OA16581A - Method for controlling a series resonant DC/DC converter. - Google Patents
Method for controlling a series resonant DC/DC converter. Download PDFInfo
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- OA16581A OA16581A OA1201300157 OA16581A OA 16581 A OA16581 A OA 16581A OA 1201300157 OA1201300157 OA 1201300157 OA 16581 A OA16581 A OA 16581A
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- résonant
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Abstract
The invention relates to a method for controlling a series resonant DC/DC converter. The method comprises the steps of: defining a switching period TP having a first half period TA and a second half period TB and defining a subsequent switching period TP+1 after the switching period TP. In a next step, a first set (S1sc1; S1sc1, S4sc1) of switches of a first switching circuit (SC1) is controlled to be ON from the beginning Tstart of the first half period TA minus a time interval ∆TAE1, where the time interval ∆TAE1 is provided at the end of the first half period TA and a second set (S2sc1; S2sc1, S3sc1) of switches of the first switching circuit (SC1) is controlled to be ON from the beginning Tcenter of the second half period TB minus a time interval ∆TBE1, where the time interval ∆TBE1 is provided at the end of the second half period TB. A first set (S1sc2; S1sc2, S4sc2) of switches of a second switching circuit (SC2) is controlled to be ON in the first half period TA minus a time interval ∆TAS1 and minus a time interval ∆TAE2, where the time interval ∆TAS1 is provided at the beginning of the first half period TA and where the time interval ∆TAE2 is provided at the end of the first half period TA and a second set (S2sc2; S2sc2, S3sc2) of switches of the second switching circuit (SC2) is controlled to be ON in the second half period TB minus time interval ∆TBS1 and minus time interval ∆TBE2, where the time interval ∆TBS1 is provided at the beginning of the second half period TB and where the time interval ∆TBE2 is provided in the end of the second half period TB. Time intervals Tsc1off1 and Tsc2off1, and time intervals Tsc1off2 and Tsc2off2, where the sets of the first and second switching circuits all are off, are at least partially overlapping.
Description
FIELD OF THE INVENTION
The présent invention relates to method for controlling a sériés résonant DC/DC converter and a sériés résonant DC/DC converter controlled according to the method.
BACKGROUND OF THE INVENTION
A typical uninterruptable power supply (UPS) system is shown in fig, 1. The UPS system comprises an input converter for converting electric power from an AC or DC power source. A typical UPS has an input power stage that converts the commercial AC mains or a renewable energy AC or DC source, to a DC voltage. The DC voltage is then converted 10 by means of a converter to a controlled AC or DC voltage thus forming a power supply to electrical loads such as computers, refrigerators etc that need uninterrupted power supply. Typically, a regulated DC bus is provided between the input converter and the output converter. The DC bus is ideally suited to be connected to a DC battery. A bidirectional DC/DC converter is needed if the battery voltage differs from the DC voltage on the DC15 bus.
A typical AC-UPS can handle a power failure in the AC mains, by using a battery to supply DC power to the DC bus via a DC/DC converter, so the power supplied to the AC load is not interrupted. When the AC mains is opérable again, power from the AC mains can be used to recharge the battery and supply energy to the load.
In many UPS Systems, one DC/DC converter is used for supplying power from the battery to the DC bus and a separate converter is used to charge the battery. The battery charging converter can either be an AC/DC converter supplied with power from the AC mains, or a separate DC/DC converter supplied with power from the DC bus.
In some applications, the input may also be a DC source, for example a renewable 25 electrical energy source such as solar cells.
There exist many proposed circuits for one-directional and bi-directional DC/DC converters for improved efficiency such as in Performance optimization of a High Current Dual Active Bridge with Wide operating Voltage Range, by Krismer, Round, Kolar published in Power Electronics Specialists Conférence, 2006, A new HE ZVZCS
Bidirectional DC/DC converter for HEV 42V Power Systems, by Kim, Han, Park, Moon published in Journal of Power Electronics, Vol. 6, No. 3, July 2006, Bidirectional DC/DC Power Conversion using Quasi-Resonant Topology, by Ray, published in Power Electronics Specialists Conférence, 1992, A Bidirectional DC_DC converter for renewable energy Systems, by Jalbrzykowski, Citko, published in Bulletin ofthe Polish Academy of
Technical Sciences Vol. 57, No. 4, 2009. Ail of these are operated at fixed frequency and controlled by either phase-shifting gâte puises or duty cycle modulation. Ail of these circuits hâve the drawback of limited operating ranges for high efficiency operation, such as zéro voltage switching (ZVS) of main switches for only a limited load range etc.
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The object of the présent invention is to provide a method for controlling a sériés résonant DC/DC converter with improved efficiency. The object is also to provide a method for controlling a sériés résonant DC/DC converter so that a bidirectional DC/DC converter is achieved. Hence, the sériés résonant DC/DC converter can be used both for supplying power from the battery to the DC bus during power failures and for supplying power from the DC bus to recharge the battery after a power failure. This reduces the number of components, and hence costs/space can be saved.
SUMMARY OF THE INVENTION
The présent invention relates to a method for controlling a sériés résonant DC/DC converter, comprising the steps of:
- defining a switching period TP from time Tstart to time Tend for the sériés résonant DC/DC converter; where the switching period TP comprises a first half period TA from time Tstart to time Tcenter and a second half period TB from time Tcenter to time Tend, and defining a subséquent switching period TP+1 after the switching period TP;
- controlling a first set of switches of a first switching circuit to be ON from the beginning Tstart of the first half period TA minus a time interval ΔΤΑΕ1, where the time interval ΔΤΑΕ1 is provided at the end of the first half period TA;
- controlling a second set of switches ofthe first switching circuit to be ON from the beginning Tcenter of the second half period TB minus a time interval ΔΤΒΕ1, where the time interval ΔΤΒΕ1 is provided at the end of the second half period TB;
- controlling the first set and the second set of switches of the first switching circuit to be OFF in the time interval ΔΤΑΕ1 and the time interval ΔΤΒΕ1;
- controlling a first set of switches of a second switching circuit to be ON in the first half period TA minus a time interval ΔΤΑδ1 and minus a time interval ΔΤΑΕ2, where the time interval ΔΤΑδ1 is provided at the beginning of the first half period TA and where the time interval ΔΤΑΕ2 is provided at the end of the first half period TA;
- controlling a second set of switches of the second switching circuit to be ON in the second half period TB minus time interval ΔΤΒ31 and minus time interval ΔΤΒΕ2, where the time interval ΔΤΒδ1 is provided at the beginning of the second half period TB and where the time interval ΔΤΒΕ2 is provided in the end ofthe second half period TB;
- controlling the first set and the second set of switches of the second switching circuit to be OFF in the time intervals ΔΤΑδ1, ΔΤΑΕ2, ΔΤΒδ1 and ΔΤΒΕ2;
where the time interval ΔΤΑΕ1 forms a first time interval Tsc1off1 wherein the first and second sets of switches of the first switching circuit are OFF, and where the time interval ΔΤΒΕ forms a second time interval Tsc1off2 wherein the first and second sets of switches of the first switching circuit are OFF;
where the time intervals ΔΤΑΕ2 and ΔΤΒ61 form a continuous time interval Tsc2off1, where the first and second set of switches of the second switching circuit are OFF; and where the time interval ΔΤΒΕ2 and a time interval ΔΤΑ51(ΤΡ+1) of the subséquent switching period TP+1 form a continuous time interval Tsc2off2, where the first and second sets of switches ofthe second switching circuit are OFF;
where the time interval Tsc1off1 and the time interval Tsc2off1 is overlapping and where the time interval Tsc1off2 and the time interval Tsc2off2 is overlapping.
