In search for soft on-off solution found
Latch and Toggle Power Circuits with as it look - simple and useful soft latch circuits. Before taking one of them decided to test them on breadboard. Also because device where I want to use them works from 9V. Due to a bit limited component supply @home at this afternoon tested them with different MOSFETs. Turned out that
1) Circuits with 2 logic inverter gates (Press ON - Press OFF soft latching circuits) when made as it is in article, with CD4011BE NAND gates (have no other "inverters" here now), switch on and off erratically in all voltage range up to desired 9V. As turned out, 1 uF capacitor charge too fast and gates become flipped before button is released. Capacitor must have higher value: at least 2.2 uF, but better 4.7-10 uF. That seems already usable. Extended version with P-channel MOSFET (tested with SPP18P06P) on VCC works too. There is side effect: when button is pressed for 3+ seconds, gates turn into multivibrator and output voltage fluctuate till button is released. Nothing of that was mentioned in description. Would like to know how to avoid multivibrating effect on long button pressing for switching off. Put a diode somewhere? Also I'm curious which logic IC author used - no mentioning about that too. It certainly was none of CD4xxx.
2) Circuit with two complementary MOSFETs (IRF7319) instantly turn on when powered and doesn't turn off on button press. I used SPP18P06P (P-channel) + STP20NE06L (N-channel) MOSFETs for that. Wrong MOSFETs?