MC33364 D

MC33364
Critical Conduction
GreenLinet SMPS
Controller
The MC33364 series are variable frequency SMPS controllers that
operate in the critical conduction mode. They are optimized for high
density power supplies requiring minimum board area, reduced
component count, and low power dissipation. Integration of the high
voltage startup saves approximately 0.7 W of power compared to the
value of the resistor bootstrapped circuits.
Each MC33364 features an on--board reference, UVLO function, a
watchdog timer to initiate output switching, a zero current detector to
ensure critical conduction operation, a current sensing comparator,
leading edge blanking, a CMOS driver and cycle--by--cycle current
limiting.
The MC33364D1 has an internal 126 kHz frequency clamp. The
MC33364D2 is available without an internal frequency clamp. The
MC33364D has an internal 126 kHz frequency clamp which is pinned
out, so that the designer can adjust the clamp frequency by connecting
appropriate values of resistance.
Features

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MARKING
DIAGRAMS
8
8
1
SO--8
D1, D2 SUFFIX
CASE 751
1
16
SO--16
D SUFFIX
CASE 751K
16
1
x
A
WL
Y
W, WW
G or G
Package
MC33364D1G
MC33364D1R2G
MC33364D2G
MC33364D2R2G
MC33364DG
MC33364DR2G
Shipping†
2500 Units / Tape & Reel
96 Units / Rail
Zero Current
1
Current Sense
2
8 Line
7 VCC
Voltage FB
3
6 Gate Drive
Vref
4
5 GND
(Top View)
2500 Units / Tape & Reel
SO--16
(Pb--Free)
1 or 2
Assembly Location
Wafer Lot
Year
Work Week
Pb--Free Package
MC33364D1
MC33364D2
96 Units / Rail
SO--8
(Pb--Free)
=
=
=
=
=
=
PIN CONNECTIONS
ORDERING INFORMATION
Device
MC33364D
AWLYWWG
1
Lossless Off--Line Startup
Leading Edge Blanking for Noise Immunity
Watchdog Timer to Initiate Switching
Operating Temperature Range --25C to +125C
Shutdown Capability
Over Temperature Protection
Optional/Adjustable Frequency Clamp to Limit EMI
This is a Pb--Free and Halide--Free Device
M64Dx
ALYW
G
48 Units / Rail
2500 Units / Tape & Reel
†For information on tape and reel specifications, including part orientation
and tape sizes, please refer to our Tape and Reel Packaging Specifications
Brochure, BRD8011/D.
MC33364D
16 Line
Zero Current
1
N/C
2
Current Sense
3
Voltage FB
4
13 N/C
N/C
Vref
5
12 Vcc
6
11 Gate Drive
N/C
7
10 P GND
Freq Clamp
8
9 A GND
(Top View)
 Semiconductor Components Industries, LLC, 2010
November, 2010 -- Rev. 18
1
Publication Order Number:
MC33364/D
MC33364
Vcc
Vref
Line
Startup
Vref regulator
UVLO
turn on
Vref
turn on
+
--
UVLO
+
--
15V/ 8.1V
-+
ZCD
Vref
10V
15V/ 7.6V
UVLO
1.2V/ 1.0V
+
--
Thermal
Shutdown
5k
45k
Vcc
15k
Reset
15V/ var
Watchdog
Timer
FB
Vcc
R
CS
R
-+
LEB
Level
Q
SNA
S
Gate
P Gnd
0.1V
A Gnd
Frequency Clamp
FC
Figure 1. Representative Block Diagram
Input
AC Voltage
Output
Voltage
MC33364D
ZCD
Line
CS
FB
FC
Vcc
Drive
P Gnd
A Gnd
R1
R2
Vref
Rsense
Figure 2. Typical Application Circuit
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2
MC33364
Startup circuit is
charging the VCC
capacitor
Startup circuit turns
off when VCC is 15V
15V
Supply Voltage, VCC
8.1V
VT (3.5 to 6V)
5V
Startup circuit turns
on when VCC reaches
the threshold VT
Reference Voltage, Vref
0V
Vref regulator turns on
when VCC reaches 15V
Vref falls faster than VCC
since Vref capacitor is much
smaller than VCC capacitor
Vref regulator turns
off when VCC falls
below 8.1 V
Maximum drain current is
limited to 1.15V / Rsense
Drain Current
0A
Switching stops when
Vref falls below 3.7V
Switching starts when
Vref reaches 5V
Figure 3. Timing Diagram in Fault Condition
Criticial Mode
Discontinous Conduction Mode
Output
Current
No load
Maximum drain current is limited to 1.15V/ Rsense
Drain
Current
LEB
toff(min)
Secondary
Side Diode
Current
Drain
Voltage
Vin
10V
Voltage
at ZCD
0.7V
ZCD is ignored during minimum off--time limit
Figure 4. Timing Diagram in Normal Condition
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3
MC33364
PIN DESCRIPTION
Pin
Function
Description
1 (1)
Zero Current Detect
The ZCD Pin ensures critical conduction mode. ZCD monitors the voltage on the auxiliary winding,
during the demagnetization phase of the transformer, comparing it to an internal reference. The
ZCD sets the latch for the output driver.
