I have 2 questions regarding zener wattage.

1. Can I parallel two 1W zener to get a 2W zener ?

2. Can I increase the wattage of a zener using a bipolar transistor
arranged as below?


Rload
Vin ___ Vout
o---------|___|-------------o-------------------o
|
| Vout=10+0.6V
+--------o
| |
| .-. o
| | | |
| | | 3k3 |
| '-' |
| | |
>| | |
tip32 |------o |
/| | |
| | |
| z |
| A 10V zener |
| | |
+--------o |
| |
| |
| |
| |
=== ===
GND GND


(created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)


Allen

On Sat, 18 Aug 2007 12:08:58 -0700, Allen Bong
<allenbsf6502@gmail.com> wrote:

>I have 2 questions regarding zener wattage.
>
>1. Can I parallel two 1W zener to get a 2W zener ?

Not advised. One will have slightly lower zener voltage and will hog
all the current, and get hot. Series is OK.


>
>2. Can I increase the wattage of a zener using a bipolar transistor
>arranged as below?
>
>
> Rload
> Vin ___ Vout
> o---------|___|-------------o-------------------o
> |
> | Vout=10+0.6V
> +--------o
> | |
> | .-. o
> | | | |
> | | | 3k3 |
> | '-' |
> | | |
> >| | |
> tip32 |------o |
> /| | |
> | | |
> | z |
> | A 10V zener |
> | | |
> +--------o |
> | |
> | |
> | |
> | |
> === ===
> GND GND
>


Yup. But zener shunt regulators are very inefficient and tend to
regulate poorly.


Try this:


NPN

in--------------+----------------c e-----------------out
| b 10-.6v
| |
| |
+--------R---------+
|
|
|
10v Zener
|
|
|
|
gnd



Or buy an LM317!

John

On Sat, 18 Aug 2007 12:08:58 -0700, Allen Bong
<allenbsf6502@gmail.com> wrote:

>I have 2 questions regarding zener wattage.
>
>1. Can I parallel two 1W zener to get a 2W zener ?

What's the purpose? Why do you want to do this???

>2. Can I increase the wattage of a zener using a bipolar transistor
>arranged as below?
>
>
> Rload
> Vin ___ Vout
> o---------|___|-------------o-------------------o
> |
> | Vout=10+0.6V
> +--------o
> | |
> | .-. o
> | | | |
> | | | 3k3 |
> | '-' |
> | | |
> >| | |
> tip32 |------o |
> /| | |
> | | |
> | z |
> | A 10V zener |
> | | |
> +--------o |
> | |
> | |
> | |
> | |
> === ===
> GND GND
>
>
>(created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)

That looks a lot more like a voltage reference, though I would
probably expect to see it more like this:

>: Vunreg
>: |
>: |
>: \
>: / R2
>: \
>: /
>: |
>: ,-----+
>: | |
>: | \
>: | / R1
>: | \
>: | /
>: | |
>: Q1 e>| |
>: PNP |---+
>: c/| +-----> Vref
>: | |
>: | |
>: | /---/
>: gnd /z\ zener
>: ---
>: |
>: |
>: gnd

That doesn't usually supply power, just a nice voltage if you don't
tax it much.

In the back of my mind, I'm wondering if you are trying to supply
regulated power using a zener and figuring on just increasing the
current through it so that there is more available for the load. If
that's your goal, you'd use a BJT this way:

>: Vunreg
>: |
>: |
>: \
>: R1 /
>: \ Vunreg
>: / |
>: | |
>: | |<e Q1
>: +---| PNP
>: | |\c
>: | |
>: | '-----> Vout
>: /---/
>: D1 /z\
>: --- zener
>: |
>: |
>: gnd

You might consider this as both a temperature and Vbe compensator:

>: Vunreg
>: |
>: |
>: \
>: R1 /
>: \ Vunreg
>: / |
>: | |
>: | |<e Q1
>: +---| PNP
>: | |\c
>: | |
>: | '-----> Vout
>: /---/
>: D1 /z\
>: --- zener
>: |
>: |
>: |
>: ---
>: D2 \ / (selected to improve
>: --- temperature effects
>: | due to Q1's Vbe)
>: |
>: |
>: gnd

But I don't know what you are trying to do, either. So?

Jon

On Sat, 18 Aug 2007 12:08:58 -0700, Allen Bong
<allenbsf6502@gmail.com> wrote:

>I have 2 questions regarding zener wattage.
>
>1. Can I parallel two 1W zener to get a 2W zener ?

---
Not normally, since the Zener voltages of the diodes won't likely be
the same.
---


>2. Can I increase the wattage of a zener using a bipolar transistor
>arranged as below?
>
>
> Rload
> Vin ___ Vout
> o---------|___|-------------o-------------------o
> |
> | Vout=10+0.6V
> +--------o
> | |
> | .-. o
> | | | |
> | | | 3k3 |
> | '-' |
> | | |
> >| | |
> tip32 |------o |
> /| | |
> | | |
> | z |
> | A 10V zener |
> | | |
> +--------o |
> | |
> | |
> | |
> | |
> === ===
> GND GND
>
>
>(created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)

---
Looks clumsy to me. Try it like this:

Q1
Vin>------+------C E---->>---+--> Vz - Vbe(Q1)
| B |
[R] | |
| | |
+--------+ [LOAD]
|K |
[ZENER] |
| |
GND>------+--------------->>---+


--
JF

On Sat, 18 Aug 2007 20:52:27 GMT, Jonathan Kirwan
<jkirwan@easystreet.com> wrote:

>On Sat, 18 Aug 2007 12:08:58 -0700, Allen Bong
><allenbsf6502@gmail.com> wrote:
>
>>I have 2 questions regarding zener wattage.
>>
>>1. Can I parallel two 1W zener to get a 2W zener ?
>
>What's the purpose? Why do you want to do this???
>
>>2. Can I increase the wattage of a zener using a bipolar transistor
>>arranged as below?
>>
>>
>> Rload
>> Vin ___ Vout
>> o---------|___|-------------o-------------------o
>> |
>> | Vout=10+0.6V
>> +--------o
>> | |
>> | .-. o
>> | | | |
>> | | | 3k3 |
>> | '-' |
>> | | |
>> >| | |
>> tip32 |------o |
>> /| | |
>> | | |
>> | z |
>> | A 10V zener |
>> | | |
>> +--------o |
>> | |
>> | |
>> | |
>> | |
>> === ===
>> GND GND
>>
>>
>>(created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)
>
>That looks a lot more like a voltage reference, though I would
>probably expect to see it more like this:
>
>>: Vunreg
>>: |
>>: |
>>: \
>>: / R2
>>: \
>>: /
>>: |
>>: ,-----+
>>: | |
>>: | \
>>: | / R1
>>: | \
>>: | /
>>: | |
>>: Q1 e>| |
>>: PNP |---+
>>: c/| +-----> Vref
>>: | |
>>: | |
>>: | /---/
>>: gnd /z\ zener
>>: ---
>>: |
>>: |
>>: gnd
>
>That doesn't usually supply power, just a nice voltage if you don't
>tax it much.
>
>In the back of my mind, I'm wondering if you are trying to supply
>regulated power using a zener and figuring on just increasing the
>current through it so that there is more available for the load. If
>that's your goal, you'd use a BJT this way:
>
>>: Vunreg
>>: |
>>: |
>>: \
>>: R1 /
>>: \ Vunreg
>>: / |
>>: | |
>>: | |<e Q1
>>: +---| PNP
>>: | |\c
>>: | |
>>: | '-----> Vout
>>: /---/
>>: D1 /z\
>>: --- zener
>>: |
>>: |
>>: gnd
>
>You might consider this as both a temperature and Vbe compensator:
>
>>: Vunreg
>>: |
>>: |
>>: \
>>: R1 /
>>: \ Vunreg
>>: / |
>>: | |
>>: | |<e Q1
>>: +---| PNP
>>: | |\c
>>: | |
>>: | '-----> Vout
>>: /---/
>>: D1 /z\
>>: --- zener
>>: |
>>: |
>>: |
>>: ---
>>: D2 \ / (selected to improve
>>: --- temperature effects
>>: | due to Q1's Vbe)
>>: |
>>: |
>>: gnd
>
>But I don't know what you are trying to do, either. So?
>
>Jon

Umm, I think Q1 should be an NPN, flipped over.

John

Allen Bong wrote:

> I have 2 questions regarding zener wattage.
>
> 1. Can I parallel two 1W zener to get a 2W zener ?

Not reliably since the 2 zeners probably won't match very well so one will take
more current.


> 2. Can I increase the wattage of a zener using a bipolar transistor
> arranged as below?

That ought to sort of work but if you have a transistor it would make more sense
to create a series regulator using it rather than use purely shunt regulation
(it'll be more efficient).

Graham

Allen Bong wrote:

> I have 2 questions regarding zener wattage.
>
> 1. Can I parallel two 1W zener to get a 2W zener ?
>
> 2. Can I increase the wattage of a zener using a bipolar transistor
> arranged as below?
>
>
> Rload
> Vin ___ Vout
> o---------|___|-------------o-------------------o
> |
> | Vout=10+0.6V
> +--------o
> | |
> | .-. o
> | | | |
> | | | 3k3 |
> | '-' |
> | | |
> >| | |
> tip32 |------o |
> /| | |
> | | |
> | z |
> | A 10V zener |
> | | |
> +--------o |
> | |
> | |
> | |
> | |
> === ===
> GND GND
>
>
> (created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)
>
>
> Allen
>
I don't know what your requirements are how ever, to save components you
could use a 78L10 100 ma voltage regulator which comes in various
packages. I was just working with a 78L12 in a 92 Package today.
they are 3 legged post regulators and very small.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

