An electrostatic discharge protection circuit and method for an intelligent power module

Abstract

This application relates to an electrostatic discharge (ESD) protection circuit and method for an intelligent power module. The ESD protection circuit includes: an intelligent power module comprising a high-voltage drive circuit, a low-voltage drive circuit, and power devices; the low-voltage drive circuit having a first reference ground terminal, and the power devices having a second reference ground terminal; the ESD protection circuit includes an ESD protection module connected in series between the first and second reference ground terminals; the ESD protection module includes a first ESD device and a second ESD device, which are connected in reverse series to form a bidirectional ESD discharge path. This invention, by setting a dedicated back-to-back ESD protection structure between the drive ground and the power ground, has the advantages of a short discharge path, fast response speed, simple circuit structure, and low cost, while effectively improving the anti-static capability and system reliability of the intelligent power module.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to an electrostatic discharge protection circuit and method for an intelligent power module. Background Technology

[0002] Intelligent power modules are power modules that integrate driver chips and power devices (such as insulated-gate bipolar transistors and metal-oxide-semiconductor field-effect transistors) into a single package. They are widely used in home appliance drives, industrial frequency conversion, and new energy fields. Because intelligent power modules contain both high-voltage power circuits and low-voltage control circuits with a significant potential difference between them, electrostatic discharge (ESD) is highly likely to occur during module manufacturing, transportation, and actual use. This is especially true between the reference ground of the driver chip and the ground of the power devices. When ESD accumulates and the discharge path is obstructed, it can cause failures such as gate oxide layer breakdown and logic circuit latch-up within the driver chip, severely impacting the module's reliability and lifespan.

[0003] Currently, the industry offers various solutions for electrostatic discharge (ESD) protection of smart power modules. One common approach relies on the high-voltage junction termination region of the driver chip itself to withstand ESD voltage. However, this method places significant pressure on the layout design of the high-voltage driver chip, requiring a large internal voltage withstand space, leading to increased chip area and cost. Another solution involves introducing the power chip's ground into the low-voltage driver chip, connecting it to the low-voltage driver chip's power supply terminal via an ESD diode, and then forming a discharge path through an ESD diode between the power supply terminal and the common terminal. However, this solution requires multiple diodes connected in series for discharge, resulting in a long overall discharge path, high equivalent impedance, limited ESD response speed, and potential coupling between signal ground and power ground through the power supply loop, which may interfere with the integrity of the drive signal. Yet another solution involves setting a bidirectional diode string structure between the functional chip's ground and the low-voltage driver chip's ground. However, this structure typically requires multiple diodes connected in series, occupying a large area of ​​the low-voltage driver chip, increasing process complexity, and hindering cost control. Summary of the Invention

[0004] Therefore, it is necessary to provide an electrostatic discharge protection circuit and method for intelligent power modules to address the aforementioned technical problems.

[0005] In a first aspect, this application discloses an electrostatic discharge protection circuit for an intelligent power module. The intelligent power module includes a high-voltage drive circuit, a low-voltage drive circuit, and power devices. The low-voltage drive circuit has a first reference ground terminal, and the power devices have a second reference ground terminal. The electrostatic discharge protection circuit includes an electrostatic discharge protection module connected in series between the first reference ground terminal and the second reference ground terminal. The electrostatic discharge protection module includes a first electrostatic discharge device and a second electrostatic discharge device. The first electrostatic discharge device and the second electrostatic discharge device are connected in reverse series to form a bidirectional electrostatic discharge path.

[0006] Furthermore, the anode of the first electrostatic discharge device is connected to the first reference ground terminal, the cathode of the first electrostatic discharge device is connected to the cathode of the second electrostatic discharge device, and the anode of the second electrostatic discharge device is connected to the second reference ground terminal.

[0007] Furthermore, the electrostatic protection module is integrated inside the chip of the low-voltage drive circuit.

[0008] Furthermore, the power device is an insulated gate bipolar transistor (IGBT), and the emitter of the IGBT serves as the second reference ground.

[0009] Furthermore, the power device is a metal-oxide-semiconductor field-effect transistor (MOSFET), and the source of the MOSFET serves as the second reference ground terminal.

[0010] Furthermore, the second reference ground terminal is introduced into the chip of the low-voltage driving circuit by wire bonding.

