Parameter calculation method and device of active clamp circuit, controller, DC / DC converter, new energy automobile and storage medium

Abstract

The application discloses a parameter calculation method and device of an active clamp circuit, a controller, a DC / DC converter, a new energy automobile and a storage medium. The method comprises the following steps: acquiring a platform voltage of a clamp capacitor. The platform voltage is a voltage of the clamp capacitor when the clamp capacitor reaches a steady state in a BUCK mode. The first device parameter is calculated according to a relationship between the first device parameter and the platform voltage of the clamp capacitor. The technical scheme is designed to solve the problems of inaccuracy and low efficiency of the existing active clamp circuit design method, and a design method with accurate calculation and bidirectional DC / DC converter is provided.

Description

Technical Field

[0001] This invention relates to the field of active clamping circuits, and particularly to a method, apparatus, controller, DC / DC converter, new energy vehicle, and storage medium for calculating parameters of an active clamping circuit. Background Technology

[0002] Currently, in practical applications of automotive DC / DC converters, active clamping circuits are typically added to effectively suppress voltage spikes. However, with the increasing functional requirements of new energy vehicles, such as the need for automotive DC / DC converters to operate in multiple modes, the design of active clamping circuits also needs to be adapted to the different operating modes of the automotive DC / DC converter.

[0003] However, when selecting components for active clamping circuits, engineers typically rely on experience to estimate and perform multiple adjustments to choose suitable component parameters. Since the circuit performance varies under different operating modes, selecting component parameters solely based on experience often leads to inaccurate parameter selection. This makes the active clamping circuit unsuitable for different operating modes of the automotive DC / DC converter, resulting in damage to the automotive DC / DC converter. Furthermore, the numerous debugging steps also result in low efficiency in determining component parameters. Summary of the Invention

[0004] The main objective of this invention is to propose a parameter calculation method, device, controller, DC / DC converter, new energy vehicle, and storage medium for an active clamping circuit. It aims to solve the problems of inaccuracy and low efficiency in existing active clamping circuit design methods and propose a design method for accurate calculation and bidirectional DC / DC converter.

[0005] To achieve the above objectives, the present invention proposes a parameter calculation method for an active clamping circuit, which is applied to a DC / DC converter. The DC / DC converter includes an active clamping circuit and a DC / DC module, and has a BUCK mode. The method includes:

[0006] Obtain the plateau voltage of the clamping capacitor, wherein the plateau voltage is the voltage of the clamping capacitor when it reaches a steady state in the BUCK mode;

[0007] The first device parameter is calculated based on the relationship between the first device parameter of the clamping capacitor and the platform voltage.

[0008] Optionally, the step of obtaining the plateau voltage of the clamping capacitor includes:

[0009] Obtain the maximum high-voltage input voltage and the primary-secondary turns ratio of the transformer in the BUCK mode, wherein the maximum high-voltage input voltage is the bus voltage on the high-voltage side of the DC / DC module in the BUCK mode;

[0010] The platform voltage is obtained based on the maximum high-voltage input voltage and the primary-secondary turns ratio of the transformer.

[0011] Optionally, the method further includes:

[0012] The second device parameter is calculated based on the relationship between the second device parameter of the clamping transistor and the platform voltage.

[0013] Optionally, the DC / DC converter also has a BOOST mode, and the method further includes:

[0014] Obtain the maximum charging current and inductor current ripple coefficient in the BOOST mode, wherein the maximum charging current is the maximum current on the low-voltage side of the DC / DC module in the BOOST mode, and the inductor current ripple coefficient is the ripple coefficient of the freewheeling inductor on the low-voltage side.

[0015] The third device parameters are calculated based on the relationship between the third device parameters of the clamping transistor and the maximum charging current and the inductor current ripple coefficient.

[0016] Optionally, the method further includes:

[0017] The fourth device parameter is calculated based on the relationship between the fourth device parameter of the clamping capacitor and the first and third device parameters.

[0018] Optionally, the step of calculating the fourth device parameter based on the relationship between the fourth device parameter of the clamping capacitor and the first device parameter and the third device parameter includes:

[0019] The maximum value of the fourth device parameter is calculated based on the relationship between the fourth device parameter and the third device parameter;

[0020] The minimum value of the fourth device parameter is calculated based on the relationship between the fourth device parameter and the first device parameter.

[0021] The fourth device parameter is obtained based on the maximum value and the minimum value of the fourth device parameter.

[0022] Optionally, the step of calculating the maximum value of the fourth device parameter based on the relationship between the fourth device parameter and the third device parameter includes:

[0023] The charging current of the clamping capacitor in the BUCK mode is obtained, and the charging current of the clamping capacitor has a functional relationship with the fourth device parameter;

[0024] The maximum value of the fourth device parameter is calculated based on the relationship between the charging current of the clamping capacitor and the third device parameter.

[0025] Optionally, the step of obtaining the charging current of the clamping capacitor in the BUCK mode includes:

[0026] The maximum high voltage input voltage, the transformer primary and secondary turns ratio, the freewheeling inductor, the transformer leakage inductance, the primary winding resistance, and the initial pulse width are obtained under the BUCK mode. The maximum high voltage input voltage is the bus voltage on the high voltage side of the DC / DC module under the BUCK mode, and the initial pulse width is the initial drive pulse width of the high voltage side switching transistor.

[0027] Based on the fourth device parameters, the maximum high voltage input voltage, the transformer primary and secondary turns ratio, the freewheeling inductance, the transformer leakage inductance, the primary winding resistance value, and the initial pulse width, the charging current of the clamping capacitor in the BUCK mode is obtained.

[0028] Optionally, the step of calculating the minimum value of the fourth device parameter based on the relationship between the fourth device parameter and the first device parameter includes:

[0029] Obtain the freewheeling current and maximum low-voltage input voltage in the BOOST mode, and the inductance value of the freewheeling inductor, wherein the freewheeling current is the current of the freewheeling inductor in the BOOST mode, and the maximum low-voltage input voltage is the maximum input voltage on the low-voltage side in the BOOST mode;

[0030] The minimum value of the fourth device parameter is calculated based on the first device parameter, the maximum low-voltage input voltage, the freewheeling current, and the inductance value of the freewheeling inductor.

[0031] Optionally, the step of obtaining the freewheeling current in the BOOST mode includes:

[0032] In the BOOST mode, if the duty cycle of the control rectifier is less than the preset duty cycle, the maximum and minimum values ​​of the freewheeling current are obtained according to the maximum charging current and the inductor current ripple coefficient, respectively.

[0033] In the BOOST mode, if the duty cycle of the rectifier is greater than the preset duty cycle, the maximum value of the freewheeling current is obtained based on the maximum charging current and the inductor current ripple coefficient.

[0034] Optionally, the step of calculating the minimum value of the fourth device parameter based on the first device parameter, the maximum low-voltage input voltage, the freewheeling current, and the inductance value of the freewheeling inductor further includes:

[0035] If the duty cycle of the rectifier is controlled to be less than the preset duty cycle, the first minimum value of the fourth device parameter is calculated based on the first device parameter, the maximum low-voltage input voltage, the inductance value of the freewheeling inductor, and the maximum and minimum values ​​of the freewheeling current.

[0036] If the duty cycle of the rectifier is controlled to be greater than the preset duty cycle, the charging current frequency of the clamping capacitor and the duty cycle of the rectifier are obtained; the maximum charging time of the clamping capacitor is obtained based on the charging current frequency and the duty cycle of the rectifier; the second minimum value of the fourth device parameter is calculated based on the first device parameter, the maximum low-voltage input voltage, the maximum value of the freewheeling current, the maximum charging time, and the duty cycle of the rectifier.

[0037] The minimum value of the fourth device parameter is obtained based on the first minimum value of the fourth device parameter and / or the first minimum value of the fourth device parameter.

[0038] This invention also proposes a parameter calculation device for an active clamping circuit, applied in a DC / DC converter. The DC / DC converter includes an active clamping circuit and a DC / DC module, and the DC / DC converter has a BUCK mode. The device includes:

[0039] The data acquisition module is used to acquire the platform voltage of the clamping capacitor, wherein the platform voltage is the voltage of the clamping capacitor when it reaches a steady state in the BUCK mode;

[0040] The parameter calculation module is used to calculate the first device parameter based on the relationship between the first device parameter of the clamping capacitor and the platform voltage.

[0041] The present invention also proposes a controller for use in a DC / DC converter, comprising a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the above-described method for calculating the parameters of the active clamping circuit.

