CN113872438B - Method and system for detecting open circuit of multiphase staggered parallel DCDC converter - Google Patents

Method and system for detecting open circuit of multiphase staggered parallel DCDC converter Download PDF

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Publication number
CN113872438B
CN113872438B CN202111029345.6A CN202111029345A CN113872438B CN 113872438 B CN113872438 B CN 113872438B CN 202111029345 A CN202111029345 A CN 202111029345A CN 113872438 B CN113872438 B CN 113872438B
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current
control unit
sampling
open
determining
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CN113872438A (en
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韦彬
张建
葛凯
施子豪
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United Automotive Electronic Systems Co Ltd
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United Automotive Electronic Systems Co Ltd
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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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/54—Testing for continuity
    • 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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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The application discloses a method and a system for detecting disconnection of a multiphase staggered parallel DCDC converter, and relates to the technical field of circuits. The open circuit detection method of the multiphase staggered parallel DCDC converter comprises the steps of obtaining sampling current of each control unit through a current sampling circuit; determining a sampling current relation according to the sampling current of each control unit; determining the open-circuit fault condition of the control unit according to the sampling current relation; the problem that open-circuit faults are ignored in the prior DCDC converter fault diagnosis is solved; the control unit for rapidly positioning the broken circuit fault is achieved, and the detection cost of the broken circuit fault of the DCDC converter is reduced.

Description

Method and system for detecting open circuit of multiphase staggered parallel DCDC converter
Technical Field
The application relates to the technical field of circuits, in particular to a method and a system for detecting disconnection of a multiphase staggered parallel DCDC converter.
Background
The DCDC converter is a structure for converting direct current into direct current, and the conversion is realized by a switching method. In order to meet the high-power design and reduce current ripple, the DCDC converter generally adopts a multiphase staggered parallel topology structure.
The multiphase interleaved parallel DCDC topology is widely applied in micro-hybrid systems by virtue of its low cost and simple control strategy, and fig. 1 exemplarily shows a schematic structure diagram of a 48V multiphase interleaved parallel DCDC topology. In the multiphase staggered parallel DCDC topological structure, when a certain power tube is damaged, a fault loop where the damaged power tube is positioned is cut off, and the rest half-bridge is output symmetrically again, so that redundancy control is achieved. Therefore, it is necessary to locate the faulty loop.
However, most of the current diagnosis methods of the DCDC converter fault loop can only identify the short-circuit fault of the power tube, and when the power tube has the open-circuit fault, the power output voltage is still constant, and the open-circuit fault of the power tube is ignored.
Disclosure of Invention
In order to solve the problems in the related art, the application provides a method and a system for detecting the open circuit of a multiphase staggered parallel DCDC converter. The technical scheme is as follows:
in a first aspect, an embodiment of the present application provides a method for detecting a shutdown of a multiphase interleaved parallel DCDC converter, where the multiphase interleaved parallel DCDC converter includes at least M control units, the number of phases of each control unit is the same, and M is an integer greater than or equal to 2;
The method comprises the following steps:
acquiring sampling currents of all the control units through a current sampling circuit;
Determining a sampling current relation according to the sampling current of each control unit;
and determining the open-circuit fault condition of the control unit according to the sampling current relation.
Optionally, determining the sampling current relationship according to the sampling currents of the respective control units includes:
when m=2, calculating the sampling current ratio of the first control unit and the second control unit according to the sampling current;
and when M is more than 2, acquiring the sampling current difference condition of the control units according to the sampling current of each control unit.
Optionally, when m=2, determining the open-circuit fault condition of the control unit according to the sampled current relationship includes:
acquiring load current of the multiphase staggered parallel DCDC converter;
Detecting whether the load current is in a first current range or a second current range;
and when the load current is detected to be in the first current range or the second current range, determining the open-circuit fault condition of the first control unit and the second control unit according to the sampling current ratio of the first control unit and the second control unit.
Optionally, when the load current is detected to be in the first current range or the second current range, determining the open-circuit fault condition of the first control unit and the second control unit according to the sampling current ratio of the first control unit and the second control unit includes:
If I 1/I2 = (n-2)/n or 1 < I 1/I2 < n/(n-2) when the load current is within the first current range, determining that the first control unit has an open circuit fault; if (n-2)/n < I 1/I2 < 1 or I 1/I2 =n/(n-2), determining that the second control unit has an open-circuit fault;
When the load current is in the second current range, if I 1/I2 is less than 1, determining that the first control unit has an open-circuit fault; if I 1/I2 is more than 1, determining that the second control unit has an open-circuit fault;
When the load current is in the first current range or the second current range, if I 1/I2 = 1, determining that the first control unit and the second control unit have no open-circuit fault;
wherein I 1 represents the sampling current of the first control unit, I 2 represents the sampling current of the second control unit, and n represents the number of phases of the DCDC converter.
