JP2000227787A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce electric power consumption when a display with a USB (Universal Serial Bus) hub function is on standby. SOLUTION: This display device is provided with a USB hub comprising a hub port (upstream) to be connected with a host such as a computer, and a hub port (downstream) to be connected with peripheral equipment like a keyboard, a mouse. In this case, when the USB upstream 7 is not connected at the time of an off-state, a main power source device 2 for supplying electric power to the USB downstream 5 is switched off and only a sub-power source device 1 of a minimum power capacity is operated, and thereby the off-state power consumption is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a display device,
In particular, the present invention relates to a display device connected to a host such as a personal computer and to a power supply method thereof.

[0002]

2. Description of the Related Art FIG. 2 shows a first conventional display device employing a USB system.

The power supply device 9 comprises a sub power supply device 1 and a main power supply device 2. When the display device 3 is in a normal operation state (hereinafter referred to as an on state), both the sub power supply device 1 and the main power supply device 2 operate. Power control unit 4
Controls. In the standby mode (hereinafter referred to as an off-state), the power supply control unit 4 controls the main power supply 2 to stop and only the sub power supply 1 to operate. For the purpose of minimizing power consumption in the standby mode, a power supply device having a very small capacity is used as the sub power supply device 1 so that the sub power supply device 1 operates efficiently with a minimum required load.

[0004] However, the power supply to the USB downstream 5 needs to be supplied even in the off-state, so that the sub power supply device 1 supplies power.

Japanese Patent Application Laid-Open No. 10-97 discloses a method for supplying power to a display device and peripheral devices such as a USB.
352 has been released.

[0006]

However, in the configuration of the prior art, since the power supply to the USB downstream is performed by the sub power supply device, a large power capacity is required for the sub power supply device, and the off state and the off state are required. There is a problem that it is difficult to design a high-efficiency design with an extremely light load without a USB downstream load, the power supply efficiency deteriorates, and the power consumption in the standby mode increases.

[0007]

According to a second aspect of the present invention, there is provided a USB having an upstream and a downstream.
In a display device including a hub and a power supply device capable of realizing a plurality of operation modes such as a standby mode depending on a load situation, an upstream detection unit that detects the presence or absence of an upstream connection, the power supply device is a sub power supply device, The main power supply unit, the upstream detection unit detects the presence or absence of the power supply voltage supplied from the host side, and the sub power supply unit requires only the minimum necessary power for the display control system in the off state excluding the USB downstream load. The main power supply is provided with a power supply capable of switching its operation mode to a light load mode in which the efficiency is optimized especially at light load. The display device is in the off state and the USB upstream detection is detected. And when the display device is in the on state, the main power supply device is operated as a USB downstream load or a display device load power supply device in addition to the sub power supply device. .

In particular, when the display device is in the off state and the USB upstream detection is detected, the operation mode of the main power supply device is set to a switching frequency of 20 k since the main power supply device is lightly loaded.
A light load mode fixed to a low value of about hz is operated to improve efficiency.

[0009]

Embodiments of the present invention will be described below with reference to FIG. In this drawing, the same members as those shown in FIG. 2 described above are denoted by the same reference numerals, and description thereof will be omitted.

The USB upstream detector 6 detects the presence or absence of power supply from the host and transmits a signal to the power controller 4.

The power supply 9 comprises a sub power supply 1 and a main power supply 2. When the display device is in a normal operation state (hereinafter referred to as an on state), both the sub power supply 1 and the main power supply 2 operate. Like, power control unit 4
Controls. In the standby mode (hereinafter referred to as an off-state), the power supply control unit 4 controls the main power supply 2 to stop and only the sub power supply 1 to operate. For the purpose of minimizing power consumption in the standby mode, a power supply device having a very small capacity is used as the sub power supply device 1 so that the sub power supply device 1 operates efficiently with a minimum required load.

When the USB upstream detection 6 is detected, the USB downstream 5
It is necessary to supply power to the display device 3 even when the display device 3 is in the off state.
Is performed by the power supply control unit 4.

The main power supply 2 has a mode dedicated to light load, that is, an oscillator 1 for fixing the SW frequency to a low value.
The operation can be switched between a light load mode and a normal load mode by a control signal from the power supply control circuit 4.

[0014]

As described above, according to the present invention, since the sub power supply device is released from the power supply to the USB downstream, it is necessary to design the sub power supply device to the necessary minimum light load during the off state. Thus, a display device in which power consumption in the off-state is significantly reduced can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a display device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sub power supply device 2 Main power supply device 3 Display device 4 Power supply control unit 5 USB downstream terminal 6 USB upstream detection unit 7 USB upstream terminal 8 Oscillator 9 Power supply device

Claims (2)

[Claims] 1. A hub port (hereinafter referred to as “upstream”) and a keyboard connected to a host such as a computer.
USB (universal serial bus) with a hub port (hereinafter referred to as “downstream”) connected to peripheral devices such as a mouse
s) In a display device including a hub, when the display device is in a standby mode (hereinafter, referred to as an off state) and there is no upstream connection, the operation mode of the power supply device is switched to a light load mode, and an off state is set. A display device characterized by reducing power consumption at the time. 2. A power supply device capable of realizing a plurality of operation modes such as an off-state mode according to a load condition, and said power supply device is a sub-power supply device having an extremely small power capacity which only supplies power to a microcomputer system of a display device. An upstream detection unit configured to detect the presence or absence of an upstream connection, and the upstream detection unit detects a host power supply supplied from the upstream. A power supply operation control unit that controls an operation mode of the power supply device,
2. The display device according to claim 1, wherein the power supply control unit is configured to operate only the sub power supply device in an off state and when there is no detection signal from the upstream detection unit.