This example shows the capability of modeling the electrothermal aspects of power dissipating circuits. The design is a 5V regulator (non-switching), driven from a 120 Vac/60 Hz input and using a transformer/rectifier circuit to step down to a much lower DC-link voltage.

The load current capability is 5A, which is well above the current limit of the linear regular component itself. This is thanks to the load sharing role of the bypass PNP transistor. The design is based on an example application circuit shown in Figure 11 of the On Semiconductor Datasheet MC7800/D, November 2014 - Rev. 27.

All of the power dissipating electronics' models are from the "Thermal and Electro-thermal" Components Library. They have a thermal port that connects to the thermal network (i.e. red wires). These models output all the power dissipated in the device as a thermal heat-flow into that network. This includes the rectifier diodes, the linear regulator and the BJT, as well as the current sense resistor and the effective winding resistances of the transformer primary and secondary.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (1 degC/Watt), as well as the datasheet published values for the junction-to-lead thermal resistances of all the active electronic components. An assumed value for the thermal capacitance of the BJT (0.005 J/degC, not provided by the manufacturer) was added for purposes of illustration. Obtaining the actual value would require deeper analysis or measurement of this important component characteristic. However, in this example, both thermal capacitance values were selected solely to give sufficiently fast thermal time constants, so that steady-state operating temperatures could be reached with minimal simulation time.

This design is based on another shared design:

https://explore.partquest.com/node/666395

That design has been modified not only to add the electrothermal aspects, but it was also adjusted to improve its observed thermal performance. For example, the DC-link capacitance (c3) was increased from 4700uF to 22000uF, to allow a reduced DC-link operating voltage (i.e. to improve efficiency) while avoiding regulation drop-out at AC zero-crossings under heavy load conditions.

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.

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

In this design, a Vishay NTCLE100 Thermistor is used in a detection circuit to monitor the enclosure temperature. It is used for thermal shut-down protection, to keep the enclosure temperature well below the "Tg" (glass transition temperature) of the spotlight's Nylon 6 polymer lens. This is particularly helpful when operating at higher 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 "thermally-aware" circuit function design and board layout processes.

This example shows the capability of modeling the electrothermal aspects of power dissipating circuits. The design is a 5V regulator (non-switching), driven from a 120 Vac/60 Hz input and using a transformer/rectifier circuit to step down to a much lower DC-link voltage.

The load current capability is 5A, which is well above the current limit of the linear regular component itself. This is thanks to the load sharing role of the bypass PNP transistor. The design is based on an example application circuit shown in Figure 11 of the On Semiconductor Datasheet MC7800/D, November 2014 - Rev. 27.

All of the power dissipating electronics' models are from the "Thermal and Electro-thermal" Components Library. They have a thermal port that connects to the thermal network (i.e. red wires). These models output all the power dissipated in the device as a thermal heat-flow into that network. This includes the rectifier diodes, the linear regulator and the BJT, as well as the current sense resistor and the effective winding resistances of the transformer primary and secondary.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (1 degC/Watt), as well as the datasheet published values for the junction-to-lead thermal resistances of all the active electronic components. An assumed value for the thermal capacitance of the BJT (0.005 J/degC, not provided by the manufacturer) was added for purposes of illustration. Obtaining the actual value would require deeper analysis or measurement of this important component characteristic. However, in this example, both thermal capacitance values were selected solely to give sufficiently fast thermal time constants, so that steady-state operating temperatures could be reached with minimal simulation time.

This design is based on another shared design:

https://explore.partquest.com/node/666395

That design has been modified not only to add the electrothermal aspects, but it was also adjusted to improve its observed thermal performance. For example, the DC-link capacitance (c3) was increased from 4700uF to 22000uF, to allow a reduced DC-link operating voltage (i.e. to improve efficiency) while avoiding regulation drop-out at AC zero-crossings under heavy load conditions.

This example shows the capability of modeling the electrothermal aspects of power dissipating circuits. The design is a 5V regulator (non-switching), driven from a 120 Vac/60 Hz input and using a transformer/rectifier circuit to step down to a much lower DC-link voltage.

The load current capability is 5A, which is well above the current limit of the linear regular component itself. This is thanks to the load sharing role of the bypass PNP transistor. The design is based on an example application circuit shown in Figure 11 of the On Semiconductor Datasheet MC7800/D, November 2014 - Rev. 27.

All of the power dissipating electronics' models are from the "Thermal and Electro-thermal" Components Library. They have a thermal port that connects to the thermal network (i.e. red wires). These models output all the power dissipated in the device as a thermal heat-flow into that network. This includes the rectifier diodes, the linear regulator and the BJT, as well as the current sense resistor and the effective winding resistances of the transformer primary and secondary.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (1 degC/Watt), as well as the datasheet published values for the junction-to-lead thermal resistances of all the active electronic components. An assumed value for the thermal capacitance of the BJT (0.005 J/degC, not provided by the manufacturer) was added for purposes of illustration. Obtaining the actual value would require deeper analysis or measurement of this important component characteristic. However, in this example, both thermal capacitance values were selected solely to give sufficiently fast thermal time constants, so that steady-state operating temperatures could be reached with minimal simulation time.

