System for operating DC motors and power converters

• US 7,659,678 B2
• Filed: 07/22/2004
• Issued: 02/09/2010
• Est. Priority Date: 07/22/2003
• Status: Active Grant

• Current Assignee: Sergio A. Maiocchi
• Original Assignee: Sergio A. Maiocchi
• Inventors: Maiocchi, Sergio A.
• Primary Examiner(s): Ro; Bentsu
• Application Number:
  US10/565,345
• Publication Number:
  US 20070247091A1
• Time in Patent Office: 2,028 Days
• Field of Search: 318/245, 318/400.22, 318/400.23, 318/400.26, 318/400.27, 318/400.28, 318/400.3, 318/400.42, 318/722, 363/15, 363/16, 363 34- 38, 363/123, 363125-128
• US Class Current: 318/400.22
• CPC Class Codes: H02M 1/0012 Control circuits using digital or numerical techniques in DC/DC converters H02M3/157, H02M3/33515; in DC-AC converters H02M7/53873
• CPC Class Codes: H02M 1/009 having two or more independently controlled outputs for DC-DC converter with intermediate AC H02M3/33561
• CPC Class Codes: H02M 3/1555 for the generation of a regulated current to a load whose impedance is substantially inductive
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/157 with digital control
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: H02M 3/3372 of the parallel type
• CPC Class Codes: H02P 2209/07 Trapezoidal waveform
• CPC Class Codes: H02P 6/085 in a bridge configuration
• CPC Class Codes: H02P 7/29 using pulse modulation
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A system is disclosed for driving a DC motor (15) under conditions of a controlled average current. An inductive element may be arranged for connection in series with the DC motor. A switch (14) is preferably coupled to the inductive element for connecting and disconnecting a terminal of the inductive element from the voltage source. A diode may be arranged for connection in parallel with a combination of the inductive element and the DC motor arranged in series, with the appropriate polarity so that current circulating through the inductive element circulates through the diode when the switch disconnects the terminal from the voltage source. A capacitor is arranged for connection in parallel with the motor, for limiting a resulting voltage over the motor or for storing charge depending on the embodiment of the invention. A device for measuring a current through the motor is provided, and a device (13) for controlling operation of the switch dependent upon the measured current in the motor is also provided. An airflow apparatus is also disclosed.

Claims

1. A system for driving a direct-current (DC) motor under conditions of controlled DC current, from a DC voltage source of a value larger than sad a motor operating voltage, independently of the operating voltage of said motor, said system comprising:

a pair of nodes for connection of said DC motor, said nodes to be referred to herein as the first node and the second node, said second node being connected to a common electrical terminal of the system through an electrical path with low impedance, including low impedance to DC current, said DC motor being connected between said first node and said second node;

an inductive element to store energy and to act as a current source for said DC motor, said inductive element being external to said DC motor, and not part of a main magnetic circuit of said DC motor, said inductive element being connected to said first node, in series with said DC motor, said inductive element being capable of operating in a buck converter at the power level required to operate said DC motor and at the frequency of commutation of a first switch, the terminal of said inductive element not connected to said first node being connected to a third node;

said first switch being connected to said inductive element at the third node, the terminal of said inductive element remote from said DC motor, said first switch for connecting and disconnecting said inductive element to a direct current (DC) voltage source, a terminal of said DC voltage source not connected to said first switch, being connected to said common electrical terminal of the system;

said first switch being a controlled switch capable of being turned off and on by control signals from a control system, said control system operating based on an error signal and a value of the desired operating current for said DC motor set externally to the system, said control system turning said first switch off and on to minimize said error signal and to keep the operating current of said DC motor at said desired value, said first switch being a single pole switch;

a second switch connected between said third node and said common electrical terminal of the system, parallel with a combination of said inductive element and said DC motor arranged in series, said second switch being controlled so that a current circulating through said inductive element circulates through said second switch if said first switch is turned off and disconnects said inductive element from said DC voltage source, said second switch being a single pole switch;

a capacitor arranged for connection in parallel with said DC motor to limit a resulting voltage over said DC motor, said capacitor being capable of operating in a buck converter at a power level required to operate said DC motor and at the frequency of commutation of said first switch, said capacitor being connected between said first node and a low impedance path to said common electrical terminal of the circuit;

a current sensor for measuring a current through said DC motor, the output of said current sensor being connected to said control system of said first switch to generate said error signal for the operation of said control system controlling the operation of said first switch; and

means for controlling operation of said second switch dependent upon the state of the first switch.

