High precision DC-DC converter

• US 5,534,771 A
• Filed: 01/21/1994
• Issued: 07/09/1996
• Est. Priority Date: 01/21/1994
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Massie, Harold L.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): HAN, YOUNGHUIE JESSICA
• Application Number:
  US08/184,387
• Time in Patent Office: 900 Days
• Field of Search: 323/282, 323/283, 323/284, 323/285, 323/286, 323/351
• US Class Current: 323/285
• CPC Class Codes: G05F 1/44 semiconductor devices only
• CPC Class Codes: H02M 3/155 using semiconductor devices only
• CPC Class Codes: H03K 17/04123 in field-effect transistor switches
• CPC Class Codes: H03K 17/063 in field-effect transistor switches

Abstract

A high precision DC-DC converter circuit having improved efficiency is disclosed. The DC-DC converter circuit includes a low accuracy switching regulator circuit for driving a switching field effect transistor (FET) on and off. A high accuracy output voltage regulator circuit is inserted into the feedback loop between the output of the DC-DC converter circuit and the sensing input of the switching regulator circuit such that the accuracy of the output voltage regulator circuit primarily determines the precision of the DC-DC converter. The DC-DC converter also includes a quick shut-off circuit coupled to the gate and source of the FET for driving the gate of the FET negative when the FET is switched off such that switching losses are minimized. A second embodiment of the high precision DC-DC converter is used to convert from 5.0 to 3.3 volts. The second embodiment includes a transformer, one winding of which is used as an output inductor. The second winding is used as part of a multiplying bootstrap circuit that approximately triples the 5.0 volt input voltage to drive the gate of an n-channel switching FET. The second embodiment also includes a circuit for extending the duty cycle of the switching regulator in response to a load transient on the output.

Claims

1. A high precision DC-DC converter circuit for converting a direct current (DC) input voltage VDD to a DC output voltage VCC having a first accuracy level, the circuit comprising:

a switching transistor coupled to VDD, the switching transistor including an input and a first output;

a switching regulator circuit coupled to the input of the switching transistor for driving the switching transistor on and off according to a sensed voltage level such that VDD is coupled to the first output when the switching transistor is on, wherein the switching regulator circuit compares the sensed voltage level to a first setpoint reference voltage level having a second accuracy level to determine a duty cycle for driving the switching transistor;

an output circuit coupled to the first output, the output circuit including a second output, the output circuit for generating a first voltage level at the second output in response to VDD being coupled and uncoupled from the first output; and

an output voltage regulator circuit coupled to the second output and the switching regulator circuit, the output voltage regulator circuit for causing the switching regulator circuit to vary the duty cycle by controlling the sensed voltage such that the first voltage level is equal to VCC at the first accuracy level, the output voltage regulator for generating the sensed voltage level in response to comparing the first voltage level to a second internal setpoint reference voltage level having a third accuracy level that is more precise than the first and second accuracy levels.

2. The DC-DC converter circuit of claim 1, wherein the switching regulator circuit further includes a quick shut-off circuit coupled to the input of the switching transistor, the quick shut-off circuit for driving a third voltage level on the input such that switching losses are minimized.

3. The DC-DC converter circuit of claim 1, wherein the DC-DC converter further includes a voltage tracking circuit coupled to the second output, the output voltage regulator circuit, and a system voltage level SVCC, the voltage tracking circuit for reducing the first voltage level if the first voltage level exceeds SVCC by a predetermined amount.

4. A high precision DC-DC converter circuit for converting a direct current (DC) input voltage VDD to a DC output voltage VCC having a first accuracy level, the circuit comprising:

a switching transistor coupled to VDD, the switching transistor including an input and a first output;

a switching regulator circuit coupled to the input of the switching transistor for driving the switching transistor on and off according to a sensed voltage level such that VDD is coupled to the first output when the switching transistor is on, wherein the switching regulator circuit compares the sensed voltage level to a first setpoint reference voltage level having a second accuracy level to determine a duty cycle for driving the switching transistor, the switching regulator circuit further including;

a switching regulator coupled to the sensed voltage level and including a third output, the switching regulator for generating a plurality of pulses having a second voltage level on the third output; and

a bootstrap circuit coupled to the third output and to the input, the bootstrap circuit for pulling up the second voltage level such that the switching transistor operates in a saturation range when switched on;

an output circuit coupled to the first output, the output circuit including a second output, the output circuit for generating a first voltage level at the second output in response to VDD being coupled and uncoupled from the first output, the output circuit further including

a transformer having a primary winding and a secondary winding, the primary and secondary windings being coupled to the first output, the secondary winding being coupled to the bootstrap circuit; and

an output voltage regulator circuit coupled to the second output and the switching regulator circuit, the output voltage regulator circuit for causing the switching regulator circuit to vary the duty cycle by controlling the sensed voltage such that the first voltage level is equal to VCC at the first accuracy level, the output voltage regulator for generating the sensed voltage level in response to comparing the first voltage level to a second internal setpoint reference voltage level having a third accuracy level that is more precise than the first and second accuracy levels.

