AN1070

Application Note 1070
Design Guideline and Application Notes of AP1681 System Solution
Prepared by Wang Zhao Kun
System Engineering Dept.
1. Introduction
•
The AP1681 is a powerful high performance AC/DC power
supply controller for dimmable LED lighting applications.
The device uses Pulse Frequency Modulation (PFM)
technology to regulate output current according to the wall
dimmer conduct angle without opto-coupler and secondary
CV/CC control circuitry.
•
•
•
•
•
•
•
•
•
The AP1681 achieves wide dimming range without visible
flicker and is compatible with diverse dimmers.
The AP1681 features low start-up current, low operation
current and high efficiency. It also has rich protection
functions including over voltage, short circuit, over current
and over temperature protections.
3. Pin Configuration and Description
The AP1681 is available in SOIC-8 package.
2. Product Features
•
•
•
•
Primary Side Control for Output Current Regulation
Without Opto-coupler and Secondary CV/CC Control
Circuitry
Eliminates Control Loop Compensation Circuitry
Adjustable Full Brightness and Full Dimming Setting
Wide Dimming Range From 100% to 1%, Down to
Pin Number
Sep. 2011
DIM
2
RD
3
RI
4
CS
5
FB
6
GND
DIM
1
8
VCC
RD
2
7
OUT
RI
3
6
GND
FB
4
5
CS
Figure 1. Pin Configuration of AP1681
Pin Name
1
Full Darkness
Adjustable Dimming Curve for Human Eye
Sensitivity
No Visible Flicker
Connectivity with Analog / Digital / Hybrid Dimming
Mode
Built-in Acceleration Start
Adjustable Soft-start Timing
CV Open-load Regulation and Reload Detection
Over Voltage and Short Circuit Protection
Over Temperature Protection
Over Current Protection
Maximum Switch On-time Protection
Function
This pin is dim signal sensing pin. It senses the dimming signal and then controls
output current. Output current will at maximum when DIM voltage reaches 3.5V.
Usually a second order RC filter is connected between rectified AC voltage and
DIM pin.
This pin is the IC internal bias pin. There is a 1.5V reference voltage at the pin. The
1.5V voltage divide RD pin resistor will determine a bias current for the IC.
Usually a 51k resistor is connected at this pin to GND.
This pin will generate a current according to DIM pin voltage. Change the RI pin
resistor will change output current dimming curve gradient. Usually a 100k to 120k
resistor is connected at this pin to GND.
The current sensing pin. The primary switch maximum current sensing threshold is
0.51V.
This pin captures the feedback voltage from the auxiliary winding. When secondary
N
V AUX = AUX × (VO + Vd )
NS
, Where
side diode turns on, the auxiliary voltage is given by:
the Vd is the output rectify diode forward drop voltage. FB voltage is used to
control no load output voltage and determine acceleration stop point at start up
phase.
Ground. Current return for gate driver and control circuits of the IC. The power
ground and signal ground should be connected by one node. The ground of
transformer must be separated from the ground of IC in order to pass ESD test.
Rev. 1. 0
BCD Semiconductor Manufacturing Limited
1
Application Note 1070
Pin Number
Pin Name
Function
7
OUT
Gate driver output pin. AP1681 is designed to drive MOSFET. A series resistor
between this pin and the power switch gate can reduce high frequency noise.
8
VCC
Supply pin of gate driver and control circuit of the IC.
VCC
8
8V
FB_OVP
COMP
SHORT_OCP
VCC_OVP
FB_OVP
OTP
1.75V
FB
4
COMP
0.1V
5
Tons
Constant
Current
Control
CC_CTRL
CV_CTRL
COMP
4V
Reference
VCC_OVP
Tonsec
Detector
CC_CTRL
CS
pro
Demag
COMP
4V
Protection
& Latch
FB_ACC
UVLO
CC_ON
pro
SHORT_OCP
COMP
Regulator
&
Bias
pfm
R
CC_ON
Driver
7
OUT
Q
0.5V
S
PEAK_CTRL
COMP
6
S
DIM
1
Dimming Control
2
Q
GND
CC_CTRL
R
3
RD
RI
Figure 2. Functional Block Diagram of AP1681
4. Operation
Guideline
Principle
and
AP1681 is a Primary Side Regulation (PSR) LED driver IC
with dimming function for narrow range application.
