Apparatus for supplying power and liquid crsytal display having the same

• US 20040145584A1
• Filed: 12/05/2003
• Published: 07/29/2004
• Est. Priority Date: 07/03/2001
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kang, Moon-Shik, Han, Song-Yi, Lee, Inn-Sung
• Granted Patent: US 7,319,600 B2
• Time in Patent Office: Days
• US Class Current: 345/212
• CPC Class Codes: G09G 2330/02 Details of power systems and of start or stop of display operation
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/36 using liquid crystals
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/009 having two or more independently controlled outputs for DC-DC converter with intermediate AC H02M3/33561
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: H02M 5/458 using semiconductor devices only
• CPC Class Codes: H05B 41/2822 using specially adapted components in the load circuit, e.g. feed-back transformers, piezoelectric transformers; using specially adapted load circuit configurations
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

Disclosed are a power supplying apparatus and a LCD having the same that reduces manufacturing cost of a large-scale LCD module and enhances powpower efficiency by integrating an external dc power supply used in a large-scale LCD panel into a LCD panel. A first voltage converter converts an external ac voltage into a first dc voltage, and changes a voltage level of the first de voltage into a second dc voltage having a highr voltage level than that of the first de voltage. A second voltage converter converts the second dc voltage into an ac voltage, raises a voltage level of the converted ac voltage, and provides the raised ac voltage to a load. A current detector detects a current flowing through the load, and provides a current detection signal as a feedback signal to the first voltage converter so that the first voltage provide a constant direct current output voltage.

Claims

1. A power supplying apparatus, comprising:

a first voltage converting means for converting a first alternating current voltage into a first direct current voltage, and for changing a voltage level of the first direct current voltage into a second direct current voltage having a higher voltage level than the voltage level of the first direct current voltage;

a second voltage converting means for converting the second direct current voltage into a second alternating current voltage, and for changing a voltage level of the second alternating current voltage into a third alternating current voltage having a higher voltage level than the voltage level of the second alternating current voltage to provide the third alternating current voltage to a first load; and

a current detector for detecting a current flowing through the first load, and for providing a current detecting signal to the first voltage converting means so that the first voltage converting means provides a constant direct current output voltage.

2. The power supplying apparatus of claim 1, wherein the first voltage converting means comprises:

a rectifying means for rectifying the first alternating current voltage into the first direct current voltage; and

a dc-to-dc converter for converting the first direct current voltage into the second direct current voltage to provide the second direct current voltage to the second voltage converting means,

wherein said dc-to-dc converter varies the voltage level of the second direct current voltage in response to the detected current signal.

3. The power supplying apparatus of claim 1, wherein the second voltage converting means is a royer inverter.

4. The power supplying apparatus of claim 1, wherein the second voltage converting means comprises:

a transformer including a primary coil and a secondary coil, the primary coil of the transformer being connected to an output terminal of the first voltage converting means, and the secondary coil of the transformer being connected the first load;

a resonance capacitor, connected in parallel with the primary coil, for forming an LC resonance circuit;

a first transistor, a base of the first transistor being connected to the output terminal of the first voltage converting means, a collector of the first transistor being connected to a first end of the resonance capacitor, and an emitter of the first transistor being connected to a ground, for driving the transformer;

a second transistor, a base of the second transistor being connected to the output terminal of the first voltage converting means, a collector of the second transistor being connected to a second end of the resonance capacitor, and an emitter of the second transistor being connected to the ground, for driving the transformer.

5. The power supplying apparatus of claim 4, wherein the second voltage converting means further comprises a first resistor, a first end of the first resistor being connected to the base of the first transistor, and a second end of the first resistor being connected to the output terminal of the first voltage converting means.

6. The power supplying apparatus of claim 1, wherein the second voltage converting means further comprises a second resistor, a first end of the second resistor being connected to the base of the second transistor, and a second end of the second resistor being connected to the output terminal of the first voltage converting means.

7. The power supplying apparatus of claim 1, wherein the first alternating current voltage is a commercial alternating current voltage, and the second direct current voltage has a voltage level between about 150 volts and about 200 volts.

8. The power supplying apparatus of claim 1, wherein the first voltage converting means further generates a third directing current voltage having a voltage level lower than the voltage level of the first direct current voltage and provides the third direct current voltage to a second load, by receiving the first alternating current voltage.

9. The power supplying apparatus of claim 8, further comprising a third voltage converting means for providing the third direct current voltage to the second load.

