CN115864814B

CN115864814B - Soft start circuit and power conversion equipment

Info

Publication number: CN115864814B
Application number: CN202310188220.0A
Authority: CN
Inventors: 邹纪元; 曹文斌; 戴富坤
Original assignee: Sungrow Power Supply Co Ltd
Current assignee: Sungrow Power Supply Co Ltd
Priority date: 2023-02-27
Filing date: 2023-02-27
Publication date: 2023-05-30
Anticipated expiration: 2043-02-27
Also published as: CN115864814A

Abstract

The application provides a soft start circuit and a power conversion device. In the soft start circuit, when the voltage difference between the input end and the output end of the soft start circuit is higher, the plurality of first switch modules are turned off, at the moment, the soft start circuit can inhibit surge current on a bus capacitor in a system where the soft start circuit is positioned through a plurality of charging branches connected in series and charge the bus capacitor, and when the voltage difference between the input end and the output end of the soft start circuit is lower, the plurality of first switch modules are turned on, at the moment, the charging current is smaller, so that the bus capacitor of the system where the soft start circuit is positioned is completely precharged, and therefore the soft start circuit achieves soft start of the system where the soft start circuit is positioned; in addition, as the switching device of the soft start circuit is at least two first switching modules connected in series, the voltage withstand level requirements on each switching module are reduced through the series voltage division of the switching modules, and therefore the soft start circuit provided by the application reduces the difficulty in selecting the type of the switching device.

Description

Soft start circuit and power conversion equipment

Technical Field

The present invention relates to the field of power electronics, and in particular, to a soft start circuit and a power conversion device.

Background

In the power conversion equipment, a bus capacitor with a larger capacitance value is usually connected between the direct current buses so as to ensure the stability of bus voltage; because of the AC-DC characteristic of the capacitor, a larger surge current is generated on the bus capacitor at the moment of the input and power connection of the power conversion equipment, thereby causing the power conversion equipment to stop or damaging the power conversion equipment.

At present, a soft start circuit is additionally arranged to inhibit surge current on a bus capacitor; normally, a relay, a contactor or a thyristor is used as a switching device of the soft start circuit; however, as the input voltage of the power conversion device increases, the difficulty in selecting the type of the switching device of the soft start circuit increases.

Therefore, how to reduce the difficulty in selecting the switching device of the soft start circuit is a technical problem to be solved.

Disclosure of Invention

In view of the above, the present invention provides a soft start circuit and a power conversion device to reduce the difficulty in selecting the type of the switching device of the soft start circuit.

In order to achieve the above object, the embodiment of the present invention provides the following technical solutions:

in one aspect, the present application provides a soft start circuit comprising: the charging system comprises at least two first switch modules, at least two switch module control circuits and at least two charging branches; wherein:

The first switch modules are connected in series, the input end of the formed serial branch is used as the input end of the soft start circuit, and the output end of the formed serial branch is used as the output end of the soft start circuit;

each first switch module is used for bypassing a charging branch corresponding to the first switch module when the first switch module is conducted by the first switch module;

each switch module control circuit is used for collecting the voltages at two ends of a detection resistor branch in the charging branch corresponding to the switch module control circuit, and conducting the first switch module corresponding to the switch module control circuit when the voltages at two ends of the detection resistor branch corresponding to the switch module control circuit are smaller than a first preset threshold value.

Optionally, the method further comprises: a feedback circuit; wherein:

the feedback circuit is used for detecting the on-off state of a serial branch formed by serial connection of all the first switch modules, and transmitting signals of complete conduction of all the first switch modules to a controller in a system where the soft start circuit is located when the serial branch is in a conduction state.

Optionally, if the first switch modules are not turned on at the same time, the feedback circuit is configured to detect an on-off state of the last turned-on first switch module, and when the last turned-on first switch module is in the on state, transmit signals of all the first switch modules that are turned on completely to the controller.

Optionally, the feedback circuit includes: the first voltage-stabilizing diode branch, the first current-limiting resistor branch and the optocoupler; wherein:

the anode of the first voltage stabilizing diode branch is connected with the input end of the primary side of the optical coupler, and the output end of the primary side of the optical coupler is connected with one end of the first current limiting resistor branch;

the cathode of the first voltage stabilizing diode branch and the other end of the first current limiting resistor branch are respectively used as two poles of the input end of the feedback circuit and are respectively connected with the corresponding ports of the corresponding first switch modules;

the input end of the secondary side of the optocoupler is connected with a first auxiliary power supply, and the output end of the secondary side of the optocoupler is used as the output end of the feedback circuit to be connected with the controller.

Optionally, the switch module control circuit includes: a bypass circuit and a voltage generation circuit; wherein:

the bypass circuit is used for collecting voltages at two ends of the detection resistor branch corresponding to the bypass circuit, and bypassing the voltage generation circuit when the voltages at two ends of the detection resistor branch are not smaller than the corresponding first preset threshold value, and not bypassing the voltage generation circuit when the voltages at two ends of the detection resistor branch are smaller than the corresponding first preset threshold value;

The voltage generating circuit is used for generating a voltage for enabling the corresponding first switch module to conduct and applying the voltage to the corresponding first switch module.

Optionally, the bypass circuit includes: a second switch module; wherein:

the corresponding ports of the second switch module are respectively connected with the two ends of the detection resistor branch;

the input end of the second switch module and the output end of the second switch module are respectively used as two poles of the output end of the bypass circuit and are respectively connected with two poles of the input end of the voltage generation circuit;

the second switch module is used for collecting voltages at two ends of the corresponding detection resistor branch, and is turned off when the voltages at two ends of the detection resistor branch are smaller than the first preset threshold.

Optionally, the bypass circuit further includes: a first switching resistor branch; wherein:

the control end of the second switch module is connected with the corresponding end of the detection resistor branch through the first conversion resistor branch.

Optionally, in the switch module control circuit, the resistance value of the first switching resistor branch determines the conduction sequence of the corresponding first switch module.

Optionally, the voltage generating circuit includes: the second auxiliary power supply, the second current-limiting resistor branch, the charging capacitor branch and the anti-reverse diode branch; wherein:

The cathode of the anti-reflection diode branch is connected with the first end of the charging capacitor branch;

the anode of the anti-reflection diode branch is connected with the second auxiliary power supply through the second current-limiting resistor branch, or the second end of the charging capacitor branch is connected with the second auxiliary power supply through the second current-limiting resistor branch;

the anode of the anti-reflection diode branch and the second end of the charging capacitor branch are respectively used as two poles of the input end of the voltage generating circuit;

and two ends of the charging capacitor branch are respectively used as two poles of the output end of the voltage generating circuit and are respectively connected with corresponding ports of the corresponding first switch modules.

Optionally, in the switch module control circuit, a product of a resistance value of the second current-limiting resistor branch and a capacitance value of the charging capacitor branch determines a conduction sequence of the corresponding first switch module.

