Driver circuit, corresponding device, apparatus and method
A (pre) driver circuit includes first and second output terminals configured to be coupled to a power transistor. A differential stage has non-inverting and inverting inputs for receiving an input voltage. The input voltage is replicated as an output voltage across the first and second output terminals as a drive signal for the power transistor. The differential stage includes a differential transconductance amplifier in a voltage follower arrangement configured to provide continuous regulation of a voltage at the first output terminal with respect to the second output terminal.
1. A circuit comprising:
a first output terminal configured to be coupled to a control terminal of a power transistor;
a second output terminal configured to be coupled to a conduction terminal of the power transistor;
a first current generator; and
a transconductance amplifier comprising:
a first transistor having a control terminal coupled to the first current generator, and
a second transistor having a current path coupled between a current path of the first transistor and the first output terminal, and a control terminal coupled to the control terminal of the first transistor; and
a capacitor coupled between the control terminal of the first transistor and the second output terminal, wherein the transconductance amplifier is configured to receive an input voltage across the capacitor, and produce a regulated output voltage at the first output terminal with respect to the second output terminal based on the input voltage, and wherein the first current generator is configured to provide slew rate control at the control terminal of the first transistor.
2. The circuit of claim 1 , further comprising a first diode having a cathode coupled to the control terminal of the first transistor, and an anode coupled at an intermediate node that is coupled between the current path of the first transistor and the current path of the second transistor.
3. The circuit of claim 1 , further comprising a second current generator coupled between the control terminal of the first transistor and the second output terminal.
4. The circuit of claim 1 , further comprising:
a first current mirror comprising third and fourth transistors, the fourth transistor having a current path coupled between a supply line and the first output terminal; and
a second current mirror comprising fifth and sixth transistors, the sixth transistor having a current path coupled between the first output terminal and the second output terminal, wherein a current path of the third transistor is coupled to the current path of the first transistor.
5. The circuit of claim 4 , further comprising a seventh transistor having a current path coupled between the current path of the third transistor and a current path of the fifth transistor.
6. The circuit of claim 5 , further comprising an eighth transistor having a current path coupled between the supply line and a control terminal of the fifth transistor.
7. The circuit of claim 4 , further comprising:
a seventh transistor having a current path coupled to the supply line; and
a first diode coupled between a control terminal of the seventh transistor and the second output terminal.
8. A circuit comprising:
a first output terminal configured to be coupled to a control terminal of a power transistor;
a second output terminal configured to be coupled to a conduction terminal of the power transistor;
a first current generator;
a transconductance amplifier comprising:
a first transistor having a control terminal coupled to the first current generator, and
a second transistor having a current path coupled between a current path of the first transistor and the first output terminal, and a control terminal coupled to the control terminal of the first transistor;
a capacitor coupled between the control terminal of the first transistor and the second output terminal;
a third transistor having a current path coupled between the first output terminal and the second output terminal;
a fourth transistor having a current path coupled to the second output terminal;
a first switch coupled between a control terminal of the third transistor and a control terminal of the fourth transistor;
a fifth transistor having a current path coupled to a supply line;
a sixth transistor having a current path coupled between the supply line and the first output terminal;
a second switch coupled between a control terminal of the fifth transistor and a control terminal of the sixth transistor; and
a control circuit, wherein the transconductance amplifier is configured to receive an input voltage alternating between on and off phases across the capacitor, and produce a regulated output voltage at the first output terminal with respect to the second output terminal based on the input voltage, wherein the control circuit is configured to turn off the first and second switches during standby phases that are interleaved between the on and off phases, and wherein the first current generator is configured to provide slew rate control at the control terminal of the first transistor.
9. The circuit of claim 8 , further comprising:
a third switch coupled between the control terminal of the third transistor and the second output terminal; and
a fourth switch coupled between the supply line and the control terminal of the sixth transistor.
10. The circuit of claim 9 , further comprising:
a seventh transistor having a current path coupled to the second output terminal;
a fifth switch coupled between a control terminal of the seventh transistor and the control terminal of the third transistor;
an eighth transistor having a current path coupled to the second output terminal; and
a sixth switch coupled between the current path of the eighth transistor and the control terminal of the sixth transistor.
11. The circuit of claim 10 , further comprising a comparator having a first input coupled to the first output terminal, and a second input coupled to the current path of the eighth transistor.
12. The circuit of claim 8 , further comprising a sensor coupled to the current path of the fourth transistor and to the current path of the fifth transistor, the sensor configured to sense the regulated output voltage and to generate an error signal at a sensor node indicative of an error between the input voltage and the regulated output voltage.
13. The circuit of claim 12 , wherein the sensor node is coupled to the current path of the first transistor.
14. The circuit of claim 8 , further comprising a first diode having a cathode coupled to the control terminal of the first transistor, and an anode coupled at an intermediate node that is coupled between the current path of the first transistor and the current path of the second transistor.
15. The circuit of claim 8 , further comprising a second current generator coupled between the control terminal of the first transistor and the second output terminal.
16. The circuit of claim 8 , further comprising:
a seventh transistor having a current path coupled to the supply line; and
a first diode coupled between a control terminal of the seventh transistor and the second output terminal.
17. The circuit of claim 16 , further comprising a bipolar transistor coupled between the control terminal of the seventh transistor and the first diode.
18. A method of operating a driver having a first output terminal coupled to a control terminal of a power transistor, and a second output terminals coupled to a first conduction terminal of the power transistor, the method comprising:
receiving an input voltage across a capacitor, wherein the capacitor has a first terminal coupled to a first input of a transconductance amplifier of the driver and a second terminal coupled to the second output terminal, wherein the input voltage alternates between on and off phases;
producing a regulated output voltage between the control terminal of the power transistor and the first conduction terminal of the power transistor based on the input voltage with the transconductance amplifier; and
selectively controlling a slew rate at the first input of the transconductance amplifier during the alternate on and off phases of the input voltage with first and second current generators, wherein the first current generator is coupled between the first input of the transconductance amplifier and a voltage supply terminal, wherein the second current generator is coupled between the first input of the transconductance amplifier and the second output terminal, and wherein selectively controlling the slew rate at the first input of the transconductance amplifier comprises:
during the on phase,
generating a first slew rate for a first time duration,
generating a second slew rate for a second time duration, wherein the second slew rate is different from the first slew rate, and
generating a third slew rate for a third time duration, wherein the third slew rate is different from the second slew rate, and
during the off phase,
generating a fourth slew rate for a fourth time duration,
generating a fifth slew rate for a fifth time duration, wherein the fifth slew rate is different from the fourth slew rate, and
generating a sixth slew rate for a sixth time duration, wherein the sixth slew rate is different from the fifth slew rate.
19. The method of claim 18 , wherein:
the first time duration is equal to the fourth time duration;
the second time duration is equal to the fifth time duration; and
the third time duration is equal to the sixth time duration.
20. The method of claim 18 , wherein:
the first slew rate has positive slope;
the second slew rate has negative slope; and
the third slew rate has positive slope.
21. The method of claim 18 , wherein:
the fourth slew rate has negative slope;
the fifth slew rate has positive slope; and
the sixth slew rate has negative slope.