9 votes

1500W wirewound resistor tripping house fuse 20A / 120V

You have connected the line and neutral wires to the threaded rod that holds the mounting bracket on, essentially shorting them. The real terminals are the ones sticking straight up. Also, please ...
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  • 7,220
8 votes

1500W wirewound resistor tripping house fuse 20A / 120V

Disconnect the resistor and measure the value to verify it is what you ordered. Mistakes happen. Short your multimeter leads first to determine the '0' value and subtract that from the subsequent ...
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8 votes

Why don't we make negative output voltage like this?

You're on the right track for one fairly common method of generating a negative output voltage. Take a look at the circuit below: simulate this circuit – Schematic created using CircuitLab The ...
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  • 20.2k
5 votes

Why don't we make negative output voltage like this?

Your idea is correct, in that the polarity of the output of a single supply just depends on which one you "call positive". You could connect any component or circuit to the output to get one ...
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  • 8,348
4 votes
Accepted

Reverse recovery time of diodes and its effect in buck converters

Your general understanding of the diode behaviour is correct. When the FET turns on, the voltage at its drain doesn't begin to fall until the FET's current exceeds the inductor + diode reverse ...
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  • 13.9k
4 votes
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Why does a flyback converter in DCM mode have a different oscillation waveform at start and end of MOSFET turn off?

Why does this primary inductance not participate during turn off or why does the leakage inductance not participate in oscillation before turning on? There is only one coupled inductor, right? Image ...
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  • 385k
4 votes
Accepted

Simple question on finding Watts and Wrms

Watts peak makes sense. Watts RMS does not (because there is no such thing). You are calculating watts average. I would generally use the formula \$ W_{peak} = V_{peak} \frac {V_{peak}}{R_{load}} \$ ...
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  • 160k
4 votes
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Where to connect the heat sink / body of SPX29300 voltage regulator?

In such cases always check the most recent datasheet provided by the manufacturer because the ones you can find on datasheet databases could be old enough not to be relied on. At p.4 it's indicated ...
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3 votes

High Side Driving of IGBT

If you want to drive your IGBT high-side, you need a floating/isolated gate drive voltage referenced to its source, which none of your schematics have. Note, if you manage to turn it on hard, it will ...
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  • 60k
3 votes
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Is there such thing as a tunable DC/DC converter?

You seem to be confusing two things: Voltage regulation, and adjustable output. Any circuit sold as a "voltage regulator" should adjust its behavior to provide the same output voltage when ...
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  • 121k
3 votes
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What is the current across the resistor given in the figure?

If you assume the 3A current flows across the short, then the voltage across the 30Ohm resistor is 0V and since the current source is ideal, it can have any voltage across it (even 0V), hence the ...
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  • 46
3 votes

Amp reading on multimeter significantly varies depending on port

A single solar cell only generates about 0.5 V (as your rating indicates). Many DMMs have a significant resistance in some of the current ranges -- needing 100-500 mV or higher voltage drop across the ...
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  • 13.9k
3 votes

Why does a flyback converter in DCM mode have a different oscillation waveform at start and end of MOSFET turn off?

In addition what Tim says in his answer which is absolutely correct, I'd like to remind you that in CCM the primary winding is not allowed to reset (the stored energy will be partially transferred to ...
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2 votes

Why does a flyback converter in DCM mode have a different oscillation waveform at start and end of MOSFET turn off?

Draw out the circuit and note which components are on and off (transistor and diode) during which phases. Then simplify the equivalent circuit for each phase: While transistor is on, it becomes an ...
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  • 3,062
2 votes

Importance of power factor

It's a quirk of the way that the electricity supply industry has developed that domestic consumers are only billed for the active power they use. Fortunately, this matches most of the generator's ...
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  • 142k
2 votes

Simple question on finding Watts and Wrms

You can measure power at any instant such as peak or averaged over 1 cycle, never RMS power. THe sine power appears as a sinusoidal power of 2f ranging from 0 to peak with a flat average of 50% of the ...
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2 votes
Accepted

How to avoid square wave parasitic oscillation?

Your design has the wrong threshold to act as Schmitt Triggers on slew-rate limited pulses in order to create "complementary-exclusive transitions" or a "deadtime control circuit." ...
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2 votes

High Side Driving of IGBT

You need a gate drive DC voltage, that is relative to the emitter of the IGBT, not relative to GND. The "safety off" resistor at the gate should be between gate and emitter or you risc ...
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  • 2,231
1 vote

Dynamic Power Path Management (DPPM): Why does the output voltage drops when the current exceeds the adapter's limit?

Your diagram shows that USB is a possible power source for the DPPM circuit. For something like USB, the host/charger is obligated to follow whichever parts of the USB specification it claims to ...
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  • 9,763
1 vote

Latching Comparator Problem

After analyzing on the oscilloscope per recommendation, it looks like there was a bunch of noise on the comparator inputs, and the no-latch condition is a result of transients. I solved the problem ...
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1 vote

Photovoltaic solar cell attached to load device

"I want to run a load off solar, but I don't want to involve a battery" gets asked a lot. It is a grail, but not a very workable idea IMO. You are dealing with hypothetical MPPT controllers ...
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1 vote

Photovoltaic solar cell attached to load device

If you try to withdraw too much current from the system, reality hits you hard in your face. The voltage at the load will drop, it can't stay at the set level. There's no energy to maintain the ...
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  • 1,051
1 vote

(Very) high frequency plasma tweeter

There are very few transformers that offer high output voltages and high bandwidths. Especially wide bandwidths (min/max ratio). There is a physical limitation at play here. Must the arc be direct ...
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  • 3,062
1 vote

Simple question on finding Watts and Wrms

The term ‘RMS’ applies to voltage and current. It does not apply to power. So that’s part of the problem.
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1 vote

Cleaning PWM input signal to reduce heating of H-bridge

Between the [14V by 50us] square wave out from the OEM controller and the voltage divider output [5V by 50us] going in to the BTS, there is a lot of distortion happening. The BTS7960 has cmos schmitt ...
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1 vote

How to calculate the scale factor of non-linear ADC output value?

So you have a scale and zero error. V = 1.019*ADC_READING + .047mV, based on the points above. Chances are the best gain factor is somewhat different from 1.019- to get an accurate factor, pick points ...
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1 vote

Types of air gaps

The cores with the gap in the center minimize fringing flux related EMC issues. The loop the magnetic flux travels crosses only one air gap in the cores with a gap in the center leg. The other types ...
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1 vote
Accepted

Step-Up Converter Design

With such a high boost ratio, my calculated duty cycle would be ~92% which is near the maximum for most controller ICs It's ~90% duty when operating in continuous conduction mode (CCM) but, if you ...
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  • 385k

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