DC converter
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From: legg on 19 Feb 2010 06:42 On Thu, 18 Feb 2010 12:16:57 -0800 (PST), john <conphiloso(a)hotmail.com> wrote: >Hi, > >I am using the following function generator to produce a 60Hz , >16Volts peak to peak output voltage. > >http://www.globaltestsupply.com/datasheets/4011a.pdf > This is an analog signal generator with an output impedance of 50 ohms, referenced to ground. If you ground an output from the bridge with a scope probe, you change the schematic to a half-wave rectifier, giving 16V/2 - 2 x diode drops. RL
From: Hammy on 19 Feb 2010 08:12 On Thu, 18 Feb 2010 12:49:51 -0800, Jon Kirwan <jonk(a)infinitefactors.org> wrote: >On Thu, 18 Feb 2010 12:16:57 -0800 (PST), john ><conphiloso(a)hotmail.com> wrote: > >>The bridge rectifier is hooked up to the function generator and the >>output of the bridge rectifier is going to the DC to DC Converter's >>pin 3. > >A function generator is _feeding_ the bridge? > >Jon Your function genarator even if you hook everything up correctly as others have suggested likely is'nt up to the task you are useing it for. When you use a bridge cap input the cap gets recharged in current pulses which your FG is probably crapping out on. Assumunig your buck is the 1.75w Buck in the AN your FG would have to supply takeing into consideration rectifier and SMPS conversion losses about 2.1W. It would have to supply larger peak power to charge the caps which its likely not able to do.The more current it provides the less the output voltage would be.Plus the other problems people have mentioned.
From: JosephKK on 19 Feb 2010 10:14
On Thu, 18 Feb 2010 12:16:57 -0800 (PST), john <conphiloso(a)hotmail.com> wrote: >Hi, > >I am using the following function generator to produce a 60Hz , >16Volts peak to peak output voltage. > >http://www.globaltestsupply.com/datasheets/4011a.pdf OK. Coming out of the gate you have introduced major problems by using a laboratory signal source as a power source. Get a decent audio power amplifier (50 W should do it), feed it from the 4011, and use that combination as the substitute for a transformer. > >I am using following DC to DC converter and Bridge Rectifier > >http://cds.linear.com/docs/Datasheet/3970f.pdf > >http://www.diodes.com/datasheets/ds17002.pdf > >The bridge rectifier is hooked up to the function generator and the >output of the bridge rectifier is going to the DC to DC Converter's >pin 3. I am using the ciruit as given on the first page of the data >sheet except I used two capacitors in parallel instead of 2.2uF , 50 >volts 10uF and 1uf 50v capacitor at the input input Vin. > > So, if the input voltage is 16 volts peak to peak , then after the >bridge I get nearly 6 volts (measured by scope) at the output of the >bridge and I get 3.6 volts (measured by voltmeter) at the output of >the DC to DC converter. This is caused by the internal impedance of the 4011. You should see about 14 V peak. and read about 12 with an average reading voltmeter (both cases without filter cap). > >The DC TO DC converter suppose to output 5 volts. but it is outputting >3.7 volts. I am unable to understand what is the problem. I hooked up >the DC to DC converter to the power supply and it produced 5 volts but >with bridge rectifier, it is not producing the appropiate voltage. Am >I using the wrong capacitor values? Please advise! > >John |