CN111525779A - Power device series connection voltage-sharing circuit containing device junction temperature and method thereof - Google Patents

Power device series connection voltage-sharing circuit containing device junction temperature and method thereof Download PDF

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CN111525779A
CN111525779A CN202010181614.XA CN202010181614A CN111525779A CN 111525779 A CN111525779 A CN 111525779A CN 202010181614 A CN202010181614 A CN 202010181614A CN 111525779 A CN111525779 A CN 111525779A
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power device
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CN111525779B (en
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李武华
李成敏
罗皓泽
杨贺雅
李楚杉
向鑫
何湘宁
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Zhejiang University ZJU
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D21/00—Measuring or testing not otherwise provided for
    • G01D21/02—Measuring two or more variables by means not covered by a single other subclass
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection

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  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Power Conversion In General (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a series voltage-sharing method for power devices containing device junction temperature, and belongs to the technical field of power electronic conversion. In the actual operation of the series voltage-sharing circuit, the unbalanced voltage of the series devices is closely related to the internal parameters of the devices and the external operation conditions. The series voltage-sharing strategy obtains unbalanced voltage and temperature among the series devices by extracting turn-off voltage, turn-on current and device temperature of the power devices, and is used for adjusting turn-off delay time of driving signals of each path of power device, so that power series voltage sharing is realized. The invention is suitable for medium-high voltage high-power application occasions, and the voltage-sharing adjustment has rapidity, instantaneity and higher stability.

Description

Power device series connection voltage-sharing circuit containing device junction temperature and method thereof
Technical Field
The invention belongs to the technical field of power electronic conversion, and particularly relates to a series voltage-sharing method for power devices containing device junction temperature.
Background
Power device characteristics are one of the main factors limiting the performance of power electronic converters. In medium-high voltage application occasions, the withstand voltage of the current power device cannot meet the blocking voltage requirement, so that the series operation of the power device is a common scheme for increasing the series voltage of the power device. Compared with a single operating power device, the power device operated in series can obtain lower loss and cost, and has wide application prospect.
The key to the series application of power devices is to solve the problem of series voltage imbalance. The series voltage imbalance includes the problem of voltage equalization of each power device during the switching dynamic process and the steady state operating state. The influence factors of voltage equalization and unbalance of the power device mainly comprise two parts: differences in device internal parameters, manufacturing processes, and the like; device external operating conditions are different. The voltage imbalance among the series power devices can cause the problems of uneven heat distribution, increased loss of power electronic equipment, overvoltage damage of the power devices with higher bearing voltage and the like.
Therefore, the power devices need to be assisted by a voltage-sharing circuit when operated in series. The voltage-sharing method widely adopted in the existing products is that passive resistor-capacitor buffer circuits are connected in parallel at two ends of a power device, so that the switching loss of the device is increased, extra loss is brought by the buffer resistors, and the performance improvement of the power device in series operation is not facilitated. As an improvement measure, an active delay voltage-sharing method is widely adopted. The active turn-off time delay method has the advantages of real-time voltage sharing and no increase of the original switching loss of the device, and has wide application prospect. The existing turn-off delay voltage-sharing method does not consider the influence of the temperature of the power device on the unbalanced voltage. However, the parameters of the power device significantly change with the temperature, and correspondingly, the unbalanced voltage of the device also significantly changes. In the traditional method, delay time is set based on the voltage and current working points of the devices, the junction temperature of the devices is not introduced as a regulation variable, and the voltage-sharing effect is limited.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides a series voltage-sharing circuit and a voltage-sharing strategy for power devices, which can detect unbalanced voltage of series power in real time and adjust the voltage balance of the series power devices in real time.