Optionally, the voltage generating circuit further includes: a bleeder circuit; wherein:

the bleeder circuit is connected with the charging capacitor branch in parallel, and the control end of the bleeder circuit is connected with the second auxiliary power supply through the second current-limiting resistor branch;

The port voltage of the second auxiliary power supply is smaller than a third preset threshold value when the input of the soft start circuit is smaller than the second preset threshold value;

and the bleeder circuit is used for bleeder the charging capacitor branch circuit when the port voltage of the second auxiliary power supply is smaller than the third preset threshold value.

Optionally, the bleeder circuit includes: a third switch module; wherein:

the input end of the third switch module is connected with the first end of the charging capacitor branch, the output end of the third switch module is connected with the second end of the charging capacitor branch, and the control end of the third switch module is connected with the second auxiliary power supply through the second current-limiting resistor branch;

the third switch module is used for being conducted when the port voltage of the second auxiliary power supply is smaller than the third preset threshold value.

Optionally, the bleeder circuit further includes: a third current limiting resistor branch; wherein:

one end of the third current-limiting resistor branch is connected with the output end of the third switch module, and the other end of the third current-limiting resistor branch is connected with the second end of the charging capacitor branch.

Optionally, the voltage generating circuit further includes at least one of: the second voltage stabilizing diode branch circuit, the third voltage stabilizing diode branch circuit, the bleeder resistor branch circuit and the filter capacitor branch circuit; wherein:

The cathode of the second voltage stabilizing diode branch is connected with the first end of the charging capacitor branch, and the anode of the second voltage stabilizing diode branch is used as one pole of the output end of the voltage generating circuit;

the third zener diode branch, the bleeder resistor branch and the filter capacitor branch are all connected with the charging capacitor branch in parallel.

Optionally, if the bypass circuit in the switch module control circuit includes a first switching resistor branch, the charging branch includes: at least one first charging resistor branch; wherein:

all the first charging resistor branches are connected in series, and two ends of the formed series branch are respectively used as two ends of the charging branch;

one of the charging resistor branches is used as the detection resistor branch.

Optionally, if the bypass circuit does not include the first switching resistor branch, the charging branch further includes: a second charging resistor branch; wherein:

one end of the second charging resistor branch is used as one end of the charging branch;

one end of a serial branch formed by all the first charging resistor branches is connected with the other end of the second charging resistor branch, and the other end of the serial branch formed by all the first charging resistor branches is used as the other end of the charging branch.

Optionally, the charging branch further includes: a first overvoltage protection circuit; wherein:

the first overvoltage protection circuit is connected in parallel with two ends of the detection resistor branch;

or alternatively, the process may be performed,

the first overvoltage protection circuit is connected in parallel to both ends of a series branch formed by at least two charging resistor branches, and the detection resistor branch is present in this series branch.

Optionally, when the first overvoltage protection circuit is connected in parallel across a series branch formed by at least two charging resistor branches, and the detection resistor branch is present in this series branch:

the ratio of the resistance of the detection resistor branch to the sum of the resistances of the other charging resistor branches in the series branch determines the conduction sequence of the first switch module.

the ratio of the sum of the resistances of the series branch and the sum of the resistances of the other charging resistor branches outside the series branch determines the turn-on sequence of the first switch module.

Optionally, the method further comprises: at least two second overvoltage protection circuits; wherein:

each of the second overvoltage protection circuits is connected in parallel with a corresponding one of the first switch modules.

Another aspect of the present application provides a power conversion apparatus, comprising: a front-stage power converter, a back-stage power converter, a bus capacitor, a controller and a soft start circuit as described in any one of the above aspects of the application; wherein:

the output side positive electrode of the front-stage power converter is connected with the input end of the soft start circuit, and the output end of the soft start circuit is connected with the input side positive electrode of the rear-stage converter through a positive direct current bus;

the output side cathode of the front-stage power converter is connected with the output side cathode of the rear-stage converter through a cathode direct current bus;

the bus capacitor is connected in parallel between the positive DC bus and the negative DC bus;

the rear stage power converter is controlled by the controller.

Optionally, the front-stage power converter is a rectifier, and the back-stage power converter is a DCDC converter or an inverter;

or alternatively, the process may be performed,

the front-stage power converter is a DCDC converter, and the rear-stage power converter is an inverter.

Optionally, the pre-stage power converter is an uncontrollable converter or a controllable converter;

if the pre-stage power converter is a controllable converter, the pre-stage power converter is controlled by the controller.

As can be seen from the above technical solution, the present invention provides a soft start circuit, which specifically includes: the charging system comprises at least two first switch modules, at least two switch module control circuits and at least two charging branches. In the soft start circuit, as each switch module control circuit conducts the first switch module corresponding to the soft start circuit when the voltage at two ends of the detection resistor branch in the charging branch corresponding to the soft start circuit is smaller than a preset threshold, when the voltage difference between the input end and the output end of the soft start circuit is higher, the first switch modules are turned off, at the moment, the soft start circuit can restrain surge current on a bus capacitor in a system where the soft start circuit is located through the charging branches connected in series and charge the bus capacitor, and when the voltage difference between the input end and the output end of the soft start circuit is lower, namely, when the bus capacitor of the system where the soft start circuit is located basically completes pre-charging, the first switch modules are conducted, at the moment, the charging current is smaller, and the bus capacitor of the system where the soft start circuit is located is indicated to complete pre-charging, so that the soft start circuit achieves soft start of the system where the soft start circuit is located; in addition, as the switching device of the soft start circuit is at least two first switching modules connected in series, the voltage withstand level requirements on each switching module are reduced through the series voltage division of the switching modules, and the switching device is convenient to select. And when the input voltage of the system where the soft start circuit is located rises, the actual requirement can be met only by increasing the number of the first switch modules connected in series, so that the soft start circuit provided by the application not only reduces the difficulty in selecting the type of the self switch device, but also is convenient to apply to occasions with higher voltage levels.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.

Fig. 1 to 16 are schematic structural diagrams of sixteen implementations of the soft start circuit provided in the embodiments of the present application;

fig. 17 and fig. 18 are schematic structural diagrams of two implementations of the power conversion apparatus provided in the embodiments of the present application, respectively;

fig. 19 is a schematic diagram showing charging of the bus capacitor 03 when the maximum input voltage of the rectifier is 456 VAC.

Detailed Description

The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.

In this application, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

In order to reduce the difficulty in selecting the type of the switching device of the soft start circuit, the embodiment of the application provides a soft start circuit, the specific structure of which can be seen in fig. 1, which specifically includes: at least two first switch modules 10, at least two switch module control circuits 20, and at least two charging branches 30.

In practical application, the first switch module 10 may be composed of one switch tube, or may be composed of at least two switch tubes connected in parallel in the same direction, which is not specifically limited herein, and may be within the protection scope of the present application according to the specific situation.

The switch tube is connected in series in the same direction specifically comprises: the output end of one switching tube is connected with the input end of the other switching tube; the switch tube is connected in parallel in the same direction: the input end of one switching tube is connected with the input end of the other switching tube, and the output end of the one switching tube is connected with the output end of the other switching tube.

Specifically, when the first switch module 10 is composed of at least two switch tubes connected in parallel in the same direction, the input end of the formed serial-parallel connection branch is used as the input end of the first switch module 10, the output end of the formed serial-parallel connection branch is used as the output end of the first switch module 10, the control ends of all the switch tubes are connected, and the connection point is used as the control end of the first switch module 10.

