CN113258807A - Low output impedance DC-AC power supply - Google Patents

Low output impedance DC-AC power supply Download PDF

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Publication number
CN113258807A
CN113258807A CN202110611521.0A CN202110611521A CN113258807A CN 113258807 A CN113258807 A CN 113258807A CN 202110611521 A CN202110611521 A CN 202110611521A CN 113258807 A CN113258807 A CN 113258807A
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output
circuit
switching device
mos tube
gate
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CN202110611521.0A
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CN113258807B (en
Inventor
汪泽
余沐阳
刘昶
周凯
李彦
陈庆
李红斌
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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
    • 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
    • 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
    • H02M1/083—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the ignition at the zero crossing of the voltage or the current
    • 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
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • 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
    • 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
    • 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

Abstract

The invention relates to a low output impedance DC-AC power supply.A switching circuit takes electricity from a DC power supply and outputs the electricity to an LC resonant cavity circuit, a control circuit controls the switching circuit to realize the resonance of the LC resonant cavity circuit, direct current is converted into high-frequency alternating current and then is output to a transformer circuit, and after the high-frequency alternating current is respectively rectified by an output anode switch tube circuit and an output cathode switch tube circuit, direct current voltages with positive polarity and negative polarity are respectively generated at two ends of a load of an output load circuit; the phase angle of the PWM wave generated by the PWM generator is controlled to make the DC gain of the circuit change in a sine way, so that the output load circuit outputs a sine wave. The soft switching function is realized through the switching circuit, and the switching loss is reduced; the transformer is used for realizing impedance transformation, so that the filter inductance loss is reduced, and the output impedance is reduced; the output level is changed in a sine way through PI control, so that the output end outputs a sine voltage with adjustable amplitude and frequency.

Description

Low output impedance DC-AC power supply
Technical Field
The invention relates to the technical field of digital power supplies, in particular to a low-output-impedance DC-AC power supply.
Background
With the rapid pace of intelligence in the industrial field, sensors are widely used in various aspects of industrial production. The input impedance of many new sensors is only milliohm, so that the power supply must work under the working condition of low voltage and large current, which puts new requirements on the power supply.
The analog power supply is basically eliminated due to the reasons of low energy conversion efficiency, small output range and the like, and the traditional H-bridge inverter is low in duty ratio under the working condition of low voltage and large current, so that a switching tube is in the switching process for most of time, the switching loss is overlarge, and harmonic waves are easily introduced to cause waveform distortion; in addition, as the LC filter needs to be additionally arranged at the output end of the traditional H-bridge circuit, part of energy is lost on the filter inductor, the energy utilization efficiency is reduced, and the overall performance of the system is indirectly influenced.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides a low-output impedance DC-AC power supply, which adopts BSSAC (Bipolar Shift Sine Amplitude Converter) topology, realizes the soft switching function through a switching circuit and reduces the switching loss; the transformer is used for realizing impedance transformation, so that the filter inductance loss is reduced, and the output impedance is reduced; the control circuit changes the direct current gain of the circuit through phase shift control, so as to change the output voltage; the output level is changed in a sine mode through PI control, so that the output end outputs sine voltage with adjustable amplitude and frequency, and the overall process is that DC-sine high-frequency AC-sine low-frequency AC can output hundreds of millivolt voltage and can drive milliohm load.
