Holtek HT7L4091 Universal step-down pwm control for high brightness led lighting control Datasheet

HT7L4091
Universal Step-Down PWM Control
For High Brightness LED Lighting Control
Features
General Description
• Input supply AC voltage range: 100V~240V
The HT7L4091 device provides a low-cost solution
for active current mode PWM controls of High
Intensity LED drive systems supplied by either AC or
DC line power lines. The device operates in constant
off-time mode which is suitable for buck LED drivers.
The low start-up and operating currents provides
flexible power requirements for high efficiency or low
cost applications. The switch frequency off-time can
be programmed using an external resistor. The peak
current mode control achieves good output current
regulation without requiring loop compensations for a
wide range of input voltages.
• Ultra low power-on start-up current < 30μA
• Integrated 25V Zener diode internally connected to
VIN pin
• 5V LDO output voltage with 6mA driving current
for external components
• Frequency jitter function for enhanced EMI
performance
• Efficiency > 85%
• Under Voltage Lockout function – UVLO
• Current mode operation with cycle-by-cycle
current limiting
Included in the device is a PWM dimming input
which can accept an external control signal with a
duty ratio from 0 to 100%. The output current can
be programmed from 0 to 250mA by applying an
external control voltage on the linear dimming control
input.
• Over temperature protection function
• High-current FET drive output
• Linear and PWM dimming function
• Enhanced short circuit protection function
The device includes a frequency jitter function which
helps to reduce EMI power supply emissions. Also
contained is an enhanced LED short circuit protection
feature to protect the internal circuitry from damage
should the LEDs be short circuited.
Applications
• AC/DC and DC/DC power control for high power
LED lighting
• RGB back lighting LED driver
The device requires a minimum number of external
standard components and is available in an 8-pin SOP
package for small area PCB applications.
• Flat panel displays back lighting
• General purpose constant current source
• Signage and decorative LED lighting
• Battery chargers
Ordering Information
Part Number
Function Description
HT7L4091
Frequency jitter function enabled, VUVLO(H)=16V (typ.)
HT7L4091-1
Frequency jitter function disabled, VUVLO(L)=8V (typ.)
Rev. 1.20
1
March 12, 2013
HT7L4091
Block Diagram
VIN
ON
UVLO
25V
LDO
VDD
PWMD
PDM
GDR
OTP
100k
Power On
Reset
0.5V
Q R
QB S
CS
Blank
0.25V
OSC
(jitter)
RT
Q R
QB S
LD
GND
Pin Assignment
VIN
1
8
RT
CS
2
7
LD
GND
3
6
VDD
GDR
4
5
PDM
HT7L4091
8 SOP-A
Pin Description
Pin Name
I/O
VIN
I
Input voltage pin
Description
LED string current sense input
CS
I
GND
—
Power ground
GDR
O
Gate driver for the external MOSFET
PDM
I
PWM dimming pin
Also functions as enable input pin.
VDD
O
Positive Power supply
Used for the internal circuits except the gate driver circuit. A 0.1μF capacitor must be
connected between the VDD and the GND pins.
LD
I
Linear dimming pin
Set the current sense threshold as long as the voltage on this pin is less than 250mV (typ.).
RT
I
Oscillator control pin
A resistor is connected between the RT and the GND pins to set the off-time.
Rev. 1.20
2
March 12, 2013
HT7L4091
Absolute Maximum Ratings
Output Current Peak ................................................1A
Storage Temperature Range................ -65°C ~ +150°C
Junction Temperature Range............... -40°C ~ +150°C
CS, PDM, LD ,RT, to GND........... -0.3V to (VDD +0.3V)
Power Dissipation at Ta<25°C..............................0.6W
Thermal Resistance, SOP-8 θJA. .................... 150°C/W
ESD Voltage Protection, Human Body Model������6KV
ESD Voltage Protection, Machine Model.............400V
Note: These are stress ratings only. Stresses exceeding the range specified under “Absolute Maximum Ratings”
may cause substantial damage to the device. Functional operation of this device at other conditions beyond
those listed in the specification is not implied and prolonged exposure to extreme conditions may affect
device reliability.
