Patent Application
20140369082
This application claims the priority of Korean Patent Application No. 10-2013-0069781 filed on Jun. 18, 2013, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a power supply device used for driving a light emitting diode (LED).
2. Description of the Related Art
As energy consumption has become a social issue, interest in energy-efficient light sources has increased. Therefore, research into light emitting diodes (LEDs) capable of replacing existing cold cathode fluorescent lamps (CCFLs) has been actively conducted. That is, by using LEDs in a backlight or similar unit of a lighting device or television, an effort to overcome inefficiency in existing CCFLs has been made.
In general, a plurality of LEDs are connected to one another in series or in parallel so as to be used. Therefore, a user may adjust a brightness of light depending on a situation.
In addition, in order to decrease current deviation between LED strings, a separate current driver is used for each string.
However, in a case of a LED driving device according to the related art, a great deal of components may be used, which results in a complicated circuit structure. In addition, when the respective drivers are used, it may be uneconomical in view of energy efficiency.
Therefore, an LED driving device in which the existing complicated structure is improved and is more efficient needs to be introduced.
Patent Document 1 described in the following related art document relates to an LED power supply device and Patent Document 2 relates to a multi-structure boost circuit, but neither thereof discloses a specific configuration for improving the complicated structure and more efficiently supplying the power.
An aspect of the present invention provides an LED power supply device having a simplified circuit structure.
Another aspect of the present invention provides an LED power supply device having improved efficiency.
According to an aspect of the present invention, there is provided a power supply device, including: an insulating direct current to direct current (DC/DC) converter unit including a primary side winding and a secondary side winding inductively coupled to the primary side winding and inducing a voltage in the secondary side winding in a first direction or a second direction; and a boost unit including a first boost converter boosting the voltage induced in the secondary side winding, in a first mode in which the voltage is induced in the secondary side winding in the first direction, and a second boost converter boosting the voltage induced in the secondary side winding, in a second mode in which the voltage is induced in the secondary side winding in the second direction.
The insulating DC/DC converter unit may include a half-bridge DC/DC converter or a full-bridge DC/DC converter.
The boost unit may include a common inductor having one end connected to one end of the secondary side winding in series.
The boost unit may include a first switching element and a first diode connected to the other end of the secondary side winding.
The boost unit may include a second switching element and a second diode connected to the other end of the common inductor.
The power supply device may further include a controlling unit controlling the insulating DC/DC converter unit and the boost unit.
The controlling unit may turn on the second switching element in the first mode.
The controlling unit may turn on the first switching element in the second mode.
The half-bridge DC/DC converter may include a third switching element and a fourth switching element, and the controlling unit may turn off the third switching element and after a predetermined time of interval has elapsed, turn on the fourth switching element, and may turn off the fourth switching element and after a predetermined time of interval has elapsed, turn on the third switching element.
According to another aspect of the present invention, there is provided a power supply device, including: an insulating direct current to direct current (DC/DC) converter unit including a primary side winding and a secondary side winding inductively coupled to the primary side winding and inducing a voltage in the secondary side winding in a first direction or a second direction; a common inductor connected to the secondary side winding in series; a first boost converter including a first switching element controlling accumulating and discharging of energy of the common inductor, and boosting the voltage induced in the secondary side winding, in a first mode in which the voltage is induced in the secondary side winding in the first direction; and a second boost converter including a second switching element controlling the accumulating and discharging of energy of the common inductor, and boosting the voltage induced in the secondary side winding, in a second mode in which the voltage is induced in the secondary side winding in the second direction.
The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being 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 invention to those skilled in the art. In the drawings, the shapes and dimensions of elements may be exaggerated for clarity, and the same reference numerals will be used throughout to designate the same or like elements.
Referring to
The input stage 10 may perform power factor correction on an input power VAC and may transfer the input power having the corrected power factor to the insulating DC/DC stage 20. Therefore, the input stage 10 may include a power factor corrector.
Specifically, the input stage 10 may convert the input power VAC into a direct current voltage VS having a preset magnitude and may provide the direct current voltage VS to the insulating DC/DC stage 20.
Meanwhile, a capacitor for stabilizing the power may be provided between the input stage 10 and the insulating DC/DC stage 20.
The insulating DC/DC stage 20 may convert the direct current voltage VS into a direct current voltage VB having a preset magnitude and may transfer the direct current voltage VB to the boost converters 30-1 and 30-2.
In a similar manner, a capacitor for stabilizing the power may be provided between the insulating DC/DC stage 20 and the boost converters 30-1 and 30-2.
The boost converters 30-1 and 30-2 may output a voltage having a level higher than that of the voltage input thereto through a switching control. That is, the boost converters 30-1 and 30-2 may transfer the voltage having a level higher than that of the direct current voltage VB to respective LED strings.
A method of controlling the boost converters is obvious to those skilled in the art. Therefore, a specific description thereof will be omitted.
Specifically, the boost converter 30-1 may transfer the voltage having a level higher than that of the direct current voltage VB to a first LED string. In addition, the boost converter 30-2 may transfer the voltage having a level higher than that of the direct current voltage VB to a second LED string.
Similarly to the foregoing description, a capacitor for stabilizing the power may be provided between the boost converters 30-1 and 30-2 and the LED strings.
In a case of the above-mentioned LED driving device, since the LED driving device includes three stages, the input stage 10, the insulating DC/DC stage 20, and the boost converters 30-1 and 30-2, a complicated circuit structure thereof is formed. Moreover, a limitation due to a hard switching of the boost converters 30-1 and 30-2 may degrade total efficiency of the driving device and may increase an electromagnetic interference (EMI).
