6
Using the Board
The evaluation board is easily prepared for use. Only minor preparations--just by soldering cables for DC supply, proper
cables for HVDC+/HVDC- high voltage bus, and load connections--are required. The evaluation board has a default con-
nection as shown in Table 1 when shipped to the customer, who is free to select dierent power supply schemes.
Power Supply Schemes
The evaluation board is built with DC supply exibility in mind and a total of 4 power supply schemes are possible. Table
1 shows all the possible power supply schemes that work for the evaluation board. A description of each scheme is
given; you are encouraged to explore each scheme and decide which one works best for your needs:
• Scheme 1 is provided by default. As the switchers used are getting bigger, driving power is also bigger. Because a
bootstrapped power supply can handle only lower driving power, it is not suitable for use when Qg of switchers goes
above 200 nC. Two isolated external supplies (+15V~30V for VCC2a and VCC2b) are needed.
• Scheme 2 is the simplest and possibly the cheapest. An external supply (+16V~30V for VCC2a) is needed for the gate
driver driving the switcher at the bottom inverter arm. VCC2b supply (slightly lower in voltage level) is obtained from
VCC2a by bootstrapping operation. For this to work, the bootstrap components D3b, D4b and R6a must be inserted,
all S1 and S2 jumpers must be shorted so that no negative supply of VEE is allowed, and the signal input 2 should be
180o out of phase to signal input 1. (If you require details of bootstrapping operation, contact Avago).
• Scheme 3 is similar to Scheme 1: it uses two external isolated supplies at VCC2a and VCC2b. Scheme 3, however,
has the advantage of getting negative supplies for VEE (or VEEa and VEEb) by introducing a 15 V Zener at D5 and R7
of around 1 kohm to provide proper biasing current at D5. For this scheme to work, all S1 and S2 jumpers must be
open while the external supplies (+18V~30V) are connected across the VCC2 and VEE pins only, not the VE pin. As the
external supply changes from +18 V to +30 V, VCC2 will stay at +15 V, but VEE changes from -3V to -15V, all w.r.t. virtual
ground at VE.
• Scheme 4 is similar to Scheme 3 in that it provides both positive and negative supplies. The dierence, however, is
that all four supplies (two positive supplies for VCC2a and VCC2b, and two negative supplies for VEEa and VEEb) are
provided externally, while VEa and VEb are real grounds. For this scheme to work, all S1 and S2 jumpers must be open.
Table 1.
Power
Supply
Scheme
V
CC2a
V
EEa
S1a S2a D5a/
R7a
V
CC2b
V
EEb
S1b S2b D5b/
R7b
Remarks
1 +15V~30V
External
0 V s/c s/c NM +15V~30V
External
0 V s/c s/c NM Higher Power (Default)
2 external supplies needed for
V
cc2a
& V
cc2b
2 +16V~30V
External
0 V s/c s/c NM
Bootstrapped
from V
CC2a
(+15V~30V)
0 V s/c s/c NM simplest
1 external supply needed for
V
cc2a
3 +18V~30V External open open 15V/
1k
+18V~30V External open open 15V/
1k
V
EE
available
2 external supplies needed for
V
cc2a
& V
cc2b
Virtual gnds V
ea
& V
eb
generated
thro D5 & R7
15V
-3V~-15V
15V -3V~-15V
4 Dual Supply External open open NM Dual Supply External open open NM V
EE
available
2 external supplies needed for
V
cc2a
& V
cc2b
Gnds V
ea
& V
eb
provided
15V
-3V~-15V
15V
-3V~-15V