FAIRCHILD FAN7710V

FAN7710V
Ballast Control IC for Compact Fluorescent Lamps
Features
Description


FAN7710V developed using Fairchild’s high-voltage
process and system-in-package (SiP) concept, are
ballast-control integrated circuits (ICs) for compact
fluorescent lamps (CFL). FAN7710V incorporates a
preheating / ignition function, controlled by a userselected external capacitor, to increase lamp life. The
FAN7710V detects switch operation after ignition mode
through an internal active Zero-Voltage Switching (ZVS)
control circuit. This control scheme enables the
FAN7710V to detect an open-lamp condition, without the
expense of external circuitry, and prevents stress on the
MOSFETs. The high-side driver in the FAN7710V has a
common-mode noise cancellation circuit that provides
robust operation against high-dv/dt noise intrusion.








Integrated Half-Bridge MOSFET
Floating Channel FAN7710V for Bootstrap Operation
to +440V
Low Startup and Operating Current: 120μA, 2.6mA
Under-Voltage Lockout with 1.8V of Hysteresis
Adjustable Run Frequency and Preheat Time
Internal Active ZVS Control
Internal Protection Function (No Lamp)
Internal Clamping Zener Diode
High Accuracy Oscillator
Soft-Start Functionality
8-DIP
Applications

Compact Fluorescent Lamp Ballast
Ordering Information
Part Number
Operating
Temperature
FAN7710VN
-40 to +125°C
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
Package
8-Lead Dual Inline Package (DIP)
Packing Method
Tube
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FAN7710V— Ballast Control IC for Compact Fluorescent Lamps
February 2012
FAN7710V — Ballast Control IC for Compact Fluorescent Lamps
Typical Applications Diagrams
FAN7710V
Figure 1. Typical Application Circuit for Compact Fluorescent Lamp
Internal Block Diagram
Figure 2. Functional Block Diagram
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
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FAN7710V — Ballast Control IC for Compact Fluorescent Lamps
Pin Configuration
Figure 3. Pin Configuration (Top View)
Pin Definitions
Pin #
Name
1
VDC
2
VB
3
VDD
4
RT
5
CPH
6
SGND
7
PGND
8
OUT
Description
High-Voltage Supply
High-Side Floating Supply
Supply Voltage
Oscillator Frequency Set Resistor
Preheating Time Set Capacitor
Signal Ground
Power Ground
High-Side Floating Supply Return
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
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Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be
operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In
addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The
absolute maximum ratings are stress ratings only. TA=25°C unless otherwise specified.
Symbol
Parameter
Min.
Typ.
Max.
Unit
VB
High-Side Floating Supply Voltage
-0.3
465.0
V
VOUT
High-Side Floating Supply Return
-0.3
440.0
V
RT, CPH Pins Input Voltage
-0.3
8.0
V
25
mA
VIN
ICL
dVOUT/dt
TA
TSTG
(1)
Clamping Current Level
Allowable Offset Voltage Slew Rate
50
V/ns
Operating Temperature Range
-40
+125
°C
Storage Temperature Range
-65
+150
°C
PD
Power Dissipation
2.1
W
ΘJA
Thermal Resistance, Junction-to-Air
70
°C/W
Note:
1. Do not supply a low-impedance voltage source to the internal clamping Zener diode between the GND and the
VDD pin of this device.
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
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FAN7710V — Ballast Control IC for Compact Fluorescent Lamps
Absolute Maximum Ratings
VBIAS (VDD, VB -VOUT)=14.0V and TA=25°C, unless otherwise specified.
Symbol
Parameter
Conditions
Min.
Typ.
Max.
