Fault detection

Abstract

The invention relates to fault detection. A fault detection system for detecting a fault in a switch of a half-bridge of an electrical circuit in a transport refrigeration system (150), the fault detection system comprising: a voltage divider; and a processor circuit wherein: when the fault detection system is used, the voltage divider is coupled in parallel with the switch of the half-bridge of the circuit; and an output of the voltage divider is coupled to an input of the processor circuit, and wherein the processor circuit is operable to: compare a detection signal indicative of a voltage at the output of the voltage divider to a reference signal; and outputting a fault detection signal in response to determining that the detection signal does not correspond to the reference signal.

Description

Technical Field

[0001] The present disclosure relates to a fault detection system and method for detecting faults in switches (such as power semiconductors of a half-bridge of a circuit such as an inverter in a transport refrigeration system). Background Art

[0002] Transport climate control systems are generally used to control one or more environmental conditions (such as temperature, humidity, air quality, or a combination thereof) of a transport unit. Examples of transport units include, but are not limited to, trucks, containers (such as containers on flatbed trucks, intermodal containers, marine containers, railway containers, etc.), box trucks, semi-trailer tractors, buses, or other similar transport units. The transport climate control system may be integrated into the transport unit or may be provided as a separate transport climate control unit (CCU), which may also be referred to as a transport refrigeration unit (TRU) that can be installed or coupled to the transport unit.

[0003] Transport climate control systems generally include (among other components) temperature control components (such as compressors, pumps, fans, heat exchangers, etc.) and associated electrical components (such as sensors (such as temperature sensors), controllers, display units, electric drives, electrical filters, etc.). The temperature control components and associated elements are generally powered by electricity.

[0004] The transport climate control system may be configured to receive power from the transport unit. For example, the transport climate control system may be configured to receive power from a prime mover of the transport unit (such as the engine of a truck, tractor unit, etc.), from a battery of the transport unit (such as the battery of a truck, tractor unit, etc.), and / or from a utility power or "shore power" source (such as a power grid or network to which the transport unit may be coupled to receive mains electricity).

[0005] The transport climate control system may include components configured to operate with direct current (DC) power and components configured to operate with single-phase or three-phase alternating current (AC) power. For example, the transport climate control system may include a DC pump and one or more DC fans or blowers, and a compressor driven by a single-phase or three-phase AC motor. To accommodate the different power requirements of its components, the transport climate control system generally includes a DC bus or DC link that receives power from a DC source such as a battery. The DC components may be coupled (if necessary, via a suitable DC-DC converter) to the DC bus or DC link. One or more inverters may also be coupled to the DC bus or DC link to convert direct current (DC) power into single-phase and / or three-phase AC power suitable for powering the AC components. Summary of the Invention

[0006] According to a first aspect, the present invention provides a fault detection system for detecting a fault in a switch of a half - bridge of a circuit in a transport refrigeration system. The fault detection system includes: a voltage divider; and a processor circuit, wherein: when the fault detection system is in use, the voltage divider is coupled in parallel with the switch of the half - bridge of the circuit; and the output of the voltage divider is coupled to the input of the processor circuit, and wherein the processor circuit is operable to: compare a detection signal indicative of the voltage at the output of the voltage divider with a reference signal; and in response to determining that the detection signal does not correspond to the reference signal, output a fault detection signal.

[0007] When the fault detection system is in use, the voltage divider can be coupled in parallel with the low - side switch of the half - bridge of the circuit.

[0008] The voltage divider can be a resistive voltage divider including a first resistor connected in series with a second resistor.

[0009] The first resistor can include a plurality of resistors connected in series. The second resistor can include a single resistor.

[0010] For example, the plurality of resistors of the first resistor and the single resistor of the second resistor can be surface - mount devices.

[0011] The voltage divider can be configured to receive an input DC voltage in the range of 0 - 900 volts and output an output DC voltage in the range of 0 - 5 volts.

[0012] The voltage divider can be configured such that the magnitude of the output DC voltage is approximately 1 / 300 of the magnitude of the input DC voltage.

[0013] The fault can be a stuck - on fault.

[0014] The processor circuit is operable to: compare a detection signal indicative of the voltage at the output of the voltage divider with a first reference signal; and in response to determining that the detection signal is less than the first reference signal, output a first fault detection signal indicative of a stuck - on fault in the low - side switch of the circuit.

