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ML4824

Micro Linear

Power Factor Correction and PWM Controller Combo

June 1998 ML4824* Power Factor Correction and PWM Controller Combo GENERAL DESCRIPTION The ML4824 is a controller for p...


ML4824

Micro Linear


Octopart Stock #: O-452947

Findchips Stock #: 452947-F

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Description
June 1998 ML4824* Power Factor Correction and PWM Controller Combo GENERAL DESCRIPTION The ML4824 is a controller for power factor corrected, switched mode power supplies. Power Factor Correction (PFC) allows the use of smaller, lower cost bulk capacitors, reduces power line loading and stress on the switching FETs, and results in a power supply t
More View hat fully complies with IEC1000-2-3 specification. The ML4824 includes circuits for the implementation of a leading edge, average current, “boost” type power factor correction and a trailing edge, pulse width modulator (PWM). The device is available in two versions; the ML4824-1 (fPWM = fPFC) and the ML4824-2 (fPWM = 2 x fPFC). Doubling the switching frequency of the PWM allows the user to design with smaller output components while maintaining the best operating frequency for the PFC. An over-voltage comparator shuts down the PFC section in the event of a sudden decrease in load. The PFC section also includes peak current limiting and input voltage brownout protection. The PWM section can be operated in current or voltage mode at up to 250kHz and includes a duty cycle limit to prevent transformer saturation. FEATURES s s s Internally synchronized PFC and PWM in one IC Low total harmonic distortion Reduces ripple current in the storage capacitor between the PFC and PWM sections Average current, continuous boost leading edge PFC Fast transconductance error amp for voltage loop High efficiency trailing edge PWM can be configured for current mode or voltage mode operation Average line voltage compensation with brownout control PFC overvoltage comparator eliminates output “runaway” due to load removal Current fed gain modulator for improved noise immunity Overvoltage protection, UVLO, and soft start s s s s s s s BLOCK DIAGRAM 16 1 *Some Packages Are Obsolete 13 VEAO VFB VEA – + – IEAO POWER FACTOR CORRECTOR OVP 3.5kΩ + VCCZ 13.5V VCC 15 2.5V IEA + – + 2.7V – 7.5V REFERENCE S Q Q VREF 14 IAC 2 VRMS 4 GAIN MODULATOR 3.5kΩ –1V + – R S R PFC OUT ISENSE 3 PFC ILIMIT Q Q 12 RAMP 1 7 RAMP 2 8 8V OSCILLATOR (-2 VERSION ONLY) x2 DUTY CYCLE LIMIT VDC 6 VCC 1.25V – + – S VFB – + Q Q PWM OUT 11 VIN OK SS 5 50µA + 1V – + 2.5V 8V R DC ILIMIT DC ILIMIT 9 PULSE WIDTH MODULATOR VCCZ UVLO 1 ML4824 PIN CONFIGURATION ML4824 16-Pin PDIP (P16) 16-Pin Wide SOIC (S16W) IEAO IAC ISENSE VRMS SS VDC RAMP 1 RAMP 2 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 VEAO VFB VREF VCC PFC OUT PWM OUT GND DC ILIMIT TOP VIEW PIN DESCRIPTION PIN NAME FUNCTION PIN NAME FUNCTION 1 2 3 4 5 6 7 8 IEAO IAC ISENSE VRMS SS VDC RAMP 1 RAMP 2 PFC transconductance current error amplifier output PFC gain control reference input 9 10 11 DC ILIMIT GND PWM current limit comparator input Ground PWM OUT PWM driver output PFC OUT VCC VREF VFB VEAO PFC driver






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