Multi-phase switching regulator

• US RE39,976 E1
• Filed: 01/26/2006
• Issued: 01/01/2008
• Est. Priority Date: 11/26/2001
• Status: Expired due to Term

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Redl, Richard, Buxton, Joseph C., Schiff, Tod F.
• Primary Examiner(s): VU, BAO Q
• Application Number:
  US11/342,235
• Time in Patent Office: 705 Days
• Field of Search: 323/222, 323/224, 323/285, 323/282
• US Class Current: 323/285
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel

Abstract

An N-phase switching voltage regulator includes N current sensing elements which carry respective phase currents. The voltages present at the switch node sides of the sensing elements are summed and presented to an amplifier which also receives the regulator'"'"'s output voltage, to produce an output which is proportional to the regulator'"'"'s total output current I_out. The invention also provides a means for direct insertion of total inductor output current information into a regulator'"'"'s voltage-mode control loop, to provide active voltage positioning (AVP) for the output voltage. A voltage based on total inductor output current is summed with the regulator'"'"'s reference voltage; this sum and V_out are applied to the voltage control error amplifier, the output of which is processed to operate the regulator'"'"'s switches. This enables the regulator'"'"'s output to have a desired droop impedance and to provide AVP of V_out as a function of total filtered inductor output current I_out(fltr).

Claims

1. A total current circuit for an N-phase switching regulator which provides an output voltage V_out at an output terminal and which includes N output inductors carrying respective phase currents which are summed together to provide a total instantaneous inductor output current I_out to a load connected to said output terminal, said total current circuit comprising:

N current sensing elements which carry respective ones of said phase currents, each of said elements having a switch node side and an output side, said elements'"'"' output sides connected to said regulator'"'"'s output terminal,

a summing circuit which sums the voltages present at the switch node sides of said sensing elements and provides said summed voltages at a summing node, and

an amplifier circuit which is connected to said summing node at a first input and to said output terminal at a second input and is arranged to produce an output voltage V_cs which is proportional to I_out.

2. The total current circuit of claim 1, wherein said summing circuit comprises N summing resistors, each of which is connected at one end to the switch node side of a respective one of said current sensing elements and is connected at its other end to said summing node.

3. The total current circuit of claim 1, wherein said N current sensing elements are said N output inductors.

4. The total current circuit of claim 1, wherein said N current sensing elements are N current sense resistors connected between respective ones of said N output inductors and said output terminal and said summing circuit sums the voltages present at the output inductor sides of said current sense resistors.

5. The total current circuit of claim 1, wherein said amplifier circuit comprises:

an operational amplifier, said first and second inputs being said op amp'"'"'s inverting and non-inverting inputs, respectively, and

a feedback resistor having a resistance R_cs connected between said op amp'"'"'s output and said inverting input which sets the gain of said op amp.

6. The total current circuit of claim 5, wherein said N current sensing elements are said N output inductors, each of which has a first temperature coefficient t_c, said feedback resistor R_cs having a second temperature coefficient which is approximately equal to −

t_c.

7. The total current circuit of claim 5, wherein each of said N output inductors has an inductance L and a resistance R₁ and said summing circuit comprises N summing resistors, each of which has a resistance R_p, is connected at one end to the switch node side of a respective one of said output inductors, and is connected at its other end to said summing node,

further comprising a filter capacitor having a capacitance C_cs connected across said feedback resistor, such that the output voltage V_cs of said op amp is given by:

$V_{\mathrm{cs}}=V_{\mathrm{out}}-\frac{R_{\mathrm{cs}}<br><br>R_i<br><br>\left(1+s<br><br>\frac{L}{R_i}\right)}{R_p<br><br>\left(1+{\mathrm{sC}}_{\mathrm{cs}}<br><br>R_{\mathrm{cs}}\right)}<br><br>\stackrel{\text{\hspace{1em}<br><br>}}{I_{\mathrm{out}}.}$

8. The total current circuit of claim 7, wherein each of said N inductors has a time constant L/R₁ and the product C_csR_cs is made substantially equal to L/R₁ such that the output voltage V_cs of said op amp is given by:

$V_{\mathrm{cs}}=V_{\mathrm{out}}-\frac{R_i<br><br>R_{\mathrm{cs}}}{R_p}<br><br>\stackrel{\text{\hspace{1em}<br><br>}}{I_{\mathrm{out}}.}$

9. The total current circuit of claim 1, further comprising a subtractor circuit which subtracts said output voltage V_out from V_cs.