In one aspect the method comprises the step of controlling the centre of interval Tsc1off1 to be close to or equal to the centre of time interval Tsc2off1 and the centre of interval Tsc1off2 to be close to or equal to the centre of time interval Tsc2off2.
In one aspect the method comprises the step of controlling the relation between the voltage between first DC terminais of the sériés résonant DC/DC converter and the voltage between second DC terminais ofthe sériés résonant DC/DC converter by varying the length of the switching period TP.
In one aspect the method comprises the step of controlling the direction of the power flow through the sériés résonant DC/DC converter by varying the switching period TP.
In one aspect the method comprises the step of controlling the switches of the first and second switching circuit to provide zéro voltage switching at switch turn on and to provide nearly zéro current switching at switch turn off by controlling the first and second switching circuit to hâve a fixed switching frequency close to the sériés résonant frequency.
In one aspect the switches of the first and second switching circuit are controlled by switching at an operating point at or near the sériés résonant frequency for ail voltages over the first DC terminais which are inside a specîfied operating range.
In one aspect the switches of the first and second switching circuit are controlled by switching at an operating point at or near the sériés résonant frequency for all load conditions at the second DC terminais.
The présent invention also relates to a sériés résonant DC/DC converter comprising: first DC terminais;
second DC terminais;
an inductor device;
a first switching circuit connected between the first DC terminais and the inductor device, where the first switching circuit comprises a first set of switches and a second set of switches;
a second switching circuit and a résonant circuit connected between the second DC terminais and the inductor device, where the second switching circuit comprises a first set of switches and a second set of switches;
a control circuit for controlling the set of switches of the first and second switching circuits according to one of the methods above.
DETAILED DESCRIPTION ï
Embodiments of the présent invention will be described in detail in the following with reference to the enclosed drawings, where:
Fig. 1 illustrâtes a a typical application for bidirectional DC/DC converters;
Fig. 2 illustrâtes a first embodiment of the DC/DC converter;
Fig. 3 illustrâtes a second embodiment of the DC/DC converter;
Fig. 4 illustrâtes a third embodiment of the DC/DC converter;
Fig. 5 illustrâtes a fourth embodiment of the DC/DC converter;
Fig. 6 illustrâtes a fifth embodiment of the DC/DC converter;
Fig. 7 illustrâtes a fifth embodiment of the DC/DC converter; this embodiment does not hâve a transformer device;
Fig. 8 shows waveforms of voltages and currents of the second embodiment at full load;
Fig. 9 shows details of fig. 9;
Fig. 10 shows waveforms of voltages and currents of the second embodiment at no load;
Fig. 11 shows details of fig. 10;
Fig. 12 shows the variation of output voltage Vout for different switching frequencies and different loads;
Fig. 13 shows the efficiency curve as a function of the output power for the embodiment in fig. 3.
It is now referred to fig. 2-7, illustrating embodiments of the sériés résonant DC/DC converter. It should be noted that by the term “sériés résonant DC/DC converter sériés it îs meant different types of sériés résonant LC DC/DC converters and different types of sériés résonant LLC DC/DC converters. The sériés résonant DC/DC converter may also be a bidirectional DC/DC converter.
The DC/DC converter comprises first DC terminais T1P, T1N and second DC terminais T2P, T2N. The first DC terminais comprise a first positive DC terminal T1P and a first négative DC terminal T1N. The second DC terminais comprise a second positive DC terminal T2P and a second négative DC terminal T2N.
The DC/DC converter further comprises an inductor device, either in the form of a single inductor device ID (as in the embodiment of fig. 7) or in the form of a transformer device TD (as in the embodiments of figs. 2 - 6).
The single inductor device ID may comprise a single inductor Lm, or may comprise several inductors, but does not provide a galvanic isolation.
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The transformer device TD may comprise a first winding and a second winding. The transformer device provides galvanic isolation between the first DC terminais and the second DC terminais. The transformer also comprises a magnetizing inductance, which forms a parallel résonance circuit together with the résonant capacitor(s).
The transformer ratio of the transformer device is 1:1 in the présent embodiments; however, other transformer ratios are also possible and can be designed in order to meet requirements for input output voltage and current ratios.
A first switching circuit SC1 (illustrated by a dashed box) is connected between the first DC terminais T1P, T1N and the inductor device (either the single inductor device ID or the transformer device TD). The first switching circuit SC1 comprises a first set of switches and a second set of switches. The first set and the second set of switches may each comprise one, two or several switches.
The first switching circuit SC1 is arranged to be controlled in three different switching states. The first state allows a current to flow through the inductor device from the first positive DC terminal T1P to the négative DC terminal T1N by commanding the first set of switches to be ON. The second state allows a current to flow through the inductor device from the first négative DC terminal T1N to the first positive DC terminal T1P by commanding the second set of switches to be ON. The third switching state is characterized by commanding both sets of switches to be OFF
A second switching circuit SC2 (illustrated by a dashed box) and a résonant circuit RC (illustrated by a dashed box) are connected between the second DC terminais T2P, T2N and the inductor device (either the single inductor device ID or the transformer device TD). The second switching circuit SC2 comprises a first set of switches and a second set of switches. The first set and the second set of switches may each comprise one, two or several switches. It can be seen that the second switching circuit SC2 and a résonant circuit RC are connected in sériés with the inductor device (the single inductor device ID or the transformer device TD) between the second DC-terminals T2P and T2N. The sériés combination of the résonant circuit RC and the inductor device is connected to the second switching circuit SC2. The second switching circuit, SC2, is arranged to be controlled in three different switching states. The first state allows a résonant current to flow through the sériés combination of the résonant circuit RC and the inductor device from the second positive DC terminal T2P to the second négative DC terminal T2N by commanding the first set of switches to be ON. The second state allows a résonant current to flow through the sériés combination of RC and the inductor device from the second négative DC terminal T2N to the second positive DC terminal T2P by commanding the second set of switches to be ON. The third switching state is characterized by commanding both sets of switches to be OFF.
