Patent Abstract:
A mechanical and thermal assembly adapted to absorb heat from a delicate, heat-producing structure having a planar surface includes a slide plate in thermal contact to said planar surface, and being held in place by a resilient system that permits, but gently resists, movement perpendicular to said planar surface and a thermal mass, suspended over said slide plate, but in thermal contact to said slide plate, so that said delicate, heat-producing structure is not damaged due to force applied from said thermal mass through said slide plate to said structure.

Full Description:
RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 12/319,259, filed Jan. 5, 2009, now U.S. Pat. No. 7,773,375 which in turn claims priority from provisional applications 61/019,207 and 61/019,209, both filed Jan. 4, 2008 and both hereby incorporated by reference as if fully set forth herein. 
    
    
     TECHNICAL FIELD 
     The present disclosure is related to a ruggedized electrical device, able to operate reliably from a power bus that suffers intermittent voltage reductions and aspects thereof. More specifically, the electrical device may be a computer. 
     BACKGROUND 
     In vehicles and devices there is an increasing need for a rugged computer assembly that is isolated from the elements and that can function with high reliability even though powered by a bus that is intermittently unable to meet the full power demand placed upon it. 
     SUMMARY 
     The embodiments described below generally address the need for a ruggedized computer that can be deployed in a physical environment where it receives physical impacts and where it may have gases, liquids and solid/liquid mixtures (eg. mud) contacting its outside surfaces. Also, available electrical power may be subject to intermittent failure. Many issues arise in the design of this type of device, and many of the solutions to these issues may find application in other fields. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is schematic diagram of a mobile power system employing a power supply unit configured in accordance with an embodiment of the disclosure. 
         FIG. 2  is a schematic diagram illustrating the power supply unit of  FIG. 1  in more detail. 
         FIG. 3  is a flow diagram showing operation of the power supply unit in accordance with an embodiment of the disclosure. 
         FIG. 4  is a schematic diagram of the power supply assembly in accordance with an embodiment of the disclosure. 
         FIG. 5  is a side cross-sectional view of an integrated circuit and a thermal assembly designed to absorb heat therefrom. 
         FIG. 6  is a cross-section plan view of a liquid-tight computer case and fan, according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Several aspects of the present disclosure are directed to aspects of a rugged computer assembly that can function with high reliability even when supplied by a bus that intermittently fails to meet power demand. Skilled persons will understand that additional embodiments may be practiced without several of the details described below, and that other embodiments may include aspects in addition to those described below. 
       FIG. 1  is a schematic diagram of a mobile power system  100  including a DC power source  102 , one or more electronic devices  104 , and a power supply unit  106  that can operably couple the power source  102  with the electronic devices  104  via input and output power busses  108  and  110 . In several embodiments, the power supply unit  106  can also exchange serial data with the electronic devices  104  via a serial link  112  (described further with reference to  FIG. 4 ). In general, the power source  102  provides raw DC power, and can include a variety of elements, such as a battery, an alternator, and/or any one of various types of AC-to-DC converters. In many embodiments, the electronic devices  104  include any of a myriad of consumer electronic devices that are configured to receive DC power (e.g., a personal computer, a mobile phone, a GPS unit, etc.). 
     In other embodiments, the electronic devices  104  can be incorporated and/or integrated with the power supply unit  106 . Such a combination can be deployed as a single unit, for example, as a computing device that can be energized by the (raw) DC power source on input bus  108  without any intervening components. In addition, embodiments of this type of device can be deployed in a single rugged and protective housing, as described further below with reference to  FIGS. 5 and 6 . 
