CN113659843B - DCDC converter with low switching loss - Google Patents
DCDC converter with low switching loss Download PDFInfo
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- CN113659843B CN113659843B CN202111010432.7A CN202111010432A CN113659843B CN 113659843 B CN113659843 B CN 113659843B CN 202111010432 A CN202111010432 A CN 202111010432A CN 113659843 B CN113659843 B CN 113659843B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
- H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
- H02M3/33592—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/36—Means for starting or stopping converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The application relates to the technical field of DCDC converters, in particular to a DCDC converter with low switching loss. The device comprises a pre-voltage stabilizing circuit, a pre-voltage stabilizing driving circuit at the front stage, an LLC resonant conversion circuit and an LLC driving circuit; the pre-voltage stabilizing circuit is used for adjusting the input voltage to the target voltage under the control of the pre-voltage stabilizing driving circuit at the front stage; the LLC resonant conversion circuit is used for generating resonance under the action of the target voltage and enabling the frequency of the switching tube to be consistent with the resonance frequency under the control of the LLC driving circuit; the pre-stage pre-voltage stabilizing driving circuit is used for controlling the pre-voltage stabilizing circuit to output target voltage according to the fed-back output voltage; the LLC drive circuit is used for controlling the frequency of a switching tube of the LLC resonant conversion circuit so that the resonant frequency of the switching tube is consistent with that of the LLC resonant conversion circuit. The pre-voltage stabilizing circuit of the front stage can boost the input voltage to the target voltage according to the control of the pre-voltage stabilizing driving circuit of the front stage, and the LLC resonant conversion circuit can work at the optimal resonant frequency point by combining the control of the LLC driving circuit, so that the purpose of reducing loss is achieved.
Description
Technical Field
The application relates to the technical field of DCDC converters, in particular to a DCDC converter with low switching loss.
Background
The direct current power supply is widely applied in the industrial field and military projects, and needs to work together with other products to form a test system in many times and be installed in a cabinet or drawer with a certain volume, so that the volume of the power supply is limited to a high degree, and the direct current power supply needs to have smaller size and weight to meet the installation requirement. Therefore, the power supply needs to adopt higher switching frequency to reduce the volumes of an internal transformer, an output filter inductor and the like of the power supply, thereby further reducing the size of the whole power supply.
The high frequency can effectively reduce the volume of the switching power supply, however, the problem of increased loss of a switching tube can be caused by the excessively high frequency, which is not beneficial to improving the efficiency of the power supply. How to reduce switching loss based on the high frequency and to improve the efficiency of the power supply becomes a big problem to be faced.
Disclosure of Invention
The application aims at overcoming the defects of the prior art, and provides a DCDC converter with low switching loss, which not only can meet the requirement of high frequency, but also has low switching loss and can realize the conversion design with high efficiency and high power density.
The application relates to a DCDC converter with low switching loss, which has the technical scheme that: the device comprises a pre-voltage stabilizing circuit, a pre-voltage stabilizing driving circuit at the front stage, an LLC resonant conversion circuit and an LLC driving circuit;
the pre-voltage stabilizing circuit is used for adjusting the input voltage to a target voltage under the control of the pre-stage pre-voltage stabilizing driving circuit and outputting the target voltage to the LLC resonant conversion circuit;
the LLC resonant conversion circuit is used for generating resonance under the action of target voltage and enabling the frequency of the switching tube to be consistent with the resonance frequency under the control of the LLC driving circuit;
the pre-stage pre-voltage stabilizing driving circuit is used for controlling the pre-voltage stabilizing circuit to output target voltage according to the fed-back output voltage;
the LLC driving circuit is used for controlling the frequency of a switching tube of the LLC resonant conversion circuit so that the resonant frequency of the switching tube is consistent with that of the LLC resonant conversion circuit.