The first switching circuit SC1 may be a push pull circuit or a bridge circuit, such as a full bridge circuit or a half bridge circuit.
The second switching circuit SC2 may also be a bridge circuit, such as a full bridge circuit or a half bridge circuit.
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The résonant circuit RC is often referred to as a résonant tank and comprises at least one capacitor or at least one inductor in a suitable configuration together with the inductor device, either the single inductor device ID or the second windîng of the transformer device T, where the inductance of the at least one capacitor and/or at least one inductor 5 together with the inductance of the single inductor device ID or the second winding of the transformer device T defines a résonance frequency so that the DC/DC converter exhibits zéro voltage turn on switching on ail active switches of SC1 and SC2.
The résonant circuit RC may also be a multi-element résonant circuit comprising several capacitors and inductors in a LC network. Hence, the converter can be considered as a 10 sériés résonant LLC DC/DC converter.
In addition, the DC/DC converter comprises a control circuit which can détermine the desired direction of power flow and control the direction of current at the first and second DC-terminals and thus make the converter supply energy either to the load connected to the first DC-terminals or the load connected to the second DC-terminals.
In the foilowing, several embodiments will be described. In ail these embodiments, the switches are MOSFET switches. Alternatively, the switches may be switches with intrinsic diodes or switches connected in parallel with anti-parallel diodes, such as IGBTs with antiparallel diodes.
First embodiment
It is now referred to fig. 2. Here the first switching circuit SC1 is a half bridge circuit comprising a first switch S1sc1 and a second switch S2sc1. The first set of switches of the first switching circuit SC1 here comprises the first switch S1sc1 and the second set of switches of the first switching circuit SC1 comprises the second switch S2sc1.
The first switch S1sc1 is connected between the first négative DC terminal T1N and a first terminal of the first winding. The source of the switch is connected to the first négative DC terminal T1N.
The second switch S2sc1 is connected between the first négative DC terminal T1N and a second terminal of the first winding. The source of the switch is connected to the first 30 négative DC terminal T1N.
The first winding of the transformer device T comprises a third terminal connected to the first positive DC terminal T1P. The third terminal of the second winding is provided between the first terminal and the second terminal of the second winding. Hence, the number of turns between the first and third terminais and the number of tums between the 35 second and third terminais is equal to the total number of turns for the second winding. In the présent embodiment, the number of turns between the first and third terminais and the number of turns between the second and third terminais is equal to each other.
A first capacitor C1 is connected between the first positive DC terminal T1P and the first négative DC terminal T1N. __
The second switching circuit SC2 is a half bridge circuit comprising a first switch S1sc2 and a second switch S2sc2. The first set of switches of the second switching circuit SC2 here comprises the first switch S1sc2 and the second set of switches of the second switching circuit SC2 comprises the second switch S2sc2
The first switch S1sc2 is connected between a first node 10 and the second positive DC terminal T2P. The second switch S2sc2 is connected between the second négative DC terminal T2N and the second node 10. The source of the first switch S1sc2 is connected to the second négative DC terminal T2N and the source of the second switch S2sc2 is connected to the first node 10. The first node 10 is also connected to a first terminal of the second winding of the transformer device T.
The résonant circuit RC comprises a résonant inductor Lrc, a first résonant capacitor C1rc and a second résonant capacitor C2rc. The résonant inductor Lrc is connected between a second terminal of the second winding of the transformer T and a second node 12. The first résonant capacitor C1rc is connected between the second node 12 and the second positive DC terminal T2P. The second résonant capacitor C2rc is connected between the second node 12 and the second négative DC terminal T2N.
Second embodiment
It is now referred to fig. 3.
The first switching circuit SC1 is a full bridge circuit comprising a first switch S1sc1, a second switch S2sc1, a third switch S3sc1 and a fourth switch S4sc1.
The first set of switches of the first switching circuit SC1 here comprises the first switch S1sc1 and the fourth switch S4sc1. The second set of switches of the first switching circuit SC1 comprises the second switch S2sc1 and the third switch S3sc1.
The first switch S1sc1 is connected between the first positive DC terminal T1P and a first node 20. The source of the switch is connected to the first node 20.
The second switch S2sc1 is connected between the first négative DC terminal T1N and the first node 20. The source of the switch is connected to the first négative DC terminal T1N.
The third witch S3sc1 is connected between the first positive DC terminal T1P and a second node 22. The source of the switch is connected to the second node 22.
The fourth switch S4sc1 is connected between the first négative DC terminai T1N and the second node 22. The source of the switch is connected to the first négative DC terminal T1N.
The first node 20 is connected to the first terminal of the first winding of the transformer device T. The second node 22 is connected to the second terminal of the first winding of the transformer device T.
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A first capacitor C1 is connected between the first positive DC terminal T1P and the first négative DC terminal T1N.
The second switching circuit SC2 is here a half bridge circuit comprising a first switch S1sc2 and a second switch S2sc2.
The first set of switches of the second switching circuit SC2 here comprises the first switch S1sc2 and the second set of switches of the second switching circuit SC2 comprises the second switch S2sc2.The first switch S1sc2 is connected between a first node 10 and the second positive DC terminal T2P, The second switch S2sc2 is connected between the second négative DC terminal T2N and the second node 10. The source of the first switch S1sc2 is connected to the node 10 and the source of the second switch S2sc2 is connected to the second négative DC terminal T2N. The first node 10 is also connected to a first terminai of the second winding of the transformer device T.
The résonant circuit RC comprises a résonant inductor Lrc, a first résonant capacitor C1rc and a second résonant capacitor C2rc. The résonant inductor Lrc is connected between a second terminal of the second winding of the transformer T and a second node 12. The first résonant capacitor C1rc is connected between the second node 12 and the second positive DC terminal T2P. The second résonant capacitor C2rc is connected between the second node 12 and the second négative DC terminal T2N.