[0015] The processor circuit is operable to: compare a detection signal indicative of the voltage at the output of the voltage divider with a second reference signal; and in response to determining that the detection signal is greater than the second reference signal, output a second fault detection signal indicative of a stuck - on fault in the high - side switch of the circuit.

[0016] The circuit can be, for example, an inverter circuit or a multilevel converter circuit.

[0017] According to a second aspect, the present invention provides a method for detecting a fault in a switch of a half - bridge of a circuit in a transport refrigeration unit, the method comprising: comparing, by a processor circuit, a signal indicative of an output voltage of a voltage divider coupled in parallel with a switch of a half - bridge of an inverter with a reference voltage; and indicating a fault condition in response to determining, by the processor circuit, that the detected voltage does not correspond to the reference voltage.

[0018] According to a third aspect, the present invention provides a transport refrigeration system comprising a circuit and a fault detection system according to the first aspect.

[0019] According to a fourth aspect, the present invention provides a machine - readable medium having a computer program stored thereon comprising instructions which, when executed by a processing device, cause the processing device to perform the method according to the second aspect.

[0020] Throughout the specification, the word "comprising" or variations such as "comprises" or "comprising" will be understood to imply the inclusion of the stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which:

[0022] Figure 1 A vehicle including a transport refrigeration system is shown;

[0023] Figure 2 is an exemplary schematic diagram showing a three - phase inverter coupled to a DC link to convert input DC power into three - phase AC power;

[0024] Figure 3 is a schematic diagram showing a fault detection system according to the present disclosure, the fault detection system being coupled to a half - bridge of a three - phase inverter in the example shown;

[0025] Figure 4 is a diagram showing Figure 3 a schematic diagram of an example arrangement of a voltage divider and an example arrangement of a balancing impedance of the fault detection system;

[0026] Figure 5 is a flowchart showing processing operations performed by a processor circuit in a method for detecting a fault using the Figure 3 fault detection system; and

[0027] Figure 6 is a schematic representation of a machine - readable medium having a computer program stored thereon comprising instructions which, when executed by a suitable processing device, cause the processing device 620 to perform Figure 5Steps in the method. Detailed implementation

[0028] Figure 1 Illustrated is a vehicle 100 including a transport refrigeration system 110. In Figure 1 the example, the transport refrigeration system 110 forms part of a road refrigeration semi-trailer having a structure 130 that supports (or forms) at least one climate control compartment 140 configured to be cooled and / or heated by a TRU 150. The climate control compartment 140 may take the form of multiple compartments or have multiple zones. The structure 130 includes a chassis. The structure 130 supports the TRU 150. The vehicle 100 also includes a tractor unit 160 detachably coupled to the trailer.

[0029] Figure 2 is a schematic diagram showing a three-phase inverter coupled to a DC link to convert input DC power into three-phase AC power for powering a load (e.g., driving a three-phase motor such as a compressor).

[0030] The three-phase inverter (commonly shown as 200 in Figure 2 ) includes a first half-bridge 210, a second half-bridge 220, and a third half-bridge 230.

[0031] The first half-bridge 210 includes a first (high-side) switch 212 connected in series with a second (low-side) switch 214. In this example, the first switch 212 and the second switch 214 are insulated gate bipolar transistors (IGBTs), but those skilled in the art will understand that other semiconductor switching devices (especially power semiconductor switching devices) may also be used.

[0032] A first freewheeling diode 216 is connected to the first switch 212 in a reverse-parallel configuration, with its anode connected to the emitter of the first switch 212 and its cathode connected to the collector of the first switch 212. A second freewheeling diode 218 is connected to the second switch 214 in a reverse-parallel configuration, with its anode connected to the emitter of the second switch 214 and its cathode connected to the collector of the second switch 214.

[0033] The emitter of the first switch 212 is connected to the collector of the second switch 214. The collector of the first switch 212 is connected to the positive power rail 242 of the DC link 240, which in turn is connected to the first terminal of a DC link capacitor 250. The emitter of the second switch 214 is connected to the ground rail 244 of the DC link 240, which in turn is connected to the second terminal of the DC link capacitor 250.

