Why We Launched Bi-Directional Power Components

July 15, 2016

In the second part of the interview series with Harry Vig, he talks about why Vicor launched bi-directional components and how they can benefit a wide range of different applications.


Harry Vig VicorYou talk about components acting as if they were DC power transformers. Why hasn’t anyone developed bi-directional parts previously?

The bi-directional parts that I covered in the webinar (Enabling Bi-Directional Energy Flow Using DC Power Transformers) were first released around ten years ago, so they aren’t new. When they were released, we weren’t trying to make a bi-directional component: we wanted to push the boundaries of efficiency by using a fixed ratio. So the components aren’t new; bi-directionality is just different usage of an existing part.

The real issue was that no one had thought of using power components in both directions previously. So it took some time to develop the idea.

There were a couple of stepping stones. In fact, these components allow reverse energy flow when dealing with a large negative-going load transient. This is what gives them their outstanding transient response, allowing the component to recover more quickly. It’s not just these components that exhibit the phenomena: you can even see it happening in synchronous buck rectifiers. With a reversible regulator, you need to change the control system, as you are regulating a different output in one direction than the reverse.  With a fixed transformer ratio, there is no regulation, hence change in control, and no recovery time.

In reality bi-directional functionality was a totally unrelated (and unexpected) advantage from the move from one topology to another. When we realized the capability, we spent some time working out if this was something power engineers really wanted before characterizing the components and promoting their bi-directional functionality.


Can you tell us about some of the applications using energy storage that can benefit from this approach?

Any application involving battery charging and discharging can obviously benefit from using bi-directional components: they’re the ones that people see immediately. But the approach is applicable to any electronic load that can also function as power supply.

In practice there are a vast number of opportunities to use this approach. Engineers should look at their system diagram and consider where there is energy storage and energy recovery: that’s where there is an opportunity for these bi-directional products. It’s not just electrical energy: it could be kinetic energy (as with an electric or hybrid-electric car), potential energy, or any other form of energy that can be converted to electricity. Power designers need to look beyond power chains and ask “How could I use this approach to improve my system?”


For some applications it will be important to be able to switch from one direction of power flow to another in a short time. How quickly can these “DC transformers” switch the energy flow?

In practice it’s instantaneous. To be completely correct it’s within the bandwidth of the component, which is related to the switching frequency. You’ll have an LC tank which will act as a filter, but because it’s designed for the very high switching frequency we use in our SAC topology, it’s always much higher than regulated stages for the same power level.

To find out more, watch the webinar, which is available as an on-demand rebroadcast or read Harry Vig’s other interviews.


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