[0011] On the other hand, this application also discloses an electrostatic discharge protection method for a smart power module, comprising the following steps:

[0012] Inside the intelligent power module, the first reference ground terminal of the low-voltage drive circuit and the second reference ground terminal of the power device are identified to confirm that there is no direct electrical connection between the two under normal operating conditions.

[0013] An electrostatic discharge (ESD) protection module is connected in series between the first reference ground terminal and the second reference ground terminal. The ESD protection module is composed of a first ESD device and a second ESD device connected in reverse series to form a bidirectional ESD discharge path.

[0014] When an electrostatic discharge event occurs, if the potential of the first reference ground terminal is higher than that of the second reference ground terminal, the first electrostatic discharge device is forward-biased, and the electrostatic charge flows from the first reference ground terminal through the first electrostatic discharge device to the second reference ground terminal for discharge; if the potential of the second reference ground terminal is higher than that of the first reference ground terminal, the second electrostatic discharge device is forward-biased, and the electrostatic charge flows from the second reference ground terminal through the second electrostatic discharge device to the first reference ground terminal for discharge.

[0015] Furthermore, both the first electrostatic discharge device and the second electrostatic discharge device are implemented using a gate-grounded metal-oxide-semiconductor diode structure.

[0016] Furthermore, the bidirectional electrostatic discharge path is independent of the power supply circuit and signal circuit of the intelligent power module. Under normal operating conditions, both the first electrostatic discharge device and the second electrostatic discharge device are in a reverse cutoff state.

[0017] Furthermore, the electrostatic discharge protection module is integrated inside the chip of the low-voltage driving circuit, and the second reference ground terminal is introduced into the chip of the low-voltage driving circuit by wire bonding; the layout of the first electrostatic discharge device and the second electrostatic discharge device adopts a multi-finger structure or an interdigitated structure.

[0018] The electrostatic discharge (ESD) protection circuit and method of the aforementioned intelligent power module achieve the following beneficial effects: This application constructs a dedicated ESD discharge channel by directly setting two back-to-back series ESD devices between the driver chip reference ground and the power device ground. ESD charges can be directly discharged between the two grounds without passing through the power supply terminal or other intermediate nodes. The discharge path is short, and the equivalent impedance is low, enabling transient high voltage to be clamped to a safe range in a very short time, effectively preventing the gate oxide layer of the power device from being broken down due to ESD overvoltage. Furthermore, this application only requires adding two small ESD devices inside the low-voltage driver chip to achieve bidirectional ESD protection. Compared to the traditional bidirectional diode string scheme, the number of devices is significantly reduced, the chip area occupied is small, the process implementation is simple, no additional external components are required, reducing material costs and printed circuit board layout complexity, facilitating mass production, and improving production efficiency and product consistency. On the other hand, the ESD discharge path of this application is independent of the main power supply circuit and signal circuit. Under normal operating conditions, both ESD devices are in a reverse cutoff state, which will not interfere with the transmission of the drive signal, avoiding the signal noise problems that may be introduced by the traditional disconnected ground connection scheme. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of an electrostatic discharge protection circuit for a smart power module in one embodiment.

[0020] Figure 2 This is a schematic diagram of the electrostatic discharge protection circuit of a GGMOS-type clamped-to-gate drive terminal smart power module in one embodiment.

[0021] Figure 3 This is a schematic diagram of the electrostatic discharge protection circuit of a GGMOS-type clamped-to-power-ground smart power module in one embodiment;

[0022] Figure 4 This is a schematic diagram of the electrostatic discharge protection circuit of an intelligent power module in one embodiment, in which a PNP bipolar transistor is clamped to the gate drive terminal. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0024] like Figure 1 As shown, this embodiment provides an electrostatic discharge protection circuit for an intelligent power module. The intelligent power module is entirely encapsulated within a single module housing, and internally includes a high-voltage drive circuit, a low-voltage drive circuit, and power devices. The high-voltage drive circuit drives the upper bridge arm power switching device, and the low-voltage drive circuit drives the lower bridge arm power switching device. The low-voltage drive circuit has a first reference ground terminal, i.e., the common reference ground terminal of the drive chip; the power devices have a second reference ground terminal, i.e., the negative terminal of the power circuit.