A second capacitor C2 is connected between the second positive DC terminal T2P and the second négative DC terminal T2N.
ln fig. 3, the first winding of the transformer device TD is denoted as Tp, the second winding of the transformer device TD is denoted as Ts. The current through the first winding is denoted as lp, the current through the second winding is denoted as Is.
As shown in fig. 3, a voltage source with input voltage Vin is connected between the first négative DC terminal and the first positive DC terminal T1P, T1N. A load Rload is connected between the second négative DC terminal and the second positive DC terminal T2P, T2N.
Third embodiment
It is now referred to fig. 4.
The first switching circuit SC1 is a full bridge circuit comprising a first switch S1sc1, a second switch S2sc1, a third switch S3sc1 and a fourth switch S4sc1.
The first set of switches of the first switching circuit SC1 here comprises the first switch S1sc1 and the fourth switch S4sc1. The second set of switches of the first switching circuit SC1 comprises the second switch S2sc1 and the third switch S3sc1. The first switch S1sc1 is connected between the first positive DC terminal T1P and a first node 20. The source of the switch is connected to the first node 20.
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The second switch S2sc1 is connected between the first négative DC terminal T1N and the first node 20. The source of the switch is connected to the first négative DC terminal T1N.
The third witch S3sc1 is connected between the first positive DC terminal T1P and a second node 22. The source of the switch is connected to the second node 22.
The fourth switch S4sc1 is connected between the first négative DC terminal T1N and the second node 22. The source of the switch is connected to the first négative DC terminal T1N.
The first node 20 is connected to the first terminal of the first winding of the transformer device T. The second node 22 is connected to the second terminal of the first winding of the transformer device T.
A first capacitor C1 is connected between the first positive DC terminal T1P and the first négative DC terminal T1N.
The second switching circuit SC2 is a full bridge circuit comprising a first switch S1sc2, a second switch S2sc2, a third switch S3sc2 and a fourth switch S4sc2.
The first set of switches of the second switching circuit SC2 here comprises the first switch S1sc2 and the fourth switch S4sc2. The second set of switches of the second switching circuit SC2 comprises the second switch S2sc2 and the third switch S3sc2.
The first switch S1sc2 is connected between the second positive DC terminal T2P and a first node 10. The source of the first switch S1sc2 is connected to the first node 10.
The second switch S2sc2 is connected between the second négative DC terminal T1N and the first node 10. The source of the switch is connected to the second négative DC terminal T2N.
The third switch S3sc2 is connected between the second positive DC terminal T2P and a second node 12. The source of the switch is connected to the second node 12.
The fourth switch S4sc2 is connected between the second négative DC terminal T2N and the second node 12. The source of the switch is connected to the second négative DC terminal T2N.
The second node 12 of the second switching circuit SC2 is also connected to a first terminal of the second winding of the transformer device T.
The résonant circuit RC comprises a résonant inductor Lrc and a résonant capacitor Crc connected in sériés between a second terminal of the second winding of the transformer device T and the first node 10.
A second capacitor C2 is connected between the second positive DC terminal T2P and the second négative DC terminal T2N.
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Fourth embodiment
It is now referred to fig. 5.
Here, the first switching circuit SC1 is a half bridge circuit comprising a first switch S1sc1 and a second switch S2sc1. The first set of switches of the first switching circuit SC1 here comprises the first switch S1sc1 and the second set of switches of the first switching circuit SC1 comprises the second switch S2sc1. The first switch S1sc1 is connected between the first négative DC terminal T1N and a first terminal ofthe first winding. The source of the switch is connected to the first négative DC terminal T1N.
The second switch S2sc1 is connected between the first négative DC terminal T1N and a second terminal of the first winding. The source of the switch is connected to the first négative DC terminal T1N.
The first winding of the transformer device T comprises a third terminal connected to the first positive DC terminal T1P. The third terminal of the second winding is provided between the first terminal and the second terminal of the second winding. Hence, the number of turns between the first and third terminais and the number of turns between the second and third terminais is equal to the total number of turns for the second winding. In the présent embodiment, the number of turns between the first and third terminais and the number of turns between the second and third terminais is equal to each other.
A first capacitor C1 is connected between the first positive DC terminal T1P and the first négative DC terminal T1N.
The second switching circuit SC2 is a full bridge circuit comprising a first switch S1sc2, a second switch S2sc2, a third switch S3sc2 and a fourth switch S4sc2.
The first set of switches of the second switching circuit SC2 here comprises the first switch S1sc2 and the fourth switch S4sc2. The second set of switches of the second switching circuit SC2 comprises the second switch S2sc2 and the third switch S3sc2.
The first switch S1sc2 is connected between the second positive DC terminal T2P and a first node 10. The source of the first switch S1sc2 is connected to the first node 10.
The second switch S2sc2 is connected between the second négative DC terminal T1N and the first node 10. The source of the switch is connected to the second négative DC terminal T2N.
The third switch S3sc2 is connected between the second positive DC terminal T2P and a second node 12. The source of the switch is connected to the second node 12.
The fourth switch S4sc2 is connected between the second négative DC terminal T2N and the second node 12. The source of the switch is connected to the second négative DC terminal T2N.
The second node 12 of the second switching circuit SC2 is also connected to a first terminal of the second winding of the transformer device T.
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The résonant circuit RC comprises a résonant inductor Lrc and a résonant capacitor Crc connected in sériés between a second terminal of the second winding of the transformer device T and the first node 10.
A second capacitor C2 is connected between the second positive DC terminal T2P and the second négative DC terminal T2N.
Fifth embodiment
It is now referred to fig. 6.
Here, the first switching circuit SC1 is a voltage doubler circuit comprising a first switch S1sc1 and a second switch S2sc1. The first set of switches of the first switching circuit SC1 here comprises the first switch S1sc1 and the second set of switches of the first switching circuit SC1 comprises the second switch S2sc1.
The first switch S1sc1 is connected between the first positive DC terminal T1P and a first terminal of the first winding of the transformer device TD. The source of the switch is connected to the first terminal of the first winding of the transformer device TD.
The second switch S2sc1 is connected between the first négative DC terminal T1N and a second terminal of the first winding of the transformer device TD. The source of the switch is connected to the second terminal of the first winding of the transformer device TD.
A first capacitor C1 is connected between the first positive DC terminal T1P and a node 20. A second capacitor C2 is connected between the node 20 and the first négative DC terminal T1 N. The node 20 is connected to a third terminal of the first winding of the transformer device TD.
