electro-thermal | PartQuest™ Explore

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Designer

Description

This&nbsp;LED spotlight example demonstrates the value of simulating both the electrical and thermal&nbsp;aspects of power dissipating circuits together, simultaneously.

In this design, a Vishay NTCLE100&nbsp;Thermistor is used in a detection circuit to monitor&nbsp;the enclosure temperature. It is used for&nbsp;thermal shut-down protection, to keep the enclosure temperature well below the "Tg" (glass transition temperature) of the spotlight's Nylon 6 polymer&nbsp;lens. This is particularly helpful when operating at higher&nbsp;external ambient temperatures.

The "Thermals" (thermal dynamics) model was automatically generated from a full 3D-CFD analysis of the spotlight board layout and enclosure, using FloTHERM. The model is in the IEEE Standard VHDL-AMS format, so it can be directly imported into the SystemVision "1D" circuit and system simulation context. The ability to include an accurate model of the thermal environment is key to having&nbsp;"thermally-aware" circuit function design&nbsp;and board layout&nbsp;processes.

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Copy of SEMI-THERM 37 BCI ROM for LED Spotlight - on Fri, 02/05/2021 - 12:36

Designer

Description

This&nbsp;LED spotlight example demonstrates the value of simulating both the electrical and thermal&nbsp;aspects of power dissipating circuits together, simultaneously.

In this design, a Vishay NTCLE100&nbsp;Thermistor is used in a detection circuit to monitor&nbsp;the enclosure temperature. It is used for&nbsp;thermal shut-down protection, to keep the enclosure temperature well below the "Tg" (glass transition temperature) of the spotlight's Nylon 6 polymer&nbsp;lens. This is particularly helpful when operating at higher&nbsp;external ambient temperatures.

Thermal dynamics&nbsp;models were&nbsp;automatically generated from a full 3D-CFD analysis&nbsp;using FloTHERM. This includes a thermal netlist model for the spotlight board layout and enclosure, as well as a BCI ROM model for MOSFET QFN package thermals. The format of both models is IEEE Standard VHDL-AMS, so it can be directly imported into the SystemVision "1D" circuit and system simulation context. The ability to include an accurate model of the thermal environment is key to having&nbsp;"thermally-aware" circuit function design&nbsp;and board layout&nbsp;processes.

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Copy of Modeling Transistor Amplifier Self-Heating - Thermal Network - on Thu, 02/04/2021 - 14:09

Designer

Description

This example shows the importance of modeling thermal interaction effects, or "thermal crosstalk", in power dissipating circuits. The "design" is a simple transistor amplifier, using just an 8 Ohm pull-up resistor and an active pull-down NPN BJT. Both of these models are from our "Thermal and Electro-thermal" Components Library, so they have a thermal port that can connect to an external thermal network. These models output all power dissipated in the device as a thermal heat-flow into that network.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (10 degC/Watt). This assumes the resistor and transistor contribute heat to the same heat-sink. The transistor's thermal heat-flow path also includes an 8.8 degC/Watt resistance, to represent the Junction-to-Lead Thermal Resistance as published in the device datasheet (Diodes Inc. FZT869).

From the simulation results it is clear that the heat-sink temperature rises to nearly 120 degC (purple waveform), causing the transistor's junction temperature to approach 150 degC (average, red waveform). This is significantly higher than the value predicted in the companion design example: "Modeling Transistor Amplifier Self-Heating - Hot Part Monitor", which assumed the two devices were thermally isolated.

About text formats

Copy of Modeling Transistor Amplifier Self-Heating - Thermal Network - on Thu, 02/04/2021 - 14:09

Designer

Description

This example shows the importance of modeling thermal interaction effects, or "thermal crosstalk", in power dissipating circuits. The "design" is a simple transistor amplifier, using just an 8 Ohm pull-up resistor and an active pull-down NPN BJT. Both of these models are from our "Thermal and Electro-thermal" Components Library, so they have a thermal port that can connect to an external thermal network. These models output all power dissipated in the device as a thermal heat-flow into that network.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (10 degC/Watt). This assumes the resistor and transistor contribute heat to the same heat-sink. The transistor's thermal heat-flow path also includes an 8.8 degC/Watt resistance, to represent the Junction-to-Lead Thermal Resistance as published in the device datasheet (Diodes Inc. FZT869).

