GB2589296A

GB2589296A - Feedback controlled gate driver

Info

Publication number: GB2589296A
Application number: GB1913775.1A
Authority: GB
Inventors: Saldanha Garcia Fellipe
Original assignee: Nidec Control Techniques Ltd
Current assignee: Nidec Control Techniques Ltd
Priority date: 2019-09-24
Filing date: 2019-09-24
Publication date: 2021-06-02
Also published as: GB201913775D0

Abstract

A gate drive circuit 100 for providing a controlled gate signal to an electronic switching module 110 comprises an amplifier 105, current derivative (di/dt) and voltage derivative (dv/dt) sensing means 102,104, and on-current derivative, off-current derivative, on-voltage derivative and off-voltage derivative feedback gain control means 120, 115, 125, 130. The current derivative sensing means measures di/dt between a kelvin terminal and a power terminal of the switching module and feeds back a current derivative feedback signal corresponding to di/dt. The voltage derivative sensing means measures dv/dt across a first switch terminal and the power terminal of the switching module and feeds back a voltage derivative feedback signal corresponding to dv/dt. The on-current, off-current, on-voltage and off-voltage derivative feedback gain control means are configured to adjust a gain of their associated derivative feedback signal (first to fourth gain adjustment respectively) during the relevant turn-on or turn-off period of the switching module. The amplifier controls the gate signal to adapt a switching speed of the switching module during a switching transient based on the adjusted derivative feedback signals, where the first to fourth gains are adjusted independently during at least a turn-off period of the switching module. The gate drive circuit may be used in applications requiring fast response time and low losses.

Description

Intellectual Property Office Application No. GII1913775.1 RTM Date March 2020 The following terms are registered trade marks and should be read as such wherever they occur in this document: Texas Instruments Toshiba Semikron Diodes Incorporated Intellectual Property Office is an operating name of the Patent Office www.gov.uk/ipo

FEEDBACK CONTROLLED GATE DRIVER

Field of the Disclosure

[0001] The present disclosure relates to gate driver circuits for transistors, and more particularly to a gate drive circuit implementing feedback based control of voltage and current slopes. Background of the Disclosure [0002] Switching modules comprising one or more transistors (e.g., IGBT, MOSFET, etc.) are widely used in switching voltage source power electronic to converters such as drives, switched-mode power supplies or solid-state transformers.

[0003] Minimizing switching losses of the switching module while limiting overvoltage and restricting electromagnetic interference (EMI) can present difficulties when designing the switching module's gate drive. Setting the current slope di/dt at turn-on can enable the peak reverse recovery current to be limited, and di/dt during turn-off can define the overvoltage that results due to the voltage drop across the total commutation loop inductance. To provide electromagnetic compatibility (EMC), the collector/emitter (or drain/source for MOSFET) voltage slope dv/dt and di/dt are generally restricted to specific values.

[0004] A common method of adjusting the switching speed of a switching module for ensuring EMI compliance and protecting the circuit components, has been to change a resistance value Re of the gate resistor. Additional gate resistance Re reduces the gate current and therefore both current and voltage slopes are reduced, thereby reducing the risk of overshoots. However, while reducing EMI, this method may also lead to excessive switching losses and risk of damage during over-current events (e.g., short circuits). To reduce switching losses, the value of gate resistor may be reduced, but this approach results in increased EMI and risk of damage to circuit components at high-current turn off.

[0005] Another method that may be used to prevent over-voltages during the switch-off transient is an Active Claim (AC) circuit, which uses several Zener diodes to detect an overvoltage and then slow down the turn-off to prevent a further increase in voltage. However, this technique suffers from poor precision of Zener diodes and there is a risk of a false trigger (e.g., when the bus voltage is too high) or the protection may start too late, thereby resulting in damage to the switching module and/or circuit components.

[0006] Active, closed-loop feedback circuits have also been implemented as means for controlling gate drivers to avoid over-voltages at the switching modules. For example, Lihua Chen et al, "Closed-Loop Gate Drive for High Power IGBTs," Twenty-Fourth Annual IEEE Applied Power Electronics Conference and Exposition, 978-1-4244-2811-3, 21 March 2009, discloses a closed-loop, active gate control method in which a plurality of op-amps are implemented to control switching transients of IGBTs. However, the method disclosed suffers from several drawbacks, for example, the complexity of the circuit, multiple points of possible failure, possible influence on switch commutation of the complementary switch during the turn-off period, and lack of precise tunability, among others.

[0007] US 2013/181750 discloses another active gate drive circuit which implments a proportional integral (PI) controller that receives an input reference signal (vrefocit) and controls a gate voltage of the gate-controlled component based on the reference signal. However, these systems and methods also suffer from a number of drawbacks such as inherent latency of PI and P ID controllers and poor tunability.

SUMMARY OF THE DISCLOSURE

[0008] The present inventors have determined that it is desirable to further improve response time of a switching circuit while reducing losses and avoiding possible damage to switching modules of the switching circuit due to over-voltage and/or over-current events, while also ensuring compliance with EMI regulations.

