Automatic PWM controlled driver circuit and method

• US 20070090766A1
• Filed: 10/25/2005
• Published: 04/26/2007
• Est. Priority Date: 10/25/2005
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Notarantonio, Raymond, LaGrave, Christopher, Beier, Robert
• Granted Patent: US 7,358,683 B2
• Time in Patent Office: Days
• US Class Current: 315/82
• CPC Class Codes: H05B 39/047 with pulse width modulation from a DC power source
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

A load driver circuit includes an output transistor configured to drive a load. The circuit further includes a power supply, and a power supply evaluation circuit configured to sense a characteristic of the power supply, and generate a control signal in response thereto. In addition, a controller circuit is provided and is configured to drive the output transistor with a pulse width modulation signal coupled to the control terminal, wherein a duty cycle of the pulse width modulation signal is a function of the control signal of the power supply evaluation circuit.

Claims

1. A load driver circuit, comprising:

an output transistor configured to drive a load, having a first terminal configured to be coupled to a power supply, a second terminal configured to be coupled to the load, and a control terminal;

a power supply evaluation circuit configured to sense a characteristic of the power supply when coupled thereto, and generate a control signal in response thereto; and

a controller circuit configured to drive the output transistor with a pulse width modulation signal coupled to the control terminal, wherein a duty cycle of the pulse width modulation signal is a function of the control signal of the power supply evaluation circuit.

2. The driver circuit of claim 1, wherein the power supply characteristic comprises a voltage magnitude.

3. The driver circuit of claim 2, wherein the controller circuit is configured to reduce a duty cycle of the pulse width modulation signal when the voltage magnitude exceeds a predetermined magnitude threshold.

4. The driver circuit of claim 1, wherein the load comprises a lamp.

5. A pulse width modulation driver system, comprising:

a power transistor comprising a first terminal configured to couple to a battery, a second terminal configured to couple to a light bulb, and a control terminal;

a battery evaluation circuit configured to monitor a state of the battery, and generate a control signal in response thereto; and

a controller circuit configured to drive the control terminal of the power transistor with a pulse width modulation signal having a duty cycle that is a function of the control signal of the battery evaluation circuit.

6. The pulse width modulation driver system of claim 5, wherein the battery evaluation circuit comprises a comparator circuit configured to compare a signal associated with the battery to a reference signal, and generate the control signal in response to the comparison.

7. The pulse width modulation driver system of claim 6, wherein the controller circuit is configured to provide an initial duty cycle if the signal associated with the battery is less than the reference signal, and a subsequent, different duty cycle if the signal associated with the battery is greater than the reference signal, wherein the second duty cycle is less than the first duty cycle, thereby reducing an average power delivered to the light bulb, wherein the signal associated with the battery is greater than the reference signal.

8. The pulse width modulation driver system of claim 5, wherein the battery evaluation circuit is configured to ascertain a magnitude of a voltage associated with the battery, and the controller circuit is configured to vary the duty cycle of the pulse width modulation signal in response thereto.

9. The pulse width modulation driver system of claim 8, wherein the controller circuit is configured to decrease the duty cycle of the pulse width modulation signal when the magnitude of the battery voltage increases.

10. A pulse width modulation lamp driver system, comprising:

switching means for driving a lamp based on a pulse width modulation signal;

means for monitoring a power supply operably associated with the switching means when operably coupled thereto, and providing a control signal in response thereto; and

controller means for altering a duty cycle of the pulse width modulation signal to the switching means in response to the control signal.

11. The pulse width modulation lamp drive system of claim 10, wherein the monitoring means is operable to monitor a voltage magnitude associated with the power supply.

12. The pulse width modulation lamp drive system of claim 11, wherein the monitoring means is operable to compare the voltage magnitude with a reference value and generate the control signal in response thereto.

13. The pulse width modulation lamp driver system of claim 12, wherein when the control signal indicates that the voltage magnitude exceeds the reference value, the controller means is operable to reduce the duty cycle of the pulse width modulation signal, thereby reducing an average power delivered to the lamp.

