Gan Systems GS-EVB-HB-0650603B-HD, Technical Manual

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GS-EVB-HB-0650603B-HD
Half Bridge Bipolar Drive Switch Board
Technical Manual
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GS-EVB-HB-0650603B-HD TM Rev. 210712 © 2021 GaN Systems Inc www.gansystems.com 7
Please refer to the Evaluation Board/Kit Important Notice on page # 16
Figure 3: HEY1011-L12C Start up sequence.
2.3 Measurement Points
The GS-EVB-HB-0650603B-HD EVB contains convenient test points for monitoring the high and low side
gate drives as well as the switch node as shown in
Figure 4
below.
When measuring V
GS_H
use a differential probe with suitable ratings for the applied bus voltage. The GS-
EVB-HB-0650603B-HD EVB uses a bipolar gate drive arrangement as shown in
Figure 5
below. When
measuring V
GS
, both gate drives are measured relative to the source of their associated GaN FET. Therefore,
the off-state voltage will be negative.
It is important to use a low inductance scope probe ground lead as shown to avoid pickup of spurious
switching noise.
2.4 Bipolar Gate Drive
Due to the high rate of change of voltages and currents in power switching circuits, unwanted inductor
currents and capacitor voltage drops can be created.
One such example is the false turn on of a FET due to a dv/dt event. In a half bridge circuit, after the low
side FET has been turned off and a suitable dead-time elapsed, the high side FET is turned on. This
produces a rapidly changing switch node voltage at the drain of the low side FET. This voltage will
produce a capacitor current:
V
GS_H
V
GS_L
SWN
Low inductance
scope measurement
Figure 4: Measurements points