b***y
发帖数: 100 | 1 Hi, all,
I have a question about Booster circuits. I am designing a circuit. I
need to get 1.8V, I can either use
one battery with a Booster or two battery with a step down converter.
What's the main advantage of a step down solution over the step up solution?
Thanks a lot for the advice.
Best |
a******w
发帖数: 774 | |
g******u
发帖数: 3060 | 3 it depends on your load current, isolation requirement, etc...you need to
provide more details. |
E*****a
发帖数: 757 | 4 如果你用一节电池，很难找到ic可以1.5V就工作，从而给你产生你要的boost
所以用2节好。而且step down比step up效率高，同一个power level的话，
inductor 体积也可以更小。
你的输出电流是多少？效率重要不？
solution?
【在 b***y 的大作中提到】
: Hi, all,
: I have a question about Booster circuits. I am designing a circuit. I
: need to get 1.8V, I can either use
: one battery with a Booster or two battery with a step down converter.
: What's the main advantage of a step down solution over the step up solution?
: Thanks a lot for the advice.
: Best
|
g*******r
发帖数: 140 | 5 Here are several general points :
1> Power efficiency, buck is usually much better than boost. (But in this
application, the buck solution needs 2 batteries and thus the efficiency
should be halved to make a fair comparison with boost?)
2> Desisgn of the start-up for buck is much easier than booster.
3> In CCM, output capacitor charging current of buck is conitunous, which is
always discontinous in boost.
4> There are many fast control methodologies for buck in literatures such as
hysteretic, V2
【在 b***y 的大作中提到】
: Hi, all,
: I have a question about Booster circuits. I am designing a circuit. I
: need to get 1.8V, I can either use
: one battery with a Booster or two battery with a step down converter.
: What's the main advantage of a step down solution over the step up solution?
: Thanks a lot for the advice.
: Best
|
r****e
发帖数: 122 | 6
当然不是弄成一半再比较 :)
Good points otherwise.
【在 g*******r 的大作中提到】
: Here are several general points :
: 1> Power efficiency, buck is usually much better than boost. (But in this
: application, the buck solution needs 2 batteries and thus the efficiency
: should be halved to make a fair comparison with boost?)
: 2> Desisgn of the start-up for buck is much easier than booster.
: 3> In CCM, output capacitor charging current of buck is conitunous, which is
: always discontinous in boost.
: 4> There are many fast control methodologies for buck in literatures such as
: hysteretic, V2
|
f*****0
发帖数: 489 | 7 "很难找到ic可以1.5V就工作"
there are many booster ICs that work down to 0.8v. Check out OnSemi's
website for example (ncp1400/1402 come to my mind). |
g*******r
发帖数: 140 | 8
haha, I made a stupid mistake. I took the battery currents in two cases same.
In fact, the input battery current in buck is much smaller than that in
boost.
Overall, the buck solution is better in terms of power efficiency.
【在 r****e 的大作中提到】
:
: 当然不是弄成一半再比较 :)
: Good points otherwise.
|
b***y
发帖数: 100 | 9 Thank you so much for your feedback. I really appreciate it!
I have some more questions based on your reply
Can you give some general numbers for the efficiency of buck compared with
Boost?
I know some boost can get a efficiency of 90% in the load range of less than
200mA.
Is buck going to get higher than that?
Could you be more specific on this? I an new to this area. Why do we
need to care so much about the
start-up?
is
Could you be more specific on this too? Or can you point me to
【在 g*******r 的大作中提到】
: Here are several general points :
: 1> Power efficiency, buck is usually much better than boost. (But in this
: application, the buck solution needs 2 batteries and thus the efficiency
: should be halved to make a fair comparison with boost?)
: 2> Desisgn of the start-up for buck is much easier than booster.
: 3> In CCM, output capacitor charging current of buck is conitunous, which is
: always discontinous in boost.
: 4> There are many fast control methodologies for buck in literatures such as
: hysteretic, V2
|
f*****0
发帖数: 489 | 10 if the current isn't too big, you can also consider switched capacitors /
charge pumps - they are much more efficient. |
|
|
r****e
发帖数: 122 | 11 我插问一下, 你的电流要求有多少, 效率是不是很重要, 1.8V要求有多准.
如果电流很少, 效率无所谓, 最简单快捷的方法恐怕就是线性regulator.
如图 :)
than
【在 b***y 的大作中提到】
: Thank you so much for your feedback. I really appreciate it!
: I have some more questions based on your reply
:
: Can you give some general numbers for the efficiency of buck compared with
: Boost?
: I know some boost can get a efficiency of 90% in the load range of less than
: 200mA.
: Is buck going to get higher than that?
: Could you be more specific on this? I an new to this area. Why do we
: need to care so much about the
|
b***y
发帖数: 100 | 12 Current is about 10 to 200mA. and the efficiency is very important.
Any suggestion on this?
