# Tag Info

6

Like Aaron said, a topology with a transformer allows for better control of the step down/step up voltage. A duty cycle of 7% seems fine on paper, but in reality you should aim for closer to 30%. In an application with changing load that 7% nominal duty cycle can drop down to 1 or 2% with low or no load. When using a PFC, especially a boost PFC, the 400V(...

4

Those two diodes perform a useful function when the external load is connected between the power supply outputs (this configuration doubles the voltage potential of the positive rail). In this case, if the load becomes short circuit then the two outputs will fight each other, one will become dominant and in this situation the diodes prevent one of the ...

4

A buck converter is a circuit that reduces an input voltage to a lower voltage with a higher current capacity. A boost converter or step-up booster increases an input voltage to a higher voltage with a lower current capacity. Those two terms are circuit descriptions and may be parts of more complex equipment including power supplies. However they be ...

4

With a simple buck converter, you only have one degree of freedom, the duty cycle. And as you are noticing, the duty cycles for those input:output ratios are very small. With a transformer design like a flyback, you get two degrees of freedom, the duty cycle and the transformer winding ratio. Usually you design the winding ratio so that you can be in the ...

2

The problem is probably interference between the power supply and the telephone line. Telephone lines and power lines should be isolated from one another, but cheap devices (the DTMF decoder, or the power supply, or both) may skimp on isolation - if it were a circuit with a speaker, you would hear a loud humming noise. This goes along with the USB ...

2

The circuit is easier to understand if it is redrawn so that voltages increase strictly from bottom to top. I've drawn the rectifier as a floating voltage source for simplicity. Since ground is defined as the point between the two output capacitors, then D15 establishes the most negative voltage as -13V. D14 then puts the ADJ pin of the regulator at +12V, ...

2

Can 5V kill you? Short answer: YES ...BUT....you'd have to broach the skin to subcutaneous layers or have lots of blood exposed in positions either side of the heart. So with a frayed USB cable (both ground and +5V exposed) an impossibly low risk for such local contact. If your skin is intact the likely resistance is in the 10-100 kOhms range, so death ...

2

The simplest way to implement reverse polarity protection is to put a diode in series with the PTC fuse. If the voltage on pin 1 is negative with respect to ground, the diode will no conduct, and the circuitry downstream won't see the negative voltage. Make sure the reverse voltage rating of the diode is large enough to handle any negative voltages you ...

2

You made the battery, shouldn't you be telling us what we need in order to charge it? Typically I would say you need a 400mA constant current with a voltage of 1.41V * number of cells. You would then charge it for 16 hours with some sort of timer. At that rate it would be fairly safe regardless of discharge level, but you still don't want to leave it ...

2

A line and neutral of a 208-volt distribution system will provide 120 volts. That is only a bit more than half of the needed 220 volts. Any 220-volt load will operate very poorly or not at all. If you can get two 120-volt hot lines from a 208-volt system, you will have 208 volts. That would probably provide reasonably acceptable operation for many 220-volt ...

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Further Datasheet research lead me to find that the popular 741 OpAmp was the replacement IC.

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A buck converter takes a voltage and outputs a lower voltage. A step-up booster takes a voltage and outputs a higher voltage. A power supply is a more generic term for either of these.

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Does it really protect my digital circuit in case of Hazardous situations like lightening and others? The data sheet says this about surges: - EN55024, heavy industry level (surge L-N : 1KV), criteria A And all that means is that the unit will survive a 1 kV surge when applied to the AC lines. It doesn't mean that a surge will not produce a knock-on ...

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The good and proven recipe is in the laptops. They use buck regulators everywhere on the motherboard. So I would recommend it to you as well. Just use buck regulator with parameters you like.

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This answer does not attempt to address your real question but is only to clarify your understanding. This is my problem, I bought this circuit to receive caller ID over protocol DTMF. As JRE has pointed out, you are confusing DTMF (dual-tone, multi-frequency) with Caller ID. Figure 1. DTMF frequency matrix. Pressing any button transmits the row and ...

1

Being exposed to 5V for extended times is absolutely harmless. Nothing to worry about. However, you should still replace the cable. A frayed cable can create partial for full shorts and these can damage the charger or the phone and result in things overheating or breaking. The cable connector itself could get hot too.

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Section 14.1 of the datasheet tells you why - the supply is monitored to allow it to switch over to the backup battery if and when it fails, and needs to not fall by more than a specified rate, such that the monitor circuit has time to make the switch over before power is lost.

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For consumer use, it is not popular, for light industry it is not common, but for heavy industry (MVA generation) as long as somewhere in the system design there is isolation and safety earth ground, there is no restriction for isolation if no service access is needed or safety hazard imposed in use. You are likely never to see the latter unless you are ...

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Look into a multiwinding flyback converter. That is likely to be least cost option. You should further consider isolation voltage requirements, isolation capacitance requirement, and required power ratings also.

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