Abstract:
A two-stage power supply system includes a standby power circuit, a main power circuit, a driver and, a rectifier. Moreover, the standby power circuit is used to convert a utility AC (Alternating Current; AC) into a standby AC. The main power circuit is used to convert the utility AC into a main AC. Furthermore, the driver is coupled to the main power circuit so as to control whether or not the main power circuit outputs the main AC to the rectifier. Finally, the rectifier is coupled to the standby power circuit, the main power circuit, and a load, wherein the rectifier rectifies the standby AC alone for outputting a standby DC (Direct Current; DC) to the load, or rectifies an integrated AC of the standby AC and the main AC for outputting a supply DC to the load.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to provisional application Ser. No. 61/057,948 filed Jun. 2, 2008, the entire contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to a two-stage power supply system; in particular, to a power supply system having a standby power supply mode and a normal power supply mode. 
     2. Description of Related Art 
     Due to rapid decrease in global storage of consumptive energy such as coal, crude oil and the like, the problem of consumptive energy waste is becoming a vital issue, resulting in people paying more attention to environmental protection objectives regarding energy savings and green energies. Currently, there are already several countries/areas such as EU, California in US, Korea, and Japan announcing regulations on product standby status (standby power&lt;1 W); meanwhile, at present there are also many home electronic devices introducing power-saving designs therein. 
     After numerous discussions, tests, and evaluations, many experts consistently agree that to achieve the purpose of power-saving in an electronic product, it is necessary to improve the power consumption of the product in standby mode, since general home electronic devices or common products, e.g. computer screen, television etc., tend not be unplugged while not in use, but are left in standby mode. Therefore, general home electronic devices or common products are frequently in the standby mode, thus wasting substantial amount of power; as a result, the reduction of standby power in electronic products has become one of the most crucial topics now-a-days. 
     Consequently, it is desirable for the industry to be able to provide a power supply system allowing for energy conservation, and also to enable smooth initiation as a product utilizing the power supply system becomes operative. 
     SUMMARY OF THE INVENTION 
     In view of this, the present invention provides a two-stage power supply system having a standby power supply mode and a normal power supply mode. The two-stage power supply system according to the present invention can be used to meet the power requirement of a load; when the load is coupled to a power source through the two-stage power supply system and the load is in a standby condition, at this moment, the two-stage power supply system is in the standby power supply mode, so as to provide the minimum power required by the load; on the other hand, when the load starts to operate, the two-stage power supply system is in the normal power supply mode so as to supply the required power to the load for normal operations. 
     The two-stage power supply system in a first preferred embodiment of the present invention has a standby power supply mode and a normal power supply mode, comprising a standby power circuit, a main power circuit, a driver, and a rectifier. Therein the standby power circuit is for receiving an alternating current (AC) power, and outputting a standby AC power. The main power circuit is for receiving the AC power and outputting a main AC power. The driver is coupled to the main power circuit, for stopping the main power circuit from outputting the main AC power when in the standby power supply mode, and controlling the main power circuit to outputting the main AC power when in the normal power supply mode. The rectifier is coupled to the standby power circuit, the main power circuit, and a load, in which the rectifier is for rectifying the standby AC power into a standby direct current (DC) power to provide to the load when in the standby power supply mode, and for rectifying an integrated power of the standby AC power and the main AC power into a supply DC power to provide to the load when in the normal power supply mode. 
     In contrast to the aforementioned first preferred embodiment of the present invention, the two-stage power supply system in a second preferred embodiment of the present invention further comprises a DC voltage step-down circuit and a voltage regulator circuit, installed between the rectifier and the load. Therein the DC voltage step-down circuit is coupled to the rectifier, in which the DC voltage step-down circuit supplies a standby DC power voltage step-down when in the standby power supply mode, and provides a supply DC power voltage step-down when in the normal power supply mode. The voltage regulator circuit is coupled to the DC voltage step-down circuit and the load, in which the voltage regulator circuit stabilizes the standby DC power to the load after the voltage step-down of the DC voltage step-down circuit when in the standby power supply mode, and stabilizes the supply DC power to the load after the voltage step-down of the DC voltage step-down circuit when in the normal power supply mode. 