3 (2)
Current Sense
The Current Sense Pin monitors the current in the power switch by measuring the voltage across
a resistor. Leading Edge Blanking is utilized to prevent false triggering. The voltage is compared to
a resistor divider connected to the Voltage Feedback Pin. A 110 mV voltage off--set is applied to
compensate the natural optocoupler saturation voltage.
4 (3)
Voltage Feedback
6 (4)
Vref
8 (NA)
Frequency Clamp
9 (5)
A GND
This pin is the ground for the internal circuitry excluding the gate drive stage.
10 (5)
P GND
This pin is the ground for the gate drive stage.
11 (6)
Gate Drive
12 (7)
VCC
Provides the voltage for all internal circuitry including the gate drive stage and Vref. This pin has
Undervoltage Lockout with hysteresis.
16 (8)
Line
The Line Pin provides the initial power to the VCC pins. Internally the line pin is a high voltage
current source, eliminating the need for an external startup network.
NOTE:
The Voltage Feedback Pin is typically connected to the collector of the optocoupler for feedback
from the isolated secondary output. The Feedback is connected to the Vref Pin via a 5 k resistor
providing bias for the external optocoupler.
The Vref Pin is a buffered internal 5.0 V reference with Undervoltage Lockout.
The Frequency Clamp Pin ensures a minimum off--time value, typically 6.9 ms. It prevents the
MOSFET from restarting within a fixed (33364D1) or adjustable (33364D) delay. The minimum
off--time is disabled in the 33364D2. Therefore the maximum switching frequency cannot exceed
1/(TON + TOFFmin).
The gate drive is the output to drive the gate of the power MOSFET.
For further information please refer to the following Application Notes;
AN1594: Critical Conduction Mode, Flyback Switching Power Supply Using the MC33364.
AN1681: How to keep a Flyback Switch--Mode Power Supply Stable with a Critical--Mode Controller.
MAXIMUM RATINGS (TA = 25C, unless otherwise noted.)
Symbol
Value
Unit
Power Supply Voltage (Operating)
VCC
16
V
Line Voltage
VLine
700
V
Current Sense, Compensation,
Voltage Feedback, Restart Delay and Zero Current Input Voltage
Vin1
--1.0 to +10
V
Zero Current Detect Input
Iin
5.0
mA
Restart Diode Current
Iin
5.0
mA
Rating
Power Dissipation and Thermal Characteristics
D1 and D2 Suffix, Plastic Package Case 751
Maximum Power Dissipation @ TA = 70C
PD
450
mW
RθJA
178
C/W
PD
550
mW
RθJA
145
C/W
TJ
150
C
Operating Ambient Temperature
TA
--25 to +125
C
Storage Temperature Range
Tstg
--55 to +150
C
Thermal Resistance, Junction--to--Air
D Suffix, Plastic Package Case 751B--05
Maximum Power Dissipation @ TA = 70C
Thermal Resistance, Junction--to--Air
Operating Junction Temperature
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
NOTE: ESD data available upon request.
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MC33364
ELECTRICAL CHARACTERISTICS (VCC = 15.5 V, for typical values TA = 25C, for min/max values TJ = --25 to 125C)
Characteristic
Symbol
Min
Typ
Max
Unit
VOLTAGE REFERENCE
Reference Output Voltage (IOut = 0 mA, TJ = 25C)
Vref
4.90
5.05
5.20
V
Line Regulation (VCC = 10 V to 20 V)
Regline
--
2.0
50
mV
Load Regulation (IOut = 0 mA to 5.0 mA)
Regload
--
0.3
50
mV
Maximum Vref Output Current
IO
--
5
--
mA
Reference Undervoltage Lockout Threshold
Vth
--
4.5
--
V
Input Threshold Voltage (Vin Decreasing)
Vth
0.9
1.0
1.1
V
Hysteresis (Vin Decreasing)
VH
--
200
--
mV
Input Clamp Voltage -- High State (IDET = 3.0 mA)
Input Clamp Voltage -- Low State (IDET = --3.0 mA)
VIH
VIL
9.0
--1.1
10.33
--0.75
12
0.5
V
Input Bias Current (VCS = 0 to 2.0 V)
IIB
--0.5
0.02
0.5
mA
Built In Offset
VIO
50
108
170
mV
ZERO CURRENT DETECTOR
CURRENT SENSE COMPARATOR
Feedback Pin Input Range
VFB
1.1
1.24
1.4
V
Feedback Pin to Output Delay
tDLY
100
232
400
ns
Source Resistance (Drive = 0 V, VGate = VCC -- 1.0 V)
Sink Resistance (Drive = VCC, VGate = 1.0 V)
ROH
ROL
10
5
36
11
70
25
Ω
Ω
Output Voltage Rise Time (25% -- 75%) (CL = 1.0 nF)
tr
--
67
150
ns
DRIVE OUTPUT
Output Voltage Fall Time (75% -- 25%) (CL = 1.0 nF)
Output Voltage in Undervoltage (VCC = 7.0 V, ISink = 1.0 mA)
tf
--
28
50
ns
VO(UV)
--
0.01
0.03
V
tPHL(in/out)
--
250
--
ns
Tsd
TH
---
180
50
---
C
tDLY
200
360
700
ms
LEADING EDGE BLANKING
Delay to Current Sense Comparator Input
(VFB = 2.0 V, VCS = 0 V to 4.0 V step, CL = 1.0 nF)
THERMAL SHUTDOWN
Shutdown (Junction Temperature Increasing)
