Apparatus and method for loosely regulated power converters

1. A converter comprising:

an input coupled to a power source;

a plurality of power switches coupled to the input; and

a controller coupled to the power switches, wherein the controller is configured to generate a plurality of gate drive signals for the power switches, and wherein the gate drive signals are arranged such that an output voltage of the converter is in between a fully regulated output voltage and an unregulated output voltage, and wherein the gate drive signals are generated from a control signal in a band, and wherein the control signal is configured to swing back and forth between a lower limit and an upper limit of the band based upon a damped gain control mechanism, and wherein a gain of a control loop of a tight control mechanism is higher than a gain of a control loop of the damped gain control mechanism.

2. The converter of claim 1 , wherein:

the gate drive signals are generated by varying a duty cycle of the converter from a tightly controlled duty cycle.

3. The converter of claim 1 , wherein:

the gate drive signals are generated by varying a switching frequency of the converter from a tightly controlled switching frequency.

4. The converter of claim 1 , wherein:

the gate drive signals are generated by varying a phase angle of the converter from a tightly controlled phase angle.

5. A method comprising:

detecting an input voltage of a power converter, wherein the power converter comprises:

an input coupled to a power source;

a plurality of power switches coupled to the input; and

a controller coupled to the power switches; and

generating a plurality of gate drive signals for the power switches, wherein the gate drive signals are arranged such that an output voltage of the power converter is in between a fully regulated output voltage and an unregulated output voltage, and wherein the gate drive signals are generated from a control signal in a band, and wherein the control signal is configured to swing back and forth between a lower limit and an upper limit of the band based upon a damped gain control mechanism, and wherein a gain of a control loop of a tight control mechanism is higher than a gain of a control loop of the damped gain control mechanism.

6. The method of claim 5 , further comprising:

determining an operation mode of the power converter; and

varying a duty cycle of the power converter when the operation mode is a loosely regulated mode.

7. The method of claim 5 , further comprising:

determining an operation mode of the power converter; and

varying a switching frequency of the power converter when the operation mode is a loosely regulated mode.

8. The method of claim 5 , further comprising:

determining an operation mode of the power converter; and

varying a phase angle of the power converter when the operation mode is a loosely regulated mode.

9. A method comprising:

detecting an input voltage of a power converter;

determining an operation mode of the power converter based upon the input voltage of the power converter; and

generating a plurality of gate drive signals based upon a damped gain control when the power converter operates a damped gain control operation mode, wherein the damped gain control is configured such that an output voltage of the power converter is in a range from a tightly regulated output voltage to an unregulated output voltage, and wherein the gate drive signals are generated from a control signal in a band, and wherein the control signal is configured to swing back and forth between a lower limit and an upper limit of the band based upon a damped gain control mechanism, and wherein a gain of a control loop of a tight control mechanism is higher than a gain of a control loop of the damped gain control mechanism.

10. The method of claim 9 , further comprising:

determining a first input voltage threshold based upon an input voltage range and the tightly regulated output voltage of the power converter;

operating the power converter in a tightly regulated mode when the input voltage of the power converter is less than the first input voltage threshold; and

operating the power converter in a loosely regulated mode when the input voltage of the power converter is greater than the first input voltage threshold.

11. The method of claim 9 , further comprising:

determining a first input voltage threshold based upon an input voltage range and the tightly regulated output voltage of the power converter;

operating the power converter in a loosely regulated mode when the input voltage of the power converter is less than the first input voltage threshold; and

operating the power converter in a tightly regulated mode when the input voltage of the power converter is greater than the first input voltage threshold.

12. The method of claim 9 , further comprising:

determining a first input voltage threshold and a second input voltage threshold based upon an input voltage range and the tightly regulated output voltage of the power converter, wherein the second input voltage threshold is greater than the first input voltage threshold; and

generating the plurality of gate drive signals, wherein the gate drive signals are arranged such that:

the power converter operates in a first loosely regulated mode when the input voltage of the power converter is less than the first input voltage threshold;

the power converter operates in a tightly regulated mode when the input voltage of the power converter is between the first input voltage threshold and the second input voltage threshold; and

the power converter operates in a second loosely regulated mode when the input voltage of the power converter is greater than the second input voltage threshold.