1 | www.centralsemi.com
Introduction
The Central Semiconductor CBRDFA4-100 features the most groundbreaking technology in any discrete rectifier.
This full-wave bridge rectifier utilizes Central’s low profile surface-mount BR DFN-A package, which both saves space and
offers remarkable thermal efficiency. Bridge rectifiers are lower cost and lighter in weight as compared to center-tapped
full-wave rectifiers, and despite these benefits, do not sacrifice performance. Additionally, a diode bridge minimizes the
ripple voltage that results from rectification compared to a less expensive half-wave rectifier, resulting in increased energy
efficiency. With a forward voltage of 1V or less, Central’s CBRDFA4-100 wastes less power than competitors’ devices, and
the 1000V, 4A rating makes it ideal for high power circuits.
Low Profile Power Supply
Switched-mode power supplies have largely replaced older linear power supplies due to their lower profile and
lighter weight. These advantages are derived from the implementation of a transformer (a requirement of any power
supply). In linear power supplies, the transformer steps down the voltage directly from the mains (60Hz in the US), which
requires a heavy iron core. Switched-mode power supplies, however, take advantage of pulse-width modulation (PWM) to
create a much higher frequency AC signal (typically above 20kHz), and voltage can be stepped down with a much smaller,
lighter weight transformer. Central’s CBRDFA4-100 provides the initial rectification before the signal is passed through the
PWM-controlled power MOSFET. The optocoupler provides feedback to the PWM controller, adjusting the duty cycle (and
therefore the output voltage) as needed to produce a constant voltage at the load.
Figure 1:
Low Profile Switched-Mode Power
Supply
CBRDFA4-100 Ideal Applications
Low Profile Power Bridge Rectifier
Application Note
Application Note
Nicholas Fortunato, Technical Marketing Specialist
2 | www.centralsemi.com
CBRDFA4-100 Ideal Applications
Fast Charger
The fast charger of a smartphone must be capable of delivering a high current (~3A) while remaining at a relatively
low voltage (~5V), for total power of about 15W. This gives a very similar circuit to a linear regulated power supply,
except with an LM338 as a voltage regulator. Since standard USB-3 only supports up to 2.5W, one of several fast charging
protocols must be implemented in the cable, such as USB Power Delivery (USB-PD), which supports up to 100W. An LED is
included as a power indicator, though this is not always required. Central’s CBRDFA4-100 is able to handle the high current
requirements of a fast charger, supporting current up to 4A.
Lithium-ion batteries used in smartphones have a two-phase charging cycle. The first phase is constant current
with rising voltage, followed by constant voltage with falling current. Fast charging takes advantage of the first stage,
pumping as much current as possible with a relatively low voltage.
Figure 2:
Fast Charger
Conclusion
Despite the fact that the U.S. power grid carries 120V AC, nearly every electronic device relies on DC for its
internal operation. This makes effective rectification paramount when interfacing between the mains power and the device
in question. Central’s CBRDFA4-100 provides the advantages of a full diode bridge rectifier with the convenience of a single,
low profile discrete device.
CBRDFA4-100
+
-
C3
10u
R1
5k
LED
V1
C1
1000u
BATTERY
R2
120
U1
LM338/TO
R3
1k
CMJA5050
C2
0.1u
R4
1k
0
4
1
2
3
ADJ
1
VIN
2
VOUT
3
AC in
DC out