From the simulation results it is clear that the heat-sink temperature rises to nearly 120 degC (purple waveform), causing the transistor's junction temperature to approach 150 degC (average, red waveform). This is significantly higher than the value predicted in the companion design example: "Modeling Transistor Amplifier Self-Heating - Hot Part Monitor", which assumed the two devices were thermally isolated.

About text formats

Copy of Modeling Transistor Amplifier Self-Heating - Thermal Network - on Thu, 02/04/2021 - 14:09

Designer

Description

This example shows the importance of modeling thermal interaction effects, or "thermal crosstalk", in power dissipating circuits. The "design" is a simple transistor amplifier, using just an 8 Ohm pull-up resistor and an active pull-down NPN BJT. Both of these models are from our "Thermal and Electro-thermal" Components Library, so they have a thermal port that can connect to an external thermal network. These models output all power dissipated in the device as a thermal heat-flow into that network.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (10 degC/Watt). This assumes the resistor and transistor contribute heat to the same heat-sink. The transistor's thermal heat-flow path also includes an 8.8 degC/Watt resistance, to represent the Junction-to-Lead Thermal Resistance as published in the device datasheet (Diodes Inc. FZT869).

From the simulation results it is clear that the heat-sink temperature rises to nearly 120 degC (purple waveform), causing the transistor's junction temperature to approach 150 degC (average, red waveform). This is significantly higher than the value predicted in the companion design example: "Modeling Transistor Amplifier Self-Heating - Hot Part Monitor", which assumed the two devices were thermally isolated.

About text formats

Copy of Modeling Transistor Amplifier Self-Heating - Thermal Network - on Thu, 02/04/2021 - 14:09

Designer

Description

This example shows the importance of modeling thermal interaction effects, or "thermal crosstalk", in power dissipating circuits. The "design" is a simple transistor amplifier, using just an 8 Ohm pull-up resistor and an active pull-down NPN BJT. Both of these models are from our "Thermal and Electro-thermal" Components Library, so they have a thermal port that can connect to an external thermal network. These models output all power dissipated in the device as a thermal heat-flow into that network.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (10 degC/Watt). This assumes the resistor and transistor contribute heat to the same heat-sink. The transistor's thermal heat-flow path also includes an 8.8 degC/Watt resistance, to represent the Junction-to-Lead Thermal Resistance as published in the device datasheet (Diodes Inc. FZT869).

From the simulation results it is clear that the heat-sink temperature rises to nearly 120 degC (purple waveform), causing the transistor's junction temperature to approach 150 degC (average, red waveform). This is significantly higher than the value predicted in the companion design example: "Modeling Transistor Amplifier Self-Heating - Hot Part Monitor", which assumed the two devices were thermally isolated.

About text formats

Copy of Modeling Transistor Amplifier Self-Heating - Thermal Network - on Thu, 02/04/2021 - 14:09

Designer

Description

This example shows the importance of modeling thermal interaction effects, or "thermal crosstalk", in power dissipating circuits. The "design" is a simple transistor amplifier, using just an 8 Ohm pull-up resistor and an active pull-down NPN BJT. Both of these models are from our "Thermal and Electro-thermal" Components Library, so they have a thermal port that can connect to an external thermal network. These models output all power dissipated in the device as a thermal heat-flow into that network.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (10 degC/Watt). This assumes the resistor and transistor contribute heat to the same heat-sink. The transistor's thermal heat-flow path also includes an 8.8 degC/Watt resistance, to represent the Junction-to-Lead Thermal Resistance as published in the device datasheet (Diodes Inc. FZT869).

From the simulation results it is clear that the heat-sink temperature rises to nearly 120 degC (purple waveform), causing the transistor's junction temperature to approach 150 degC (average, red waveform). This is significantly higher than the value predicted in the companion design example: "Modeling Transistor Amplifier Self-Heating - Hot Part Monitor", which assumed the two devices were thermally isolated.

