Abstract:
The present invention relates to a control circuit of power supply with selectable current-limiting modes. Via a select circuit in the control circuit of the power supply of the present invention, the user himself can select and switch the operating mode of the current-limiting compare circuit to be one to one, one to multiple, multiple to multiple, or multiple to one mode in order to enable the loads to be compared by an individual set or integrated sets of current-limiting compare circuits; thereby, according to the power usage conditions of the various combinations of the loads, the user himself can select and switch the current-limiting mode in just a single power supply of the present invention, and further, the manufacturer is needless to fabricate variant specifications of power supplies.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a control circuit of power supply with selectable current-limiting modes, particularly to a select circuit, which possesses a current-limiting compare circuit to determine whether a power supply is loaded over an energy-limiting level in order to decide whether the power supply outputs the power normally or shunts the power&#39;s output. 
   BACKGROUND OF THE INVENTION 
   Generally speaking, as the DC voltages needed by the motherboard and the peripheral devices (such as the floppy disc drive, hard disc drive, optical disc drive, electric fan, etc.) of the computer are variant, the power supply, which provides the DC power for the computer system, has to output at least two different levels of DC power to satisfy the variant voltage demands of various devices in the computer system. 
   Recently, as the computer&#39;s working speed demanded by the user becomes higher and higher, the electric power needed by CPU and the peripheral devices in the computer system grows responsively; therefore, the power supply of the computer system has to provide more power output. However, owing to the variation of the computer design, the power of the output ports have an energy-limiting level (maximum output power Max VA) in some systems; thus, these output ports need the design of multiple sets of current-limiting compare units  31  to satisfy those users who demand high-grade safety standard. In general, for a power supply, there is an energy hazard standard, such as in SSI or UL, which requires that the highest power output by the power supply should not exceed 240 VA, in order to secure the user&#39;s safety. 
   The computer systems shift rapidly, and the power demand is higher and higher. For the user who just persists in the high-grade safety standard, the only way to satisfy the power demand is to increase more and more current-limiting compare units  31  so as to raise the power output. However, this is not a good method in the long run as the more current-limiting compare units  31 , the harder the design of the power supply, and the cost of the power supply will be further raised as the users who require the high-grade safety standard are still the fewer. Therefore, if the power demand of the computer system keeps on rising, the system manufacturer will choose a lower-grade safety standard to design the system, i.e. to utilize less or even only one current-limiting compare unit  31  in the system, and the case will return to the starting point. The current power supply having the current-limiting compare units  31  in the market will be described below with the drawing and its connecting and operating manner. 
   Refer to  FIG. 1  a block diagram of the conventional power supply with a single current-limiting compare unit  31 . As shown in the drawing, the conventional power supply comprises: a power output circuit  10 , which provides the power, wherein a constant current source  32  and a reference resistance  34  generate a current-limiting reference value Va and a sampling circuit having a level resistance  33  generates a current-limiting compare value Vb; the current-limiting reference value Va and the current-limiting compare value Vb are separately coupled to two input terminals of the compare unit  31  to compare each other in order to determine whether the compare unit  31  should output normal-state signal or false-state signal to the power output circuit  10 . If the current-limiting compare value Vb is equal to or less than the current-limiting reference value Va, the compare unit  31  outputs a high electric signal to enable the power output circuit  10  of the power supply to enter a shut-down state to shut off the power of the computer. Conversely, if the current-limiting compare value Vb is more than the current-limiting reference value Va, the compare unit  31  outputs a low electric signal to the power supply to enable the power supply to operate normally, and thus the user can continue to use the computer. it is to be noted that in this drawing, the compare unit  31  takes the integrated current-limiting compare value Vb of all the power output to multiple loads  40  to undertake the comparison. 
   As shown in  FIG. 2 , another specification of power supply adopts multiple sets of compare units  31 , wherein each individual set of compare unit  31  operates in the same mode as that in  FIG. 1 . This specification of power supply is designed according to the highest-grade design standard for the upmost user safety level, and even only a single set of compare unit  31  overloaded, the power supply enters a shut-down state to shut off the power of the computer in order to protect the user&#39;s safety; however, far those persons skilled in the computer technology, this way will limit the configuration of the devices with the loads  40 . 
   It is to be known from those described above that there are two kinds of compare units  31  of the power supply in the current market; one is the multiple-set compare unit  31  for the general computer user, and the other is the single-set compare unit  31  for the computer technician; thus, the manufacturer of the power supply has to design variant specifications of power supplies to satisfy the need of various users, which not only makes the products lowly compatible and the fabrication harder, but also consumes higher cost. Thus, the problems mentioned above are those the manufacturer desires to solve. 
   SUMMARY OF THE INVENTION 