Recommended Operating Ranges
Operating Temperature Range............ -40°C ~ +105°C
Input Supply Voltage................... VUVLO(H)+0.1V~VCLAMP
Note 1: Absolute maximum ratings indicate limits beyond which damage to the device may occur. Operating
Ratings indicate conditions for which the device is intended to be functional, but do not guarantee
specific performance limits. The guaranteed specifications apply only for the test conditions listed.
Note 2: The power supply pin should not be driven by a DC, low impedance power source greater than the VCLAMP
voltage specified in the Electrical Characteristics section.
Electrical Characteristics
Symbol
(VIN=17V, Ta=25°C, unless otherwise specified)
Description
Test Condition
Min.
Typ.
Max.
Unit
—
Input
VINDC
Input DC supply voltage
8.5
—
VClamp
V
—
0.6
1
mA
—
15
30
μA
IIN
Input Operation Current
VINDC≥17V, RT=410kW
GDR pin floating
IINST
Startup Input current
VINDC<15V, RT=410kW
VCLAMP
VIN Clamp Voltage
IIN=10mA
22.4
25
27.6
V
4.5
5
5.5
V
Internal Regulator
VDD
Internally regulated voltage
VINDC=12V~26V
ΔVDD, line
Line regulation of VDD
VINDC=12V~26V, IDD=0mA
0
—
100
mV
ΔVDD, load
Load regulation of VDD
VINDC=17V, IDD=0mA~3mA
0
—
100
mV
VUVLO(H)
VINDC under voltage lockout high threshold
VINDC rising for HT7L491
15
16
17
V
VINDC rising for HT7L491-1
7.5
8.0
8.5
V
VUVLO(L)
VINDC under voltage lockout low threshold
9
10
11
V
VINDC falling for HT7L491-1
6.7
7.2
7.7
V
VEN(L)
Input low voltage for PDM pin
VINDC=12V~26V
—
—
0.8
V
VEN(H)
Input high voltage for PDM pin
VINDC=12V~26V
2.0
—
—
V
REN
PDM pin Pull-low resistor
—
50
100
150
kW
VCS(TH)
Current sense trip threshold voltage
—
0.24
0.248
0.255
V
Rev. 1.20
VINDC falling for HT7L491
3
March 12, 2013
HT7L4091
Symbol
Description
Test Condition
VCS=VCS_TH+50mV
Min.
Typ.
Max.
Unit
—
110
—
ns
Tdelay
Delay from CS trip to GDR
VLD
Linear Dimming pin voltage range
—
0
—
VCS_TH
V
Tblank
Blanking interval
—
200
300
400
ns
Toff
Off time
RT=410kW
14.7
16.4
18.1
μs
VOL
GATE Output Low Level
VINDC=17V, Io=-20mA
—
—
0.3
V
VOH
GATE Output High Level
VINDC=17V, Io=20mA
12
—
—
V
Trise
Gate output rise time
CGATE=500pF
—
120
—
ns
Tfall
Gate output fall time
CGATE=500pF
—
50
—
ns
TOTP
Thermal shutdown temperature
—
—
140
—
—
∆TOTP
Thermal shutdown temperature hysteresis
—
—
25
—
—
∆fJitter
Switch frequency jitter ratio
—
—
±4
—
%
TJP
Jitter Period
—
4
—
ms
VCS-short
Short circuit protection Voltage
0.45
0.5
0.55
V
fsw = 60kHz
—
Note 3: Specifications are production tested at TA=room temperature. Specifications over the -40°C to 85°C
operating temperature range are assured by design, characterization and correlation with Statistical Quality
Controls (SQC).
Functional Description
LED gate driving circuitry will be turned on. While
the voltage on the CS pin is larger than the internal
reference voltage, the LED gate driving circuitry
will be turned off for a constant Toff time. After the
Toff time, the gate driving circuitry will be turn on
if the voltage on the CS pin is less than the internal
reference voltage. Good line regulation is a feature
of constant off-time operation and the LED current is
independent of the input voltage. Since the inductor
current ripple is dependent on the LED string voltage,
the LED string voltage variation will result in LED
current variation. This is typically not a problem since
the LED voltage variation for a given load is fairly
small.
The HT7L4091 is a universal AC/DC constant current
LED driver designed for peak current mode control.
