M51995AP Ovp Circuit - MITSUBISHI
Manufacturer Part Number
Switching regulator control
Fig.27 DC source circuit for stable start-up
(1)To avoid the miss operation of OVP
It is recommended to connect the capacitor between OVP
terminal and GND for avoiding the miss operation by the spike
The OVP terminal is connected with the sink current source
(~150µA) in IC when OVP does not operate,for absorbing the
leak current of the photo coupler in the application.
So the resistance between the OVP terminal and GND for leak-
cut is not necessary.
If the resistance is connected,the supply current at the OVP
reset supply voltage becomes large.
As the result,the OVP reset supply voltage may become higher
than the operation stop voltage.
In that case,the OVP action is reset when the OVP is triggered
at the supply voltage a little high than the operation stop
So it should be avoided absolutely to connect the resistance
between the OVP terminal and GND.
Fig.28 Peripheral circuit of OVP terminal
FIG.30 OVP setting method using the induced
(2)Application circuit to make the OVP-reset time fast
The reset time may becomes problem when the discharge time
constant of C
condition,it is recommended to discharge the C
to make the Vcc low value.This makes the OVP-reset time fast.
(3)OVP setting method using the induced third winding
voltage on fly back system
For the over voltage protection (OVP),the induced fly back type
third winding voltage can be utilized,as the induced third
winding voltage depends on the output voltage.Fig.30 shows
one of the example circuit diagram.
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SWITCHING REGULATOR CONTROL
THE TIME CONSTANT OF
THIS PART SHOULD BE SHORT
Fig.29 Example circuit diagram to make the
third winding voltage on fly back system
• (R1+R2) is long. Under such the circuit