CN113890324B - Alternating current switching power supply for realizing mixed conduction mode based on long dead time - Google Patents

Alternating current switching power supply for realizing mixed conduction mode based on long dead time Download PDF

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CN113890324B
CN113890324B CN202111139463.2A CN202111139463A CN113890324B CN 113890324 B CN113890324 B CN 113890324B CN 202111139463 A CN202111139463 A CN 202111139463A CN 113890324 B CN113890324 B CN 113890324B
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current
switching
module
switching tube
dead time
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CN113890324A (en
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张宇
鲁博
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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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/38—Means for preventing simultaneous conduction of switches
    • 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
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H02M1/126—Arrangements for reducing harmonics from ac input or output using passive filters
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal 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
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal 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, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal 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, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal 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, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • 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)
  • Inverter Devices (AREA)

Abstract

The invention discloses an alternating current switching power supply for realizing a mixed conduction mode based on long dead time, which belongs to the field of switching power supplies and comprises the following components: an inversion module; the outer ring control module is used for carrying out PID control on the signals after LC filtration in the inversion module and outputting the signals; the inner loop control module performs delta-sigma modulation on the difference value between the signal before LC filtering and the signal output by the outer loop control module and outputs the difference value; a dead zone setting module that sets a long dead zone time; the driving logic signal output by the inner loop control module drives a switching tube in the bridge inverter circuit after long dead time, so that the switching frequency is reduced, the working mode of the switching tube is a mixed conduction mode or an intermittent mode, the switching tube can realize zero current switching on and give consideration to larger system output power capacity, and the input alternating current signal is converted into a direct current signal and then output. By setting and adjusting the long dead time, soft switching of the power switching device is achieved and high accuracy is achieved without the need for an externally applied resonant circuit.

Description

Alternating current switching power supply for realizing mixed conduction mode based on long dead time
Technical Field
The invention belongs to the field of switching power supplies, and particularly relates to an alternating current switching power supply for realizing a mixed conduction mode based on long dead time.
Background
High precision ac power has important applications in precision manufacturing, precision measurement and medical fields. The delta-sigma modulation control can achieve good accuracy, but in order to obtain excellent accuracy performance, delta-sigma modulation is required to achieve low latency. Low delay results in very high switching frequency, which is limited by the performance of the existing switching devices, making them unsuitable for high power applications, and in addition, too high switching frequency can cause electromagnetic compatibility problems. In order to reduce the switching frequency while ensuring accuracy, a common approach is to add a filter in the delta-sigma modulated sampling loop. The larger the filter is, the lower the switching frequency is, but the filter reduces the sampling bandwidth, reduces the error suppression capability of the system in a medium frequency band, and reduces the available high-precision bandwidth of the system. Furthermore, the way the filter is changed to change the switching frequency has limited tuning capability and the engineering changes are complex. It is therefore important how to simply reduce the switching frequency while ensuring accuracy and system bandwidth.
In addition to the high precision requirements, the more common requirement is high efficiency, while soft switching is an effective way to achieve high efficiency. Current approaches to soft switching typically require peripheral auxiliary devices to achieve resonance, which increases control and design complexity. Zero current turn-on of the switching tube can be realized through inductor current interruption, and an inverter in an interruption mode (Discrete Current Mode, DCM) does not need auxiliary devices, but the inverter in a traditional inductor current interruption mode usually adopts a current hysteresis mode and needs a large number of analog devices to realize control. In addition, since the voltage comparator cannot accurately detect the comparison voltage, adverse effects are caused on the output waveform and control of the inverter. Moreover, the state average model of the inverter of the traditional DCM is a nonlinear and time-varying model related to the duty cycle and the output voltage at the moment in each switching period, and due to difficult modeling, hysteresis control depends on trial and error and lacks a higher-level feedback control strategy. To sum up, it is of great importance how to have a switching power supply achieve high accuracy at a suitable switching frequency and achieve high efficiency like in the case of DCM, while facilitating modeling to achieve advanced control.