The device provides both LED Linear and PWM
dimming current functions. The high input voltage
from a rectified 85V to 260V AC power is clamped
to under 25V by an external circuit and an internal
Zener diode. The device also contains an input UnderVoltage-Lockout (UVLO) circuit. When the voltage
supplied on the VIN pin exceeds the UVLO high
threshold, the gate driver is enabled. If the input
voltage falls below the UVLO low threshold, the gate
driver is turned off.
RCS can be calculated using the following equation:
LED Current Control
0.25
RCS = 0.25 =
I peak ( 1 + 1/ 2 × Ripple) ⋅ I LED
The HT7L4091 device is a constant off-time
peak current mode controller. With reference to
the Application Circuit, the LED peak current is
programmed by an external current sense resistor (RCS)
connected between the CS and the ground pins. The
CS pin is connected to a non-inverting terminal of
an internal comparator of which an internal 250mV
reference is tied to the inverting terminal. The LED
peak current through the RCS resistor will generate
a voltage which is applied on the comparator noninverting terminal and compare with the internal
250mV reference voltage. If the voltage on the CS pin
is less than the internal reference voltage 250mV, the
Rev. 1.20
Where Ipeak is the Maximum LED Current, Ripple
is the Peak to Peak LED Current, and I LED is the
Average LED Current. Ripple can be controlled by
the inductor. 0
I LED × Ripple = I Ripple =
Toff × Vout
L
Refer to “Inductor Design” for the inductor
calculation. Refer to “Programmable Off Time” for
Toff calculation.
4
March 12, 2013
HT7L4091
Programmable Off Time
Input Supply Current
The device operates in a constant off-time mode. A
resistor connected between the RT pin and the ground
pin generates a constant current source which is used
to charge an internal capacitor and determine the offtime. Increasing the resistance reduces the amplitude
of the current source and increases the off-time. The
relationship between the resistor RT and the off-time
is given by the following formula:
The input supply current is determined by the input
operating current and the current drawn by the
external MOSFET gate driver. This means that the
input supply current depends upon the switching
frequency and the external MOSFET gate charge.
IINSP = IIN + Qgate × fS
In addition, where IINSP is the input supply current
taken from the VIN pin, fS is the switching frequency
Qgate is the gate charge of the external MOSFET and
IIN is the input operation current.
Toff = CT × RT CT=36pF~44pF, CT_typ=40pF.
For a given Toff and duty cycle, the switching
frequency (f s) can be decided. The duty cycle is
determined by the input and output voltages.
The application circuit should provide enough IINSP to
ensure the application can work properly
Current Sense
Start-up Current and Auxiliary Power
Source
The current sense input is connected to the noninverting inputs of two comparators. The inverting
terminal of one comparator is tied to an internal
250mV reference whereas the other comparator
inverting terminal is connected to the LD pin. The
outputs of both these comparators are fed into an
OR gate and the output of the OR gate is fed into
the reset pin of a flip-flop. If a flip-flop reset event is
triggered by the OR gate output a signal occurs where
the external MOSFET gate driving circuitry will be
turned off. Therefore, the comparator which has the
lower voltage at the inverting terminal determines
when the gate driving output is turned off.
The power consumption of the HT7L4091 is one of
the major efficiency losses if IINSP drops from the
rectified AC source whose voltage is much higher
than the voltage used by the device. For efficiency
improvements, a small start-up current from the
rectified AC source is used to start up the HT7L4091
and IINSP can be provided from the auxiliary power
source, for example: auxiliary winding.
The start-up current should take into consideration
the Cin (Vin Capacitor) charge current and the current
consumption of the HT7L4091 during start-up (Iinst).
The Cin charge current shall consider how fast (tstart-up)
the application is required to start operation. The start-up
current can be calculated using the follow equation:
Leading-Edge Blanking
Each time the power MOSFET is switched on, a
turn-on transient spike will occur on the CS pin. To
avoid premature termination of the switching pulse, a
TBlank leading-edge blank time is generated during the
MOSFET switch turn-on to prevent false triggering
of the current sense comparator. During this blanking
period, the current-limit comparator is disabled and
the gate driving circuitry will not be switched off.