[0009] A gate drive circuit for providing a controlled gate signal to an electronic switching module is therefore, provided. The circuit includes current derivative (di/dt) sensing means configured to measure a current time derivative between a kelvin terminal and a power terminal of the electronic switching module, and to feed back a current derivative feedback signal corresponding to the current derivative (di/dt), voltage derivative (dv/dt) sensing means configured to measure a voltage time derivative across a first switch terminal and the power terminal of the electronic switching module, and to feed back a voltage derivative feedback signal corresponding to the voltage derivative (dv/dt), on-current derivative (di/dt) feedback gain control means configured to adjust a first gain of an on-current derivative feedback signal measured during a turn-on period of the switching module, off-current derivative (di/dt) feedback gain control means configured to adjust a second gain of the off-current derivative feedback signal measured during a turn-off period of the switching module, on-voltage derivative (dv/dt) feedback gain control means configured to adjust a third gain of the on-voltage derivative feedback signal measured during the turn-on period of the switching module, off-voltage derivative (dv/dt) feedback gain control means configured to adjust a fourth gain of the off-voltage derivative feedback signal measured during the turn-off period of the switching module, and an amplifier configured to control the gate signal to adapt a switching speed of the electronic switching module during a switching transient of the electronic switching module, based on the adjusted on-current derivative feedback signal, the adjusted off-current derivative feedback signal, the adjusted on-voltage derivative feedback signal, and the adjusted off-voltage derivative feedback signal. The first, second, third, and fourth gains are adjusted independently of one another during at least a turn-off period of the switching module.

[0010] By providing such a circuit, voltage and current derivatives may be limited thereby improving electromagnetic compatibility (EMC). Moreover, the configuration also limits overvoltage occurrence, therefore protecting the switching module and improving reliability. The configuration achieves these effects with little impact on the switching losses, therefore improving efficiency.

[0011] In addition, because only one amplifier may be implemented in the gate control circuit, cost and complexity may be reduced while further improving reliability.

[0012] Moreover, based on the present configuration, there is no need for complex digital circuits like field-programmable gate arrays (FPGAs), and no varying operation modes.

[0013] Still further, because each of the first, second, third, and fourth gains may be adjusted independently, tuning of each gain may be designed to achieve a specific outcome without heavily impacting outcomes of the other transient scenario for the switching module.

[0014] The amplifier may be a high-speed amplifier.

[0015] The switching module may include one or more insulated gate bipolar transistors (IGBT), where the kelvin terminal corresponds to a kelvin emitter terminal of the IGBT, the power terminal corresponds to a power emitter terminal of the IGBT, and the first switch terminal corresponds to a collector io terminal of the IGBT.

[0016] The switching module may include one or more metal oxide field effect transistors (MOSFET), where the kelvin terminal corresponds to a kelvin source terminal of the MOSFET, the power terminal corresponds to a power source terminal of the MOSFET, and the first switch terminal corresponds to a is drain terminal of the MOSFET.

[0017] The control of the gate signal may be configured to delay a turn-off signal to the switching module.

[0018] The first, second, third, and fourth gains may be returned to an unadjusted value at a turn-on period of the switching module.

[0019] The gate drive circuit may include one or more desaturation protection diodes and/or a current buffer circuit.

[0020] The amplifier may be configured as a summing amplifier.

[0021] Each of the off-current derivative (di/dt) feedback gain control means, off-voltage derivative (dV/dt) feedback gain control means may be optimized to reduce voltage overshoot.

[0022] Each of the on-current derivative (di/dt) feedback gain control means and on-voltage derivative (dV/dt) feedback gain control means may be optimized to reduce EMI.

[0023] According to further embodiments, a method for providing a controlled gate signal to an electronic switching module is provided. The method includes sensing a current time derivative (di/dt) between a kelvin terminal and a power terminal of the electronic switching module, and feeding back a current derivative feedback signal corresponding to the current derivative (di/dt), sensing a voltage time derivative (dv/dt) across a first switch terminal and the power terminal of the electronic switching module, and feeding back a voltage derivative feedback signal corresponding to the voltage derivative (dv/dt), adjusting a first gain of an on-current derivative feedback signal measured during a turn-on period of the switching module, adjusting a second gain of the off-current derivative feedback signal measured during a turn-off period of the switching module, adjusting a third gain of the on-voltage derivative feedback signal measured during the turn-on period of the switching module, adjusting a fourth gain of the off-voltage derivative feedback signal measured during the turn-off period of the switching module, and during a switching transient of the electronic switching module, controlling, by an amplifier, the gate signal to adapt a switching speed of the electronic switching module based on the adjusted on-current derivative feedback signal, the adjusted off-current derivative feedback signal, the adjusted on-voltage derivative feedback signal, and the adjusted off-voltage derivative feedback signal. The first, second, third, and fourth gains are adjusted independently of one another during at least a turn-off period of the switching module.

[0024] By providing such a method, voltage and current derivatives may be limited thereby improving electromagnetic compatibility (EMC). Moreover, the configuration also limits overvoltage occurrence, therefore protecting the switching module and improving reliability. The configuration achieves these effects with little impact on the switching losses, therefore improving efficiency.