[0025] In this embodiment, the core of the electrostatic discharge protection circuit is an electrostatic discharge protection module, which is connected in series between the first reference ground terminal and the second reference ground terminal. The electrostatic discharge protection module includes a first electrostatic discharge device and a second electrostatic discharge device. The first electrostatic discharge device and the second electrostatic discharge device are connected in reverse series, which is commonly known as a back-to-back series structure, thereby forming a bidirectional electrostatic discharge path.

[0026] Specifically, combined Figure 2 and Figure 3 As shown, two different protection circuits are disclosed, in which, Figure 2 This is an electrostatic discharge protection circuit for a GGMOS (Gate-Grounded NMOSFET) type clamped-to-gate drive intelligent power module. Figure 3Both are electrostatic discharge (ESD) protection circuits for GGMOS-type clamped-to-power-ground intelligent power modules, and both use gate-grounded metal-oxide-semiconductor field-effect transistors (MOSFETs) as ESD protection devices. Their device types, symbolic representations, and source-to-ground common-terminal configurations are identical. The difference lies in the drain discharge connection node: (See attached diagram). Figure 2 In the middle, the drains of two gate-grounded metal-oxide-semiconductor field-effect transistors are shorted and then connected upwards to the output terminal of the gate of the insulated-gate bipolar transistor driven by the low-voltage drive circuit. This protects against electrostatic discharge stress between the logic ground and the gate drive signal line, preventing gate oxide breakdown. (Attached) Figure 3 In this configuration, the drains of two gate-grounded metal-oxide-semiconductor field-effect transistors (MOSFETs) are shorted and connected to the power ground pin (i.e., the emitter of the lower transistor) to protect against electrostatic discharge stress between the logic ground and power ground, preventing the potential difference between the two grounds from breaking down the internal circuitry of the low-voltage drive. Both devices cover different pin combinations of electrostatic discharge paths. Specifically, the anode of the first electrostatic discharge device is connected to the first reference ground, the cathode of the first electrostatic discharge device is connected to the cathode of the second electrostatic discharge device, and the anode of the second electrostatic discharge device is connected to the second reference ground. Thus, when the potential of the first reference ground is higher than that of the second reference ground and the voltage difference reaches the forward conduction threshold of the electrostatic discharge device, the first electrostatic discharge device conducts forward, and the electrostatic charge flows from the first reference ground through the first electrostatic discharge device to the second reference ground for discharge. Conversely, when the potential of the second reference ground is higher than that of the first reference ground and the voltage difference reaches the forward conduction threshold of the electrostatic discharge device, the second electrostatic discharge device conducts forward, and the electrostatic charge flows from the second reference ground through the second electrostatic discharge device to the first reference ground for discharge.

[0027] Under normal operating conditions, the potential difference between the first and second reference ground terminals is typically small, insufficient to enable forward conduction of either electrostatic discharge (ESD) device. Therefore, the ESD protection module exhibits a high-resistance state and does not affect the normal operation of the intelligent power module. However, when an ESD event occurs, the potential difference between the two terminals increases instantaneously. Once the conduction threshold of the ESD device is reached, the corresponding ESD device rapidly conducts, quickly dissipating the electrostatic energy and clamping the voltage across the terminals within a safe range, protecting the low-voltage drive circuit and power devices from ESD damage.

[0028] In this embodiment, the electrostatic discharge (ESD) protection module is integrated within the chip of the low-voltage drive circuit. That is, the entire ESD protection module is implemented as part of the low-voltage drive chip, along with other functional units of the low-voltage drive circuit, on the same chip. The advantage of this approach is that it eliminates the need for additional package pins and external components, minimizing parasitic parameters and improving the response speed of ESD discharge.

[0029] The second reference ground terminal is introduced into the chip of the low-voltage drive circuit by wire bonding. Specifically, during the packaging process of the smart power module, metal leads (such as gold wire, copper wire, or aluminum wire) are used to connect the second reference ground terminal (i.e., the power ground pad) of the power device to the corresponding pad on the low-voltage drive chip, thereby introducing the power ground potential into the low-voltage drive chip and connecting it to one end of the electrostatic protection module.

[0030] In this embodiment, the power device is an insulated-gate bipolar transistor (IGBT) or a silicon carbide (SiC) power device. The emitter of the IGBT serves as the second reference ground. In the half-bridge topology, the emitter of the IGBT in the lower bridge arm is connected to the negative terminal of the power circuit, which is the second reference ground. The collector of the IGBT in the upper bridge arm is connected to the positive terminal of the DC bus, and the emitter is connected to the midpoint output terminal of the half-bridge. In practical applications, the intelligent power module may also include a freewheeling diode, which is connected in reverse parallel between the collector and emitter of the IGBT for freewheeling protection of inductive loads. When the power device is turned off, the current in the inductive load flows through the freewheeling diode, preventing the power device from experiencing excessively high reverse voltage spikes.