Disclosure of Invention
In order to overcome the defects and improvement requirements of the prior art, the invention provides an alternating current switching power supply for realizing a mixed conduction mode based on long dead time, and aims to realize soft switching and mixed conduction of a power switching device under the condition of no additional resonant circuit by setting and adjusting the long dead time.
To achieve the above object, the present invention provides an ac switching power supply for realizing a hybrid conduction mode based on a long dead time, comprising: the inverter module comprises a bridge type inverter circuit and an LC filter circuit connected with the middle point of a bridge arm of the bridge type inverter circuit; the outer ring control module is used for carrying out PID control on the signals after LC filtration in the inversion module and outputting the signals; the inner loop control module is used for performing delta-sigma modulation on the difference value between the signal before LC filtering in the inversion module and the signal output by the outer loop control module and then outputting a driving logic signal; the dead zone setting module is connected between the inner loop control module and the bridge inverter circuit and is used for setting long dead zone time, and the range of the long dead zone time is 5 mu s-500 mu s; and driving logic signals output by the inner ring control module drive a switching tube in the bridge inverter circuit after passing through the long dead time, so that the working mode of the switching tube is a mixed conduction mode or an intermittent mode, and the input alternating current signals are converted into direct current signals and then output.
Furthermore, the switching tube is reversely connected with a diode in parallel, and the dead zone setting module is used for adjusting the long dead zone time, so that in the long dead zone time, the inductance current in the LC filter circuit is continuously reduced to zero through the diode of the upper bridge arm or the lower bridge arm, so that the switching tube is controlled to work in an intermittent mode, and zero current opening is realized.
Furthermore, the switch tube is reversely connected with a diode in parallel, and the dead zone setting module is also used for setting two types of long dead zone time with different sizes; the inductance current in the LC filter circuit is continuously reduced through the diode of the upper bridge arm or the lower bridge arm, the switching tube is conducted when the inductance current is not reduced to zero in the smaller long dead time, and the switching tube is conducted when the inductance current is reduced to zero in the larger long dead time, so that the switching tube is controlled to work in the mixed conduction mode.
Still further, the dead zone setting module is further configured to adjust a ratio of the two types of long dead times with unequal sizes to adjust a ratio of continuous conduction and discontinuous conduction in the hybrid conduction mode.
Furthermore, the switch tube is reversely connected with a diode in parallel, and the dead zone setting module is also used for setting long dead zone time with fixed duration; in the switching process of the upper bridge arm and the lower bridge arm switching tube, the inductance current in the LC filter circuit is continuously reduced through the diode of the upper bridge arm or the diode of the lower bridge arm, if the inductance current is larger than a current threshold value, the switching tube is conducted when the inductance current is not reduced to zero, otherwise, the switching tube is conducted when the inductance current is reduced to zero, so that the switching tube is controlled to work in a mixed conduction mode.
Still further, the switching tube is reversely connected with a diode in parallel, and the dead zone setting module is further used for adjusting the long dead zone time, so that the long dead zone time is longer than the driving duration of the switching tube, and the switching tube is kept to be turned off to reduce the turn-on and turn-off times of the switching tube.
Still further, the ac switching power supply is an ac voltage source, the ac voltage source further includes a voltage sampling module, the voltage sampling module is configured to sample the voltage signal after LC filtering by the inversion module, and the outer loop control module is configured to output the voltage signal obtained by sampling after PID control.
Still further, the ac switching power supply is an ac current source, the ac current source further includes a current sampling module, the current sampling module is configured to sample the current signal after LC filtering by the inversion module, and the outer loop control module is configured to output the current signal obtained by sampling after PID control.
