CN1171377C

CN1171377C - Power supply and computer device using same

Info

Publication number: CN1171377C
Application number: CNB001286900A
Authority: CN
Inventors: 吴宗训; 陈专助
Original assignee: BenQ Corp
Current assignee: BenQ Corp
Priority date: 2000-09-20
Filing date: 2000-09-20
Publication date: 2004-10-13
Anticipated expiration: 2020-09-20
Also published as: CN1344056A

Abstract

A power supply is suitable for controlling the power output of the power supply according to a first signal input by a computer host, comprising a rectifier device for providing a DC power supply, a power transformer for receiving the DC power supply and outputting the output power supply and a second signal, a power control circuit for controlling the output power of the power transformer according to the second signal, and a switch device, which is turned on and provides the second signal to drive the power control circuit when the first signal is detected, thereby enabling the power supply to work normally, thereby enabling the power supply to operate according to the status of the computer host.

Description

Power supply and computer devices using it

本发明涉及一种电源供应器，特别涉及一种由检测计算机主机所提供的外部电源以启动显示器的电源供应器。The invention relates to a power supply, in particular to a power supply which detects the external power provided by the computer host to start the display.

目前，大部分的计算机产品及周边装置均采用切换式电源(switchingpower)，其利用脉冲调变(pulse width modulation)控制集成电路(IC)来做为电源控制线路。一般此类脉冲调变控制IC都必须有足够的电压及电流才得以启动，例如3842、及3844系列的IC控制器，因此需要一启动电路使IC能够正常动作。然而，启动电路仅在启动电路时使用，在IC启动以后，即改由辅助电源来供应后续操作的电力，此时该启动电路反而成为无用且消耗功率的累赘。At present, most computer products and peripheral devices adopt switching power supply, which utilizes a pulse width modulation control integrated circuit (IC) as a power control circuit. Generally, this type of pulse modulation control IC must have sufficient voltage and current to start, such as 3842 and 3844 series IC controllers, so a startup circuit is required to enable the IC to operate normally. However, the start-up circuit is only used when starting up the circuit. After the IC is started up, the auxiliary power supply is used to supply power for subsequent operations. At this time, the start-up circuit becomes a useless and power-consuming burden.

图1表示一传统电源供应器的线路方块图，在此图中输出电压的回授稳压控制线路则省略不予图示以精简发明。如图1所示，一整流器1，例如桥式整流器，将交流输入电压转换成为直流电压。一整流电容器2，用以降低直流电压的脉动(ripple)电压。上述直流电压通过启动电阻3充电启动电容器4而启动电源控制芯片5(在此以3842控制器为例)，当电源控制芯片5启动后，输出一高频脉冲信号至控制晶体管6(在此以N型金属氧化物半导体晶体管NMOS为例)的栅极，藉以使得控制晶体管6进行快速的切换动作。变压器7，包含第一绕组7a(或称主要绕组)、第二绕组7b、及第三绕组7c，其中第一绕组7a耦接至NMOS晶体管6的漏极，由上述控制晶体管6的动作，使得第一绕组7a的磁通量发生变化，因而第二绕组7b、及第三绕组7c分别感应得到一高频脉冲电压。第二绕组7b所感应的脉冲电压经一输出二极管9整流、及一输出电容器10降低脉动后，作为电源供应器的输出，而第三绕组7c所感应的脉冲电压经一辅助二极管8整流及启动电容器4降低脉动后提供至电源控制芯片5，而电源控制芯片5即由此电源做为其工作的驱动电压。FIG. 1 shows a circuit block diagram of a conventional power supply. In this figure, the output voltage feedback regulation control circuit is omitted to simplify the invention. As shown in FIG. 1, a rectifier 1, such as a bridge rectifier, converts an AC input voltage into a DC voltage. A rectification capacitor 2 is used to reduce the ripple voltage of the DC voltage. The above-mentioned DC voltage charges the starting capacitor 4 through the starting resistor 3 to start the power control chip 5 (take the 3842 controller as an example here), and when the power control chip 5 starts, it outputs a high-frequency pulse signal to the control transistor 6 (take the The gate of the N-type metal-oxide-semiconductor transistor (NMOS, for example) is used to make the control transistor 6 perform a fast switching operation. The transformer 7 includes a first winding 7a (or main winding), a second winding 7b, and a third winding 7c, wherein the first winding 7a is coupled to the drain of the NMOS transistor 6, and the operation of the above-mentioned control transistor 6 makes The magnetic flux of the first winding 7a changes, so the second winding 7b and the third winding 7c respectively induce a high-frequency pulse voltage. The pulse voltage induced by the second winding 7b is rectified by an output diode 9 and the ripple is reduced by an output capacitor 10, and then used as the output of the power supply, and the pulse voltage induced by the third winding 7c is rectified and started by an auxiliary diode 8 The capacitor 4 reduces the ripple and provides it to the power control chip 5, and the power control chip 5 uses this power as its working driving voltage.

