AN-1820| Application Note

LM5032 Interleaved Boost Converter

National Semiconductor Application Note 1820 Ron Crews May 22, 2008

Abstract
The LM5032 dual current mode PWM controller contains all the features needed to control an interleaved boost converter. The two outputs operate 180 degrees out of phase and have separate current limit inputs for each channel. In addition to a high input voltage range, the controller contains all the auxiliary features needed to control a complete converter.

Introduction
A basic boost converter converts a DC voltage to a higher DC voltage. Interleaving adds additional benefits such as reduced ripple currents in both the input and output circuits. Higher efficiency is realized by splitting the output current into two paths, substantially reducing I2R losses and inductor AC losses. Figure 1 shows the basic interleaved boost topology. When Q1 turns on, current ramps up in L1 with a slope depending on the input voltage, storing energy in L1. D1 is off during this time since the output voltage is greater than the input voltage. Once Q1 turns off, D1 conducts delivering part of its stored energy to the load and the output capacitor. Current in L1 ramps down with a slope dependent on the difference between the input and output voltage. One half of a switching period later, Q2 also turns on completing the same cycle of events. Since both power channels are combined at the output capacitor, the effective ripple frequency is twice that of a conventional single channel boost regulator.

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FIGURE 1. Interleaved Boost Basic Diagram

AN-1820

2008 National Semiconductor Corporation

300576

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