voltage regulator that drops out of circuit
 

i have a flat panel TV/monitor that's going in a motorhome, it's powered via
a switched mode psu from the mains, which takes 230 volts in, gives 12.33
volts out,

the motorhome uses a 12 volt battery, so most people just connect the tv to
the battery and it all works,

however i've heard of a few people with this type of TV that have had
problems when they are hooked upto shore power, the battery charger being
on-line produces upto 14.8 volts, also if the tv is used when driving for
some reason, the alternator ups the voltage the TV sees to 14.4 volts,

and as the TV is designed to work on exactly 12.33 volts, part of it burns
out when it's fed a higher voltage.. i know this shouldent happen, but it
does, and the TV's makers say the tv was designed for home use not vehicle
use, and it's electronics are optimized for 12.33 volts only, that should be
supplied by the main adaptor, not the 11 to 15 volts automotive electrical
items are designed to handle.

the people who have used this TV in their motorhomes had no problems when
they're not on mains power so the battery charger is off line, the tv works
fine on 12.8 right down to 11 volts, way past when most 12 volt CRT tv's
have turned off, so undervoltage is not a problem really, jsut overvoltage.

So.. i need to build a voltage regulator to power the TV, it pulls 4 amps
max, that's not a problem at first sight,

but voltage regulators need their input voltage to be above the output
voltage, and that's where my problem is,

when the battery is on charge it will have a terminal voltage of 14.8 volts
for a few hours while the charger equalizes the battery bank, then it'll
settle to around 13.8 to 14 volts, still too high for the TV.
when i'm boondocking, the battery will start off at 12.8 volts, and fall as
i use power, i'll stop drawing power when the terminal voltage reaches 11.5
volts usually.

is there a regulator circuit out ther that can handle the 4 amps throughput
i need, and when the voltage is over 12.33 volts on the input side, limit
the output to that voltage, but when the input voltage reaches or goes below
that voltage, it drops out of the circuit? or is able to just pass the
voltage straight through it unregulated.. untill it gets over 12.33 volts
again when i start the engine or plug into a power socket.. where it
regulates the voltage again??

voltage regulator that drops out of circuit
 

"CampinGazz" wrote in message
...
i have a flat panel TV/monitor that's going in a motorhome, it's powered
via
a switched mode psu from the mains, which takes 230 volts in, gives 12.33
volts out,

the motorhome uses a 12 volt battery, so most people just connect the tv
to
the battery and it all works,

however i've heard of a few people with this type of TV that have had
problems when they are hooked upto shore power, the battery charger being
on-line produces upto 14.8 volts, also if the tv is used when driving for
some reason, the alternator ups the voltage the TV sees to 14.4 volts,

and as the TV is designed to work on exactly 12.33 volts, part of it burns
out when it's fed a higher voltage.. i know this shouldent happen, but it
does, and the TV's makers say the tv was designed for home use not vehicle
use, and it's electronics are optimized for 12.33 volts only, that should
be
supplied by the main adaptor, not the 11 to 15 volts automotive electrical
items are designed to handle.

the people who have used this TV in their motorhomes had no problems when
they're not on mains power so the battery charger is off line, the tv
works
fine on 12.8 right down to 11 volts, way past when most 12 volt CRT tv's
have turned off, so undervoltage is not a problem really, jsut
overvoltage.

So.. i need to build a voltage regulator to power the TV, it pulls 4 amps
max, that's not a problem at first sight,

but voltage regulators need their input voltage to be above the output
voltage, and that's where my problem is,

when the battery is on charge it will have a terminal voltage of 14.8
volts
for a few hours while the charger equalizes the battery bank, then it'll
settle to around 13.8 to 14 volts, still too high for the TV.
when i'm boondocking, the battery will start off at 12.8 volts, and fall
as
i use power, i'll stop drawing power when the terminal voltage reaches
11.5
volts usually.

is there a regulator circuit out ther that can handle the 4 amps
throughput
i need, and when the voltage is over 12.33 volts on the input side, limit
the output to that voltage, but when the input voltage reaches or goes
below
that voltage, it drops out of the circuit? or is able to just pass the
voltage straight through it unregulated.. untill it gets over 12.33 volts
again when i start the engine or plug into a power socket.. where it
regulates the voltage again??