I start −up = I inst +
C in × VUVLO( H )
t start −up
The current from auxiliary power source should be:
Iaux=IINSP-Istart-up
The start-up current allows a start-up resistor with a
high resistance and a low-power rating. The start-up
resistor (RINST) is used to supply the start-up power for
the device from the rectified AC source. RINST can be
calculated using the following equation:
In certain rare situations, the internal blanking time
might not be long enough to filter out the turn-on
spike. In such situations, it will be necessary to add an
external RC filter between the external sense resistor
(RCS) and the CS pin.
R INST =
Frequency Jitter Function
2 ⋅ Vmin, AC − VUVLO ( H )
I start −up
The device also includes a frequency jitter function.
The frequency has a variation range of +4% to -4%
within four milliseconds. The frequency jitter function
helps reduce power supply line EMI emissions with
minimum line filters.
Rev. 1.20
5
March 12, 2013
HT7L4091
Linear Dimming
The operation state is shown in the accompanying
figure. When the circuit is operating normally, VCS can
be limited to VCS-TH, while some LEDs are shorted,
the LED current is still limited and the output voltage
is adjusted to meet the current requirement. If the
circuit encounters a serious short, the voltage increase
of (current) in TBlank would be larger than the decrease
in TOFF, VCS will exceed VCS-TH and reach VCS-Short. The
HT7L4091 will then shut down the gate driver until
UVLO resets the HT7L4091.
The Linear Dimming pin is used to control the LED
current. The VDD pin voltage can be connected to
the LD pin to obtain a voltage corresponding to the
desired voltage across RCS. The LD pin can adjust the
current level to reduce the illumination intensity of
the LEDs. To adjust the external LD pin voltage from
0mV to 250mV can adjust the LED current during
operation. To use the internal 250mV as the reference
voltage, the LD pin can be connected to VDD.
Normal
PWM Dimming
Slight
Short
Serious
Short
Shut Down
VCS-Short
An external enable input named PDM is provided and
can be utilized for PWM dimming of the LED string.
When the external PWM signal is zero, the gate
driving circuitry is turned off while the gate driving
circuits are turned on when the PWM signal is high.
VCS-TH
VCS
TBlank
TOff
LED Open and Short Circuit Protection
There will be no abnormal behavior if the LEDs
are open circuit. While some LEDs are shorted, the
output voltage will be adjusted automatically for the
condition. Cin
D1
L1
CVDD
Enhanced Short Circuit Protection
VDD
LD
PDM
When most LEDs are shorted in the application
circuit, the current regulation may lose control
resulting in the current increasing to an extremely
high level. When the current is more than twice of the
set Ipeak, resulting from externally shorted LEDs, the
device will shut down gate driving operations.
Rev. 1.20
Rlim
RT
Vin
GDR
CS
GND
Clim
6
RCS
March 12, 2013
HT7L4091
Application Description
Input Bulk Capacitor – C1
This section shows how to design a buck circuit
LED application using a simple example. For other
application conditions, such as high efficiency
solutions, refer to the HT7L4091 application notes for
more details.
The input Bulk Capacitor determines the ripple
amplitude of input voltage after rectification. A large
capacitance generates a smaller input voltage ripple
amplitude. The first design criterion to meet is that
the maximum LED string voltage should be less than
80% of the minimum AC input voltage (Vmin,AC). Note
that 80% is a rough estimate here. Here the large
ripple amplitude has a wide frequency variation which
leads to increase in circuit power losses. Assume that
the input voltage DC ripple (ΔVDCripple%) is equal to
30% and then calculate the C1 value.
For example:
AC Input voltage: VAC_typ = 110Vrms; VAC_min = 95Vrms;
VAC_max = 125Vrms; fAC = 60Hz
Target working condition: FPWM > 40kHz
Output Voltage: LED string × LED Voltage = 8×(3~3.3)
= 24V~26.4V, typical 25.2V
2 × VAC_ min × (1 − ∆VDCripple %) × 0.8
Average Output LED Current: ILED = 400mA
= 2 × 95 × (1 − 30%) × 0.8
= 75.2V > 26.4V (maximum output voltage)
Expected efficiency: η = 90%
Refer to the typical application circuit.
Above formula means 30% input voltage ripple is
approved that exceed output voltage.
Finally, a useful rule can find the valley voltage of the
input voltage. Using the figure below, it is necessary
to calculate the charge time and discharge time of the
input bulk capacitor.