The power supply device according to the embodiment of the present invention may supply power to the LED string based on the direct current voltage VS from the input stage in the LED driving device shown in
In addition, the power supply device according to the embodiment of the present invention has a structure in which the insulating DC/DC stage 20 and the boost converters 30-1 and 30-2 shown in
Referring to
The insulating DC/DC converter unit 100 may include a primary side winding and a secondary side winding inductively coupled to the primary winding. In addition, a voltage across the primary side winding may be induced in the secondary side winding in a first direction or a second direction.
Specifically, the insulating DC/DC converter unit 100 may be implemented as a half-bridge DC/DC converter or a full-bridge DC/DC converter.
The present specification will be described based on the half-bridge DC/DC converter for convenience of explanation. However, it may be easily appreciated by those skilled in the art that a configuration according to the embodiment of the present invention described in the present specification may be applied to the full-bridge DC/DC converter.
The insulating DC/DC converter unit 100 may include a third switching element Qp1, a fourth switching element Qp2, a first capacitor, a primary side winding Np, and a secondary side winding Ns.
As shown in
The boost unit 200 may include a first boost converter boosting the voltage induced in the secondary side winding, in a first mode in which the voltage is induced in the secondary side winding in the first direction.
The first direction is defined as a state in which negative polarity is induced in one end a of the secondary side winding Ns and positive polarity is induced in the other end b of the secondary side winding Ns.
As shown in
In addition, the boost unit 200 may include a first switching element Qs1 and a first diode Ds1 connected to the other end b of the secondary side winding.
In addition, the boost unit 200 may include a second switching element Qs2 and a second diode Ds2 connected to the other end of the common inductor LB.
The first boost converter may include the common inductor LB, the first switching element Qs1, and the first diode Ds1.
In addition, the boost unit 200 may include a second boost converter boosting the voltage induced in the secondary side winding, in a second mode in which the voltage is induced in the secondary side winding in the second direction.
The second direction is defined as a state in which positive polarity is induced in the one end a of the secondary side winding Ns and negative polarity is induced in the other end b of the secondary side winding Ns.
The second boost converter may include the common inductor LB, the second switching element Qs2, and the second diode Ds2.
Meanwhile, according to the embodiment of the present invention, the power supply device may include a controlling unit controlling the first switching element Qs1, the second switching element Qs2, the third switching element Qp1, and the fourth switching element Qp2.
Hereinafter, an operation principle of the power supply device according to the embodiment of the present invention will be described in detail with reference to
Referring to
In the present embodiment, one period of the operation of the power supply device is defined as Ts.
In addition, the first mode may be continued during Ts/2. In addition, the second mode may be continued during Ts/2.
In addition, a duty ratio of the first switching element QS1 in the first mode is defined as DB1.
In addition, a duty ratio of the second switching element Qs2 in the second mode is defined as DB2.
The controlling unit may turn on the third switching element QP1 and the second switching element Qs2 in the first interval M1.
As the third switching element QP1 is turned on, a voltage Vpri in the primary side winding Np corresponds to half of the direct current voltage VS.
In addition, a primary side current ipri flowing through the third switching element QP1, the first capacitor, and the first side winding Np is increased at a predetermined gradient.
Meanwhile, since the second switching element QS2 is turned on, a voltage in the secondary side winding Ns becomes Vs/2n according to a turns ratio of n:1, such that a current isec flowing through the secondary side winding Ns is increased at a gradient of (Vs/2n)/LB.
In the first interval M1, energy may be accumulated in the common inductor LB.
The controlling unit may turn off the first switching element QS1 in the second interval M2.
As the first switching element QS1 is turned off, a voltage V01 may be applied to the secondary side winding Ns and the common inductor LB.
Meanwhile, as the second switching element QS2 is turned off, the current isec flowing through the secondary side winding Ns is decreased at a gradient of −(V01−VS/2n)/LB.
In the second interval M2, the energy accumulated in the common inductor LB may be discharged so as to supply driving power to a first LED string S1.
As the switching state in the second interval is continued, the current isec flowing through the secondary side winding Ns may become zero.
That is, according to the embodiment of the present invention, the power supply device may be controlled to perform a discontinuous mode (DCM) operation.
Meanwhile, the controlling unit may turn off the third switching element QP1 in the fourth interval M4.
In addition, after a predetermined time of interval has elapsed, the controlling unit may turn on the fourth switching element QP2.
Referring to
In addition, referring to
Referring to
Referring to
As described above, the power supply device according to the embodiment of the present invention has a structure in which the insulating DC/DC converter and the boost converter are integrated, such that the LED driving device may be simply configured using a small quantity of components.
In addition, the common inductor is used in the plurality of boost converter, such that the LED driving device may be simply configured using a small quantity of components.
In addition, according to the embodiment of the present invention, a current iLm flowing in a parasitic inductor Lm of the secondary side winding Ns may freewheel before respective switching elements are turned on. Therefore, respective switching elements may perform zero-voltage switching (ZVS). In the power supply device according to the embodiment of the present invention, all switching elements may perform zero-voltage switching (ZVS) and a hard switching defect of the existing boost converter may be solved. Therefore, the power supply device according to the embodiment of the present invention may have improved efficiency and may have alleviated EMI.
The power supply device may include a plurality of secondary side windings Ns. In this case, the power supply device may supply power to four LED strings S1, S2, S3, and S4.
In the case in which the above-mentioned method is used, the power supply device according to another embodiment of the present invention may supply the power to three or more LED strings.
As set forth above, according to the embodiment of the present invention, the LED power supply device simplifying a circuit structure may be provided.
In addition, according to another embodiment of the present invention, the LED power supply device improving efficiency may be provided.
While the present invention has been shown and described in connection with the embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2013-0069781 | Jun 2013 | KR | national |
