Questions tagged [thermal]

Relating to temperature rise, the flow of heat, or cooling of components

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84 views

Calculating Junction Temp of Switching Regulator

I was looking at TI web bench to find a regulator, my question is my calculation is correct and if it is why we have different value on webbench. The IC is TPS565208 P = (Vout - Vin)*Iout => (12-...
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Infineon IPOSIM tool for IGBT thermal loss calculations

I used the infineon IPOSIM power tool for simulating a motor drive for my required conditions and got the results for a custom input drive cycle. The results were given as power dissipation per IGBT(...
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1answer
47 views

Application based Heat sink design for Power diode

Instead of having a heatsink directly connected to the diode, I want to have a 2 mm layer of cold rolled steel in between case and heat sink(aluminium){for waterproofing as needed in the application}. ...
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Heatsink on underside of PCB

I have prototyped some DC-DC converter modules, and they work well. However due to size, I don't have a huge amount of copper pour for them to dissipate their heat. I have used 2oz copper but the ...
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1answer
70 views

Would leakage through a JFET create thermal noise

The impedance through the gate of a JFET is very high and leakage current very small. Would this impedance act like a large resistor creating thermal noise? Would this be a low noise way of ...
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134 views

Colpitts oscillator: how to reduce amplitude thermal drift?

I have built this circuit, supply ±12V: I am using a LM6172 amplifier. I have found the transfer function of the filter involved: \$H(j\omega)=\frac{1}{1 + \frac{R_3}{R_1} - L\omega^2(C_2+C_1\frac{...
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22 views

Heat transfer coefficient in a Module Baseplate

Today, for example in a power IGBT module cooled by a heatsink, it has been found that the heat transfer coefficient (htc) distribution may not be uniform across the bottom surface of the module ...
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1answer
89 views

Thermal resistance Junction - Maximum Power dissipation

I want to understand the real meaning of the parameter 'Thermal Resistance Junction to Air (°C/W) to calculate the power dissipation. So for example if the value of this parameter is 250°C/W, should I ...
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Resources for finding thermal impedances for common IC packages

I'm just looking for some extra resources for thermal impedances of JEDEC standardized packages. I've already found one such article posted by JRC, https://www.njr.com/semicon/package/thermal.html , ...
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121 views

Thermal Glue solvent

I have a PCB with many chips on it - it's a "hashboard" for an ASIC bitcoin miner. There are 63 chips on every hashboard, and each chip has a small heatsink on it. I tried heating the heatsinks with ...
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POWER MOSFET - Thermal Design

i have some doubts about with this thermal design? first, the calculations and infos: My load (a motor) uses an average current of 7A, I could not measure the current peak at the beginning of the ...
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1answer
54 views

Wire gauge and combined wires for 3D printer hotend through PCB

So I've been designing a wiring harness PCB for my 3D printer to provide connections and easily swappable tools. I settled on a TE 34-pin connector to use as input on the PCB. The current design ...
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1answer
161 views

LD1117V33 voltage regulator heatsink, thermal paste needed?

I want to screw a heatsink to my LD1117V33 voltage regulator. It's a normal 3mm screw and nothing inbetween. Do I need to use thermal paste or something like that? It will be regulating 12V down to 3....
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107 views

Water-Based Heat Sink

I am trying to incorporate a TEC in a portable system. The heat from the interior of the system needs to be transfered to the exterior where it can be dissipated freely into the environment. Now, I ...
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1answer
44 views

Cold activated heater control

I would like to build a simple control circuit for a 12v silicone heating pad. I think what I'm looking to make is a thermally controlled relay: I want current to flow when the temperature is below ...
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1answer
140 views

Circuit thermal analysis in PSPICE and temperature coefficients

I am tying to perform a thermal analysis in pspice. Resistors needs two temperature coefficients as TC1 and TC2 (if we assume linear change of R vs. T, it's zero) in pspice. But in resistor datasheets ...
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318 views

What is reasoning behind the common wisdom of limiting the temperature rise of a PCB trace to 5/10/20°C?

