# Questions tagged [power-dissipation]

Anything related to power dissipation in electrical and electronic circuits and components, i.e. the process in which electrical energy is converted to heat when current flows through them.

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### Efficient Voltage Divider Battery Monitoring for 42V system

I'm designing a system that is powered from a 10S2P LiPo battery pack and I was looking for an efficient way to monitor the battery level. My microcontroller is 5V logic level, and I understand I can ...
1 vote
68 views

### Is it bad practice to connect a heatsink to my PCB's ground plane?

So, basically, I have this LED project which is going to dissipate lots of heat (I am assuming close to 50W) inside a case. The LEDs themselves are on a separate aluminum board which will be attached ...
39 views

### Current limiter for VOD3120AB

I want to supply VOD3120AB with a voltage of 24v/2A from Power Supply. What is the value of the Resistor that I must add to the VCC of the VOD3120AB so that the VOD3120AB works properly? Information ...
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1 vote
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### Power loss and voltage drop for a parallel wiring system

I'm looking to power a 50W load approximately 140m away using 48V DC. At the far end I will use a DC-DC converter to convert this to 12VDC where it will power a small DC powered network switch I have. ...
129 views

### Calculate power dissipation of split-supply op amp for sinusoidal input

I want to calculate the total supply current and power dissipation of an op amp in a non-inverting voltage follower configuration with a split supply: simulate this circuit – Schematic created ...
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1 vote
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### Buck regulator thermals calculations

Schematic: Specification: Vin = 24V Vout =5V Iout max = 8A Freq = 0.691 Mhz Assumptions: Good layout and FETs mounted on 1-2 inch^2 of copper. Calculations based on this doc: https://www.ti.com/lit/...
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1 vote
82 views

### Calculation of power dissipation of a MOSFET circuit

As a part of an assignment to design a common source amplifier, I came up with this circuit: simulate this circuit – Schematic created using CircuitLab The transistor is a 180nm technology with ...
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260 views

### Using 110 Vac incandescent light bulb at 220 Vac with a series diode

I have a 110 Vac incandescent light bulb but I need to use it in 220 Vac. If I add a diode in series with the bulb, the RMS power is the same as before but the peak value of voltage and current is ...
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193 views

### About power dissipation of capacitors and inductors & I-V phase difference

For instance, The Art of Electronics (by Horowitz & Hill) states that ideal capacitors cannot dissipate power, even though current can flow through them, because the voltage and current are 90° ...
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76 views

### Does voltage drop resistor affect power dissipation?

I need to power an RFID from 24 V DC voltage. The RFID requires max. 9 V and max. 120 mA. The RFID suggests a 7809 linear voltage regulator. I thought too much and I want to use a 7809 because if I ...
1 vote
55 views

### Mosfet power dissipation in this example

I am trying to design a buck regulator with the following specification: Vin = 24V Vout = 5V I max = 8A Fsw=300k. The load is basically a long strip of RGB LED's. Which in certain cases would be all ...
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88 views

### Is there a "rule of thumb" for power dissipation of an enclosed circuit to help determine when to do a thorough analysis?

I'm starting a project and the electronics will be enclosed in a wood sign outside. Even though it's shaded, I'm concerned about heat buildup in the summer. Is there some rule of thumb that says if ...
140 views

### LM317 is dissipating too much power

I used an LM317 in my circuit to get a regulated 1.5 volts output from a 3.7 volt battery using two resistors (220 and 60 ohm.) It worked fine, but the circuit dissipated too much power even when not ...
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154 views

### How to calculate the pulsating current flowing through a shunt resistor?

If the current flowing through the shunt (0.5 ohm) is in pulsating form (PWM with 50% duty cycle and 100 Hz frequency,) how do I calculate power loss through shunt in order to choose proper for ...
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229 views

### Buck / step down voltage in limited space

I am designing a small PCB. The supply voltage is 12V, but I also need 5V with supply of maximum 250mA. The most obvious solution is to use voltage regulator - there are plenty of them and some like ...
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254 views

