ADP1055-EVALZ User Guide
UG-710
Rev. B | Page 3 of 43
EVALUATION BOARD OVERVIEW
This
ADP1055-EVALZ
evaluation board and
ADP1055DC1-
EVALZ
daughter card feature the
ADP1055
in a dc-to-dc
switching power supply in full bridge topology with
synchronous rectification operating at 125 kHz switching
frequency.
Figure 4 shows the block diagram of the evaluation board. The
circuit is designed to provide a rated load of 12 V, 20 A from a
dc input voltage source of 38 V dc to 60 V dc. The
ADP1055
provides functions, including output voltage regulation,
synchronization, constant current control, pre-bias start up,
and comprehensive protection functions.
The evaluation kit consists of a power board, daughter card, and
the auxiliary circuit board.
POWER BOARD AND POWER TRAIN OVERVIEW
The power board is shown in Figure 1. Referring to the
Schematics and Artwork section, the circuit components are
described as follows. The primary and secondary H bridges are
formed with MOSFETs QA through QD (primary side) and
MOSFETs Q30, Q34, Q38, and Q40 (secondary side).
Transformer T2 provides the isolation. The output filter consists
of L8 and a capacitor bank (C48, C49, C51, C70, C73, and C74).
This is the main power stage. The active snubber is made up of
clamp capacitor C192, MOSFET Q23 (pMOS), and driver U19.
Additional circuitry around the power train is described as
follows. The input filter consists of a single state LC (L10 and
C6-13). Components U2 and U5 are half bridge 4 A drivers
based on the Analog Devices, Inc.,
i
Coupler technology that
provides gate drive for driving the primary H bridge. Secondary
side H bridge drivers consist of U20 and U21.
The primary current is sensed using a current transformer T1
that provides primary fast and accurate over current protection
whereas the secondary side current (that is, the load current) is
sensed using a sense resistor (R5, R9).
ADP1055
DAUGHTER CARD
The daughter card is shown in Figure 2. The
ADP1055
daughter
card consists of a 3.3 V LDO that powers the
ADP1055
IC. The
PWMs for the primary switches (OUTA to OUTD) and for the
secondary switches (SR1 and SR2) are connected from the
daughter board to the power board
12
386
-00
2
Figure 2.
ADP1055
Mounted on Daughter Card
AUXILARY POWER BOARD CIRCUIT
The auxiliary power board, included in the kit, is shown in
Figure 3. The auxiliary power circuit provides 9 V on the
primary side and 9 V and 5 V (derived using a Zener diode)
on the secondary side. The approximate minimum operating
voltage of the auxiliary power board is 30 V.
123
86
-003
Figure 3. Auxiliary Power Board
VDD_SEC = 9V
OR
5V FROM USB
VDD_PRI = 9V
ADP1055
DAUGHTER CARD SOCKET
MOSFET
DRIVERS
FULL BRIDGE
SYNC
RECTIFIER
38V TO 60V DC
I
2
C INTERFACE
AUXILLARY PSU
PRIMARY = +9V
SECONDARY1 = +9V
SECONDARY2 = +5V
ADuM3223
i
Coupler
+DRIVER
OUTA
TO
OUTD
12V, 20A
3.3V LDO
SR1
AND
SR2
5V
123
86-
004
Figure 4.
ADP1055-EVALZ
Evaluation Board Block Diagram