Unit
High-Voltage Supply Section
VDC
High-Voltage Supply Voltage
440
V
Low-Side Supply Section (VDD)
VDDTH(ST+) VDD UVLO Positive-Going Threshold
VDD Increasing
12.4
13.4
14.4
VDDTH(ST-) VDD UVLO Negative-Going Threshold
VDD Decreasing
10.8
11.6
12.4
VDDHY(ST)
VDD-Side UVLO Hysteresis
1.8
14.8
V
VCL
Supply Camping Voltage
IDD=10mA
IST
Startup Supply Current
VDD=10V
15.2
120
µA
IDD
Dynamic Operating Supply Current
50kHz, CL=1nF
2.6
mA
High-Side Supply Characteristics (VB-VOUT)
VHSTH(ST+) High-Side UVLO Positive-Going Threshold
VB-VOUT Increasing
8.5
9.2
10.0
VHSTH(ST-) High-Side UVLO Negative-Going Threshold
VB-VOUT Decreasing
7.9
8.6
9.5
VHSHY(ST)
High-Side UVLO Hysteresis
V
0.6
IHST
High-Side Quiescent Supply Current
VB -VOUT=14V
50
IHD
High-Side Dynamic Operating Supply Current
50kHz, CL=1nF
250
µA
Oscillator Section
VMPH
2.5
3.0
3.5
IPH
CPH Pin Preheating Voltage Range
CPH Pin Charging Current During Preheating
VCPH=1V
1.25
2.00
2.85
IIG
CPH Pin Charging Current During Ignition
VCPH=4V
8
12
16
VMO
CPH Pin Voltage Level at Running Mode
fPRE
Preheating Frequency
fOSC
Running Frequency
RT=80kΩ
DTMAX
Maximum Dead Time
VCPH=1V, VOUT=SGND
During Preheat Mode
3.1
µs
DTMIN
Minimum Dead Time
VCPH=6V, VOUT=SGND
During Run Mode
1.0
µs
7.0
RT=80kΩ, VCPH=2V
V
µA
V
72
85
98
kHz
48.7
53.0
57.3
kHz
Protection Section
VCPHSD
Shutdown Voltage
ISD
Shutdown Current
TSD
VRT=0 After Run Mode
Thermal Shutdown(2)
2.6
V
250
450
+165
µA
°C
Internal MOSFET Section
ILKMOS
Internal MOSFET Leakage Current
VDS=400V
RON
Static Drain-Source On-Resistance
VGS=10V, ID=190mA
4.6
50
µA
6.0
Ω
IS
Maximum Continuous Drain-Source Diode Forward Current
0.38
ISM
Maximum Pulsed Continuous Drain-Source Diode Forward Current
3.04
VSD
Drain-Source Diode Forward Voltage
VGS=0V, IS=0.38A
Note:
2. These parameters, although guaranteed, is not 100% tested in production.
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
1.4
A
V
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FAN7710V — Ballast Control IC for Compact Fluorescent Lamps
Electrical Characteristics
Figure 4. Startup Current vs. Temperature
Figure 5. Preheating Current vs. Temperature
Figure 6. Ignition Current vs. Temperature
Figure 7. Operating Current vs. Temperature
Figure 8. High-Side Quiescent Current
vs. Temperature
Figure 9. Shutdown Current vs. Temperature
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
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FAN7710V — Ballast Control IC for Compact Fluorescent Lamps
Typical Performance Characteristics
Figure 10. VDD UVLO vs. Temperature
Figure 11. VBS UVLO vs. Temperature
Figure 12. VDD Clamp Voltage vs. Temperature
Figure 13. Shutdown Voltage vs. Temperature
Figure 14. Running Frequency vs. Temperature
Figure 15. Preheating Frequency vs. Temperature
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
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FAN7710V — Ballast Control IC for Compact Fluorescent Lamps
Typical Performance Characteristics (Continued)
Figure 16. Minimum Dead Time vs. Temperature
Figure 17. Maximum Dead Time vs. Temperature
Figure 18. On-Region Characteristics
Figure 19. On-Resistance Variation vs.
Drain Current and Gate Voltage
Figure 20. Body Diode Forward Voltage Variation
vs. Source Current and Temperature
Figure 21. Breakdown Voltage Variation
vs. Temperature
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
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FAN7710V — Ballast Control IC for Compact Fluorescent Lamps
Typical Performance Characteristics (Continued)
Figure 22. On-Resistance Variation vs. Temperature
Figure 23. Maximum Safe Operating Area
Figure 24. Maximum Drain-Current
vs. Case Temperature
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
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FAN7710V — Ballast Control IC for Compact Fluorescent Lamps
Typical Performance Characteristics (Continued)
1. Under-Voltage Lockout (UVLO) Function
The FAN7710V has UVLO circuits for both high-side and
low-side circuits. When VDD reaches VDDTH(ST+), UVLO is
released and the FAN7710V operates normally. At UVLO
condition, FAN7710V consumes little current, noted as
IST. Once UVLO is released, FAN7710V operates
normally until VDD goes below VDDTH(ST-), the UVLO
hysteresis. At UVLO condition, all latches that determine
the status of the IC are reset. When the IC is in the
shutdown mode, the IC can restart by lowering VDD
voltage below VDDTH(ST-).
