CN116317463A

CN116317463A - Parameter calculation method and device of active clamp circuit, controller, DC/DC converter, new energy automobile and storage medium

Info

Publication number: CN116317463A
Application number: CN202310306043.1A
Authority: CN
Inventors: 姜礁
Original assignee: Huichuan New Energy Vehicle Technology Shenzhen Co ltd
Current assignee: Huichuan New Energy Vehicle Technology Shenzhen Co ltd
Priority date: 2023-03-21
Filing date: 2023-03-21
Publication date: 2023-06-23

Abstract

The invention 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, wherein the method comprises the following steps: acquiring a platform voltage of a clamp capacitor, wherein the platform voltage is a voltage when the clamp capacitor reaches a steady state in the BUCK mode; calculating a first device parameter of the clamp capacitor according to the relation between the first device parameter and the platform voltage; the technical scheme of the invention aims to solve the problems of inaccurate and low efficiency of the existing active clamp circuit design method and provides a design method which is accurate in calculation and has a bidirectional DC/DC converter.

Description

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

Technical Field

The invention relates to the field of active clamp circuits, in particular to a parameter calculation method, a device, a controller, a DC/DC converter, a new energy automobile and a storage medium of an active clamp circuit.

Background

At present, in the actual application scene of the vehicle-mounted DC/DC converter, an active clamping circuit is generally added in the vehicle-mounted DC/DC converter, so that voltage spikes can be effectively restrained. However, as the functional requirements of new energy vehicles are increasing, for example, the on-board DC/DC converter is required to be able to operate in multiple operation modes, the design of the active clamp circuit is also required to be suitable for different operation modes of the on-board DC/DC converter.

However, when the device of the active clamp circuit is selected, the proper device parameters are usually selected after being estimated according to the experience of an engineer and being debugged for many times, and the device parameters are selected only through the experience estimation due to different circuit performances according to different working modes, so that the problem that the device parameters are not accurately selected often occurs, the active clamp circuit cannot be suitable for different working modes of the vehicle-mounted DC/DC converter, the vehicle-mounted DC/DC converter is damaged, and the problem that the efficiency of determining the device parameters is lower due to more debugging steps is also caused.

Disclosure of Invention

The invention mainly aims to provide a parameter calculation method, a device, a controller, a DC/DC converter, a new energy automobile and a storage medium of an active clamp circuit, and aims to solve the problems of inaccurate and low efficiency of the existing active clamp circuit design method, and provides a design method which is accurate in calculation and has a bidirectional DC/DC converter.

In order to achieve the above objective, the present invention provides a method for calculating parameters of an active clamp circuit, which is applied to a DC/DC converter, wherein the DC/DC converter includes an active clamp circuit and a DC/DC module, and the DC/DC converter has a BUCK mode; the method comprises the following steps:

Acquiring a platform voltage of a clamp capacitor, wherein the platform voltage is a voltage when the clamp capacitor reaches a steady state in the BUCK mode;

and calculating the first device parameter according to the relation between the first device parameter of the clamping capacitor and the platform voltage.

Optionally, the step of acquiring the platform voltage of the clamping capacitor includes:

obtaining the maximum high-voltage input voltage and the primary and secondary side turn ratio of the transformer in the BUCK mode, wherein the maximum high-voltage input voltage is the bus voltage of the high-voltage side of the DC/DC module in the BUCK mode;

and obtaining the platform voltage according to the maximum high-voltage input voltage and the primary and secondary side turn ratio of the transformer.

Optionally, the method further comprises:

and calculating a second device parameter of the clamping tube according to the relation between the second device parameter and the platform voltage.

Optionally, the DC/DC converter further has a BOOST mode, and the method further includes:

obtaining the maximum charging current and the inductance current ripple coefficient in the BOOST mode, wherein the maximum charging current is the maximum current of the low-voltage side of the DC/DC module in the BOOST mode, and the inductance current ripple coefficient is the ripple coefficient of the freewheeling inductor of the low-voltage side;

And calculating a third device parameter of the clamping tube according to the relation between the third device parameter of the clamping tube, the maximum charging current and the inductance current ripple coefficient.

Optionally, the method further comprises:

and calculating a fourth device parameter of the clamp capacitor according to the relation between the fourth device parameter and the first and third device parameters.

Optionally, the step of calculating the fourth device parameter according to the relationship between the fourth device parameter of the clamp capacitor and the first and third device parameters includes:

calculating a maximum value of the fourth device parameter according to the relation between the fourth device parameter and the third device parameter;

calculating a minimum value of the fourth device parameter according to the relation between the fourth device parameter and the first device parameter;

and obtaining the fourth device parameter according to the maximum value of the fourth device parameter and the minimum value of the fourth device parameter.

Optionally, the step of calculating a maximum value of the fourth device parameter according to a relation between the fourth device parameter and the third device parameter includes:

Acquiring the charging current of the clamping capacitor in the BUCK mode, wherein the charging current of the clamping capacitor has a functional relation with the fourth device parameter;

and calculating the maximum value of the fourth device parameter according to the relation between the charging current of the clamping capacitor and the third device parameter.

Optionally, the step of obtaining the charging current of the clamp capacitor in the BUCK mode includes:

obtaining the maximum high-voltage input voltage, the primary-secondary turn ratio of a transformer, the follow current inductance, the leakage inductance of the transformer, the resistance value of a primary winding and an initial pulse width in the BUCK mode, wherein the maximum high-voltage input voltage is the bus voltage of the high-voltage side of the DC/DC module in the BUCK mode, and the initial pulse width is the initial driving pulse width of a switching tube of the high-voltage side;

and acquiring the charging current of the clamping capacitor in the BUCK mode according to the fourth device parameter, the maximum high-voltage input voltage, the primary and secondary side turn ratio of the transformer, the follow current inductance, the transformer leakage inductance, the primary side winding resistance value and the initial pulse width.

Optionally, the step of calculating the minimum value of the fourth device parameter according to the relation between the fourth device parameter and the first device parameter includes:

Obtaining a follow current in the BOOST mode, a maximum low-voltage input voltage and an inductance value of the follow current inductor, wherein the follow current is the current of the follow current inductor in the BOOST mode, and the maximum low-voltage input voltage is the maximum input voltage of the low-voltage side in the BOOST mode;

and calculating the minimum value of the fourth device parameter according to the first device parameter, the maximum low-voltage input voltage, the freewheel current and the inductance value of the freewheel inductor.

Optionally, the step of obtaining the freewheel current in the BOOST mode includes:

in the BOOST mode, if the duty ratio of the control rectifier tube is smaller than a preset duty ratio, respectively acquiring the maximum value and the minimum value of the follow current according to the maximum charging current and the inductance current ripple coefficient;

and in the BOOST mode, if the duty ratio of the rectifying tube is controlled to be larger than the preset duty ratio, acquiring the maximum value of the follow current according to the maximum charging current and the inductance current ripple coefficient.

Optionally, the step of calculating the minimum value of the fourth device parameter according to the first device parameter, the maximum low voltage input voltage, the freewheel current and the inductance value of the freewheel inductor further includes:

If the duty ratio of the rectifying tube is controlled to be smaller than the preset duty ratio, calculating a first minimum value of the fourth device parameter according to the first device parameter, the maximum low-voltage input voltage, the inductance value of the follow current inductor, the maximum value and the minimum value of the follow current;

if the duty ratio of the rectifying tube is controlled to be larger than the preset duty ratio, the charging current frequency of the clamping capacitor and the duty ratio of the rectifying tube are obtained; obtaining the maximum charging time of the clamping capacitor according to the charging current frequency and the duty ratio of the rectifying tube; calculating a second minimum value of the fourth device parameter according to the first device parameter, the maximum low-voltage input voltage, the maximum value of the freewheel current, the maximum charging time and the duty cycle of the rectifying tube;

and acquiring the minimum value of the fourth device parameter according to the first minimum value of the fourth device parameter and/or the first minimum value of the fourth device parameter.

