The ML4830 is a complete solution for a dimmable, high
power factor, high efficiency electronic ballast.
Contained in the ML4830 are controllers for “boost” type
power factor correction as well as for a dimming ballast.
The Power factor circuit uses the average current sensing
method with a gain modulator and over-voltage
protection. This system produces power factors of better
than 0.99 with low input current THD at > 95%
efficiency. Special care has been taken in the design of
the ML4830 to increase system noise immunity by using a
high amplitude oscillator, and a gain modulator. An overvoltage protection comparator stops the PFC section in
the event of sudden load decrease.
The ballast section provides for programmable starting
scenarios with programmable preheat and lamp out-ofsocket interrupt times. The IC controls lamp output
through either frequency or Pulse Width control using
lamp current feedback.
The ML4830 is designed using Micro Linear‘s SemiStandard tile array methodology. Customized versions of
this IC, optimized to specific ballast architectures can be
made available. Contact Micro Linear or an authorized
representative for more information.
FEATURES
■ Complete Power Factor Correction and Dimming
Ballast Control on one IC
■ Low Distortion, High Efficiency Continuous Boost,
Average Current sensing PFC section
■ Programmable Start Scenario for Rapid or Instant Start
Lamps
■ Selectable Variable Frequency dimming and starting
PFC average current error amplifier
3I(SINE)PFC gain modulator input
4IA+/I(LIM)Non-Inverting input of the PFC
average current error amplifier and
input of peak current limit comparator
5LAMP F.B.Inverting input of an Error Amplifier
used to sense (and regulate) lamp arc
current. Also the input node for
dimming control
6LFB OUTOutput from the Lamp Current Error
Amplifier used for lamp current loop
compensation
7R(SET)External resistor which sets oscillator
FMAX, and R(X)/C(X) charging current
8MODEControls how the Lamp Current Error
Amp and preheat timers modulate the
ballast outputs. Two Variable
Frequency and 1 PWM mode are
available through this pin
9R(T)/C(T)Oscillator timing components
11 OVP/When the voltage of this pin exceeds
INHIBIT5V, the PFC output is inhibited. When
the voltage exceeds 6.7V, the IC
function is inhibited and the IC is
reset. This pin can be used for a
remote ballast shutdown.
12 R(X)/C(X)Sets the timing for the preheat,
dimming lockout and interrupt
13 GNDIC Ground
14 OUT BBallast MOSFET drive output
15 OUT ABallast MOSFET drive output
16 PFC OUTPower Factor MOSFET drive output
17 VCCPositive Supply for the IC
18 V
REF
Buffered output for the 7.5V voltage
reference
19 EA–Inverting input to PFC error amplifier
20 EA OUTPFC Error Amplifier output and
compensation node
20
19
18
17
16
15
14
13
12
11
EA OUT
EA–
V
REF
VCC
PFC OUT
OUT A
OUT B
GND
R(X)/C(X)
OVP/INHIBIT
10 INTERRUPT A voltage of greater than V
the chip and causes a restart after a
delay of 3 times the start interval. Used
for lamp-out detection and restart
2
REF
resets
Page 3
ABSOLUTE MAXIMUM RATINGS
ML4830
Absolute maximum ratings are those values beyond which
the device could be permanently damaged. Absolute
maximum ratings are stress ratings only and functional
device operation is not implied.
Supply Current (ICC) ............................................... 75mA
Output Current, Source or Sink (Pins 14)
Junction Temperature ............................................ 150°C
Storage Temperature Range ................... –65°C to +150°C
Lead Temperature (Soldering 10 Sec.) .................. +260°C
Output VoltageTA = 25°C, IO = 1mA7.47.57.6V
Line regulationV
Load regulation1mA < IO < 20mA215mV
Temperature stability0.4%
Total VariationLine, load, temp7.357.65V
Output Noise Voltage10Hz to 10KHz50µV
Long Term StabilityTJ = 125°C, 1000 hrs5mV
Short Circuit CurrentVCC < V
Output Voltage Low in UVLOI
Output Rise/Fall TimeCL = 1000pF50ns
Under-Voltage Lockout and Bias Circuits
IC Shunt Voltage (V
V
Load Regulation25mA < ICC < 68mA150300mV
CCZ
V
Total VariationLoad, Temp12.414.6V
CCZ
Start-up CurrentVCC - 12.3V1.31.7mA
Operating CurrentVCC = V
Start-up ThresholdV
Shutdown ThresholdV
Shutdown Temperature (TJ)120°C
Hysteresis (TJ)30°C
)I
CCZ
(Continued)
= 20mA0.40.8V
OUT
I
= 200mA2.13.0V
OUT
= –20mAVCC – 2.5VCC – 1.9V
OUT
I
= –200mAVCC – 3.0VCC – 2.2V
OUT
= 10mA, VCC = 8V0.81.5V
OUT
= 25mA12.813.514.2V
CC
– 0.5V1519mA
CCZ
– 0.5V
CCZ
– 3.5V
CCZ
FUNCTIONAL DESCRIPTION
OVERVIEW
The ML4830 consists of an Average Current controlled
continuous boost Power Factor front end section with a
flexible ballast control section. Start-up and lamp-out retry
timing are controlled by the selection of external timing
components, allowing for control of a wide variety of
different lamp types. The ballast control section can be set
up to adjust lamp power using either Pulse Width (PWM)
or frequency modulation (FM). Either non-overlapping or
overlapping conduction can be selected for the FM mode.