[0031] The working principle of this embodiment is as follows: Under normal operating conditions, the potential difference between the first reference ground terminal and the second reference ground terminal is small, and both the first and second electrostatic discharge (ESD) devices are in the off state. The ESD protection module does not affect the normal operation of the low-voltage drive circuit and power devices. When an ESD event occurs, if electrostatic charge accumulates on one side of the first reference ground terminal, making the potential of the first reference ground terminal significantly higher than that of the second reference ground terminal, when the voltage difference reaches the forward conduction voltage of the first ESD device, the first ESD device conducts forward, and the electrostatic charge is rapidly discharged to the second reference ground terminal through the first ESD device, and then released through the power circuit. Conversely, if electrostatic charge accumulates on one side of the second reference ground terminal, making the potential of the second reference ground terminal significantly higher than that of the first reference ground terminal, the second ESD device conducts forward, and the electrostatic charge is discharged to the first reference ground terminal through the second ESD device.

[0032] During electrostatic discharge, because the on-resistance of the electrostatic discharge device is very small and the equivalent impedance of the entire discharge path is very low, the discharge can be completed in nanoseconds, clamping the voltage at both ends within a safe range (usually between a few volts and tens of volts, depending on the conduction characteristics of the device and the amount of electrostatic energy), effectively protecting the gate oxide layer and thin gate dielectric inside the low-voltage drive circuit from electrostatic high voltage breakdown.

[0033] Based on the above description, this embodiment further specifies that both the first electrostatic discharge device and the second electrostatic discharge device are implemented using a gate-grounded metal-oxide-semiconductor diode (hereinafter referred to as a gate-ground diode) structure.

[0034] In this embodiment, the gate-grounded metal-oxide-semiconductor diode is a commonly used device structure in the field of electrostatic discharge protection. It is basically a metal-oxide-semiconductor field-effect transistor, with its gate and source shorted together and grounded (or connected to a low potential end), and the drain serving as one end of the device. When the drain potential rises relative to the source, the PN junction between the drain and the substrate is reverse biased. When the reverse voltage reaches a certain value, avalanche breakdown occurs near the drain, generating a large number of electron-hole pairs, thereby forming a large discharge current and realizing the discharge of electrostatic energy.

[0035] In this embodiment, the first electrostatic discharge device is implemented using a first gate-to-ground diode, and the second electrostatic discharge device is implemented using a second gate-to-ground diode. Specifically, the drain of the first gate-to-ground diode is connected to a first reference ground, and the source and gate of the first gate-to-ground diode are shorted and then connected to an intermediate node; the drain of the second gate-to-ground diode is connected to a second reference ground, and the source and gate of the second gate-to-ground diode are shorted and also connected to the intermediate node. Thus, the two gate-to-ground diodes are connected in series with their drains facing outwards and their sources facing each other, forming a back-to-back bidirectional electrostatic discharge protection structure.

[0036] When a positive electrostatic pulse occurs at the first reference ground terminal (i.e., the potential of the first reference ground terminal is higher than that of the second reference ground terminal), the drain potential of the first gate ground diode rises. When it rises to the avalanche breakdown voltage, the first gate ground diode undergoes avalanche breakdown. The electrostatic current flows from the first reference ground terminal through the drain of the first gate ground diode to the source, and then through the intermediate node to the source of the second gate ground diode. At this time, the source and drain of the second gate ground diode are forward biased (the source potential is higher than the drain potential), and its parasitic body diode is forward conducting. The current continues to flow from the source of the second gate ground diode through the body diode to the drain, and finally flows to the second reference ground terminal to complete the discharge.

[0037] Conversely, when a positive electrostatic pulse occurs at the second reference ground terminal (i.e., the potential of the second reference ground terminal is higher than that of the first reference ground terminal), the drain potential of the second gate ground diode rises, causing avalanche breakdown. The electrostatic current flows from the second reference ground terminal through the drain of the second gate ground diode to the source, and then through the intermediate node to the source of the first gate ground diode. At this time, the source and drain of the first gate ground diode are forward biased, and its parasitic body diode is forward conducting. The current continues to flow from the source of the first gate ground diode through the body diode to the drain, and finally flows to the first reference ground terminal to complete the discharge.

