Claims:1. A method for thermal protection of a power converter, the method comprising:
monitoring, by a device (702), a rate of rise of temperature in at least one heat producing element of a power converter (103) using at least one sensor (703); and
controlling, by the device (702), charging current of the power converter (103) based on the monitored rate of rise of temperature in the associated at least one heat producing element for the thermal protection of the power converter.

2. The method of claim 1, wherein the power converter includes one of, a battery charger, a Direct Current (DC)-DC converter, an electric vehicle charger, and a Constant Current (CC)-Constant Voltage (CV) charger.

3. The method of claim 1, wherein the at least one heat producing element includes one of, a power MOSFETs, bridge rectifiers, switching devices, power switches, and power resistors.

4. The method of claim 1, wherein controlling, by the device, the charging current of the power converter includes:
identifying a change of a temperature zone for the at least one heat producing element of the power converter using a look-up table, on determining the change in the rate of rise of temperature in the at least one heat producing element from a first temperature threshold to a second temperature threshold; and
controlling the charging current of the power converter based on the identified change of the temperature zone for the at least one heat producing element.

5. The method of claim 4, wherein the look-up table includes a mapping of the temperature zone for each rate of rise of temperature in the at least one heat producing element, wherein the temperature zone includes one of, a safe zone, a warning zone, a critical zone, and an unsafe zone.

6. The method of claim 4, wherein controlling the charging current of the power converter based on based on the identified temperature zone includes: recursively performing steps of:
incrementing a power derating count for the power converter each time on determining the change in the rate of temperature rise in the at least one heat producing element from the first temperature threshold to the second temperature threshold and the respective change from a first temperature zone to a second temperature zone; and
derating the charging current of the power converter when the power derating count reaches at least one respective count threshold each time, till the change in the rate of temperature rise in the at least one heat producing element crosses all defined temperature zones.

7. The method of claim 6, further comprising: recursively performing steps of:
decrementing the power derating count for the power converter each time on determining that the power derating count reaches at least one maximum count threshold, or zero power is delivered or the rate of rise of temperature in the at least one heat producing element changes from the second temperature threshold to the first temperature threshold and the respective change from the second temperature zone to the first temperature zone; and
decreasing temperature gradient and increasing the charging current of the power converter on reducing the power derating count, till a pre-defined temperature is reached.

8. A device coupled to the power converter comprising:
a sensor (703);
at least one sensor coupled to the power converter (103) configured to:
monitor a rate of rise of temperature in at least one heat producing element of a power converter using at least one sensor; and
a controller coupled to the at least one senor configured to:
control charging current of the power converter based on the monitored rate of rise of temperature in the associated at least one heat producing element for the thermal protection of the power converter.

9. The device of claim 8, wherein the power converter includes one of, a battery charger, a Direct Current (DC)-DC converter, an electric vehicle charger, and a Constant Current (CC)-Constant Voltage (CV) charger.

10. The device of claim 8, wherein the at least one heat producing element includes one of, a power MOSFETs, bridge rectifiers, switching devices, power switches, and power resistors.

11. The device of claim 8, wherein the controller is configured to:
identify a change of a temperature zone for the at least one heat producing element of the power converter using a look-up table, on determining the change in the rate of rise of temperature in the at least one heat producing element from a first temperature threshold to a second temperature threshold; and
control the charging current of the power converter based on the identified change of the temperature zone for the at least one heat producing element.

12. The device of claim 11, wherein the look-up table includes a mapping of the temperature zone for each rate of rise of temperature in the at least one heat producing element, wherein the temperature zone includes one of, a safe zone, a warning zone, a critical zone, and an unsafe zone.

13. The device of claim 11, wherein the controller is configured to: recursively perform steps of:
incrementing a power derating count for the power converter each time on determining the change in the rate of temperature rise in the at least one heat producing element from the first temperature threshold to the second temperature threshold and the respective change from a first temperature zone to a second temperature zone; and
derating the charging current of the power converter when the power derating count reaches at least one respective count threshold each time, till the change in the rate of temperature rise in the at least one heat producing element crosses all defined temperature zones.

