Power supply device

This application claims the benefit under 35 U.S.C. §119 of Korean Patent Application No. 10-2012-0098787, filed Sep. 6, 2012, which is hereby incorporated by reference in its entirety.

1. Field of the Invention

Embodiments relate to a power supply device.

2. Description of the Related Art

Power supply devices include converters, such as alternating current (AC)-to-direct current (DC) or DC-to-AC converters.

DC-to-DC converters convert a DC input into a DC output and operate in a load mode or a power mode depending on an input-to-output ratio.

A DC-to-DC converter includes a transformer and also includes a full bridge circuit as a rectifier.

However, during the switching operation of the full bridge circuit (particularly, during a zero-voltage switching operation), noise may be generated, and the magnitude and cycle of noise may become irregular due to deviations in transmission delays between the elements of the full bridge circuit. To inhibit these problems, a snubber condenser may be added to a driving switch of the full bridge circuit, which, however, incurs additional cost and may lead to decreases in effective transmission time and efficiency.

Embodiments provide a power supply device capable of reducing switching loss during the turning on or off of a switch.

In one embodiment, a power supply device includes: a transformer configured to include first and second windings; a half bridge circuit configured to be connected to first and second nodes and both ends of the first wiring; and a full bridge circuit configured to be connected to third and fourth nodes and both ends of the second winding.

The half bridge circuit may be further configured to include first and second switches connected in series between the first and second nodes and first and second capacitors connected in series between the first and second nodes.

The full bridge circuit may be further configured to include third and fourth switches connected in series between the third and fourth nodes and fifth and sixth switches capacitors connected in series between the third and fourth nodes.

The first winding may be connected between the first and second switches and between the first and second capacitors.

The second winding may be connected between the third and fourth switches and between the fifth and sixth switches.

The first to sixth switches may be transistors.

Each of the first to sixth switches may include a diode.

The first and second switches may be alternately driven.

The first and second switches may be driven at a duty cycle of ½.

A switching frequency for the first and second switches may be the same as a leakage inductance of the transformer and a resonant frequency of the first and second capacitors.

The first and second capacitors may have the same capacitance.

The power supply device may also include a controller configured to drive the first to sixth switches.

The third to sixth switches may be turned off when the first and second switches are alternately being driven.

The first and second switches may be turned off when the third to sixth switches are alternately being driven.

The diodes of the first to sixth switches may be connected to each other in a backward direction.

The power supply device may also include: a first output capacitor configured to be disposed between the first and second nodes; and a second output capacitor configured to be disposed between the third and fourth nodes.

According to embodiments, SINCE the leakage inductance of the transformer and the bridge capacitor of the half bridge circuit form a direct current (DC) resonant tank, switching loss that may occur during the turning on or off of switches can be reduced. As a result, power conversion efficiency can be improved, and noise can be reduced.

FIG. 1 is a circuit diagram of a power supply device according to an embodiment.

FIG. 2 is a waveform diagram illustrating an operation of the power supply device in a load mode.

FIG. 3 is a waveform diagram illustrating an operation of the power supply device in a power mode.

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. However, the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. The present disclosure is defined only by the subject matters of the claims.

The terminology used in the present disclosure is for the purpose of describing particular embodiments only and is not intended to limit the disclosure. As used in the disclosure and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

FIG. 1 is a circuit diagram of a power supply device 100 according to an embodiment.

Referring to FIG. 1 , the power supply device 100 includes a DC-to-DC converter 110 and a controller 120 .

The DC-to-DC converter 110 includes a first circuit unit disposed on the left side of a transformer T and a second circuit unit disposed on the right side of the transformer T.

The first circuit unit includes a first capacitor C 1 formed between first and second nodes n 1 and n 2 . First and second switches Q 1 and Q 2 are connected in series between the first and second nodes n 1 and n 2 .

Third and fourth capacitors C 3 and C 4 are connected in series between the first node n 1 and the second node n 2 .

A first winding connects the third node n 3 between the first and second switches Q 1 and Q 2 and the fourth node n 4 between the third and fourth capacitors C 3 and C 4 . The first winding is included in the transformer T.

The first and second switches Q 1 and Q 2 and the third and fourth capacitors C 3 and C 4 form a half bridge between the first to fourth nodes N 1 to N 4 .

