Switching power supply having dual current feedback
View Patent ↗An arrangement for use in a switching power supply includes a power supply output line, a current sensing circuit, and a feedback circuit. The output line is operably coupled to an output winding of a transformer. The transformer has a first winding operably connected to a switching device configured to be switched in accordance with a first control signal. The current sensing circuit is operable to generate a current signal that is representative of current on the output line. The feedback circuit is operable to generate a feedback signal as a function of the current on the output line. The feedback signal has a first relationship with respect to the current when the current is below a threshold, and has a second relationship with respect to the current when the current is above the threshold.
1. An arrangement for use in a switching power supply, comprising:
an output line operably coupled to an output winding of a transformer, the transformer having a first winding operably connected to a switching device configured to be switched in accordance with a first control signal;
a current sensing circuit operable to generate a current signal representative of the current on the output line;
a first feedback circuit operable to generate a first feedback signal dependent upon the current signal;
a second feedback circuit operable to generate a second feedback signal dependent upon the current signal;
a feedback line operably coupled to the first feedback circuit and the second feedback circuit, the feedback line operable to provide a current feedback signal to a control circuit, the control circuit operable to generate the first control signal based on the current feedback signal.
2. The arrangement of claim 1 , wherein the feedback line is operably coupled to the first feedback circuit via a first diode, and operably coupled to the second feedback circuit via a second diode.
3. The arrangement of claim 1 , wherein the feedback line is operably coupled to generate the current feedback signal as substantially an or combination of the first feedback signal and the second feedback signal.
4. The arrangement of claim 3 , wherein the first feedback circuit is configured to generate the first feedback signal as a linear function of the current signal.
5. The arrangement of claim 4 , wherein the current feedback signal is substantially equal to the second feedback signal when the current signal is below a threshold.
6. The arrangement of claim 1 , wherein the current sensing circuit includes a series resistance and first and second signal lines electrically coupled to opposing ends of the series resistance.
7. The arrangement of claim 6 , wherein the first feedback circuit includes a first differential amplifier coupled to the first and second signal lines.
8. The arrangement of claim 7 , wherein the second feedback circuit includes a second differential amplifier coupled to the first and second signal lines.
9. The arrangement of claim 7 , wherein the first feedback circuit further comprises a comparator operably coupled to receive a current measurement signal from the first differential amplifier and configured to generate a comparator signal based on a comparison of the current measurement signal with a first threshold, and wherein the comparator is operably coupled to provide the comparator signal to a diode, the diode connected to the feedback line.
10. An arrangement for use in a switching power supply, comprising:
an output line operably coupled to an output winding of a transformer, the transformer having a first winding operably connected to a switching device configured to be switched in accordance with a first control signal;
a current sensing circuit operable to generate a current signal representative of current on the output line;
a feedback circuit operable to generate a feedback signal as a function of the current on the output line, the feedback signal having a first relationship with respect to the current when the current is below a threshold, and having a second relationship with respect to the current when the current is above the threshold, and wherein the feedback signal is non-zero when the current is above the threshold.
11. The arrangement of claim 10 , wherein the first relationship comprises a feedback signal voltage to current relationship having a first slope, and the second relationship comprises a feedback signal voltage to current relationship having a second slope, the second slope steeper than the first slope.
12. The arrangement of claim 10 , wherein the feedback circuit is operable to generate the feedback signal as substantially an or combination of a first component and a second component.
13. The arrangement of claim 12 , wherein the feedback circuit includes a diode configured to suppress the second component when the current is below the threshold.
14. The arrangement of claim 12 , wherein the feedback circuit includes a first comparator and a second comparator, and wherein the first component is generated in part by the first comparator, and wherein the second component is generated in part by the second comparator, the first comparator and the second comparator operably coupled to receive a signal representative of the current.
15. An arrangement, comprising:
a first power supply configured to generate a first output voltage at a first output; and
a second power supply configured to generate a second output voltage at a second output, the second output coupled in parallel with the first output, the second power supply including
a current sensing circuit operable to generate a current signal representative of an output current of the second power supply;
a feedback circuit operable to generate a feedback signal as a function of the output current, the feedback signal having a first relationship with respect to the output current when the output current is below a threshold, and having a second relationship with respect to the output current when the output current is above the threshold, and wherein the feedback signal is non-zero when the current is above the threshold.
16. A method for use in a switching power supply, comprising:
a) generating a current signal representative of current on an output line of a switching converter circuit;
b) generating a feedback signal as a function of the current on the output line, the feedback signal having a first relationship with respect to the current when the current is below a threshold, and having a second relationship with respect to the current when the current is above the threshold, wherein the feedback signal is non-zero when the current is above the threshold; and
c) using the feedback signal to adjust an operation of the switching converter circuit.
17. The method of claim 16 , wherein step c) further comprises using the feedback signal to adjust the output voltage of the switching converter.
18. The method of claim 16 , further comprising a step of first connecting the output line to a load and to an output line of another switching converter.
19. The method of claim 16 , wherein step c) further comprises providing the feedback signal to a pulse width modulation control circuit of a switching converter.
20. The method of claim 19 , wherein step c) further comprises providing the feedback signal to the pulse width modulation control circuit through an isolation device.