Control circuit and method for a DC-to-DC converter to improve transient response thereof

Abstract

For a DC-to-DC converter including a plurality of channels for converting an input voltage to an output voltage, a control circuit comprises a load transient detector to detect the output voltage to provide a quick response signal. In a load transient, the quick response signal triggers a quick transient response period to increase the operational frequency of the converter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings, in which:

FIG. 1 shows a traditional DC-to-DC converter;

FIG. 2 shows a conventional control circuit for the converter of FIG. 1;

FIG. 3 is a waveform diagram of various signals in the control circuit of FIG. 2;

FIG. 4 shows the waveforms of the reference voltage V_REF and the feedback voltage VFB;

FIG. 5 shows a first embodiment of the present invention;

FIG. 6 is a waveform diagram of various signals during a load transient of the first embodiment;

FIG. 7 shows waveform of the reference voltage V_REF1, the feedback voltage VFB, and the quick response signal QR of FIG. 6;

FIG. 8 shows another embodiment of the load transient detector 3036 shown in FIG. 5;

FIG. 9 is a waveform diagram of various signals during load transient when the circuit of FIG. 8 is employed;

FIG. 10 shows an embodiment of the oscillator 3010 shown in FIG. 5;

FIG. 11 shows the waveform of the clock CLK and the state table of the signals Q, S#, and R# of FIG. 10;

FIG. 12 shows a second embodiment of the present invention; and

FIG. 13 shows another embodiment of load transient detector 3036 shown in FIG. 12.

Claims

1. A control circuit for a DC-to-DC converter including a plurality of channels for converting an input voltage to an output voltage, the control circuit comprising: an oscillator for providing a clock to determine an operation frequency of said converter; anda load transient detector for detecting said output voltage to generate a quick response signal to trigger a quick transient response period in response to a load transient, in which period said clock oscillates more quickly.

2. The control circuit of claim 1, wherein said quick response signal drives at least two of said plurality of channels during said quick transient response period.

3. The control circuit of claim 1, wherein said oscillator comprises: a first switch being turned on by said quick response signal during said quick transient response period;an adder having a first input connected with a first current and a second input connected with a second current via said first switch for combining the first and second currents to generate a third current;a first current mirror for mirroring said third current to generate a fourth current and a fifth current;a second current mirror for mirroring said fourth current to generate a sixth current;a capacitor;a second switch for connecting said fifth current to charge said capacitor; anda third switch connected between said second current mirror and said capacitor for discharging said capacitor with said sixth current;wherein said second and third switches alternatively switch to charge and discharge said capacitor to thereby generate said clock.

4. The control circuit of claim 1, wherein said load transient detector comprises a comparator for comparing a third voltage proportional to said output voltage with a predetermined quick response trigger voltage to generate said quick response signal.

5. A control method for a DC-to-DC converter including a plurality of channels for converting an input voltage to an output voltage, the control method comprising the steps of: detecting said output voltage for triggering a quick transient response period in response to a load transient;increasing an operational frequency of said converter during said quick transient response period.

6. The method of claim 5, further comprising the step of driving at least two of said plurality of channels during said quick transient response period.

7. The method of claim 5, wherein said step of increasing an operational frequency of the converter comprises the step of increasing said operational frequency of the converter when a difference between said output voltage and a reference voltage reaches a predetermined value.

8. The method of claim 7, further comprising the step of increasing said operational frequency of the converter further when said difference reaches a second predetermined value.