[0038] This embodiment employs a gate-to-ground diode structure to implement an electrostatic discharge (ESD) device. Its advantages include: the gate-to-ground diode is fully compatible with standard complementary metal-oxide-semiconductor (CMOS) processes, requiring no additional process steps or masks, resulting in low manufacturing costs; simultaneously, the gate-to-ground diode exhibits strong discharge capability and a large discharge current per unit area, enabling a high ESD protection level with a relatively small chip area. In practical designs, the dimensions of the gate-to-ground diode (such as channel width and drain area) can be adjusted according to the required ESD protection level. A larger channel width results in a stronger discharge current capability, but also increases the occupied chip area, requiring a trade-off design based on actual needs. Furthermore, in the layout design of the gate-to-ground diode, multi-finger or interdigitated structures can be used to increase the effective aspect ratio of the device, improve the discharge capability per unit area, and simultaneously improve the uniformity of current distribution within the device, avoiding device failure caused by localized overheating.

[0039] Based on the above description, this embodiment further specifies that both the first electrostatic discharge device and the second electrostatic discharge device are implemented using a PNP (Positive-Negative-Positive transistor) type electrostatic discharge diode structure. For example... Figure 4 As shown, the PNP type electrostatic discharge diode is another commonly used electrostatic discharge protection device. Its basic structure is a lateral PNP type bipolar junction transistor, with the emitter as the anode, the collector as the cathode, and the base either floating or connected to a low potential. When the anode potential rises relative to the cathode and reaches the forward conduction voltage of the emitter junction, the PNP transistor conducts, forming a large discharge current.

[0040] In this embodiment, the first electrostatic discharge device is implemented using a first PNP type electrostatic discharge diode, and the second electrostatic discharge device is implemented using a second PNP type electrostatic discharge diode. Specifically, the anode (collector) of the first PNP type electrostatic discharge diode is connected to the first reference ground, and the cathode (emitter) of the first PNP type electrostatic discharge diode is connected to the intermediate node; the anode (collector) of the second PNP type electrostatic discharge diode is connected to the second reference ground, and the cathode (emitter) of the second PNP type electrostatic discharge diode is also connected to the intermediate node. Thus, the two PNP type electrostatic discharge diodes are connected in series with their cathodes facing each other, forming a back-to-back bidirectional electrostatic discharge protection structure.

[0041] In this embodiment, when the potential of the first reference ground terminal is higher than that of the second reference ground terminal, the first PNP type electrostatic discharge diode is forward biased (anode high, cathode low) and conducts forward. The electrostatic current flows from the first reference ground terminal through the first PNP type diode to the intermediate node. At this time, the second PNP type electrostatic discharge diode is reverse biased, but when the reverse voltage reaches its reverse breakdown voltage, the second PNP type diode undergoes avalanche breakdown. The current continues to flow from the intermediate node through the second PNP type diode to the second reference ground terminal, completing the electrostatic discharge. Conversely, when the potential of the second reference ground terminal is higher than that of the first reference ground terminal, the second PNP type electrostatic discharge diode is forward biased and conducts, and the first PNP type electrostatic discharge diode undergoes reverse breakdown and conducts. The electrostatic current flows from the second reference ground terminal through the second PNP type diode, the intermediate node, and the first PNP type diode to the first reference ground terminal, completing the electrostatic discharge.

[0042] The advantages of using a PNP electrostatic discharge diode structure in this embodiment are: PNP devices have lower on-resistance and lower clamping voltage, which can more effectively protect the internal circuitry; at the same time, PNP devices have stronger latch-up immunity, are less prone to latch-up effects, and have higher reliability. On certain specific process platforms, PNP electrostatic discharge diodes can achieve better protection performance than gate-to-ground diodes.

[0043] In practical applications, the emitter area, base width, and other parameters of a PNP electrostatic discharge diode can be optimized according to specific protection requirements. A larger emitter area results in stronger current handling capability; a smaller base width leads to higher gain and faster turn-on speed.