[0042] The present invention also proposes a DC / DC converter, including the controller, DC / DC module and active clamping circuit described above, wherein the output terminal of the controller is connected to the controlled terminal of the DC / DC module and the controlled terminal of the active clamping circuit respectively; the DC / DC module and the active clamping circuit are electrically connected.

[0043] Optionally, the DC / DC module includes a high-voltage full-bridge rectifier, an isolation transformer, a low-voltage synchronous rectifier circuit, and a filter circuit connected in sequence.

[0044] The active clamping circuit includes a first clamping transistor, a second clamping transistor, and a clamping capacitor. The first end of the first clamping transistor is connected to the first end of the secondary winding of the isolation transformer. The first end of the second clamping transistor is connected to the second end of the secondary winding of the isolation transformer. The second ends of the first clamping transistor and the second clamping transistor are respectively connected to the first end of the clamping capacitor. The controlled ends of the first clamping transistor and the second clamping transistor are respectively connected to the output end of the controller. The second end of the clamping capacitor is grounded.

[0045] The present invention also proposes a new energy vehicle, including the aforementioned DC / DC converter.

[0046] The present invention also proposes a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the above-described method.

[0047] This invention provides a parameter calculation method for selecting components for the active clamping circuit of a DC / DC converter. Based on the required input voltage, input current, output voltage, and output current values ​​of the DC / DC converter under different operating modes, and their relationship with component parameters, the method calculates the component parameters of the active clamping circuit. This allows for the selection of appropriate component parameters based on the known input and output requirements of the DC / DC module, reducing the reliance on engineer experience, eliminating the need for multiple trials, lowering the difficulty of component selection for active clamping circuits, and improving the accuracy and efficiency of active clamping circuit design. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0049] Figure 1 This is a flowchart of an embodiment of the parameter calculation method for the active clamping circuit of the present invention;

[0050] Figure 2 for Figure 1 The flowchart of the sub-steps included in step S100;

[0051] Figure 3This is a flowchart of another embodiment of the parameter calculation method for the active clamping circuit of the present invention;

[0052] Figure 4 This is a flowchart of another embodiment of the parameter calculation method for the active clamping circuit of the present invention;

[0053] Figure 5 This is a flowchart of another embodiment of the parameter calculation method for the active clamping circuit of the present invention;

[0054] Figure 6 for Figure 5 The flowchart of the sub-steps included in step S600;

[0055] Figure 7 for Figure 6 The flowchart of the sub-steps included in step S610;

[0056] Figure 8 for Figure 7 The flowchart of the sub-steps included in step S611;

[0057] Figure 9 for Figure 6 The flowchart of the sub-steps included in step S620;

[0058] Figure 10 for Figure 9 The flowchart of the sub-steps included in step S621;

[0059] Figure 11 for Figure 9 The flowchart of the sub-steps included in step S622;

[0060] Figure 12 This is a schematic diagram of the circuit structure of an embodiment of the DC / DC converter of the present invention;

[0061] Figure 13 This is a schematic diagram of the power flow in an embodiment of the DC / DC converter of the present invention;

[0062] Figure 14 This is a schematic diagram of the power flow in another embodiment of the DC / DC converter of the present invention;

[0063] Figure 15 This is a schematic diagram of the power flow in another embodiment of the DC / DC converter of the present invention;

[0064] Figure 16 This is a schematic diagram of the equivalent circuit of an embodiment of the DC / DC converter of the present invention;

[0065] Figure 17 This is a circuit structure block diagram of another embodiment of the parameter calculation device for the active clamping circuit of the present invention;

[0066] Figure 18 This is a circuit structure block diagram of an embodiment of the controller of the present invention.

[0067] Explanation of icon numbers:

[0068]

[0069] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0070] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0071] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0072] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0073] This invention proposes a method for calculating the parameters of an active clamping circuit.

[0074] In practical applications of automotive DC / DC converters, active clamping circuits are typically added to effectively suppress voltage spikes. However, with the increasing functional requirements of new energy vehicles, such as the need for automotive DC / DC converters to operate in multiple modes, the design of active clamping circuits also needs to be adapted to the different operating modes of the automotive DC / DC converter.

[0075] However, when selecting components for active clamping circuits, engineers typically rely on experience to estimate and perform multiple adjustments to choose suitable component parameters. Since the circuit performance varies under different operating modes, selecting component parameters solely based on experience often leads to inaccurate parameter selection. This makes the active clamping circuit unsuitable for different operating modes of the automotive DC / DC converter, resulting in damage to the automotive DC / DC converter. Furthermore, the numerous debugging steps also result in low efficiency in determining component parameters.

[0076] To solve the above problems, refer to Figure 1 and Figure 12 In one embodiment, it is applied in a DC / DC converter, the DC / DC converter including an active clamping circuit and a DC / DC module, the DC / DC converter having a BUCK mode;

[0077] It should be noted that the DC / DC converter used in this invention can be a BUCK-BOOST topology circuit, and in other embodiments it can also be a BUCK topology circuit. In this embodiment, a BUCK-BOOST topology circuit is used as an example, namely a buck-boost topology. A buck-boost converter is a single-transistor non-isolated DC-DC converter whose output voltage can be lower or higher than the input voltage, but the polarity of its output voltage is opposite to that of the input voltage. A BUCK-BOOST converter can be regarded as a BUCK converter and a BOOST converter connected in series, combining the switching transistor and its clamping circuit. Therefore, both the BUCK topology circuit and the BUCK-BOOST topology circuit include a high-voltage full-bridge, a transformer, and a low-voltage synchronous rectifier circuit, used to step down the input high-voltage power supply. The transformer includes N turns. p The primary winding and secondary winding are provided. The secondary winding includes an upper secondary winding and a lower secondary winding, both with N turns. s The primary-to-secondary turns ratio N of the transformer ps With N p / N s express.

[0078] The methods include:

[0079] Step S100: Obtain the plateau voltage of the clamping capacitor. The plateau voltage is the voltage of the clamping capacitor when it reaches a steady state in BUCK mode.

[0080] In this embodiment, the plateau voltage U of the clamping capacitor clamp Voltage can be acquired by a voltage detection circuit with ADC functionality.

[0081] When a DC / DC converter is operating in BUCK mode, the plateau voltage U of the clamping capacitor... clampThe clamping voltage of the clamping transistor is determined. Within one cycle, when different circuits within the high-voltage full-bridge are conducting, the transformer transfers energy to the circuit connected to the secondary winding. The upper and lower secondary windings of the transformer work alternately, and the center tap of the transformer is always positive. This leads to an increase in voltage stress on the rectifier devices at both ends of the secondary winding of the transformer because the freewheeling current is not completely discharged when the upper and lower secondary windings of the transformer work alternately. For example, if... Figure 12 and Figure 13 As shown, when the first primary-side switch Q1 and the fourth primary-side switch Q4 in the high-voltage full-bridge are closed, energy is transferred from the transformer to the circuit connected to the secondary side. At this time, the first rectifier switch Q4 in the low-voltage synchronous rectifier circuit... sr1 The second rectifier diode Q is turned on. sr2 Disconnect the transformer from the first rectifier diode Q. sr1 The circuit in question receives energy, with the center tap of the transformer being the positive terminal, and the first rectifier diode Q... sr1 The drain of the transformer is at the negative terminal, and the current flows from the negative terminal to the positive terminal. When the first primary-side switch Q1 and the fourth primary-side switch Q4 are turned off, the transformer stops transmitting energy, and the freewheeling inductor L flows through the first rectifier diode Q4 at both ends of the secondary winding. sr1 Second rectifier Q sr2 During freewheeling, no induced electromotive force is generated in the secondary winding of the transformer due to flux neutralization. Before the second primary-side switch Q2 and the third primary-side switch Q3 are ready to conduct, the first rectifier diode Q... sr1 First, the circuit is turned off, and at this time, the freewheeling current flows through its body diode. When the second primary-side switch Q2 and the third primary-side switch Q3 are turned on, the transformer transfers energy, and at this time, the second rectifier diode Q... sr2 The first rectifier diode Q is turned on. sr1 Disconnect. The center tap of the transformer is the positive terminal, and the second rectifier diode Q... sr2 The drain terminal is the negative terminal, and the current flows from the negative terminal to the positive terminal. Because the induced electromotive force on the lower secondary winding of the transformer is oriented as follows... Figure 13 As shown by the dashed arrow, this causes the first rectifier tube Q to... sr1 The voltage stress at both ends DS (Drain to Source) increases.

