Resumen
A method of operating a switching power converter is provided. The power converter (10) comprises an inductor (25) and plural switches (21-24) and is operable in a modulation mode in which a current (iL) through the inductor (25) is modulated by operating the power converter (10) in a repeating sequence of predetermined switching states (26, 27, 28). The method includes controlling a current waveform (50) of the current through the inductor (25) in the modulation mode by controlling the transition between the switching states (26,27, 28) of the sequence. The current waveform (50) is controlled to include within one period (T) of the current wave- form (50) a first section (A) of rising current corresponding to a first switching state (26), a second section (B) corresponding to a second switching state (27), wherein the second section (B) of the current waveform does not reach or cross a zero value of the current, and a third section (C) of falling current corresponding to a third switching state (28). The control of the current waveform (50) allows the length of the period (T) of the current waveform (50) to change.
Reivindicaciones
Patent claims 1. A method of operating a switching power converter, wherein the power converter (10) comprises an inductor (25) and plu ral switches (21-24) that are switchable to couple the induc tor (25) to terminals (11-14) of the power converter (10), wherein the method comprises operating the power converter in a modulation mode in which a current (iL) through the inductor (25) is modu lated by operating the power converter (10) in a repeat ing sequence of predetermined switching states (26, 27, 28) of the switches (21-24), controlling a current waveform (50) of the current through the inductor (25) in said modulation mode by controlling the transition between the switching states (26, 27, 28) of the sequence, wherein the current wave form (50) is controlled to include within one period (T) of the current waveform (50): o a first section (A) of rising current corresponding to a first switching state (26), o a second section (B) corresponding to a second switching state (27), wherein the second section (B) of the current waveform does not reach or cross a zero value of the current, and o a third section (C) of falling current correspond ing to a third switching state (28), wherein the first section (A) of the current waveform (50) follows in direct succession to the third sec tion (C) of the preceding period of the current wave form, and wherein the control of the current waveform (50) allows the length of the period (T) of the current waveform (50) to change, wherein in the modulation mode, the transition from the first section (A) to the second section (B) of the current waveform is controlled by transitioning the operation of the power converter (10) from the first switching state (26) to the second switching state (27) upon the inductor current reach- ing a first threshold (55) and wherein the transition from the second section (B) to the third section (C) of the cur rent waveform is controlled by transitioning the operation of the power converter (10) from the second switching state (27) to the third switching state (28) upon the inductor current reaching a second threshold (56), wherein one of the first and second thresholds (55, 56) is derived from a comparison of a current reference (85) for an output current of the power converter (10) and a monitored output current (83, 84) of the power converter (10), and wherein the other (iL-ref-B) of the first and second thresh olds (55, 56) is determined from the derived threshold (iL- ref) and a desired duration (Tb) of the second section (B). 2. The method according to claim 1, wherein the modulation mode is at least one of a buck mode in which the first threshold (55) is the threshold (iL-ref) derived from the comparison, or a boost mode in which the second threshold (56) is the threshold (iL-ref) derived from the comparison. 3. The method according to claim 1 or 2, wherein within one waveform period (T), the waveform consists of the first sec tion (A), the second section (B), and the third section (C). 4. The method according to any of the preceding claims, wherein a magnitude of the slope of the second section (B) of the current waveform is less that a magnitude of the slope of the first section (A) and/or the third section (C) of the current waveform. 5. The method according to any of the preceding claims, wherein in said modulation mode, the power converter (10) is operable in at least one of a buck mode in which the second section (B) of the cur rent waveform is controlled to be a rising current, a boost mode in which the second section (B) of the cur rent waveform is controlled to be a falling current, and an equal voltage mode in which the second section (B) of the current waveform is controlled to be a constant cur rent. 6. The method according to any of the preceding claims, wherein controlling the transition between the switching states comprises controlling the duration (Tb) of the second section (B) of the current waveform (50) to adjust the period (T) of the current waveform (50). 7. The method according to any of the preceding claims, wherein during the period (T) of the current waveform (50), the current flow through the inductor (25) is not reversed. 8. The method according to any of the preceding claims, wherein controlling the transition between the switching states (26, 27, 28) of the sequence comprises setting the current reference (85) for the output current of the power converter (10), monitoring the output current of the power converter, and applying an error signal between the current reference and the monitored output current to a controller (91) to derive the threshold value (iL-ref) for the inductor current upon the reaching of which the power converter tran sitions to a next switching state. 9. The method according to claim 8, wherein the controller is a proportional integral (PI) regulator (91). 10. The method according to any of the preceding claims, wherein the current waveform (50) is controlled to have a transition from the third section (C) to a first section (A) of a subsequent period of the current waveform (50) by tran sitioning the operation of the power converter from the third switching state (28) to the first switching state (26) upon the inductor current (iL) reaching a zero current. 11. The method according to any of the preceding claims, wherein the power converter (10) comprises: first and second terminals (11, 12) on a first side of the power converter, and third and fourth terminals (13, 14) on a second side of the power converter, a first interconnection point (18) between a first switch (21) and a second switch or diode (22), the first switch (21) and the second switch or diode (22) being connected in series between the first and second termi nals (11, 12), and a second interconnection point (19) between a third switch or diode (23) and a fourth switch (24), the third switch or diode (23) and the fourth switch (24) being connected in series between the third and fourth termi nals (23, 24), wherein the inductor (25) is connected between the first and second interconnection points (18, 19). 12. The method according to claim 11, wherein the first switching state (26) corresponds to the first switch (21) be ing in a closed state and the fourth switch (24) being in a closed state, wherein the second switch or diode (22) is not conducting and the third switch or diode (23) is not conduct ing, and/or wherein the second switching state (27) corresponds to the first switch (21) being in a closed state and the third switch or diode (23) being in a conducting state, wherein the second switch or diode (22) is not conducting and the forth switch (24) is not conducting, and/or wherein the third switching state (28) corresponds to the second switch or diode (22) being in a conducting state and the third switch or diode (23) being in a conducting state, wherein the first switch (21) is not conducting and the forth switch (24) is not conducting. 13. A controller of a switching power converter, wherein the power converter (10) comprises an inductor (25) and plural switches (21-24) that are switchable to couple the inductor (25) to terminals (11-14) of the power converter, wherein the controller (80) is configured to provide a control signal (87) for switching the plural switches (21-24) in accordance with a repeating sequence of predetermined switching states, wherein the controller (80) is further configured to perform the method of any one of the preceding claims. 14. A switching power converter comprising an inductor (25) and plural switches (21-24) that are switchable to couple the inductor (25) to terminals of the power converter (10), wherein the power converter (10) further comprises a control- ler (80) according to claim 13. 15. A computer program for controlling the operation of a switching power converter (10), wherein the computer program comprises control instructions which, when executed by a pro- cessing unit (81) of a controller (80) of the power convert er, cause the processing unit (81) to perform the method of any of claims 1-12.
