IK3401 데이터 시트보기 (PDF) - IK Semicon Co., Ltd

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IK3401

Green Mode PWM Controll

IK Semicon Co., Ltd 

IK3401

OPERATION DESCRIPTION

Start-Up Current

The typical start-up current is only 14uA.

This allows a high resistance, low-wattage

start-up resistor to be used, to minimize power

loss. A 1.5MOhm, 0.25W, start-up resistor and

a 10uF/25V VDD hold-up capacitor would be

sufficient for an AC/DC adapter with a universal

input range.

Leading Edge Blanking

Each time the power MOSFET is switched

on, a turn-on spike will inevitably occur at the

sense-resistor. To avoid premature termination

of the switching pulse, a leading-edge blanking

time is build in. During this blanking period, the

current-limit comparator is disabled, and it

cannot switch off the gate drive.

Operating Current

The required operating current has been

reduced to 4mA. This results in higher

efficiency and reduces the VDD hold-up

capacitance requirement.

Under-Voltage Lockout (UVLO)

The turn-on/turn-off thresholds are fixed

internally at 16.5V/10.5V. To enable a IK3401

controller during start-up, the hold-up capacitor

must first be charged to 16.5V through the

Green-Mode Operation.

start-up resistor.

The proprietary green-mode function

provides off-time modulation to continuously

The hold-up capacitor will continue to

decrease the PWM frequency under light-load supply VDD before energy can be delivered

conditions. To avoid acoustic-noise problem, from the auxiliary winding of the main

the minimum PWM frequency set above 22KHz. transformer. VDD must not drop below 1035V

This green-mode function dramatically reduces during this start-up process. This UVLO

power consumption under light-load and zero- hysteresis window ensures that the hold-up

load conditions. Power supplies using a IK3401 capacitor can adequately supply VDD during

Controller can easily meet even the most

start-up.

restrictive international regulations regarding

standby power consumption.

Gate Output/Soft Driving

The IK3401 BiCMOS output stage is a fast

Oscillator Operation

A resistor connected from the RI pin to

GND pin generates a constant current source

for the IK3401 controller. This current is used to

determinate the center PWM frequency. Using

a 26KOhm resistor RI results in a

corresponding 65KHz PWM frequency. The

relationship between RI and switching

totem pole gate driver. Cross-conduction has

been avoided to minimize heat dissipation,

increase efficiency, and enhance reliability. The

output driver is clamped by an internal 18V

Zener diode in order to protect the power

MOSFET transistors from any harmful over-

voltage gate signals. A soft driving waveform is

implemented to minimize EMI.

frequency is:

Slope Compensation

The sensed voltage across the current

sense resistor is used for peak-current-mode

control and cycle-by-cycle current limiting. The

The range of the PWM oscillation frequency build-in slope compensation function improves

Is designed as 47KHz~109KHz.

power supply stability and prevents peak-

current-mode control from causing sub-

IK3401 also integrates frequency hopping harmonic oscillations. Within every switching

function internally. The frequency variation

cycle, the IK3401 controller produces a

ranges from around 62KHz to 68KHz for a

positively sloped, synchronized ramp signal.

center frequency 65KHz. The frequency

hopping function helps reduce EMI emission of

a power supply with minimum line filters.

Rev 00

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