[0082] Meanwhile, all stray inductances (including transformer secondary leakage inductance and lead inductance, etc.) are uniformly represented as L. k1 During the freewheeling phase, the current decreases rapidly, resulting in a large di / dt (current change rate), which manifests as a voltage spike in the leakage inductance. This spike is related to the internal components of the low-voltage synchronous rectifier circuit, such as the rectifier diode Q. sr1 The junction capacitance within the diodes resonates together with the rectifier diode Q. This process is accompanied by the rectifier diode Q. sr1The reverse recovery voltage of devices such as the body diode will generate voltage stress spikes, and the presence of voltage stress spikes will cause the rectifier device to suffer large voltage stress.

[0083] If voltage stress spikes are not addressed promptly, they can easily damage rectifier devices and cause ripple at the output of the DC / DC module, reducing its output efficiency. Therefore, to suppress voltage stress spikes, clamping capacitors are needed to clamp them. These voltage stress spikes must exceed the plateau voltage U of the clamping capacitor. clamp Current flows through the first clamping transistor Q. c1 Or the second clamping tube Q c2 The body diode flows into the clamping capacitor, which charges, thus clamping the voltage and reducing the voltage stress on the rectifier. The plateau voltage U... clamp This is the voltage at which the clamping capacitor is charged to steady state in BUCK mode. At this point, the plateau voltage U of the clamping capacitor is... clamp The induced voltage of the entire secondary winding of the transformer should be taken, that is, the sum of the induced voltages of the upper and lower secondary windings of the transformer. Therefore, the designer can determine the required plateau voltage U of the clamping capacitor based on the required output voltage of the DC / DC converter. clamp .

[0084] Step S200: Calculate the first device parameters based on the relationship between the first device parameters of the clamping capacitor and the platform voltage;

[0085] In this embodiment, the first device parameter can be the current or voltage of the clamping capacitor; specifically, in this embodiment, it is the rated voltage V of the clamping capacitor. clamp .

[0086] When absorbing rectifier diode stress in BUCK mode, in order for the clamping capacitor to clamp voltage stress spikes, the voltage spikes flowing into the clamping capacitor must be higher than the plateau voltage U of the clamping capacitor during DC / DC converter operation. clamp To prevent the clamping capacitor from being damaged by overvoltage, its ability to withstand voltage stress spikes needs to be considered. Simultaneously, to ensure proper clamping and extend its service life, the platform voltage U... clamp With rated voltage V clamp The difference between them should not be too large, platform voltage U clamp It can be taken as no more than the rated voltage V clamp 75% of the rated voltage, therefore, when selecting parameters for the clamping capacitor, the rated voltage V of the clamping capacitor can be used as a reference. clamp With platform voltage U clamp The relationship between the clamping capacitor and the rated voltage V is used to calculate the clamping capacitor. clamp Rated voltage V clampWith platform voltage U clamp The relationship between them can be represented as:

[0087]

[0088] Among them, V clamp U is the rated voltage of the clamping capacitor. clamp This is the plateau voltage of the clamping capacitor.

[0089] This invention provides a parameter calculation method for selecting components for the active clamping circuit of a DC / DC converter. Based on the required input voltage, input current, output voltage, and output current values ​​of the DC / DC converter under different operating modes, and their relationship with component parameters, the method calculates the component parameters of the active clamping circuit. This allows for the selection of appropriate component parameters based on the known input and output requirements of the DC / DC module, reducing the reliance on engineer experience, eliminating the need for multiple trials, lowering the difficulty of component selection for active clamping circuits, and improving the accuracy and efficiency of active clamping circuit design.

[0090] Reference Figure 2 and Figure 12 In one embodiment, the step of obtaining the plateau voltage of the clamping capacitor includes:

[0091] Step S110: Obtain the maximum high-voltage input voltage and the primary-secondary turns ratio of the transformer in BUCK mode, wherein the maximum high-voltage input voltage is the bus voltage on the high-voltage side of the DC / DC module in BUCK mode.

[0092] Step S120: Obtain the platform voltage based on the maximum high voltage input voltage and the primary-secondary turns ratio of the transformer.

[0093] In this embodiment, to ensure that the voltage after clamping by the clamping capacitor matches the output voltage of the DC / DC module, and to prevent the clamping capacitor from being damaged by overvoltage, it is necessary to set the plateau voltage U of the clamping capacitor. clamp This is equal to the maximum induced voltage of the transformer's secondary winding, which is also the maximum low-voltage output voltage of the DC / DC module in BUCK mode. Therefore, based on the transformer's transformation principle, the maximum high-voltage input voltage of the DC / DC module and the transformer's primary-secondary turns ratio N can be used to determine the voltage. ps The maximum low-voltage output voltage is obtained. Since the transformer parameters in the DC / DC module are known when the engineer designs the active clamping circuit, the maximum high-voltage input voltage U is taken. HVmax The primary-to-secondary turns ratio N of the transformer ps In this case, because the topology includes a center tap, and the voltage used to charge the clamping capacitor is the voltage across the entire secondary side, and the upper and lower secondary windings have the same number of turns, the turns ratio is N when calculated.ps / 2. Therefore, based on the maximum high-voltage input voltage U HVmax The primary-to-secondary turns ratio N of the transformer ps Obtain the maximum low-voltage output voltage of the DC / DC module as the plateau voltage U of the clamping capacitor. clamp The platform voltage U is obtained. clamp Voltage formula:

[0094]

[0095] Among them, U HVmax N is the maximum high voltage input voltage. ps This represents the turns ratio of the primary and secondary sides of the transformer.

[0096] Reference Figures 12 to 15 and Figure 3 In one embodiment, the method further includes:

[0097] Step S300: Calculate the second device parameters based on the relationship between the second device parameters of the clamping transistor and the platform voltage.

[0098] In this embodiment, the second device parameter can specifically be the drain-source voltage V of the clamping transistor. DS .

[0099] When absorbing rectifier tube stress in BUCK mode, if the first clamping tube Q c1 Or the second clamping tube Q c2 When the circuit is turned on, current flows through the first clamping transistor Q. c1 Or the second clamping tube Q c2 The body diode flows into the clamping capacitor to prevent the first clamping transistor Q from being connected. c1 Or the second clamping tube Q c2 The first clamping transistor Q was broken down by overvoltage stress spike. c1 Or the second clamping tube Q c2 Drain-source voltage V DS It should be greater than the plateau voltage U of the clamping capacitor. clamp Due to the plateau voltage U of the clamping capacitor clamp Equal to the induced voltage of the secondary winding of the transformer, therefore the maximum high-voltage input voltage U is taken. HVmax Calculate the critical value of the induced voltage in the secondary winding of the transformer, and set the drain-source voltage V of the clamping transistor as the reference value. DS A voltage margin is set, and the margin setting for the clamping transistor can be set by the designer according to requirements, which is not limited here. In this embodiment, the platform voltage U clamp Take a value not exceeding the drain-source voltage V DS 75%, based on drain-source voltage V DS With platform voltage U clamp The relationship between the drain and source voltages V is used to obtain the drain-source voltage V. DS:

[0100]

[0101] Among them, V DS This is the drain-source voltage of the clamping transistor.

[0102] Reference Figures 12 to 15 and Figure 4 In one embodiment, the DC / DC converter also has a BOOST mode, and the method further includes:

[0103] Step S400: Obtain the maximum charging current and inductor current ripple coefficient in BOOST mode, wherein the maximum charging current is the maximum current on the low-voltage side of the DC / DC module in BOOST mode, and the inductor current ripple coefficient is the ripple coefficient of the freewheeling inductor on the low-voltage side.

[0104] Step S500: Calculate the third device parameters based on the relationship between the third device parameters of the clamping transistor and the maximum charging current and inductor current ripple coefficient.

[0105] In this embodiment, the third device parameter is specifically the forward current I of the body diode of the clamping transistor. SD .

[0106] Since the parameters of the freewheeling inductor L in a DC / DC module are known when engineers design active clamping circuits for the module, the corresponding current inductance ripple factor r can be obtained from L. A common design rule is to design the inductor current ripple to be approximately 30% of the average current of the freewheeling inductor L. Engineers can also adjust the current inductance ripple factor r according to actual needs. Maximum charging current I BOOST To determine the maximum input current of the DC / DC module when charging from the low-voltage side to the high-voltage side in BOOST mode, the inductor current ripple factor *r* is chosen. Since the ripple includes both positive and negative half-waves, the impact of the inductor current ripple on the maximum charging current *I* is considered. BOOST When considering the impact of current imbalance, the inductor current ripple factor r needs to be divided by 2. Simultaneously, to account for the actual situation of uneven current distribution, it can be multiplied by a coefficient A, such as 1.2. This value must be less than the forward current I of the body diode of the selected clamping transistor. SD Therefore, based on the forward current I of the body diode of the clamping transistor... SD With the maximum charging current I BOOST The relationship between the inductor current ripple coefficient r and the forward current I of the body diode is used to obtain the forward current I of the body diode. SD :

[0107]

[0108] Among them, I SD I is the forward current of the body diode of the clamping transistor. BOOSTdenoted as the maximum charging current, and r as the inductor current ripple coefficient.

