Monitor

A monitor includes a display device, a signal interface, a power interface, and a power controller. The display device is configured for displaying information to users. The signal interface is configured for receiving display signals, and providing the display signals for the display device. The power interface is configured for receiving power from an external power source, and providing the source for the display device. The power controller monitors the existence of the display signal at the signal interface, and accordingly controls the power interface to selectively provide the power for the display device.

BACKGROUND

1. Field of the Invention

The present invention generally relates to monitors. Particularly, the present invention relates to a monitor, which is able to cut off power supplied thereto when there is no display signal.

2. Description of Related Art

Computers, media players and other electronic devices display information to users on monitors. A typical monitor includes a signal interface for receiving display signals and a power interface for receiving power. Typically, when there is no display signal supplied to the monitor, the monitor displays a dark screen or message like “no signal”.

During the time no display signal is sent to the monitor, the monitor is still active and ready to display which wastes power and further ages the components therein

Therefore, a need exists in the industry to provide a monitor which is able to cut off the power supplied thereto when there is no display signal.

SUMMARY

In one embodiment, a monitor includes a display device, a signal interface, a power interface, and a power controller. The display device is configured for displaying information to users. The signal interface is configured for receiving display signals, and providing the display signals to the display device. The power interface is configured for receiving power from an external power source, and providing power to the display device. The power controller monitors the existence of the display signal at the signal interface, and accordingly controls the power interface to selectively provide the power to the display device.

Other advantages and novel features of the monitor will become more apparent from the following detailed description of embodiments when taken in conjunction with the accompanying drawings, in which:

DETAILED DESCRIPTION

Referring toFIG. 1, a monitor in accordance with an exemplary embodiment includes a display device12, a signal interface14, a power interface16, and a power controller18.

The display device12is configured for displaying information to users, such as interfaces of operation systems installed in the computer, interfaces of application software, images, documents, and movies. The display device12can be a traditional Cathode Ray Tube (CRT), Liquid Crystal Display (LCD), or Plasma Display Panel (PDP), etc.

Referring toFIGS. 2 and 3, the signal interface14is configured for receiving display signals from signal sources such as computers or media players. The signal interface14can be a Video Graphic Array (VGA) (as shown inFIG. 2) used for transmitting analog signals, a Digital Video Interface (DVI) (as shown inFIG. 3), or a High Definition Multimedia Interface (HDMI) used for transmitting digital signals.

Referring toFIG. 2, in the case that the signal interface14is the VGA interface, the signal interface14has a power pin indicating the presence of the display signal. In the VGA interface, the power pin is the 9th pin NC. Referring toFIG. 3, the CLK14pin in the DVI interface is also a power pin. The power signal at the power pin of the signal interface14is 5V when the display signal is present, zero otherwise.

The power interface16is configured for being connected to an external power source such as an 110V alternating current (AC) power source, and converting the external voltage to a suitable form for use by the monitor, if necessary.

The power controller18is configured for monitoring the presence of the display signal, and controlling the power interface16to selectively provide the power supply to the display device12. In the case that the signal interface14receives a display signal, the power controller18allows the power interface16to provide the power supply to the display device12, otherwise, the power controller18cuts off the power supply.

Referring toFIG. 4, the power controller18includes a first switch circuit20, a filter circuit22, a damping circuit24, a rectifying circuit26, an amplifying circuit28, and a second switch circuit30.

The first switch circuit20is configured for receiving the power signal from the power pin of the signal interface14, and generating a first switch signal according to the power signal. The first switch circuit20may be a 4N28 photocoupler. The first switch circuit20includes a light emitting diode (LED)402and a phototransistor404. The power signal received from the power pin of the signal interface14turns on the LED402. Light emitted by the LED402strikes the phototransistor404, causing the phototransistor404to become conductive, and generating the first switch signal.

The filter circuit22receives the power provided by the power interface16, and filters ripples in the power, thus avoiding sudden spikes in power to the elements. In this embodiment, the filter circuit22includes a capacitor C1and a resistor R1. The capacitor C1and the resistor R1are connected in parallel, and then connected to the neutral wire N of the external power source. The filtered power is transmitted to the damping circuit24.

The damping circuit24is configured for absorbing induced voltages in the power controller18, thereby avoiding sudden spikes in voltage to elements in the circuit. The damping circuit24includes a diode D1and a resistor R2. The anode of the diode D1is connected to the output end of the filter circuit22, the cathode of the diode D1is connected to one end of the resistor R2. The other end of the resistor R2is connected to the rectifying circuit26, and is also connected to the collector of the phototransistor404.

The rectifying circuit26is configured for filtering high-frequency components in the power provided by the external power source, thereby avoiding signal distortion in following circuits. The rectifying circuit26includes a diode D2and a capacitor C2. The anode of the diode D2is connected to the cathode of the capacitor C2, and further connected to ground, while the cathode of the diode D2is connected to the anode of the capacitor C2, and further connected to the output end of the damping circuit24.

The amplifying circuit28is connected to the emitter of the phototransistor404of the first switch circuit20, for amplifying the first switch signal. The amplifying circuit28includes two cascaded transistors T1and T2. Both of the transistors T1and T2are NPN type. The base of the transistor T1is connected to the emitter of the phototransistor404of the first switch circuit20through a resistor R3, for receiving the first switch signal. The collector of the transistor T1is connected to the output end of the rectifying circuit26. The emitter of the transistor T1is connected to ground through a resistor R4. The emitter of the transistor T1is also connected to the base of the transistor T2through a resistor R5. The emitter of the transistor T2is connected to ground. The collector of the transistor T2is connected to the rectifying circuit26through the second switch circuit30. Therefore, the first switch signal can be used for controlling the on/off state of the second switch circuit after being amplified by the amplifying circuit28.

The second switch circuit30is configured for connecting or cutting off the power supplied to the display device12according to the amplified signal of the amplifying circuit28. The second switch circuit30includes an electromagnetic relay406and a diode D3. The anode of the diode D3is connected to the collector of the transistor T2of the amplifying circuit28, and the cathode thereof is connected to the output end of the rectifying circuit26. The diode D3is able to conduct the two ends of the electromagnetic relay406, thereby protecting the electromagnetic relay406in the case that the electromagnetic relay406is powered off and generates a rather high negative voltage.

Referring toFIGS. 5 and 6, symbol502refers to the wave form of the power signal on the power pin of the signal interface14, and symbol504refers to the wave form of the power that the display device12receives. When the power signal on the power pin of the signal interface14is 0V, the LED402does not emit light, therefore the phototransistor404is not conductive. The first switch circuit20therefore generates the first switch signal with a low voltage. The transistors T1and T2are not conductive accordingly, and the electromagnetic relay406is not conducted. Therefore, the power received by the power interface16cannot be provided to the display device12. When the power signal on the power pin of the signal interface14is 5V, the LED402emits light to the phototransistor404. The phototransistor404is conductive, and sends out the first switch signal with a high voltage. The high voltage first switch signal causes the transistors T1and T2of the amplifying circuit28to be conductive. Therefore, the electromagnetic relay406is conducted, and the power introduced by the power interface16can be provided to the display device12.