According to different requirements, the AP1681 can be
applied to three types of circuit structure as Table 1.
Design
4.1 Circuit Structure Introduction of AP1681
Application
Table 1. AP1681 Application Architecture Types
Structure Types
Single Stage
Single Stage with Valley-Fill Circuit
Two Stages with Boost
Input Voltage Range
90-132VAC or 220-264VAC
90-132VAC or 220-264VAC
90-132VAC or 220-264VAC
PF
No
Low
High
THD
Very bad
Bad
Very good
Cost
Very Low
Low
Very high
Sep. 2011
Rev. 1. 0
BCD Semiconductor Manufacturing Limited
2
Application Note 1070
Figure 3. Block of Two Stages
THD and good dimmable function. This document is based
on a two stage design with AP1662 boost converter and
AP1681dimmable LED driver. The document contents
focus on AP1681 design guideline and application notes,
the detailed design information of AP1662 refers to the
BCD relative document.
For low cost application, the simple single stage structure
with AP1681 is the better solution to realize dimmable
LED driver. Combined with valley-fill circuit, the single
stage structure can not only improve PF performance to
meet basic PFC requirement, but also keep the lower cost
benefit. It is noticed that a bleeding circuit is required to
maintain the conduction current of dimmer switch when
the conduction angle is too small. As to high end
application which needs the higher PF and very low THD,
it is recommended to select two stages structure with boost
converter and AP1681 PSR LED driver. The AP1662
controller from BCD is a cost efficient choice for boost
converter. The combined solution with AP1662 and
AP1681 is a best solution for wall dimmer application to
achieve the better performance: the higher PF, the lower
4.2 Introduction of PSR LED Driver with AP1681
Compare to Secondary Side Regulation (SSR) solution on
LED driver application, PSR is very simple and low cost
solution without secondary side CC control circuit,
opto-coupler and even external loop compensation circuit.
Figure 4 shows a common used flyback schematic with
AP1681 PSR controller, which can realize output constant
current function with very simple circuit.
T1
VBUS
R1
+
D2
C2
R2
+
VO
D1
R5
C1
R6
VCC FB
AP1681
R3
Q1 R7
OUT
GND
CS
R4
Figure 4. Simple Schematic of PSR
time of secondary side “ON”, TSW is the switching period.
primary peak current IPK is
The AP1681 uses PFM control strategy and keeps the
flyback converter operating at Discontinuous Current Mode
(DCM). Figure 5 shows the basic operation waveform. The
output current IO is
Io =
Tons
⋅ I pks
2 ⋅ Tsw
I pk =
I pks = N t ⋅ I pk ⋅η tr
(1)
(2)
(3)
VCS is the primary current sense voltage on CS pin, RCS is
the primary current sense resistor, Nt is the primary to
Here IPKS is the peak current of secondary side, TONS is the
Sep. 2011
Vcs
Rcs
Rev. 1. 0
BCD Semiconductor Manufacturing Limited
3
Application Note 1070
threshold on CS pin is a constant value at non-dimming
mode. Therefore, by means of parameter design of Nt,
TONS/TSW and RCS, it can be realized output constant current
control with PSR structure. Furthermore, FB pin senses the
auxiliary winding voltage of the transformer, which reflects
the secondary side output voltage, to carry out Constant
Voltage (CV) mode control. The CV mode control can
keeps output voltage below the rating voltage at no load
condition.
secondary winding turns ratio of transformer and ηtr is the
transformer conversion ratio considering the transformer
power loss and VCC winding output power loss. From above
equations, the output current IO could be
Io =
N t ⋅ Tons ⋅ Vcs ⋅η tr
2 ⋅ Tsw ⋅ Rcs
(4)
As to AP1681 control scheme, the turn off voltage
Figure 5. Basic Operation Waveform
proportional to the voltage of DIM pin flows out the CS
pin which will cause a voltage across the RCS_EXT (in Figure
6). Then the primary peak current will change with the
voltage on DIM pin because the voltage threshold on CS
pin is constant. The internal algorithm for TONS/TSW and
VCS realizes exponential dimming curve which is
compatible with human eye perception.
