Adaptive control for multilevel converters

Abstract

An apparatus includes a two-level converter circuit (120), a higher-level converter circuit (130) (with a switch), and a controller (140). The controller receives a feedback signal (112) associated with the two-level / higher-level converter circuit and generates a control signal (142) based on the feedback signal. The apparatus operates in one of three modes (first / second / third mode) based on the control signal (142). In the first mode, the apparatus operates as a two-level converter to generate a two-level output voltage from an input voltage. In a second mode, the apparatus operates as a higher-level converter to increase the number of levels of the output voltage to more than two levels. In a third mode, the apparatus transitions between the first / second mode, where the apparatus operates as the two-level converter, and where the switch of the higher-level converter circuit is activated for a period of time to generate a zero voltage at a switching junction of the apparatus.

Description

Background Technology

[0001] In recent years, high-power applications have increased. For example, the increasing number of electric vehicles (EVs), renewable energy generation such as solar power, and battery backup from solar panels have led to an increase in high-power applications such as battery charging / discharging. Many high-power applications use traction inverters to convert direct current (DC) to alternating current (AC). Some have used three-level T-type converters (a three-level bidirectional power converter topology that converts DC voltage to AC voltage and vice versa, and can operate as an inverter or power factor correction device) or, for example, four-level converters, to improve efficiency and reduce electromagnetic interference (EMI) compared to lower-level converters such as two-level converters.

[0002] A multilevel converter can generate a sinusoidal voltage from multiple voltage levels, for example, obtained from a capacitor voltage source. For instance, in a three-level converter, each phase leg may contain two pairs of switches connected in series. The resulting stepped quasi-square wave output can be improved as the number of levels increases, approximating a sine wave.

[0003] Three-level converters use more power switches than two-level converters, thus increasing cost. When switched on, the power switches have a low resistance (RDSON) between drain and source, such as 5 mΩ, to support high current drive, such as 400 Amp. Generally, in a T-type converter, the external power switch is rated at full V. bus Voltage. For example, V for 800V. bus The external switch can be rated at 1200 V, and the intermediate power switch can be rated at 600 V, which is half the 1200 V rating of the external switch. However, the current ratings of the intermediate power switch and the external power switch remain the same. Therefore, even if the intermediate power switch can be rated at full V... bus Even at half the voltage, a low RDSON of the intermediate power switch is still required to address the current rating. Therefore, the cost associated with switching to a T-type converter is further increased due to the low RDSON rating associated with the intermediate power switch. Summary of the Invention

[0004] In one example, a device includes a two-level converter circuit, a higher-level converter circuit, and a controller. The two-level converter circuit includes a first switch and a second switch. The higher-level converter circuit includes a third switch and a fourth switch. The controller is configured to receive feedback signals associated with the two-level converter circuit and the higher-level converter circuit. The controller is configured to generate control signals based on the feedback signals. The device is configured to operate in one of three modes based on the control signals. In a first mode, the device is configured to operate as a two-level converter, wherein the two-level converter is configured to generate a two-level output voltage from an input voltage. In a second mode, the device is configured to operate as a higher-level converter, wherein the higher-level converter is configured to increase the number of output voltage levels to more than two levels. In a third mode, the device is configured to switch between the first mode and the second mode. Furthermore, in the third mode, in response to the device operating as a two-level converter and the third and fourth switches of the higher-level converter circuit being activated for a period of time, the device is configured to generate zero voltage at the switching connection point of the device.

[0005] In one example, a method includes receiving a feedback signal associated with a multilevel converter circuit of a device. The multilevel converter circuit includes a two-level converter circuit and a higher-level converter circuit, the two-level converter circuit including a first switch and a second switch, and the higher-level converter circuit including a third switch and a fourth switch. The method further includes generating a control signal based on the feedback signal. The control signal causes the multilevel converter circuit to operate in one of a first mode, a second mode, or a third mode. In the first mode, the device is configured to operate as a two-level converter, and the two-level converter is configured to generate a two-level output voltage from an input voltage. In the second mode, the device is configured to operate as a higher-level converter, and the higher-level converter is configured to increase the number of output voltage levels to more than two levels. In the third mode, the device is configured to switch between the first mode and the second mode. Furthermore, in the third mode, in response to the device operating as a two-level converter and the third and fourth switches of the higher-level converter circuit being activated for a period of time, the multilevel converter circuit is configured to generate a zero voltage at the switching connection point of the device. Attached Figure Description

[0006] Figure 1 This is a schematic diagram of an adaptive control system for a multilevel converter in one example.

[0007] Figure 2 This is a schematic diagram of a multilevel converter in one example.

[0008] Figure 3 For generating in an instance Figure 2A schematic diagram of the control system for the power switch control signal in a multilevel converter.

[0009] Figure 4 For generating in an instance Figure 2 A schematic diagram of another control system for the control signal of the power switch in a multilevel converter.

[0010] Figures 5A-5B A device is shown in one example that operates as a two-level converter.

