P
Peter
I have a multi output power supply box, 28V DC in, and inside are
several DC-DC converters from firms like TRACO.
It is used to power various bits in a light aircraft e.g. a Lenovo T2
tablet, a satellite phone, etc.
The problem I have is that Lenovo have cheated on their USB charging.
Unlike Apple who cheated by using four resistors on the data pins
http://www.euroga.org/forums/website/714-5v-2a-usb-charging
(but who can charge from 5.0V) Lenovo need 5.25V. In fact their own
USB chargers output 5.49V (no load).
I thought about lifting the output up by 0.6V with a diode through
which the input current passes (then I have 5.6V which I can use) but
since the switch-mode DC-DC converter's input current will always be
less than the output current, the net current through the diode will
be below zero...
I cannot see any way of doing it...
Obviously with a DC-DC conv which has resistor-programmable o/p
voltage, or even remote sense terminals which can be fooled with
resistors, it's easy. But the smaller modules don't have this.
I have a "Lineage Power" open-style DC-DC conv which can do 5V-7V at
up to 20A, but it's a bit too big, has no shielding, and would need
tons of i/p and o/p filtering.
Is there some trick way of doing it?
I know how to make a 0.25V or 0.5V dropper, with a transistor... so
that bit is not a problem.
several DC-DC converters from firms like TRACO.
It is used to power various bits in a light aircraft e.g. a Lenovo T2
tablet, a satellite phone, etc.
The problem I have is that Lenovo have cheated on their USB charging.
Unlike Apple who cheated by using four resistors on the data pins
http://www.euroga.org/forums/website/714-5v-2a-usb-charging
(but who can charge from 5.0V) Lenovo need 5.25V. In fact their own
USB chargers output 5.49V (no load).
I thought about lifting the output up by 0.6V with a diode through
which the input current passes (then I have 5.6V which I can use) but
since the switch-mode DC-DC converter's input current will always be
less than the output current, the net current through the diode will
be below zero...
I cannot see any way of doing it...
Obviously with a DC-DC conv which has resistor-programmable o/p
voltage, or even remote sense terminals which can be fooled with
resistors, it's easy. But the smaller modules don't have this.
I have a "Lineage Power" open-style DC-DC conv which can do 5V-7V at
up to 20A, but it's a bit too big, has no shielding, and would need
tons of i/p and o/p filtering.
Is there some trick way of doing it?
I know how to make a 0.25V or 0.5V dropper, with a transistor... so
that bit is not a problem.