Frequency control circuit for unregulated inductorless DC/DC converters

• US 6,414,863 B1
• Filed: 08/30/2001
• Issued: 07/02/2002
• Est. Priority Date: 08/30/2001
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Schmeller, Hans, Bayer, Erich-Johann
• Primary Examiner(s): Vu, Bao Q.
• Application Number:
  US09/943,482
• Time in Patent Office: 306 Days
• Field of Search: 363/59, 363/60, 363/61, 307/109, 307/110, 323/228
• US Class Current: 363/60
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps

Abstract

An unregulated inductorless direct current to direct current converter comprising a first voltage-to-current converter configured to convert a first voltage to a first current and a second voltage-to-current converter configured to convert a second voltage to a second current. A regulation circuit is coupled to the first and second voltage-to-current converters and configured to generate an output current proportional to the difference between the first and second currents. Also a variable frequency oscillator is coupled to the regulation circuit, the oscillator receiving as a control current the output current therefrom and outputting a clock signal having a frequency proportionate to the control current. The converter further comprises an output stage coupled to receive the clock signal and receiving an input voltage and outputting an output voltage, the output voltage and the input voltage having a ratio that is determined by the clock signal.

Claims

1. An unregulated inductorless direct current to direct current converter comprising:

a first voltage-to-current converter configured to convert a first voltage to a first current;

a second voltage-to-current converter configured to convert a second voltage to a second current;

a regulation circuit coupled to the first and second voltage-to-current converters and configured to generate an output current proportional to the difference between the first and second currents;

a variable frequency oscillator coupled to the regulation circuit, the oscillator receiving as a control current the output current therefrom and outputting a clock signal having a frequency proportionate to the control current; and

an output stage coupled to receive the clock signal and receiving an input voltage and outputting an output voltage, the output voltage and the input voltage having a ratio that is determined by the clock signal.

2. The converter of claim 1 wherein the first voltage is the input voltage of the output stage land the second voltage is output voltage of the output stage.

3. The converter of claim 1 wherein the first current is inverted before it is input into the regulation circuit.

4. The converter of claim 3 wherein the inverter comprises a current mirror.

5. The converter of claim 1 wherein the first voltage-to-current converter comprises:

a first transistor and a second transistor having gate nodes coupled together and source nodes tied to a ground node; and

a resistor coupled between the first transistor and an input node that receives the input voltage;

whereby the first current is proportional in magnitude to the input voltage.

6. The converter of claim 5 wherein the second voltage-to-current converter comprises:

a third transistor and a fourth transistor having gate nodes coupled together and source nodes tied to a ground node; and

a resistor coupled between the third transistor and an output node that receives the output voltage;

whereby the second current is proportional in magnitude to the output voltage.

7. The converter of claim 1 wherein the first and second voltage-to-current converters are matched converters.

8. The converter of claim 1 further comprising a maximum current source that generates a maximum current.

9. The converter of claim 8 further comprising a minimum current source that generates a minimum current.

10. The converter of claim 9 wherein the regulation circuit compares the maximum current and the control current which controls the frequency of the variable frequency oscillator to limit the control current to a value that is less than or equal to the maximum current but greater than the minimum current.

11. The converter of claim 1 wherein the regulation circuit comprises multiple transistors to control the sensitivity of the variable frequency oscillator.

12. The converter of claim 9 wherein the maximum and minimum currents define the frequency sweep range of the variable frequency oscillator.

13. A control circuit for a variable frequency oscillator comprising:

a first voltage-to-current converter configured to convert a first voltage to a first current;

a second voltage-to-current converter configured to convert a second voltage to a second current; and

a regulation circuit coupled to the first and second voltage-to-current converters and configured to generate an output current proportional to the difference between the first and second currents.

14. The circuit of claim 13 wherein the first voltage-to-current converter comprises:

a first transistor and a second transistor having gate nodes coupled together and source nodes tied to a ground node; and

a resistor coupled between the first transistor and an input node that receives the input voltage;

whereby the first current is proportional in magnitude of the input voltage.

15. The circuit of claim 13 wherein the second voltage-to-current converter comprises:

a third transistor and a fourth transistor having gate nodes coupled together and source nodes tied to a ground node; and

a resistor coupled between the third transistor and an output node that receives the output voltage;

whereby the second current is proportional in magnitude to the output voltage.

16. The circuit of claim 13 wherein the first and second voltage-to-current converters are matched converters.

17. The circuit of claim 13 wherein the regulation circuit comprises multiple transistors to control the sensitivity of the variable frequency oscillator.

18. The circuit of claim 13 further comprising an inverter that inverts the first current before the first current is input into the regulation circuit.

19. The circuit of claim 18 wherein the inverter comprises a current mirror.

20. The circuit of claim 13 further comprising a maximum current source that generates a maximum current.

21. The circuit of claim 20 further comprising a minimum current source that generates a minimum current.

22. The converter of claim 21 wherein the regulation circuit compares the maximum current and the control current which controls the frequency of the variable frequency oscillator to limit the control current to a value that is less than or equal to the maximum current but greater than the minimum current.

23. The circuit of claim 21 wherein the maximum and minimum currents define the frequency sweep range of the variable frequency oscillator.