CN115441746A - Direct current converter topological structure with adjustable output voltage in wide input range - Google Patents

Direct current converter topological structure with adjustable output voltage in wide input range Download PDF

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Publication number
CN115441746A
CN115441746A CN202211123994.7A CN202211123994A CN115441746A CN 115441746 A CN115441746 A CN 115441746A CN 202211123994 A CN202211123994 A CN 202211123994A CN 115441746 A CN115441746 A CN 115441746A
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converter
dcx
pwm
direct current
output voltage
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陈材
伍纵横
胡至祎
康勇
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Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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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
    • 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
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
    • 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
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H02M1/007—Plural converter units in cascade
    • 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
    • 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

Abstract

The invention discloses a direct current converter topological structure with adjustable output voltage in a wide input range, belongs to the technical field of direct current-direct current converter topological structures, and particularly comprises two transmission paths for transmitting energy from an input port to an output port. The main channel is an LLC-based DCX. The auxiliary channel comprises two stages, a non-isolated PWM (pulse width modulation) direct current converter is adopted in the first stage, then high-efficiency isolation conversion is realized by cascading a small DCX based on LLC with the PWM direct current converter, and the output voltage is regulated by regulating the PWM direct current converter. The main channel and the auxiliary channel are connected in series at the input port, and the output ports are connected in parallel. The invention carries out triangular wave current mode (TCM) modulation on the PWM converter, realizes zero voltage switching-on of a switching tube of the PWM converter and obviously reduces the switching loss of an energy transmission auxiliary channel. The proposed converter topology thus enables high transmission efficiency over a wide input voltage range.

Description

Direct current converter topological structure with adjustable output voltage in wide input range
Technical Field
The invention belongs to the technical field of direct current-direct current converter topological structures, and particularly relates to a direct current converter topological structure with adjustable output voltage in a wide input range.
Background
Information technology has developed vigorously over the last several decades, and with the ever-increasing demand for large-scale information storage and computing, the size of data centers has also increased dramatically. Therefore, more and more servers are installed in the data center. This results in significant energy consumption and electricity costs. In order to reduce energy loss and improve space utilization, it is necessary to achieve high efficiency and high power density in the energy conversion stage.
In practice, in any power distribution system, once the grid is disconnected, the voltage of the battery floats within a large range due to discharge, which results in the output voltage of the DCX (direct current converter) no longer maintaining a constant value. Therefore, there is a need for an efficient isolated DC-DC converter with wide input voltage range regulation capability.
In addition to efficiency and wide input regulation, high frequency and high power density are also trends in development, since high switching frequency can improve emi performance and high power density can improve space utilization. Many efforts have been made to achieve high efficiency of isolated DC-DC converters. The traditional hard switching pulse width modulation circuit has a simple structure, and the control scheme is widely applied to the industrial field, but for high switching frequency, the traditional hard switching pulse width modulation circuit can generate larger switching loss. The phase-shifted full-bridge converter (PSFB) is popular in the application occasions of medium power grade because the primary side switching tube of the PSFB is switched on at zero voltage. However, since the turn-off current of the primary side switching tube is large and the secondary side rectifier has no zero current turn-off, the PSFB is not suitable for the application of high switching frequency and wide input range. Dual Active Bridge (DAB) converters find wide application in energy storage systems due to their simple design and control. However, DAB has large turn-off loss and large circulating current, so DAB is not suitable for application of high switching frequency and wide input range.
Among the various converters that provide Zero Voltage Switching (ZVS), LLC converters provide zero voltage turn-on of the primary switching tube and zero current turn-off of the secondary rectifier, are widely used in applications requiring electrical isolation and high efficiency, and are potential candidate topologies for achieving high efficiency at high switching frequencies. However, LLC converters regulate output by adjusting phase shift angle, switching frequency, or duty cycle. These methods require a large resonant inductor to regulate the output, which not only occupies a large volume, but also generates large losses. On the other hand, for high frequency regulated LLC converters with phase shift modulation or frequency modulation, it is difficult to obtain an efficient control strategy. Synchronous rectification logic is also difficult to implement. These disadvantages are even more pronounced for a wide input range LLC resonant converter.