VIN
8.333ms 
1
120Hz
ΔV
Tdischarge
Tcharge
t
The Waveform of Input Voltage in the C1
Charge period: TCP =
1
= 8.333ms
2 × f AC


sin −1 (1 − ∆V ) 

V
, where ∆V
T
IN

Tch arg e = CP × 1 −
= ∆VDCripple %
2 
90

VIN
Tdischarge=TCP– Tcharge
Tdich arg e = 8.333ms −
Rev. 1.20
8.333ms  sin −1 (1 − 30%) 
× 1 −
 = 6.2232ms
90
2


7
March 12, 2013
HT7L4091
Off-time Resistor – RT
Then, the minimum capacitor value can be calculated
as:
C1 ≥
A resistor connected to the RT pin determines the offtime which has a variation range from -10% to +10%.
Since the working frequency has a minimum target,
the CT is considered to calculated the RT:
(2 × n × VLED _max × I LED ) × Tdischarg e
(
) (
)
2
2
η ×  2 × VAC _min − VDC _min 


(2 × 8 × 3.3V × 400mA)× 6.2232ms
= 15.9µF
=
2
2
0.9 ×  2 × 95 − 2 × 95 × 0.7 


(
) (
)
Toff = CT × RT → RT ≤
18.173µs
= 413.03kΩ
44 pF
Choose 390kW and 13kW for RT are used
Choose C1=22mF
The off time is:
Considering ±20% capacitance variation, the worst
case lower value of the capacitance is 17.6mF, which
is much larger than 14.3mF. It can be calculated that
the input DC ripple is 24.5% when the input Buck
capacitor is 17.6mF.
Toff_typ = CT_typ × RT = 40p × 403K = 16.1ms
Toff_max = CT_max × RT = 44p × 403K = 17.7ms
Toff_min = CT_max × RT = 36p × 403K = 14.5ms
Therefore, if the real capacitor value is less than
the calculated value, the voltage ripple will exceed
the maximum range of 30% which is the specified
assumption in the calculation.
The actual minimum frequency can be calculated as:
Switching Frequency and Duty Cycle
fPWM_TYP@Vac_min= 45.2kHz, fPWM_MAX@Vac_min=50.1kHz
f PWM _ min =
Frequency interference should be taken into account to
minimise interference with other electrical appliances.
Here set the minimum switching frequency to a value
of 40kHz for safety. If EMI suppression is good, the
switching frequency can be decreased to 30kHz to
obtain better efficiency.
1 − D max
Toff _ max
=
1 − 0 .2731
17 .7µ
= 41 .07 K
Inductor Design
The ripple current is selected to be 30% of the
nominal LED current. If the LED average current
ILED is 400mA, the LED string Voltage = n × VLED,
max = 8 × 3.3V where VLED, max is the LED maximum
forward voltage, then the inductor can be calculated
by the following formula.
Since the HT7L4091 operates in constant off time, the
switching frequency would be changed by the input
and output voltage. The slowest switching frequency
occurs when the duty cycle is at a maximum value.
L=
The maximum duty cycle can be calculated as,
Toff × n × VLED_max 17.7 µs × 8 × 3.3
= 3.894 mH
=
I LED × Ripple
400mA× 0.3
Choose L=3.8 mH
VO _ max
n ⋅ VLED _max + VF , D1
Dmax =
=
VDC _ min
2 ⋅ VAC _min − (1 − Vripple )
3
.
3
×
8
+
1.3
=
= 0.2731
2 × 95 × (1 − 24.5% )
Turn-off Time
Toff =
Rev. 1.20
1 − Dmax
1 − 0.2731
=
= 18.173µs
f PWM _ min
40k
8
March 12, 2013
HT7L4091
Current Sense Resistor – RCS
Input Limit Resistor (RIN)
This current flows through the external sense resistor
RCS and produces a ramp voltage on the CS pin. The
comparators are constantly comparing the CS pin
voltage with both the voltage on the LD pin and the
internal 250mV reference voltage. Once the blanking
time has elapsed, the output of these comparators can
then reset the flip flop. When one output of these two
comparators switches high, the flip flop is reset and
the gate drive output switches low. The gate drive
output stays low until the SR flip flop is set by the
oscillator. In assuming a 30% ripple in the inductor,
the current sense resistor RCS can be obtained using
the following formula:
In this design, VAC_min = 95Vrms, VUVLO(H)_max = 17V
2 ⋅ VAC _ min × (1 − ∆VDCripple%) − VUVLO( H ) _ max
I INSP
2 × 95 × (1 − 30%) − 17
=
= 48.1kΩ
1.6mA
Rin =
Choose Rin=60kW
The input limit resistor consider the high input voltage
from the rectified clamp voltage of the internal Zener
diode and operating current. Two 30kW/1W resistors
are used for Rin.