5. The DC-DC converter circuit of claim 4, wherein the DC-DC converter circuit further includes a simulated minimum load circuit comprising a plurality of resistors coupled to the second output, the simulated minimum load circuit for sinking a predetermined minimum of current such that the transformer continues operation and the DC-DC converter maintains a regulated output.

6. The DC-DC converter circuit of claim 4, wherein the DC-DC converter circuit further includes a simulated minimum load circuit coupled to the bootstrap circuit, the simulated minimum load circuit providing voltage to the bootstrap circuit such that the bootstrap circuit drives switching transistor normally when no minimum load is present on the second output.

7. The DC-DC converter circuit of claim 4, wherein the DC-DC converter further includes a duty cycle extender circuit coupled to the switching regulator circuit, the duty cycle extender circuit for extending the duty cycle of the switching regulator circuit beyond a predefined maximum duty cycle.

8. The DC-DC converter circuit of claim 4, wherein the switching regulator circuit further includes a quick shut-off circuit coupled to the input of the switching transistor, the quick shut-off circuit for driving a third voltage level on the input such that switching losses are minimized.

9. A computer system comprising:

a power supply for outputting a nominal direct current (DC) voltage VDD at a first accuracy level;

a plurality of components coupled to the power supply, each of the components using a system operating voltage SVCC as its operating voltage;

a processor coupled to at least one of the plurality of components, the processor requiring a DC voltage of VCC at a second accuracy level as its operating voltage; and

a high precision DC-DC converter circuit coupled to the power supply and the processor, the DC-DC converter circuit for converting the DC voltage VDD to the DC voltage VCC at the second accuracy level, the DC-DC converter circuit further including;

a switching transistor coupled to VDD, the switching transistor including an input and a first output;

a switching regulator circuit coupled to the input of the switching transistor for driving the switching transistor on and off according to a sensed voltage level such that VDD is coupled to the first output when the switching transistor is on, wherein the switching regulator circuit compares the sensed voltage level to a first setpoint reference voltage level having a second accuracy level to determine a duty cycle for driving the switching transistor;

an output circuit coupled to the first output, the output circuit including a second output, the output circuit for generating a first voltage level at the second output in response to VDD being coupled and uncoupled from the first output; and

an output voltage regulator circuit coupled to the second output and the switching regulator circuit, the output voltage regulator circuit for causing the switching regulator circuit to vary the duty cycle by controlling the sensed voltage such that the first voltage level is equal to VCC at the first accuracy level, the output voltage regulator for generating the sensed voltage level in response to comparing the first voltage level to a second internal setpoint reference voltage level having a third accuracy level that is more precise than the first and second accuracy levels.

10. The computer system of claim 9, wherein the switching regulator circuit further includes a quick shut-off circuit coupled to the input of the switching transistor, the quick shut-off circuit for driving a third voltage level on the input such that switching losses are minimized.

11. The computer system of claim 9, wherein the DC-DC converter further includes a voltage tracking circuit coupled to the second output, the output voltage regulator circuit, and a system voltage level SVCC, the voltage tracking circuit for reducing the first voltage level if the first voltage level exceeds SVCC by a predetermined amount.

12. The computer system of claim 11, wherein the processor is a Pentium™

microprocessor manufactured by Intel Corporation of Santa Clara, Calif.

13. A computer system comprising:

a power supply for outputting a nominal direct current (DC) voltage VDD at a first accuracy level;

a plurality of components coupled to the power supply, each of the components using a system operating voltage SVCC as its operating voltage;

a processor coupled to at least one of the plurality of components, the processor requiring a DC voltage of VCC at a second accuracy level as its operating voltage; and

a high precision DC-DC converter circuit coupled to the power supply and the processor, the DC-DC converter circuit for converting the DC voltage VDD to the DC voltage VCC at the second accuracy level, the DC-DC converter circuit further including;

a switching transistor coupled to VDD, the switching transistor including an input and a first output;

a switching regulator circuit coupled to the input of the switching transistor for driving the switching transistor on and off according to a sensed voltage level such that VDD is coupled to the first output when the switching transistor is on, wherein the switching regulator circuit compares the sensed voltage level to a first setpoint reference voltage level having a second accuracy level to determine a duty cycle for driving the switching transistor, the switching regulator circuit further including;

