［AP1601］

MS 1454-E-01

2

2012/08

BLOCK DIAGRAM

Depletion

MOSFET

HV

VDD

BLEED

5V

Regulator

SWVDD

UVLO

BLEEDER

OVP

RESET

Driver

TSD

OCP

x5

S

HOLD

CLK

ZCD

LD

VFC

OSC

PW M

GND

CS

OUT

REF

2.5V

1.2V

LEB

SEL

-

-

+

R

Q

S

R

Q

Driver

2.8uA

2uA

100kΩ

2MΩ

Figure 1. AP1601 Block diagram

Block

Description

BLEEDER

By monitoring the BLEED pin voltage and SWVDD condition, a bleed from HV

pin or VDD charge ON/OFF is controlled.

5V Regulator

5V for internal circuits is generated from VDD pin.

SWVDD

By monitoring VDD pin voltage and if VDD voltage is deficient, a signal to

BLEEDER is output.

RESET

By monitoring 5V regulator startup condition, malfunction of internal circuits

using 5V is prevented.

UVLO

By monitoring VDD pin voltage, Driver output is held to GND level and 5V

regulator is inactivated so that malfunction at low voltage is prevented.

OVP

Over voltage detection circuit on VDD pin.

Driver

Driver for external N type MOSFET.

TSD

Overheat detection circuit.

OCP

Over current detection circuit for external MOSFET.

CLK

Internal clock / Off-time generation circuit.

ZCD

Bottom voltage detection circuit.

HOLD

By sampling the auxiliary winding voltage, which is proportional to the Vf of the

LEDs, a internal voltage is generated, which compensates for the CLK frequency

on DCM or the off-time on CCM.

LEB

Leading edge blank circuit