When deciding on the trace thickness required to carry a certain amount of current on a PCB, the answer depends on how much temperature rise you are willing to accept. This leads the designer into the ...
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127 views

Understanding the thermal images of planar pcb coils

Why is only the first turn in the coil hotter compared to other two turns? In this, only the turns of the top part seem to be hotter compared to the bottom. Current through the coils is 2 A. It is ...
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1answer
59 views

General Peltier-tivity

[EDIT: Found a couple of 12715 units in the pile that did suck the full amperage, but despite excellent cooling of the hot side, could not deliver much cooling.] I'm waist deep in project to keep ...
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1answer
66 views

Open-circuit alternator

Is it dangerous to run a permanent magnet alternator open-circuited? No current can flow so is all the power dissipated as heat? Is there even power generated in the inductive coils?
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Modeling the thermal part of the Time-current curve

G’ day, I am working on designing protection devices for my research work and I am struggling to model the thermal part for the low voltage circuit breakers based on IEC standards. Based on the ...
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1answer
65 views

Is there a difference between a tempco resistor and a thermistor?

That is, other than just the nomenclature.
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2answers
77 views

Temperature specificiations on MOSFET Safe Operating Area

Here's a SOA graph: What I don't fully understand is the notes area at the bottom: *Notes: Tc=25°C Tj=150°C Single pulse Every MOSFET datasheet seems to have a similar set of notes,...
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277 views

How do I determine the junction-to-ambient thermal resistance?

For a project I'm working on, I was considering using an AS7805 to supply low-noise 5V power to some sensors. (due to the uncertainty that resulted in asking this question, I've since changed to a ...
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2answers
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LM317 - Calculate dissipation due to voltage drop

If I use a linear voltage regulator as LM317: Input voltage = 24 V Output voltage = 5 V (so a voltage drop of 19 V) Mean load = 480 mA (peak load = 700 mA) From the datasheet, I read that maximum ...
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2answers
53 views

Magnitude of \$I_{CBO}\$ in a typical transistor

I read in a book that \$I_{CBO}\$ doubles for every 10 degree rise in temperature and hence contributes to thermal runaway. However I am confused since essentially it is the reverse saturation current ...
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Why are electrically insulating heatsinks so rare? Is it just cost?

Edit: It seems my initial question (Why are there no insulating heatsinks?) was based on a false premise, and there are in fact insulating heatsinks--I just wasn't able to find them with a cursory ...
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117 views

Thermal calculation in case of duty cycle for a mosfet

For a multiplex LED matrix, I am intending to use two ULN2803's as sink source for 16 times 20 mA per column (channel). However, maybe I will try a test with 100 mA LEDs (10% duty cycle). For that I ...
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1answer
40 views

Thermal generation of electron-hole couples and reverse biasing

I'm studying the PN junction and I have some problems figuring out thermal generation of couples electron-hole in reverse biasing. The analysis is the standard one (for example, one can find it in the ...
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1answer
59 views

Macroscopic physical significance of Thermal Voltage in Diodes

Everywhere I search, the thermal voltage in diodes is described either as the microscopic property related to the average energy of electrons due to thermal motion The constant in the ideal diode ...
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1answer
55 views

How do I exactly calculate the amount of heat generated in MOSFET?

I am using two IRFP260N MOSFETs (datasheet) in parallel for my application. I am using it to drive a motor rated at 24VDC and consumes 8 to 10 Amps. I found some answers here and calculated the ...
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2answers
189 views

Why should the bias servo transistor not be placed on the main heat sink for a Sziklai pair?