Optionally, when M > 2, determining the open-circuit fault condition of the control unit according to the sampling current relationship includes:
When the sampling current relation of the M control units is that the sampling current of the ith control unit is different from the sampling current of the remaining M-1 control units and the sampling currents of the remaining M-1 control units are the same, determining that the ith control unit has an open-circuit fault; i is an integer, and the value range of i is 1 to M;
and when the sampling current relation of the M control units is the same as the sampling current relation of the M control units, determining that the M control units have no circuit breaking fault.
In a second aspect, an embodiment of the present application provides a circuit break detection system of a multiphase interleaved parallel DCDC converter, including a multiphase interleaved parallel DCDC converter, a current sampling circuit, and a controller;
The multiphase staggered parallel DCDC converter comprises at least M control units, wherein the phase numbers of the control units are the same, and M is an integer greater than or equal to 2;
each control unit is connected with a current sampling circuit, and the current sampling circuit is connected with the controller;
The current sampling circuit is used for acquiring the sampling current of the control unit;
the controller is used for acquiring the sampling current of each control unit through the current sampling circuit; determining a sampling current relation according to the sampling current of each control unit; and determining the open-circuit fault condition of the control unit according to the sampling current relation.
Optionally, the controller is configured to calculate, when m=2, a sampling current ratio of the first control unit and the second control unit according to the sampling current;
When M > 2, detecting whether the sampling current of each control unit is the same according to the sampling current of each control unit.
Optionally, the controller is configured to obtain a load current of the multiphase interleaved parallel DCDC converter when m=2;
Detecting whether the load current is in a first current range or a second current range;
and when the load current is detected to be in the first current range or the second current range, determining the open-circuit fault condition of the first control unit and the second control unit according to the sampling current ratio of the first control unit and the second control unit.
Optionally, the controller is configured to determine that the first control unit has an open circuit fault when the load current is within the first current range, I 1/I2 = (n-2)/n or 1 < I 1/I2 < n/(n-2); when (n-2)/n < I 1/I2 < 1 or I 1/I2 =n/(n-2), determining that the second control unit has an open-circuit fault;
When the load current is in the second current range and I 1/I2 is less than 1, determining that the first control unit has an open-circuit fault; when I 1/I2 is more than 1, determining that the second control unit has an open-circuit fault;
When the load current is in the first current range or the second current range, I 1/I2 = 1, determining that the first control unit and the second control unit have no open-circuit fault;
wherein I 1 represents the sampling current of the first control unit, I 2 represents the sampling current of the second control unit, and n represents the number of phases of the DCDC converter.
Optionally, the controller is configured to determine that the ith control unit has an open circuit fault when the sampling current relationship of the M control units is that the sampling current of the ith control unit is different from the sampling current of the remaining M-1 control units and the sampling current of the remaining M-1 control units is the same; i is an integer, and the value range of i is 1 to M;
and when the sampling current relation of the M control units is the same as the sampling current relation of the M control units, determining that the M control units have no circuit breaking fault.
The technical scheme of the application at least comprises the following advantages:
the sampling current of each control unit in the DCDC converter is obtained through the current sampling circuit, the sampling current relation is determined according to the sampling current of each control unit, and the open-circuit fault condition of the control unit is determined according to the adopted current relation, so that the problem that the open-circuit fault is ignored in the current DCDC converter fault diagnosis is solved; the control unit for rapidly positioning the broken circuit fault is achieved, and the detection cost of the broken circuit fault of the DCDC converter is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present application, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a 48V multiphase interleaved parallel DCDC topology;
Fig. 2 is a schematic structural diagram of a circuit break detection system of a multiphase interleaved parallel DCDC converter according to an embodiment of the present application;
fig. 3 is a flowchart of a method for detecting open circuit of a multiphase interleaved parallel DCDC converter according to an embodiment of the present application;
Fig. 4 is a schematic diagram of a relationship between a load current of a 4-phase staggered parallel DCDC converter and a control unit circuit breaking fault provided by an embodiment of the present application;
FIG. 5 is a schematic diagram of four-phase inductor current when the 1 st phase down tube is open in a 4-phase offset parallel DCDC converter under heavy load conditions provided by an embodiment of the present application;
fig. 6 is a schematic diagram of four-phase inductor current when the 1 st phase down tube in the 4-phase staggered parallel DCDC converter is disconnected under the light load condition provided by the embodiment of the present application;
fig. 7 is a schematic diagram of a relationship between a load current and a control unit circuit breaking fault of a 6-phase staggered parallel DCDC converter according to an embodiment of the present application.