The invention also provides a parameter calculation device of the active clamp circuit, which is applied to a DC/DC converter, wherein the DC/DC converter comprises the active clamp circuit and a DC/DC module, and the DC/DC converter has a BUCK mode; the device comprises:

The data acquisition module is used for acquiring the platform voltage of the clamp capacitor, wherein the platform voltage is the voltage when the clamp capacitor reaches a steady state in the BUCK mode;

and the parameter calculation module is used for calculating the first device parameter according to the relation between the first device parameter of the clamping capacitor and the platform voltage.

The invention also provides a controller which is applied to the DC/DC converter and comprises a memory and a processor, wherein the memory stores a computer program, and the processor realizes the parameter calculation method of the active clamp circuit when executing the computer program.

The invention also provides a DC/DC converter which comprises the controller, a DC/DC module and an active clamping circuit, wherein the output end of the controller is respectively connected with the controlled end of the DC/DC module and the controlled end of the active clamping circuit; the DC/DC module and the active clamp circuit are electrically connected.

Optionally, the DC/DC module comprises a high-voltage full bridge, an isolation transformer, a low-voltage synchronous rectification circuit and a filter circuit which are sequentially connected;

the active clamp circuit comprises a first clamp tube, a second clamp tube and a clamp capacitor, wherein a first end of the first clamp tube is connected with a first end of a secondary winding of the isolation transformer, a first end of the second clamp tube is connected with a second end of the secondary winding of the isolation transformer, a second end of the first clamp tube and a second end of the second clamp tube are respectively connected with a first end of the clamp capacitor, a controlled end of the first clamp tube and a controlled end of the second clamp tube are respectively connected with an output end of the controller, and a second end of the clamp capacitor is grounded.

The invention also provides a new energy automobile, which comprises the DC/DC converter.

The invention also proposes a computer-readable storage medium, on which a computer program is stored, which computer program, when being executed by a processor, implements the steps of the method described above.

The parameter calculation method is used for carrying out device model selection on the active clamp circuit of the DC/DC converter, and calculating the device parameter of the active clamp circuit according to the input voltage value, the input current value, the output voltage value and the output current value of the DC/DC converter in different working modes and the relation between the input voltage value, the input current value, the output voltage value and the output current value and the device parameter; therefore, when the device of the active clamp circuit is selected, proper device parameters can be selected according to the input and output required by the known DC/DC module, the experience requirement of engineers is reduced, multiple tests are not required, the difficulty of the active clamp circuit in the device selection is reduced, and the accuracy and the efficiency of the active clamp circuit design are improved.

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 in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a block flow diagram of an embodiment of a method for calculating parameters of an active clamp circuit according to the present invention;

FIG. 2 is a block flow diagram of the sub-steps involved in step S100 of FIG. 1;

FIG. 3 is a block flow diagram of another embodiment of a method for calculating parameters of an active clamp circuit according to the present invention;

FIG. 4 is a block flow diagram of a method for calculating parameters of an active clamp circuit according to another embodiment of the present invention;

FIG. 5 is a block flow diagram of a method for calculating parameters of an active clamp circuit according to another embodiment of the present invention;

FIG. 6 is a block flow diagram of the sub-steps involved in step S600 of FIG. 5;

fig. 7 is a flow chart of the sub-steps involved in step S610 in fig. 6;

fig. 8 is a flow chart of the sub-steps included in step S611 in fig. 7;

fig. 9 is a flow chart of the sub-steps involved in step S620 in fig. 6;

fig. 10 is a flow chart of the sub-steps included in step S621 in fig. 9;

fig. 11 is a flow chart of the sub-steps included in step S622 in fig. 9;

fig. 12 is a schematic circuit diagram of a DC/DC converter according to an embodiment of the invention;

FIG. 13 is a schematic diagram illustrating a power flow of an embodiment of a DC/DC converter according to the present invention;

FIG. 14 is a schematic diagram showing a power flow of another embodiment of the DC/DC converter of the present invention;

FIG. 15 is a schematic diagram illustrating a power flow of a DC/DC converter according to another embodiment of the present invention;

FIG. 16 is a schematic diagram of an equivalent circuit of an embodiment of a DC/DC converter according to the present invention;

FIG. 17 is a block diagram illustrating a circuit configuration of a parameter calculation device of an active clamp circuit according to another embodiment of the present invention;

fig. 18 is a block diagram illustrating a circuit configuration of an embodiment of a controller according to the present invention.

Reference numerals illustrate:

the achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.

Detailed Description

The following description of the embodiments of the present invention 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 embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It should be noted that, if directional indications (such as up, down, left, right, front, and rear … …) are included in the embodiments of the present invention, the directional indications are merely used to explain the relative positional relationship, movement conditions, etc. between the components in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indications are correspondingly changed.

In addition, if there is a description of "first", "second", etc. in the embodiments of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention.

The invention provides a parameter calculation method of an active clamp circuit.

In the practical application scene of the vehicle-mounted DC/DC converter, an active clamping circuit is added in the vehicle-mounted DC/DC converter generally, so that voltage spikes can be effectively restrained. However, as the functional requirements of new energy vehicles are increasing, for example, the on-board DC/DC converter is required to be able to operate in multiple operation modes, the design of the active clamp circuit is also required to be suitable for different operation modes of the on-board DC/DC converter.

In order to solve the above-mentioned problems, referring to fig. 1 and 12, in one embodiment, the DC/DC converter is applied to a DC/DC converter, the DC/DC converter includes an active clamp circuit and a DC/DC module, and the DC/DC converter has a BUCK mode;

it should be noted that the DC/DC converter used in the present invention may be a BUCK-BOOST topology circuit, and in other embodiments, a BUCK-BOOST topology circuit is taken as an example, that is, a BUCK-BOOST topology, where the BUCK-BOOST converter is a single-tube non-isolated DC converter whose output voltage may be lower or higher than the input voltage, but whose polarity of the output voltage is opposite to the input voltage. The BUCK-BOOST converter can be regarded as a series connection of a BUCK converter and a BOOST converter, and a switching tube and a clamping circuit thereof are combined. Therefore, the high-voltage power supply comprises a high-voltage full-bridge, a transformer and a low-voltage synchronous rectification circuit, and is used for carrying out step-down output on an accessed high-voltage power supply, wherein the transformer comprises a turn number N _p The secondary winding comprises an upper secondary winding and a lower secondary winding, the turns of the upper secondary winding and the lower secondary winding are N _s Primary-secondary side turn ratio N of transformer _ps By N _p /N _s And (3) representing.

The method comprises the following steps:

step S100, obtaining the platform voltage of the clamping capacitor, wherein the platform voltage is the voltage when the clamping capacitor reaches a steady state in a BUCK mode;

in the present embodiment, the platform voltage U of the capacitor is clamped _clamp The acquisition may be performed by a voltage detection circuit of the ADC function.

