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UPS602 Datasheet(PDF) 7 Page - Unisonic Technologies |
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UPS602 Datasheet(HTML) 7 Page - Unisonic Technologies |
7 / 12 page UPS602 LINEAR INTEGRATED CIRCUIT UNISONICTECHNOLOGIESCO.,LTD 7 of 12 www.unisonic.com.tw QW-R119-005.I FUNCTIONAL DESCRIPTION(Cont.) (2) Switch Frequency Set The maximum switch frequency is set to 68kHz. Switch frequency is modulated by output power POUT during IC operating. At no load or light load condition, most of the power dissipation in a switching mode power supply is from switching loss on the MOSFET transistor, the core loss of the transformer and the loss on the subber circuit. The magnitude of power loss is in proportion to the number of switching events within a fixed period of time. So lower switch frequency at lower load, which more and more improve IC’s efficiency at light load. At from no load to light load condition, The IC will operate at from Burst mode to Reducing Frequency Mode. The relation curve between fSW and POUT/POUT (MAX) as followed FIG.4. FIG.4 The relation curve between fSW and relative output power POUT/ POUT (MAX) (3) Internal Synchronized Slope Compensation Built-in slope compensation circuit adds voltage ramp onto the current sense input voltage for PWM generation, this greatly improves the close loop stability at CCM and prevents the sub-harmonic oscillation and thus reduces the output ripple voltage. (4) Frequency Hopping For EMI Improvement The Frequency hopping is implemented in the IC; there are two oscillators built-in the IC. The first oscillator is to set the normal switching frequency; the switching frequency is modulated with a period signal generated by the 2nd oscillator. The relation between the first oscillator and the 2nd oscillator as followed FIG.5. So the tone energy is evenly spread out, the spread spectrum minimizes the conduction band EMI and therefore eases the system design in meeting stringent EMI requirement. FIG.5 Frequency Hopping |
Similar Part No. - UPS602_15 |
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Similar Description - UPS602_15 |
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