[0011] Figures 6A-6B A device is shown in one example that operates as a three-level converter.

[0012] Figures 7A-7B A device is shown in an example operating in a switching mode between two-level and three-level modes.

[0013] Figure 8 The operation of a multilevel converter is shown in another example.

[0014] Figure 9 This is a schematic diagram of an electric vehicle system with adaptive control for a multilevel converter in one example.

[0015] Figure 10 This is a schematic diagram of a 3-phase three-level T-type inverter in an example.

[0016] Figure 11 This section compares the performance of a three-level converter in one example with that of a multi-level converter that can operate in transition modes.

[0017] Figure 12 This illustrates the relationship between conduction loss and junction temperature in a specific example. Detailed Implementation

[0018] The same reference numerals or other reference designators are used in the accompanying drawings to designate the same or similar features (functionally and / or structurally). Various examples are described in more detail below. However, the examples are not limiting, as elements in such examples can vary. Furthermore, the specific examples described and / or illustrated herein have elements that can be readily separated from the specific example and optionally combined with or substituted for elements in any of the several other examples described herein. Moreover, the terminology used herein is for descriptive purposes only and should not be construed as limiting. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as in the field to which the examples pertain.

[0019] Adaptive control mechanisms can be used to control the operation of multilevel converters, allowing them to operate as two-level converters, higher-level converters (e.g., three-level converters, four-level converters, etc.), or in transition modes (when transitioning from a one-level (e.g., two-level) converter to a higher-level converter), thereby improving efficiency and reducing cost. For example, a three-level T-type converter can operate in two-level or three-level mode or in transition modes as needed to improve its efficiency and EMI. The cost associated with a three-level T-type converter can be reduced by allowing the intermediate power switches of the T-type converter to be replaced with lower-cost switches (e.g., MOSFETs with high RDSON, such as 20 mΩ-40 mΩ) with low-capacitance outputs (e.g., 150 pF) instead of the high currents (e.g., low RDSON, such as 2 mΩ-6 mΩ) that must be rated for a 3-L-type converter. Furthermore, during transition modes, at least one of the intermediate switches can be activated for a short period of time to make the output voltage approximately 0 volts for a short period of time. Thus, the overall switching losses of the device are reduced due to the reduced switching losses on the external switches. According to one example, feedback signals associated with the intermediate power switch (e.g., switch terminal current, junction temperature, etc.) can be used to generate control signals (e.g., pulse width modulation (PWM)) for controlling each switch of the T-type converter (e.g., one or more switches among the intermediate power switch and / or external power switches). Configurations according to non-limiting examples enable the device to operate as a two-level converter or a three-level converter (or higher-level converter), while also enabling the device to operate in transition mode when the converter transitions from one level to another (e.g., from a two-level converter to a three-level converter, from a three-level converter to a two-level converter, from a three-level converter to a four-level converter, etc.). Under light loads, the adaptive control mechanism described herein can improve efficiency by up to 50% and improve EMI compared to a two-level converter, while under heavy loads, it achieves an efficiency improvement of up to 30%.

[0020] It should be understood that throughout this application, examples of three-level T-type converters are provided for illustrative purposes and this does not limit the scope of the examples. For example, the description of a three-level converter in a T-type converter is equally applicable to 4-level or higher level converters that may or may not be configured as T-type. Throughout this specification, reference is made to a two-level converter in which a two-level output voltage is generated from an input voltage. Furthermore, reference is made to higher-level converters in which the number of output voltages generated from the input voltage is increased compared to a two-level converter, for example, three output voltages for a three-level converter, four output voltages for a 4-level converter, etc. It should be understood that the terms operation, regulation, and mode are used interchangeably throughout this application.

[0021] Figure 1This is a schematic diagram of an adaptive control system 100 for a multilevel converter in one example. System 100 includes a multilevel converter circuit system 110 coupled to a controller 140. The multilevel converter circuit system 110 includes a two-level converter circuit system 120 and a higher-level converter circuit system 130. According to one example, the two-level converter circuit system 120 is a converter with two levels, and the higher-level converter circuit system 130 is a circuit system that converts the two-level converter circuit system 120 into a higher-level converter (e.g., three-level, four-level, etc.). In one example, the two-level converter circuit system 120 generates two voltage outputs from an input voltage. In one example, the two-level converter circuit system 120 includes a power switch (also referred to as an external power switch), and the higher-level converter circuit system 130 includes a power switch (also referred to as an intermediate power switch), such as... Figure 2 The following describes the process in more detail. The higher-level converter circuit system 130 is configured to produce more than two voltage outputs when activated together with the two-level converter circuit system 120. In one example, the multilevel converter circuit system 110 may be a three-level T-type converter. The multilevel converter circuit system 110 may generate a feedback signal 112 (e.g., switch terminal current, junction temperature, etc.), which is used by a controller 140 (e.g., a central processing unit (CPU), microcontroller, field-programmable gate array (FPGA), application-specific integrated circuit (ASIC), etc.) to generate control signals 142 (e.g., PWM signals) for controlling one or more power switches of the multilevel converter circuit system 110.