The invention provides a low output impedance DC-AC power supply, comprising: the control circuit, the DC power supply, the switching circuit, the LC resonant cavity circuit, the transformer circuit, the output anode switch tube circuit, the output cathode switch tube circuit and the output load circuit;
the control circuit includes: a comparator C1, a comparator C2, a PI ring, a PWM generator, an AND gate N1, an AND gate N2, an AND gate N3, an AND gate N4, a NOT gate A1 and an output voltage measurer Mv;
two input ends of the comparator C1 input a modulation wave and a constant variable zero respectively, and an output end is connected with the PI ring input end; two input ends of the comparator C2 input the modulated wave and the output signal of the output load circuit, respectively; the output voltage measurer Mv measures the output voltage of the output voltage measurer;
the output end of the PI ring is connected with the input end of the PWM generator, the first output end of the PWM generator is respectively connected with one input end of the AND gate N1 and one input end of the AND gate N3, and the second output end of the PWM generator is respectively connected with one input end of the AND gate N2 and one input end of the AND gate N4; the output end of the comparator C2 is respectively connected with the other input ends of the AND gate N1 and the AND gate N2, and the output end of the comparator C2 is respectively connected with the other input ends of the AND gate N3 and the AND gate N4 after passing through the NOT gate A1;
the switch circuit takes electricity from the DC power supply and outputs the electricity to the LC resonant cavity circuit, the control circuit controls the switch circuit to realize the resonance of the LC resonant cavity circuit, direct current is converted into high-frequency alternating current and then is output to the transformer circuit, and after the high-frequency alternating current is rectified by the output anode switch tube circuit and the output cathode switch tube circuit respectively, positive-polarity direct current voltage and negative-polarity direct current voltage are generated at two ends of a load of the output load circuit respectively;
and controlling the phase angle of the PWM wave generated by the PWM generator to enable the direct current gain of the circuit to change in a sine mode, so that the output load circuit outputs sine waves.
On the basis of the technical scheme, the invention can be improved as follows.
Optionally, the switching circuit includes a MOS transistor switching device S1 and a MOS transistor switching device S2, two output ends of the PWM generator are respectively connected to control ends of the MOS transistor switching device S1 and the MOS transistor switching device S2, and the MOS transistor switching device S1 and the MOS transistor switching device S2 are controlled to be alternately turned on to take power from the DC power supply;
the power input end of the MOS tube switch device S1 and the power output end of the MOS tube switch device S2 are respectively connected with the anode and the cathode of the DC power supply, the power output end of the MOS tube switch device S1 and the power input end of the MOS tube switch device S2 are connected with each other to serve as the anode of power taking output, and the cathode of the power taking output is connected with the cathode of the DC power supply.
Optionally, the LC resonant cavity circuit includes a resonant capacitor Cr and a resonant inductor Lr;
one end of the resonance inductor Lr is connected to the output end of the switch circuit, the other end of the resonance inductor Lr is connected to one end of the resonance inductor Lr, the other end of the resonance inductor Lr is connected to one end of the transformer circuit, and the other end of the transformer circuit is connected to the negative electrode of the DC power supply.
Optionally, the transformer circuit includes a primary winding, a secondary winding Ns1, a secondary winding Ns2, a secondary winding Ns3, and a secondary winding Ns 4;
the homonymous end and the heteronymous end of the primary winding are respectively connected with the output end of the LC resonant cavity circuit and the negative electrode of the DC power supply, and the divided voltage is respectively output through the secondary winding Ns1, the secondary winding Ns2, the secondary winding Ns3 and the secondary winding Ns 4.
Optionally, the output positive switch tube circuit includes a MOS tube switch device S3 and a MOS tube switch device S4; the control ends of the MOS tube switching device S3 and the MOS tube switching device S4 are respectively connected with the output ends of the AND gate N1 and the AND gate N2; the control circuit sends out a control signal to enable the MOS tube switching device S3 and the MOS tube switching device S4 to be conducted alternately;
the power input ends of the MOS tube switching device S3 and the MOS tube switching device S4 are respectively connected with the homonymous end of the secondary winding Ns1 and the heteronymous end of the secondary winding Ns2, the power output ends of the MOS tube switching device S3 and the MOS tube switching device S4 are both connected with the positive input end of the output load circuit, and the negative input end of the output load circuit is connected with the heteronymous end of the secondary winding Ns1 and the homonymous end of the secondary winding Ns 2.
Optionally, the output cathode switching tube circuit includes a MOS tube switching device S5 and a MOS tube switching device S6; the control ends of the MOS tube switching device S5 and the MOS tube switching device S6 are respectively connected with the output ends of the AND gate N3 and the AND gate N4; the control circuit sends out control signals to enable the MOS tube switching device S5 and the MOS tube switching device S6 to be alternately conducted, and only one of the two groups of control signals of the MOS tube switching device S3, the MOS tube switching device S4, the MOS tube switching device S5 and the MOS tube switching device S6 can be conducted;
the power input ends of the MOS tube switching device S5 and the MOS tube switching device S6 are respectively connected with the homonymous end of the secondary winding Ns3 and the heteronymous end of the secondary winding Ns4, the power output ends of the MOS tube switching device S3 and the MOS tube switching device S4 are both connected with the positive input end of the output load circuit, and the negative input end of the output load circuit is connected with the heteronymous end of the secondary winding Ns3 and the homonymous end of the secondary winding Ns 4.