0.25
0.25
=
I peak ( 1 + 1/ 2 × Ripple) ⋅ I LEDavg
0.25
=
= 0.543 Ω
(1 + 0.5 × 0.3) × 400mA
Output Capacitor – CO
RCS =
The capacitor, CO, filters the current through the LEDs
thus limiting the peak current of the LED string.
Increasing the inductor ripple current corresponds
to decreasing the inductor value and inductor size.
In order to reduce the inductor value and size and
obtain a smaller LED current ripple, the addition
of a capacitor CO is a good way to do this. Usually,
a several μF output capacitor is added in practical
application circuits.
Choose RCS = 0.54W
Input Supply Current
Assume that the input current drawn by the internal
circuit from the VIN pin is the sum of the current
with a value of 1.0mA and the current drawn by the
gate driver of the external MOSFET (which in turn
depends upon the switching frequency and the gate
charge of the external FET). Assume that the gate
charge Qgate is equal to 12nC.
Adding C O connected across the LED strings can
reduce the LED current ripple and while increasing
the inductor current ripple variation can decrease the
inductor value and size.
To assume inductor current ripple is 80%, a smaller
inductor value could be calculated.
IINSP = IIN + Qgate × FPWM
= 1mA + 12nC × 50kHz = 1.6mA
L=
In addition, where I INSP is the input current taken
from the VIN pin, FPWM is the switching frequency,
Qgate is the gate charge of the external FET and IIN
is the current taken by the internal circuit. FPWM is
considered about the minimum input voltage and CT
has a minimum value.
Rev. 1.20
Toff × n × VLED_max 17.7 µs × 8 × 3.3
=
= 1.460mH
I LED × Ripple
400mA× 0.8
Choose L=1.4mH and CO=1mF
The actual values of C O and R CS may need to be
adjusted to reduce the current ripple and obtain the
target average LED current. A 1mF capacitor and an
R CS as shown in the above calculation are a good
start point to obtain an acceptable result. Since it
takes some effort, it can reduce the inductor size/cost
significantly.
9
March 12, 2013
HT7L4091
Typical Performance Characteristics
Efficiency for Resistor Only Power and
Single Input Voltage
There are many different factors to influence
efficiency of the application, such as the output
power, working frequency, power supply circuit of
the HT7L4091 and so on. The following are some
measured results.
The results of these curves are that each voltage
corresponds to each input limit resistor. Theseresults
show how good the application is designed for a
narrow voltage range using a resistor to power the
device.
Efficiency vs. Power Supply Circuit –
Working Frequency
The “LED string” means how many LEDs are in one
string. 16S means there are 16 LEDs in one string.
There are several different power supply circuits for
the device. Reference to the “Application circuit”
for some examples. The different circuits provide
different advantages, such as high efficiency or low
cost.
The output (LED) power is kept at 10W.
Input Voltage vs. Efficiency
95
90
Efficiency(%)
Follow are some efficiency compare for different
power supply circuits. The condition is VAC=
85V~260V, F PWM ≥ 50kHz (working frequency),
o u t p u t = 5 2 V × 0 . 2 A = 1 0 . 4 W. D e c r e a s i n g F P W M
or increasing the output power can enhance the
efficiency.
