Ripple free measurement and control methods for switched power converters
View Patent ↗Interfering effects of output ripple on measurement of output voltage and output current in a switched power converter may be obviated by taking sampled measurements at time points which are synchronized to the cause of the output ripple to drop out. Different waveform features within the switch driving signal may be used as synchronization markers for respectively determining when to take measurement samples of converter output voltage and converter current.
1. A method for measuring an operation of a switching power converter which includes at least one switch which is enabled to conduct by an application of a control pulse to a control electrode of the switch, the method comprising:
applying a control pulse to the control electrode of the switch in successive switching cycles to permit the switch to conduct and produce a voltage; and
measuring by sampling an output voltage in the successive switching cycles at the same relative position in each of the switching cycles.
2. The method of claim 1 , wherein applying a control pulse comprises applying a control pulse having a leading edge and a trailing edge and further wherein the measuring is performed just before the leading edge of control pulse.
3. The method of claim 1 , wherein applying a pulse in successive switching cycles comprises applying a pulse width modulated pulse.
4. A method for measuring an operation of a switching power converter which includes at least one switch which is enabled to conduct by an application of a control pulse to a control electrode of the switch, the method comprising:
applying a control pulse to the control electrode of the switch in successive switching cycles to permit the switch to conduct resulting in the generation of a current; and
measuring by sampling a magnitude of the current flowing in successive switching cycles at the same relative position in each of the switching cycles.
5. The method of claim 4 , wherein applying a control pulse comprises applying a control pulse having a leading edge and a trailing edge and further wherein the measuring is performed after the leading edge but before the trailing edge of the control pulse.
6. A method for concurrently measuring an operation of a first and a second switching power converter, each of which includes at least one switch which is enabled to conduct by an application of a respective control pulse, each having a leading edge and a trailing edge, to a control electrode of the first and second switches, the method comprising:
applying a first series of control pulses to the switch in the first power converter;
applying a second series of control pulses to the switch in the second power converter, wherein a leading edge of pulses in said second series is offset from a leading edge of pulses in said first series; and
measuring by sampling an output voltage of each converter at a time just prior to a leading edge of a control pulse to the respective switch.
7. A control method for use in a pulse-driven power converter, where said power converter has a converter output voltage that, when applied to a load, is prone to include an output ripple voltage portion that is a result of the pulsed-driving of the power converter,
where said power converter includes an inductor subjected to inductor-driving voltage pulses each having pulse waveform features including a leading edge and a trailing edge, the inductor developing an inductor current in response to said inductor-driving voltage pulses,
where said power converter includes an capacitor coupled to receive at least part of said inductor current and to convert the received inductor current into said converter output voltage; the method comprising:
(a) obtaining first samples of the converter output voltage by sampling the converter output voltage only at first sampling time points synchronized to substantially coincide with a predefined first waveform feature of the inductor-driving voltage pulses thereby substantially excluding from the first samples, effects of the output ripple voltage portion.
8. The control method of claim 7 and further comprising:
(b) using the obtained first samples to control said inductor-driving voltage pulses.
9. The control method of claim 7 and further comprising:
(b) using the obtained first samples to control said inductor-driving voltage pulses so as to maintain said converter output voltage at or above a predefined minimum voltage level.
10. The control method of claim 7 wherein:
(a.1) said predefined first waveform feature occurs immediately before or at leading edges of the inductor-driving voltage pulses.
11. The control method of claim 7 wherein said inductor-driving voltage pulses are produced by a plurality of complementary-wise driven transistors and
(a.1) said first sampling time points are synchronized to substantially coincide with first waveform features of a switching control signal applied to one of the complementary-wise driven transistors.
12. The control method of claim 7 where said power converter has a converter output current that, when applied through a load, is prone to include an output ripple current portion that is a result of the pulsed-driving of the power converter, the method further comprising:
(b) obtaining second samples of the converter output current by sampling the converter output current only at second sampling time points synchronized to substantially coincide with a predefined second waveform feature of the inductor-driving voltage pulses thereby substantially excluding from the second samples, effects of the output ripple current portion.
13. The control method of claim 12 and further comprising:
(c) using the obtained second samples to control said inductor-driving voltage pulses.
14. The control method of claim 12 and further comprising:
(c) using the obtained second samples to control said inductor-driving voltage pulses to so as to maintain said converter output current at or below a predefined maximum current level.
15. The control method of claim 7 wherein:
(b.1) said predefined second waveform feature occurs immediately before or at trailing edges of the inductor-driving voltage pulses.
16. A control method for use in a pulse-driven power converter, where said power converter has a converter output current that, when applied through a load, is prone to include an output ripple current portion that is a result of the pulsed-driving of the power converter,
where said power converter includes an inductor subjected to inductor-driving voltage pulses each having pulse waveform features including a leading edge and a trailing edge, the inductor developing an inductor current in response to said inductor-driving voltage pulses,
where said power converter includes an capacitor coupled to receive at least part of said inductor current and to convert the received inductor current into a voltage which results in said converter output current; the method comprising:
(a) obtaining first samples of the converter output current by sampling the converter output current only at first sampling time points synchronized to substantially coincide with a predefined second waveform feature of the inductor-driving voltage pulses thereby substantially excluding from the first samples, effects of the output ripple current portion.
17. The control method of claim 16 and further comprising:
(b) using the obtained first samples to control said inductor-driving voltage pulses.
18. The control method of claim 16 and further comprising:
(b) using the obtained first samples to control said inductor-driving voltage pulses to so as to maintain said converter output current at or below a predefined maximum current level.
19. A control method for use in a multi-output pulse-driven power converter, where said power converter has a plurality of converter output voltages that, when applied to respective loads, are prone to include respective output ripple voltage portions that are respective results of the pulsed-drivings of the power converter,
where said power converter includes a plurality of inductors each subjected to respective inductor-driving voltage pulses each having respective pulse waveform features including leading edges and a trailing edges, the plural inductors developing respective inductor currents in response to said respective inductor-driving voltage pulses,
where said power converter includes a plurality of capacitors coupled to receive at least parts of said inductor currents and to convert the respectively received inductor currents into said converter output voltages; the method comprising:
(a) obtaining first samples of a first of the converter output voltages by sampling the first converter output voltage only at first sampling time points synchronized to substantially coincide with a predefined first waveform feature of the corresponding inductor-driving voltage pulses thereby substantially excluding from the first samples, effects of the output ripple voltage portion of the first converter output voltage;
(b) obtaining second samples of a second of the converter output voltages by sampling the second converter output voltage only at second sampling time points synchronized to substantially coincide with a predefined second waveform feature of the corresponding inductor-driving voltage pulses thereby substantially excluding from the second samples, effects of the output ripple voltage portion of the second converter output voltage; and
(c) scheduling said predefined first and second waveform features to occur at substantially different times so as to reduce noise coupling between the pulse-driving of the corresponding converter output voltages and said obtaining of the first and second samples.