Power circuitry design for battery operated device

multiple battery input design

Hi,

Suppose I use alkaline batteries with total voltage range from +4.8V to +9.6V to operate a device, how should I design the power circuitry to supply those parts which require higher voltage supply.

For example, if I need to turn on a LED backlight which requires +12V supply, should I design a boost switching regulator circuit to step up the input voltage to +12V in order to supply to the LED backlight?

What if I need to operate a motor which requires +6V (@2.5A start surge, <500ms)? Should I design the +12V boost switching regulator circuit to be capable of supplying output current up to 3A and then step-down to +6V using a standard regulator or LDO for operating the motor? Or would it be better if I design another boost switching circuit to supply +6V directly to the motor from the input source?

In fact, I do also need +3.3V and +1.8V voltage supply for the rest of the circuit but I guess this is fine as I can immediately step-down from battery input source since the voltage is lower than the min. input voltage.

Please advice. Thanks.

Regards,
Eric

battery operated 3.3v supply

your are right, for the internal vcc=3.3/1.8v, you can use a regulator or ldo to generate this supply.
but for the +12, you have to use a boost circuit or charge pump. the +6v value, you can use a clamp circuit, the power could be +12v and the battery supply, when the supply is <6v, you use the +12v, if the value >6v, you can direct supply use the supply. hope it is helpful, good luck.

how to use a battery operated device with ac

Areky_qin said:

your are right, for the internal vcc=3.3/1.8v, you can use a regulator or ldo to generate this supply.
but for the +12, you have to use a boost circuit or charge pump. the +6v value, you can use a clamp circuit, the power could be +12v and the battery supply, when the supply is <6v, you use the +12v, if the value >6v, you can direct supply use the supply. hope it is helpful, good luck.

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Hi there,

Thanks for your reply. However, I am not quite clear about the clamp circuit you mentioned. Is it possible for you to give me an example?

Thanks again.

Regards,
Eric

I remember there is an one chip solution which includes Buck, Boost, LDO and some other Power circuitry inside. Many companies provide such kind of chip, like Skyworks.

jwfan said:

I remember there is an one chip solution which includes Buck, Boost, LDO and some other Power circuitry inside. Many companies provide such kind of chip, like Skyworks.

Click to expand...

Yes. In fact, I was advised to design a flyback converter which can provide multiple outputs. However, I am reluctant to do so due to the complexity and tedious calculations.

Regards,
Eric