     In summary of the aforementioned descriptions, when the two-stage power supply system according to the present invention is in the standby power supply mode, the standby AC power provided by the standby power circuit thereof passes through the rectifier, the DC voltage step-down circuit and the voltage regulator circuit to generate a standby DC power. The generated standby DC power is used to provide the minimum power consumption required for the standby of the load. At this moment, the main power circuit is not initiated yet, thus it has no power consumption. Therefore, the two-stage power supply system according to the present invention allows general home electronic devices or common electronic products to effectively reduce power consumption during standby mode, further meeting the regulations on power saving (standby power&lt;1 W). 
     Additionally, when the two-stage power supply system according to the present invention is in the normal power supply mode, the standby AC power provided by the standby power circuit and the main AC power provided by the main power circuit will be integrated (i.e. the integrated power), and, meanwhile, through the rectifier, the DC voltage step-down circuit, and, the voltage regulator, it is possible to generate a DC supply power which can be used to provide the required power consumed by the load for normal operations. In this way, the two-stage power supply system according to the present invention can supply power to general home electronic devices or common electronic products in a normal fashion, allowing them to successfully start and perform normal operations. 
     The aforementioned illustrations and following detailed descriptions are exemplary for the purpose of further explaining the scope of the present invention. Other objectives and advantages related to the present invention will be illustrated in the subsequent descriptions and appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a circuit block diagram of the two-stage power supply system in a first preferred embodiment of the present invention; 
         FIG. 2  is a circuit block diagram of the two-stage power supply system in a second preferred embodiment of the present invention; and 
         FIG. 3  is a diagram of circuit components in the second preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Refer to  FIG. 1 , wherein a circuit block diagram of the two-stage power supply system in a first preferred embodiment of the present invention is shown. The two-stage power supply system  1  has a standby power supply mode and a normal power supply mode, which can respectively provide require power to a load  3  for operating in a standby mode or in an active mode. The two-stage power supply system  1  comprises a standby power circuit  10 , a main power circuit  12 , a driver  14 , and a rectifier  16 . Therein the standby power circuit  10  is used to receive an alternating current (AC) power and performs voltage step-down on the AC power to output a standby AC power AC 1 . The main power circuit  12  is similarly used to receive the AC power and performs voltage step-down on the AC power to output a main AC power AC 2 . 
     Referring again to  FIG. 1 , the driver  14  is coupled to the main power circuit  12 ; and the rectifier  16  is coupled to the standby power circuit  10 , the main power circuit  12 , and a load  3 . When the load  3  is in the standby mode, the driver  14  is controlled by a control signal SC 1  to output a termination signal S 1  to the main power circuit  12 , causing the main power circuit  12  to stop outputting the main AC power AC 2 , thus controlling the two-stage power supply system  1  to operate in the standby power supply mode. At this moment, the rectifier  16  alone rectifies the standby AC power AC 1  into a standby DC power DC 1  so as to provide power to the load  3  for operations in the standby mode, thereby effectively reducing power consumption and further meeting the regulations on power saving (standby power&lt;1 W). 
     Referring once again to  FIG. 1 , when the load  3  is in the active mode, the driver  14  is controlled by the control signal SC 1  to output a drive signal S 2  to the main power circuit  12 , causing the main power circuit  12  to output the main AC power AC 2 , thereby controlling the two-stage power supply system  1  to operate in the normal power supply mode. At this time, the rectifier  16  rectifies an integrated power of the standby AC power AC 1  and the main AC power AC 2  into a supply DC power DC 2  so as to provide to the load  3 , allowing the load  3  to successfully start in the active mode for normal operations. 
     In conjunction with  FIG. 1 , refer now to  FIG. 2  illustrating a circuit block diagram of the two-stage power supply system in a second preferred embodiment of the present invention. The components in the second preferred embodiment of the present invention that are the same to the counterparts found in the first preferred embodiment are identically marked. The circuit operation principle and effects achieved by the first and second preferred embodiments are identical, the major difference is in that: the two-stage power supply system  2  in the second preferred embodiment further comprises a DC voltage step-down circuit  28  and a voltage regulator circuit  29 . The DC voltage step-down circuit  28  is coupled to the rectifier  16 , providing voltage step-down on the standby DC power DC 1  when in the standby power supply mode, and providing voltage step-down on the supply DC power DC 2  when in the normal power supply mode. The voltage regulator circuit  29  is coupled to the DC voltage step-down circuit  28  and the load  3 , providing the standby DC power DC 1  to the load  3  after voltage stabilization and voltage step-down when in the standby power supply mode, and providing the supply DC power DC 2  to the load  3  after voltage stabilization and voltage step-down when in the normal power supply mode. 