Detailed Description
The following description of the embodiments of the present application will be made more apparent and fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the application are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
In the description of the present application, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present application, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; the two components can be directly connected or indirectly connected through an intermediate medium, or can be communicated inside the two components, or can be connected wirelessly or in a wired way. The specific meaning of the above terms in the present application will be understood in specific cases by those of ordinary skill in the art.
In addition, the technical features of the different embodiments of the present application described below may be combined with each other as long as they do not collide with each other.
Fig. 2 is a schematic diagram illustrating a schematic structure of a circuit breaking detection system of a multiphase interleaved parallel DCDC converter according to an embodiment of the present application. As shown in fig. 2, the system includes a multiphase interleaved parallel DCDC converter 110, a current sampling circuit, and a controller 120.
The multiphase interleaved parallel DCDC converter 110 includes at least M control units, each of which has the same number of phases, M being an integer of 2 or more.
Each control unit in the multiphase interleaved parallel DCDC converter 110 is connected to 1 current sampling circuit, each current sampling circuit is connected to a controller 120, and the controller 120 is connected to the multiphase interleaved parallel DCDC converter 110.
Each current sampling circuit is used for acquiring the sampling current of one control unit. For example, the current sampling current 1 is used to obtain the sampling current I 1 of the control unit 1, and the current sampling circuit M is used to obtain the sampling current I M of the control unit M.
The controller 120 is configured to obtain the sampling current of each control unit through the current sampling circuit, determine a sampling current relationship according to the sampling current of each control unit, and determine an open-circuit fault condition of each control unit in the multiphase interleaved parallel DCDC converter 110 according to the sampling current relationship.
The open circuit fault condition includes the control unit having an open circuit fault and the control unit having no open circuit fault.
The controller 120 is connected to the multiphase interleaved parallel DCDC converter 110. When the controller 120 detects that the control unit has an open circuit fault, the control unit having the open circuit fault in the multiphase interleaved parallel type DCDC converter 110 is actively turned off.
Referring to fig. 3, a flowchart of a method for detecting a shutdown of a multi-phase interleaved parallel DCDC converter according to an embodiment of the application is shown, and the method is applicable to the controller 120 in the shutdown detection system of the multi-phase interleaved parallel DCDC converter shown in fig. 2. As shown in fig. 3, the method for detecting the open circuit of the multiphase interleaved parallel DCDC converter at least comprises the following steps:
In step 301, sampling currents of the respective control units are obtained by a current sampling circuit.
The multiphase staggered parallel DCDC converter comprises at least M control units, wherein the phase numbers of the control units are the same; each control unit has several phases, each phase including 2 power tubes, namely an upper tube and a lower tube.
M is an integer greater than or equal to 2.
Each control unit corresponds to a current sampling circuit, and the current sampling circuit obtains the output current of the control unit and sends the output current to the controller.
Optionally, the controller periodically obtains the sampling current of each control unit through the current sampling circuit.
Step 302, determining a sampling current relation according to the sampling current of each control unit.
And obtaining a sampling current relation according to the obtained sampling current of each control unit. The sampling current relationship is used to indicate whether the sampling currents of the respective control units are the same, and the proportional relationship between the sampling currents.
Step 303, determining the open-circuit fault condition of the control unit according to the sampled current relationship.
If all control units in the multiphase staggered parallel DCDC converter have no open-circuit faults, sampling currents of all the control units are the same; if a control unit in the multiphase staggered parallel DCDC converter has a circuit breaking fault, the sampling current of the control unit with the circuit breaking fault is different from the sampling current of other control units without the circuit breaking fault.
Taking the number of the control units as 2 as an example, when the power tubes in the multiphase staggered parallel DCDC converter have no open-circuit fault, each control unit corresponds to a loop to work normally, and the output currents of the two control units are the same, namely the sampling currents of the two control units are the same; when the power tube in the multiphase staggered parallel DCDC converter has an open-circuit fault, the sampling current of the control unit where the open-circuit power tube is positioned can change, so that the sampling currents of the two control units are different.
