Power supply circuit with temperature-dependent output current

• US 20080129267A1
• Filed: 11/02/2006
• Published: 06/05/2008
• Est. Priority Date: 11/02/2006
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Lenz, Michael
• Granted Patent: US 7,741,825 B2
• Time in Patent Office: Days
• US Class Current: 323/285
• CPC Class Codes: H05B 45/18 using temperature feedback
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]

Abstract

A power supply circuit is disclosed herein comprising a load current path for connecting a load which has a switching element. The power supply circuit also includes a current sensor for providing a current measurement signal dependent on a current through the load current path. A drive circuit is also included which provides a clocked drive signal with a number of drive cycles, in each case having an on period and an off period, for the switching element. A temperature sensor arrangement with a temperature sensor is provided for determining an environmental temperature in the area of the temperature sensor, which provides a temperature measurement signal dependent on the environmental temperature. The clocked drive signal is dependent on the current measurement signal and the temperature measurement signal.

Claims

1. A power supply circuit comprising:

a load current path configured for connection to a load, the load current path including a switching element;

a current sensor configured to provide a current measurement signal dependent on a load current through the load current path;

a temperature sensor arrangement including a temperature sensor configured to determine an environmental temperature in the area of the temperature sensor, the temperature sensor arrangement configured to provide a temperature measurement signal dependent on the environmental temperature; and

a drive circuit configured to provide a clocked drive signal with a plurality of drive cycles for the switching element, each of the plurality of drive cycles including an on period and an off period, the clocked drive signal being dependent on the current measurement signal and the temperature measurement signal.

2. The power supply circuit of claim 1 wherein a duty ratio of the clocked drive signal is dependent on the current measurement signal and the temperature measurement signal.

3. The power supply circuit of claim 2 wherein the duty ratio decreases at least temporarily with an increasing environmental temperature indicated by the temperature measurement signal.

4. The power supply circuit of claim 1 wherein the drive signal is dependent on the temperature measurement signal and the current measurement signal such that the load current increases with a rising temperature until a threshold value is reached and the load current decreases after this threshold value has been reached.

5. The power supply circuit of claim 4 wherein a slope of an increase in the current for temperatures below the threshold value is smaller than a slope of a decrease in the current for temperatures above the threshold value.

6. The power supply circuit of claim 1 wherein the drive circuit is configured to block the switching element for a predetermined off period during a drive cycle, wherein the predetermined off period begins when the current measurement signal rises up to a value dependent on the temperature measurement signal.

7. The power supply circuit of claim 1 wherein the switching element is a power transistor.

8. The power supply circuit of claim 1 further comprising an enable circuit including an input configured to receive an enable signal, wherein the enable circuit is configured to enable the power supply circuit to provide a load current on the load current path in dependence on the enable signal.

9. A circuit arrangement comprising:

a power supply circuit comprising,

(i) a load current path including a switching element;

(ii) a current sensor configured to provide a current measurement signal dependent on a load current through the load current path;

(iii) a temperature sensor arrangement including a temperature sensor configured to determine an environmental temperature in the area of the temperature sensor, the temperature sensor arrangement configured to provide a temperature measurement signal dependent on the environmental temperature; and

(iv) a drive circuit configured to provide a clocked drive signal with a plurality of drive cycles for the switching element, each of the plurality of drive cycles including an on period and an off period, the clocked drive signal being dependent on the current measurement signal and the temperature measurement signal; and

a load connected to the load current path of the power supply circuit, the load including at least one light-emitting diode.

10. The circuit arrangement of claim 9 further comprising an inductive storage element connected in series with the at least one light-emitting diode.

11. The circuit arrangement of claim 10 further comprising a freewheeling element connected in parallel with a series circuit that includes the least one light-emitting diode and the inductive storage element.

12. The circuit arrangement of claim 9 wherein the power supply circuit and the load are arranged on a common support.

13. The circuit arrangement of claim 12 wherein the temperature sensor is arranged spaced apart from the load on the support.

14. The circuit arrangement of claim 9 wherein the power supply circuit is at least partially integrated in a semiconductor chip separated from the load.

15. The circuit arrangement of claim 14 wherein the temperature sensor is integrated in the semiconductor chip of the power supply circuit.

16. The circuit arrangement of claim 9 wherein a duty ratio of the clocked drive signal is dependent on the current measurement signal and the temperature measurement signal.

17. The circuit arrangement of claim 16 wherein the duty ratio decreases at least temporarily with an increasing environmental temperature indicated by the temperature measurement signal.

18. The circuit arrangement of claim 9 wherein the drive signal is dependent on the temperature measurement signal and the current measurement signal such that the load current increases with a rising temperature until a threshold value is reached and the load current decreases after this threshold value has been reached.

19. The circuit arrangement of claim 9 wherein the drive circuit is configured to block the switching element for a predetermined off period during a drive cycle, wherein the predetermined off period begins when the current measurement signal rises up to a value dependent on the temperature measurement signal.

20. A circuit arrangement comprising:

a load;

a load current path connected to the load, the load current path including a switching element;

means for providing a current measurement signal dependent on a load current flowing through the load current path;

means for determining an environmental temperature in an area of the load and for providing a temperature measurement signal dependent on the environmental temperature; and

means for providing a clocked drive signal with a number of drive cycles for the switching element, each drive cycle having an on period and an off period, the clocked drive signal being dependent on the current measurement signal and the temperature measurement signal.