MIC4605 datasheet(23/34 Pages) MICROCHIP

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DS20005853E-page 23

MIC4605

FIGURE 7-10:

3-Phase Brushless DC Motor Driver – 24V Block Diagram.

The MIC4605 is offered in a small 2.5 mm x 2.5 mm

TDFN package for applications that are space

constrained and an 8-lead SOIC package for ease of

manufacturing. The motor trend is to put the motor

control circuit inside the motor casing, which requires

small packaging because of the size of the motor.

The MIC4605 offers low UVLO threshold and program-

mable gate drive, which allows for longer operation

time in battery-operated motors, such as power hand

tools.

Cross conduction across the half bridge can cause

catastrophic failure in a motor application. Engineers

typically add dead time between states that switch

between high input and low input to ensure that the

low-side MOSFET completely turns off before the

high-side MOSFET turns on and vice versa. The dead

time depends on the MOSFET used in the application,

but 200 ns is typical for most motor applications.

7.11

Power Inverter

Power inverters are used to supply AC loads from a DC

operated battery system, mainly during power failure.

The battery voltage can be 12 VDC, 24 VDC or up to

36 VDC, depending on the power requirements. There

are two popular conversion methods: Type I and

Type II that convert the battery energy to AC line

voltage (110 VAC or 230 VAC).

FIGURE 7-11:

Type I Inverter Topology.

As shown in Figure 7-11, Type I is a dual stage topology,

where line voltage is converted to DC through a trans-

former to charge the storage batteries. When a power

failure is detected, the stored DC energy is converted to

AC through another transformer to drive the AC loads

connected to the inverter output. This method is simplest

to design, but tends to be bulky and expensive because

it uses two transformers.

Type II is a single-stage topology that uses only one

transformer to charge the bank of batteries to store the

energy. During a power outage, the same transformer

is used to power the line voltage. The Type II switches

at a higher frequency as compared to the Type I

topology to maintain a small transformer size.

Both types require a half-bridge or full-bridge topology

to boost the DC to AC. This application can use two

MIC4605s. The 85V operating voltage offers enough

margin to address all of the available banks of batteries

commonly used in inverter applications. The 85V oper-

ating voltage allows designers to increase the bank of

batteries up to 72V, if desired. The MIC4605 can sink

as much as 1A, which is enough current to overcome

the MOSFET’s input capacitance and switch the

MOSFET up to 50 kHz. This makes the MIC4605 an

ideal solution for inverter applications.

KEY

BOARD

ZNEO CORE

CONTROLLER

3.3V

MIC5225

LDO

EMF

POSITION

SENSING

MIC4605

MOSFET

DRIVER

PHASE A

MIC4605

MOSFET

DRIVER

PHASE B

MIC4605

MOSFET

DRIVER

PHASE C

MIC4680

BUCK

REGULATOR

12V

24V

MIC38C44A

FLYBACK

BRIDGE

RECTIFIER

PFC

MOSFETs

PHASE A

MOSFETs

PHASE B

MOSFETs

PHASE C

POWER SWITCHES FROM

INPUT AC TO DC/AC SUPPLY

DURING POWER OUTAGE

OUTPUT AC

BYPASS PATH

INPUT AC

BATTERY

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