EE6821Special Topics in

Advanced Utilization ICoursework ppt2

Student Name: FONG Yat ChiStudent ID: 14900129R

Skin Effect◦Derivate the Skin Depth

Level-shifting Circuits for Controlling Signal◦Non-isolating Techniques

Some Results of Capacitor Test

Content

◦ Increase in → Increase in Because the current concentrated near to the

surface of the conductor

Skin depth:δ =

Skin Effect

AC current distribution in a cylindrical conductor(Picture from the Internet)

◦ Cause of Skin Effect:Magnetic Induction

(due to the changing field in the conductor)

◦ Inside the conductor:

Skin Effect (Cont’d)

Coordinates for the cylindrical conductor

◦ Relationship between J and B

• J: flow in y-direction Equal in x-direction

B: flow in x-direction Equal in y-direction

◦ J and B only change in z-direction

Skin Effect (Cont’d)

Coordinates for the cylindrical conductor

◦ J and B only change in z-direction

◦ This become a 2nd Order ODE

◦ Solution:

→

Skin Effect (Cont’d)

Coordinates for the cylindrical conductor

𝐽 𝑠

◦ Extract the attenuation term:

◦ Attenuation term:

◦ Skin depth (Decay Constant)

Skin Effect (Cont’d)

Coordinates for the cylindrical conductor

𝐽 𝑠

Shift Signal level from V1 to V2

◦ A Passive Level Shifting Circuit

Easy to implement Suffer from many problems

Level-shifting Circuits

◦ Active Level-Shifting Circuits Often use in digital interface

Require a voltage source for output Use active switch

Level-shifting Circuits (Cont’d)

◦ Active Level-Shifting Circuits

Level-shifting Circuits (Cont’d)

Higher Voltage Version The resistors limit the current→ Low Speed

Higher Speed→ Higher Current

→ Higher Loss Some solutions in the

industry

◦ Reduce the Duty-ratio of the Switch

◦ Use encoding and latch◦ Mature technique in commercial Products

Level-shifting Circuits (Cont’d)

Functional diagram for a high-side gate drive IC(from Fairchild Application Note)

Conclusion◦ Passive Level-Shifter Easy to implement No voltage source (use Vs to supply) Easily get malfunction

◦ Active Level-Shifter Require a voltage supply More complicated digital circuits

Level-shifting Circuits (Cont’d)

Capacitor Test

1st Sample

3rd Sample

2nd Sample4th Sample

5th Sample

Network Analyzer with Impedance Module

FRA5087 Network Analyzer

Impedance Module

Result:

1st Sample: Panasonic 1μF 275V Polypropylene

Compare with LCR Meter (Con’t)

From LCR MeterCs ≈ 0.86μFLs ≈ 41.4nHRs ≈ 0.037Ωfr ≈ 850kHz

From Network AnalyzerCs ≈ 0.86μFLs ≈ 188nHRs < 0.037Ωfr ≈ 400kHz

2nd Sample: Epcos 4.4μF 250V Polypropylene

Compare with LCR Meter (Con’t)

From LCR MeterCs ≈ 4.42μFLs ≈ 28.6nHRs ≈ 0.0155Ωfr ≈ 440kHz

From Network AnalyzerCs ≈ 4.48μFLs ≈ 213nHRs < 0.0123Ωfr ≈ 160kHz

3rd Sample: Unknown 0.56μF 275V Polypropylene

Compare with LCR Meter (Con’t)

From LCR MeterCs ≈ 0.57μFLs ≈ 30.4nHRs ≈ 0.041Ωfr ≈ 1.21MHz

From Network AnalyzerCs ≈ 0.58μFLs ≈ 254nHRs < 0.0329Ωfr ≈ 410kHz

4th Sample: BC 2.2μF 100V Polypropylene

Compare with LCR Meter (Con’t)

From LCR MeterCs ≈ 2.24μFLs ≈ 20.5nHRs ≈ 0.0226Ωfr ≈ 742kHz

From Network AnalyzerCs ≈ 2.21μFLs ≈ 251nHRs < 0.0222Ωfr ≈ 210kHz

5th Sample: Kemet 680nF 50V Ceramic

Compare with LCR Meter (Con’t)

From LCR MeterCs ≈ 0.58μFLs ≈ 16.1nHRs ≈ 0.0619Ωfr ≈ 1.68MHz

From Network AnalyzerCs ≈ 0.56μFLs ≈ 238nHRs < 0.0281Ωfr ≈ 440kHz

Network Analyzer◦ Resonant frequency shift to left due to the

increase in Ls◦ Low resolution of phase angle◦ Convenient to plot the frequency response

Further Works to be Done◦ More samples of each model◦ Try different of types (e.g. Electrolyte)◦ Test with higher voltage/current using amplifier◦ AC vs AC superposed with DC◦ Reduce the effect of additional inductance

Comments

Thankyou!Q&A