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Need Help on this power supply. — Parallax Forums

Need Help on this power supply.

ArchiverArchiver Posts: 46,084
edited 2002-01-03 22:48 in General Discussion
I am designing a supply with 6V battery and a 9 Volt DC Source, what
I want is that when I connect the circuit on the 9 V DC, the 6 V
Battery supply will diconnect and when I disconnect the 9 V DC the 6
V Battery will reconnect, this will happen without variation in the
output voltage of the circuit.

Please help.

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2002-01-03 06:19
    If you can afford approx. 0.7 volts diode drop, you can connect the 6 volt
    battery to the load thru a diode. This will leave about 5.3 volts available
    to the load. When the 9 volt source is connected directly to the load, load
    voltage will rise to 9 volts; the battery will be "off" because the diode is
    reverse biased. When you disconnect the 9 volts, the battery will again
    take over. The diode must be rated for your load current.

    Hope this helps,
    Ray McArthur

    Original Message
    From: mysemicon2000 <semiconductor@p...>
    To: <basicstamps@yahoogroups.com>
    Sent: Thursday, January 03, 2002 12:33 AM
    Subject: [noparse][[/noparse]basicstamps] Need Help on this power supply.


    > I am designing a supply with 6V battery and a 9 Volt DC Source, what
    > I want is that when I connect the circuit on the 9 V DC, the 6 V
    > Battery supply will diconnect and when I disconnect the 9 V DC the 6
    > V Battery will reconnect, this will happen without variation in the
    > output voltage of the circuit.
  • ArchiverArchiver Posts: 46,084
    edited 2002-01-03 07:30
    Have you tried this circuit already?


    --- In basicstamps@y..., "Ray McArthur" <rjmca@u...> wrote:
    > If you can afford approx. 0.7 volts diode drop, you can connect the
    6 volt
    > battery to the load thru a diode. This will leave about 5.3 volts
    available
    > to the load. When the 9 volt source is connected directly to the
    load, load
    > voltage will rise to 9 volts; the battery will be "off" because the
    diode is
    > reverse biased. When you disconnect the 9 volts, the battery will
    again
    > take over. The diode must be rated for your load current.
    >
    > Hope this helps,
    > Ray McArthur
    >
    >
    Original Message
    > From: mysemicon2000 <semiconductor@p...>
    > To: <basicstamps@y...>
    > Sent: Thursday, January 03, 2002 12:33 AM
    > Subject: [noparse][[/noparse]basicstamps] Need Help on this power supply.
    >
    >
    > > I am designing a supply with 6V battery and a 9 Volt DC Source,
    what
    > > I want is that when I connect the circuit on the 9 V DC, the 6 V
    > > Battery supply will diconnect and when I disconnect the 9 V DC
    the 6
    > > V Battery will reconnect, this will happen without variation in
    the
    > > output voltage of the circuit.
  • ArchiverArchiver Posts: 46,084
    edited 2002-01-03 14:04
    Try a pair of low Vd shottky diodes (~0.25V)(look at International
    Rectifier site, these diodes comes 2 in a TO-220 package, common
    cathode) and a low dropout regulator.
    the 9v and the 6V sources at the anodes of the or'ing diodes.

    --- In basicstamps@y..., "mysemicon2000" <semiconductor@p...> wrote:
    > I am designing a supply with 6V battery and a 9 Volt DC Source,
    what
    > I want is that when I connect the circuit on the 9 V DC, the 6 V
    > Battery supply will diconnect and when I disconnect the 9 V DC the
    6
    > V Battery will reconnect, this will happen without variation in the
    > output voltage of the circuit.
    >
    > Please help.
  • ArchiverArchiver Posts: 46,084
    edited 2002-01-03 22:48
    Yes, I have used the principle before... it is a commonly used circuit. As
    another post suggested, you can gain a few tenths of a volt with a schottky
    diode.

    Ray McArthur

    Original Message
    From: mysemicon2000 <semiconductor@p...>
    To: <basicstamps@yahoogroups.com>
    Sent: Thursday, January 03, 2002 2:30 AM
    Subject: [noparse][[/noparse]basicstamps] Re: Need Help on this power supply.


    > Have you tried this circuit already?
    >
    >
    > --- In basicstamps@y..., "Ray McArthur" <rjmca@u...> wrote:
    > > If you can afford approx. 0.7 volts diode drop, you can connect the
    > 6 volt
    > > battery to the load thru a diode. This will leave about 5.3 volts
    > available
    > > to the load. When the 9 volt source is connected directly to the
    > load, load
    > > voltage will rise to 9 volts; the battery will be "off" because the
    > diode is
    > > reverse biased. When you disconnect the 9 volts, the battery will
    > again
    > > take over. The diode must be rated for your load current.
    **************** etc.
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