Optionally, the switching tube in the first switching module 10 may be an NMOS tube, may be a PMOS tube, or may be an IGBT, which is not specifically limited herein, and may be within the protection scope of the present application as the case may be.

It should be noted that, in practical application, the switching tubes in each first switching module 10 preferably select the same type of switching tube to ensure the normal operation of the soft start circuit.

The connection relationship between the devices is specifically as follows:

the first switch modules 10 are connected in series, the input end of the formed series branch is used as the input end of the soft start circuit, and the output end of the formed series branch is used as the output end of the soft start circuit.

It should be noted that, in practical application, the sum of the maximum voltages that can be borne between the input terminal and the output terminal of each first switch module 10 is slightly greater than the maximum voltage difference between the input terminal and the output terminal of the soft start circuit, that is, the input of the soft start circuit should be properly derated.

Each charging branch 30 is connected in parallel between the input and output of a respective first switching module 10; each first switch module 10 is configured to bypass a charging branch 30 corresponding to itself when itself is turned on.

The two poles of the input end of each switch module control circuit 20 are respectively connected with two ends of a detection resistor branch in the corresponding charging branch 30, and are used for collecting voltages at two ends of the corresponding detection resistor branch.

The two poles of the output end of each switch module control circuit 20 are respectively connected with the corresponding ports of the corresponding first switch modules 10, and are used for conducting the corresponding first switch modules 10 when the voltages at the two ends of the corresponding detection resistor branches are smaller than a first preset threshold value, and for switching off the first switch modules 10 corresponding to the switch modules when the voltages at the two ends of the corresponding detection resistor branches are larger than or equal to the first preset threshold value.

The first preset threshold is set according to the actual parameter of the first switch module 10, which is not specifically limited herein, and is within the scope of protection of the present application.

In a specific example, the switching transistors in the first switch module 10 are NMOS transistors or IGBTs, and the specific connection relationship between the switch module control circuit 20 and the first switch module 10 is shown in fig. 1, specifically: the positive electrode of the output end of the switch module control circuit 20 is connected with the control end of the corresponding first switch module 10, and the negative electrode of the output end of the switch module control circuit 20 is connected with the output end of the corresponding first switch module 10.

In another specific example, the switch tubes in the first switch module 10 are PMOS tubes, and the specific connection relationship between the switch module control circuit 20 and the first switch module 10 is specifically: the positive electrode of the output end of the switch module control circuit 20 is connected with the input end of the corresponding first switch module 10, and the negative electrode of the output end of the switch module control circuit 20 is connected with the control end of the corresponding first switch module 10.

Optionally, each first switch module 10 may or may not be turned on simultaneously, and when each first switch module 10 is not turned on simultaneously, each first switch module 10 may also be turned on partially sequentially, turned on partially simultaneously, or even turned on fully sequentially, which is not limited herein, and may be within the scope of protection of the present application according to specific conditions; in the following, a detailed description will be given of how to make or break each first switch module 10 conduct simultaneously or not simultaneously in combination with different structures of the soft start circuit, which is not repeated here.

It should be noted that, all the first switch modules 10 are turned on sequentially, so that the equivalent resistance of the soft start circuit can be gradually reduced from large to small, and compared with the case that all the first switch modules 10 are turned on simultaneously, the case that all the first switch modules 10 are turned on sequentially can shorten the charging time of the bus capacitor in the system where the soft start circuit is located and reduce the soft start time, so that all the first switch modules 10 are preferably turned on sequentially.

Therefore, when the voltage difference between the input end and the output end of the soft start circuit is high, the plurality of first switch modules 10 are turned off, and at this time, the soft start circuit can inhibit the surge current on the bus capacitor in the system where the soft start circuit is located through the plurality of charging branches 30 connected in series, and charge the bus capacitor; when the voltage difference between the input end and the output end of the soft start circuit is low, the plurality of first switch modules 10 are conducted, and the charging current is low at the moment, so that the bus capacitor of the system where the soft start circuit is located is indicated to finish pre-charging; therefore, the soft start circuit realizes the soft start of the system where the soft start circuit is located.

In addition, since the switching device of the soft start circuit is at least two first switching modules 10 connected in series, the voltage withstand level requirements of each switching module are reduced by the series voltage division of the switching modules, thereby facilitating the switching device type selection.

And when the input voltage of the system where the soft start circuit is located rises, the actual requirement can be met only by increasing the number of the first switch modules 10 connected in series, so that the soft start circuit provided by the application not only reduces the difficulty in selecting the type of the self switch device, but also is convenient to apply to occasions with higher voltage levels.

For example, when the input end of the soft start circuit is connected with the positive pole of the direct current side of the rectifier, if the rated input voltage of the rectifier is 380VAC and the maximum input voltage of the rectifier is 1.2 times of the rated input voltage, a 1200V relay or a thyristor is required to be selected in the soft start circuit in the prior art, and the soft start circuit provided by the application only needs to include two first switch modules 10, each first switch module 10 selects a 600V switch tube, namely only needs to select two 600V switch tubes to be connected in series; in addition, if the rated input voltage of the rectifier is 690VAC and the maximum input voltage thereof is 1.2 times of the rated input voltage, a 1700V relay or a thyristor is required to be selected for the soft start circuit in the prior art, and the soft start circuit provided by the application only needs to include two first switch modules 10, and each first switch module 10 selects a 900V switch tube, namely only needs to select two 900V switch tubes to be connected in series.

It is worth to say that the input of the system where the soft start circuit provided by the application is located can be alternating current input or direct current input, so that the application scene of the soft start circuit is widened; in addition, the soft start circuit is realized through a hardware circuit, namely, control errors are not easy to occur, so that the soft start circuit improves the reliability of the soft start circuit; in addition, under the condition that the switching tube can not be switched on by mistake, in theory, the switch life of the switching tube is far longer than that of a mechanical switch such as a relay, so the service life of the soft start circuit provided by the application is longer.

Another embodiment of the present application provides another implementation manner of the soft start circuit, and the specific structure of the implementation manner may be shown in fig. 2, and the implementation manner further includes, based on the foregoing implementation manner: a feedback circuit 40; the feedback circuit 40 is used for detecting the on-off state of a serial branch formed by connecting all the first switch modules 10 in series, and transmitting a signal of complete conduction of all the first switch modules 10 to a controller in a system where the soft start circuit is located when the serial branch is in a conduction state.

If each first switch module 10 is turned on simultaneously, the feedback circuit 40 is configured to detect the on-off state of one of the first switch modules 10, and when the first switch module 10 is in the on state, transmit the signal that all the first switch modules 10 are completely turned on to the controller in the system where the soft start circuit is located.

If the first switch modules 10 are not turned on at the same time, the feedback circuit 40 is configured to detect the on-off state of the last turned-on first switch module 10, and transmit the signal of complete conduction of all the first switch modules 10 to the controller when the last turned-on first switch module 10 is in the on state.