[0109] Reference Figures 12 to 15 and Figure 5 In one embodiment, the method further includes:

[0110] Step S600: Calculate the fourth device parameter based on the relationship between the fourth device parameter of the clamping capacitor and the first and third device parameters.

[0111] In this embodiment, the fourth device parameter can specifically be the capacitance value C of the clamping capacitor. clamp .

[0112] It should be noted that the input voltage of a DC / DC module gradually increases over a short period of time during startup. This process of voltage gradually increasing from 0 to the input voltage value is the startup phase of the DC / DC module. When a DC / DC module starts up in BOOST mode, it consists of two phases: In the first phase, the drive duty cycle of the secondary rectifier diode is less than 50%. At this time, when the secondary rectifier diode Q... sr1 When switched on, the low-voltage source on the secondary side transfers energy to the primary side through the freewheeling inductor L, which in turn affects the high-voltage capacitor C. HV Pre-charge is performed. At this point, the following relationship exists:

[0113] U HV =U LV ·N ps 2D

[0114] In the formula U HV U is the high-voltage side voltage output by the DC / DC module in BOOST mode. LV N represents the low-side voltage input to the DC / DC module in BOOST mode. ps Let L be the turns ratio of the primary and secondary sides of the transformer, and D be the duty cycle of the rectifier diode. When the rectifier diode is turned off, the low-voltage side of the secondary side no longer transfers energy to the primary side, and the current in the freewheeling inductor L flows through the first clamping transistors Q on both sides. c1 and the second clamping tube Q c2 The body diode charges the clamping capacitor and freewheels.

[0115] In the second stage, the drive duty cycle of the secondary rectifier diodes is greater than 50%. At this time, when the first rectifier diode Q on the secondary side of the transformer... sr1 Second rectifier Q sr2 When both sides are simultaneously turned on, the low-voltage source on the secondary side stores energy through the freewheeling inductor L. At this time, no induced electromotive force is generated on the transformer secondary side due to magnetic flux neutralization. This process of boosting voltage through energy storage in the freewheeling inductor L involves the following relationship:

[0116]

[0117] When the rectifier tube Q sr1and Q sr2 A larger duty cycle means a longer charging time for the freewheeling inductor L from the low-voltage source, resulting in a higher high-voltage side voltage and a larger inductor ripple current. When Q... sr1 When switched off, energy is transferred from the low-voltage secondary side to the primary side through the transformer. For example... Figure 11 As shown, the induced electromotive force on the secondary side of the transformer is E+, which is transmitted through the first clamping transistor Q. c1 Absorption rectifier Q sr1 The energy of stress and induced electromotive force. At this instant, it flows through the first clamping transistor Q. c1 The current in the body diode is the same as that in the rectifier diode Q. sr1 The initial current is half of the current in the freewheeling inductor L. Then, the current in the freewheeling inductor L quickly flows through Q. sr2 Energy is transferred to the primary side, and then the first clamping transistor Q... c1 When the circuit is turned on, the absorbed energy is released back into the circuit.

[0118] Therefore, when selecting the first clamping tube Q c1 Second clamping tube Q c2 At this time, the first clamping tube Q needs to be considered. c1 Second clamping tube Q c2 Regarding the carrying capacity of freewheeling current, and because in BOOST mode, when the rectifier duty cycle is less than 50%, all the energy of the freewheeling inductor L is absorbed by the clamping capacitor, the current flowing through the first clamping transistor Q is selected when the DC / DC module is operating in BOOST mode. c1 Second clamping tube Q c2 The current is a critical value. Since the freewheeling inductor L has an inductance current ripple factor r, it will affect the charging current. Therefore, considering the first clamping transistor Q... c1 Second clamping tube Q c2 When considering the freewheeling current carrying capacity, it is necessary to comprehensively consider the inductor current ripple coefficient r and the maximum charging current I. BOOST The value of Q is used to improve the first clamping tube. c1 Second clamping tube Q c2 Reliability during continuous current operation.

[0119] In addition, to prevent the first clamping tube Q c1 Second clamping tube Q c2 Overcurrent breakdown occurs, so the charging current during the clamp capacitor's energy absorption and charging process in BOOST mode cannot exceed the forward current I of the clamp transistor's body diode. SD Therefore, when selecting the parameters of the clamping capacitor, the capacitance value C can be used as a reference. clamp Charging current, and the forward current I of the body diode of the clamping transistor. SD Based on the relationship between the capacitance values, select a capacitance value that satisfies this condition, and then select the capacitance value C. clamp At the same time, the plateau voltage U of the clamping capacitor also needs to be considered.clamp Platform voltage U clamp The selection of the clamping capacitor is related to its rated voltage V. clamp Therefore, when selecting the parameters of the clamping capacitor, the capacitance value C can be used as a reference. clamp Platform voltage U clamp Rated voltage V clamp Based on the relationship between the two capacitance values, select a capacitance value that satisfies this condition. Finally, choose the required clamping capacitor value C from the range of the two capacitance values ​​mentioned above. clamp .

[0120] Reference Figures 12 to 15 and Figure 6 In one embodiment, the step of calculating the fourth device parameter based on the relationship between the fourth device parameter of the clamping capacitor and the first and third device parameters includes:

[0121] Step S610: Calculate the maximum value of the fourth device parameter based on the relationship between the fourth device parameter and the third device parameter;

[0122] Step S620: Calculate the minimum value of the fourth device parameter based on the relationship between the fourth device parameter and the first device parameter;

[0123] Step S630: Obtain the fourth device parameter based on the maximum value and the minimum value of the fourth device parameter.

[0124] In this embodiment, when the clamping capacitor absorbs rectifier diode stress in BUCK mode, the plateau voltage U of the clamping capacitor... clamp Equal to the induced voltage of the secondary winding, therefore the maximum high-voltage input voltage U is taken. HVmax Calculate the critical value of the induced voltage in the secondary winding, and the plateau voltage U. clamp Take a voltage not exceeding the rated voltage V clamp 75%, thus obtaining the rated voltage V clamp :

[0125]

[0126] Among them, U HVmax N is the maximum high voltage input voltage. ps N is the primary-to-secondary turns ratio of the transformer. ps .

[0127] When designing an active clamping circuit based on BUCK mode, the main consideration is that during high-voltage sudden changes or startup, the input terminal charges the clamping capacitor, so that the instantaneous charging current during DC / DC converter startup exceeds that of the first clamping transistor Q. c1 Second clamping tube Q c2 The flow capacity causes the first clamping tube Q to... c1Second clamping tube Q c2 Damage, in order to ensure that the current does not exceed the first clamping transistor Q c1 Second clamping tube Q c2 The current carrying capacity and clamping capacitance cannot be too large, thus depending on the first clamping transistor Q. c1 Second clamping tube Q c2 The current-carrying capacity determines the capacitance value C of the clamping capacitor. clamp That is, based on the capacitance value C clamp Charging current, and the forward current I of the body diode of the clamping transistor. SD The relationship between the capacitance values ​​determines the capacitance C. clamp The maximum value C clamp_max When designing an active clamping circuit based on BOOST mode, the main consideration is the current flowing through the freewheeling inductor on the low-voltage side to the first clamping transistor Q. c1 Second clamping tube Q c2 When current flows to the clamping capacitor for freewheeling, due to the transformer leakage inductance L... r Due to the influence of the transformer leakage inductance, the DC / DC module charges the clamping capacitor during startup, causing a voltage ripple to be generated by the clamping capacitor. This ripple, combined with the freewheeling inductor L and the primary winding resistance R, makes the startup waveform approximate a step signal. According to the voltage ripple formula ΔV = Q... clamp / C clamp Furthermore, the voltage ripple variation of the clamping capacitor must not exceed the rated value; therefore, the capacitance value C of the clamping capacitor is... clamp The value of the capacitor C cannot be too small, thus determining the capacitance value. clamp The minimum value C clamp_min Finally, the capacitance value C of the clamping capacitor is used. clamp The maximum value C clamp_max With minimum value C clamp_min The clamping capacitor capacity is determined within the specified range.

