AN1965 Freescale Semiconductor / Motorola, AN1965 Datasheet - Page 3

• Manufacturer Part Number: AN1965
• Description: Design of Indirect Power Using the 56F800/E
• Manufacturer: Freescale Semiconductor / Motorola

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The PWM outputs are configured in the complementary mode in this application.
The main idea of the PFC algorithm is the transformation of an input current waveform into be a sine
signal with the same input voltage frequency. IEC standards do not require ideal sine waveform for
compatibility; providing simple three-point approximation is sufficient. In this case, the current
waveform will be nearly rectangular; this simplification saves processor resources. The hardware
control of the inverter power switch is the second step of simplification. For this approach, the
hardware provides instant value of the PFC input current. Thus, software controls only the average
value and does not have direct access to the inverter switch; see
The system is designed to provide power supply with a maximum 180W power. The system
incorporates the following hardware circuits:
Power Factor Correction (PFC) Theory
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Integral reload rates from one to 16
Individual software-controlled PWM outputs
Programmable fault protection
Polarity control
20-mA current sink capability on PWM pins
Write-protectable registers
Power supply rectifier
Boost inverter
Hardware Pulse Width Modulator (PWM)
Zero-crossing detector
Output voltage sensor
56F80x or 56F83xx Evaluation Module (EVM)
Freescale Semiconductor, Inc.
For More Information On This Product,
Indirect Power Factor Correction
Go to: www.freescale.com
Power Factor Correction (PFC) Theory
Figure 3-1.
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