The present embodiment further provides a specific implementation of the feedback circuit 40, whose specific structure is shown in fig. 2, including: a first zener diode branch 41 (shown in fig. 2 as a zener diode Z1 only), a first current limiting resistor branch 42 (shown in fig. 2 as a resistor Rx1 only), and an optocoupler 43.

In practical applications, the first zener diode branch 41 may be formed by one zener diode, or may be formed by at least two zener diodes connected in parallel and in the same direction, which is not specifically limited herein, and may be within the scope of protection of the present application as the case may be.

In practical application, each current limiting resistor branch may be composed of one resistor, or may be composed of at least two resistors connected in series-parallel, which are not specifically limited herein, and may be within the protection scope of the present application as the case may be.

The connection relationship between the devices is specifically as follows:

The anode of the first zener diode branch 41 is connected with the input end of the primary side of the optocoupler 43, and the output end of the primary side of the optocoupler 43 is connected with one end of the first current-limiting resistor branch 42; the cathode of the first zener diode branch 41 and the other end of the first current-limiting resistor branch 42 are respectively used as two poles of the input end of the feedback circuit 40, and are respectively connected with the corresponding ports of the corresponding first switch module 10.

The input of the secondary side of the optocoupler 43 is connected to a first auxiliary power supply (only V1 in fig. 2 represents the port voltage of the first auxiliary power supply), and the output of the secondary side of the optocoupler 43 is connected as an output of the feedback circuit 40 to a controller in the system in which the soft start circuit is located (this is not shown in fig. 2 for simplicity of illustration).

Optionally, the first auxiliary power supply may take power from an independent power supply, or may take power from an input side of a system where the soft start circuit is located, which is not specifically limited herein, and may be within the protection scope of the present application as the case may be.

In a specific example, the switching transistors in the first switch module 10 are NMOS transistors or IGBTs, and the connection relationship between the two poles of the input end of the feedback circuit 40 and the corresponding first switch module 10 is shown in fig. 2, specifically: the cathode of the first zener diode branch 41 is connected to the control terminal of the corresponding first switch module 10, and the other end of the first current limiting resistor branch 42 is connected to the output terminal of the corresponding first switch module 10.

In a specific example, the switching transistors in the first switching module 10 are PMOS transistors, and at this time, the connection relationship between the two poles of the input end of the feedback circuit 40 and the corresponding first switching module 10 is specifically: the cathode of the first zener diode branch 41 is connected to the input terminal of the corresponding first switch module 10, and the other end of the first current limiting resistor branch 42 is connected to the control terminal of the corresponding first switch module 10.

In practical application, when the first switch module 10 is in the on state, a voltage difference exists between the control end and the output end of the first switch module 10 or between the input end and the control end of the first switch module 10, so that the first zener diode branch 41 and the first current limiting resistor branch 42 need to be reasonably set to ensure the normal operation of the optocoupler 43.

The present embodiment also provides another specific implementation of the feedback circuit 40, whose specific structure can be seen in fig. 3 (fig. 3 is only shown on the basis of fig. 2), and this implementation further includes, on the basis of the above implementation: bypass resistor branch 44 (shown in fig. 3 as resistor Rp only); wherein a shunt resistor branch 44 is connected in parallel between the two ends of the primary side of the optocoupler 43.

In practical applications, the shunt resistor 44 may be composed of one resistor, or may be composed of at least two resistors connected in series and parallel, which are not limited herein, and may be within the scope of the present application as the case may be.

The above embodiments of the feedback circuit 40 are only two embodiments, and in practical applications, including but not limited to the above embodiments, are not limited herein, and may be within the scope of the present application as the case may be.

Another embodiment of the present application provides an implementation manner of the switch module control circuit 20, the specific structure of which can be seen in fig. 4 (fig. 4 only shows, on the basis of fig. 3, a specific structure of one switch tube control circuit 20 as an example, and omits the rest of switch tube control circuits 10 and feedback circuits 40 for simplifying the drawing), which specifically includes: a bypass circuit 21 and a voltage generation circuit 22.

The bypass circuit 21 is configured to collect voltages at two ends of the detection resistor branch corresponding to the bypass circuit 21, bypass the voltage generating circuit 22 when the voltages at two ends of the detection resistor branch are not less than the corresponding first preset threshold, and not bypass the voltage generating circuit 22 when the voltages at two ends of the detection resistor branch are less than the corresponding first preset threshold.

The voltage generation circuit 22 is configured to generate a voltage for turning on the corresponding first switch module 10 and apply the voltage to the corresponding first switch module 10.

Another embodiment of the present application further provides a specific implementation of the bypass circuit 21, the specific structure of this implementation may be referred to fig. 5 (fig. 5 is only shown on the basis of fig. 4), specifically including: the second switching module 211 (shown in fig. 5 as a switching tube Q2 only).

In practical applications, the second switch module 211 may be composed of one switch tube, or may be composed of at least two switch tubes connected in parallel in the same direction, which is not specifically limited herein, and may be within the protection scope of the present application according to the specific situation.

It should be noted that, when the second switch module 211 is formed by at least two switch tubes connected in parallel in the same direction, the connection principle of each switch tube in the second switch module 211 is the same as that of each switch tube in the first switch module 10, and the description thereof is omitted herein.

Optionally, the switching tube in the second switching module 211 may be a MOS tube or an IGBT, which is not specifically limited herein, and may be within the protection scope of the present application as the case may be.

The connection relation of the device is as follows:

The corresponding ports of the second switch module 211 are respectively connected with the two ends of the detection resistor branch; the input end of the second switch module 211 and the output end of the second switch module 211 are respectively used as two poles of the output end of the bypass circuit 21 and are respectively connected with two poles of the input end of the voltage generating circuit 22; the second switch module 211 is used for collecting voltages at two ends of the corresponding detection resistor branch.

In a specific example, the switching transistors in the second switching module 211 are NMOS transistors or IGBTs, and the connection relationship between the second switching module 211 and the detection resistor branch is shown in fig. 4, which specifically is: the control end of the second switch module 211 is connected with the high voltage end of the detection resistor branch, and the output end of the second switch module 211 is connected with the low voltage end of the detection resistor branch.

In a specific example, the switching transistors in the second switching module 211 are PMOS transistors, and at this time, the connection relationship between the second switching module 211 and the detection resistor branch is specifically: the input end of the second switch module 211 is connected with the high voltage end of the detection resistor branch, and the control end of the second switch module 211 is connected with the low voltage end of the detection resistor branch.

In operation, when the voltage across the detection resistor branch is smaller than the first preset threshold, the second switch module 211 is turned off, and the second switch module 211 does not short-circuit the two poles of the input end of the voltage generating circuit 22, so the bypass circuit 21 does not bypass the voltage generating circuit 22, i.e. the voltage generating circuit 22 still has an output; when the voltage across the detection resistor branch is not less than the first preset threshold, the second switch module 211 is turned on, and at this time, the second switch module 211 shorts the two poles of the input terminal of the voltage generating circuit 22, so the bypass circuit 21 bypasses the voltage generating circuit 22, that is, the voltage generating circuit 22 does not output.