When the DC/DC converter works in BUCK mode, the platform voltage U of the capacitor is clamped _clamp The clamping voltage of the clamping tube is determined, in one period, when different loops in the high-voltage full bridge are conducted, the transformer transmits energy to a circuit connected with the secondary windings, the upper secondary winding and the lower secondary winding of the transformer work alternately, the center tap of the transformer is always positive, and the low-voltage synchronous rectification current is caused when the upper secondary winding and the lower secondary winding of the transformer work alternatelyThe voltage stress of the rectifying devices at both ends of the secondary winding of the transformer rises due to incomplete discharge of the free-wheeling current, for example, as shown in fig. 12 and 13, when the first primary switching tube Q in the high-voltage full bridge ₁ And a fourth primary side switching tube Q ₄ When closed, the transformer transmits energy to the secondary side connected circuit, and the first rectifying tube Q of the low-voltage synchronous rectifying circuit _sr1 Conducting, second rectifying tube Q _sr2 Disconnecting the transformer from the first rectifying tube Q _sr1 The loop receives energy, the center tap of the transformer is the positive pole, the first rectifying tube Q _sr1 The drain electrode of (2) is the negative electrode, and the current flows from the negative electrode to the positive electrode. When the first primary side switch tube Q ₁ And a fourth primary side switching tube Q ₄ After the turn-off, the transformer stops transmitting energy, and the follow current inductance L passes through the first rectifying tube Q at two ends of the secondary winding _sr1 And a second rectifying tube Q _sr2 The secondary winding of the transformer is free from induced potential due to flux neutralization. When the second primary side switch tube Q ₂ And a third primary side switch tube Q ₃ Before ready to be conducted, the first rectifying tube Q _sr1 First turn off, at which time freewheeling is performed through its body diode. When the second primary side switch Q ₂ And a third primary side switch tube Q ₃ After conduction, the transformer transmits energy, and at the moment, the second rectifying tube Q _sr2 Conducting and the first rectifying tube Q _sr1 And (5) disconnecting. The center tap of the transformer is the positive electrode, and the second rectifying tube Q _sr2 The drain electrode of (2) is the negative electrode, and the current flows from the negative electrode to the positive electrode. The direction of the induced potential on the lower secondary winding of the transformer is shown by the dotted arrow in fig. 13, resulting in a first rectifier tube Q _sr1 The DS (Drain and Source) voltage stress rises across.

Meanwhile, various stray inductances (including secondary side leakage inductance of the transformer, lead inductance and the like, collectively denoted as L) _k1 ) The current during the previous stage will decrease rapidly to form a large di/dt (i.e. current change rate), which is represented by voltage spike on leakage inductance, and the internal components of the low-voltage synchronous rectifying circuit, such as rectifier Q _sr1 The junction capacitances in the capacitors together form a resonance, which is accompanied by a rectifying tube Q _sr1 Reverse recovery of devices such as body diodes inComplex voltages can produce voltage stress spikes, the presence of which can cause the rectifying device to be subjected to greater voltage stresses.

If the voltage stress peak is not processed in time, the rectifying device is easy to damage, ripple is generated at the output end of the DC/DC module, and the output efficiency of the DC/DC module is reduced. Therefore, in order to suppress the voltage stress spike, a clamping capacitor needs to be introduced to clamp the voltage stress spike, and the voltage stress spike exceeds the platform voltage U of the clamping capacitor _clamp The current passes through the first clamping tube Q _c1 Or a second clamping tube Q _c2 The body diode of the rectifier device flows into the clamping capacitor, and the clamping capacitor is charged, so that the clamping effect is achieved, the voltage stress of the rectifier device is reduced, and the voltage U of the platform is reduced _clamp Is the voltage at which the clamp capacitor charges to steady state in BUCK mode. At this time, the platform voltage U of the clamp capacitor _clamp The induction voltage of the whole secondary winding of the transformer, namely the sum of the induction voltages of the upper secondary winding and the lower secondary winding of the transformer, is taken. Therefore, the designer can determine the platform voltage U required for the clamp capacitor from the required output voltage of the DC/DC converter _clamp 。

Step 200, calculating a first device parameter according to the relation between the first device parameter of the clamp capacitor and the platform voltage;

in this embodiment, the first device parameter may be a current or a voltage of the clamp capacitor, and in this embodiment, the rated voltage V of the clamp capacitor is specifically _clamp 。

In order to clamp the voltage stress peak of the clamp capacitor when absorbing the rectifying tube stress in the BUCK mode, the voltage peak potential of the inrush clamp capacitor is required to be higher than the platform voltage U of the clamp capacitor when the DC/DC converter works _clamp In order to prevent the clamping capacitor from being damaged due to overvoltage, the bearing capacity of the clamping capacitor to voltage stress peak needs to be considered, and in order to enable the clamping capacitor to be normally clamped and prolong the service life, the voltage U of the platform is required to be _clamp And rated voltage V _clamp The gap between the two voltages is not too large, the voltage U of the platform is not too large _clamp Can take the voltage not exceeding the rated voltageV _clamp 75% of the total voltage, therefore, can be determined according to the rated voltage V of the clamp capacitor when the clamp capacitor is subjected to the parameter selection _clamp With the platform voltage U _clamp The relation between the voltage and the rated voltage V of the clamping capacitor is calculated _clamp Rated voltage V _clamp With the platform voltage U _clamp The relationship between them can be expressed as:

wherein V is _clamp For rated voltage of clamping capacitor, U _clamp Is the platform voltage of the clamp capacitor.

Referring to fig. 2 and 12, in an embodiment, the step of obtaining the platform voltage of the clamp capacitor includes:

step S110, obtaining the maximum high-voltage input voltage and the primary and secondary side turn ratio of the transformer in the BUCK mode, wherein the maximum high-voltage input voltage is the bus voltage of the high-voltage side of the DC/DC module in the BUCK mode;

and step S120, obtaining the platform voltage according to the maximum high-voltage input voltage and the primary and secondary side turn ratio of the transformer.

In the present embodiment, in order to make the voltage clamped by the clamping capacitor conform to the output voltage of the DC/DC module and prevent the clamping capacitor from being damaged by overvoltage, it is necessary to set the platform voltage U of the clamping capacitor _clamp Equal to the maximum induction voltage of the secondary winding of the transformer, namely the maximum low-voltage output voltage of the DC/DC module in BUCK mode, so according to the transformation principle of the transformer, the maximum high-voltage input voltage of the DC/DC module and the primary-secondary turn ratio N of the transformer can be used _ps Obtaining the maximum low-voltage output voltage. When an engineer designs an active clamp circuit for a DC/DC module, the parameters of a transformer in the DC/DC module are known, and the maximum high-voltage input voltage U is obtained _HVmax Primary-secondary side turn ratio N of transformer _ps Wherein, because the topology is provided with a center tap, the voltage when charging the clamping capacitor is the whole secondary side voltage, and the turns of the upper secondary side winding and the lower secondary side winding are the same, the turn ratio is N when converting _ps /2. Thereby according to the maximum high voltage input voltage U _HVmax And the primary-secondary side turn ratio N of the transformer _ps Obtaining the maximum low-voltage output voltage of the DC/DC module as the platform voltage U of the clamping capacitor _clamp Obtaining the platform voltage U _clamp The voltage formula:

wherein U is _HVmax For maximum high voltage input voltage, N _ps Is the primary and secondary side turn ratio of the transformer.

Referring to fig. 12 to 15 and 3, in an embodiment, the method further comprises:

and step S300, calculating a second device parameter according to the relation between the second device parameter of the clamping tube and the platform voltage.

In this embodiment, the second device parameter may be a drain-source voltage V of the clamp _DS 。

When absorbing the rectifying tube stress in BUCK mode, if the first clamping tube Q _c1 Or a second clamping tube Q _c2 Conducting, current passing through the first clamping tube Q _c1 Or a second clamping tube Q _c2 To prevent the first clamping tube Q from flowing into the clamping capacitor _c1 Or a second clamping tube Q _c2 Breakdown by voltage stress peak overvoltage, first clamping tube Q _c1 Or a second clamping tube Q _c2 Drain-source voltage V of (2) _DS Platform voltage U greater than clamp capacitance _clamp Platform voltage U due to clamp capacitance _clamp Equal to the induced voltage of the secondary winding of the transformer, thus taking the maximum high voltage input voltage U _HVmax Calculating the critical value of the induction voltage of the secondary winding of the transformer and obtaining the drain-source voltage V of the clamping tube _DS Setting a voltage margin, wherein the margin setting of the clamping tube can be set by a designer according to requirements, and the voltage margin is not limited herein, in this embodiment, the platform voltage U _clamp Taking the voltage V not exceeding the drain-source voltage _DS 75% according to drain-source voltage V _DS With the platform voltage U _clamp The relation between the source and drain voltages V _DS ：

Wherein V is _DS Is the drain-source voltage of the clamp.