14. The device of claim 8, wherein the controller is configured to: recursively perform steps of:
decrementing the power derating count for the power converter each time on determining that the power derating count reaches at least one maximum count threshold, or zero power is delivered or the rate of rise of temperature in the at least one heat producing element changes from the second temperature threshold to the first temperature threshold and the respective change from the second temperature zone to the first temperature zone; and
decreasing temperature gradient and increasing the charging current of the power converter on reducing the power derating count, till a pre-defined temperature is reached.
, Description:TECHNICAL FIELD
[001] The embodiments herein relate to electric vehicles and more particularly the embodiments herein relate to managing the thermal performance of an Electric Vehicle power converter.

BACKGROUND
[002] Generally, in automobile industry, electric vehicles have an increasing share of the automobile market. There is a need for cars to charge more quickly and have a higher range on a single charge. This implies that the electrical and electronics circuit within the vehicle should be able to handle extremely high power and manage losses effectively. There is a need for robust thermal-management solutions to ensure that safety-critical applications remain operational.
[003] Each subsystem within an Electric Vehicle (EV) requires temperature monitoring. Accurate temperature information allows the processor to temperature control the system, so that the electronic modules can optimize their performance and maximize their reliability no matter the driving conditions. This includes temperature sensing of power switches, power magnetic components, heat sinks, PCB, etc.
[004] In some of the existing technologies, to avoid thermal runaway problems, temperature sensors are incorporated. When the temperature of heat producing elements rise to a predefined value, the charging operation will cut-off or de-rate. The unit will reset to normal operation, when the heat producing elements become cool. However, with this method, the charging time will increase drastically and DCDC Converters will shut down or will be able to support only critical loads (on detecting over heating conditions).
[005] In some other technologies, the charging current is reduced based on the temperature of heat producing elements. However, these solutions do not consider the amount of temperature rise in the components and the duration of operation. If the heat producing elements such as Power MOSFETs (metal-oxide semiconductor field-effect transistor), Bridge rectifiers are operated for longer duration at high thermal stresses, the components may get damaged. In addition, if electrolytic capacitors are operated at high temperature conditions, their useful life will reduce drastically. It severely effects the reliability of the converter.

OBJECTS
[006] The principal object of embodiments herein is to provide methods and apparatus for managing the thermal performance of an electric power converter.
[007] Another object of embodiments herein is to protect critical components inside Lithium-ion battery charger and DC-DC converters.
[008] Another object of embodiments herein is to operate in safe thermal limits, thereby increasing the reliability and life of the power converter.
[009] Another object of embodiments herein is to design the power converter stage used in on-board/off-board charger/DCDC converter or in any application where temperature control is performed by controlling load current.
[0010] Another object of embodiments herein is to monitor the temperature rise in heat producing elements like magnetics, power resistors and power switches, that are operated for a longer time at high currents, as thermal stress is high on these components.
[0011] Another object of embodiments herein is to adjust the charging current or load current based on the rate of rise temperature of critical heat producing devices or hot spot temperatures inside the unit.
[0012] Another object of embodiments herein is to divide the temperature profile into different zones, based on the temperature of the module and increment/decrement a counter, on the temperature entering a zone.
[0013] Another object of embodiments herein is to divide the temperature into a plurality of zones, wherein the zones comprises a safe zone (where the temperature of the module is in a safe region and where no action done on count), one or more warning zones (where the temperature of the module is close to an unsafe region and count is proportional to temperature), an unsafe zone (where the temperature of the module is too high for the module to be doing normal operations and where the count is increasing (at different rates) irrespective of temperature rise or fall) and a critical zone (where the module is not operated).
[0014] Another object of embodiment herein is to switch the DC-DC converter to a lower current, derate the charger current (which increases the charging time of the High Voltage battery), during derating conditions and during this, AUX Battery is supporting the remaining current.
[0015] These and other objects of embodiments herein will be better appreciated and understood when considered in conjunction with following description and accompanying drawings. It should be understood, however, that the following descriptions, while indicating embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF DRAWINGS
[0016] The embodiments are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0017] FIGs. 1A and 1B depict examples of heat flow in air cooled power converter, according to embodiments disclosed herein;
[0018] FIG. 2 depicts an example of heat flow in liquid cooled power converter, according to embodiments disclosed herein;
[0019] FIG. 3 is a block diagram depicting the process of measuring the temperature of sensors in power converters, according to embodiments disclosed herein;
[0020] FIG. 4A is an example graph depicting the relation between Temperature, Count and Current at the time of Increment, according to embodiments disclosed herein;
[0021] FIG. 4B is an example graph depicting the relation between temperature, count and current at the time of decrement, according to embodiments disclosed herein;
[0022] FIG. 4C is an example lookup table depicting the relation between temperature, count and current at the time of increment/decrement, according to embodiments disclosed herein;
[0023] FIG. 5 depicts state machine for logic implementation of temperature controller, according to embodiments disclosed herein;
[0024] FIG. 6 illustrates a flow chart of counter increment and decrement with respect to temperature, according to embodiments disclosed herein;
[0025] FIG. 7 illustrates the flow with multiple temperature sensors, according to embodiments disclosed herein;
[0026] FIG. 8 illustrates the rate of increase of temperature is slower than sampling instances of temperature, according to embodiments disclosed herein; and
[0027] FIG.9 illustrates controlling output based on power_derating_count, according to embodiments disclosed herein.
 
