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Electronic Equipment > Electronics Design > Feedback for lo...
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Feedback for low frequency PWM regulator

by "JMini" <j.minihane@[EMAIL PROTECTED] > Jul 4, 2008 at 08:44 PM

I'm building a PWM regulator for an incandescent bulb. Some of thos was
described in a thread called "RMS Approximation of PWM/Square wave". In
any
case. Since there is no inductor/diode/cepacitor in the output stage I'll
be
using an RMS converter (LTC1968). For the PWM section I'm using the
MIC1557
(SOT-23 size 555 equiv) for a R-C sawtooth to a comparator (TLV7211a)
inverting input. I can choose the frequency (probably in the 200-800Hz
range). The feedback is sent through the LTC1968 RMS converter to the FB
pin
(0.8V) of a tiny (SC-70) 5mA voltage regulator (OnSemi NCP102). It's
really
just a powerful error amplifier. The Output of that is sent to the
non-inverting input of the comparator. So if the feedback voltage drops,
the
NCP102 increases voltage ot the non-inverting input of the TLV7211, thus
increasing duty cycle. I've tested this type of layout on breadboard using
different components. I got to thinking though.
Question:
Would it be possible to use a resistor divider between the MIC1557 and
comparator to reduce the voltage of the sawtooth and feed it to the
NON-inverting comparator input and send the RMS converter output directly
to
the INVERTING input of the comparator? That way, a falling output voltage
would cause a reduction in voltage to the INVERTING input and increase
duty
cycle? I could reduce the component count.
I realize there is no true reference voltage in the system, but since the
1557 is fed from a fixed 5V source, the sawtooth would be a constant 5*1/3
to
5*2/3 V. Thoughts guys?
 




 65 Posts in Topic:
Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-04 20:44:37 
Re: Feedback for low frequency PWM regulator
Martin Griffith <mart_  2008-07-04 22:59:49 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-04 21:20:56 
Re: Feedback for low frequency PWM regulator
"Mook Johnson"   2008-07-04 16:39:52 
Re: Feedback for low frequency PWM regulator
"Phil Allison"   2008-07-05 10:23:20 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-06 13:19:50 
Re: Feedback for low frequency PWM regulator
John Popelish <jpopeli  2008-07-04 19:13:09 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-06 13:23:49 
Re: Feedback for low frequency PWM regulator
John Larkin <jjlarkin@  2008-07-04 18:06:10 
Re: Feedback for low frequency PWM regulator
Martin Griffith <mart_  2008-07-05 09:18:21 
Re: Feedback for low frequency PWM regulator
legg <legg@[EMAIL PROT  2008-07-05 20:50:32 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-06 13:38:03 
Re: Feedback for low frequency PWM regulator
legg <legg@[EMAIL PROT  2008-07-06 23:01:11 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-07 13:02:22 
Re: Feedback for low frequency PWM regulator
legg <legg@[EMAIL PROT  2008-07-07 22:11:09 
Re: Feedback for low frequency PWM regulator
legg <legg@[EMAIL PROT  2008-07-08 10:58:49 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-14 12:45:59 
Re: Feedback for low frequency PWM regulator
legg <legg@[EMAIL PROT  2008-07-14 09:06:25 
Re: Feedback for low frequency PWM regulator
John Popelish <jpopeli  2008-07-14 12:00:30 
Re: Feedback for low frequency PWM regulator
nospam <nospam@[EMAIL   2008-07-14 16:59:51 
Re: Feedback for low frequency PWM regulator
legg <legg@[EMAIL PROT  2008-07-14 12:08:51 
Re: Feedback for low frequency PWM regulator
jpopelish@[EMAIL PROTECTE  2008-07-14 15:58:26 
Re: Feedback for low frequency PWM regulator
"HarryD" <ha  2008-07-07 15:25:55 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-07 16:56:39 
Re: Feedback for low frequency PWM regulator
"HarryD" <ha  2008-07-09 18:20:48 
Re: Feedback for low frequency PWM regulator
nospam <nospam@[EMAIL   2008-07-10 00:24:05 
Re: Feedback for low frequency PWM regulator
"HarryD" <ha  2008-07-11 15:44:22 
Re: Feedback for low frequency PWM regulator
John Popelish <jpopeli  2008-07-11 13:33:59 
Re: Feedback for low frequency PWM regulator
"HarryD" <ha  2008-07-11 20:46:27 
Re: Feedback for low frequency PWM regulator
nospam <nospam@[EMAIL   2008-07-12 13:08:12 
Re: Feedback for low frequency PWM regulator
"HarryD" <ha  2008-07-12 19:02:09 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-14 12:54:13 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-14 13:00:34 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-16 18:13:10 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-16 19:29:04 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-16 19:45:36 
Re: Feedback for low frequency PWM regulator
"HarryD" <ha  2008-07-16 21:05:57 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-17 00:31:14 
Re: Feedback for low frequency PWM regulator
"HarryD" <ha  2008-07-18 15:22:08 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-20 15:50:59 
Re: Feedback for low frequency PWM regulator
"HarryD" <ha  2008-07-20 17:21:18 
Re: Feedback for low frequency PWM regulator
nospam <nospam@[EMAIL   2008-07-07 17:55:21 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-07 17:13:32 
Re: Feedback for low frequency PWM regulator
nospam <nospam@[EMAIL   2008-07-07 18:52:46 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-07 18:25:29 
Re: Feedback for low frequency PWM regulator
nospam <nospam@[EMAIL   2008-07-07 20:58:00 
Re: Feedback for low frequency PWM regulator
Spehro Pefhany <speffS  2008-07-05 09:52:26 
Re: Feedback for low frequency PWM regulator
Spehro Pefhany <speffS  2008-07-07 16:52:45 
Re: Feedback for low frequency PWM regulator
"HarryD" <ha  2008-07-07 18:29:51 
Re: Feedback for low frequency PWM regulator
Spehro Pefhany <speffS  2008-07-05 09:41:00 
Re: Feedback for low frequency PWM regulator
nospam <nospam@[EMAIL   2008-07-07 21:44:10 
Re: Feedback for low frequency PWM regulator
Spehro Pefhany <speffS  2008-07-07 16:59:34 
Re: Feedback for low frequency PWM regulator
"HarryD" <ha  2008-07-07 18:22:29 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-07 19:58:36 
Re: Feedback for low frequency PWM regulator
Jamie <jamie_ka1lpa_no  2008-07-07 17:37:33 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-08 10:22:38 
Re: Feedback for low frequency PWM regulator
"HarryD" <ha  2008-07-07 20:08:49 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-07 20:14:43 
Re: Feedback for low frequency PWM regulator
"HarryD" <ha  2008-07-07 20:35:53 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-08 10:18:31 
Re: Feedback for low frequency PWM regulator
"HarryD" <ha  2008-07-08 15:01:22 
Re: Feedback for low frequency PWM regulator
Jim Thompson <To-Email  2008-07-08 09:25:43 
Re: Feedback for low frequency PWM regulator
"HarryD" <ha  2008-07-08 16:48:43 
Re: Feedback for low frequency PWM regulator
"JMini" <j.m  2008-07-14 12:48:42 
Re: Feedback for low frequency PWM regulator
Jamie <jamie_ka1lpa_no  2008-07-14 20:07:06 

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tan12V112 Sat Nov 22 11:47:46 CST 2008.