Optionally, the MOS transistor switching device includes an MOS transistor, a diode, and a capacitor;
the grid electrode, the source electrode and the drain electrode of the MOS tube are respectively a control end, a power input end and a power output end of the MOS tube switch device;
after the diode is connected with the capacitor in parallel, the anode of the diode is connected with the source electrode of the MOS tube, and the cathode of the diode is connected with the drain electrode of the MOS tube.
Optionally, the output load circuit includes a filter capacitor Cout and a load resistor Rout, and two ends of the filter capacitor Cout and the load resistor Rout connected in parallel are an input end and an output end of the output load circuit.
According to the low-output impedance DC-AC power supply, the modulated wave Vm is compared with a constant zero through the comparator C1 and is used for judging the polarity of the modulated wave Vm at the moment, so that whether the secondary side of the circuit works as an output positive switch tube circuit or a negative switch tube circuit is determined, and the polarity of the output level of the circuit is determined. The output voltage of the circuit measured by the output voltage measurer is sent to a comparator C2 to be compared with the modulation wave Vm, so that the error between the modulation wave Vm and the output voltage is obtained, the error is sent to a PI ring, the PI ring obtains the phase-shifting angle of the PWM wave through calculation, the information is sent to a PWM generator, and the PWM generator generates a corresponding PWM wave control circuit, so that the output level follows the modulation wave Vm, and a sine wave is output. Because the output waveform of the circuit does not contain a large number of higher harmonics, a filter inductor is not required to be additionally arranged at the output end like an H-bridge circuit, and therefore the energy conversion efficiency of the circuit is greatly improved.
Drawings
FIG. 1 is a schematic circuit diagram of a low output impedance DC-AC power supply according to an embodiment of the present invention;
fig. 2 is a schematic circuit diagram of a MOS transistor switching device according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a fundamental analysis method provided by an embodiment of the present invention;
FIG. 4 is a graph of circuit gain as a function of circuit operating frequency according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of phase shifting of PWM waves according to an embodiment of the present invention;
FIG. 6 shows phase shift angles of a low output impedance DC-AC power circuit according to an embodiment of the present invention
Figure 769235DEST_PATH_IMAGE001
A waveform diagram of (a);
FIG. 7 is a waveform diagram of the output of a low output impedance DC-AC power circuit according to an embodiment of the present invention;
in the drawings, the components represented by the respective reference numerals are listed below:
1. the circuit comprises a switch circuit 2, an LC resonant cavity circuit 3, a transformer circuit 4, an output anode switch tube circuit 5, an output cathode switch tube circuit 6, an output load circuit 7 and a control circuit.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.
As shown in fig. 1, which is a schematic circuit diagram of a low-output-impedance DC-AC power supply according to an embodiment of the present invention, it can be known from fig. 1 that a low-output-impedance DC-AC power supply according to the present invention includes: the circuit comprises a control circuit 7, a DC power supply Vd0, a switch circuit 1, an LC resonant cavity circuit 2, a transformer circuit 3, an output anode switch tube circuit 4, an output cathode switch tube circuit 5 and an output load circuit 6.
The control circuit 7 includes: comparator C1, comparator C2, PI loop, PWM generator G1, and gate N1, and gate N2, and gate N3, and gate N4, not gate a1, and output voltage measurer Mv.
Two input ends of the comparator C1 input the modulation wave Vm and the constant variable zero respectively, and the output end is connected with the PI ring input end; two input ends of the comparator C2 input the modulation wave Vm and output signals of the output load circuit respectively; the output voltage measurer Mv measures the output voltage of the output voltage measurer.