DETAILED DESCRIPTION
[0028] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0029] The embodiments herein provide methods and apparatus for managing the thermal performance of an electric power converter to protect critical components inside Lithium-ion battery charger and DC-DC converters, to ensure that the power converter operates in safe thermal limits, thereby increasing the reliability and life of the power converter. Referring now to the drawings, FIGs. 1 through 9 where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0030] FIGs. 1A and 1B depict examples of heat flow in an air-cooled power converter according to embodiments disclosed here. The power converter 103 is configured with a heat sink 104, and a fan 101. The heat sinks 104 can be used to cool electronic devices in power converters by increasing heat dissipating surface area. The heat sink performance is improved by improving the inflow of the cool air and the outflow of hot air. In the example depicted in FIG. 1B, the heat sink 104 can be provided with fins. The power converter includes one of, an electric vehicle battery charger, a Direct Current (DC)-DC converter, an electric vehicle charger, a Motor Control Unit, and a Constant Current (CC)-Constant Voltage (CV) charger.
[0031] FIGs. 2A and 2B depict examples of heat flow in a liquid cooled power converter according to embodiments disclosed herein. The liquid cooling system can take the heat from a heat source and move the heat to a location, from where the heat can be expelled efficiently. The liquid cooling system can comprise of a plurality of tube or heat pipe, the tube may be made of copper or aluminum-copper, wherein the tubes carry liquid from the reservoir to a cold plate that is directly attached to the heat source. The heated liquid then moves on to a radiator, where fans use cold air to move the heat away from the liquid. The cooled liquid is then redirected back to the reservoir, for the cycle to repeat.
[0032] In the example depicted in FIG. 2A, the tubes carry liquid from the reservoir to a cold plate 202 that is directly attached to the heat source 201. The heated liquid 203 then moves on to a radiator 205, where fans 204 use cold air to move away the heat from the liquid. The cooled liquid is then redirected back to the reservoir for the cycle to repeat.
[0033] In the example depicted in FIG, 2B, the closed loop comprises a power converter 210, which is coupled with a heat sink 211. The pump 212 pumps the liquid from the tank to the heat sink 211, where heat is dissipated in the form of hot liquid is passed through a condenser 213.
[0034] In an embodiment herein, multiple temperature sensors are coupled with a counter to monitor critical heat producing elements or monitor temperature of multiple hot spots inside the power converter. The counter is variable and stores the number of times a particular event or process has occurred. Often in relationship to a clock. Count is only 1 and count increase/decrease based on temperature. Temperature is independent of the count.
[0035] Another object of embodiments herein is to divide the temperature into 4 zones, wherein the zones comprises: safe zone, where module temperature is under is under safe limits. warning zone, warning zone can be multiple as well, it is a prediction where temperature might reach to zone which is unsafe. Unsafe zone, it is a zone where module is danger to be doing full operations. Critical zone, where module should not be operated at all.
[0036] Based on the temperature zone of operation (i.e. the temperature thresholds), a counter (termed as power derating count) is incremented by a pre-defined number (wherein the pre-defined number depends on the application where the power converter is being used). Temperature and counter thresholds will be defined based on the combination of readings from different sensors. For example, the temperature sensor 1, and temperature sensor 2 are calculated with respect to temperature and time, and reading are taken, depending on reading the threshold value is taken, predetermined threshold value is set. Once the counter reaches a first predefined threshold level (T_Th1), the power converter is derated, i.e., charging current (or power level) is reduced. If the temperature further rises and crosses a second predefined threshold level (T_Th2), the counter will be increased by the pre-defined number. In an embodiment herein, the counter may be increased, if the temperature is higher than a pre-defined threshold temperature. If the counter reaches a third threshold level (T_Th3) or a fourth threshold level (T_Th4), the charging current/power level will be reduced further. Thus, with this method, heat producing components will be subjected to less thermal stresses, thereby reliability increasing the reliability of the power converter.
