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EP-4736304-A1 - POWER CONVERTER AND METHOD FOR OPERATING A POWER CONVERTER

EP4736304A1EP 4736304 A1EP4736304 A1EP 4736304A1EP-4736304-A1

Abstract

A power converter (10) comprises a switching circuit (11) and a control circuit (12). The switching circuit (11) is configured as a rectifier or an inverter. The control circuit (12) is configured to provide a number of control signals (SC1 to SC6) to the switching circuit (11). The number of control signals (SC1 to SC6) are pulse-width modulated signals with a switching frequency (fC). The control circuit (12) is configured to select the switching frequency (fC) out of a first number N of predefined discrete frequency values. Moreover, a method for operating a power converter is provided.

Inventors

  • MARTIN, Sandro Philippe
  • HOSKERI, Kishore
  • ZHANG, ZHE
  • KIM, HONGRAE
  • UUSITALO, Jari Arto

Assignees

  • Eaton Intelligent Power Limited

Dates

Publication Date
20260506
Application Date
20240726

Claims (17)

  1. 1. A power converter (10) , comprising a switching circuit (11) which is configured as a rectifier or an inverter, and a control circuit (12) configured to provide a number of control signals (SCI to SC6) to the switching circuit (11) , wherein the number of control signals (SCI to SC6) are pulsewidth modulated signals with a switching frequency (fC) , and wherein the control circuit (12) is configured to select the switching frequency (fC) out of a first number N of predefined discrete frequency values.
  2. 2. The power converter (10) of claim 1, wherein the first number N is in a range between two and five .
  3. 3. The power converter (10) of claim 1 or 2, wherein a first frequency value and a second frequency value of the first number N of frequency values are fl and f2, and wherein f2 = 2 • fl .
  4. 4. The power converter (10) of any one of claims 1 to 3, wherein the first number N is three and the switching frequency is a value out of a first, a second and a third frequency value (fl, f2, f3) .
  5. 5. The power converter (10) of claim 4, wherein the first, the second and the third frequency value fl, f2, f3 of the first number N of predefined discrete frequency values follow the equations: f3 = 2 • f2 and f2 = 2 • fl .
  6. 6. The power converter (10) of claim 4 or 5, wherein the control circuit (12) is configured to set the switching frequency (fC) starting from a start point of time from the third frequency value (f3) via the second frequency value (f2) , the first frequency value (fl) , the second frequency value (f2) , the third frequency value (f3) , the second frequency value (f2) , the first frequency value (fl) and the second frequency value (f2) to the third frequency value ( f 3 ) .
  7. 7. The power converter (10) of any one of claims 1 to 6, wherein the power converter (10) comprises an analog-to- digital converter (13) coupled to an output side of the switching circuit (11) or of the power converter (10) and configured to operate at a constant frequency (fA) .
  8. 8. The power converter (10) of claim 7, wherein the constant frequency fA follows the equation: fA = 2 • n • fl, wherein n is an integer number such as 1, 2, 3 etc. and fl is the smallest frequency value of the switching frequency (fC) .
  9. 9. The power converter (10) of any one of claims 1 to 8, wherein the control circuit (12) is configured such that the switching frequency (fC) changes its switching frequency at predetermined times or at predetermined phase angles of an AC voltage.
  10. 10. The power converter (10) of any one of claims 1 to 9, wherein the switching circuit (11) is realized as a rectifier and the AC voltage is an input voltage tapped at an input side of the rectifier.
  11. 11. The power converter (10) of any one of claims 1 to 9, wherein the switching circuit (11) is realized as an inverter and the AC voltage is an output voltage tapped at an output side of the inverter or of the power converter (10) or an AC voltage desired at the output side of the inverter or the power converter (10) .
  12. 12. The power converter (10) of claim 11, wherein the switching circuit (11) comprises: a first input (14) , a second input (15) and an output (16) , a first switch (21) coupled to the first input (14) and to the output (16) and a second switch (22) coupled to the output (16) and to the second input (15) .
  13. 13. The power converter (10) of claim 12, wherein the control circuit (12) is configured to provide a first control signal (SCI) of the number of control signals (SCI to SC6) to a control terminal of the first switch (21) and a second control signal (SC2) of the number of control signals (SCI to SC6) to a control terminal of the second switch ( 22 ) .
  14. 14. The power converter (10) of claim 12 or 13, wherein the power converter (10) comprises a first output terminal (31) and a filter circuit (20) which is coupled to a first output (16) of the switching circuit (11) and to the first output terminal ( 31 ) .
  15. 15. The power converter (10) of claim 14, wherein the filter circuit (20) comprises a first inductor (34) which couples the first output (16) of the switching circuit (11) to the first output terminal (31) .
  16. 16. The power converter (10) of claim 14 or 15, wherein the filter circuit (20) comprises a first capacitor (34) which couples the first output terminal (31) to a neutral line (30) .
  17. 17. A method for operating a power converter (10) , comprising generating a number of control signals (SCI to SC6) by a control circuit (12) , wherein the number of control signals (SCI to SC6) are pulse-width modulated signals with a switching frequency (fC) having a switching frequency, and providing the number of control signals (SCI to SC6) to the switching circuit (11) which is configured as a rectifier or an inverter, and wherein the control circuit (12) selects the switching frequency out of a first number N of predefined discrete frequency values.