[0025] The amplifier may be a high-speed amplifier.

[0026] The switching module may include one or more insulated gate bipolar transistors (IGBT), the kelvin terminal corresponds to a kelvin emitter terminal of the IGBT, the power terminal corresponds to a power emitter terminal of the IGBT, and the first switch terminal corresponds to a collector terminal of the IGBT.

[0027] The switching module may include one or more metal oxide field effect transistors (MOSFET), the kelvin terminal corresponds to a kelvin source terminal of the MOSFET, the power terminal corresponds to a power source terminal of the MOSFET, and the first switch terminal corresponds to a drain terminal of the MOSFET.

[0028] The controlling may be configured to delay a turn-off signal to the switching module.

[0029] The method may further include returning the first, second, third, and fourth gains to an unadjusted value at a turn-on period of the switching module.

[0030] The amplifier may be configured as a summing amplifier.

[0031] It is intended that combinations of the above-described elements and those within the specification may be made, except where otherwise contradictory.

B

[0032] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure, as claimed.

[0033] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description, serve to explain the principles thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Fig. 1 is functional block diagram of an exemplary feedback controlled gate driver circuit according to embodiments of the present

disclosure;

[0035] Figs. 2A and 2B are exemplary depictions of turn-on and turn-off transients and graphical representations of their respective theoretical current and voltage derivatives di/dt and dV/dt; [0036] Fig. 3 illustrates the diagram of Fig. 1 during a turn-on transient of the switching module; [0037] Fig. 4 illustrates the diagram of Fig. 1 during a turn-off transient of the switching module; [0038] Fig. 5 illustrates exemplary on-and off-transient dV/dt feedback control means according to embodiments of the present disclosure; [0039] Fig. 6 illustrates exemplary on-and off-transient di/dt feedback control means according to embodiments of the present disclosure; [0040] Fig. 7 is a flowchart showing an exemplary series of steps associated

with methods of the present disclosure;

[0041] Figs. 8A and 8B illustrate exemplary traces generated by a reference system and a system according to embodiments of the present disclosure showing reduced turn-off voltage overshoot at similar switching loss for high current situations; [0042] Fig. 9A and 9B illustrate exemplary traces generated by a reference system and a system according to embodiments of the present disclosure showing reduced turn-off voltage overshoot at similar switching loss for normal operating current situations; [0043] Figs. 10A and 10B illustrate exemplary traces generated by a reference system and a system according to embodiments of the present disclosure showing reduced turn-on dVidt at normal operating currents; and [0044] Fig. 11 illustrate exemplary traces generated by embodiments of the present disclosure during a short circuit event of the switching module.

DESCRIPTION OF THE EMBODIMENTS

[0045] Reference will now be made in detail to the present exemplary embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[0046] In the present disclosure, circuits and methods for adaptively varying the gate drive signal to actively limit slopes associated with power terminal current and a switching module are discussed. For purposes of the discussion, functional circuit diagrams as shown in Figs. 1-6 will be used, and components of those circuits described.

[0047] Fig. 1 is a logical diagram of an exemplary feedback controlled gate driver according to embodiments of the present disclosure. According to embodiments of the present disclosure, the feedback controlled gate driver 100 includes a switching module 110 including current derivative sensing means 102 and voltage derivative sensing means 104, an operational amplifier 105, and a driver 135. In addition, the gate driver includes off-current derivative feedback control means 115, on-current derivative feedback control means 120, on-voltage derivative feedback control means 125, and off-voltage derivative feedback control means 130.

[0048] Switching module 110 may include one or more switching components 117, 119 connected in any suitable arrangement. According to embodiments of the present disclosure, the switching components 117, 119 of switching module 110 may be configured as an inverter, a converter, etc. [0049] One or more switching components of switching module 110 may include insulated gate bipolar transistors (IGBT) 117 and/or one or more metal oxide semiconductor field effect transistors (MOSFET) 119. While Fig. 1 shows both an IGBT and MOSFET as part of switching module 110, this depiction is exemplary only, and switching module 110 may be limited to only IGBTs or only MOSFETs, as desired [0050] As is known in the art each type of switching components IGBT and MOSFET includes at least three terminals, a first terminal, a gate terminal (common name on both IGBT and MOSFET), and a power terminal. In some configurations, these switching components may further include a Kelvin terminal, permitting direct Kelvin connection to the power terminal of the switching component.

[0051] When an IGBT is implemented as a switching component in switching module 110, the first terminal 207 corresponds to the collector (C) of the IGBT, the power terminal 205 corresponds to the emitter (E) of the IGBT, and the Kelvin terminal corresponds to the Kelvin emitter (KE) of the IGBT. A gate terminal 210 is also present.

[0052] When the switching module 110 includes one or more metal oxide MOSFETs, the first switch terminal 207 corresponds to a drain terminal (D) of the MOSFET, the power terminal 205 corresponds to a power source (S) terminal of the MOSFET, and the kelvin terminal corresponds to a kelvin to source (KS) terminal of the MOSFET. A gate terminal 210 is also provided for the MOSFET.