FAN7710V has a high-side gate driver circuit. The supply
for the high-side driver is applied between VB and VOUT.
To protect from malfunction of the driver at low supply
voltage between VB and VOUT, there is an additional
UVLO circuit between the supply rails. If VB-VOUT is under
VHSTH(ST+), the driver holds LOW state to turn off the highside switch, as shown in Figure 25. As long as VB-VOUT is
higher than VHSTH(ST-) after VB-VOUT exceeds VHSTH(ST+),
operation of the driver continues.
2. Oscillator
The ballast circuit for a fluorescent lamp is based on the
LCC resonant tank and a half-bridge inverter circuit, as
shown in Figure 25. To accomplish Zero-Voltage
Switching (ZVS) of the half-bridge inverter circuit, the
LCC is driven at a higher frequency than its resonant
frequency, which is determined by L, CS, CP, and RL;
where RL is the equivalent lamp's impedance.
RT
Inverter
Oscillator
VDD
CPH
CPH
fIG = 0.3 × ( 5-VCPH ) + 1 × fOSC
Equation 2 is valid only when VCPH is between 3V and 5V
before entering running mode. Once VCPH reaches 5V,
the internal latch records the exit from ignition mode.
Unless VDD is below VDDTH(ST-), the preheating and
ignition modes appear only during lamp-start transition.
Finally, the lamp is driven at a fixed frequency by an
external resistor, RT, shown as (C) in Figure 26. If VDD is
higher than VDDTH(ST+) and UVLO is released, the voltage
of the RT pin is regulated to 4V. This voltage adjusts the
oscillator's control current according to the resistance of
RT. Because this current and an internal capacitor set the
oscillation frequency, the FAN7710V does not need any
external capacitors.
fOSC =
L
LCC resonant tank
Filament
CS
OUT
Low-side
driver
SGND
(2)
where VCPH is the voltage of CPH capacitor.
VB
Dead-time
controller
(1)
After the warm-up, the FAN7710V decreases the
frequency, shown as (B) of Figure 26. This action
increases the voltage of the lamp and helps the
fluorescent lamp ignite. The ignition frequency is
described as a function of CPH voltage, as follows:
VDC
High-side
driver
RT
fPRE = 1.6 × fOSC
The proposed oscillation characteristic is given by:
VDC
FAN7710
VDD
result, the current warms up the filament for easy
ignition. The amount of the current can be adjusted by
controlling the oscillation frequency or changing the
capacitance of CP. The driving frequency, fPRE, is called
preheating frequency and is derived by:
RL
CP
4 × 10 9
RT
(3)
Even in the active ZVS mode, shown as (D) in Figure 26,
the oscillation frequency is not changed. The dead time
is varied according to the resonant tank characteristic.
PGND
40dB
equivalent lamp impedance
FAN7710 Rev. 1.00
Figure 25. Typical Connection Method
RL=100k
The transfer function of LCC resonant tank is heavily
dependent on the lamp impedance, RL, as illustrated in
Figure 26. The oscillator in FAN7710V generates
effective driving frequencies to assist lamp ignition and
improve lamp life longevity. Accordingly, the oscillation
frequency is changed in following sequence:
20dB
RL=10k
(B)
0dB
Preheating Frequency → Ignition Frequency → Normal
Running Frequency
(C)
RL=1k
(A)
Running frequency
Before the lamp is ignited, the lamp impedance is very
high. Once the lamp is turned on, the lamp impedance
significantly decreases. Since the resonant peak is very
high due to the high-resistance of the lamp at the instant
of turning on the lamp, the lamp must be driven at higher
frequency than the resonant frequency, shown as (A) in
Figure 26. In this mode, the current supplied by the
inverter mainly flows through CP. CP connects both
filaments and makes the current path to ground. As a
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
Preheating
frequency
RL=500
FAN7710 Rev. 1.00
(D) Dead-time control mode
at fixed frequency
Figure 26. LCC Transfer Function in Terms
of Lamp Impedance
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FAN7710V — Ballast Control IC for Compact Fluorescent Lamps
Typical Application Information
3.2 Ignition Mode (t1~t2)
FAN7710V has four operation modes: (A) preheating
mode, (B) ignition mode, (C) active ZVS mode and (D)
shutdown mode; all depicted in Figure 27. The modes
are automatically selected by the voltage of CPH
capacitor shown in Figure 27. In modes (A) and (B), the
CPH acts as a timer to determine the preheating and
ignition times. After preheating and ignition modes, the
role of the CPH is changed to stabilize the active ZVS
control circuit. In this mode, the dead time of the inverter
is selected by the voltage of CPH. Only when in active
ZVS mode is it possible to shut off the whole system
using the CPH pin. Pulling the CPH pin below 2V in
active ZVS mode causes the FAN7710V series to enter
shutdown mode. In shutdown mode, all active operation
is stopped except UVLO and some bias circuitry. The
shutdown mode is triggered by the external CPH control
or the active ZVS circuit. The active ZVS circuit
automatically detects lamp removal (open-lamp
condition) and decreases CPH voltage below 2V to
protect the inverter switches from damage.
