ANP007 Datasheet, PDF(4/11 Page) Anachip Corp

English

English German Russian Spanish Italian Polish Chinese Japanese Korean French Portuguese	Language :

ANP007 Datasheet, PDF (4/11 Pages) Anachip Corp – Dual Buck Converter

◁

Application Note

AP2001 Dual Buck Converter

2. Hardware

ANP007

2.1 Introduction

The dual-buck demo board supply two constant dc output voltage that are 3.3V and 5V. This board can supply

output power up to 15W for buck1 output (5V / 3A) and up to 10W for buck2 output (3.3V / 3A). Using a dc

input voltage of 10.8 V to 13.2 V, full load efficiency up to 86 percent. This type of converter converts an

unregulated input voltage to 2 regulated output voltage that they are always lower than the input voltage. The

control method used in the board is fixed frequency, variable on-time pulse-width-modulation (PWM). The

feedback method used is voltage-mode control. Other features of the board include undervoltage lockout

(UVLO), short-circuit protection (SCP), and adjustable dead time control (DTC).

2.2 Typical Application

The AP2001 may operate in either the CCM (Continuous Conduction Mode) or the DCM (Discontinuous

Conduction Mode). The following applications are designed for CCM (Continuous Conduction Mode)

operation. That is, the inductor current is not allowed to fall to zero. To compare the disadvantage and

advantage for CCM and DCM, the main disadvantage of CCM is the inherent stability problems (caused

by the right-half-plane zero and the double pole in the small-signal control to output voltage transfer

function). However, The main disadvantage of DCM that peak currents of switch and diode are larger

than CCM when converting. Using power switch and output diode with larger current and power

dissipation ratings should solve this issue of large peak current. The designer has to use larger output

capacitors, and take more effort on EMI/RFI solution also. Designer could make a choice for each mode.

For a low loading current, DCM is preferred for buck. If the load current requirement is high, CCM is

preferred for buck. Figure 1 shows the basic buck topology. When the switch SW is turned on, energy is

stored in the inductor L and it has constant voltage âVL =VI â VOâ, the inductor current iL ramps up at a

slope determined by the input voltage. Diode D is off during this period. Once the switch, SW, turns off,

diode D starts to conduct and the energy stored in the inductor is released to the load. Current in the

inductor ramps down at a slope determined by the difference between the input and output voltages.

Anachip Corp.

www.anachip.com.tw

Figure 1. Typical Buck Converter Topology

Rev. A.0 Feb. 20, 2003

4/11

▷