More preferably, the pre-voltage stabilizing circuit comprises a rectifying circuit, a slow starting circuit, a Boost voltage boosting circuit, an overvoltage protection circuit and a voltage sampling circuit, wherein the input voltage is sequentially input to the Boost voltage boosting circuit through the rectifying circuit and the slow starting circuit, and the overvoltage protection circuit and the voltage sampling circuit are arranged at the output end of the Boost voltage boosting circuit in parallel.
Preferably, the slow start circuit comprises a resistor R12 and a resistor R13 which are connected in series and a relay K1 connected with the resistor R12 and the resistor R13 in parallel;
the pre-stage pre-voltage stabilizing driving circuit collects input sampling voltage VINAC and output sampling voltage VSENSE of the pre-voltage stabilizing circuit, calculates a difference value between the input sampling voltage VINAC and the output sampling voltage VSENSE, and controls a relay K1 of the slow starting circuit to be attracted when the difference value is smaller than a set voltage threshold value.
More preferably, the Boost circuit includes a switching tube V9, a diode V8, a diode V12, an inductor L1 and an inductor L2, where the inductor L1, the inductor L2 and the diode V12 are sequentially connected in series and in parallel with the diode V8, the switching tube V9 is connected between the anode of the diode V12 and the ground, and a control end of the switching tube V9 is connected with a control signal output end of the pre-stage pre-stabilizing driving circuit.
Preferably, the transformer further comprises a main transformer circuit and a synchronous rectification circuit, wherein the main transformer circuit is connected in series with the output end of the LLC resonant conversion circuit, and the synchronous rectification circuit is connected in series with the output end of the main transformer circuit.
More preferably, the LLC resonant conversion circuit is an upper half-bridge circuit and a lower half-bridge circuit which are composed of a switching tube V13, a switching tube V14, resonant capacitors C10-C13, a resonant inductor L4 and an excitation inductor L3, wherein the control ends of the switching tube V13 and the switching tube V14 are respectively connected with a first control signal output end and a second control signal output end of the LLC driving circuit.
Preferably, the synchronous rectification circuit comprises four rectification units, and the synchronous rectification control circuit is used for controlling the rectification units to conduct alternately in pairs.
More preferably, the main transformer circuit comprises a transformer T2A and a transformer T2B which are arranged in series, the synchronous rectification circuit comprises two rectification units which are arranged at the output end of the transformer T2A in parallel and two rectification units which are arranged at the output end of the transformer T2B in parallel, each rectification unit comprises a pair of switching tubes which are arranged in parallel, and the control end of each switching tube is respectively connected with each control signal output end of the synchronous rectification control circuit.
Preferably, the pre-stage pre-voltage stabilizing driving circuit controls the pre-voltage stabilizing circuit to output the target voltage according to the fed-back output voltage, including:
the pre-stage pre-voltage stabilizing driving circuit inquires a pre-calibrated output voltage and target voltage comparison table according to the fed-back output voltage to obtain a target voltage corresponding to the current output voltage;
the pre-stage pre-voltage stabilizing driving circuit adjusts the frequency and the duty ratio of the switching tube V9, so that the Boost circuit outputs the target voltage.
The beneficial effects of the application are as follows: the pre-voltage stabilizing circuit of the front stage can boost the input voltage to the target voltage according to the control of the pre-voltage stabilizing driving circuit of the front stage, and the switching tube of the LLC resonant conversion circuit is consistent with the resonant frequency of the LLC resonant conversion circuit by combining the control of the LLC driving circuit, so that the LLC resonant conversion circuit works at an optimal resonant frequency point, and the purpose of reducing loss is achieved. The working condition of the main converter is greatly improved, the working efficiency of the main converter is improved, and the volume of the main converter is reduced.
