Patent Publication Number: US-2019199922-A1

Title: Camera module power supply

Description:
TECHNICAL FIELD 
     The present invention relates to a camera module and, more specifically, relates to a camera module that recycles heat generated by the camera module into an alternate power source for the camera module. 
     BACKGROUND 
     Vehicle camera and sensor systems are used in a variety of applications to assist operation of the vehicle. The systems can include one or more printed circuit boards (PCB), software, sensors, wireless transmitters, and other electronic components to capture images of the vehicle surroundings to be subsequently processed and analyzed. The systems are powered by the vehicle and generate heat when in use. 
     SUMMARY 
     In accordance with an aspect of the present invention, a camera module for a vehicle includes a camera unit and a thermo-electric converter for converting heat generated by the camera unit into electricity. An electric converter electrically connected to the thermo-electric converter selectively routes electricity generated by the thermo-electric converter to the camera unit. 
     In another aspect of the invention, a method of powering a camera module for a vehicle includes capturing heat generated by the camera module. The heat is converted into electricity. The electricity is used to power the camera module. 
     Other objects and advantages and a fuller understanding of the invention will be had from the following detailed description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a camera module in accordance with a first embodiment of the present invention. 
         FIG. 2  is a front view of a thermal energy storage device in the camera module of  FIG. 1 . 
         FIG. 3A  is a top view of a thermoelectric converter in the camera module of  FIG. 1 . 
         FIG. 3B  is a section view taken along line  3 B- 3 B of  FIG. 3A-3A . 
         FIG. 4  is a schematic illustration of the thermoelectric converter of  FIG. 3A . 
         FIG. 5  is a circuit diagram of a portion of the camera module of  FIG. 1 . 
         FIG. 6  is a schematic illustration of a camera module in accordance with a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates to a camera module and, more specifically, relates to a camera module that recycles heat generated by the camera module into an alternate power source for the camera module. A camera module  10  in accordance with the present invention is shown in  FIG. 1 . In one example, the camera module  10  is part of a vehicle electronics system, such as an advanced driver-assistance (ADAS) system. The camera module  10  includes a vehicle camera unit  32 , such as a front camera unit, a rear camera unit and/or side camera unit. The camera unit  32  includes an image processing unit  34  for acquiring and processing image data from the camera unit to help the driver operate a vehicle. The camera unit  32  can include one or more printed circuit boards (PCB), image processing chips, RF transceivers, sensors, analog circuitry, controller(s), and other electronic components interconnecting the same (not shown). 
     A primary power source  40  supplies electrical signals  41  to the camera unit  32 . The primary power source  40  can be the vehicle battery. When the camera unit  32  operates, its components, e.g., the image processing unit  34 , generate heat, indicated generally by the arrows  42 , that radiates outward from the module. The camera module  10  includes a series of components for converting or recycling the heat  42  into an alternate or backup power source for the camera module. In other words, the heat  42  can be repurposed into electricity for operating the camera unit  32 . 
     The camera module  10  includes a thermal energy storage device or module  60  positioned within the path of the radiated heat  42  for capturing and dissipating the generated heat. The thermal energy storage module  60  can constitute a sensible heat storage module (when the generated heat  42  is expected to be variable) or a latent heat storage module (when the generated heat is expected to be constant or substantially constant). Whether the thermal energy storage module  60  is of the sensible heat or latent heat construction depends on the operating nature of the camera unit  32 , e.g., constant or variable. The thermal energy storage module  60  can be, for example, a heat sink, metal cover or thermal pad capable of capturing and dissipating heat generated by the camera unit  32 . 
     As shown in  FIG. 2 , the thermal energy storage module  60  is a heat sink. The heat sink  60  extends from a first end  62  to a second end  64 . The heat sink  60  includes a base  61  at the first end  62 . A plurality of projections or fins  66  extends away from the base  61  to the second end  64 . The projections  66  are arranged in an array about the base  62  and extend parallel to one another. The projections  66  are spaced apart from one another by gaps or passages  68  filled with air. The projections  66  can be the same or different from one another in length, cross-section, etc. The heat sink  60  is formed from a material having high thermal conductivity, e.g., a metal such as aluminum. 
     The base  62  of the heat sink  60  is positioned adjacent the camera unit  32  in the direct path of the heat  42 . Heat  42  emanating from the camera unit  32  strikes the base  61  and is conducted therethrough to the projections  66 . The heat  42  then radiates from the projections  66  into the passages  68 , ultimately being directed away from the second end  64  of the heat sink  60  in the manner indicated by the arrows  50 . 
     A thermo-electric converter or generator  80  ( FIG. 1 ) is positioned adjacent the second end  64  of the heat sink  60  and in the direct path of the heat  50 . The thermo-electric converter  80 , also known as a Seebeck generator, is a solid state device that converts heat flux directly into electricity via the Seebeck effect. The thermo-electric generator  80  is a solid state module designed to provide DC power over a high number of thermal cycles. The thermo-electric generator  80  has a continuous hot side operation capability that can exceed 200° C. Example thermo-electric generators for use in the present invention are sold by II-VI Marlow of Dallas, Tex., e.g. thermoelectric generator module TG12-2.5-01LS. 