The present embodiment also provides another implementation of the bypass circuit 21, whose specific structure is shown in fig. 6 (fig. 6 is only shown in the implementation of fig. 5), where the switching tube in the second switching module 211 is a triode, and further includes, based on the above implementation: first switching resistor branch 212 (shown in fig. 6 as resistor Rz1 only); the control end of the second switch module 211 is connected to the corresponding end of the detection resistor branch through a first switching resistor branch 212, where the first switching resistor branch 212 is used to convert the voltage at two ends of the detection resistor branch into the current of the control end of the second switch module 211, that is, the base current of each triode in the second switch module 211.

It should be noted that, the connection relationship between the control end of the second switch module 211 and the detection resistor branch is already described in detail above, and will not be described herein again.

In practical applications, the first switching resistor branch 212 may be composed of one resistor, or may be composed of at least two resistors connected in series and parallel, which are not limited herein, and may be within the scope of the present application as the case may be.

Wherein, the resistance of the first switching resistor branch 212 determines the turn-on sequence of the corresponding first switch module 10; specifically, the larger the resistance value of the first switching resistor branch 212, the smaller the current at the control end of the second switch module 211, the easier the second switch module 211 is turned off, and the first switch module 10 is turned on first; conversely, the smaller the resistance of the first switching resistor branch 212, the greater the current at the control terminal of the second switch module 211, the easier the second switch module 211 is turned on, and the later the first switch module 10 is turned on.

The above-mentioned two embodiments of the bypass circuit 21 are only two embodiments, and in practical applications, including but not limited to the above-mentioned embodiments, the present invention is not limited thereto, and the present invention is applicable to any case.

Another embodiment of the present application further provides a specific implementation of the voltage generating circuit 22, and the specific structure of this implementation may be referred to fig. 7 (fig. 7 is only shown on the basis of fig. 6), specifically including: the second auxiliary power supply (only V2 in fig. 7 represents the port voltage of the second auxiliary power supply), the second current limiting resistor branch 221 (only resistor Rx2 in fig. 7 is shown as an example), the charging capacitor branch 222 (only capacitor Cc in fig. 7 is shown as an example), and the anti-reflection diode branch 223 (only anti-reflection diode Zf in fig. 7 is shown as an example).

In practical applications, the charging capacitor branch 222 may be composed of one capacitor, or may be composed of at least two capacitors connected in series-parallel, which are not limited herein, and may be within the scope of the present application as the case may be.

In practical applications, the anti-reflection diode branch 223 may be formed by one anti-reflection diode, or may be formed by at least two anti-reflection diodes connected in parallel and in the same direction, which is not limited herein, and may be within the protection scope of the present application according to the specific situation.

Optionally, the second auxiliary power supply may take power from an independent power supply, or may take power from an input side of a system where the soft start circuit is located, which is not specifically limited herein, and is within the protection scope of the present application, and may be determined according to specific situations, and is within the protection scope of the present application.

The connection relationship between the devices is specifically as follows:

the cathode of the anti-reflection diode branch 223 is connected to the first end of the charging capacitor branch 222, and the anode of the anti-reflection diode branch 223 is connected to the second auxiliary power supply through the second current limiting resistor branch 221, as shown in fig. 7.

The anode of the anti-reflection diode branch 223 and the second terminal of the charging capacitor branch 222 are respectively used as two poles of the input terminal of the voltage generating circuit 22.

Both ends of the charging capacitor branch 222 are respectively used as two poles of the output end of the voltage generating circuit 22, and are respectively connected with corresponding ports of the corresponding first switch modules 10.

In a specific example, the switching transistors in the first switch module 10 are NMOS transistors or IGBTs, and the connection relationship between the charging capacitor branch 222 and the corresponding first switch module 10 is shown in fig. 7, specifically: the first end of the charging capacitor branch 222 is connected to the control end of the corresponding first switch module 10, and the second end of the charging capacitor branch 222 is connected to the output end of the corresponding first switch module 10.

In a specific example, the switching transistors in the first switch module 10 are PMOS transistors, and the connection relationship between the charging capacitor branch 222 and the corresponding first switch module 10 is specifically: the first end of the charging capacitor branch 222 is connected to the input of the corresponding first switch module 10, and the second end of the charging capacitor branch 222 is connected to the control end of the corresponding first switch module 10.

As can be seen from the embodiment of the bypass circuit 21, the anode of the anti-reflection diode branch 223 and the second end of the charging capacitor branch 222 are respectively connected to the detection resistor branch and the second auxiliary power supply, so that the voltage generating circuit 22 can form a loop by using the input of the soft start circuit and the second auxiliary power supply, and the charging of the charging capacitor branch 222 can be realized; then, when the voltage across the charging capacitor branch 222 is charged to be greater than the turn-on threshold of the first switch module 10, the corresponding first switch module 10 can be turned on.

Wherein, the product of the resistance value of the second current-limiting resistor branch 221 and the capacitance value of the charging capacitor branch 222 determines the conduction sequence of the corresponding first switch module 10; since the product of the resistance of the second current-limiting resistor branch 221 and the capacitance of the charging capacitor branch 222 is equal to the time constant, the smaller the product of the capacitance is, the faster the charging rate of the charging capacitor branch 222 is, and the first switch module 10 is turned on first; conversely, the larger the product of the capacitance, the slower the charging rate of the charging capacitor branch 222, and the later the corresponding first switch module 10 is turned on.

Another embodiment of the present application provides another implementation of the voltage generating circuit 22, whose specific structure can be seen in fig. 8 (fig. 8 is shown on the basis of fig. 7), further includes, on the basis of the above implementation: a bleeder circuit 224; the connection relation of the device is as follows:

the bleeder circuit 224 is connected in parallel with the charging capacitor branch 222, and the control end of the bleeder circuit 224 is connected with the second auxiliary power supply through the second current limiting resistor branch 221.

The port voltage of the second auxiliary power supply is smaller than a third preset threshold value when the input of the soft start circuit is smaller than the second preset threshold value.

The second preset threshold is set to prevent erroneous judgment in the process of judging whether the soft start circuit has input or not, and the setting is required according to actual conditions and is not particularly limited herein; specifically, when the input of the soft start circuit is smaller than the second preset threshold value, the soft start circuit is indicated to have no input approximately, namely, the input of the system where the soft start circuit is located is approximately disconnected, and otherwise, the soft start circuit is indicated to have the input.

In addition, the third preset threshold is set to prevent the second auxiliary power supply from judging whether the port voltage exists or not, and the setting is required according to the actual situation and is not particularly limited herein; specifically, when the port voltage of the second auxiliary power supply is less than the third preset threshold, it indicates that the second auxiliary power supply is approximately free of the port voltage, and otherwise indicates that the second auxiliary power supply is free of the port voltage.

The bleeder circuit 224 bleeder the charging capacitor leg 222 when the port voltage of the second auxiliary power supply is less than a third predetermined threshold.

It should be noted that, when the port voltage of the second auxiliary power supply is smaller than the third preset threshold, it indicates that the port voltage of the second auxiliary power supply does not exist, so that the loop formed by the voltage generating circuit 22 becomes approximately open circuit at this time, and thus the potential of the control end of the bleeder circuit 224 is equal to the port voltage of the second auxiliary power supply, that is, the bleeder circuit 224 may collect the port voltage of the second auxiliary power supply.