It should be noted that, when the number of the control units is 2, a certain control unit has an open circuit fault, the sampling current I 1 of the first control unit is different from the sampling current I 2 of the second control unit, and the controller can only determine that the multiphase interleaved parallel DCDC converter has an open circuit fault, but cannot locate the control unit having an open circuit fault, so that the control unit having an open circuit fault needs to be determined by combining the proportional relationship between the sampling current I 1 and the sampling current I 2.
Taking the number of the control units as 3 or more as an example, when the power tubes in the multiphase staggered parallel DCDC converter have no open-circuit fault, each control unit works normally corresponding to a loop, and the output currents of the control units are the same, namely the sampling currents of the control units are the same; when the power tube in the multiphase staggered parallel DCDC converter has a break fault, the sampling current of the control unit where the break power tube is located changes, the sampling current of the control unit with the break fault is different from the sampling current of other control units without the break fault (namely, the remaining 2 and more control units) and the sampling current of the other control units without the break fault are the same, and therefore, the controller can directly determine the control unit with the break fault according to the difference of the sampling currents.
When the controller locates the control unit with the open circuit fault, the controller cuts off the control unit with the open circuit fault.
In summary, according to the method for detecting the open circuit of the multiphase interleaved parallel type DCDC converter provided by the embodiment of the application, the sampling current of each control unit in the DCDC converter is obtained through the current sampling circuit, the sampling current relation is determined according to the sampling current of each control unit, and the open circuit fault condition of the control unit is determined according to the adopted current relation, so that the problem that the open circuit fault is ignored in the fault diagnosis of the current DCDC converter is solved; the control unit for rapidly positioning the broken circuit fault is achieved, and the detection cost of the broken circuit fault of the DCDC converter is reduced.
Optionally, the power tube in the multiphase interleaved parallel DCDC converter is bootstrap driven.
In an alternative embodiment based on the embodiment shown in fig. 3, the step 302, i.e. the step "determining the sampling current relation from the sampling currents of the respective control units", is implemented by:
1. When m=2, the sampling current ratio of the first control unit and the second control unit is calculated from the sampling current.
2. When M > 2, detecting whether the sampling current of each control unit is the same according to the sampling current of each control unit.
When m=2, the open-circuit fault condition of the control unit is determined according to the sampling current ratio of the first control unit and the second control unit.
And when M is more than 2, determining the open-circuit fault condition of the control unit according to the sampling current difference condition of the control unit.
When m=2, i.e. the multiphase interleaved parallel DCDC converter comprises 2 control units, the above step 303, i.e. "determining the open fault condition of the control units according to the sampling current relationship", may be implemented by the following steps:
Step 401, obtaining a load current of a multiphase interleaved parallel type DCDC converter.
The controller obtains a load current of the multiphase interleaved parallel type DCDC converter.
Optionally, the controller obtains the load current of the multiphase interleaved parallel DCDC converter according to a predetermined period.
Step 402, it is detected whether the load current is within a first current range or a second current range.
The maximum current value in the first current range is smaller than the minimum current value in the second current range.
The first current range and the second current range are determined according to actual conditions. The current threshold that distinguishes the load current from heavy and light loads is not within the first current range and the second current range.
Optionally, the first current range belongs to a light load condition, and the second current range belongs to a heavy load condition.
When it is detected that the load current is not within the first current range and is not within the second current range, positioning of the fault control unit is not performed.
And when the load current is detected to be in the first current range or the second current range, determining the open-circuit fault condition of the first control unit and the second control unit according to the sampling current ratio of the first control unit and the second control unit.
Note that I 1 is the sampling current of the first control unit, I 2 is the sampling current of the second control unit, and n is the number of phases of the DCDC converter.
(1) When the load current is in the first current range
If I 1/I2 = (n-2)/n or 1 < I 1/I2 < n/(n-2), determining that the first control unit has an open circuit fault; if (n-2)/n < I 1/I2 < 1 or I 1/I2 =n/(n-2), then it is determined that the second control unit has a disconnection fault.
(2) When the load current is in the second current range
If I 1/I2 is less than 1, determining that the first control unit has an open-circuit fault; if I 1/I2 > 1, it is determined that the second control unit has an open circuit fault.
(3) When the load current is in the first current range or the second current range
If I 1/I2 = 1, it is determined that the first control unit and the second control unit have no open circuit fault.
Steps 401 and 402 are performed by the controller 120 in the open circuit detection system of the multiphase interleaved parallel DCDC converter shown in fig. 2.
