IRPLLNR3 Просмотр технического описания (PDF) - International Rectifier
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IRPLLNR3 Datasheet PDF : 27 Pages
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Figure 1:
Top trace: Half-bridge output voltage
Middle trace: Bus Voltage
Bottom trace: VCC of the IR2167
IRPLLNR3
Preheat Mode
When the ballast reaches the end of the UVLO mode, the Preheat mode is entered. At this point the
ballast control oscillator of the IR2167 has begun to operate and the half-bridge output is driving the
resonant load (lamp) circuit. The ballast control section oscillator of the IR2167 is similar to oscillators
found in many popular PWM voltage regulator ICs and consists of a timing capacitor and resistor
connected to ground. Resistors RT and RPH program a current which determines the ramp up time
of capacitor CT and resistor RDT determines the ramp down time. The downward ramping time of CT
is the dead time between the switching off of the LO (HO) and the switching on of the HO (LO) pins on
the IR2167. The Preheat mode frequency of oscillation is selected such that the voltage appearing
across the lamp is below the minimum lamp ignition voltage while supplying enough current to preheat
the lamp filaments to the correct emission temperature within the Preheat mode period. The preheat-
ing of the lamp filaments is performed with a constant voltage during the Preheat mode. The wave-
form in Figure 2 shows the lamp filament current while Figure 3 shows lamp filament voltage during
the normal Startup, Preheat and Ignition Ramp modes of the ballast.
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