Referring to fig. 12 to 15 and fig. 4, in an embodiment, the DC/DC converter further has a BOOST mode, and the method further includes:

step S400, obtaining the maximum charging current and the inductance current ripple coefficient in the BOOST mode, wherein the maximum charging current is the maximum current of the low-voltage side of the DC/DC module in the BOOST mode, and the inductance current ripple coefficient is the ripple coefficient of the freewheeling inductor of the low-voltage side;

and S500, calculating a third device parameter according to the relation between the third device parameter of the clamping tube and the maximum charging current and inductance current ripple coefficient.

In the present embodiment, the third device parameter is specifically the body diode forward current I of the clamp _SD 。

When an engineer designs an active clamp circuit for a DC/DC module, the parameters of the follow current inductance L in the DC/DC module are known, so that the corresponding current inductance ripple coefficient r can be obtained according to the follow current inductance L. The common design rule is that the inductor current ripple is designed to be about 30% of the average current of the freewheeling inductor L, and the engineer can also select The current inductance ripple coefficient r is actually required to be adjusted. Maximum charging current I _BOOST In order to obtain the maximum input current when the low-voltage side of the DC/DC module is charged to the high-voltage side in the BOOST mode, the inductance current ripple coefficient r is taken, and the ripple wave comprises a positive half wave and a negative half wave, so that the maximum charging current I is considered by taking the inductance current ripple _BOOST The inductor current ripple coefficient r is divided by 2, and a coefficient A, such as 1.2, is multiplied by considering the actual condition of non-current sharing, and this value must be smaller than the body diode forward current I of the selected clamp _SD The method comprises the steps of carrying out a first treatment on the surface of the Therefore, according to the body diode forward current I of the clamping tube _SD And maximum charging current I _BOOST And the inductance current ripple coefficient r to obtain the forward current I of the body diode _SD ：

Wherein I is _SD For the forward current of the body diode of the clamping tube, I _BOOST And r is the ripple coefficient of the inductance current for the maximum charging current.

Referring to fig. 12 to 15 and 5, in an embodiment, the method further comprises:

step S600, calculating a fourth device parameter according to the relation between the fourth device parameter of the clamping capacitor, the first device parameter and the third device parameter.

In this embodiment, the fourth device parameter may specifically be a capacitance value C of the clamp capacitor _clamp 。

It should be noted that, when the DC/DC module is started, the input voltage is gradually increased in a short time, and the process of gradually increasing the voltage from 0 to the input voltage value is the start-up stage of the DC/DC module. When the BOOST mode is started, the DC/DC module is divided into two stages: in the first stage, the driving duty ratio of the secondary rectifying tube is less than 50%. At this time, when the secondary rectifying tube Q _sr1 When the secondary side low-voltage source is switched on, the secondary side low-voltage source transmits energy to the primary side through the follow current inductor L, and the secondary side low-voltage source is connected with the primary side low-voltage source through the follow current inductor L _HV And (5) pre-charging. At this time, there is a relationship:

U _HV ＝U _LV ·N _ps ·2D

u in _HV U for the high-side voltage output by the DC/DC module in the BOOST mode _LV For the low-side voltage input by the DC/DC module in the BOOST mode, N _ps The primary and secondary side turn ratio of the transformer is obtained, and D is the duty ratio of the rectifying tube. When the rectifying tube is turned off, the secondary side low-voltage side does not transmit energy to the primary side, and the current of the freewheeling inductor L passes through the first clamping tubes Q at two sides _c1 Second clamping tube Q _c2 The body diode of (1) charges the clamping capacitor with freewheeling.

In the second stage, the driving duty ratio of the secondary rectifying tube is more than 50%. At this time, when the primary rectifying tube Q of the secondary side of the transformer _sr1 And a second rectifying tube Q _sr2 And when the power supply is simultaneously turned on, the secondary side low-voltage source stores energy through the follow current inductor L. The secondary side of the transformer does not generate an induced potential due to flux neutralization. The process is boosted by energy storage of the follow current inductor L, and the following relations exist:

When rectifying tube Q _sr1 And Q _sr2 The larger the duty cycle, the longer the charging time of the freewheeling inductor L is represented by the low-voltage source, the higher the high-side voltage, and the larger the inductor ripple current. When Q is _sr1 When the transformer is turned off, the low-voltage secondary side transmits energy to the primary side through the transformer. As shown in fig. 11, the induced potential at the secondary side of the transformer is e+ and passes through the first clamp Q _c1 Absorption rectifying tube Q _sr1 Is a stress of the steel sheet and the energy of induced potential. This instant flows through the first clamping tube Q _c1 The current of the body diode being rectifier Q _sr1 The current at turn-on, i.e., half of the freewheeling inductor L current. The free-wheeling inductor L current then rapidly passes through Q _sr2 To the primary side, and then the first clamping tube Q _c1 Conducting, releasing the absorbed energy back to the circuit.

Thus, the first clamping tube Q is selected _c1 Second clamping tube Q _c2 In the case of consideration of the first clamp Q _c1 Second clamping tube Q _c2 The load-carrying capacity of the freewheeling current is also that in the BOOST mode, when the duty ratio of the rectifying tube is less than 50%, the freewheeling energy of the freewheeling inductance L is absorbed by the clamping capacitor, so that the DC/DC module is selected to flow through the first clamping tube Q when the BOOST mode is operated _c1 Second clamping tube Q _c2 Wherein the charging current is affected by the existence of the inductance current ripple coefficient r of the freewheeling inductor L, and thus the first clamping tube Q is considered _c1 Second clamping tube Q _c2 When the load carrying capacity of the follow current is to be improved, the inductance current ripple coefficient r and the maximum charging current I need to be comprehensively considered _BOOST To increase the value of the first clamping tube Q _c1 Second clamping tube Q _c2 Reliability during freewheel.

In addition to preventing the first clamping tube Q _c1 Second clamping tube Q _c2 Overcurrent breakdown, so that the charging current in the energy absorption charging process of the clamping capacitor in the BOOST mode cannot exceed the forward current I of the body diode of the clamping tube _SD Therefore, when the parameters of the clamp capacitor are selected, the capacitor value C can be used as the reference value _clamp Charging current, body diode forward current I of clamping tube _SD The relation between the capacitance values is selected to satisfy the condition, and the capacitance value C is selected _clamp In this case, the stage voltage U of the clamp capacitor is also required to be considered _clamp Platform voltage U _clamp Is selected and the rated voltage V of the clamping capacitor _clamp In relation to this, therefore, when selecting the parameters of the clamp capacitance, the capacitance value C can be used _clamp Platform voltage U _clamp Rated voltage V _clamp The relation between the two values is selected to satisfy the condition, and the capacitance C of the required clamping capacitor can be selected from the range of the two values _clamp 。

Referring to fig. 12 to 15 and fig. 6, in one embodiment, the step of calculating a fourth device parameter according to a relationship between the fourth device parameter of the clamp capacitor and the first and third device parameters includes:

Step S610, calculating the maximum value of the fourth device parameter according to the relation between the fourth device parameter and the third device parameter;

step S620, calculating the minimum value of the fourth device parameter according to the relation between the fourth device parameter and the first device parameter;

step S630, obtaining the fourth device parameter according to the maximum value and the minimum value of the fourth device parameter.