The output end of the PI ring is connected with the input end of a PWM generator, the first output end of the PWM generator is respectively connected with one input end of an AND gate N1 and one input end of an AND gate N3, and the second output end of the PWM generator is respectively connected with one input end of an AND gate N2 and one input end of an AND gate N4; the output end of the comparator C2 is respectively connected with the other input ends of the AND gate N1 and the AND gate N2, and the output end of the comparator C2 is respectively connected with the other input ends of the AND gate N3 and the AND gate N4 after passing through the NOT gate A1.
The switching circuit 1 takes electricity from a DC power supply Vd0 and outputs the electricity to the LC resonant cavity circuit 2, the control circuit 7 controls the switching circuit 1 to realize resonance of the LC resonant cavity circuit 2, converts direct current into high-frequency alternating current and outputs the alternating current to the transformer circuit 3, and after the alternating current is rectified by the output positive switch tube circuit 4 and the output negative switch tube circuit 5, positive and negative direct current voltages are respectively generated at two ends of a load of the output load circuit 6.
The phase angle of the PWM wave generated by the PWM generator is controlled to make the DC gain of the circuit change in a sine way, so that the output load circuit 6 outputs a sine wave.
The low-output impedance DC-AC power supply provided by the invention adopts BSSAC (Bipolar Shift Sine Amplitude Converter) topology, realizes the soft switching function through a switching circuit and reduces the switching loss; the transformer is used for realizing impedance transformation, so that the filter inductance loss is reduced, and the output impedance is reduced; the control circuit changes the direct current gain of the circuit through phase shift control, so as to change the output voltage; the output level is changed in a sine mode through PI control, so that the output end outputs sine voltage with adjustable amplitude and frequency, and the overall process is that DC-sine high-frequency AC-sine low-frequency AC can output hundreds of millivolt voltage and can drive milliohm load.
Example 1
Embodiment 1 provided in the present invention is an embodiment of a low output impedance DC-AC power supply provided in the present invention, and as can be seen from fig. 1, the low output impedance DC-AC power supply provided in the present invention includes: the circuit comprises a control circuit 7, a DC power supply Vd0, a switch circuit 1, an LC resonant cavity circuit 2, a transformer circuit 3, an output anode switch tube circuit 4, an output cathode switch tube circuit 5 and an output load circuit 6.
The control circuit 7 includes: comparator C1, comparator C2, PI loop, PWM generator Np, and gate N1, and gate N2, and gate N3, and gate N4, not gate a1, and output voltage measurer Mv. Fig. 1 also includes an inductor Lm connected in parallel with the primary winding Np, which can be replaced by the primary leakage inductance of the transformer in engineering.
Two input ends of the comparator C1 input the modulation wave Vm and the constant variable zero respectively, and the output end is connected with the PI ring input end; two input ends of the comparator C2 input the modulation wave Vm and output signals of the output load circuit respectively; the output voltage measurer Mv measures the output voltage of the output voltage measurer.
The output end of the PI ring is connected with the input end of a PWM generator, the first output end of the PWM generator is respectively connected with one input end of an AND gate N1 and one input end of an AND gate N3, and the second output end of the PWM generator is respectively connected with one input end of an AND gate N2 and one input end of an AND gate N4; the output end of the comparator C2 is respectively connected with the other input ends of the AND gate N1 and the AND gate N2, and the output end of the comparator C2 is respectively connected with the other input ends of the AND gate N3 and the AND gate N4 after passing through the NOT gate A1.
The switching circuit 1 takes electricity from a DC power supply Vd0 and outputs the electricity to the LC resonant cavity circuit 2, the control circuit 7 controls the switching circuit 1 to realize resonance of the LC resonant cavity circuit 2, converts direct current into high-frequency alternating current and outputs the alternating current to the transformer circuit 3, and after the alternating current is rectified by the output positive switch tube circuit 4 and the output negative switch tube circuit 5, positive and negative direct current voltages are respectively generated at two ends of a load of the output load circuit 6.
Preferably, the switching circuit 1 includes a MOS transistor switching device S1 and a MOS transistor switching device S2, two output terminals of the PWM generator are respectively connected to control terminals of the MOS transistor switching device S1 and the MOS transistor switching device S2, and the MOS transistor switching device S1 and the MOS transistor switching device S2 are controlled to be alternately turned on to take power from the DC power supply.