In order to extend the gain range of LLC resonant converters, different approaches have been proposed in the literature, such as researchers have proposed a PWM controlled dual-bridge LLC resonant converter with DCX operating at a fixed frequency switching frequency, but since the output voltage is regulated by duty cycle, it is still difficult to implement synchronous rectification logic under high switching conditions. There is also a document that proposes a double half-bridge series LLC converter in which topology a Frequency Adaptive Phase Shift Modulation (FAPSM) control is implemented. By adjusting the phase shift angle of the primary side switching tube and the secondary side switching tube, large-range gain can be obtained. However, the phase shift modulation method generates cyclic energy at a high switching frequency, thereby causing a decrease in efficiency.
LLC resonant converters provide optimum performance at the series resonant frequency. The zero-voltage switching-on and low-current switching-off circuit can realize zero-voltage switching-on and low-current switching-off and zero-current switching-off of the secondary rectifier, and is beneficial to obtaining high efficiency and high power density. In addition, the rectifier on the secondary side can be driven by using a driving signal of the switching tube on the primary side, and the synchronous logic is greatly simplified. But since the voltage ratio of DCX is fixed, an auxiliary circuit is required to regulate the output. Conventional solutions employ cascaded non-isolated PWM regulators for output regulation. However, since the PWM converter is subjected to a full input or full output voltage and current, there is a problem in that a switching loss is large. Furthermore, full-load regulators are bulky, resulting in a reduction in power density.
Therefore, for an efficient LLC resonant converter with high power density and wide input voltage range regulation capability, which DCX operates at a fixed switching frequency, it is necessary to further optimize its topology and modulation method of the PWM converter therein, so as to improve its power density and efficiency.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a direct current converter topological structure with adjustable output voltage in a wide input range, and aims to solve the technical problems that the LLC resonant converter under the existing high-frequency working condition has insufficient power density, insufficient efficiency, insufficient adjusting capacity in the wide input voltage range, complex control strategy, difficult realization of synchronous rectification control logic and the like due to the topological structure.
To achieve the above object, the present invention provides a dc converter topology with adjustable output voltage in a wide input range, which includes two transmission paths for transferring energy from an input port to an output port: the main channel and the auxiliary channel are connected in series at input ports, and are connected in parallel at output ports.
The main channel is a DCX based on LLC, and works at a fixed switching frequency to transmit most input energy to an output port;
the auxiliary channel comprises two stages for processing the regulated portion of the input energy. The first stage adopts a non-isolated PWM DC-DC converter, the second stage adopts a small DCX based on LLC, thereby realizing high-efficiency isolation conversion, and the non-isolated PWM DC-DC converter and the small DCX are cascaded on the primary side of a DCX transformer. The output voltage is regulated by a non-isolated PWM DC-DC converter that regulates the auxiliary channel.
The beneficial effects of the invention are: since the output voltage of this topology is regulated by a non-isolated PWM converter, LLC-based DCXs are only used for isolation and buck. The voltage regulation is achieved at a fixed switching frequency, so the structure simplifies the control strategy and the synchronous rectification logic, and is suitable for wide input range applications. In addition, the partial power regulation structure contributes to reduction of power loss.
On the basis of the technical scheme, the invention can be further improved as follows.
Further, the DCX used for the main channel and the DCX used for the auxiliary channel of the energy transmission are operated at the series resonant frequency of the respective resonant cavities.
Further, the switching frequency of the PWM converter used by the energy transfer auxiliary channel is independent of the two DCXs.
The invention has the further beneficial effects that: the DCXs of the energy transmission main channel and the auxiliary channel can obtain a stable transformation ratio, the advantages of high efficiency and high power density of the LLC resonant converter are reserved, the DCXs do not need to be additionally controlled, and only the PWM converter needs to be controlled to regulate the output voltage.