In general, through the above technical solutions conceived by the present invention, the following beneficial effects can be obtained:
(1) The delta-sigma modulation is utilized to realize the high-precision index of the alternating current switching power supply, the PID control is combined to further improve the precision, and on the basis, the soft switching and the mixed conduction of the power switching device are realized under the condition that a resonant circuit is not required to be additionally arranged by setting long dead time, so that the high efficiency is realized; compared with the mode of reducing the switching frequency by adding loop delay in a delta-sigma inner loop, the long dead time mode can better ensure the precision; in addition, the delta-sigma modulation model solves the problems that a mathematical model obtained according to a state equation in an inductance current intermittent mode is nonlinear and time-varying and cannot be unified with the mathematical model in a continuous current mode by injecting an error source, so that the system is convenient for analysis control, and an analysis basis is established for more advanced control;
(2) Because of the existence of long dead time, the switching frequency is reduced, and the inductor current can be interrupted, so that zero current switching on of the switching tube is realized, the loss of the switching tube is greatly reduced, and the overall efficiency is improved;
(3) Because of the existence of two long dead time with different lengths, the switching frequency is reduced, and the inductive current can be intermittent or partially intermittent, so that the mixed conduction of the switching tube is realized, the peak value of the inductive current in the mixed conduction mode is smaller than that in the intermittent mode, and the current stress of the switching device and the inductor can be reduced, thereby reducing the inductance loss, the turn-off loss and the on-state loss of the switching tube;
(4) By setting the long dead time longer than the given driving time of the switching tube, the switching tube keeps turned off, and the turn-on and turn-off times of the switching tube can be reduced, so that the loss of the switching tube is reduced.
Drawings
Fig. 1 is a schematic structural diagram of an ac switching voltage source for implementing a hybrid conduction mode based on a long dead time according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of an ac switching current source for implementing a hybrid conduction mode based on a long dead time according to an embodiment of the present invention;
FIG. 3 is a waveform diagram of delta-sigma+PID voltage dual loop control provided by an embodiment of the present invention;
FIG. 4 is a waveform diagram after loop delay increase under delta-sigma control;
FIG. 5 is a waveform diagram of delta-sigma control with increased dead time according to an embodiment of the present invention;
FIG. 6 is a waveform diagram after increasing dead time under the control of the delta-sigma voltage inner loop PID current outer loop provided by the embodiment of the invention;
FIG. 7 is a graph of the output waveform of the high switching frequency resulting from setting the lower delay of the inner loop under delta-sigma+PID voltage dual loop control;
FIG. 8 is a detailed waveform diagram of a switching tube for realizing zero current turn-on after increasing dead time under delta-sigma control provided by an embodiment of the present invention;
fig. 9 is a modulation model of delta-sigma modulation applied to an inverter according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. 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 invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
In the present invention, the terms "first," "second," and the like in the description and in the drawings, if any, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order.
Fig. 1 and fig. 2 are schematic structural diagrams of an ac switching voltage source and an ac switching current source for implementing a hybrid conduction mode based on a long dead time according to an embodiment of the present invention. Referring to fig. 1 and 2, an ac switching power supply for implementing a hybrid conduction mode based on a long dead time in this embodiment will be described in detail with reference to fig. 3 to 9.
The alternating current switching power supply for realizing the mixed conduction mode based on the long dead time comprises an inversion module, an outer ring control module, an inner ring control module and a dead time setting module. The inverter module comprises a bridge inverter circuit and an LC filter circuit connected with the middle point of a bridge arm of the bridge inverter circuit, wherein the bridge inverter circuit is used for converting an input direct current signal into an alternating current signal and outputting the alternating current signal, and the LC filter circuit is used for carrying out LC filtering on the alternating current signal output by the bridge inverter circuit. The outer loop control module is used for carrying out PID control on the signals after LC filtration in the inversion module and outputting the signals. The inner loop control module is used for performing delta-sigma modulation on the difference value between the signal before LC filtering in the inversion module and the signal output by the outer loop control module and outputting a driving logic signal. The dead zone setting module is connected between the inner ring control module and the bridge type inverter circuit, the input of the dead zone setting module is connected with the output of the inner ring control module, the output of the dead zone setting module is connected with a driving link for driving the bridge type inverter circuit, and the dead zone setting module is used for setting long dead zone time, wherein the range of the long dead zone time is 5 mu s-500 mu s. The driving logic signals output by the inner loop control module drive the switching tubes in the bridge inverter circuit after long dead time, so that the working modes of the switching tubes comprise a mixed conduction mode and/or an intermittent mode, and the input alternating current signals are converted into direct current signals and then output.