4.3 Dimming Principle
The AP1681 regulates the output current according to the
DIM pin voltage. From formula (4), IO can be adjusted
accordingly by changing TONS/TSW if the turn ratio Nt and
RCS are fixed. In AP1681, the TONS/TSW is positively
proportional to the voltage on DIM pin whose limited
voltage is 3.5V.
Furthermore, there is micro-current which is inversely
RCS_EXT
CS
C1
RCS
Figure 6. Peripheral Component of CS Pin
Sep. 2011
Figure 7. Dimming Curve for AP1681
Rev. 1. 0
BCD Semiconductor Manufacturing Limited
4
Application Note 1070
voltage will be charged by external source. Because of the
external capacitor, DIM pin and the output current are
increased gradually to the settle value. The soft start time is
determined by DIM pin outside capacitor and external
source.
4.4 Acceleration Start
For LED lighting application, quickly start-up is necessary.
In order to reduce start-up time, an acceleration start-up
function is embedded in AP1681. At start-up, after VCC
voltage is higher than turn on threshold, DIM pin voltage is
pulled to zero by internal switch to realize soft start
function for next phase. When FB pin voltage keeps below
1.75V, AP1681 system will neglect the dimming function,
which means TONS/TSW keeping the maximum value and
CS pin sourcing current keeping zero. Then the switch
operates at the maximum IPK mode to provide more energy
to secondary side. The acceleration start phase will stop
when the FB pin voltage reaches soft start threshold 1.75V,
and the DIM pin voltage will start increasing from zero.
When open load, the system works in CV mode and output
voltage is clamped to a higher level. DIM pin is pulled to
zero by internal switch. At reloading situation, sensed FB
pin voltage drops to below 4V, then DIM pin internal
switch is open and DIM pin voltage will be charged by
external source. The output current is increased gradually
to the settle value. This procedure is called soft reloading
stage. This effect will help for safe reloading and prevent
output capacitor high discharge current when reloading.
4.5 Soft Start and Soft Reloading
After acceleration start phase, AP1681 will enter soft start
phase. The DIM pin internal switch is open and DIM pin
4.6 FB Pin Voltage Region
Figure 8. Diagram for the FB Function
higher power pulse push output voltage rising and power
system entering CV mode again. It is recommended to add
dummy load at output side to balance the transferred power
from primary side at CV mode. If abnormal condition
happened, such as fault connection or excess auxiliary
winding turns, FB pin voltage reaches to 8V, and then
AP1681 will enter FB OVP latch mode protection state.
Figure 8 shows the FB pin working regions diagram.
The FB pin has several voltage thresholds to realize the
different function. When FB pin voltage is below 1.75V,
the AP1681 system works in acceleration start phase. The
acceleration start phase stop when FB pin sensed voltage
reach 1.75V. From 1.75V to 4V, the system works in
Constant Current (CC) region, the LED driver normal
operation situation. When FB pin voltage is higher than 4V,
the system will work in Constant Voltage (CV) state.
AP1681 will output 7kHz switching frequency pulse and
source the maximum current to CS pin resistor so that the
power converter operates with the minimum peak current
and very low switching frequency. Generally the
transferred power at CV mode is lower than the required
power which maintains the power system working at
standby mode. With the output voltage decreasing, the FB
pin voltage may drop to below 4V, then there will be the
Sep. 2011
4.7 CS Pin
As for CS block, AP1681 includes two comparator functions:
the comparator for primary peak current control and OCP.
The CS pin turn off voltage threshold is 0.5V for current
loop control. The OCP threshold is 4V. When OCP
happened, AP1681 will enter latch mode and switch stops
working. The latch mode will be reset when input power off.