This allows for the IC to be used with a variety of different
ouput networks.
POWER FACTOR SECTION
The ML4830 Power Factor section is an average current
sensing boost mode PFC control circuit which is
architecturally similar to that found in the ML4821. For
detailed information on this control architecture, please
refer to Application Note 16 and the ML4821 data sheet.
GAIN MODULATOR
The ML4830 gain modulator provides high immunity to
the disturbances caused by high power switching. The
rectified line input sine wave is converted to a current via
a dropping resistor. In this way, small amounts of ground
noise produce an insignificant effect on the reference to
the PWM comparator.
5
Page 6
ML4830
The output of the gain modulator appears as a voltage
across the 14K resistor (Figure 1) on the positive terminal
of IA to form the reference for the current error amplifier.
When the loop is in regulation, the negative voltage on
IA+/I(LIM) (Pin 4) keeps the positive terminal of IA at 0V.
VISINEVEAk
≈××−×Ω0 0341 114.()( .)()
MUL
(1)
where: I(SINE) is the current in the dropping resistor,
V(EA) is the output of the error amplifier (Pin 20).
The output of the gain modulator is limited to 0.88V.
AVERAGE CURRENT AND OUTPUT VOLTAGE
REGULATION
The PWM regulator in the PFC Control section will act to
offset the positive voltage caused by the multiplier output
by producing an offsetting negative voltage on the current
sense resistor at Pin 4. A cycle-by-cycle current limit is
included to protect the MOSFET from high speed current
transients. When the voltage at Pin 4 goes negative by
more than 1V, the PFC cycle is terminated.
For more information on compensating the average
current and boost voltage error amplifier loops, see
Application Note 16 .
OVERVOLTAGE PROTECTION AND INHIBIT
The OVP/INHIBIT pin serves to protect the power circuit
from being subjected to excessive voltages if the load
should change suddenly (lamp removal). A divider from
the high voltage DC bus (Figure 8: R14, R24) sets the
OVP trip level. When the voltage on Pin 11 exceeds 5V,
the PFC transistor is inhibited. The ballast section will
continue to operate. If Pin 11 is driven above 6.8V, the
IC is inhibited and goes into the low quiescent mode.
The OVP threshold should be set to a level where the
power components are safe to operate, but not so low
as to interfere with the boost voltage regulation loop
(R11, R12, R23).
BALLAST OUTPUT SECTION
The IC controls output power to the lamps in one of three
different modes. The Mode pin (Pin 8) sets the operating
mode of the IC. With Pin 8 at GND, the output section is
in the Frequency Modulation mode with non-overlapping
conduction, which means that both ballast output drivers
will be low during t
(Figure 2). In the overlapping mode
DIS
(VCO-O), Pin 8 is left open and the transition from OUT A
high to OUT B high occurs with no dead time. This mode
is typically used in current fed ballast topologies.
R(X)/C(X)
12
INTERRUPT
10
VCC
17
V
REF
18
GND
13
OVP/INHIBIT
11
IA OUT
2
IA –
1
–1V
IA+/
I(LIM)
4
V
REF
UNDER-VOLTAGE
AND THERMAL
SHUTDOWN
+
I(LIM)
–
+
–
14K
5V
PREHEAT
AND
INTERRUPT
TIMER
INH
–
2.6V
A1
+
+
+
–
–
IA
+
+
–
6.8V
–
R
S
Q
VCO–O
LOGIC
VCO–O PWM
OSCILLATOR
CLK
2.5V
–
+
MODE
LFB OUT
LAMP F.B.