As can be seen from the above, when the input of the soft start circuit is smaller than the second preset threshold, it indicates that the input of the system where the soft start circuit is located is disconnected, so that the port voltage of the second auxiliary power supply is smaller than the third preset threshold when the input of the system where the soft start circuit is located is disconnected, and the bleeder circuit 224 performs bleeder on the charging capacitor branch 222 when the input of the system where the soft start circuit is located is disconnected.

The voltage at two ends of the charging capacitor branch 222 drops rapidly due to the leakage current of the charging capacitor branch 222 when the input of the system where the soft start circuit is located is disconnected, so that the first switch module 10 can be turned off rapidly, and the soft start circuit enters a shutdown state when the input of the system where the soft start circuit is located is disconnected.

In addition, when the input of the system where the soft start circuit is located is quickly reestablished, for example, under the condition of instant shutdown and restarting, the soft start circuit can be quickly restarted, and the error conduction of the first switch module 10 caused by the stored electricity of the charging capacitor branch 222 can not be caused, so that the anti-interference capability of the soft start circuit is enhanced.

The embodiment provides a specific implementation of the bleeder circuit 224, and the specific structure thereof may be seen in fig. 9, specifically including: third switch module 2241 (shown in fig. 9 as only switch Q3); the switch tubes in the third switch module 2241 are PMOS tubes.

In practical application, the third switch module 2241 may be formed by one switch tube, or may be formed by at least two switch tubes connected in parallel and in the same direction, which is not specifically limited herein, and may be within the protection scope of the present application according to the specific situation.

The connection relation of the device is as follows:

an input end of the third switch module 2241 is connected with a first end of the charging capacitor branch 222, an output end of the third switch module 2241 is connected with a second end of the charging capacitor branch 222, and a control end of the third switch module 2241 is connected with a second auxiliary power supply through the second current limiting resistor branch 221; the third switch module 2241 is configured to be turned on when the port voltage of the second auxiliary power supply is less than a third preset threshold.

Since the third switch module 2241 is connected in parallel with the charging capacitor branch 222, after the third switch module 2241 is turned on, the charging capacitor branch 222 and the third switch module 2241 may form a loop; in addition, in practical applications, the third switch module 2241 has an internal resistance, so the discharging of the charging capacitor branch 222 can be completed by using the internal resistance of the third switch module 2241.

The present embodiment also provides another specific implementation of the bleeder circuit 224, whose specific structure can be seen in fig. 10 (fig. 10 is only shown on the basis of fig. 9), and this implementation further includes, on the basis of the above implementation: third current limiting resistor branch 2242 (only resistor Rx3 is shown in fig. 10 as an example).

The connection relation of the device is as follows:

one end of the third current-limiting resistor branch 2242 is connected to the output end of the third switch module 2241, and the other end of the third current-limiting resistor branch 2242 is connected to the second end of the charging capacitor branch 222, so as to limit the current during the leakage current, so as to avoid the damage of the leakage current to the third switch module 2241.

The present embodiment also provides another implementation of the bleeder circuit 224, whose specific structure is shown in fig. 11 (fig. 11 is only shown on the basis of fig. 10), in this implementation, the switching tube in the third switching module 2241 is a PNP triode, and further includes, on the basis of the above implementation: second transition resistance branch 2243 (only resistance Rz2 is shown in fig. 11 as an example).

In practical applications, the second converting resistor branch 2243 may be composed of one resistor, or may be composed of at least two resistors connected in series and parallel, which are not limited herein, and may be within the protection scope of the present application as the case may be.

The connection relation of the device is as follows:

one end of the second converting resistor branch 2243 is connected with the control end of the third switch module 2241, and the other end of the second converting resistor branch 2243 is connected with the second auxiliary power supply through the second current limiting resistor branch 221; the second current limiting resistor branch 221 is configured to convert the voltage into a current at the control terminal of the third switch module 2241, i.e. a base current of each PNP transistor in the third switch module 2241.

The above embodiments are merely three embodiments of the bleeder circuit 224, and in practical applications, including but not limited to, the disclosure is not limited thereto, and the disclosure is applicable to the present application as the case may be.

Another embodiment of the present application further provides another specific implementation of the voltage generating circuit 22, the specific structure of which can be seen in fig. 12 (fig. 12 is only shown on the basis of fig. 11), and this implementation further includes at least one of the following on the basis of the above implementation: the second zener diode leg 225 (shown in fig. 12 as an example of only zener diode Z2), the third zener diode leg 226 (shown in fig. 12 as an example of only zener diode Z3), the bleeder resistor leg 227 (shown in fig. 12 as an example of only resistor Rxf), the filter capacitor leg 228 (shown in fig. 12 as an example of only capacitor CL), and the divider resistor leg 229 (shown in fig. 12 as an example of only resistor Re).

In practical application, each zener diode branch may be composed of one zener diode, or may be composed of at least two zener diodes connected in parallel in the same direction, which is not specifically limited herein, and may be within the protection scope of the present application as the case may be.

In practical applications, the bleeder resistor branch 227 may be composed of one resistor, or may be composed of at least two resistors connected in series and parallel, which are not specifically limited herein, and may be within the protection scope of the present application as the case may be.

In practical applications, the voltage dividing resistor branch 229 may be composed of one resistor, or may be composed of at least two resistors connected in series and parallel, which are not limited herein, and may be within the protection scope of the present application as the case may be.

In practical applications, the filter capacitor branch 228 may be composed of one capacitor, or may be composed of at least two capacitors connected in series-parallel, which are not limited herein, and may be within the scope of protection of the present application as the case may be.

The connection relationship between the devices is specifically as follows:

the cathode of the second zener diode leg 225 is connected to the first end of the charging capacitor leg 222, and the anode of the second zener diode leg 225 serves as a pole of the output terminal of the voltage generating circuit 22.

The third zener diode leg 226, the bleeder resistor leg 227, and the filter capacitor leg 228 are all connected in parallel with the charging capacitor leg 222.

One end of the voltage dividing resistor branch 229 is connected to the anode of the anti-reflection diode branch 223, and the other end of the voltage dividing resistor branch 229 is connected to the second end of the charging capacitor branch 222.

The third zener diode branch 226 is configured to prevent the voltage generated by the voltage generating circuit 22 from damaging the first switch module 10; the bleeder resistor branch 227 is used to bleed off the float voltage when the corresponding first switch module 10 is turned off; the filter capacitor branch 228 is used for filtering the voltage generated by the voltage generating circuit 22 to prevent the erroneous conduction of the first switch module 10.

Another embodiment of the present application provides a specific implementation of the charging branch 30, which is applicable in the case where the bypass circuit 21 in the switching module control circuit 20 comprises the first switching resistor branch 212; the specific structure of this embodiment can be seen in fig. 13 (fig. 13 is only shown on the basis of fig. 12), specifically including: at least one first charging resistor branch 31 (only two first charging resistor branches 31 are shown in fig. 13 as an example, and two first charging resistor branches 31 are shown with a resistance Rc1 and a resistance Rc2, respectively).

