NCP1216P065 7 pin package (8 pin dip with missing pin), MOSFET switcher, blah blah.
Standby and run mode use same cold side 5V and power supply base on it for regulation via optisolator to switcher IC.
But one thing that is driving me NUTS is this thing will NOT come out of standby mode due to PNP transistor not switching completely off from 40V supply disconnecting from 5V. PNP base is pulled up by 40V supply via bias resistor and it's not pulling all the way up with transistor in place. Unsolder emitter or collector of PNP and power supply comes to full power. Tried another PNP transistor with no luck and even I measured disconnected base signal for PNP and it's swinging enough.
The PNP is driven by pair of NPN transistors (inverts the power control signal from high to low via the current limiting resistor and divider on the PNP's base.
And that circuit is working as it supposed to be.
What this insane idea is that designer used 40V supply via PNP transistor onto 5V supply is to "trick" the regulation and enter into low power mode by forcing 40V down to 6Vish (measured) via the PNP transistor to 5V supply.
SIGH. Totally stumped. The microcontroller is switching the power control up and down properly. Help?
Cheers, Wizard
Standby and run mode use same cold side 5V and power supply base on it for regulation via optisolator to switcher IC.
But one thing that is driving me NUTS is this thing will NOT come out of standby mode due to PNP transistor not switching completely off from 40V supply disconnecting from 5V. PNP base is pulled up by 40V supply via bias resistor and it's not pulling all the way up with transistor in place. Unsolder emitter or collector of PNP and power supply comes to full power. Tried another PNP transistor with no luck and even I measured disconnected base signal for PNP and it's swinging enough.
The PNP is driven by pair of NPN transistors (inverts the power control signal from high to low via the current limiting resistor and divider on the PNP's base.
And that circuit is working as it supposed to be.
What this insane idea is that designer used 40V supply via PNP transistor onto 5V supply is to "trick" the regulation and enter into low power mode by forcing 40V down to 6Vish (measured) via the PNP transistor to 5V supply.
SIGH. Totally stumped. The microcontroller is switching the power control up and down properly. Help?
Cheers, Wizard