   The primary objective of the present is to provide a control circuit of power supply with selectable current-limiting modes in order to solve the aforementioned problem. Via a select circuit in the control circuit of the power supply of the present invention, the user himself can select and switch the operating mode of the current-limiting compare circuit to be one to one, one to multiple, multiple to multiple, or multiple to one mode in order to enable the loads to be compared by an individual set or integrated sets of current-limiting compare circuits; thereby, according to the power usage condition of the load combinations, the user can select and switch the current-limiting mode in a single power supply of the present invention; before the product is delivered, according to the power output condition of the load combinations required by the customer, the manufacturer can also select and switch the current-limiting mode in a single power supply of the present invention, and the manufacturer is needless to fabricate variant specifications of power supplies. 
   Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood tat the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
       FIG. 1  is a schematic diagram of the conventional control circuit with a single current-limiting compare unit. 
       FIG. 2  is a schematic diagram of the conventional control circuit with multiple current-limiting compare units. 
       FIG. 3  is a schematic block diagram of the total circuitry of the present invention. 
       FIG. 4  is a schematic detailed block diagram of the circuit of the present invention. 
       FIG. 5  is a schematic detailed block diagram of the circuit of another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The detailed description and technical contents of the present invention will be stated below in conjunction with the attached drawings. 
   Refer to  FIG. 3  and  FIG. 4 . The present invention is a control circuit of power supply with selectable current-limiting modes, wherein the power supply possesses a power output circuit  10  that provides multiple sets of power outputs to drive multiple loads  40 , and the power output circuit  10  can output the power in one to multiple mode or multiple to multiple mode. A current-limiting compare circuit  30  is disposed between the power output circuit  10  and the load  40  to determine whether the power output circuit  10 &#39;s outputting the power to drive the load  40  is normal or false, wherein the power output circuit  10  is coupled to a select circuit  20 , which provides the current-limiting compare circuit  30  with the operating mode of one to one, multiple to multiple, one to multiple, or multiple to one in order to enable the loads  40  to be compared by a single or integrated current-limiting compare circuits  30 . 
   The power output circuit  10  and the current-limiting compare circuit  30  of the present invention have variant designs, which are exemplified by the embodiment described below. 
   The current-limiting compare circuit  30  adopts a voltage-drop way to perform the compare logic operation. A compare unit  31  is installed between each power output and each load  40 , and one of the input terminals of the compare unit  31  is coupled to a constant current source  32  and a reference resistance  34 , which generate a current-limiting reference value Va, and the other input terminal is coupled to a power input and a level resistance  33 , which generate a current-limiting compare value Vb. Comparing the current-limiting reference value Va with the current-limiting compare value Vb determines that the compare unit  31  outputs whether a normal-state signal or a false-state signal to the power output circuit  10 . In the select circuit  20 , a first switch element  21  is disposed in the line of the compare unit  31 &#39;s output terminal that generates the current-limiting reference value Va, and a second switch element  22  is disposed in the line of the compare unit  31 &#39;s input terminal that generates the current-limiting compare value Vb, and the line of the compare unit  31 &#39;s input terminal that generates the current-limiting compare value Vb is coupled to a third switch element  23 , which is integrated to connect at least a line of the compare unit  31 &#39;s input terminal that generates the current-limiting compare value Vb. The first switch element  21 , the second switch element  22 , and the third switch element  23  mentioned above are switch circuits. 
   According to the preferred embodiment of the present invention, the single power output circuit  10  (or the four sets of power output circuits  10 ) provides four sets of power outputs for four loads  40 ; four compare units  31 , four first switch elements  21 , and four third switch elements  23  are separately disposed between the power outputs and the loads  40 , and a second switch element  22  is disposed in the first set of power line, and the third switch elements  23  are integrated to connect the first set of power line where the second switch element  22  is disposed. 
   This preferred embodiment has the following operating modes: 
   Mode one, wherein four current-limiting protection devices operate individually, and wherein 
   SA 1 , SA 2 , SA 3 , SA 4 , and SB 1  are on, and 
   SC 1 , SC 2 , SC 3 , and SC 4  are off, and 
   wherein each of the loads L 1 , L 2 , L 3 , and L 4  is under an individual current-limiting protection separately; for example, 
   when the output power is at 12V and the maximum current of each load  40  is limited to 20 A, and when the energy hazard standard is set to be 240 VA max, and supposing the constant current source  32  is 100 uA and the each of the level resistance  34  RA 1 , RA 2 , RA 3  and RA 4  is 0.002 Ω, then the voltage drop will be 0.04V, i.e. the current-limiting reference value Va will be 11.96 V; when any one of the loads  40  is overloaded owing to abnormal operation, etc. and has a current over 20 A, such as 25 A, the current-limiting compare value Vb will voltage-drop to 11.95V; after the current-limiting reference value Va and the current-limiting compare value Vb each separately from two input terminals of the compare unit  31  are compared by the compare unit  31 , the result is then that the current-limiting reference value Va is larger than the current-limiting compare value Vb, and an interrupt signal (high voltage) will be output to the power supply to enable the power supply to enter into a close state and stop providing the power for the load  40 ; in this mode, corresponding to each load  40 , there are an individual current-limiting compare value Vb and an individual current-limiting reference value Va sent to the compare unit  31  for comparison, and even just only one of the loads  40  having an abnormal condition, the power supply will stop operating in order to avoid the energy hazard so as to provide the best safety security for the user;
 