In an example, taking the 4-phase offset parallel type DCDC converter shown in fig. 1 as an example, each control unit has 2 phases, the number of phases n=4 of the DCDC converter, fig. 4 shows a schematic diagram of a relationship between a load current of the 4-phase offset parallel type DCDC converter and an open-circuit fault of the control unit, in fig. 4, a region S1 corresponds to a first current range, and a region S2 corresponds to a second current range.
The open circuit fault condition of the control unit in the 4-phase staggered parallel type DCDC converter is analyzed by combining fig. 1 and 4:
1. Upper pipe break in control unit
When the upper pipe in a certain control unit is disconnected, the energy transmission path of the control unit branch is completely cut off.
Assuming that the upper tube in the first control unit is open, the output capacity of the first control unit is only half that of the second control unit, and the sampling current ratio of the sampling current I 1 of the first control unit to the sampling current I 2 of the second control unit is I 1/I2 =0.5.
Assuming that the upper tube in the second control unit is open, the output capacity of the second control unit is only half that of the first control unit, and the sampling current ratio of the sampling current I 1 of the first control unit to the sampling current I 2 of the second control unit is I 1/I2 =2.
2. The lower tube in the control unit is broken, and the body diode of the broken lower tube is normal
It is assumed that the 1 st or 2 nd phase down tube in the first control unit is open because of the existence of the body diode of the down tube, the 1 st or 2 nd phase is changed into a Buck circuit with asynchronous rectification. The following 2 cases are adopted:
(1) The load current being heavy-duty
The current threshold is set, the load current exceeding the current threshold is determined as heavy load, and the load current not exceeding the current threshold is determined as light load.
Taking the example of the open circuit of the phase 1 down tube, in the heavy load mode, the inductive current of any phase is larger than 0 in one period. The 1 st phase inductance current can follow current through the body diode of the lower tube, and the bootstrap capacitor of the 1 st phase driving circuit completes charging during follow current of the lower tube, so that each phase half bridge works normally during heavy load. Since phase 1 freewheels through the lower body diode, phase 1 loop impedance is larger, resulting in phase 1 currents that are smaller but not 0, as shown in fig. 5.
Thus, the sampling current ratio of the sampling current I 1 of the first control unit and the sampling current I 2 of the second control unit is 0.5 < I 1/I2 < 1.
Correspondingly, when the 3 rd phase or 4 th phase lower pipe in the second control unit is disconnected, the sampling current ratio of the sampling current I 1 of the first control unit to the sampling current I 2 of the second control unit is 1 < I 1/I2 < 2.
(2) The load current is light load
It is assumed that the phase 1 or phase 2 down pipe in the first control unit is open.
In the light load mode, due to the characteristics of the synchronous rectification circuit, negative current exists in the inductance freewheeling stage under the normal working condition, when the 1 st phase lower tube is disconnected or the 2 nd phase lower tube is disconnected, the synchronous rectification circuit works in the DCM mode, and the negative current is not output after the inductance current is reduced to 0.
Taking the example of the phase 1 down-pipe circuit breaking, in the light load mode, the duty ratio of the phase 1 is consistent with other phases, and the output voltage is consistent with other phases due to the characteristics of a parallel circuit, so that the volt-second balance of the phase 1 inductor is broken. When the 1 st phase upper pipe is conducted, the inductance current starts from 0, and the inductance gradually magnetizes in the process of transition from steady state, so that new volt-second balance is achieved; in the process of transition to the new volt-second balance, the average current of the 1 st phase gradually rises, the body diode of the lower tube gradually and completely conducts, and the mode is forcedly changed into a continuous mode. Since the output side load is unchanged, the current of other phases which do not fail correspondingly decreases, and the smaller the output load is, the larger the ratio of the current of the open-circuit phase to the normal phase is, as shown in fig. 6.
Thus, the sampling current ratio of the sampling current I 1 of the first control unit and the sampling current I 2 of the second control unit is I 1/I2 > 1.
Correspondingly, when the 3 rd phase or 4 th phase lower pipe in the second control unit is disconnected, the sampling current ratio of the sampling current I 1 of the first control unit to the sampling current I 2 of the second control unit is 1 < I 1/I2.
3. The lower tube in the control unit is broken, and the body diode of the broken lower tube is damaged
When the lower tube is broken in a certain control unit and the lower tube body diode is damaged, the energy transmission path of the branch of the control unit is completely cut off.
Assuming that the lower tube in the first control unit is open and the lower tube body diode is damaged, the output capacity of the first control unit is only half that of the second control unit, and the sampling current ratio of the sampling current I 1 of the first control unit to the sampling current I 2 of the second control unit is I 1/I2 =0.5.
