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Resonant circuit and resonant dc/dc converter

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Resonant circuit and resonant dc/dc converter


The present disclosure relates to a resonant circuit (20). The resonant circuit comprises three resonant circuit input nodes (11, 12, 13) and three resonant circuit output nodes (21, 22, 23), a transformer device and resonant tank devices. The transformer device (TR) comprises three primary windings (LP1, LP2, LP3) and three secondary windings (LS1, LS2, LS3) magnetically connected to each other, where the three secondary windings (LS1, LS2, LS3) are connected to the three resonant circuit output nodes (21, 22, 23). The first, second and third resonant tank devices (RT1, RT2, RT3) are each connected between the respective three resonant circuit input nodes (11, 12, 13) and the respective primary windings (LP1, LP2, LP3). The disclosure also relates to a resonant DC-DC converter comprising such a resonant circuit (20).

Browse recent Eltek As patents - Drammen, NO
Inventors: Kjetil Boysen, Roar Myhre
USPTO Applicaton #: #20120320638 - Class: 363 2102 (USPTO) - 12/20/12 - Class 363 


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The Patent Description & Claims data below is from USPTO Patent Application 20120320638, Resonant circuit and resonant dc/dc converter.

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FIELD OF THE INVENTION

The present invention relates to a resonant circuit and a resonant DC/DC converter.

BACKGROUND OF THE INVENTION

High efficiency galvanic isolation is needed in many power electronic applications. Transformer based isolation may be needed due to safety, change of voltage levels, or functional issues. Some renewable energy sources need galvanic isolation to work properly; among them are different types of thin film solar panels.

A solar cell panel generates DC power. To supply the DC power to an AC load, either directly or via an AC power distribution network, a power converter system must be connected between the solar cell panel and the AC load for converting the DC power to AC power. Such power converter systems normally comprise a DC/DC converter and a DC/AC converter, the DC/AC converter normally being referred to as an inverter. In addition, the system comprises a control system for controlling the converters, and other components such as filters, fuses, cooling systems etc.

The DC output power generated by a solar cell panel is changing with sun intensity and temperature. High conversion efficiency is very important to maximize energy harvest from a solar plant in the context of making the investment profitable.

The series resonant LLC DC/DC converter has become a popular alternative to PWM type converters in many applications. One advantage with the resonant converter is that it can be designed for high efficiency for all load and input/output voltage conditions since it can maintain zero-voltage switching for all operating conditions.

The practical limitation for a single resonant LLC converter is set by the increasing size and cost of the resonant inductor as the output power increases. Therefore, high power DC/DC-converters are provided as many smaller series resonant LLC converters in parallel, which increase the cost considerably due to the number of components.

The object of the present invention is to provide a resonant circuit with high efficiency and low cost, and which has high efficiency for a wide input voltage range. Moreover, the object is to reduce the number of components, and thereby reducing the complexity and costs involved. In addition, it is an object of the invention to reduce the ripple currents generated by the converter.

The object of the invention is also to provide a resonant DC/DC converter with such a resonant circuit.

SUMMARY

OF THE INVENTION

The present invention relates to a resonant circuit comprising three resonant circuit input nodes and three resonant circuit output nodes; a transformer device comprising three primary windings and three secondary windings magnetically connected to each other, where the three secondary windings are connected to the three resonant circuit output nodes; first, second and third resonant tank devices each connected between the respective three resonant circuit input nodes and the respective primary windings; first, second and third transformer switching devices for reconfiguring the three secondary windings between a delta-configuration and a star-configuration.

In one aspect each resonant tank device comprises a resonant inductor and a resonant capacitor.

In one aspect the three primary windings together with the three resonant tank devices are configured in a delta-configuration.

In one aspect first, second and third transformer switching devices are provided for reconfiguring the three primary windings between a delta-configuration and a star-configuration.