Drawings
FIG. 1 is a schematic diagram of the connection principle of the present application;
FIG. 2 is a schematic diagram of a pre-voltage stabilizing circuit according to the present application;
FIG. 3 is a schematic diagram of a Boost control circuit according to the present application;
FIG. 4 is a schematic diagram of an LLC resonant conversion circuit, a main transformer circuit, and a synchronous rectification circuit of the present application;
FIG. 5 is a schematic diagram of an LLC driving circuit according to the present application;
FIG. 6 is a schematic diagram of a synchronous rectification control circuit according to the present application;
in the figure: the device comprises a 1-EMC filtering and lightning protection circuit, a 2-pre-voltage stabilizing circuit, a 201-rectifying circuit, a 202-slow starting circuit, a 203-Boost circuit, a 204-overvoltage protection circuit, a 205-voltage sampling circuit, a 3-LLC resonant conversion circuit, a 4-main transformer circuit, a 5-synchronous rectifying circuit, a 6-output blocking circuit, a 7-output EMC circuit, an 8-fan and temperature control circuit, a 9-auxiliary power supply, a 10-pre-stage pre-voltage stabilizing driving circuit, an 11-LLC driving circuit, a 12-synchronous rectifying control circuit and a 13-CAN communication circuit.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects to be solved more clear, the application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
It will be understood that when an element is referred to as being "mounted" or "disposed" on another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.
It is to be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are merely for convenience in describing and simplifying the description based on the orientation or positional relationship shown in the drawings, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus are not to be construed as limiting the application.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are 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 one or more such feature. In the description of the present application, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
Fig. 1 shows a schematic structural diagram of a DCDC converter with low switching loss according to a preferred embodiment of the present application (fig. 1 shows a first embodiment of the present application), and for convenience of explanation, only the relevant parts of the present embodiment are shown, which is described in detail below:
a DCDC converter with low switching loss comprises an EMC filtering and lightning protection circuit 1, a pre-stabilizing circuit 2, a rectifying circuit 201, a slow starting circuit 202, a Boost circuit 203, an overvoltage protection circuit 204, a voltage sampling circuit 205, an LLC resonance conversion circuit 3, a main transformer circuit 4, a synchronous rectifying circuit 5, an output blocking circuit 6, an output EMC circuit 7, a fan and temperature control circuit 8, an auxiliary power supply 9, a Boost controller circuit 10, an LLC driving circuit 11, a synchronous rectification control circuit 12 and a CAN communication circuit 13.
The pre-voltage stabilizing circuit 2 is used for adjusting the input voltage to a target voltage under the control of the pre-voltage stabilizing driving circuit 10 at the front stage and outputting the target voltage to the LLC resonant conversion circuit 3;
the LLC resonant conversion circuit 3 is used for generating resonance under the action of a target voltage and enabling the frequency of the switching tube to be consistent with the resonance frequency under the control of the LLC driving circuit 11;
the pre-stage pre-voltage stabilizing driving circuit 10 is used for controlling the pre-voltage stabilizing circuit 2 to output target voltage according to the fed-back output voltage;
the LLC driving circuit 11 is configured to control the frequency of the switching tube of the LLC resonant conversion circuit 3 so that the switching tube coincides with the resonant frequency of the LLC resonant conversion circuit 3.
As shown in fig. 2, the pre-stabilizing circuit 2 includes a rectifying circuit 201, a soft start circuit 202, a Boost voltage-boosting circuit 203, an overvoltage protection circuit 204 and a voltage sampling circuit 205, wherein an input voltage is sequentially input to the Boost voltage-boosting circuit 203 through the rectifying circuit 201 and the soft start circuit 202, and the overvoltage protection circuit 204 and the voltage sampling circuit 205 are arranged at an output end of the Boost voltage-boosting circuit 203 in parallel.
The rectifier circuit 201 includes V1, V2 rectifier bridges.
The slow start circuit 202 comprises a resistor R12 and a resistor R13 which are connected in series and a relay K1 which is connected with the resistor R12 and the resistor R13 in parallel;
the pre-stage pre-voltage stabilizing driving circuit 10 collects the input sampling voltage VINAC and the output sampling voltage VSENSE of the pre-voltage stabilizing circuit 2 (obtained by the voltage sampling circuit 205), calculates a difference value between the input sampling voltage VINAC and the output sampling voltage VSENSE, and when the difference value is smaller than a set voltage threshold value, the pre-stage pre-voltage stabilizing driving circuit 10 controls the relay K1 of the slow start circuit 202 to be attracted.