2. The system according to claim 1, wherein the voltage of said DC voltage source is larger than the nominal rated voltage of said DC motor.

3. The system according to claim 1, wherein said second switch is a diode connected with appropriate polarity so that current circulating through said inductive element circulates through said diode and if said first switch is open, disconnecting said inductive element.

4. The system according to claim 1, wherein said second switch is an electronic switch for synchronous rectification connected with appropriate polarity so that current circulating through said inductive element circulates through said electronic switch and if said first switch is open, disconnecting said inductive element.

5. The system according to claim 1, wherein said first switch is an electronic switch.

6. The system according to claim 1, wherein said inductive element is an inductor, or a winding of a transformer.

7. The system according to claim 1, wherein a current through the inductive element is controlled independently from a current through the motor, the balance of electrical charge being accumulated or taken from the capacitor in parallel with the motor.

8. The system according to claim 7, wherein the current through the motor is calculated from the variation of the voltage across the capacitor in parallel with the motor.

9. The system according to claim 7, wherein said DC motor is an electronically driven motor, including a brushless motor, said motor being braked electronically so that a current produced during the braking process further charges said capacitor in parallel with said motor.

10. The system according to claim 1, wherein a current through the inductive element is modulated as a full wave rectified sinusoid synchronous with the AC main voltage so that the power factor of the system, as a load to the AC main is improved.

11. The system according to claim 10, wherein the instant in which the sinusoidal waveform of the AC main crosses zero is sensed to synchronize the modulation performed to the current through the inductive element with the waveform in the AC main.

12. The system according to claim 1, wherein said DC motor includes a brushless DC motor.

13. The system according to claim 12, wherein said DC motor includes an electronic commutator for said brush less brushless DC motor.

14. The system according to claim 1, further comprising means for calculating said current through the motor dependent upon current measured in another part of said system.

15. The system according to claim 1, wherein a frequency of a pulse width modulated waveform, resulting from operation of said switches, is randomized to facilitate EMI compliance.

16. The system according to claim 1, wherein the voltage over the DC motor is used to estimate the speed of the motor.

17. The system according to claim 1, wherein said first switch and said direct current (DC) voltage source are implemented by an electronic system that connects said inductive element either to a given voltage or to a high impedance for a period of time determined by said control system controlling said first switch, said high impedance being measured with respect to said common electrical terminal of said system, said given voltage being set externally to said system, said electronic system being connected to said common electrical terminal of the system, said electronic system being controlled by said control system controlling said first switch.

18. A system for driving a direct-current (DC) motor under conditions of controlled DC current, independently of the operating voltage of said motor, said system comprising:

a pair of nodes for connection of said DC motor, said nodes to be referred to herein as the first node and the second node, said second node being connected to a common electrical terminal of the system through an electrical path with low impedance, including low impedance of DC current, said DC motor is being connected between said first node and said second node;

a capacitor arranged for connection in parallel with said motor to limit a resulting voltage over said motor, one terminal of said capacitor being connected to said first node, the other terminal of said capacitor to be connected through a low impedance to said common terminal of the system, said capacitor being capable of operating in a buck converter at the power level required to operate said DC motor and at the frequency of commutation of a first switch;

an inductive element with one terminal being connected to said common terminal of the system through a low impedance path, the other terminal of said inductive element, referred to herein as the third node, being connected to said first switch, said inductive element being used to store energy and to act as a current source for said DC motor, said inductive element being external to said DC motor and not part of a main magnetic circuit of said DC motor, said inductive element being capable of operating in a buck converter at the power level required to operate said DC motor and at the frequency of commutation of said first switch;

said first switch being connected to said inductive element in the third node, said first switch for connecting and disconnecting said third node to a DC voltage source, a terminal of said DC voltage source not connected to said first switch, being connected to said common electrical terminal of the system, said first switch being a controlled switch capable of being turned off and on by control signals from a control system, said control system operating based on an error signal and a value of a desired operating current for said DC motor, set externally to the system, said control system for turning said first switch off and on to minimize said error signal and to keep the operating current of said DC motor at said desired value, said first switch being a single pole switch;