14. An intelligent lamp driver system, comprising:

a lamp operable to provide interior or exterior illumination;

a drive transistor operably coupled to the lamp, and operable to selectively drive the lamp, and configured to be coupled to a battery, wherein a power delivered to the lamp by the drive transistor is a function of a magnitude of a voltage of the battery;

a battery voltage detection circuit configured to monitor the voltage magnitude of the battery when coupled thereto, and generate a control signal in response thereto; and

a controller circuit configured to receive the control signal and generate a pulse width modulation signal having a duty cycle that is a function of the control signal, wherein the pulse width modulation signal drives the drive transistor, and wherein a change in the duty cycle of the pulse width modulation signal varies an average power delivered to the lamp.

15. The lamp driver system of claim 14, further comprising a temperature sensing circuit configured to sense a temperature associated with the drive transistor, or the lamp, or both, and generate a thermal control signal in response thereto, and wherein the controller circuit is configured to alter the duty cycle of the pulse width modulation signal or turn off the drive transistor based on the thermal control signal.

16. The lamp driver system of claim 14, further comprising a current sensing circuit configured to sense a magnitude of current flowing to the lamp and generate a current sense control signal in response thereto, and wherein the controller circuit is configured to alter the duty cycle of the pulse width modulation signal or turn off the drive transistor based on the current sense control signal.

17. The lamp driver system of claim 14, further comprising a charge pump coupled between the controller circuit and the drive transistor, and configured to receive the pulse width modulation signal, and generate a boosted pulse width modulation signal, and provide the boosted pulse width modulation signal to a control terminal of the drive transistor.

18. The lamp driver system of claim 14, wherein the battery voltage detection circuit is configured to compare a voltage associated with the battery to one or more predetermined thresholds, and generate the control signal having a value or state based on the comparison.

19. The lamp driver system of claim 18, wherein the controller circuit reduces the duty cycle of the pulse width modulation signal from a first duty cycle to a second, reduced duty cycle when the control signal indicates that the voltage associated with the automotive battery exceeds one of the predetermined thresholds.

20. A method of driving a load, comprising:

monitoring a characteristic associated with a power supply associated with the load; and

altering a duty cycle of a pulse width modulation signal that is fed to a drive transistor that is employed to drive the load based on the monitored characteristics.

21. The method of claim 20, wherein monitoring the characteristic comprises:

determining whether a voltage magnitude associated with the power supply exceeds a predetermined threshold; and

generating a control signal in response to the determination.

22. The method of claim 20, wherein the characteristic comprises a voltage associated with the power supply, the power supply comprises an automotive battery, and the load comprises an exterior or interior lamp, and wherein altering the duty cycle of the pulse width modulation signal comprises reducing the duty cycle from a first duty cycle to a second, reduced duty cycle if the voltage is greater than a predetermined threshold, thereby reducing an average power delivered to the lamp.

23. The method of claim 20, further comprising:

sensing a temperature associated with the drive transistor, or sensing a current associated with the load; and

altering the duty cycle of the pulse width modulation signal if the sensed temperature associated with the drive transistor or sensed current exceeds a respective predetermined threshold.

24. The method of claim 23, wherein the altered duty cycle is zero, thereby turning off the drive transistor.

25. A method of driving an exterior or interior lamp in an automotive system, comprising:

driving the lamp with a drive transistor, wherein an average power delivered to the lamp is a function of an automotive battery condition;

monitoring a characteristic associated with the automotive battery; and

controlling a duty cycle associated with a pulse width modulation signal at a control terminal of the drive transistor based on the monitored characteristic.

26. The method of claim 25, wherein the characteristic comprises a voltage magnitude associated with the automotive battery, and wherein monitoring the characteristic comprises comparing the voltage magnitude to a predetermined threshold.

27. The method of claim 26, wherein controlling the duty cycle comprises reducing the duty cycle from a first duty cycle to a second, reduced duty cycle if the voltage magnitude associated with the automotive battery exceeds the predetermined threshold, thereby reducing the average power delivered to the lamp.

28. The method of claim 27, further comprising:

monitoring a temperature associated with the drive transistor; and

controlling a duty cycle associated with a pulse width modulation signal at a control terminal of the drive transistor based on the monitored temperature.

29. The method of claim 27, further comprising:

monitoring a current associated with the lamp; and

controlling a duty cycle associated with a pulse width modulation signal at a control terminal of the drive transistor based on the monitored current.