上述电源供应器的工作原理如下，当上述电源供应器输入交流电压时，交流电压经整流器1、及整流电容器2转换成为直流电压，而此直流电压经由启动电阻3而对启动电容器4充电，随着A端点直流电压的增加，B端点的电压电位亦随之升高。当B端点的电压到达一特定电压时(以3842控制器为例是16V)电源控制芯片5将会启动而输出一高频脉冲信号。控制晶体管6在接受上述高频信号后，进行切换动作，以便将第一绕组7a所存储的电力转换至第二绕组7b、及第三绕组7c。第二绕组7b所感应的脉冲电压经一输出二极管9整流、及一输出电容器10降低脉动后藉以作为电源供应器的输出以供其他线路(未图示)操作。第三绕组7c所感应的脉冲电压经辅助二极管8整流及启动电容器4降低脉动后，提供至电源控制芯片5使其得以操作。The working principle of the above-mentioned power supply is as follows. When the above-mentioned power supply inputs an AC voltage, the AC voltage is converted into a DC voltage by the rectifier 1 and the rectification capacitor 2, and the DC voltage charges the startup capacitor 4 through the startup resistor 3, and then As the DC voltage at terminal A increases, the voltage potential at terminal B also increases. When the voltage at terminal B reaches a specific voltage (16V in the case of the 3842 controller), the power control chip 5 will start and output a high-frequency pulse signal. After receiving the above-mentioned high-frequency signal, the control transistor 6 performs a switching operation so as to convert the electric power stored in the first winding 7a to the second winding 7b and the third winding 7c. The pulse voltage induced by the second winding 7 b is rectified by an output diode 9 and reduced by an output capacitor 10 to be used as an output of a power supply for operation of other circuits (not shown). The pulse voltage induced by the third winding 7 c is rectified by the auxiliary diode 8 and reduced by the startup capacitor 4 , and then provided to the power control chip 5 for operation.

由上可知，电源供应器在输入交流电压之初，启动电源控制芯片5所需的电压是由直流电压经启动电阻对启动电容器4充电而提供，而控制晶体管6开始进行其切换动作后，电源控制芯片5工作所需的电压则由变压器7的第三绕组7c所提供。然而，在启动电阻上流通电流将造成额外功率的损耗。启动电阻3的功率消耗可计算如下(以电源控制线路是3842控制器为例)。It can be seen from the above that, at the beginning of the power supply inputting the AC voltage, the voltage required to start the power supply control chip 5 is provided by charging the startup capacitor 4 with the DC voltage through the startup resistor, and after the control transistor 6 starts its switching action, the power supply The voltage required for the operation of the control chip 5 is provided by the third winding 7c of the transformer 7 . However, passing current through the startup resistor will cause additional power loss. The power consumption of the starting resistor 3 can be calculated as follows (taking the power control circuit as a 3842 controller as an example).