[0037] In an embodiment herein, multiple temperature sensors may be incorporated to monitor critical heat producing elements. In an embodiment herein, multiple temperature sensors may be incorporated to monitor the temperature at multiple spots inside the power converter. Embodiments herein can define the temperature and counter thresholds, based on the readings taken from different sensors.
[0038] FIGs. 3A and 3B depicts block diagram of temperature measurement of sensors in power converters according to embodiments disclosed herein. In step 301, the temperature measurement is performed. The temperature may be measured using sensors, such as, but not limited to, thermocouple, RTD (Resistance Temperature Detector) and thermistor. Multiple temperature sensors may be incorporated to monitor critical heat producing elements or multiple hot spots inside the power converter. Depending on the range of temperature exhibited by temperature sensors used in power converters, a maximum temperature is obtained (step 302). In step 303, the rate of change of the temperature is determined. The change of temperature can be an increase in the temperature or a decrease in the temperature. The rate of change of the temperature can be determined using maximum temperature readings received from different sensors with respect to time. In step 304, zones are identified, based on the temperature. Based on the identified zones, in step 305, the temperature thresholds, the power derating count is incremented or decremented. If the temperature is found to be increasing, then the power_derating_count is incremented at the predefined rate. If the temperature is decreasing, then the power_derating_count is decremented, based on the defined zone. In step 306, the current derating is obtained, wherein the current derating can be based on the predefined count threshold. When the counter reaches the predefined threshold level, the derating of the power converter is started, i.e., charging current (or power level) is reduced.
[0039] In another embodiment herein (as depicted in FIG. 3B), when the rate of change of the temperature is determined, in step 304, the current derating at predefined temperature threshold values are obtained based on a combination of reading from different sensors with respect to time.
[0040] FIG. 4A illustrates graph depicting relation between Temperature, Count and Current at the time of Increment according to embodiments disclosed herein. In FIG. 4A, initially, the power derating count starts increasing by when temperature crosses T_Th0 402 (414). When temperature crosses T_Th1 403, count enters next temperature zone, and the power derating count starts increasing by 2. An increase in the slope of the power derating count may be observed in FIG. 4A. As the count crosses C_Th1 410 threshold, the output current limit is derated to 90% of full load value (a, 411). This can lead to a reduction in the temperature. This effect can be verified in terms of a reduction in the gradient of the temperature profile. This phenomenon continues and as temperature rises and crosses respective zones. Accordingly, the count increases and output current gets derated. This results in stabilization of temperature to safe value. As seen, in FIG.4A, before 411, controller is delivering full power or full current and its temperature is raising.
[0041] For example, when Cnt_th1 410 count is reached, the output current is derated to 0.9. When Cnt_th2 409 count is reached, the output current is derated to 0.7. When Cnt_th3 408 count is reached, the output current is derated to 0.5. Further, when the temperature is more than the first temperature zone T_th0 402, the counter is started and is increased by 1. Similarly, when the second temperature zone T_Th1 403 is reached, the count is increased by 2. When the third temperature zone T_Th2 404 is crossed, the count is increased by 5. When the fourth temperature zone T_Th3 405 is crossed, the count is increased by 10. The count values may vary based on the application.
