M51995 Mitsubishi, M51995 Datasheet - Page 19

• Manufacturer Part Number: M51995
• Description: SWITCHING REGULATOR CONTROL
• Manufacturer: Mitsubishi

Fig.23 CIRCUIT CURRENT VS. SUPPLY VOLTAGE
6
2
1
0
4
3
8
7
5
Vcc
0
GND
OVP
OVP RESET POINT
8.82V(-30°C)
8.97V(25°C)
9.07V(85°C)
Fig.22 Detail diagram of OVP circuit
5
SUPPLY VOLTAGE Vcc(V)
10
12k
8k
(OVP OPERATION)
15
I
2
Ta=-30°C
Ta=25°C
Ta=85°C
7.8V
20
I1=0 when OVP operates
400
Q1
Q2
2.5k
25
30
Q3
I
1
35
100µA
40
(
19
/ 27 )
Output section
It is required that the output circuit have the high sink and
source abilities for MOS-FET drive.It is well known that the
"totempole circuit has high sink and source ability.However,it
has the demerit of high through current.
For example,the through current may reach such the high
current level of 1A,if type M51995A has the "conventional"
totempole circuit.For the high frequency application such as
higher than 100kHz,this through current is very important factor
and will cause not only the large Icc current and the inevitable
heat-up of IC but also the noise voltage.
This IC uses the improved totempole circuit,so without
deteriorating the characteristic of operating speed,its through
current is approximately 100mA.
APPLICATION NOTE OF TYPE M51995AP/FP
Design of start-up circuit and the power supply
of IC
Fig.24 shows one of the example circuit diagram of the start-up
circuit which is used when it is not necessary to set the start
and stop voltage.
It is recommended that the current more than 300µA flows
through R1 in order to overcome the operation start-up current
Icc
R1 by Cvcc causes the time delay of operation,so the response
time will be long if the product is too much large.
(1)The start-up circuit when it is not necessary to set the
Just after the start-up,the Icc current is supplied from
Cvcc,however,under the steady state condition ,IC will be
supplied from the third winding or bias winding of
transformer,the winding ratio of the third winding must be
designed so that the induced voltage may be higher than the
operation-stop voltage Vcc
The Vcc voltage is recommended to be 12V to 17V as the
normal and optimum gate voltage is 10 to 15V and the output
voltage(V
Fig.24 Start-up circuit diagram when it is not
start and stop input voltage
(START)
RECTIFIED DC
VOLTAGE FROM
SMOOTHING CAPACITOR
M51995A
necessary to set the start and stop input voltage
OH
and Cvcc is in the range of 10 to 47µF.The product of
) of type M51995AP/FP is about(Vcc-2V).
SWITCHING REGULATOR CONTROL
GND
Vcc
(STOP)
.
M51995AP/FP
R1
CVcc
VF
MAIN TRANSFORMER
THIRD WINDING OR
BIAS WINDING