In order to achieve the purpose, the invention adopts the following specific technical scheme:
a series voltage-sharing circuit of power devices with device junction temperature compensation function comprises: the power supply comprises a control unit, N driving circuits and N power devices connected in series, wherein the N driving circuits are connected with the N power devices in a one-to-one correspondence mode, and N is a positive integer greater than or equal to 2; each driving circuit comprises a sampling unit, a communication unit and a driving unit;
the sampling unit is used for collecting the voltage, the current and the junction temperature of the connected power device;
the driving unit is used for providing a switch control signal for the grid electrode of the connected power device so as to control the on-off state switching of the power device and further regulate and control the on-current of the power device;
the communication unit is used for transmitting the sampling information of the sampling unit to the control unit through a communication link, receiving the switch control signal sent by the control unit and sending the switch control signal to the drive circuit;
the control unit is used for collecting the voltage, current and junction temperature information of the power devices collected by the N sampling units, executing a series voltage-sharing strategy, calculating the turn-off time delay of the switch control signals of each power device, and then sending the switch control signals to the corresponding driving units according to the turn-off time delay of each power device so as to regulate and control the turn-off voltage balance of each power device.
Preferably, the driving circuit further comprises a processor, and the sampling unit, the communication unit and the driving unit are all connected to the processor for central control.
Furthermore, the driving circuit further comprises a fault detection circuit, and the sampling unit is connected to the processor through the fault detection circuit.
Preferably, the communication unit forms a communication link with the control unit in a wired or wireless manner.
Preferably, the power device is a gate voltage controlled power device, and includes: insulated Gate Bipolar Transistors (IGBTs), silicon carbide metal-oxide semiconductor field effect transistors (SiC MOSFETs), or gallium nitride power devices (GaN).
Another object of the present invention is to provide a method for equalizing voltage of a series of power devices based on the above-mentioned equalizing circuit for a series of power devices, which includes the following steps:
s1: under the condition that the maximum working voltage, the maximum working current and the maximum working junction temperature of the power devices connected in series are not exceeded, the device temperature of the power devices and the turn-off delay time of the switch control signal are used as control variables, parameters to be measured of series unbalanced voltage of the power devices are used, and multiple groups of test working conditions with different gradients are set for the control variables to carry out a correlation test; in each group of test working conditions, when the power devices are switched from a conducting state to a switching-off state, respectively recording the switching-off voltage dynamic switching-off amplitude of each power device connected in series to obtain corresponding series unbalanced voltage; then, based on data obtained under each test working condition, a relation function model between the device temperature of the power device, the turn-off delay time of the switch control signal and the series unbalanced voltage is established through data fitting;
s2: in the operation process of the power device series connection voltage-sharing circuit, in each switching period, the control unit calls the turn-off voltage V and the device temperature T of each power device, then the mean value of the turn-off voltages of all the power devices connected in series is used as a reference voltage, and the difference value delta V between the turn-off voltage of each power device and the reference voltage is respectively calculatedDS(ii) a Then for eachOne path of power device utilizes the temperature T of the device and the difference value delta V of the turn-off voltageDSCalculating the turn-off delay time delta t needed for compensating the turn-off voltage difference value through the relation function modeldoff. The turn-off delay time is active in the next switching cycle;
s3: after the control unit receives the power device total switch control signal pulse sent by the superior controller, the first power device is taken as the reference, and the turn-off delay time delta t of each power device is determined according to the turn-off delay time delta t of the power devicedoffAfter the main switch control signal pulse is correspondingly delayed relative to the reference, the main switch control signal pulse is sent to a driving unit corresponding to the power device through the communication unit; and the driving unit provides a gate driving signal to the power devices when receiving the pulse signal, and simultaneously triggers the sampling unit to acquire the turn-off voltage V and the device temperature T of each path of power devices in the current switching period for the series voltage-sharing adjustment of the next switching period.
Preferably, in step S1, the correlation test is performed in a pulse test system, where the pulse test system includes two power devices, a freewheeling diode, a bus capacitor, and a load inductor; the fly-wheel diode is connected with a load inductor in parallel, is connected with two power devices in series at the same time and then is connected with the bus capacitor in parallel; during testing, the power devices are heated to a set device temperature, then the two power devices are closed, the load inductor is charged by using a bus capacitor with given voltage, the two power devices are turned off after a set current point is reached, the turn-off time difference of the two power devices is set switch control signal turn-off delay time, and the series unbalanced voltage difference is measured after the two power devices are turned off.
Preferably, in step S1, the relationship function model among the device temperature of the power device, the turn-off delay time of the switching control signal, and the series unbalanced voltage is in the form of:
ΔVDs＝(AΔtdoff+B)(C-DT)
in the formula: A. b, C, D are all fitting parameters.