[0053] Importantly, throughout the present disclosure the terms related to the terminals of the switching components, as noted in the preceding paragraph, may be used interchangeably. However, the use of any such terms is not intended to limit the scope of the discussed feature or embodiment to any particular switching component, and it is intended that where a module specific term is used (e.g., collector (C)) it is intended to also refer to the corresponding terminal (e.g., drain (D)) of the other component.

[0054] Driver 135 may be any suitable driver configured to provide a pulsed voltage signal at a first voltage Vreri and a second voltage VI-era According to embodiments of the present disclosure, driver 135 may be implemented as a galvanically isolated device, the device being configured to provide pulse width modulated signals at a first reference voltage Vren and a second reference voltage Vref2. Exemplary voltage ranges between the first voltage Vrefl and the second voltage Vre2 may be about +20V to -20V (e.g., +15V to -10y). Any suitable voltage range is intended to fall within the scope of the present disclosure.

[0055] The output of driver 135 may be provided as a square wave, e.g., pulse modulated square wave, and peak current outputs of driver 135 at the set reference voltages may range between about 0.5A and 6A, such that sufficient current may be sourced and sinked to drive the gate of an IGBT or MOSFET in a rapid switching configuration.

[0056] Driver 135 may include other suitable features for use as a driver for a switching module comprising one or more IGBT or MOSFET switching devices. For example, driver 135 may include fault protection and/or active voltage clamping of a gate signal voltage, as well as desaturation detection/protection in combination with one or more desaturation diodes of the driver circuit. One exemplary driver 135 available in the market at the time of filing is Toshiba's TLP5214 isolated IGBT/Power MOSFET gate driver.

[0057] Driver 135 may be powered in any suitable manner for providing adequate voltage and current enabling driver 135 to function as noted above. For example, driver 135 may be provided power from the drive power rails of a power application, and may be provided with one or more current buffer circuits, for example, comprising a plurality of capacitors, to ensure sufficient current source for performing desired operations in the switching application.

[0058] Amplifier 105 may comprise any suitable amplifier configured to receive an input and provide a predetermined gain associated with that input. According to some embodiments of the present disclosure, only one amplifier 105 may be provided.

[0059] Amplifier 105 may comprise a high-speed operational amplifier, one such exemplary amplifier available in the market as of the filing date of the present application being the LM7171 manufactured by Texas Instruments.

[0060] Amplifier 105 may be configured to receive output feedback at its inverting terminal, the output feedback being measured between amplifier 105 and pre-gate resistor 190, for example. Any suitable circuit for providing the desired feedback while protecting amplifier 105 may be implemented without departing from the scope of the present disclosure.

[0061] Inputs provided to the non-inverting input of amplifier 105 may 1() include a gate signal as well as controlled/adjusted feedback signals from the feedback control means 115, 120, 125, and 130 corresponding to determined values of di/dt and dV/dt in both rising and falling situations (i.e., on and off transients of switching module 110). Amplifier 105 may therefore be configured as a noninverting summing amplifier, and may be configured to receive the plurality of adjusted feedback signals from the on-current, off-current, on-voltage, off-voltage gain control means 115, 120, 125, and 130, as well as a reference signal from driver 135 at its non-inverting input, and output a controlled gate drive signal to switching module 110 via gate resistor 190 based on these inputs, among others.

[0062] Similar to driver 135, amplifier 105 may be powered via the drive rails of a power application. Alternatively, another power source may be provided for amplifier 105.

[0063] The combination (e.g., "adding" together) of the original gate signal with the feedback signals received from each of the feedback control means 115, 120, 125, and 130, by amplifier 105 results in a manipulation/adjustment of the gate voltage output from amplifier 105, thereby resulting in increasing or decreasing the commutation rate of switch module 110 (in conjunction with gate resistor 190). The feedback signals becomes stronger when the current change di/dt and/or voltage change dV/dt is faster, for example, when the current is very large (e.g., during short circuit) or because of low temperature.

By feeding back the appropriate signals during the on and off transients of switching module 110, a dynamic equilibrium may be obtained between the system and the feedback that increases or decreases the transition as desired. Adjustment/control (e.g., tuning) of the feedback signals by the feedback control means 115, 120, 125, and 130 for specific scenarios will be discussed in greater detail below.

[0064] Figs. 2A and 2B are exemplary depictions of turn-on and turn-off transients and graphical representations of their respective theoretical current and voltage derivatives di/dt and dV/dt for an IGBT. The IGBT is depicted for purposes of example, and is not intended to be limiting. Further, Figs. 3 and 4 illustrate feedback flow during a turn-on and turn-off transients of switching module 110 according to embodiments of the present disclosure.

[0065] During a turn-on transient of switching module 110, as shown at Figs. 2A and 3, a gate voltage is "turned on" by driver 135, which changes the pulse from Vref2 to Vren (e.g. from -10V to +15V), and current flowing from a first terminal 207 to the power terminal 205 of the switching module 110 begins to increase as a result of the gate of the IGBT or MOSFET becoming saturated. A voltage is therefore induced across a parasitic inductance LEe 220 formed by the load and circuit components, and this voltage can be approximated by current time derivative di/dt sensing means 102 by measuring the voltage across the parasitic inductance 220.

