Power output stage with limited current absorption during high-impedance phase

An integrated motor driver circuit, comprising:

• a first N-channel power field-effect transistor connected between an output node and a first positive supply voltage, and a second N-channel power field-effect transistor connected between said output node and supply reference voltage;
• a switchable current source connected between the gate of said first transistor and a second positive supply voltage which is higher than said first positive supply voltage, and a switchable current sink connected between the gate of said first transistor and said supply reference voltage;
• a string of components, connected to each other at a plurality of nodes, and connected to provide voltage-limiting between the gate of said first transistor and said output node;
• and
• at least one decoupling transistor having a control terminal connected to said output node, a first current-carrying terminal functionally connected to said second positive supply voltage, and a second current-carrying terminal connected to a first node of said string which is not said output node.

An integrated motor driver circuit, comprising:

• a first N-channel power field-effect transistor connected between an output node and a first positive supply voltage, and a second N-channel power field-effect transistor connected between said output node and supply reference voltage;
• a switchable current source connected between the gate of said first transistor and a second positive supply voltage which is higher than said first positive supply voltage, and a switchable current sink connected between the gate of said first transistor and said supply reference voltage;
• a string of components connected to each other at a plurality of nodes, and connected to provide voltage-limiting between the gate of said first transistor and said output node;
• and
• at least one decoupling transistor having a control terminal connected to said output node, a first current-carrying terminal functionally connected, through a diode, to said first positive supply voltage, and a second current-carrying terminal connected to a first node of said string which is not said output node.

An integrated circuit for driving a power transistor which is connected between an output node and a first supply voltage having a control voltage which is necessary to turn on said power transistor if connected to the gate thereof, comprising:

• a first switchable current generator connected between the gate of said power transistor and a second supply voltage which is more extreme than said first supply voltage, and a second switchable current generator connected between the gate of said power transistor and a supply reference voltage;
• a string of components connected between the gate of said power transistor and said output node to provide voltage-limiting;
• and
• at least one decoupling transistor having a control terminal connected to said output node, a first current-carrying terminal functionally connected to one of said supply voltages, and a second current-carrying terminal connected to a first node of said string which is not said output node.

A power stage, comprising:

• a first transistor in common-source configuration;
• a second transistor in common-drain configuration;
• wherein said first and said second transistors are field-effect transistors;
• said first transistor being connected at its drain to an output node of the power stage and said second transistor being connected at its source to an output node of the power stage, and driven alternatively into conduction by first and second control circuits coupled to their respective gate terminals;
• said second transistor, connected in common-drain configuration, being driven with a driving voltage higher than the common voltage of the drain thereof;
• and
• at least one pair of back-to-back zener limiting diodes, connected between source and gate of said second transistor to limit the gate-source voltage thereof;
• further comprising at least one circuit component connected to said output node and said at least one pair of back-to-back zener limiting diodes for limiting the current drawn from a load connected to said output node of the power stage when said first and second transistors are turned off and said pair of back-to-back zener limiting diodes is turned on.

An integrated circuit, comprising:

• first and second transistors, which are power transistors, connected in series respectively between first and second supply terminals, and connected to alternatively drive a load connected to an output terminal common to said first and second transistors;
• a driver circuit connected to control said first transistor at the gate thereof by means of first and second current signals respectively turning on and turning off said first transistor, said driver circuit driving said first transistor with a third supply voltage, provided by a third supply terminal and higher than the voltages at said first and second supply terminals;
• a limiting circuit connected between the gate of said first transistor and said output terminal, to limit the voltage therebetween;
• and
• circuit components coupled to said output node, said limiting circuit and said third supply terminal, and connected to control the current drawn from the load through said output node, when said first and second transistors are turned off and said limiting circuit is turned on, and accordingly to provide an amplified current which augments said second current signal.

An integrated circuit, comprising:

• first and second power field effect transistors connected in series between first and second supply terminals, wherein the source of said first power field effect transistor is connected to said first supply terminal and the drain of said second power field effect transistor is connected to said second supply terminal, said first and second power field effect transistors being connected to alternatively drive a load connected to an output terminal, common to said first and second power field effect transistors;
• a driver circuit connected to control said first power field effect transistor at the gate thereof by means of first and second current signals respectively turning on and turning off said first power field effect transistor, said driver circuit driving said first power field effect transistor with a third supply voltage higher than the voltage at said first and second supply terminals and provided by a third supply terminal;
• first and second zener diodes connected back to back between the gate of said first power field effect transistor and said output terminal, to limit the voltage therebetween;
• and
• an amplifier stage connected to be controlled by said output node, and connected between said output node and said third supply terminal to supply the current which would otherwise be drawn from said output node through said zener diodes upon turnoff of said power transistors, and accordingly to provide an amplified current which augments said second current signal of said driver circuit.

A method for controlling the current drawn from a load to be driven alternatively by a pair of power transistors, comprising the steps of:

• using respective control circuits to alternatively turn on said power transistors;
• when both of said pair of power transistors are off, sensing the voltage at an output node between the load and the pair of power transistors;
• and
• forcing the current drawn by the load through an additional amplifier stage, which is isolated from the control nodes of said power transistors, directly from a power supply node, when said voltage at the output node has reached a threshold value corresponding to starting of the current flow from the load.