I have two power rails: 3V and 12V. Both of them have variable loads (e.g., microcontrollers, motors) and power sources (e.g., solar cell, battery) on them. The typical max current is ~1A on both rails. I want to couple them, so that if there is more load on the 12V side than the 12V sources can supply, but the power sources on the 3V rail can provide power, power shall be converted from 3V to 12V and vice versa. Basically, what a transformer would do for AC power.
A block diagram of the setting might look as follows:
As requested from the comments, here are a few more details on the scenario:
- Any kind of consumer/producer combination must be possible. Obviously, the system needs one producer on one of the rails.
- Max total current on the 3V does not exceed 2A.
- Max total current on the 12V does not exceed 1A.
- If there is higher load than supply, any kind of degradation is acceptable. A voltage drop would be the best scenario, but any kind of failure is ok, as long as the hardware does not take damage and there are no excessive overvoltage spikes.
The potential solutions I found so far are:
- A dual-active bridge: Here I only found components and controllers that are designed for several kW of power, which is obviously too much.
- Bidirectional converters like the Richtek RT6190GQW. However, if I understand the datasheet correctly, these need external switching between Buck and Boost mode.
(I imagine one would do this with a microcontroller and a simple control like
if v_a > 3V then boost_enable, else buck_enable, but I have the feeling that this is prone to oscillations. Maybe a comparator circuit is the solution here?)
So the question basically is: Is there is a simple IC or circuit that could achieve this behavior for a low-power scenario. Simplicity and few parts would be a design goal. (I'm rather inexperienced with DC-DC converters, so perhaps I'm missing something fundamental here.)
- How to implement step-up DC-DC converter with reverse current capability - higher power scenario. Suggests the use of the LT8708 IC, which is somehow what I want, but needs >5V VCC power to be functional. (Also the example application looks quite complicated)
- bidirectional buck/boost converter vs separate buck and boost converters , Adding a 24V battery to an existing 12V RV system with bidirectional charging - Basic design of a bi-directional converter. However, both leave the question of the control of the buck-boost converter unresolved.