Rev. 1. 0
BCD Semiconductor Manufacturing Limited
5
Application Note 1070
The primary peak current depends on the CS pin resistor
RCS_EXT when the voltage on DIM pin is changing because
there is a micro-current flowing out the CS pin. Under the
condition of same DIM pin voltage, the larger value of
RCS_EXT, the lower primary peak current. Figure 9 shows
the relation curve of primary peak current with DIM pin
voltage VDIM and RCS_EXT Value.
From the curve it can be seen that the higher RCS_EXT value,
the lower primary peak current. The lower IPEAK means the
LED driver achieve the lower output current, and then the
lower darkness LED lighting performance. Usually it is
recommended to use 5.1k value CS resistor.
4.8 RD and RI Pin
IPEAK (A)
RD and RI pin feature to set the dimming curve of output
current with external resistor. The RD pin resistor RRD,
usually recommended as 51k, is used to generate reference
bias current for internal dimming function circuit.
RCS_EXT=1K
RCS_EXT=2.2K
RCS_EXT=3.3K
RCS_EXT=3.9K
RCS_EXT=5.1K
VDIM (V)
Figure 10. Resistor for RD Pin and RI Pin
IOUT (A)
Figure 9. Curve of IPEAK and VDIM
VDIM (V)
Figure 11. Curve of VDIM and IOUT
The RI pin resistor (RRI) is used to set the dimming curve
of output current. Figure 11 is the curve of output current
with DIM pin voltage under the different RI resistor. From
the curves it can be seen that the LED brightness changes
faster with the smaller RRI. The designer can select suitable
resistor according to this dimming curve to achieve the
required dimming characteristics.
Sep. 2011
4.9 Max TONP Protection
When primary side switch turns on, the current will increase
because of input voltage and flyback primary inductor. If the
sensed CS pin voltage doesn’t reach 0.5V over 16.5µs,
maximum TONP protection happens, the switch will be
turned off immediately.
Rev. 1. 0
BCD Semiconductor Manufacturing Limited
6
Application Note 1070
The output voltage of boost circuit is a constant DC
voltage, so the flyback system could be designed to operate
on quasi resonant mode to improve efficiency, and the
quasi resonant mode could be reached by adjusting fSW,
turn ratio and VBUS. Usually fSW and VBUS are determined
firstly and the turn ratio is adjusted to realize the quasi
resonant mode. (For designing method, please refer to
designing file by BCD). Figure 12 shows the working
waveform of flyback MOSFET drain voltage and current
sensing resistor voltage VCS waveform. The MOSFET
works at quasi resonant mode.
4.10 Over Temperature Protection (OTP)
For LED application, the LED driver usually works in high
ambient temperature. Over temperature protection (OTP) is
necessary to avoid improper installation and protect LED
lifetime. If AP1681 junction temperature reaches 140°C,
OTP happens. The AP1681 system will be shut down. 20°C
hysteresis is provided for robust operation. The OTP will
be relieved after the IC junction temperature drops below
120°C.
5. Operation Parameter Design and
Components Selection for Two Stages
5.3 Calculate Current Sensed Resistor
Usually, Boost + PSR flyback topology is suggested for
triac dimming LED driver application because of excellent
dimming compatibility, no flickering operation, high power
factor, low THD and extremely low output current ripple.
The boost PFC stage output voltage is constant. So this
makes easy for flyback system design. Below is the design
procedure only for PSR with AP1681 (please refer to the
application of AP1662 for design of boost circuit).
The voltage threshold on CS pin is 0.5V. The primary
current sense resistor can be calculated according to
equation
Rcs =
In order to guarantee flyback operating at DCM, the
maximum turn ratio Nt_max is
0.978 ⋅ Vbus
Vo + Vd
(8)
ηtr is the efficiency of transformer, usually about 0.9. A RC
filter is recommended to be added between the CS pin and
sampling resistor and the maximum value of resistor is
recommended for 5.1kΩ for dimming consideration.
5.1 Calculate the Maximum Turn Ratio of XFMR
N t _ max =
0.127 ⋅ N t ⋅η tr
Io
5.4 Calculation of the Inductance of Primary
Side---LP
(7)
The primary peak current is
Firstly the designer should determine the turns ratio and
then calculate the other design parameter.
