Contents
Preface
v
Acknowledgements
vi
1. Power Transformers
Earthing and safety
Mains voltage
Transformer operation
Transformer losses
Saturation
Types of transformers
Transformer ratings
Transformer regulation
Testing transformers
Voltages
Phasing
Power and current capability
Inductance
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1
2
3
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11
12
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14
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15
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17
2. Rectification
Basic rectifier theory
The reservoir capacitor
Ripple voltage
Ripple current
DC magnetisation
Power factor and VA ratings
Half-wave rectification
Full-wave rectification
Two-phase rectifiers
Voltage rating of rectifier diodes
Current rating of rectifier diodes
Reverse recovery and switching noise
Relative output voltages of rectifier circuits
Mathematical treatment of capacitor-input rectifiers
Ripple voltage
Ripple current
Rectifiers with series resistance, and valve rectifiers
DC output voltage of rectifiers with series resistance
Ripple current in rectifiers with series resistance
Characteristics of valve rectifiers
Maximum current ratings
Maximum reservoir capacitance
Limiting resistance
Heaters
Switching noise
Warm-up time
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40
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46
i
Valve rectifier load regulation and sag
Choke-input rectifiers
Theory of choke-input rectifiers
Some worked examples
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49
49
53
3. Voltage Multipliers
Half-wave voltage doubler
Full-wave voltage doubler
Full-wave voltage tripler
Full-wave voltage quadrupler
1.5x voltage multiplier
Obtaining multiple voltages from one transformer
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58
60
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65
4. Smoothing, Filtering and Decoupling
Resistor-capacitor (RC) smoothing
nth order RC filters
Filter chains
High-frequency performance
Inductor-capacitor (LC) smoothing
Avoiding resonance in LC filters
nth order LC filters
Tuned LC filters
Practical chokes
Gyrators or simulated inductors
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76
78
80
80
81
82
5. Switching and Fusing
Fuses
Mains fusing
Secondary fusing
Fuse status indicator
Switching
Mains switching
Secondary switching
Standby switches
Standby switch myths
Cathode stripping
Cathode poisoning
Some better standby switches
Automatic soft start
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84
85
86
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90
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92
94
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96
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98
6. Shunt Voltage Stabilisers
Line and load regulation
Shunt stabilisation
Passive shunt stabilisers
Zener diodes
Avalanch and Zener effects
Dynamic resistance of diodes
Directionality of zener diodes
ii
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100
101
101
102
103
104
106
Amplified zener
Cold-cathode, glow discharge stabilisers
Principle of operation
Gas stabiliser tubes
Neon lamps
Designing passive shunt stabilisers using load lines
High voltage, active shunt stabilisers
Simple feedforward, fixed bias, valve shunt stabiliser
Simple feedforward, cathode bias, valve shunt stabiliser
The King stabiliser
Feedback shunt stabilisers
Basic operation of feedback stabilisers
Simple, feedback shunt stabiliser
Cascode and pentode feedback shunt stabilisers
Two-valve shunt stabilisers
Feedback King regulator
Hunt and Hickman regulator
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108
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120
122
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126
7. Series Voltage Stabilisers
Cooling and heat sinking
Mounting the device
Cooling and layout
Series stabilisation
The capacitor multiplier
Designing a BJT capacitor multiplier
Cascoding devices
Designing a MOSFET capacitor multiplier
Darlington arrangements
Current limiting
Passive constant-current limiting
Active constant-current limiting
Foldback current limiting
Zener-follower stabilisers
Cascaded stabilisers
Feedback series stabilisers
Simple transistor series regulators
More advanced transistor series regulators
Adding constant-current sources and sinks
Semi-integrated regulators
High-voltage semi integrated regulator
Multiple opamp-buffered nodes
Voltage-regulator ICs
Adjusting the output voltage
Regulator ICs at high voltages
Hybrid three-pin regulator
Valve series stabilisers
Valve series voltage regulators
SRPP series-shunt valve regulator
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8. Valve Bias Supplies
Charge time and blown fuses
Voltage stabilisation and regulation
Bias adjustment and balancing
Bias voltage adjustment
Bias balance adjustment
Traditional bias supply
Full-wave traditional bias supply
Capacitor-coupled bias supply
Auxiliary transformer bias supply
Back biasing
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185
9. Valve Heater Supplies
AC heater supplies
Series and parallel heater operation
Heaters and hum
Magnetic interference and lead dress
Electric field (capacitative) interference
Rectifier-induced heater hum
Electrical heater balancing
Heater-cathode leakage and heater elevation
Dropping heater voltage
DC heaters
Unstabilised heater supplies
Stabilised DC heater supplies
Regulated, 1A DC heater supply
Regulated, 3A DC heater supply
Regulated, 5A DC heater supply
Constant-current DC heater supply
Universal heater supplies for popular dual triodes
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196
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201
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202
203
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205
10. Voltage Control
Mains voltage control
Secondary voltage control
Output-power control for guitar amps
Power and perceived loudness
Simple power reduction
Power reduction by proportional voltage control
Variable-voltage circuits
Voltage and power limitations
Power adjustment circuit for cathode-biased amps
Power-adjustment circuit for fixed-biased amps
Bias tracking
Practical application of power reduction circuits
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223
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225
227
Bibliography
230
Index
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