Boost circuit 203 includes switching tube V9, diode V8, diode V12, inductance L1 and inductance L2, inductance L1, inductance L2, diode V12 establish ties in proper order to parallelly connected with diode V8, switching tube V9 is connected between diode V12 positive pole and ground, and the control end of switching tube V9 is connected with the control signal output of preceding stage pre-voltage stabilizing drive circuit 10.
The rectifying circuit 201, the slow start circuit 202, the Boost circuit 203, the overvoltage protection circuit 204 and the voltage sampling circuit 205 in the pre-voltage stabilizing circuit 2 can be replaced by conventional circuits besides the circuit form in fig. 2, so long as rectifying, slow start, boosting, overvoltage protection and voltage sampling can be realized.
In the pre-voltage stabilizing circuit 2, the input high voltage passes through the rectifier bridge of the rectifier circuit 201 and the slow start circuit 202, and then enters the Boost circuit 203 to perform pre-voltage stabilization of the input voltage. The switching tube V9 duty ratio and frequency of the pre-stabilized driving circuit 10 can be regulated and controlled by the pre-stabilized driving circuit 10, the 122-618V wide input voltage is pre-stabilized to a certain voltage value in 630-710V (namely the target voltage which the pre-stabilized driving circuit 10 wants to realize), the post-stage LLC can work at the optimal resonance point to the greatest extent, the working condition of the main converter is greatly improved, the working efficiency of the main converter is improved, and the volume of the main converter is reduced. The method also samples input voltage, bus voltage, front-stage cooling fin temperature and driving auxiliary voltage; performing on-off time sequence control, including controlling a soft start circuit; performing output voltage stabilizing closed-loop control on Boost topology, outputting peak current reference and outputting PWM control chip synchronizing signals, so as to realize PFC circuit function; controlling the state of the indicator lamp according to the state information and information sent by a later stage; and the serial port and the later stage are used for carrying out isolation communication, and mutual transmission and reception of training information and states are carried out.
The specific working mode of the pre-voltage stabilizing circuit 2 is as follows: after rectifying input voltages of three-phase alternating current, single-phase alternating current or direct current and other different modes through a V1 rectifier bridge and a V2 rectifier bridge, firstly, passing through a Boost circuit through auxiliary circuits of resistors R12 and R13, controlling the conduction Boost of a MOS tube V9 through a PWM driving signal GDAO to charge capacitors C4 and C5, pre-stabilizing the voltages to a certain voltage value in 630V-710V, closing a relay K1 when the pressure difference between an input voltage sampling VINAC and a pre-stabilized output voltage sampling VSENSE value is smaller than 25V, and completing slow start, wherein the main circuit of the relay is conducted; meanwhile, voltage equalizing hard protection is arranged between the capacitors C4 and C5, when the upper and lower voltage is over-voltage, the upper and lower voltage can be conducted through the optocoupler N1, and the control signal BUS-OVP turns off the driving circuit, so that protection is achieved.
The pre-stage pre-voltage stabilizing driving circuit 10 controls the pre-voltage stabilizing circuit 2 to output a target voltage according to the fed-back output voltage, including:
the pre-stage pre-voltage stabilizing drive circuit 10 queries a pre-calibrated output voltage and target voltage comparison table according to the fed-back output voltage to obtain a target voltage corresponding to the current output voltage;
the pre-stage pre-voltage stabilizing driving circuit 10 adjusts the frequency and the duty ratio of the switching transistor V9 so that the Boost circuit 203 outputs the target voltage.
The output voltage and the target voltage are calibrated in advance and then stored in the MCU of the pre-stage pre-voltage stabilizing driving circuit 10. And when the LLC resonant circuit is calibrated, acquiring target voltage which is favorable for the LLC resonant circuit to work at a resonant point according to different output voltage requirements. The target voltage belongs to data which can be obtained by a person skilled in the art through limited calculation and test according to parameters of each element of the LLC resonant circuit, output voltage requirements and the like.