The Wikipedia page on Sziklai pairs contains the following statement (emphasis mine) Sziklai pairs can also have the benefit of superior thermal stability. [...]. [Q]uiescent current is much more ...
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284 views

Cooling Methods for Voltage Regulators

I have a NCP1117 5V voltage regulator that is on an Arudino Mega. The Arduino Mega, with all of the necessary electronics parts for the project, draws around 200mA when operational. When using a ...
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1k views

heat dissipation in watts of equipment in a box

Here is the situation, some electrical equipment will be in low ambient temperatures and I need to make it warmer so that there is no damage to it. I want to calculate how much power in watts is ...
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Thermal Faliure of thermal overload protected ICs

I have encountered a number of instances now where ICs that supposedly include "thermal overload protection" will still heat up until they fry. Examples: LM338,LM2576. These devices datasheets ...
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1answer
71 views

Heating issues with solar charging circuit

I am using the above circuit to charge a 7.4V Li-ion Battery.With input MPPT voltage set at 12V, I have applied 13V input voltage to the circuit. The battery is charging at 1.4A. (according to the ...
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2answers
80 views

Does this circuit adequately represent the thermal considerations for a boost converter?

I'm new to electronics, and I'm trying to use a boost converter to get 5V at 1.2A from a lithium ion battery. I've selected the TPS61232 step up converter for this solution. The datasheet has a ...
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2answers
157 views

install heatsink on BJT

I am facing the problem with the heat of transistor disturb sensor reading. Here the link refer problem I am using BC548 transistor. It is a bit hot when operating because it disipates power around ...
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2answers
592 views

Shot or thermal noise of a MOS transistor

I'm trying to compare the shot and thermal noise contributions in a MOS transistor. In the literature, the above-threshold MOS transistor has only thermal noise, which is found by integrating the ...
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1answer
233 views

Control board powered up with reverse polarity. power transistor blown. Is this repairable? [closed]

My dog chewed through the power cord. I 'repaired' it not paying attention to polarity. It was a 2A, 9V wall wart type power supply. The motherboard is from an elliptical exercise machine. The one ...
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292 views

Wha't the difference to use the junction to case thermal resistance instead of the junction to lead thermal resitance?

In case I have a diode, and I want to know it could dissipate the power, I have two values, but I can't choose between them: - Junction to ambient thermal resitance \$R_{ja}\$ - Junction to lead ...
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800 views

How do electrons carry thermal energy in Peltier coolers?

I've read that when electrons enter from metal to semiconductor type N, they gain thermal energy and make that side cooler and the reverse happens when they leave semiconductor to the conductor. Why ...
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50 views

Am I misunderstanding steady state power disspation calculations?

I am looking at the Littlefuse 5KP series. It says on the datasheet: I am trying to understand how they arrive at \$P_D\$ = 8.0W. Given thermal resistances of 40°C/W or 8.0°C/W, and 100°C ...
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295 views

Where would Iceo flow through and would it cause thermal runaway?

I was reading this page about thermal run away. And it mentions: Due to increase in the temperature of collector junction, Ico will increase, Vbe will decrease. But for Ico to increase Ic and ...
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4answers
651 views

MOSFET thermal resistance

I am trying to calculate the total thermal resistance of my FET to see what heat sinks are required, are the following calculations correct? $$ Power = \frac{T_{jmax} - T_a}{\theta_{JC} + \theta_{CA}}...
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1answer
123 views

Name of fabric insulator found inside motors

What is the name of the fabric sleeve insulator used for components (typically fuses) and solder joints found inside motor windings? Can regular heat shrink tubing be used as a substitute? Image by ...
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Can a thermal fuse of a higher rated current be used safely?

I want to replace a 115°C 250V 2A thermal fuse used in a fan motor. The only fuses available locally are 115°C 277V 15A. Can I use the higher current rated thermal fuse? Since it is a thermal fuse, I ...
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1answer
308 views

IC product lifetime as function of junction temperature

If an IC is rated for an absolute maximum junction temperature of say 170 Celsius, obviously it is not recommended to operate there - but how drastically is product lifetime impacted if we are close, ...
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86 views

May I use a smaller wattage resistor as mosfet's gate driver for a very short time?

In a H-Bridge circuit, i am using gate resistors on all the mosfets. My calculations for one of them, Gate voltage 4.5 V and Resistor 100 ohm gives me 45 mA, means 203 mW. In a pulse of 16 us i ...
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1answer
50 views

Thermal hysteresis of shunt regulator

What is the meaning of the "Thermal hysteresis" in shunt regulator datasheet ? Will it contribute to output tolerance ? FYI: It's TL4050C50-Q1 datasheet.

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