IRS2168DSPBF International Rectifier, IRS2168DSPBF Datasheet - Page 15

• Manufacturer Part Number: IRS2168DSPBF
• Description: IC PFC/BALLAST CONTROL 16-SOIC
• Manufacturer: International Rectifier
• Type: PFC/Ballast Controllerr

Specifications of IRS2168DSPBF

• Frequency: 42.5 ~ 46.5 kHz
• Current - Supply: 10mA
• Current - Output: 260mA
• Voltage - Supply: 12.5 V ~ 15.6 V
• Operating Temperature: -25°C ~ 125°C
• Package / Case: 16-SOIC (3.9mm Width)
• Package: 16-lead SOIC
• Circuit: PFC Ballast Control and Half-Bridge Driver
• Offset Voltage (v): 600
• Output Source Current Min (ma): 180
• Output Sink Current Min (ma): 260
• Pbf: Yes
• For Use With: IRPLLNR5 - KIT BALLAST UNIV FLUOR 54W TL5
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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II. PFC Section
Functional Description
In most electronic ballasts it is necessary to have the
circuit act as a pure resistive load to the AC input line
voltage. The degree to which the circuit matches a pure
resistor is measured by the phase shift between the input
voltage and input current and how well the shape of the
input current waveform matches the shape of the
sinusoidal input voltage. The cosine of the phase angle
between the input voltage and input current is defined as
the power factor (PF), and how well the shape of the input
current waveform matches the shape of the input voltage
is determined by the total harmonic distortion (THD). A
power factor of 1.0 (maximum) corresponds to zero
phase shift and a THD of 0% and represents a pure
sinusoidal waveform (no distortion). For this reason it is
desirable to have a high PF and a low THD. To achieve
this, the IRS2168D includes an active power factor
correction (PFC) circuit.
The control method implemented in the IRS2168D is for a
boost-type converter (Fig. 10) running in critical-
conduction mode (CCM). This means that during each
switching cycle of the PFC MOSFET, the circuit waits
until the inductor current discharges to zero before turning
the PFC MOSFET on again. The PFC MOSFET is turned
on and off at a much higher frequency (>10 kHz) than the
line input frequency (50 to 60 Hz).
When the switch M
connected between the rectified line input (+) and (-)
causing the current in L
M
line input (+) and the DC bus capacitor C
diode D
M
voltage on C
feedback loop of the IRS2168D regulates this voltage to a
fixed value by continuously monitoring the DC bus
voltage and adjusting the on-time of M
For an increasing DC bus the on-time is decreased, and
for a decreasing DC bus the on-time is increased. This
negative feedback control is performed with a slow loop
speed and a low loop gain such that the average inductor
current smoothly follows the low-frequency line input
voltage for high power factor and low THD. The on-time
of M
modulation to be discussed later) over several cycles of
the line voltage. With a fixed on-time, and an off-time
determined by the inductor current discharging to zero,
the result is a system where the switching frequency is
free-running and constantly changing from a high
frequency near the zero crossing of the AC input line
voltage, to a lower frequency at the peaks (Fig. 11).
PFC
PFC
PFC
is turned off, L
is turned on and off at a high frequency and the
PFC
therefore appears to be fixed (with an additional
) and the stored current in L
Figure 10: Boost converter circuit
(+)
BUS
(-)
charges up to a specified voltage. The
LPFC
PFC
PFC
MPFC
is connected between the rectified
is turned on, the inductor L
PFC
to charge up linearly. When
DPFC
+
CBUS
DC Bus
PFC
PFC
flows into C
BUS
accordingly.
(through
PFC
BUS
is
.
Figure 11:
triangular PFC Inductor current and smoothed sinusoidal
line input current (dashed line) over one half-cycle of the
AC line input voltage
When the line input voltage is low (near the zero
crossing), the inductor current will charge up to a small
amount and the discharge time will be fast resulting in a
high switching frequency. When the input line voltage is
high (near the peak), the inductor current will charge up to
a higher amount and the discharge time will be longer
giving a lower switching frequency.
The PFC control circuit of the IRS2168D (Fig. 12)
includes five control pins: V
The V
external resistor voltage divider. The COMP pin programs
the on-time of M
with an external capacitor. The ZX pin detects when the
inductor current discharges to zero each switching cycle
using a secondary winding from the P
pin is the low-side gate driver output for the external
MOSFET, M
through M
protection.
The V
reference voltage for regulating the DC bus voltage (Fig.
13). The feedback loop is performed by an operational
transconductance amplifier (OTA) that sinks or sources a
current to the external capacitor at the COMP pin. The
resulting voltage on the COMP pin sets the threshold for
the charging of the internal timing capacitor (C1, Figure
13) and therefore programs the on-time of M
preheat and ignition modes of the ballast section, the gain
of the OTA is set to a high level to raise the DC bus level
quickly and to minimize the transient on the DC bus that
can occur during ignition. During run mode, the gain is
then decreased to a lower level necessary for a slower
V, I
Figure 12: IRS2168D simplified PFC control circuit
(+)
(-)
BUS
BUS
RVBUS1
RVBUS2
RVBUS
pin is regulated against a fixed internal 4.0 V
PFC
pin measures the DC bus voltage via an
PFC
Sinusoidal line input voltage (solid line),
and performs cycle-by-cycle over-current
. The OC pin senses the current flowing
PFC
COMP
and the speed of the feedback loop
VBUS
CCOMP
Control
PFC
LPFC
COM
BUS
PFC
ZX
OC
, COMP, ZX, PFC and OC.
IRS2168D(S)PbF
RZX
RPFC
FC
inductor. The P
MPFC
ROC
DFPC
PFC
t
CBUS
. During
FC
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