In this embodiment, the dead time refers to a protection period set for preventing the upper and lower switching tubes of the bridge inverter circuit from being simultaneously turned on due to a switching speed problem when the inner ring control module outputs the driving logic signal, that is, the driving response time of the inner ring control module. It is understood that the long dead time in this embodiment may have other ranges as long as the duration is enough to make the operation mode of the switching tube be the hybrid conduction mode or the intermittent mode. In the ac switching power supply of this embodiment, due to the feedback attribute of delta-sigma modulation, the switching frequency will be forced to be reduced, and the lower switching frequency makes the inductor current realize intermittent or partially intermittent, so as to realize zero current turn-on of the switching tube, thereby greatly reducing the loss of the switching tube.
Each switching tube in the bridge inverter circuit is connected in reverse parallel with a diode, as shown in fig. 1 and 2. When the switch tube is a MOS tube, the body diode of the MOS tube can be directly used without additionally arranging an anti-parallel diode for the MOS tube; when the switching tube is an IGBT, the IGBT is generally integrated with an antiparallel diode, and the antiparallel diode is not required to be additionally provided for the IGBT. The control process of the alternating current switching power supply working in the intermittent mode is as follows: the dead zone setting module increases the long dead zone time, so that the inductance current in the LC filter circuit is continuously reduced to zero through the diode of the upper bridge arm or the lower bridge arm in the long dead zone time, and the switching tube is controlled to work in an intermittent mode, so that zero current opening is realized. The specific value of the long dead time is determined by the specific application scene of the LC filter circuit, and the inductor current in the LC filter circuit can be reduced to zero only by meeting the requirement.
The implementation of inductor current interruption (interruption mode) is described by taking half-bridge topology as an example. When the comparator in the inner loop control module acts, a corresponding switch tube driving logic signal is generated, the dead zone setting module sets a long-time dead zone, the switch tubes are all blocked in the dead zone time, the inductance current flows through the diode of the upper tube or the diode of the lower tube according to the direction, the inductance current is prevented from being continuously reduced in the dead zone time, when the dead zone time is long enough, the inductance current can be reduced to zero, and after that, the inductance current is maintained to be near zero until the comparator acts again and the new dead zone time is finished, so that the switch tubes are conducted when the current is zero, and the switching loss is reduced.
In an embodiment of the present invention, a control process of the ac switching power supply operating in the hybrid conduction mode is: the dead zone setting module sets two types of long dead zone time with different sizes; the inductance current in the LC filter circuit is continuously reduced through the diode of the upper bridge arm or the lower bridge arm; in the small long dead time, the switching tube is conducted when the inductance current is not reduced to zero, namely, the inductance current works in a continuous conduction mode; in a larger long dead time, the switching tube is conducted when the inductance current is reduced to zero, namely, the inductance current works in a discontinuous conduction mode; thereby, the switching tube is controlled to operate in the hybrid conduction mode. The specific values of the two types of long dead time are determined by specific application scenes, and the inductor current in the LC filter circuit can be reduced to zero only by meeting the requirement of larger long dead time, and the inductor current in the LC filter circuit can be reduced to zero only by smaller long dead time.
Further, the dead zone setting module may also adjust the ratio of continuous conduction and discontinuous conduction in the hybrid conduction mode by adjusting the ratio of the two types of unequal long dead times (e.g., by adjusting the frequency of occurrence of the two types of long dead times).
