Abstract:
This invention relates to an insulator for a multi-power system, which is used to resolve the current leakage which comes from each power supplied to the corresponding devices which are not being correctly operated. The isolating device includes: a first power supply for providing an operating power to the isolating device; a level detector for detecting the voltage level of the operating power; a signal isolation controller for changing the output level of the circuit supplied by the operating power based on the operating power detected; and a second power for supplying a real-time power to circuit for power saving operation based on the changed output level.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an insulator for a multi-power system, which is used to resolve the current leakage that comes from the power supplied to the corresponding devices which are not being operated. 
     2. Description of the Related Art 
     In a personal computer system, a common device is the power management unit. The system can have different power consumption with differently operating modes by using the power management unit. The differently operating modes, referring to FIG. 1, includes an operating power mode (referred to as a VCC mode hereinafter) for a circuit  11 , such as a main circuit, a standby power mode (referred to as a VSB mode hereinafter), and a battery mode (referred to as a VBAT mode hereinafter). A standby power or a battery is applied when the system is not operated. In other words, the system enters into a VSB mode or a VBAT mode based on the selection of a selector  12 . The selected mode is referred to as a real-time voltage (VRTC) mode to power a circuit  13 , such as a power control circuit. At this point, if the power consumption on a standard power or a battery is minimized, we can effectively increase the system power utilization without the influence on a normal operation with the operating power in the system. However, when a PC is connected with its peripheral devices, a voltage leakage occurs from the peripherals to the VCC power supply on the PC board if the power applied to the peripherals is not reduced after the power is supplied to the PC. The voltage leakage is about 0-1.5V. Even though the value of the voltage leakage is small, the value will cause different input signal levels between the power VCC and the power VSB or VBAT. That is, the standby circuit powered by the power VSB or VBAT may receive an unknown voltage state, so as to make a correct response impossible. Therefore, a current leakage happens in this situation. 
     Referring to FIG. 2, a shifter is shown in U.S. Pat. No. 5,223,751. In FIG. 2, Vc and Vr are two power supply levels with about 3V and about 5V respectively, PIN is an input signal and POUT is an output signal. As shown in FIG. 2, when Vc=IN is higher than the NMOS threshold voltage but insufficient to turn the voltage level of the node B from logic high to logic low, such a shifter may have current leakage. When Vc=0V, the node B is floated. At this point, block  26  may have current leakage if the immediately previous input state of block  26  is on logic low. 
     Both examples as mentioned above cause the current leakage so as to waste the power resources of the system. To reduce the power consumption when not operating, a shifter or an isolating device, such as insulator, is needed for a multi-power system to reduce the current leakage, thereby increasing the efficiency of the power utilization. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the invention is to provide an isolating device, which can avoid the current leakage when power is switched to different levels, thereby effectively utilizing power resources. 
     To realize the above and other objects, the invention provides an isolating device. The isolating device includes: a first power supply for providing an operating power to the isolating device; a level detector for detecting the voltage level of the operating power; a signal isolation controller for changing the output level of the circuit supplied by the operating power based on the operating power detected; and a second power for supplying a real-time power to circuit for power saving operation based on the changed output level. 
     Accordingly, when the isolating device of the invention is provided to completely or mostly reduce the current leakage, a system with multi-power can prevent the current leakage when power is switched to different levels, so that the system can not only save the power consumption but also avoid an operating mistake in the system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will become apparent by referring to the following detailed description of a preferred embodiment with reference to the accompanying drawings, wherein: 
     FIG. 1 is a block diagram of a conventional multi-power system; 
     FIG. 2 is a block diagram of a conventional shifter; 
     FIG. 3 is a block diagram of a multi-power system of the invention; 
     FIG. 4 is a block diagram of a level detector of the invention; 
     FIG. 5 is a block diagram of another level detector of the invention; and 
     FIG. 6 is a schematic diagram of a signal isolation controller of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     To realize the above and other objects, the invention provides an isolating device, which is used to resolve the current leakage which comes from the power supplied to the corresponding devices which are not being correctly operated. 
     Refer to FIG. 3, a block diagram of a multi-power system of the invention. In FIG. 3, the multi-power system comprises: a selector  1 , a level detector  2 , a circuit  3  powered by VCC, a signal isolation controller  4 , and a circuit  5  powered by VRTC. 
     As shown in FIG. 3, the selector  1  selects a power source from either a VSB or a VBAT, whichever has the higher voltage value as a VRTC power source. The selected result from the selector  1  is outputted to the level detector  2  and is outputted to the circuit  5  for powering. The level detector  2  detects an operating voltage (VCC) by comparison to the input value from the selector  1  or by comparison its split voltage to a predetermined voltage level. When the VCC value is greater than the input value, e.g. 3V, from the selector  1 , the level detector  2  outputs a logic low, otherwise, it outputs a logic high. The detecting operation is described in detail below in conjunction with FIGS. 4 and 5. The logic high or low is inputted to the signal isolation controller  4  in order to adjust the voltage of an output signal SIG from a circuit  3  powered by the VCC, thereby eliminating the current leakage between the circuit  3  and the circuit  5  as happens with the prior art. This is described in detail below in conjunction with FIG.  6 . The adjusted signal SIGM is inputted to the circuit  5  powered by the VRTC such that the circuit  5  accurately responds to an acknowledgement signal (ACK) to the circuit  3  powered by the VCC and performs the respective operation of the signal ACK. 