       FIG. 2  is a schematic diagram illustrating the power supply unit  106  in more detail. In the example shown in  FIG. 2 , the power supply unit  106  includes a preregulator  210  coupled to the input bus  108 . For example, in an automobile electronic system, the voltage at the input bus  108  can be in a range of about −50 to +60V, and the preregulator  210  can step down this voltage to a range of about +8 to +22V. In several embodiments the preregulator  210  includes an automotive grade switching regulator to achieve this task. A preregulator output diode  216 , couples the output of preregulator  210  to a first internal bus  214 . In turn, a main switch  212  couples (and de-couples) bus  214  to output bus  110 . The power supply unit  106  also includes a battery  220  (e.g., a sealed lead acid, NiMH, LiPo battery, or UPS battery system of sufficient current capability for the application), the positive terminal of which being connected to an output diode  226  terminal. The other terminal of diode  226  is connected to a second internal power bus  224 . A boost converter  228  is electrically interposed between the first and second buses  214  and  224 . For example, the boost converter  228  can output a regulated voltage in a range of about 13-14V, which can trickle charge a 12 V battery  220 , or a range of 25 to 27V for charging a 24 V battery. A battery switch  222  is couples first bus  214  to second bus  224 . In a representative embodiment, the power supply unit  106  includes a logic/control assembly  230  that controls the main switch  212 , the battery switch  222 , and the boost converter  226 . In addition, the logic/control assembly  230  can also exchange serial communications  232  with the electronic devices  104 . For example, the serial communications  232  can indicate events such as whether the battery  220  is recharging or whether the battery  220  is supplying power to the electric devices  104 . Communications  232  can also provide a way to change other programmable power supply  106  features during operation such as program timing changes and trigger points and can even replace the entire program for the logic control assembly  230  with a newer version (described further with reference to  FIG. 4 ). 
     The logic control/control assembly  230  generally operates the power supply unit  106  in one of at least two states of operation. In a first state of operation and/or when the preregulator output voltage V 1  is at or above a predetermined trigger point, the boost converter  226  charges battery  220  with a boosted voltage V 2  and maintains battery switch  222  in an open state so that first internal bus  214  is powered by preregulator  210 , rather than battery  220 . In a second state of operation commanded when the preregulator output voltage V 1  is below the trigger point, the logic/control assembly  230  de-activates the boost converter  228  and couples the second bus  224  with the first bus  214  via the battery switch  222 , thereby powering devices  104  from the battery  220 . 
       FIG. 3  is a flow diagram showing an embodiment of a method of operating the power supply unit  106 . The flow chart begins with unit  106  in the first operational state, its most typical condition, receiving above-trigger point voltage on bus  108  and with boost converter  228  activated and switch  222  closed. In the next instant, the logic control assembly  230  detects whether the preregulator output voltage V 1  is still above the trigger point (block  342 ), indicating an adequate voltage V 1 . If it is, nothing is changed (block  344 ). If the first bus voltage V 1  is less than the predetermined trigger point, the second operational state is commanded. Boost converter  228  is disabled and the battery switch  222  is closed (block  348 ). In this second state, the battery  220  drives the first bus  214 , thereby powering devices  104 . From this state, V 1  is tested against the trigger point (block  350 ). The diode  216  permits a higher voltage to exist on bus  214  than at the output of preregulator  210 . This is essential for sensing the restoration of preregulator output voltage after a voltage low condition. (decision box  350 ). When V 1  again rises above the trigger point, it is determined if time conditions have been met (decision box  360 ) to switch back to the first state (block  370 ), in which converter  228  is activated and  222  is closed. 
     The time conditions of decision box  360  are designed to prevent a rapid toggling between states. If, for example, V 1  has been lowered due to a current demand from another device, the removal of the load of power supply  106  may be enough to cause the V 1  to recover in, for example, a millisecond. If there were no timing conditions, this would cause converter  228  to be immediately reactivated, causing V 1  to go low again in, for example, a millisecond. In this manner unit  106  could oscillate between states at a 0.5 mHz rate, which would be harmful to system operation. In one preferred embodiment a one second timeout is implemented from the time converter  228  is deactivated, to the time when it may be reactivated. Typically battery  220  stores enough charge so that the timeout period could be made quite a bit longer than one second, without threatening to drain battery  220 . In a preferred embodiment, timing conditions are set to match the characteristics of the overall system. In many embodiments the timeout function is performed by a hysteresis circuit associated to the boost converter  226 . In other preferred embodiments, the timeout function is performed by the logic/control assembly  230 . 