【在 r****e 的大作中提到】
: 我插问一下, 你的电流要求有多少, 效率是不是很重要, 1.8V要求有多准.
: 如果电流很少, 效率无所谓, 最简单快捷的方法恐怕就是线性regulator.
: 如图 :)
:
: than
|
r****e
发帖数: 122 | 13 电池占好大地方, 一节电池加boost是不错的选择, 我拆过一个mp3, 一节电池,
里面用boost实现2.0V (珠海炬力的芯片).
否则buck的优点goodoffer说了不少.
两种情况你都需要买控制芯片(maxim, linear什么的), 200mA买那种集成了功率管
的控制芯片. 但是一般boost控制芯片还是要外加一个肖特基功率二极管.
【在 b***y 的大作中提到】
: Current is about 10 to 200mA. and the efficiency is very important.
: Any suggestion on this?
|
c*******h
发帖数: 4883 | 14 借人气问一下：现在便携设备里面的电源管理基本上都是集成的吧？不同的设备（射频
/存储器/CPU/DSP/LCD/...）的电源电压各不相同（1.2/1.8/2.5/3.0/...），而且可能
为了省电要关闭暂时不用的芯片的电源。这个好像对PWIC的集成度要求相当高啊，要不
然光是PWIC就要一堆了。这种解决方案有哪些公司做得比较好？ |
g*****g
发帖数: 3623 | 15 一个朋友在TI在AE，貌似他们的比较好
【在 c*******h 的大作中提到】
: 借人气问一下：现在便携设备里面的电源管理基本上都是集成的吧？不同的设备（射频
: /存储器/CPU/DSP/LCD/...）的电源电压各不相同（1.2/1.8/2.5/3.0/...），而且可能
: 为了省电要关闭暂时不用的芯片的电源。这个好像对PWIC的集成度要求相当高啊，要不
: 然光是PWIC就要一堆了。这种解决方案有哪些公司做得比较好？
|
g*****g
发帖数: 3623 | 16 buck吧
很多芯片现成的，电流不大的话 high side and low side MOSFET integrated in
chip. 有些连补偿都作进去了，plus external inductor and capacitor it will
work..
solution?
【在 b***y 的大作中提到】
: Hi, all,
: I have a question about Booster circuits. I am designing a circuit. I
: need to get 1.8V, I can either use
: one battery with a Booster or two battery with a step down converter.
: What's the main advantage of a step down solution over the step up solution?
: Thanks a lot for the advice.
: Best
|
g******u
发帖数: 3060 | 17 要省电而关闭稍微复杂一点。很多buck芯片应该有个disable pin,在芯片disable以后
功率消耗很小， 而buck converter的开关紧接电源，应该是损耗很小的。你需要编个
程序，多久没见负载就关断所有芯片。
【在 c*******h 的大作中提到】
: 借人气问一下：现在便携设备里面的电源管理基本上都是集成的吧？不同的设备（射频
: /存储器/CPU/DSP/LCD/...）的电源电压各不相同（1.2/1.8/2.5/3.0/...），而且可能
: 为了省电要关闭暂时不用的芯片的电源。这个好像对PWIC的集成度要求相当高啊，要不
: 然光是PWIC就要一堆了。这种解决方案有哪些公司做得比较好？
|
j***j
发帖数: 324 | 18 light load 或者standby 工作在burst mode /PFM control， very standard， not
complex at all.
【在 g******u 的大作中提到】
: 要省电而关闭稍微复杂一点。很多buck芯片应该有个disable pin,在芯片disable以后
: 功率消耗很小， 而buck converter的开关紧接电源，应该是损耗很小的。你需要编个
: 程序，多久没见负载就关断所有芯片。
|
g*******r
发帖数: 140 | 19 Generally speaking, tt is easy for buck to achieve more than 90% power
efficiency. For light load, PFM has to be applied to achieve high effieincy.
While the power efficiency is quite depending on the output/input as well,
so you'd better to check some specific datasheet for detailed informations.
If you are using an IC component, start-up should have been well handled by
the chip itself, no need to care too much about it.
Regarding to your loading range (10mA~200mA), if your input is 1.8V and
o
【在 b***y 的大作中提到】
: Thank you so much for your feedback. I really appreciate it!
: I have some more questions based on your reply
:
: Can you give some general numbers for the efficiency of buck compared with
: Boost?
: I know some boost can get a efficiency of 90% in the load range of less than
: 200mA.
: Is buck going to get higher than that?
: Could you be more specific on this? I an new to this area. Why do we
: need to care so much about the
|
c*******h
发帖数: 4883 | 20 TI的PWIC好像最多集成两个通道？
【在 g*****g 的大作中提到】
: 一个朋友在TI在AE，貌似他们的比较好
|
|
|
b***y
发帖数: 100 | 21 Thanks a lot for your reply. It is very helpful. I am one more question.