10. A total current circuit for an N-phase switching regulator which provides an output voltage V_out at an output terminal and which includes N output inductors carrying respective phase currents, each of said inductors having a switch node side and an output side, said output sides connected together at said output terminal such that said phase currents are summed together to provide a total instantaneous inductor output current I_out to a load connected to said output terminal, comprising:

N summing resistors, each of which is connected at one end to the switch node side of a respective one of said output inductors and is connected at its other end to a summing node,

an operational amplifier which is connected to said summing node at its inverting input and to said regulator'"'"'s output terminal at its non-inverting input,

a feedback resistor having a resistance R_cs connected between said op amp'"'"'s output and said inverting input which sets the gain of said op amp, and

a filter capacitor having a capacitance C_cs connected across said feedback resistor,

wherein each of said N summing resistors has a resistance R_p, and each of said N output inductors has an inductance L and a resistance R₁, such that the output voltage V_cs of said op amp is given by;

$V_{\mathrm{cs}}=V_{\mathrm{out}}-\frac{R_{\mathrm{cs}}<br><br>R_i<br><br>\left(1+s<br><br>\frac{L}{R_i}\right)}{R_p<br><br>\left(1+{\mathrm{sC}}_{\mathrm{cs}}<br><br>R_{\mathrm{cs}}\right)}<br><br>\stackrel{\text{\hspace{1em}<br><br>}}{I_{\mathrm{out}}.}$

11. The total current circuit of claim 10, wherein each of said N inductors has a time constant L/R₁ and the product C_csR_cs is made substantially equal to L/R₁ such that the output voltage V_cs of said op amp is given by:

$V_{\mathrm{cs}}=V_{\mathrm{out}}-\frac{R_i<br><br>R_{\mathrm{cs}}}{R_p}<br><br>\stackrel{\text{\hspace{1em}<br><br>}}{I_{\mathrm{out}}.}$

12. The total current circuit of claim 10, wherein each of said output inductors has a first temperature coefficient t_c and said feedback resistor R_cs has a second temperature coefficient which is approximately equal to −

t_c.

13. A voltage-mode control loop for providing adaptive voltage positioning (AVP) of the output voltage V_out of an N-phase switching regulator which provides V_out at an output terminal and which includes N output inductors, each of which is connected between a respective one of N switching elements and said output terminal and carries a respective phase current, said phase currents summed together to provide a total instantaneous inductor output current I_out to a load connected to said output terminal, comprising:

a control circuit which operates said switching elements in response to a voltage V_err,

a total current circuit which produces an output voltage V_droop which varies with said total instantaneous inductor output current I_out,

a voltage V_ref which represents a desired output voltage for said regulator,

a summation circuit arranged to produce an output voltage V_set which is given by;

V_set=V_ref+V_droop, and

a voltage control error amplifier circuit which receives a signal which varies with V_out at a first input and V_set at a second input and which produces an output which varies with the difference between said first and second inputs, said output being said voltage V_err,

said control circuit, said total current circuit, said summation circuit, and said voltage control error amplifier circuit arranged such that the output of said regulator has a desired droop impedance R_o to provide AVP of V_out as a function of the total instantaneous inductor output current after it has been filtered to remove its ripple component (I_out(fltr)).

14. The voltage-mode control loop of claim 13, wherein said control circuit, said total current circuit, said summation circuit, and said voltage control error amplifier circuit are arranged such that V_out is given by:

V_out=V_ref−

I_out(fltr)R_o.

