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7

RPLLNR3

The IR2167 Ballast Control IC is used to program the ballast operating points and protect the ballast

against conditions such as lamp strike failures, low DC bus, thermal overload or lamp failure during

normal operations. It is also used to regulate the DC bus and for power factor control allowing high

power factor and low harmonic distortion.

Power Factor Correction Section

The power factor correction section contained in the IR2167 forms the control for a boost topology

circuit operating in critical conduction mode. This topology is designed to step-up and regulate the

output DC bus voltage while drawing sinusoidal current from the line (low THD) which is “in phase”

with the AC input line voltage (HPF).

Ballast Control Section

The ballast control section of the IR2167 Ballast Control IC contains an oscillator, a high voltage half-

bridge gate driver and lamp fault protection circuitry. Please, refer to the datasheet of this IC for the

block diagram and the state diagram. Following is a breakdown of the operation of the ballast in all of

the different modes of operation. Please, refer to the AN: IRPLLNR2 for the ballast section design

(www.irf.com/Lighting).

Startup Mode

When power is initially applied to the ballast, the voltage on the VCC pin of the IR2167 begins to

charge up. The voltage for the IR2167 is derived from the current supplied from the rectified AC line

through startup resistor RSUPPLY. During this initial startup when the VCC voltage of the IR2167 is

below its rising under-voltage lock-out threshold (11.4V), it is in its UVLO and also its micro-power

mode. The micro-power mode of the IR2167 allows the use of a large value, low wattage startup

resistor (RSUPPLY). When the voltage on the IR2167 reaches the rising under-voltage lockout threshold,

the oscillator is enabled (this assumes that there are no fault conditions) and drives the half-bridge

output MOSFETs (MHS and MLS). When the half-bridge is oscillating, capacitor CSNUB, diodes

DCP1 and DCP2 form a snubber /charge pump circuit which limits the rise and fall time at the half-

bridge output and also supplies the current to charge capacitor CVCC2 to the VCC clamp voltage

(approx. 15.6V) of IR2167. When the rising under-voltage lockout threshold of the IR2167 is reached,

the PFC oscillator starts to oscillate and drive MOSFET MPFC to boost and regulate the bus voltage to

400 VDC. Oscillagraph of the start up of the VCC of the IR2167 DC is shown in figure 1.