[0034] In this example, a node 215 between a first switch 212 and a second switch 214 is coupled to a first input of a three-phase motor 270 via a first-phase output path 262.

[0035] The gates of the first switch 212 and the second switch 214 are connected to an output of a controller 280 via a suitable gate drive circuit (as would be well known to a person skilled in the art), and the controller 280 is configured to generate control signals to turn on or off the first switch 212 and the second switch 214 in a predetermined sequence to convert a DC input voltage at a DC link 240 into a first phase of a three-phase AC output voltage at the first-phase output path 262.

[0036] Thus, when the first switch 212 is turned on (in response to a suitable control signal from the controller 280), the first-phase output path 262 is coupled to the positive power rail 242 of the DC link 240. When the second switch 214 is turned on (in response to a suitable control signal from the controller 280), the first-phase output path 262 is coupled to the ground rail 244 of the DC link 240.

[0037] A second half-bridge 220 has a structure similar to that of the first half-bridge 210 and includes a first (high-side) switch 222 and a second (low-side) 224 (IGBTs in this example), as well as a first freewheeling diode 226 and a second freewheeling diode 228, which are connected in the same manner as the first switch 212 and the second switch 214 and the first freewheeling diode 216 and the second freewheeling diode 218 of the first half-bridge 210. A node 225 between the first switch 222 and the second switch 224 is coupled to a second input of the three-phase motor 270 via a second-phase output path 264.

[0038] As described above for the first half-bridge 210, the gates of the first switch 222 and the second switch 224 are connected to an output of the controller 280, and the controller 280 is configured to generate control signals to turn on and off the first switch 222 and the second switch 224 in a predetermined sequence to convert a DC input voltage at the DC link 240 into a second phase of a three-phase AC output voltage at the second-phase output path 264.

[0039] A third half-bridge 230 has a structure similar to that of the first half-bridge 210 and the second half-bridge 220 and includes a first (high-side) switch 232 and a second (low-side) switch 234 (IGBTs in this example), as well as a first freewheeling diode 236 and a second freewheeling diode 238, which are connected in the same manner as the first switch 212 and the second switch 214 and the first freewheeling diode 216 and the second freewheeling diode 218 of the first half-bridge 210. A node 235 between the first switch 232 and the second switch 234 is coupled to a third input of the three-phase motor 270 via a third-phase output path 266.

[0040] As described above for the first half - bridge 210, the gates of the first switch 232 and the second switch 234 are connected to the output of a controller 280 configured to generate control signals to turn on or off the first switch 232 and the second switch 234 in a predetermined sequence to convert the DC input voltage at the DC link 240 into the third phase of the three - phase AC output voltage at the third - phase output path 266.

[0041] Importantly, the first and second switches of any half - bridge are not turned on at the same time because this would cause a short - circuit between the positive power rail 242 and the ground rail 244 of the DC link 240, and as the DC - link capacitor 250 discharges rapidly through the first and second switches, this could generate a very high "breakdown" current. Such a high current could damage or destroy the switches, and thus they would need to be replaced, which could be both time - consuming and costly.

[0042] Accordingly, the controller 280 is configured to control the timing of the control signals to the first and second switches of each of the half - bridges 210, 220, 230 to ensure complementary operation of the first and second switches (i.e., when the first switches 212, 222, 232 are on, the second switches 214, 224, 234 are off, and vice versa). However, one or more of the switches 212, 214, 222, 224, 232, 234 may develop a fault (sometimes referred to as a "stuck - on" fault), which causes the switch to remain on even when no control signal is present or when a control signal that should have the effect of turning off the switch is applied to its gate.

[0043] The present disclosure provides a fault - detection system and method for detecting faults in switches of a half - bridge of an inverter.

[0044] Figure 3 is a schematic diagram showing a fault - detection system coupled to a three - phase inverter according to the present disclosure. Figure 3 has many elements in common with Figure 2 These common elements are denoted by common reference numerals in Figure 2 and Figure 3 and will not be described in detail again here for the sake of brevity and clarity.