a switching regulator coupled to the sensed voltage level and including a third output, the switching regulator for generating a plurality of having a second voltage level on the third output; and

a bootstrap circuit coupled to the third output and to the input, the bootstrap circuit for pulling up the second voltage level such that the switching transistor operates in a saturation range when switched on;

an output circuit coupled to the first output, the output circuit including a second output, the output circuit for generating a first voltage level at the second output in response to VDD being coupled and uncoupled from the first output, the output circuit further including

a transformer having a primary winding and a secondary winding, the primary and secondary windings being coupled to the first output, the secondary winding being coupled to the bootstrap circuit; and

an output voltage regulator circuit coupled to the second output and the switching regulator circuit, the output voltage regulator circuit fox causing the switching regulator circuit to vary the duty cycle by controlling the sensed voltage such that the first voltage level is equal to VCC at the first accuracy level, the output voltage regulator for generating the sensed voltage level in response to comparing the first voltage level to a second internal setpoint reference voltage level having a third accuracy level that is more precise than the first and second accuracy levels.

14. The DC-DC converter circuit of claim 13, wherein the DC-DC converter circuit further includes a simulated minimum load circuit comprising a plurality of resistors coupled to the second output, the simulated minimum load circuit for sinking a predetermined minimum of current such that the transformer continues operation and the DC-DC converter maintains a regulated output.

15. The DC-DC converter circuit of claim 13, wherein the DC-DC converter circuit further includes a simulated minimum load circuit coupled to the bootstrap circuit, the simulated minimum load circuit providing voltage to the bootstrap circuit such that the bootstrap circuit drives the gate of the switching transistor normally when no minimum load is present on the second output.

16. The DC-DC converter circuit of claim 13, wherein the DC-DC converter further includes a duty cycle extender circuit coupled to the switching regulator circuit, the duty cycle extender circuit for extending the duty cycle of the switching regulator circuit beyond a predetermined maximum duty cycle.

17. The DC-DC converter circuit of claim 13, wherein the switching regulator circuit further includes a quick shut-off circuit coupled to the input of the switching transistor, the quick shut-off circuit for driving a third voltage level on the input such that switching losses are minimized.

18. A method for converting a direct current (DC) input voltage VDD into a DC output voltage VCC having a first accuracy level, the method comprising the steps of:

providing a switching transistor;

switching the switching transistor on and off to produce an output voltage level equal to VDD multiplied by a duty cycle, the duty cycle being a percentage of time that the switching transistor is turned on;

varying the duty cycle of the switching transistor in response to a comparison of a sensed voltage level to a first setpoint reference voltage having a second accuracy level;

sensing the output voltage level; and

generating the sensed voltage level in response to a comparison of the output voltage level to a second setpoint reference voltage having a third accuracy level that is more precise than the first and second accuracy levels such that the output voltage level is VCC within the first accuracy level.

19. The method according to claim 18, wherein the method further includes the step of:

driving a negative voltage on an input of the switching transistor such that the switching transistor switches off quickly, reducing switching losses.

20. The method according to claim 18, wherein the method further includes the step of:

reducing the output voltage level if the output voltage level exceeds a system operating voltage level SVCC by a predetermined amount.

21. A method for converting a direct current (DC) input voltage VDD into a DC output voltage VCC having a first accuracy level, the method comprising the steps of:

providing a switching transistor;

switching the switching transistor on and off to produce an output voltage level equal to VDD multiplied by a duty cycle, the duty cycle being a percentage of time that the switching transistor is turned on;

varying the duty cycle of the switching transistor in response to a comparison of a sensed voltage level to a first setpoint reference voltage having a second accuracy level;

sensing the output voltage level;

generating the sensed voltage level in response to a comparison of the output voltage level to a second setpoint reference voltage having a third accuracy level that is more precise than the first and second accuracy levels such that the output voltage level is VCC within the first accuracy level; and

extending the duty cycle of the switching transistor beyond a predetermined maximum duty cycle if a load increases such that extension of the duty cycle is necessary to provide sufficient power.

22. The method according to claim 21, wherein the method further includes the step of:

driving a negative voltage on an input of the switching transistor such that the switching transistor switches off quickly, reducing switching losses.

23. The method according to claim 21, wherein the method further includes the step of:

simulating the load when the load is less than a predetermined minimum.

24. A high precision DC-DC converter circuit for converting a direct current (DC) input voltage VDD to a DC output voltage VCC having a first accuracy level, the circuit comprising:

a switching transistor;

means for switching the switching transistor on and off to produce an output voltage level equal to VDD multiplied by a duty cycle, the duty cycle being a percentage of time that the switching transistor is turned on;

means for varying the duty cycle of the switching transistor in response to a comparison of a sensed voltage level to a first setpoint reference voltage having a second accuracy level;

means for sensing the output voltage level; and

means for generating the sensed voltage level in response to a comparison of the output voltage level to a second setpoint reference voltage having a third accuracy level that is more precise than the first and second accuracy levels such that the output voltage level is VCC within the first accuracy level.

