MC33262PG

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PMIC - Power Factor Correction (PFC) is an advanced and important technology in the field of power management. The MC33262PG is an example of an application field and working principle. It is a single-chip synchronous step-down converter integrated with a high-efficiency PFC boost pre-regulator in the same package. It is designed to enable very high power factor, efficiency and low stand-by power requirements.

The MC33262PG uses the boost PFC technique to achieve high power factor, fast transient response and zero output current during instantaneous power de-rating. Its input voltage range covers the AC mains line voltage from 85VAC to 265VAC. Its wide output voltage range and internal feedback loop for improved stability enable the device to be used as a general purpose switcher. The PFC operation of MC33262PG features both current mode control and voltage mode control with rapid transient response.

In order to ensure reliable and precise operation of the converter system, the MC33262PG needs to be driven by precise trimming of the reference voltage. A voltage divider is implemented to divide the 5V internal supply voltage into two levels. The PWRGD pin is used to generate two separate trimming voltages. The VTRIM voltage is used as the reference voltage of the PFC converter, while the RTRIM voltage is used as the feedback reference of the VCOM output. The combination of the two trimming voltages can help to precisely trim the converter’s transfer function.

The PFC power stage of the MC33262PG incorporates the MC44C114 synchronous rectifier control IC. The device integrates the control logic, PWM comparator, power switches and dead-time control necessary to drive two N-channel MOSFETs. The power stages of the MC33262PG are also capable of driving two additional inductive loads, such as flyback converters, in order to increase the output power stage efficiency and improve the overall converter performance. The dead-time control and the internal soft-start controller allow for seamlessly transitioning from continuous conduction mode (CCM) to discontinuous conduction mode (DCM).

The MC33262PG also uses two separate power loops. The first loop is responsible for charging the inductor start-up capacitor and then continues to maintain the inductor current at the set level. The second loop is responsible for controlling the output voltage and the PFC boost pre-regulator output. The main control loop includes error amplifiers and a control comparator. The control comparator compares the output voltage to the reference voltage and derives a control signal for the main power switch.

The MC33262PG also features various protection functions such as brown-out detection, over-voltage protection, current limit protection, and over-temperature protection. The device is evaluated with 12V input and 5V constant output voltage on a 3.3A load. The measured output voltage stays within the specified tolerance over the temperature range despite the variation of the input voltage.

In conclusion, the MC33262PG is a versatile and high performance device designed to help achieve high power factor, fast transient response and low stand-by power requirements. The synchronous rectifier control IC, PFC power stage and two separate power loops combine to enable the device to meet the desired system specifications. Moreover, the device offers a range of protection functions which, together with its high power efficiency, provide robust protection and peace of mind.

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