Resonant Converter -> Resonant Inverter

Diplomarbeit von Thorsten Borresch, Jörn Krüger

Abstract:

The report describes the building of a simple resonant converter with a series resonant circuit as load. This work is a subject in the field of power electronics.

The report includes a complete describtion of the analytical fundamentals of a DC/AC converter with a resonant circuit as load.

Modern semiconductor devices like IGBTs, MBGTs, MOSFETs, Thyristors, ... are also tested for a succesfull using in converter circuits.

The most important thing in this work is the minimizing of the switching losses in the semiconductor devices. For that purpose the switching point lays near the current and voltage zero. The special difficulties for the dimensioning of the components are commented.

The practical building of the resonant converter is descripted with all details: dimensioning of the components-, circuit diagrams; breadboard arrangement; ...

The function of the constructed resonant converter is tested by measurements. In addition there is a comparison of the measurements and the caIculations made before.

The report ends with a detailed bibliography.

Zusammenfassung:

Die Diplomarbeit befaßt sich mit einem Thema aus der elektrischen Leistungselektronik:

Dem Aufbau eines simplen Schwingkreisumrichters mit Reihenschwingkreis.

Neben einer ausführlichen analytischen Betrachtung der Grundlagen eines Wechselumrichters mit Reihenschwingkreises, werden auch moderne Halbleiterschalter wie IGBT, MBGT, MOSFET, Thyristoren,.... auf ihre Tauglichkeit für den gegebenen Verwendungszweck untersucht.

Das Hauptaugenmerk wird bei dieser Arbeit auf die Minimierung der Schaltverluste in den Halbleiterbauelementen gelegt. Dazu ist der Schaltpunkt in die Nähe des Strom- und Spannungsnulldurchgangs gelegt. Die besonderen Schwierigkeiten, die sich daher für die Bauteileauswahl ergeben, sind kommentiert, Für den praktischen Aufbau eines Schwingkreisumrichters sind alle notwendigen Dimensionierungen für die Bauteile, Stromlaufpläne, Platinenaufbaupläne,.... in der Arbeit zu finden.

Die Funktion des dimensionierten und aufgebauten Schwingkreisumrichters wird durch abschließende Messungen überprüft. Im Anschluß werden die Meßergebnisse mit den zuvor durchgeführten Berechnungen verglichen.

Die Arbeit enthält darüberhinaus ein ausführliches Literaturverzeichnis.

Table of Contents:

	ABSTRACT	2
	CHAPTER 1
1.	NOMENCLATURE	8
	CHAPTER 2
2.	INTRODUCTION	10
2.1	GENERAL	10
2.2	APPLICATIONS FOR RESONANT INVERTERS	10
2.3	ADVANTAGEs/DISADVANTAGES OF RESONANT INVERTER	10
2.4	TASK	11
	CHAPTER 3
3.	SEMICONDUCTORS	13
3.1	THYRISTOR	13
3.1.1	Introduction	13
3.1.2	Method of operation	13
3.2	SPECIAL FORMS OF THYRISTORS	15
3.2.1	Gate turn-off thyristor (GTO)	15
3.2.2	Amplifying gate thyristor	16
3.3	POWER MOSFET	17
3.4	IGBT	19
3.4.1	Introduction	19
3.4.2	Method of operation	19
3.4.3	IGBT in modular construction	21
3.4.4	Applications	21
3.5	BIPOLAR JUNCTION TRANSISTOR (BJT)	21
3.6	SILICON CONTROLLED TRANSISTOR (SIT)	23
3.7	SILICON CONTROLLED THYRISTOR (SITH)	24
3.8	MOS CONTROLLED THYRISTOR (MCT)	24
3.9	MOS AND BIPOLAR GATED THYRISTOR (MBGT)	25
3.10	COMPARISON OF MODERN SEMICONDUCTOR DEVICES	27
	CHAPTER 4
4.	DESCRIPTION OF THE SINGLE PHASE FULL-BRIDGE INVERTER	29
4.1	VOLTAGE SOURCE INVERTERS	29
4.1.1	Principle of operation	29
4.2	DESCRIPTION OF THE RESONANT CIRCUIT	30
4.3	THE SERIES RESONANT INVERTER	33
4.3.1	System Description	33
4.3.2	Modes of operation	34
4.3.2.1	DCM - Discontinuous mode	34
4.3.2.2	CCM - Continuous current mode	37
4.4	DAMPING	39
4.4.1	High damping circuit (Psi > 1)	40
4.4.2	Low Damping (Psi < 1)	42
4.4.3	Response of the resonant circuit if it switched for a single time	47
4.5	OPERATION AND CONTROL FOR SERIES LOADED RESONANT INVERTER	48
4.5.1	Capacitive load	48
4.5.2	Inductive load	49
4.6	CHARACTERISTICS	49
4.6.1	First harmonic method	49
4.6.2	First harmonic approximation	54
	CHAPTER 5
5.	CHARACTERISTICS AND LIMITATIONS FOR DESIGN	60
5.1	CAPACITIVE LOAD INVERTERS	60
5.2	INDUCTIVE LOAD INVERTERS	61
5.3	CONCLUSION FOR THE CONSTRUCTION OF RESONANT INVERTER	61
5.4	DESCRIPTION OF THE DC-VOLTAGE SUPPLY	61
5.4.1	The low pass-filter	62
5.5	PROTECTION OF THE SEMICONDUCTOR DEVICES	63
5.5.1	Protection of a thyristor	63
5.5.1.1	The turn-off snubber	63
5.5.1.2	Analysis of the turn-off snubber	64
5.5.1.3	The tum - on snubber	66
	CHAPTER 6
6.	THE BREADBOARD	68
6.1	THE NEEDED MODULES	68
6.2	DESIGN OF THE MODULES	68
6.2.1	Frequency generator	68
6.2.1.1	Astable multivibrator	69
6.2.1.1.1	Given facts	70
6.2.1.1.2	Calculations	70
6.2.1.2	Alternatives	72
6.2.1.2.1	Integrated circuits / Timer	72
6.2.1.2.2	Microprocessor	72
6.2.2	Trigger circuit	73
6.2.3	Inverter	74
6.2.4	Resonant circuit	75
6.2.4.1	Given facts	75
6.2.4.2	Limitations	75
6.2.4.2.1	Minimum of the smallest possible phase angle 9	75
6.2.4.3	Device dimensioning	76
6.2.4.3.1	Calculation	76
6.2.4.3.2	Selection of the components	77
6.2.4.3.2.1	Comparison	77
6.2.4.3.2.2	Arrangement of the components	77
6.2.4.3.3	Cross-check	77
6.2.4.4	Expected line diagrams	79
6.2.4.4.1	Is; Vc, VRL = f (w/w0)	79
6.3	CIRCUIT DIAGRAMS	81
6.3.1	Frequency generator	81
6.3.2	Trigger circuit	81
6.3.2.1	for SCRI	81
6.3.2.2	for SCR2	81
6.3.2.3	for SCR3	82
6.3.2.4	for SCR4	82
6.3.3	Inverter	82
6.3.4	Resonant circuit (load)	82
6.4	MOUNTING ARRANGEMENT	83
6.5	LIST OF USED COMPONENTS	85
	CHAPTER 7
7.	MEASUREMENTS	88
7.1	THE SERIES RESONANT CIRCUIT	88
7.1.1	The measuring circuit	88
7.1.2	Primary data	89
7.1.3	Waveforms	90
7.1.4	Oscillograms	91
7.1.4.1	Discussion	93
7.2	THE FREQUENCY GENERATOR	94
7.2.1	The measuring circuit	94
7.2.2	Oscillogram	94
7.3	THE TRIGGER CIRCUIT OUTPUT SIGNAL	95
7.3.1	The measuring circuit	95
7.3.2	Oscillograms	95
7.3.2.1	open-circuited	95
7.3.2.2	with the inverter circuit as "load"	96
7.3.2.2.1	Direct comparison	96
7.4	FINAL MEASUREMENTS	97
7.4.1	The measuring circuit	97
7.4.2	Oscillograms	97
7.5	LIST OF DEVICES USED FOR MEASUREMENTS	99
	CHAPTER 8
8.	CONCLUSION	101
8.1	SWITCH-ON PROBLEMS WITH A EXTERNAL TRIGGERED RESONANT INVERTER	101
8.2	RECOVERY TIME OF THE THYRISTORS	101
8.3	DETERMINATION OF THE PHASE ANGLE	102
8.4	NON REACTIVE VOLTAGE SUPPLY	102
8.5	CONCLUSIONS FOR THE CONSTRUCTION OF A RESONANT INVERTER	102
	CHAPTER 9
9.	BIBLIOGRAPHY	105
9.1	BOOKS	105
9.2	REPORTS	106
9.3	CATALOGUES	107
9.4	DICTIONARIES	107
9.5	INTERNET INVESTIGATIONS	108
	CHAPTER 10
10.	APPENDICES	110
10.1	PASSIVE DIPOLES	110
10.1.1	Resistors	110
10.1.1.1	Construction methods	110
10.1.1.2	Electrical basics	111
10.1.1.3	Particulars	111
10.1.2	Capacitor	112
10.1.2.1	Electrical basics	112
10.1.2.2	Particulars	113
10.1.2.3	The Q factor of a capacitor	114
10.1.3	Inductance, Coil	114
10.1.3.1	Electrical basics	114
10.1.3.2	Particulars	115
10.1.3.3	The Q factor of an inductance	116
10.2	THE COMPLETE CIRCUIT	117
10.3	INDEX OF THE FIGURES	118