[0044] This embodiment, based on the above description, further specifies that the power device is implemented using a metal-oxide-semiconductor (MOSFET). The source of the MOSFET serves as the second reference ground. In the half-bridge topology, the source of the MOSFET in the lower arm is connected to the negative terminal of the power circuit, i.e., the second reference ground; the drain is connected to the midpoint output terminal of the half-bridge. The drain of the MOSFET in the upper arm is connected to the positive terminal of the DC bus, and the source is connected to the midpoint output terminal of the half-bridge. The MOSFET can be either an N-channel enhancement-mode or a P-channel enhancement-mode, depending on the application requirements and circuit topology design. In most low- to medium-voltage applications, N-channel enhancement-mode MOSFETs are widely used due to their advantages such as low on-resistance, fast switching speed, and low cost.

[0045] In this embodiment, the metal-oxide-semiconductor field-effect transistor (MOSFET) may also include a body diode. The body diode is naturally located between the source and drain of the MOSFET, with its direction from source to drain (for N-channel devices). The body diode acts as a freewheeling diode, providing a freewheeling path for the inductive load when the power device is turned off. For scenarios where the performance of the body diode (such as reverse recovery time and on-state voltage drop) does not meet application requirements, an external or additionally integrated fast recovery diode can be used as a freewheeling diode.

[0046] The electrostatic discharge (ESD) protection principle of this embodiment is basically the same as that of Embodiment 1, and will not be repeated here. The intelligent power module using metal-oxide-semiconductor field-effect transistors (MOSFETs) as power devices can also effectively improve the ESD protection capability between the driver chip's reference ground and power ground through the ESD protection module of this invention, reducing the risk of failure caused by ESD.

[0047] On the other hand, this embodiment describes the present invention from a methodological perspective, providing a method for electrostatic discharge protection of a smart power module. The electrostatic discharge protection method includes the following steps:

[0048] Step 1: Inside the intelligent power module, identify the first reference ground terminal of the low-voltage drive circuit and the second reference ground terminal of the power device, and confirm that there is no direct electrical connection between the two under normal operating conditions.

[0049] In intelligent power modules, the reference ground (first reference ground terminal) of the low-voltage drive circuit mainly provides a potential reference for the drive logic and signal processing circuits, and its potential is relatively stable. However, the ground of the power device (second reference ground terminal) is the negative terminal of the power circuit, and may experience significant current changes and potential fluctuations during high-frequency switching. To ensure the accuracy of the drive signal and its anti-interference capability, in normal design, the first and second reference ground terminals are usually not directly shorted, but indirectly connected through specific paths (such as power supply circuits, bootstrap circuits, etc.). It is precisely because there is no direct low-resistance connection between the two that static charge easily accumulates at both ends, forming a high static voltage, which can damage the internal circuitry.

[0050] Step 2: Connect an electrostatic discharge (ESD) protection module in series between the first reference ground terminal and the second reference ground terminal. The ESD protection module consists of a first ESD device and a second ESD device connected in reverse series to form a bidirectional ESD discharge path.

[0051] In this step, the electrostatic discharge (ESD) protection module is the core of this invention. The reverse-connected (back-to-back) structure of two ESD devices ensures a conductive discharge path regardless of the polarity of the ESD voltage. The reverse-connection refers to either the cathodes of two diodes connected together, with their anodes facing opposite ends; or the anodes of two diodes connected together, with their cathodes facing opposite ends. Both connection methods achieve bidirectional conduction; the specific method used depends on the type of ESD device and the ease of manufacturing.

[0052] The electrostatic discharge (ESD) protection module is preferably integrated within the low-voltage driver chip. This minimizes parasitic inductance and resistance, and improves the response speed and efficiency of ESD discharge. Integration methods include, but are not limited to, fabricating it on the same chip as other functional modules of the low-voltage driver circuit, sharing the same substrate and process platform.

[0053] Step 3: When an electrostatic discharge event occurs, the corresponding electrostatic discharge device is turned on according to the polarity of the potential difference between the two ends, so as to quickly discharge the electrostatic energy.

[0054] Specifically, if the potential of the first reference ground terminal is higher than that of the second reference ground terminal, the first electrostatic discharge device is forward-biased, and the electrostatic charge flows from the first reference ground terminal through the first electrostatic discharge device to the second reference ground terminal for discharge; if the potential of the second reference ground terminal is higher than that of the first reference ground terminal, the second electrostatic discharge device is forward-biased, and the electrostatic charge flows from the second reference ground terminal through the second electrostatic discharge device to the first reference ground terminal for discharge.

