MC33364 Datasheet, PDF (5/14 Pages) ON Semiconductor – Critical Conduction GreenLine SMPS Controller

MC33364
FUNCTIONAL DESCRIPTION
INTRODUCTION
With the goal of reducing the size and cost of off–line
power supplies, there is an ever increasing demand for an
economical method of obtaining a regulated galvanically
isolated dc output voltage using a control which operates
directly from the ac line. This data sheet describes a
monolithic control IC that was specifically designed for power
supply control with a minimal number of external
components. It offers the designer a simple cost effective
solution to obtain the benefits of off–line power regulation.
Figure 7. Functional Block Diagram
92 to
270 Vac
C5
1N4006 1N4006 ₁₀
D2
D4
EMI
D1
Filter _1N4006
D3
1N4006
R2
22 k
Zero Current
MC33364
Zero
Current
Detect
QR
Timer
R
RQ
0.3/
0.25 V
SQ
En
R
Q
S
Frequency
Clamp 4.0 K
C2 10 V
0.01
5.0 V
3.0 µA
10 pF
2.0 V
2.0 V
D9
1N4148
R13
100
Line
T1
UVLO
+
15/7.6
Leading
Edge
Blanking
44 K
1.5 V 14 K
5.0 k
VCC
5.0 V
UVLO ^{+ Reference En}
A Gnd
C3
20 + 1N4934
R1 56 D5
VCC
R5 47 k
D8
MBRS340T3
R6 ^C4
C5
P VCC _{47 K .001}
300
Gate Drive
470 R4
P Gnd
D7
1N4148
R12 100
D6
MURS160T3
Q1
MTD1N60
6.0 V
2 Amp
Current C9 .01
Sense
R7
2.2
Voltage FB
U3
MOC8102
R8
430
R10
14 k
R3
1.2 K
5
1
Vref
C10
0.1
4
2
R9
39 k
U2 ^{3 1}
TL431 2
C7
10
C8
330 pF
R11
10 k
ǒ Ǔ + ) VO
2.5
R10
R11
1
Operating Description
The MC33364 contains many of the building blocks and
protection features that are employed in modern high
performance current mode power supply controllers.
Referring to the block diagram in Figure 7, note that this
device does not contain an oscillator. A description of each of
the functional blocks is given below.
Zero Current Detector
The MC33364 operates as a critical conduction current
mode controller, whereby output switch conduction is
initiated by the Zero Current Detector and terminated when
the peak inductor current reaches the input threshold level.
The Zero Current Detector initiates the next on–time by
setting the RS Latch at the instant the inductor current
reaches zero. This critical conduction mode of operation has
two significant benefits. First, since the MOSFET cannot
turn–on until the inductor current reaches zero, the output
rectifier’s reverse recovery time becomes less critical
allowing the use of an inexpensive rectifier. Second, since
there are no deadtime gaps between cycles, the ac line
current is continuous thus limiting the peak switch to twice
the average input current
The Zero Current Detector indirectly senses the inductor
current by monitoring when the auxiliary winding voltage falls
below 0.25 V. To prevent false tripping, 50 mV of hysteresis is
provided. The Zero Current Detector input is internally
MOTOROLA ANALOG IC DEVICE DATA
5