Ground loss detection

Abstract

A ground loss detector is described. A power electronics device having a ground loss detector may receive power from a main source and a secondary source. Such a power electronics device can include a main ground port; a secondary ground port; and a ground loss detector connected to the secondary ground port. The ground loss detector includes circuitry to detect when a secondary source ground current level exceeds a threshold; and output a signal to direct a shut off of power from the main source when the secondary source ground current level exceeds the threshold. The ground loss detector can utilize a resettable fuse and current detector that detects the current through the resettable fuse in order to detect when the secondary source ground current level exceeds a threshold.

Description

ETN-122XINPCT P24-1264 GROUND LOSS DETECTIONBACKGROUND

[0001] A number of electronic systems, such as those used in vehicles, include a main power source and a secondary power source. Generally, the main power source has a higher voltage than the secondary power source. For example, the main power source can be a 48-volt battery while the secondary power source can be a 12-volt battery. The ground lines of the main power source and the secondary power source can connect to an environmental ground, such as a vehicle chassis. In a vehicle electrical system, maintaining proper ground can be extremely important for a vehicle safety system.

[0002] At times, a loss of the main source’s ground occurs, which damages internal components of a system or affects communication signals. A loss of a main source ground is often not able to be detected, as such an event is generally not communicated to an electronic control unit (ECU).BRIEF SUMMARY

[0003] Ground loss detection is described. The described ground loss detection can be applied to a power electronics device that includes a main power source and a secondary power source. At times, overheating or a short circuit can occur at the main source, which can cause a loss of the main source’s ground. The loss of the ground can result in high current flow along wires connected to a secondary ground port of the power electronics device. This high current flow to the secondary ground port can be harmful to internal components of the power electronics device. As provided herein, a ground loss detector is added to power electronics device that detects when current bleeds from a ground line connected to the main source to the secondary source ground line, Specifically, the ground loss detector measures a current level at the secondary ground line and determines whether this current level exceeds a threshold. When the current level exceeds the threshold, protective measures can be performed.

[0004] In some aspects, a power electronics device is provided that includes: a main ground port; a secondary ground port; and a ground loss detector connected to the secondary ground port, the ground loss detector including circuitry to: detect when a secondary source ground current level exceeds a threshold; and output a signal to direct a shut off of power from a main source when the detected secondary source ground current level exceeds the threshold.

[0005] In some aspects, the techniques described herein relate to a power electronics system including: a power electronics device including a main ground port, a secondary ground port,ETN-122XINPCT P24-1264 and a ground loss detector. The main ground port is connected to a main source ground, the secondary ground port is connected to a secondary source ground, and the main source ground and the secondary source ground are connected to common ground wires that connect to a chassis of a vehicle. The secondary source ground current level exceeds the threshold when current from the main source travels along the common ground wire.

[0006] In some aspects, a ground loss detector for a power electronics device is provided that includes: a first connection for a secondary source ground; a second connection for a microcontroller of the power electronics device; a measurement circuit coupled to the first connection for the secondary source ground to measure a current of the secondary source ground; and circuitry to selectively convey a signal to the microcontroller via the second connection, said signal indicating an existence of a ground loss condition between a main source and the power electronics device, wherein the signal is selectively conveyed when the current of the secondary source ground exceeds a threshold.

[0007] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 illustrates a power electronics system for a power electronics device that uses a ground loss detector to intelligently provide protection for ground loss with a main source.

[0009] FIG. 2 illustrates a ground loss detector able to be connected to a secondary source ground of a power electronics device.DETAILED DESCRIPTION

[0010] Ground loss detection is described. The described ground loss detection can be applied to an electronics device that includes a main power source and a secondary power source, for example a power electronics device, such as power converter.

[0011] A nominal current, which is close to zero, will generally be present in the ground wires. However, a loss of a ground between a main source and a main source ground port of a power electronics device can cause current to travel along common ground wires, to secondary source ground wires, to a secondary source ground port of the power electronics device. This current from the main source can be harmful to internal components of the power electronicsETN-122XINPCT P24-1264 device and can negatively affect communication signals to / from the power electronics device. The ground loss can occur through a short or overheating.

[0012] The disclosure introduces a ground loss detector between the ground wire of the secondary source and a microcontroller of the power electronics device. The ground loss detector detects a presence of a current greater than a defined threshold. In some embodiments, the ground loss detector includes a resettable fuse, which is tripped when the current threshold is exceeded. The resettable fuse acts as a resistor, causing a change in current on the line.