In another embodiment of the present invention, the control process of the ac switching power supply operating in the hybrid conduction mode is: the dead zone setting module sets long dead zone time with fixed duration; in the switching process of the upper bridge arm and the lower bridge arm switching tube, the inductance current in the LC filter circuit is continuously reduced through the diode of the upper bridge arm or the lower bridge arm; if the inductor current is greater than the current threshold (e.g., the inductor current is at the current peak), the switching tube is turned on when the inductor current is not reduced to zero, i.e., the inductor current operates in a continuous conduction mode; if the inductor current is not greater than the current threshold (e.g., the inductor current is near zero current), the switching tube is turned on when the inductor current decreases to zero, i.e., the inductor current operates in a discontinuous conduction mode; thereby, the switching tube is controlled to operate in the hybrid conduction mode. The current threshold is a value related to a specific application scenario, and is only used for explaining that when the upper bridge arm switching tube and the lower bridge arm switching tube are switched, if the inductance current is larger at the moment, the inductance current works in a continuous conduction mode, otherwise, the inductance current works in a discontinuous conduction mode, and the mixed conduction of the switching tubes is realized.
The implementation process of inductor current interruption + continuity (hybrid conduction mode) is described by taking a half-bridge topology as an example. The implementation process of the inductor current interruption is the same as the implementation process of the inductor current interruption described above, and is not repeated here; the realization process of the inductor current continuity comprises the following steps: when the inductance current is overlarge or the dead time is smaller, the inductance current is not reduced to zero, the switching tube is already conducted, and then the mixed conduction mode with discontinuous current parts is realized. The mixed conduction mode has the advantage that the peak value of the inductance current is smaller than that in the discontinuous mode, so that the current stress of the switching device and the inductance can be reduced, and the inductance loss, the turn-off loss of the switching tube and the on-state loss are reduced. Thus, a mixed conduction mode of a suitable ratio is more advantageous for achieving high efficiency.
According to the embodiment of the invention, the dead zone setting module is further used for adjusting the long dead zone time, so that the long dead zone time is longer than the driving duration of the switching tube, and the switching tube is kept to be turned off to reduce the turn-on and turn-off times of the switching tube. Since the inductor current is continuously reduced in value during the dead zone regardless of direction, the dead zone has the same effect as the corresponding control sequence of blocking the inductor current, and since the dead zone time may exceed the driving duration of the switching tube, the switching tube will remain turned off, thereby reducing the number of on-off times of the switching tube and thus the switching tube loss.
In an embodiment of the present invention, the ac switching power supply is an ac voltage source, as shown in fig. 1. The alternating current voltage source further comprises a voltage sampling module, the voltage sampling module is used for sampling the voltage signal filtered by the inversion module LC, and the outer ring control module is used for performing PID control on the sampled voltage signal and then outputting the voltage signal.
Specifically, referring to fig. 1, the ac voltage source includes a bridge inverter circuit, an LC filter circuit, a load, a sampling module, a voltage sampling module, an outer loop control module, an inner loop control module, a dead zone setting module, and a driving link. The voltage sampling module samples voltage signals flowing through two ends of the load after LC filtering; the outer ring control module subtracts the voltage signal obtained by the voltage sampling module from the input reference signal, carries out PID adjustment and outputs the voltage signal; the sampling module samples a voltage signal of the middle point of the bridge arm; the inner ring control module integrates, compares and converts the difference between the signal output by the outer ring control module and the voltage signal obtained by sampling by the sampling module to obtain a driving logic signal; the dead zone setting module sets a long-time dead zone, and the driving logic signal drives a switching tube in the bridge inverter circuit through a driving link after passing through the long-time dead zone, so that the alternating current output by the bridge inverter circuit is equal to the target alternating current.
In another embodiment of the present invention, the ac switching power supply is an ac current source, as shown in fig. 2. The alternating current source further comprises a current sampling module, the current sampling module is used for sampling the current signal filtered by the inversion module LC, and the outer ring control module is used for carrying out PID control on the sampled current signal and then outputting the current signal.
Specifically, referring to fig. 2, the ac current source includes a bridge inverter circuit, an LC filter circuit, a load, a sampling module, a current sampling module, an outer loop control module, an inner loop control module, a dead zone setting module, and a driving link. The current sampling module samples a current signal flowing through the load after LC filtering; the outer ring control module subtracts the current signal obtained by the current sampling module from the input reference signal, carries out PID adjustment and outputs the current signal; the sampling module samples a voltage signal of the middle point of the bridge arm; the inner ring control module integrates, compares and converts the difference between the signal output by the outer ring control module and the voltage signal obtained by sampling by the sampling module to obtain a driving logic signal; the dead zone setting module sets a long-time dead zone, and the driving logic signal drives a switching tube in the bridge inverter circuit through a driving link after passing through the long-time dead zone, so that the alternating current output by the bridge inverter circuit is equal to the target alternating current.