[0022] Controller 140 generates control signal 142, which causes the device (e.g., multilevel converter circuit system 110) to operate in one of three modes. A first mode may be associated with multilevel converter circuit system 110 operating as a two-level converter, thereby generating two output voltages (i.e., two levels). A second mode may be associated with multilevel converter circuit system 110 operating as a higher-level converter (e.g., a three-level converter, a four-level converter, etc.), thereby generating more than two output voltages, such as three output voltages. A third operating mode is the case when the converter transitions from one level to another (e.g., from a two-level converter to a three-level converter, from a three-level converter to a two-level converter, from a three-level converter to a four-level converter, etc.). In the third mode, controller 140 activates one or more switches of higher-level converter 130 for a period of time to generate approximately zero voltage at switch connection 299 of multilevel converter 110. Therefore, the overall switching losses of the device are reduced due to the reduced switching losses on the external switches.

[0023] It will be apparent that the components depicted in this and subsequent figures can be arbitrarily combined or divided into individual software, firmware, and / or hardware components. Furthermore, it will be apparent that, regardless of their combination or division, such components can execute on the same host or multiple hosts, and these hosts can be connected via one or more networks.

[0024] Now for reference Figure 2 A schematic diagram of a multilevel converter 110 in one example is shown. Figure 2 The multilevel converter 110 in the example is a three-level T-type one-phase converter circuit. The multilevel converter 110 includes a two-level converter circuit 120, which includes power switches 210-220 (external power switches) and capacitors 230-240. The power switches 210-220 can have low RDSON, for example, 2 mΩ-6 mΩ. Figure 2 The higher-level converter circuit 130 is a circuit system that converts the two-level converter circuit 120 into a three-level converter circuit, and it includes power switches 250 and 260 (intermediate power switches). Power switches 250 and 260 are located between power switches 210 and 220 of the two-level converter circuit 120 and capacitors 230 and 240. Power switches 250 and 260 can be lower-cost switches (e.g., MOSFETs with high RDSON, such as 20mΩ-40 mΩ) with low capacitance output (e.g., 150 pF) instead of the high current (e.g., low RDSON, such as 2 mΩ-6 mΩ) that must be rated for a 3-L type converter.

[0025] In one example, feedback signal 112 may be a signal associated with the current at the switching terminal of higher-level converter circuit 130. For example, Figure 2 The feedback signal 112 can be the switching terminal current of the power switches 250 and 260 of the higher-level converter circuit 130. In one example, an inductor (not shown) connected to the power switches 250 and 260 can be used to measure the switching terminal current. In a non-limiting example, the current can be measured by various means (e.g., Hall effect, shunt-based solutions, current transformers, etc.). In yet another example, Figure 2The feedback signal 112 may be the junction temperature associated with the power switches 250-260 of the higher-level converter circuit 130. According to one example, the junction temperature may be measured using a diode or a GaN device capable of measuring the temperature of the GaN device, which is also responsible for power conversion. In one example, the temperature may be measured internally within the power device using a temperature sensor, or it may be estimated by measuring parameters associated with the switch (e.g., a FET) (e.g., a real-time measurement by RDSON). In one example, a GaN device or diode may measure the junction temperature associated with power switches 250 and / or 260. The feedback signal 112, which may include switch terminal current and / or junction temperature, is sent to the controller 140 for processing.

[0026] Controller 140 generates control signal 142, which causes the device (e.g., multilevel converter circuit system 110) to operate in one of three modes. A first mode may be associated with multilevel converter circuit system 110 operating as a two-level converter, thereby generating two output voltages (i.e., two levels). In the first mode, higher-level converter circuit 130 is inactive, for example, power switches 250 and 260 are disabled.

[0027] The second mode can be associated with a multilevel converter circuit system 110 operating as a higher-level converter (e.g., a three-level converter, a four-level converter, etc.), thereby generating more than two output voltages, such as three output voltages for a three-level converter. In a non-limiting example, in the second mode, the controller 140 controls the power switches such that power switches 210 and 260 are switching, while power switch 250 is asserted and power switch 220 is deasserted (disabled). In another non-limiting example, in the second mode, the controller 140 controls the power switches such that power switches 220 and 250 are switching, while power switch 260 is asserted and power switch 210 is deasserted (disabled).

[0028] The third operating mode is for when the converter transitions between one level and another (e.g., from a two-level converter to a three-level converter, from a three-level converter to a two-level converter, from a three-level converter to a four-level converter, etc.). In the third mode, the controller 140 activates one or more switches of the higher-level converter 130 for a period of time to generate approximately zero voltage at the switch connection 299 of the multilevel converter 110. Therefore, the overall switching losses of the device are reduced due to the reduced switching losses on the external switches. Figures 7A-7B The document provides an example of power switch operation in the third mode. The following section discusses... Figure 8 Describe voltages 232, 234, and 236.