[0013] The ground loss detector can also include a current sensor. The current sensor can be in the form of an analog-to-digital (ADC) measurement circuit, for example implemented by a Hall effect sensor, to measure the current level through the resettable fuse (when acting as a resistor) as a value. This value is conveyed to the microcontroller of the power electronics device, which places itself in a safe or standby mode whenever the current value exceeds the threshold. The safe or standby mode is a power off or lower power mode, where power from the main source is shut off.

[0014] In one arrangement the fuse state is detectable by the power electronics device. Some embodiments exist where the ground loss detector lacks a current measurement circuit and instead includes reactive circuitry based on whether the fuse state is “ON” or “OFF”. In certain embodiments, an addition of the current measuring circuit in the ground loss detector provides more control of the protective power shutoff function than is possible by detecting fuse state alone. In one embodiment, tripping of the fuse can intentionally be a failsafe that occurs slightly above the threshold that is established for power shutoff from the main source.

[0015] In a specific use-case, the ground loss detector can be introduced into a vehicle electronics system. The power electronics device can be a power converter of the vehicle electronics system, the main source can be a 48-volt battery, and the secondary source can be a 12-volt battery. In some embodiments, a main voltage of a main source is at least twice a secondary voltage of the secondary source.

[0016] Different types and grades of electrical wiring exist for handling different current levels. Higher power wiring is typically thicker and more expensive than lower power wiring. The secondary source is generally operating at lower power than the main source and is therefore typically connected through thinner wires not designed to handle the current of the main source.

[0017] FIG. 1 illustrates a power electronics system 100 for a power electronics device 120 that uses a ground loss detector 150 to intelligently provide protection for ground loss with a main source 110. Power electronics device 120 receives power from main source 110 and fromETN-122XINPCT P24-1264 secondary source 112. For example, the power electronics device 120 can be a vehicle power converter, the secondary source can be a 12-volt battery, and the main source can be a battery of at least 24 volts. Of course, voltage levels of the main source are not limited and lower voltage levels than 24 volts are contemplated in some embodiments. Indeed, the described ground loss protection is applicable for any system regardless of voltage level. A main source 110 ground connects to a main ground port 124. A secondary source 112 ground connects to a secondary ground port 126. The ground loss detector 150 is connected to the secondary ground port 126. The ground loss detector 150 includes circuitry to: detect when a secondary source ground current level exceeds a threshold; and output a signal to direct a shut off of power from the main source 110 when the secondary source ground current level exceeds the threshold.

[0018] A ground of the main source 110 is connected to the power electronics device 120 via wiring 132 and 134, where wiring 134 connects to the main ground port 124. Thus, main wires connect the main source 110 to the power electronics device, where the main wires include the main source ground wire (e.g., wire 134). The ground of the secondary source 112 is connected to the power electronics device by wiring 138, which connects to the secondary ground port 126. Thus, secondary wires connect the secondary source 112 to the power electronics device, where the secondary wires include the secondary source ground wire (e.g., wire 138). Common ground wires (e.g., wiring 135) connect the main source ground wire (e.g., wire 134) to the secondary source ground wire (e.g., wire 138). A vehicle chassis ground 133 is connected to the common ground wires.

[0019] When wire 134 shorts or overheats, current travels through wire 132, wire 135, wire 138, and into power electronics device 120 through secondary ground port 126. Circuitry of ground loss detector 150 ensures excessive current from a main source 110 ground loss is detected and gracefully handled. Excessive current that travels through the environmental ground during a main source 110 ground loss scenario can lead to internal damage and / or can affect communication signals. Excessive current is defined herein as any current exceeding an established threshold. In one arrangement, this threshold can be 150mA. In another, the threshold can be between 2 and 3A. The threshold is variable in different use cases depending on hardware and software design, variance of which will alter the threshold value correspondingly. Wire 138 and / or components within power electronics device 120 connected to wire 138 can overheat, short, or otherwise become damaged when carrying current over the threshold. In certain embodiments, the threshold value established by ground loss detector 150ETN-122XINPCT P24-1264 can be slightly lower than a current level that would lead to damage to ensure a safety state is triggered prior to circuit damage occurring.