This design is based on another shared design:

https://explore.partquest.com/node/666395

That design has been modified not only to add the electrothermal aspects, but it was also adjusted to improve its observed thermal performance. For example, the DC-link capacitance (c3) was increased from 4700uF to 22000uF, to allow a reduced DC-link operating voltage (i.e. to improve efficiency) while avoiding regulation drop-out at AC zero-crossings under heavy load conditions.

This example shows the capability of modeling the electrothermal aspects of power dissipating circuits. The design is a 5V regulator (non-switching), driven from a 120 Vac/60 Hz input and using a transformer/rectifier circuit to step down to a much lower DC-link voltage.

The load current capability is 5A, which is well above the current limit of the linear regular component itself. This is thanks to the load sharing role of the bypass PNP transistor. The design is based on an example application circuit shown in Figure 11 of the On Semiconductor Datasheet MC7800/D, November 2014 - Rev. 27.

All of the power dissipating electronics' models are from the "Thermal and Electro-thermal" Components Library. They have a thermal port that connects to the thermal network (i.e. red wires). These models output all the power dissipated in the device as a thermal heat-flow into that network. This includes the rectifier diodes, the linear regulator and the BJT, as well as the current sense resistor and the effective winding resistances of the transformer primary and secondary.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (1 degC/Watt), as well as the datasheet published values for the junction-to-lead thermal resistances of all the active electronic components. An assumed value for the thermal capacitance of the BJT (0.005 J/degC, not provided by the manufacturer) was added for purposes of illustration. Obtaining the actual value would require deeper analysis or measurement of this important component characteristic. However, in this example, both thermal capacitance values were selected solely to give sufficiently fast thermal time constants, so that steady-state operating temperatures could be reached with minimal simulation time.

This design is based on another shared design:

https://explore.partquest.com/node/666395

That design has been modified not only to add the electrothermal aspects, but it was also adjusted to improve its observed thermal performance. For example, the DC-link capacitance (c3) was increased from 4700uF to 22000uF, to allow a reduced DC-link operating voltage (i.e. to improve efficiency) while avoiding regulation drop-out at AC zero-crossings under heavy load conditions.

This example shows the capability of modeling the electrothermal aspects of power dissipating circuits. The design is a 5V regulator (non-switching), driven from a 120 Vac/60 Hz input and using a transformer/rectifier circuit to step down to a much lower DC-link voltage.

The load current capability is 5A, which is well above the current limit of the linear regular component itself. This is thanks to the load sharing role of the bypass PNP transistor. The design is based on an example application circuit shown in Figure 11 of the On Semiconductor Datasheet MC7800/D, November 2014 - Rev. 27.

All of the power dissipating electronics' models are from the "Thermal and Electro-thermal" Components Library. They have a thermal port that connects to the thermal network (i.e. red wires). These models output all the power dissipated in the device as a thermal heat-flow into that network. This includes the rectifier diodes, the linear regulator and the BJT, as well as the current sense resistor and the effective winding resistances of the transformer primary and secondary.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (1 degC/Watt), as well as the datasheet published values for the junction-to-lead thermal resistances of all the active electronic components. An assumed value for the thermal capacitance of the BJT (0.005 J/degC, not provided by the manufacturer) was added for purposes of illustration. Obtaining the actual value would require deeper analysis or measurement of this important component characteristic. However, in this example, both thermal capacitance values were selected solely to give sufficiently fast thermal time constants, so that steady-state operating temperatures could be reached with minimal simulation time.

This design is based on another shared design:

https://explore.partquest.com/node/666395

That design has been modified not only to add the electrothermal aspects, but it was also adjusted to improve its observed thermal performance. For example, the DC-link capacitance (c3) was increased from 4700uF to 22000uF, to allow a reduced DC-link operating voltage (i.e. to improve efficiency) while avoiding regulation drop-out at AC zero-crossings under heavy load conditions.

This design represents a simple automotive (12V) coffee cup warmer, with digital thermostat. It is not meant to be a practical design, but rather to show some of the capabilities of modeling multi-discipline electro-thermal systems in SystemVision Cloud.

The design includes a "plant" model with both static and dynamic thermal aspects, including a tungsten heater element, conduction and radiation heat transfer, and heat capacitance. A "graphical" model of the temperature sensor includes math function-blocks to set the bandwidth (LPF), gain (sensitivity), offset bias and output voltage limiting. It also includes an output resistance.

The closed loop performance of the system depends on the sensor bandwidth and the sampling rate. Try using 1 Hz instead of 0.1 Hz for the pole frequency "FP" in LPF1, and a 0.2 second period for the sample clock. You'll notice that the faster sensor and sampling greatly improves the temperature regulation.

The thermostat includes a simple amplifier and a single-bit voltage-to-digital converter, with a threshold level that specifies the temperature regulation set-point. A digital clock and D flip-flop sample and preserve the desired state of the heater switch during each clock cycle.