Multi-phase converter with improved load step-up transient response

1. A multi-phase converter comprising:

a plurality of switching circuits each providing a switched voltage to an output node of the converter and wherein each switching circuit sequentially provides a switched output voltage to the output node at which an output voltage of the converter is developed;

a clock circuit for providing a plurality of out of phase clock signals to the switching circuits to determine when each switching circuit provides the switched voltage to the output node; each switching circuit comprising first and second series connected switches connected across a DC voltage bus; further comprising a first circuit comparing a first signal proportional to a difference between the output voltage of the converter at the output node and a first reference voltage with a second signal comprising a ramp signal and for producing a pulse width modulated signal to control the on-times of the switches of the connected switching circuit;

further comprising a second circuit comparing the first signal proportional to the difference between the output voltage and the first reference voltage to a second reference voltage and if the first signal exceeds the second reference voltage by a prescribed amount, for turning on at least one switching circuit to provide the switched output voltage to the output node prior to occurrence of the clock signal.

2. The multi-phase converter of claim 1 wherein each switching circuit comprises a control switch and a synchronous switch coupled in series with a switched node at a common connection point between the two switches and wherein the control switch of at least one of the switching circuits is turned on in response to the error amplifier output voltage exceeding the second reference voltage by the prescribed amount.

3. The multi-phase converter of claim 2 wherein the control switches of at least two switching circuits are turned on in response to the error amplifier output voltage exceeding the second reference voltage by the prescribed amount.

4. The multi-phase converter of claim 3 wherein the control switch of each of the switching circuits are turned on in response to the error amplifier output voltage exceeding the second reference voltage by the prescribed amount.

5. The multi-phase converter of claim 1 wherein the second circuit comprises a comparator circuit.

6. The multi-phase converter of claim 1 wherein the second reference voltage is adjusted by the output of a current sharing circuit that adjusts the first reference voltage to produce the second reference voltage in response to an output current provided by the switching circuit to equalize the output currents provided by the switching circuits.

7. The multi-phase converter of claim 1 , wherein the ramp signal has a first slope, and wherein the slope is increased when the first signal exceeds the second reference voltage by the prescribed amount.

8. The multi-phase converter of claim 7 , wherein the increased slope is twice the first slope.

9. The multi-phase converter of claim 1 , wherein the first and second reference voltages are the same.

10. The multi-phase converter of claim 2 , wherein each switching circuit comprises a buck converter having an output inductor coupling the switched node to the converter output node.