[0042] FIG. 4B illustrates graph depicting relation between temperature, count and current at the time of decrement according to embodiments disclosed herein. Initially, when count reaches the maximum limit, no power or less power will be delivered, and the temperature is reduced by a pre-determined cooling method such as liquid cooling using pump or compressor or condenser and air cooling using fan (before A, 430 in FIG. 4B). When the count reduces below C_Th4’ 425, the output current slowly starts building up and the temperature gradient reduces (A, 430). Since the temperature has reached the maximum limit, threshold values are selected, such that the temperature of the power converter goes to a lower zone (i.e., T_Th4’ 429 to T_Th3’428). Based on the temperature zone of operation, the count will be reduced by a pre-defined value (such as, but not limited to, 1, 2, 5). As the count value reduces below C_Th3’ 424, the current will increase further, and the temperature gradient will reduce (A,431). This phenomenon repeats at every threshold, till the optimum temperature is reached.
[0043] For example, at point 430, when the counter threshold C_th4’ 425 is reached, the output current is 0.5. At point 431 when the counter threshold C_th3’ 424 is reached, the output current is 0.7. At point 432 when the counter threshold C_th2’ 423 is reached, the output current is 0.9. When C_th1’ 422 is reached, the full load current may be delivered. At point 436, above the threshold level (i.e., C_th4’), the temperature reduces, and the count reduces by 1. Further at point 434, T_Th3, the temperature reduces, and the count reduces by 2. At point 435, T_th2, the temperature reduces and crosses the threshold, the count reduces by 5.
[0044] FIG. 4C is an example lookup table depicting the relation between temperature, count and current at the time of increment/decrement, according to embodiments disclosed herein. As shown in FIG.4C, the lookup table when temperature increases from t_th1 to t_th2, the power_derating_count increases by 1 (shown in FIG.4A). Similarly, for other zones the power_derating_count increases. The rate of power_derating_count increment increases as the temperature goes above as it is reaching to unsafe temperature(t_th4). When temperature decreases from t_th4 to t_th3, the power decrement count behavior depends on the zones.
[0045] FIG. 5 depicts state machine for logic implementation of temperature controller. As shown in FIG. 5, the temperature of the converter can be measured by one or more ADCs (analog to digital converters). After initialization of peripherals, a controller converts respective voltage to temperature. In one embodiment, there are a plurality of protection methodologies implemented within the controller. Embodiments herein also include a conventional multi-step derating approach, which can be implemented at higher temperature thresholds valveT_th4(FIG.4A). This is done if the rate of rise of temperature is very slow, and embodiments herein take time to derate power.
[0046] Further, embodiments herein calculate the difference between the instances of temperature, where the instance depends on the application or the rate at which the protections are supposed to run. Based on the difference, embodiments herein decide if temperature is increasing or decreasing. If the temperature is found to be increasing, then the power_derating_count is incremented at the predefined rate shown in FIG. 4A. If the temperature is decreasing, then the power_derating_count is decremented depending on the temperature zones. Based on the power_derating_count, the current is respectively derated, or the converter is shutdown.
[0047] For example, as shown in FIG. 5, in 501, when power is ON (i.e., the microcontroller is powered ON), in 502, peripheral initialization of microcontroller starts, i.e., after initialization, the converter starts. In step 503, the temperature is measured, and the measured temperature is multiplied with the scale factor and offset. The scale factors and offsets are post-measurement calculations applied to normalize or convert data. To define a scale factor and offset definition, navigate the scale factor and offset system table. Wherein, the offset specifies an offset to the measured value and the scale factor specifies the factor by which the raw value is multiplied to obtain the physical value. In step 505, the difference between temperature instances is performed, to check if the temperature is increasing or decreasing. If the difference between instances of temperature is less than 0 (i.e., the temperature is decreasing), in 506, the power_derating_count is decremented by a predefined factor (which depends on the temperature zone). If the difference between the temperature is greater than 0 (i.e., the temperature is increasing), in step 507, the power_derating_count is incremented by a predefined factor (which depends on the temperature zone).