Hysteresis (Junction Temperature Decreasing)
TIMER
Watchdog Timer
UNDERVOLTAGE LOCKOUT
Startup Threshold (VCC Increasing)
Minimum Operating Voltage After Turn--On (VCC Decreasing)
Vth(on)
14
15
16
V
VShutdown
6.5
7.6
8.5
V
fmax
104
126
145
kHz
FREQUENCY CLAMP
Internal FC Function (pin open)
Internal FC Function (pin grounded)
fmax
400
564
800
kHz
Frequency Clamp Input Threshold
Vth(FC)
1.89
1.95
2.01
V
Frequency Clamp Control Current Range (Sink)
IControl
30
70
110
mA
Td
3.5
5.0
6.5
ms
Line Startup Current (VLine = 50 V) (VCC = Vth(on) -- 1.0 V)
Restart Delay Time
ILine
tDLY
5.0
8.5
100
12
mA
ms
Line Pin Leakage (VLine = 500 V)
ILine
0.5
32
70
mA
Line Startup Current (VCC = 0 V, VLine = 50 V)
ILine
6.0
10
12
mA
ICC
1.5
2.75
4.5
mA
ICC Off
300
544
800
mA
Dead Time (FC pin = 1.7 V)
TOTAL DEVICE
VCC Dynamic Operating Current (50 kHz, CL = 1.0 nF)
VCC Off State Consumption (VCC = 11 V)
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MC33364
30
20
t DLY, WATCHDOG TIME DELAY ( s)
25
OUTPUT VOLTAGE (V)
500
VCC = 14 V
CL = 1000 pF
TA = 25C
15
10
5.0
0
--5.0
350
--25
0
25
50
75
100
5.0 ms/DIV
TA, AMBIENT TEMPERATURE (C)
Figure 5. Drive Output Waveform
Figure 6. Watchdog Timer Delay
versus Temperature
R JA(t), THERMAL RESISTANCE
JUNCTION--TO--AIR ( C/W)
4.0
Circuit of Figure
12
TA = 25C
2.0
40
6.0
8.0
10
12
14
125
0.1
1.0
10
100
t, TIME (s)
Figure 7. Supply Current
versus Supply Voltage
Figure 8. Transient Thermal Resistance
1.4
1.2
30
25
20
15
10
5 FC--to--Gnd
10
100
VCC, SUPPLY VOLTAGE (V)
FC--to--Vref
35
D Suffix
16 Pin SOIC
10
0.01
16
CURRENT SENSE VOLTAGE
I CC , SUPPLY CURRENT (mA)
400
1000
0
4.0
MINIMUM OFF--TIME (ms)
VCC = 15 V
300
--55
6.0
0
450
D Suffix
16 Pin SOIC
TA = 25C
VCC = 15 V
1.0
0.8
0.6
0.4
0.2
0
--0.2
100
--0.4
1000
0
0.5
1.0
1.5 2.0
2.5 3.0
3.5
4.0
4.5 5.0
RESISTOR (kΩ)
FEEDBACK VOLTAGE
Figure 9. Minimum Off--time versus Timing Resistor
on the FC Pin
Figure 10. Feedback Voltage versus
Current Sense Voltage
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5.5 6.0
MC33364
OPERATING DESCRIPTION
Introduction
this case. Figure 3 shows the timing diagram in a fault
condition. There are three Under--Voltage Lock--Out
(UVLO) thresholds with respect to VCC. The upper
threshold is 15 V. When this limit is reached, the startup
circuit block turns off and VCC declines due to power
consumption of the circuitry. The startup circuit block turns
on when VCC reaches 7.6 V and if Vref is higher than 3.7 V.
It is the second threshold of VCC. If Vref is smaller than
3.7 V, the startup circuit will turn on when VCC reaches a
temperature dependent value VT ranging between 3.5 V and
6 V. It is the last threshold of VCC. This temperature
dependent threshold is lower when temperature is higher so
that it takes a longer time to restore the VCC. It is a protection
feature, which allows more dead time for cooling in high
temperature condition.
There is an UVLO in the Vref regulator block. When VCC
falls below typical 8.1 V in abnormal situation, the Vref
regulator block stops. Vref and VCC collapses due to power
consumption of the circuitry. When Vref collapses to below
3.7 V, the device cannot provide the Drive output and makes
a dead time. This dead time is designed for minimal power
transfer in the abnormal conditions. The dead time ends
when VCC reaches 15 V after reaching the UVLO limit VT
(3.5 to 6 V). Reaching VT enables the startup circuit block,
charging up the VCC capacitor again. When VCC reaches
15 V again, the Vref regulator block turns on and allows the
output to work again.
It is recommended to put a 0.1 uF capacitor on Vref pin for
stability of the voltage buffer. The VCC capacitor is
relatively larger than this 0.1 uF capacitor, making a longer
VCC charging time from VT to 15 V and a longer dead time
in the abnormal or fault conditions.
The MC33364 series represents a variable--frequency
current--mode critical--conduction solution with integrated
high voltage startup and protection circuitry to implement an
off--line flyback converter for modern consumer electronic
power supplies. Different frequency clamp options offer
different customized needs. This device series includes an
integrated 700 V Very High--Voltage (VHV) start--up
circuit. Thus, it is possible to design an application with
universal input voltage from 85 Vac to 265 Vac without any
additional startup circuits or components.