I
R(SET)
R(T)/C(T)
PFC OUT
R(SET)
8
6
5
7
9
16
6
3
20
19
I(SINE)
EA OUT
EA –
GAIN
MODULATORS
V
REF
SRQ
OUT A
OUT B
15
14
+
–
LFB OUT
EA
+
–
PWM
Q
T
Q
Figure 1. ML4830 Block Diagram
Page 7
ML4830
ModePin 8Definition
VCOGNDFrequency Modulation
VCO-OOPENOverlapping VCO F.M.
PWMVREFPulse Width Modulation
Table 1. ML4830 Operating Modes
OSCILLATOR
In Table 1 above, the two VCO frequency ranges are
controlled by the output of the LFB amplifier (Pin 6). As
lamp current decreases, Pin 6 rises in voltage, causing the
C(T) charging current to decrease, thereby causing the
oscillator frequency to decrease. Since the ballast output
network attenuates high frequencies, the power to the
lamp will be increased.
In PWM Mode, I
is 0 so the oscillator’s frequency is
CHG
set per (1) below.
V
R(T)
C(T)
18
9
REF
R(T)/C(T)
I
CHG
1.25/3.75
CONTROL
+
–
V
REF
Also, in both VCO modes, the when LFB OUT is high,
I
= 0 and the minimum frequency occurs. The
CHG
charging current varies according to two control inputs to
the oscillator:
1. The output of the preheat timer
2. The voltage at Pin 6 (lamp current output)
In preheat condition, charging current is fixed at
.
I
CHG PREHEAT()
In running mode, charging current decreases as the V
=
R SET
25
()
(1)
PIN7
rises from 0V to VOH of trhe LAMP FB amplifier. The
highest frequency will be attained when I
which is attained when V
I
CHG( )
PIN6
0
is at 0V:
5
=
()
R SET
is highest,
CHG
(2)
The oscillator frequency is determined by the following
equations:
F
OSC
1
=
tt
+
CHGDIS
(3)
and
625
IR
+
tRCIn
=
CHGT T
375..
CHG T
IR
+
CHG T
The oscillator’s minimum frequency is set when I
CHG
(4)
= 0
where:
5 mA
CLOCK
V
TH
C(T)
V
t
DIS
TL
t
CHG
Figure 2. Oscillator Block Diagram and Timing
051.
DIS
.
1
RC
×
TT
(5)
This assumes that t
F
OSC
CHG
≅
>> t
Highest lamp power, and lowest output frequency are
attained when V
is at its maximum output voltage
PIN6
(VOH).
In this condition, the minimum operating frequency of the
ballast is set per (5) above.
For the IC to be used effectively in dimming ballasts with
higher Q output networks a larger CT value and lower R
T
value can be used, to yield a smaller frequency excursion
over the control range (V
to 5mA. Assuming that I
tC
DIS VCOT()
). The discharge current is set
PIN6
>> IRT:
DIS
≅×490
(6)
7
Page 8
ML4830
IC BIAS, UNDER-VOLTAGE LOCKOUT AND THERMAL
SHUTDOWN
The IC includes a shunt regulator which will limit the
voltage at VCC to 13.5 (V
). The IC should be fed with
CCZ
a current limited source, typically derived from the ballast
transformer auxiliary winding. When VCC is below V
CCZ
– 0.7V, the IC draws less than 1.7mA of quiescent current
and the outputs are off. This allows the IC to start using a
“bleed resistor” from the rectified AC line.
VCCZ
V(ON)
V
CC
V(OFF)
15mA
I
CC
1.3mA
t
t
Figure 3. Typical VCC and ICC waveforms when ML4830
is started with a bleed resistor from the rectified AC line
and bootstrapped from the ballast transformer.
To help reduce ballast cost, the ML4830 includes a
temperature sensor which will inhibit ballast operation if
the IC’s junction temperature exceeds 120°C. In order to
use this sensor in lieu of an external sensor, care should be
taken when placing the IC to ensure that it is sensing
temperature at the physically appropriate point in the
ballast. The ML4830’s die temperature can be estimated
with the following equation:
This will produce a high frequency (or low duty cycle) for
filament preheat, but will not produce sufficient voltage to
ignite the lamp.
After cathode heating, the inverter frequency drops to
F
causing a high voltage to appear to ignite the lamp.
MIN
If the voltage does not drop when the lamp is supposed to
have ignited, the lamp voltage feedback coming into Pin
10 rises to above V
, the C(X) charging current is shut off
REF
and the inverter is inhibited until C(X) is discharged by
R(X) to the 1.2V threshold. Shutting off the inverter in this
manner prevents the inverter from generating excessive
heat when the lamp fails to strike or is out of socket.