[0066] The voltage VEe resulting across the parasitic inductance 220 between the kelvin emitter terminal and the power emitter terminal can be measured, and this voltage VEe has a di/dt factor included inherently according to equation 1) [0067] 1) VEe = LEe * di/dt where LEe is equivalent to the parasitic inductance of the load circuit. This forms the basis for the feedback signal provided to on-current derivative (di/dt) 10 feedback gain control means 120.

[0068] Similarly, during a turn-off transient of switching module 110, the gate voltage VG is reduced passing through DV and moving back to Vre2 (e.g., -10y), resulting in turn-off of switching module 110. Therefore, current flowing through the parasitic inductance 220 is reduced and finally terminated, causing a field collapse in the parasitic inductance LEe. This induces a negative voltage proportional to the current time derivative di/dt to form across the parasitic inductance 220 according to the inverse of equation 1, as shown at Fig. 2B As shown at Fig. 4, this signal forms the basis of the di/dt feedback signal provided to off-current derivative (di/dt) feedback gain control means 115.

[0069] Voltage derivative sensing means 104 is configured to measure a voltage time derivative dV/dt across a first switch terminal (i.e., collector for IGBT and drain for MOSFET) and the power terminal (i.e., emitter for IGBT and source for MOSFET) of the electronic switching module 110, and to feed back the voltage derivative feedback signal corresponding to the voltage derivative (dV/dt) to on-and/or off-voltage derivative (dV/dt) feedback gain control means 125, 130.

[0070] Voltage derivative sensing means 104 is configured to perform an analog determination of the voltage time derivative dV/dt from the voltage over the load path of switching module 110, i.e., the voltage across the collector 207 and emitter 205 of an IGBT 117 or across the drain and source of a MOSFET. This determination results in a signal corresponding to the voltage time derivative dV/dt and may be measured by using one or more capacitors and optionally one or more resistors at the first terminal 207 (i.e., collector for IGBT 1() and drain for MOSFET) of the switching module. The determination may be based on the equation of dV/dt = ic where i is the current flowing through the summed reciprocal of the capacitance C -E Vc1+1/c2+11c"..

of a plurality of capacitors in series within voltage derivative sensing means 104. The resulting measured signal corresponding to dV/dt is fed back to on-voltage derivative (dV/dt) feedback gain control means 125 during a turn-on transient and off-voltage derivative (dV/dt) feedback gain control means 130 during an off-transient of switching module 110.

[0071] Fig. 5 illustrates exemplary on-and off-voltage dV/dt feedback control means 125, 130 according to embodiments of the present disclosure.

Importantly, the presently described exemplary circuits for adjusting/controlling dV/dt feedback signals are not intended to be limiting. Any suitable circuit for adjusting/controlling the dV/dt feedback signal may be implemented without departing from the scope of the present disclosure.

[0072] According to embodiments of the disclosure, each of the on-and off-voltage derivative feedback gain control means 125, 130 include one or more resistors 510, 520 wired in parallel with one or more capacitors 515, 525, and one or more Zener diodes 530, 535 for enabling transmission of the dVidt feedback signal according to the transient (i.e., on or off) in which switching module 110 is operating.

[0073] The values of the RC pairs may be individually selected (i.e., tuned) for each of the on-and off-voltage derivative feedback gain control means 125, 130, such that, given a known/desired operating configuration of switching module 110 and its associated load circuit, a desired scenario is achieved for dVidt. For example, where voltage overshoot limiting during a turn-off transient of switching module 110 is prioritized, a value of resistor 520 and capacitor 525 may be selected such that feedback provided to amplifier 105 will more greatly slow the commutation of switch module 110 during the turn-off transient of switch module 110.

[0074] Further, Zener diode 535 may be selected appropriately to allow feedback from off-voltage derivative feedback control means 130 to flow to amplifier 105. In other words, resistor 520 and capacitor 525 may be selected such that the value of the feedback signal proceeding to amplifier 105 slightly increases the original gate signal (which during a turn-off transient has become a negative value Vref2) coming from driver 135 to result in a delayed turnoff of switch module 110 over an unadjusted scenario. By so doing, rising dVidt may be reduced and voltage overshoot during the turn-off transient may be prevented.

[0075] Fig. 6 illustrates exemplary on-and off-transient di/dt feedback control means 115, 120 according to embodiments of the present disclosure. Importantly, the presently described exemplary circuits for adjusting/controlling di/dt feedback signals are not intended to be limiting. Any suitable circuit for adjusting/controlling the di/dt feedback signal may be implemented without departing from the scope of the present disclosure.

