description of the Embodiments
[0035] The following uses specific specific examples to illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.
[0036] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation to the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged, or reduced, and do not represent the dimensions of actual products; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.
[0037] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and should not be construed as a limitation of the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.
[0038] As Figure 1 shown, a gate drive circuit applied to an optocoupler provided by an embodiment of the present invention includes a photodiode module, a reference circuit module, a TIA module, a comparator module, and a digital logic function module.
[0039] Among them, the photodiode module includes two photodiodes formed on the same substrate, and one of the photodiodes is shielded by a metal cover. The cathodes of these two photodiodes are connected to a set of positive voltages Vb generated inside the circuit, and the anodes are respectively connected to the input terminals of the TIA module. The anode of the shielded photodiode is connected to the negative input terminal of the TIA module.
[0040] The two output terminals of the TIA module are connected to the input terminals of the comparator module. After the comparator determines the magnitudes of the two voltage values, it outputs a high level or a low level.
[0041] The digital logic function module receives the output signal of the comparator and outputs a logic high level or a logic low level according to the result of the comparator.
[0042] The reference circuit module provides a reference voltage for the corresponding circuit.
[0043] The working principle of this gate drive circuit is as follows: When there is no light irradiation, no photocurrent is generated in both photodiodes. The voltage at the negative output terminal of the TIA module is higher than the voltage at the positive output terminal. After passing through the comparator module and the digital logic function module, a low level is output; when there is light irradiation, the unshielded photodiode generates a photocurrent that is linearly related to the light intensity, causing the voltage at the positive output terminal of the TIA module to increase. When the photocurrent is large enough, the voltage at the positive output terminal of the TIA module is greater than the voltage at the negative output terminal, and the comparator module flips at this time. Finally, the entire circuit outputs a high level of 30V.
[0044] The overall structure of the gate drive circuit applied to the optocoupler provided by the present invention is simple, and the electrical signal transmission path is not complex. The transmission delay can be adjusted by the device size.
[0045] As Figure 2As shown in the photodiode module described above, it can be seen that in the photodiode, a deep N-well is formed on the P-type substrate as the cathode of the photodiode, and the deep N-well is in contact with a high potential. Additionally, a partial region is dug out in the deep N-well to form a P-well for doping P-type carriers to form the anode of the photodiode, and the anode is at a low potential. The anode of the photodiode is connected to a low potential, and the cathode is connected to a high potential. This connection method can ensure that the photodiode is in a reverse-biased state, thereby enabling the photocurrent to vary linearly with the light intensity.
[0046] In addition, the photodiode module is composed of two photodiodes with a symmetric structure. One photodiode can receive light normally without treatment, while the other photodiode is shielded by a top metal cover and only generates dark current, thereby suppressing the influence of dark current on the circuit result. The photocurrent of the photodiode is converted into a voltage signal through the subsequent TIA module circuit and then forms a high-speed rail-to-rail output in the comparator module circuit.
[0047] The digital logic function module described above includes a digital function sub-module and a drive circuit output sub-module. Among them, the digital function sub-module includes a resistor, a Zener diode, and a two-input AND gate. As Figure 3 shown, the negative electrode of the Zener diode D1 is connected to the power supply VCC, and the positive electrode is grounded through two series resistors R1 and R2; at the connection point of the two resistors, the voltage V1 is led out as one input of the AND gate; at the same time, the negative electrode of the Zener diode D2 is connected to the voltage V1, and the positive electrode is grounded.
[0048] In the digital function sub-module, during the process of VCC changing from 0 to 30V, if there is light illumination at the front end causing the photodiode to generate photocurrent, the output voltage V2 of the comparator is constantly at a high level at this time. Due to the existence of the Zener diode, when the voltage across its two ends or the power supply voltage is less than the reverse breakdown voltage, the voltage V1 is basically 0; when the power supply voltage is greater than the breakdown voltage, current starts to flow through the resistor, but under normal operating conditions, no matter how much the power supply voltage increases, the voltage V1 increases to the breakdown voltage of the Zener diode and then basically remains unchanged. At this time, V1 also changes from a low level to a high level, and the output V0 changes to a high level in the control signal, enabling the subsequent output circuit to output a high voltage of 30V. Therefore, introducing a hysteresis unit into this circuit can form a circuit with an under-voltage lockout function. Among them, the under-voltage lockout threshold of the entire circuit can be adjusted by adjusting the ratio of the two resistors R1 and R2.
[0049] The drive circuit output sub-module is composed of a PMOS transistor and an NMOS transistor, as Figure 4As shown in the figure, the source of the PMOS transistor is connected to the power supply VCC, the drain is connected to the drain of the NMOS transistor, and the source of the NMOS transistor is grounded. The connection point between the drain of the PMOS transistor and the drain of the NMOS transistor leads out the voltage Vout, which serves as the output of the digital logic function module. Among them, the gate of the PMOS transistor is connected to the voltage Vp, and the gate of the NMOS transistor is connected to the voltage Vn. The voltages Vp and Vn are from Figure 3 the output voltage VO of the digital function sub-module shown. Specifically, the reference circuit module and the voltage conversion module generate two sets of voltages Vn and Vp according to the voltage VO. The voltage range of Vn is 0 to 5V, and the voltage range of Vp is 25 to 30V. Among them, when VO is the low level 0V, Vn is 0V and Vp is 25V; when VO is the high level 30V, Vn is 5V and Vp is 30V. This can drive the MOS transistors operating at 5V without having to select devices operating at 30V, thereby reducing the circuit power consumption.
