Method and apparatus for modifying right half-plane zero in a cascaded DC-DC buck-boost converter

1. A direct current to direct current power converter comprising:

an energy storage element;

a first switching circuit coupled between a substantially direct current (DC) input source and a first terminal of said energy storage element, wherein said first switching circuit comprises a first electronically controlled switch controlled by a first driving signal with a first duty cycle;

a second switching circuit coupled between a second terminal of said energy storage element and a substantially DC output, wherein said second switching circuit comprises a second electronically controlled switch controlled by a second driving signal with a second duty cycle, and wherein the substantially DC output exhibits one of a voltage level and a current level that is controlled at least in part by the first duty cycle and the second duty cycle; and

a control circuitry configured to receive a feedback signal indicative of the substantially DC output and to generate the first driving signal and the second driving signal responsive to a difference between the feedback signal and a reference signal, wherein the first duty cycle is responsive to a first function of the difference and the second duty cycle is responsive to a second function of the difference, the first function having an emphasized high frequency portion of the difference in relation to the second function, and wherein the first driving signal and the second driving signal respectively control said first electronically controlled switch and said second electronically controlled switch such that the direct current to direct current power converter operates in a continuous conduction mode wherein said energy storage element continuously conducts non-zero currents.

2. The direct current to direct current power converter of claim 1 , wherein said control circuitry comprises a high pass filter in communication with a gain circuit and a summing circuit, said arrangement of the high pass filter, gain circuit and summing circuit operative to emphasize the high frequency portion of the difference.

3. The direct current to direct current power converter of claim 1 , wherein said energy storage element is constituted of an inductor.

4. The direct current to direct current power converter of claim 1 , wherein said first switching circuit performs a buck function and said second switching circuit performs a boost function.

5. The direct current to direct current power converter of claim 1 , wherein said first switching circuit further comprises a third electronically controlled switch controlled by a third driving signal with a duty cycle complementary to the first duty cycle, said third electronically controlled switch coupled between the first terminal of said energy storage element and a reference potential, and said first electronically controlled switch is coupled between the substantially DC input source and the first terminal of said energy storage element.

6. The direct current to direct current power converter of claim 1 , wherein said first switching circuit further comprises a first unidirectional electronic valve coupled between the first terminal of said energy storage element and a reference potential, and said first electronically controlled switch is coupled between the substantially DC input source and the first terminal of said energy storage element.

7. The direct current to direct current power converter of claim 1 , wherein said second switching circuit further comprises a fourth electronically controlled switch controlled by a fourth driving signal with a duty cycle complementary to the second duty cycle, said fourth electronically controlled switch coupled between the second terminal of said energy storage element and the substantially DC output, and said second electronically controlled switch is coupled between the second terminal of said energy storage element and a reference potential.

8. The direct current to direct current power converter of claim 1 , wherein said second switching circuit further comprises a second unidirectional electronic valve coupled between the first terminal of said energy storage element and a reference potential, and said second electronically controlled switch is coupled between the second terminal of said energy storage element and a reference potential.

9. The direct current to direct current power converter of claim 1 , wherein said control circuitry comprises:

an error amplifier configured to receive the reference signal and the feedback signal to generate an error signal responsive to the difference between the feedback signal and the reference signal;

a filter circuit arranged to receive the error signal and configured to output a filtered error signal which substantially passes frequencies of the error signal above a threshold frequency and attenuates frequencies of the error signal below the threshold frequency;

a gain circuit configured to receive the filtered error signal and output an amplified filtered error signal;

a summing circuit configured to receive the amplified filtered error signal and the error signal and output a control signal, the control signal thus having an emphasized high frequency portion of the error signal; and

a first drive signal generating circuit coupled to an output of the summing circuit and arranged to generate the first driving signal with the first duty cycle responsive to the control signal.

10. The direct current to direct current power converter of claim 9 , wherein said control circuitry further comprises a second drive signal generating circuit coupled to the output of said error amplifier, and arranged to generate the second driving signal with the second duty cycle.

11. The direct current to direct current power converter of claim 9 , wherein said control circuitry further comprises a first DC gain circuit arranged between the output of said summing circuit and the input of said first drive signal generating circuit.

12. The direct current to direct current power converter of claim 11 , wherein said control circuitry further comprises a second drive signal generating circuit coupled to the output of said error amplifier, and arranged to generate the second driving signal with the second duty cycle.

13. The direct current to direct current power converter of claim 12 , wherein said control circuitry further comprises a second DC gain circuit arranged between the output of said error amplifier and the input of said second drive signal generating circuit.

14. The direct current to direct current power converter of claim 13 , wherein said first DC gain circuit and said second DC gain circuit have substantially similar gain factors, and wherein the first duty cycle and the second duty cycle are substantially similar during steady-state operation.

15. The direct current to direct current power converter of claim 1 , wherein said control circuitry comprises:

an error amplifier configured to receive the reference signal and the feedback signal to generate an error signal responsive to the difference between the feedback signal and the reference signal;

a filter circuit arranged to receive the error signal and configured to output a filtered error signal which substantially passes frequencies of the error signal below a threshold frequency and attenuates frequencies of the error signal above the threshold frequency;

a gain circuit configured to receive the filtered error signal and output an amplified filtered error signal;

a summing circuit configured to receive the amplified filtered error signal and the error signal and output a control signal, the control signal thus having an emphasized low frequency portion of the error signal; and

a drive signal generating circuit coupled to an output of the summing circuit and arranged to generate the second driving signal with the second duty cycle responsive to the control signal.

16. A method to generate a substantially direct current (DC) output, the method comprising:

using a power conversion circuit capable of both a boost function and a buck function to generate the substantially DC output;

receiving a feedback signal representing at least one of the voltage level and the current level of the generated substantially DC output;

comparing the received feedback signal with a reference signal to produce a difference signal;

controlling the buck function with a first switching signal having a first duty cycle, the first duty cycle being a first function of the difference signal; and

controlling the boost function with a second switching signal having a second duty cycle, the second duty cycle being a second function of the difference signal, the first function having an emphasized high frequency portion of the difference signal in relation to the second function,

wherein the first switching signal and the second switching signal are continuously enabled to facilitate a continuous conduction mode in which an energy storage element in the power conversion circuit continuously conducts current.

17. The method of claim 16 , further comprising:

filtering the difference signal so as to attenuate frequency portions of the difference signal below a threshold frequency while substantially passing frequency portions above the threshold frequency;

amplifying the filtered difference signal; and

adding the amplified filtered difference signal to the produced difference signal to generate a high frequency portion emphasized difference signal,

wherein the first duty cycle is responsive to the high frequency portion emphasized difference signal.

18. The method of claim 17 , further comprising amplifying the high frequency portion emphasized difference signal and the difference signal with substantially similar gain factors, wherein the first duty cycle and the second duty cycle are substantially similar during steady-state operation.

19. The method of claim 16 , further comprising:

filtering the difference signal so as to attenuate frequencies above a threshold frequency while substantially passing frequencies below the threshold frequency;

amplifying the filtered difference signal; and

adding the amplified filtered difference signal to the difference signal to generate a low frequency portion emphasized difference signal,

wherein the second duty cycle is responsive to the low frequency portion emphasized difference signal.

20. The method of claim 16 , wherein the energy storage element is constituted of an inductor.