[0045] The fault - detection system includes a voltage divider 310 and a processor circuit 320. In Figure 3In the example shown, the voltage divider 310 includes a first resistor 312 and a second resistor 314 coupled in series, and a voltage divider output node 316 between the first resistor 312 and the second resistor 314 is coupled to an input of the processor circuit 320. However, those skilled in the art will understand that the voltage divider 310 can have different configurations. For example, the voltage divider 310 can be a capacitive voltage divider instead of a resistive voltage divider as shown in Figure 3 In addition, although the voltage divider output node 316 is shown as being directly coupled to an input of the processor circuit 320, it will be understood that in an actual implementation of the fault detection system, the voltage divider output node 316 can be indirectly coupled to an input of the processor circuit 320 via one or more intermediate components or circuits (e.g., an analog-to-digital converter (ADC) and / or a filter).

[0046] The processor circuit 320 can include a microprocessor, a microcontroller, a state machine, etc., or can include discrete circuits or integrated circuits configured to perform the processing functions and operations described below. In some examples, the controller 280 can include the processor circuit 320, or can be configured to perform the processing functions and operations of the processor circuit 320.

[0047] In Figure 3 In the example shown, the voltage divider 310 is coupled in parallel with the second (low-side) switch of the first half-bridge 210. Accordingly, a first terminal of the voltage divider 310 is coupled to a node 215 between the first switch 212 and the second switch 214 of the first half-bridge 210, and a second terminal of the voltage divider 310 is coupled to a ground rail 244 of the DC link 240.

[0048] The fault detection system further includes a balancing impedance 330 coupled in parallel with the first switch 212 of the first half-bridge 210. Accordingly, a first terminal of the balancing impedance 330 is coupled to a positive power rail 242 of the DC link 240, and a second terminal of the balancing impedance 330 is coupled to the node 215 between the first switch 212 and the second switch 214 of the first half-bridge 210. The purpose of the balancing impedance 330 is to balance the total impedance of the voltage divider 310. In Figure 3In the example shown, the balancing impedance 330 includes a first resistor 332 having a resistance equal to the first resistor 312 of the voltage divider 310. The first resistor 332 is serially coupled with a second resistor 334 having a resistance equal to the second resistor 314 of the voltage divider 310, such that the total resistance of the balancing impedance 330 is equal to the total resistance of the voltage divider 310. However, it will be understood that the balancing impedance 330 may be implemented using a single resistor having a resistance equal to the total resistance of the voltage divider 310. Additionally, if the voltage divider 310 is not a resistive voltage divider, the balancing impedance 330 may be implemented using components other than resistors. For example, if the voltage divider 310 is a capacitive voltage divider, the balancing impedance may be implemented using one or more capacitors (or other capacitive components).

[0049] When the inverter 200 is coupled to the DC link 240 and the switches 212, 214, 222, 224, 232, 234 are all off (e.g., when the inverter 200 is not activated), the resistance of each of the switches 212, 214, 222, 224, 232, 234 (i.e., the off-resistance) is in the megohm range. The off-resistance of the first switch 212 of the first half-bridge 210 is approximately equal to the off-resistance of the second switch 214 of the first half-bridge 210. Thus, when there is no fault in either the first switch 212 or the second switch 214, the voltage at node 215 (equal to the phase voltage Um of the first phase output path 262) is approximately equal to half of the DC link voltage UDC (i.e., Um≈UDC / 2).

[0050] In the event of a "short-circuit" fault in the first (high-side) switch 212, the off-resistance of the first switch 212 will approach zero, such that the voltage at node 215 is approximately equal to the DC link voltage UDC, and thus the phase voltage Um of the first phase output path 262 is approximately equal to the DC link voltage UDC (i.e., Um≈UDC).

[0051] In the event of a "short-circuit" fault in the second (low-side) switch 214, the off-resistance of the second switch 214 will approach zero, such that the voltage at node 215 is approximately equal to zero, and thus the phase voltage Um of the first phase output path 262 is approximately equal to zero (i.e., Um≈0).

[0052] The fault detection system of the present disclosure can detect such faults by monitoring the voltage divider output voltage at the voltage divider output node 316, which indicates the voltage at node 215. If the monitored voltage divider output voltage does not correspond to the expected voltage, the fault detection system can output a fault detection signal to enable appropriate measures to be taken in response to the detection of the fault. For example, the fault detection circuit can output a fault detection signal to the controller 280. In response to the fault detection signal indicating a stuck-on fault in the second switch 214, the controller 280 can output a control signal to open the first switch 212, thereby preventing the possibility of a short circuit between the positive power rail 242 and the ground rail 244 of the DC link.

