AP3103 BCDSEMI [BCD Semiconductor Manufacturing Limited], AP3103 Datasheet - Page 10

• Manufacturer Part Number: AP3103
• Description: VERSATILE COST EFFECTIVE GREEN PWM CONTROLLER
• Manufacturer: BCDSEMI [BCD Semiconductor Manufacturing Limited]

Operation Description
The AP3103 is specifically designed for off-line AC-
DC power supply used in LCD monitor, notebook
adapter and battery charger applications. It offers a cost
effective solution with a versatile protection function.
Start-up Current and UVLO
The start-up current of AP3103 is optimized to realize
ultra low current (5µA typical) so that VCC capacitor
can be charged more quickly. The direct benefit of low
start-up current is the availability of using large start-
up resistor, which minimizes the resistor power loss for
high voltage AC input.
An UVLO comparator is included in AP3103 to detect
the voltage on the VCC pin. It ensures that AP3103 can
draw adequate energy from hold-up capacitor during
power on. The turn-on threshold is 15V and the turn-
off threshold is 8.8V.
Oscillator
The oscillation frequency is programmed by the value
of resistor R1, connected from pin RI to ground. The
resistor will make a constant current source to
determine the oscillation frequency by charging and
discharging an internal capacitor. Normally, RI pin
should not be placed where exists too much noise, as
the disturbance may make the IC work abnormally.
The oscillation frequency can be expressed as:
The recommended oscillation frequency is 50 to 100
kHz from the EMI consideration.
Current Sense Comparator and PWM
Latch
The AP3103 operates as a current mode controller; the
output switch conduction is initiated by every
oscillator cycle and is terminated when the peak
inductor current reaches the threshold level established
by the FB pin. The inductor current signal is converted
to a voltage signal by inserting a reference sense
resistor R
operating conditions is controlled by the voltage at FB
Feb. 2010 Rev. 1. 0
VERSATILE COST EFFECTIVE GREEN PWM CONTROLLER
f
≈
R
6500
( 1
k
Ω
S
)
. The inductor current under normal
(
kHz
)
10
pin, the relation between peak inductor current (I
and V
Leading-edge Blanking
A narrow spike on the leading edge of the current
waveform can usually be observed when the power
MOSFET is turned on. A 250ns leading-edge blank is
built-in to prevent the false-triggering caused by the
turn-on spike. During this period, the current limit
comparator is disabled and the gate driver can not be
switched off.
FB Pin and Short Circuit Protection
This pin is normally connected to the opt-coupler and
a l w a y s p a r a l l e l e d w i t h a c a p a c i t o r f o r l o o p
compensation. When the voltage at this pin is great
than 4.2V (such as output short to ground or the opt-
coupler is broken) and lasts for about 25ms, the IC will
enter the protection mode. For AP3103, the system will
enter hiccup mode to wait the VCC decreasing to low
UVLO level, then the IC will try to restart until the
failure removed. And when this voltage is less than
1.5V, the IC will stop the drive pulse immediately.
Therefore, this feature can be used for short circuit
protection, which makes the systemimmune from
catastrophic failure. Normally, output short makes the
VFB value to the maximum because the opt-coupler is
cut off.
System Protection and Pin Fault
Protection
The AP3103 provides versatile system and pin fault
protections. The OCP comparator realizes the cycle-
by-cycle current limiting (OCP).In universal input line
voltage, the IC realizes the constant over load
protection (OLP). VCC over voltage protection can be
applied as the primary OVP or opt-coupler broken
protection. The AP3103 also has pin fault connection
protection including floating and short connection. The
floating pin protection include the RI, SENSE, FB, etc;
The short pin protection includes the RI pin short
protection. When these pins are floated or RI pin is
shorted to ground, PWM switching will be disabled,
thus protecting the power system.
I
PK
=
FB
(
V
FB
is:
BCD Semiconductor Manufacturing Limited
−
. 0
) 8
3 /
R
S
Preliminary Datasheet
AP3103
PK
)