I pk =
5.2 Determine Full Load Working Frequency fSW
and Turn Ratio
I pks
N t ⋅ η tr
=
3.952 ⋅ I o
N t ⋅ η tr
(9)
According to the rule of conservation of energy, we can get
The switch working frequency of AP1681 is relative to
system efficiency and transformer size. Usually 50kHz to
75kHz is recommended to balance the efficiency and size.
P
1
2
⋅ f sw = o
L p ⋅ I pk
2
ηp
(10)
Here, ηp is the total power conversion efficiency. So, the
primary inductance can be calculated by:
0.128 ⋅ Po ⋅ N t ⋅ η tr2
I o2 ⋅ f sw ⋅ η p
2
Lp =
(11)
5.5 Calculate the Turns of Primary, Secondary and
Auxiliary Sides
The primary winding turns is
Np =
L p ⋅ I pk
Ae ⋅ Bmax
(12)
Figure 12. Flyback MOSFET Q2 Drain Voltage and VCS
Waveform at Full Load
Sep. 2011
Rev. 1. 0
BCD Semiconductor Manufacturing Limited
7
Application Note 1070
The turn of secondary winding is
Ns =
The maximum drain to source current (RMS value) is
Np
I d _ max = I pk ⋅
(13)
Nt
(16)
The maximum voltage on secondary diode is
The turn of auxiliary winding is
Na =
T
D
= I pk ⋅ onp
3
3Tsw
N s ⋅ Vccmax
Vo _ max + Vd
(14)
Vd _ max =
Vbus
+ Vo _ max + Vd
Nt
(17)
Here, VCCmax can be set a typical value of 23V, Bmax is
usually selected between 0.25T and 0.3T.
The maximum average current of secondary diode is
output current.
5.6 Primary MOSFET and Secondary Diode
Selection
5.7 Output Capacitor Selection
Output capacitor is key factor for output current ripple.
Because of Boost PFC stage, there is no line frequency
ripple at output side. But there is still the switching
frequency output voltage and current ripple since of output
capacitor ESR. In order to achieve the lower output ripple
performance, it’s preferred to select low ESR capacitor.
The below table shows the recommended value of output
capacitance.
The maximum voltage on primary MOSFET is
Vds _ max = Vbus + N t ⋅ (Vo + Vd ) + Vspike
(15)
Where VSPIKE is the spike voltage which is result from the
leakage inductance and depends on the primary peak
current value and leakage inductance value, it is
approximately about 100V to 200V.
Output Power
1W to 10W
10W to 20W
20W to 30W
Output Capacitor
82µF to 120µF
120µF to 180µF
180µF to 250µF
5.8 DIM Pin Elements Selection
turns on.
The function of DIM pin is to control output current by
sensing input AC voltage. Usually a second order filter is
connected between rectified AC voltage and DIM pin. The
voltage on DIM pin could be set between 3.5V and 4V at
typical input voltage and full load. The second order filter
which is 100kΩ and 1 micro Farad is recommended to get
a small ripple of output current.
6.2 Iron Powder core is suggested for EMI filter because of
high saturation flux density. When Triac dimmer turns on,
high inrush current will flow into the filter. Iron Powder
core inductor can effectively limit the peak inrush and
makes the system works stable.
6.3 Quick response of PFC control loop is needed. The
designed PFC output feedback capacitor is small to give
fast response when dimming.
5.9 FB Pin Elements Selection
The system will operate at CV mode if the voltage on FB
pin reaches 4V. So the voltage on FB pin is recommended
to be set at 3.5V at full load.
6.4 Be careful for the AP1661 and AP1681 VCC supply.
The PFC is controlled by AP1661 and flyback is controlled
by AP1681. The two IC VCC supply comes from the same
auxiliary winding of flyback. But the two ICs have
different VCC operation range. Usually, a linear regulator is
needed for AP1661 power supply.
6. Dimming Consideration
Though PFC circuit makes the whole system act as
resistive load for dimmer in theory, improper components
value design can still cause flickering when dimming. Here
is some design tips for no flickering dimming.