In this embodiment, when the clamp capacitor absorbs the rectifying tube stress in the BUCK mode, the platform voltage U of the clamp capacitor _clamp Is equal to the induction voltage of the secondary winding, thus taking the maximum high voltage input voltage U _HVmax Calculating the critical value of secondary winding induced voltage and platform voltage U _clamp Taking not to exceed rated voltage V _clamp 75% of the nominal voltage V _clamp ：

Wherein U is _HVmax For maximum high voltage input voltage, N _ps For the primary-secondary side turn ratio N of the transformer _ps 。

When the active clamp circuit is designed based on BUCK mode, the main consideration is that the input end charges the clamp capacitor when the high voltage is suddenly changed or the power is started, so that the instant charging current when the DC/DC converter is started can exceed the first clamp tube Q _c1 Second clamping tube Q _c2 The current capacity of (1) causes the first clamping tube Q _c1 Second clamping tube Q _c2 Damage to the first clamp Q so that the current does not exceed _c1 Second clamping tube Q _c2 The current capacity, the clamping capacitance cannot be too large, so that according to the first clamping tube Q _c1 Second clamping tube Q _c2 The current capacity of (2) determines the capacitance value C of the clamping capacitor _clamp I.e. according to capacitance C _clamp Charging current, body diode forward current I of clamping tube _SD Relationship between each other, determine capacitance value C _clamp Maximum C of (2) _{clamp_max} . When designing an active clamp circuit based on the BOOST mode, the main consideration is that the current of the freewheeling inductor on the low-voltage side passes through the first clamp Q _c1 Second clamping tube Q _c2 When flowing to the clamping capacitor, the leakage inductance L of the transformer _r The DC/DC module charges the clamping capacitor through the leakage inductance of the transformer during starting up to enable the clamping capacitor to generate voltage ripple and act together with the freewheel inductor L and the primary winding resistance value R to enable the starting up waveform to approximate a step signal, and the voltage ripple formula DeltaV=Q is adopted _clamp /C _clamp And the voltage ripple of the clamping capacitor cannot exceed the rated value, so the capacitance value C of the clamping capacitor _clamp Cannot be too small to determine the capacitance value C _clamp Minimum value C of (2) _{clamp_min} Finally, from the capacitance value C of the clamping capacitor _clamp Maximum C of (2) _{clamp_max} And minimum value C _{clamp_min} The clamp capacitance capacity is determined within the range of (2).

Referring to fig. 12 to 15 and 7, in one embodiment, the step of calculating the maximum value of the fourth device parameter according to the relationship between the fourth device parameter and the third device parameter includes:

Step S611, obtaining the charging current of the clamping capacitor in the BUCK mode, wherein the charging current of the clamping capacitor has a functional relation with the fourth device parameter;

step S612, calculating the maximum value of the fourth device parameter according to the relation between the charging current of the clamping capacitor and the third device parameter.

In this embodiment, in the BUCK mode, the clamp capacitor is charged through the leakage inductance of the transformer when the high-side input voltage starts up, and the start-up waveform can be regarded as a step signal approximately, so that the clamp capacitor cannot be excessively large, otherwise, the instantaneous charging current during start-up will exceed the first clamp tube Q _c1 Second clamping tube Q _c2 The current capacity of (1) causes the first clamping tube Q _c1 Second clamping tube Q _c2 Damage. Taking the maximum high voltage input voltage U _HVmax Charging current I of clamping capacitor _charge And capacitance C _clamp With a functional relationship, the charging current I of the clamping capacitor _charge Body diode forward current I not exceeding clamp _SD Capacitance value C _clamp Maximum C of (2) _{clamp_max} Calculated as follows:

I _SD ≥I _charge

take the proper capacitance value C _clamp Maximum C of (2) _{clamp_max} Meets the above requirements.

Referring to fig. 12 to 15 and fig. 8, in an embodiment, the step of obtaining the charging current of the clamp capacitor in the BUCK mode includes:

step S613, obtaining the maximum high-voltage input voltage, the primary-secondary turn ratio of the transformer, the follow current inductance, the leakage inductance of the transformer, the resistance value of the primary winding and the initial pulse width, wherein the maximum high-voltage input voltage is the bus voltage of the high-voltage side of the DC/DC module in the BUCK mode, and the initial pulse width is the initial driving pulse width of the switching tube of the high-voltage side;

And step S614, obtaining the charging current of the clamping capacitor in the BUCK mode according to the fourth device parameter, the maximum high-voltage input voltage, the primary and secondary side turn ratio of the transformer, the follow current inductance, the transformer leakage inductance, the primary winding resistance value and the initial pulse width.

In this embodiment, in the BUCK mode, the high-side input voltage charges the clamp capacitor through the leakage inductance of the transformer when the power is turned on, and the power-on waveform can be regarded as a step signal approximately, so that the clamp capacitor cannot be excessively large, otherwise, the instantaneous charging current during power-on will exceed the current capacity of the clamp tube, and the clamp tube is damaged. Taking the maximum high voltage input voltage U _HVmax Charging current I of clamping capacitor _charge Body diode forward current I not exceeding clamp _SD Leakage inductance L of transformer _r . The primary winding resistance value of the transformer is R, C _clamp For converting the secondary side to the primary side clamping capacitance through a transformer, the primary side winding resistance, the converted clamping capacitance and the transformer leakage inductance L _r An equivalent circuit schematic diagram of the RLC series circuit is shown in fig. 16.

According to the equivalent circuit schematic diagram 16, and C _clamp Maximum high voltage input voltage U _HVmax Primary-secondary side turn ratio N of transformer _ps Follow current inductance L and transformer leakage inductance L _r The primary winding resistance value R and the initial pulse width b to obtain the charging current I of the clamping capacitor _charge Is a second order function of (2):

wherein, the liquid crystal display device comprises a liquid crystal display device,

i in the above _charge Is a solution to the RLC series circuit step response, C _clamp The clamping capacitance of the secondary side is converted to the clamping capacitance of the primary side through the transformer. Because the topology is provided with a center tap, the voltage when the clamping capacitor is charged is the voltage of the whole secondary winding, and the actual turn ratio is N _ps And 2, b is the initial driving pulse width of the switching tube at the high voltage side, and can be obtained according to the actual design requirement, if the starting pulse width is 40ns, the initial driving pulse width is substituted into calculation, and the charging current I of the secondary side clamping capacitor during starting can be obtained _charge 。

Therefore, according to the charging current I of the clamp capacitor _charge Body diode forward current I not exceeding clamp _SD Thereby taking a suitable capacitance value C _clamp Maximum C of (2) _{clamp_max} To meet this requirement.

Referring to fig. 12 to 15 and 9, in one embodiment, the step of calculating the minimum value of the fourth device parameter according to the relationship between the fourth device parameter and the first device parameter includes:

step S621, obtaining a follow current in a BOOST mode, a maximum low-voltage input voltage and an inductance value of a follow current inductor, wherein the follow current is the current of the follow current inductor in the BOOST mode, and the maximum low-voltage input voltage is the maximum input voltage at the low-voltage side in the BOOST mode;

Step S622, calculating the minimum value of the fourth device parameter according to the first device parameter, the maximum low voltage input voltage, the freewheel current and the inductance value of the freewheel inductor.

In the present embodiment, the main consideration is the low-side freewheeling inductance when designing the active clamp based on the BOOST modeL current through the first clamping tube Q _c1 Second clamping tube Q _c2 When flowing to the clamping capacitor, the leakage inductance L of the transformer _r The DC/DC module charges the clamping capacitor through the leakage inductance of the transformer during starting up to enable the clamping capacitor to generate voltage ripple and act together with the freewheel inductor L and the primary winding resistance value R to enable the starting up waveform to approximate a step signal, and the voltage ripple formula DeltaV=Q is adopted _clamp /C _clamp And the voltage ripple of the clamping capacitor cannot exceed the rated value, so the capacitance value C of the clamping capacitor _clamp Cannot be too small. Therefore, the voltage ripple change of the clamping capacitor cannot exceed the rated value, and the voltage V of the clamping capacitor can be determined according to the rated voltage V _clamp Maximum low voltage input voltage U _LVmax The free-wheeling current and the free-wheeling inductance L, and a proper capacitance value C is selected _clamp Minimum value C of (2) _{clamp_min} 。

Referring to fig. 12 to 15 and 10, in one embodiment, the step of obtaining the freewheel current in the BOOST mode includes:

Step S623, under the BOOST mode, if the duty ratio of the control rectifier tube is smaller than the preset duty ratio, respectively obtaining the maximum value and the minimum value of the follow current according to the maximum charging current and the inductance current ripple coefficient;

step S624, in the BOOST mode, if the duty ratio of the control rectifier tube is larger than the preset duty ratio, obtaining the maximum value of the follow current according to the maximum charging current and the inductance current ripple coefficient.