16S LED
14S LED
12S LED
85
80
10S LED
75
8S LED
70
65
80
130
180
230
280
Vac(V)
efficiency compare in different application circuits
(freq,min=50kHz)
92
LED String vs. Efficiency
88
95
86
84
82
BJT circuit
80
typical circuit
78
80
130
180
230
85Vac
110Vac
170Vac
220Vac
260Vac
90
auxiliary circuit
Efficiency(%)
efficiency (%)
90
85
80
75
70
280
65
Vac (V)
6
8
LED Current(mA)
efficiency (%)
89
auxiliary circuit 30kHz
BJT circuit 30kHz
auxiliary circuit 50kHz
83
80
130
180
230
18
8S LED
400
350
10S LED
300
12S LED
250
14S LED
16S LED
200
150
80
130
180
BJT circuit 50kHz
81
16
450
91
85
14
Input voltage vs. LED Current
efficiency compare with different frequency in two application
circuits
87
12
LED String
The following is an example to enhance the efficiency
by reducing the F PWM (working frequency) to ≥
30kHz.
93
10
230
280
Vac(V)
280
Vac (V)
LED String vs. LED current
LED current(mA)
450
85Vac
110Vac
170Vac
220Vac
400
350
300
260Vac
250
200
150
6
8
10
12
14
16
18
LED String
Rev. 1.20
10
March 12, 2013
HT7L4091
Efficiency Using Resistor Only Power
and 85~265 VAC Input
Input voltage vs. LED Current
460
LED Current(mA)
These result curves use the same input limit resistor
with different voltages. These results show the
performance only using a resistor to power up the
device for a full range voltage input. For improved
efficiency with a full range voltage input, refer to the
following application circuit.
8S LED
410
360
10S LED
310
12S LED
260
14S LED
16S LED
210
160
80
130
180
230
280
Vac(V)
Input Voltage vs. Efficiency
95
LED String vs. LED current
85
460
16S LED
14S LED
12S LED
10S LED
8S LED
80
75
70
65
LED current(mA)
Efficiency(%)
90
60
80
130
180
230
280
Vac(V)
410
360
310
260Vac
220Vac
170Vac
110Va
85Vac
260
210
160
6
8
10
12
14
16
18
LED String
LED String vs. Efficiency
95
85Vac
110Vac
170Vac
220Vac
260Vac
Efficiency(%)
90
85
80
75
70
65
60
6
8
10
12
14
16
18
LED String
Rev. 1.20
11
March 12, 2013
HT7L4091
Typical Application Circuit
EMI
Lc
RIN
AC
Ca1
Ca2
VLED
L
0.1uF
400V
22uF
400V
Co
D1
Cfilter
C1
CIN
Zin
Lc
1uF/50V
VIN
LD
Essential components
Used optional components
Unused optional components
0.1uF
C7
MOSFET
G DR
VDD
Rc
CS
PDM
GND
RT
CT
5pF
Rcs
CC
RT
This typical application circuit uses a fundamental buck converter circuit. Adding a CO capacitor can reduce the
LED current ripple or reduce the inductor size while adding the RC and CC components can reduce spikes on the
CS pin.
If frequency jittering is considered to reduce EMI an optional 5pF CT may be used to stabilise the effect.
Other Application Circuit
No Input Bulk Capacitor Circuit
EMI
Lc
RIN
Ra
AC
Ca1
Ca2
VLED
L
0.1uF
400V
Rb
CIN
1uF/50V
Lc
VIN
LD
Essential components
Used optional components
Unused optional components
Co
D1
Cfilter
0.1uF
C7
CS
PDM
RT
CT
5pF
MOSFET
GDR
VDD
GND
Rc
CC
Rcs
RT
The application circuit is a low cost implementation which can improve the PF used within the signal input voltage
range.
The auxiliary winding application circuit can be chosen when used for a universal input voltage. If frequency
jittering is considered to reduce EMI effects, an optional 5pF capacitor may be added for stabilisation purposes.
Refer to the application notes for more details.
For more details refer to the application note.
Rev. 1.20
12
March 12, 2013
HT7L4091
High Efficiency Circuit
EMI
Lc
RIN
AC
Ca1
Ca2
C1
Cfilter
22uF
400V
0.1uF
400V
D1
VLED
Tr
CIN
Zin
1uF/50V
Lc
Ra
MOSFET
Rc
CS
P DM
RT
CT
5pF
Dg
Rg
GDR
VDD
C7
Essential components
Used optional components
Unused optional components
Rsb
VIN
LD
Da
Rs
Cc
GND
RT
The application circuit uses the auxiliary inductor to supply the device power to obtain better efficiency.