The critical conduction feature offers some advantages.
First, the MOSFET turns on at zero current and the diode
turns off at zero current. The zero current reduces these
turn--on and turn--off switching losses. It also reduces the
Electro--Magnetic Interface (EMI) of the SMPS and a less
expensive rectifier can be used. Second, by preventing the
SMPS from entering the discontinuous conduction mode
(DCM), the peak MOSFET drain current is limited to only
twice the average input current. It needs a smaller and less
expensive MOSFET. Third, by preventing the SMPS from
entering the Continuous Conduction Mode (CCM), the
flyback topology transfer function stays first--order and its
feedback compensation network is considerably simplified.
It also maximizes the power transfer by the flyback
transformer to its 1/2 L I2 limits.
A description of each of the functional blocks is given
below. The representative block diagram and typical
application circuit are in Figure 1 and Figure 2.
Line, VCC, Startup Circuit and Reference Voltage
The Line pin is capable of a maximum 700 V so that it is
possible to connect this pin directly to the rectified
high--voltage Alternating Current (AC) input for
minimizing the number of external components. There is a
startup circuit block that regulates voltage from the Line pin
to the VCC pin in an abnormal situation. In normal
conditions, the auxiliary winding powers up the VCC and
this startup circuit is opened and saves approximate 0.7 W
of power compared to the resistor bootstrapped circuits.
In normal operation, the auxiliary winding powers up the
VCC voltage. This voltage is a constant value between the
UVLO limits (7.6 V and 15 V). It is further regulated to a
constant 5 V reference voltage Vref for the internal circuitry
usage. As long as the VCC voltage is between 7.6 V and
15 V, it means the auxiliary winding can provide voltage as
in normal condition. The device recognizes that there is no
fault in the circuit and the device remains in the normal
operation status.
However, when the auxiliary winding cannot power up
VCC, the VCC voltage will reach its UVLO limit. The device
recognizes that it is an abnormal situation (such as startup or
output short--circuited). The VCC voltage is not constant in
Zero Current Detect
To achieve critical conduction mode, MOSFET
conduction is always initiated by sensing a zero current
signal from the Zero Current Detect (ZCD) pin. The ZCD
pin indirectly monitors the inductor current by sensing the
auxiliary winding voltage. When the voltage falls below a
threshold of 1.0V, the comparator resets the RS latch to turn
the MOSFET on. There is 200 mV of hysteresis built into the
comparator for noise immunity and to prevent false tripping.
There are 10 V and 0.7 V clamps in the ZCD pin for
protection. An external resistor is recommended to limit the
input current to 2 mA to protect the clamps.
Watchdog Timer
A watchdog timer block is added to the device to start or
restart the Drive output when something goes wrong in the
ZCD. When the inductor current reaches zero for longer than
approximate 410 ms, the timer reset the RS latch and that
turns the MOSFET on.
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MC33364
Current Sense and Feedback Regulation
Frequency Clamp Options
Current--mode control is implemented with the Current
Sense (CS) pin and Feedback (FB) pin. The FB pin is
internally pulled up with a 5 kOhm resistor from the 5 V
Vref. There is a resistor divider circuit and a 0.1 V offset in
this functional block. The following equation describes the
relation between the voltages of the FB and CS pins, VFB
and VCS respectively.
The drawback of critical conduction mode is variable
switching frequency. The switching frequency can increase
dramatically to hundreds of kHz when the output current is
too low or vanishes. It is a big problem when EMI above
150 kHz is concerned. Frequency Clamp (FC) is an optional
feature in the device to limit the upper switching frequency
to nominal 126 kHz by inserting a minimum off--time
(toff(min)). When a minimum off--time is inserted, the
maximum frequency (fmax) limit is set.
VCS(max) = VFB∕4 − 0.1 V
When the output is short circuited, there is no feedback
signal from the opto coupler and the FB pin is opened. It
gives VFB = 5 V and the maximum voltage of the CS pin is
1.15 V. When the voltage exceeds 1.15 V, the current sense
comparator turns on and terminates the MOSFET
conduction. It stops current flowing through the sense
resistor (RSense) and hence the sense resistor limits the
maximum MOSFET drain current by the following
equation.
f max =
1
ton(min) + toff(min)
The SMPS is forced to operate in DCM when the
maximum frequency is reached. The minimum off--time is
immediately counted after the driving signal goes low. If the
ZCD signal comes within this minimum off--time, the ZCD
information is ignored until the minimum off--time expires.
The next ZCD signal starts the MOSFET conduction.
There are three available FC options: MC33364D -adjustable minimum off--time by external resistor,
MC33364D1 -- 6.9 us fixed minimum off--time, and
MC33364D2 -- no minimum off--time (FC disable).
The MC33364D has a FC pin, which can vary the
minimum off--time (or the maximum frequency) externally
in Figure 11. If the FC pin is opened, the minimum off--time
is fixed at 6.9 us. If the FC pin is grounded, the clamp is
disabled, and the SMPS will always operate in critical mode.
It is generally not recommended to sink or source more than
80 uA from the FC pin because high currents may cause
unstable operation.
