Power supply voltage converting circuit, control method thereof, display apparatus, and portable terminal

• US 20050184942A1
• Filed: 04/20/2005
• Published: 08/25/2005
• Est. Priority Date: 12/06/2000
• Status: Active Grant

• Current Assignee: Japan Display Incorporated
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Nakajima, Yoshiharu
• Granted Patent: US 7,148,886 B2
• Time in Patent Office: Days
• US Class Current: 345/87
• CPC Class Codes: G09G 2300/0408 Integration of the drivers onto the display substrate
• CPC Class Codes: G09G 2310/04 Partial updating of the display screen
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2330/02 Details of power systems and of start or stop of display operation
• CPC Class Codes: G09G 2330/022 in absence of operation, e.g. no data being entered during a predetermined time
• CPC Class Codes: G09G 2340/0428 Gradation resolution change
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers
• CPC Class Codes: H02M 1/0012 Control circuits using digital or numerical techniques in DC/DC converters H02M3/157, H02M3/33515; in DC-AC converters H02M7/53873
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps
• CPC Class Codes: H02M 3/071 adapted to generate a negative voltage output from a positive voltage source
• 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

In a power supply voltage converting circuit using a charge pump circuit having a switch device (Nch MOS transistor Qn(12) and Pch MOS transistor Qp(12)) in an output unit, a first clamp circuit (13) diode-clamps a switching pulse voltage (control pulse voltage) for the switch device at the time of starting the power supply voltage converting circuit, and a second clamp circuit (16) clamps the switching pulse voltage at a ground level (negative side circuit power supply potential) on the basis of a clamp pulse obtained by using an output voltage Vout at the time of an end of the starting process. A sufficient driving voltage is thereby provided for the Pch MOS transistor Qp(12) in particular. Thus, a power supply voltage converting circuit that can obtain a high current capacity on a small-area circuit scale, a control method thereof, a display apparatus having the power supply voltage converting circuit as a power supply circuit, and a portable terminal having the display apparatus are provided.

Claims

1. A power supply voltage converting circuit using a charge pump circuit having a switch device in an output unit, characterized by comprising:

a first clamp circuit for diode-clamping a control pulse voltage for said switch device at the time of a start; and

a second clamp circuit for clamping said control pulse voltage at a circuit power supply potential on the basis of a voltage outputted through said switch device at the time of an end of the start process.

2. A power supply voltage converting circuit as claimed in claim 1, wherein said switch device is a thin film transistor.

3. A power supply voltage converting circuit as claimed in claim 1, said second clamp circuit characterized by comprising:

clamp pulse generating means for generating a clamp pulse using a value of the voltage outputted through said switch device; and

a switching transistor connected between a node where said control pulse voltage is supplied and the circuit power supply potential for performing switching operation in synchronism with said clamp pulse.

4. A power supply voltage converting circuit as claimed in claim 3, wherein said switch device and said switching transistor are a thin film transistor.

5. A power supply voltage converting circuit as claimed in claim 3, said clamp pulse generating means comprises a pulse generating source for generating a clamp pulse, and a level shift circuit for level-shifting a voltage value of said clamp pulse to the value of the voltage outputted through said switch device and then supplying said clamp pulse to said switching transistor.

6. A control method of a power supply voltage converting circuit using a charge pump circuit having a switch device in an output unit, characterized by comprising the steps of:

first diode-clamping a control pulse voltage for said switch device at the time of a start; and

next clamping said control pulse voltage at a circuit power supply potential on the basis of a voltage outputted through said switch device at the time of an end of the start process.

7-50. -50. (canceled)