10. A LCD apparatus comprising:

a LCD panel driving means for generating a driving signal;

a LCD panel for displaying an image based on the driving signal from the LCD panel driving means;

a backlight unit, disposed under the LCD panel, for providing a light to the LCD panel;

a first voltage converting means for converting a first alternating current voltage into a first direct current voltage;

a second voltage converting means for converting the first direct current voltage into a second alternating current voltage to provide the second alternating current voltage to the backlight unit; and

a third voltage converting means for converting the first direct current voltage into a second directing current voltage to provide the second directing current voltage to the LCD panel driving means.

11. A LCD apparatus of claim 10, wherein the first voltage converting means performs a power factor correction function when converting the first alternating current voltage into the first direct current voltage.

12. A LCD apparatus of claim 11, wherein the first voltage converting means comprises a diode rectifier circuit or an active PWM rectifier circuit.

13. A LCD apparatus of claim 10, wherein the second voltage converting means comprises one selected from the group consisting of a buck converter, a boost converter, a half-bridge converter, a flyback converter, a push-pull converter and a forward converter.

14. A LCD apparatus of claim 10, wherein the third voltage converting means comprises one selected from the group consisting of a royer Inverter, a push-pull Inverter, a half bridge Inverter and a full-bridge Inverter.

15. A LCD apparatus of claim 10, wherein the first voltage converting means receives a current detecting signal in respond to a current flowing through the backlight unit and provides the first directing current voltage based on the current detecting signal.

16. A LCD apparatus, comprising:

a LCD panel for displaying an image based on a driving signal from a plurality of LCD panel drivers;

a backlight unit, disposed under the LCD panel, for providing a light to the LCD panel;

a first voltage converting means for converting a first alternating current voltage into a first direct current voltage, and for changing a voltage level of the first direct current voltage into a second direct current voltage having a higher voltage level than the voltage level of the first direct current voltage in respond to a voltage raising-control signal;

a second voltage converting means for converting the second direct current voltage into a second alternating current voltage, and for changing a voltage level of the second alternating current voltage into a third alternating current voltage having a higher voltage level than the voltage level of the second alternating current voltage to provide the third alternating current voltage to the backlight unit;

a current detector for detecting a current flowing through the backlight, and for providing the voltage raising-control signal to the first voltage converting means; and

a third voltage converting means for converting the second directing current voltage into a plurality of third directing current voltage to provide the third direct current voltage to each of the LCD panel driver.

17. A LCD apparatus of claim 16, wherein the first voltage converting means comprises:

a rectifying means for rectifying the first alternating current voltage into the first direct current voltage; and

a dc-to-dc converter for changing a voltage level of the first direct current voltage into a second direct current voltage having a higher voltage level than the voltage level of the first direct current voltage in respond to the voltage raising-control signal to provide the second direct current voltage to the second voltage converting means.

18. A LCD apparatus of claim 16, wherein the second voltage converting means is a royer inverter.

19. A LCD apparatus of claim 16, wherein the second voltage converting means comprises:

a transformer including a primary coil and a secondary coil, the primary coil of the transformer being connected to an output terminal of the first voltage converting means, and the secondary coil of the transformer being connected the backlight unit;

a resonance capacitor, being connected parallel with the primary coil, to form a LC resonance circuit;

a first transistor, a base of the first transistor being connected to the output terminal of the first voltage converting means, a collector of the first transistor being connected to a first end of the resonance capacitor, and an emitter of the first transistor being connected to a ground, for driving the transformer;

a second transistor, a base of the second transistor being connected to the output terminal of the first voltage converting means, a collector of the second transistor being connected to a second end of the resonance capacitor, and an emitter of the second transistor being connected to the ground, for driving the transformer.

20. A LCD apparatus of claim 19, wherein the second voltage converting means further comprises a first resistor, a first end of the first resistor being connected to the base of the first transistor, and a second end of the first resistor being connected to the output terminal of the first voltage converting means.

21. A LCD apparatus of claim 19, wherein the second voltage converting means further comprises a second resistor, a first end of the second resistor being connected to the base of the second transistor, and a second end of the second resistor being connected to the output terminal of the first voltage converting means.

22. A LCD apparatus of claim 16, wherein the first alternating current voltage is a commercial alternating current voltage, the second direct current voltage has a voltage level between about 150 volts and about 200 volts, and a voltage level of the second directing current voltage applied to the third voltage converting means is smaller than the voltage level of the second directing current voltage applied to the second voltage converting means.