I have to wonder is it overvoltage that is the problem, or is the TV seeing
excessive ripple from the charging circuit? Every 12VDC TV I have seen can
handle the Automotive charging circuits! Once in the TV the voltages are
changed and regulated IE: 5VDC, etc...

Perhaps you should obtain a Schematic of the TV and see whats in the input
circuit. Get the white papers on the model TV, see what the input range is,
including alowable ripple!

voltage regulator that drops out of circuit
 

"scada" wrote in message
et...

"CampinGazz" wrote in message
...
i have a flat panel TV/monitor that's going in a motorhome, it's powered
via
a switched mode psu from the mains, which takes 230 volts in, gives
12.33
volts out,

the motorhome uses a 12 volt battery, so most people just connect the tv
to
the battery and it all works,

however i've heard of a few people with this type of TV that have had
problems when they are hooked upto shore power, the battery charger
being
on-line produces upto 14.8 volts, also if the tv is used when driving
for
some reason, the alternator ups the voltage the TV sees to 14.4 volts,

and as the TV is designed to work on exactly 12.33 volts, part of it
burns
out when it's fed a higher voltage.. i know this shouldent happen, but
it
does, and the TV's makers say the tv was designed for home use not
vehicle
use, and it's electronics are optimized for 12.33 volts only, that
should
be
supplied by the main adaptor, not the 11 to 15 volts automotive
electrical
items are designed to handle.

the people who have used this TV in their motorhomes had no problems
when
they're not on mains power so the battery charger is off line, the tv
works
fine on 12.8 right down to 11 volts, way past when most 12 volt CRT tv's
have turned off, so undervoltage is not a problem really, jsut
overvoltage.

So.. i need to build a voltage regulator to power the TV, it pulls 4
amps
max, that's not a problem at first sight,

but voltage regulators need their input voltage to be above the output
voltage, and that's where my problem is,

when the battery is on charge it will have a terminal voltage of 14.8
volts
for a few hours while the charger equalizes the battery bank, then it'll
settle to around 13.8 to 14 volts, still too high for the TV.
when i'm boondocking, the battery will start off at 12.8 volts, and fall
as
i use power, i'll stop drawing power when the terminal voltage reaches
11.5
volts usually.

is there a regulator circuit out ther that can handle the 4 amps
throughput
i need, and when the voltage is over 12.33 volts on the input side,
limit
the output to that voltage, but when the input voltage reaches or goes
below
that voltage, it drops out of the circuit? or is able to just pass the
voltage straight through it unregulated.. untill it gets over 12.33
volts
again when i start the engine or plug into a power socket.. where it
regulates the voltage again??



I have to wonder is it overvoltage that is the problem, or is the TV
seeing
excessive ripple from the charging circuit? Every 12VDC TV I have seen can
handle the Automotive charging circuits! Once in the TV the voltages are
changed and regulated IE: 5VDC, etc...

Perhaps you should obtain a Schematic of the TV and see whats in the input
circuit. Get the white papers on the model TV, see what the input range
is,
including alowable ripple!



Probably the best solution would be to purchase a DC to DC converter. That
will guarantee a stable output voltage with a low ripple value.

voltage regulator that drops out of circuit
 

"CampinGazz" wrote in message
...
i have a flat panel TV/monitor that's going in a motorhome, it's powered
via
a switched mode psu from the mains, which takes 230 volts in, gives 12.33
volts out,

the motorhome uses a 12 volt battery, so most people just connect the tv
to
the battery and it all works,

however i've heard of a few people with this type of TV that have had
problems when they are hooked upto shore power, the battery charger being
on-line produces upto 14.8 volts, also if the tv is used when driving for
some reason, the alternator ups the voltage the TV sees to 14.4 volts,

and as the TV is designed to work on exactly 12.33 volts, part of it burns
out when it's fed a higher voltage.. i know this shouldent happen, but it
does, and the TV's makers say the tv was designed for home use not vehicle
use, and it's electronics are optimized for 12.33 volts only, that should
be
supplied by the main adaptor, not the 11 to 15 volts automotive electrical
items are designed to handle.

the people who have used this TV in their motorhomes had no problems when
they're not on mains power so the battery charger is off line, the tv
works
fine on 12.8 right down to 11 volts, way past when most 12 volt CRT tv's
have turned off, so undervoltage is not a problem really, jsut
overvoltage.