Maximum Drain Current = 1.15∕Rsense
When the output voltage is too high, the FB pin voltage is
pulled down by the opto coupler current and the duty ratio
is reduced. The output voltage is then regulated.
There is a Leading Edge Blanking (LEB) circuit with
250 ns propagation delay to prevent false triggering due to
parasitics in the CS pin. It makes a minimum on--time of the
MOSFET (ton(min)).
Thermal Shutdown
There is a thermal shutdown block to prevent overheating
condition and protect the device from overheating. When
temperature is over 180_C, the Drive output and startup
circuit block are disable. The device resumes operation
when temperature falls below 130_C.
Gate Drive Output
The IC contains a CMOS output driver specifically
designed for direct drive of power MOSFET. The Drive
Output typical rise and fall times are 50 ns with a 1.0 nF
load. Unbalanced Source and Sink eliminates the need for an
external resistor between the device Drive output and the
Gate of the external MOSFET. Additional internal circuitry
has been added to keep the Drive Output in a sinking mode
whenever the UVLO is active. This characteristic eliminates
the need for an external gate pull--down resistor.
Vref
FC
FC
GND
Increase toff
FC
Decrease toff
FC
GND
toff = 6.9us
toff = 0us
(FC disable)
Figure 11. Frequency Clamp Setting
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MC33364
APPLICATION INFORMATION
Design Example
startup switch is turned off by the undervoltage and the
overvoltage control circuit. Because the power supply can
be shorted on the output, causing the auxiliary voltage to be
zero, the MC33364 will periodically start its startup block.
This mode is named “hiccup mode”. During this mode the
temperature of the chip rises but remains protected by the
thermal shutdown block. During the power supply’s normal
operation, the high voltage internal MOSFET is turned off,
preventing wasted power, and thereby, allowing greater
circuit efficiency.
Since a bridge rectifier is used, the resulting minimum and
maximum dc input voltages can be calculated:
Design an off--line Flyback converter according to the
following requirements:
Output Power:
12 W
Output:
6.0 V @ 2 Amperes
Input voltage range: 90 Vac -- 270 Vac, 50/60 Hz
The operation for the circuit shown in Figure 12 is as
follows: the rectifier bridge D1--D4 and the capacitor C1
convert the ac line voltage to dc. This voltage supplies the
primary winding of the transformer T1 and the startup
circuit in U1 through the line pin. The primary current loop
is closed by the transformer’s primary winding, the TMOS
switch Q1 and the current sense resistor R7. The resistors
R5, R6, diode D6 and capacitor C4 create a snubber
clamping network that protects Q1 from spikes on the
primary winding. The network consisting of capacitor C3,
diode D5 and resistor R1 provides a VCC supply voltage for
U1 from the auxiliary winding of the transformer. The
resistor R1 makes VCC more stable and resistant to noise.
The resistor R2 reduces the current flow through the internal
clamping and protection zener diode of the Zero Crossing
Detector (ZCD) within U1. C3 is the decoupling capacitor
of the supply voltage. The resistor R3 can provide additional
bias current for the optoisolator’s transistor. The diode D8
and the capacitor C5 rectify and filter the output voltage. The
TL431, a programmable voltage reference, drives the
primary side of the optoisolator to provide isolated feedback
to the MC33364. The resistor divider consisting of R10 and
R11 program the voltage of the TL431. The resistor R9 and
the capacitors C7 and C8 provide frequency compensation
of the feedback loop. Resistor R8 provides a current limit for
the opto coupler and the TL431.
Since the critical conduction mode converter is a variable
frequency system, the MC33364 has a built--in special block
to reduce switching frequency in the no load condition. This
block is named the ”frequency clamp” block. MC33364
used in the design example has an internal frequency clamp
set to 126 kHz. However, optional versions with a disabled
or variable frequency clamp are available. The frequency
clamp works as follows: the clamp controls the part of the
switching cycle when the MOSFET switch is turned off. If
this ”off--time” (determined by the reset time of the
transformer’s core) is too short, then the frequency clamp
does not allow the switch to turn--on again until the defined
frequency clamp time is reached (i.e., the frequency clamp
will insert a dead time).
There are several advantages of the MC33364’s startup
circuit. The startup circuit includes a special high voltage
switch that controls the path between the rectified line
voltage and the VCC supply capacitor to charge that
capacitor by a limited current when the power is applied to
the input. After a few switching cycles the IC is supplied
from the transformer’s auxiliary winding. After VCC
reaches the undervoltage lockout threshold value, the
V
V
in(min)
in(max)
dc = 2 xV
dc = 2 xV
in(min)
in(max)
ac = 290 Vac = 127 V
ac = 2270 Vac = 382 V
The maximum average input current is:
I
in
=
P out
nV
in(min)
=
12 W
= 0.118 A
0.8127 V
where n = estimated circuit efficiency.