The power supply input end of the MOS tube switch device S1 and the power supply output end of the MOS tube switch device S2 are respectively connected with the anode and the cathode of a DC power supply, the power supply output end of the MOS tube switch device S1 and the power supply input end of the MOS tube switch device S2 are connected to serve as the anode of power taking output, and the cathode of the power taking output is connected with the cathode of the DC power supply.
A first driving signal for driving the MOS tube switching device S1 to be switched on and switched off and a second driving signal for driving the MOS tube switching device S2 to be switched on and switched off are complementary and dead zones exist; and when the MOS tube switching device S1 is conducted with the MOS tube switching device S2, the voltages at the two ends of the switching tube are both 0, so that the soft switching of the switching tube is realized.
Preferably, the LC tank circuit 2 includes a resonant capacitor Cr and a resonant inductor Lr.
One end of the resonance inductor Lr is connected with the output end of the switch circuit, the other end of the resonance inductor Lr is connected with one end of the resonance inductor Lr, the other end of the resonance inductor Lr is connected with one end of the transformer circuit, and the other end of the transformer circuit is connected with the negative electrode of the DC power supply.
Preferably, the transformer circuit 3 includes a primary winding Np, a secondary winding Ns1, a secondary winding Ns2, a secondary winding Ns3, and a secondary winding Ns 4. Fig. 1 also includes an inductor Lm connected in parallel with the primary winding Np, which can be replaced by the primary leakage inductance of the transformer in engineering.
The homonymous end and the heteronymous end of the primary winding are respectively connected with the output end of the LC resonant cavity circuit and the negative electrode of the DC power supply, and the divided voltage is respectively output through the secondary winding Ns1, the secondary winding Ns2, the secondary winding Ns3 and the secondary winding Ns 4.
Preferably, the output anode switching tube circuit comprises a MOS tube switching device S3 and a MOS tube switching device S4; the control ends of the MOS tube switching device S3 and the MOS tube switching device S4 are respectively connected with the output ends of the AND gate N1 and the AND gate N2.
The power input ends of the MOS tube switching device S3 and the MOS tube switching device S4 are respectively connected with the homonymous end of the secondary winding Ns1 and the heteronymous end of the secondary winding Ns2, the power output ends of the MOS tube switching device S3 and the MOS tube switching device S4 are respectively connected with the positive input end of the output load circuit, and the negative input end of the output load circuit is connected with the heteronymous end of the secondary winding Ns1 and the homonymous end of the secondary winding Ns 2.
Preferably, the output cathode switching tube circuit comprises a MOS tube switching device S5 and a MOS tube switching device S6; the control ends of the MOS tube switching device S5 and the MOS tube switching device S6 are respectively connected with the output ends of the AND gate N3 and the AND gate N4.
The power input ends of the MOS tube switching device S5 and the MOS tube switching device S6 are respectively connected with the homonymous end of the secondary winding Ns3 and the heteronymous end of the secondary winding Ns4, the power output ends of the MOS tube switching device S3 and the MOS tube switching device S4 are respectively connected with the positive input end of the output load circuit, and the negative input end of the output load circuit is connected with the heteronymous end of the secondary winding Ns3 and the homonymous end of the secondary winding Ns 4.
The third driving signal for driving the MOS tube switching device S3 to be switched on and switched off and the fourth driving signal for driving the MOS tube switching device S4 to be switched on and switched off are complementary and dead zones exist; the fifth driving signal for driving the MOS transistor switch device S5 is complementary to the sixth driving signal for driving the MOS transistor switch device S6, and a dead zone exists; and only one set of complementary signals of the third and fourth driving signals and the fifth and sixth driving signals can be conducted at the same time.
When the MOS tube switching device S3 and the MOS tube switching device S4 are alternately switched on, the MOS tube switching device S5 and the MOS tube switching device S6 are both in an off state, and at the moment, the circuit outputs a positive polarity direct current level; when the MOS transistor switch device S5 and the MOS transistor switch device S6 are turned on alternately, the MOS transistor switch device S3 and the MOS transistor switch device S4 are both in an off state, and at this time, the negative dc level output by the circuit is at this time.