[0053] The DC link 240 can supply a high DC link voltage UDC (e.g., on the order of 800 - 900 v DC), such that the voltage at node 215 can be in the range of 0–800 or 900 v DC. In contrast, the processor circuit 320 can be configured to receive a low voltage DC input (e.g., in the range of 0 - 5 v DC). Thus, the voltage divider 310 is configured to generate a voltage divider output voltage from the voltage at node 215 such that the level of the voltage divider output voltage is suitable for (either directly or indirectly) input to the processor circuit 320.

[0054] Figure 4 is a schematic diagram showing an example arrangement of the voltage divider 310 and an example arrangement of the balanced impedance 300.

[0055] In Figure 4 the example shown, the first resistor 312 of the voltage divider 310 includes a string of six resistors 132a - 312f connected in series with a resistance of 75 kΩ each, such that the value of the first resistor 312 is 450 kΩ. The second resistor 314 of the voltage divider 310 includes a single resistor with a resistance of 1.5 kΩ. Thus, the total resistance of the voltage divider 310 in the example shown is 451.5 kΩ, and the voltage divider output voltage at the voltage divider output node 316 is equal to 15 / 4510 (about 1 / 300) of the voltage at node 215.

[0056] Thus, when the inverter 200 is coupled to the DC link 240 but not activated (i.e., switches 212, 214, 222, 224, 232, 234 are all off), if the DC link voltage UDC is 900 V, in the event of a stuck-on fault in the second switch 214, the voltage divider output voltage is approximately 0 v, and in the event of a stuck-on fault in the first switch 212, the voltage divider output voltage is approximately 3 v.

[0057] In Figure 4In the example shown, the balancing impedance 330 has the same structure and configuration as the voltage divider 310. Thus, the first resistor 332 of the balancing impedance 330 includes a string of six resistors 332a - 332f connected in series with a resistance of 75 kΩ each, such that the value of the first resistor is 450 kΩ, and the second resistor 334 of the balancing impedance 330 includes a single resistor with a resistance of 1.5 kΩ. Thus, the total resistance of the balancing impedance 330 is 451.5 kΩ, which is equal to the total resistance of the voltage divider 310.

[0058] The resistors 312a - 312f and 314 of the voltage divider 310 and the resistors 332a - 332f and 324 of the balancing impedance 330 can be, for example, surface - mount resistors (also known as surface - mount devices or SMDs). Such resistors are small and inexpensive and thus provide a space - efficient and cost - efficient way to implement the voltage divider 310 and the balancing impedance 330.

[0059] As described above, the voltage - divider output node 316 can be indirectly coupled to the input of the processor circuit 320 via one or more intermediate components or circuits (e.g., an analog - to - digital converter (ADC) and / or a filter). Figure 4 An example of such an arrangement is shown, where the input of a filter 410 (including a resistor 412 and a capacitor 414) is coupled to the voltage - divider output node 316. The filter 410 can operate to filter the voltage - divider output voltage (e.g., remove or attenuate high - frequency components of the voltage - divider output voltage). The output of the filter 410 is coupled to the input of an ADC 420. The ADC 420 is configured to convert the filtered voltage - divider output voltage into a digital signal indicative of the voltage - divider output voltage, which can be output (via the output of the ADC 420) to the input of the processor circuit 320. However, those skilled in the art will understand that other arrangements for coupling the voltage - divider output node 316 to the input of the processor circuit 320 are also possible.

[0060] Figure 5 is a flowchart showing the processing operations performed by the processor circuit 320 in a method for detecting a fault using the fault - detection system described above with reference to Figure 3 description.

[0061] The processor circuit 320 compares a detection signal indicative of the voltage - divider output voltage (which can be the voltage - divider output voltage, or can be, for example, a digital signal indicative of the voltage - divider output voltage) with one or more predefined reference signals (e.g., one or more predefined reference voltages, or digital signals indicative of predefined reference voltages). If the processor circuit 320 determines that the detection signal does not correspond to the predefined reference signal, the processor circuit 320 outputs a fault - detection signal.