       FIG. 4  is a schematic diagram of components of the power supply unit  106 , including the first and second busses  214  and  224 , the boost converter  228 , the switches  212  and  222 , and individual logic/control components  230 . More specifically, the logic control components  230  include a microcontroller  360  and voltage detect components  362  and  364  hardware wired to the enables of the boost converter  228  and the battery switch  222 , respectively (in many embodiments, the boost converter  228  and the battery switch  222  can also be coupled to the microcontroller  360 ). In general, the microcontroller  360  includes a processor, associated program instructions, and system control and serial communication components. The voltage detect component  362  can measure whether the first bus voltage V 1  is at or above the trigger point voltage, and the microcontroller  360  can enable the battery switch  222  and the boost converter  228  based on the detected first bus voltage V 1 . The voltage detect component  364 , on the other hand, can measure the voltage level of the second bus  224  and/or the battery  220 . For example, the microcontroller  360  can use the voltage detect component  364  to determine whether the battery  220  is operational and/or to determine charge level at the battery —   
     In many embodiments, the microcontroller  360  can also enable the main switch  212  depending on the state of the first and/or second busses  214  and  224 . If the electronic device  104  is a PC motherboard, for example, the microcontroller  360  can be configured to disable the standby or sleep voltage demand of the power supplied to the motherboard by disabling the main switch  212  only after the motherboard has communicated to the microcontroller  360  that it is completely shut down. In such an example, the motherboard may have one of two interactive logic level bits attached to the front panel header. One bit is an LED output for “CPU-on” and the other is a front panel switch input bit. 
     The microcontroller  360  can be configured to sense the voltage at the first bus  214 , interpret this as a “computer-on” command and activate the motherboard. To do this, the microcontroller  360  can pulse an off/on switch bit on the motherboard and also verify at the “CPU-on” output that the motherboard has booted. For example, whenever the input bus  108  (or first bus  214 ) is powered, the microcontroller  360  can be configured to verify that the motherboard is running or needs to be booted. When the input bus  108  (or first bus  214 ) has been down for a predetermined amount of time, the microcontroller  360  can interpret this is a command to “turn off” the motherboard and do so by pulsing the on/off front panel bit on the motherboard and request a shutdown from a (power aware) operating system. Battery  220  provides power during an orderly motherboard “turn off” sequence. One aspect of such a configuration of the microcontroller  360  is that many or all of processes carried out by the power supply unit  106  use no (or limited) software drivers, and system control can accordingly be carried out exclusively in hardware, based on the state of power at the input bus  108  and the operating state of the motherboard. This eliminates the need for a third wire, needed to indicate the beginning of a “turn off” sequence, that complicates prior art designs. 
     The above described system addresses numerous deficiencies in previously available power supply systems. For example, conventional power supplies use a boost converter-regulated front-end to maintain a tightly regulated intermediate bus voltage during DC power deviation or “sag” at the main bus. Such a topology demands proportionally increased current from the main bus in order to offset voltage sag. This creates a conflict condition when another device on the main bus is demanding high current, resulting in neither device being able to draw enough current to maintain its required internal voltage. Also, although the typical boost converter includes storage capacitors to provide power during power interrupts, these capacitors are quickly drained, again resulting in an insufficient intermediate bus voltage. Additionally, although existing uninterruptible power supply (UPS) systems include a battery, the battery is typically in-line-float-charged from the boost converter. Such an arrangement causes the battery to always be in-circuit and prevents the battery from being charged at the optimum charge voltage level. This compromises the life of a conventional battery system and the ability to meet current demand. Furthermore, conventional (controllable) DC based power supplies use fixed timers to control the shutdown and/or reboot sequences and times and are not interactive with external devices or components of an external device (e.g., a motherboard). In general, these supplies require a ‘three wire’ connection with a user switch for shutdown activation, and they have no user communication ports for real-time parameter changes or to control sequences of operation. 
     Embodiments of the power supply unit  106 , however, mitigate these and other issues associated with conventional power supplies and converters. For example, the boost converter  228  is disabled when the main bus voltage drops below a programmable trigger point, reducing current demand from the pre-regulator  210  and thereby avoiding competition with other devices for main bus current. During these periods switch  222  is closed, permitting battery  220  to maintain proper voltage on intermediate bus  214  for far longer than do the converter storage capacitors in existing systems. Battery  220  is either supplying power or being charged at an ideal charging voltage. This preserves battery life and maximized the probability that when the battery is called upon to supply power it will be able to do so adequately. 