[0048] If the temperature measured in 503 is less than a warning threshold (as per conventional methodologies), in 508, the full current (power) will be delivered. If the temperature measured in 503 is greater than the shutdown threshold (according to embodiments as disclosed herein), in 509, the current delivered will be 0 (i.e., there is a fault). If temperature is greater than the warning threshold and less than the shutdown threshold, in 510, the current delivered will be at a derated level, as per thresholds.
[0049] When count has been decremented (506) based on 4 zones of temperature mentioned above, if temperature is greater than the warning threshold and less than the shutdown threshold, in 510, the current delivered will be at a derated level, as per thresholds. If the temperature is greater than the shutdown threshold, in 509, the current delivered will be 0 (i.e., there is a fault). At 507, when the count is incremented, if temperature is less than the warning threshold, in 508, the full current (power) will be delivered.
[0050] FIG. 6 illustrates a flow chart of counter increment and decrement with respect to temperature. In an example herein, the temperature of the power converter is sensed by a temperature sensor. The sensed temperature is sent to the microcontroller. The microcontroller controls the output power of the power converter, based on the power derating count(also referred to herein as the power_derating_count). Any temperature below a lower threshold (Temp_Min_Limit) is considered as a safe temperature. Any temperature above a higher threshold (Temp_Max_Limit) is considered as a fault. As shown in FIG. 6, at step 602, pre-defined tasks, such as, turning the power of the microcontroller ON, initializing peripherals, and so on, are performed. In step 603, the readings from the temperature sensor are monitored. The temperature can be sensed from multiple spots inside the power converter. The controller checks if the currently sensed temperature is within limits or not, and checks in which zone, the sensed temperature belongs to (based on the temperature thresholds). In step 604, if the sensed temperature is less than the maximum threshold limit, then no charging is performed (step 605). If the sensed temperature is not less than the maximum threshold limit, in step 606, charging is started. If the charging current is equal to max rated current, in step 607, the power derating count is started. At step 608, if the threshold temperature is greater than 0 and the temperature is greater than T_th1 (step 609), in step 613, the counter is incremented with power_derating_count by 1. When the temperature threshold crosses the second temperature zone (i.e., temp>T_th2), (step 610), in step 614, the counter is incremented with power_derating_count by 2. When the temperature threshold crosses the third temperature zone (i.e. temp>T_th3) (step 611), in step 615, the counter is incremented with power_derating_count by 5. Similarly, when the temperature threshold crosses the fourth temperature zone (i.e., temp>T_th4) (step 612), in step 616, the counter is incremented with power_derating count by 10.
[0051] If the temperature difference is not greater than zero, and if the count has reached the maximum limit, no power or less power will be delivered, and the temperature reduces using a suitable cooling method. When the threshold temp>T_Th4(step 624), there is no action on power_derating count. When the temp>T_th3 (step 619), in step 623, the power_derating count is decremented by 1. When the temp>T_th2(step 618), in step 622, the power_derating count is decremented by 2. When the temp>T_th1 (step 617), in step 621, the power_derating count is decremented by 5.
[0052] FIG. 7 illustrates the flow with multiple temperature sensors. Multiple temperature sensors may be incorporated to monitor critical heat producing elements or to monitor temperature of multiple hot spots inside the power converter. In FIG. 7, when the microcontroller is turned on, in step 701, the initialization is started. In steps 702, 703, 704, the temperature sensors 1, 2 and 3 are monitored and the count values are obtained as count1(705), count2(706) and count3(707) respectively. In step 708, the Power_derating_count is obtained as the maximum count from counts 1, 2 and c3.