A TMOS switch with 600 V avalanche breakdown
voltage is used. The voltage on the switch’s drain consists of
the input voltage and the flyback voltage of the
transformer’s primary winding. There is a ringing on the
rising edge’s top of the flyback voltage due to the leakage
inductance of the transformer. This ringing is clamped by the
RCD network. Design this clamped wave for an amplitude
of 50 V below the avalanche breakdown of the TMOS
device. Add another 50 V to allow a safety margin for the
MOSFET. Then a suitable value of the flyback voltage may
be calculated:
V
flbk
= V
− V
− 100 V
in(max)
TMOS
= 600 V − 382 V − 100 V = 118 V
Since this value is very close to the Vin(min), set:
V
flbk
= V
in(min)
= 127 V
The Vflbk value of the duty cycle is given by:
∂max =
V
V
127 V
flbk
=
= 0.5
[127 V + 127 V]
+V
in(min)
flbk
The maximum input primary peak current:
I
ppk
=
2I
in = 2.00.118 A = 0.472 A
∂max
0.5
Choose the desired minimum frequency fmin of operation
to be 70 kHz.
After reviewing the core sizing information provided by
a core manufacturer, a EE core of size about 20 mm was
chosen. Siemens’ N67 magnetic material is used, which
corresponds to a Philips 3C85 or TDK PC40 material.
http://onsemi.com
9
MC33364
The primary inductance value is given by:
Lp =
∂max V
in(min)
Ippkfmin
=
The approximate value of rectifier capacitance needed is:
t (I )
(5 m sec)(0.118 A)
C1 = off in =
= 11.8 mF
V
50 V
ripple
0.5127 V
= 1.92 mH
0.472 A70 kHz
where the minimum ripple frequency is 2 times the 50 Hz
line frequency and toff, the discharge time of C1 during the
haversine cycle, is assumed to be half the cycle period.
Because we have a variable frequency system, all the
calculations for the value of the output filter capacitors will
be done at the lowest frequency, since the ripple voltage will
be greatest at this frequency. When selecting the output
capacitor select a capacitor with low ESR to minimize ripple
from the current ripple. The approximate equation for the
output capacitance value is given by:
The manufacturer recommends for that magnetic core a
maximum operating flux density of:
B max = 0.2 T
The cross--sectional area Ac of the EF20 core is:
A c = 33.5 mm 2
The operating flux density is given by:
B max =
L pI
ppk
N pA c
From this equation the number of turns of the primary
winding can be derived:
np =
C5 =
ppk
B maxA c
A =
=
L n 2p
L pB maxA c

 
=
2

R7 =
2
L p I ppk
0.2 T33.5 E--6 m 2
.00192 H0.472 A
np =
 
AL
1∕2

0.00192 H
=
100 nH

2
2
= 105 nH
1∕2
= 139 turns
R
The number of turns needed by the 6.0 V secondary is
(assuming a Schottky rectifier is used):
ns =
Vs + Vfwd1–∂maxnp
=
=
lower
V (TL431)
2.5 V
= R11 = ref
=
= 10 k
I
0.25
mA
div
V out − V
I
ref
(TL431)
div
6.0 V − 2.5V
=
= 14 k
0.25 mA
∂maxVin(min)
6.0 V + 0.3 V1 − 0.5139
= 7 turns
0.5127 V
(V aux + V
2A
= 286 mF
(70 kHz)(0.1 V)
V cs
1.2 V
=
= 2.54 Ω ≈ 2.2 Ω
I
0.472
A
ppk
R upper = R10 =
The value of the resistor that would provide the bias
current through the optoisolator and the TL431 is set by the
minimum operating current requirements of the TL431.
This current is minimum 1.0 mA. Assign the maximum
current through the branch to be 5 mA. That makes the bias
resistor value equal to:
The auxiliary winding to power the control IC is 16 V and
its number of turns is given by:
naux =
=
The error amplifier function is provided by a TL431 on the
secondary, connected to the primary side via an optoisolator,
the MOC8102.
The voltage of the optoisolator collector node sets the
peak current flowing through the power switch during each
cycle. This pin will be connected to the feedback pin of the
MC33364, which will directly set the peak current.
Starting on the secondary side of the power supply, assign
the sense current through the voltage--sensing resistor
divider to be approximately 0.25 mA. One can immediately
calculate the value of the lower and upper resistor:
From the manufacturer‘s catalogue recommendation the
core with an AL of 100 nH is selected. The desired number
of turns of the primary winding is:
Lp
)(V )
min rip
Determining the value of the current sense resistor (R7),
one uses the peak current in the predesign consideration.
Since within the IC there is a limitation of the voltage for the
current sensing, which is set to 1.2 V, the design of the
current sense resistor is simply given by:
L pI
The AL factor is determined by:
Lp
(f
I out
)(1 − ∂max)n p
fwd
∂max(Vin(min))
R
bias
(16 V + 0.9 V)(1 − 0.5)139
= 19 turns
[0.5(127 V)]
=R =
S
=
http://onsemi.com
10
V out − [V
(TL431) + V
]
LED
ref
I
LED
6.0 V − [2.5V + 1.4V]
= 420 Ω ≈ 430 Ω
5.0 mA
MC33364
The MOC8102 has a typical current transfer ratio (CTR)
of 100% with 25% tolerance. When the TL431 is full--on,
5 mA will be drawn from the transistor within the
MOC8102. The transistor should be in saturated state at that
time, so its collector resistor must be
R
collector
The gain exhibited by the open loop power supply at the
high input voltage will be:
2
Vin max − Vout Ns 382 V − 6.0 V2(7)
A=
=
(Vin max)(Verror)(Np) (382 V)(1.2 V)(139)
V − V sat
5.0 V − 0.3 V
= ref
=
= 940 Ω
I
5.0 mA
LED
= 15.53 = 23.82 dB
Since a resistor of 5.0 k is internally connected from the
reference voltage to the feedback pin of the MC33364, the
external resistor can have a higher value
The
maximum
approximately:
f c = fs min =
5
(R
)(R
)
int collector = (5.0 k)(940)
R ext = R3 =
(R ) − (R
)
5.0 k − 940
int
collector
= 1157 Ω ≈ 1200 Ω
noload
=
(I
Gc = 20 log
heavy
R
1
in
( 2π R noload C out )
fc
ph
14177kHz − 23.82 dB
− A = 20 log
= R upper || R
lower
= 10 k || 14 k = 5833 Ω
R9 = (Ac) (R ) = 29.75 k ≈ 30 k
in
1
= 0.46 Hz
(2π)(1143)(300 mF)
C8 =
1
2π (Ac) (Rin) (fc)
= 382 pF ≈ 390 pF
The compensation zero must be placed at or below the
light load filter pole:
V
6.0 V
= out =
= 3.0 Ω
I out
2.0 A
C7 =
The output filter pole at heavy load of this output is
f ph =
f
Now the compensation circuit elements can be calculated.