[0029] Figure 3For generating in an instance Figure 2 A schematic diagram of a control system 300 for the control signals of the power switches in a multilevel converter. The control system 300 includes a PWM generator 310 and a controller 140. In one example, a modulation index signal 302 (whether externally generated or created by the controller 140) is input to the PWM generator 310 to generate a PWM signal associated with the operating mode of the multilevel converter 110 controlled by the controller 140 (e.g., a first mode (two-level), a second mode (three-level), a third mode (switching between two different levels), etc.). In one example, the controller 140 receives a feedback signal 112 and controls the PWM generator 310 to generate appropriate PWM signals (e.g., control signal 142, which includes signals 142a-142d respectively associated with power switches 210, 220, 250, and 260) to control each of the power switches 210, 220, 250, and 260 so that the multilevel converter circuit 110 operates in one of the three modes. According to some examples, the transition between two-level and three-level modes or between two different levels (e.g., one level shifter to another level shifter) can be performed within the same cycle of the sine wave being controlled. For example, a 3-L PWM signal is used for current peaks up to 40 Amp, and a 2-L PWM signal is used for current peaks from 40 Amp to 200 Amp.

[0030] In this example, for a three-level converter with four power switches, four control signals can be output (one control signal for each power switch). For example, one control signal can be generated to control power switch 210, one control signal can be generated to control power switch 220, one control signal can be generated to control power switch 250, and one control signal can be generated to control power switch 260. Thus, the PWM generator 310 can generate four PWM signals (one PWM signal for each power switch) to enable the converter to operate at any given level (e.g., two-level, three-level, transition, etc.).

[0031] The description of a control signal for each power switch is for illustrative purposes and not to limit the scope of the examples. For example, one control signal may be used to control the operation of the power switches (e.g., switches 210-220) of the two-level converter circuit 120, while another control signal may be used to control the operation of the power switches (e.g., switches 250-260) of the higher-level converter circuit 130.

[0032] In one example, a memory component may be used to store a lookup table (LUT) accessed by controller 140 to determine control signal 142. The LUT may be stored and implemented to improve efficiency by determining the PWM signal associated with a particular power switch based on feedback signal 112. For example, the LUT may have a corresponding PWM signal (for a given power switch, such as switch 210, 220, 250, or 260) associated with a specific feedback signal (e.g., switch terminal current and / or junction temperature, etc.). In other words, the LUT may indicate the specific PWM signal to be used for a given switch (e.g., switch 210, switch 220, switch 250, switch 260) based on the feedback signal (e.g., based on switch terminal current and / or junction temperature). An example of a table associated with switch 210 is given below. Similar tables may be used for other power switches in a multilevel converter circuit system. According to one example, the LUT associated with each power switch may be the same or different from each other. In other words, control of each power switch may be programmable (via the LUT), and the operation of each power switch may be controlled based on the feedback signal.

[0033]

[0034] According to one example, based on a determined PWM signal, controller 140 controls PWM generator 310 to output the desired PWM signal as control signal 142. Control signal 142 is sent to multilevel converter 110 to control the operation of power switches. In one example, control signal 142 may include multiple signals (e.g., control signals 142a, 142b, 142c, and 142d) to control multiple power switches.

[0035] Figure 4 For generating in an instance Figure 2 A schematic diagram of another control system 400 for the control signal of the multilevel converter. Figure 4 Similar to Figure 3 The logic circuit 410 is used instead of controller 140, except that it uses logic circuit 410 instead of controller 140. Logic circuit 410 may include one or more logic circuits (e.g., AND gates, OR gates, NOR gates, XOR gates, etc.). Logic circuit 410 may receive current signal 416 and signals 412-414 as its feedback signals. As described above, current signal 416 is a signal associated with the current of the switch terminals. Signals 412 and 414 may be signals associated with the junction temperatures of power switches 250 and 260, respectively. Logic circuit 410 controls the operation of PWM generator 310 based on the received signals (e.g., current signal 416 and / or signals 412 and / or signals 414) to generate appropriate PWM signals for each power switch as control signals 142 (e.g., control signals 142a-142d).

[0036] It should be understood that control system 300 or 400 as described above can be replicated for each phase of the system. For example, control system 300 or 400 as described above can be replicated for each phase of a 3-phase converter, such as a control system for the first phase, a control system for the second phase, and a control system for the third phase.