When the CPH voltage exceeds 3V, the internal
current source charging CPH is increased about six
times larger than IPH, noted as IIG, causing rapid
increase in CPH voltage. The internal oscillator
decreases the oscillation frequency from fPRE to fOSC as
CPH voltage increases. As depicted in Figure 27,
lowering the frequency increases the voltage across
the lamp. Finally, the lamp ignites. Ignition mode is
when CPH voltage is between 3V and 5V. Once CPH
voltage reaches 5V, the FAN7710V does not return to
ignition mode, even if the CPH voltage is in that range,
until the FAN7710V restarts from below VDDTH(ST-).
Since the ignition mode continues when CPH is from
3V to 5V, the ignition time is given by:
CPH voltage [V]
DTMAX
6
5
(A) Preheating Mode
DTMIN
3
2
(D) Shutdown
mode
1
0
time
3
2 1
0
Dead-Time[μs]
Oscillation
frequency
Preheating Frquency:fPRE
Preheating
Mode
Ignition
Mode
t0
Running frequency:
fOSC
Running
Mode
t1 t2 t3
time
FAN7710 Rev. 1.00
Figure 27. Operation Modes
3.1 Preheating Mode (t0~t1)
When VDD exceeds VDDTH(ST+), the FAN7710V series
starts operation. At this time, an internal current source
(IPH) charges CPH. CPH voltage increases from 0V to
3V in preheating mode. Accordingly, the oscillation
frequency follows Equation 4. In this mode, the lamp is
not ignited, but warmed up for easy ignition. The
preheating time depends on the size of CPH:
t preheat =
3 × CPH
[sec onds]
IPH
(5)
In this mode, dead time varies according to the CPH
voltage.
3.3 Running Mode and Active Zero-Voltage Switching
(AZVS) Mode (t2~)
CPH voltage varies by
active ZVS control
circuit
(B) Ignition Mode
4
2 × CPH
[sec onds]
IIG
(C) Active ZVS mode
8
7
t ignition =
When CPH voltage exceeds 5V, the operating
frequency is fixed to fOSC by RT. However, active ZVS
operation is not activated until CPH reaches ~6V. Only
the FAN7710V prepares for active ZVS operation from
the instant CPH exceeds 5V during t2 to t3. When
CPH becomes higher than ~6V at t3, the active ZVS
operation is activated. To determine the switching
condition, FAN7710V detects the transition time of the
output (VS pin) of the inverter by using the VB pin.
From the output-transition information, FAN7710V
controls the dead time to meet the ZVS condition. If
ZVS is satisfied, the FAN7710V slightly increases the
CPH voltage to reduce the dead time and to find
optimal dead time, which increases the efficiency and
decreases the thermal dissipation and EMI of the
inverter switches. If ZVS fails, the FAN7710V
decreases CPH voltage to increase the dead time.
CPH voltage is adjusted to meet optimal ZVS
operation. During the active ZVS mode, the amount of
the charging / discharging current is the same as IPH.
Figure 28 depicts normal operation waveforms.
(4)
According to the preheating process, the voltage
across the lamp to ignite is reduced and the lifetime of
the lamp is increased. In this mode, the dead time is
fixed at its maximum value.