[0128] Reference Figures 12 to 15 and Figure 7 In one embodiment, the step of calculating the maximum value of the fourth device parameter based on the relationship between the fourth device parameter and the third device parameter includes:

[0129] Step S611: Obtain the charging current of the clamping capacitor in BUCK mode. The charging current of the clamping capacitor has a functional relationship with the fourth device parameter.

[0130] Step S612: Calculate the maximum value of the fourth device parameter based on the relationship between the charging current of the clamping capacitor and the third device parameter.

[0131] In this embodiment, during startup in BUCK mode, the high-voltage input voltage charges the clamping capacitor through the transformer leakage inductance. The startup waveform can be approximated as a step signal. Therefore, the clamping capacitor cannot be too large; otherwise, the instantaneous charging current during startup will exceed that of the first clamping transistor Q. c1 Second clamping tube Q c2 The flow capacity causes the first clamping tube Q to... c1 Second clamping tube Q c2 Damaged. Take the maximum high-voltage input voltage U. HVmax The charging current I of the clamping capacitor charge With capacitance value C clamp The charging current I of the clamping capacitor has a functional relationship. charge The forward current I of the body diode of the clamping transistor does not exceed the value of the clamping transistor. SD Capacitance C clamp The maximum value C clamp_max Calculate using the following formula:

[0132] I SD ≥I charge

[0133] Choose an appropriate capacitance value C clamp The maximum value C clamp_max The above requirements must be met.

[0134] Reference Figures 12 to 15 and Figure 8 In one embodiment, the step of obtaining the charging current of the clamping capacitor in BUCK mode includes:

[0135] Step S613: Obtain the maximum high voltage input voltage, transformer primary and secondary turns ratio, freewheeling inductance, transformer leakage inductance, primary winding resistance, and initial pulse width in BUCK mode. The maximum high voltage input voltage is the bus voltage on the high voltage side of the DC / DC module in BUCK mode, and the initial pulse width is the initial drive pulse width of the high voltage side switching transistor.

[0136] Step S614: Based on the fourth device parameters, maximum high voltage input voltage, transformer primary and secondary turns ratio, freewheeling inductance, transformer leakage inductance, primary winding resistance value and initial pulse width, obtain the charging current of the clamping capacitor in BUCK mode.

[0137] In this embodiment, in BUCK mode, the high-voltage input voltage charges the clamping capacitor through the transformer leakage inductance during startup. The startup waveform can be approximated as a step signal. Therefore, the clamping capacitor cannot be too large; otherwise, the instantaneous charging current during startup will exceed the current-carrying capacity of the clamping transistor, causing damage. The maximum high-voltage input voltage U is taken. HVmax The charging current I of the clamping capacitor charge The forward current I of the body diode of the clamping transistor does not exceed the value of the clamping transistor. SDTransformer leakage inductance L r The resistance value of the primary winding of the transformer is R, C'. clamp The values ​​are: the clamping capacitance calculated from the secondary side to the primary side via the transformer, the primary winding resistance, the converted clamping capacitance, and the transformer leakage inductance L. r The equivalent circuit diagram of an RLC series circuit is as follows: Figure 16 As shown.

[0138] Based on the principle of equivalent circuit Figure 16 , and C` clamp Maximum high voltage input voltage U HVmax The primary-to-secondary turns ratio N of the transformer ps Freewheeling inductance L, transformer leakage inductance L r Given the primary winding resistance R and the initial pulse width b, the charging current I of the clamping capacitor is obtained. charge Second-order function:

[0139]

[0140] in,

[0141]

[0142] In the above formula, I charge The function is the solution to the step response of an RLC series circuit, C` clamp This represents the clamping capacitor size calculated from the secondary winding to the primary winding via the transformer. Because the topology includes a center tap, and the voltage used to charge the clamping capacitor is the voltage across the entire secondary winding, the actual turns ratio in the calculation is N. ps / 2, b is the initial drive pulse width of the high-voltage side switching transistor, which can be selected according to the actual design requirements. For example, if the startup pulse width is 40ns, then substitute it into the calculation to obtain the charging current I of the secondary clamping capacitor during startup. charge .

[0143] Therefore, based on the charging current I of the clamping capacitor charge The forward current I of the body diode of the clamping transistor does not exceed the value of the clamping transistor. SD This allows us to select a suitable capacitance value C, based on the requirements. clamp The maximum value C clamp_max To meet this requirement.

[0144] Reference Figures 12 to 15 and Figure 9 In one embodiment, the step of calculating the minimum value of the fourth device parameter based on the relationship between the fourth device parameter and the first device parameter includes:

[0145] Step S621: Obtain the freewheeling current, maximum low-voltage input voltage, and inductance value of the freewheeling inductor in BOOST mode. The freewheeling current is the current of the freewheeling inductor in BOOST mode, and the maximum low-voltage input voltage is the maximum input voltage on the low-voltage side in BOOST mode.

[0146] Step S622: Calculate the minimum value of the fourth device parameter based on the first device parameter, the maximum low-voltage input voltage, the freewheeling current, and the inductance value of the freewheeling inductor.

[0147] In this embodiment, when designing an active clamping circuit based on BOOST mode, the main consideration is the current flowing through the first clamping transistor Q from the freewheeling inductor L on the low-voltage side. c1 Second clamping tube Q c2 When current flows to the clamping capacitor for freewheeling, due to the transformer leakage inductance L... r Due to the influence of the transformer leakage inductance, the DC / DC module charges the clamping capacitor during startup, causing a voltage ripple to be generated by the clamping capacitor. This ripple, combined with the freewheeling inductor L and the primary winding resistance R, makes the startup waveform approximate a step signal. According to the voltage ripple formula ΔV = Q... clamp / C clamp Furthermore, the voltage ripple variation of the clamping capacitor must not exceed the rated value; therefore, the capacitance value C of the clamping capacitor is... clamp It cannot be too small. Therefore, based on the requirement that the voltage ripple variation of the clamping capacitor must not exceed the rated value, the rated voltage V of the clamping capacitor can be used as a reference. clamp Maximum low-voltage input voltage U LVmax Given the freewheeling current and freewheeling inductance L, select an appropriate capacitor value C. clamp The minimum value C clamp_min .

[0148] Reference Figures 12 to 15 and Figure 10 In one embodiment, the step of obtaining the freewheeling current in BOOST mode includes:

[0149] Step S623: In BOOST mode, if the duty cycle of the control rectifier is less than the preset duty cycle, the maximum and minimum values ​​of the freewheeling current are obtained according to the maximum charging current and the inductor current ripple coefficient.

[0150] Step S624: In BOOST mode, if the duty cycle of the control rectifier is greater than the preset duty cycle, obtain the maximum value of the freewheeling current based on the maximum charging current and the inductor current ripple coefficient.

[0151] In this embodiment, when the DC / DC converter is in BOOST mode and the rectifier duty cycle is less than a preset duty cycle (which can be 50%), based on the aforementioned platform voltage U... clampThe calculation formula and the high-voltage side voltage U under this mode HV With low-voltage side voltage U LV The relationship is given by the plateau voltage U of the clamping capacitor at this time. clamp Less than 2U LV The energy of the freewheeling inductor L is entirely absorbed by the clamping capacitor. Here, a large margin is used in the calculation, and the inductor current ripple factor r is taken. Since the maximum charging current in BOOST mode is I... BOOST The maximum value of the freewheeling current I can be calculated using the following formula. Lmax and minimum value I Lmin :

[0152]

[0153] Therefore, if the rectifier diode's duty cycle is less than 50%, it can be determined based on the rated voltage V of the clamping capacitor. clamp Maximum low-voltage input voltage U LVmax The maximum and minimum values ​​of the freewheeling current and the freewheeling inductance L are used to calculate the capacitance C. clamp The minimum value C clamp_min .

[0154] Of course, if the rectifier duty cycle is greater than 50%, the maximum value of the freewheeling current I can also be obtained according to the above formula. Lmax And according to the rated voltage V of the clamping capacitor clamp Maximum low-voltage input voltage U LVmax The capacitance value C is calculated from the maximum value of the freewheeling current and the freewheeling inductance L. clamp The minimum value C clamp_min .