[0050] In the driving circuit output sub-module, both the PMOS transistor and the NMOS transistor use a large width-to-length ratio to ensure that a large current can be driven at the back end. At the same time, the |Vgs| of these two MOS transistors is less than 5V. High-voltage N-type and P-type transistors with thin gate oxides can be selected, thereby greatly reducing the device size, reducing the parasitic capacitance, and improving the chip response speed. VCC is the power supply voltage of 30V, VEE is grounded, the voltage range of Vn is 0 to 5V, and the voltage range of Vp is 25 to 30V. And Vn and Vp are relatively co-directional voltages, that is, when Vn is 5V, Vp is guaranteed to be 30V. At this time, the lower NMOS transistor drives the output and the PMOS transistor does not work, and the output Vout of the driving circuit output sub-module is the low level of 0V; conversely, when Vn is 0, Vp is guaranteed to be 25V. At this time, the lower NMOS transistor does not work and the PMOS transistor drives the output, and the output Vout of the driving circuit output sub-module is the high level of 30V. In either case, only one MOS transistor works normally, thereby preventing the MOS transistor from being burned out due to simultaneous conduction.
[0051] In summary, the present invention proposes a gate driving circuit applied to an optocoupler. The overall structure of the circuit is simple, and the electrical signal transmission path is not complex, which can improve the overall response speed of the circuit, and the transmission delay can be adjusted by the device size; in addition, the gate driving circuit also has a hysteresis function, which can effectively reduce the mis-opening situation and support undervoltage locking.
[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.
Claims
1. A gate drive circuit for an optocoupler, characterized in that: It includes a photodiode module, a TIA module, a comparator and a digital logic function module; the photodiode module generates a current according to the light signal, and the current is transmitted to the input end of the TIA module; the TIA module converts the current signal into a voltage signal and outputs it to the input end of the comparator through two output ends; the comparator compares the voltages of the two input ends and outputs the comparison result to the digital logic function module; The digital logic function module outputs a high level or low level driving signal according to the comparison result of the comparator.
2. The gate drive circuit for an optical coupler according to claim 1, characterized in that: The photodiode module includes two photodiodes formed on the same substrate; one of the photodiodes is shielded and only generates dark current; the photodiode that is shielded is connected to the negative input terminal of the TIA module, and the photodiode that is not shielded is connected to the positive input terminal of the TIA module.
3. The gate drive circuit for optical coupler according to claim 2, characterized in that: The two photodiodes are both reverse-biased connected, that is, the cathode of the photodiode is connected to a high potential, and the anode is connected to a low potential.
4. The gate driving circuit for an optical coupler according to claim 1, characterized in that: It also includes a reference circuit module, which provides reference voltages for the TIA module, the comparator and the digital logic function module respectively.
5. The gate drive circuit for optical coupler according to claim 1 or 4, characterized in that: The digital logic function module includes a digital function sub-module and a drive circuit output sub-module; the digital function sub-module obtains a high-level or low-level control signal according to the reference voltage provided by the reference circuit module and the voltage output by the comparator; the drive circuit output sub-module outputs a high-level or low-level drive signal according to the control signal.
6. The gate driving circuit for optical coupler according to claim 5, characterized in that: The digital function submodule includes Zener diodes D1 and D2, resistors R1 and R2, and an AND gate; wherein the cathode of the Zener diode D1 is connected to the power supply voltage, and the anode is grounded through the series-connected resistors R1 and R2; a voltage V1 is drawn at the connection point of the resistors R1 and R2, the cathode of the Zener diode D2 is connected to the voltage V1, and the anode is grounded; the first input terminal of the AND gate is connected to the voltage V1, the second input terminal is connected to the voltage V2 output by the comparator, and a high-level or low-level control signal VO is output.
7. The gate driving circuit for an optical coupler according to claim 6, characterized in that: According to the control signal VO, two groups of voltages of different ranges, Vn and Vp, are generated through a reference voltage module and a voltage conversion module, wherein the voltage Vn is less than the voltage Vp; the voltages Vn and Vp are transmitted to a drive circuit output submodule, and the drive circuit output submodule outputs a drive signal according to the values of the voltages Vn and Vp.
8. The gate driving circuit for optical coupler according to claim 7, characterized in that: The drive circuit output submodule includes a PMOS tube and an NMOS tube; the source of the PMOS tube is connected to the power supply voltage, the drain is connected to the drain of the NMOS tube, and the source of the NMOS tube is grounded; the gate of the PMOS tube is connected to the voltage Vp, and the gate of the NMOS tube is connected to the voltage Vn, and the driving signal is output by the PMOS tube or the NMOS tube according to the values of the voltages Vn and Vp.