Compared with the prior art, the invention has the following beneficial effects:
in the actual operation of the series voltage-sharing circuit, the unbalanced voltage of the series devices is closely related to the internal parameters and the external operation conditions of the devices, and the series voltage-sharing circuit and the junya strategy provided by the invention can obtain the unbalanced voltage and temperature between the series devices by extracting the turn-off voltage and the device temperature of the power devices, and are used for adjusting the turn-off delay time of the driving signals of all the power devices, so that the series voltage sharing of power is realized. The invention is suitable for medium-high voltage high-power application occasions, and the voltage-sharing adjustment has rapidity, instantaneity and higher stability.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
Fig. 2 is a schematic structural diagram of the driving circuit.
FIG. 3 shows the unbalanced voltage Δ VDSWith the temperature T of the series SiC MOSFET device and the turn-off delay time delta T of the switch control signaldoffSchematic representation of the three-dimensional data of the variation.
FIG. 4 is a schematic diagram of a circuit for testing a double-transistor serial single pulse
Detailed Description
In order to describe the present invention more specifically, a detailed description of embodiments of the present invention will be given below with reference to the accompanying drawings.
As shown in fig. 1, taking a SiC MOSFET as an example of a power device, the invention provides a series voltage-sharing circuit of a power device with a device junction temperature compensation function, where the circuit includes: the device comprises a control unit, N driving circuits and N power devices connected in series. The N driving circuits are connected with the N power devices in a one-to-one correspondence mode, and N is a positive integer larger than or equal to 2. The structure of each driving circuit is the same, each driving circuit comprises a sampling unit, a communication unit and a driving unit, and the functions of the driving circuits are as follows:
the sampling unit is used for collecting the voltage, the current and the junction temperature of the connected power device.
The driving unit is used for providing a switch control signal for the grid electrode of the connected power device so as to control the on-off state switching of the power device and further regulate and control the on-current of the power device.
The communication unit is used for being connected with the control unit through a communication link to carry out bidirectional transmission, transmits sampling information of the sampling unit to the control unit on one hand, and receives a switch control signal sent by the control unit on the other hand and sends the switch control signal to the driving circuit. The communication unit forms a communication link with the control unit in a wired or wireless manner.
Certainly, the driving circuit should also include necessary lower control components such as a processor, and the sampling unit, the communication unit and the driving unit are all connected to the processor for central control, so as to implement the corresponding signal transmission function.
The control unit is used as a calculation and integral control part of the whole power device series voltage-sharing circuit and is used for collecting the voltage, current and junction temperature information of the power device, which is acquired by N sampling units and sent by the communication unit, and then executing a series voltage-sharing strategy, wherein in the series voltage-sharing strategy, the turn-off time delay of each power device switch control signal is calculated according to the voltage, current and junction temperature information of each power device, and then the switch control signal is sent to the driving unit corresponding to the device through the communication unit according to the calculated turn-off time delay of each power device so as to regulate and control the turn-off voltage balance of each power device.
The power device in the invention is a grid voltage control power device, and can be an Insulated Gate Bipolar Transistor (IGBT), a silicon carbide metal-oxide semiconductor field effect transistor (SiC MOSFET), a gallium nitride power device (GaN) or the like.
Based on the power device series voltage-sharing circuit, the specific implementation manner of the power device series voltage-sharing strategy is described in detail as follows:
s1: firstly, a relation function model among the device temperature, the turn-off delay time of the switch control signal and the series unbalanced voltage needs to be established for the series power devices, the model can be established based on the series voltage-sharing circuit shown in fig. 1 to obtain data, and the power devices with the same model parameters can be used for forming a simplified pulse test system to simplify the data obtaining process. When the relation function model is constructed, the device temperature of the power device and the turn-off delay time of the switch control signal are used as control variables, the series unbalanced voltage to be measured parameters of the power device are set according to the control variables, and a plurality of groups of test working conditions with different gradients are set for carrying out the correlation test. In order to fit an accurate relation function model, both the device temperature of the power device and the turn-off delay time of the switch control signal need to set enough gradient groups according to a certain step length. It should be noted, however, that the test should be conducted under conditions that do not exceed the maximum operating voltage, the maximum operating current, and the maximum operating junction temperature of the series-connected power devices. In each group of test working conditions, when the power devices are switched from the on state to the off state, the off voltage dynamic off amplitude and the device on current of each power device connected in series are respectively recorded, and the corresponding series unbalanced voltage can be obtained according to the off voltage dynamic off amplitude of each power device. After corresponding data are obtained under each test working condition, a relation function model among the device temperature of the power device, the turn-off delay time of the switch control signal and the series unbalanced voltage is established through data fitting based on the obtained data, and the fitting parameter optimal value of the model is obtained.