In this embodiment, when the DC/DC converter is in BOOST mode and the duty cycle of the rectifier is smaller than the preset duty cycle, the preset duty cycle may be 50%, according to the above-mentioned platform voltage U _clamp Is calculated by the formula of (C) and the high-side voltage U in this mode _HV And low-side voltage U _LV In the (a) relationship, at this time, the platform voltage U of the capacitor is clamped _clamp Less than 2U _LV The energy of the freewheeling inductor L is absorbed entirely by the clamping capacitor. The inductance current ripple coefficient r is calculated according to a larger margin, and the maximum charging current in the BOOST mode is I _BOOST The maximum value of the free-wheeling current can be calculated as followsValue I _Lmax And minimum value I _Lmin ：

Therefore, if the duty ratio of the rectifying tube is less than 50%, the rated voltage V of the clamping capacitor can be used _clamp Maximum low voltage input voltage U _LVmax Maximum value and minimum value of the follow current, follow current inductance L, capacitance value C is calculated _clamp Minimum value C of (2) _{clamp_min} 。

Of course, if the duty cycle of the rectifying tube is greater than 50%, the maximum value I of the follow current can be obtained according to the above formula _Lmax And according to rated voltage V of clamping capacitor _clamp Maximum low voltage input voltage U _LVmax The maximum value of the follow current and the follow current inductance L, and the capacitance value C is calculated _clamp Minimum value C of (2) _{clamp_min} 。

Referring to fig. 11 to 15, in an embodiment, the step of calculating the minimum value of the fourth device parameter according to the first device parameter, the maximum low voltage input voltage, the freewheel current and the inductance value of the freewheel inductor further includes:

step S625, if the duty ratio of the control rectifier tube is smaller than the preset duty ratio, calculating a first minimum value of a fourth device parameter according to the first device parameter, the maximum low-voltage input voltage, the inductance value of the follow current inductor, and the maximum and minimum values of the follow current;

step S626, if the duty ratio of the rectifying tube is controlled to be larger than the preset duty ratio, the charging current frequency of the clamping capacitor and the duty ratio of the rectifying tube are obtained; obtaining the maximum charging time of the clamping capacitor according to the charging current frequency and the duty ratio of the rectifying tube; calculating a second minimum value of the fourth device parameter according to the first device parameter, the maximum low-voltage input voltage, the maximum value of the follow current, the maximum charging time and the duty ratio of the rectifying tube;

Step S627, obtaining the minimum value of the fourth device parameter according to the first minimum value of the fourth device parameter and/or the second minimum value of the fourth device parameter.

In this embodiment, if the duty cycle of the rectifier is less than 50%, the capacitance C can be calculated according to the following formula _clamp Is the first minimum value C of (2) _clamp _min1 ：

If the duty ratio of the rectifying tube is more than 50%, the rectifying tube is switched off and instantaneously passes through the first clamping tube Q _c1 Or a second clamping tube Q _c2 Is half the current of the freewheeling inductor L. Since the charge and discharge of the clamp capacitor are approximately equal during the turn-off period of the rectifying tube, the charge current waveform is approximately triangular, the charge current frequency is f, and the maximum charge time t is:

where D is the duty cycle of the rectifier. According to the above-mentioned platform voltage U _clamp Is calculated by the formula of (C) and the high-side voltage U in this mode _HV And low-side voltage U _LV The relationship of (2) can be known the platform voltage U of the clamp capacitor _clamp Maximum value U _LVmax (1-D) the capacitance C can be calculated as follows _clamp Is the second minimum value C of (2) _{clamp_min2} ：

Therefore, the capacitance C can be selected _clamp Is the first minimum value C of (2) _{clamp_min1} Or the capacitance value C _clamp Is the second minimum value C of (2) _{clamp_min2} As capacitance C _clamp Minimum value C of (2) _{clamp_min} . In order to make the clamping capacitor suitable for the duty ratio of different rectifying tubes, the larger one of the two calculated values can be selected as the capacitance value C _clamp Minimum value C of (2) _{clamp_min} 。

To sum up, the capacitance C of the clamping capacitor _clamp Can be at C _{clamp_min} To C _{clamp_max} Is selected within the range between.

As shown in fig. 1 to 17, in one embodiment, the parameter calculating device of the active clamp circuit is applied to a DC/DC converter, wherein the DC/DC converter comprises an active clamp circuit and a DC/DC module, and the DC/DC converter has a BUCK mode; the device comprises:

the data acquisition module is used for acquiring the platform voltage of the clamp capacitor, wherein the platform voltage is the voltage when the clamp capacitor reaches a steady state in a BUCK mode;

and the parameter calculation module is used for calculating the first device parameter according to the relation between the first device parameter of the clamp capacitor and the platform voltage.

In this embodiment, the data acquisition module may employ an ADC circuit, and the parameter calculation module may include a module having a data calculation function, such as a microprocessor or a control chip.

When the DC/DC converter is operated in BUCK mode, the first primary side switch tube Q ₁ And a fourth primary side switching tube Q ₄ When closed, the transformer transmits energy to the secondary side connected circuit, and the first rectifying tube Q _sr1 Conducting, second rectifying tube Q _sr2 Disconnecting the transformer from the first rectifying tube Q _sr1 The half of the connection works, the center tap of the transformer is the positive electrode, the first rectifying tube Q _sr1 The drain electrode of the capacitor is a cathode, current flows from the cathode to the anode, and at the moment, the data acquisition module detects the output voltage of the DC/DC converter and outputs the output voltage to the parameter calculation module as the platform voltage of the clamp capacitor.

The parameter calculation module calculates the platform voltage U according to the clamping capacitor _clamp Selecting not to exceed rated voltage V _clamp 75% of the total secondary side voltage due to the center tap in the topology, the turn ratio is N _ps /2. So that the parameter calculation module calculates the maximum high voltage input voltage U according to the transformer principle _HVmax Primary-secondary side turn ratio N of transformer _ps The relation between the voltage and the platform voltage of the clamping capacitor is calculated, and the platform voltage of the clamping capacitor is calculated according to the platform voltage U _clamp And forehead (sum of sum)Constant voltage V _clamp The relation between the voltage and the rated voltage V of a proper clamping capacitor is selected _clamp ：

Wherein V is _clamp For rated voltage of clamping capacitor, U _HVmax For maximum high voltage input voltage, N _ps Is the primary and secondary side turn ratio of the transformer.

In an embodiment, the data acquisition module is configured to acquire a maximum high-voltage input voltage and a primary-secondary side turn ratio of the transformer in a BUCK mode, where the maximum high-voltage input voltage is a bus voltage on a high-voltage side of the DC/DC module in the BUCK mode;

And the parameter calculation module is used for obtaining the platform voltage according to the maximum high-voltage input voltage and the primary and secondary side turn ratio of the transformer.

In an embodiment, the parameter calculation module is further configured to calculate a second device parameter of the clamping tube according to a relationship between the second device parameter and the platform voltage.

In an embodiment, the DC/DC converter further has a BOOST mode, and the data obtaining module is configured to obtain a maximum charging current and an inductance current ripple coefficient in the BOOST mode, where the maximum charging current is a maximum current on a low-voltage side of the DC/DC module in the BOOST mode, and the inductance current ripple coefficient is a ripple coefficient of a freewheeling inductor on the low-voltage side;

and the parameter calculation module is used for calculating the third device parameter according to the relation between the third device parameter of the clamping tube, the maximum charging current and the inductance current ripple coefficient.

