Droop circuits and multi-phase DC-DC converters
A droop circuit of a DC-DC converter is provided, wherein the DC-DC converter includes an output inductor coupled between an output of the DC-DC converter and a phase node for providing an output voltage. A current sense device is coupled between the phase node and the output of the DC-DC converter, includes an inductor coupled to the phase node and senses a current from the phase node. A first resistor is coupled to the current sense device. An amplifier circuit includes an amplifier having an inverting input, a non-inverting input coupled to the first resistor and an output directly connected to the inverting input, and a second resistor coupled between the inverting input and the output of the DC-DC converter. The amplifier circuit provides a droop current according to the second resistor and a voltage difference between the non-inverting input and the output of the DC-DC converter, and the voltage difference is related to the current.
1. A droop circuit for a DC-DC converter, comprising:
a current sense device coupled between a phase node and an output of the DC-DC converter, comprising an inductor coupled to the phase node and sensing a current from the phase node;
a first resistor coupled to the current sense device; and
an amplifier circuit comprising:
an amplifier having an inverting input, a non-inverting input coupled to the first resistor and an output directly connected to the inverting input; and
a second resistor coupled between the inverting input and the output of the DC-DC converter,
wherein the amplifier circuit provides a droop current according to the second resistor and a voltage difference between the non-inverting input and the output of the DC-DC converter, and the voltage difference is related to the current.
2. The droop circuit as claimed in claim 1 , wherein the current sense device comprises:
a third resistor coupled between the inductor and the output of the DC-DC converter;
a capacitor coupled between the output of the DC-DC converter and the first resistor; and
a fourth resistor coupled between the phase node and the first resistor.
3. The droop circuit as claimed in claim 1 , further comprising a capacitor coupled between the non-inverting input and the DC-DC converter output.
4. The droop circuit as claimed in claim 3 , wherein the current sense device comprises a third resistor coupled between the inductor and the output of the DC-DC converter.
5. The droop circuit as claimed in claim 4 , further comprising a resistor network coupled between the first resistor and the non-inverting input for adjusting an R-C time constant to generate the droop current.
6. The droop circuit as claimed in claim 4 , further comprising a resistor network coupled between the DC-DC converter output and the non-inverting input for adjusting an R-C time constant to generate the droop current.
7. A multi-phase DC-DC converter, comprising:
a plurality of switching sets for generating an output voltage at a first output, wherein each switching set comprises a phase node and receives a pulse width modulation signal to generate the output voltage;
a pulse width modulation circuit for providing the pulse width modulation signals according to the output voltage and a droop current; and
a droop circuit for providing the droop current, comprising:
a plurality of current sense devices respectively coupled between the phase nodes and the first output, wherein each current sense device comprises an inductor and senses a current from the corresponding phase node;
a plurality of first resistors respectively coupled to the current sense devices; and
an amplifier circuit comprising:
an amplifier having an inverting input, a non-inverting input coupled to the first resistors and a second output directly connected to the inverting input; and
a second resistor coupled between the inverting input and the first output,
wherein the amplifier circuit provides the droop current according to the second resistor and a voltage difference between the non-inverting input and the first output, and the voltage difference is related to an average of the currents.
8. The multi-phase DC-DC converter as claimed in claim 7 , wherein the current sense device comprises:
a third resistor coupled between the inductor and the first output;
a capacitor coupled between the first output and the first resistor; and
a fourth resistor coupled between the phase node and the first resistor.
9. The multi-phase DC-DC converter as claimed in claim 7 , further comprising a capacitor coupled between the non-inverting input and the first output.
10. The multi-phase DC-DC converter as claimed in claim 9 , wherein the current sense device comprises a third resistor coupled between the inductor and the first output.
11. The multi-phase DC-DC converter as claimed in claim 10 , further comprising a fourth resistor coupled between the first resistors and the non-inverting input for adjusting an R-C time constant to generate the droop current.
12. The multi-phase DC-DC converter as claimed in claim 10 , further comprising a resistor network coupled between the first output and the non-inverting input for adjusting an R-C time constant to generate the droop current.