IR2520D International Rectifier, IR2520D Datasheet - Page 9

• Manufacturer Part Number: IR2520D
• Manufacturer: International Rectifier

Specifications of IR2520D

• Operating Temperature (max): 125C
• Operating Temperature (min): -25C
• Pin Count: 8
• Mounting: Through Hole
• Package Type: PDIP
• Screening Level: Commercial
• Lead Free Status / Rohs Status: Not Compliant

V VCO
lamp removal (open circuit), a dropping DC bus during a
mains brown-out or mains interrupt, lamp variations over
time, or component variations. To protect against this, an
internal high-voltage MOSFET is turned on at the turn-off of
HO and the VS-sensing circuit measures VS at each rising
edge of LO. If the VS voltage is non-zero, a pulse of current
is sinked from the VCO pin (Figures 5 and 6) to slightly
discharge the external capacitor, CVCO, causing the
frequency to increase slightly. The VCO capacitor then
charges up during the rest of the cycle slowly due to the
internal current source.
I MHS
The frequency is trying to decrease towards resonance
by charging the VCO capacitor and the adaptive ZVS cir-
cuit “nudges” the frequency back up slightly above reso-
nance each time non-ZVS is detected at the turn-on of LO.
The internal high-voltage MOSFET is then turned off at the
turn-off of LO and it withstands the high-voltage when VS
slews up to the DC bus potential. The circuit then remains in
this closed-loop adaptive ZVS mode during running and
maintains ZVS operation with changing line conditions, com-
ponent tolerance variations and lamp/load variations. Dur-
ing a lamp removal or filament failure, the lamp resonant
tank will be interrupted causing the half-bridge output to go
www.irf.com
I MLS
Fig. 6 IR2520D non-ZVS protection timing diagram.
V
V
V
HO
LO
VS
I L
!
Too close to resonance.
Hard-switching and high
peak MOSFET currents!
!
!
Frequency shifted higher
to maintain ZVS.
open circuit (Figure 7). This will cause capacitive switching
(hard-switching) resulting in high peak MOSFET currents
that can damage them. The IR2520D will increase the fre-
quency in attempt to satisfy ZVS until the VCO pin de-
creases below 0.82V (V
Mode and latch the LO and HO gate driver outputs ‘low’ for
turning the half-bridge off safely before any damage can
occur to the MOSFETs.
V VCO
I MHS
Crest Factor Over-current Protection
During normal lamp ignition, the frequency sweeps through
resonance and the output voltage increases across the
resonant capacitor and lamp until the lamp ignites. If the
lamp fails to ignite, the resonant capacitor voltage, the inductor
voltage and inductor current will continue to increase until
the inductor saturates or the output voltage exceeds the
maximum voltage rating of the resonant capacitor or inductor.
The ballast must shutdown before damage occurs. To
protect against a lamp non-strike fault condition, the IR2520D
uses the VS-sensing circuitry (Figure 5) to also measure
the low-side half-bridge MOSFET current for detecting an
I MLS
V
V
V
HO
LO
VS
Fig. 7 Lamp removal or open filament fault
!
Capacitive switching. Hard-switching
and high peak MOSFET currents!
!
IR2520D(S) & (PbF)
condition timing diagram
!
VCOSD
). The IC will enter Fault
RUN MODE
Frequency shifted higher
until VCO < 0.82V. LO and
HO are latched low before
damage occurs to MOSFETs.
FAULT MODE
0.85V
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