Further, the DCX used by the energy transmission main channel and the DCX used by the energy transmission auxiliary channel are designed by proper resonant cavity parameters and work under the same series resonance frequency and duty ratio.
Further, the main channel comprises a PWM DC-DC converter and a first filter capacitor C in1 A second filter capacitor C in2 A first switch tube Q 1 A second switch tube Q 2 First resonant inductor L r1 And a first resonant capacitor C r1 A first resonant cavity is formed; a first filter capacitor C in1 Connected in parallel to the input of the PWM converter and a second filter capacitor C in2 Connected in parallel with the output of the PWM converter, the output of the PWM converter is applied to the first switch tube Q 1 And a second switching tube Q 2 On the bridge arms which are formed together, the output of the middle point of the bridge arms is applied to a first resonant cavity;
the auxiliary channel comprises a third filter capacitor C in3 And a third switching tube Q 3 And a fourth switching tube Q 4 A second resonant inductor L r2 And a second resonant capacitor C r2 A second resonant cavity is formed; third filter capacitor C in3 Is connected in parallel to the third switching tube Q 3 And a fourth switching tube Q 4 On the bridge arms which are formed together, the output of the middle point of the bridge arms is applied to a second resonant cavity;
the main channel and the auxiliary channel share a common excitation inductor L m The center-tapped transformer T and the first synchronous rectification switch tube S 1 And a second rectifying switch tube S 2 A synchronous rectifier is formed; the outputs of the first and second resonators are applied to the input side of a center tapped transformer T,the output side of the transformer T is connected with a synchronous rectifier. Namely, the transformers of the DCXs of the two energy transmission paths can be combined, namely, secondary windings of the DCXs transformers are connected in parallel and share the same set of synchronous rectification switch tube, so that the two DCXs transformers are combined into a three-port transformer consisting of two input ports and one output port.
The invention has the further beneficial effects that: the topology of the circuit is greatly simplified and a single transformer helps to increase the power density.
Further, the topological structure of the PWM converter adopts a triangular wave current mode (TCM) modulation mode.
The invention has the following further beneficial effects: zero voltage switching-on of a switching tube in the PWM converter is realized, in the holding time, when the input voltage changes, the energy flowing through an auxiliary energy transmission channel where the PWM converter is located is increased, and the switching loss of the PWM converter is greatly reduced under TCM, so that the integral efficiency of the converter can be improved in a wide input voltage range.
Furthermore, a primary side switching tube of the topological structure adopts gallium nitride equipment.
The invention has the following further beneficial effects: the turn-off loss of the primary side switching tube is greatly reduced.
Further, the topological structure of the synchronous rectifier adopts silicon devices.
The invention has the following further beneficial effects: the conduction loss of the secondary side rectifier bridge under the condition of high output current is greatly reduced.
Further, a driving signal of the synchronous rectifier of the topological structure is synchronous with a driving signal of the primary side switching tube, and the synchronous rectifier has fixed frequency and duty ratio.
Compared with the prior art, the technical scheme of the invention ensures that the DCXs of the main channel and the auxiliary channel always work under the resonant frequency of the resonant cavity, ensures the highest energy transmission efficiency of the DCXs and simplifies the control logic of synchronous rectification. The PWM converter in the auxiliary channel works in a TCM mode, zero voltage switching-on of the switch tube is achieved, and when the working state of the PWM converter is adjusted to adjust output voltage, most energy is transmitted through the main channel with higher energy transmission efficiency, and higher efficiency is achieved. The main channel and the auxiliary channel share the secondary winding and the synchronous rectifier of the transformer, so that a large amount of space is saved, the equipment volume is reduced, and the power density of the converter is improved. Thus, the proposed converter topology achieves high efficiency and high power density.