一般计算机及其周边装置的输入电源规格为交流电压90V～264V之间，当交流输入电压为最低90V时，经由整流器1、及整流电容器2得到的直流电压约为90V×1.414＝127.6V，3842控制器所需的启动电流最少为1mA，因此启动电阻3的最大阻值为：(DC电压-启动电压)/1mA＝(127.26V-16V)²/1mA＝111260Ω；当交流输入电压为最高264V时，经由整流器1、及整流电容器2得到的直流电压约为264V×1.414＝373.296V，因为3842控制器启动后只需10V以上的工作电压，所以启动电阻3的功率消耗为(DC电压-工作电压)²/(启动电阻值)＝(373.296V-10V)/111260Ω＝1.18W。一般计算机及其周边设备所必备的省电功能(power saving function)均要求在省电模式(off-mode)下的功率消耗需小于3W，而上述约1.18W的消耗常使得无法达到在DPMS的模式中，功率消耗小于3W的标准。Generally, the input power specification of computers and their peripheral devices is AC voltage between 90V and 264V. When the AC input voltage is at least 90V, the DC voltage obtained through rectifier 1 and rectifier capacitor 2 is about 90V×1.414=127.6V, 3842 The starting current required by the controller is at least 1mA, so the maximum resistance value of the starting resistor 3 is: (DC voltage-starting voltage)/1mA=(127.26V-16V) ² /1mA=111260Ω; when the AC input voltage is up to 264V , the DC voltage obtained through the rectifier 1 and the rectifier capacitor 2 is about 264V×1.414=373.296V, because the 3842 controller only needs a working voltage of more than 10V after starting, so the power consumption of the starting resistor 3 is (DC voltage - working voltage) ² /(starting resistance value)=(373.296V-10V)/111260Ω=1.18W. The power saving function (power saving function) necessary for general computers and peripheral equipment requires that the power consumption in off-mode should be less than 3W, and the above-mentioned consumption of about 1.18W often makes it impossible to achieve the power saving function in DPMS. In the mode, the power consumption is less than 3W standard.

然而，公知技术可以降低启动电阻的功率消耗，但是无法配合省电IC动作，而进行快速再启动(restart)。现今的电源供应器常需要配合省电IC(powersaving IC)在其DPMS模式下操作，一般是由省电IC控制切断一些暂不使用线路的电源，例如荧光屏的水平、及垂直扫描信号，但是电源供应器又必须能够继续供应省电IC所需的约+5V电压、及约数10mA电流的输出。为了满足此项要求，若让电源供应器持续动作，仅将其他输出切断而留下+5V输出给省电IC(如此水平、垂直信号恢复时才能自动回复)则无法达到功率消耗需低于3W的规格要求。如此一来，并无法确实达到省电的效果，显示需要改进上述电路结构以确实达到省电的目的。However, the known technology can reduce the power consumption of the start-up resistor, but cannot cooperate with the operation of the power-saving IC to perform a quick restart. Today's power supplies often need to cooperate with a power saving IC (powersaving IC) to operate in its DPMS mode. Generally, the power saving IC controls to cut off the power of some temporarily unused lines, such as the horizontal and vertical scanning signals of the fluorescent screen, but the power The supplier must be able to continue to supply the voltage of about +5V and the output of about several 10mA required by the power saving IC. In order to meet this requirement, if the power supply continues to operate, only cut off the other outputs and leave the +5V output to the power saving IC (so that it can automatically recover when the horizontal and vertical signals are restored), the power consumption must be less than 3W. specification requirements. As a result, the effect of power saving cannot be achieved, which shows that the above circuit structure needs to be improved to achieve the purpose of power saving.

由此，本发明主要目的是为提供一种电源供应器，其根据主机在一般模式下所输出的电源信号而运作。当主机进入DPMS模式时，会中断输出至显示器的电源信号，而此时显示器的电源供应器即随之停止操作，达到确实节省电力的目的，并可以简化电路的复杂度以及降低制造成本。Therefore, the main purpose of the present invention is to provide a power supply that operates according to the power signal output by the host in normal mode. When the host enters the DPMS mode, it will interrupt the power signal output to the display, and at this time the power supply of the display will stop operating, so as to achieve the purpose of saving power, simplify the complexity of the circuit and reduce the manufacturing cost.