     In one example shown in  FIGS. 3A-3B , the thermoelectric generator  80  is composed of materials of different Seebeck coefficients configured as a thermoelectric circuit. The Seebeck coefficient of a material or device is its ability to generate a voltage per unit of temperature (stated in V/° C.). The thermal-electric generator  80  extends from a first side or end  82  to a second side or end  84 . The thermal-electric generator  80  includes a dielectric substrate formed from a pair of spaced-apart plates  86 ,  87  defining an interior space  88 . The plates  86 ,  87  can be made from, for example, ceramic, and define a pair of opposing, outer surfaces  90 ,  92  facing away from one another. 
     A series of semiconductor elements  100 ,  102  are secured to the substrate  86  within the interior space  88 . The semiconductor elements  100  are P-type semiconductor pellets. The semiconductor elements  102  are N-type semiconductor pellets. The semiconductor elements  100 ,  102  are electrically connected to one another in series by conductor strips  104 . A negative terminal wire  96  is secured via solder, adhesive, etc. at  110  to a conductor tab  108  electrically connected to one of the N-type semiconductor elements  102 . A positive terminal wire  98  is secured via solder, adhesive, etc. at  110  to a conductor tab  108  electrically connected to one of the P-type semiconductor elements  100 . The semiconductor elements  100 ,  102  are thermally connected in parallel with one another. The semiconductor pellets  100 ,  102  can be, for example, bismuth telluride or antimony telluride. The substrate  86  can be formed from, for example, aluminum oxide. 
     The thermo-electric converter  80  forms a circuit (shown in  FIG. 4 ) that generates electricity directly from heat. As noted, the two dissimilar thermoelectric materials, namely, the N-type semiconductor elements  100  and the P-type semiconductor elements  102 , are electrically joined at their ends to the negative terminal wire  96  and the positive terminal wire  98 , respectively. A dielectric current will flow in the circuit when there is a temperature difference between the two semiconductor elements  100 ,  102  that exceeds a predetermined threshold, e.g., from about 1° C.-5° C. The current magnitude is generally proportional to the temperature difference between the semiconductor elements  100 ,  102  and, thus, the greater the temperature difference, the higher the output current produced. 
     With this in mind, the surface  90  of the substrate  86  is aligned with and in close proximity to the second end  64  of the heat sink  60 . Consequently, the heat  50  exiting the heat sink  60  strikes the surface  90  of the substrate  86 . The heat  50  conducts through the substrate  86 , thereby creating a thermal gradient between the surfaces  90 ,  92 . As a result, a dielectric current is generated and is output from the thermo-electric converter  80  as a signal represented generally by the arrows  52  in  FIG. 4 . 
     The thermal-electric converter  80  is electrically connected to an electric converter  114 . In one example, the electric converter  114  is a DC-to-DC converter for converting the incoming signal  52  from one voltage to another. Referring to  FIG. 5 , the electric converter  114  can include an integrated circuit (IC)  116  and a transformer T to perform step-up conversion of the incoming signal  52  on the order of, for example, 1:100. The IC  116  contains components (not shown) for setting the input-to-output ratios of the electric converter  114 . 
     A capacitor C 1  can be provided between the thermo-electric converter  80  and the electric converter  114  for filtering the incoming signal  52 . A capacitive-resistive network C 2 -R-C 3  receives an input from the transformer T and provides a desired output signal to the IC  116 . A secondary winding SW of the transformer T feeds a charge pump and rectifier circuit (not shown) used to power the IC  116  via a V AUX  pin. 
     The electric converter  114  includes a series of outputs electrically connected to the camera unit  32  for sending electrical signals  54 ,  55  thereto. A V LDO  pin is designed to be in regulation first for powering a low power microprocessor on board the camera unit  32  as soon as possible. For instance, the V LDO  pin can be used to provide a signal  54  to the camera unit  32  during start-up thereof, which can last about 10 ms. 
     A main output capacitor C 4  of the converter  114  is charged to the voltage programmed by VS 1  and VS 2  pins, e.g., 2.35 V, 3.3 V, 4.1 V or 5.0 V, for powering sensors, analog circuitry, RF transceivers, etc. on the camera unit  32  via the signal  54 . A V OUT  reservoir capacitor supplies burst energy required during the low duty cycle pulse when any sensors in the module  30  are active and transmitting. A switched output V OUT2   _   EN  pin is controlled by the camera unit  32  and outputs a signal  55  for powering circuits on the camera unit that do not have a shutdown or lower power sleep mode. A power good output PGD pin alerts the module  30  that the main output voltage of the converter  114  is close to its regulated value. 
     A V STORE  pin is electrically connected to a storage cell  130  for selectively storing the electric output of the thermo-electric generator  80 . More specifically, the V STORE  pin sends a signal  56  to the storage cell  130  in lieu of or in addition to sending the signals  54  and/or  55  to the module  30 . The storage cell  130  can be, for example, a rechargeable battery or capacitor. The V STORE  pin is electrically connected to the V LDO , V OUT , and V OUT2   _   EN  pins within the electric converter  114  to electrically connect the storage cell  130  to the camera unit  32 . 