If frequency jittering is used to reduce EMI interference effects, an optional 5pF capacitor may be used for
stabilisation purposes. For more details, refer to the application note for auxiliary inductor applications.
For more details refert to the application note.
BJT Power Supply Application Circuit
The application circuit uses a BJT to supply the device power to obtain better efficiency.
EMI
Lc
RIN
BJT
AC
Ca1
Ca2
Cfilter CIN
C1
22uF
400V
0.1uF
400V
Co
D1
Zin
1uF
50V
VLED
L
Lc
VIN
LD
0.1uF
C7
PDM
RT
CT
5pF
MOSFET
GDR
VDD
CS
GND
Rc
CC
Rcs
RT
If frequency jittering is considered to reduce EMI an optional 5pF CT may be used to stabilise the effect.
For more details refer to the application note.
Rev. 1.20
13
March 12, 2013
HT7L4091
Bill of Materials
AC Input voltage: VAC_typ =110Vrms; VAC_min =95Vrms; VAC_max =115Vrms, fPWM ≥ 40kHz
Output Voltage: LED string Voltage =24~26.4V
Average Output LED Current: ILED= 400mA
R+L+EMI circuit (8S20P)
Components
Quantity
Value
Package
Part Number
RT
1
390kW+ 13kW
SMD 0805
—
RCS
1
R300(0.3W)+R240(0.24W)
SMD 1206
—
C1
1
22mF/ 200V
CapXon Radial
FK series
Cfilter
1
0.1mF/ 200V
Radial
—
RIN
1
30kW/1W x 2
AXIAL-0.6
—
CIN
1
1mF / 50V
SMD 0805
—
LED
160
3~3.3V/30mA
Everlight P-LCC-2
L2C-B4556AC2CB2
MOSFET
1
2A/600V
NIKO-SEM DPAK
P0260AD
C7
1
0.1mF
SMD 0805
—
DBridge
1
1A/400V
DF-S
DF04S-T
D1
1
2A/600V
SMB
STTH2R06U
U1
1
HT7L4091
NSOP8
HOLTEK
L
1
3.8mH
Coilcraft 335D
CM6676-AL
Rev. 1.20
14
March 12, 2013
HT7L4091
Package Information
Note that the package information provided here is for consultation purposes only. As this information may be
updated at regular intervals users are reminded to consult the Holtek website for the latest version of the package
information.
Additional supplementary information with regard to packaging is listed below. Click on the relevant section to be
transferred to the relevant website page.
• Further Package Information (include Outline Dimensions, Product Tape and Reel Specifications)
• Packing Meterials Information
• Carton information
• PB FREE Products
• Green Packages Products
Rev. 1.20
15
March 12, 2013
HT7L4091
8-pin SOP (150mil) Outline Dimensions
• MS-012
Symbol
Nom.
Max.
A
0.228
―
0.244
B
0.150
―
0.157
C
0.012
―
0.020
C’
0.188
―
0.197
D
―
―
0.069
E
―
0.050
―
F
0.004
―
0.010
G
0.016
―
0.050
H
0.007
―
0.010
α
0°
―
8°
Symbol
Rev. 1.20
Dimensions in inch
Min.
Dimensions in mm
Min.
Nom.
Max.
A
5.79
―
6.20
B
3.81
―
3.99
C
0.30
―
0.51
C’
4.78
―
5.00
1.75
D
―
―
E
―
1.27
―
F
0.10
―
0.25
G
0.41
―
1.27
H
0.18
―
0.25
α
0°
―
8°
16
March 12, 2013
HT7L4091
Copyright© 2013 by HOLTEK SEMICONDUCTOR INC.
The information appearing in this Data Sheet is believed to be accurate at the time of publication.
However, Holtek assumes no responsibility arising from the use of the specifications described.
The applications mentioned herein are used solely for the purpose of illustration and Holtek makes
no warranty or representation that such applications will be suitable without further modification,
nor recommends the use of its products for application that may present a risk to human life due to
malfunction or otherwise. Holtek's products are not authorized for use as critical components in life
support devices or systems. Holtek reserves the right to alter its products without prior notification. For
the most up-to-date information, please visit our web site at http://www.holtek.com.
Rev. 1.20
17
March 12, 2013