Stepping down from 100VDC to 5V-15V?

Greetings.

Let's say i want to make an 220VAC inverter from a battery pack in the 72V-100V range.
The converter would need 15V and/or 5V to power the electronics and gate drivers.
How can these voltages be obtained from a 100VDC battery?

A brute force approach would be to make a tap in the battery pack at about 24V level, and regulate down from there, but i wonder if there is some sort of common non-battery-specific solution to this problem.

There are LDOs that go up to 125V, so one way would be to bear the heat dissipation from these, or use one to power a smaller step-down converter that would give the main use voltage.

However, i've found electric vehicles and large backup systems that use battery packs in 200-300V range, where there are no ICs at all.
There i can only think of going 101 and using an astable multivibrator of HV bipolar transistors to drive a common step-down transformer. Crude, but might well be effective.

So, the question is - how that sort of a problem is being solved usually?
Or is the "brute-force" approach the usual one?

How about a buck converter?

barry said:

How about a buck converter?

Click to expand...

Powered by what?
Except for a few exotics, all control ICs or things like 555 need low voltage, as do MOSFET gates.

Or am i missing something obvious?

The simplest way would be to use an off the shelf DC - DC SMPS as your step down power source. There are loads of them designed specifically for DC input in the voltage ranges you are talking about.

The typical approach is using a step-down or buck converter or a flyback converter. Linear regulator from 120 V would be extremely inefficient!

While a 125V input buck IC may be a bit difficult to find, there are many flyback converter solutions like Power Integrations TOP243GN-TL that should work fine. Set the output voltage at 15 V and obtain the 5 V with a LDO.

Ah, nice.
So there are ICs for the purpose after all.

Thanks for clarifying.

i will advice you to go for bulk or flyback its more reliable...

Artlav said:

Powered by what?
Except for a few exotics, all control ICs or things like 555 need low voltage, as do MOSFET gates.

Or am i missing something obvious?

Click to expand...

Usually when dealing with a HV input, there will be some low-efficiency shunt regulator (a zener or a LDO) which supplies some of the control circuitry. Sometimes this shunt regulator is only used during startup, afterwards the circuit bootstraps its power supply from its output (like an auxiliary winding on a transformer or inductor, for example), which increases efficiency a bit.

So there are ICs for the purpose after all.

Click to expand...

Surely.

There's a however a broad range between integrated switch IC converters and all-discrete "multivibrators". A few dedicated HV switchers are available, but in many cases a comination of low or medium voltage switch controllers and HV transistor gives more flexibility. Just a matter of creative circuit design.