[0053] FIG. 8 illustrates the rate of increase of temperature is slower than sampling instances of temperature. In step 801, the power is started, the power converter is turned ON and full power/current is delivered. In step 802, temperature of one or more potential hotspot points of the unit is being monitored through the ADC. If the temperature is greater than Th1(first temperature zone) (step 803), in step 804, the derated current 1 is delivered. Here rated current > derated current_1> derated current 2> derated current 3. If the temperature is greater than Th2 (second temperature zone) (step 805), in step 806, the current is derated by 2. If the temperature is greater than Th3 (third temperature zone) (step 807), in step 808, the current is decremented by 3. In step 809, if the temperature Th1 C_Th2, the count crosses the next level. In step 905, if the power_derating_count is not greater than C_Th2, Iout (output power derating) is equal to Irated (rated contact current) * 0.8 (step 908). In step 906, if the power_derating_count > C_Th3, the count crosses the next level. In step 906, if the power_derating_count is not greater than C_Th3, Iout (output power derating) is equal to Irated * 0.7 (step 909). In step 907, if the power_derating_count > C_Th4, Iout is equal to 0/fault. In step 907, if the power_derating_count is not greater than C_Th4, Iout is equal to Irated * 0.5 (step 910).
[0055] For example, when temperature increases from t_th1 to t_th2, (shown in FIG 3A) the power_derating_count increases by 1 based on application. Similarly, for other zones, behaviour are based on 4 zones defined above. The rate of power_derating_count increment increases as the temperature goes above the unsafe temperature. When temperature decreases from t_th4 to t_th3, the power_derating_count decreases by 1 based on 4 zones defined above and based on application. As shown in FIG.9 The rate of power_derating_count decrement increases, as the temperature decreases as it is reaching a safe temperature. Similarly, when count threshold C_th1 is reached, output current is derated to 0.9. When C_th2 is reached, the output current is derated to 0.8. When C_th3 is reached, the output current is derated to 0.7. When C_th4 is reached, the output current is derated to 0.
[0056] In an embodiment herein, the threshold is obtained by plotting temperature rise with respect to time. Accordingly, the slope rate (amount of increment or decrement in count), free running data is obtained at different temperatures. The temperature rise is plotted with respect to time. Accordingly, the slope rates and zones, where different slope rates are required, is concluded. Once slope rates are finalized, FIG. 6 is implemented, and experiments are repeated at different temperatures. Power_derating_count is monitored in each experiment. As per the power_derating_count, a relation between the temperature and the power_derating_count is plotted. Accordingly, the current derating is decided based on the power_derating_count at a particular temperature. For example, if the maximum temperature that may be sustained by the power converter is 100 degrees (through theoretical data) and from experiments at 100 degrees, power_derating_count is mostly 60000, then C_Th4 will be 60000. (for example, in FIGs.4A and 4B) Similarly, current derating is decided based on power_derating_count (for example in FIG. 5). Current derating allows the converter to work more consistently and prevent battery drain.
[0057] The derating logic allows the converter to work effectively and prevent battery drain. From FIG. 4, when shutdown occurs, the converter drains the aux battery completely and requires a manual intervention; whereas in derating conditions, the converter switches to lower current and during this, the AUX Battery is supporting the remaining current and hence the temperature decreases accordingly.
[0058] In another embodiment, for example a few power electronic components in which the degradation of components, depend on the rate of rise in the temperature.
[0059] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modifications within the scope of the embodiments as described herein.