Mode two, wherein three sets of current-limiting protection devices are integrated to operate cooperatively and the other one operates individually, and wherein
 
SA 1 , SA 4 , SC 1 , SC 2 , and SC 3  are on, and
 
SA 2 , SA 3 , SB 1 , and SC 4  are off, and
 
wherein the loads L 1 , L 2 , and L 3  are under an integrated current-limiting protection, and the load L 4  is under an individual current-limiting protection, and wherein
 
in the case of L 1 , L 2 , and L 3 , the calculation of the integrated current-limiting compare value Vb is based on the level resistances  33  RB 1 , RB 2 , and RB 3 ; similar to those assigned values in Mode one, and supposing L 1 &#39;s current is 25 A, L 2 &#39;s 18 A, and L 3 &#39;s 12 A, the current-limiting compare value Vb=12V−[(25 A+18 A+12 A)*0.002 Ω]/3=11.963V, and the current-limiting reference value Va=12V−(100 uA*400 Ω)=11.96V; in this mode, it is to be known from those described above that as the loads L 1 , L 2 , and L 3  are under the integrated current-limiting protection, only the overload of the individual load L 1  will not enable the power supply to shut down, and only when the integrated output power of the loads L 1 , L 2 , and L 3  are overloaded or the individual current-limiting protection load L 4  is overloaded, the power supply can be enabled to shut down; this mode can also select the case that two loads are under the integrated current-limiting protection, and each of the other two loads is separately under the individual current-limiting protection;
 
Mode three, wherein all four sets of current-limiting protection devices are integrated to operate cooperatively, and wherein
 
SA 1 , SC 1 , SC 2 , SC 3 , and SC 4  are on, and
 
SA 2 , SA 3 , SA 4 , and SB 1  are off, and
 
wherein all the loads  40  are under one integrated current-limiting protection;
 
the calculation method of Va and Vb is similar to that in Mode two; just only an individual load&#39;s energy hazard will not necessarily enable the power supply to shut down; and only the overload of the total integrated output power can enable the power supply to shut down;
 
in addition to the aforementioned one to one and multiple to one modes of the current-limiting protections, the current-limiting protection can also be of multiple to multiple or one to multiple mode;
 
Mode four, wherein two of those four sets of current-limiting protection devices are integrated to operate cooperatively and the other two are also integrated to operate cooperatively, and wherein two loads are under the integrated current-limiting protection, and the other two loads are also under the integrated current-limiting protection, and supposing
 
SA 1 , SA 3 , SC 1 , SC 2 , SC 5 , and SC 6  are on, and
 
SA 2 , SA 4 , SB 1 , SB 2 , SC 3 , and SC 4  are off,
 
the loads L 1  and L 2  will be under the integrated current-limiting protection, and the other two loads L 3  and L 4  will also be under the integrated current-limiting protection; in this mode, only when the total integrated energy of the loads L 1  and L 2  is overloaded, the respective compare unit  31  can output the false signal to the power supply, and also only when the total integrated energy of the loads L 3  and L 4  is overloaded, the respective compare unit  31  can output the false signal to the power supply; this mode adopts the multiple to multiple mode of current-limiting protection.
 
   Those mentioned above are only the preferred embodiments of the present invention, and not intended to limit the scope of the present invention. Any modification and variation according to the claims of the present invention is to be included within the scope of the present invention.