Drawings
Fig. 1 is a schematic diagram of the original topology of the dc converter proposed in the present invention;
fig. 2 is a schematic diagram of a circuit topology of the dc converter proposed in the present invention;
fig. 3 is the main waveforms of the topology of the dc converter proposed in the present invention in steady state operation;
fig. 4 is an equivalent circuit diagram of each stage in one cycle when the dc converter proposed in the present invention is in a steady state;
FIG. 5 is a schematic diagram of a circuit topology of a DC converter provided by an embodiment of the invention;
fig. 6 is a schematic diagram of an equivalent circuit of a boost converter in the dc converter provided by the embodiment of the present invention and main waveforms in a steady operation.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
The invention provides a direct current converter topological structure with adjustable output voltage in a wide input range, which comprises two transmission paths for transmitting energy from an input port to an output port: the input ports of the main channel and the auxiliary channel are connected in series, and the output ports of the main channel and the auxiliary channel are connected in parallel.
The main channel is a DCX based on LLC, and works at a fixed switching frequency to transmit most input energy to an output port;
the auxiliary channel comprises two stages for processing the regulated portion of the input energy. The first stage adopts a non-isolated PWM DC-DC converter, the second stage adopts a small DCX based on LLC, thereby realizing high-efficiency isolation conversion, and the non-isolated PWM DC-DC converter and the small DCX are cascaded on the primary side of a DCX transformer. The output voltage is regulated by a non-isolated PWM DC-DC converter that regulates the auxiliary channel.
Fig. 1 is a schematic diagram of the original topology of the dc converter proposed in the present invention. In this topology, the process of energy transfer from the input port to the output port can be divided into two transmission paths, and these two paths are called a main path and an auxiliary path respectively as the paths for energy transfer. The main channel transmits most of the input energy to the output port, and the main channel only consists of a DC converter working at a fixed switching frequency to form DCX, specifically, the main channel for energy transmission consists of a single LLC resonant converter working at a fixed switching frequency, converts the input DC voltage into the output DC voltage, and bears most of the work of the converter for transmitting energy. The auxiliary channel is responsible for energy transfer only for the majority of the energy input to the output port, but it also assumes the task of regulating the output voltage. Specifically, the auxiliary channel comprises two stages in total, and the first stage is a non-isolated PWM DC-DC converter, such as a Buck converter, a Boost converter and the like. The non-isolated PWM dc-dc converter is also required to be cascaded with a small DCX, specifically, an LLC resonant converter operating at a fixed switching frequency in the auxiliary channel, and is used to handle the regulated portion of the input energy. In addition, the input ports of the main channel and the auxiliary channel are connected in series, and the output ports are connected in parallel.
In FIG. 1, V in The input voltage of the DC converter is formed by connecting the main path and the auxiliary path of energy transmission in parallel, namely the sum of the input voltages of the main path and the auxiliary path of energy transmission is V in (ii) a Main path and auxiliary path due to energy transferThe auxiliary path is connected in parallel at the output port, i.e. the output voltage of the main path and the auxiliary path for energy transmission is V o 。DCX 1 Is a DC-DC converter based on LLC resonant converter on the auxiliary path of energy transmission, DCX 1 Is T 1 The turn ratio is m:1, transformer T 1 Primary side of, DCX 1 The converter is cascaded with a non-isolated PWM converter, and the PWM converter can be a Buck converter or a Boost converter and the like; DCX 2 Is a DC-DC converter based on LLC resonant converter on the energy transmission main path, DCX 2 Is T 2 The turn ratio of the mixed solution is n:1,R L Is an output voltage V o A load to which power is supplied.
When DCX 1 And DCX 2 The resonant frequencies of the two DCX rectifiers and the secondary winding of the transformer can be combined into one: to transformer T 1 And T 2 The secondary windings of the transformer are connected in parallel, so that two transformers can be integrated into one transformer and can share the same set of synchronous rectification device.