The third terminal of the second winding is provided between the first terminal and the second terminal of the second winding. Hence, the number of turns between the first and third terminais and the number of turns between the second and third terminais is equal to the total number of turns for the second winding. In the présent embodiment, the number of turns between the first and third terminais and the number of turns between the second and third terminais is equal to each other.
The second switching circuit SC2 is here a half bridge circuit comprising a first switch S1sc2 and a second switch S2sc2.
The first set of switches of the second switching circuit SC2 here comprises the first switch S1sc2 and the second set of switches of the second switching circuit SC2 comprises the second switch S2sc2.
The first switch S1sc2 is connected between a first node 10 and the second positive DC terminal T2P. The second switch S2sc2 is connected between the second négative DC terminal T2N and the second node 10.
t t
The source of the first switch S1sc2 is connected to the node 10. The source of the second switch S2sc2 is connected to the second négative DC terminal T2N. The first node 10 is also connected to a first terminal of the second winding of the transformer device T.
The résonant circuit RC comprises a résonant inductor Lrc, a first résonant capacitor C1rc and a second résonant capacitor C2rc. The résonant inductor Lrc is connected between a second terminal of the second winding of the transformer T and a second node 12. The first résonant capacitor C1rc is connected between the second node 12 and the second positive DC terminal T2P. The second résonant capacitor C2rc is connected between the second node 12 and the second négative DC terminal T2N.
Sixth embodiment
It is now referred to fig. 7.
The first switching circuit SC1 is a full bridge circuit comprising a first switch S1sc1, a second switch S2sc1, a third switch S3sc1 and a fourth switch S4sc1.
The first set of switches of the first switching circuit SC1 here comprises the first switch S1sc1 and the fourth switch S4sc1. The second set of switches of the first switching circuit SC1 comprises the second switch S2sc1 and the third switch S3sc1.
The first switch S1sc1 is connected between the first positive DC terminal T1P and a first node 20. The source of the switch is connected to the first node 20.
The second switch S2sc1 is connected between the first négative DC terminal T1N and the first node 20. The source of the switch is connected to the first négative DC terminal T1N.
The third switch S3sc1 is connected between the first positive DC terminal T1P and a second node 22. The source of the switch is connected to the second node 22.
The fourth switch S4sc1 is connected between the first négative DC terminal T1N and the second node 22. The source of the switch is connected to the first négative DC terminal T1N.
As mentioned above, there is no transformer device TD in the présent embodiment. Instead, an inductor device ID in the form of a magnetizing inductor Lm is provided.
The first node 20 is connected to the first terminal of the magnetizing inductor Lm. The second node 22 is connected to the second terminal of the magnetizing inductor Lm.
A first capacitor C1 is connected between the first positive DC terminal T1P and the first négative DC terminal T1N.
The second switching circuit SC2 is here a half bridge circuit comprising a first switch S1sc2 and a second switch S2sc2.
f i
The first set of switches of the second switching circuit SC2 here comprises the first switch S1sc2 and the second set of switches of the second switching circuit SC2 comprises the second switch S2sc2.
The first switch S1sc2 is connected between a first node 10 and the second positive DC terminal T2P. The second switch S2sc2 is connected between the second négative DC terminal T2N and the second node 10. The source of the first switch S1sc2 is connected to the node 10 and the source of the second switch S2sc2 is connected to the second négative DC terminal T2N. The first node 10 is also connected to the second terminal of the magnetizing inductor Lm.
The résonant circuit RC comprises a résonant inductor Lrc, a first résonant capacitor C1rc and a second résonant capacitor C2rc. The résonant inductor Lrc is connected between the first terminal of the magnetizing inductor Lm and a second node 12. The first résonant capacitor C1rc is connected between the second node 12 and the second positive DC terminal T2P. The second résonant capacitor C2rc is connected between the second node 12 and the second négative DC terminal T2N.
A second capacitor C2 is connected between the second positive DC terminal T2P and the second négative DC terminal T2N.
Control circuit
A control circuit is provided for controlling the switches of the first and second switching circuits SC1 and SC2 to be ON and OFF. The control circuit may be implemented as a software program executed by a digital signal processor (DSP) or it may be implemented as an analogue circuit.
Ail switches are uni-polar, meaning that the switches can only block conduction in one direction. An example of a uni-polar switch is the MOSFET switch comprising an antiparallel diode. Another example is the IGBT switch with an anti-parallel diode connected from emitter to drain.
The control method according to the invention will now be described in detail below with reference to figs. 8-12. Here, the control signais and resulting voltages and/or currents are shown for the embodiment shown in fig. 3. The input voltage Vin was set to 50 VDC, and an output voltage was regulated to 350 VDC. The switching frequency is approximately 110kHz.
It is now referred to fig. 8.
In a first step a switching period TP is defined from time Tstart to time Tend for the sériés résonant DC/DC converter. The switching period TP comprises a first half period TA from time Tstart to time Tcenter and a second half period TB from time Tcenter to time Tend. A next switching period after the switching period TP is denoted as a subséquent switching period TP+1.
r
Λ
As is described above, the sériés résonant DC/DC converter has a résonance frequency defined by the properties of the inductor device (ID or TD) and the éléments (capacitors and inductors) of the résonance circuit RC.
The switching period TP, and hence the switching frequency, can be controlled by the control circuit to be be higher than, equal to, or lower than the résonance frequency. Hence, the switching period TP is not dépendant of the résonance frequency.
In fig. 8, relevant times TO (equal to Tstart) to T8 (equal to Tend) for the first switching period TP are indicated by dashed lines, and several time intervals are also defined, as will be apparent from the description below. Time T8 (equal to Tend) is the start (i.e. time T0(TP+1)) of the subséquent switching period TP+1. Time T4 is here equal to Tcenter, but the length of the time intervals TO - T1, T1 - T2, T2 - T3, T3 - T4, T4 - T5, T5 - T6, T6 T7, T7 - T8 are not ail equal to each other.
The duty cycle of ail set of switches are essentîally 50%, meaning that the switches hâve a control signal demanding the switch to be in a conducting state, ON, during nearly half of the switching period and having the control signal demanding the switch to be in a nonconducting state, OFF, during nearly half of the switching period. The set of switches are controlled independently to hâve different delays and yet synchronized.