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
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FAN7710V — Ballast Control IC for Compact Fluorescent Lamps
3. Operation Modes
The FAN7710V can automatically detect an open-lamp
condition. When the lamp is opened, the resonant tank
fails to make a closed-loop to the ground, as shown in
Figure 30. The supplied current from the OUT pin is used
to charge and discharge the charge pump capacitor, CP.
Since the open-lamp condition means resonant tank
absence, it is impossible to meet ZVS condition. In this
condition, the power dissipation of the FAN7710V, due to
capacitive load drive, is estimated as:
Pdissipation =
1
× CP × VDC 2 × f
2
[W ]
(6)
where f is driving frequency and VDC is DC-link voltage.
Figure 28. LCC Transfer Function in Terms
of Lamp Impedance
3.4 Shutdown Mode
If the voltage of capacitor CPH is decreased below
~2.1V by an external application circuit or internal
protection circuit, the IC enters shutdown mode. Once
the IC enters shutdown mode, this status continues
until an internal latch is reset by decreasing VDD below
VDDTH(ST-). Figure 29 shows an example of external
shutdown control circuit.
Figure 29.
External Shutdown Circuit
Figure 30. Current Flow When the Lamp is Open
Assuming that CP, VDC, and f are 1nF, 311V, and 50kHz,
respectively; the power dissipation reaches about 2.4W
and the temperature of is increased rapidly. If no
protection is provided, the IC can be damaged by the
thermal attack. Note that a hard-switching condition
during the capacitive-load drive causes EMI.
Figure 31 illustrates the waveforms during the open-lamp
condition. In this condition, the charging and discharging
current of CP is directly determined by FAN7710V and
considered hard-switching condition. The FAN7710V
tries to meet ZVS condition by decreasing CPH voltage
to increase dead time. If ZVS fails and CPH goes below
2V, even though the dead time reaches its maximum
value, FAN7710V shuts off the IC to protect against
damage. To restart FAN7710V, VDD must be below
VDDTH(ST-) to reset an internal latch circuit, which
remembers the status of the IC.
The amount of the CPH charging current is the same
as IPH, making it possible to shut off the IC using a
small signal transistor. Only the FAN7710V provides
active ZVS operation by controlling the dead time
according to the voltage of CPH. If ZVS fails, even at
the maximum dead time, FAN7710V stops driving
the inverter.
VDD
VDDTH(ST+)
VDDTH(ST-)
CPH
6V
5V
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
time
Active ZVS activated
Automatic
Shutdown
3V
2V
The FAN7710V thermal shutdown circuit senses the
junction temperature of the IC. If the temperature
exceeds ~160°C, the thermal shutdown circuit stops
operation of the FAN7710V.
The current usages of shutdown mode and undervoltage lockout status are different. In shutdown mode,
some circuit blocks, such as bias circuits, are kept
alive. Therefore, the current consumption is slightly
higher than during under-voltage lockout.
Shutdown
Release Restart
time
Running mode
OUT
Active ZVS mode
0V
Preheating period
(Filament warm-up)
time
Shutdown
Ignition period mode
FAN7710 Rev. 1.00
Figure 31. CPH Voltage Variation During Open-Lamp
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FAN7710V — Ballast Control IC for Compact Fluorescent Lamps
4. Automatic Open-Lamp Detection
When VDD is lower than VDDTH(ST+), it consumes very little
current, IST, making it possible to supply current to the
VDD pin using a resistor with high resistance (Rstart in
Figure 32). Once UVLO is released, the current
consumption is increased and whole circuit is operated,
which requires additional power supply for stable
operation. The supply must deliver at least several mA. A
charge pump circuit is a cost-effective method to create
an additional power supply and allows CP to be used to
reduce the EMI.
VDC
Rstart
dv/dt
VDC
RT
CVDD
CPH
VB
Shunt
regulator
SGND
(2)
L
CS
OUT
RL
PGND
(1)
CP
When OUT goes HIGH, the diode DB is reverse-biased
and CB supplies the current to the high-side driver. At this
time, since CB discharges, VB-VOUT voltage decreases. If
VB-VOUT goes below VHSTH(ST-), the high-side driver
cannot operate due to the high-side UVLO protection
circuit. CB must be chosen to be large enough not to fall
into UVLO range, due to the discharge during a half of
the oscillation period, especially when the high-side
MOSFET is turned on.