为获致上述的目的，本发明提出一种电源供应器，适用于根据由外部输入的一第一信号而控制上述电源供应器的一输出电源，该供应器包括：一整流装置，用以提供一直流电源；一电源变压器，用以接收所述直流电源，并输出所述输出电源及一第二信号；一电源控制电路，用以根据所述第二信号而控制所述电源变压器的输出电源；其特征在于，还包括：一开关装置，该开关装置是依据所述第一信号的状态，将所述第二信号关闭或导通至所述电源控制电路，从而使所述电源变压器接通工作，或断开从而使外部交流电源无法输入所述电源供应器；其中所述电源控制电路包括：一电源控制芯片，耦接于所述开关装置；及一控制晶体管，耦接于所述电源控制芯片及电源变压器之间，用以根据所述电源控制芯片所输出的切换信号而开关切换以控制所述电源变压器的输出电压大小；所述电源变压器包括：一第一绕组、一第二绕组及第三绕组，其中所述直流电源是施加在所述第一绕组及控制晶体管上，并通过所述控制晶体管的切换动作使得所述第二绕组及第三绕组分别产生所述输出电源及第二信号，所述第二信号做为所述电源控制电路的电源。In order to achieve the above purpose, the present invention proposes a power supply, which is suitable for controlling an output power of the above power supply according to a first signal input from the outside. The power supply includes: a rectifying device for providing constant A DC power supply; a power transformer, used to receive the DC power supply, and output the output power and a second signal; a power control circuit, used to control the output power of the power transformer according to the second signal; It is characterized in that it also includes: a switch device, the switch device is based on the state of the first signal, the second signal is turned off or turned on to the power control circuit, so that the power transformer is turned on and working , or disconnected so that the external AC power cannot be input into the power supply; wherein the power control circuit includes: a power control chip, coupled to the switching device; and a control transistor, coupled to the power control Between the chip and the power transformer, it is used to switch according to the switching signal output by the power control chip to control the output voltage of the power transformer; the power transformer includes: a first winding, a second winding and The third winding, wherein the DC power is applied to the first winding and the control transistor, and through the switching action of the control transistor, the second winding and the third winding respectively generate the output power and the second signal, the second signal is used as the power supply of the power control circuit.

另外，本发明的另一目的，在于提供一种计算机装置，包括：一主机，用以提供一第一信号；及一显示器，具有一电源供应器，根据所述第一信号而输出一输出电源以供所述显示器使用，其中所述电源供应器包括：一整流装置，用以提供一直流电源；一电源变压器，用以接收所述直流电源，并输出所述输出电源及一第二信号；一电源控制电路，用以根据所述第二信号而控制所述电源变压器的输出电源的大小；其特征在于，还包括：一开关装置，该开关装置是依据所述第一信号的状态，将所述第二信号关闭或导通至所述电源控制电路，从而使所述电源变压器接通工作，或断开从而使外部交流电源无法输入所述电源供应器；其中所述电源控制电路包括：一电源控制芯片，耦接于所述开关装置；及一控制晶体管，耦接于所述电源控制芯片及电源变压器之间，用以根据所述电源控制芯片所输出的切换信号而开关切换以控制所述电源变压器的输出电压大小；所述电源变压器包括：一第一绕组、一第二绕组及第三绕组，其中所述直流电源是施加在所述第一绕组及控制晶体管上，并通过所述控制晶体管的切换动作使得所述第二绕组及第三绕组分别产生所述输出电源及第二信号，所述第二信号做为所述电源控制电路的电源。In addition, another object of the present invention is to provide a computer device, including: a host computer for providing a first signal; and a display with a power supply for outputting an output power supply according to the first signal For use by the display, wherein the power supply includes: a rectifying device for providing a DC power; a power transformer for receiving the DC power and outputting the output power and a second signal; A power control circuit, used to control the size of the output power of the power transformer according to the second signal; it is characterized in that it also includes: a switch device, the switch device is based on the state of the first signal, The second signal is turned off or turned on to the power control circuit, so that the power transformer is turned on, or turned off so that the external AC power cannot be input to the power supply; wherein the power control circuit includes: A power control chip, coupled to the switch device; and a control transistor, coupled between the power control chip and the power transformer, for switching according to the switching signal output by the power control chip to control The output voltage of the power transformer; the power transformer includes: a first winding, a second winding and a third winding, wherein the DC power is applied to the first winding and the control transistor, and passed through the The switching action of the control transistor makes the second winding and the third winding respectively generate the output power and the second signal, and the second signal is used as the power of the power control circuit.

