DC-DC CONVERTER AND ORGANIC LIGHT EMITTING DISPLAY DEVICE USING THE SAME

• US 20140118414A1
• Filed: 03/15/2013
• Published: 05/01/2014
• Est. Priority Date: 10/30/2012
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: PARK, Sung-Cheon, SEO, Jeong-Min
• Granted Patent: US 9,535,440 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G05F 1/595 semiconductor devices connected in series
• CPC Class Codes: G09G 2330/028 Generation of voltages supplied to electrode drivers in a matrix display other than LCD
• CPC Class Codes: G09G 3/3208 organic, e.g. using organic light-emitting diodes [OLED]
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H03K 17/122 in field-effect transistor switches
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/44 with an active control inside an LED matrix
• CPC Class Codes: H05B 45/60 Circuit arrangements for operating LEDs comprising organic material, e.g. for operating organic light-emitting diodes [OLED] or polymer light-emitting diodes [PLED]
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

There are provided a DC-DC converter and an organic light emitting display device using the same. A DC-DC converter includes a converting module and a sensing unit. The converting module includes a switching module and a control module. The switching module has a plurality of switches, and each of the plurality of switches converts an input voltage into a first voltage and outputs the first voltage while being turned on/off in response to a corresponding pulse width modulation (PWM) signal. The control module controls a switching operation of the switching module by generating the PWM signal. The sensing unit senses driving current supplied to a load to which the first voltage is provided.

Claims

1. A DC-DC converter, comprising:

a converting module comprising;

a switching module that includes a plurality of switches, each of the plurality of switches converting an input voltage into a first voltage and outputting the first voltage while being turned on or off in response to a corresponding pulse width modulation (PWM) signal, and

a control module that controls a switching operation of the switching module by generating the PWM signal; and

a sensing unit that senses driving current supplied to a load to which the first voltage is provided, wherein the control module is configured to adaptively control the frequency of the PWM signal according to a sensed result of the sensing unit.

2. The DC-DC converter according to claim 1, wherein the switching module comprises:

a first switch coupled between a first node and an input node to form or block a current path, the input voltage is supplied to the input node;

an inductor coupled between the first node and a ground; and

a second switch coupled between the first node and a second node so as to form or block a current path, wherein the sensing unit comprises;

a third switch coupled between the second node and an output node; and

a sensing voltage generating unit coupled to both terminals of the third switch so as to output a sensing voltage according to the driving current, the control module comprising;

a PWM signal generating unit that generates the PWM signal having a frequency determined according to the sensing voltage; and

a switch driving unit that controls the first, the second and the third switches.

3. The DC-DC converter according to claim 2, wherein the PWM signal generating unit comprises:

a frequency selection unit that compares the sensing voltage with a plurality of reference voltages, and generates a plurality of selection signals according to the compared result;

a sawtooth wave generating unit that generates a sawtooth wave having a corresponding frequency in response to the frequency selection signal; and

a square wave generating unit that converts the sawtooth wave into the PWM signal, using offset information on a feedback voltage generated by dividing the first voltage and a setting voltage.

4. The DC-DC converter according to claim 3, wherein the square wave generating unit comprises:

a voltage divider that generates the feedback voltage by dividing the first voltage;

an amplifier that amplifies and outputs the difference between the feedback voltage and the setting voltage; and

a comparator that compares the sawtooth wave with the output of the amplifier, and output the PWM signal.

5. The DC-DC converter according to claim 3, further comprising a reference voltage setting unit that sets the plurality of reference voltages.

6. The DC-DC converter according to claim 5, wherein the first switch is implemented as a PMOS transistor, and the second and third switches are implemented as NMOS transistors.

7. The DC-DC converter according to claim 1, wherein the switching module comprises:

an inductor coupled between a first node and an input node to which the input voltage is input;

a first switch coupled between the first node and a ground so as to form or block a current path; and

a second switch coupled between the first node and a second node so as to form or block a current path, wherein the sensing unit comprises;

a third switch coupled between the second node and an output node; and

a sensing voltage output unit coupled to both terminals of the third switch so as to output a sensing voltage according to the driving current, wherein the control module comprises;

a PWM signal generating unit that generates the PWM signal having a frequency determined according to the sensing voltage; and

a switching driving unit that controls the first to third switches.

8. The DC-DC converter according to claim 7, wherein the PWM signal generating unit comprises:

a frequency selection unit that compares the sensing voltage with a plurality of reference voltages, and generates frequency selection signals according to the compared result;

a sawtooth wave generating unit that generates a sawtooth wave having a corresponding frequency in response to the frequency selection signal; and

a square wave generating unit that converts the sawtooth wave into the PWM signal, using offset information on a feedback voltage generated by dividing the first voltage and a setting voltage.