[0155] Reference Figures 11 to 15 In one embodiment, the step of calculating the minimum value of the fourth device parameter based on the first device parameter, the maximum low-voltage input voltage, the freewheeling current, and the inductance value of the freewheeling inductor further includes:

[0156] Step S625: If the duty cycle of the control rectifier is less than the preset duty cycle, calculate the first minimum value of the fourth device parameter based on the first device parameter, the maximum low voltage input voltage, the inductance value of the freewheeling inductor, and the maximum and minimum values ​​of the freewheeling current.

[0157] Step S626: If the duty cycle of the control rectifier is greater than the preset duty cycle, obtain the charging current frequency of the clamping capacitor and the duty cycle of the rectifier; obtain the maximum charging time of the clamping capacitor based on the charging current frequency and the duty cycle of the rectifier; calculate the second minimum value of the fourth device parameter based on the first device parameter, the maximum low voltage input voltage, the maximum value of the freewheeling current, the maximum charging time, and the duty cycle of the rectifier.

[0158] Step S627: Obtain the minimum value of the fourth device parameter based on the first minimum value and / or the second minimum value of the fourth device parameter.

[0159] In this embodiment, if the rectifier diode's duty cycle is less than 50%, the capacitance value C can be calculated using the following formula. clamp The first minimum value C clamp min1 :

[0160]

[0161] If the rectifier duty cycle is greater than 50%, the rectifier will pass through the first clamping transistor Q at the moment of turn-off. c1 Or the second clamping tube Q c2 The current is half the current of the freewheeling inductor L. Since the clamping capacitor charges and discharges approximately equally during the rectifier diode's off-state, the charging current waveform is approximately triangular, and the charging current frequency is f. Therefore, the maximum charging time t is:

[0162]

[0163] In the formula, D is the duty cycle of the rectifier diode. Based on the aforementioned plateau voltage U... clamp The calculation formula and the high-voltage side voltage U under this mode HV With low-voltage side voltage U LV From the relationship, we can know the plateau voltage U of the clamping capacitor. clamp The maximum value is U LVmax / (1-D), the capacitance value C can be calculated according to the following formula. clamp The second minimum value C clamp_min2 :

[0164]

[0165] Therefore, the capacitance value C can be selected. clamp The first minimum value C clamp_min1 Or the capacitance value C clamp The second minimum value C clamp_min2 As capacitance value C clamp The minimum value C clamp_min To ensure the clamping capacitor is applicable under different rectifier diode duty cycles, the larger of the two calculated values ​​above can be selected as the capacitance value C. clamp The minimum value C clamp_min .

[0166] In summary, the clamping capacitor value C clamp Can be found in C clamp_min To C clamp_max Choose from the range between them.

[0167] A parameter calculation device for an active clamping circuit, such as Figures 1 to 17 As shown, in one embodiment, the device is applied in a DC / DC converter, which includes an active clamping circuit and a DC / DC module, and has a BUCK mode; the device includes:

[0168] The data acquisition module is used to acquire the platform voltage of the clamping capacitor, which is the voltage of the clamping capacitor when it reaches a steady state in BUCK mode.

[0169] The parameter calculation module is used to calculate the first device parameters based on the relationship between the first device parameters of the clamping capacitor and the platform voltage.

[0170] In this embodiment, the data acquisition module may employ an ADC circuit, and the parameter calculation module may include modules with data calculation functions, such as microprocessors or control chips.

[0171] When the DC / DC converter operates in BUCK mode, energy is transferred from the transformer to the secondary side circuit when the first primary-side switch Q1 and the fourth primary-side switch Q4 are closed. At this time, the first rectifier diode Q1... sr1 The second rectifier diode Q is turned on. sr2 Disconnect the transformer from the first rectifier diode Q. sr1 With the connected half working, the center tap of the transformer is the positive terminal, and the first rectifier diode Q... sr1 The drain is the negative terminal, and the current flows from the negative terminal to the positive terminal. At this time, the data acquisition module detects the output voltage of the DC / DC converter and outputs it as the platform voltage of the clamping capacitor to the parameter calculation module.

[0172] The parameter calculation module calculates the plateau voltage U of the clamping capacitor. clamp Select a voltage not exceeding the rated voltage V clamp 75%, and because the topology has a center tap, the voltage when charging the clamping capacitor is the entire secondary side voltage, therefore the turns ratio is N when calculated. ps / 2. Therefore, the parameter calculation module calculates the parameters based on the transformer principle and the maximum high-voltage input voltage U. HVmax The primary-to-secondary turns ratio N of the transformer ps The relationship between the clamping capacitor and its plateau voltage is established; the plateau voltage of the clamping capacitor is calculated; and based on the plateau voltage U... clamp With rated voltage V clamp The relationship between the two factors determines the appropriate rated voltage V of the clamping capacitor. clamp :

[0173]

[0174] Among them, V clamp U is the rated voltage of the clamping capacitor. HVmax N is the maximum high voltage input voltage.ps This represents the turns ratio of the primary and secondary sides of the transformer.

[0175] In one embodiment, the data acquisition module is used to acquire the maximum high-voltage input voltage and the primary-secondary turns ratio of the transformer in BUCK mode, wherein the maximum high-voltage input voltage is the bus voltage on the high-voltage side of the DC / DC module in BUCK mode.

[0176] The parameter calculation module is used to obtain the platform voltage based on the maximum high-voltage input voltage and the primary-secondary turns ratio of the transformer.

[0177] In one embodiment, the parameter calculation module is further configured to calculate the second device parameters based on the relationship between the second device parameters of the clamping transistor and the platform voltage.

[0178] In one embodiment, the DC / DC converter further includes a BOOST mode and a data acquisition module for acquiring the maximum charging current and inductor current ripple coefficient in BOOST mode, wherein the maximum charging current is the maximum current on the low-voltage side of the DC / DC module in BOOST mode, and the inductor current ripple coefficient is the ripple coefficient of the freewheeling inductor on the low-voltage side.

[0179] The parameter calculation module is used to calculate the parameters of the third device based on the relationship between the third device parameters of the clamping transistor and the maximum charging current and the inductor current ripple coefficient.

[0180] In one embodiment, the parameter calculation module is further configured to calculate the fourth device parameter based on the relationship between the fourth device parameter of the clamping capacitor and the first and third device parameters.

[0181] In one embodiment, the parameter calculation module is further configured to calculate the maximum value of the fourth switch device parameter based on the relationship between the fourth switch device parameter and the third switch device parameter; calculate the minimum value of the fourth switch device parameter based on the relationship between the fourth switch device parameter and the first switch device parameter; and obtain the fourth switch device parameter based on the maximum value and the minimum value of the fourth switch device parameter.

[0182] In one embodiment, the data acquisition module is used to acquire the charging current of the switch clamping capacitor in the switch BUCK mode, wherein the charging current of the switch clamping capacitor has a functional relationship with the parameters of the fourth switching device.

[0183] The parameter calculation module is used to calculate the maximum value of the fourth switch device parameter based on the relationship between the charging current of the switch clamping capacitor and the parameters of the third switch device.

[0184] In one embodiment, the data acquisition module is used to acquire the maximum high-voltage input voltage, the transformer primary-secondary turns ratio, the switch freewheeling inductance, the transformer leakage inductance, the primary winding resistance value, and the initial pulse width in switch BUCK mode. The maximum high-voltage input voltage is the bus voltage on the high-voltage side of the switch DC / DC module in switch BUCK mode, and the initial pulse width is the initial drive pulse width of the switch transistor on the high-voltage side of the switch.

[0185] The parameter calculation module is used to obtain the charging current of the switch clamping capacitor in switch BUCK mode based on the parameters of the fourth device of the switch, the maximum high voltage input voltage of the switch, the turns ratio of the primary and secondary sides of the switch transformer, the freewheeling inductance of the switch, the leakage inductance of the switch transformer, the resistance value of the primary winding of the switch, and the initial pulse width of the switch.

[0186] In one embodiment, the data acquisition module is used to acquire the freewheeling current and maximum low-voltage input voltage, and the inductance value of the switch freewheeling inductor in the switch BOOST mode, wherein the switch freewheeling current is the current of the switch freewheeling inductor in the switch BOOST mode, and the maximum low-voltage input voltage is the maximum input voltage on the low-voltage side of the switch in the switch BOOST mode.

[0187] The parameter calculation module is used to calculate the minimum value of the fourth device parameter of the switch based on the parameters of the first device of the switch, the maximum low voltage input voltage of the switch, the freewheeling current of the switch, and the inductance value of the freewheeling inductor of the switch.