15. The voltage-mode control loop of claim 13, wherein said total current circuit comprises:

N current sensing elements which carry respective ones of said phase currents, each of said sensing elements having a switch node side and an output side, said elements'"'"' output sides connected to said regulator'"'"'s output terminal,

a summing circuit which sums the voltages present at the switch node sides of said sensing elements and provides said summed voltages at a summing node,

an amplifier circuit which is connected to said summing node at a first input and to said output terminal at a second input and is arranged to produce an output voltage V_cs which is proportional to I_o, and

a subtractor circuit which subtracts said output voltage V_out from V_cs to produce V_droop.

16. The voltage-mode control loop of claim 15, wherein each of said N output inductors has an inductance L and a resistance R₁ and a time constant L/R₁, said summing circuit comprising N summing resistors, each of which has a resistance R_p, is connected at one end to the switch node side of a respective one of said current sensing elements, and is connected at its other end of said summing node,

further comprising a filter capacitor having a capacitance C_cs connected across said feedback resistor, the product C_csR_cs made substantially equal to L/R₁ such that the output voltage V_droop of said total current circuit is given by:

$V_{\mathrm{droop}}=\frac{R_i<br><br>R_{\mathrm{cs}}}{R_p}<br><br>\stackrel{\text{\hspace{1em}<br><br>}}{I_{\mathrm{out}}}=R_o<br><br>I_{\mathrm{out}},$

and

V_out=V_ref−

I_out(fltr)R_o.

17. The voltage-mode control loop of claim 16 13, wherein said voltage control error amplifier circuit comprises:

an operational amplifier,

a resistor having a resistance R_b connected between said op amp'"'"'s inverting input and V_out, and

a current source providing a current I_fb to said op amp'"'"'s inverting input, said resistance R_b and current I_fb arranged to set said regulator'"'"'s no-load offset voltage from V_ref such that V_out=V_ref−

I_out(fltr)R_o−

I_fbR_b.

18. The voltage-mode control loop of claim 13, wherein said voltage control error amplifier circuit comprises an operational amplifier.

19. The voltage-mode control loop of claim 18, wherein said voltage control error amplifier circuit further comprises a compensation network connected between said op amp'"'"'s output and its inverting input.

20. The voltage-mode control loop of claim 18, further comprising:

a resistor having a resistance R_b connected between said op amp'"'"'s inverting input and V_out, and

a current source providing a current I_fb to said op amp'"'"'s inverting input, said resistance R_b and current I_fb arranged to set said regulator'"'"'s no-load offset voltage from V_ref.

21. A voltage-mode control loop for providing adaptive voltage positioning (AVP) of the output voltage V_out of an N-phase switching regulator which provides V_out at an output terminal and which includes N output inductors, each of which is connected between a respective one of N switching elements and said output terminal and carries a respective phase current, said phase currents summed together to provide a total instantaneous inductor output current I_out to a load connected to said output terminal, comprising:

a control circuit which operates said switching elements in response to a voltage V_err,

a total current circuit which produces an output voltage V_droop which varies with said total instantaneous inductor output current I_out,

a voltage V_ref which represents a desired output voltage for said regulator,

a summation circuit arranged to produce an output voltage V_set which is given by;

V_set=V_ref+V_droop, and

a voltage control error amplifier circuit which comprises;

an operational amplifier which receives a signal which varies with V_out at its inverting input and V_set at its non-inverting input and which produces an output which varies with the difference between said inverting and non-inverting inputs, said output being said voltage V_err, and

a loop compensation network connected between said op amp'"'"'s output and its inverting input,

said control circuit, said total current circuit, said summation circuit, and said voltage control error amplifier circuit arranged such that the output of said regulator has a desired droop impedance R_o to provide AVP of V_out as a function of the total instantaneous inductor output current after it has been filtered to remove its ripple component (I_out(fltr)).

22. The voltage-mode control loop of claim 21, further comprising:

a resistor having a resistance R_b connected between said op amp'"'"'s inverting input and V_out, and

a current source providing a current I_fb to said op amp'"'"'s inverting input, said resistance R_b and current I_fb arranged to set said regulator'"'"'s no-load offset voltage from V_ref.

