LD5532

13

Leadtrend Technology Corporation

www.leadtrend.com.tw

LD5532-DS-00 July 2014

it

’s released, the VCC will trip the OVP level again and

re-shutdown the output in hiccup mode. Fig. 23 shows the

operation.

Otherwise, when the OVP condition is removed, the Vcc

level will be resumed and the output will automatically return

to the normal operation.

VCC

UVLO(on)

UVLO(off)

t

OVP Tripped

t

OUT

Switching

Switching

Non-Switching

OVP Level

Fig. 23

Brownout Protection

The LD5532 is programmable for the brownout protection

point though BNO pin. The voltage across the BNO pin is

proportional to the bulk capacitor voltage, referred as the

line voltage.

A brownout comparator is implemented to

detect the abnormal line condition. As soon as the condition

is detected, it will shut down the controller to prevent the

damage.

Fig. 24 shows the operation.

When VBNO falls

below 0.80V, the gate output will remain off even as Vcc

achieved UVLO(ON). It therefore makes Vcc hiccup

between UVLO(ON) and UVLO(OFF).

Unless the line

voltage is large enough to pull VBNO over 1.05V, the gate

output will not start switching even when the next UVLO(ON)

is tripped. A hysteresis is implemented to prevent the false

trigger during turn-on and turn-off.

1.05V

t

Vcc

t

OUT

Switching

Non-Switching

t

VBNO

t

Line Voltage

0.80V

Non-

Switching

Normal Range

UVLO(on)

UVLO(off)

Fig. 24

Oscillator and Switching Frequency

The LD5532 is implemented with Frequency Swapping

function which helps the power supply designers to optimize

EMI performance in lower system cost.

The switching

frequency substantially centers at 65KHz, and swaps in the

range of ±4KHz.

Green-Mode Operation

By using the green-mode control, the switching frequency

can be reduced under the light load condition. This feature

helps to improve the efficiency in light load conditions. The

green-mode

control

is

Leadtrend

Technology

’s own

property.