[0020] In certain embodiments, when in a ground loss state, the ground loss detector 150 sends a ground loss message / signal to the microcontroller 122, which conveys a ground loss message to electronic control unit (ECU) 114 via data channel 116. The microcontroller 122 can take actions to place the power electronics device in the safety state. ECU 114 can log main ground loss occurrences, which can be used to diagnose the underlying electrical problem.

[0021] In one arrangement, the power electronics system 100 is a vehicle’s electronic system that delivers power to various subsystems, such as engine control, safety systems, lighting, and infotainment. Engine control includes various engine functions like ignition control that starts a vehicle’s engine. Safety systems include anti-lock braking (ABS), electronic stability control (ESC), and the like. Lighting controls headlights and other in-vehicle lighting components. Infotainment includes a vehicle’s navigation system, stereo, and other entertainment features.

[0022] Power electronics system 100 can be a dual power system that includes main source 110 and secondary source 112, which in certain embodiments are configured to function as two isolated systems. The main source 110 has a higher voltage rating than the secondary source 112. In certain embodiments, both the main source 110 and the secondary source 112 are direct current batteries providing at least 12-volts of power. Main source 110 can provide 24-volts or 48-volts. In one embodiment, the main source 110 and secondary source 112 can conform to the LV 148 standard.

[0023] ECU 114 can be considered the brains of power electronics system 100, which typically includes a main processing unit, a memory, an interface port, and a set of instructions implemented as firmware or software. Errors are often logged and diagnosed through the ECU 114. The ECU 114 is often connected to numerous submodules and subsystems. An ECU 114 of a vehicle, for example, is often connected to a vehicle control module (VCM) that manages a powertrain, a central vehicle controller (CVC) that manages electrical loads including lights and climate control, a vehicle control unit (VCU) that manages electric vehicle (EV) systems like the motor drive and battery management functions, and a domain control unit (DCU) that processes data and handles command and operation functions.

[0024] Power electronics device 120 includes a set of components that control and convert electrical energy to ensure optimal performance of power electronics system 100. In vehicles, especially hybrids and EVs, power electronics devices 120 are responsible for controlling the motor, managing the batteries, charging batteries, regenerative braking, and the like. In certainETN-122XINPCT P24-1264 embodiments, power electronics device 120 is a power converter. The power converter can be a DC to DC converter that changes 48V to 12V.

[0025] Microcontroller 122 is a small computer designed for embedded applications of the power electronics device 120. Microcontroller 122 can include one or more processors along with memory and programmable input / output. Microcontroller 122 can include receive and transmission functionality for digitally encoded data, which is conveyed over data channel 116.Microcontroller 122 can be selected for having reduced power consumption in sleep mode, adjustable drive current, adjustable maximum duty cycle, the ability to make certain adjustments by only changing the program instructions, and the like. While microcontroller 122 is shown as separate from ground loss detector 150, in some implementations, ground loss detector 150 can include an independent controller or processor that may perform some of the functionality attributed to microcontroller 122.

[0026] Data channel 116 is a communication pathway through which digitally encoded information is conveyed. Communications between power electronics device 120 and ECU 114 can occur over a wired pathway forming data channel 116. In certain embodiments, data channel can include one or more wireless data channel, such as a BLUETOOTH or WIFI one. The data channel 116 can be useful for updating firmware of the microcontroller 122.

[0027] Wires 130, 132, 134, 135, 136, and 138, which are sometimes referred to as lines, are conductive pathways used to connect components of power electronics system 100 to each other. In automative applications, wires 130, 132, 134, 135, 136, and 138 are generally coated and possess a stranded copper core, although other materials such as aluminum are sometimes used. Wires 130, 132, 134, 135, 136, and 138 have different thicknesses and characteristics depending upon the amount of power each is designed to handle.

[0028] Chassis ground 133 is generally connected to metal or other conductive components of a system.