### Calculation of heat generated by a battery pack

I have to calculate the heat generated by a 40 cell battery. The max. voltage is 4.2 V, nominal voltage is 3.7 V and the cell capacity is 1.5 Ah, discharging at a rate of 2 C. If I calculate the heat ...
1k views

### Can PCB dissipate heat from MOSFET so that a heatsink is not needed

I am using a DMP3007 as a reverse polarity and over voltage MOSFET. The maximum planned load is 10 A and voltage may vary as the load is a constant current load. simulate this circuit – ...
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119 views

### With a constant-current, constant-voltage power supply, does the total length of the wire affect the heat produced per metre?

This seems like it should be obvious, but I can't seem to get my head around it. If I have a length of wire 7 metres long and it has a total resistance across its whole length of 2 ohms, and I connect ...
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51 views

### use of power dissipation in transistor and using higher current rated transistor

I am using using a PNP transistor in one of my application to switch on and off the boost convertor. My requirement for collector current is 500mA. My question is does it matter if I use 500mA/600mA/...
68 views

### SiC MOSFETS power dissipation; for heat sink sizing

I want to calculate the max. power dissipated for SiC Mosfet in a 6.6KW CLLLC resonant converter with full bridges on primary and secondary sides. Let's consider the case when the input voltage is ...
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110 views

### Is power dissipation for SMD resistor rated only for air dissipation or air + PCB?

I know that PCB with good copper area will dissipate much more heat than air surrounding the resistor. However, the datasheet for Yageo resistors is vague about whether the dissipation ratings take ...
367 views

### Very hot live pin on kettle plug

I moved my kettle just after boiling it yesterday and noticed the live pin was very hot. None of the other pins are hot. It's a bs 1363 type plug and socket. And a <2 year old kettle. After a full ...
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### How to create a design that uses specific % of DFF and LUT count in FPGA to measure power dissipation?

I want to create a design which does not perform any specific useful function but utilizes specified amount of logic resource in the FPGA e.g 50% DFF and LUT or 50% DFF and 25% LUT e.t.c. I shall then ...
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68 views

### How to create a copper pad for heat dissipation in Eagle?

The data sheet for this component, the RPX-1.0, says SW Switch node. Connect 6, 7, and 8 to large copper pad for optimal heat dissipation. Is a "large copper pad" an extra component that ...
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138 views

### Heat sink sizing for LDMOS

There are many heatsink calculation Q&A's on SE that I've looked through. One very reasonable answer tells me that I can calculate heatsink C/W as follows: \frac{T_j - T_a}{P_d} - R_{JC} = R_{...
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### Power Dissipation - Sizing up Power Supply Needed

I wanted to understand what size power supply is needed for the following: I am getting confused with the Icc value and Ioh,Iol etc values in the datasheet. My question is, how much current will I ...
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257 views

### CAN physical layer fault conditions Short circuit to battery on CANH and CANL lines analysis

In case of short circuit to battery on CANH, would the current flow as analysed below ? This is in the case of CAN transceiver TJA1042T and I got the internal block of the transciever by NXP. Data ...
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1k views

### How to be sure that a ceramic capacitor can manage a RMS current?

I'm in the middle of a design and I need a capacitor of: 10µF Rated at 10V Has to handle a ripple current of 250mA RMS, at 400kHz Most electrolytic capacitor data sheets give a maximum RMS value for ...
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### How can I determine PD for given impulse, based on transient thermal impedance for BJT?

I have (selected) a BJT to work with rectified mains application. Transistor is PBHV9560Z (600 V, 0.5 A PNP) https://assets.nexperia.com/documents/data-sheet/PBHV9560Z.pdf Under normal operation ...
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105 views

### Power dissipation calculation for FPGA-ADC interface

An FPGA can be interfaced with an ADC using CMOS or LVDS. Is there a way to use simulation to predict the power dissipation of the I/O blocks for a given operating frequency for this interface? If so, ...
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### Maximal power dissipation of the resistances in this circuit

Assuming I have this circuit below with : Ic = 200mA , β = 100 , UCE = 15 V So with some calculations : Ib = 2mA , R1 = 4k7 Ohm , R2 = 75 Ohm If I want to calculate the power dissipation of both URV1 ...
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### How can FPGA differential signal use lower power when it has two lines instead of one?