The output resistance of the voltage sense divider is given by
the parallel combination of resistors in the divider:
In heavy load condition the ILED and Idiv is negligible. The
heavy load resistance is given by:
R
 
A c = 10 (Gc∕20) = 10 (14.14∕20) = 5.1
+I
The output filter pole at no load is:
=
70 kHz
= 14 kHz
5
The gain in absolute terms is:
)
div
6.0 V
=
= 1143 Ω
(5.0 mA + 0.25 mA)
f ph =
is
= 14.14 dB
V out
LED
bandwidth
The gain needed by the error amplifier to achieve this
bandwidth is calculated at the rated load because that yields
the bandwidth condition, which is:
This completes the design of the voltage feedback circuit.
In no load condition there is only a current flowing
through the optoisolator diode and the voltage sense divider
on the secondary side.
The load at that condition is given by:
R
recommended
1
1
=
= 177 Hz
(2π R heavyC out)
(2π)(3)(300 mF)
http://onsemi.com
11
1
2π (R9) (fpn)
= 11.63 mF ≈ 10 mF
MC33364
1N4006
D1
EMI
Filter
85 to
265 VAC
D2
+
D3
C1
10mF
400V
D4
T1
D5 1N4934
D8
MBR340
R1 56
Vcc UVLO
Vcc
Reference
C3
20mF
15 / 7.6
ZCD
R2
22 k
StartUp
Vref
Buffer
ZCD
10V
R3
5k
FB
R
R
S
45k
GATE
R4 470
(optional)
Thermal
shutdown
0.1V
4k
FC
Vcc
Q
Frequency
clamp
2V
C4
1mF
D6
MUR160
Restart
Delay
Watchdog
Timer
Current Sense
1.25V
15k
4.7
MC33364D
1.2/1.0
VREF
C10
0.1mF
R5
47 K
R6
47 K
Ref UVLO
6.0 V
2.0 A
C5
300mF
Line
PGND
Q1
MTD1N60
R7
2.2
R8
430
R10
14 k
CS
LEB
10V
AGND
U3
MOC8102
5
1
4
2
R9
39 k
U2
TL431
Figure 12. Circuit in the Design Example
http://onsemi.com
12
3
1
2
C7
10 mF
C8
330 pF
R11
10 k
MC33364
The described critical conduction mode flyback converter has the following performance and maximum ratings:
Output power
12W
Output
12V @ 1Amp max
Input voltage range
90VAC -- 270VAC
J1
D1
S380
10uF
400V
1
C4
10uF 220
2
1
R1
D2
1N4148
Gnd
1
MBRD360
+Vout
C6 300uF
R6
2k7
C5 1nF
R7
820
R8
18k
1
2
D3
MURS160T3
4
Q1
MTD1N60
1
C9
3
6
100nF
2
FB
R5
2.2
U3
MOC8102
U2
1
5
3
4
4
R3 47k
ZCD
7
GATE
MC33364
GND
CS
VREF
5
VCC
8
LINE
U1
9
7
R4
47k
R2
100k
J3
D4
T1
3
2
0.1uF
4
1
TL431
R9
4k7
2
Line
J2
3
1
2
J4
1
--Vout
Figure 13. Critical Conduction Mode Flyback Converter
CONVERTER TEST DATA
Test
Conditions
Results
Line Regulation
Vin = 120VAC to 240VAC, Iout = 0.8A
ΔV = 50mV
Load
Vin = 120VAC, Iout = 0.2A to 0.8A
ΔV = 40mV
Vin = 240VAC, Iout = 0.2A to 0.8A
ΔV = 40mV
Vin = 120VAC, Iout = 0.8A
ΔV = 290mV
Vin = 240VAC, Iout = 0.8A
ΔV = 24mV
Vin = 120VAC, Iout = 0.8A
η = 78.0%
Vin = 240VAC, Iout = 0.8A
η = 79.4%
Vin = 120VAC, Iout = 0.8A
Pf = 0.491
Vin = 240VAC, Iout = 0.8A
Pf = 0.505
Output Ripple
Efficiency
Power Factor
Vout
Vout
Iout
Iout
Ch1: 2.0V/div
Ch2: 200mA/div
2.0 msec/div
Ch1: 2.0V/div
Ch2: 200mV/div
Figure 14. Load Regulation 120V
2.0 msec/div
Figure 15. Load Regulation 240V
http://onsemi.com
13
MC33364
J2
1
Output 12 V @ 0.8 Amp max
Input Voltage Range 90 -- 270 Vac, 50/60 Hz
2
R13
22 k
R12
82 k
R11
10 k
5 VS
GND 4
6 CSB
CMP 3
U2
7 VCC MC33341 CTA 2
CSA 1
8 DO
5.1 V
R8
4.7 k
D8
B2X84C5V1LT1
R9
100
C5
100 mF
C6
1.0 mF
R7
100
D7
1N4148
R10
0.25
C7
33 nF
D6
MURS320T3
9
7
2
1
5
4
T1
4
3
R6
47 k
2
C4 1.0 nF
5
D5
MURS
160T3
R5
47 k
Q1
MTD1N60E
R4
2.2
U3
MOC8102
D3
1N4148
R1
220
R3
22 k
C2
20 mF
6
2
CS
Gate
1 ZCD
7 VCC
C1
D1 B250R
8 Line
10 mF
400 V
F1
T 0.2 A
U1
MC33364D1
GND
5
FB 3
C3
Vref
4
0.1 mF
T1 = 139 Turns #28 Awg, primary winding 2 -- 3
7 Turns, Bifilar 2 x #26 Awg, output winding 9 -- 7
19 Turns #28 Awg, auxiliary winding 4 -- 5 on Philips
EF20--3C85 core gap for a primary inductor of 1.92 mH.