23. An N-phase switching regulator which provides an output voltage V_out at an output terminal and which includes N output inductors, each of which is connected between a respective one of N switching elements and said output terminal and carries a respective phase current, said phase currents summed together to provide a total instantaneous inductor output current I_out to a load connected to said output terminal, comprising:

a control circuit which operates said switching elements in response to a voltage V_err,

a total current circuit which produces an output voltage V_droop which varies with said total instantaneous inductor output current I_out, said total current circuit comprising;

N current sensing elements which carry respective ones of said phase currents, each of said sensing elements having a switch node side and an output side, said sensing elements'"'"' output sides connected to said regulator'"'"'s output terminal,

a summing circuit which sums the voltages present at the switch node sides of said sensing elements and provides said summed voltages at a summing node,

an amplifier circuit which is connected to said summing node at a first input and to said regulator'"'"'s output terminal at a second input and is arranged to produce an output voltage V_cs which is proportional to I_out, and

a subtractor circuit which subtracts said output voltage V_out from V_cs to produce V_droop,

a voltage V_ref which represents a desired output voltage for said regulator,

a summation circuit arranged to produce an output voltage V_set which is given by;

V_set=V_ref+V_droop, and

a voltage control error amplifier circuit which receives a signal which varies with V_out at a first input and V_set at a second input and which produces an output which varies with the difference between said first and second inputs, said output being said voltage V_err,

said control circuit, said total current circuit, said summation circuit, and said voltage control error amplifier circuit arranged such that the output of said regulator has a desired droop impedance R_o to provide active voltage ositioning (AVP) of V_out as a function of the total instantaneous inductor output current after it has been filtered to remove its ripple component (I_out(fltr)).

24. The switching regulator of claim 23, wherein said control circuit, said total current circuit, said summation circuit, and said voltage control error amplifier circuit are arranged such that V_out is given by:

V_out=V_ref−

I_out(fltr)R_o.

25. The switching regulator of claim 23, wherein each of said N output inductors has an inductance L, a resistance R₁, and a time constant L/R₁, said summing circuit comprising N summing resistors, each of which has a resistance R_p, is connected at one end to the switch node side of a respective one of said output inductors, and is connected at its other end to said summing node,

further comprising a filter capacitor having a capacitance C_cs connected across said feedback resistor, the product C_csR_cs made substantially equal to L/R₁ such that the output voltage V_droop of said total current circuit is given by:

$V_{\mathrm{droop}}=\frac{R_i<br><br>R_{\mathrm{cs}}}{R_p}<br><br>\stackrel{\text{\hspace{1em}<br><br>}}{I_{\mathrm{out}}}=R_o<br><br>I_{\mathrm{out}},$

and

V_out=V_ref−

I_out(fltr)R_o.

26. The switching regulator of claim 25, wherein said voltage control error amplifier circuit comprises:

an operational amplifier,

a resistor having a resistance R_b connected between said op amp'"'"'s inverting input and V_out, and

a current source providing a current I_fb to said op amp'"'"'s inverting input, said resistance R_b and current I_fb arranged to set said regulator'"'"'s no-load offset voltage from V_ref such that V_out=V_ref−

I_out(fltr)R_o−

I_fbR_b.

27. A total current circuit for an N-phase switching regulator which provides an output voltage V_out at an output terminal and which includes N output inductors carrying respective phase currents which are summed together to provide a total instantaneous inductor output current I_out to an output terminal, said total current circuit comprising:

N current sensing elements which carry respective ones of said phase currents, each of said elements having a switch node side and an output side, said elements'"'"' output sides connected to said regulator'"'"'s output terminal,

a summing circuit which sums the voltages present at the switch node sides of said sensing elements and provides said summed voltages at a summing node, and

a single amplifier circuit which is connected to said summing node at a first input and to said output terminal at a second input and is arranged to produce an output voltage V_cs which is proportional to I_out.

