Abstract:
A voltage adjusting circuit includes a voltage regulator module, a control chip, a platform controller hub (PCH), a basic input-output system (BIOS), a number of switching units, and a number of resistors. The voltage adjusting circuit is utilized to receive a voltage signal to supply a working voltage to a liquid crystal display (LCD). The voltage adjusting circuit controls switching units to turn on or turn off, and changes the current of the control chip, and further outputs different voltages to different LCDs. The disclosure further provides an all-in-one computer including the voltage adjusting circuit.

Description:
FIELD 
     The subject matter herein generally relates to a voltage adjusting circuit and an all-in-one computer including the voltage adjusting circuit. 
     BACKGROUND 
     In some all-in-one computers, a converting board converts a +19 volt (V) voltage of a motherboard to a working voltage to power a liquid crystal display (LCD). Different LCDs may require different working voltages. However, the converting board generally cannot convert the +19V to a variety of different working voltages for different LCDs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Implementations of the present technology will now be described, by way of example only, with reference to the attached figures. 
         FIG. 1  is a circuit diagram of an embodiment of a voltage adjusting circuit. 
         FIG. 2  is a circuit diagram of an embodiment of a switching unit of the voltage adjusting circuit. 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate details and features of the present disclosure. 
     Several definitions that apply throughout this disclosure will now be presented. 
     The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The connection can be such that the objects are permanently connected or releasably connected. The term “comprising,” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series and the like. 
     The present disclosure is described in relation to a voltage adjusting circuit  100 . 
       FIG. 1  illustrates an embodiment of the voltage adjusting circuit  100  employed in an all-in-one computer  1 . The voltage adjusting circuit  100  can comprise a voltage regulator module (VRM)  10 , a control chip  20 , a platform controller hub (PCH)  30 , a basic input-output system (BIOS)  40 , four switching units  50 , and four resistors R 1 -R 4 . 
     An input terminal Vin of the VRM  10  receives a +19 volt (V) voltage from the all-in-one computer  1 . An output terminal Vout of the VRM  10  is coupled to a liquid crystal display (LCD)  200  of the all-in-on computer  1 . The VRM  10  converts the +19V voltage to an appropriate working voltage to the LCD  200  through the output terminal Vout. 
     A control terminal CT of the VRM  10  is coupled to a slave terminal D of the control chip  20 . Four sensor terminals ISEN 1 -ISEN 4  of the control chip  20  are coupled to the LCD  200 . The control chip  20  senses a current of the LCD  200  through the four sensor terminals ISEN 1 -ISEN 4 , and outputs a control signal to control the VRM  10  to output the proper working voltage to the LCD  200 . An input terminal of the control chip  20  receives a pulse width modulation (PWM) signal for adjusting brightness of the LCD  200 . 
     Each switching unit  50  comprises a first terminal, a second terminal, and a control terminal. The first terminals of the four switching units  50  are respectively coupled to the four sensor terminals ISEN 1 -ISEN 4 . The second terminals of the four switching units  50  are respectively coupled to ground through the four resistors R 1 -R 4 . The BIOS  40  is coupled to the PCH  30 . First to fourth input output pins GPIO 1 -GPIO 4  are respectively coupled to the control terminals of the four switching units  50 . 
       FIG. 2  illustrates an embodiment of the switching unit  50 . The switching unit  50  can comprise electronic switches Q 1 , Q 2 , resistors R 5 , R 6 , and a capacitor C. A control terminal of the electronic switch Q 1  is coupled to a first end of the resistor R 5 . A second end of the resistor R 5  is defined as the control terminal of the switching unit  50 . The control terminal of the electronic switch Q 1  is also coupled to ground through the capacitor C. A first terminal of the electronic switch Q 1  is coupled to a power supply P 3 V 3  through the resistor R 6 . A second terminal of the electronic switch Q 1  is coupled to ground. A control terminal of the electronic switch Q 2  is coupled to the first terminal of the electronic switch Q 1 . A first terminal of the electronic switch Q 2  is defined as the first terminal of the switching unit  50 . A second terminal of the electronic switch Q 2  is defined as the second terminal of the switching unit  50 . 
     In the embodiment, the control chip  20  is an OZ9967 type control chip. According to the specification table of the OZ9967 type control chip, an equation of V LCD  may be as follows: 
                 V   LCD     =       2   ⁢           ⁢     LI   LCD             C   ⁡     (     1   -   C     )       2     ⁢   T         ,         
wherein V LCD  stands for a voltage output from the VRM  10 , L stands for an output inductance of the control chip  20 , I LCD  stands for a sum of the current sensed by the four sensor terminals ISEN 1 -ISEN 4 , C stands for a duty cycle of the PWM signals received by the control chip  20 , T stands for an operation period of the control chip  20 .
 
     According to the equation, the voltage V LCD  is in proportion to the current I LED . The voltage V LCD  varies with the current of the LCD  200  which can be adjusted by controlling the switching units  50  respectively to be turned off or turned on. 
     For example, when the LCD  200  of a first type is connected to the voltage adjusting circuit  100 , the corresponding rated voltage is selected in the menu of the BIOS  40 , the input output pins GPIO 1 -GPIO 4  of the PCH  30  are controlled to output high level signals. The electronic switches Q 1  of the four switching units  50  are turned on, the electronic switches Q 2  of the four switching units  50  are turned off. Thus, the current I LCD  is adjusted and the voltage V LCD  output from the VRM  10  is accordingly adjusted to be equal to the rated voltage of the LCD  200  of the first type. 
     When the LCD  200  of a second type is connected to the voltage adjusting circuit  100 , the corresponding rated voltage of the LCD  200  is selected in the menu of the BIOS  40 , the input output pin GPIO 1  of the PCH  30  outputs a low level signal and input output pins GPIO 2 -GPIO 4  of the PCH  30  output high level signals. The electronic switch Q 1  of the switching unit  50  coupled to the first input output pin GPIO 1  is turned off, the electronic switch Q 2  of the switching unit  50  coupled to the first input output pin GPIO 1  is turned on. The electronic switches Q 1  of the switching units  50  respectively coupled to the input output pins GPIO 2 -GPIO 4  are turned on, the electronic switches Q 2  of the switching units  50  respectively coupled to the input output pins GPIO 2 -GPIO 4  are turned off. Thus, the current I LCD  is adjusted and the voltage V LCD  output from the VRM  10  is accordingly adjusted to be equal to the rated voltage of the LCD  200  of the second type. 
     In at least one embodiment, the electronic switch Q 1  can be an npn bipolar junction transistor, and the electronic switch Q 2  can be an n-channel field effect transistor. 
     The embodiments shown and described above are only examples. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, especially in matters of shape, size and arrangement of the parts within the principles of the present disclosure up to, and including the full extent established by the broad general meaning of the terms used in the claims. It will therefore be appreciated that the embodiments described above may be modified within the scope of the claims.