Assuming that the lower tube in the second control unit is open and the lower tube body diode is damaged, the output capacity of the second control unit is only half that of the first control unit, and the sampling current ratio of the sampling current I 1 of the first control unit to the sampling current I 2 of the second control unit is I 1/I2 =2.
As can be seen from fig. 4, the I 1/I2 curves of different open circuit conditions have a junction, so in order to avoid a situation that the fault control unit cannot be judged according to the ratio, a first current range S1 and a second current range S2 are set, and when the load current is in the first current range S1 or the second current range S2, the I 1/I2 curves have no junction.
In another example, taking a 6-phase staggered parallel type DCDC converter as an example, the 6-phase staggered parallel type DCDC converter has 2 control units, each control unit has 3 phases, the number of phases of the DCDC converter n=6, fig. 7 shows a schematic diagram of a relationship between a load current of the 6-phase staggered parallel type DCDC converter and a circuit breaking fault of the control units, in fig. 7, a region S3 corresponds to a first current range, and a region S4 corresponds to a second current range.
The structure of the 6-phase staggered parallel type DCDC converter and the open circuit fault condition of a control unit in the 6-phase staggered parallel type DCDC converter are combined for analysis, and the open circuit fault condition is analyzed in FIG. 7:
1. Upper pipe break in control unit
When the upper pipe of a certain control unit is disconnected, the energy transmission path of the branch circuit of the control unit is completely cut off, and only 5 phases of the 6-phase staggered parallel DCDC converter normally output.
Assuming that the upper tube in the first control unit is open, the output capacity of the first control unit is only 2/3 of that of the second control unit, and the sampling current ratio of the sampling current I 1 of the first control unit to the sampling current I 2 of the second control unit is I 1/I2 =2/3≡0.667.
Assuming that the upper tube in the second control unit is open, the output capacity of the second control unit is only 2/3 of that of the first control unit, and the sampling current ratio of the sampling current I 1 of the first control unit to the sampling current I 2 of the second control unit is I 1/I2 =1.5.
2. The lower tube in the control unit is broken, and the body diode of the broken lower tube is normal
It is assumed that the lower tube of any one phase in the first control unit is open because the body diode of the lower tube exists and is normal, and the open phase of the lower tube becomes a Buck circuit with asynchronous rectification. The following 2 cases are adopted:
(1) The load current being heavy-duty
The current threshold is set, the load current exceeding the current threshold is determined as heavy load, and the load current not exceeding the current threshold is determined as light load.
Taking the example of the open circuit of the phase 1 down tube, in the heavy load mode, the inductive current of any phase is larger than 0 in one period. The 1 st phase inductance current can follow current through the body diode of the lower tube, and the bootstrap capacitor of the 1 st phase driving circuit completes charging during follow current of the lower tube, so that each phase half bridge works normally during heavy load. Since phase 1 freewheels through the lower body diode, phase 1 loop impedance is larger, resulting in phase 1 current that is smaller but not 0.
Thus, the sampling current ratio of the sampling current I 1 of the first control unit and the sampling current I 2 of the second control unit is 0.667 < I 1/I2 < 1.
Correspondingly, when the down pipe of any one phase in the second control unit is disconnected, the sampling current ratio of the sampling current I 1 of the first control unit to the sampling current I 2 of the second control unit is 1 < I 1/I2 < 1.5.
(2) The load current is light load
It is assumed that the down pipe of any one phase in the first control unit is open.
In the light load mode, due to the characteristics of the synchronous rectification circuit, negative current exists in the inductance freewheeling stage under the normal working condition, when any one phase of lower tube is disconnected, the synchronous rectification circuit works in the DCM mode, and the negative current is not output after the inductance current is reduced to 0.
Taking the example of the phase 1 down pipe open circuit, in the light load mode, the duty ratio of the phase 1 is consistent with other phases, and the output voltage is consistent with other phases due to the characteristics of a parallel circuit, so that the volt-second balance of the phase 1 inductor is broken. When the 1 st phase upper pipe is conducted, the inductance current starts from 0, and the inductance gradually magnetizes in the process of transition from steady state, so that new volt-second balance is achieved; in the process of transition to the new volt-second balance, the average current of the 1 st phase gradually rises, the body diode of the lower tube gradually and completely conducts, and the mode is forcedly changed into a continuous mode. Since the load on the output side is unchanged, the current of other phases which do not have faults correspondingly decreases, and the smaller the output load is, the larger the ratio of the current of the open-circuit phase relative to the normal phase is.
