Help with USB - need a soft start circuit

Hello,

I=B4m new into electronics (i=B4ve studied theory the last year but now i=B4m trying to build some real stuff). There=B4s a project i need to do that the device is charged through USB. My problem is the following: Once it powers on,a high-power device (it means a device that draws up to 500mA from the BUS) can't draw more than 100 milliamperes until the host has said it's OK to do so(this happens during enumeration process). Up to this point(during enumeration) the rest of the circuit have to be off. So, I have this soft-start logic circuit

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that allows the power to the load to be switched off and on, and it provides a 'slow start' feature . Unfortunately, it isn=B4t working properly.Suddenly the results on the computer get lost. I think its a problem with this soft start circuit. Maybe the transistor consumes too much power, i don=B4t know. Or it isn=B4t slow enough. Does anyone know another kind of soft start circuit, like that one? Maybe suggesting another transistor, I don=B4t know. Anything will be helpful. Thanks a lot and sorry if i=B4m being "too begginer". :-) Victor

Reply to
Victor hyppolito
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Have you checked this? Put a scope on a small resistor in the +5V line, and measure the current with a scope.

Reply to
Ian Stirling

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