On Aug 19, 4:52 am, Jonathan Kirwan <jkir...@easystreet.com> wrote:
> On Sat, 18 Aug 2007 12:08:58 -0700, Allen Bong
>
> <allenbsf6...@gmail.com> wrote:
> >I have 2 questions regarding zener wattage.
>
> >1. Can I parallel two 1W zener to get a 2W zener ?
>
> What's the purpose? Why do you want to do this???
>
>
>
>
>
> >2. Can I increase the wattage of a zener using a bipolar transistor
> >arranged as below?
>
> > Rload
> > Vin ___ Vout
> > o---------|___|-------------o-------------------o
> > |
> > | Vout=10+0.6V
> > +--------o
> > | |
> > | .-. o
> > | | | |
> > | | | 3k3 |
> > | '-' |
> > | | |
> > >| | |
> > tip32 |------o |
> > /| | |
> > | | |
> > | z |
> > | A 10V zener |
> > | | |
> > +--------o |
> > | |
> > | |
> > | |
> > | |
> > === ===
> > GND GND
>
> >(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
> That looks a lot more like a voltage reference, though I would
> probably expect to see it more like this:
>
>
>
>
>
> >: Vunreg
> >: |
> >: |
> >: \
> >: / R2
> >: \
> >: /
> >: |
> >: ,-----+
> >: | |
> >: | \
> >: | / R1
> >: | \
> >: | /
> >: | |
> >: Q1 e>| |
> >: PNP |---+
> >: c/| +-----> Vref
> >: | |
> >: | |
> >: | /---/
> >: gnd /z\ zener
> >: ---
> >: |
> >: |
> >: gnd
>
> That doesn't usually supply power, just a nice voltage if you don't
> tax it much.
>
> In the back of my mind, I'm wondering if you are trying to supply
> regulated power using a zener and figuring on just increasing the
> current through it so that there is more available for the load. If
> that's your goal, you'd use a BJT this way:
>
>
>
>
>
> >: Vunreg
> >: |
> >: |
> >: \
> >: R1 /
> >: \ Vunreg
> >: / |
> >: | |
> >: | |<e Q1
> >: +---| PNP
> >: | |\c
> >: | |
> >: | '-----> Vout
> >: /---/
> >: D1 /z\
> >: --- zener
> >: |
> >: |
> >: gnd
>
> You might consider this as both a temperature and Vbe compensator:
>
>
>
>
>
> >: Vunreg
> >: |
> >: |
> >: \
> >: R1 /
> >: \ Vunreg
> >: / |
> >: | |
> >: | |<e Q1
> >: +---| PNP
> >: | |\c
> >: | |
> >: | '-----> Vout
> >: /---/
> >: D1 /z\
> >: --- zener
> >: |
> >: |
> >: |
> >: ---
> >: D2 \ / (selected to improve
> >: --- temperature effects
> >: | due to Q1's Vbe)
> >: |
> >: |
> >: gnd
>
> But I don't know what you are trying to do, either. So?
>
> Jon- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -

For Question 1, I need to do this as I can only get 400mW and 1W zener
locally. The
spare part shop charges 4 to 5 times for a 5W zener, so I thought may
be I can use five
1W zener to get a 5W zener equilvalent.

As for Q #2, my friend showed me a circuit and wants me to duplicate
it. The schematic
is as follows:


Q1 10W
2N3055 0.1 ohm
Vunreg (42V) ___ Vout (24V)
o-----------------o---o----------- ------|___|----o---o------o
| | \ ^ | |
| | --- | .-.
| | | +----+ | |
| o------- --+ | | |2k2
.-. | \ ^ mje3055t | '-'
| | | --- Q2 .-. |
4k7 | | | | | | |
'-' +--- --+ | | 1k |
| \ ^ mje3055t '-' |
| --- Q3 | |
| | || | |
+----------+--------o-----||--+ | |
| \| || | .-. |
| mje3055t |-------o------->| | |
| Q4 <| | |1k | I=5mA
| | '-' |
|+ I=4.26mA | | |
=== o----------------------------+
/-\ | |
| | .-.
| z | |
| 1N5342B x 2 A | |1k5
| 13.6V 5W | '-'
| | I=10mA |
| === |
=== GND ===
GND GND

(created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)


The circuit on my original post is supposed to replace the 13.6V 5W
zener. Will the
circuit work in this situation?

I have also calculated the current flowing through the 13.6V zener
which is about 10mA. If I
put a 1W zener, will the current exceed 76mA if one of the BJT Q2-Q4
is shorted ? I
have no idea why the designer wanted to put a 5W zener here.....

Allen

On Aug 19, 7:04 am, Jamie
<jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
> Allen Bong wrote:
> > I have 2 questions regarding zener wattage.
>
> > 1. Can I parallel two 1W zener to get a 2W zener ?
>
> > 2. Can I increase the wattage of a zener using a bipolar transistor
> > arranged as below?
>
> > Rload
> > Vin ___ Vout
> > o---------|___|-------------o-------------------o
> > |
> > | Vout=10+0.6V
> > +--------o
> > | |
> > | .-. o
> > | | | |
> > | | | 3k3 |
> > | '-' |
> > | | |
> > >| | |
> > tip32 |------o |
> > /| | |
> > | | |
> > | z |
> > | A 10V zener |
> > | | |
> > +--------o |
> > | |
> > | |
> > | |
> > | |
> > === ===
> > GND GND
>
> > (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
> > Allen
>
> I don't know what your requirements are how ever, to save components you
> could use a 78L10 100 ma voltage regulator which comes in various
> packages. I was just working with a 78L12 in a 92 Package today.
> they are 3 legged post regulators and very small.
>
> --
> "I'm never wrong, once i thought i was, but was mistaken"
> Real Programmers Do things like this.http://webpages.charter.net/jamie_5- Hide quoted text -
>
> - Show quoted text -

That's a good idea too. Never thought of that before. SO to get 13.6
I'll just use a 7812 and stick 3 1N4001 in series on the COM pin of
the regulator, right?

Then where does my Vin comes from? The 24V regulated or 42V Vunreg ?

Allen

Allen Bong wrote:

> On Aug 19, 7:04 am, Jamie
> <jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
>
>>Allen Bong wrote:
>>
>>>I have 2 questions regarding zener wattage.
>>
>>>1. Can I parallel two 1W zener to get a 2W zener ?
>>
>>>2. Can I increase the wattage of a zener using a bipolar transistor
>>>arranged as below?
>>
>>> Rload
>>> Vin ___ Vout
>>> o---------|___|-------------o-------------------o
>>> |
>>> | Vout=10+0.6V
>>> +--------o
>>> | |
>>> | .-. o
>>> | | | |
>>> | | | 3k3 |
>>> | '-' |
>>> | | |
>>> >| | |
>>> tip32 |------o |
>>> /| | |
>>> | | |
>>> | z |
>>> | A 10V zener |
>>> | | |
>>> +--------o |
>>> | |
>>> | |
>>> | |
>>> | |
>>> === ===
>>> GND GND
>>
>>>(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>>
>>>Allen
>>
>>I don't know what your requirements are how ever, to save components you
>>could use a 78L10 100 ma voltage regulator which comes in various
>>packages. I was just working with a 78L12 in a 92 Package today.
>> they are 3 legged post regulators and very small.
>>
>>--
>>"I'm never wrong, once i thought i was, but was mistaken"
>>Real Programmers Do things like this.http://webpages.charter.net/jamie_5- Hide quoted text -
>>
>>- Show quoted text -
>
>
> That's a good idea too. Never thought of that before. SO to get 13.6
> I'll just use a 7812 and stick 3 1N4001 in series on the COM pin of
> the regulator, right?
>
> Then where does my Vin comes from? The 24V regulated or 42V Vunreg ?
>
> Allen
>
the 78Lxx and maybe the 78xx series are rated for something like 36
volts on the input.
But I suppose you could tailor the components to work around that.
something like a resistor divider;


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

Allen Bong wrote:

> For Question 1, I need to do this as I can only get 400mW and 1W zener
> locally. The
> spare part shop charges 4 to 5 times for a 5W zener, so I thought may
> be I can use five
> 1W zener to get a 5W zener equilvalent.
>
> As for Q #2, my friend showed me a circuit and wants me to duplicate
> it. The schematic
> is as follows:
>
>
> Q1 10W
> 2N3055 0.1 ohm
> Vunreg (42V) ___ Vout (24V)
> o-----------------o---o----------- ------|___|----o---o------o
> | | \ ^ | |
> | | --- | .-.
> | | | +----+ | |
> | o------- --+ | | |2k2
> .-. | \ ^ mje3055t | '-'
> | | | --- Q2 .-. |
> 4k7 | | | | | | |
> '-' +--- --+ | | 1k |
> | \ ^ mje3055t '-' |
> | --- Q3 | |
> | | || | |
> +----------+--------o-----||--+ | |
> | \| || | .-. |
> | mje3055t |-------o------->| | |
> | Q4 <| | |1k | I=5mA
> | | '-' |
> |+ I=4.26mA | | |
> === o----------------------------+
> /-\ | |
> | | .-.
> | z | |
> | 1N5342B x 2 A | |1k5
> | 13.6V 5W | '-'
> | | I=10mA |
> | === |
> === GND ===
> GND GND
>
> (created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)
>
>
> The circuit on my original post is supposed to replace the 13.6V 5W
> zener. Will the
> circuit work in this situation?
>
> I have also calculated the current flowing through the 13.6V zener
> which is about 10mA. If I
> put a 1W zener, will the current exceed 76mA if one of the BJT Q2-Q4
> is shorted ? I
> have no idea why the designer wanted to put a 5W zener here.....

I hope you realize that using the same part number for Q2,3
and 4 is a pretty big compromise for this circuit, since
they have such different operating points.

With all the current gain in this output pass configuration
(double darlington), there is no real need for high power
zeners to make it work.

And, unless there is more stuff in the circuit that is not
shown, there is no particular point in having 0.1 ohm, 10
watt resistor in series with the output current. It does,
however, indicate that the highest possible output current
is less than 10 amperes (or it would overheat). But at that
current, the single 2N3055 is totally inadequate for the
pass device. At 10 amperes, it would produce
(42-24-1)*10=170 watts of heat. It is rated at 115 watts,
and only if you keep the heat case at no more than 25 degrees C.
http://www.onsemi.com/pub/Collateral/2N3055-D.PDF

So what actual output current are you needing from this
regulator?

I suggest you read the application notes for the LM723
regulator control IC as a replacement for this kludge (after
you have learned lots from what it takes to make it work
cheaply, if not well). It doesn't quite handle the 42 volt
input, but fixing that is easier than making this circuit
work well.
http://www3.national.com/mpf/LM/LM723.html

"John Fields"
Allen Bong
>
>>2. Can I increase the wattage of a zener using a bipolar transistor
>>arranged as below?
>>
>>
>> Rload
>> Vin ___ Vout
>> o---------|___|-------------o-------------------o
>> |
>> | Vout=10+0.6V
>> +--------o
>> | |
>> | .-. o
>> | | | |
>> | | | 3k3 |
>> | '-' |
>> | | |
>> >| | |
>> tip32 |------o |
>> /| | |
>> | | |
>> | z |
>> | A 10V zener |
>> | | |
>> +--------o |
>> | |
>> | |
>> | |
>> | |
>> === ===
>> GND GND
>>
>>
>>(created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)
>
> ---
> Looks clumsy to me. Try it like this:
>
> Q1
> Vin>------+------C E---->>---+--> Vz - Vbe(Q1)
> | B |
> [R] | |
> | | |
> +--------+ [LOAD]
> |K |
> [ZENER] |
> | |
> GND>------+--------------->>---+



** Which is in no way similar.

An active zener is a voltage clamp, unlike a series regulator.




........ Phil

On Sat, 18 Aug 2007 15:10:56 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

>Umm, I think Q1 should be an NPN, flipped over.

Yes. I was doing an ASCII flip and screwed up. Thanks for the catch!

Jon

"Jonathan Kirwan"
John Farkin Fuckwit


>>Umm, I think Q1 should be an NPN, flipped over.
>
> Yes. I was doing an ASCII flip and screwed up. Thanks for the catch!


