Evaluation Board Overview; Power Train Overview; Transformer; Connectors - Analog Devices ADP1071-1EVALZ User Manual

ADP1071-1EVALZ

EVALUATION BOARD OVERVIEW

This evaluation board features the
switching power supply in flyback topology with multiple
outputs in a compact form factor.
The ADP1071-1EVALZ circuit is designed to provide +5.5 V,
+24 V, and −15 V at a total rated power of 15 W from a dc input
voltage source of 18 V to 32 V
DC
load conditions, the ADP1071-1
frequency of 50 kHz. The switching frequency minimizes
switching losses of the converter and is high enough to keep the
transformer size small.

POWER TRAIN OVERVIEW

The ADP1071-1EVALZ is shown in Figure 1 and Figure 2. The
circuit components on the ADP1071-1EVALZ are described as
follows:
•
The input filter consists of a capacitor bank including
Capacitor 24 (C24) to Capacitor 57 (C57).
•
Q3 is an N channel, metal-oxide semiconductor field effect
transistor (MOSFET) used as the main switch on the
primary side.
•
Transformer T1 provides isolation.
•
The secondary side of the circuitry has three windings
followed by one rectifying diode and one resistor/capacitor
(RC) snubber.
•
The output filter consists of two capacitors for each of the
rails. These capacitors include C60 and C65 at the 24 V
rail, C62 and C66 at the 5.5 V rail, and C7 and C67 at the
−15 V rail.
The snubber for the main switch is composed of D11 and D12.
The ADP1071-1 flyback controller (U1) is the power controller.
The power controller integrates gate drive for driving the
primary switch and synchronous rectifier based on the Analog
Devices, Inc., iCoupler® technology.
During startup, U1 is powered by the J2 or J4 input via an external
start-up circuit (Q7, R17, D5, or C38). When switching and
power conversion starts, the auxiliary winding provides power
User Guide
ADP1071-1 in a dc-to-dc
. To maximize efficiency at light
DC
operates at a switching
to the VREG1 pin. R15 is the sense resistor that senses the
primary current.

TRANSFORMER

The transformer has 10 pins and five windings, including
primary winding (Pin 4 to Pin 3), auxiliary winding (Pin 2 to
Pin 1), and three output windings (Pin 6 to Pin 7, Pin 8 to Pin 9,
and Pin 9 to Pin 10).
PRI
18V TO 36V
DC DC
66kHz
AUX
10V AND 20mA

CONNECTORS

The connections to the ADP1071-1EVALZ are shown in Table 1.
Table 1. Evaluation Board Connections
Connector Pin Function
J2 Pin 1, VIN+, dc input
Pin 2, VIN−, ground return for dc input
J5 Pin 1, 24 V
Pin 2, 5.5 V
Pin 3, GND, return for dc output
Pin 4, −15 V

CAUTION

The ADP1071-1EVALZ uses high voltages. Take extreme
caution, especially on the primary side, to ensure safety. It is
advised to switch off the evaluation board when not in use. Use
a current limited, isolated dc source at the input.
Rev. 0 | Page 3 of 13
6
4
7
3
8
OUTPUT WINDING
2
5.5V AND 500mA
9
OUTPUT WINDING
1
15V AND 200mA
10
Figure 3. Transformer Diagram
output
DC
output
DC
output
DC
UG-1384
OUTPUT WINDING
24V AND 400mA