[0037] Figures 5A-5B A device operating as a two-level converter is shown in one example. Figure 5A In this embodiment, controller 140 has determined, based on feedback signal 112, that multilevel converter 110 will operate in a first mode (e.g., as a two-level converter). In a non-limiting example, controller 140 causes PWM generator 310 to generate an appropriate PWM signal for each power switch. In this example, the PWM signal generated for power switch 210 causes switches 210 and 220 to switch opposite to each other, for example, when switch 210 is asserted, switch 220 is deasserted, and when switch 210 is deasserted, switch 220 is asserted. In other words, as described above, the control switches control the dead time between the switches (e.g., when the voltage is forced to 0 V). The duty cycle associated with each switch 210 and 220 can be controlled by PWM generator 310 based on controller 140. In this non-limiting example, power switches 250 and 260 are deasserted (using the PWM signal generated by PWM generator 310) to disable higher-level converter circuit 130, thereby enabling the device to operate as a two-level converter circuit. In this example, with a DC link voltage of 400 V, the average voltage achieved in the switch connection voltage 299 relative to the connection with voltage 234 will be approximately 200 V (average 200 V). Now refer to Figure 5B ,exhibit Figure 5A A variant in which the duty cycles of switches 210 and 220 are varied, and in which an average voltage of -200 V is achieved with a DC link voltage of 400 V.

[0038] Figures 6A-6B A device operating as a three-level converter is shown in one example. Figure 6AIn this example, controller 140 has determined, based on feedback signal 112, that multilevel converter 110 will operate in a second mode (e.g., as a three-level converter). In a non-limiting example, controller 140 causes PWM generator 310 to generate an appropriate PWM signal for each power switch. In this example, the PWM signals generated for the power switches cause switches 210 and 260 to switch in opposite directions (when switch 210 is asserted, switch 260 is deasserted, and when switch 210 is deasserted, switch 260 is asserted), while switch 250 is asserted and switch 220 is deasserted. In other words, as described above, the control switches control the dead time between switches (e.g., when the voltage is forced to 0 V). In this example, with a DC link voltage of 400 V, an average voltage of 200 V is achieved at the switch connection voltage 299.

[0039] Figure 6B The display is similar to Figure 6A Another example. In this example, switch 210 is deasserted (switch deactivated), while switch 260 is asserted, and switches 220 and 250 toggle in opposite directions (e.g., when switch 250 is asserted, switch 220 is deasserted, and when switch 250 is deasserted, switch 220 is asserted). In other words, as described above, the control switch controls the dead time between switches (e.g., when the voltage is forced to 0 V). In this non-limiting example, with a DC link voltage of 400 V, an average voltage of -200 V is achieved at switch connection voltage 299.

[0040] Figures 7A-7B A device is shown in an example operating in a switching mode between two-level and three-level modes. Figure 7AIn this embodiment, controller 140 has determined, based on feedback signal 112, that multilevel converter 110 will operate in a third mode (e.g., transitioning between two different levels, such as from a two-level converter to a three-level converter or from a three-level converter to a two-level converter). In a non-limiting example, controller 140 causes PWM generator 310 to generate an appropriate PWM signal for each power switch. In this non-limiting example, controller 140 causes switches 210 and 220 to switch such that when switch 210 is asserted, switch 220 is deasserted, and when switch 210 is deasserted, switch 220 is asserted only for the period during which the switch is deasserted (e.g., switch 220 is asserted for a quarter of the period during which switch 210 is deasserted, switch 220 is asserted for a third of the period during which switch 210 is deasserted, etc.). During the period when both switches 210 and 220 are deasserted (also known as the transition time), switches 250 and 260 can be activated to generate approximately 0 V at the switch connection 299 of the multilevel converter 110. In some instances, the transition time can be adjusted based on junction temperature, current associated with the switch connection voltage 299, etc. For example, as shown below... Figure 9 In the motor application described herein, the switching time can be adjusted based on the length of the cable connecting the motor to the inverter. The overall switching loss of the device is reduced due to the reduced switching losses on the external switch. In this non-limiting example, switches 250 and 260 are activated twice during each time period when both switches 210 and 220 are deasserted, thereby generating 0 V at switch connection 299. The generation of two 0 V values ​​at switch connection 299 during each time period when both switches 210 and 220 are deasserted is for illustrative purposes and not to limit the scope of the example. For example, in another non-limiting example, switch 220 is activated two or more times during the time period when switch 210 is deasserted, and therefore, activation of switches 250 and 260 during the time period when both switches 210 and 220 are deasserted generates 0 V three or more times. The voltage at switch connection 299 is also shown. In this example, with a DC link voltage of 400 V, an average voltage of 200 V is achieved.

[0041] exist Figure 7BIn this embodiment, controller 140 has determined, based on feedback signal 112, that multilevel converter 110 will operate in a third mode (e.g., transitioning between two different levels, such as from a two-level converter to a three-level converter or from a three-level converter to a two-level converter). In a non-limiting example, controller 140 causes PWM generator 310 to generate an appropriate PWM signal for each power switch. In this example, controller 140 causes switches 210 and 220 to switch such that when switch 210 is asserted, switch 220 is deasserted, and switch 210 is asserted within at least a subset of the time during which switch 220 is deasserted (e.g., switch 210 is asserted within a quarter of the time period during which switch 220 is deasserted, switch 210 is asserted within a third of the time period during which switch 220 is deasserted, etc.). During the time period during which both switches 210 and 220 are deasserted, switches 250 and 260 may be activated to generate approximately 0 V at switch connection 299 of multilevel converter 110. In some instances, the transition time can be adjusted based on junction temperature, current associated with switch connection voltage 299, etc. The overall switching losses of the device are reduced due to the reduced switching losses on the external switches. In this non-limiting example, switches 250 and 260 are activated twice during each time period when switches 210 and 220 are deasserted, thereby generating 0 V at switch connection 299. The generation of two 0 V values ​​at switch connection 299 during each time period when both switches 210 and 220 are deasserted is for illustrative purposes and not to limit the scope of the example. For example, in another non-limiting example, switch 220 is activated two or more times during the time period when switch 210 is deasserted, and therefore, activation of switches 250 and 260 during the time period when both switches 210 and 220 are deasserted generates 0 V three or more times. The voltage at switch connection 299 is also shown. In this example, with a DC link voltage of 400 V, an average voltage of -200 V is achieved.

