Volt-second integration cable compensation circuit

Patent metadata

Field	Value
Publication number	US-9331582-B2
Application number	US-201314015349-A
Country	US
Kind code	B2
Filing date	Aug 30, 2013
Priority date	Dec 21, 2012
Publication date	May 3, 2016
Grant date	May 3, 2016

Abstract

A power converter (such as a battery charger) includes a cable configured to deliver a source voltage and current to a load, where the cable is anticipated to drop some voltage as the load current increases. The power converter also includes a regulator having a feedback-adjusting transistor configured to gradually compensate for the dropped cable voltage as the load current increases. The transistor has a gate capacitance and a resistance forming an integrator configured to filter a volt-second product of an output waveshape of the converter to derive an average voltage correlated to the load current as the load current increases. The regulator is configured to increase a gate voltage of the transistor through a threshold region of the transistor and gradually turn the transistor on. The transistor is configured to apply an adjusting resistance coupled to a feedback sensing node of the regulator to increase the source voltage to compensate for the cable voltage drop and improve the load voltage regulation.

First claim

What is claimed is:

1. For use in a converter configured to provide a source voltage to a cable extending between the source voltage and a load where the cable drops a cable voltage as a load current to the load increases, a method comprising:
providing an output waveshape to a regulator having a feedback adjusting transistor configured to gradually compensate for the dropped cable voltage as the load current increases; and
using a gate capacitance of the transistor and a resistance as an integrator to filter a volt-second product of an output waveshape of the converter to derive an average voltage correlated to the load current as the load current increases;
wherein the transistor is a signal-level MOSFET and a gate voltage of the transistor increases through a threshold region of the transistor and gradually turns the transistor on, the transistor applying an adjusting resistance coupled to a feedback sensing node of the regulator to increase the source voltage.

2. The method as specified in claim 1 , wherein the converter comprises an input transformer receiving an input voltage and delivering a rectified secondary output voltage and a rectified secondary tap voltage, the rectified secondary tap voltage used to create the gate voltage coupled to a gate of the transistor.

3. The method as specified in claim 2 , wherein the gate voltage is created by a resistive divide network coupled to the rectified secondary tap voltage.

4. The method as specified in claim 2 , wherein the regulator is coupled between the rectified secondary output voltage and ground and provides a feedback adjustment path to the transistor.

5. The method as specified in claim 4 , wherein the transistor has a drain voltage coupled to the feedback sensing node of the regulator.

6. The method as specified in claim 4 , wherein a feedback sensing voltage is created at least in part by a resistive divide network coupled to the rectified secondary output voltage.

7. The method as specified in claim 4 , wherein a feedback adjusting resistor is coupled between the feedback sensing voltage and the transistor.

8. A converter configured to deliver a source voltage and current to a load via a cable, wherein the cable is anticipated to drop a cable voltage as the load current increases, comprising:
a regulator having a feedback adjusting transistor configured to gradually compensate for the dropped cable voltage as the load current increases, the transistor having a gate capacitance and external resistance forming an integrator configured to filter a volt-second product of an output waveshape of the converter to derive an average gate voltage correlated to the load current as the load current increases;
wherein the regulator is configured to increase a gate voltage of the transistor through a threshold region of the transistor and gradually turn the transistor on, the transistor configured to apply an adjusting resistance coupled to a feedback sensing node of the regulator to increase the load voltage.

9. The converter as specified in claim 8 , wherein:
the converter further comprises an input transformer configured to receive an input voltage and deliver a rectified secondary output voltage and a rectified secondary tap voltage; and
the rectified secondary tap voltage is configured to be used, in part, to create the gate voltage of the transistor.

10. The converter as specified in claim 9 , further comprising a rectifier and resistive divide network coupled to the secondary output voltage and configured to create the gate voltage.

11. The converter as specified in claim 9 , wherein the regulator is coupled between the rectified secondary output voltage and ground and is configured to provide a feedback sensing adjustment path to the transistor.

12. The converter as specified in claim 11 , wherein the transistor has a drain voltage coupled to the feedback sensing node of the regulator.

13. The converter as specified in claim 11 , wherein a feedback sensing voltage is created at least in part by a resistive divide network coupled to the rectified secondary output voltage.

14. The converter as specified in claim 13 , wherein a feedback adjusting resistor is coupled between the feedback sensing voltage and the transistor.

15. The converter as specified in claim 8 , wherein the regulator includes an optical coupler configured to provide a feedback error signal to regulate a converter output voltage.

16. A regulator configured to regulate a source voltage as a load current is delivered to a load using a cable, comprising:
a feedback adjusting transistor configured to gradually compensate for dropped cable voltage as the load current increases, the transistor having a gate capacitance and a gate external resistance forming an integrator configured to filter a volt-second product of an output waveshape of the regulator to derive an average voltage correlated to the load current as the load current increases;
wherein the transistor is a signal-level MOSFET and the regulator is configured to increase a gate voltage of the transistor through a threshold region of the transistor and gradually turn the transistor on, the transistor configured to apply an adjusting resistance coupled to a feedback sensing node of the regulator to increase the source voltage.

17. The regulator as specified in claim 16 , further comprising a rectifier and a resistive divide network configured to create the gate voltage, wherein the integrator is configured to filter a volt-second product of an output waveshape of the rectifier.

18. The regulator as specified in claim 16 , wherein an external capacitance is connected between the transistor gate and GND, to provide additional volt-second integration filtering.

19. The regulator as specified in claim 16 , wherein the regulator is configured to provide a feedback sensing adjustment path to the transistor.

20. The regulator as specified in claim 19 , further comprising a feedback adjusting resistance coupling a drain of the transistor to the feedback sensing node of the regulator.

Assignees

• Texas Instruments Inc

Inventors

• Goerke Ulrich B

Classifications

• H02M2001/0025

  Electricity · mapped topic

• H02M3/33507 Primary

  with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence) · CPC title

• H02M2001/0048

  Electricity · mapped topic

• Y02B70/10

  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 · CPC title

• H02M1/0025

  Arrangements for modifying reference values, feedback values or error values in the control loop of a converter · CPC title