FIG. 2 is a schematic diagram of a circuit topology of a DC converter proposed in the present invention, S 1 And S 2 For the secondary side synchronous rectification switch tube of the proposed DC converter, the DCX is designed by proper resonant cavity parameters 1 And DCX 2 Has the same resonant frequency, and the secondary synchronous rectifiers of the two DCXs are integrated into a whole by S 1 And S 2 A set of rectifiers is formed; in the proposed circuit topology of the DC converter, the transformer T of the DCX is composed of T 1 And T 2 The integration greatly improves the power density of the proposed dc converter. The transformer T having three windings, N A Is DCX 1 Primary winding in a three-winding transformer, N P Is DCX 2 In the primary winding of a three-winding transformer, the secondary winding of the transformer T has N turns s The turn ratio of the three-winding transformer is m: n:1.Q 1 And Q 2 Together form DCX 1 Bridge arm, Q of transformer primary side generating input square wave voltage 1 Is an upper switch tube, Q of the bridge arm 2 Is the bridgeLower switch tube of arm, L r1 Is DCX 1 Resonant inductance of, C r1 Is DCX 1 Resonant capacitance of L m The excitation inductance of a three-winding transformer for the proposed converter; q 3 And Q 4 Together form DCX 2 Bridge arm, Q of transformer primary side generating input square wave voltage 3 Is an upper switch tube, Q of the bridge arm 42 A lower switching tube of the bridge arm, L r2 Is DCX 2 Resonant inductance of, C r2 Is DCX 2 The resonance capacitance of (a); v 0 Is the input voltage, V, of the auxiliary path of energy transfer 1 Output voltage, V, of a PWM converter being an auxiliary path for energy transfer 2 Is the input voltage of the main path of energy transmission, C in1 Is a capacitor for input regulation and filtering of the auxiliary path of energy transmission, C in2 Is a capacitor, C, for output regulation and filtering of a PWM converter for the auxiliary path of energy transmission in3 Is a capacitor for input voltage stabilization and filtering of the main path of energy transmission, C o Is the output voltage-stabilizing and filtering capacitor of the proposed dc converter; the output voltages of the main path and the auxiliary path of the energy transmission are connected in parallel, are the same as the output voltage of the proposed DC converter, and are both V o ，R L Is the load resistance of the proposed converter.
In fig. 2, the switching frequency of the non-isolated PWM converter is independent of the two DCXs, and the capability of adjusting the output voltage in a wide input voltage range can be realized by changing the duty ratio of the PWM converter. By operating the two bridge arms at the same switching frequency, which is DCX 1 And DCX 2 When the switching frequency and the series resonant frequency of the resonant cavity are equal, the LLC resonant converter can enable the primary side switching tube to be switched on and off at zero voltage and the secondary side rectifier to be switched off at zero current, so that the DCX converter has the advantages of low power consumption, high efficiency, low power consumption and low cost 1 And DCX 2 The best performance, i.e. high efficiency, high power density, and DCX can be obtained 1 And DCX 2 The driving signals required by the primary side switching tube and the secondary side rectifier are completely consistent, so that the control strategy and the control logic of synchronous rectification are greatly simplified.
FIG. 3 isThe proposed topology of the dc converter has the main waveforms in steady state operation, where (a), (b), (c) in fig. 4 are t in fig. 3 0 ～t 1 、t 1 ～t 2 、t 2 ～t 3 Equivalent circuit diagram corresponding to time interval, V in FIG. 4 gs_Q1 And V gs_Q2 Are each DCX 1 Primary side switch tube Q 1 And Q 2 Drive signal of V gs_Q3 And V gs_Q4 Are respectively DCX 2 Primary side switch tube Q 3 And Q 4 Of the driving signals of which the frequencies are all DCX 1 And DCX 2 The series resonant frequency of the resonant cavity. V ds_Q2 Is a primary side switching tube Q 2 Drain-source voltage of V ds_Q4 Is a primary side switching tube Q 4 The drain-source voltage of (1). i' r1 Is DCX 1 Of resonant current i' r2 Is DCX 2 The resonant current of (2). i.e. i m1 Is the excitation current, i, of the transformer T s1 、i s2 Respectively, the currents of the secondary rectifier of the transformer T.