I am doing analysis of a boost. I want to derive a equation that shows how
the inductance value and
the capacitance value effect the output voltage ripple. I know generally,
as I increase the inductance's
value or the capacitance value, the output voltage ripple will decrease.
But I couldn't find a equation
that describe this relationship. Do you know how to derive this equation?
or where I can get this
【在 g*******r 的大作中提到】
: Generally speaking, tt is easy for buck to achieve more than 90% power
: efficiency. For light load, PFM has to be applied to achieve high effieincy.
: While the power efficiency is quite depending on the output/input as well,
: so you'd better to check some specific datasheet for detailed informations.
: If you are using an IC component, start-up should have been well handled by
: the chip itself, no need to care too much about it.
: Regarding to your loading range (10mA~200mA), if your input is 1.8V and
: o
|
f*****0
发帖数: 489 | 22
for chips with the disable pin, you may be able to apply the feedback to the
disable pin and turn off the controller when the voltage has reached the
desired level, thus turning the controller into a gated controller, to
preserve energy consumption.
Of course, this works best for static load and high frequency controllers.
【在 g******u 的大作中提到】
: 要省电而关闭稍微复杂一点。很多buck芯片应该有个disable pin,在芯片disable以后
: 功率消耗很小， 而buck converter的开关紧接电源，应该是损耗很小的。你需要编个
: 程序，多久没见负载就关断所有芯片。
|
g*******r
发帖数: 140 | 23 A rough calculate for boost converter output ripple:
During DT when inductor is charging, output is purely discharged by ILoad.
Thus Vo(ripple)=Iload*DT/Co.
Thus the inductor does not affect the output ripple very much in boost.
Of course, if taking ESR into account, output voltage will have jump due to
discontinous capacitor charging current.
If you want to find the proper L&C, you could just do some simple openloop
simulations with ideal component and obeserve output ripple for that.
question
【在 b***y 的大作中提到】
: Thanks a lot for your reply. It is very helpful. I am one more question.
:
: I am doing analysis of a boost. I want to derive a equation that shows how
: the inductance value and
: the capacitance value effect the output voltage ripple. I know generally,
: as I increase the inductance's
: value or the capacitance value, the output voltage ripple will decrease.
: But I couldn't find a equation
: that describe this relationship. Do you know how to derive this equation?
: or where I can get this
|
b***y
发帖数: 100 | 24 Thanks again for your reply. Your replies have been very helpful for me.
One more question: although the inductor doesn't have much effect on the
output ripple, if I really
want to calculate the effect of inductance on the output voltage ripple is
there a formula can do the
job?
How do we usually pick a inductor in boost/buck circuit design? Smaller
inductor can provide more
current and large inductor can provide less but more stable current?
Thanks,
to
【在 g*******r 的大作中提到】
: A rough calculate for boost converter output ripple:
: During DT when inductor is charging, output is purely discharged by ILoad.
: Thus Vo(ripple)=Iload*DT/Co.
: Thus the inductor does not affect the output ripple very much in boost.
: Of course, if taking ESR into account, output voltage will have jump due to
: discontinous capacitor charging current.
: If you want to find the proper L&C, you could just do some simple openloop
: simulations with ideal component and obeserve output ripple for that.
:
: question
|
g******u
发帖数: 3060 | 25 你可以去linear.com，st.com之类datasheet写得很详细的公司查查application note.
具体还是很复杂的。
the
【在 b***y 的大作中提到】
: Thanks again for your reply. Your replies have been very helpful for me.
: One more question: although the inductor doesn't have much effect on the
: output ripple, if I really
: want to calculate the effect of inductance on the output voltage ripple is
: there a formula can do the
: job?
: How do we usually pick a inductor in boost/buck circuit design? Smaller
: inductor can provide more
: current and large inductor can provide less but more stable current?
: Thanks,
|
g*******r
发帖数: 140 | 26 I did not calculate the relationship accurately. But it should not be
difficult. During phase1, output is solely discharged by load; During phase2
, output is charging by inductor, output will be increased until inductor
current is lower than loading current. You could calculate the output
voltage drop in phase1 plus that in phase2..
For choosing L&C, I suggest you find some typical products matching to your
design, and follow their L&C configuration.
the
【在 b***y 的大作中提到】
: Thanks again for your reply. Your replies have been very helpful for me.
: One more question: although the inductor doesn't have much effect on the
: output ripple, if I really
: want to calculate the effect of inductance on the output voltage ripple is
: there a formula can do the
: job?
: How do we usually pick a inductor in boost/buck circuit design? Smaller
: inductor can provide more
: current and large inductor can provide less but more stable current?
: Thanks,
|
f*****0
发帖数: 489 | 27 if you are using a modern chp (frequency > 150Khz), a 33u inductor is good
enough.
with higher frequency and lower output current, you will likely go down to
11uf or even a few uf.
in general, higher inductance provides smoother output voltage but makes the
power supply less able to respond to dynamic load. |