In one aspect the first transformer switching device comprises a common terminal connected to second terminal of the second transformer switching device, a first terminal connected to the first resonant output node and a second terminal connected to the common terminal of the third transformer switching device; the second transformer switching device comprises a common terminal connected to second terminal of the third transformer switching device, a first terminal connected to the second resonant circuit output node and a second terminal connected to the common terminal of the first transformer switching device; the third transformer switching device comprises the common terminal connected the second terminal of the first transformer switching device, a first terminal connected to the third resonant circuit output node and a second terminal connected to the common terminal of the second transformer switching device; where the first secondary winding is connected between the first and second terminals of the first transformer switching device, the second secondary winding is connected between the first and second terminals of the second transformer switching device and the third secondary winding is connected between the first and second terminals of the third transformer switching device, where the transformer device is connected in a delta-configuration when the first terminals of the respective transformer switching devices are connected to their common terminal and where the transformer device is connected in a star-configuration when the second terminals of the respective transformer switching devices are connected to their common terminals.

In one aspect the first resonant inductor, the first resonant capacitor and the first primary winding are connected in series between the first resonant circuit input node and the third resonant circuit input node; the second resonant inductor, the second resonant capacitor and the second primary winding are connected in series between the second resonant circuit input node and the first resonant circuit input node; and the third resonant inductor, the third resonant capacitor and the third primary winding are connected in series between the third resonant circuit input node and the second resonant circuit input node.

In one aspect a magnetic inductor is connected in parallel with each of the primary windings.

In one aspect the first resonant inductor, the first resonant capacitor and the first primary winding are connected in series between the first resonant circuit input node and a primary common node; the second resonant inductor, the second resonant capacitor and the second primary winding are connected in series between the second resonant circuit input node and a primary common node; and the third resonant inductor, the third resonant capacitor and the third primary winding are connected in series between the third resonant circuit input node and a primary common node.

The invention also relates to a resonant DC-DC converter comprising first and second input terminals and first and second output terminals; a switching device connected between the first and second input terminals and three resonant circuit input nodes of a resonant circuit; a rectifier device connected between three resonant circuit output nodes and the first and second output terminals; where the resonant circuit comprises a transformer device comprising three primary windings and three secondary windings magnetically connected to each other, where the three secondary windings are connected to the three resonant circuit output nodes; where the resonant circuit comprises first, second and third resonant tank devices each connected between the respective three resonant circuit input nodes and the respective primary windings; and where the resonant circuit comprises first, second and third transformer switching devices for reconfiguring the three secondary windings between a delta-configuration and a star-configuration.

In one aspect each resonant tank device comprises a resonant inductor and a resonant capacitor.

In one aspect the three primary windings are configured in a delta-configuration.

In one aspect first, second and third transformer switching devices for reconfiguring the three primary windings between a delta-configuration and a star-configuration.

In one aspect the switching device comprises six switching devices, where each switching device is connected between one of the first or second input terminals and one of the respective switch output nodes.

In one aspect the rectifier device is a diode rectifier or a synchronous rectifier.

DETAILED DESCRIPTION

In the following, embodiments of the invention will be described with reference to the enclosed drawings, where:

FIG. 1 illustrates a power converter system for converting DC power from a solar cell panel to AC power supplied to an AC power distribution network or an AC load;

FIG. 2 is a schematic block diagram of the DC/DC converter of FIG. 1;

FIG. 3 is a first embodiment of a resonant DC/DC converter;

FIG. 4 is a second embodiment of a resonant DC/DC converter;

FIG. 5 is a third embodiment of a resonant DC/DC converter;

FIG. 6 is a fourth embodiment of a resonant DC/DC converter;

FIG. 7 is a fifth embodiment of a resonant DC/DC converter;

FIG. 8 is a sixth embodiment of a resonant DC/DC converter;

FIG. 9 is a seventh embodiment of a resonant DC/DC converter;

FIG. 10 is an eight embodiment of a resonant DC/DC converter;

FIG. 11 is a ninth embodiment of a resonant DC/DC converter;

FIG. 12 is an illustration of a prior art converter typically used in such applications, comprising two series resonant LLC converters in parallel phase shifted 90 degrees;

FIG. 13a shows the results of a simulation of the circuit in FIG. 12; and

FIG. 13b shows the results of a simulation of the circuit in FIG. 3.