FIG. 4 (a) is the proposed circuit topology t in FIG. 3 0 ～t 1 Equivalent circuit diagram of time period, primary side switch tube Q 1 、Q 3 Synchronous rectifier S 1 At t 0 And is turned on at any moment. Equivalent output voltage mV of transformer o And (4) clamping. Thus, the exciting current i m1 Increasing linearly. DC voltage V 1 And V 2 Respectively applied to the two resonant cavities. Under the steady state, the DC bias of the two resonant capacitors is V respectively 1 And V 2 Half of that. Then, the sinusoidal currents of the two resonant cavities deviate from the excitation current, and the energy passes through Q 1 、Q 3 And S 1 To the load. The amplitude of the two resonant currents is determined by the power ratio regulated by the PWM converter.
FIG. 4 (b) is the proposed circuit topology t in FIG. 3 1 ～t 2 Equivalent circuit diagram of time period, at t 1 ～t 2 Meanwhile, since the switching frequency is equal to the series resonance frequency of the resonator, i r1 And
Figure BDA0003847580570000091
the sum is at t 1 Is equal to exciting current i at any moment m1 。Q 1 And Q 3 At t 1 And the moment is disconnected. At the same time, flows through S 1 Is equal to zero, S 1 While the zero current is off. t is t 1 After the moment, all switches are kept in an off state until t 2 The time of day. During this time, no energy is transferred from the input to the load, which is supplied by the output stabilizing filter capacitor C o And (5) supplying power. Since all the switching tubes are turned off, the excitation inductance L m Is not clamped by the output voltage but rather a resonance is added. Switch tube Q 1 、Q 3 、S 1 The body capacitor is charged by exciting current, and the switch tube Q 2 、Q 4 、S 2 The body capacitance of (a) is discharged by the excitation current. Up to t 2 Time of day, switch tube Q 2 、Q 4 、S 2 Discharge to zero, Q 2 、Q 4 、S 2 And realizing zero voltage switching-on. After that, the converter starts to enter the next stage of operation.
FIG. 4 (c) is the proposed circuit topology t in FIG. 3 2 ～t 3 Equivalent circuit diagram of time period, at t 2 Time of day, switch tube Q 2 、Q 4 And S 2 And (4) opening. The bias voltage on the resonant capacitor is applied to the corresponding resonant tank. The exciting inductor is clamped to-mV by equivalent output voltage o Excitation current i m1 Increasing with a negative slope. The resonant current deviates from the excitation current by a sinusoidal function and energy is transferred to the load. Until t 3 Time, i r1 And
Figure BDA0003847580570000101
the sum is again equal to the excitation current i m1 ，Q 2 And Q 4 And simultaneously turned off. When the primary side current is equal to the exciting current, the current passes through S 2 Is equal to zero, S 2 While zero current turn-off is accomplished.
In FIG. 3 t 3 ～t 4 In the time period, since the circuit is at t 3 Another dead time is entered, and the equivalent circuit at this time is similar to (b) in fig. 4. Due to the fact thatThe switch tube is turned off, the excitation inductor participates in resonance again, and the switch tube Q 1 、Q 3 、S 1 Is discharged by the excitation current. Up to t 4 Time, Q 1 、Q 3 、S 1 Has a zero drain to source voltage, Q 1 、Q 3 、S 1 And meanwhile, zero voltage switching-on is realized.
FIG. 5 is a schematic diagram of a circuit topology of a DC converter according to an embodiment of the present invention, wherein the auxiliary energy transmission channel of the circuit topology shown in FIGS. 1, 2, 3, and 5 requires DCX 1 Primary side PWM converters such as Buck converters and Boost converters are cascaded. In the embodiment, the non-isolated PWM converter adopts a Boost converter. The Boost converter is composed of a switch tube Q 5 、Q 6 A pair of bridge arms and an inductor L ave Capacitor C in2 Is formed of a switching tube Q 5 Is the upper switch tube and the switch tube Q of the bridge arm 6 Is the lower switch tube of the bridge arm. In addition, the primary side switching tube of the DCXs and the switching tube of the PWM converter adopt gallium nitride (GaN) equipment to reduce turn-off loss, and the secondary side rectifier adopts silicon (Si) equipment to reduce conduction loss.