** What " catch " ?





........ Phil

On Sun, 19 Aug 2007 13:19:43 +1000, "Phil Allison"
<philallison@tpg.com.au> wrote:

>
>"John Fields"
> Allen Bong
>>
>>>2. Can I increase the wattage of a zener using a bipolar transistor
>>>arranged as below?
>>>
>>>
>>> Rload
>>> Vin ___ Vout
>>> o---------|___|-------------o-------------------o
>>> |
>>> | Vout=10+0.6V
>>> +--------o
>>> | |
>>> | .-. o
>>> | | | |
>>> | | | 3k3 |
>>> | '-' |
>>> | | |
>>> >| | |
>>> tip32 |------o |
>>> /| | |
>>> | | |
>>> | z |
>>> | A 10V zener |
>>> | | |
>>> +--------o |
>>> | |
>>> | |
>>> | |
>>> | |
>>> === ===
>>> GND GND
>>>
>>>
>>>(created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)
>>
>> ---
>> Looks clumsy to me. Try it like this:
>>
>> Q1
>> Vin>------+------C E---->>---+--> Vz - Vbe(Q1)
>> | B |
>> [R] | |
>> | | |
>> +--------+ [LOAD]
>> |K |
>> [ZENER] |
>> | |
>> GND>------+--------------->>---+
>
>
>
> ** Which is in no way similar.
>
> An active zener is a voltage clamp, unlike a series regulator.

---
The Zener keeps the base clamped to Vz and, since Vbe is a diode
drop, the voltage into the load will stay 'clamped' at Vz - Vbe if
either the load resistance or Vin change. Within limits, of course.


--
JF

"John Fields"
" Phil Allison "
>
>>
>> ** Which is in no way similar.
>>
>> An active zener is a voltage clamp, unlike a series regulator.
>
> ---
> The Zener keeps the base clamped to Vz and, since Vbe is a diode
> drop, the voltage into the load will stay 'clamped' at Vz - Vbe if
> either the load resistance or Vin change. Within limits, of course.


** Which is in NO WAY similar to a ** voltage clamp ** !!

An active zener IS a voltage clamp, unlike a series regulator.

Are you ASLEEP !!!!!!!!






........ Phil

On Aug 18, 4:20 pm, Allen Bong <allenbsf6...@gmail.com> wrote:

[snip]
> my friend showed me a circuit and wants me to duplicate
> it. The schematic
> is as follows:
>
> Q1 10W
> 2N3055 0.1 ohm
> Vunreg (42V) ___ Vout (24V)
> o-----------------o---o----------- ------|___|----o---o------o
> | | \ ^ | |
> | | --- | .-.
> | | | +----+ | |
> | o------- --+ | | |2k2
> .-. | \ ^ mje3055t | '-'
> | | | --- Q2 .-. |
> 4k7 | | | | | | |
> '-' +--- --+ | | 1k |
> | \ ^ mje3055t '-' |
> | --- Q3 | |
> | | || | |
> +----------+--------o-----||--+ | |
> | \| || | .-. |
> | mje3055t |-------o------->| | |
> | Q4 <| | |1k | I=5mA
> | | '-' |
> |+ I=4.26mA | | |
> === o----------------------------+
> /-\ | |
> | | .-.
> | z | |
> | 1N5342B x 2 A | |1k5
> | 13.6V 5W | '-'
> | | I=10mA |
> | === |
> === GND ===
> GND GND
>
> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
[snip]

Who designed that, the Geico caveman?
Probably not, 'cause he would have done a better job.
Check out the design in this next link
and consider how in its simplicity and rationality
it contrasts to your friend's circuit:

http://www.rason.org/Projects/discreg/discreg.htm


The following link explains some of the basics
about linear voltage regulating. You should read
a little bit before you jump into anything.

http://www.national.com/appinfo/power/files/f4.pdf

Jamie wrote:
> Allen Bong wrote:
>
>> On Aug 19, 7:04 am, Jamie
>> <jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
>>
>>> Allen Bong wrote:
>>>
>>>> I have 2 questions regarding zener wattage.
>>>
>>>> 1. Can I parallel two 1W zener to get a 2W zener ?
>>>
>>>> 2. Can I increase the wattage of a zener using a bipolar transistor
>>>> arranged as below?
>>>
>>>> Rload
>>>> Vin ___ Vout
>>>> o---------|___|-------------o-------------------o
>>>> |
>>>> | Vout=10+0.6V
>>>> +--------o
>>>> | |
>>>> | .-. o
>>>> | | | |
>>>> | | | 3k3 |
>>>> | '-' |
>>>> | | |
>>>> >| | |
>>>> tip32 |------o |
>>>> /| | |
>>>> | | |
>>>> | z |
>>>> | A 10V zener |
>>>> | | |
>>>> +--------o |
>>>> | |
>>>> | |
>>>> | |
>>>> | |
>>>> === ===
>>>> GND GND
>>>
>>>> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>>>
>>>> Allen
>>>
>>> I don't know what your requirements are how ever, to save components you
>>> could use a 78L10 100 ma voltage regulator which comes in various
>>> packages. I was just working with a 78L12 in a 92 Package today.
>>> they are 3 legged post regulators and very small.
>>>
>>> --
>>> "I'm never wrong, once i thought i was, but was mistaken"
>>> Real Programmers Do things like
>>> this.http://webpages.charter.net/jamie_5- Hide quoted text -
>>>
>>> - Show quoted text -
>>
>>
>> That's a good idea too. Never thought of that before. SO to get 13.6
>> I'll just use a 7812 and stick 3 1N4001 in series on the COM pin of
>> the regulator, right?
>>
>> Then where does my Vin comes from? The 24V regulated or 42V Vunreg ?
>>
>> Allen
>>
> the 78Lxx and maybe the 78xx series are rated for something like 36
> volts on the input.
> But I suppose you could tailor the components to work around that.
> something like a resistor divider;
>
>

I seem to recall that the limits of the 78xx family was 35Vin wrt
common, limited by power disssipation of the package. The TO-220
versions were good for 1W package dissipation I believe, depending on
how much Cu was underneath. At 24Vin to 10V out, then that limits the OP
to about 70mA for a hefty package. The TO92 variants are 100mW (I think
- don't have the datasheet in front of me) so that's about 7mA.


