Inverter for liquid crystal display

• US 9,082,369 B2
• Filed: 05/12/2014
• Issued: 07/14/2015
• Est. Priority Date: 09/04/2002
• Status: Expired due to Fees

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: Min, Woong-Kyu, Jang, Hyeon-Yong
• Primary Examiner(s): Moon, Seokyun
• Application Number:
  US14/275,521
• Publication Number:
  US 20140247205A1
• Time in Patent Office: 428 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers
• CPC Class Codes: H05B 41/3927 by pulse width modulation H05B41/3922 takes precedence

Abstract

An inverter of driving a light source for a display device is provided. The inverter includes a temperature sensor sensing a temperature and generating an output voltage based on the sensed temperature, a buffer generating an output signal having a state depending on the output voltage of the temperature sensor, an oscillator generating an oscillating signal having a frequency depending on the state of the output signal of the buffer, and an inverter performing a switching operation in response to the oscillating signal from the oscillator. Therefore, the inverter increases the voltage applied to the light source when the temperature near the light source is lower than a predetermined temperature since the frequency of the oscillating signal is increased.

Claims

1. An inverter for a liquid crystal display, the inverter comprising:

a triangular wave generator for generating a triangular wave using charging and discharging based on switching operation of a first transistor;

a reset block for resetting the generation of the triangular wave by the triangular wave generator based on the pulses of the vertical synchronization start signal; and

a comparator for comparing a dimming signal with the triangular wave from the triangular wave generator and generating a pulse width modulated (“

PWM”

) signal having on/off duty ratio,

wherein the reset block comprises a second transistor turned on to turn on the first transistor in response to the pulses of the vertical synchronization start signal.

2. The inverter of claim 1, wherein the triangular wave generator comprises:

a capacitor connected to a negative voltage for discharging path and providing an output voltage for the comparator; and

a first operational amplifier for turning off the first transistor when the output voltage of the capacitor is equal to or larger than a predetermined value and turning on the first transistor when the output voltage of the capacitor is smaller than the predetermined value,

wherein the first transistor selectively provides a positive voltage for the capacitor.

3. The inverter of claim 1, wherein the first transistor includes a pnp bipolar transistor and the second transistor includes a npn bipolar transistor.

4. The inverter of claim 2, wherein the comparator comprises a second operational amplifier comparing the dimming signal with the output voltage of the capacitor and outputting a high value when the dimming signal is lower than the output voltage of the capacitor and a low value when the dimming signal is higher than the output voltage of the capacitor.

5. The inverter of claim 1, wherein the liquid crystal display comprises a signal controller for providing the vertical synchronization start signal, and the dimming signal is provided from the signal controller or an external device.

6. The inverter of claim 1, further comprising:

a power driver selectively transmitting a DC voltage in response to a signal from the comparator; and

a voltage booster for driving a lamp in response to a signal from the switching element.

7. An inverter for a liquid crystal display, the inverter comprising:

a triangular wave generator for generating a triangular wave using charging and discharging;

a reset block for resetting the generation of the triangular wave by the triangular wave generator based on the pulses of the vertical synchronization start signal; and

a comparator for comparing a dimming signal with the triangular wave from the triangular wave generator and generating a pulse width modulated (“

PWM”

) signal having on/off duty ratio,

wherein the triangular wave generator comprises;

a capacitor connected to a negative voltage for discharging path and providing an output voltage for the comparator;

a first transistor for selectively providing a positive voltage for the capacitor; and

a first operational amplifier for turning off the first transistor when the output voltage of the capacitor is equal to or larger than a predetermined value and turning on the first transistor when the output voltage of the capacitor is smaller than the predetermined value, and

wherein the reset block comprises a second transistor turned on to turn on the first transistor in response to the pulses of the vertical synchronization start signal.

8. The inverter of claim 7, wherein the first transistor includes a pnp bipolar transistor and the second transistor includes a npn bipolar transistor.

9. The inverter of claim 7, wherein the comparator comprises a second operational amplifier comparing the dimming signal with the output voltage of the capacitor and outputting a high value when the dimming signal is lower than the output voltage of the capacitor and a low value when the dimming signal is higher than the output voltage of the capacitor.

10. The inverter of claim 7, wherein the liquid crystal display comprises a signal controller for providing the vertical synchronization start signal, and the dimming signal is provided from the signal controller or an external device.

11. The inverter of claim 7, further comprising:

a power driver selectively transmitting a DC voltage in response to a signal from the comparator; and

a voltage booster for driving a lamp in response to a signal from the switching element.