After the relation function model is obtained, the relation function model can be stored in a control unit and used for realizing a power device series connection voltage-sharing strategy.
S2: in the operation process of the power device series connection voltage-sharing circuit, in each switching period (the power devices are switched on and off), the control unit calls the turn-off voltage V and the device temperature T (collected by each sampling unit and sent to the control unit through the communication unit) of each power device in the last switching period, then the mean value of the turn-off voltages of all the power devices connected in series is used as a reference voltage, and the difference value delta V between the turn-off voltage of each power device and the reference voltage is respectively calculatedDSEach power device having its specific difference Δ VDS. Then, aiming at each path of power device, the temperature T and the turn-off voltage difference value delta V of the power device are utilizedDSBy substituting the relation function model, the turn-off delay time Deltat required for compensating the turn-off voltage difference can be calculateddoff. The turn-off delay time is in the next switching cycleAnd the effect is exerted.
S3: after the control unit receives the power device total switch control signal pulse sent by the superior controller, the turn-off delay time delta t of each power device in the previous step needs to be calleddoffFor controlling the time for which the signal pulses are sent to the respective driver circuits. Generally, the turn-off delay time Δ t of each power device can be based on the first power devicedoffAnd after the main switch control signal pulse is correspondingly delayed relative to the reference, the main switch control signal pulse is sent to the driving unit corresponding to the power device through the communication unit. When the driving unit receives the pulse signal, the driving unit immediately provides a gate driving signal for the power device, so that different power devices can automatically adjust the turn-off delay time of the driving signal of each power device, and the power series connection voltage sharing is realized. In addition, when the driving unit receives the pulse signal, the sampling unit should be triggered to acquire the turn-off voltage V and the device temperature T of the corresponding power device in the current switching period, and the turn-off voltage V and the device temperature T are fed back to the control unit for the series voltage-sharing adjustment of the next switching period.
The specific implementation of the above-mentioned series grading circuit and series grading strategy in a preferred embodiment will be described below with SiC MOSFETs as power devices, so as to facilitate better understanding of the essence of the present invention for those skilled in the art.
As shown in fig. 1, the SiC MOSFET series voltage equalizing circuit of the present embodiment includes a control unit, N driving circuits, N SiC MOSFETs, and N diodes. The control unit is in communication connection with the N drive circuits through high-speed optical fiber lines. The source of the previous MOSFET is connected to the drain of the next MOSFET, and the rest is similar, namely the (k-1) th MOSFET (MOS)k-1) Source electrode S ofk-1And the kth MOSFET (MOS)k) Drain electrode D ofkConnected with the cathode and anode of the kth diode respectively at the kth MOSFET (MOS)k) The drain electrode of the transistor is connected with the source electrode; n and k are natural numbers, N is more than or equal to 2, and k is more than or equal to 1 and less than or equal to N. The diode is one of an internal parasitic diode, an internal integrated fast diode and an external parallel fast diode of the SiC MOSFET device.
As shown in fig. 2, the driving circuit of the SiC MOSFET is composed of a plurality of functional units, including a processor, a MOSFET driving unit and fault detection circuit, a communication unit and a sampling unit, where k in the drawing indicates the kth group of driving circuits or the kth power device. The processor serves as a central control component of the overall drive circuit and is connected to other circuits and units. The fault detection circuit is used for detecting circuit faults; the sampling unit is used for sampling the connected power device, and the sampling information comprises the turn-off drain-source voltage V of the MOSFET deviceDSTemperature T of MOSFET device and on-current I of MOSFET deviceDS(ii) a The driving unit is used for providing a switch control signal for the grid electrode of the connected power device so as to control the on-off state switching of the power device and further regulate and control the on-current of the power device; the communication unit is connected with the control unit through a high-speed optical fiber line for bidirectional transmission, transmits sampling information and fault information of the sampling unit to the control unit on one hand, and receives a switch control signal (driving pulse) sent by the control unit and sends the switch control signal to the driving circuit on the other hand.