7. Layout Consideration
6.1 Design EMI filter capacitor as small as possible. Filter
The PCB layout rules are highlighted as following:
capacitor is necessary to pass EMI standard, but big filter
capacitor may cause Triac dimming oscillation when Triac
7.1 The boost converter and flyback converter loop area
Sep. 2011
Rev. 1. 0
BCD Semiconductor Manufacturing Limited
8
Application Note 1070
8. Design example
should be minimized for better EMI performance.
Here is a design example of dimmable LED driver.
The specification is:
AC mains RMS voltage: VIN_RMS=85V to 150V
DC output regulated voltage: VO=21V
Rated output current: IO=0.5A
Flyback full load switching frequency: fSW = 65kHz
Expected efficiency: η> 80%
Figure 13 shows the designed electrical schematic.
7.2 The RCD clamp snubber and output rectifier loop areas
should be minimized to achieve good EMI performance.
7.3 The power ground and signal ground should be
connected by one node. Common connection of GND will
introduce disturbances to small signals. The ground of
transformer must be separated from the ground of IC in
order to pass ESD test.
7.4 C1 should be placed as close as possible to Pin VCC of
the AP1681 respectively.
L
F1
R2
AC
Input
D7
L2
R38
BD1
L3
R1
R8
R5 U1 AP1661
VR1
C1
N
L1
C2
C3
R6
R39
GD
MULT
R7
CS
R12
R11
R37
C6
R15
R16
C5
Q1
+
R10
VCC COMP INV
C4
D2
C16
R9 D1
ZCD
GND
R13
R14
T1
R24
ZD1
R29
C17
R19
C13 R32
D6
D8
R17
R25
C14
R20
D4
8-VCC
U2 AP1681
4-FB
D5
6-GND
R21 C8
1-DIM
7-OUT
2-RD 3-RI 5-CS
R18
R22
R23
C15
R33
OUT
R35
C10
C9
+
+
Q3
D3
C7
C11
R26
R34
R27
C12
R31
CY
Q2
R30
R28
Figure 13. Typical Application Schematic of AP1681 Solution
BOM
Item
Sep. 2011
Description
QTY
C1
68nF/400V, capacitor CL21
1
C2
100nF/400V, capacitor CL21
1
C3
33nF/400V, capacitor CL21
1
C4
1nF/25V, 0603, ceramic capacitor
1
Rev. 1. 0
BCD Semiconductor Manufacturing Limited
9
Application Note 1070
Item
QTY
C5
100nF/25V, 0603, ceramic capacitor
1
C6
470nF/50V, 1206, ceramic capacitor
1
C7
1µF/25V, 0603, ceramic capacitor
1
C8
1µF/25V, 0603, ceramic capacitor
1
C9,C10
1µF/50V, 1206, ceramic capacitor
2
C11
10µF/400V, 105°C, 10mm*11mm electrolytic capacitor
low ESR(R<3.5Ω)
1
C12
10pF/25V, 0603, ceramic capacitor
1
C13
1nF/100V, 0805, ceramic capacitor
1
120µF/50V, 105°C, 8mm*11mm electrolytic capacitor
low ESR(R<0.15Ω)
2
C16
2.2nF/275V, Y safety capacitor
1
C17
1nF/500V, 1206, ceramic capacitor
1
Diode, 1N4148, SOD323
2
STTH2L06A, 2A/600V, SMA, ultrafast diode, 60ns
1
BAV21WS, 250V, 200mA, SOD323
2
D6
3A/100V, Schottky Diode, SMA, SS310
1
D7
1A/600V, SMA, US1J
1
D8
1A/1000V, SMA, 1N4007
1
L1
4.5mH, Differential-Mode Inductor, EF16, 250Ts
1
L2
6.8mH, Inductor,6mm*8mm
1
L3
3mH, Inductor, EE16
1
F1
Fuse, 1A/250V
1
VR1
Varistor 07D471K
1
BD1
Bridge diode, 0.5A/600V, TO-269AA, MB6S
1
R1 to R4