a second switch being connected between said first node and said third node, in series with the parallel combination of said motor and said capacitor, and being connected to the common node between the first switch and said inductive element, said second switch being controlled so that a current circulating through said inductive element circulates through said second switch if the first switch is turned off and disconnects the third node from said DC voltage source, said second switch being a single pole switch;

a current sensor for measuring a current through said DC motor, the output of said current sensor being connected to said control system of said first switch to generate said error signal for the operation of said control system, controlling the operation of said first switch; and

means for controlling operation of said second switch dependent upon the state of the first switch.

19. The system according to claim 18, wherein said first switch is an electronic switch, and said second switch is a diode connected with appropriate polarity so that current circulating through said inductive element circulates through said diode and if said first switch is open, disconnecting said inductive element.

20. The system according to claim 18, wherein said inductive element is an inductor, or a winding of a transformer.

21. The system according to claim 18, wherein a current through the inductive element is controlled independently from a current through the motor, the balance of electrical charge being accumulated or taken from the capacitor in parallel with the motor.

22. The system according to claim 21, wherein said DC motor is an electronically driven motor, including a brushless motor, said motor being braked electronically so that a current produced during the braking process further charges said capacitor in parallel with said motor.

23. The system according to claim 18, wherein a current through the inductive element is modulated as a full wave rectified sinusoid synchronous with the AC mains voltage so that the power factor of the system, as a load to the AC main is improved.

24. The system according to claim 18, wherein said first switch and said direct current (DC) voltage source are implemented by an electronic system that connects said inductive element either to a given voltage or to a high impedance for a period of time determined by said control system controlling said first switch, said high impedance being measured with respect to said common electrical terminal of said system, said given voltage being set externally to said system, said electronic system being connected to said common electrical terminal of the system, said electronic system being controlled by said control system controlling said first switch.

25. The system according to claim 18, wherein said inductive element is an inductor and said second switch is connected to a terminal of said inductor that is not connected to said third node or to said common electrical terminal of the system.

26. A system for driving a direct-current (DC) motor under conditions of controlled DC current, independently of the operating voltage of said motor, said system comprising:

a pair of nodes for connection of said DC motor, said nodes to be referred to herein as the first node and the second node, said DC motor being connected between said first and said second node;

a capacitor arranged for connection in parallel with said motor, between said first node and said second node, to limit a resulting voltage over said motor, said first node, connected to a terminal of said capacitor and said motor, being also connected to a DC voltage source, said capacitor being capable of operating in a buck converter at the power level required to operate said DC motor and at the frequency of commutation of a first switch, the other terminal of said DC voltage source being connected to a common electrical terminal of the system;

an inductive element with one terminal connected to said first node, a common node of said DC voltage source, said capacitor and said DC motor, the other terminal of said inductive element, referred to herein as the third node and being connected to said first switch, said inductive element being used to store energy and to act as a current source for said DC motor, said inductive element being external to said DC motor, and not part of a main magnetic circuit of said DC motor, said inductive element being capable of operating in a buck converter at the power level required to operate said DC motor and at the frequency of commutation of said first switch;

said first switch being connected to said inductive element in the third node, the other terminal of said first switch, not connected to the third node being connected to said common electrical terminal of the system through an electrical path with low impedance, including low impedance to DC current, said first switch for connecting and disconnecting the third node to said common electrical terminal of the system, said first switch being a controlled switch capable of being turned off and on by control signals from a control system, said control system operating based on an error signal and a value of a desired operating current for said DC motor set externally to the system, said control system for turning said first switch off and on to minimize said error signal and to keep the operating current of said DC motor at said desired value, said first switch being a single pole switch;

a second switch being connected between said second and said third node, said second switch being controlled so that a current circulating through said inductive element circulates through said second switch if the first switch is turned off and disconnects the third node from said common electrical terminal of the system, said second switch being a single pole switch;

a current sensor for measuring a current through said DC motor, the output of said current sensor being connected to said control system of said first switch to generate said error signal for the operation of said control system, controlling the operation of said first switch; and

means for controlling operation of said second switch dependent upon the state of the first switch.