     Based on this construction, the electric converter  114  receives a time variable, DC signal  52  from the thermo-electric converter  80  and supplies a time invariable DC signal to the storage cell  130  [as a signal  56 ] and/or to the module  30  [as signal  54  and/or signal  55 ]. A controller  120  determines whether the incoming signal  52  is directed to the camera unit  32  or the storage cell  130 . The controller  120  can be integrated into the electric converter  114  or be a stand-alone unit (not shown) electrically connected to the converter. In any case, the controller  120  monitors the power level demand of the primary power source  40  and the amount of power stored in both the primary power source and the storage cell  130 . The controller  120  performs calculations/algorithms, etc. and, when appropriate or desirable, determines which power source  40  or  130  powers the camera unit  32 . Consequently, the storage cell  130  can be a backup or alternate power source for the camera unit  32 . 
     Referring to  FIG. 1 , during normal operation of the vehicle, the controller  120  generally relies on the primary power source  40  to power the camera unit  32 . When the primary power source  40  is used, the controller  120  ensures that any electricity generated by the heat  40  is routed to the storage cell  130 . More specifically, the heat  40  is converted by the thermo-electric converter  80  into an electrical signal  52 , which is converted by the electric converter  114  into the signal  56  and routed through the V STORE  pin to the storage cell  130 . This provides a stored surplus of electricity for selectively powering the camera unit  32 . 
     The circumstances surrounding operation of the camera unit  32  can change over time. For example, a faulty electrical connection can exist between the camera unit  32  and the primary power source  40 . There could also be insufficient power stored in or accessible from the primary power source  40 , e.g., the vehicle is not running. 
     The particulars and timing of the camera unit  32  operation can also change over time. In certain instances the camera unit  32  may not require constant power for operation and/or may only be active for a short duration. In response to these considerations, the controller  120  can prevent the transmission of the signal  41  between the primary power source  40  and the camera unit  32  and initiate the transmission of the signal  54  and/or the signal  55  from the electric converter  114  to the camera unit. 
     When it is desirable to rely on the stored electricity in the storage cell  130  to generate the signals  54 ,  55 , the controller  120  routs power from the storage cell  130 , through the V STORE  pin, through the IC  116 , and to the module  30  through one or both of the V LDO  pin and V OUT2   _   EN  pin. The controller  120  may determine, for example, that it is desirable to rely on the storage cell  130  to power the camera unit  32  during the wakeup phase of the camera module  10 , which can be about 10 ms in duration and utilizes a small amount of power. 
     Stored electricity within the storage cell  130  can be used to maintain regular operation of the IC  116  and the camera unit  32 , even when the heat generated by the camera unit is intermittent and/or insufficient to generate the signal  52 . In other words, the storage cell  130  can maintain power to the IC  116  and the camera unit  32  even when the camera unit does not run continuously and/or does not generate heat sufficient for the electric converter  80  to produce the signal  52 . Some camera unit  32  applications operate continuously instead of having a pulsed load. When the power demand of the continuous application is below a predetermined threshold, the storage cell  130  can continuously power the camera unit  32  with the recycled thermal energy. 
     The controller  120  can alternatively bypass the storage cell  130  by directly generating the signals  54 ,  55  from the incoming signal  52 . Since the camera unit  32  may not be continuously in use, they will not continuously generate heat  42  to be converted into the signal  52 . Consequently, the controller  120  can periodically rely on the storage cell  130  to supplement the incoming signal  52  to ensure an adequate power supply to the camera unit  32 . 
     The controller  120  can advantageously switch between using the primary power source  40  and the recycled thermal energy throughout use of the camera unit  32  and operation of the vehicle. For example, as shown in  FIG. 5 , the camera unit  32  is powered by the V LDO  pin. When the controller  120  determines the camera unit  32  requires a low power demand, e.g., during startup, the controller briefly electrically connects the storage cell  130  to the V LDO  pin to supply the camera unit with power. Once the operation is performed, the controller  120  routes power from the primary power source  40  to the camera unit  32 . 
       FIG. 6  illustrates another example camera module  200 . In  FIG. 6 , elements that are the same as the corresponding element in  FIG. 1  are given the same reference numeral. In the camera module  200 , the thermal energy storage device  60  is omitted and, thus, heat  40  radiated from the module  30  flows directly into the thermo-electric converter  80  to be converted into the electrical signal  52 . The signal  52 , in turn, is converted by the electric converter  114  and routed to the storage cell  130  and/or to the camera unit  32 . Absent the omission of the thermal energy storage module  60 , the operation of the camera module  200  is the same as operation of the camera module  10  previously described. 
     The present invention is advantageous because heat generated by operating the camera unit, e.g., by the image processing unit, that is otherwise lost to the environment is instead recycled as an additional power source for the camera module. This additional power source can be used in lieu of or in addition to the primary power source, typically the vehicle battery. The controller in the present invention monitors operation of the camera module and determines when it is desirable to rely on the recycled thermal energy to power the camera module. 
     What have been described above are examples of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims.