Method and system for determining ambient temperature of an electronic device

Abstract

A method for determining the ambient temperature of an electronic device, the device comprising heat-generating components (102) and a temperature sensor (105) positioned within a common casing (101), the method comprising the steps of: in an environment with a controlled ambient temperature: determining (307) a device-specific coefficient of power dissipation change (a) between a first (E.sub.min) and second (E.sub.max) power modes, wherein in the second power mode (E.sub.max) the device dissipates more power than in the first power mode (E.sub.min); and in an environment for which the ambient temperature is to be determined: measuring (203-205) temperatures (T.sub.min, T.sub.max) by the temperature sensor (105) for the first power mode (E.sub.min) and the second power mode (E.sub.max), calculating (206) ambient temperature (T.sub.amb) as a function of the measured temperatures (T.sub.min, T.sub.max) and the device-specific coefficient of power dissipation change (a).

Claims

1. A method for determining the ambient temperature of an electronic device, the device comprising heat-generating components (102) and a temperature sensor (105) positioned within a common casing (101), the method comprising the steps of: installing the device in an environment with a constant ambient temperature: determining (307) a device-specific coefficient of power dissipation change (a) between a first (E.sub.min) and second (E.sub.max) power modes, wherein in the second power mode (E.sub.max) the device dissipates more power than in the first power mode (E.sub.min), subsequently, deploying the device in a work environment: measuring (203-205) temperatures (T.sub.min, T.sub.max) by the temperature sensor (105) for the first power mode (E.sub.min) and the second power mode (E.sub.max), calculating (206) ambient temperature (T.sub.amb) as a function of the measured temperatures (T.sub.min, T.sub.max) and the device-specific coefficient of power dissipation change (a) as: $T\mathrm{amb}=\frac{T\max -a*T\min }{1-a};$  wherein $\frac{T\max -T\mathrm{amb}}{T\min -T\mathrm{amb}}=a.$

2. The method according to claim 1, further comprising the step of comparing the determined ambient temperature (T.sub.amb) with a maximum allowed ambient temperature (T.sub.ambmax) and invoking an alarm (209) in case the determined ambient temperature (T.sub.amb) is higher than the maximum allowed ambient temperature (T.sub.ambmax).

3. The method according to claim 2, further comprising the steps of: in the environment with the constant ambient temperature: determining (308) device-specific product (R*P.sub.min) of thermal resistance (R) between the device and device's ambient and power dissipation (P.sub.min) in the first power mode (E.sub.min), in the work environment: determining (207) a coefficient of thermal resistance device-device's ambient change (b) as a function of the measured temperatures (T.sub.min, T.sub.max) and device-specific product (R*P.sub.min) as: $b=\frac{T\min -T\mathrm{amb}}{R*P\min }.$

4. A computer program comprising program code means for performing all the steps of the method according to claim 2 when said program is run on a computer.

5. A non-transitory computer readable medium storing computer-executable instructions performing all the steps of the method according to claim 2 when executed on a computer.

6. The method according to claim 1, further comprising the steps of: in the environment with the constant ambient temperature: determining (308) device-specific product (R*P.sub.min) of thermal resistance (R) between the device and device's ambient and power dissipation (P.sub.min) in the first power mode (E.sub.min), in the work environment: determining (207) a coefficient of thermal resistance device-device's ambient change (b) as a function of the measured temperatures (T.sub.min, T.sub.max) and device-specific product (R*P.sub.min) as: $b=\frac{T\min -T\mathrm{amb}}{R*P\min }.$

7. The method according to claim 6, further comprising the step of, in case the calculated coefficient of thermal resistance (b) exceeds the value of 1, invoking an alarm (211).

8. A computer program comprising program code means for performing all the steps of the method according to claim 7 when said program is run on a computer.

9. A non-transitory computer readable medium storing computer-executable instructions performing all the steps of the method according to claim 7 when executed on a computer.

10. A computer program comprising program code means for performing all the steps of the method according to claim 6 when said program is run on a computer.

11. A non-transitory computer readable medium storing computer-executable instructions performing all the steps of the method according to claim 6 when executed on a computer.

12. A computer program comprising program code means for performing all the steps of the method according to claim 1 when said program is run on a computer.

13. A computer readable medium storing computer-executable instructions performing all the steps of the method according to claim 1 when executed on a computer.

14. An electronic device comprising heat-generating components (102) and a temperature sensor (105) positioned within a common casing (101), characterized in that the device further comprises: a non-volatile memory (111) configured to store a device-specific coefficient of power dissipation change (a) between a first (E.sub.min) and second (E.sub.max) power modes, wherein in the second power mode (E.sub.max) the device dissipates more power than in the first power mode (E.sub.min), a controller (104) configured to determine the ambient temperature by: measuring (203-205) temperatures (T.sub.min, T.sub.max) by the temperature sensor (105) for the first power mode (E.sub.min) and the second power mode (E.sub.max), calculating (206) the ambient temperature (T.sub.amb) as a function of the measured temperatures (T.sub.min, T.sub.max) and the device-specific coefficient of power dissipation change (a), read from the non-volatile memory (111) as: $T\mathrm{amb}=\frac{T\max -a*T\min }{1-a};$  wherein $\frac{T\max -T\mathrm{amb}}{T\min -T\mathrm{amb}}=a.$

15. The device according to claim 14, characterized in that the controller (104) is further configured to compare the determined ambient temperature (T.sub.amb) with a maximum allowed ambient temperature (T.sub.ambmax) and to invoke an alarm (209) in case the determined ambient temperature (T.sub.amb) is higher than the maximum allowed ambient temperature (T.sub.ambmax).

16. The device according to claim 15, characterized in that: the non-volatile memory (111) is further configured to store device-specific product (R*P.sub.min) of thermal resistance (R) between the device and device's ambient and power dissipation (P.sub.min) in the first power mode (E.sub.min), and the controller (104) is further configured to detect a coefficient of thermal resistance device-device's ambient change by determining (207) a coefficient of thermal resistance device-device's ambient change (b) as a function of the measured temperatures (T.sub.min, T.sub.max) and device-specific product (R*P.sub.min) as: $b=\frac{T\min -T\mathrm{amb}}{R*P\min }.$

17. The device according to claim 14, characterized in that: the non-volatile memory (111) is further configured to store device-specific product (R*P.sub.min) of thermal resistance (R) between the device and device's ambient and power dissipation (P.sub.min) in the first power mode (E.sub.min), and the controller (104) is further configured to detect a coefficient of thermal resistance device-device's ambient change by determining (207) a coefficient of thermal resistance device-device's ambient change (b) as a function of the measured temperatures (T.sub.min, T.sub.max) and device-specific product (R*P.sub.min) as $b=\frac{T\min -T\mathrm{amb}}{R*P\min }.$

18. The device according to claim 17, wherein the controller is further configured to, in case the calculated coefficient of thermal resistance (b) exceeds the value of 1, invoke an alarm (211).

Description

BRIEF DESCRIPTION OF FIGURES

(1) The present invention is shown by means of exemplary embodiments on a drawing, in which:

(2) FIG. 1 presents a schematic of a typical electronic device in which the present invention can be applied;

(3) FIG. 2 presents a method for determining the ambient temperature;

(4) FIG. 3 presents a method for determining device-specific parameters.

DETAILED DESCRIPTION

(5) FIG. 1 presents a schematic of a typical electronic device in which the present invention can be applied. The device has a casing 101, in which heat-generating components 102 are mounted.

(6) The typical heat-generating components 102 include data processors, signal amplifiers or power supplies. A controller 104 is used to determine the temperature by analyzing the properties of the temperature sensor 105 and operating the power generating components according to the procedure shown in FIG. 2. The power generating components may be controlled by a power mode regulator 103, configured to set the device to operate in a specific power mode, such as active (including maximum power dissipation mode), inactive, off or standby.

(7) The controller 104 comprises a non-volatile memory 111 for storing device-specific parameters: a coefficient of power dissipation change (a), a product (R*P.sub.min) of thermal resistance (R) between the device and device's ambient and power dissipation (P.sub.min), as well as the maximum allowed ambient temperature (T.sub.ambmax). The controller 104 further comprises operational registers 112 for storing measurement data: the measured temperatures (T.sub.min, T.sub.max) and calculated coefficients: a coefficient of thermal resistance device-device's ambient change (b) and the determined ambient temperature (T.sub.amb).

(8) The following is a theoretical introduction to the present method.

(9) In an inactive mode, called E.sub.min, the following relation occurs in E.sub.min mode:
T.sub.min=T.sub.ambEmin+R.sub.min*P.sub.min   (1)
where:

(10) T.sub.min—the temperature indicated by temperature sensor 105 in E.sub.min mode,

(11) T.sub.ambEmin—the device's ambient temperature in E.sub.min mode,

(12) R.sub.min—thermal resistance device-device's ambient in E.sub.min mode, P.sub.min—power dissipated in E.sub.min mode.

(13) In a higher power consumption mode, called E.sub.max, wherein the device consumes more power than in the E.sub.min mode, the following relation occurs:
T.sub.max=T.sub.ambEmax+R.sub.max*P.sub.max   (2)
where:

(14) T.sub.max—the temperature indicated by temperature sensor 105 in E.sub.max mode,

(15) T.sub.ambEmax—the device's ambient temperature in E.sub.max mode,

(16) R.sub.max—thermal resistance device-device's ambient in E.sub.max mode,

(17) P.sub.max—power dissipated in E.sub.max mode.

(18) The present invention assumes the ambient temperature is constant in E.sub.min and E.sub.max modes. In a typical set top box on average 30 minutes pass between a time when the device may reach a stable temperature in E.sub.max starting from a stable temperature in E.sub.min. In other devices this time may be longer i.e. several hours.

(19) Assuming that the ambient temperature is constant in E.sub.min, and E.sub.max modes, T.sub.amb=T.sub.ambEmin=T.sub.ambEmax and the thermal resistance device-device's ambient is constant in E.sub.min and E.sub.max modes R.sub.th=R.sub.min=R.sub.max, the equations (1) and (2) occurs in form:

(20) $\begin{array}{cc}\{\begin{array}{c}T\min =T\mathrm{amb}+R\mathrm{th}*P\min \\ T\max =T\mathrm{amb}+R\mathrm{th}*P\max \end{array}& \left(3\right)\end{array}$
while
Rth=R+ΔR   (4)
where:

(21) R.sub.th—thermal resistance device-device's ambient in work environment,

(22) R—thermal resistance device-device's ambient in lab environment i.e. an environment with a controlled ambient temperature, the device is working in environment compliant with this required by manual,

(23) ΔR—the difference between thermal resistance in work and lab environment,

(24) and
Pmax=Pmin+ΔP   (5)
where ΔP—difference between power dissipation in E.sub.max and E.sub.min modes,
the set of equations (3) equals

(25) $\begin{array}{cc}\{\begin{array}{c}T\min =T\mathrm{amb}+\left(R+\Delta R\right)*P\min \\ T\max =T\mathrm{amb}+\left(R+\Delta R\right)*\left(P\min +\Delta P\right)\end{array}& \left(6\right)\end{array}$
Dividing bilaterally (6) by product R*P.sub.min it gives

(26) $\begin{array}{cc}\{\begin{array}{c}\frac{T\min -T\mathrm{amb}}{R*P\min }=\frac{\left(R+\Delta R\right)*P\min }{R*P\min }=\frac{R+\Delta R}{R}\\ \frac{T\max -T\mathrm{amb}}{R*P\min }=\frac{\left(R+\Delta R\right)*\left(P\min +\Delta P\right)}{R*P\min }=\frac{R+\Delta R}{R}*\frac{P\min +\Delta P}{P\min }\end{array}& \left(7\right)\end{array}$
Assuming

(27) $\begin{array}{cc}b=\frac{R+\Delta R}{R}& \left(8\right)\end{array}$
where b—coefficient of thermal resistance device-device's ambient change,
and

(28) $\begin{array}{cc}a=\frac{P\min +\Delta P}{P\min }& \left(9\right)\end{array}$
where a—coefficient of power dissipation change,
the set of equations (7) equals

(29) $\begin{array}{cc}\{\begin{array}{c}\frac{T\min -T\mathrm{amb}}{R*P\min }=b\\ \frac{T\max -T\mathrm{amb}}{R*P\min }=b*a\end{array}& \left(10\right)\end{array}$
Dividing bilaterally (10) it gives

(30) $\begin{array}{cc}\frac{T\max -T\mathrm{amb}}{T\min -T\mathrm{amb}}=a& \left(11\right)\end{array}$
Hence the device's ambient temperature is

(31) $\begin{array}{cc}T\mathrm{amb}=\frac{T\max -a*T\min }{1-a}& \left(12\right)\end{array}$
and coefficient of thermal resistance device-device's ambient change is

(32) $\begin{array}{cc}b=\frac{T\min -T\mathrm{amb}}{R*P\min }& \left(13\right)\end{array}$
Replacing T.sub.amb with (12) it gives

(33) 0$\begin{array}{cc}b=\frac{T\min -\frac{T\max -a*T\min }{1-a}}{R*P\min }=\frac{T\min -T\max }{R*P\min *\left(1-a\right)}& \left(14\right)\end{array}$
b=1 indicates that the device is working in environment compliant with this required by manual as shown by (8).

(34) The coefficient a and product R*P.sub.min are constant and specific for each particular device. They may differ slightly between devices of the same type, due to variable parameters of electric or mechanical components used in each device. They are to be determined before device deployment in lab according to the procedure of FIG. 3.

(35) As stated in (11), in lab environment i.e. for constant ambient temperature in E.sub.min and E.sub.max modes and constant thermal resistance device-device's ambient in E.sub.min and E.sub.max modes where ΔR=0;

(36) $\begin{array}{cc}a=\frac{T\max l-T\mathrm{ambl}}{T\min l-T\mathrm{am}\mathrm{bl}}& \left(15\right)\\ R*P\min =T\min l-T\mathrm{ambl}& \left(16\right)\end{array}$
where

(37) T.sub.max1—the temperature indicated by temperature sensor in E.sub.max mode in lab environment,

(38) T.sub.mini—the temperature indicated by temperature sensor in E.sub.min mode in lab environment,

(39) T.sub.amb1—the device's ambient temperature in lab environment.

(40) FIG. 2 presents a method for determining the ambient temperature, the method being operated by the controller 104. The procedure starts after powering on the device in step 201, when the device is switched to an inactive mode in step 202. Then, the temperature T.sub.min is acquired in step 203 by reading the temperature measurement from the temperature sensor 105. Next, the power consumption is increased in step 204 by turning the device into higher power consumption mode via the power mode regulator 103, for example by activating the most power-consuming functions which are normally off in the inactive mode.

(41) Then, in step 205, the temperature T.sub.max is read from the temperature sensor 105. Then, in step 206 the ambient temperature T.sub.amb is calculated on the basis of the equation (12) specified above. Next in step 207 the coefficient b can be calculated on the basis of the equation (13) specified above. In step 208 the controller checks whether the ambient temperature T.sub.amb is higher than the maximum allowed ambient temperature T.sub.ambmax and if so, it invokes an alarm in step 209.

(42) Next, the controller can check in step 210 whether the coefficient b is higher than 1 and if so, it invokes an alarm in step 211. The procedure returns then to the inactive mode and the measurement procedure can be repeated upon a predetermined temperature measurement event. Therefore, the procedure of FIG. 2 allows determining, firstly, what is the ambient temperature (T.sub.amb) and secondly, if there is a change of the device thermal resistance (b).

(43) The temperature measurement event determines the moment at which the temperature should be measured. The temperature can be measured when the device operates in a mode which allows setting two distinct power modes, where in the second mode the device dissipates more power than in the first mode. For example, this can be done when the device is in a stand-by mode, where the higher power dissipation mode may be invoked temporarily. Alternatively, this can be done even when the device is in a normal operation mode, but not all the functions of the device are active and the device can be switched to a higher power mode (by activation additional functions) temporarily.

(44) The event may be invoked cyclically, e.g. every hour or once per day (e.g. at specific time periods, such as at noon). Alternatively, the event may be invoked upon a change of state of the device, e.g. each time the device is switched to a stand-by mode or turned on from a power-off mode (with possible limitation that the measurement will be done e.g. once per day only).

(45) FIG. 3 presents a procedure for measuring the parameters ‘a’, ‘R*P.sub.min’ for the particular device. The parameters are product specific and the measurements (calculation) should be performed at the designtests stage and or could be specific for a particular device and the procedure should be performed at the manufacturing stage after the device is fully assembled. For example, the procedure can be performed during burn-in tests of the device. First, in step 301 the device is powered on and the ambient temperature T.sub.amb is acquired using external sensor in step 302. The device is switched into inactive mode in step 303 and the temperature T.sub.min is read from the device temperature sensor 105 in step 304. Next, the device is switched to a higher power consumption mode in step 305 and the temperature T.sub.max is read in step 306 from the device temperature sensor 105. Then, in step 307 the value of coefficient a is calculated using formula (15) and stored in the non-volatile memory 111 of the device. Next, the value of R*P.sub.min is calculated in step 308 using formula (16) and stored in the non-volatile memory 111 of the device. The values (a) and (R*P.sub.min) are stored in the non-volatile memory 111 of the device's controller together with allowed maximum temperature T.sub.ambmax.

(46) It can be easily recognized, by one skilled in the art, that the aforementioned method for determining ambient temperature of an electronic device may be performed and/or controlled by one or more computer programs. Such computer programs are typically executed by utilizing the computing resources of the device. The computer programs can be stored in a non-volatile memory, for example a flash memory or in a volatile memory, for example RAM and are executed by the processing unit. These memories are exemplary recording media for storing computer programs comprising computer-executable instructions performing all the steps of the computer-implemented method according the technical concept presented herein.

(47) While the invention presented herein has been depicted, described, and has been defined with reference to particular preferred embodiments, such is references and examples of implementation in the foregoing specification do not imply any limitation on the invention. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader scope of the technical concept. The presented preferred embodiments are exemplary only, and are not exhaustive of the scope of the technical concept presented herein. Accordingly, the scope of protection is not limited to the preferred embodiments described in the specification, but is only limited by the claims that follow.