The pre-stage pre-voltage stabilizing driving circuit 10 comprises a pre-stage control chip and a Boost control circuit arranged at the output end of the pre-stage control chip. The front-stage control chip is used for looking up a table according to the output voltage to obtain target voltage, and outputting a control signal to the Boost control circuit, wherein the Boost control circuit is used for outputting a GDAO signal acting on V9. The control of the front-end control chip further comprises the step of controlling the relay K1 to be attracted when the pressure difference between the input voltage sample VINAC and the pre-stabilized output voltage sample VSENSE is smaller than 25V. As shown in fig. 3, the Boost control circuit sends the input voltage and bus voltage sampling signals of the pre-stage pre-voltage stabilizing driving circuit 10 to the ADC10 and ADC12 PINs of the MCU, calculates a corresponding peak current reference value PWM signal, sends the signal out by PIN41 tim1_ch1, forms a peak current reference after filtering, and sends the peak current reference to the COMP PIN of the driving chip as the peak reference of the current comparator. Through the design of an independent overvoltage sampling loop, when the voltage of the main feedback loop abnormal bus is overvoltage, the driving chip can be closed in time by hardware, and the subsequent stage is protected from being damaged by high voltage. The driving chip oscillation frequency FPWM1A signal is synchronized by pulse control given by PIN58 PIN TIM4_CH1 of the MCU.
As shown in fig. 4, a main transformer circuit 4 is connected in series with the output terminal of the LLC resonant converter circuit 3, and a synchronous rectifier circuit 5 is connected in series with the output terminal of the main transformer circuit 4.
The LLC resonance conversion circuit 3 is an upper half-bridge circuit and a lower half-bridge circuit which are composed of a switching tube V13, a switching tube V14, resonance capacitors C10-C13, a resonance inductor L4 and an excitation inductor L3, wherein the control ends of the switching tube V13 and the switching tube V14 are respectively connected with a first control end and a second control end of the LLC driving circuit 11.
The synchronous rectification circuit 12 includes four rectification units, and the four rectification units can be alternately conducted in groups of two under the control of the synchronous rectification control circuit 12. The main transformer circuit 4 includes a transformer T2A and a transformer T2B that are arranged in series, the synchronous rectification circuit 5 includes two rectification units that are arranged in parallel at the output end of the transformer T2A and two rectification units that are arranged in parallel at the output end of the transformer T2B, the rectification units include a pair of switching tubes that are arranged in parallel, and the control end of each switching tube is connected with each control signal output end of the synchronous rectification control circuit 12 respectively.
The LLC resonant conversion circuit 3 is used for converting direct-current high voltage output by the pre-voltage stabilizing circuit into required 28V voltage; collecting information such as output voltage, output current, far-end voltage drop, rear-stage temperature, +12V auxiliary voltage, fan current and the like, calculating and judging abnormal conditions, and protecting or alarming; soft start, voltage stabilization and current limiting control are carried out on the half-bridge LLC topology, a half-bridge complementary driving control signal and a synchronous rectification driving control signal are output, the LLC circuit function is realized, and high-efficiency isolation conversion of electric energy is completed; reading address configuration information and determining the address of a power supply module; performing distal pressure drop calculation and compensation control; performing multiple parallel current sharing calculation and control; performing CAN bus transmission control, and analyzing, processing or storing the received data; controlling the start and stop of the fan, and regulating the rotating speed of the fan in real time according to the temperature of the front stage and the instructions of the rear stage; main output current detection: because excitation is independently output, the primary current of the transformer is directly proportional to the output current, and the primary current is directly used for measuring and calculating the output current.
