Abstract:
Communication methods and apparatus and power supply controllers using the same. The method includes transferring information over a line from a first location to a second location as a voltage signal while simultaneously transferring information over the same line from the second location to the first location as a current signal. Further, digital information may be transmitted over the same line. When applied to a power supply controller system, a master controller may control a plurality of slave controllers by initially setting up the slave controllers by transmitting digital information to the slave controllers, and then maintaining a set point for each controller while monitoring controller characteristics over the same lines.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/496,962 filed Jun. 14, 2011. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of communication methods and power supply controllers. 
     2. Prior Art 
     Most electronic systems today require multiple power supply rails. In notebook computers, there are about 10 different rails. This number is increased to 25 or more in more complex servers and networking equipment. As the number of rails increase, there is more need for sequencing and tracking of the outputs which makes the entire system complex and requires central control on the board. 
     Additionally it has become important to have current monitoring capability for most of the rails. In enterprise equipment, this information helps understand the health of the overall unit, and in battery operated systems such in Notebook computers, this information helps make more efficient use of the system. Nonetheless this is a common desire for everyone across the board. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an exemplary embodiment of a master device in accordance with the present invention. 
         FIG. 2  is a block diagram of an exemplary slave device in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiment of the present invention is used in power supply controllers for systems requiring a plurality of power supply rails. Accordingly such systems will use a single master device and a plurality of slave devices, each slave device being coupled to the master device and being responsive thereto to receive information from the master device and simultaneously provide information to the master device over the same line or lines. 
     Referring first to  FIG. 1 , a block diagram of a typical master device may be seen. The connections at the left side of this Figure are connections which include connections from and to an overall system controller which may communicate with the master controller of  FIG. 1 , in this embodiment particularly through the SMBus interface  20 . In addition, a Dallas 1-WIRE® engine  22  may provide output information as may be received from the slave units. 1-WIRE® is a proprietary interface developed by Dallas Semiconductor that normally uses a single wire for both data and power. Dallas Semiconductor is now owned by Maxim Integrated Products, Inc., assignee of the present invention, which is also the owner of the 1-WIRE® trademark registration. The SMBus logic interface  20  is coupled to a digital control  24  which in turn is coupled to an analog to digital converter  26  and a digital to analog converter DAC  28 , as well as to the controls for 12 input multiplexer  30  and 6 output differential multiplexer  32  and to the Dallas 1-WIRE® engine  22 . In one embodiment, the DAC is a 10 bit DAC. 
     In the embodiment being described, up to six slave units may be connected to the master unit of  FIG. 1 . Thus there are six differential mixed signal interfaces  34 , each having connections to a respective slave device DACPn and DACNn. Thus the first is labeled DACP 1  and DACN 1 , etc. Each differential mixed signal interface includes amplifiers A 1  and A 2  as well as resistor R 1 , and amplifiers A 3  and A 4  as well as resistor R 2 . These devices provide an important function in the present invention, as is best illustrated by cooperative aspects of each slave device. 
     Referring now to  FIG. 2 , a block diagram of an exemplary slave device may be seen. The slave device has inputs DACP and DACN from a master device such as that shown in  FIG. 1  that are coupled to inputs of a slave Dallas engine  36 . Also coupled to the connections DACP and DACN are the inputs to amplifier A 5  and the drains of transistors T 1  and T 2 . The source of transistor T 1  is coupled to ground through resistor R 3 , with the gate of transistors T 1  being controlled by amplifier A 6  coupled as a unity gain amplifier responsive to a current monitor. The source of transistor T 2  is coupled to VCC through resistor R 4 , with the gate of transistor T 2  being controlled by amplifier A 7  coupled as a unity gain amplifier responsive to an output of a temperature monitor. The current monitor may be, by way of example, a sense resistor in series with the power supply or some other appropriate current sense device, such as a fuel gauge. The temperature monitor, on the other hand, may be by way of example a thermistor, though in many systems would be a temperature monitor on the power supply board having a digital output, in which case a simple digital to analog converter would be required to provide the positive input to amplifier A 7 . 
     With respect to the current monitor, amplifier A 6  controls the gate of transistor T 1  so that the voltage across resistor R 3  is equal to the voltage on the positive input of amplifier A 6 , i.e., the voltage output of the current monitor. Consequently, the current through resistor R 3  will be equal to V CM /R 3 , where V CM  is the output voltage of the current monitor. Similarly, the current through transistor T 2  will be equal to VCC minus the output voltage of the temperature monitor divided by R 4 . The current to the current monitor and the current from the temperature monitor are coupled through the respective connections DACPn and DACNn for each respective slave device. 
     Referring back to  FIG. 1 , the Dallas 1-WIRE® engine  22  may provide an output on six lines to communicate with up to six slave devices connected to the master device through the DACP lines, dependent on the position of switch  38  for the respective differential mixed signal interface  34 . In particular, when switches  38  are in the lower position, each of the six outputs of the 1-WIRE® engine  22  is coupled to a respective one of the DACP outputs. Thus the 1-WIRE® engine  22  in the master device of  FIG. 1  may communicate with the Dallas engine  36  in each of the slaves coupled thereto through the single DACP line connected thereto. 
     After the digital communication to the slave devices for the initial setup thereof, the digital control  24  will provide digital outputs to the digital to analog converter  28 , which ultimately sets the set point (regulated output voltages) of the DC-DC converter  40  of each of the slave devices ( FIG. 2 ). The DC-DC converter controller  40 , as well as other components associated with the DC-DC converter such as power transistors T 3  and T 4  coupled between the power supply and the slave circuit ground, the inductor (not shown) that will be coupled between the output LX and an output capacitor (not shown) and the feedback of the power supply output on the output capacitor (not shown) through the differential amplifier Dif Amp, etc., are well known in the switching regulator art and will not be described in further detail herein. In particular, the output of the digital to analog converter  28  is coupled one at a time through the 6 output differential MUX  32  to the positive inputs of amplifiers A 2  and A 4  in their respective differential mixed signal interface  34 . Capacitor C 1  acts as a sample and hold capacitor (one for each differential mixed signal interface), with capacitor C 2  acting as a charge transferring capacitor for the 6 output differential MUX  32 . As may be seen in the upper differential mixed signal interface  34 , amplifier A 2  is effectively coupled as a unity gain amplifier in that the output (node  42 ) to the respective DACP terminal through switch  38  will be equal to the input to the positive terminal of the amplifier. However note that while the input to the Dallas engine  36  in the slave devices ( FIG. 2 ) is a high impedance input, the respective DACP output from resistor R 1  in the respective differential mixed signal interface  34  must source the current through resistor R 3  ( FIG. 2 ) which is proportional to the output of the current monitor for the power supply controlled by the respective slave. Thus the output of amplifier A 2  on node  44  will be higher than the voltage on node  42  by R 1 /R 3  times the output voltage output of the current monitor. The voltage difference between nodes  44  and  42  is sensed by amplifier A 1  and will be passed through the 12 input MUX to analog to digital converter ADC  26 , and from there to the digital control  24  in digital form. In one embodiment, the ADC is an 8 bit ADC. 
     Similarly, the current sourced through resistor R 4  ( FIG. 2 ) by the temperature monitor through amplifier A 7  and transistor T 2  will be provided by the slaves through their DACN connection to the master ( FIG. 1 ). Now the voltage on node  48  will be lower than the voltage on node  46  because of the current through resistor R 2  from the temperature monitor circuit, which voltage differential is sensed by amplifier A 3  and also passed through 12 input MUX  30  to be converted to digital form by the analog to digital converter  26  and also passed to the digital control. Thus at the same time that the set point for each of the power supplies controlled by a respective slave is provided to the respective slave through the respective DACP and DACN lines, these two lines are also providing signals from the respective slave back to the master device in the form of current signals which are ultimately successively digitized and transferred to the digital control as digital signals. These digital signals can be monitored by the digital control and provided through the SMBus logic to the overall system controller (not shown), as an alert to indicate an extraordinary event and/or simply occasionally for monitoring by the overall system controller. Similarly, the digital control  24  can shut down any or all power supplies controlled by slaves coupled to the master, either by driving the set points to zero or alternatively, or in addition, by sending digital commands to the slave devices through the Dallas 1-WIRE® engine  22 . 