It is now referred to FIG. 1. A power converter system 1 is connected between a DC power source 2 and an AC load or AC distribution network 3. The DC power source is here a solar cell panel or a module comprising several solar cell panels, but can be any other type of suitable energy source.

The power converter system converts the input DC power to an AC output power. The power converter system comprises a DC/DC converter and an inverter (DC/AC converter), filters etc as mentioned in the description above. Moreover, the system comprises a control system for controlling the DC/DC converter, the inverter and other components. The system in FIG. 1 is in general known for a skilled person.

The present invention relates to the DC/DC converter in FIG. 1. It is now referred to FIG. 2. FIG. 2 illustrates a resonant DC/DC converter comprising a switching device 10, a resonant circuit 20 and a rectifier 30 connected to each other between first and second input terminals IT1, IT2 and first and second output terminals OT1, OT2.

The switching device 10 comprises six switches S1, S2, S3, S4, S5, S6, where each switch is connected between one of the first or second input terminals IT1, IT2 and one of the respective input nodes of the resonant circuit, hereinafter referred to as resonant circuit input nodes 11, 12, 13.

The first switch S1 is connected between the first input terminal IT1 and the first switch output terminal 11, a second switch S2 is connected between the first switch output node 11 and the second input terminal IT2, a third switch S3 is connected between the first input terminal IT1 and the second switch output terminal 12, a fourth switch S4 is connected between the second switch output node 12 and the second input terminal IT2, a fifth switch S5 is connected between the first input terminal IT1 and the third switch output terminal 13 and a sixth switch S6 is connected between the third switch output node 13 and the second input terminal IT2. The switches S1, S2, S3, S4, S5, and S6 are MOSFET switches. Alternatively, the switches may be switches with intrinsic diodes or switches connected in parallel with anti-parallel diodes.

The switching device 10 further comprises switch capacitors CS1, CS2, CS3, CS4, CS5 and CS6, each connected in parallel with one of the respective switches 51, S2, S3, S4, S5, S6.

The switches S1, S2, S3, S4, S5, and S6 are controlled by the control system illustrated in FIG. 1. It should be noted that the switches S1-S6 can be controlled by frequency, PWM, or as a hybrid of both of these.

As mentioned above, the resonant circuit 20 comprises three resonant circuit input nodes 11, 12, 13. The resonant circuit 20 also comprises three resonant circuit output nodes 21, 22, 23.

The rectifier device 30 is connected between the three resonant circuit output nodes 21, 22, 23 and the first and second output terminals OT1, OT2. The rectifier device 30 of FIG. 2 is a diode rectifier.

The rectifier device 30 of FIG. 2 comprises a first diode D1 with its anode connected to the first rectifier input node 21 and its cathode connected to the first output terminal OT1, a second diode D2 with its anode connected to the second output terminal OT2 and its cathode connected to the first rectifier input node 21, a third diode D3 with its anode connected to the second rectifier input node 22 and its cathode connected to the first output terminal OT1, a fourth diode D4 with its anode connected to the second output terminal OT2 and its cathode connected to the second rectifier input node 22, a fifth diode D5 with its anode connected to the third rectifier input node 23 and its cathode connected to the first output terminal OT1 and a sixth diode D6 with its anode connected to the second output terminal OT2 and its cathode connected to the third rectifier input node 23.

Alternatively, the rectifier device 30 may be a synchronous rectifier.



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stats Patent Info
Application #
US 20120320638 A1
Publish Date
12/20/2012
Document #
13516375
File Date
12/10/2010
USPTO Class
363 2102
Other USPTO Classes
International Class
02M3/335
Drawings
14



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