Description

DESCRIPTION POWER CONVERTER AND METHOD FOR OPERATING A POWER CONVERTER TECHNICAL FIELD A power converter and a method for operating a power converter are provided . BACKGROUND A power converter is e . g . implemented as uninterruptible power supply ( abbreviated UPS ) or uninterruptible power source . In the UPS market , customers want products that have a high electrical ef ficiency . Even incremental changes in electrical ef ficiency can lead to signi ficant di f ferences in operating costs . However, many techniques for increasing the ef ficiency also require designing and implementing expensive hardware changes which drive up the development and material costs and may make the product unattractive to customers . Developments that increase the electrical ef ficiency with little cost increase are thus highly desirable . A power converter comprises switches . A part of the losses of the power converter results from switching losses of the switches . These losses often increase with an increasing number of switching procedures during a period of time . It is an obj ect of the present application to provide a power converter and a method for operating a power converter with reduced switching losses . This obj ect is achieved by the sub ect-matter of the independent claims . Further embodiments and developments are given in the dependent claims . SUMMARY In an embodiment , a power converter comprises a switching circuit and a control circuit . The switching circuit is implemented as a recti fier or an inverter . The control circuit is configured to provide a number of control signals to the switching circuit . The number of control signals are pulse-width modulated signals , abbreviated PWM signals , with a switching frequency . The control circuit is configured to select the switching frequency out of a first number N of predefined discrete frequency values . Advantageously, the switching frequency is a variable frequency . The switching frequency can be kept low such that switching losses are low . The control circuit is configured to select a higher switching frequency only when advantageous for power conversion . The first number N of predefined discrete frequency values are N di f ferent frequency values . The switching frequency can also be named carrier frequency . In an embodiment of the power converter, the switching frequency is a value out of at least two di f ferent predefined frequency values . In an embodiment of the power converter, the first number N is in a range between two and five . In an embodiment of the power converter, a first frequency value f l and a second frequency value f2 of the first number N of frequency values follow the equation : f2 = 2 • f l In an embodiment of the power converter, the switching frequency is a value out of at least three di f ferent frequency values . In an embodiment of the power converter, the first number N is three . The switching frequency is a value out of a group consisting of a first , a second and a third frequency value . The third frequency value is higher than the second frequency value . The second frequency value is higher than the first frequency value . In an embodiment of the power converter, the first frequency value f l , the second frequency value f2 and the third frequency value f3 of the first number N of predefined discrete frequency values follow the equations : f3 = 2 • f2 and f2 = 2 • f l In an embodiment of the power converter, the control circuit is configured to set the switching frequency of the switching frequency starting from a start point of time during a period of time from the third frequency value via the second frequency value , the first frequency value , the second frequency value , the third frequency value , the second frequency value , the first frequency value , the second frequency value to the third frequency value . For example , the start point of time is a zero crossing of an AC voltage , such as e.g. a desired AC voltage at an output side of the power converter or of an input AC voltage at an input side of the power converter. In an embodiment of the power converter, the power converter comprises an analog-to-digital converter, abbreviated AD converter. The AD converter is coupled to an output side of the switching circuit or of the power converter. In an example, the AD converter is configured to operate at a constant frequency. In an embodiment of the power converter, the constant frequency fA of the AD converter follows the equation: fA = 2 • n • fl, wherein n is an integer number such as 1, 2, 3 etc. and fl is the smallest frequency value of the first number N of predefined discrete frequency values. In an embodiment of the power converter, the control circuit is configured such that the switching frequency changes its value at predetermined times (e.g. during a period of an AC voltage) or at predetermined phase angles of the AC voltage. The AC voltage is e.g. the desired AC voltage at the output