     Of course, when switches  38  ( FIG. 1 ) are in the lower position the Dallas 1-WIRE® engine  22  in the master device may talk to the Dallas engine  36  in the slave devices in digital form as a two-way communication, depending on the programming of the system. Thus using merely two lines, a DACP and DACN line for each slave device, the master device and slave devices may talk to each other over these two lines in digital form, and in addition, the master may provide unique set points to each slave device in analog voltage form for controlling the respective power supply and simultaneously therewith receive over the same lines current signals representing the output of a current monitor and a temperature monitor on each power supply board from each slave device. Thus, simultaneous two-way analog signal communication is provided by transferring a voltage signal over the lines in one direction, while at the same time transferring current signals over the same lines in the opposite direction. Thus in the particular embodiment disclosed, a set point for each power supply is transmitted as a voltage signal from the master device to the slave devices, while at the same time the slave devices provide analog current signals back to the master device, representing the output of a current monitor and a temperature monitor for each power supply. 
     In the foregoing embodiment, the DACP and DACN lines between the master device and each slave device provide a double ended signal to establish the set point at each slave device. However in alternate embodiments a single ended signal may be used so that the only connection between the master unit and each slave unit would be a single DAC line, which would still allow communication in digital form, in both directions if desired, between the master and slave units and would also provide analog communication of the unique set points from the master device to each slave device with simultaneous transmission of another analog signal from the slave device to the master device. Also, although the Dallas 1-Wire® communication system is used in the embodiment disclosed, other embodiments may use other communication systems as desired. By way of example, in the embodiment disclosed wherein there are two wires available, one can use a simple SMBus or some other clocked buss. Even with one wire, one is not limited to the Dallas 1-Wire® communication system or protocol (which uses one wire plus a ground connection). In that regard, one difference in the typical application of the present invention and the Dallas 1-Wire® communication system is that in applications of the present invention, the slaves will generally be powered, allowing use of a wide variety of serial communication techniques and protocols. 
     Note that the set point is sent to the slave devices as a form of differential analog signal, though as described above, the set point could be sent over a single line as a single ended analog signal. Similarly, the current signals are sent as single ended analog signals on each of two lines separately, and accordingly each current signal is sent over a single line. As further alternatives, analog signals may be time multiplexed on one to two lines, if desired. Further, either or both the voltage and current signals could be sent in digital form, though if digital signals are used for both signals, preferably both are sent at the same synchronized frequency, or the lower frequency signal is sent at a frequency that is a sub-harmonic of the higher frequency and synchronized therewith so that digital transitions of the lower frequency signal always occur on a transition of the higher frequency signal. Actually in the embodiment shown, digital information is sent over the DACN lines for slave setup purposes when the multiplexer  38  is in the opposite state from that shown. Also either or both signals could be modulated on a carrier for transmission, though this is not preferred because of its complexity and noise. 
     In the Figures, certain differential amplifiers, such as differential amplifiers A 2  and A 4  are illustrated with their feedback, as the feedback is a functional part of one aspect of the invention. In other cases, differential amplifiers such as differential amplifiers A 1  and A 3  are shown without feedback, though feedback or other means would obviously be used to provide the desired, controlled gain of such amplifiers. Finally, in the claims to follow, reference is made to the fact that the master and slave devices are at different locations. Note that the different locations will usually be locations within the same system, or even locations on the same circuit board, and include master and slave devices that may be side by side on a circuit board. 
     Thus the present invention has a number of aspects, which aspects may be practiced alone or in various combinations or sub-combinations, as desired. While a preferred embodiment of the present invention has been disclosed and described herein for purposes of illustration and not for purposes of limitation, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.