Fig. 6 (a) shows an equivalent circuit of a half bridge in a Boost converter in a dc converter according to an embodiment of the present invention, V L Is the voltage of the low voltage port, V H Is the voltage of the high voltage port. In the conventional Continuous Conduction Mode (CCM), the upper switch tube Q H Natural zero voltage turn-on can be achieved within a suitable dead time. However, the lower switch tube Q L Due to the forward inductor current i L And natural zero voltage turn-on cannot be achieved. In critical conduction mode (CRM), when the input voltage V is lower than the threshold value L Below the output voltage V H Half of the time, the lower switch tube Q L Zero voltage turn-on can be achieved. However, when the input voltage V is L Higher than the output voltage V H Half of the time, the effective energy in the inductor is not sufficient to discharge the bridge arm node voltage to zero. To achieve zero voltage turn-on, a suitable negative current through the inductor is required. Therefore, a triangular wave current mode (TCM) is used to make the upper switch tube Q H Is still connected when the inductive current is zero-crossedIn general, a sufficient negative current is provided to realize the lower switch tube Q L The zero voltage of (2) turns on.
Fig. 6 (b) shows a Boost converter in the dc converter provided by the embodiment of the present invention
Figure BDA0003847580570000111
A typical input inductor current and switching leg node voltage waveform. At t 0 ～t 1 In time period, Q L At t 0 Moment on, V L Applied to the inductor L, the inductor current i L Increasing linearly. Once at t 1 Reach a given T at time on Or I s When is, Q L Turning off; at t 1 ～t 2 In the time period, due to Q H And Q L Are all in an off state, an inductor L and two switching tubes Q H And Q L Output capacitor C oss_H And C oss_L Resonance occurs therebetween. C oss_L Charged by an inductive current, C oss_H Discharged by the inductor current. Once C is present oss_H The voltage across the terminals is at t 2 Discharge to zero at all times, Q H The switch is immediately conducted to realize zero voltage switching-on; at t 2 ～t 3 In the time period, Q H At time t2, is turned on, V H And V L The voltage difference between the two is applied to the inductor L, and the current of the inductor L decreases linearly. Inductor current i L At t 3 The time drops to zero. In the case of traditional CRM, Q H At t 3 Is turned off at a moment and then resonates. However, when V L Greater than V H Half of the time, when the zero voltage of CRM is lost, the voltage C is turned on oss_L The voltage on cannot reach zero. To overcome V L Higher than V H At half time, at t 3 ～t 4 In the time period, Q H At i L The conducting state is maintained after the zero crossing. Until t 4 At the moment a given reverse current or T is reached R When Q is H And (5) disconnecting. At t 4 ～t 5 In the time period, due to Q H At t 4 Turn off, inductance L and C oss Generates resonance and outputs electricityThe capacitor is charged or discharged by a negative inductor current. At t, an extra reverse current is added 5 Time of day, C oss_L The voltage across can be reduced to zero. At this time Q L Turn on simultaneously, i.e. Q is realized L The zero voltage of (2) turns on.
Fig. 6 (c) shows a Boost converter in the dc converter provided by the embodiment of the present invention
Figure BDA0003847580570000112
A typical input inductor current and switching leg node voltage waveform. At the moment, an upper switch tube Q is not required to be added H The reverse conduction time of the lower switch tube Q can be obtained L The zero voltage of (c) is on. Because the capacitance of the switch tube node is completely discharged, the body diode commutation time T appears R . To reduce the conduction loss of the body diode, Q is set at zero node voltage L Zero voltage turn-on can be done immediately.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (9)

1. A direct current converter topology with adjustable output voltage in a wide input range is characterized by comprising two transmission paths for transferring energy from an input port to an output port: the input ports of the main channel and the auxiliary channel are connected in series, and the output ports are connected in parallel;
the main channel is a DCX based on LLC, and works at a fixed switching frequency;
the auxiliary channel comprises two stages, a first stage adopts a non-isolated PWM direct current-direct current converter, a second stage adopts DCX based on LLC, the first stage and the second stage are cascaded at the input side of the DCX of the auxiliary channel, and the output voltage is regulated by regulating the non-isolated PWM direct current-direct current converter of the auxiliary channel.