1kΩ, 5%, 1206, resistor
4
R5
1MΩ, 5%,1206, resistor
1
R6
1.5MΩ, 5%,1206, resistor
1
R7
15kΩ, 5%, 0603, resistor
1
R8
82kΩ, 5%,0603, resistor
1
R9
27Ω, 5%, 0603, resistor
1
R10
330Ω, 5%, 0603, resistor
1
C14,C15
D1,D5
D2
D3,D4
Sep. 2011
Description
Rev. 1. 0
BCD Semiconductor Manufacturing Limited
10
Application Note 1070
Item
R11
Description
100kΩ, 5%,0603 , resistor
1
4.7Ω, 5%,1206 , resistor
2
R14
2.2MΩ, 5%,1206 , resistor
1
R15
82kΩ, 5%,1206, resistor
1
R16
18kΩ, 5%,0603, resistor
1
R17
10kΩ, 5%, 0603, resistor
1
R18
39kΩ, 5%, 0603, resistor
1
R19,R20
470kΩ, 5%,1206, resistor
2
R21
100kΩ, 5%,0603, resistor
1
R22
51kΩ, 1%,0603, resistor
1
R23
120kΩ, 1%,0603, resistor
1
R24, R25
510kΩ, 5%, 1206, resistor
2
R26
100Ω, 5%,1206, resistor
1
R27
2.2Ω, 1%,1206, resistor
1
R28
2.4Ω, 1%,1206, resistor
1
R29
10MΩ, 5%, 1206, resistor
1
R30
8.2kΩ, 5%,0603, resistor
1
R31
51kΩ, 5%, 1206, resistor
1
R32
47Ω, 5%, 1206, resistor
1
R33
18kΩ, 5%, 1206, resistor
1
R34
5.1kΩ, 5%, 0603, resistor
1
R35
10Ω, 5%, 1206, resistor
1
R37
220kΩ,5%, 0603, resistor
1
R38, R39
10kΩ,5%, 1206, resistor
2
T1
EE19 10 pin 1.8mH, 5%, Transformer
1
U1
AP1661AMTR-G1, SOIC-8, BCD’s IC
1
U2
AP1681MTR-G1, SOIC-8, BCD’s IC
1
Q1
MOSFET, Fairchild, SSR4N60B, TO252
1
Q2
MOSFET, ST, P4NK60Z, TO220
1
Q3
Transistor, NPN, BC847,SOT-23
1
Z1
Zener 15V, SOD-80
1
R12,R13
The Flyback transformer use EE19 bobbin and core,
Sep. 2011
QTY
LP=1.8mH, NP=140T, NS=32T, Na=34T.
Rev. 1. 0
BCD Semiconductor Manufacturing Limited
11
Application Note 1070
Figure 14. Demo Board PCB and Component Layout (Top View, Real Size 55mm×45mm )
Figure 15. Demo Board PCB and Component Layout (Bottom View, Real Size 55mm×45mm)
Sep. 2011
Rev. 1. 0
BCD Semiconductor Manufacturing Limited
12
Application Note 1070
The tested IO Vs. dimmer conduct angle has exponential
relation which is compatible with human eye perception.
500
IO (mA)
400
300
200
100
0
0
20
40
60
80
100
120
140
160
180
Dimmer Conductor Angle
Figure 16. IO vs. Dimmer Conduct Angle
The input current is in shape with input ac voltage and
there is very low inrush current when dimmer begins to
conduct. Leading edge and trailing edge type dimmers are
both tested. The input voltage and input current are shown
below. Test condition is VIN=120Vac.
Figure 17. ө=150o(leading), IPEAK=147mA
Sep. 2011
Figure 18. ө=135o(leading), IPEAK=192mA
Rev. 1. 0
BCD Semiconductor Manufacturing Limited
13
Application Note 1070
Figure 19. ө=90o(leading), IPEAK=370mA
Figure 20. ө=30o(leading), IPEAK=160mA
Figure 21. ө=140o(trailing), IPEAK=169mA
Figure 22. ө=115o(trailing), IPEAK=150mA
Figure 23. ө=90o(trailing), IPEAK=119mA
Sep. 2011
Figure 24. ө=45o(trailing), IPEAK=106mA
Rev. 1. 0
BCD Semiconductor Manufacturing Limited
14
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