[0076] According to embodiments of the disclosure, each of the on-and off-current derivative feedback gain control means 115, 120 include one or more resistors 610, 620 wired in parallel with one or more capacitors 615, 625, and a Zener diode 630, 635 for enabling transmission of the current derivative di/dt feedback signal according to the transient (i.e., on or off) in which switching module 110 is operating. Similar to the discussion above with regard to Fig. 5, the values of the RC pairs may be individually selected (i.e., tuned) for each of the on-and off-current derivative feedback gain control means 115, 120, such that, given a known operating configuration of switching module 110 and its associated load circuit, a desired scenario is achieved for di/dt.

[0077] Using the example discussed above with regard to figure 5, a situation where limiting voltage overshoot is a primary concern for switching module 110 is discussed here. In such a scenario, because turnoff of the switch results in cessation of the current flow through the load path thereby inducing a large voltage across the parasitic inductance 220, reducing the current rate of change di/dt during the turn-off transient can be used to limit voltage overshoot to manageable values. To reduce the current rate of change di/dt during turnoff, it may be desirable to reduce the gate voltage (i.e., transition from Vrefl to Vref2 as measured at gate terminal 210) at a slower rate such that commutation of switch module 110 is delayed over a non-controlled scenario. Therefore, resistor 610 and capacitor 615 may be chosen such that the feedback signal provided by off-current derivative feedback control means 120 during a turn-off transient of switch module 110 results in an increased voltage over the original gate signal Vre2 provided by driver 135 when combined therewith via amplifier [0078] Taking into consideration the problem of ringing (i.e. EMI) in high-speed switching systems, such as those presently disclosed, control of both di/dt and dV/dt may be implemented to limit or even prevent such ringing while still allowing rapid switching with reduced losses.

[0079] In order to meet EMI regulations and/or improve power quality, it may be desirable to reduce ringing by reducing change rates of voltage and current during turn-on and turn-off transients. The presently disclosed systems and methods enable a balance to be achieved between circuit component protection, power loss, and EMI concerns, by allowing individual tuning of each of the rising and falling current and voltage derivatives.

[0080] Thus, according to another example, RC pair values for each of the on-and off-current and voltage feedback gain control means may be adapted such that a balance between each of the factors is taken into account, based on

the disclosure provided herein.

[0081] Other optimizations and configurations may also be obtained based on a particular implementation of the switching system. Any such configuration and optimization is intended to fall within the scope of the present disclosure.

[0082] Fig. 7 is a flowchart showing an exemplary series of steps associated with methods of the present disclosure. During switching transients of switch module 110, a current derivative di/dt associated with a power terminal of the switching module 110 may be sensed and fed back by current derivative sensing means 102 (step 702). Simultaneously, a voltage derivative dV/dt associated with a first terminal and the power terminal of the switching module 110 may also be sensed and fed back by voltage derivative sensing means 104 (step 704).

[0083] Gains associated with each of the fed back signals may then be adjusted by the respective feedback gain control means 115, 120, 125, 130 (step 706). The adjusted gains may then be provided to amplifier 105 along with the control gate signal provided by driver 135 for adjustment of the gate signal (step 708).

[0084] Figs. 8 to 10 illustrate traces from a reference system similar to that available in the prior art, and of exemplary systems according to the present disclosure. For purposes of generating these traces, driver 135 corresponds to a Toshiba TLP5714, amplifier 105 corresponds to a Texas Instruments LM7171 high-speed operational amplifier, switching module 110 corresponds to a lower arm of a switched power inverter implemented using IGBTs (e.g., Semikron 5KM1400GB12P4), and the resistor/capacitor pairs for each of the feedback control means 115, 120, 125, 130, are listed below in Table 1.

Module Resistor Capacitor Off-Current di/dt 390 100pF Control means On-Current di/dt 220 220pF Control Means Off-Voltage dV/dt 4.70 220pF Control Means On-Voltage dV/dt 150 220pF Control Means

TABLE 1

[0085] Zener diodes in each of the feedback control means 115, 120, 125, are all BAT54SDW, available as of the filing date from Diodes Incorporated.

[0086] Figs. 8A and 8B illustrate exemplary traces generated by a reference system and a system according to embodiments of the present disclosure showing reduced turn-off voltage overshoot at similar switching loss for high current situations (e.g., fault). Fig. 8A corresponds to a reference system utilizing a gate driver without feedback, similar to systems readily available in the prior art, while Fig. 8B corresponds to an implementation of the present disclosure in which feedback is provided and adjusted as described above. For 1() purposes of generating the traces of Fig. 8A and figure 8B, a plurality of IGBTs were operated as a switched power inverter at turn-off transient with a high current of 2250 A at 600 V at time of switching. A gate resistor value of 1.3 ohms was provided for the no-feedback example shown in figure 8A, and a gate resistor value of 0.75 ohms for the example according to embodiments of the present disclosure shown in figure 88. Each of the traces is labeled, where SIE corresponds to emitter current of switching module 110, SVcE corresponds to a voltage across the collector 207 and emitter 205 of switching module 110, SVGE corresponds to a voltage across the gate terminal 210 and the emitter 205 of switching module 110, and CF corresponds to a calculated power. As shown based on the calculated power CP, the turnoff loss in each system is approximately 380 mJ, however the voltage overshoot at turnoff in the example with no feedback is 416 V, while the voltage overshoot in the example including feedback according to embodiments of the present disclosure is only 360 V. In other words, approximately 14 percent less voltage overshoot occurred for the same switching power loss in switching module 110 of the system according to embodiments of the present disclosure as compared to prior art systems. Thus, this case demonstrates the effectiveness of systems of the present disclosure in preventing voltage overshoot at high currents.