CCP
Dp1 Dp2
FAN7710 Rev. 1.00
When OUT is changing from HIGH to LOW state, CCP is
discharged through Dp2, shown as path 2 in Figure 32.
These charging/discharging operations are continued
until FAN7710V is halted by shutdown operation. The
charging current, I, must be large enough to supply the
operating current of FAN7710V.
The supply for the high-side gate driver is provided by
the boot-strap technique, as illustrated in Figure 33.
When the low-side MOSFET connected between OUT
and PGND pins is turned on, the charging current for VB
flows through DB. Every low OUT gives the chance to
charge the CB. Therefore, CB voltage builds up only when
FAN7710V operates normally.
FAN7710
VDD
This current flows along path 1 in Figure 32. It charges
CVDD, which is a bypass capacitor to reduce the noise on
the supply rail. If CVDD is charged over the threshold
voltage of the internal shunt regulator, the shunt
regulator turns on and regulates VDD with the trigger
voltage.
Charge pump
Figure 32. Local Power Supply for VDD Using a
Charge-Pump Circuit
VDC
As presented in Figure 32; when OUT is HIGH, the
inductor current and CCP create an output transition with
the slope of dv/dt. The rising edge of OUT charges CCP.
At that time, the current that flows through CCP is:
I ≅ CCP ×
dv
dt
(7)
DB
FAN7710
Rstart
CVDD
Bootstrap circuit
VDD
VDC
RT
VB
CPH
OUT
SGND
PGND
CB
L
Chraging path
CS
RL
CP
Cp
Dp1 Dp2
FAN7710 Rev. 1.00
Figure 33. Implementation of Floating Power Supply
Using the Bootstrap Method
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
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FAN7710V — Ballast Control IC for Compact Fluorescent Lamps
5. Power Supply
1. Startup Circuit
The startup current (IST) has to be supplied to the IC
through the startup resistor, Rstart. Once operation starts,
the power is supplied by the charge pump circuit. To
reduce the power dissipation in Rstart, select Rstart as high
as possible, considering the current requirements at
startup. For 220VAC power, the rectified voltage by the
full-wave rectifier makes DC voltage, as shown in
Equation 8. The voltage contains lots of AC component,
due to poor regulation characteristic of the simple fullwave rectifier:
VDC = 2 × 220[V ] ≅ 311[V ]
If Rstart meets Equation 14, restart operation is possible.
However, it is not recommended to choose Rstart at that
range since VDD rising time could be long and increase
the lamp's turn-on delay time, as depicted in Figure 34.
VDD
VCL
VDDTH(ST+)
VDDTH(ST-)
tstart
(8)
Considering the selected parameters, Rstart must satisfy
the following equation:
VDC − VDDTH (ST + )
R start
> IST
(9)
From Equation 9, Rstart is selected as:
VDC − VDDTH (ST + )
IST
> R start
(10)
Note that if choosing the maximum Rstart, it takes a long
time for VDD to reach VDDTH(st+). Considering VDD rising
time, Rstart must be selected as shown in Figure 34.
Another important concern for choosing Rstart is the
available power rating of Rstart. To use a commercially
available, low-cost 1/4Ω resistor, Rstart must obey the
following rule:
(VDC − VCL )
Rstart
2
1
<
[W ]
4
(11)
Assuming VDC=311V and VCL=15V,
resistance of Rstart is about 350kΩ.
the
minimum
When the IC operates in shutdown mode due to thermal
protection, open-lamp protection, or hard-switching
protection; the IC consumes shutdown current, ISD, which
is larger than IST. To prevent restart during this mode,
Rstart must be selected to cover ISD current consumption.
The following equation must be satisfied:
VDC − VDDTH (ST + )
ISD
0
> R start
Figure 34. VDD Build-up
Figure 35 shows the equivalent circuit for estimating tstart.
From the circuit analysis, VDD variation versus time is
given by:
(
VDD (t ) = (VDC − Rstart ⋅ IST ) 1 − e −t /( Rstart ⋅CVDD )
tstart = −Rstart ⋅ CVDD ⋅ ln
ISD
VDC − Rstart ⋅ IST − VDDTH (ST + )
VDD − Rstart ⋅ IST
(16)
In general, Equation 16 can be simplified as:
tstart ≈
Rstart ⋅ CVDD ⋅ VDDTH (ST + )
(17)
VDC − Rstart ⋅ IST − VDDTH (ST + )
Accordingly, tstart can be controlled by adjusting the value
of Rstart and CVDD. For example, if VDC=311V,
Rstart=560kΩ, CVDD=10µF, Ist=120µA, and VDDTH(ST+)=
13.5V; tstart is about 0.33s.