     Referring to  FIGS. 5 and 6 , the electrical network described above finds application in a rugged computer system. In a preferred embodiment, this system includes a processor integrated circuit (IC)  606  and two hard disk drives sealed within a metal case  608  ( FIG. 6 ). One challenge in providing a system of this type is cooling and providing thermal stability for the electrical components without a capability of blowing air in from the outside. To meet the need of cooling the processor IC  606 , a thermal assembly  610  is provided. This system includes the IC  606 , which is electrically and physically connected to a printed circuit board (PCB) substrate  614  by a set of solder balls (not shown). A slide plate  616  is positioned above and placed in thermal contact with the IC  606 . In turn, a thermal mass  618  is positioned above and placed in thermal contact with the slide plate  616 . Finally, the thermal mass  618  is in thermal contact with the case  608 . Thermal grease  619  is interposed between and permits thermal flow between the four components  606 ,  616 ,  618  and  608 . Accordingly, the heat produced by IC  606  flows to slide plate  616 , from whence it flows to thermal mass  618 , and then to case  608 . Thermal mass  618  also acts as a heat reservoir, changing only slowly and preventing an overly rapid change in the temperature of IC  606 . The whole assembly  610  must maintain a tension to resist shock and vibration so elastomeric bumpers  612  are used to help constrain the PCB substrate  614  and to dampen vibration. 
     A great challenge in the design of thermal assembly is avoiding physical damage to the system, in particular to the solder balls connecting IC  606  to PCB substrate  614 . If permitted, in the environment of physical shocks in which the rugged computer is designed to be deployed, the physical mass of thermal mass  618  could easily impact slide plate  616  into IC  606 , thereby crushing the solder balls or cracking IC  606 . Also the heating and cooling of the product over its lifetime will expand and contract the internal parts at different rates creating shear conditions on the connections to the IC  606 . To prevent damage to the solder balls, slide plate  616  is mounted from pins  620  mounted in PCB substrate  614  and is suspended from pins  620  by tension springs  622 . Accordingly, slide plate  616  can ride up and down with IC  606  and shift in coplanar dimension relative to the contact surfaces of IC  606 , thereby avoiding stress to the solder balls and to IC  606 . 
     Thermal mass  618  is fastened to the case  608  by stud  630 . This connection suspends mass  618  over slide plate  616 , to control the pressure of mass  618  on slide plate  616 . As noted, thermal contact is maintained between mass  618  and slide plate  616  by thermal grease  619 , which permits relative movement between the two components. 
     Referring specifically to  FIG. 6 , the above described assembly is housed in case  608  (bottom half shown), which has an internal fan  640  to blow air through a series of plenums, thereby distributing heat throughout the system, and stabilizing any heat contributions not already mechanically connected to the thermal structure. In a preferred embodiment, IC  606  produces 35 Watts of heat at full operation and assembly  610  (including case  608 ) takes 7 hours for its temperature to be elevated from a starting temperature of 15° C. to 50° C. The temperature of assembly  610  thereafter remains at a stable 50° C. in ambient air temperatures of up to 30° C. Moreover, a preferred embodiment includes a chip set that supports IC  606  and that also requires a thermal stack, similar to assembly  610  to remove heat and lessen thermal cycling while avoiding physical damage. In this embodiment slide plate  616  and thermal mass  618  are made of 2024 aluminum alloy, case  608  is of cast aluminum. Slide plate  616  has a mass of 40.8 grams for the CPU assembly  610  and 49.9 grams for the parallel assembly for the chip set. Also, thermal mass  618  has a mass of 99.8 grams for the CPU assembly  610  and 136.1 grams for the parallel assembly for the chip set. Finally, case  608  has a mass of 2536 grams and a surface area of 1332.4 cm 2 . 
     From the foregoing, it will be appreciated that representative embodiments have been described herein for purposes of illustration, but that various modifications may be made to these embodiments, including adding and/or eliminating particular features. For example, in some embodiments the main switch  212  can be omitted. Also, in other embodiments, the logic/control components  230  may include other components and/or configurations. For example, one or more of the voltage detect circuits  362  and  364  can be functionally programmed into the microcontroller  360  (see also Appendix C). In addition, while representative examples of the system were described above in the context of DC power, other embodiments may include other types of power, such as DC-pulsed power or AC power. Further, while advantages associated with certain embodiments have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the invention. The following examples and appendices provide further representative embodiments.

Technology Classification (CPC): 7