[0042] According to some non-limiting examples, when controller 140 causes multilevel converter 110 to operate as a two-level converter, switches 250-260 are deactivated (in the first mode). In one non-limiting example, when controller 140 causes multilevel converter 110 to operate as a three-level converter, switch 210 is deactivated (de-asserted) when switch 220 is switching, and switch 250 is asserted (on) when switch 260 is switching. The control signals associated with switches 210, 220, 250, and 260 are controlled by controller 140, which controls PWM generator 310. In one example, switch 210 is on (asserted), and switch 220 is off (de-asserted), and vice versa, while switches 210 and 260 are not asserted simultaneously (for the same time period), and switches 220 and 250 are not asserted simultaneously (for the same time period). Power switches 250 and 260 can be lower-cost switches with low MOSFET capacitance output (e.g., 150pF) (e.g., high RDSON, such as 20 mΩ-40 mΩ), instead of the high current ratings (e.g., low RDSON, such as 2 mΩ-6 mΩ) required for 3-L type converters. The higher RDSON of switches 250 and 260 reduces parasitic capacitance while enabling faster switching (and lower cross-losses for switches 250 and 260).

[0043] Figure 8 The operation of a multilevel converter is illustrated in another example. In this example, the modulation index signal 302 is shown together with the voltage (AC) at connection 299 and the current at connection 299. This example shows that although it appears the converter is performing a 2-L switching operation, upon magnification, it becomes apparent that the converter is performing a 3-L switching operation, as described above. Figure 8 The switch node voltage 299 (DC voltage) and the current through connection 299 are also shown. Therefore, switches 210 and 220 can be rated for a DC voltage of 1200 V, while switches 250 and 260 can be rated for a much lower voltage of 600 / 650 V.

[0044] Figure 9 This is a schematic diagram of an electric vehicle system with adaptive control for a multilevel converter in one example. The EV system may include a PWM unit 910, a converter 920, a motor 930, and a battery 940. The PWM unit 910 may be similar to... Figure 3System 300 or 400, or 4, generates control signals associated with the power switching of the converter 920 circuit system (e.g., multilevel converter circuit system 110). Battery 940 is a power storage device for powering motor 930. PWM unit 910 and converter 920 may be traction inverters for EVs. According to a non-limiting example, motor overvoltages caused by long cables connecting the inverter to the motor, as described above, can be mitigated by using PWM unit 910 and converter 920. For example, the mode transition time can be tuned relative to the cable length and the signal propagation speed in the power line.

[0045] Figure 1-9 A one-phase converter is described for illustrative purposes, not to limit the scope. For example, Figure 10 This is a schematic diagram of a 3-phase three-level T-type inverter in an example. Figure 10 In this configuration, external power switches 1020-1025 are associated with a two-level converter circuit system, while intermediate power switches 1030-1035 are associated with a higher-level converter circuit system (e.g., three-level). In one example, the three-phase three-level T-type inverter may also include capacitors 1041 and 1042 and a battery 1010.

[0046] According to one example, this can be done for each power switch (e.g., Figure 10 Switches 1021-1035 in the power switch generate PWM signals (control signals). In other words, 12 PWM signals can be generated, one PWM signal for each power switch. In another example, a control signal can be generated to control switches 1034-1035, a control signal can be generated to control switches 1032-1033, a control signal can be generated to control switches 1030-1031, a control signal can be generated to control switch 1020, and so on. In yet another example, a control signal can be generated to control more than one of the external power switches, such as switches 1021-1025.

[0047] According to one example, the feedback signal may include one or more of the following: the switching current terminals of switches 1034-1035, the switching current terminals of switches 1032-1033, the switching current terminals of switches 1030-1031, the junction temperature of switch 1030, the junction temperature of switch 1031, the junction temperature of switch 1032, the junction temperature of switch 1033, the junction temperature of switch 1034, and the junction temperature of switch 1035. Therefore, the number and type of feedback signals can be changed as needed to control the operation of each power switch. In other words, the number and type of feedback signals, the number of control signals, etc., are configurable and controllable to control the operation of one or more power switches in the converter circuit system.