So.. i need to build a voltage regulator to power the TV, it pulls 4 amps
max, that's not a problem at first sight,

but voltage regulators need their input voltage to be above the output
voltage, and that's where my problem is,

when the battery is on charge it will have a terminal voltage of 14.8
volts
for a few hours while the charger equalizes the battery bank, then it'll
settle to around 13.8 to 14 volts, still too high for the TV.
when i'm boondocking, the battery will start off at 12.8 volts, and fall
as
i use power, i'll stop drawing power when the terminal voltage reaches
11.5
volts usually.

is there a regulator circuit out ther that can handle the 4 amps
throughput
i need, and when the voltage is over 12.33 volts on the input side, limit
the output to that voltage, but when the input voltage reaches or goes
below
that voltage, it drops out of the circuit? or is able to just pass the
voltage straight through it unregulated.. untill it gets over 12.33 volts
again when i start the engine or plug into a power socket.. where it
regulates the voltage again??

Hi
Have you thought about buying a cheap (low power) inverter (12 volt
dc---ac)?
might get you around most of your TV problems and you also get to
use some other
mains powered stuff

bj

voltage regulator that drops out of circuit
 

The easiest thing may be to just put a couple or 3 of diodes in series with
the TV power input. Now short the diodes with the contacts of a Normally
Closed relay. Wire the relay so it is activated from a point in the RV that
is hot only when the engine is running. With the engine running the diodes
willl be in the circuit and drop enough voltage to safley operate the TV
then will be bypassed with the engine off when the voltage is now 12. I have
a little TV too that doesnt like 14.8Volts either. While I have yet to add
the auto switching the diodes do work quite well in droping the voltage to
the correct level. Switching could be done any number of other ways too with
some sort of voltage sensing circuit that would cause a rely to switch at
say 13 volts. Not hard to do either.


"bj" wrote in message
...

"CampinGazz" wrote in message
...
i have a flat panel TV/monitor that's going in a motorhome, it's powered
via
a switched mode psu from the mains, which takes 230 volts in, gives
12.33
volts out,

the motorhome uses a 12 volt battery, so most people just connect the tv
to
the battery and it all works,

however i've heard of a few people with this type of TV that have had
problems when they are hooked upto shore power, the battery charger
being
on-line produces upto 14.8 volts, also if the tv is used when driving
for
some reason, the alternator ups the voltage the TV sees to 14.4 volts,

and as the TV is designed to work on exactly 12.33 volts, part of it
burns
out when it's fed a higher voltage.. i know this shouldent happen, but
it
does, and the TV's makers say the tv was designed for home use not
vehicle
use, and it's electronics are optimized for 12.33 volts only, that
should
be
supplied by the main adaptor, not the 11 to 15 volts automotive
electrical
items are designed to handle.

the people who have used this TV in their motorhomes had no problems
when
they're not on mains power so the battery charger is off line, the tv
works
fine on 12.8 right down to 11 volts, way past when most 12 volt CRT tv's
have turned off, so undervoltage is not a problem really, jsut
overvoltage.

So.. i need to build a voltage regulator to power the TV, it pulls 4
amps
max, that's not a problem at first sight,

but voltage regulators need their input voltage to be above the output
voltage, and that's where my problem is,

when the battery is on charge it will have a terminal voltage of 14.8
volts
for a few hours while the charger equalizes the battery bank, then it'll
settle to around 13.8 to 14 volts, still too high for the TV.
when i'm boondocking, the battery will start off at 12.8 volts, and fall
as
i use power, i'll stop drawing power when the terminal voltage reaches
11.5
volts usually.

is there a regulator circuit out ther that can handle the 4 amps
throughput
i need, and when the voltage is over 12.33 volts on the input side,
limit
the output to that voltage, but when the input voltage reaches or goes
below
that voltage, it drops out of the circuit? or is able to just pass the
voltage straight through it unregulated.. untill it gets over 12.33
volts
again when i start the engine or plug into a power socket.. where it
regulates the voltage again??

Hi
Have you thought about buying a cheap (low power) inverter (12
volt
dc---ac)?
might get you around most of your TV problems and you also get to
use some other
mains powered stuff

bj