pq1cf2 ETC-unknow, pq1cf2 Datasheet - Page 9

• Manufacturer Part Number: pq1cf2
• Description: To-220 Type Chopper Regulator
• Manufacturer: ETC-unknow

Chopper Regulators
(3) Thermal protection design
e Output capacitor(Co)
r Catch diode
t Input capacitor(C
When ambient temperature T
plate which allows the element to operate within the safety operation area specified by the derating curve. Insufficient
radiation gives an unfavorable influence to the normal operation and reliability of the device.
operate to shut-down output. However, please avoid keeping such condition for a long time.
Internal power dissipation (P)of device is generally obtained by the following equation.
––––––––––––––
––––––––––––––––––––
In the external area of the safety operation area shown by the derating curve, the overheat protection circuit may
P=I
Step down type
Polarity inversion type
The output ripple voltage is highly influenced by ESR(Equivalent Series Resistor) of output capacitor, and can be
minimized by selecting low ESR capacitor.
Generally, smaller capacitance, lower breakdown voltage of capacitor make ESR of capacitor high. By use of high
grade "low impedance" electrolytic capacitor, output ripple voltage will decrease.
In continuous mode, output ripple voltage and ripple allowance current of capacitor are obtained by the following
equations.
High switching speed and low forward voltage type schottky barrier diode should be recommended for the catch-
diode D because it affects the efficiency. Please select the diode which the current rating is at least 1.2 times greater
than maximum switching current.
Please select the input capacitor with low ESR and sufficient ripple current rating, wiring as near as possible the
regulator.
In low temperature operating, ESR of capacitor increases, capacitance will greater than usual.
In continuous mode, ripple allowance current of capacitor is obtained by the following equation.
<Step down type>
Output ripple voltage (V
Ripple allowance current (effective value)= I
Ripple allowance current (effective value)=I
SW
I
L
= ––––––––––– x D x= ––
(Average) x V
D(Duty)= ––––––––– = ––––––––––––
I
D(Duty)= ––––––––– = –––––––––––––––––
I
V
SW
SW
IN
(Average)=I
(Average)= ––––– x I
–V
L
SAT
–V
T(period)
T(period)
O
IN
SAT
T
T
)
O
ON
ON
1–D
x D + V
(Output current)
1
RIP P–P
f
1
O
a
and maximum power dissipation P
IN
O
V
)= I
V
(voltage between V
IN
IN
+ |V
V
–V
L
O
|V
x ESR
+V
SAT
O
O
| –V
| +V
F
+V
F
SAT
F
O
+V
L
x ––––––––––––––
I
V
Q
F
F
' : Consumption current in operating mode
V
: Forward voltage of the diode
IN
(V)
(A)
O
to COM terminal) x I
x (V
V
IN
IN
–V
O
)
D
(MAX.)during operation are determined, use a Cu
(A)
Q
'(consumption current) . . . q
PQ1CF2