In an embodiment, the parameter calculating module is further configured to calculate a fourth device parameter according to a relationship between the fourth device parameter of the clamp capacitor and the first and third device parameters.

In an embodiment, the parameter calculation module is further configured to calculate a maximum value of the fourth device parameter of the switch according to a relationship between the fourth device parameter of the switch and the third device parameter of the switch; calculating the minimum value of the fourth device parameter of the switch according to the relation between the fourth device parameter of the switch and the first device parameter of the switch; and obtaining the fourth device parameter of the switch according to the maximum value and the minimum value of the fourth device parameter of the switch.

In an embodiment, the data acquisition module is configured to acquire a charging current of the switch clamp capacitor in the switch BUCK mode, where the charging current of the switch clamp capacitor has a functional relationship with a fourth device parameter of the switch;

and the parameter calculation module is used for calculating the maximum value of the fourth device parameter of the switch according to the relation between the charging current of the switch clamping capacitor and the third device parameter of the switch.

In an embodiment, the data acquisition module is configured to acquire a maximum high-voltage input voltage in a switch BUCK mode, a primary-secondary turn ratio of the transformer, a switch freewheeling inductance, a transformer leakage inductance, a primary winding resistance value, and an initial pulse width, where the maximum high-voltage input voltage of the switch is a bus voltage on a high-voltage side of the switch DC/DC module in the switch BUCK mode, and the initial pulse width of the switch is an initial driving pulse width of a switching tube on the high-voltage side of the switch;

the parameter calculation module is used for obtaining the charging current of the switch clamping capacitor in the switch BUCK mode according to the fourth device parameter of the switch, the maximum high-voltage input voltage of the switch, the primary and secondary side turn ratio of the switch transformer, the switch follow current inductance, the switch transformer leakage inductance, the resistance value of the primary side winding of the switch and the initial pulse width of the switch.

In an embodiment, the data acquisition module is configured to acquire a freewheeling current in a switch BOOST mode, a maximum low-voltage input voltage, and an inductance value of a switch freewheeling inductor, where the switch freewheeling current is a current of the switch freewheeling inductor in the switch BOOST mode, and the switch maximum low-voltage input voltage is a maximum input voltage of a switch low-voltage side in the switch BOOST mode;

and the parameter calculation module is used for calculating the minimum value of the fourth device parameter of the switch according to the first device parameter of the switch, the maximum low-voltage input voltage of the switch, the switch freewheel current and the inductance value of the switch freewheel inductance.

In an embodiment, the parameter calculation module is further configured to, in a switch BOOST mode, if a duty cycle of the control rectifier is smaller than a preset duty cycle, respectively obtain a maximum value and a minimum value of the switch freewheel current according to a maximum charging current of the switch and a ripple coefficient of the switch inductor current; and in the switch BOOST mode, if the duty ratio of the control switch rectifier tube is larger than the preset duty ratio of the switch, acquiring the maximum value of the switch freewheel current according to the maximum charging current of the switch and the ripple coefficient of the current of the switch inductor.

In an embodiment, the parameter calculating module is configured to calculate a first minimum value of a fourth device parameter of the switch according to the first device parameter of the switch, the maximum low-voltage input voltage of the switch, the inductance value of the freewheeling inductor of the switch, and the maximum and minimum values of the freewheeling current of the switch if the duty ratio of the control switch rectifier is smaller than the preset duty ratio of the switch;

The data acquisition module is used for acquiring the charging current frequency of the switch clamping capacitor and the duty ratio of the switch rectifying tube if the duty ratio of the switch rectifying tube is controlled to be larger than the preset duty ratio of the switch;

the parameter calculation module is also used for obtaining the maximum charging time of the switch clamping capacitor according to the switch charging current frequency and the duty ratio of the switch rectifying tube; calculating a second minimum value of a fourth device parameter of the switch according to the first device parameter of the switch, the maximum low-voltage input voltage of the switch, the maximum value of the follow current of the switch, the maximum charging time of the switch and the duty ratio of the switching rectifier tube; and obtaining the minimum value of the fourth device parameter according to the first minimum value of the fourth device parameter and/or the first minimum value of the fourth device parameter.

The parameter calculation device is used for carrying out device model selection on an active clamping circuit of the DC/DC converter, and calculating device parameters of the active clamping circuit according to the input voltage value, the input current value, the output voltage value and the output current value of the DC/DC converter in different working modes and the relation between the input voltage value, the input current value, the output voltage value and the output current value and the device parameters; therefore, when the device of the active clamp circuit is selected, proper device parameters can be selected according to the input and output required by the known DC/DC module, the experience requirement of engineers is reduced, multiple tests are not required, the difficulty of the active clamp circuit in the device selection is reduced, and the accuracy and the efficiency of the active clamp circuit design are improved.

The invention also provides a controller which is applied to the DC/DC converter, as shown in fig. 18, and comprises a processor, a memory and a parameter calculation program of an active clamp circuit which is stored in the memory and can run on a main control chip, wherein the parameter calculation program of the active clamp circuit realizes the steps of the parameter calculation method of the active clamp circuit when being executed by the processor, and the processor is connected with the memory. The specific process of the parameter calculation program of the active clamp circuit refers to the above embodiments, and since the controller adopts all the technical solutions of all the embodiments, at least has all the beneficial effects brought by the technical solutions of the embodiments, and will not be described in detail herein.

The invention also provides a DC/DC converter, which comprises a DC/DC module, the controller and an active clamping circuit, wherein the output end of the controller is connected with the controlled end of the active clamping circuit; the DC/DC module and the active clamp circuit are electrically connected. The specific structure of the controller refers to the above embodiments, and since the DC/DC converter adopts all the technical solutions of all the embodiments, the controller has at least all the beneficial effects brought by the technical solutions of the embodiments, and will not be described in detail herein.

Referring to fig. 12 to 16, in an embodiment, the DC/DC module includes a high voltage full bridge, an isolation transformer, a low voltage synchronous rectification circuit, and a filter circuit connected in sequence;

the active clamping circuit comprises a first clamping tube, a second clamping tube and a clamping capacitor, wherein the first end of the first clamping tube is connected with the first end of the secondary winding of the isolation transformer, the first end of the second clamping tube is connected with the second end of the secondary winding of the isolation transformer, the second end of the first clamping tube and the second end of the second clamping tube are respectively connected with the first end of the clamping capacitor, the controlled end of the first clamping tube and the controlled end of the second clamping tube are respectively connected with the output end of the controller, and the second end of the clamping capacitor is grounded.

In this embodiment, the high-voltage full bridge is used for accessing and outputting a high-voltage source;

the primary winding of the isolation transformer is connected with the output end of the high-voltage full bridge, and the secondary winding of the isolation transformer is connected with the input end of the low-voltage synchronous rectification circuit and is used for outputting the high-voltage source after the connected high-voltage source is subjected to step-down treatment; or, the connected low-voltage source is subjected to boosting treatment and then output;

the low-voltage synchronous rectification circuit is used for rectifying the high-voltage source subjected to depressurization and outputting the high-voltage source; or the low-voltage source is connected and output;

The high-voltage full bridge is also used for rectifying the boosted low-voltage source and outputting the low-voltage source;

the filter network is used for carrying out filter treatment on the high-voltage source after depressurization or the connected low-voltage source.