The first setS1sc1; S1sc1, S4sc1 of switches ofthe first switching circuit SC1 is controlled to be ON from the beginning Tstart of the first half period TA minus a time interval ΔΤΑΕ1, where the time interval ΔΤΑΕ1 is provided at the end of the first half period TA. The first set S1sc1; S1sc1, S4sc1 of switches ofthe first switching circuit SC1 îs controlled to be OFF in the second half period TB. The time interval ΔΤΑΕ1 in the présent embodiment is starting at time T3 and is ending at time T4.
The second set S2sc1; S2sc1, S3sc1 of switches of the first switching circuit SC1 is controlled to be ON from the beginning Tcenter of the second half period TB minus a time interval ΔΤΒΕ1, where the time interval ΔΤΒΕ1 is provided at the end of the second half period TB. The second set S2sc1; S2sc1, S3sc1 of switches of the first switching circuit SC1 is controlled to be OFF in the first half period TA. The time interval ΔΤΒΕ1 is in the présent embodiment starting at time T7 and is ending at time T8.
The first set S1sc1; S1sc1, S4sc1 and the second set S2sc1; S2sc1, S3sc1 of switches of the first switching circuit SC1 is controlled to be OFF in the time interval ΔΤΑΕ1 and the time interval ΔΤΒΕ1.
The time interval ΔΤΑΕ1 forms a first time interval Tsc1off1 wherein the first and second sets of switches of the first switching circuit SC1 are OFF. The time interval ΔΤΒΕ forms a second time interval Tsc1off2 wherein the first and second sets of switches of the first switching circuit SC1 are OFF.
The first set S1sc2; S1sc2, S4sc2 of switches of the second switching circuit SC2 is controlled to be ON in the first half period TA minus a time interval ATAS1 and minus a time interval ΔΤΑΕ2, where the time interval ATAS1 is provided at the beginning ofthe first half period TA and where the time tnterval ΔΤΑΕ2 is provided at the end of the first t
fi half period TA. The first set S1sc2; S1sc2, S4sc2 of switches of the second switching circuit SC is controlled to be OFF in the second half period TB. The time interval ATAS1 in the présent embodiment is starting at time TO and is ending at time T1. The time interval ΔΤΑΕ2 in the présent embodiment is starting at time T2 and îs ending at T4.
The second set S2sc2; S2sc2, S3sc2 of switches of the second switching circuit SC2 is controlled to be ON in the second half period TB minus time interval ATBS1 and minus time interval ΔΤΒΕ2, where the time interval ΔΤΒβ1 îs provided at the beginning ofthe second half period TB and where the time interval ΔΤΒΕ2 is provided in the end of the second half period TB. The second set S2sc2; S2sc2, S3sc2 of switches of the second switching circuit SC2 is controlled to be OFF in the first half period TA. The time interval ΔΤΒδ1 in the présent embodiment is starting at time T4 and is ending at time T5. The time interval ΔΤΒΕ2 in the présent embodiment is starting at T6 and is ending at T8.
The first set S1sc2; S1sc2, S4sc2 and the second set S2sc2; S2sc2, S3sc2 of switches of the second switching circuit SC2 are controlled to be OFF in the time intervals ΔΤΑ81, ΔΤΑΕ2, ΔΤΒβ1 and ΔΤΒΕ2.
The time intervals ΔΤΑΕ2 and ATBS1 form a continuous time interval Tsc2off1 from time T2 to time T5 where the first and second sets of switches of the second switching circuit SC2 are OFF. The time intervals ΔΤΒΕ2 and ΔΤΑ31(ΤΡ+1) (that is, the time interval ΔΤΑβ1 of a subséquent switching period TP+1) form a continuous time interval Tsc2off2 from time T6 to time T1 (TP+1 ) (that is, the time instance T1 of a subséquent switching period TP+1) where the first and second sets of switches of the second switching circuit SC2 are OFF.
Table 1 below shows the states for the first and second set of switches for the first switching circuit SC1 for the switching period TP. The start time and end time of each interval are also given.
TA | TB | |||
TA minus ΔΤΑΕ1 (ΤΟ - T3) | ΔΤΑΕ1 (T3-T4) | TB minus ΔΤΒΕ1 (T4 - T7) | ΔΤΒΕ1 (T7-T8) | |
Tsc1off1 | Tsc1off2 | |||
First set of SC1 | ON | OFF | OFF | OFF |
Second set of SC1 | OFF | OFF | ON | OFF |
Table 1 : ON/OFF states for first and second set of switches of the first switching circuit SC1.
Table 2 below shows the states for the first and second set of switches for the second switching circuit SC2 for the switching period TP. The start time and end time of each interval are also given.
»
A
TA (T0-T4) | TB (T4-T8) | |||||
ATAS1 (T0-T1) TA minus (ATASIand | ΔΤΑΕ2) (T1 -T2) | ΔΤΑΕ2 (T2-T4) | ΔΤΒβΙ (T4 - T5) | TB minus TBS1 and ΔΤΒΕ2 | (T5 - T6) ΔΤΒΕ2 (T6- T8) | |
Tsc2off2 | Tsc2off1 | Tsc2off2 | ||||
First set of SC2 | OFF | ON | OFF | OFF | OFF | OFF |
Second set of SC2 | OFF | OFF | OFF | OFF | ON | OFF |
Table 2: ON/OFF states for first and second set of switches of the second switching circuit SC2.
The time interval Tsdoffl and the time interval Tsc2off1 are at least partially overlapping, i.e. the time interval Tsdoffl starts before the time interval Tsc2off1 ends or the time interval Tsc2off1 starts before the time interval Tsdoffl ends. Moreover, the time interval Tsc1off2 and the time interval Tsc2off2 are at least partially overlapping, i.e. the time interval Tsc1off2 starts before the time interval Tsc2off2 ends or the time interval Tsc2off2 starts before the time interval Tsc1off2 ends, ln this way the switches of the first switching circuit SC1 and switches of the second switching circuit SC2 are synchronized.
ln the présent embodiment, the length of time interval Tsc2off1 is equal to the length of time interval Tsc2off2, and the length of time interval Tsdoffl is equal to the length of time interval Tsc1off2.
ln the embodiment above, the time intervals Tsc2off1 and Tsc2off2 are longer than the time intervals Tsdoffl and Tsc1off2. However, they could have the same duration, or the time interval Tsdoff could be longer than the period Tsc2off. This dépends on the required time for achieving Zéro Voltage Switching (ZVS) in the switching circuits and may also dépend on the voltage between the first positive and négative DC terminais and the voltage between the second positive and négative DC terminais.
ln the embodiment above, the centre of time interval Tsdoffl is controlled to be close to or equal to the centre of time interval Tsc2off1 and the centre of time interval Tsc1off2 is controlled to be close to or equal to the centre of time interval Tsc2off2 .