9. The DC-DC converter according to claim 8, wherein the square wave generating unit comprises:

a voltage divider that generates the feedback voltage by dividing the first voltage;

an amplifier that amplifies and outputs the difference between the feedback voltage and the setting voltage; and

a comparator that compares the sawtooth wave with the output of the amplifier, and outputs the PWM signal.

10. The DC-DC converter according to claim 8, further comprising a reference voltage setting unit that sets the plurality of reference voltages.

11. The DC-DC converter according to claim 10, wherein the first switch is implemented as an NMOS transistors, and the second and third switches are implemented as PMOS transistors.

12. An organic light emitting display device, comprising:

a display panel that has a plurality of pixels, and displays a gray scale according to the luminance of an organic light emitting diode in each pixel;

a timing controller that provides the display panel with scan and data signals for allowing the organic light emitting diode in each pixel to emit light; and

a DC-DC converter that receives an input voltage so as to generate first and second voltages for supplying current to the organic light emitting diode and to provide the first and second voltages to the display panel, wherein the DC-DC converter comprises;

a first converting module that receives the input voltage so as to generate the first voltage;

a second converting module that receives the input voltage so as to generate the second voltage; and

a sensing unit that senses driving current supplied to the display panel, wherein each of the first and second converting modules comprises;

a switching module that has a plurality of switches, each of the plurality of switches converting an input voltage into a first voltage and outputting the first voltage while being turned on or off in response to a corresponding PWM signal; and

a control module that controls a switching operation of the switching module by generating the PWM signal, wherein at least one of the control modules of the first and second converting modules is configured to adaptively control the frequency of the PWM signal according to the sensed result of the sensing unit.

13. The organic light emitting display device according to claim 12, wherein the switching module of the second converting module comprises:

a first switch coupled between the input node and a first node so as to form or block a current path;

an inductor coupled between the first node and a ground; and

a second switch coupled between the first node and a second node so as to form or block a current path, wherein the control module of the second converting module comprises;

a PWM signal generating unit that generates the PWM signal having a frequency determined according to the sensed result of the sensing unit; and

a switch driving unit that controls the first and second switches.

14. The organic light emitting display device according to claim 13, wherein the sensing unit is coupled between an output node of the first converting module and a first output node from which the first voltage is provided to the display panel so as to sense the driving current.

15. The organic light emitting display device according to claim 14, wherein the sensing unit comprises:

a third switch coupled between the output node of the first converting module and the first output node; and

a sensing voltage generating unit coupled to both terminals of the third switch so as to output a sensing voltage according to the driving current.

16. The organic light emitting display device according to claim 15, wherein the PWM signal generating unit comprises:

a frequency selection unit that compares the sensing voltage with a plurality of reference voltages, and generates a plurality of frequency selection signals according to the compared result;

a sawtooth wave generating unit that generates a sawtooth wave having a corresponding frequency in response to the frequency selection signal; and

a square wave generating unit that converts the sawtooth wave into the PWM signal, using offset information on a feedback voltage generated by dividing the output voltage and a setting voltage.

17. The organic light emitting display device according to claim 13, wherein the sensing unit is coupled between the second node and a second output node from which the second voltage is provided to the display panel so as to sense the driving current.

18. The organic light emitting display device according to claim 12, wherein the switching module of the first converting module comprises:

a first inductor coupled between the input node and a first node;

a first switch coupled between the first node and a ground so as to form or block a current path; and

a second switch coupled between the first node and a second node so as to form or block a current path, wherein the control module of the first converting module comprises;

a first PWM signal generating unit that generates a first PWM signal having a frequency determined according to the sensed result of the sensing unit; and

a first switch driving unit that controls the first and second switches, wherein the switching module of the second converting module comprises;

a third switch coupled between the input node and a third node so as to form or block a current path;

a second inductor coupled between the third node and a ground; and

a fourth switch coupled between the third node and a fourth node so as to form or block a current path, wherein the control module of the second converting module comprises;

a second PWM signal generating unit that generates a second PWM signal having a frequency determined according to the sensed result of the sensing unit; and

a second switch driving unit that controls the third and fourth switches.

19. The organic light emitting display device according to claim 18, wherein the sensing unit is coupled between the second node and a first output node from which the first voltage is provided to the display panel so as to sense the driving current.

20. The organic light emitting display device according to claim 19, wherein the sensing unit comprises:

a third switch coupled between the second node and the first output node; and

a sensing voltage generating unit coupled to both terminals of the third switch so as to sense a sensing voltage according to the driving current.

21. The organic light emitting display device according to claim 20, wherein each of the first and second PWM signal generating units comprises:

a frequency selection unit that compares the sensing voltage with a plurality of reference voltages, and generates frequency selection signals according to the compared result;

a sawtooth wave generating unit that generates a sawtooth wave having a corresponding frequency in response to the frequency selection signal; and

a square wave generating unit that converts the sawtooth wave into the first or second PWM signal, using offset information on a feedback voltage generated by dividing the output voltage and a setting voltage.