为使本发明的上述目的、特征和优点能更明显易懂，下文特举一较佳实施例，并结合附图，作详细说明。In order to make the above objects, features and advantages of the present invention more comprehensible, a preferred embodiment will be described in detail below with reference to the accompanying drawings.

图1是显示一传统电源供应器的线路方块图。FIG. 1 is a block diagram showing a circuit of a conventional power supply.

图2是显示根据本发明实施例电源供应器的线路方块图。FIG. 2 is a block diagram showing a circuit of a power supply according to an embodiment of the present invention.

图3是显示根据本发明实施例中计算机主机及显示器的外观图。FIG. 3 is an external view showing a computer host and a display according to an embodiment of the present invention.

参照图2，图2表示根据本发明实施例的电路方块图。为简化起见，在图2中输出电压的回授稳压控制线路则省略不予图示，其中与公知传统技术相同的元件以相同的符号标示。Referring to FIG. 2, FIG. 2 shows a circuit block diagram according to an embodiment of the present invention. For the sake of simplification, the output voltage feedback regulation control circuit in FIG. 2 is omitted from the figure, and the same components as those in the known conventional technology are marked with the same symbols.

如图2所示，整流装置11，包括一桥式整流器1及一电容器2，用以将外部提供的交流电源整流为直流电源。电源变压器7，包括第一绕组7a、第二绕组7b及第三绕组7c。电源控制电路12，包括电源控制芯片5及控制晶体管6，在此以上述控制晶体管6为一NMOS晶体管，而上述电源控制芯片5可为集成电路型号3842及3844系列中的一集成电路为例。电源控制芯片5输出切换信号以开关切换控制晶体管6，藉以使电源变压器7第一绕组7a的电流发生变化而分别在第二绕组7b及第三绕组7c产生感应电压以分别产生输出电源。开关装置13，在此为一继电器，用以检测计算机主机(未图示)所提供的电源信号Vin，此电源信号Vin是由如图3所示的主机31，经由序列传输线传送至显示器32内部的电源供应器。当开关装置13检测到上述电源信号Vin时，则导通，从而提供第三绕组7c所产生的电压至电源控制电路12。此处是以开关装置13检测到上述电源信号Vin存在时则导通为例，当然反之，若以开关装置13检测不到上述电源信号Vin存在时则导通亦为可行，在此不再赘述。再者，在本实施例中，上述开关装置13是根据主机31所提供的电源信号Vin而改变其导通或关闭的状态，本发明的开关装置13能够检测任何由主机31所发出的信号而改变其导通或关闭的状态。电源变压器7的第三绕组7c及开关装置13之间，具有一保护二极管8，其正极是耦接至电源变压器7的第三绕组7c，而负极是耦接至开关装置13。启动电路14，由多个电阻3及电容4所组成。As shown in FIG. 2 , the rectification device 11 includes a bridge rectifier 1 and a capacitor 2 for rectifying the external AC power to DC power. The power transformer 7 includes a first winding 7a, a second winding 7b and a third winding 7c. The power control circuit 12 includes a power control chip 5 and a control transistor 6. Here, the control transistor 6 is an NMOS transistor, and the power control chip 5 can be an integrated circuit in the integrated circuit model 3842 and 3844 series as an example. The power control chip 5 outputs switching signals to switch the control transistor 6, so as to change the current of the first winding 7a of the power transformer 7 to generate induced voltages in the second winding 7b and the third winding 7c respectively to generate output power. The switch device 13, which is a relay here, is used to detect the power signal Vin provided by the host computer (not shown), and the power signal Vin is transmitted from the host computer 31 as shown in FIG. of the power supply. When the switch device 13 detects the above-mentioned power signal Vin, it is turned on, so as to provide the voltage generated by the third winding 7c to the power control circuit 12 . Here, the switching device 13 turns on when the power signal Vin is detected as an example. Of course, on the contrary, it is also feasible to switch on when the switching device 13 does not detect the presence of the power signal Vin, which will not be repeated here. . Furthermore, in this embodiment, the above-mentioned switch device 13 changes its on or off state according to the power signal Vin provided by the host 31, and the switch device 13 of the present invention can detect any signal sent by the host 31 and change its on or off state. Between the third winding 7 c of the power transformer 7 and the switching device 13 , there is a protection diode 8 , whose anode is coupled to the third winding 7 c of the power transformer 7 , and whose cathode is coupled to the switching device 13 . The starting circuit 14 is composed of a plurality of resistors 3 and capacitors 4 .