[0029] FIG. 2 illustrates a ground loss detector 210 able to be connected to a secondary source ground of a power electronics device. Ground loss detector 210 is one implementation of ground loss detector 150 detailed in FIG. 1. Ground loss detector 210 can include a connection 212 (via a secondary ground port) to a secondary source ground. In certain embodiments, ground loss detector 210 includes a connection 214 to a microcontroller 122 of the power electronics device 120. The connection of the ground loss detector 210 to various components can be embodied as a releasable connector or a hard-wired connection, depending on implementation. Ground loss detector 210 includes circuitry to detect when a secondary source ground current level exceeds a threshold and output a signal to direct a shut off of powerETN-122XINPCT P24-1264 from a main source when the detected secondary source ground current level exceeds the threshold. For example, ground loss detector 210 can include a measurement circuit 215 coupled to the secondary ground port / connector 212 to measure a current of the secondary source ground. The measurement circuit 215 includes a fuse 220. The fuse 220 can be coupled to the secondary source ground, for example, by being coupled to the secondary ground port 212. The measurement circuit 215 further includes circuitry (e.g., current sensor 222) to measure the current of the secondary source ground, for example, as a result of the change in resistance from the fuse 220. Ground loss detector 210 can further include a memory or adjustable setting for threshold 230. In some cases, the threshold 230 can be stored at and / or controlled by the microcontroller 122.

[0030] The ground loss detector 210 can further include detector circuit 235. In some embodiments, the ground loss detector includes circuitry (e.g., as part of detector circuit 235) to selectively convey a signal to the microcontroller 122. The signal indicates the existence of a ground loss condition between the main source 110 and the power electronics device 120. The signal is selectively conveyed when the detected current exceeds threshold 230, for example, when detected by detector circuit 235. In some cases, detector circuit 235 includes an analog-to-digital converter that converts an analog read-out of the current to a digital value (e.g., when the current sensor outputs an analog signal or when an analog comparator is used).

[0031] As noted above, threshold 230 may be stored within a memory (e.g., a register or other memory structure) at the ground loss detector 210 and, optionally or additionally, may also be stored and / or provided by microcontroller 122. In some embodiments threshold 230 is stored within memory of microcontroller 122. In other embodiments, a different memory is used to store threshold 230, which can include a dedicated memory added for this purpose. In certain embodiments, threshold 230 is inherently established through circuitry taking action when the threshold 230 is exceeded. When the threshold 230 is exceeded, the ground loss detector 210 can ensure power from the main source 110 is shut off, which may require signaling microcontroller 122 that takes actions resulting in the shut off. Shutting off this power can, for example, cause the power electronics device 120 to enter a standby mode, where significant current is not traveling from the main source 110 to the power electronics device 120.

[0032] In one embodiment, fuse 220 is tripped when the current value exceeds a threshold. Fuse 220 has at least two functional states of ON and OFF. When fuse 220 is ON it is considered tripped. A tripped fuse 220 offers very high resistance to limit current flow. In certain embodiments, the fuse 220 can be a resettable fuse. A resettable fuse is one able to beETN-122XINPCT P24-1264 reset from an ON or tripped state to an OFF or active state. In a further use case, fuse 220 is a positive temperature coefficient (PTC) resettable fuse that consists of a positive temperature coefficient material whose internal resistance increases exponentially with an increase in operating temperature. When a PTC fuse cools it reverts to low resistance mode or OFF state. Thus, a PTC fuse can be considered a self-re setting fuse.

[0033] Current sensor 222 is a component able to measure the current of secondary ground port 212, which is the same current being conveyed over wire 138. In some cases, the current sensor 222 is a Hall effect sensor. In one embodiment, detector circuit 235 includes an analog-to-digital converter (ADC) that receives an analog signal (e.g., voltage of the current flowing through fuse 220 as output by current sensor 222) and quantifies this analog signal as a digital value. This value can be conveyed to microcontroller 122 along with the signal indicating an existence of the ground loss condition.

[0034] Generally, fuse 220 is selected for a given threshold value 230 so that the fuse 220 is tripped when this value is exceeded. In one embodiment, the threshold value 230 is approximately 150 mA, where approximately represents plus or minus twenty five percent. In other arrangements, the threshold value can be set to 2 or 3 A. The appropriate value for the threshold 230 depends on the amount of current internal components of the power electronics device 120 and / or wires 138 can handle.

[0035] In some embodiments, the threshold value 230 can be established as a variable value in a memory of the microcontroller 122, which takes a programmed action to shutting off power from the main source 110 when the threshold value 230 is exceeded. In such a case, the detector circuit 235 simply converts the analog signal of a current level from the measurement circuit 215 to a digital value of the current level and the microcontroller 122 receives the digital value of the current level, which allows for this comparison of current levels within a processor of microcontroller 122.