[0055] During electrostatic discharge (ESD) operation, the ESD device clamps the voltage across its terminals to a lower level, ensuring that sensitive structures such as the gate oxide layer and thin gate dielectric inside the low-voltage drive circuit are not damaged by excessive voltage. The specific value of the clamping voltage depends on the conduction characteristics of the ESD device. For diode-type devices, the forward clamping voltage is approximately 0.7V to 1.5V; for avalanche breakdown devices, the reverse clamping voltage is approximately the breakdown voltage, typically between a few volts and tens of volts, and can be adjusted according to the withstand voltage level of the protected circuit.

[0056] In the electrostatic discharge protection method described in this embodiment, the bidirectional electrostatic discharge path is independent of the power supply circuit and signal circuit of the intelligent power module. That is, under normal operating conditions, since the potential difference between the first reference ground terminal and the second reference ground terminal is insufficient to turn on the electrostatic discharge device, the electrostatic protection module has no impact on the power supply circuit and signal circuit, and the drive signal can be transmitted normally without introducing additional noise or interference. This is fundamentally different from some existing solutions (such as those using multi-stage diodes at the power supply terminal for discharge), and the solution of this invention offers better signal integrity.

[0057] The electrostatic discharge (ESD) protection method of this embodiment can be applied to the field of home appliance drives, including but not limited to refrigerator compressor drives, air conditioner inverter drives, and washing machine motor drives. In home appliances, the intelligent power module, as a core component of the motor drive, directly affects the lifespan of the entire appliance and the user experience. The ESD protection method of this invention can also be applied to the field of industrial control, including but not limited to industrial inverters, servo drives, and switching power supplies.

[0058] This embodiment further describes in detail the specific integration method and layout considerations of the electrostatic protection module in the low-voltage driver chip.

[0059] In the design of low-voltage driver chips, the electrostatic discharge (ESD) protection module is typically placed near the chip's input / output pads, specifically close to the first reference ground pad and the second reference ground connection pad. This is done to shorten the metal interconnect length between the pads and the ESD protection device, reducing parasitic resistance and inductance, and improving the efficiency of ESD discharge.

[0060] Specifically, the chip typically has a dedicated power ground pad for connecting to the ground terminal (second reference ground) of an external power device via wire bonding. Below or near this pad, one end of a second electrostatic discharge (ESD) device (anode or drain, depending on the device type) is placed; near the pad of the first reference ground, one end of a first ESD device is placed; the other ends of the two ESD devices (intermediate connection terminals) are connected together by a metal interconnect.

[0061] To ensure reliability when high current is passed through, the metal wire connecting the electrostatic protection module and the pad needs to be of sufficient width.

[0062] Furthermore, the design of substrate contacts is crucial in the layout design. During electrostatic discharge (ESD), a large current is injected into the substrate. Insufficient substrate contact can cause a rise in substrate potential, leading to latch-up or other parasitic effects. Therefore, sufficient substrate contact vias and well contact vias need to be provided around the ESD protection device to ensure substrate potential stability and prevent latch-up. A guard ring structure can also be placed between the ESD protection device and the internal core circuitry to further block the impact of ESD injection current on the internal circuitry. The guard ring can be a ring-shaped heavily doped diffusion region connected to a fixed potential (such as the first reference ground potential), effectively collecting the injected carriers from the substrate and preventing them from diffusing into the internal circuitry area.

[0063] This embodiment describes a specific implementation of a three-phase intelligent power module incorporating the electrostatic discharge protection circuit of the present invention. In applications such as three-phase motor drives, a three-phase half-bridge circuit is typically required, with each half-bridge containing upper and lower bridge arm power devices. The corresponding driver chip may contain three high-side drive channels and three low-side drive channels.

[0064] In this three-phase intelligent power module, the electrostatic protection module of the present invention can be configured in several ways:

[0065] Method 1: A shared ESD protection module is set up in the low-voltage drive circuit to provide unified ESD protection for the three-phase lower bridge arm drive. That is, the first reference ground (drive ground) of all phases is connected together, sharing a single ESD protection module connected to the second reference ground (power ground). This method has the simplest structure and lowest cost because it only requires one ESD protection module. Method 2: An independent ESD protection module is set up in the lower bridge arm drive circuit of each phase. That is, each phase has its own first reference ground and its own ESD protection module, each connected to a common second reference ground. Although this method increases the number of components, the ESD protection between each phase is relatively independent; an ESD event in one phase will not affect other phases, resulting in higher independence and reliability of protection.