The high-voltage full bridge comprises a first primary side switch tube Q ₁ Second primary side switch tube Q ₂ Third primary side switch tube Q ₃ Fourth primary side switch tube Q ₄ The method comprises the steps of carrying out a first treatment on the surface of the First primary side switch tube Q ₁ Drain electrode of (d) and third primary side switch tube Q ₃ The drain electrodes of the second primary side switch tube Q are respectively connected with the positive output end of the high voltage source ₂ Source electrode of (and fourth) primary side switch tube Q ₄ The source electrodes of the first primary side switch tube Q are respectively connected with the negative output end of the high voltage source ₁ Source electrode of (and second) primary side switch tube Q ₂ The source electrodes of the third primary side switch tube Q are respectively connected with the first end of the high voltage side of the isolation transformer ₃ Drain electrode of (and fourth) primary side switch tube Q ₄ The drain electrodes of the isolation transformers are respectively connected with the second ends of the high voltage sides of the isolation transformers; first primary side switch tube Q ₁ Gate electrode of (B) and second primary side switch tube Q ₂ Gate electrode of (d), third primary side switch tube Q ₃ Gate and fourth primary side switch tube Q ₄ The grid electrodes of the two-way valve are respectively and electrically connected with the output end of the controller.

The low-voltage synchronous rectification circuit comprises a first rectifying tube Q _sr1 Second rectifying tube Q _sr2 First rectifying tube Q _sr1 A source electrode of the second rectifying tube Q is connected with a first end of the low-voltage side of the isolation transformer _sr2 A first rectifying tube Q connected with the second end of the low-voltage side of the isolation transformer _sr1 Drain electrode of (2)Second rectifying tube Q _sr2 The drains of the first rectifying tube Q are respectively grounded _sr1 Gate of (2) and second rectifying tube Q _sr2 The grid electrodes of the control unit are respectively used for being electrically connected with the output end of the controller.

The filter network comprises a follow current inductance L, an energy storage capacitor C and an electromagnetic inductance L _emc Electromagnetic capacitor C _emc The method comprises the steps of carrying out a first treatment on the surface of the The first end of the follow current inductance L is connected with the tap end of the isolation transformer, and the second end of the follow current inductance L is respectively connected with the first end of the energy storage capacitor C and the electromagnetic inductance L _emc Is connected with the first end of the electromagnetic inductor L _emc And an electromagnetic capacitor C _emc Is connected to the first end of the housing; second end of energy storage capacitor C and electromagnetic capacitor C _emc The second ends of which are respectively grounded.

Specifically, when the DC/DC converter is in BUCK mode, the high-voltage full bridge is connected to a high-voltage source, and when the high-voltage source is in positive half-wave state, the controller of the DC/DC converter controls the first primary side switching tube Q ₁ Fourth primary side switch tube Q ₄ Conducting to form a current loop in the high-voltage full bridge, so that the low-voltage synchronous rectification circuit on the secondary side of the transformer obtains energy, and a first rectifying tube Q _sr1 Conduction, induced current and first rectifying tube Q _sr1 The conducting direction of the body diode of the DC/DC converter is the same, and the current from the tap end of the transformer to the low-voltage output end is formed, and the controller of the DC/DC converter controls the second primary side switching tube Q during the negative half wave of the high-voltage source ₂ Third primary side switch tube Q ₃ Conducting to form a current loop in the high-voltage full bridge, so that the low-voltage synchronous rectification circuit on the secondary side of the transformer obtains energy, and a second rectifying tube Q _sr2 Conduction, induced current and second rectifying tube Q _sr2 The conducting directions of the body diodes are the same, and the current from the tap end of the transformer to the low-voltage output end is formed, so that the low-voltage direct current output in the BUCK mode is realized.

When the DC/DC converter is in the BOOST mode, the low-voltage synchronous rectification circuit is connected with a low-voltage source, and in the charging process, the first MOS tube Q _sw1 Second MOS transistor Q _sw2 In the BOOST mode, the first rectifying tube Q is always turned on _sr1 Second rectifying tube Q _sr2 Alternate conduction is carried out in the low-voltage synchronous rectification circuitThe DC-DC converter converts the input low-voltage DC power supply into a low-voltage AC power supply, then the low-voltage AC power supply is coupled into a high-voltage AC power supply, and the high-voltage AC power supply is rectified into a high-voltage DC power supply at the high-voltage side for output, so that the conversion from low-voltage DC to high-voltage DC is realized.

The invention also provides a new energy automobile, which comprises the DC/DC converter, and the specific structure of the DC/DC converter refers to the embodiment, and because the new energy automobile adopts all the technical schemes of all the embodiments, the new energy automobile at least has all the beneficial effects brought by the technical schemes of the embodiments, and the description is omitted herein.

The invention also provides a computer readable storage medium, on which a computer program is stored, which when executed by a processor, implements the processes of the above-mentioned parameter calculation method embodiment of the active clamp circuit, and can achieve the same technical effects, so that repetition is avoided, and no further description is given here. Among them, a computer readable storage medium such as Read-only memory (ROM), random Access Memory (RAM), magnetic disk or optical disk, and the like.

The foregoing description is only of the optional embodiments of the present invention, and is not intended to limit the scope of the invention, and all the equivalent structural changes made by the description of the present invention and the accompanying drawings or direct/indirect application in other related technical fields are included in the scope of the invention.

Claims

1. The parameter calculation method of the active clamp circuit is characterized by being applied to a DC/DC converter, wherein the DC/DC converter comprises an active clamp circuit and a DC/DC module, and the DC/DC converter has a BUCK mode; the method comprises the following steps:

2. The method of claim 1, wherein the step of obtaining the platform voltage of the clamp capacitor comprises:

3. The method of parameter calculation for an active clamp circuit of claim 1, further comprising:

4. The method of parameter calculation for an active clamp circuit of claim 1, wherein the DC/DC converter further has a BOOST mode, the method further comprising:

5. The method of parameter calculation for an active clamp circuit of claim 4, further comprising:

6. The method of calculating parameters of an active clamp circuit according to claim 5, wherein said calculating a fourth device parameter of said clamp capacitor based on a relationship between said fourth device parameter and said first and third device parameters comprises:

7. The method of calculating parameters of an active clamp circuit of claim 6, wherein said step of calculating a maximum value of said fourth device parameter based on a relationship between said fourth device parameter and said third device parameter comprises:

8. The method of calculating parameters of an active clamp circuit according to claim 7, wherein the step of obtaining a charging current of the clamp capacitor in the BUCK mode comprises:

9. The method of calculating parameters of an active clamp circuit of claim 6, wherein said step of calculating a minimum value of said fourth device parameter based on a relationship between said fourth device parameter and said first device parameter comprises:

10. The method of claim 9, wherein the step of obtaining the freewheel current in the BOOST mode comprises:

11. The method of calculating parameters of an active clamp circuit of claim 10, wherein the step of calculating a minimum value of the fourth device parameter based on the first device parameter, the maximum low voltage input voltage, the freewheel current, and an inductance value of the freewheel inductor further comprises:

12. The parameter calculation device of the active clamp circuit is characterized by being applied to a DC/DC converter, wherein the DC/DC converter comprises an active clamp circuit and a DC/DC module, and has a BUCK mode; the device comprises:

13. A controller for use in a DC/DC converter, comprising a memory and a processor, the memory storing a computer program, the processor implementing the method of calculating parameters of the active clamp circuit of any one of claims 1-11 when executing the computer program.

14. The DC/DC converter is characterized by comprising the controller, the DC/DC module and the active clamp circuit according to claim 13, wherein the output end of the controller is respectively connected with the controlled end of the DC/DC module and the controlled end of the active clamp circuit; the DC/DC module and the active clamp circuit are electrically connected.

15. The DC/DC converter of claim 14 wherein the DC/DC module comprises a high voltage full bridge, an isolation transformer, a low voltage synchronous rectification circuit, and a filtering circuit connected in sequence;

16. A new energy vehicle comprising a DC/DC converter according to claim 14 or 15.

17. A computer readable storage medium, on which a computer program is stored, characterized in that the computer program, when being executed by a processor, carries out the steps of the method according to any of the preceding claims 1-11.