[0087] Fig. 9A and 9B illustrate exemplary traces generated by a reference system and a system according to embodiments of the present disclosure showing reduced voltage overshoot at similar switching loss for normal operating current situations. Fig. 9A corresponds to a reference system utilizing a gate driver without feedback, similar to systems readily available in the prior art, while Fig. 9B corresponds to an implementation of the present disclosure in 10 which feedback is provided and adjusted as described above. For purposes of generating the traces of Fig. 9A and figure 9B, a plurality of IGBTs were operated as a switched power inverter at turn-off transient at a normal operating current of 1000 A at 600 V at time of switching. A gate resistor value of 0.75 ohms was provided for both the no-feedback example shown at Fig. 9A and the example according to embodiments of the present disclosure shown in figure 9B. Trace labelling in Figs. 9A and 9B is identical to that of Figs. 8A and 8B. As shown based on the calculated power CP, the turnoff loss in the reference example is 166 mJ, while losses of 176 mJ were incurred in the system according to embodiments of the present invention, i.e., a 6 percent increase in losses. However the voltage overshoot for the reference example was 226V, while that of the present disclosure was only 181V, i.e., at turnoff in the example with no feedback is 416 V, while the voltage overshoot in the example including feedback according to embodiments of the present disclosure is only 360 V, i.e., 20 percent lower than the reference example. Thus, in the case where voltage overshoot management is prioritized, a balance between voltage overshoot and power loss may still be achieved, with a limited increase in switching losses.

[0088] Figs. 10A and 10B illustrate exemplary traces generated by a reference system and a system according to embodiments of the present disclosure showing reduced turn-on transient voltage time derivative dV/dt at normal operating currents (e.g, 1000A). Fig. 10A corresponds to a reference system utilizing a gate driver without feedback, similar to systems readily available in the prior art, while Fig. 10B corresponds to an implementation of the present disclosure in which feedback is provided and adjusted as described above. For purposes of generating the traces of Fig. 10A and figure 10B, a plurality of IGBTs were operated as a switched power inverter at turn-on transient at a normal operating current of 1000 A at 600 V at time of switching. A gate resistor value of 0.75 ohms was provided for both the no-feedback example shown at Fig. 10A and the example according to embodiments of the present disclosure shown in figure 10B. Trace labelling in Figs. 10A and 10B is identical to that of Figs. 8A and 8B, except that a dV/dt slope (shown as a dashed line) has been superimposed on the SVcE trace. As shown by the superimposed dV/dt on the SVcE trace, the voltage time derivative dV/dt was reduced by approximately 30 percent for the feedback example according to

embodiments of the present disclosure.

[0089] Fig. 11 illustrates exemplary traces generated by one embodiment of the present disclosure during an emergency turn-off transient caused by a short circuit event of the switching module 110. Once again, a gate resistor value of 0.750 was provided, and the short circuit current generated was 3500A at 600V. Trace labelling of Fig. 11 is identical to Figs. 8, 9, and 10. As shown at Fig. 11, implementing the feedback system according to embodiments of the present disclosure results in an overvoltage of approximately 430V, which is manageable by the switching module 110. Although no traces are provided for a no-feedback system under similar short circuit circumstances, it is well known that the overvoltage generated in such an event can be excessively high, resulting in destruction of the associated switching module. Therefore, protection of circuit components can be adequately achieved through implementation of embodiments of the disclosure, while also achieving a balance between EMI and switching losses.

[0090] Throughout the description, including the claims, the term "comprising a" should be understood as being synonymous with "comprising at least one" unless otherwise stated. In addition, any range set forth in the description, including the claims should be understood as including its end value(s) unless otherwise stated. Specific values for described elements should be understood to be within accepted manufacturing or industry tolerances known to one of skill in the art, and any use of the terms "substantially" and/or "approximately" and/or "generally" should be understood to mean falling within such accepted tolerances.

[0091] Where any standards of national, international, or other standards body are referenced (e.g., ISO, etc.), such references are intended to refer to the standard as defined by the national or international standards body as of the priority date of the present specification. Any subsequent substantive changes to such standards are not intended to modify the scope and/or definitions of the present disclosure and/or claims.

[0092] It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims.