     In conjunction with  FIG. 2 , refer now to  FIG. 3 .  FIG. 3  shows a diagram of circuit components in the second preferred embodiment of the present invention. The standby power circuit  10  placed in the two-stage power supply system  2  is an AC voltage step-down circuit, composed of a first capacitor C 1  and a first resistor R 1  connected in parallel; or alternatively, it may be a voltage step-down integrated circuit (IC) or a component thereof with voltage step-down feature. In the standby power circuit  10 , after the AC power AC passing through the first capacitor C 1  and first resistor R 1 , or otherwise passing through the voltage step-down IC or component thereof with voltage step-down feature, it will generate the standby AC power AC 1  with stepped-down voltage. 
     Refer now again to  FIGS. 2 and 3 . The main power circuit  12  placed in the two-stage power supply system  2  can be a capacitor C 4 , a resistor R 3  connected in parallel with the capacitor C 4 , a buffer circuit  120 , and a controller  122 . The buffer circuit  120  has an input end, an output end, and a control end, in which the input end is connected in series with the capacitor C 4  and resistor R 3  that are connected in parallel, the output end is connected in series with the rectifier  16 , and the control end is connected to the output of the controller  122 . The buffer circuit  120  is formed by a diode or other buffering integrated circuit (IC). 
     Refer once again to  FIGS. 2 and 3 . The driver  14  consists of a transistor Q 1  or drive component thereof wherein the transistor or drive component thereof is controlled by the control signal SC 1  in order to form an OFF state or ON state, and generates the termination signal S 1  when in the OFF state, and generates the drive signal S 2  when in the ON state. The termination signal S 1  and drive signal S 2  are used by the controller  122  as the basis of controlling the buffer circuit  120 . 
     Meanwhile, the controller  122  is composed of a photo-coupler U 2  or controlled switch component, which controls the nodes A and B in the buffer circuit  120  so as to form an open circuit state according to the termination signal S 1  when in the standby power supply mode; at this moment, the main AC power AC 2  can not be transferred via the buffer circuit  120 , thus there is no power supplied on the output end AC 3  of the buffer circuit  120 . Additionally, when the controller  122  is in the normal power supply mode, it controls the nodes A and B in the buffer circuit  120  so as to form a short circuit state based on the drive signal  82 ; now the main AC power AC 2  can be transferred through the buffer circuit  120 , and thereby a power supply can be generated on the output end AC 3  of the buffer circuit  120 . 
     Furthermore, the DC voltage step-down circuit  28  is a commonly used DC/DC voltage step-down converter, essentially consisting of capacitors C 2 -C 3  and a resistor R 2  together with a Zener diode ZD (not shown). Meanwhile, the voltage regulator circuit  29  adopts a commonly used voltage regulator integrated circuit U 1 . 
     In summary of the aforementioned descriptions, when the two-stage power supply system according to the present invention is in the standby power supply mode, it provides the standby AC power alone to the rectifier, the DC voltage step-down circuit, and the voltage regulator circuit, allowing to generate a standby DC power to the load for use, thereby offering the minimum power consumption required by the load while the load is in standby. At this moment, the main power source has not started yet, accordingly there is no generation of any power consumption. Therefore, the two-stage power supply system according to the present invention allows general home electronic devices or common electronic products to reduce power consumption during standby, further meeting the requirement of power saving regulations (standby power&lt;1 W). 
     Additionally, when the two-stage power supply system according to the present invention is in the normal power supply mode, which provides the integrated power of the standby AC power and the main DC power to the rectifier, the DC voltage step-down circuit, and the voltage regulator circuit so as to generate a DC power supply to the load for use, thereby meets the power consumption required by the load for normal operations. In this way, the two-stage power supply system according to the present invention can supply the general home electronic devices or common electronic products with required power in a normal fashion, enabling successful initiation and normal operations. 
     The descriptions illustrated supra set forth simply the preferred embodiments of the present invention; however, the characteristics of the present invention are by no means restricted thereto. All changes, alternations, or modifications conveniently considered by those skilled in the art are deemed to be encompassed within the scope of the present invention delineated by the following claims.