1 2
J1
Line
Figure 16. Universal Input Battery Charger
http://onsemi.com
14
MC33364
PACKAGE DIMENSIONS
SO--8
D1, D2 SUFFIX
CASE 751--07
ISSUE AJ
--X--
NOTES:
1. DIMENSIONING AND TOLERANCING PER
ANSI Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSION A AND B DO NOT INCLUDE
MOLD PROTRUSION.
4. MAXIMUM MOLD PROTRUSION 0.15 (0.006)
PER SIDE.
5. DIMENSION D DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOWABLE DAMBAR
PROTRUSION SHALL BE 0.127 (0.005) TOTAL
IN EXCESS OF THE D DIMENSION AT
MAXIMUM MATERIAL CONDITION.
6. 751--01 THRU 751--06 ARE OBSOLETE. NEW
STANDARD IS 751--07.
A
8
5
S
B
1
0.25 (0.010)
M
Y
M
4
--Y--
K
G
C
N
DIM
A
B
C
D
G
H
J
K
M
N
S
X 45 _
SEATING
PLANE
--Z--
0.10 (0.004)
H
D
0.25 (0.010)
M
Z Y
S
X
M
J
S
SOLDERING FOOTPRINT*
1.52
0.060
7.0
0.275
4.0
0.155
0.6
0.024
1.270
0.050
SCALE 6:1
mm 
inches
*For additional information on our Pb--Free strategy and soldering
details, please download the ON Semiconductor Soldering and
Mounting Techniques Reference Manual, SOLDERRM/D.
http://onsemi.com
15
MILLIMETERS
MIN
MAX
4.80
5.00
3.80
4.00
1.35
1.75
0.33
0.51
1.27 BSC
0.10
0.25
0.19
0.25
0.40
1.27
0_
8_
0.25
0.50
5.80
6.20
INCHES
MIN
MAX
0.189
0.197
0.150
0.157
0.053
0.069
0.013
0.020
0.050 BSC
0.004
0.010
0.007
0.010
0.016
0.050
0 _
8 _
0.010
0.020
0.228
0.244
MC33364
PACKAGE DIMENSIONS
SO--16
D SUFFIX
CASE 751K--01
ISSUE O
--A-16
--B--
P
1
0.25 (0.010)
M
B
S
9
M_
F
8
G
R
X 45 _
C
--T-K
14 X D
0.25 (0.010)
M
T A
S
B
SEATING
PLANE
J
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSIONS A AND B DO NOT INCLUDE MOLD PROTRUSION.
4. MAXIMUM MOLD PROTRUSION 0.15 (0.006) PER SIDE.
5. DIMENSION D DOES NOT INCLUDE DAMBAR PROTRUSION.
ALLOWABLE DAMBAR PROTRUSION SHALL BE 0.127 (0.005)
TOTAL IN EXCESS OF THE D DIMENSION AT MAXIMUM
MATERIAL CONDITION.
DIM
A
B
C
D
F
G
J
K
M
P
R
MILLIMETERS
MIN
MAX
9.80
10.00
3.80
4.00
1.35
1.75
0.35
0.49
0.40
1.25
1.27 BSC
0.19
0.25
0.10
0.25
0_
7_
5.80
6.20
0.25
0.50
INCHES
MIN
MAX
0.368
0.393
0.150
0.157
0.054
0.068
0.014
0.019
0.016
0.049
0.050 BSC
0.008
0.009
0.004
0.009
0_
7_
0.229
0.244
0.010
0.019
S
GreenLine is a trademark of Motorola, Inc.
ON Semiconductor and
are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice
to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability
arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages.
“Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All
operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under its patent
rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other
applications intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur.
Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries,
affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury
or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an
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16
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MC33364/D