Vicor PI2003-EVAL1 Active ORing Evaluation Board - Manual (Page 5)

Before initial power-up follow these steps to configure the
evaluation board for specific end application requirements:
2.0 Controller Bias Voltage (VC):
2.1 The PI2003 Controller has a separate input (VC) that
provides power to the control circuitry and the gate
driver. An internal voltage regulator (VC) clamps the
VC voltage to 11 V typically. PI2003 EVAL1 is
configured to bias the controllers directly from the
bus voltage (Vin1 and Vin2). Two bias resistors
(R1 and R3: 11 k
Ω, 1/4 W, 0805) are connected from
the return input (Vin1+ and Vin2+) to each controller
VC pin, see schematic in figure 2. The bias resistors
are selected to support -48 V bus voltage (36 V to 60 V).
2.2 If the bus voltage (Vin1 and Vin2) range is
different from 36 V to 60 V and higher than the
Clamp voltage, 11 V typical, the Rbias value has
to be changed using the following equations:
2.2.1 Select the value of Rbias using the
following equations:
Rbias =
Vbus min – VC clampMAX
IC max
2.2.2 Calculate Rbias maximum power
dissipation:
Pd Rbias =
(Vbus max – VC clampMIN ) 2
Rbias
Where:
Vbus min : V(bus) minimum voltage
Vbus max : V(bus) maximum voltage
VC clampMAX : Maximum controller clamp
voltage, 12 V
VC clampMIN : Minimum controller clamp
voltage, 10 V
IC MAX : Controller maximum bias current,
use 2.0 mA
2.2.3 For example, if the minimum
V(bus) = 36 V and the maximum
V(bus) = 60 V
Rbias =
Vbus min – VC clampMAX
IC MAX
Rbias =
36 V – 12 V
= 12 K Ω
2.0 mA
Rbias maximum power dissipation is at maximum
input voltage.
PD Rbias =
(Vbus
max
– VC
clampMIN
) 2
=
(60 V – 10 V) 2
= 208 mW
Rbias 12 K Ω
2.3 The PI2003-EVAL1 is configured to allow the customer
to use a direct bias voltage to the controller VC pin
independent of the bus input. VC1 and VC2 terminals
can be connected directly to the controller VC pins
after removing R1 and R3 and populating R5 and R6.
3.0 Hook Up of the Evaluation Board,
refer to Figures 3 and 4.
3.1 If isolated power supplies are used, Figure 3.
3.1.1. Connect the positive terminal of PS1 power
supply to Vin1+. Connect the negative terminal
of PS1 Vin1-. Set the power supply to 48 V.
Keep PS1 output disabled (OFF).
3.1.2. Connect the positive terminal of PS2 power
supply to Vin2+. Connect the negative terminal
of PS2 Vin2-. Set the power supply to 48 V.
Keep PS2 output disabled (OFF).
3.2 If non-isolated power supplies are used, Figure 4.
3.2.1. Connect the positive terminal of PS1 power
supply to Vin1+ through a Schottky diode.
Connect the negative terminal of PS1 Vin1-.
Set the power supply to 48 V. Keep PS1 output
disabled (OFF).
3.2.2. Connect the positive terminal of PS2 power
supply to Vin2+ through a Schottky diode.
Connect the negative terminal of PS2 Vin2-.
Set the power supply to 48 V. Keep PS2 output
disabled (OFF).
Picor Corporation • www.picorpower.com PI2003-EVAL1 User Guide Rev 1.0 Page 5 of 8