©
Semiconductor Components Industries, LLC, 2012
November, 2012
−
Rev. 1
1
Publication Order Number:
EVBUM2162/D
NCP1608BOOSTGEVB
NCP1608 100 W Boost
Evaluation Board User's
Manual
Introduction
The NCP1608 is a voltage mode power factor correction
(PFC) controller designed to implement converters to
comply with line current harmonic regulations. The device
operates in critical conduction mode (CrM) for optimal
performance in applications up to 350 W. Its voltage mode
scheme enables it to obtain near unity power factor (PF)
without the need for a line-sensing network. The output
voltage is accurately controlled with an integrated high
precision transconductance error amplifier. The controller
also implements a comprehensive set of safety features that
simplify system design.
This application note describes the design and
implementation of a 400 V, 100 W, CrM boost PFC
converter using the NCP1608. The converter exhibits high
PF, low standby power dissipation, high active mode
efficiency, and a variety of protection features.
The Need for PFC
Most electronic ballasts and switch
−
mode power supplies
(SMPS) use a diode bridge rectifier and a bulk storage
capacitor to produce a dc voltage from the utility ac line.
This causes a non-sinusoidal current consumption and
increases the stress on the power delivery infrastructure.
Government regulations and utility requirements mandate
control over line current harmonic content. Active PFC
circuits are the most popular method to comply with these
harmonic content requirements. System solutions consist of
connecting a PFC pre
−
converter between the rectifier bridge
and the bulk capacitor (Figure 1). The boost converter is the
most popular topology for active PF correction. It produces
a constant output voltage and consumes a sinusoidal input
current from the line.
Figure 1. Active PFC Stage with the NCP1608
Rectifiers
+
AC Line
High
Frequency
Bypass
Capacitor
NCP1608
PFC Pre
−
Converter
Converter
Load
+
Bulk
Storage
Capacitor
Basic Operation of a CrM Boost Converter
For medium power (< 350 W) applications, CrM is the
preferred control method. CrM operates at the boundary
between discontinuous conduction mode (DCM) and
continuous conduction mode (CCM). In CrM, the drive on
time begins when the inductor current reaches zero.
CrM combines the reduced peak current of CCM
operation with the zero current switching of DCM
operation. This control method causes the frequency to vary
with the instantaneous line input voltage (V
in
) and the output
load. The operation and waveforms of a CrM PFC boost
converter are illustrated in Figure 2. For detailed
information on the operation of a CrM boost converter for
PFC applications, please refer to AND8123 at
www.onsemi.com
.
http://onsemi.com
EVAL BOARD USER’S MANUAL