As you noted, we don't know the OP output requirements. In any event,
there's going to be a fair amount of heat in any linear regulator in
this case.

One thing - Rload seems to be upstream of the regulator. Is that really
the case?

Cheers

PeteS

On Aug 19, 8:11 am, John Popelish <jpopel...@rica.net> wrote:
> Allen Bong wrote:
> > For Question 1, I need to do this as I can only get 400mW and 1W zener
> > locally. The
> > spare part shop charges 4 to 5 times for a 5W zener, so I thought may
> > be I can use five
> > 1W zener to get a 5W zener equilvalent.
>
> > As for Q #2, my friend showed me a circuit and wants me to duplicate
> > it. The schematic
> > is as follows:
>
> > Q1 10W
> > 2N3055 0.1 ohm
> > Vunreg (42V) ___ Vout (24V)
> > o-----------------o---o----------- ------|___|----o---o------o
> > | | \ ^ | |
> > | | --- | .-.
> > | | | +----+ | |
> > | o------- --+ | | |2k2
> > .-. | \ ^ mje3055t | '-'
> > | | | --- Q2 .-. |
> > 4k7 | | | | | | |
> > '-' +--- --+ | | 1k |
> > | \ ^ mje3055t '-' |
> > | --- Q3 | |
> > | | || | |
> > +----------+--------o-----||--+ | |
> > | \| || | .-. |
> > | mje3055t |-------o------->| | |
> > | Q4 <| | |1k | I=5mA
> > | | '-' |
> > |+ I=4.26mA | | |
> > === o----------------------------+
> > /-\ | |
> > | | .-.
> > | z | |
> > | 1N5342B x 2 A | |1k5
> > | 13.6V 5W | '-'
> > | | I=10mA |
> > | === |
> > === GND ===
> > GND GND
>
> > (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
> > The circuit on my original post is supposed to replace the 13.6V 5W
> > zener. Will the
> > circuit work in this situation?
>
> > I have also calculated the current flowing through the 13.6V zener
> > which is about 10mA. If I
> > put a 1W zener, will the current exceed 76mA if one of the BJT Q2-Q4
> > is shorted ? I
> > have no idea why the designer wanted to put a 5W zener here.....
>
> I hope you realize that using the same part number for Q2,3
> and 4 is a pretty big compromise for this circuit, since
> they have such different operating points.
>
> With all the current gain in this output pass configuration
> (double darlington), there is no real need for high power
> zeners to make it work.
>
> And, unless there is more stuff in the circuit that is not
> shown, there is no particular point in having 0.1 ohm, 10
> watt resistor in series with the output current. It does,
> however, indicate that the highest possible output current
> is less than 10 amperes (or it would overheat). But at that
> current, the single 2N3055 is totally inadequate for the
> pass device. At 10 amperes, it would produce
> (42-24-1)*10=170 watts of heat. It is rated at 115 watts,
> and only if you keep the heat case at no more than 25 degrees C.http://www.onsemi.com/pub/Collateral/2N3055-D.PDF
>
> So what actual output current are you needing from this
> regulator?
>
> I suggest you read the application notes for the LM723
> regulator control IC as a replacement for this kludge (after
> you have learned lots from what it takes to make it work
> cheaply, if not well). It doesn't quite handle the 42 volt
> input, but fixing that is easier than making this circuit
> work well.http://www3.national.com/mpf/LM/LM723.html- Hide quoted text -
>
> - Show quoted text -

Hi John,

You're quite right about something I didnt mention in the circuit. Q1
is actually 6 x 2N3055 in parallel mounted on 2 pieces of heatsink
measuring 12" x 4" each. The heatsinks were cooled by 2 mini fans on
each end. And I also know that using MJE3055Ts as drivers were
overkill. Maybe the original designer had too many 3055 in hand or
got them in bulk. Can you help me with what transistors are adequate
for Q2-Q4 ? The output was supposed to give 60A of regulated 24V
supply.

What is the best way to reduce the amount of heat wasted on Q1 ?
Reduce the Vin to say 32V ? Change 2n3055 to something better? What
about 2N3772 or 2N3773?

http://www.onsemi.com/pub/Collateral/2N3771-D.PDF
http://www.onsemi.com/pub/Collateral/2N3773-D.PDF

I have no intention to change the design to a SMPS but just to improve
it. Any other suggestions are welcome.

I totlly agree with you and I'll study the A.N. of LM723 as suggested.