[0048] Figure 11 This section compares the performance of a three-level converter in one example with that of a multi-level converter that can operate in transition modes. Figure 11 The diagram shows that with a three-level converter, power loss is generally reduced at a junction temperature of 50 degrees Celsius, but it increases once the current threshold is reached, and its operation in three-level mode is not efficient. In contrast, adaptively switching the intermediate switch to operate in transition mode, such as... Figure 1-10 As described, this facilitates further reductions in power loss under high loads. As shown, in one example, the converter can operate in three-level operation up to a threshold of 73 Amp, at which point power loss cannot be reduced under three-level operation. Therefore, in one example, the system controls the power switch to operate in a transition mode at or above 65 Amp to switch the intermediate switch of the higher-level converter circuit 130, thereby achieving a further reduction in power loss, as shown. The results at a junction temperature of 50 degrees are provided for illustrative purposes and are not intended to limit the scope of the examples. Under light loads, the adaptive control mechanism described above can improve efficiency by up to 50% and improve EMI compared to a two-level converter, while under heavy loads, it can achieve an efficiency improvement of up to 30%.

[0049] Figure 12 This illustrates the relationship between conduction losses and junction temperature in a GaN device in one example. As shown, conduction losses depend on the junction temperature within the GaN device. Therefore, real-time monitoring of the junction temperature and control of the power switch operation (using a PWM signal) enables improvements in efficiency and EMI, and further allows for longer three-level regulation even under high loads.

[0050] Therefore, the real-time current (switch terminal current) from one or more power switches (e.g., intermediate power switches) and / or one or more junction temperatures associated with one or more power switches (e.g., intermediate power switches) can be used to control the operation of the power switches (e.g., intermediate power switches and / or external power switches) to enable the converter to operate as a three-level T-type switch across the entire load range, thereby improving efficiency; to enable the converter to operate as a two-level T-type switch; or to operate in a switching mode where the intermediate switch is activated for a short period of time to generate approximately 0 voltage at connection 299, thereby reducing losses. Thus, the overall switching losses of the device are reduced due to the reduced switching losses on the external switch. Power switches 250 and 260 can be lower-cost switches (e.g., high RDSON, such as 20 mΩ-40 mΩ) with low capacitance output (e.g., 150 pF) instead of the high current (e.g., low RDSON, such as 2 mΩ-6 mΩ) that must be rated for a 3-L type converter, while reducing switch-related losses by activating the intermediate switch as described above.

[0051] As described above, Figure 1-12 The configurations and examples provided enable the controller to control the PWM generator to operate the converter as a two-level converter, a three-level converter, a higher-level converter, or in a transition mode where the output voltage is forced to approximately 0 by activating the intermediate switch of the higher-level circuit system 130. Operation may depend on current and / or temperature occurring within the electrical cycle, which provides feedback signals. Controlling the operation of the converter allows the intermediate power switch to be rated for lower currents (e.g., high RDSON), thereby reducing cost compared to a fully rated multilevel inverter, while still achieving high efficiency, lower EMI, and less partial discharge (on the motor side). In one example, in a motor application, adaptive control for the multilevel converter allows the DC current in the motor to be in a low-speed / suspended condition, while the junction temperature and / or current are used to switch between three levels until an appropriate temperature threshold is reached. According to one example, the adaptive control for controlling the operation of the multilevel converter, as described above, is used at lower operating temperatures to improve battery efficiency. According to one example, the intermediate power switch can operate at high currents for short periods, even if it is not rated for high currents, as described above, thereby reducing cost. In other words, even when the phase current has a high amplitude, the intermediate power switch can operate for a certain period of time within a cycle. Furthermore, activating the intermediate switch to force approximately zero voltage at connection 299 contributes to reducing switching-related losses (e.g., achieving greater power loss reduction under high loads), as described above.

[0052] In this specification, the term "coupled" may encompass a connection, communication, or signaling path that enables the functional relationship to be consistent with this specification. For example, if device A generates a signal to control device B to perform an action, then: (a) in a first instance, device A is coupled to device B via a direct connection; or (b) in a second instance, device A is coupled to device B via an intermediate component C, provided that the intermediate component C does not alter the functional relationship between device A and device B, such that device B is controlled by device A via the control signal generated by device A.

[0053] Furthermore, in this specification, the term "based on" means "at least partially based on". Therefore, if X is based on Y, then X may depend on Y and any number of other factors.

[0054] A device “configured” to perform a task or function may be configured (e.g., programmed and / or hardwired) by the manufacturer to perform the function and / or may be configured (or reconfigured) by the user after manufacturing to perform the function and / or other additional or alternative functions. The configuration may be performed through firmware and / or software programming of the device, through the construction and / or layout of hardware components and the interconnection of the device, or a combination thereof.

[0055] Within the scope of the claims, modifications may be made to the described embodiments, and other embodiments are possible.

