Power device with current sense
According to a first aspect of the disclosure, there is provided an electronic device comprising: a power device circuit comprising: (i) a main power transistor, comprising a main drain terminal, a main source terminal and a main gate terminal, (ii) a resistive sensing load, and (iii) a sensing transistor comprising a source connected to the main source terminal, a gate connected to the main gate terminal and a drain connected to a first terminal of the resistive sensing load. The electronic device further comprises: a feedback circuit comprising at least one operational amplifier and at least one transconductor, and a switching circuit comprising at least one switch for connecting and disconnecting the power device circuit to the feedback circuit. A first input of the at least one operational amplifier and a second terminal of the resistive sensing load are selectively connected to the main drain terminal through the switching circuit. A second input of the at least one operational amplifier and at least one output of the at least one transconductor are selectively connected to the drain of the sensing transistor through the switching circuit. The main power transistor has a first area or gate perimeter and the sensing transistor has a second area or gate perimeter smaller than the first area or gate perimeter. During an ON state of the main power transistor, the output current of the transconductor of the feedback circuit is proportional to the potential difference between the main drain terminal and the drain of the sensing transistor, resulting in a voltage across the resistive sensing load of substantially zero.
1 . An electronic device comprising:
a power device circuit comprising:
a main power transistor, comprising a main drain terminal, a main source terminal and a main gate terminal,
a resistive sensing load, and
a sensing transistor comprising a source connected to the main source terminal, a gate connected to the main gate terminal and a drain connected to a first terminal of the resistive sensing load,
a feedback circuit comprising at least one operational amplifier and at least one transconductor, and
a switching circuit comprising at least one switch for connecting and disconnecting the power device circuit to the feedback circuit,
wherein a first input of the at least one operational amplifier and a second terminal of the resistive sensing load are selectively connected to the main drain terminal through the switching circuit,
wherein a second input of the at least one operational amplifier and at least one output of the at least one transconductor are selectively connected to the drain of the sensing transistor through the switching circuit, and
wherein the main power transistor has a first area or gate perimeter, and
wherein the sensing transistor has a second area or gate perimeter smaller than the first area or gate perimeter, and
whereby, during an ON state of the main power transistor, an output current of the at least one transconductor of the feedback circuit is proportional to a potential difference between the main drain terminal and the drain of the sensing transistor, resulting in a voltage across the resistive sensing load of substantially zero.
2 . The electronic device of claim 1 , wherein during an OFF state of the main power transistor, the switching circuit is configured to disconnect the feedback circuit from the power device circuit, resulting in an increase of a drain to source voltage of the sensing transistor until said voltage is substantially the same as a drain to source voltage of the main power transistor.
3 . The electronic device of claim 1 , wherein an output current of the feedback circuit is directly proportional to a current flowing through the main power transistor.
4 . The electronic device of claim 1 , wherein the operational amplifier is configured to amplify a potential difference between the main drain terminal and the drain of the sensing transistor,
wherein an output of the operational amplifier is connected to an input of the transconductor, and
wherein an output current of the transconductor is proportional to the output of the operational amplifier.
5 . The electronic device of claim 4 , wherein the feedback circuit is configured to provide the output current of the transconductor to the drain terminal of the sensing transistor to create a feedback loop configured to maintain the potential difference between the main drain terminal and the drain of the sensing transistor at a constant value.
6 . The electronic device of claim 1 , wherein the operational amplifier is configured to be operated in a low power consumption mode by a conditioned gate drive signal wherein the gate drive signal is inverted, time shifted, or level shifted.
7 . The electronic device of claim 1 , wherein the at least one transconductor is a p-channel transistor.
8 . The electronic device of claim 1 , wherein the switching circuit is configured to: (i) connect the feedback circuit to the power device circuit a predetermined time after turn-on of the power device circuit and (ii) disconnect the feedback circuit from the power device circuit a predetermined time before turn-off of the power device circuit.
9 . The electronic device of claim 1 , wherein the switching circuit comprises a first, a second and a third switch configured to connect and disconnect:
the main drain terminal to the first input of the operational amplifier of the feedback circuit,
the drain of the sensing transistor to the second input of the operational amplifier, and
an output of the transconductor to the drain of the sensing transistor, respectively.
10 . The electronic device of claim 9 , wherein the first, second and third switches comprise enhancement mode HEMTs.
11 . The electronic device of claim 9 , wherein the first, second and third switches comprise T-type switches with two enhancement mode transistors connected in series, respective gate terminals of the first, second and third switches being connected to a switch enable signal and a high impedance component having a first end connected between the respective two enhancement mode transistors and a second end connected to ground.
12 . The electronic device of claim 1 , wherein the feedback circuit comprises a current mirror circuit configured to generate an output current identical to the output current of the transductor.
13 . The electronic device of claim 12 , wherein the electronic device is configured to convert the output current of the current mirror circuit into an output voltage signal using a resistor.
14 . The electronic device of claim 12 , comprising a digitally programmable decoder configured to adjust a gain of the current mirror circuit responsive to one or more digital inputs to the digitally programmable decoder.
15 . The electronic device of claim 1 , comprising a wide-bandgap semiconductor die and a silicon semiconductor die, wherein the power device circuit and the switching circuit are provided on the wide-bandgap semiconductor die and the feedback circuit is provided on a silicon semiconductor die.
16 . The electronic device of claim 15 , wherein the wide-bandgap semiconductor die and the silicon semiconductor die are incorporated in a single system-in-package.
17 . The electronic device of claim 15 , wherein the silicon semiconductor die comprises at least one of:
a gate driving circuit;
an over-current protection circuit;
an over-temperature detection and protection circuit;
an under-voltage detection or lock out circuit;
a voltage regulator;
a bandgap reference circuit;
a level shifter; an ESD protection circuit; a start-up circuit; a logic circuit; memory storage; and/or
a slew rate control circuit.
18 . The electronic device of claim 15 , wherein the wide-bandgap semiconductor die is a gallium nitride (GaN) die.
19 . The electronic device of claim 1 , comprising a wide-bandgap semiconductor die and a silicon semiconductor die, wherein the power device circuit is provided on the wide-bandgap semiconductor die, and the switching circuit and the feedback circuit are provided on a silicon semiconductor die.
20 . The electronic device of claim 1 , wherein the main power transistor comprises an active heterojunction transistor comprising a, Miller clamp transistor, and wherein the Miller clamp transistor is monolithically integrated with driving circuitry of the active heterojunction transistor.