Zéro Voltage Switching is maintained for ail switches at turn ON at high to full load as is illustrated in 8.
ln fig. 9, voltage V10 at node 10 and voltage V20 at node 20 are both high before time instance T2, thus switches S1sc1, S4sc1 (first set of SC1) and S1sc2 (first set of SC1) are ail conducting and the switches S2sc1, S3sc1 (second set of SC1) and S2sc2 (second set of SC2) are ail non-conducting.
I7
The first set S1sc2 of switches in the second switching circuit SC2 is turned off at time instance T2. At the time instance when current ls becomes positive it is capable of bringing the voltage at node 10 from high to low by discharging the output capacitances in both the first and second set of switches of the second switching circuit. The second set of switches S2sc2 of the second switching circuit is commanded to be ON at T5, and are thus turned on with a voltage close to zéro without any significant switching losses, so called Zéro Voltage Switching (ZVS).
Since lP is positive, turning off first set of switches S1sc1 and S4sc1 at T3 results in a 10 rapid change of voltage at node 20 from high to low and voltage at node 22 from low to high, caused by the discharging/charging of the output capacitances in the first and second sets of switches S1sc1, S3sc1 and S2sc1, S4sc1 of the first switching circuit. The second set of switches S2sc1 and S3sc1 of the first switching circuit SC1 are commanded to be ON at T4, and are thus turned on with a voltage close to zéro without any significant 15 switching losses, so called ZVS.
Note that in the présent embodiment, the time interval T2 to T5, between turning off S1sc2 and turning on S2sc2 is longer then the time interval T3 to T4 for turning off S1sc1, S4sc1 and turning on S2sc1, S3sc1 since it will take longer time for the voltage Vout of 350 V of 20 the second switching circuit SC2 to commutate than for the voltage Vin of 50 V of the first switching circuit SC1.
ZVS is also maintained for ali switches at turn on even at low to no load which is illustrated in figure 10. We are now referring to figure 11.
Voltage V10 at node 10 and the voltage V20 at node 20 are both high before time instance T2, thus switches S1sc1, S4sc1, and S1sc2 are ail conducting.
The switch S1sc2 is turned off at time instance T2. The current Is is positive and is therefore capable of bringing V10 from high to low by discharging the output capacitances in the switches S1sc2 and S2sc2.
The current Is is decaying due to the changed voltage over résonant inductor, LRC, during the time period T2 to T3. However the magnetîzing current ILm in winding Ls, is still increasing and is therefore reflected to primary winding, LP| and causes the current lP to increase. Since lP is increasing and positive, turning off switches S1sc1 and S4sc1 results in a rapid change of voltage V20 at node 20 from high to low and voltage V22 at node 22 from low to high, caused by the discharging/charging of the output capacitances in the switches S1sc1, S3sc1 and S2sc1, S4sc1.
The output voltage Vout may be controlled by changing the switching frequency. This is illustrated in fig. 12, where it is shown that the output voltage Vout may be varied for different loads and different switching frequencies, The ZVS operation of ail switches is controlled by proper delays, i.e. the time intervals Tsc1off1, Tsc1off2, Tsc2off1 and
Tsc2off2, between switching instances as described in the text and in figure 8 and table 2 and table 3.
The relation between the voltage between first DC terminais T1P, T1N of the sériés résonant DC/DC converter and the voltage between second DC terminais T2P, T2N of the sériés résonant DC/DC converter can be controlled by varying the length of the switching period TP.
The direction of the power flow through the sériés résonant DC/DC converter can be controlled by varying length of the switching period TP. Hence, the sériés résonant DC/DC converter can be controlled to be a bidirectional sériés résonant DC/DC converter.
The switches of the first and second switching circuit SC1, SC2 are controlled to provide zéro voltage switching ZVS at switch turn on and to provide nearly zéro current switching ZCS at switch turn off by controlling the first and second switching circuit to hâve a fixed switching frequency close to the sériés résonant frequency.
The switches of the first and second switching circuit SC1, SC2 can be controlled by switching at an operating point at or near the sériés résonant frequency for ail voltages over the first DC terminais which are inside a specified operating range.
The switches of the first and second switching circuit SC1, SC2 can be controlled by switching at an operating point at or near the sériés résonant frequency for ail load conditions at the second DC terminais.
UPS system with sériés résonant DC/DC converter
In the introduction above, the typical uses of a sériés résonant DC/DC converter was described. In a typical UPS system there will be one common control system for ail the components of the UPS system, including the sériés résonant DC/DC converter. The common control circuit can for example comprise a status flag signal as an indicator for the direction of the power flow through the bidirectional DC/DC converter.
Moreover, the control circuit comprises sensors for sensing the current and/or the voltage at the first DC terminais T1P, T1N and the second DC terminais T2P, T2N.
In a first mode of operation the status flag signal indicates that the power should flow from the first DC terminais T1P, T1N to the second DC terminais T2P, T2N. Here, the control circuit is controlling the current and/or voltage of the second DC terminais T2P, T2N based on a predetermined reference signal for the first mode of operation.
In a second mode of operation the status flag signal indicates that the power should flow from the second DC terminais T2P, T2N to the first DC terminais T1P, T1N. Here, the control circuit is controlling the current and/or voltage of the first DC terminais T1P, T1N based on a predetermined reference signal for the second mode of operation.
As mentioned above, the sériés résonant DC/DC converter may be used as a DC/DC converter for an UPS system, as shown in fig. 1, where its first DC terminais T1 P, T1N are connected to the battery and its second DC terminais T2P, T2N connected to a DC bus (not shown).
The status flag signal may be switched to the first mode of operation when a failure in the AC mains is detected. In such a situation power should be transferred from the battery connected to the first DC terminais to the DC bus connected to the second DC terminais. Here, the control circuit is controlling the voltage and/or current at the second DC terminais T2P, T2N at a predetermined level suitable as input to the DC/AC converter as long as the battery power supply allows it.
The status flag signal may be switched to the second mode of operation when the AC mains is working again, then supplying power from the DC bus to the battery for recharging the battery. Here, the control circuit is controlling the voltage and/or current at the first DC terminais T1 P, T1N at a predetermined level suitable as input to the battery.
The status flag signal may hâve a third mode of operation for indicating that no power should be transferred through the bidirectional DC/DC converter. In this mode of operation, ail switches should be switched off. In this mode of operation there is no failure in the AC mains, and the battery is fuliy charged.