Allen

On Aug 20, 12:30 am, gearhead <nos...@billburg.com> wrote:
> On Aug 18, 4:20 pm, Allen Bong <allenbsf6...@gmail.com> wrote:
>
> [snip]
>
>
>
> > my friend showed me a circuit and wants me to duplicate
> > it. The schematic
> > is as follows:
>
> > Q1 10W
> > 2N3055 0.1 ohm
> > Vunreg (42V) ___ Vout (24V)
> > o-----------------o---o----------- ------|___|----o---o------o
> > | | \ ^ | |
> > | | --- | .-.
> > | | | +----+ | |
> > | o------- --+ | | |2k2
> > .-. | \ ^ mje3055t | '-'
> > | | | --- Q2 .-. |
> > 4k7 | | | | | | |
> > '-' +--- --+ | | 1k |
> > | \ ^ mje3055t '-' |
> > | --- Q3 | |
> > | | || | |
> > +----------+--------o-----||--+ | |
> > | \| || | .-. |
> > | mje3055t |-------o------->| | |
> > | Q4 <| | |1k | I=5mA
> > | | '-' |
> > |+ I=4.26mA | | |
> > === o----------------------------+
> > /-\ | |
> > | | .-.
> > | z | |
> > | 1N5342B x 2 A | |1k5
> > | 13.6V 5W | '-'
> > | | I=10mA |
> > | === |
> > === GND ===
> > GND GND
>
> > (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
> [snip]
>
> Who designed that, the Geico caveman?
> Probably not, 'cause he would have done a better job.
> Check out the design in this next link
> and consider how in its simplicity and rationality
> it contrasts to your friend's circuit:
>
> http://www.rason.org/Projects/discreg/discreg.htm
>
> The following link explains some of the basics
> about linear voltage regulating. You should read
> a little bit before you jump into anything.
>
> http://www.national.com/appinfo/power/files/f4.pdf- Hide quoted text -
>
> - Show quoted text -

Thanks for your good suggestions and I will surely read all
suggested. Boy, that's a lot to learn on a non-SMPS regulated power
supply. You know, just the transformer alone weighs a ton!

Allen

On Sun, 19 Aug 2007 22:08:11 +1000, "Phil Allison"
<philallison@tpg.com.au> wrote:

>
>"John Fields"
>" Phil Allison "
>>
>>>
>>> ** Which is in no way similar.
>>>
>>> An active zener is a voltage clamp, unlike a series regulator.
>>
>> ---
>> The Zener keeps the base clamped to Vz and, since Vbe is a diode
>> drop, the voltage into the load will stay 'clamped' at Vz - Vbe if
>> either the load resistance or Vin change. Within limits, of course.
>
>
>** Which is in NO WAY similar to a ** voltage clamp ** !!
>
> An active zener IS a voltage clamp, unlike a series regulator.
>
> Are you ASLEEP !!!!!!!!

---
Clamp, schlamp. You know very well that we both know the difference
between a series and a shunt regulator and, regardless of all this
fol-de-rol, you should have noticed that I called his implementation
clumsy and offered him a better alternative with the series
regulator, which essentially gets rid of the constant dissipation in
the current-limiting resistor that the OP calls "Rload".

LOL, I suppose, in your book, that now elevates me to the rank of a
!!!!!!!! PSYCHOTIC CRIMINAL SOCIOPATH !!!!!!!!




--
JF

On Aug 20, 12:30 am, gearhead <nos...@billburg.com> wrote:
> On Aug 18, 4:20 pm, Allen Bong <allenbsf6...@gmail.com> wrote:
>
> [snip]
>
>
>
> > my friend showed me a circuit and wants me to duplicate
> > it. The schematic
> > is as follows:
>
> > Q1 10W
> > 2N3055 0.1 ohm
> > Vunreg (42V) ___ Vout (24V)
> > o-----------------o---o----------- ------|___|----o---o------o
> > | | \ ^ | |
> > | | --- | .-.
> > | | | +----+ | |
> > | o------- --+ | | |2k2
> > .-. | \ ^ mje3055t | '-'
> > | | | --- Q2 .-. |
> > 4k7 | | | | | | |
> > '-' +--- --+ | | 1k |
> > | \ ^ mje3055t '-' |
> > | --- Q3 | |
> > | | || | |
> > +----------+--------o-----||--+ | |
> > | \| || | .-. |
> > | mje3055t |-------o------->| | |
> > | Q4 <| | |1k | I=5mA
> > | | '-' |
> > |+ I=4.26mA | | |
> > === o----------------------------+
> > /-\ | |
> > | | .-.
> > | z | |
> > | 1N5342B x 2 A | |1k5
> > | 13.6V 5W | '-'
> > | | I=10mA |
> > | === |
> > === GND ===
> > GND GND
>
> > (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
> [snip]
>
> Who designed that, the Geico caveman?
> Probably not, 'cause he would have done a better job.
> Check out the design in this next link
> and consider how in its simplicity and rationality
> it contrasts to your friend's circuit:
>
> http://www.rason.org/Projects/discreg/discreg.htm
>
> The following link explains some of the basics
> about linear voltage regulating. You should read
> a little bit before you jump into anything.
>
> http://www.national.com/appinfo/power/files/f4.pdf- Hide quoted text -
>
> - Show quoted text -

Hi gearhead,

I just found another design similar to my friend's. What do you think
about it ? Is it more efficient? Is it ok to let the 7812 which is
rated at 1A to work at 866mA?

http://www.zen22142.zen.co.uk/Circuits/ ... 230psu.htm

Allen

On Sun, 19 Aug 2007 14:32:58 -0700, Allen Bong
<allenbsf6502@gmail.com> wrote:

><snip>
>You're quite right about something I didnt mention in the circuit. Q1
>is actually 6 x 2N3055 in parallel mounted on 2 pieces of heatsink
>measuring 12" x 4" each.
><snip>

How does the circuit arrange things so that the six 2N3055's fairly
evenly share the load current?