In practical applications, the first charging resistor branch 31 may be composed of one resistor, or may be composed of at least two resistors connected in series and parallel, which are not specifically limited herein, and may be within the protection scope of the present application as the case may be.

The connection relationship between the devices is specifically as follows:

all the first charging resistor branches 31 are connected in series, and two ends of the formed series branch are respectively used as two ends of the charging branch 30; one of the charging resistor branches serves as a detection resistor branch.

The present embodiment also provides another specific implementation of the charging branch 30, which is applicable to the case where the bypass circuit 21 in the switch module control circuit 20 does not include the first switching resistor branch 212; the specific structure of this embodiment can be seen in fig. 14 (fig. 14 is only shown on the basis of fig. 13), and this embodiment further includes, on the basis of the above embodiment: the second charging resistor branch 32 (shown in fig. 14 by way of example only as resistor Rc 3).

In practical applications, the second charging resistor branch 32 may be composed of one resistor, or may be composed of at least two resistors connected in series and parallel, which are not limited herein, and may be within the scope of protection of the present application as the case may be.

The connection relation of the device is as follows:

one end of the second charging resistor branch 32 serves as one end of the charging branch 30; one end of the series branch formed by all the first charging resistor branches 31 is connected to the other end of the second charging resistor branch 32, and the other end of the series branch formed by all the first charging resistor branches 31 serves as the other end of the charging branch 30.

The present embodiment also provides a further specific implementation of the charging branch 30, the specific structure of which can be seen in fig. 15 (fig. 15 is only shown on the basis of fig. 14), this implementation further includes, on the basis of the above implementation: the first overvoltage protection circuit 33 (only the fourth zener diode leg 331 is shown in fig. 15 as an example for the first overvoltage protection circuit 33, and only the fourth zener diode leg Z4 is shown in fig. 15 as an example for the second overvoltage protection circuit).

Optionally, the first overvoltage protection circuit 33 may include a zener diode branch, and may also include a TVS (Transient Voltage Suppressor, transient diode) branch; the present invention is not limited to the specific embodiments, and may be applied to any case as appropriate.

In practical application, the zener diode branch may be composed of one zener diode, or may be composed of at least two zener diodes connected in parallel in the same direction, which is not specifically limited herein, and may be within the protection scope of the present application according to the specific situation.

In practical application, the TVS branch may be composed of one TVS, or may be composed of at least two TVS connected in series-parallel, which are not specifically limited herein, and may be within the scope of protection of the present application as the case may be.

The connection relation of the device is as follows:

the first overvoltage protection circuit 33 is connected in parallel to two ends of the detection resistor branch; alternatively, the first overvoltage protection circuit 33 is connected in parallel across a series branch formed by at least two charging resistor branches, and there is a detection resistor branch in this series branch; the first overvoltage protection circuit 33 is configured to clamp voltages at two ends of the serial branch formed by the first charging resistor branch 31, so that when a voltage difference between an input end and an output end of the soft start circuit is high, the second charging resistor branch 32 obtains a higher voltage, and thus the charging current is larger and the charging speed is faster.

For example, as shown in fig. 15, one of the two first charging resistor branches 31 is used as a detection resistor, and a first overvoltage protection resistor is connected in parallel to both ends of a series branch formed by the two first charging resistor branches 31.

In addition, when the first overvoltage protection circuit 33 is connected in parallel to two ends of a series branch formed by at least two charging resistor branches, and a detecting resistor branch exists in the series branch, the ratio of the resistance value of the detecting resistor branch to the sum of the resistances of other charging resistor branches in the series branch determines the conduction sequence of the first switch module 10.

Specifically, when the overvoltage threshold value of the first overvoltage protection circuit 33 is the same, the smaller the ratio of the resistance value of the detection resistor branch to the sum of the resistance values of the other charging resistor branches in the series branch, the harder the second switch module 211 is turned on, the first switch module 10 is turned on first, and the larger the ratio of the resistance value of the detection resistor branch to the sum of the resistance values of the other charging resistor branches in the series branch, the easier the second switch module 211 is turned on, and the first switch module 10 is turned on later.

Also, when the first overvoltage protection circuit 33 is connected in parallel to both ends of a series branch formed by at least two charging resistor branches, and a detecting resistor branch exists in the series branch, the ratio of the sum of the resistances of the series branch to the sum of the resistances of the other charging resistor branches except the series branch determines the turn-on sequence of the first switch module 10.

Specifically, when the overvoltage threshold value of the first overvoltage protection circuit 33 is the same, the smaller the ratio of the sum of the resistances of the series branch and the sum of the resistances of the other charging resistor branches except for the series branch is, the harder the second switch module 211 is turned on, and the first switch module 10 is turned on first; the larger the ratio of the sum of the resistances of the series branch to the sum of the resistances of the other charging resistor branches outside the series branch, the easier the second switch module 211 is turned on, and the later the first switch module 10 is turned on.

The above embodiments of the charging branch 30 are only three embodiments, and in practical applications, including but not limited to, the present invention is not limited thereto, and the present invention is not limited thereto.

Another embodiment of the present application provides another implementation of the soft start circuit, and the specific structure of the soft start circuit may be referred to fig. 16 (fig. 16 is only shown on the basis of fig. 3), and further includes, on the basis of the foregoing implementation: at least two second overvoltage protection circuits 50 (in fig. 16, the second overvoltage protection circuit 50 is shown only by way of example for the varistor branch 41 and in fig. 16, the varistor branch is shown only by way of example for the varistor MOV), each second overvoltage protection circuit 50 being connected in parallel with a respective first switching module 10 for preventing the first switching module 10 from being damaged when the input of the soft-start circuit is large.

Optionally, the second overvoltage protection circuit 50 may include a bidirectional TVS branch, and may also include a varistor branch; the present invention is not limited to the specific embodiments, and may be applied to any case as appropriate.

In practical application, the bidirectional TVS branch may be composed of one bidirectional TVS, or may be composed of at least two bidirectional TVS connected in parallel in the same direction, which is not specifically limited herein, and may be within the scope of protection of the present application as the case may be.

In practical application, the piezoresistor branch may be composed of one piezoresistor, or may be composed of at least two piezoresistors connected in series-parallel, which are not limited in detail herein, and may be within the protection scope of the present application as the case may be.

Another embodiment of the present application provides a power conversion apparatus, with specific structure as can be seen in fig. 17 (fig. 17 is only shown on the basis of fig. 16), specifically including: a front-stage power converter 01, a rear-stage power converter 02, a bus capacitor 03, a controller 04, and a soft start circuit 05 as provided in the above embodiments; the connection relation between the devices is specifically as follows:

the positive electrode of the output side of the front-stage power converter 01 is connected with the input end of the soft start circuit 05, and the output end of the soft start circuit 05 is connected with the positive electrode of the input side of the rear-stage converter through a positive direct current bus; the negative electrode of the output side of the front-stage power converter 01 is connected with the negative electrode of the output side of the rear-stage converter through a negative direct current bus; the bus capacitor 03 is connected in parallel between the positive DC bus and the negative DC bus; the rear stage power converter 02 is controlled by the controller 04.