In the AC switching power supply, a delta-sigma modulation model adopted by an inner loop control module is shown as figure 9, K represents the equivalent gain of a loop integrator, and e -st Representing time delay, the model of its injected noise source is timeThe system is suitable for analyzing the state of the inverter in the intermittent mode, so that the problems that a mathematical model obtained according to a state equation in the intermittent mode of the inductance current is nonlinear and time-varying and cannot be unified with the mathematical model in the continuous current mode are solved, the system is convenient for analysis and control, and an analysis basis is established for advanced control of PID and other control.
Referring to FIG. 3, an output voltage u under delta-sigma+PID voltage double loop control is shown o Output current i o Inductor current i L And switching tube voltage u G1 Is a waveform of the experiment. In the waveform diagram shown in fig. 3, the total harmonic distortion (Total Harmonic Distortion, THD) of the voltage is 0.287% and the efficiency is 94.8%.
For delta-sigma control, loop delay is increased to realize mixed conduction of inductance and current, and the voltage u is output at the moment o Output current i o Inductor current i L And switching tube voltage u G1 The experimental waveforms of (2) are shown in FIG. 4. In the waveform diagram shown in fig. 4, THD is only 1.09%, and efficiency is 94.9%, and it can be seen that the power supply accuracy is greatly affected by implementing the mixed conduction mode in the long-delay mode.
For delta-sigma control, the long dead time proposed in the embodiment is increased to realize the mixed conduction of the inductor and the current, and the output voltage u is output at the moment o Output current i o Inductor current i L And switching tube voltage u G1 The experimental waveforms of (2) are shown in fig. 5. In the waveform diagram shown in fig. 5, THD is 0.432% and efficiency is 94.9%, and it can be seen that the long dead time mode in this embodiment can maintain high voltage source accuracy and high efficiency.
Comparing fig. 4 and fig. 5, it can be seen that, under the same switching frequency, higher accuracy can be achieved by increasing the dead zone to achieve inductor current interruption compared to increasing the loop delay to achieve inductor current interruption. Comparing fig. 3 and fig. 5, it can be seen that the delta-sigma+pid dual-loop control can further improve the precision on the basis of realizing the intermittent, thereby realizing the high-precision and high-efficiency ac power supply.
Further, in delta-sigma voltage inner loop, PID current outer loop controlUnder the condition, the long dead time proposed in the embodiment is increased to realize the mixed conduction of the inductance and the current, and the output voltage u is output at the moment o Output current i o Inductor current i L And switching tube voltage u G1 The experimental waveforms of (2) are shown in fig. 6. In the waveform diagram shown in fig. 6, THD is 0.212% and efficiency is 94.8%, and it can be seen that the long dead time mode in this embodiment can realize a high-precision and high-efficiency ac current source.
For the delta-sigma + PID voltage dual loop control shown in fig. 3, the inner loop control adds a lower delay, the output waveform of which is shown in fig. 7, the average switching frequency is 90kHz in fig. 7, resulting in a high switching frequency, voltage THD of 0.089%. In the result shown in fig. 7, the inductor current is not interrupted in most cases due to the higher switching frequency, and the switching tube is turned on hard, so that the efficiency is only 82.5%. Comparing fig. 6 and fig. 7, the delta-sigma+pid control in the present embodiment has the advantage of high efficiency in the long dead time mode and still has high accuracy compared with the delta-sigma+pid inner loop control with lower delay.
In addition, under the control of delta-sigma, the long dead time proposed in the embodiment is increased to realize the mixed conduction of the inductor and the current, and the output voltage u is output at the moment o Output current i o Inductor current i L And bridge arm midpoint voltage u G1 The experimental waveform of' is shown in fig. 8, it can be seen that the interruption of the inductor current is realized, the upper switching tube is turned on when the inductor current is zero, and the zero current is turned on.