Jon

Allen Bong wrote:
> On Aug 19, 8:11 am, John Popelish <jpopel...@rica.net> wrote:
>> Allen Bong wrote:
(snip)
>>> As for Q #2, my friend showed me a circuit and wants me to duplicate
>>> it. The schematic
>>> is as follows:
>>> Q1 10W
>>> 2N3055 0.1 ohm
>>> Vunreg (42V) ___ Vout (24V)
>>> o-----------------o---o----------- ------|___|----o---o------o
>>> | | \ ^ | |
>>> | | --- | .-.
>>> | | | +----+ | |
>>> | o------- --+ | | |2k2
>>> .-. | \ ^ mje3055t | '-'
>>> | | | --- Q2 .-. |
>>> 4k7 | | | | | | |
>>> '-' +--- --+ | | 1k |
>>> | \ ^ mje3055t '-' |
>>> | --- Q3 | |
>>> | | || | |
>>> +----------+--------o-----||--+ | |
>>> | \| || | .-. |
>>> | mje3055t |-------o------->| | |
>>> | Q4 <| | |1k | I=5mA
>>> | | '-' |
>>> |+ I=4.26mA | | |
>>> === o----------------------------+
>>> /-\ | |
>>> | | .-.
>>> | z | |
>>> | 1N5342B x 2 A | |1k5
>>> | 13.6V 5W | '-'
>>> | | I=10mA |
>>> | === |
>>> === GND ===
>>> GND GND
>>> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
(snip)
> Hi John,
>
> You're quite right about something I didnt mention in the circuit. Q1
> is actually 6 x 2N3055 in parallel mounted on 2 pieces of heatsink
> measuring 12" x 4" each. The heatsinks were cooled by 2 mini fans on
> each end. And I also know that using MJE3055Ts as drivers were
> overkill. Maybe the original designer had too many 3055 in hand or
> got them in bulk. Can you help me with what transistors are adequate
> for Q2-Q4 ? The output was supposed to give 60A of regulated 24V
> supply.

Well, that explains what the .1 ohm resistor is there for
(to help balance the current division between multiple
transistors), but it still means that the wasted power is
pretty scary at 170 watts per transistor.

> What is the best way to reduce the amount of heat wasted on Q1 ?
> Reduce the Vin to say 32V ?

Or lower. You want the input voltage as low as you can get
it while still leaving a few volts to drop across the pass
transistors at the bottom of the ripple voltage at low line.
Any more than that is just room heater.

Do you really need 60 amps continuous capability?

> Change 2n3055 to something better? What
> about 2N3772 or 2N3773?
I hate to use a pass transistor above the current where its
gain falls to less than half the peak value.
For a hot 2N3055:
http://www.onsemi.com/pub/Collateral/2N3055-D.PDF
that is about 2 or 3 amperes.
The 2N3055 is really not much of a 15 amp transistor.

Keep in mind that whatever you use for the pass transistors,
they have to stay well below the safe operating area curve
for DC. This transistor is red lined at about 10 volts drop
at 10 amperes. The 17 volt drop in the design is outside
this safe area, though the DC input may sag enough to just
get in inside. Too close for me unless the input voltage is
lowered. And if the output is ever shorted all bets are
off, even if you add short current limit to the design,
because there will be 24 volts extra dropped under that
condition. It takes a moment for a fuse to blow, and in
that moment, you could fry a half dozen transistors.

> http://www.onsemi.com/pub/Collateral/2N3771-D.PDF

Much more capable as a 10 amp pass transistor. It has good
gain out to 10 amps and a 15 volt 10 amp DC safe operating
area. Pretty safe with a 5 to 10 volt drop at 10 amps.

> http://www.onsemi.com/pub/Collateral/2N3773-D.PDF

I wouldn't use this as a linear pass transistor above 5 amps.

A cheap transistor that is good for linear operation out to
about 7 amps is the TIP35. I would use about 8 of them in
parallel for 60 amps.
http://www.ortodoxism.ro/datasheets/Pow ... Xqwzus.pdf

One of any of these would work for Q2, the next driver down
the chain, but there should be a low value resistor from its
emitter to the output, to speed up the response of those
output transistors. Something like 2.7 ohms 2 watts.

A much smaller transistor could drive that. Perhaps Q3
could be a TIP31:
http://rocky.digikey.com/WebLib/On-Semi ... _A_B_C.pdf
It should also have a load resistor from its emitter to the
output, to speed the response of Q2. Something like 100
ohms 1/4 watt.

This chain could be used as the pass device for an LM723
based design, also, except that you would be able to add
current limit and current limit foldback on short circuit
functions.

TIP31 could also be used for Q4.

> I have no intention to change the design to a SMPS but just to improve
> it. Any other suggestions are welcome.
>
> I totlly agree with you and I'll study the A.N. of LM723 as suggested.
>
> Allen
>

"John Fields"
" Phil Allison "
>>
>>>>
>>>> ** Which is in no way similar.
>>>>
>>>> An active zener is a voltage clamp, unlike a series regulator.
>>>
>>> ---
>>> The Zener keeps the base clamped to Vz and, since Vbe is a diode
>>> drop, the voltage into the load will stay 'clamped' at Vz - Vbe if
>>> either the load resistance or Vin change. Within limits, of course.
>>
>>
>>** Which is in NO WAY similar to a ** voltage clamp ** !!
>>
>> An active zener IS a voltage clamp, unlike a series regulator.
>>
>> Are you ASLEEP !!!!!!!!
>
> ---
> Clamp, schlamp. You know very well that we both know the difference
> between a series and a shunt regulator and, regardless of all this
> fol-de-rol, you should have noticed that I called his implementation
> clumsy and offered him a better alternative with the series
> regulator, which essentially gets rid of the constant dissipation in
> the current-limiting resistor that the OP calls "Rload".


** Read what the OP asked - you PITA fuckwit.

" 2. Can I increase the wattage of a zener using a bipolar transistor
arranged as below? "

An active zener IS a voltage clamp, unlike a series regulator !!

A 2 terminal device, not 3.

There are not interchangeable and so one is NOT clumsy compared the other.



........ Phil