Page 31 - PEN Ebook March 2021

POWER SUPPLY Power Supply

PHASE ONE: MONOLITHIC HALF son is that the power loop inductance has been
BRIDGES reduced from about 400 pH to about the 200 pH

Approximately six years ago, EPC started its first range and, when operating at a megahertz, that
phase of integration with the monolithic half makes a significant impact. The second reason is
bridge. The compelling reason for this first step that in an asymmetric buck converter, the high-
was that the half bridge is the most common side device or control device tends to run hotter
building block used in power conversion. The first than the low-side device. When those two devic-
IC devices put both the high-side and low-side es are together on the same chip, they balance
transistors onto one substrate as shown in figure each other thermally and can achieve a lower peak
1. The advantages of integration included the temperature, and an overall better efficiency.

reduction in size and cost, and, by virtue of the
close coupling of the two transistors, the parasit-
ic common source inductances were also re-
duced. Also, the advantage of increased switching
speed enables even faster and more efficient
switching power conversion systems.

Figure 2 compares the performance of discrete
devices versus a monolithic half bridge device in
a buck converter with an input voltage of 12 volts
and an output voltage of 1.2 volts operating at
1 MHz. The blue line represents the result from Figure 2: Performance comparison of GaN discrete (blue line)
How GaN Integrated two GaN discrete transistors being driven by a and GaN monolithich half bridge (green line) in a 12 V input,
12 V output buck converter operating at 1 MHz.
silicon driver in a very efficient layout on a PCB
Circuits Are Redefining board. The green line represents the performance PHASE TWO: EGAN® FET PLUS
DRIVER
of the monolithic half-bridge device.
Power Conversion The efficiency for the monolithic solution is In gallium nitride, the distance between the gate
and the drain largely determines the voltage
that the device can withstand. By shrinking that
much higher for multiple reasons. The first rea-
By Alex Lidow, Ph.D., Efficient Power Conversion

Gallium nitride (GaN) power devices have been GaN-based ICs have gone through various phas-

in production for over 10 years and, beyond just es of integration, from pure discrete devices to
performance and cost improvements, the most monolithic half-bridge devices, to power FETs
significant opportunity for GaN technology to that included their own monolithically integrat-
impact the power conversion market comes from ed driver, and, more recently, to fully monolithic
the intrinsic ability to integrate multiple devices power stages containing power FETs, drivers,
on the same substrate. This capability will allow level shifting circuits, logic, and protection.
monolithic power systems to be designed on a
single chip in a more straightforward, higher effi-
Figure 1: (left) Cross section diagram of an integrated half bridge and (right) die images of a selection of 30 V – 100 V
ciency, and more cost-effective way. symmetrical and asymmetrical half bridges.

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