[0066] In practical applications, the appropriate method can be selected based on cost budget and protection requirements. For most conventional applications, method one is sufficient; for special applications with extremely high reliability requirements, method two can be considered. It should be noted that regardless of the method used, the basic working principle is the same: a bidirectional electrostatic discharge channel is constructed between the drive ground and the power ground by connecting electrostatic discharge devices in back-to-back series.

[0067] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0068] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. An electrostatic discharge protection circuit for an intelligent power module, characterized in that, The intelligent power module includes a high-voltage drive circuit, a low-voltage drive circuit, and power devices. The low-voltage drive circuit has a first reference ground terminal, and the power devices have a second reference ground terminal. The electrostatic discharge protection circuit includes an electrostatic discharge protection module connected in series between the first reference ground terminal and the second reference ground terminal. The electrostatic discharge protection module includes a first electrostatic discharge device and a second electrostatic discharge device. The first electrostatic discharge device and the second electrostatic discharge device are connected in reverse series to form a bidirectional electrostatic discharge path.

2. The electrostatic discharge protection circuit for the intelligent power module according to claim 1, characterized in that, The anode of the first electrostatic discharge device is connected to the first reference ground terminal, the cathode of the first electrostatic discharge device is connected to the cathode of the second electrostatic discharge device, and the anode of the second electrostatic discharge device is connected to the second reference ground terminal.

3. The electrostatic discharge protection circuit of the intelligent power module according to claim 1, characterized in that, The electrostatic discharge protection module is integrated inside the chip of the low-voltage drive circuit.

4. The electrostatic discharge protection circuit of the intelligent power module according to claim 1, characterized in that, The power device is an insulated gate bipolar transistor (IGBT), and the emitter of the IGBT serves as the second reference ground.

5. The electrostatic discharge protection circuit of the intelligent power module according to claim 1, characterized in that, The power device is a metal-oxide-semiconductor field-effect transistor (MOSFET), and the source of the MOSFET serves as the second reference ground terminal.

6. The electrostatic discharge protection circuit of the intelligent power module according to claim 1, characterized in that, The second reference ground terminal is introduced into the chip of the low-voltage drive circuit by wire bonding.

7. A method for electrostatic discharge protection of an intelligent power module, characterized in that, Includes the following steps: Inside the intelligent power module, the first reference ground terminal of the low-voltage drive circuit and the second reference ground terminal of the power device are identified to confirm that there is no direct electrical connection between the two under normal operating conditions. An electrostatic discharge (ESD) protection module is connected in series between the first reference ground terminal and the second reference ground terminal. The ESD protection module is composed of a first ESD device and a second ESD device connected in reverse series to form a bidirectional ESD discharge path. When an electrostatic discharge event occurs, if the potential of the first reference ground terminal is higher than that of the second reference ground terminal, the first electrostatic discharge device is forward-biased, and the electrostatic charge flows from the first reference ground terminal through the first electrostatic discharge device to the second reference ground terminal for discharge. If the potential of the second reference ground terminal is higher than that of the first reference ground terminal, the second electrostatic discharge device is forward-biased, and the electrostatic charge flows along the second reference ground terminal through the second electrostatic discharge device to the first reference ground terminal for discharge.

8. The electrostatic discharge protection method for the intelligent power module according to claim 7, characterized in that, Both the first electrostatic discharge device and the second electrostatic discharge device are implemented using a gate-grounded metal-oxide-semiconductor diode structure.

9. The electrostatic discharge protection method for the intelligent power module according to claim 7, characterized in that, The bidirectional electrostatic discharge path is independent of the power supply circuit and signal circuit of the intelligent power module. Under normal operating conditions, both the first electrostatic discharge device and the second electrostatic discharge device are in a reverse cutoff state.

10. The electrostatic discharge protection method for the intelligent power module according to claim 7, characterized in that, The electrostatic discharge protection module is integrated inside the chip of the low-voltage driving circuit, and the second reference ground terminal is introduced into the chip of the low-voltage driving circuit by wire bonding; the layout of the first electrostatic discharge device and the second electrostatic discharge device adopts a multi-finger structure or an interdigitated structure.

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