Claims

1. An apparatus comprising: A two-level converter circuit, comprising a first switch and a second switch; A higher-level converter circuit, which includes a third switch and a fourth switch; as well as A controller configured to receive feedback signals associated with the two-level converter circuit and the higher-level converter circuit. The controller is configured to generate control signals based on the feedback signal. The device is configured to operate in one of three modes based on the control signal. In the first mode, the device is configured to operate as a two-level converter, wherein the two-level converter is configured to generate a two-level output voltage from an input voltage. In the second mode, the device is configured to operate as a higher-level converter, wherein the higher-level converter is configured to increase the number of output voltage levels to more than two levels, and In the third mode, the device is configured to switch between the first mode and the second mode. Furthermore, in the third mode, in response to the device operating as the two-level converter and the third and fourth switches of the higher-level converter circuit being activated for a period of time, the device is configured to generate zero voltage at the switching connection point of the device.

2. The device according to claim 1, wherein the feedback signal is the amount of current drawn by the two-level converter circuit and the higher-level converter circuit.

3. The device of claim 1, wherein the feedback signal is associated with temperature, and the temperature is associated with the third switch or the fourth switch of the higher-level converter circuit.

4. The device according to claim 1, wherein the control signal is a pulse width modulation (PWM) signal.

5. The device according to claim 1, wherein the third switch and the fourth switch are deactivated in the first mode.

6. The device according to claim 1, wherein when the device is in the second mode, the first switch is turned off while the second switch is switching, and the third switch is turned on while the fourth switch is switching.

7. The device according to claim 1, wherein in the third mode, the first switch, the second switch, the third switch and the fourth switch are switched based on the control signal.

8. The device according to claim 1, wherein when the first switch is turned on, the second switch is turned off, and vice versa, wherein the first switch and the fourth switch are not turned on at the same time, and wherein the second switch and the third switch are not turned on at the same time.

9. The device of claim 1, wherein the controller is a pulse width modulation (PWM) unit, and wherein the controller is configured to generate a pulse width modulation (PWM) signal associated with each of the first switch, the second switch, the third switch, and the fourth switch.

10. The device of claim 1, wherein the first or second switch of the two-level converter circuit is rated to support a current of approximately 200 Amp to 400 Amp, and has a resistance of approximately 2 mΩ to 6 mΩ between the drain and source when the first or second switch of the two-level converter circuit is turned on, and wherein the third or fourth switch of the higher-level converter circuit has an RDSON of approximately 20 mΩ to 40 mΩ.

11. The device according to claim 1, wherein the two-level converter circuit is a three-phase circuit.

12. The device of claim 1, wherein the higher-level converter circuit is a T-type converter.

13. A method comprising: Receive a feedback signal associated with a multilevel converter circuit of the device, wherein the multilevel converter circuit includes a two-level converter circuit and a higher-level converter circuit, the two-level converter circuit includes a first switch and a second switch, and the higher-level converter circuit includes a third switch and a fourth switch; A control signal is generated based on the feedback signal, wherein the control signal causes the multilevel converter circuit to operate in one of a first mode, a second mode, or a third mode. In the first mode, the device is configured to operate as a two-level converter, wherein the two-level converter is configured to generate a two-level output voltage from an input voltage. In the second mode, the device is configured to operate as a higher-level converter, wherein the higher-level converter is configured to increase the number of output voltage levels to more than two levels, and In the third mode, the device is configured to switch between the first mode and the second mode. Furthermore, in the third mode, in response to the device operating as the two-level converter and the third and fourth switches of the higher-level converter circuit being activated for a period of time, the multilevel converter circuit is configured to generate zero voltage at the switching connection point of the device.

14. The method of claim 13, wherein the feedback signal is a current drawn by the multilevel converter circuit.

15. The method of claim 13, wherein the feedback signal is associated with a temperature, the temperature being associated with the third or fourth switch of the higher-level converter circuit.

16. The method of claim 13, wherein the control signal is a pulse width modulation (PWM) signal.

17. The method of claim 13, further comprising activating the third switch and the fourth switch in the first mode.

18. The method of claim 13, wherein the method of the second mode further comprises: Switch the second switch; Turn off the first switch; Turn on the third switch; as well as Switch the fourth switch.

19. The method of claim 13, wherein in the third mode, the method further comprises switching the first switch, the second switch, the third switch, and the fourth switch based on the control signal.

20. The method of claim 13, wherein when the first switch is turned on, the second switch is turned off, and vice versa, wherein the first switch and the fourth switch are not turned on simultaneously, and wherein the second switch and the third switch are not turned on simultaneously.

21. The method of claim 13, wherein at least one switch of the two-level converter circuit is rated to support a current of approximately 200 Amp to 400 Amp, and when the at least one switch of the two-level converter circuit is turned on, it has a resistance of approximately 2 mΩ to 6 mΩ between the drain and source (RDSON), and wherein at least another switch of the higher-level converter circuit has an RDSON of approximately 20 mΩ to 40 mΩ.

22. The method of claim 13, wherein the control signal comprises a pulse width modulation (PWM) signal for each of the first switch, the second switch, the third switch, and the fourth switch.

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