As shown in fig. 2, which is a schematic circuit diagram of a MOS transistor switching device according to an embodiment of the present invention, the MOS transistor switching device includes MOS transistor switching devices S1-S6, and any one of the switching devices S1-S6 includes a body diode Dm (m = 1-6) and a parasitic capacitor Cossm (m = 1-6). As can be seen from fig. 2, the MOS transistor switching device includes a MOS transistor, a diode and a capacitor.
The grid electrode, the source electrode and the drain electrode of the MOS tube are respectively a control end, a power input end and a power output end of the MOS tube switch device.
After the diode is connected with the capacitor in parallel, the anode of the diode is connected with the source electrode of the MOS tube, and the cathode of the diode is connected with the drain electrode of the MOS tube.
Preferably, the output load circuit includes a filter capacitor Cout and a load resistor Rout, and two ends of the filter capacitor Cout and the load resistor Rout connected in parallel are an input end and an output end of the output load circuit.
The phase angle of the PWM wave generated by the PWM generator is controlled to make the DC gain of the circuit change in a sine way, so that the output load circuit 6 outputs a sine wave.
The circuit is a resonant circuit, and therefore, a fundamental wave analysis method is adopted to analyze the specific principle of changing the circuit gain through phase shifting, as shown in fig. 3, which is a schematic diagram of the fundamental wave analysis method provided by the embodiment of the invention, wherein all the switch tube, the diode, the inductor, the capacitor and the transformer are ideal; the parasitic capacitance of the switching tube does not participate in resonance, and the influence can be ignored; output filter capacitor
Figure 63950DEST_PATH_IMAGE002
The value is large, so the output voltage ripple is small, and the output voltage ripple can be approximately regarded as direct current voltage.
With reference to fig. 3, a specific principle of changing the circuit gain by phase shifting includes:
in the context of figure 3, it is shown,
Figure 524012DEST_PATH_IMAGE003
the AC equivalent load of the voltage type load full-wave rectification circuit is obtained by converting an actual load from a secondary side to a primary side:
Figure 677913DEST_PATH_IMAGE004
n is the turn ratio of the primary side and the secondary side of the transformer,
Figure 747369DEST_PATH_IMAGE005
representing the load resistance.
According to the circuit shown in FIG. 3, the following can be obtained by applying an AC analysis method:
input square wave voltage fundamental wave effective value
Figure 398056DEST_PATH_IMAGE006
Wherein
Figure 527555DEST_PATH_IMAGE007
Is an input dc voltage.
Fundamental wave effective value of output square wave voltage
Figure 903172DEST_PATH_IMAGE008
Wherein
Figure 12205DEST_PATH_IMAGE009
To output a dc voltage.
Ac fundamental voltage gain:
Figure 78250DEST_PATH_IMAGE010
wherein
Figure 660541DEST_PATH_IMAGE011
Is a coefficient, defined as
Figure 8608DEST_PATH_IMAGE012
；
Figure 452490DEST_PATH_IMAGE013
In order to be at the resonant frequency,
Figure 700937DEST_PATH_IMAGE014
；
Figure 560789DEST_PATH_IMAGE015
is the switching frequency; quality factor of series resonant circuit
Figure 566791DEST_PATH_IMAGE016
，
Figure 548784DEST_PATH_IMAGE017
Is a parallel resonance inductor and is characterized in that,
Figure 402471DEST_PATH_IMAGE018
and
Figure 451198DEST_PATH_IMAGE019
respectively a series resonance inductor and a series resonance capacitor.
The dc gain is then:
Figure 977120DEST_PATH_IMAGE020
rewriting the above formula into
Figure 730181DEST_PATH_IMAGE011
、
Figure 703953DEST_PATH_IMAGE021
、
Figure 18522DEST_PATH_IMAGE015
The DC gain of the circuit is as follows:
Figure 343324DEST_PATH_IMAGE022
referring to fig. 4, which is a graph showing the variation of the circuit gain with the circuit operating frequency according to the embodiment of the present invention, fig. 4 is a graph showing the variation of the circuit dc gain with the circuit switching frequency when k =2, n =15, and Q =0.162, where the ordinate is the circuit dc gain Gdc, i.e., the ratio of the output voltage to the input voltage, and the abscissa is the per unit value fn of the switching frequency, i.e., the ratio of the switching frequency f to the circuit resonant frequency fs.