About text formats

Copy of Modeling Transistor Amplifier Self-Heating - Thermal Network - on Thu, 02/04/2021 - 14:09

Designer

Description

This example shows the importance of modeling thermal interaction effects, or "thermal crosstalk", in power dissipating circuits. The "design" is a simple transistor amplifier, using just an 8 Ohm pull-up resistor and an active pull-down NPN BJT. Both of these models are from our "Thermal and Electro-thermal" Components Library, so they have a thermal port that can connect to an external thermal network. These models output all power dissipated in the device as a thermal heat-flow into that network.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (10 degC/Watt). This assumes the resistor and transistor contribute heat to the same heat-sink. The transistor's thermal heat-flow path also includes an 8.8 degC/Watt resistance, to represent the Junction-to-Lead Thermal Resistance as published in the device datasheet (Diodes Inc. FZT869).

From the simulation results it is clear that the heat-sink temperature rises to nearly 120 degC (purple waveform), causing the transistor's junction temperature to approach 150 degC (average, red waveform). This is significantly higher than the value predicted in the companion design example: "Modeling Transistor Amplifier Self-Heating - Hot Part Monitor", which assumed the two devices were thermally isolated.

About text formats

Copy of Linear Regulator Temperature Finder - on Tue, 01/26/2021 - 15:15

Designer

Description

This "virtual test circuit" can help designers predict the temperatures of a linear regulator, based on readily available information from the manufacturer's datasheet. Users can simply make a copy of this circuit, then adjust the regulator model's parameters to match the electrical and thermal characteristics for their particular part.

These parameters include the output voltage, VDO and current limit, as well as the junction-to-case and junction-to-ambient or heat-sink thermal resistance values. In this example, an L78S05 with direct case to ambient heat transfer is modeled (i.e. no heat-sink). The datasheet specifies the junction-to-case resistance is 5degC/Watt, and the junction-to-ambient resistance for a T0-220 package is 50 degC/Watt. Therefore, the difference of 45 degC/Watt is assumed to be the case-to-ambient thermal resistance. This value is assigned as the "heat-sink" resistance.

If an actual heat sink is being used, its published thermal resistance would be used instead. If the heat sink heat capacitance is also provided, that value can be applied to the thermal capacitor, and then the simulation will predict not only the steady-state operating temperature, but also temperature transients.

The input voltage function generator can also be adjusted to apply any time-varying input voltage profile, and the test circuit will show the corresponding time-varying temperature profile. This can be used to identify peak as well as average operating temperatures.

The user can also change the load current level and/or the load type using any relevant models in the Component Library, or create custom load models.

About text formats

Copy of Linear Regulator Temperature Finder - on Tue, 01/26/2021 - 15:15

Designer

Description

This "virtual test circuit" can help designers predict the temperatures of a linear regulator, based on readily available information from the manufacturer's datasheet. Users can simply make a copy of this circuit, then adjust the regulator model's parameters to match the electrical and thermal characteristics for their particular part.

These parameters include the output voltage, VDO and current limit, as well as the junction-to-case and junction-to-ambient or heat-sink thermal resistance values. In this example, an L78S05 with direct case to ambient heat transfer is modeled (i.e. no heat-sink). The datasheet specifies the junction-to-case resistance is 5degC/Watt, and the junction-to-ambient resistance for a T0-220 package is 50 degC/Watt. Therefore, the difference of 45 degC/Watt is assumed to be the case-to-ambient thermal resistance. This value is assigned as the "heat-sink" resistance.

If an actual heat sink is being used, its published thermal resistance would be used instead. If the heat sink heat capacitance is also provided, that value can be applied to the thermal capacitor, and then the simulation will predict not only the steady-state operating temperature, but also temperature transients.

The input voltage function generator can also be adjusted to apply any time-varying input voltage profile, and the test circuit will show the corresponding time-varying temperature profile. This can be used to identify peak as well as average operating temperatures.

The user can also change the load current level and/or the load type using any relevant models in the Component Library, or create custom load models.

About text formats

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