I am a bit confused about differential signaling on FPGAs. I am trying to figure out how does power dissipation in FPGA differential signaling compare with power dissipation in FPGA single ended ...
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303 views

### Can I choose a heatsink based on its thermal design power (TDP) for cooling LED chips?

I am confused about TDP ratings and what they refer to actually. The reason I am confused is because most modern CPUs and GPUs, although not ideal, are able to sustain very high temperatures (80 C or ...
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### Power input connector for power distribution board

I have been looking at several different power distribution module designs and the all seems to use a large bolt for the main power input. I am curious what these connectors are called and how they ...
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1 vote
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### Power dissipated between two points

In the follwing, if the power dissipated between a and b is 210 watts, what is the value of Vb?
81 views

### How does complex loading affect an op amp's power dissipation

I'm trying to calculate power dissipation in a complex load. I know that the power loss due to the resistive component is dissipated, and that the power loss due to the reactive component is canceled ...
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136 views

### TTL Gates Power Dissipation Values

I am not finding any datasheets that provide clear information about the power dissipation of some gates of the 74LS series: 08, 02, 04, 00, 32 and 86. Can someone help?
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### Reduce DC power supply for battery charging

I have a DC power supply from either a WIFI router or printer (not sure) rated for 13.5V @ 1.2A output. This is a replacement charger for an electric ride on car as it was originally 6V and I've ...
83 views

### Comparing power consumption of different FPGAs

I want to compare power dissipation of FPGAs from different vendors, the I/O count and the logic resource shall be matched as close as possible when choosing the FPGAs. I want to create a trivial ...
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166 views

### Lower duty cycle less efficient?

Assume you have a DC voltage V, ideal switch (no switching losses) operating at some frequency f and duty cycle ...
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100 views

### Over voltage protection IC keeps burning

I am currently working on a project where over voltage protection is necessary. I made a test circuit using an LP5300 (SOT23-6 type.) https://datasheet.lcsc.com/szlcsc/1912111437_LOWPOWER-...
422 views

### Mosfet Thermal Resistance calculation

I went through the application notes of infineon and TI. In the datasheet on the MOSFET, there is a junction to case Thermal Resistance given. Can we use these values to calculate the power ...
1 vote
189 views

### Finding the power dissipation in a wye-connection given resistors

The problem that I'm attempting to solve is the following: Three 1000 Ω resistors are connected in Y to a 200-Vac line. The power dissipation of the Y combination would be _____W. a. 42 b. 41 c. 40 d....
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1 vote
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### Why do I get such high values when calculating the power dissipation of MOSFET in boost-converter circuit?

I'm a hobbist interested in electronics so I don't have any "professional" training on that. Currently I'm trying to design a boost converter and now I'm stuck at some calculations. I wonder ...
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### Calculate voltage drop across Linear MOSFET in saturation region

Considering the below schematic, how is the voltage drop across the MOSFET calculated when it is operated in the saturation region? I am trying to calculate the power dissipated by the MOSFET so that ...
1 vote
60 views

### Can I exceed the 120mA per channel on the TLC5940 if I use external resistors in series with LEDs?

Datasheet The TLC5940 drives 16 channels of LEDs at constant current using PWM. I assume the 120mA limitation per channel as described in the datasheet has to do with how much power the HTSSOP ...
83 views

### Am I calculating my shunt FET power dissipation correctly?

simulate this circuit – Schematic created using CircuitLab I'm designing an LED driver circuit that requires very fast PWM switching at a high resolution (10bit at 30khz requiring a minimum ...
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1 vote
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### High thermal load PCB for short duration

I got 30 buck converters on 4 layer pcb (70x130mm). Each will dissipate ~2W for typically 30 seconds followed by a very long break >10min, and I'm worried about overheating. Although it is not a ...
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