The first and second switches Q 1 and Q 2 may be transistors. A first diode D 1 is formed between the source and drain of the first switch Q 1 , and a second diode D 2 is formed between the source and drain of the second switch Q 2 .

That is, the first diode D 1 is formed between the first and third nodes n 1 and n 3 in a backward direction, and the second diode D 2 is formed between the third and second nodes n 3 and n 2 in the backward direction.

The second circuit unit includes a second capacitor C 2 formed between fifth and sixth nodes n 5 and n 6 .

Third to sixth switches Q 3 to Q 6 are formed between the fifth and sixth nodes n 5 and n 6 . The third to sixth switches Q 3 to Q 6 form a full bridge.

More specifically, the third switch Q 3 is connected between the fifth node n 5 and a seventh node n 7 , the fourth switch Q 4 is connected between the seventh node n 7 and the sixth node n 6 , the fifth switch Q 5 is connected between the fifth node n 5 and an eighth node n 8 , and the sixth switch Q 6 is connected between the eighth node n 8 and the sixth node n 6 .

A second winding that forms the transformer T is formed between and connects the seventh and eighth nodes n 7 and n 8 .

The third to sixth switches Q 3 to Q 6 may be transistors. Third, fourth, fifth and sixth diodes D 3 , D 4 , D 5 and D 6 are formed to connect the sources and drains of the third, fourth, fifth and sixth switches Q 3 , Q 4 , Q 5 and Q 6 , respectively.

More specifically, the third diode D 3 is formed between the fifth and seventh nodes n 5 and n 7 in the backward direction, the fourth diode D 4 is formed between the seventh and sixth nodes n 7 and n 6 in the backward direction, the fifth diode D 5 is formed between the fifth and eighth nodes n 5 and n 8 in the backward direction, and the sixth diode D 6 is formed between the eighth and sixth nodes n 8 and n 6 in the backward direction.

The first and second windings of the transformer T may be formed to have a turns ratio of n:m.

The first and second switches Q 1 and Q 2 may be turned on or off due to leakage inductance generated by the transformer T and the resonant frequency of the third and fourth capacitors C 3 and C 4 , which are bridge capacitors of the first circuit unit, thereby inducing the circuitry to resonate. In this manner, it is possible to reduce any current loss that may be generated by turning on or off the first and second switches Q 1 and Q 2 .

The third and fourth capacitors C 3 and C 4 may have the same capacitance.

The power supply device 100 may include the controller 120 , which outputs a control signal for controlling the first to sixth switches Q 1 to Q 6 of the DC-to-DC converter 110 .

The controller 120 may operate in a load mode or a power mode by controlling the output of the first or second circuit unit in accordance with the operating mode of the power supply device 100 .

The operation of the power supply device 100 will hereinafter be described with reference to FIGS. 2 and 3 .

FIG. 2 is a waveform diagram illustrating an operation of the DC-to-DC converter 110 in a load mode.

The transformer T may have a fixed turns ratio of n:m, and the second winding may have fewer turns than the first winding.

Referring to FIG. 2 , in response to an input DC voltage being applied between the first and second nodes n 1 and n 2 of the first circuit unit, the second circuit unit outputs a lower voltage than the input DC voltage due to the turns ratio (i.e., n:m) of the transformer T, and as a result, the DC-to-DC converter 110 operates in a load mode.

More specifically, the controller 120 alternately turns on or off the first and second switches Q 1 and Q 2 .

That is, the controller 120 turns on the first switch Q 1 and turns off the second switch Q 2 during a first period d 1 , and turns on the second switch Q 2 and turns off the first switch Q 1 during a second period d 2 .

The first and second periods d 1 and d 2 may have the same duty cycle of ½.

The switching frequency for the first and second switches Q 1 and Q 2 may be the same as the resonant frequency of the first and second capacitors C 1 and C 2 .

The controller 120 turns off the third to sixth switches Q 3 to Q 6 that form the bridge circuit of the second circuit unit.

During the load mode, when the first switch Q 1 is turned on and the second switch Q 2 is turned off, the input DC voltage, which is applied between the first and second nodes n 1 and n 2 , is applied to the third node n 3 via the first switch Q 1 . Accordingly, the fourth capacitor C 4 is charged with the input DC voltage, and thus, the voltage and current at the third node n 3 become as illustrated in FIG. 2 . As a result, an induction current may be induced by the transformer, as illustrated in FIG. 2 .