Another application for the sériés résonant DC/DC converter is for re-use of energy stored in battery storages.
Results
The efficiency of the sériés résonant DC/DC converter according to fig. 3 of has been tested. Fig. 12 shows the results of the testing. In the testing, two efficiency curves are illustrated, the first curve shows the efficiency as a function of output power for a circuit having an input voltage Vin of 50V and the second curve shows the efficiency as a function of output power for a circuit having an input voltage Vin of 48V. The output voltage Vout was controlled to be 355V.
As seen, the efficiency is above 96% in the power output range from ca 400W to 2200W. The maximum power efficiency is above 97.5%. This is a considérable improvement over the prior art DC/DC converters mentioned in the introduction, which showed efficiencies of ca 92%.
Claims (7)
1. Method for controlling a sériés résonant DC/DC converter, comprising the steps of:
- defining a switching period TP from time Tstart to time Tend for the sériés résonant DC/DC converter; where the switching period TP comprises a first half period TA from time Tstart to time Tcenter and a second half period TB from time Tcenter to time Tend, and defining a subséquent switching period TP+1 after the switching period TP;
- controlling a first set (S1sc1; S1sc1, S4sc1) of switches of a first switching circuit (SC1) to be ON from the beginning Tstart of the first half period TA minus a time ïnterval ΔΤΑΕ1, where the time interval ΔΤΑΕ1 is provided at the end of the first half period TA;
- controlling a second set (S2sc1 ; S2sc1, S3sc1) of switches of the first switching circuit (SC1) to be ON from the beginning Tcenter of the second half period TB minus a time interval ΔΤΒΕ1, where the time interval ΔΤΒΕ1 is provided at the end of the second half period TB;
- controlling the first set (S1sc1 ; S1sc1, S4sc1) and the second set (S2sc1 ; S2sc1, S3sc1) of switches of the first switching circuit (SC1) to be OFF in the time interval ΔΤΑΕ1 and the time interval ΔΤΒΕ1;
- controlling a first set (S1sc2; S1sc2, S4sc2) of switches of a second switching circuit (SC2) to be ON in the first half period TA minus a time interval ΔΤΑ31 and minus a time interval ΔΤΑΕ2, where the time interval ATAS1 is provided at the beginning of the first half period TA and where the time interval ΔΤΑΕ2 is provided at the end of the first half period TA;
- controlling a second set (S2sc2; S2sc2, S3sc2) of switches of the second switching circuit (SC2) to be ON in the second half period TB minus time interval ΔΤΒ81 and minus time interval ΔΤΒΕ2, where the time interval ATBS1 is provided at the beginning of the second half period TB and where the time interval ΔΤΒΕ2 is provided in the end of the second half period TB;
- controlling the first set (S1sc2; S1sc2, S4sc2) and the second set (S2sc2; S2sc2, S3sc2) of switches of the second switching circuit (SC2) to be OFF in the time intervals ATAS1, ΔΤΑΕ2, ΔΤΒδ1 and ΔΤΒΕ2;
where the time interval ΔΤΑΕ1 forms a first time ïnterval Tsc1off1 wherein the first and second sets of switches of the first switching circuit (SC 1 ) are OFF, and where the time interval ΔΤΒΕ forms a second time interval Tsc1off2 wherein the first and second sets of switches of the first switching circuit (SC1) are OFF;
where the time intervals ΔΤΑΕ2 and ATBS1 form a continuous time interval Tsc2off1, where the first and second set of switches of the second switching circuit (SC2) are OFF; and where the time interval ΔΤΒΕ2 and a time interval ΔΤΑβ1(ΤΡ+1) of the subséquent switching period TP+1 form a continuous time interval Tsc2off2, where the first and second sets of switches of the second switching circuit (SC2) are OFF;
2l where the time interval Tsc1off1 and the time interval Tsc2off1 is overlapping and where the time interval Tsc1off2 and the time interval Tsc2off2 is overlapping where the method comprises the step of controliing the relation between the voltage between first DC terminais (T1 P, T1N) of the sériés résonant DC/DC converter and the voltage between second DC terminais (T2P, T2N) of the sériés résonant DC/DC converter by varying the length of the switching period TP.
2. Method according to claim 1, where the method comprises the step of controliing the centre of interval Tsc1off1 to be close to or equal to the centre of time interval Tsc2off1 and the centre of interval Tsc1off2 to be close to or equal to the centre of time interval Tsc2off2.
3. Method according to any one of claims 1 - 2, where the method comprises the step of controliing the direction of the power flow through the sériés résonant DC/DC converter by varying the switching period TP.
4. Method according to any one of claims 1 - 3, where the method comprises the step of controliing the switches of the first and second switching circuit (SC 1, SC2) to provide zéro voltage switching (ZVS) at switch turn on and to provide nearly zéro current switching (ZCS) at switch turn off by controliing the first and second switching circuit to hâve a fixed switching frequency close to the sériés résonant frequency.
5. Method according to claim 4, where the switches of the first and second switching circuit (SC1, SC2) are controlled by switching at an operating point at or near the sériés résonant frequency for ail voltages over the first DC terminais which are inside a specified operating range.
6. Method according to claim 4, where the switches of the first and second switching circuit (SC1, SC2) are controlled by switching at an operating point at or near the sériés résonant frequency for ail load conditions at the second DC terminais.
7. Sériés résonant DC/DC converter comprising:
first DC terminais (T1 P, T1 N);
second DC terminais (T2P, T2N);
an inductor device (ID; TD);
a first switching circuit (SC1) connected between the first DC terminais (T1P, T1N) and the inductor device (ID; TD), where the first switching circuit (SC1) comprises a first set (S1sc1; S1sc1, S4sc1) of switches and a second set (S2sc1 ; S2sc1, S3sc1) of switches;
a second switching circuit (SC2) and a résonant circuit (RC) connected between the second DC terminais (T2P, T2N) and the inductor device (ID; TD), where the second switching circuit (SC2) comprises a first set (S1sc2; S1sc2, S4sc2) of switches second set (S2sc2; S2sc2, S3sc2) of switches;
a control circuit for controliing the set of switches of the first and sei circuits (SC1, SC2) according to the method of any one of claims 1 ; r switching
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB1018262.4 | 2010-10-28 | ||
US61/407,466 | 2010-10-28 |
Publications (1)
Publication Number | Publication Date |
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OA16581A true OA16581A (en) | 2015-11-20 |
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