DC-DC converter control circuit and DC-DC converter control method

• US 20070139027A1
• Filed: 03/28/2006
• Published: 06/21/2007
• Est. Priority Date: 12/20/2005
• Status: Active Grant

• Current Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Original Assignee: Fujitsu Limited
• Inventors: Nishimori, Eiji
• Granted Patent: US 7,595,621 B2
• Time in Patent Office: Days
• US Class Current: 323/283
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/0019 the disturbance parameters being load current fluctuations
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load

Abstract

There are provided a DC-to-DC converter control circuit capable of implementing compatibility between low ripple voltage characteristics, and stable and fast response characteristics at the time of a sudden change in load, and a DC-to-DC converter control method using the same. An add-up signal of an output voltage signal obtained according to an output voltage of a DC-to-DC converter, and an AC current signal obtained according to an AC current component of a coil current is outputted from an arithmetic circuit, and the add-up signal is compared with a reference signal by a comparator. Switching control of the DC-to-DC converter is executed according to a result of comparison by the comparator. Even if an equivalent series-connected resistance ESR of a smoothing capacitor, connected to an output terminal of the DC-to-DC converter, is reduced, and a voltage ripple becomes very small in value, it is possible to detect variation in a coil current of the DC-to-DC converter, thereby obtaining an add-up signal obtained by adding a variation component of the coil current to the output voltage. By comparing the add-up signal with the reference signal, variation in the coil current, due to a change in load, can be captured with reliability.

Claims

1. A DC-to-DC converter control circuit comprising:

an arithmetic circuit for outputting an add-up signal of an output voltage signal obtained according to an output voltage of a DC-to-DC converter, and an AC current signal obtained according to an AC current component of a coil current; and

a comparator for comparing the add-up signal with a reference signal,

wherein switching control is executed according to a result of comparison by the comparator.

2. A DC-to-DC converter control circuit according to claim 1, further comprising a high-pass filter for extracting the AC current signal.

3. A DC-to-DC converter control circuit according to claim 2, wherein the arithmetic circuit comprises an adder for adding the AC current signal outputted from the high-pass filter to the output voltage signal.

4. A DC-to-DC converter control circuit according to claim 1, further comprising a reference signal circuit for retaining a DC current component of a coil current signal as a reference signal, on the basis of a detection signal obtained by adding the coil current signal according to the coil current containing the DC and AC current components to the output voltage signal,

wherein the arithmetic circuit comprises an inverting amplifier for inverting a signal variation component of the output voltage signal, at the reference signal, and adding the same to the output voltage signal, and an adder for adding the detection signal to an output signal from the inverting amplifier.

5. A DC-to-DC converter control circuit according to claim 4, wherein the reference signal circuit comprises a sample hold circuit, and a switch circuit for capturing a value of the detection signal into the sample hold circuit in a preceding switching cycle of the DC-to-DC converter.

6. A DC-to-DC converter control circuit according to claim 5, wherein the switch circuit captures a value of the detection signal in a switching cycle preceding to the present switching cycle by one switching cycle.

7. A DC-to-DC converter control circuit according to claim 5, further comprising a clamping circuit connected in parallel with the switch circuit, for limiting a drop amount of the reference signal, against the detection signal.

8. A DC-to-DC converter control circuit according to claim 5, wherein the switch circuit captures the detection signal at the time of detection by comparison in the DC-to-DC converter or at a time immediately thereafter.

9. A DC-to-DC converter control circuit according to claim 5, wherein the switch circuit captures the detection signal in a switching cycle preceding to the present switching cycle by at least two switching cycles.

10. A DC-to-DC converter control circuit according to claim 5, further comprising a frequency divider for dividing a switching control signal of the DC-to-DC converter, wherein the switch circuit is controlled by an output signal of the frequency divider.

11. A DC-to-DC converter control circuit according to claim 5, wherein the sample hold circuit comprises a first capacitor for capturing the detection signal, and a low-pass filter coupled to the first capacitor, and the reference signal is given from an output of the low-pass filter.

12. A DC-to-DC converter control circuit according to claim 11, wherein the sample hold circuit comprises a time-constant circuit parallel-coupled to the first capacitor, including a second capacitor, and the reference signal is retained by the second capacitor.

13. A DC-to-DC converter control circuit according to claim 4, wherein the reference signal circuit comprises a low-pass filter with the detection signal inputted thereto.

14. A DC-to-DC converter control circuit according to claim 4, further comprising a noninverting amplifier for amplifying a variation component of a signal for the output voltage, based on an original signal obtained by adding a voltage component of the coil current to the output voltage, and adding the variation component to the output voltage, wherein the detection signal is an output signal from the noninverting amplifier.

15. A DC-to-DC converter control method comprising the steps of:

adding an output voltage signal obtained according to an output voltage of a DC-to-DC converter to an AC current signal obtained according to an AC current component of a coil current;

comparing an addition result of the step of adding an output voltage signal with a reference signal; and

executing switching control according to a comparison result of the step of comparing the addition result.

16. A DC-to-DC converter control method according to claim 15, further comprising a step for retaining a reference signal of the AC current signal, on the basis of a detection signal obtained by adding the coil current signal according to the coil current containing the DC and AC current components to the output voltage signal, wherein the addition step comprises the steps of:

inverting a signal variation component of the reference signal according to the output voltage signal,

adding the signal variation component to the output voltage signal; and

adding the detection signal to a signal obtained by the step of adding the signal variation component.

17. A DC-to-DC converter control method according to claim 16, wherein the step of retaining the reference signal comprises a step of capturing a value of the detection signal as the reference signal in a preceding switching cycle of the DC-to-DC converter.

18. A DC-to-DC converter control method according to claim 17, wherein the step of capturing the value of the detection signal is taken in a switching cycle preceding to the present switching cycle by one switching cycle.

19. A DC-to-DC converter control method according to claim 17, wherein the step of capturing the value of the detection signal is taken in a switching cycle preceding to the present switching cycle by at least two switching cycles.

20. A DC-to-DC converter control method according to claim 17, wherein the step of retaining the reference signal further comprises a step of further averaging the detection signal as captured and a mean value of the detection signals already captured and retained prior thereto.