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CM6805A Datasheet(PDF) 7 Page - Champion Microelectronic Corp. |
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CM6805A Datasheet(HTML) 7 Page - Champion Microelectronic Corp. |
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7 / 15 page  CM6805A 10-PIN Green-Mode PFC/PWM Combo CONTROLLER 2010/04/20 Rev 1.4 Champion Microelectronic Corporation Page 7 Functional Description The CM6805A consists of an ICST (Input Current Shaping Technique), CCM (Continuous Conduction Mode) or DCM (Discontinuous Conduction Mode) boost PFC (Power Factor Correction) front end and a synchronized PWM (Pulse Width Modulator) back end. The CM6805A is designed to replace FAN4803 (8 pin SOP package), which is the second generation of the ML4803 with 8 pin package. It is distinguished from earlier combo controllers by its low count, innovative input current shaping technique, and very low start-up and operating currents. The PWM section is dedicated to peak current mode operation. It uses conventional trailing-edge modulation, while the PFC uses leading-edge modulation. This patented Leading Edge/Trailing Edge (LETE) modulation technique helps to minimize ripple current in the PFC DC bus capacitor. The main improvements from ML4803 are: 1. Add Green Mode Functions for both PFC and PWM 2. Remove the one pin error amplifier and add back the slew rate enhancement GMv, which is using voltage input instead of current input. This transconductance amplifier will increase the transient response 5 to 10 times from the conventional OP 3. VFB PFC OVP comparator 4. PFC Tri-Fault Detect for UL1950 compliance and enhanced safety 5. A feed forward signal from IAC pin is added to do the automatic slope compensation. This increases the signal to noise ratio during the light load; therefore, THD is improved at light load and high input line voltage. 6. CM6805A does not require the bleed resistor and it uses the more than 800k ohm resistor between IAC pin and rectified line voltage to feed the initial current before the chip wakes up. 7. VIN-OK comparator is added to guaranteed PWM cannot turn on until VFB reaches 2.5V in which PFC boost output is about steady state, typical 380V. 8. A 10mS digital PWM soft start circuit is added 9. 10 pin SOP package 10. No internal Zener and VCCOVP comparator The CM6805A operates both PFC and PWM sections at 67.5kHz. This allows the use of smaller PWM magnetic and output filter components, while minimizing switching losses in the PFC stage. Several protection features have been built into the CM6805A. These include soft-start, redundant PFC over voltage protection, PFC Tri-Fault Detect, VIN-OK, peak current limiting, duty cycle limiting, under-voltage lockout, reference ok comparator PFCOFFB. Detailed Pin Descriptions IAC (Pin 2) Typically, it has a feed-forward resistor, RAC, 4Mega~10Mega ohm resistor connected between this pin and rectified line input voltage. The current of RAC will program the automatic slope compensation for the system. This feed-forward signal can increase the signal to noise ratio for the light load condition or the high input line voltage condition. ISENSE (Pin 3) This pin ties to a resistor which senses the PFC input current. This signal should be negative with respect to the IC ground. It internally feeds the pulse-by-pulse current limit comparator and the current sense feedback signal. The ILIMIT trip level is –1V. The ISENSE feedback is internally multiplied by a gain of four and compared against the internal programmed ramp to set the PFC duty cycle. The intersection of the boost inductor current down-slope with the internal programming ramp determines the boost off-time. It requires a RC filter between ISENSE and PFC boost sensing resistor. VEAO (Pin 4) This is the PFC slew rate enhanced transconductance amplifier output which needs to connected with a compensation network Ground. VFB (Pin 5) Besides this is the PFC slew rate enhanced transconductance input, it also tie to a couple of protection comparators, PFCOVP, and PFC Tri-Fault Detect V + I (Pin 6) This pin is tied to the primary side PWM current sense resistor or transformer. It provides the internal pulse-by-pulse current limit for the PWM stage (which occurs at 1.5V) and the peak current mode feedback path for the current mode control of the PWM stage. Besides current information, the photo-couple also goes into V + I pin. Therefore, it is the SUM Amplifier input. Soft Start is around 10mS after the startup(VCC is greater than 13V). |
Similar Part No. - CM6805A_10 |
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Similar Description - CM6805A_10 |
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