27. The system according to claim 26, wherein said first switch is an electronic switch, and said second switch is a diode connected with appropriate polarity so that current circulating through said inductive element circulates through said diode and if said first switch is open, disconnecting said inductive element.

28. The system according to claim 26, wherein said inductive element is an inductor, or a winding of a transformer.

29. The system according to claim 26, wherein a current through the inductive element is controlled independently from a current through the motor, the balance of electrical charge being accumulated or taken from the capacitor in parallel with the motor.

30. The system according to claim 29, wherein said DC motor is an electronically driven motor, including a brushless motor, said motor being braked electronically so that a current produced during the braking process further charges said capacitor in parallel with said motor.

31. The system according to claim 26, wherein a current through the inductive element is modulated as a full wave rectified sinusoid synchronous with the AC mains voltage so that the power factor of the system, as a load to the AC main is improved.

32. The system according to claim 26, wherein said first switch and said direct current (DC) voltage source are implemented by an electronic system that connects said inductive element either to a given voltage or to a high impedance for a period of time being measured with respect to said common electrical terminal of said system, said given voltage being set externally to said system, said electronic system being connected to said common electrical terminal of the system, said electronic system being controlled by said control system controlling said first switch.

33. The system according to claim 26, wherein said inductive element is an inductor and said second switch is connected to a terminal of said inductor that is not connected to said third node or to said direct current (DC) voltage source.

34. A system for driving a direct-current (DC) motor under conditions of controlled DC current, from a DC voltage source of a value larger than a motor operating voltage, independently of the operating voltage of said motor, said system comprising:

a pair of nodes for connection of said DC motor, said nodes referred to as the first node and the second node, said second node being connected to a direct current (DC) voltage source, a terminal of said DC voltage source not connected to said second node being connected to a common electrical terminal of the system through an electrical path with low impedance, including low impedance to DC current, said DC motor being connected between said first node and said second node;

an inductive element to store energy and to act as a current source for said DC motor, said inductive element being external to said DC motor and not part of a main magnetic circuit of said DC motor, said inductive element being connected to said first node in series with said DC motor, said inductive element being capable of operating in a buck converter at the power level required to operate said DC motor and at the frequency of commutation of a first switch, the terminal of said inductive element not connected to said first node being connected to a third node;

said first switch being connected to said inductive element at said third node, the terminal of said inductive element remote from said DC motor, said first switch for connecting and disconnecting said inductive element to said common electrical terminal of the system, a terminal of said first switch not connected to said third node being connected to said common electrical terminal of the system, said first switch being a controlled switch capable of being turned off and on by control signals from a control system, said control system operating based on an error signal and a value of the desired operating current for said DC motor set externally to the system, said control system turning said first switch off and on to minimize said error signal and to keep the operating current of said DC motor at said desired value, said first switch being a single pole switch;

a second switch connected between said third node and said second node, parallel with a combination of said inductive element and said DC motor arranged in series, said second switch being controlled so that a current circulating through said inductive element circulates through said second switch if said first switch is turned off and disconnects said inductive element from said common electrical terminal of the system, said second switch being a single pole switch;

a capacitor arranged for connection in parallel with said DC motor to limit a resulting voltage over said DC motor, said capacitor being capable of operating in a buck converter at a power level required to operate said DC motor and at the frequency of commutation of said first switch, said capacitor being connected between said first node and said second node;

a current sensor for measuring a current through said DC motor, the output of said current sensor being connected to said control system of said first switch to generate said error signal for the operation of said control system controlling the operation of said first switch; and

means for controlling operation of said second switch dependent upon the state of the first switch.

35. The system according to claim 34, wherein said first switch is an electronic switch, and said second switch is a diode connected with appropriate polarity so that current circulating through said inductive element circulates through said diode and if said first switch is open, disconnecting said inductive element.

36. The system according to claim 34, wherein said inductive element is an inductor, or a winding of a transformer.

37. The system according to claim 34, wherein a current through the inductive element is controlled independently from a current through the motor, the balance of electrical charge being accumulated or taken from the capacitor in parallel with the motor.

38. The system according to claim 37, wherein said DC motor is an electronically driven motor, including a brushless motor, said motor being braked electronically so that a current produced during the braking process further charges said capacitor in parallel with said motor.