2. The wide input range output voltage adjustable dc converter topology of claim 1, wherein the DCX used for the main channel and the DCX used for the auxiliary channel both operate at a series resonant frequency of their respective resonators.
3. The wide input range output voltage adjustable dc converter topology of claim 1, wherein the switching frequency of the PWM converter used by the auxiliary channel is independent of the two DCXs.
4. The wide input range output voltage adjustable dc converter topology according to claim 1 or 2, wherein the DCX used by the main channel and the DCX used by the auxiliary channel operate at the same series resonance frequency and duty cycle.
5. The wide input range output voltage adjustable DC converter topology of claim 1 or 2, wherein the main channel comprises a PWM DC-DC converter, a first filter capacitor C in1 A second filter capacitor C in2 A first switch tube Q 1 A second switch tube Q 2 A first resonant inductor L r1 And a first resonant capacitor C r1 A first resonant cavity is formed; a first filter capacitor C in1 A second filter capacitor C connected in parallel with the input of the PWM converter in2 Connected in parallel with the output of the PWM converter, the output of the PWM converter is applied to the first switch tube Q 1 And a second switching tube Q 2 On the bridge arms which are formed together, the output of the middle point of the bridge arms is applied to a first resonant cavity;
the auxiliary channel comprises a third filter capacitor C 3 And a third switching tube Q 3 A fourth switch tube Q 4 A second resonant inductor L r2 And a second resonant capacitor C r2 A second resonant cavity is formed; third filter capacitor C in3 Is connected in parallel to the third switching tube Q 3 And a fourth switching tube Q 4 On the bridge arms which are formed together, the output of the middle point of the bridge arms is applied to a second resonant cavity;
the main channel and the auxiliary channel share a common excitation inductor L m The center-tapped transformer T and the first synchronous rectification switch tube S 1 And a second rectifying switch tube S 2 A synchronous rectifier is formed; the outputs of the first and second resonators are applied to the input side of a center tapped transformer T, the output side of which is connected to a synchronous rectifier.
6. The wide input range output voltage adjustable direct current converter topology structure of claim 1, wherein the PWM converter of the auxiliary channel adopts a triangular wave current mode modulation mode.
7. The topology of claim 1, wherein the switching tubes of the auxiliary channel PWM converter and the primary side switching tubes of the DCXs are GaN devices.
8. The wide input range output voltage regulated DC converter topology according to claim 5, characterized in that said topology synchronous rectifiers are silicon devices.
9. The DC converter topology structure with adjustable output voltage within wide input range according to claim 5, wherein the driving signal of the synchronous rectifier and the driving signal of the primary side switching tube of the topology structure are synchronous and have the same and fixed frequency and duty ratio.
CN202211123994.7A 2022-09-15 2022-09-15 Direct current converter topological structure with adjustable output voltage in wide input range Pending CN115441746A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117277821A (en) * 2023-11-17 2023-12-22 湖南北顺源智能科技有限公司 Mixed type high-voltage direct-current electric energy converter system of submarine observation network and control method

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117277821A (en) * 2023-11-17 2023-12-22 湖南北顺源智能科技有限公司 Mixed type high-voltage direct-current electric energy converter system of submarine observation network and control method
CN117277821B (en) * 2023-11-17 2024-02-06 湖南北顺源智能科技有限公司 Mixed type high-voltage direct-current electric energy converter system of submarine observation network and control method

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