Thermally compensated current sensing of intrinsic power converter elements

• US 6,812,677 B2
• Filed: 08/15/2002
• Issued: 11/02/2004
• Est. Priority Date: 08/21/2001
• Status: Active Grant

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: Walters, Michael M., Duduman, Bogdan M., Harris, Matthew B.
• Primary Examiner(s): NGUYEN, MATTHEW VAN
• Application Number:
  US10/219,555
• Publication Number:
  US 20030038614A1
• Time in Patent Office: 810 Days
• Field of Search: 323/222, 323/223, 323/226, 323/265, 323/269, 323/271, 323/273, 323/275-277, 323/282, 323/285, 323/290, 323/907, 363/50, 363/56.02, 363/98, 363/132
• US Class Current: 323/277
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: H02M 3/285 Single converters with a plurality of output stages connected in parallel parallel operation of a plurality of converters in dc distribution networks H02J1/10
• 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 DC-to-DC converter includes one or more power switches, a pulse width modulation circuit for generating control pulses for the power switches, and an output inductor connected to the power switches. A thermally compensated current sensor is connected to an intrinsic current sensing element exhibiting a temperature-based parameter non-linearity. The thermally compensated current sensor has a temperature coefficient that substantially matches a temperature coefficient of an intrinsic power converter element used to measure current flow, thus linearizing the current measurement. Also, a current feedback loop circuit cooperates with the pulse width modulation circuit to control the power switches responsive to the thermally compensated current sensor.

Claims

1. A method of regulating a DC-to-DC converter comprising at least one power switch, a pulse width modulation circuit for generating control pulses for the at least one power switch, an output inductor connected to the at least one power switch, and a current feedback loop circuit cooperating with the pulse width modulation circuit for controlling the at least one power switch, the method comprising:

sensing current passing through the inductor using a thermally compensated current sensor connected in parallel to the output inductor and comprising a resistor and capacitor connected in series, the thermally compensated current sensor having a temperature coefficient that substantially matches a temperature coefficient of the output inductor; and

operating the current feedback loop circuit to control the at least one power switch in response to the thermally compensated current sensor.

2. A method according to claim 1 wherein the at least one power switch comprises at least one field effect transistor.

3. A method according to claim 1 wherein the at least one power switch comprises a low side field effect transistor and a high side field effect transistor connected together.

4. A method according to claim 2 wherein the resistor of the thermally compensated current sensor comprises a positive temperature coefficient resistor.

5. A method of regulating a DC-to-DC converter comprising at least one power switch, a pulse width modulation circuit for generating control pulses for the at least one power switch, an output inductor connected to the at least one power switch, and a current feedback loop circuit cooperating with the pulse width modulation circuit for controlling the at least one power switch, the method comprising:

providing a sensed current related to a current being conducted through the output inductor using a thermally compensated current sensor connected to the at least one power switch, the thermally compensated current sensor having a temperature coefficient that substantially matches a temperature coefficient of an on-state resistance of the at least one power switch; and

operating the current feedback loop circuit to control the at least one power switch in response to the thermally compensated current sensor.

6. A method according to claim 5 wherein the at least one power switch comprises at least one field effect transistor.

7. A method according to claim 5 wherein the at least one power switch comprises a low side field effect transistor and a high side field effect transistor connected together.

8. A method according to claim 5 wherein the thermally compensated current sensor is connected between the at least one power switch and the current feedback loop circuit, and the thermally compensated current sensor comprises a resistor.

9. A method according to claim 6 wherein the resistor of the thermally compensated current sensor comprises a positive temperature coefficient resistor.