MC44604_05 ONSEMI [ON Semiconductor], MC44604_05 Datasheet - Page 20

• Manufacturer Part Number: MC44604_05
• Description: High Safety Pulsed Mode Standby GreenLine TM PWM Controller
• Manufacturer: ONSEMI [ON Semiconductor]

(obtained at the end of the switching phase) and a valley
level (reached at the end of the off phase).
current higher than I
the desired value.
operation. A zener diode Z is connected so that a current
limited by R
voltage gets higher than V
in the pin 15 increases and when this current is detected as
higher than I
startup (Note 1).
(when the zener is activated):
where: CTR is the opto coupler gain, V
I
low resistance just to limit the current when V
higher than V
Note 1. If the pin 15 current is higher than I
reg
As a consequence, V
The level of the peak value is controlled by forcing a
The arrangement in Figure 41 allows to obtain this
Practically, the pin 15 current can be expressed as follows
So, as the Vstby peak value is obtained when (I
Practically, R
), it can be calculated using the following equation:
m P supply
V pin 15
I pin 15
voltage
I zener
V stby
output is just shutdown but not latched. The circuit must
output
voltage drop.
V
V
I
CC
pin15
stby pk
reg
Figure 42. Standby Regulation
reg
z
, is drawn by this device, when the mP supply
):
Stby V disable 2 (12.5 V)
reg
, the output gets disabled until the next
+ CTR
V
I reg
I det
+ V z ) V opto )
stby pk
is chosen very low (in the range of 10 W,
reg
V
in pin 15 when this level has reached
stup
Î Î Î Î
Î Î Î Î
stby
z
^ V z ) V opto
. By this way, the current injected
(14.5 V)
The output is latched off
V
until the next re−start
varies between a peak value
stby
* V opto * V z
R reg
R reg
opto
CTR
reg
is opto coupler
I reg
at startup, the
stby pk
time
pin15
http://onsemi.com
gets
MC44604
=
20
Transitions Between Normal Mode and Standby Mode
(Refer to Figure 43)
15 current to:
− I
− I
so that the device can work in the new mode after the
following restart.
• transition normal mode to standby:
to the threshold current (I
for the regulation, never exceeds this value.
of operation. The mP initializes the standby mode by turning
on the switch T. This results in the C capacitor charge that
produces a peak current in the primary side of the opto
coupler. C and R
coupler primary side generates a pin 15 current higher than
I
• transition standby to normal mode:
operation, the circuit is turned off. So, if the normal mode is
maintained at the following startup, the circuit will restart in
a normal mode configuration.
detection. When the mP detects the end of the standby, it
turns off the switch T and the opto coupler stops supplying
current to the circuit.
init
V CC
V CC
The MC44604 detects a transition by comparing the pin
Each transition detection results in the circuit turning off,
This transition is detected by comparing the I
I
The arrangement in Figure 41 is well adapted to this mode
If the circuit detects that (I
The arrangement in Figure 41 allows to perform this
init
during more than 1 ms.
det
init
is high enough so that the opto coupler current used
The transition stand−by to normal mode occurs while
detect a sequence during which I
before being able to latch gets higher than V
The transition stand−by to normal mode occurs while
(transition standby to normal mode)
(transition normal mode to standby)
Figure 43. Transitions Between Modes
Normal
Normal
14.5 V
12.5 V
14.5 V
12.5 V
Mode
Mode
Standby
Standby
the circuit is off (V
the circuit is on (working phase)
init
must be dimensioned so that the opto
Standby Burst Mode
Standby Burst Mode
init
).
pin15
CC
(
....
)
charge phase)
< I
(
....
)
det
pin15
Normal
Mode
Normal
) during standby
Mode
lower than I
Normal
Mode
pin15
z
).
Normal
Mode
current
time
time
reg