28. A total current circuit for an N-phase switching regulator which provides an output voltage V_out at an output terminal, said regulator phases adapted to be coupled to respective output inductors which, when so coupled, carry respective phase currents which are summed together to provide a total instantaneous inductor output current I_out to an output terminal, said total current circuit comprising:

N current sensing elements which carry respective ones of said phase currents, each of said elements having a switch node side and an output side, said elements'"'"' output sides connected to said regulator'"'"'s output terminal,

a summing circuit which sums the voltages present at the switch node sides of said sensing elements and provides said summed voltages at a summing node, and

an amplifier circuit which is connected to said summing node at a first input and to said output terminal at a second input and is arranged to produce an output voltage V_cs which is proportional to I_out.

29. A total current circuit for an N-phase switching regulator which provides an output voltage V_out at an output terminal and which includes N output inductors carrying respective phase currents which are summed together to provide a total instantaneous inductor output current I_out to an output terminal, said total current circuit comprising:

N current sensing elements which carry respective ones of said phase currents, each of said elements having a switch node side and an output side, said elements'"'"' output sides connected to said regulator'"'"'s output terminal, the switch node sides of said sensing elements adapted to be coupled to a summing circuit which, when so coupled, sums the voltages present at the switch node sides of said sensing elements at a summing node, and

an amplifier circuit which is connected to said summing node at a first input and to said output terminal at a second input and is arranged to produce an output voltage V_cs which is proportional to I_out.

30. A total current circuit for an N-phase switching regulator which provides an output voltage V_out at an output terminal and which includes N output inductors carrying respective phase currents, each of said inductors having a switch node side and an output side, said switch node sides adapted to be coupled to respective summing resistors, the other ends of which are connected together at a summing node, said output sides connected together at said output terminal such that said phase currents are summed together to provide a total instantaneous inductor output current I_out to an output terminal, comprising:

an operational amplifier which is connected to said summing node at its inverting input and to said regulator'"'"'s output terminal at its non-inverting input,

a feedback resistor having a resistance R_cs connected between said op amp'"'"'s output and said inverting input which sets the gain of said op amp, and

a filter capacitor having a capacitance C_cs connected across said feedback resistor,

wherein each of said N summing resistors has a resistance R_p, and each of said N output inductors has an inductance L and a resistance R₁, such that the output voltage V_cs of said op amp is given by;

$V_{\mathrm{cs}}=V_{\mathrm{out}}-\frac{R_{\mathrm{cs}}<br><br>R_i<br><br>\left(1+s<br><br>\frac{L}{R_i}\right)}{R_p<br><br>\left(1+{\mathrm{sC}}_{\mathrm{cs}}<br><br>R_{\mathrm{cs}}\right)}<br><br>\stackrel{\text{\hspace{1em}<br><br>}}{I_{\mathrm{out}}.}$

31. A total current circuit for an N-phase switching regulator which provides an output voltage V_out at an output terminal, said regulator phases adapted to be coupled to respective output inductors which, when so coupled, carry respective phase currents which are summed together to provide a total instantaneous inductor output current I_out to an output terminal, said total current circuit comprising:

N current sensing elements which carry respective ones of said phase currents, each of said elements having a switch node side and an output side, said elements'"'"' output sides connected to said regulator'"'"'s output terminal, the switch node sides of said sensing elements adapted to be coupled to a summing circuit which, when so coupled, sums the voltages present at the switch node sides of said sensing elements at a summing node, and

an amplifier circuit which is connected to said summing node at a first input and to said output terminal at a second input and is arranged to produce an output voltage V_cs which is proportional to I_out.

32. A total current circuit for an N-phase switching regulator which provides an output voltage V_out at an output terminal, said regulator phases adapted to be coupled to respective output inductors which, when so coupled, carry respective phase currents which are summed together to provide a total instantaneous inductor output current I_out to an output terminal, said total current circuit comprising:

N current sensing elements which carry respective ones of said phase currents, each of said elements having a switch node side and an output side, said elements'"'"' output sides connected to said regulator'"'"'s output terminal, the switch node sides of said sensing elements adapted to be coupled to a summing circuit which, when so coupled, sums the voltages present at the switch node sides of said sensing elements at a summing node, and

a single amplifier circuit which is connected to said summing node at a first input and to said output terminal at a second input and is arranged to produce an output voltage V_cs which is proportional to I_out.