The control unit is the core for executing the voltage-sharing strategy, and the specific functions thereof will be described in detail later.
The voltage-sharing method based on the SiC MOSFET series voltage-sharing circuit comprises the following steps:
(1) setting operation condition under the condition of not exceeding the maximum working voltage, the maximum working current and the maximum working junction temperature of the MOSFET device, wherein the operation condition variables comprise the device temperature and the turn-off delay time difference delta t of the switch control signaldoff。
(2) Fixed switch control signal turn-off delay time difference delta tdoffAnd the temperature of the control device is uniformly changed according to the gradient. In this example, 6 different temperature points of-25 deg.C, 0 deg.C, 25 deg.C, 50 deg.C, 75 deg.C and 100 deg.C were selected at equal intervals within the range of-25 deg.C to 100 deg.C. Extracting dynamic turn-off amplitude imbalance delta V of drain-source voltage of the MOSFET device at each temperature point respectivelyDSAnd recording the turn-off delay time difference delta t of the switch control signal at the momentdoffObtaining the temperature T of the series device and the dynamic turn-off amplitude of the drain-source voltage of the MOSFET device according to the temperature T of the deviceDegree of balance DeltaVDSThe corresponding relationship (i.e., the unbalanced voltage) is stored in the database.
(3) Then, the switch control signal turn-off delay time difference delta t is adjusted according to a certain step gradientdoffIn the embodiment, 9 different turn-off delay time differences of-20 ns, -15ns, -10ns, -5ns, 0ns, 5ns, 10ns, 15ns and 20ns are selected at equal intervals in the range of-20 ns to 20 ns. And then repeating the step (2) for each turn-off delay time difference gradient to obtain the turn-off delay time delta t of the switch control signaldoffThe dynamic turn-off amplitude imbalance degree delta V of the drain-source voltage of the MOSFET deviceDSThe corresponding relationship of (1).
In general, the SiC MOSFET device is fixed at constant temperature, and the SiC MOSFET is connected with an unbalanced voltage delta V in seriesDSControl signal turn-off delay time delta t connected with series SiC MOSFET switchdoffIs in positive correlation. Fixed SiC MOSFET switch control signal turn-off delay time DeltatdoffInvariable, SiC MOSFET series unbalanced voltage DeltaVDSIs inversely related to the temperature of the series SiC MOSFET device.
(4) By the method, the series unbalanced voltage delta V of the SiC MOSFET can be establishedDSControl signal turn-off delay time delta t connected with series SiC MOSFET switchdoffAnd the three-dimensional relationship curve of the temperature of the series SiC MOSFET device is shown in figure 3. Based on the method, the turn-off delay time delta t of the switch control signal under each operation working condition is constructeddoffThe imbalance degree delta V between the temperature T of the series device and the dynamic turn-off amplitude of the drain-source voltage of the MOSFET deviceDSOf the form:
ΔVDs＝(AΔtdoff+B)(C-DT)
in the formula: A. b, C, D are all fitting parameters.
By the series unbalanced voltage delta V of the SiC MOSFETs under different working conditions maintained in the databaseDSAnd the turn-off delay time delta t of the series SiCSMOSFET switch control signaldoffThe coefficient A, B, C, D in the function model and the delta V can be obtained by fitting the data information of the temperature T of the series SiC MOSFET deviceDSAnd Δ tdoffAnd a specific expression of T, and storing the specific expression in the control unit.
(5) In the actual operation process of the series voltage-sharing circuit of the power device, the power device is detected on line in each switching period, and the dynamic turn-off amplitude V of the drain-source voltage of each MOSFET device is acquired by the acquisition unitDSAnd the device temperature T, which is sent to the control unit.
When the power device is started to work and enters a new switching period, the control unit calls the data of the previous period in advance and calculates the turn-off unbalanced voltage delta V of the kth MOSFET deviceDS，k(i.e., the difference between the drain-source voltage of the kth MOSFET device and the average voltage of the N series devices), k is 1, 2.
