Common mode noise reduction circuit utilizing dual primary windings
View Patent ↗A common mode noise cancellation circuit eliminates common mode noise generated by a high-frequency switching device. The common mode noise reduction circuit includes a single switching device and a transformer. The switching device receives a rectified voltage and produces a switched voltage. The transformer includes a first primary winding, a second primary winding, and a secondary winding. The transformer couples the switched output from the first and the second primary winding to the secondary winding to generate a transformed voltage. A positive signed common mode noise waveform generated by the switching device is coupled from the first primary winding to the first secondary winding, and a negative signed common mode noise waveform generated by the switching device is coupled from the second primary winding to the first secondary winding, which results in a lower magnitude common mode noise waveform being present at the secondary winding.
1. A common mode noise reduction circuit, comprising:
a switching device to receive a DC voltage and to produce a switched voltage; and
a transformer, including a first primary winding, a second primary winding, and a secondary winding, to couple the switched output from the first primary winding and the second primary winding to the secondary winding and generate a transformed voltage, wherein a positive signed common mode noise waveform generated by the switching device is coupled from the first primary winding to the first secondary winding, and a negative signed common mode noise waveform generated by the switching device is coupled from the second primary winding to the first secondary winding, which results in a lower magnitude common mode noise waveform being present at the secondary winding.
2. The common mode noise cancellation circuit of claim 1 , wherein the negative signed common mode noise waveform cancels out the positive signed common mode noise waveform.
3. The common mode noise cancellation circuit of claim 1 , wherein an output terminal of the single switching device is coupled to a bottom winding of the first primary winding.
4. The common mode noise cancellation circuit of claim 1 , wherein an output terminal of the single switching device is coupled to a top winding of the second primary winding.
5. A power supply, comprising:
an input voltage system for providing an input voltage;
a switching device to receive the input voltage and to produce a switched voltage; and
a transformer, the transformer coupled to the switching device to receive the switched voltage and to generate a transformed voltage, the transformer including:
a first primary winding;
a second primary winding; and
a secondary winding, wherein a positive signed common mode noise waveform generated by the single switching device is coupled from the first primary winding to the first secondary winding, and a negative signed common mode noise waveform generated by the switching device is coupled from the second primary winding to the first secondary winding, which results in a reduction of a common mode noise waveform being present at the secondary winding.
6. The power supply of claim 5 , further including an output rectifier to receive the transformed voltage and to generated a rectified output voltage.
7. The power supply of claim 5 , wherein the input voltage subsystem receives an AC voltage, rectifies the AC voltage to generate an input rectified voltage and supplies the input rectified voltage to the single switching device.
8. The power supply of claim 7 , wherein the input voltage subsystem further includes a noise filter to reduce EMI noise input into the power supply.
9. The power supply of claim 5 , wherein the negative signed common mode noise waveform cancels out the positive signed common mode noise waveform.
10. A common mode noise reduction circuit, comprising:
a switching device to receive an input voltage and to output a switched voltage;
a transformer, including a first primary winding with a first number of turns, a second primary winding with a second number of turns, and a secondary winding, to receive the switched voltage at the first primary winding and the second primary winding, and to couple the switched voltage to the secondary winding to produce a transformed voltage,
wherein a first part of a common mode noise waveform generated by the switching device is coupled from the first primary winding to the secondary winding and a second part of the common mode noise waveform generated by the switching device is coupled from the second primary winding to the secondary winding and a relationship of the first number of turns to the second number of turns causes movement of a node at the secondary winding where a noise cancellation waveform is minimized.
11. The common mode noise reduction circuit of claim 10 , wherein the first part of the common mode noise waveform is positively signed and the second part of the common mode noise waveform is negatively signed and the addition of the first part and the second part results in the minimized common mode noise waveform at the node of the secondary winding.
12. The common mode noise reduction circuit of claim 11 , wherein the first part of the common mode noise waveform and the second part of the common mode noise waveform cancel each other which results in no common mode noise waveform being present at the node the secondary winding.
13. The common mode noise reduction circuit of claim 10 , wherein the first number of turns is equal to the second number of turns and the node is in a center of the secondary winding.
14. The common mode noise reduction circuit of claim 10 , wherein the first number of turns is greater than the second number of turns which causes the node having the minimized common mode noise waveform to be moved to a bottom terminal of the secondary winding.
15. The common mode noise reduction circuit of claim 10 , wherein the bottom terminal of the secondary winding is coupled to ground.
16. A power supply, comprising:
an input voltage subsystem to receive a voltage from an external power source and to generate an input voltage;
a switching device to receive the input voltage and to output a switched voltage;
a transformer, including a first primary winding with a first number of turns, a second primary winding with a second number of turns, and a secondary winding, to receive the switched voltage at the first primary winding and the second primary winding, and to couple the switched voltage to the secondary winding to produce a transformed voltage,
wherein a first part of a common mode noise waveform generated by the switching device is coupled from the first primary winding to the secondary winding and a second part of the common mode noise waveform generated by the switching device is coupled from the second primary winding to the secondary winding and a relationship of the first number of turns to the second number of turns determines location of a node at the secondary winding where a noise cancellation waveform is reduced.
17. The power supply of claim 16 , wherein the first part of the common mode noise waveform is positively signed and the second part of the common mode noise waveform is negatively signed and the addition of the first part and the second part results in the reduced common mode noise waveform at the node of the secondary winding.
18. The power supply of claim 16 , wherein the first part of the common mode noise waveform and the second part of the common mode noise waveform cancel each other which results in no common mode noise waveform being present at the node the secondary winding.
19. The power supply of claim 16 , wherein the first number of turns is equal to the second number of turns and the node is in a center location of the secondary winding.
20. The power supply of claim 16 , wherein the first number of turns is greater than the second number of turns which causes the node having the minimized common mode noise waveform to be moved to a bottom terminal of the secondary winding.
21. The power supply of claim 20 , wherein the bottom terminal of the secondary winding is coupled to ground.
22. The power supply of claim 16 , wherein the second number of turns is greater than the first number of turns which results in the node being moved to a location higher on the secondary winding.
23. The power supply of claim 16 , wherein the input voltage subsystem receives an AC input voltage, filters out the EMI noise, rectifies the AC input voltage to produce a rectified voltage and the rectified voltage is provided as the input voltage to the switching device.