As shown in fig. 5-7, which are a schematic phase-shift diagram and a phase-shift angle of a PWM wave provided by the embodiment of the present invention
Figure 431235DEST_PATH_IMAGE001
The ordinate in figure 5 is the amplitude Vin of square wave, because the low output impedance DC-AC power circuit provided by the invention is a resonance circuit, the energy transmission essentially depends on the fundamental wave in the circuit, when the phase shift angle of the PWM wave is not 0 (refer to figure 5), because the duty ratio of the PWM wave is changed, the amplitude of the fundamental wave contained in the PWM wave is changed to the original amplitude
Figure 259514DEST_PATH_IMAGE023
The DC gain of the circuit is changed to the original one
Figure 10563DEST_PATH_IMAGE023
The circuit gain can be changed by changing the phase angle of the PWM (see fig. 6) and switching the polarity of the secondary circuit at the zero crossing point of the output sine wave to make the circuit output the sine wave (see fig. 7), where fig. 7 is a waveform diagram of the output voltage, the ordinate is the magnitude of the output voltage in volts, and the abscissa is time in seconds.
The control principle of the control circuit 7 is as follows: the modulated wave Vm is compared with a constant zero by a comparator C1 to determine the polarity of the modulated wave Vm at that time, thereby determining whether the circuit secondary side operates as an output positive switching tube circuit or an output negative switching tube circuit, and determining the polarity of the circuit output level. The output voltage of the circuit measured by the output voltage measurer is sent to a comparator C2 to be compared with the modulation wave Vm, so that the error between the modulation wave Vm and the output voltage is obtained, the error is sent to a PI ring, the PI ring obtains the phase-shifting angle of the PWM wave through calculation, the information is sent to a PWM generator, and the PWM generator generates a corresponding PWM wave control circuit, so that the output level follows the modulation wave Vm, and a sine wave is output. Because the output waveform of the circuit does not contain a large number of higher harmonics, a filter inductor is not required to be additionally arranged at the output end like an H-bridge circuit, and therefore the energy conversion efficiency of the circuit is greatly improved.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (8)

1. A low output impedance DC-AC power source, comprising: the control circuit, the DC power supply, the switching circuit, the LC resonant cavity circuit, the transformer circuit, the output anode switch tube circuit, the output cathode switch tube circuit and the output load circuit;
the control circuit includes: a comparator C1, a comparator C2, a PI ring, a PWM generator, an AND gate N1, an AND gate N2, an AND gate N3, an AND gate N4, a NOT gate A1 and an output voltage measurer Mv;
two input ends of the comparator C1 input a modulation wave and a constant variable zero respectively, and an output end is connected with the PI ring input end; two input ends of the comparator C2 input the modulated wave and the output signal of the output load circuit, respectively; the output voltage measurer Mv measures the output voltage of the output voltage measurer;
the output end of the PI ring is connected with the input end of the PWM generator, the first output end of the PWM generator is respectively connected with one input end of the AND gate N1 and one input end of the AND gate N3, and the second output end of the PWM generator is respectively connected with one input end of the AND gate N2 and one input end of the AND gate N4; the output end of the comparator C2 is respectively connected with the other input ends of the AND gate N1 and the AND gate N2, and the output end of the comparator C2 is respectively connected with the other input ends of the AND gate N3 and the AND gate N4 after passing through the NOT gate A1;
the switch circuit takes electricity from the DC power supply and outputs the electricity to the LC resonant cavity circuit, the control circuit controls the switch circuit to realize the resonance of the LC resonant cavity circuit, direct current is converted into high-frequency alternating current and then is output to the transformer circuit, and after the high-frequency alternating current is rectified by the output anode switch tube circuit and the output cathode switch tube circuit respectively, positive-polarity direct current voltage and negative-polarity direct current voltage are generated at two ends of a load of the output load circuit respectively;
and controlling the phase angle of the PWM wave generated by the PWM generator to enable the direct current gain of the circuit to change in a sine mode, so that the output load circuit outputs sine waves.