Claims

CLAIMS1. A gate drive circuit for providing a controlled gate signal to an electronic switching module, comprising: current derivative (di/dt) sensing means configured to measure a current time derivative between a kelvin terminal and a power terminal of the electronic switching module, and to feed back a current derivative feedback signal corresponding to the current derivative (di/dt); voltage derivative (dv/dt) sensing means configured to measure a voltage time derivative across a first switch terminal and the power terminal of the electronic switching module, and to feed back a voltage derivative feedback signal corresponding to the voltage derivative (dv/dt); on-current derivative (di/dt) feedback gain control means configured to adjust a first gain of an on-current derivative feedback signal measured during a turn-on period of the switching module; off-current derivative (di/dt) feedback gain control means configured to adjust a second gain of the off-current derivative feedback signal measured during a turn-off period of the switching module; on-voltage derivative (dv/dt) feedback gain control means configured to adjust a third gain of the on-voltage derivative feedback signal measured during the turn-on period of the switching module; off-voltage derivative (dv/dt) feedback gain control means configured to adjust a fourth gain of the off-voltage derivative feedback signal measured during the turn-off period of the switching module; and an amplifier configured to control the gate signal to adapt a switching speed of the electronic switching module during a switching transient of the electronic switching module, based on the adjusted on-current derivative feedback signal, the adjusted off-current derivative feedback signal, the adjusted on-voltage derivative feedback signal, and the adjusted off-voltage derivative feedback signal, and wherein the first, second, third, and fourth gains are adjusted independently of one another during at least a turn-off period of the switching module.
2. The gate drive circuit according to claim 1, wherein the amplifier is a high-speed amplifier.
3. The gate drive circuit according to any of claims 1-2, wherein the switching module comprises one or more insulated gate bipolar transistors (IGBT), the kelvin terminal corresponds to a kelvin emitter terminal of the IGBT, the power terminal corresponds to a power emitter terminal of the IGBT, and the first switch terminal corresponds to a collector terminal of the IGBT.
4. The gate drive circuit according to any of claims 1-2, wherein the switching module comprises one or more metal oxide field effect transistors (MOSFET), the kelvin terminal corresponds to a kelvin source terminal of the MOSFET, the power terminal corresponds to a power source terminal of the MOSFET, and the first switch terminal corresponds to a drain terminal of the MOSFET.
5. The gate drive circuit according to any of claims 1-4, wherein the control of the gate signal is configured to delay a turn-off signal to the switching module.
6. The gate drive circuit according to any of claims 1-5, wherein the first, second, third, and fourth gains are returned to an unadjusted value at a turn-on period of the switching module.
7. The gate drive circuit according to any of claims 1-6, further comprising one or more desaturation protection diodes and/or a current buffer circuit.
8. The gate drive circuit according to any of claims 1-7, wherein the amplifier is configured as a summing amplifier.
9. The gate drive circuit according to any of claims 1-8, wherein each of the off-current derivative (di/dt) feedback gain control means, off-voltage derivative (dV/dt) feedback gain control means are optimized to reduce voltage overshoot.
10. The gate driver circuit according to any of claims 1-9, wherein each of the on-current derivative (di/dt) feedback gain control means and on-voltage derivative (dV/dt) feedback gain control means are optimized to reduce EMI.
11. A method for providing a controlled gate signal to an electronic switching module, comprising: sensing a current time derivative (di/dt) between a kelvin terminal and a power terminal of the electronic switching module, and feeding back a current derivative feedback signal corresponding to the current derivative (di/dt); sensing a voltage time derivative (dV/dt) across a first switch terminal and the power terminal of the electronic switching module, and feeding back a voltage derivative feedback signal corresponding to the voltage derivative (dV/dt); adjusting a first gain of an on-current derivative feedback signal measured during a turn-on period of the switching module; adjusting a second gain of the off-current derivative feedback signal measured during a turn-off period of the switching module; adjusting a third gain of the on-voltage derivative feedback signal measured during the turn-on period of the switching module; adjusting a fourth gain of the off-voltage derivative feedback signal measured during the turn-off period of the switching module; and during a switching transient of the electronic switching module, controlling, by an amplifier, the gate signal to adapt a switching speed of the electronic switching module based on the adjusted on-current derivative feedback signal, the adjusted off-current derivative feedback signal, the adjusted on-voltage derivative feedback signal, and the adjusted off-voltage derivative feedback signal, and wherein the first, second, third, and fourth gains are adjusted independently of one another during at least a turn-off period of the switching module.
12. The method according to claim 11, wherein the amplifier is a high-speed amplifier.
13. The method according to any of claims 11-12, wherein the switching module comprises one or more insulated gate bipolar transistors (IGBT), the kelvin terminal corresponds to a kelvin emitter terminal of the IGBT, the power terminal corresponds to a power emitter terminal of the IGBT, and the first switch terminal corresponds to a collector terminal of the IGBT.
14. The method according to any of claims 11-12, wherein the switching module comprises one or more metal oxide field effect transistors (MOSFET), the kelvin terminal corresponds to a kelvin source terminal of the MOSFET, the power terminal corresponds to a power source terminal of the MOSFET, and the first switch terminal corresponds to a drain terminal of the MOSFET.
15. The method according to any of claims 11-14, wherein the controlling is configured to delay a turn-off signal to the switching module.
16. The method according to any of claims 11-15, comprising returning the first, second, third, and fourth gains to an unadjusted value at a turn-on period of the switching module.
17. The method according to any of claims 11-16, wherein the amplifier is configured as a summing amplifier.