And then looking up a three-dimensional relation curved surface of the switch signal delay time, the unbalanced voltage and the device temperature according to the unbalanced voltage and the device temperature, so that the turn-off delay time required by compensating the turn-off voltage difference value can be calculated. Since the curved surface is already fitted to the function model in this embodiment, the turn-off imbalance voltage Δ V of the kth MOSFET device can be directly obtained through the function modelDS，kAnd the device temperature T of the kth MOSFET devicekSubstituting into the function model, and calculating to obtain the turn-off delay time delta t of the kth MOSFET devicedoff，kThe calculation formula is as follows:
Figure BDA0002412761320000071
(6) after the control unit receives a series SiC MOSFET control signal pulse sent by a superior controller, for any kth power device, the 1 st MOSFET device is selected as a reference, and the total switch control signal pulse is delayed for a turn-off delay time delta t corresponding to the referencedoff，kAnd then the optical fiber is distributed to a driving circuit corresponding to the device through a high-speed optical fiber line. After receiving the pulse driving signal, the controller of the driving circuit immediately provides a gate driving signal for the SiC MOSFET device, and simultaneously collects the dynamic turn-off amplitude of drain-source voltage of each path of SiC MOSFET in the current switching period and the temperature of the series MOSFET device through the sampling unit for series voltage-sharing adjustment in the next switching period, and sends the signals to the sampling unitTo the control unit.
In some embodiments, to obtain the corresponding curved surface shown in fig. 3 quickly, the above steps (1) - (3) may be implemented by a pulse testing system to simplify the data acquisition process. Fig. 4 shows a schematic circuit diagram of a pulse test, which is an inductive load test circuit composed of a bus capacitor, two power devices MOSFET 1, MOSFET 2, a freewheeling diode, and a load inductor. In the figure, Rg2_LDenotes the drive resistance, Vg1_L、Vg2_LRepresenting a drive signal, Cgd2_L、Cgs2_L、Cds2_L、Cgd1_L、Cgs1_L、Cds1_LAll the capacitors are self-contained capacitors in the power device, and the explanation is not needed. The two ends of the freewheeling diode are connected with the load inductor in parallel, and are connected with the two power devices in series and then connected with the bus capacitor in parallel, and each power device is provided with a controllable junction temperature adjusting device. During testing, the power device is heated to a set device temperature, then the two power devices connected in series are closed, the load inductor is charged by using the bus capacitor with a given voltage, and correspondingly, the current flowing through the device is increased. And after the circuit reaches the specified test point, the two power devices are turned off according to the test requirement. The switching time of the two power devices connected in series is adjustable. Clearly, given different turn-off times of the device, a significant difference in voltage across the device will occur. Therefore, the difference value of the turn-off time of the two power devices is the set turn-off delay time of the switch control signal, and the voltage difference can be measured. And continuously adjusting the temperature of the device and the difference value of the turn-off time, and measuring the voltage difference of the series unbalance to obtain the corresponding relation between the voltage unbalance and the turn-off voltage, the turn-on current and the junction temperature of the device.
The above-described embodiments are merely preferred embodiments of the present invention, which should not be construed as limiting the invention. Various changes and modifications may be made by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present invention. Therefore, the technical scheme obtained by adopting the mode of equivalent replacement or equivalent transformation is within the protection scope of the invention.

Claims (8)

1. A series voltage-sharing circuit of a power device with a device junction temperature compensation function is characterized by comprising the following components: the power supply comprises a control unit, N driving circuits and N power devices connected in series, wherein the N driving circuits are connected with the N power devices in a one-to-one correspondence mode, and N is a positive integer greater than or equal to 2; each driving circuit comprises a sampling unit, a communication unit and a driving unit;
the sampling unit is used for collecting the voltage, the current and the junction temperature of the connected power device;
the driving unit is used for providing a switch control signal for the grid electrode of the connected power device so as to control the on-off state switching of the power device and further regulate and control the on-current of the power device;
the communication unit is used for transmitting the sampling information of the sampling unit to the control unit through a communication link, receiving the switch control signal sent by the control unit and sending the switch control signal to the drive circuit;
the control unit is used for collecting the voltage, current and junction temperature information of the power devices collected by the N sampling units, executing a series voltage-sharing strategy, calculating the turn-off time delay of the switch control signals of each power device, and then sending the switch control signals to the corresponding driving units according to the turn-off time delay of each power device so as to regulate and control the turn-off voltage balance of each power device.
