The present invention relates to a multi-mode switch, and more specifically, to a multi-mode switch for a plasma display panel (PDP) or other applications.
2. Description of the Prior Art
The power switches in PDP driving circuits act in three modes. The first is in off-mode, the second is in fully on-mode and the third is in variable resistor mode or large resistor mode. In the prior art, it is necessary to use two power switches to cover the three modes.
It is therefore an objective of the invention to provide a multi-mode switch for PDP or other applications that solves the problems of the prior art.
Briefly summarized, the claimed multiple mode switch includes an input signal interface for receiving a first input signal and a second input signal and producing a combined input signal; a driving circuit for receiving the combined input signal and producing driving signals accordingly; a resistor mode circuit electrically connected to a first output of the driving circuit, to a first node, and to a second node for enabling the multiple mode switch to operate in variable resistor mode or in large resistor mode; a fully-on mode circuit electrically connected to the second input signal, the first output of the driving circuit and the second node for enabling the multiple mode switch to operate in fully-on mode; a power switch electrically connected to the first node, the second node and a third node for controlling switching of the multiple mode switch between off mode, fully-on mode and variable resistor mode or large resistor mode.
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.
Fig.1 is a functional block diagram of a multi-mode switch according to the present invention.
Fig.2 is an equivalent circuit diagram of the multi-mode switch shown in
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The fully-on mode circuit 110 comprises resistors R211, R212, R213, R214 and R215, a diode D211, and transistors Q211 and Q212. In
The power switch 120 comprises transistor Q221, a resistor R221, and a Zener diode ZD221, although the resistor R221 and the Zener diode ZD221 are optional. The input signal interface 140 comprises a resistor R241 and diodes D241 and D242. The input signals S1 and S2 are input through the anodes of diodes D241 and D242, respectively. The input signal interface 140 receives the input signals S1 and S2 and produces the combined input signal IN.
The transistor Q221 is preferably an insulated gate bipolar transistor (IGBT), and is shown as being an N-type metal oxide semiconductor (NMOS) transistor. The transistors Q211 and Q212 are preferably BJT transistors, and are shown as being PNP and NPN types, respectively.
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When input signal S1 is high and input signal S2 is low, the combined input signal IN is high since one of the input signals is high, and the voltage value at node C is also high. This means that transistor Q211 is turned off and transistor Q221 is turned on, and the power switch 120 is driven via the variable large resistor mode circuit 105. Therefore, nodes A and B have a variable resistance between them, according to the resistance of the variable resistor VR201.
When input signal S1 is low and input signal S2 is high, the combined input signal IN is high since one of the input signals is high, and the voltage value at node C is also high. Input S2 being high causes transistors Q211 and Q221 to turn on, and nodes A and B have almost no resistance between them, resulting in a near short between nodes A and B, thereby turning on the power switch 120. As shown in
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The present invention can also be implemented with two or more multi-mode switches 100 coupled in parallel. These switches can have different variable rates of resistance for PDP or other applications. In addition, when these paralleled switches are all in fully on-mode, they can share the current in loop together.
In summary, the present invention provides a single power switch that can accomplish switching between three different modes of operation that traditionally required at least two power switches. Through the use of the present invention, the number of power switches can be reduced. Furthermore, power loss due to the power switch can be reduced along with the overall cost of the power switch.
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 claims the benefit of the filing date of U.S. provisional patent application No. 60/595,305, filed Jun. 22, 2005, the contents of which are hereby incorporated by reference.
Number | Date | Country | |
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60595305 | Jun 2005 | US |