39. The system according to claim 34, wherein a current through the inductive element is modulated as a full wave rectified sinusoid synchronous with the AC mains voltage so that the power factor of the system, as a load to the AC main is improved.

40. The system according to claim 34, wherein said first switch and said direct current (DC) voltage source are implemented by an electronic system that connects said inductive element either to a given voltage or to a high impedance for a period of time being measured with respect to said common electrical terminal of said system, said given voltage is being set externally to said system, said electronic system being connected to said common electrical terminal of the system, said electronic system is being controlled by said control system controlling said first switch.

41. A system for driving a direct-current (DC) motor under conditions of controlled DC current, from a DC voltage source of a value smaller than a motor operating voltage, independently of the operating voltage of said motor, said system comprising:

a pair of nodes for connection of said DC motor, said nodes to be referred to herein as the first node and the second node, said DC motor being connected between said first and said second node;

a capacitor arranged for connection in parallel with said motor, between said first node and said second node, to limit a resulting voltage over said motor, said first node being connected to a common electrical terminal of the system through an electrical path with low impedance, including low impedance to DC current, said capacitor being capable of operating in a buck converter at the power level required to operate said DC motor and at the frequency of commutation of a first switch;

wherein said direct current (DC) voltage source has one terminal of said being connected to an inductive element, the other terminal of said DC voltage source being connected to said common electrical terminal of the system;

said inductive element with one terminal connected to said DC voltage source, the other terminal of said inductive element, referred to herein as the third node, being connected to said first switch, said inductive element being used to store energy and to act as a current source for said DC motor, said inductive element being external to said DC motor, and not part of a main magnetic circuit of said DC motor, said inductive element being capable of operating in a buck converter at the power level required to operate said DC motor and at the frequency of commutation of said first switch;

said first switch being connected to said inductive element in the third node, the other terminal of said first switch, not connected to the third node being connected to said common electrical terminal of the system through an electrical path with low impedance, including low impedance to DC current, said first switch for connecting and disconnecting the third node to said common electrical terminal of the system, said first switch being a controlled switch capable of being turned off and on by control signals from a control system, said control system operating based on an error signal and a value of a desired operating current for said DC motor set externally to the system, said control system for turning said first switch off and on to minimize said error signal and to keep the operating current of said DC motor at said desired value, said first switch being a single pole switch;

a second switch connected between said second and said third node, said second switch being controlled so that a current circulating through said inductive element circulates through said second switch if the first switch is turned off and disconnects the third node from said common electrical terminal of the system, said second switch being a single pole switch;

a current sensor for measuring a current through said DC motor, the output of said current sensor being connected to said control system of said first switch to generate said error signal for the operation of said control system, controlling the operation of said first switch; and

means for controlling operation of said second switch dependent upon the state of the first switch.

42. The system according to claim 41, wherein said first switch is an electronic switch, and said second switch is a diode connected with appropriate polarity so that current circulating through said inductive element circulates through said diode and if said first switch is open, disconnecting said inductive element.

43. The system according to claim 41, wherein said inductive element is an inductor, or a winding of a transformer.

44. The system according to claim 41, wherein a current through the inductive element is controlled independently from a current through the motor, the balance of electrical charge being accumulated or taken from the capacitor in parallel with the motor.

45. The system according to claim 44, wherein said DC motor is an electronically driven motor, including a brushless motor, said motor being braked electronically so that a current produced during the braking process further charges said capacitor in parallel with said motor.

46. The system according to claim 41, wherein a current through the inductive element is modulated as a full wave rectified sinusoid synchronous with the AC mains voltage so that the power factor of the system, as a load to the AC main is improved.

47. The system according to claim 41, wherein said first switch and said direct current (DC) voltage source are implemented by an electronic system that connects said inductive element either to a given voltage or to a high impedance for a period of time determined by said control system controlling said first switch, said high impedance being measured with respect to said common electrical terminal of said system, said given voltage being set externally to said system, said electronic system being connected to said common electrical terminal of the system, said electronic system being controlled by said control system controlling said first switch.

48. The system according to claim 41, wherein said inductive element is an inductor and said second switch is connected to a terminal of said inductor that is not connected to said third node or to said direct current (DC) voltage source.