CM6805BG

The CM6805A and CM6806A are Green-Mode PFC/PWM combination controllers designed for high-density AC adapters and switching power supplies.

The IC integrates two major control functions:

• PFC (Power Factor Correction);
• PWM (Pulse Width Modulation) for the DC-DC conversion stage.

The PFC section uses an input-current-shaping technique providing performance close to the leading-edge average-current topology used in the CM6800 and ML4800.

Both PFC and PWM sections incorporate Green Mode functionality to reduce power consumption under light-load conditions and support compliance with Blue Angel and Energy Star requirements.

The CM6805A/CM6806A allows smaller and lower-cost bulk capacitors to be used, reduces power-line loading and stress on the switching MOSFETs, and enables power supplies designed to meet IEC 1000-3-2 requirements.

Features

• 10-pin SOIC package.
• PWM pulse skipping in Green Mode.
• Approximately 5 MΩ RAC startup resistor connected to the IAC pin.
• High-voltage bipolar transistor startup capability.
• Easy Boost Follower configuration.
• Low external component count.
• Internally synchronized PFC and PWM sections.
• Slew-rate-enhanced voltage error amplifier with advanced input-current shaping.
• Universal line input voltage.
• CCM or DCM boost PFC with leading-edge modulation.
• IAC feed-forward for automatic slope compensation.
• PFCOVP and VCCOVP protection.
• Precision −1 V PFC current limit.
• PFC Tri-Fault Detect comparator.
• Low supply current:
  • startup: approximately 100 µA;
  • operating: approximately 2 mA.
• Synchronized leading-edge PFC and trailing-edge PWM modulation.
• VINOK comparator to enable PWM after the PFC reaches steady state.
• High-efficiency trailing-edge current-mode PWM.
• Exact 50% maximum PWM duty cycle.
• UVLO, REFOK and brownout protection.
• Digital PFC and PWM soft-start of approximately 10 ms.
• Precision 1.5 V PWM current limit.
• PWMtrifault input for DC-DC short-circuit detection and PFC shutdown at the GMth threshold.
• PWMtrifault can also be programmed for thermal protection.

Operating Frequency

The PFC and PWM sections of the CM6805A operate at the same frequency:

67.5 kHz.

Green Mode Operation

Both the PFC and PWM sections incorporate Green Mode functions.

When the load falls below the programmed GMth (Green Mode Threshold), PFCOUT is turned off.

The GMth threshold can be programmed by the designer.

For the PWM section, Green Mode occurs when the PWMCMP duty cycle falls below approximately 6%. In the following oscillator cycle, the PWMOUT pulse is skipped.

PWMOUT remains skipped until the PWMCMP duty cycle rises above approximately 6%. The PWMOUT pulse then resumes in the following cycle.

PWMtrifault

The PWMtrifault pin can be used to:

• detect a short circuit in the DC-DC/PWM section;
• determine or program the GMth threshold;
• turn off the PFC section;
• implement thermal protection when appropriately configured.

Tags: CM6805BG, CM6805B, PFC controller, PWM controller, 95kHz, SMPS, AC-DC, power supply IC, SOIC-10