25. The DC-DC converter circuit of claim 24, further including:

means for driving a negative voltage on an input of the switching transistor such that the switching transistor switches off quickly, reducing switching losses.

26. The DC-DC converter circuit of claim 24, further including:

means for reducing the output voltage level if the output voltage level exceeds a system operating voltage level SVCC by a predetermined amount.

27. A high precision DC-DC converter circuit for converting a direct current (DC) input voltage VDD to a DC output voltage VCC having a first accuracy level, the circuit comprising:

;

a switching transistor;

means for switching the switching transistor on and off to produce an output voltage level equal to VDD multiplied by a duty cycle, the duty cycle being a percentage of time that the switching transistor is turned on;

means for varying the duty cycle of the switching transistor in response to a comparison of a sensed voltage level to a first setpoint reference voltage having a second accuracy level;

means for sensing the output voltage level;

means for generating the sensed voltage level in response to a comparison of the output voltage level to a second setpoint reference voltage having a third accuracy level that is more precise than the first and second accuracy levels such that the output voltage level is VCC within the first accuracy level; and

means for extending the duty cycle of the switching transistor beyond a predetermined maximum duty cycle if a load increases such that extension of the duty cycle is necessary to provide sufficient power.

28. The DC-DC converter circuit of claim 27, further including:

means for driving a negative voltage on an input of the switching transistor such that the switching transistor switches off quickly, reducing switching losses.

29. The DC-DC converter circuit of claim 27, further including:

means for simulating the load when the load is less than a predetermined minimum.

30. A computer system comprising:

a power supply for outputting a nominal direct current (DC) voltage VDD at a first accuracy level;

an integrated circuit coupled to at least one of the plurality of components, the integrated circuit requiring a DC voltage of VCC at a second accuracy level as its operating voltage; and

a high precision DC-DC converter circuit coupled to the power supply and the integrated circuit, the DC-DC converter circuit for converting the DC voltage VDD to the DC voltage VCC at the second accuracy level, the DC-DC converter circuit further including;

a switching transistor;

means for switching the switching transistor on and off to produce an output voltage level equal to VDD multiplied by a duty cycle, the duty cycle being a percentage of time that the switching transistor is turned on;

means for varying the duty cycle of the switching transistor in response to a comparison of a sensed voltage level to a first setpoint reference voltage having a second accuracy level;

means for sensing the output voltage level; and

means for generating the sensed voltage level in response to a comparison of the output voltage level to a second setpoint reference voltage having a third accuracy level that is more precise than the first and second accuracy levels such that the output voltage level is VCC within the first accuracy level.

31. The computer system of claim 30, further including:

means for driving a negative voltage on an input of the switching transistor such that the switching transistor switches off quickly, reducing switching losses.

32. The computer system of claim 30, further including:

means for reducing the output voltage level if the output voltage level exceeds a system operating voltage level SVCC by a predetermined amount.

33. A computer system comprising:

a power supply for outputting a nominal direct current (DC) voltage VDD at a first accuracy level;

an integrated circuit coupled to at least one of the plurality of components, the integrated circuit requiring a DC voltage of VCC at a second accuracy level as its operating voltage; and

a high precision DC-DC converter circuit coupled to the power supply and the integrated circuit, the DC-DC converter circuit for converting the DC voltage VDD to the DC voltage VCC at the second accuracy level, the DC-DC converter circuit further including;

a switching transistor;

means for switching the switching transistor on and off to produce an output voltage level equal to VDD multiplied by a duty cycle, the duty cycle being a percentage of time that the switching transistor is turned on;

means for varying the duty cycle of the switching transistor in response to a comparison of a sensed voltage level to a first setpoint reference voltage having a second accuracy level;

means for sensing the output voltage level;

means for generating the sensed voltage level in response to a comparison of the output voltage level to a second setpoint reference voltage having a third accuracy level that is more precise than the first and second accuracy levels such that the output voltage level is VCC within the first accuracy level; and

means for extending the duty cycle of the switching transistor beyond a predetermined maximum duty cycle if a load increases such that extension of the duty cycle is necessary to provide sufficient power.

34. The computer system of claim 33, further including:

means for driving a negative voltage on an input of the switching transistor such that the switching transistor switches off quickly, reducing switching losses.

35. The computer system of claim 33, further including:

means for simulating the load when the load is less than a predetermined minimum.