Thus, the sampling current ratio of the sampling current I 1 of the first control unit and the sampling current I 2 of the second control unit is I 1/I2 > 1.
Correspondingly, when the down pipe of any one phase in the second control unit is disconnected, the sampling current ratio of the sampling current I 1 of the first control unit to the sampling current I 2 of the second control unit is 1< I 1/I2.
3. The lower tube in the control unit is broken, and the body diode of the broken lower tube is damaged
When the lower tube is broken in a certain control unit and the lower tube body diode is damaged, the energy transmission path of the branch of the control unit is completely cut off.
Assuming that the lower tube in the first control unit is broken and the lower tube body diode is damaged, the output capacity of the first control unit is only 2/3 of that of the second control unit, and the sampling current ratio of the sampling current I 1 of the first control unit to the sampling current I 2 of the second control unit is I 1/I2 =2/3≡0.667.
Assuming that the lower tube in the second control unit is open and the lower tube body diode is damaged, the output capacity of the second control unit is only 2/3 of that of the first control unit, and the sampling current ratio of the sampling current I 1 of the first control unit to the sampling current I 2 of the second control unit is I 1/I2 =1.5.
As can be seen from fig. 7, the I 1/I2 curves of different open circuit conditions have a junction, so in order to avoid a situation that the fault control unit cannot be judged according to the ratio, a first current range S3 and a second current range S4 are set, and when the load current is in the first current range S3 or the second current range S4, the I 1/I2 curves have no junction.
When M > 2, i.e. the multiphase interleaved parallel DCDC converter comprises more than 2 control units, the above step 303, i.e. "determining the open-circuit fault condition of the control units according to the sampling current relationship", may be implemented as follows:
(1) When the sampling current relation of the M control units is that the sampling current of the ith control unit is different from the sampling current of the remaining M-1 control units, and the sampling currents of the remaining M-1 control units are the same, determining that the ith control unit has an open-circuit fault.
Wherein i is an integer, and the value range of i is 1 to M.
Taking m=3 as an example, that is, the multiphase interleaved parallel DCDC converter includes 3 control units, if the sampling current of the first control unit is different from the sampling current of the second control unit and the sampling current of the third control unit, and the sampling current of the second control unit is the same as the sampling current of the third control unit, it is determined that the first control unit has an open circuit fault.
(2) And when the sampling current relation of the M control units is the same as the sampling current relation of the M control units, determining that the M control units have no circuit breaking fault.
The method and the device have the advantages that as the probability of the open circuit faults of 2 or more than 2 control units in the multiphase staggered parallel DCDC converter is low, the controller detects the open circuit faults of the DCDC converter according to a preset period, the open circuit faults can be detected in time and the control units with the open circuit faults can be positioned when the open circuit faults of 1 control unit occur, so that the strategy complexity of the controller for detecting the open circuit faults is reduced, the detection cost is reduced, and the embodiment of the application does not detect the condition that the open circuit faults of 2 or 2 control units occur simultaneously.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the application.

Claims (8)

1. The open circuit detection method of the multiphase staggered parallel type DCDC converter is characterized in that the multiphase staggered parallel type DCDC converter comprises at least M control units, the phases of the control units are the same, and M is an integer greater than or equal to 2;
The method comprises the following steps:
acquiring sampling currents of all the control units through a current sampling circuit;
determining a sampling current relation according to the sampling current of each control unit:
When m=2, calculating a sampling current ratio of the first control unit and the second control unit according to the sampling current;
When M is more than 2, acquiring the sampling current difference condition of the control units according to the sampling current of each control unit;
and determining the open-circuit fault condition of the control unit according to the sampling current relation.
2. The method according to claim 1, wherein when M = 2, said determining an open circuit fault condition of the control unit from the sampled current relationship comprises:
acquiring load current of the multiphase staggered parallel DCDC converter;
Detecting whether the load current is in a first current range or a second current range;
And when the load current is detected to be in the first current range or the second current range, determining the open-circuit fault condition of the first control unit and the second control unit according to the sampling current ratio of the first control unit and the second control unit.