Alternatively, the combination of the front-stage power converter 01 and the rear-stage power converter 02 may be: the front-stage power converter 01 is a rectifier, and the rear-stage power converter 02 is a DCDC converter or an inverter; the method can also be as follows: the front-stage power converter is a DCDC converter, and the rear-stage power converter 02 is an inverter; the present invention is not limited to the specific embodiments, and may be applied to any case as appropriate.

In practical applications, the front-stage power converter 01 may be an uncontrollable converter, such as a rectifier, or may be a controllable converter, such as a DCDC converter; if the front-stage power converter 01 is a controllable converter, the front-stage power converter 01 is controlled by the controller 04.

The embodiment also provides another implementation manner of the power conversion device, the specific structure of which is shown in fig. 18, and the implementation manner further includes: common mode inductance 06; the connection relationship between the devices is specifically as follows:

the output end of the soft start circuit 05 is connected with the positive DC bus through one inductor in the common mode inductor 06; the negative electrode of the output side of the front-stage power converter 01 is connected with a negative direct current bus through the other inductor in the common mode inductor 06.

It should be noted that, the working principle of the power conversion device is already mature, and the working principle of the power conversion device is not repeated in the two embodiments.

Taking the power conversion equipment shown in fig. 18 as an example, the soft start performance of the power conversion equipment is verified through a simulation experiment; the following describes the configuration of each device in the power conversion apparatus in detail, specifically as follows:

assuming that the front-stage power converter 01 in fig. 18 is a rectifier, the soft start circuit 05 adopts the configuration shown in fig. 15; as can be seen from the above, when the rated input voltage of the rectifier is 380VAC and the maximum input voltage thereof is 1.2 times of the rated input voltage, the soft start circuit only needs to include two first switch modules 10, and each first switch module 10 selects a 600V switch tube; when the rated input voltage of the rectifier is 690VAC and the maximum input voltage thereof is 1.2 times the rated input voltage, the soft start circuit only needs to include two first switch modules 10, and each first switch module 10 selects a 900V switch tube.

According to the connection relationship shown in fig. 18 and 15, a simulation model is built using Spice (Simulation program with integrated circuit emphasis, general purpose analog circuit simulator) or Multisim, and a simulation test is performed, and when the maximum input voltage of the rectifier is 456VAC, as can be seen from fig. 19, each first module is turned on in a time-sharing manner, so that the charging speed of the bus capacitor can be gradually increased.

The features described in the various embodiments of the present disclosure may be interchanged or combined with each other in the above description of the disclosed embodiments to enable those skilled in the art to make or use the present application. The above description is only of the preferred embodiment of the present invention, and is not intended to limit the present invention in any way. While the invention has been described with reference to preferred embodiments, it is not intended to be limiting. Any person skilled in the art can make many possible variations and modifications to the technical solution of the present invention or modifications to equivalent embodiments using the methods and technical contents disclosed above, without departing from the scope of the technical solution of the present invention. Therefore, any simple modification, equivalent variation and modification of the above embodiments according to the technical substance of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A soft start circuit, comprising: the charging system comprises at least two first switch modules, at least two switch module control circuits and at least two charging branches; wherein:

2. The soft start circuit of claim 1, further comprising: a feedback circuit; wherein:

3. The soft start circuit of claim 2, wherein if each of the first switch modules is not turned on at the same time, the feedback circuit is configured to detect an on-off state of the last turned-on first switch module, and transmit a signal that all of the first switch modules are completely turned on to the controller when the first switch modules are in the on state.

4. The soft start circuit of claim 2, wherein the feedback circuit comprises: the first voltage-stabilizing diode branch, the first current-limiting resistor branch and the optocoupler; wherein:

5. The soft start circuit of any one of claims 1 to 4, wherein the switch module control circuit comprises: a bypass circuit and a voltage generation circuit; wherein:

6. The soft start circuit of claim 5, wherein the bypass circuit comprises: a second switch module; wherein:

7. The soft start circuit of claim 6, wherein the bypass circuit further comprises: a first switching resistor branch; wherein:

8. The soft start circuit of claim 7, wherein in the switch module control circuit, the resistance of the first switching resistor branch determines the turn-on sequence of the corresponding first switch module.

9. The soft start circuit of claim 5, wherein the voltage generation circuit comprises: the second auxiliary power supply, the second current-limiting resistor branch, the charging capacitor branch and the anti-reverse diode branch; wherein:

10. The soft start circuit of claim 9, wherein in the switch module control circuit, a product of a resistance value of the second current limiting resistor branch and a capacitance value of the charging capacitor branch determines a turn-on sequence of the corresponding first switch module.

11. The soft start circuit of claim 9, wherein the voltage generation circuit further comprises: a bleeder circuit; wherein:

12. The soft start circuit of claim 11, wherein the bleeder circuit comprises: a third switch module; wherein:

13. The soft start circuit of claim 12, wherein the bleeder circuit further comprises: a third current limiting resistor branch; wherein:

14. The soft start circuit of claim 9, wherein the voltage generation circuit further comprises at least one of: the second voltage stabilizing diode branch circuit, the third voltage stabilizing diode branch circuit, the bleeder resistor branch circuit and the filter capacitor branch circuit; wherein:

15. The soft start circuit of any one of claims 1 to 4, wherein if the bypass circuit in the switching module control circuit includes a first switching resistor branch, the charging branch comprises: at least one first charging resistor branch; wherein:

one of the charging resistor branches is used as the detection resistor branch.

16. The soft start circuit of claim 15, wherein the charging branch if the bypass circuit does not include the first switching resistor branch, further comprising: a second charging resistor branch; wherein:

17. The soft start circuit of claim 16, wherein the charging branch further comprises: a first overvoltage protection circuit; wherein:

or alternatively, the process may be performed,

18. The soft start circuit of claim 17, wherein when the first overvoltage protection circuit is connected in parallel across a series leg formed by at least two charging resistor legs, and the sense resistor leg is present in this series leg:

19. The soft start circuit of claim 17, wherein when the first overvoltage protection circuit is connected in parallel across a series leg formed by at least two charging resistor legs, and the sense resistor leg is present in this series leg:

20. The soft start circuit of any one of claims 1 to 4, further comprising: at least two second overvoltage protection circuits; wherein:

21. A power conversion apparatus, comprising: a front-end power converter, a back-end power converter, a bus capacitor, a controller, and a soft start circuit as claimed in any one of claims 1 to 20; wherein:

the output side positive electrode of the front-stage power converter is connected with the input end of the soft start circuit, and the output end of the soft start circuit is connected with the input side positive electrode of the rear-stage power converter through a positive direct current bus;

the output side cathode of the front-stage power converter is connected with the output side cathode of the rear-stage power converter through a cathode direct current bus;

the rear stage power converter is controlled by the controller.

22. The power conversion apparatus according to claim 21, wherein the front-stage power converter is a rectifier and the rear-stage power converter is a DCDC converter or an inverter;

or alternatively, the process may be performed,

23. A power conversion device according to claim 21 or 22, wherein the pre-stage power converter is an uncontrollable converter or a controllable converter;