Control of current in an inductance with pulse width modulation at control frequency

• US 7,271,993 B2
• Filed: 07/27/2004
• Issued: 09/18/2007
• Est. Priority Date: 07/28/2003
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: ON Semiconductor Corporation
• Inventors: De Cock, Bart, Plojhar, Jan
• Primary Examiner(s): Jackson; Stephen W.
• Assistant Examiner(s): CLARK, CHRISTOPHER JAY
• Application Number:
  US10/899,653
• Publication Number:
  US 20050040880A1
• Time in Patent Office: 1,148 Days
• Field of Search: 361/159, 388/811
• US Class Current: 361/154
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• 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 7/53803 with automatic control of output voltage or current

Abstract

A PWM controller for a bridge driver circuit for controlling current in an inductive load such as a motor, can set the driver into a forward mode, a slow decay mode or a fast decay mode, and can switch from slow decay mode into forward mode or into fast decay mode for the duration of pulses at controlled time intervals to provide pulse width modulated control of the current. This is a simpler control scheme avoiding complex switching schemes related to mixed mode decay. By using a controlled PWM frequency, it is easier to avoid the problems of variable frequency such as increased heat dissipation or acoustic noise generation. It can have a selector for selecting top or bottom sense switching, enabling a wider range of stable PWM duty-cycles to be used (e.g. 0% to 100%), which is useful to compensate for Back emf influence on coil-drive.

Claims

1. A controller for a bridge driver circuit for controlling current in an inductive load, the controller including one single pulse width modulator and one single current sensor providing feedback to the controller, the controller being arranged to set the driver into a forward mode, a slow decay mode or a fast decay mode, and being arranged to switch from slow decay mode into forward mode or into fast decay mode at controlled time intervals to provide pulse width modulated control of the current whereby both, the switching into said forward mode and the switching into said fast decay mode is done under the control of said single pulse width modulator.

2. The controller of claim 1 having a selector for selecting top or bottom sense switching.

3. The controller of claim 2, the selector being arranged to select according to a duty cycle of an output of the controller.

4. The controller of claim 3, having a detector for detecting when the duty cycle reaches a pre-determined value between 0.5 and 1, and using this to make the selection.

5. The controller of claim 1, having a latch for outputting a drive control signal, the latch being set by a clock signal and reset by a signal indicating a current in the inductive load has reached a desired level.

6. The controller of claim 1, arranged to delay a switching of the bridge driver to provide a guard band to avoid an overlap between modes.

7. A pulse width modulation controller for controlling current in an inductive load, according to a comparison of a desired and a measured current, the controller including only one single pulse width modulator, the controller being arranged to carry out top sensing where for each pulse the current is driven up until it reaches the desired value, then allowed to decay, or to carry out a bottom sensing where for each pulse the current is driven away from the desired value and allowed to decay towards the desired value, the controller having a selector for selecting top or bottom sense switching.

8. The controller of claim 7, the selector being arranged to select according to a duty cycle of an output of the controller.

9. An integrated circuit comprising:

a controller for a bridge driver circuit for controlling current in an inductive load, the controller including one single pulse width modulator and one single current sensor providing feedback to the controller, the controller being arranged to set the driver into a forward mode, a slow decay mode or a fast decay mode, and being arranged to switch from slow decay mode into forward mode or into fast decay mode at controlled time intervals to provide pulse width modulated control of the current.

10. An integrated circuit comprising:

a pulse width modulation controller for controlling current in an inductive load, according to a comparison of a desired and a measured current, the controller including only one single pulse width modulator, the controller being arranged to carry out top sensing where for each pulse the current is driven up until it reaches the desired value, then allowed to decay, or to carry out a bottom sensing where for each pulse the current is driven away from the desired value and allowed to decay towards the desired value, the controller having a selector for selecting top or bottom sense switching.

11. A system comprising:

a motor; and

a controller for a bridge driver circuit for controlling current in the motor, the controller including one single pulse width modulator and one single current sensor providing feedback to the controller, the controller being arranged to set the driver into a forward mode, a slow decay mode or a fast decay mode, and being arranged to switch from slow decay mode into forward mode or into fast decay mode at controlled time intervals to provide pulse width modulated control of the current whereby both, the switching into said forward mode and the switching into said fast decay mode is done under the control of said single pulse width modulator.

12. A system comprising:

a motor; and

a pulse width modulation controller for controlling current in the motor, according to a comparison of a desired and a measured current, the controller including only one single pulse width modulator, the controller being arranged to carry out top sensing where for each pulse the current is driven up until it reaches the desired value, then allowed to decay, or to carry out a bottom sensing where for each pulse the current is driven away from the desired value and allowed to decay towards the desired value, the controller having a selector for selecting top or bottom sense switching.

13. A method of controlling a current in an inductive load by switching between a forward mode, a slow decay mode or a fast decay mode, the method having the act of switching from slow decay mode into forward mode or into fast decay mode for the duration of pulses at controlled time intervals to provide pulse width modulated control of the current whereby a single pulse width modulator is controlling the time and duration of said pulses at controlled time intervals for said switching into forward mode and for said switching into fast decay mode.

14. The method of claim 13, further comprising selecting top or bottom sense switching.

15. The method of claim 14, wherein the selection is made according to a duty cycle of an output of the controller.

16. The method of claim 15, further comprising detecting when the duty cycle reaches a pre-determined value between 0.5 and 1, and using this to make the selection.

17. The method of claim 13, further comprising sensing a current in the inductive load to provide feedback control.

18. The method of claim 13, further comprising outputting a drive control signal which is set by a clock signal and reset by a signal indicating a current in the inductive load has reached a desired level.

19. The method of claim 13, further comprising delaying a switching to provide a guard band to avoid an overlap between modes.

20. A method of controlling a current in an inductive load by pulse width modulation according to a comparison of a desired and a measured current, the measured current being delivered by one single current sensor and the pulse width modulation obtained from one single pulse width modulator, the method having the act of selecting between top sensing where for each pulse the current is driven up until it reaches the desired value, then allowed to decay, or bottom sensing where for each pulse the current is driven away from the desired value and allowed to decay towards the desired value.

21. The method of claim 20, wherein the selecting is arranged according to a duty cycle or an output of a controller.