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NCP1608 Datasheet(PDF) 10 Page - ON Semiconductor |
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NCP1608 Datasheet(HTML) 10 Page - ON Semiconductor |
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10 / 24 page  NCP1608 http://onsemi.com 10 Introduction The NCP1608 is a voltage mode, power factor correction (PFC) controller designed to drive cost−effective pre-converters to comply with line current harmonic regulations. This controller operates in critical conduction mode (CrM) suitable for applications up to 350 W. Its voltage mode scheme enables it to obtain near unity power factor without the need for a line-sensing network. A high precision transconductance error amplifier regulates the output voltage. The controller implements comprehensive safety features for robust designs. The key features of the NCP1608 are: • Constant On Time (Voltage Mode) CrM Operation. A high power factor is achieved without the need for input voltage sensing. This enables low standby power consumption. • Accurate and Programmable On Time Limitation. The NCP1608 uses an accurate current source and an external capacitor to generate the on time. • Wide Control Range. In high power applications (> 150 W), inadvertent skipping can occur at high input voltage and high output power if noise immunity is not provided. The noise immunity provided by the NCP1608 prevents inadvertent skipping. • High Precision Voltage Reference. The error amplifier reference voltage is guaranteed at 2.5 V ±1.6% over process and temperature. This results in accurate output voltages. • Low Startup Current Consumption. The current consumption is reduced to a minimum (< 35 mA) during startup, enabling fast, low loss charging of VCC. The NCP1608 includes undervoltage lockout and provides sufficient VCC hysteresis during startup to reduce the value of the VCC capacitor. • Powerful Output Driver. A Source 500 mA / Sink 800 mA totem pole gate driver enables rapid turn on and turn off times. This enables improved efficiencies and the ability to drive higher power MOSFETs. A combination of active and passive circuits ensures that the driver output voltage does not float high if VCC does not exceed VCC(on). • Accurate Fixed Overvoltage Protection (OVP). The OVP feature protects the PFC stage against excessive output overshoots that may damage the system. Overshoots typically occur during startup or transient loads. • Undervoltage Protection (UVP). The UVP feature protects the system if there is a disconnection in the power path to Cbulk (i.e. Cbulk is unable to charge). • Protection Against Open Feedback Loop. The OVP and UVP features protect against the disconnection of the output divider network to the FB pin. An internal resistor (RFB) protects the system when the FB pin is floating (Floating Pin Protection, FPP). • Overcurrent Protection (OCP). The inductor peak current is accurately limited on a cycle-by-cycle basis. The maximum inductor peak current is adjustable by modifying the current sense resistor. An integrated LEB filter reduces the probability of noise inadvertently triggering the overcurrent limit. • Shutdown Feature. The PFC pre-converter is shutdown by forcing the FB pin voltage to less than VUVP. In shutdown mode, the ICC current consumption is reduced and the error amplifier is disabled. Application Information Most electronic ballasts and switching power supplies use a diode bridge rectifier and a bulk storage capacitor to produce a dc voltage from the utility ac line (Figure 24). This DC voltage is then processed by additional circuitry to drive the desired output. Figure 24. Typical Circuit without PFC Load Converter Rectifiers Bulk Storage Capacitor + AC Line This rectifying circuit consumes current from the line when the instantaneous ac voltage exceeds the capacitor voltage. This occurs near the line voltage peak and the resulting current is non-sinusoidal with a large harmonic content. This results in a reduced power factor (typically < 0.6). Consequently, the apparent input power is higher than the real power delivered to the load. If multiple devices are connected to the same input line, the effect increases and a “line sag” is produced (Figure 25). Figure 25. Typical Line Waveforms without PFC Line Sag Rectified DC AC Line Voltage AC Line Current 0 0 Vpeak Government regulations and utilities require reduced line current harmonic content. Power factor correction is implemented with either a passive or an active circuit to comply with regulations. Passive circuits contain a combination of large capacitors, inductors, and rectifiers that operate at the ac line frequency. Active circuits use a |
Similar Part No. - NCP1608_10 |
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Similar Description - NCP1608_10 |
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