Example 1
In this embodiment, the transmission voltage is 28V, and the target voltage is 680V. The pre-voltage stabilizing circuit 2 of the front stage is optimally set at 680V (taking output 28V as an example), at the moment, the LLC resonant conversion circuit 3 just works at a resonant point, at the moment, the switching frequency is matched with a resonant capacitor and a resonant inductor, and ZVS soft switching of the switching tubes V13 and V14 and ZCS soft switching of the secondary rectifying tube can be realized within a full load range, so that the loss of the switching tube in a high-frequency state is greatly reduced. Meanwhile, through follow-up setting, communication is carried out through a front-stage controller and a rear-stage controller, and meanwhile, the output voltage of the front-stage voltage stabilizing circuit 2 is also controlled by the front-stage pre-voltage stabilizing driving circuit 10 to be changed to a set voltage stabilizing value, so that LLC always works at an optimal resonance frequency point, and the purpose of reducing loss is achieved. Meanwhile, the synchronous rectification control circuit 12 controls the four rectification units to be alternately conducted in pairs, and the LLC resonant circuit works at an optimal resonance point due to the pre-stabilized voltage of the front stage, so that the ZCS soft switch of the secondary rectifying tube is realized, and the switching loss during rectification is further reduced.
As shown in fig. 5, after receiving the control signal output by the later-stage controller, the LLC driving circuit 11 amplifies the 3.3V PWM driving signal output by the microcontroller through the driving of the driving chip, and then enters the transformer to perform isolation, and the driving signal is changed into a PWM signal at the primary side of the transformer through the auxiliary circuit to drive the MOS transistor on the bridge arm, and the two driving signals are complementary signals, so that the upper bridge arm and the lower bridge arm of the LLC are alternately conducted. The LLC driving circuit 11 controls the frequencies of the switching transistors V13 and V14 through H-DR and L-DR signals, respectively, so that the switching transistors operate at an optimal resonance frequency point.
The LLC resonant converter becomes less efficient due to excessive rectifier diode losses on the secondary side of the transformer. In order to improve the efficiency of the half-bridge LLC, synchronous rectification can be adopted to further reduce the loss of the rectifying tube, thereby improving the conversion efficiency of the LLC.
The power supply of this scheme is two-stage isolation formula DCDC converter, and preceding stage is pre-voltage stabilizing circuit, with high voltage direct current input to high voltage direct current busbar, through hardware current loop and digital control voltage loop with the second grade LLC input voltage stable at best resonance voltage. The rear stage is an isolated LLC series-parallel resonant converter which converts high-voltage direct current into low-voltage direct current. The switching frequency is matched with the resonance capacitor and the resonance inductor, so that the switching tube ZVS soft switching and the secondary rectifying tube ZCS soft switching are realized in the whole range. And the secondary side arrangement adopts a MOSFET synchronous rectification technology, so that voltage drop loss is reduced.
As shown in fig. 6, synchronous rectification adopts a control chip, which sends out corresponding driving signals by sensing the drain-source voltage of each secondary rectifying MOS tube.
The above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application, and are intended to be included in the scope of the present application.
Claims (7)
1. A DCDC converter with low switching losses, characterized by: comprises a pre-voltage stabilizing circuit (2), a pre-stage pre-voltage stabilizing driving circuit (10), an LLC resonant conversion circuit (3) and an LLC driving circuit (11);
the pre-voltage stabilizing circuit (2) is used for adjusting an input voltage to a target voltage under the control of the pre-voltage stabilizing driving circuit (10) at the front stage and outputting the target voltage to the LLC resonant conversion circuit (3), and the pre-voltage stabilizing circuit (2) comprises a Boost circuit (203);
the LLC resonant conversion circuit (3) is used for generating resonance under the action of target voltage and enabling the frequency of the switching tube to be consistent with the resonance frequency under the control of the LLC driving circuit (11);
the pre-stage pre-voltage stabilizing driving circuit (10) is used for controlling the pre-voltage stabilizing circuit (2) to output target voltage according to the fed-back output voltage;