[0062] For example, at Figure 5 step 510 of

[0063] the processor circuit 320 may compare the sense signal with a first reference signal indicative of a lower first reference voltage. For example, the first reference voltage may be on the order of 0.1v DC.

[0064] If the sense signal is less than the first reference signal, this may indicate a hard - on fault in the second (low - side) switch 214, and thus at step 520, the processor circuit 320 may output (e.g., to the controller) a fault detection signal indicative of the detected hard - on fault in the second (low - side) switch 214.

[0065] Alternatively or additionally, at Figure 5 step 530 of

[0066] the processor circuit 320 may compare the sense signal with a second reference signal indicative of a relatively higher second reference voltage. For example, the second reference voltage may be on the order of 2.8v DC.

[0067] If the sense signal is greater than the second reference signal, this may indicate a hard - on fault in the first (high - side) switch 212, and thus at step 540, the processor circuit 320 may output (e.g., to the controller) a fault detection signal indicative of the detected hard - on fault in the first (high - side) switch 212.

[0068] It will be understood from the foregoing description that the fault detection system of the present disclosure provides a simple, reliable, and cost - effective means to detect faults in the switches of the half - bridge of an inverter to protect the inverter from damage caused by breakdown currents resulting from such switch faults.

[0069] As in Figure 3In the example shown, if a three-phase motor 270 is coupled to the output of the inverter 200, since the three half-bridges 210, 220, 230 are connected via a star or delta connection of the motor 270, only a single fault detection system of the above kind is needed to detect a stuck-on fault in any one of the switches 212, 214, 222, 224, 232, 234 of the inverter 200. More generally, if the load coupled to the output of the inverter 200 has a low DC impedance (e.g., if the load includes three chokes connected in a star configuration with a star point), only a single fault detection system of the above kind is needed to detect a stuck-on fault in any one of the switches 212, 214, 222, 224, 232, 234 of the inverter 200.

[0070] If a load that does not have a low DC impedance is coupled to the output of the inverter 200, it may be necessary to provide a fault detection system for each of the half-bridges 210, 220, 230 by coupling a separate voltage divider 310 in parallel with the second (low-side) switch 214, 224, 234 of each of the half-bridges 210, 220, 230. A separate instance of the processor circuit 320 may be provided for each of these separate voltage dividers, or alternatively, a single instance of the processor circuit 320 may be provided, where the output node of each separate voltage divider 310 (directly or indirectly as described above) is coupled to a corresponding different input of the processor circuit 310.

[0071] In the foregoing description, the fault detection system has been described in the context of a three-phase inverter, but those skilled in the art will readily understand that the fault detection system of the present disclosure is equally applicable to a single-phase inverter. More generally, the fault detection system of the present disclosure is applicable to any circuit topology that uses one or more half-bridges (e.g., a multilevel converter such as a modular multilevel converter (MMC)). Thus, the application of the fault detection system of the present disclosure is not limited to inverters, but also applies to any circuit that uses one or more half-bridges.

[0072] Figure 6 A machine-readable medium 600 having stored thereon a computer program 610 including instructions that, when executed by a suitable processing device 620 (e.g., the processor circuit 320), cause the processing device 620 to perform the steps of the above-described method is shown highly schematically.

[0073] Features described in connection with any one of the above aspects may be applied, with necessary modifications, to any other aspect, unless mutually exclusive. Additionally, unless mutually exclusive, any feature described herein may be applied to any aspect and / or combined with any other feature described herein. Further, although this disclosure is in the context of a transport refrigeration system and / or a vapor compression circuit, it will be understood that the disclosure has other possible applications in other technical fields.

[0074] This disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that would be understood by a person of ordinary skill in the art. Similarly, where appropriate, the appended claims encompass all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that would be understood by a person of ordinary skill in the art. Additionally, the mention in the appended claims of a device or system or a component of a device or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that device, system, or component, whether or not the particular function is activated, turned on, or unlocked, so long as the device, system, or component is adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to do so. Accordingly, the systems, devices, and methods described herein may be modified, added to, or omitted without departing from the scope of this disclosure. For example, components of the systems and devices may be integrated or separated. Additionally, the operations of the systems and devices disclosed herein may be performed by more, fewer, or other components, and the methods described may include more, fewer, or other steps. Additionally, the steps may be performed in any suitable order. As used herein, "each" refers to each member of a set or each member of a subset of a set.