2. The series voltage-sharing circuit of power devices according to claim 1, wherein the driving circuit further comprises a processor, and the sampling unit, the communication unit and the driving unit are connected to the processor for central control.
3. The series voltage-sharing circuit of power devices according to claim 2, further comprising a fault detection circuit, wherein the sampling unit is connected to the processor through the fault detection circuit.
4. The power device series voltage equalizing circuit according to claim 1, wherein said communication unit forms a communication link with said control unit in a wired or wireless manner.
5. The series voltage-sharing circuit of claim 1, wherein the power device is a gate voltage controlled power device, comprising: insulated Gate Bipolar Transistors (IGBTs), silicon carbide metal-oxide semiconductor field effect transistors (SiC MOSFETs), or gallium nitride power devices (GaN).
6. A power device series connection voltage-sharing method based on the power device series connection voltage-sharing circuit of any claim 1 to 5 is characterized by comprising the following steps:
s1: under the condition that the maximum working voltage, the maximum working current and the maximum working junction temperature of the power devices connected in series are not exceeded, the device temperature of the power devices and the turn-off delay time of the switch control signal are used as control variables, parameters to be measured of series unbalanced voltage of the power devices are used, and multiple groups of test working conditions with different gradients are set for the control variables to carry out a correlation test; in each group of test working conditions, when the power devices are switched from a conducting state to a switching-off state, respectively recording the switching-off voltage dynamic switching-off amplitude of each power device connected in series to obtain corresponding series unbalanced voltage; then, based on data obtained under each test working condition, a relation function model between the device temperature of the power device, the turn-off delay time of the switch control signal and the series unbalanced voltage is established through data fitting;
s2: in the operation process of the power device series connection voltage-sharing circuit, in each switching period, the control unit calls the turn-off voltage V and the device temperature T of each power device, then the mean value of the turn-off voltages of all the power devices connected in series is used as a reference voltage, and the difference value delta V between the turn-off voltage of each power device and the reference voltage is respectively calculatedDS(ii) a Then, aiming at each path of power device, the temperature T and the turn-off voltage difference value delta V of the power device are utilizedDSCalculating the turn-off delay time delta t needed for compensating the turn-off voltage difference value through the relation function modeldoff. The switchThe off delay time plays a role in the next switching cycle;
s3: after the control unit receives the power device total switch control signal pulse sent by the superior controller, the first power device is taken as the reference, and the turn-off delay time delta t of each power device is determined according to the turn-off delay time delta t of the power devicedoffAfter the main switch control signal pulse is correspondingly delayed relative to the reference, the main switch control signal pulse is sent to a driving unit corresponding to the power device through the communication unit; and the driving unit provides a gate driving signal to the power devices when receiving the pulse signal, and simultaneously triggers the sampling unit to acquire the turn-off voltage V and the device temperature T of each path of power devices in the current switching period for the series voltage-sharing adjustment of the next switching period.
7. The method for equalizing voltage of series connection of power devices according to claim 6, wherein in step S1, the correlation test is performed in a pulse test system, wherein the pulse test system comprises two power devices, a freewheeling diode, a bus capacitor and a load inductor; the fly-wheel diode is connected with a load inductor in parallel, is connected with two power devices in series at the same time and then is connected with the bus capacitor in parallel; during testing, the power devices are heated to a set device temperature, then the two power devices are closed, the load inductor is charged by using a bus capacitor with given voltage, the two power devices are turned off after a set current point is reached, the turn-off time difference of the two power devices is set switch control signal turn-off delay time, and the series unbalanced voltage difference is measured after the two power devices are turned off.
8. The method for equalizing voltage of power devices in series according to claim 6, wherein in step S1, the relationship function model among the device temperature of the power devices, the turn-off delay time of the switching control signal and the series unbalanced voltage is as follows:
ΔVDS＝(AΔtdoff+B)(C-DT)
in the formula: A. b, C, D are all fitting parameters.
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