the LLC driving circuit (11) is used for controlling the frequency of a switching tube of the LLC resonant conversion circuit (3) so that the resonant frequency of the switching tube is consistent with that of the LLC resonant conversion circuit (3);
the Boost circuit (203) comprises a switching tube V9, a diode V8, a diode V12, an inductor L1 and an inductor L2, wherein the inductor L1, the inductor L2 and the diode V12 are sequentially connected in series and are connected in parallel with the diode V8, the switching tube V9 is connected between the anode of the diode V12 and the ground, and the control end of the switching tube V9 is connected with the control signal output end of the pre-stage pre-voltage stabilizing drive circuit (10);
the pre-stage pre-voltage stabilizing driving circuit (10) controls the pre-voltage stabilizing circuit (2) to output target voltage according to the fed-back output voltage, and the pre-stage pre-voltage stabilizing driving circuit comprises:
the pre-stage pre-voltage stabilizing driving circuit (10) queries a pre-calibrated output voltage and target voltage comparison table according to the fed-back output voltage to obtain a target voltage corresponding to the current output voltage;
the pre-stage pre-voltage stabilizing driving circuit (10) adjusts the frequency and the duty ratio of a switching tube V9, so that the Boost circuit (203) outputs the target voltage;
the pre-stage pre-voltage stabilizing driving circuit (10) comprises a pre-stage control chip and a Boost control circuit arranged at the output end of the pre-stage control chip, wherein the pre-stage control chip is used for obtaining target voltage according to the lookup table of output voltage and outputting a control signal to the Boost control circuit, and the Boost control circuit is used for outputting a PWM driving signal acting on the switching tube V9.
2. The low switching loss DCDC converter of claim 1, wherein: the pre-voltage stabilizing circuit (2) comprises a rectifying circuit (201), a slow starting circuit (202), a Boost circuit (203), an overvoltage protection circuit (204) and a voltage sampling circuit (205), wherein input voltage is sequentially input to the Boost circuit (203) through the rectifying circuit (201) and the slow starting circuit (202), and the overvoltage protection circuit (204) and the voltage sampling circuit (205) are connected in parallel to the output end of the Boost circuit (203).
3. The low switching loss DCDC converter of claim 2, wherein: the slow start circuit (202) comprises a resistor R12 and a resistor R13 which are connected in series and a relay K1 connected with the resistor R12 and the resistor R13 in parallel;
the pre-stage pre-voltage stabilizing driving circuit (10) collects input sampling voltage VINAC and output sampling voltage VSENSE of the pre-voltage stabilizing circuit (2), calculates a difference value between the input sampling voltage VINAC and the output sampling voltage VSENSE, and controls a relay K1 of the slow starting circuit (202) to be attracted when the difference value is smaller than a set voltage threshold value.
4. The low switching loss DCDC converter of claim 1, wherein: the transformer also comprises a main transformer circuit (4) and a synchronous rectification circuit (5), wherein the main transformer circuit (4) is connected in series with the output end of the LLC resonant conversion circuit (3), and the synchronous rectification circuit (5) is connected in series with the output end of the main transformer circuit (4).
5. The low switching loss DCDC converter of claim 1, wherein: the LLC resonance conversion circuit (3) is an upper half-bridge circuit and a lower half-bridge circuit which are composed of a switching tube V13, a switching tube V14, resonance capacitors C10-C13, a resonance inductor L4 and an excitation inductor L3, and control ends of the switching tube V13 and the switching tube V14 are respectively connected with a first control signal output end and a second control signal output end of the LLC driving circuit (11).
6. The low switching loss DCDC converter of claim 4, wherein: the synchronous rectification circuit (5) comprises four rectification units, and the synchronous rectification control circuit (12) is used for controlling the rectification units to conduct alternately in pairs.
7. The low switching loss DCDC converter of claim 6, wherein: the main transformer circuit (4) comprises a transformer T2A and a transformer T2B which are arranged in series, the synchronous rectification circuit (5) comprises two rectification units which are arranged at the output end of the transformer T2A in parallel and two rectification units which are arranged at the output end of the transformer T2B in parallel, each rectification unit comprises a pair of switching tubes which are arranged in parallel, and the control end of each switching tube is respectively connected with each control signal output end of the synchronous rectification control circuit (12).
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