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Diodes Semiconductor Electronic Components Datasheet

AP3105NV Datasheet

High Voltage Green Mode PWM Controller

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AP3105NV pdf
Application Note 1096
High Voltage Green Mode PWM Controller AP3105NA/NV/NL/NR
Prepared by Wu Qikun
System Engineering Dept.
1. Introduction
The AP3105NX is a low start-up current, current
mode PWM controller with green-mode
power-saving operation. Different from AP3103,
AP3105NX’s PWM switching frequency at normal
operation is fixed at 65kHz dithering with a narrow
range. The difference between AP3103 and
AP3105NX is shown in Table 1. The dithering of
frequency will improve EMI feature. When the load
decreases, the frequency will reduce and when at a
very low load, the IC will enter the “burst mode” to
minimize switching loss. A minimum 20kHz
frequency switching is to avoid the audible noise as
well as to reduce the standby loss. A so-called VCC
Maintain Mode is applied under light load to realize a
stable output and to reduce the loss on the start-up
resistor. The standby power of the system using
AP3105NX can be reduced to 60mW at 230V input.
Frequency
VFB Resistor
Standby
Performance
External Protection
VCC OVP
OLP & FOCP
AP3103
Adjustable
4.5k
Better
NA
Auto-recoverable
Auto-recoverable
AP3105NX
Fixed at 65kHz
10k
Best
By “CTRL” pin
Latch
/Auto-recoverable
Latch
/Auto-recoverable
Table 1. The Difference between AP3103/AP3105NX
The AP3105NX integrates a lot of functions such as
the Lead Edge Blanking (LEB) of the current sensing,
internal slope compensation and several protection
features which include cycle-by-cycle current limit
(OCP), fast OCP (FOCP), VCC over voltage
protection, OTP, OLP protection. The “CTRL” pin is
designed for customers to add external protection
functions such as OVP and OTP.
The AP3105NX is specially designed for off-line
AC-DC power supply, such as LCD monitors,
notebook adapters and battery charger applications. It
can offer the designers a cost-effective solution while
keeping versatile protection features. The IC uses the
SOT-23-6 package type to realize its compact size.
This application note includes detailed explanation of
the IC’s major functions, some considerations about
the PCB layout, and methods for reducing the
standby power loss, and finally presents a demo
design of a 12V 2A adaptor.
2. Function Description
2.1 CTRL Pin
For some applications, the system requires external
programmable protection function. The CTRL pin
has two kinds of modes to trigger the protection: high
level trigger and low level trigger. The low threshold
voltage is 0.5V and high threshold voltage is 2.5V.
When the CTRL pin voltage is lower than 0.5V or
higher than 2.5V, latch or auto-restart protection will
be triggered (different versions of AP3105NX offer
different protection combinations, which are shown
in Table 2).
Version
AP3105NA
AP3105NV
AP3105NL
AP3105NR
VCC
OVP
Auto-
recoverable
Latch
Latch
Auto-
recoverable
OLP&
FOCP
Auto-
recoverable
Auto-
recoverable
Latch
Auto-
recoverable
CTRL
(Low)
Latch
Latch
Latch
Auto-
recoverable
CTRL
(High)
Auto-
recoverable
Latch
Latch
Latch
Table 2. Version Classification of AP3105NX
CTRL pin voltage maintains 1.6V if the pin is
floating, so leave CTRL pin open if the designer does
not need this function. Once the latch protection is
triggered, the bulk capacitor will provide the energy
to the IC through start-up resistor to ensure the IC
disable the output signal (latch mode). This mode
will not be released until the AC input is shut off.
Therefore, the de-latch time is mainly depending on
the value of HV startup bulk capacitor. If the system
needs a short de-latch time, it is better for the startup
resistor to take power from the point before the
rectifier bridge. Typical application of CTRL pin is
shown in Figure 1.
Note:
1. The sink current to the CTRL pin should be lower
Dec. 2012 Rev. 1. 0
BCD Semiconductor Manufacturing Limited
1


Diodes Semiconductor Electronic Components Datasheet

AP3105NV Datasheet

High Voltage Green Mode PWM Controller

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AP3105NV pdf
than 5mA by selecting a proper pull up resistor.
2. If the designer needs to apply a bypass capacitor
on CTRL pin, the capacitor should not be more than
1nF.
Application Note 1096
Figure 2. Shorter OLP Delay Time
OVP and OTP
OVP
OTP
Figure 1. CTRL Pin Application
2.2 Difference of AP3105&AP3105NX
Table 3 shows the difference
AP3105&AP3105NX.
between
OLP
Delay Time
VCS
Adjustable
@ start-up
AP3105
48ms@start-up
32ms@normal operating
NA
AP3105NX
100ms@start-up
64ms@normal operating
Adjustable
Table 3. AP3105 vs. AP3105NX
2.3 Longer OLP Delay Time for Capacitive Load
A capacitive load needs more power to be charged at
start-up time. One solution is to enlarge the OCP
point and keep the same start-up time, otherwise it
will trigger OLP protection mode. Another solution is
to extend the OCP delay time, which can simplify the
transformer design since it is no need to rise the OCP
point. Thus AP3105NX makes the OLP delay time
longer to 100ms at start-up state and 64ms at
operating mode. If FB pin’s value is over 4V for
64ms at operating state or for 100ms at start-up, IC
will enter OLP mode to limit the input power. Figure
2 and Figure 3 show the startup state with different
OLP delay time under capacitive load. A shorter
delay time may trigger OLP under capacitive load
while a longer OLP delay time resulting start-up
succeed.
Figure 3. Longer OLP Delay Time
2.4 Adjusting the Primary Peak Current at
Start-up
AP3105NX makes the primary peak current
adjustable to limit the VDS crossing MOSFET at
start-up. An 85μA DC current source is added on
SENSE pin, generating a DC voltage difference
between SENSE pin and VCS, which makes the VCS
equal to 0.95V to 85μA*RF (as shown in Figure 5).
As a result, MOSFET’s peak current is limited at start
up time, resulting a lower VDS crossing MOSFET.
This current source will be taken off after 37ms and
not be effective under normal operating mode (as
shown in Figure 4). RF cannot be too large that makes
the peak current too small and leads start-up fail at
low line input. A proper value of RF is 680Ω to
2.5kΩ.
Dec. 2012 Rev. 1. 0
Figure 4. Current Source at SENSE Pin
BCD Semiconductor Manufacturing Limited
2


Part Number AP3105NV
Description High Voltage Green Mode PWM Controller
Maker BCD
Total Page 9 Pages
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