Due to the induction current, which is generated by the turns ratio of the transformer T, a voltage is applied between the seventh and eighth nodes n 7 and n 8 , and the induction current is transmitted to the fifth node n 5 via the third diode D 3 .

Accordingly, the current at the fourth switch Q 4 has a value of 0, but the voltage at the fourth switch Q 4 is the same as the voltage at the seventh node n 7 .

During the second period d 2 , in response to the first switch Q 1 being turned off and the second switch Q 2 being turned on, the third node n 3 is grounded, and the third capacitor C 3 is charged with the input DC voltage. As a result, the voltage at the third node n 3 has a value of 0, and the voltage at the fourth node n 4 has the same level as the voltage at the third node n 3 during the first period d 1 .

Accordingly, a resonant current that flows through the first winding has a sine wave, and a resonant voltage at the first winding (OK?) alternately becomes positive or negative every half a cycle.

Since the third to sixth switches Q 3 to Q 6 of the second circuit unit are turned off and a current flows in the backward direction, the fourth and fifth diodes D 4 and D 5 are turned on so that the output voltage of the second circuit unit is uniformly maintained.

Accordingly, the second circuit unit can serve as a rectifier having a uniform output voltage throughout both the first and second periods d 1 and d 2 .

As described above, a current can be generated by the second and third capacitors C 2 and C 3 during both the first and second periods d 1 and d 2 . Accordingly, the DC-to-DC converter 110 can serve as an interleaver, and thus, the current efficiency of the DC-to-DC converter 110 can be improved.

Also, since capacitors that resonate in response to leakage inductance without a requirement of an additional inductor for LC resonance are provided, the efficiency of the DC-to-DC converter 110 can be improved.

FIG. 3 is a waveform diagram illustrating an operation of the DC-to-DC converter 110 in a power mode.

Referring to FIG. 3 , in response to an input DC voltage being applied between the fifth and sixth nodes n 5 and n 6 of the second circuit unit, the first circuit unit outputs a higher voltage than the input DC voltage so that the DC-to-DC converter 110 operates in the power mode.

More specifically, the controller 120 turns off the first and second switches Q 1 and Q 2 .

The controller 120 alternately turns on the third to sixth switches Q 3 to Q 6 of the full bridge circuit of the second circuit unit.

That is, the controller 120 turns on the third and sixth switches Q 3 and Q 6 during the first period d 1 , and turns on the fourth and fifth switches Q 4 and Q 5 during the second period d 2 .

The first and second periods d 1 and d 2 may have the same duty cycle of ½.

The switching frequency for the third to sixth switches Q 3 to Q 6 may be the same as the resonant frequency of the first and second capacitors C 1 and C 2 .

During the power mode, in response to the third and sixth switches Q 3 and Q 6 being turned on, the input DC voltage is distributed between the third and sixth switches Q 3 and Q 6 and the second winding. Due to the voltage distributed to the second winding and a current flowing through the second winding, an induced current flows into the first winding.

Due to the induced current, a positive voltage is applied to the third node n 3 , and the first diode D 1 is turned on so that an output DC voltage is applied between the first and second nodes n 1 and n 2 .

During the second period d 2 , in response to the fourth and fifth switches Q 4 and Q 5 being turned on, an inverse current and an inverse voltage are applied to the second winding. As a result, a resonant current that flows through the first winding of the transformer T has a sine wave, and a resonant voltage at the first winding (OK?) alternately becomes positive or negative every half a cycle.

The energy of the resonant current is stored in the third capacitor C 3 during the first period d 1 , and is then stored in the fourth capacitor C 4 during the second period d 2 . Accordingly, it is possible to inhibit ripple from being caused by a switching operation during the first and second periods d 1 and d 2 .

As described above, a current can be generated by the third and fourth capacitors C 3 and C 4 during both the first and second periods d 1 and d 2 . Accordingly, the DC-to-DC converter 110 can serve as an interleaver, and thus, the current efficiency of the DC-to-DC converter 110 can be improved.

Also, since capacitors that resonate in response to leakage inductance without a requirement of an additional inductor for LC resonance are provided, the efficiency of the DC-to-DC converter 110 can be improved.

Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.