上述电源供应器的工作原理如下所述，在此预设计算机主机31是操作在一般模式，因此其提供一电源信号Vin至显示器32以导通开关装置13。当显示器32内部的电源供应器接收交流电压时，交流电压经整流器1、及整流电容器2转换成为直流电压，而上述直流电压经由启动电路14提供至电源控制芯片5，将会启动电源控制芯片5以提供一高频脉冲信号至控制晶体管6。控制晶体管6接受上述高频信号而进行切换动作，藉以将能量转换至第二绕组7b、及第三绕组7c。第二绕组7b所感应的脉冲电压经一输出二极管9整流、及一输出电容器10降低脉动后藉以作为电源供应器的输出，以供给其他线路(未图示)动作所需。The working principle of the above-mentioned power supply is as follows. Here, the host computer 31 is preset to operate in a normal mode, so it provides a power signal Vin to the display 32 to turn on the switch device 13 . When the power supply inside the display 32 receives an AC voltage, the AC voltage is converted into a DC voltage by the rectifier 1 and the rectifier capacitor 2, and the above-mentioned DC voltage is provided to the power control chip 5 through the startup circuit 14, and the power control chip 5 will be started. To provide a high frequency pulse signal to the control transistor 6 . The control transistor 6 receives the above-mentioned high-frequency signal and performs a switching operation, so as to convert energy to the second winding 7b and the third winding 7c. The pulse voltage induced by the second winding 7 b is rectified by an output diode 9 and reduced by an output capacitor 10 to be used as an output of a power supply for supplying other circuits (not shown) for operation.

当主机31操作在省电模式(DPMS)时，此时计算机主机不再提供电源信号Vin，因此开关装置13关闭而导致电源控制芯片5因为无法接收到驱动电源而停止动作，因为电源控制芯片5的失能，造成控制开关6无法切换操作而导致电源变压器7无法产生感应电压，而外部交流电源也因为此电源供应器缺乏电流通路而无法输入至此电源供应器。因此不再有电力消耗。When the host computer 31 is operating in the power saving mode (DPMS), the computer host computer no longer provides the power signal Vin, so the switch device 13 is turned off and causes the power control chip 5 to stop acting because it cannot receive the drive power, because the power control chip 5 The failure of the control switch 6 causes the power transformer 7 to fail to generate induced voltage, and the external AC power cannot be input to the power supply because the power supply lacks a current path. So there is no more power consumption.

通过上述电路的设计，当主机31操作在省电模式(DPMS)时，电源供应器即停止操作。不仅如此，其内部其他的电路元件也不再消耗电力，解决了传统技术的缺点。Through the design of the above circuit, when the host 31 operates in the power saving mode (DPMS), the power supply stops operating. Not only that, other circuit components inside it no longer consume power, which solves the shortcomings of traditional technologies.

本发明虽以较佳实施例揭露如上，然其并非用以限定本发明的范围，任何本领域的技术人员，在不脱离本发明的精神和范围内，可做些许的更动与润饰，因此本发明的保护范围应当以权利要求范围所界定的为准。Although the present invention is disclosed above with preferred embodiments, it is not intended to limit the scope of the present invention. Any person skilled in the art can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore The protection scope of the present invention should be defined by the claims.