3. The method of claim 2, wherein the determining the open circuit fault condition of the first control unit and the second control unit from the sampled current ratio of the first control unit and the second control unit when the load current is detected to be within the first current range or the second current range comprises:
Determining that an open circuit fault exists in the first control unit if I 1/I2 = (n-2)/n or 1 < I 1/I2 < n/(n-2) when the load current is within the first current range; if (n-2)/n < I 1/I2 < 1 or I 1/I2 =n/(n-2), determining that the second control unit has an open circuit fault;
When the load current is in the second current range, if I 1/I2 is less than 1, determining that the first control unit has an open-circuit fault; if I 1/I2 is more than 1, determining that the second control unit has an open-circuit fault;
When the load current is in the first current range or the second current range, if I 1/I2 = 1, determining that the first control unit and the second control unit have no open-circuit fault;
wherein I 1 represents the sampling current of the first control unit, I 2 represents the sampling current of the second control unit, and n represents the number of phases of the DCDC converter.
4. The method according to claim 1, wherein said determining an open circuit fault condition of said control unit from said sampled current relationship when M > 2 comprises:
when the sampling current relation of the M control units is that the sampling current of the ith control unit is different from the sampling current of the remaining M-1 control units and the sampling currents of the remaining M-1 control units are the same, determining that the ith control unit has an open-circuit fault; i is an integer, and the value range of i is 1 to M;
And when the sampling current relation of the M control units is the same as the sampling current relation of the M control units, determining that the M control units have no circuit breaking fault.
5. The open circuit detection system of the multiphase staggered parallel type DCDC converter is characterized by comprising the multiphase staggered parallel type DCDC converter, a current sampling circuit and a controller;
The multiphase staggered parallel DCDC converter comprises at least M control units, wherein the phases of the control units are the same, and M is an integer greater than or equal to 2;
each control unit is connected with one current sampling circuit, and the current sampling circuits are connected with the controller;
the current sampling circuit is used for acquiring the sampling current of the control unit;
The controller is used for acquiring sampling current of each control unit through the current sampling circuit; determining a sampling current relation according to the sampling current of each control unit:
When m=2, calculating a sampling current ratio of the first control unit and the second control unit according to the sampling current;
when M is more than 2, detecting whether the sampling currents of the control units are the same according to the sampling currents of the control units;
and determining the open-circuit fault condition of the control unit according to the sampling current relation.
6. The open circuit detection system of a multiphase interleaved parallel DCDC converter according to claim 5 wherein the controller is configured to obtain a load current of the multiphase interleaved parallel DCDC converter when m=2;
Detecting whether the load current is in a first current range or a second current range;
And when the load current is detected to be in the first current range or the second current range, determining the open-circuit fault condition of the first control unit and the second control unit according to the sampling current ratio of the first control unit and the second control unit.
7. The open circuit detection system of a multiphase interleaved parallel DCDC converter according to claim 6 wherein the controller is configured to determine that an open circuit fault exists with the first control unit when the load current is within the first current range, I 1/I2 = (n-2)/n or 1 < I 1/I2 < n/(n-2); when (n-2)/n < I 1/I2 < 1 or I 1/I2 =n/(n-2), determining that the second control unit has an open circuit fault;
When the load current is in the second current range, I 1/I2 is less than 1, determining that the first control unit has an open-circuit fault; when I 1/I2 is more than 1, determining that the second control unit has an open-circuit fault;
Determining that the first control unit and the second control unit have no open-circuit fault when the load current is within the first current range or the second current range, I 1/I2 =1;
wherein I 1 represents the sampling current of the first control unit, I 2 represents the sampling current of the second control unit, and n represents the number of phases of the DCDC converter.
8. The open circuit detection system of a multiphase interleaved parallel DCDC converter according to claim 5 wherein the controller is configured to determine that an open circuit fault exists in an ith control unit when M > 2, the sampling current relationship of the M control units is such that the sampling current of the ith control unit is different from the sampling current of the remaining M-1 control units and the sampling currents of the remaining M-1 control units are the same; i is an integer, and the value range of i is 1 to M;
And when the sampling current relation of the M control units is the same as the sampling current relation of the M control units, determining that the M control units have no circuit breaking fault.
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CN104049171A (en) * 2014-06-12 2014-09-17 中南大学 Open-circuit fault diagnosis method and system for staggered flyback type micro inverter
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CN109334937B (en) * 2018-11-13 2023-06-02 中国船舶重工集团公司第七0四研究所 Ship battery electric propulsion system and control method thereof
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CN104049171A (en) * 2014-06-12 2014-09-17 中南大学 Open-circuit fault diagnosis method and system for staggered flyback type micro inverter
CN108768175A (en) * 2018-06-15 2018-11-06 大连海事大学 A kind of multiphase interleaving DC-DC converter device

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