[0188] In one embodiment, the parameter calculation module is further configured to, in switch BOOST mode, if the duty cycle of the control rectifier is less than the preset duty cycle, obtain the maximum and minimum values ​​of the switch freewheeling current based on the maximum charging current of the switch and the ripple coefficient of the switch inductor current, respectively; and in switch BOOST mode, if the duty cycle of the control switch rectifier is greater than the preset duty cycle of the switch, obtain the maximum value of the switch freewheeling current based on the maximum charging current of the switch and the ripple coefficient of the switch inductor current.

[0189] In one embodiment, the parameter calculation module is used to calculate the first minimum value of the fourth device parameter of the switch if the duty cycle of the control switch rectifier is less than the preset duty cycle of the switch, based on the first device parameter of the switch, the maximum low voltage input voltage of the switch, the inductance value of the switch freewheeling inductor, and the maximum and minimum values ​​of the switch freewheeling current.

[0190] The data acquisition module is used to acquire the charging current frequency of the switch clamping capacitor and the duty cycle of the switch rectifier if the duty cycle of the control switch rectifier is greater than the preset duty cycle of the switch.

[0191] The parameter calculation module is also used to obtain the maximum charging time of the switch clamping capacitor based on the frequency of the switch charging current and the duty cycle of the switch rectifier; to calculate the second minimum value of the fourth device parameter based on the first device parameter of the switch, the maximum low-voltage input voltage of the switch, the maximum value of the switch freewheeling current, the maximum charging time of the switch and the duty cycle of the switch rectifier; and to obtain the minimum value of the fourth device parameter based on the first minimum value of the fourth device parameter and / or the first minimum value of the fourth device parameter.

[0192] This parameter calculation device is used for component selection in the active clamping circuit of a DC / DC converter. Based on the required input voltage, input current, output voltage, and output current values ​​of the DC / DC converter in different operating modes, and their relationship with component parameters, it calculates the component parameters of the active clamping circuit. Therefore, when selecting components for the active clamping circuit, it can choose appropriate component parameters based on the known input and output requirements of the DC / DC module, reducing the need for engineers' experience, eliminating the need for multiple trials, lowering the difficulty of component selection for active clamping circuits, and improving the accuracy and efficiency of active clamping circuit design.

[0193] This invention also proposes a controller for use in DC / DC converters, such as... Figure 18 As shown, the system includes a processor, a memory, and a parameter calculation program for an active clamping circuit stored in the memory and executable on the main control chip. When executed by the processor, the parameter calculation program for the active clamping circuit implements the steps of the parameter calculation method for the active clamping circuit as described above. The processor is connected to the memory. The specific process of the parameter calculation program for the active clamping circuit is as described in the above embodiments. Since the controller adopts all the technical solutions of all the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated further here.

[0194] This invention also proposes a DC / DC converter, including a DC / DC module, the aforementioned controller, and an active clamping circuit. The output terminal of the controller is connected to the controlled terminal of the active clamping circuit; the DC / DC module and the active clamping circuit are electrically connected. The specific structure of the controller is as described in the above embodiments. Since the DC / DC converter adopts all the technical solutions of all the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated further here.

[0195] Reference Figures 12 to 16 In one embodiment, the DC / DC module includes a high-voltage full-bridge rectifier, an isolation transformer, a low-voltage synchronous rectifier circuit, and a filter circuit connected in sequence.

[0196] The active clamping circuit includes a first clamping transistor, a second clamping transistor, and a clamping capacitor. The first end of the first clamping transistor is connected to the first end of the secondary winding of the isolation transformer. The first end of the second clamping transistor is connected to the second end of the secondary winding of the isolation transformer. The second ends of the first and second clamping transistors are respectively connected to the first end of the clamping capacitor. The controlled ends of the first and second clamping transistors are respectively connected to the output end of the controller. The second end of the clamping capacitor is grounded.

[0197] In this embodiment, the high-voltage full bridge is used to connect to and output a high-voltage source;

[0198] The primary winding of the isolation transformer is connected to the output terminal of the high-voltage full-bridge rectifier, and the secondary winding of the isolation transformer is connected to the input terminal of the low-voltage synchronous rectifier circuit. This circuit is used to step down the voltage of the connected high-voltage source before outputting it, or to step up the voltage of the connected low-voltage source before outputting it.

[0199] The low-voltage synchronous rectifier circuit is used to rectify the stepped-down high-voltage source and output it; or, it is used to connect to a low-voltage source and output it.

[0200] The high-voltage full-bridge converter is also used to rectify the boosted low-voltage source and output it.

[0201] Filtering networks are used to filter the stepped-down high-voltage source or the connected low-voltage source.

[0202] The high-voltage full-bridge transistor includes a first primary-side switch Q1, a second primary-side switch Q2, a third primary-side switch Q3, and a fourth primary-side switch Q4. The drains of the first primary-side switch Q1 and the third primary-side switch Q3 are connected to the positive output terminal of the high-voltage source, the sources of the second primary-side switch Q2 and the fourth primary-side switch Q4 are connected to the negative output terminal of the high-voltage source, the sources of the first primary-side switch Q1 and the second primary-side switch Q2 are connected to the first terminal of the high-voltage side of the isolation transformer, and the drains of the third primary-side switch Q3 and the fourth primary-side switch Q4 are connected to the second terminal of the high-voltage side of the isolation transformer. The gates of the first primary-side switch Q1, the second primary-side switch Q2, the third primary-side switch Q3, and the fourth primary-side switch Q4 are electrically connected to the output terminal of the controller.

[0203] The low-voltage synchronous rectifier circuit includes the first rectifier diode Q. sr1 and the second rectifier tube Q sr2 The first rectifier tube Q sr1 The source of the diode is connected to the first terminal of the low-voltage side of the isolation transformer, and the second rectifier diode Q... sr2 The first rectifier diode Q is connected to the second terminal of the low-voltage side of the isolation transformer. sr1 The drain and the second rectifier Q sr2The drains of the first rectifier diode Q are grounded. sr1 The gate and the second rectifier Q sr2 The gates are used to electrically connect to the output of the controller.

[0204] The filter network includes a freewheeling inductor L, an energy storage capacitor C, and an electromagnetic inductor L. emc and electromagnetic capacitor C emc The first terminal of the freewheeling inductor L is connected to the tap of the isolation transformer, and the second terminal of the freewheeling inductor L is connected to the first terminal of the energy storage capacitor C and the electromagnetic inductor L. emc The first end is connected to the electromagnetic inductor L. emc The second terminal is connected to the electromagnetic capacitor C emc The first terminal is connected; the second terminal of the energy storage capacitor C and the electromagnetic capacitor C emc The second end is grounded respectively.

[0205] Specifically, when the DC / DC converter is in BUCK mode, the high-voltage full-bridge is connected to a high-voltage source. During the positive half-wave of the high-voltage source, the DC / DC converter's controller controls the first primary-side switch Q1 and the fourth primary-side switch Q4 to conduct, forming a current loop inside the high-voltage full-bridge, thereby providing energy to the low-voltage synchronous rectifier circuit on the secondary side of the transformer. At this time, the first rectifier switch Q1... sr1 When the circuit is turned on, the induced current interacts with the first rectifier diode Q. sr1 The two diodes conduct in the same direction, forming a current from the transformer tap to the low-voltage output. During the negative half-wave of the high-voltage source, the DC / DC converter controller turns on the second primary-side switch Q2 and the third primary-side switch Q3, creating a current loop inside the high-voltage full-bridge circuit. This allows the low-voltage synchronous rectifier circuit on the secondary side of the transformer to receive energy. At this time, the second rectifier diode Q... sr2 When the circuit is turned on, the induced current interacts with the second rectifier diode Q. sr2 The body diodes have the same conduction direction, forming a current from the transformer tap terminal to the low-voltage output terminal, thereby realizing low-voltage DC output in BUCK mode.

[0206] When the DC / DC converter is in BOOST mode, the low-voltage synchronous rectifier circuit is connected to a low-voltage source. During charging, the first MOSFET Q... sw1 and the second MOSFET Q sw2 In BOOST mode, it is always on, and the first rectifier diode Q is always conducting. sr1 and the second rectifier tube Q sr2Alternating conduction forms a current loop inside the low-voltage synchronous rectifier circuit, charging the freewheeling inductor L from the low-voltage source. At this time, the primary side of the transformer obtains energy and is rectified through the high-voltage full bridge, thereby enabling the DC-DC converter to invert the input low-voltage DC power supply into a low-voltage AC power supply and couple it into a high-voltage AC power supply. On the high-voltage side, the high-voltage AC power supply is rectified into a high-voltage DC power supply for output, thus realizing the conversion from low-voltage DC to high-voltage DC.

