Linear Regulator | PartQuest™ Explore

LinReg

Designer138696

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7 years 11 months

65

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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.

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Coordinated Electrical and Thermal Design for a Linear Regulator Circuit

Designer19

Member for

11 years 7 months

1,833

designs

10

groups

Member of the PartQuest Explore Development Team. Focused on modeling and simulation of analog, mixed-signal and multi-discipline systems covering a broad range of applications, including power electronics, controls and mechatronic systems.

Description

This design example demonstrates electro-thermal trade-off analysis for power dissipating circuits. The design includes a 3.3V linear regulator that drives up to 1A of load current. To reduce the input voltage to the regulator and thereby reduce its power dissipation, a series NPN transistor with a zener diode controlling its base voltage is used.To explore the design trade-offs, the user can change the zener voltage and re-run the simulation. This will result in not only a change to the electrical voltage split across the transistor and regulator, but also a corresponding change to their observed junction temperatures. The user can also change the values of the thermal resistances (from case to ambient*) for those components, to identify the heat-sink or other thermal mitigation required to meet all the design constraints of this circuit.The user can also change the circuit's operating environment, including the battery voltage, the ambient temperature and the load resistance (initial and pulse values).*Note: The junction to case thermal resistances are specified by the manufacturer for these parts, so they cannot be changed by the circuit's thermal designer.

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ePower_040

Designer152721

Member for

7 years 8 months

109

designs

1

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ePower_050

Designer152721

Member for

7 years 8 months

109

designs

1

groups

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Linear Regulator Temperature Finder

Designer19

Member for

11 years 7 months

1,833

designs

10

groups

Member of the PartQuest Explore Development Team. Focused on modeling and simulation of analog, mixed-signal and multi-discipline systems covering a broad range of applications, including power electronics, controls and mechatronic systems.

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.

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Buck DC to DC Converter vs. Linear Regulator

Designer30

Member for

11 years 6 months

188

designs

1

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Description

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Buck DC to DC Converter vs. Linear Regulator

Designer19

Member for

11 years 7 months

1,833

designs

10

groups

Member of the PartQuest Explore Development Team. Focused on modeling and simulation of analog, mixed-signal and multi-discipline systems covering a broad range of applications, including power electronics, controls and mechatronic systems.

Description

About text formats

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