     Refer to FIG. 4, a block diagram of a level detector. In FIG. 4, a voltage divider  41 , a NAND gate  42 , and an inverter  43  are shown. As shown in FIG. 4, a power from the selector  1  of FIG. 3 is supplied to both the NAND gate  42  and the inverter  43  as an operating power. When an input voltage VCC from an external source(not shown) is inputted to point A through the voltage divider  41 , the voltage on point A interacts with the result of the VRTC power acting on the NAND gate  42  and the inverter  43 . Hence, the output OUT is changed based on the resulting voltage on point A. That is, if the input voltage VCC is equal to or greater than 3V in the VBAT or VSB mode, the input voltage VCC to point A becomes a value just at the control point of the NAND  42  for the logic state transition. At this point, the output OUT=0V. Alternately, if the input voltage VCC is smaller than 3V, the OUT logic turns from low to high, i.e., OUT=1. Thus, the level detection is accomplished by detecting the logic value of the output OUT. However, this circuit easily causes a current leakage (static current) between the NAND gate  42  and the inverter  43  if the voltage of the VRTC is greater than that of the point A in the VBAT or VSB mode. Accordingly, the invention further provides another level detection circuit as follows. 
     Refer to FIG. 5, another level detection circuit, which can save more power than that of the detection circuit in FIG.  4 . In FIG. 5, the circuit includes: an input terminal for receiving the power VRTC of the selector  1 ; an input terminal for receiving the power VBAT from a battery (not shown); an input terminal from an operating power supply VCC; two PMOSs M 1 , M 4 ; five NMOSs M 2 , M 3 , M 5 -M 7 ; an inverter R; and outputs of a pair of complementary output signals OUT and {overscore (OUT)}. 
     As shown in FIG. 5, transistors M 1 , M 2 , and M 3  are serially connected together in order. The channel of the transistor M 1  is coupled between the input terminal of the power VRTC and the node P. The channel of the transistor M 3  is coupled between transistor M 2  and a grounding voltage GND. Transistors M 1  and M 2  are serially connected at node P to form an inverter, wherein gates of the transistors M 1  and M 2  are connected together to the input terminal of the power VCC. Transistors M 7 , M 4 , M 5 , and M 6  are serially connected together in order. The channel of the transistor M 7  is coupled between the input terminal of the power VRTC and a node B. The gate of the transistor M 7  is connected to the gate of the transistor M 1 . The node B is connected to the gate of the transistor M 3 . Transistor M 6  is coupled between a node C and the grounding voltage GND. The gate of the transistor M 6  is connected to the node P and to one end of an inverter R in the opposite direction of the node P. The other end of the inverter R is connected to the output of a complementary output signal {overscore (OUT)}. Transistors M 4  and M 5  serially connected between the node B and C form an inverter and gates of transistors M 4  and M 5  are connected together to the input terminal of the power VBAT. 
     Refer to FIG. 5 in conjunction with the cell standard. This discloses the power level about 0-1.5V from VCC and about 1.8-2.7V from VBAT, if VCC is less than 5V. At this point, transistors M 2  and M 7  are closed and then transistor M 3  is closed through the node B. Also, transistors M 1  and M 5  are turned on such that transistor M 6  is turned on by the power VRTC through transistor M 1  and the node P. Hence, OUT=VRTC (logic 1) is outputted while {overscore (OUT)}=0V (logic 0) after passing through the inverter P. On the other hand, when the circuit is on the VCC mode (VCC=5V), OUT=0V (logic 0) while {overscore (OUT)}=VRTC (logic 1) after passing through the inverter P. The circuit is cross-coupled as shown in figure to be a control gate so as to avoid the current leakage from the operation under VBAT or VSB mode. Hence, the efficiency of the power utilization is increased. 
     Refer to FIG. 6, the schematic diagram of a signal isolation controller. In FIG. 6, the circuit includes a tri-state buffer  61  and an optional switch  62 . As shown in FIG. 6, a signal SIG from the circuit powered by the VCC is inputted and a function for the signal isolation control is performed by the buffer  61  and the switch  62 . The signal first passes through the buffer  61  to isolate the signal by means of the switch  62  according to the input signal of the detector  2 . In the switch  62 , only one action of a pull-up circuit controlled by the {overscore (OUT)} terminal or a pull-down circuit controlled by the OUT terminal exists at same time. As the signal SIG is isolated, the pull-up circuit acts if the desired output signal from the SIGM terminal is set to logic 1. On the other hand, the pull-down circuit acts if the desired output signal from the SIGM terminal is set to logic 0. This makes no current leakage happen because such a circuit is operated in the region of all operating voltage to be set. Thus, the circuit is optionally adjustable in the input to the signal logic level of the circuit powered by the VRTC. The tri-state buffer  61  can also be replaced by a transmission gate. Additionally, the signal isolation controller also acts as a latch to latch the newest logic value of the input SIG in order to restore the previous state. 
     Although the invention has been described in its preferred embodiment, it is not intended to limit the invention to the precise embodiment disclosed herein. Those who are skilled in this technology can still make various alterations and modifications without departing from the scope and spirit of this invention. Therefore, the scope of the invention shall be defined and protected by the following claims and their equivalents.