Typically this time is set to be fairly long by choosing a
large value of R(X).
LFB OUT is ignored until C(X) reaches 6.8V threshold.
The lamps are therefore driven to full power and then
dimmed. The C(X) pin is clamped to about 7.5V.
A timing diagram of lamp ignition and restart sequences
provided by the circuit of Figure 4 is given in Figure 7.
.625
R(SET)
1.2/3.4
1.2/6.8
–
+
+
–
+
–
HEAT
DIMMING
LOCKOUT
R
Q
S
INHIBIT
R(X)
C(X)
R(X)/C(X)
12
10
INT
6.8
V
REF
TT PCW
≅××°65/
JAD
(7)
STARTING, RE-START, PREHEAT AND INTERRUPT
The lamp starting scenario implemented in the ML4830 is
designed to maximize lamp life and minimize ballast
heating during lamp out conditions.
The circuit in Figure 4 controls the lamp starting scenarios:
Filament preheat and Lamp Out interrupt. C(X) is charged
with a current of
I
R SET()
4
or
.
0 625
R SET
()
and disched
arg
through R(X). The voltage at C(X) is initialized to 0.7V
(VBE) at power up. The time for C(X) to rise to 3.4V is the
filament preheat time. During that time, the oscillator
ching current Iis
arg()
CHG
.
inboth VCOes
()
R SET
mod .
25
8
Figure 4. Lamp Preheat and Interrupt Timers
ModePWMFM
[F(MAX) to F(MIN)]
Preheat50%2
Dimming
Lock-outD(MAX)%F(MIN)
Dimming
Control0 to D(MAX)%F(MIN) to F(MAX)
Figure 5. Lamp Starting Summary
A summary of the lamp starting scenarios are given in
figure 5 for both PWM and Frequency Modulation modes.
The PWM duty cycle is defined as:
t
Duty Cycle
ON
=
t
CLK
Page 9
CLOCK
OUT A
OUT B
t
ON(MAX)
t
CLK
t
ON
t
ON
Figure 6. Definition of Duty Cycles
ML4830
SEMI-STANDARD CAPABILITIES
The ML4830 is designed to work in a wide variety of
electronic ballast applications. For high volume, cost
sensitive applications, a ballast design can be implemented
and debugged using the ML4830. From that design, Micro
Linear can produce a reduced feature set, optimized
ballast IC design quickly and easily with low risk.
Contact your Micro Linear representative or call Micro
Linear for more information on Semi-Standard options.
R(X)/C(X)
HEAT
DIMMING
LOCKOUT
INT
INHIBIT
6.8
3.4
1.2
0.65
0
7.5
Figure 7. Lamp Starting and Restart Timing
9
Page 10
ML4830
APPLICATIONS
Y
T3
C22
D11D12
R
Y
Q2
T2
R20
R
B
B
C23
T5
C17
Q3
C19
T4
R19
R22
R21
C20
D13
INHIBIT
CC
V
R18
D10
R23
Dimming
Control
C21
R17
R12
+
+
C10
C8
D8
D9
T1
D7
R7
R6
D1D3
L1
D2D4
–+
C3
C1
C2
L2
C9
C11
D5
R11
Q1
R1
R13
R8
D6
R9
CC
C24
+
V
R14
C12
201918171615141312
R10
123456789
C5
C4
IC1
11
10
R3
R2
R5
R4
R24
C16
C15
C14
R15
C13
R16
C7
C6
F1
120V
Figure. 8 Typical Application: 2-Lamp Isolated Dimming Ballast with Active Power Factor Correction for 120VAC Input
10
Page 11
APPLICATIONS (continued)
The schematic (Figure 8) and the bill of materials on the
following pages represents a complete parts list for the
schematic (Figure 8). Designators refer to Micro Linear’s
“rev B” PCB.
TABLE 1: PARTS LIST FOR THE ML4830 TYPICAL APPLICATION
Micro Linear reserves the right to make changes to any product herein to improve reliability, function or
design. Micro Linear does not assume any liability arising out of the application or use of any product
described herein, neither does it convey any license under its patent right nor the rights of others. The
circuits contained in this data sheet are offered as possible applications only. Micro Linear makes no
warranties or representations as to whether the illustrated circuits infringe any intellectual property rights of
others, and will accept no responsibility or liability for use of any application herein. The customer is urged
to consult with appropriate legal counsel before deciding on a particular application.
DS4830-01
2092 Concourse Drive
San Jose, CA 95131
Tel: 408/433-5200
Fax: 408/432-0295
15
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