Dynamic bias soft start control apparatus and methods

摘要

Apparatus and methods operate to disable a dynamically biased apparatus and a dynamic bias current source providing dynamic bias current to the apparatus at the beginning of a static bias startup period shortly after power-on. The dynamically biased apparatus is then gradually enabled in a static bias mode of operation during the static bias startup period. Following the end of the static bias startup period, operation of the dynamically biased apparatus in a dynamic transconductance mode is gradually enabled during a dynamic bias startup period. Such startup sequence operates to prevent damaging in-rush currents in a system employing the dynamically biased apparatus in a feedback control loop.

主权项

1. A soft start control system, comprising: a dynamic bias current source to source a dynamic bias current in a magnitude proportional to a bias control signal received at the dynamic bias current source; a dynamically biased apparatus communicatively coupled to the dynamic bias current source to sink the dynamic bias current; and a dynamic bias hold-off circuit communicatively coupled to the dynamically biased apparatus to delay operation of the dynamic bias current source at power-on until completion of a static bias startup period; and an operating current source communicatively coupled to the dynamic bias current source to supply operating current to the dynamic bias current source; and a time-delayed current mirror configured in series between the operating current source and the dynamic bias current source, the time-delayed current mirror to ramp up a time-delayed operating current to the dynamic bias current source following the static bias startup period; and the time-delayed current mirror further comprising: an operating current input transconductance device in series with the operating current source; an operating current output transconductance device to provide the operating current to the dynamic bias current source following the dynamic bias hold-off period; a dynamic bias startup resistor coupled in series between an input element associated with the operating current input transconductance device and an input element associated with the operating current output transconductance device; and a dynamic bias startup capacitor coupled between the input element associated with the operating current output transconductance device and ground, the dynamic bias startup resistor and the dynamic bias startup capacitor to establish a time constant associated with a dynamic bias ramp up period.