[0207] The present invention also proposes a new energy vehicle, including the above-mentioned DC / DC converter. The specific structure of the DC / DC converter is as described in the above embodiments. Since the new energy vehicle adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.

[0208] This invention also proposes a computer-readable storage medium storing a computer program. When executed by a processor, this computer program implements the various processes of the above-described active clamping circuit parameter calculation method embodiment and achieves the same technical effect. To avoid repetition, it will not be described again here. The computer-readable storage medium may be a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0209] The above description is merely an optional embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for calculating the parameters of an active clamping circuit, characterized in that, Applied in a DC / DC converter, the DC / DC converter includes an active clamping circuit and a DC / DC module, and the DC / DC converter has a BUCK mode; the method includes: Obtain the plateau voltage of the clamping capacitor, wherein the plateau voltage is the voltage of the clamping capacitor when it reaches a steady state in the BUCK mode; The first device parameters are calculated based on the relationship between the first device parameters of the clamping capacitor and the platform voltage; The step of obtaining the platform voltage of the clamping capacitor includes: Obtain the maximum high-voltage input voltage and the primary-secondary turns ratio of the transformer in the BUCK mode, wherein the maximum high-voltage input voltage is the bus voltage on the high-voltage side of the DC / DC module in the BUCK mode; The platform voltage is obtained based on the maximum high-voltage input voltage and the primary-secondary turns ratio of the transformer; The method further includes: The second device parameters are calculated based on the relationship between the second device parameters of the clamping transistor and the platform voltage; The DC / DC converter also has a BOOST mode, and the method further includes: Obtain the maximum charging current and inductor current ripple coefficient in the BOOST mode, wherein the maximum charging current is the maximum current on the low-voltage side of the DC / DC module in the BOOST mode, and the inductor current ripple coefficient is the ripple coefficient of the freewheeling inductor on the low-voltage side. The third device parameters are calculated based on the relationship between the third device parameters of the clamping transistor and the maximum charging current and the inductor current ripple coefficient. The method further includes: The fourth device parameter is calculated based on the relationship between the fourth device parameter of the clamping capacitor and the first device parameter and the third device parameter; The first device parameter includes the current or voltage of the clamping capacitor, the second device parameter includes the drain-source voltage of the clamping transistor, the third device parameter includes the forward current of the body diode of the clamping transistor, and the fourth device parameter includes the capacitance value of the clamping capacitor.

2. The parameter calculation method for the active clamping circuit as described in claim 1, characterized in that, The step of calculating the fourth device parameter based on the relationship between the fourth device parameter of the clamping capacitor and the first device parameter and the third device parameter includes: The maximum value of the fourth device parameter is calculated based on the relationship between the fourth device parameter and the third device parameter; The minimum value of the fourth device parameter is calculated based on the relationship between the fourth device parameter and the first device parameter. The fourth device parameter is obtained based on the maximum value and the minimum value of the fourth device parameter.

3. The parameter calculation method for the active clamping circuit as described in claim 2, characterized in that, The step of calculating the maximum value of the fourth device parameter based on the relationship between the fourth device parameter and the third device parameter includes: The charging current of the clamping capacitor in the BUCK mode is obtained, and the charging current of the clamping capacitor has a functional relationship with the fourth device parameter; The maximum value of the fourth device parameter is calculated based on the relationship between the charging current of the clamping capacitor and the third device parameter.

4. The parameter calculation method for the active clamping circuit as described in claim 3, characterized in that, The step of obtaining the charging current of the clamping capacitor in the BUCK mode includes: The maximum high voltage input voltage, the transformer primary and secondary turns ratio, the freewheeling inductor, the transformer leakage inductance, the primary winding resistance, and the initial pulse width are obtained under the BUCK mode. The maximum high voltage input voltage is the bus voltage on the high voltage side of the DC / DC module under the BUCK mode, and the initial pulse width is the initial drive pulse width of the high voltage side switching transistor. Based on the fourth device parameters, the maximum high voltage input voltage, the transformer primary and secondary turns ratio, the freewheeling inductance, the transformer leakage inductance, the primary winding resistance value, and the initial pulse width, the charging current of the clamping capacitor in the BUCK mode is obtained.

5. The parameter calculation method for the active clamping circuit as described in claim 2, characterized in that, The step of calculating the minimum value of the fourth device parameter based on the relationship between the fourth device parameter and the first device parameter includes: Obtain the freewheeling current and maximum low-voltage input voltage in the BOOST mode, and the inductance value of the freewheeling inductor, wherein the freewheeling current is the current of the freewheeling inductor in the BOOST mode, and the maximum low-voltage input voltage is the maximum input voltage on the low-voltage side in the BOOST mode; The minimum value of the fourth device parameter is calculated based on the first device parameter, the maximum low-voltage input voltage, the freewheeling current, and the inductance value of the freewheeling inductor.

6. The parameter calculation method for the active clamping circuit as described in claim 5, characterized in that, The step of obtaining the freewheeling current in the BOOST mode includes: In the BOOST mode, if the duty cycle of the control rectifier is less than the preset duty cycle, the maximum and minimum values ​​of the freewheeling current are obtained according to the maximum charging current and the inductor current ripple coefficient, respectively. In the BOOST mode, if the duty cycle of the rectifier is greater than the preset duty cycle, the maximum value of the freewheeling current is obtained based on the maximum charging current and the inductor current ripple coefficient.

7. The parameter calculation method for the active clamping circuit as described in claim 6, characterized in that, The step of calculating the minimum value of the fourth device parameter based on the first device parameter, the maximum low-voltage input voltage, the freewheeling current, and the inductance value of the freewheeling inductor further includes: If the duty cycle of the rectifier is controlled to be less than the preset duty cycle, the first minimum value of the fourth device parameter is calculated based on the first device parameter, the maximum low-voltage input voltage, the inductance value of the freewheeling inductor, and the maximum and minimum values ​​of the freewheeling current. If the duty cycle of the rectifier is controlled to be greater than the preset duty cycle, the charging current frequency of the clamping capacitor and the duty cycle of the rectifier are obtained; the maximum charging time of the clamping capacitor is obtained based on the charging current frequency and the duty cycle of the rectifier; the second minimum value of the fourth device parameter is calculated based on the first device parameter, the maximum low-voltage input voltage, the maximum value of the freewheeling current, the maximum charging time, and the duty cycle of the rectifier. The minimum value of the fourth device parameter is obtained based on the first minimum value of the fourth device parameter and / or the first minimum value of the fourth device parameter.

8. A parameter calculation device for an active clamping circuit, characterized in that, The parameter calculation method for the active clamping circuit as described in any one of claims 1 to 7 is applied to a DC / DC converter, wherein the DC / DC converter includes an active clamping circuit and a DC / DC module, and the DC / DC converter has a BUCK mode; the device includes: The data acquisition module is used to acquire the platform voltage of the clamping capacitor, wherein the platform voltage is the voltage of the clamping capacitor when it reaches a steady state in the BUCK mode; The parameter calculation module is used to calculate the first device parameter based on the relationship between the first device parameter of the clamping capacitor and the platform voltage.

9. A controller, applied in a DC / DC converter, characterized in that, It includes a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the parameter calculation method for the active clamping circuit according to any one of claims 1-7.

10. A DC / DC converter, characterized in that, The system includes the controller, DC / DC module, and active clamping circuit as described in claim 9, wherein the output terminal of the controller is connected to the controlled terminal of the DC / DC module and the controlled terminal of the active clamping circuit, respectively; the DC / DC module and the active clamping circuit are electrically connected.

11. The DC / DC converter as described in claim 10, characterized in that, The DC / DC module includes a high-voltage full-bridge rectifier, an isolation transformer, a low-voltage synchronous rectifier circuit, and a filter circuit connected in sequence. The active clamping circuit includes a first clamping transistor, a second clamping transistor, and a clamping capacitor. The first end of the first clamping transistor is connected to the first end of the secondary winding of the isolation transformer. The first end of the second clamping transistor is connected to the second end of the secondary winding of the isolation transformer. The second ends of the first clamping transistor and the second clamping transistor are respectively connected to the first end of the clamping capacitor. The controlled ends of the first clamping transistor and the second clamping transistor are respectively connected to the output end of the controller. The second end of the clamping capacitor is grounded.

12. A new energy vehicle, characterized in that, Includes the DC / DC converter as described in claim 10 or 11.

13. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method described in any one of claims 1-7.

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