IRS2573D Ver la hoja de datos (PDF) - International Rectifier
Número de pieza
componentes Descripción
Fabricante
IRS2573D Datasheet PDF : 28 Pages
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IRS2573D
on VCC reaches the start-up threshold (UVLO+), and, the voltage on RST pin is less than 1.5V, the IC turns on
and the full-bridge oscillator (CT) and gate driver outputs (HO1, LO1, HO2 and LO2) begin to oscillate. The
capacitor from VCC to COM begins to discharge due to the increase in IC operating current. An auxiliary supply
(secondary winding, charge pump, etc.) should then take over as the main supply voltage before VCC discharges
to the IC turn-off threshold (Figure 3) and charge VCC up to the internal zener clamp diode voltage (15.6V
typical). During UVLO mode, the full-bridge and buck are off, the ignition timer and clock are off, the fault and
good counters are reset, and the fault latch is reset.
VCC
IC 'OFF'
VUVLO+
CVCC
DISCHARGE
VHYST
VUVLO-
IC 'ON'
INTERNAL VCC
ZENER CLAMP VOLTAGE
DISCHARGE
TIME
RSUPPLY & CVCC
TIME CONSTANT
AUXILIARY SUPPLY
OUTPUT
t
Figure 3, IC supply voltage during turn-on
General Mode
During General Mode, the IC reacts to the different load conditions (open-circuit, short-circuit, lamp warm-up,
constant power running, under-voltage lamp faults, transient under-voltage lamp faults, over-voltage lamp faults,
lamp non-strike, etc.) by turning the buck circuit on or off, adjusting the buck circuit on-time, or counting the
occurrence of the different fault conditions and turning the complete IC off. The IC senses the different load
conditions at the VSENSE and ISENSE pins, compares the voltages at these pins against the programmed
thresholds at the OV and OC pins, and determines the correct operating mode of the IC (see State Diagram).
Ignition Timer
The ignition timer is enabled when the IC first enters IGN Mode. The ignition timer frequency is programmed with
the external capacitor at the TIGN pin. CTIGN charges up and down linearly through internal sink and source
currents between a fixed voltage window of 2V and 4V (Figure 4). This sets up an internal clock (666ms typical)
that is divided out 128 times and then used to turn the ignition gate driver output (IGN pin) on and off for a given
on and off-time (21sec ‘high’/64sec ‘low’ typical). A logic ‘high’ at the IGN pin will turn the external ignition
MOSFET on and enable the external sidac-controlled pulse ignition circuit (see Figure 5, and Typical Application
Diagram). The ignition circuit will continuously try to ignite the HID lamp for 21sec ‘on’ and 64sec ‘off’ until the
lamp ignites. If the lamp does not ignite after 787sec then the IC will enter Fault Mode and latch off. If the lamp
ignites successfully, the voltage at the VSENSE pin will fall below VOV(2/5) due to the low impedance of the lamp
and the ignition timer will be disabled (logic ‘low’ at the IGN pin).
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