RESONANT CONVERTER FOR ACHIEVING LOW COMMON-MODE NOISE, ALONG WITH ISOLATED POWER SUPPLY AND METHOD EMPLOYING THE SAME

• US 20100328974A1
• Filed: 06/30/2009
• Published: 12/30/2010
• Est. Priority Date: 06/30/2009
• Status: Active Grant

• Current Assignee: Keysight Technologies, Inc.
• Original Assignee: Keysight Technologies, Inc.
• Inventors: Miller, Daniel, Mueller, Katherine, Marriott, Joe E., Benes, Michael J., Kenny, John F.
• Granted Patent: US 9,240,729 B2
• Time in Patent Office: Days
• US Class Current: 363/126
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 1/123 Suppression of common mode voltage or current
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current
• CPC Class Codes: H02M 7/4815 Resonant converters H02M7/4811 and H02M7/4826 take precedence
• CPC Class Codes: H02M 7/53878 by time shifting switching signals of one diagonal pair of the bridge with respect to the other diagonal pair
• 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

Embodiments are described for reducing common-mode current in electronic devices. In the various embodiments, a resonant converter is employed, for example in a power supply, and the resonant converter is driven by a DC input to generate an AC primary voltage on the primary windings of a power transformer. The DC input may be derived from an AC line voltage or a DC-to-DC converter. The AC primary voltage drives the primary winding of the transformer to generate an AC secondary voltage on at least one secondary winding of the transformer. The AC secondary voltage may then drive a rectifier, which in turn drives a low-pass filter to produce a DC output voltage. Phase-shift modulation is employed which, in conjunction with the resonant converter, applies a sinusoidal waveform to the primary of the transformer resulting in a reduced amount of common-mode current injected onto the secondary.

Claims

1. An isolated resonant converter for achieving reduced common mode noise, comprising:

an input signal source for generating at least one square wave signal;

a resonant circuit driven by said at least one square wave signal for generating a primary alternating current (AC) voltage signal; and

a transformer having a primary winding coupled to said resonant circuit, said transformer driven by the primary AC voltage signal to generate at least one secondary AC voltage at a secondary winding.

2. An isolated resonant converter according to claim 1 wherein said input signal source includes a phase-shift modulated H-bridge driven by a DC input voltage for generating said at least one square wave signal.

3. An isolated resonant converter according to claim 2 wherein said H-bridge includes a first ½

bridge portion driven by the DC input voltage for generating a respective first square wave signal, and a second ½

bridge portion driven by the DC input voltage for generating a respective second square wave signal.

4. An isolated resonant converter according to claim 3 wherein said resonant circuit includes a first resonant sub-circuit driven by said first square wave signal for generating a first AC signal, and a second resonant sub-circuit driven by said second square wave signal for generating a second AC signal, and wherein said primary (AC) voltage signal represents a composite of said first and second AC signals.

5. An isolated resonant converter according to claim 1 further comprising a rectifier configured to be driven by the secondary AC voltage to generate a rectified voltage, and a first low-pass filter configured to be driven by the rectified voltage to produce a DC output voltage.

6. An isolated resonant converter according to claim 1 wherein said primary AC voltage signal is sinusoidal.

7. An isolated resonant converter according to claim 1 further comprising a DC input voltage source configured to generate said DC input voltage.

8. An isolated resonant converter according to claim 1 wherein said resonant circuit behaves as a low-pass filter to reduce harmonic and high frequency content of said square wave signal.

9. An isolated resonant converter according to claim 1 wherein said resonant circuit includes an LC filter formed by a parallel arrangement of at least two inductors and a resonant capacitor, said resonant capacitor tying a primary side of said transformer to a common rail of the resonant converter.

10. An isolated resonant converter according to claim 9 wherein said LC filter has a single resonant frequency and operates to prevent current spikes from the input signal source from passing through to said transformer.

11. An isolated resonant converter according to claim 1 wherein a primary side of said transformer is tied to ground to minimize voltage differential across an interwinding capacitance of the transformer.

12. An isolated resonant converter according to claim 11 wherein said primary winding is wound in a direction opposite said secondary winding.

13. An isolated resonant converter according to claim 1 wherein an exit on a primary side of said transformer is tied to ground and is aligned with an adjacent exit on a secondary side of said transformer, thereby minimizing voltage differential across an interwinding capacitance of the transformer.

14. A power supply employing the isolated resonant converter of claim 1.

15. An electronic device employing the resonant converter of claim 1.

17. An electronic circuit according to claim 12 wherein said means for converting said first and second square wave signals into said composite AC signal includes means for converting said first square wave signal into a first AC signal, means for converting said second square wave signal into a second AC signal, and means for combining said first and second AC signals to produce said composite AC signal.

18. A resonant converter according to claim 12 further comprising means for rectifying the secondary AC signal to yield a rectified signal;

and means for low-pass-filtering the rectified signal to yield a DC signal.

16. An electronic circuit for converting first and second input signals of a first type into a derived signal of a second type different than the first type, comprising:

means for generating first and second square wave input signals;

means for converting each of said first and second square wave input signals into a composite alternating current (AC) signal; and

means for applying said composite AC signal to a primary winding of a transformer to derive a secondary AC signal at a secondary winding of the transformer.

19. An isolated power supply comprising:

a. a power isolation transformer have a primary winding connectable to an AC line voltage to produce a smaller AC line voltage in at least one secondary winding of the transformer;

b. a rectifier driven by the smaller AC line voltage for generating a first rectified voltage;

c. a low pass filter for converting the first rectified voltage into a DC input voltage;

d. an resonant converter for achieving reduced common mode noise, comprising;

i. a phase-shift modulated H-bridge driven by said DC input voltage for generating at least one square wave signal;

ii. a resonant circuit driven by the at least one square wave signal for generating a primary alternating current (AC) voltage signal; and

iii. a transformer having a primary winding coupled to said resonant converter sub-circuit, said transformer driven by the primary AC voltage signal to generate at least one secondary AC voltage at a secondary winding;

e. a rectifier configured to be driven by the secondary AC voltage to generate a second rectified voltage; and

f. a first low-pass filter configured to be driven by the second rectified voltage to produce a DC output voltage.

20. A method for reducing common mode noise in an electronic circuit, comprising:

generating a plurality of square wave signals;

passing said square wave signals into a resonant circuit that is operative to remove harmonics and high frequency content therefrom and convert said square wave signals into a primary alternating current (AC) voltage signal; and

applying said primary AC voltage to the primary winding of a transformer to yield a secondary AC voltage on at least one secondary winding of the transformer.