In the embodiment, the delta-sigma modulation has the characteristic of noise shaping, so that various errors such as bridge arm midpoint quantization, dead zone effect and the like can be effectively restrained, and the high-precision inverter power supply can be realized. The outer ring PID control module samples output voltage or current, so that a high-precision voltage source or current source is realized. The dead zone setting module reduces the switching frequency by setting a dead zone for a long time, thereby realizing the interruption and/or partial interruption of the inductive current, effectively reducing the switching loss and reducing the switching on and off times of the switching tube so as to reduce the switching tube loss.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.

Claims (5)

1. An ac switching power supply for implementing a hybrid conduction mode based on a long dead time, comprising:
the inverter module comprises a bridge type inverter circuit and an LC filter circuit connected with the middle point of a bridge arm of the bridge type inverter circuit;
the outer ring control module is used for carrying out PID control on the signals after LC filtration in the inversion module and outputting the signals;
the inner loop control module is used for performing delta-sigma modulation on the difference value between the signal before LC filtering in the inversion module and the signal output by the outer loop control module and then outputting a driving logic signal;
the dead zone setting module is connected between the inner loop control module and the bridge inverter circuit and is used for setting long dead zone time, and the range of the long dead zone time is 5 mu s-500 mu s;
the driving logic signals output by the inner ring control module drive the switching tubes in the bridge inverter circuit after passing through the long dead time, so that the working modes of the switching tubes are mixed conduction modes, and the input direct current signals are converted into alternating current signals and then output;
the switching tube is reversely connected with a diode in parallel, and the dead zone setting module is also used for setting two types of long dead zone time with different sizes;
the inductance current in the LC filter circuit is continuously reduced through the diode of the upper bridge arm or the lower bridge arm, the switching tube is conducted when the inductance current is not reduced to zero in the smaller long dead time, and the switching tube is conducted when the inductance current is reduced to zero in the larger long dead time so as to control the switching tube to work in a mixed conduction mode;
the dead zone setting module is also used for adjusting the proportion of the two types of long dead zone time with unequal sizes so as to adjust the proportion of continuous conduction and discontinuous conduction in the mixed conduction mode.
2. The ac switching power supply for realizing a hybrid conduction mode based on a long dead time as claimed in claim 1, wherein the switching tube is connected in anti-parallel with a diode, and the dead time setting module is further configured to set the long dead time of a fixed duration;
in the switching process of the upper bridge arm and the lower bridge arm switching tube, the inductance current in the LC filter circuit is continuously reduced through the diode of the upper bridge arm or the diode of the lower bridge arm, if the inductance current is larger than a current threshold value, the switching tube is conducted when the inductance current is not reduced to zero, otherwise, the switching tube is conducted when the inductance current is reduced to zero, so that the switching tube is controlled to work in a mixed conduction mode.
3. The ac switching power supply for implementing a hybrid conduction mode based on a long dead time as claimed in claim 1, wherein the switching tube is connected in inverse parallel with a diode, and the dead time setting module is further configured to adjust the long dead time such that the long dead time is longer than a driving duration of the switching tube, and the switching tube is kept turned off to reduce the number of turn-on/off times of the switching tube.
4. An ac switching power supply for implementing a hybrid conduction mode based on long dead time as claimed in any one of claims 1 to 3, wherein the ac switching power supply is an ac voltage source, the ac voltage source further comprises a voltage sampling module, the voltage sampling module is configured to sample a voltage signal after LC filtering by the inverter module, and the outer loop control module is configured to perform PID control on the sampled voltage signal and output the sampled voltage signal.
5. A long dead time based ac switching power supply for implementing a hybrid conduction mode according to any one of claims 1 to 3, wherein the ac switching power supply is an ac current source, the ac current source further comprises a current sampling module, the current sampling module is configured to sample a current signal after LC filtering by the inverter module, and the outer loop control module is configured to perform PID control on the sampled current signal and output the current signal.
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