(12)
RSTART
IST
VDC − VDDTH (ST + )
ISD
VDD
(13)
CVDD
(2) For safe startup with restart from shutdown mode:
VDC − VDDTH (ST + )
(15)
From Equation 15, it is possible to calculate tstart by
substituting VDD(t) with VDDTH(ST+):
(1) For safe startup without restart in shutdown mode:
4 (VDC − VCL ) < Rstart <
)
where CVDD is the total capacitance of the bypass
capacitors connected between VDD and GND.
From Equations 10 - 12; it is possible to select Rstart:
2
time
FAN7710 Rev. 1.00
< Rstart <
VDC − VDDTH (ST + )
IST
SGND
(14)
Figure 35. Equivalent Circuit During Startup
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
www.fairchildsemi.com
14
FAN7710V — Ballast Control IC for Compact Fluorescent Lamps
Design Guide
3. Lamp Turn-On Time
For the IC supply, the charge pump method is used in
Figure 36. Since CCP is connected to the half-bridge
output, the supplied current by CCP to the IC is
determined by the output voltage of the half-bridge.
The turn-on time of the lamp is determined by supply
build-up time tstart, preheating time, and ignition time;
where tstart has been obtained by Equation 17. When the
IC's supply voltage exceeds VDDTH(ST+) after turn-on or
restart, the IC operates in preheating mode. This
operation continues until CPH pin's voltage reaches ~3V.
In this mode, CPH capacitor is charged by IPH current, as
depicted in Figure 37. The preheating time is achieved
by calculating:
When the half-bridge output shows rising slope, CCP is
charged and the charging current is supplied to the IC.
The current can be estimated as:
I = CCP
V
dV
≈ CCP DC
dt
DT
(18)
where DT is the dead time and dV/dt is the voltage
variation of the half-bridge output.
When the half-bridge shows falling slope, CCP is
discharged through Dp2. Total supplied current, Itotal, to
the IC during switching period, t, is:
Itotal = I ⋅ DT = CCP ⋅ VDC
t preheat =
3 × CPH
[sec onds]
IPH
The preheating time is related to lamp life (especially
filament). Therefore, the characteristics of a given lamp
should be considered when choosing the time.
(19)
IPH
From Equation 19, the average current, Iavg, supplied to
the IC is obtained by:
Iavg =
Itotal CCP ⋅ VDC
=
= CCP ⋅ VDC ⋅ f
t
t
(20)
For stable operation, Iavg must be higher than the
required current. If Iavg exceeds the required current, the
residual current flows through the shunt regulator
implemented on the chip, which can cause unwanted
heat generation. Therefore, CCP must be selected
considering stable operation and thermal generation.
For example, if CCP=0.5nF, VDC=311V, and f=50kHz, Iavg
is ~7.8mA; it is enough current for stable operation.
Charging mode
CCP
Dp1
To VDD
Idp1
Dp2
CVDD
Discharging mode
CCP
Dp1
To VDD
Idp1=0
Dp2
CVDD
f=1/t
VDC
DT:dead time
Half-bridge output
CPH
CPH
SGND
Figure 37. Preheating Timer
Compared to the preheating time, it is almost impossible
to exactly predict the ignition time, whose definition is the
time from the end of the preheating time to ignition. In
general, the lamp ignites during the ignition mode.
