Development of a universal bidirectional galvanic isolated switch module for power converter applications

Kopano Mokhalodi

Vaal University of Technology

Energy Postgraduate Conference 2013

Outline

• Introduction

• Objectives

• Structure and operation

• Electrical characteristics

• Testing and results

• Conclusion

Objectives

• Development of a switch module that can be used to

implement control algorithms in experimental setups

without having any interface problems between the

control circuit and the conversion topology.

• Usable in both DC and AC converter applications.

• Capable supplying a continuous (DC) output of either polarity for Pulse Width Modulation (PWM) applications.

• Easy and cheap to construct, low drive impedance to achieve high switching performance.

• Prevents interference between power stage and control.

C1

PC925L

DC Bus

R1

Opto-coupler

-15V1

Rb

Q2

Q1

15 V2

V3

Rg

Q3

Cs

Rs

R2

C2

Structure with Floating voltage supply technique

Electrical characteristics of the module

Control circuit

Switch module

Power Converter

Dead-time

Gate and drain-to-source voltage signals

Q1-

G /

V

-15

-10

-5

0

5

10

Time/uSecs 2uSecs/div

0 2 4 6 8 10 12 14

Q1-

D /

V

2

6

10

14

18

Gate voltage

Peak To Peak=30.046359V

Frequency=100.00414kHertz

Drain-to-source voltage

Peak To Peak=20.067475V

Gate voltage

Drain output voltage

Gate voltage

Drain output voltage

Time/uSecs 2uSecs/div

0 2 4 6 8 10 12 14

Gat

e vo

ltage

/ V

-10

-5

0

5

10

15

Gate voltage

Peak To Peak=30.691472V

Frequency=99.932241kHertz

DC practical results

Q1-

S /

V

0

6

12

18

Time/uSecs 5uSecs/div

175 180 185 190 195 200

I(L1-

P) /

mA

0

400

800

VOLTAGE

Peak/@=21.189672V/240.02354uSecs

Frequency=99.995015kHz

INDUCTOR CURRENT

Peak/@=1.3862005A/85.030273uSecs

Steps down voltage 10 - 30 V to 5 V,

Dead-time

AC converter results at 30 % duty cycle

The rms output voltage is given as

(1 - ) sin V k V to s

k ≡ duty cycle

Conclusion

The switch module has over-come the problem of interfacing the control with the power stage. From the results obtained the prototype module proved to be able to be used both in DC and AC applications.

Students involved in other power converters will be able to use thismodule.

Thank you