Patent Application
20100164944
1. Field of the Invention
The present invention relates to a display system, and more particularly, to a display system disposing a charge pump circuit on a flexible printed circuit (FPC) externally coupled to its display device for improving its voltage converting efficiency.
2. Description of the Prior Art
A charge pump is a type of DC to DC converter that uses capacitors as energy storage elements to create either a higher or lower voltage power source. Charge pumps use some form of switching devices to control the connection of voltages to the capacitor. The charge pumps can also double voltages, triple voltages, halve voltages, invert voltages, fractionally multiply or scale voltages such as × 3/2, × 4/3, ×⅔, etc. and generate arbitrary voltages, depending on the controller and circuit topology. A traditional charge pump circuit includes a voltage source, one or more charge capacitances, a load capacitance, a number of circuit switches and a fixed-frequency clock used to control the circuit switches. Using a clock period as an example (e.g. a doubled two phase circuit), in the first half period, circuit switches are used to make a parallel connection between a voltage source and a charge capacitance so as to charge the charge capacitance to a voltage level; in the second half period, circuit switches are used to make a serial connection between the voltage source and the charge capacitance and a load capacitance. After a number of periods are repeated, the voltage difference between two sides of the load capacitance will be lifted up to a voltage level that is much higher than that of the original voltage source.
In traditional small-sized and medium-sized thin-film transistor liquid crystal display (TFT-LCD) devices, with the growing size of the screen, the current consumption is also growing. If the charge pump circuit is disposed in the driving circuit of the TFT-LCD device, its voltage converting efficiency will get worse due to being limited by the indium tin oxide (ITO) resistors.
In addition, since the system end hopes to provide an input voltage ranging from 2.0V to 4.8V to the driving circuit of the TFT-LCD device directly, the charge pump circuit should be able to support a voltage converting ratio with different multiples (such as 1.5 times, 2 times, or 3 times) to provide the desired output voltage. Therefore, an important research and development subject in the industry is how to dispose a charge pump circuit in the TFT-LCD device without it being affected by the ITO resistors, and how to control the charge pump circuit.
It is therefore one of the objectives of the claimed invention to provide a display system disposing a charge pump circuit on a flexible printed circuit (FPC) externally coupled to its display device to solve the abovementioned problems.
According to an exemplary embodiment, a display system is provided. The exemplary display system includes a display device, a driving circuit, an FPC, a charge pump circuit and a control circuit. The driving circuit is disposed on the display device, for driving the display device. The FPC is externally coupled to the display device. The charge pump circuit is disposed on the FPC, for generating at least an output voltage to the driving circuit. The control circuit is disposed on the display device and coupled to the driving circuit, for generating a control signal to control the charge pump circuit. The charge pump circuit has a control pin coupled to the control circuit for receiving the control signal generated from the control circuit.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
Certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, hardware manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but in function. In the following discussion and in the claims, the terms “include”, “including”, “comprise”, and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”. The terms “couple” and “coupled” are intended to mean either an indirect or a direct electrical connection. Thus, if a first device couples to a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections.
In a case where the charge pump circuit is moved from the driving circuit of the thin-film transistor liquid crystal display (TFT-LCD) device to a flexible printed circuit (FPC), it is necessary to consider how to control operations of the charge pump circuit disposed on the FPC. Please refer to
In this exemplary embodiment, the charge pump circuit 160 includes a control pin 162, a charge pump unit 164, a separating circuit 166 and a processing unit 168. As shown in
In addition, the separating circuit 166 in this embodiment includes a low pass filter 1662 and a high pass filter 1664. The low pass filter 1662 is coupled to the control pin 162, for filtering the control signal SC to generate the clock signal Sclock. The high pass filter 1664 is coupled to the control pin 162, for filtering the control signal SC to generate the process signal Sprocess. Please note that, in this embodiment, the separating circuit 166 utilizes two filters to derive the clock signal Sclock and the process signal Sprocess from the control signal SC, but this should not be taken as a limitation of the present invention. In other words, the separating circuit 166 can derive the clock signal Sclock and the process signal Sprocess by utilizing other kinds of circuits, depending upon the actual design considerations. Operations of the control circuit 140 and the charge pump circuit 160 will be detailed using certain figures and embodiments.
Please note that, for clarity and simplicity, this embodiment of the present invention will be described in detail with reference to the accompanying drawings. It is to be noted, however, that the present invention is not limited thereto. Please refer to
The separating circuit 166 of the charge pump circuit 160 receives the control signal SC via the control pin 162. The low pass filter 1662 and the high pass filter 1664 filter the received control signal SC to generate the clock signal Sclock and the process signal Sprocess shown in
As can be seen from
The abovementioned embodiments are presented merely for describing features of the present invention, and in no way should be considered to be limitations of the scope of the present invention. In summary, the present invention provides a display system disposing a charge pump circuit on an FPC externally coupled to its display device for improving its voltage converting efficiency. The display system of the present invention utilizes a single control pin and a control signal to control the charge pump circuit disposed on the FPC. Therefore, the voltage converting efficiency of the charge pump circuit in this display system will not be limited by the indium tin oxide (ITO) resistors.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
This application is a continuation-in-part of co-pending U.S. application Ser. No. 12/370,585, filed on Feb. 12, 2009, which claims the benefit of U.S. provisional application No. 61/109,193, filed on Oct. 29, 2008, the contents thereof being incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61109193 | Oct 2008 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12370585 | Feb 2009 | US |
| Child | 12719873 | US |