[0075] Although example embodiments are shown in the drawings and described below, any number of techniques may be used to implement the principles of this disclosure, whether currently known or not. This disclosure should in no way be limited to the example embodiments and techniques shown in the drawings and described above.

[0076] Unless otherwise specifically noted, items depicted in the drawings are not necessarily drawn to scale.

[0077] All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the disclosure and the concepts contributed by the inventors to further the art, and are to be construed as not being limited to such specifically recited examples and conditions. While the embodiments of this disclosure have been described in detail, it should be understood that various changes, substitutions, and alternatives may be made without departing from the spirit and scope of the invention.

[0078] Although the specific advantages are listed above, various embodiments may include some or all of the listed advantages, or may not include the listed advantages. Additionally, other technical advantages can be readily understood by those of ordinary skill in the art after reading the foregoing drawings and description.

[0079] It should be noted that the above embodiments are for illustration purposes only and not for limiting the present invention, and those skilled in the art can design many alternative embodiments without departing from the scope of the appended claims. The word "comprising" does not exclude the presence of elements or steps other than those listed in the claims, "a" or "an" does not exclude a plurality, and a single feature or other unit may perform the functions of several units recited in the claims. Any reference signs or labels in the claims should not be construed as limiting their scope.

Claims

1. A fault detection system for detecting a fault in a switch of a half - bridge of a circuit (200) in a transport refrigeration system, the fault detection system comprising: A voltage divider; And A processor circuit, Wherein: When using the fault detection system, the voltage divider is coupled in parallel with the switch of the half - bridge of the circuit; and The output of the voltage divider is coupled to the input of the processor circuit, And wherein the processor circuit is operable to: Compare a detection signal indicative of the voltage at the output of the voltage divider with a reference signal; and In response to determining that the detection signal does not correspond to the reference signal, output a fault detection signal.

2. The fault detection system according to claim 1, wherein, When using the fault detection system, the voltage divider is coupled in parallel with the low - side switch of the half - bridge of the circuit.

3. The fault detection system according to claim 1, wherein, The voltage divider is a resistive voltage divider comprising a first resistor connected in series with a second resistor.

4. The fault detection system according to claim 3, wherein: The first resistor comprises a plurality of resistors connected in series, and The second resistor comprises a single resistor.

5. The fault detection system according to claim 4, wherein, The plurality of resistors of the first resistor and the single resistor of the second resistor are surface - mount devices.

6. The fault detection system according to claim 1, wherein, The voltage divider is configured to receive an input DC voltage in the range of 0 - 900 volts and output an output DC voltage in the range of 0 - 5 volts.

7. The fault detection system according to claim 6, wherein, The voltage divider is configured such that the magnitude of the output DC voltage is approximately 1 / 300 of the magnitude of the input DC voltage.

8. The fault detection system according to claim 1, wherein, The fault is a stuck - on fault.

9. The fault detection system according to claim 1, wherein, The processor circuit is operable to: Compare the detection signal indicative of the voltage at the output of the voltage divider with a first reference signal; And In response to determining that the detection signal is less than the first reference signal, output a first fault detection signal indicative of a stuck - on fault in the low - side switch of the circuit.

10. The fault detection system according to claim 1, wherein, The processor circuit is operable to: Compare the detection signal indicative of the voltage at the output of the voltage divider with a second reference signal; And In response to determining that the detection signal is greater than the second reference signal, output a second fault detection signal indicative of a stuck - on fault in the high - side switch of the circuit.

11. The fault detection system according to claim 1, wherein, The circuit is an inverter circuit or a multilevel converter circuit.

12. A method for detecting a fault in a switch of a half - bridge of a circuit in a transport refrigeration unit, the method comprising: Comparing, by a processor circuit, a signal indicative of the output voltage of a voltage divider coupled in parallel with a switch of a half - bridge of an inverter with a reference voltage; And In response to determining, by the processor circuit, that the detected voltage does not correspond to the reference voltage, indicating a fault condition.

13. A transport refrigeration system comprising a circuit and the fault detection system according to claim 1.

14. A machine - readable medium having a computer program stored thereon comprising instructions which, when executed by a processing device, cause the processing device to perform the method according to claim 12.

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