2. The DC-AC power supply according to claim 1, wherein the switching circuit comprises a MOS transistor switching device S1 and a MOS transistor switching device S2, two output terminals of the PWM generator are respectively connected with control terminals of the MOS transistor switching device S1 and the MOS transistor switching device S2, and the MOS transistor switching device S1 and the MOS transistor switching device S2 are controlled to be alternately conducted to take power from the DC power supply;
the power input end of the MOS tube switch device S1 and the power output end of the MOS tube switch device S2 are respectively connected with the anode and the cathode of the DC power supply, the power output end of the MOS tube switch device S1 and the power input end of the MOS tube switch device S2 are connected with each other to serve as the anode of power taking output, and the cathode of the power taking output is connected with the cathode of the DC power supply.
3. The DC-AC power supply of claim 1, wherein the LC tank circuit comprises a resonant capacitor Cr and a resonant inductor Lr;
one end of the resonance inductor Lr is connected to the output end of the switch circuit, the other end of the resonance inductor Lr is connected to one end of the resonance inductor Lr, the other end of the resonance inductor Lr is connected to one end of the transformer circuit, and the other end of the transformer circuit is connected to the negative electrode of the DC power supply.
4. The DC-AC power supply of claim 1, wherein the transformer circuit comprises a primary winding, a secondary winding Ns1, a secondary winding Ns2, a secondary winding Ns3, and a secondary winding Ns 4;
the homonymous end and the heteronymous end of the primary winding are respectively connected with the output end of the LC resonant cavity circuit and the negative electrode of the DC power supply, and the divided voltage is respectively output through the secondary winding Ns1, the secondary winding Ns2, the secondary winding Ns3 and the secondary winding Ns 4.
5. The DC-AC power supply of claim 4, wherein the output positive switching transistor circuit comprises a MOS transistor switching device S3 and a MOS transistor switching device S4; the control ends of the MOS tube switching device S3 and the MOS tube switching device S4 are respectively connected with the output ends of the AND gate N1 and the AND gate N2; the control circuit sends out a control signal to enable the MOS tube switching device S3 and the MOS tube switching device S4 to be conducted alternately;
the power input ends of the MOS tube switching device S3 and the MOS tube switching device S4 are respectively connected with the homonymous end of the secondary winding Ns1 and the heteronymous end of the secondary winding Ns2, the power output ends of the MOS tube switching device S3 and the MOS tube switching device S4 are both connected with the positive input end of the output load circuit, and the negative input end of the output load circuit is connected with the heteronymous end of the secondary winding Ns1 and the homonymous end of the secondary winding Ns 2.
6. The DC-AC power supply of claim 5, wherein the output negative switching transistor circuit comprises a MOS transistor switching device S5 and a MOS transistor switching device S6; the control ends of the MOS tube switching device S5 and the MOS tube switching device S6 are respectively connected with the output ends of the AND gate N3 and the AND gate N4; the control circuit sends out control signals to enable the MOS tube switching device S5 and the MOS tube switching device S6 to be alternately conducted, and only one of the two groups of control signals of the MOS tube switching device S3, the MOS tube switching device S4, the MOS tube switching device S5 and the MOS tube switching device S6 can be conducted;
the power input ends of the MOS tube switching device S5 and the MOS tube switching device S6 are respectively connected with the homonymous end of the secondary winding Ns3 and the heteronymous end of the secondary winding Ns4, the power output ends of the MOS tube switching device S3 and the MOS tube switching device S4 are both connected with the positive input end of the output load circuit, and the negative input end of the output load circuit is connected with the heteronymous end of the secondary winding Ns3 and the homonymous end of the secondary winding Ns 4.
7. The DC-AC power supply of claim 2 or 5, wherein the MOS transistor switching device comprises a MOS transistor, a diode and a capacitor;
the grid electrode, the source electrode and the drain electrode of the MOS tube are respectively a control end, a power input end and a power output end of the MOS tube switch device;
after the diode is connected with the capacitor in parallel, the anode of the diode is connected with the source electrode of the MOS tube, and the cathode of the diode is connected with the drain electrode of the MOS tube.
8. The DC-AC power supply according to claim 1, wherein the output load circuit comprises a filter capacitor Cout and a load resistor Rout, and two ends of the filter capacitor Cout and the load resistor Rout connected in parallel are an input end and an output end of the output load circuit.
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