Therefore, assume that the maximum ignition time is the
same as the duration of ignition mode, from 3V until CPH
reaches 5V. Thus, ignition time can be defined as:
t ignition = (5 − 3 )
CPH
CPH
=2
IIG
IIG
(22)
Note that in ignition mode, CPH is charged by IIG, which
is six times larger than IPH. Consequently, total turn-on
time is approximately VDD Build-Time + Preheating Time
+ Ignition Time, or:
t ignition = (5 − 3 )
Idp1
(21)
CPH
CPH
=2
[sec onds]
IIG
IIG
(23)
FAN7710 Rev. 1.00
Figure 36. Charge Pump Operation
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
www.fairchildsemi.com
15
FAN7710V — Ballast Control IC for Compact Fluorescent Lamps
2. Current Supplied by Charge Pump
Part
Value
Note
Part
Resistor
Value
Note
Diode
R1(4)
470kΩ
0.25W
D1
1N4007
1kV, 1A
R2
90kΩ
0.25W, 1%
D2
1N4007
1kV, 1A
D3
1N4007
1kV, 1A
Capacitor
C1
10μF/400V
Electrolytic Capacitor, 105°C
D4
1N4007
1kV, 1A
C2(5)
10μF/50V
Electrolytic Capacitor, 105°C
D5
UF4007
1kV, 1A
C3
100nF/25V
Miller Capacitor
D6
UF4007
1kV, 1A
C4
470pF/500V
Ceramic Capacitor
D7
UF4007
1kV, 1A
C5(6)
680nF/25V
Miller Capacitor, 5%
C6(7)
2.7nF/1kV
Miller Capacitor
C7(7)
33nF/630V
Miller Capacitor
IC
IC
FAN7710V
Ballast IC
Inductor
L2(7)
2.5mH
EE1916S,280T
Notes:
3. Refer to the Typical Application Circuit for 3U type CFL lamp provided in Figure 1.
4. Refer to the Design Guide startup circuit in Figure 35. Due to reducing power loss on the startup resistor (R1) for
high-efficiency systems, it is possible to use a higher resistor value than recommended. In this case, the IC doesn’t
reliably keep SD (shutdown) state for protection. Carefully select the startup resistor (R1) or use the recommended
value (470k) to sufficiently supply shutdown current (ISD) and startup current (IST).
5. Normally, this component could be changed to a normal miller capacitor to increase system reliability instead of
the electrolytic capacitor with high temperature characteristics.
6. Temperature dependency of the capacitance is important to prevent destruction of the IC. Some capacitors show
capacitance degradation in high temperatures and cannot guarantee enough preheating time to safely ignite the
lamp during the ignition period at high temperatures. If the lamp does not ignite during the ignition period, the IC
cannot guarantee ZVS operation, Thus, the peak current of the switching devices can be increased above
allowable peak current level of the switching devices. Especially in high temperatures, the switching device can be
easily destroyed. Consequently, CPH capacitor (C5) must be large enough to warm the filaments of the lamp up
over the concerning temperature range.
7. Consider the components (L2, C6, C7) of resonant tank variation over the concerning temperature range. Normally,
these components would be changed toward increasing inductance and capacitance in high temperature. That
means that the resonant frequency is decreased. In the lower resonant frequency condition, the preheating current
reduces, so the resonant tank cannot supply enough to preheat the filaments before lamp turn on. If the preheating
current is insufficient, the ignition voltage / current is increased. Check the ignition current in high temperature: the
current capacity of internal MOSFETs on IC must be larger than ignition current.
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
www.fairchildsemi.com
16
FAN7710V — Ballast Control IC for Compact Fluorescent Lamps
Component List for 20W CFL Application (3)
FAN7710V — Ballast Control IC for Compact Fluorescent Lamps
Physical Dimensions
9.83
9.00
6.67
6.096
8.255
7.61
3.683
3.20
5.08 MAX
7.62
0.33 MIN
3.60
3.00
(0.56)
2.54
0.356
0.20
0.56
0.355
9.957
7.87
1.65
1.27
7.62
NOTES: UNLESS OTHERWISE SPECIFIED
A) THIS PACKAGE CONFORMS TO
JEDEC MS-001 VARIATION BA
B) ALL DIMENSIONS ARE IN MILLIMETERS.
C) DIMENSIONS ARE EXCLUSIVE OF BURRS,
MOLD FLASH, AND TIE BAR EXTRUSIONS.
D) DIMENSIONS AND TOLERANCES PER
ASME Y14.5M-1994
E) DRAWING FILENAME AND REVSION: MKT-N08FREV2.
Figure 38. 8-Lead, Dual Inline Package (DIP)
Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner
without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify or
obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions,
specifically the warranty therein, which covers Fairchild products.
Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings:
http://www.fairchildsemi.com/packaging/.
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
www.fairchildsemi.com
17
FAN7710V — Ballast Control IC for Compact Fluorescent Lamps
© 2009 Fairchild Semiconductor Corporation
FAN7710V • 1.0.4
www.fairchildsemi.com
18