Claims

1. a power supply unit is applicable to an out-put supply of controlling above-mentioned power supply unit according to one first signal of being imported by the outside, and this supply comprises:

One rectifying device is in order to provide a direct current power supply;

One power transformer in order to receiving described DC power supply, and is exported a described out-put supply and a secondary signal;

One power control circuit is in order to control the out-put supply of described power transformer according to described secondary signal; It is characterized in that, also comprise:

One switching device, this switching device is the state according to described first signal, described secondary signal closed or conducting to described power control circuit, thereby make described power transformer connection work, thereby or disconnect and make external ac power source can't import described power supply unit;

Wherein said power control circuit comprises:

One power supply control chip is coupled to described switching device; And

One oxide-semiconductor control transistors is coupled between described power supply control chip and the power transformer, and switch switches to control the output voltage size of described power transformer in order to the switching signal of exporting according to described power supply control chip;

Described power transformer comprises: one first winding, one second winding and the tertiary winding, wherein said DC power supply is to be applied on described first winding and the oxide-semiconductor control transistors, and making described second winding and the tertiary winding produce described out-put supply and secondary signal respectively by the change action of described oxide-semiconductor control transistors, described secondary signal is as the power supply of described power control circuit.

2. power supply unit as claimed in claim 1, wherein said first signal is a power supply signal.

3. power supply unit as claimed in claim 1, wherein said oxide-semiconductor control transistors are a nmos pass transistor.

4. power supply unit as claimed in claim 1, wherein said power supply control chip can be integrated circuit model 3842, reach the integrated circuit in 3844 series.

5. power supply unit as claimed in claim 1 also comprises a protection diode, and the positive pole of described protection diode is coupled to the tertiary winding of described power transformer, and negative pole is coupled to described switching device.

6. power supply unit as claimed in claim 1, wherein said rectifying device comprise a bridge rectifier and a capacitor.

7. power supply unit as claimed in claim 1, wherein said switching device are a relay.

8. power supply unit as claimed in claim 1 also comprises a start-up circuit, is made up of a plurality of resistance of the described DC power supply of acceptance and the electric capacity that charged by described DC power supply.

9. computer installation comprises:

One main frame is in order to provide one first signal; And

One display has a power supply unit, exports an out-put supply according to described first signal and uses for described display, and wherein said power supply unit comprises:

One rectifying device is in order to provide a direct current power supply;

One power control circuit is in order to control the size of the out-put supply of described power transformer according to described secondary signal; It is characterized in that, also comprise:

Wherein said power control circuit comprises:

One power supply control chip is coupled to described switching device; And

10. computer installation as claimed in claim 9, wherein said first signal is a power supply signal.

11. computer installation as claimed in claim 9, wherein said oxide-semiconductor control transistors are a nmos pass transistor.

12. computer installation as claimed in claim 9, wherein said power supply control chip can be integrated circuit model 3842, reach the integrated circuit in 3844 series.

13. computer installation as claimed in claim 9 also comprises a protection diode, the positive pole of described protection diode is coupled to the tertiary winding of described power transformer, and negative pole is coupled to described switching device.

14. computer installation as claimed in claim 9, wherein said rectifying device comprise a bridge rectifier and a capacitor.

15. computer installation as claimed in claim 9, wherein said switching device are a relay.

16. computer installation as claimed in claim 9 also comprises a start-up circuit, is made up of a plurality of resistance of the described DC power supply of acceptance and the electric capacity that charged by described DC power supply.

17. a display equipment is connected in a main frame that one first signal can be provided, described display equipment comprises:

One power supply unit is exported an out-put supply according to described first signal and is used for described display, and wherein said power supply unit comprises:

One rectifying device is in order to provide a direct current power supply;

Wherein said power control circuit comprises:

One power supply control chip is coupled to described switching device; And

18. display equipment as claimed in claim 17, wherein said first signal is a power supply signal.

19. display equipment as claimed in claim 17, wherein said oxide-semiconductor control transistors are a nmos pass transistor.

20. display equipment as claimed in claim 17, wherein said power supply control chip can be integrated circuit model 3842, reach the integrated circuit in 3844 series.

21. display equipment as claimed in claim 17 also comprises a protection diode, the positive pole of described protection diode is coupled to the tertiary winding of described power transformer, and negative pole is coupled to described switching device.

22. display equipment as claimed in claim 17, wherein said rectifying device comprise a bridge rectifier and a capacitor.

23. display equipment as claimed in claim 17, wherein said switching device are a relay.

24. display equipment as claimed in claim 17 also comprises a start-up circuit, is made up of a plurality of resistance of the described DC power supply of acceptance and the electric capacity that charged by described DC power supply.