[0036] In some embodiments, a threshold value of fuse 220 can be higher than that used to cause a shutdown of power from main source 110 to power electronics device 120. For example, fuse 220 can be tripped to protect wire 138 from receiving a first threshold of current, which is effectively a hard shutoff. A second level of current, lower than the first threshold can be the threshold 230, which is used by microcontroller 122 to perform a soft shutoff. When fuse 220 is a PTC resettable one, it automatically increases resistance as temperature increases and is effectively a variable cutoff component that provides an automatic reset as temperature cools.ETN-122XINPCT P24-1264

[0037] Although the subject matter has been described in language specific to structural features and / or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims.

Claims

ETN-122XINPCT P24-1264 CLAIMSWhat is claimed is:

1. A power electronics device comprising:a main ground port;a secondary ground port; anda ground loss detector connected to the secondary ground port, the ground loss detector comprising circuitry to:detect when a secondary source ground current level exceeds a threshold; and output a signal to direct a shut off of power from a main source when the detected secondary source ground current level exceeds the threshold.

2. The power electronics device of claim 1, wherein the ground loss detector comprises a measurement circuit coupled to the secondary ground port to measure a current of the secondary source ground.

3. The power electronics device of claim 2, wherein the measurement circuit comprises:a resettable fuse coupled to the secondary source ground port; anda current sensor coupled to measure current through the resettable fuse.

4. The power electronics device of claim 3, wherein the ground loss detector further comprises circuitry structured to detect when the measured current exceeds the threshold and output the signal.

5. The power electronics device of claim 3, wherein the current sensor comprises a hall effect sensor.

6. The power electronics device of claim 1, wherein the ground loss detector comprises:a resettable fuse coupled to the secondary ground port;a current sensor coupled to measure current through the resettable fuse; and circuitry structured to detect when the measured current exceeds the threshold and output the signal.ETN-122XINPCT P24-1264 7. The power electronics device of claims 4 or 6. wherein the circuitry structured to detect when the measured current exceeds the threshold and output the signal comprises an analog-to-digital converter.

8. The power electronics device of claim 1, further comprising:a microcontroller connected to the ground loss detector, wherein the ground loss detector conveys the signal to the microcontroller when the secondary source ground current level exceeds the threshold.

9. The power electronics device of claim 8, wherein the microcontroller is configured to convey a ground loss message over a data channel responsive to receiving the signal from the ground loss detector.

10. The power electronics device of claim 1, wherein the power electronics device is a vehicle power converter.

11. A power electronics system comprising:the power electronics device of any of claims 1-10,wherein the main ground port is connected to a main source ground,wherein the secondary ground port is connected to a secondary source ground of a secondary source, andwherein the main source ground and the secondary source ground are connected to common ground wires that connect to a chassis of a vehicle, wherein the secondary source ground current level exceeds the threshold when current from the main source travels along the common ground wire.

12. The power electronics system of claim 11, wherein a main voltage of the main source is greater than a secondary voltage of the secondary source.

13. The power electronics system of claim 11 or 12, wherein main wiring connecting the main source to the power electronics device is configured to handle greater current than secondary wiring connecting the secondary source to the power electronics device.ETN-122XINPCT P24-1264 14. The power electronics system of any of claims 11-13, further comprising:the main source;a secondary source;main wires connecting the main source to the power electronics device, said main wires including a main source ground wire coupling the main source ground to the main ground port;secondary wires connecting the secondary source to the power electronics device, said secondary wires including a secondary source ground wire coupling the secondary source ground to the secondary ground port; andcommon ground wires connecting the main source ground wire and to the secondary source ground wire.

15. The power electronics system of claim 14, wherein the power electronics system is a vehicle electrical system, wherein a vehicle chassis ground is connected to the common ground wires.

16. The power electronics system of any preceding claim, wherein the threshold is approximately 150 mA.

17. A ground loss detector for a power electronics device comprising:a first connection for a secondary source ground;a second connection for a microcontroller of the power electronics device;a measurement circuit coupled to the first connection for the secondary source ground to measure a current of the secondary source ground; anda detector circuit to selectively convey a signal to the microcontroller via the second connection, said signal indicating an existence of a ground loss condition between a main source and the power electronics device, wherein the signal is selectively conveyed when the current of the secondary source ground exceeds a threshold.

18. The ground loss detector of claim 17, wherein the measurement circuit comprises: a resettable fuse coupled to the secondary source ground; anda current sensor coupled to measure current through the resettable fuse.

19. The ground loss detector of claim 18, wherein the current sensor comprises a hall effect sensor.

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