24 Questions
What is the typical regulation of integrated circuit regulators?
Less than 1%
What is the function of capacitor C1 in a voltage doubler circuit?
To charge to the positive peak secondary voltage
What can be deduced from the load test data of the d.c. power supply?
The power supply has a high output resistance
What is the purpose of a ripple filter in a power supply circuit?
To filter out the AC component
What is the output voltage of a voltage tripler?
Three times the input voltage
What is the function of a Zener diode in a voltage regulator circuit?
To regulate the output voltage
What is the equivalent output resistance of the power supply calculated from?
The load test data
What is the purpose of a voltage doubler circuit?
To double the output voltage
What is the turns ratio of the step-down transformer T1?
20:1
During positive half-cycles, which diodes allow conduction in the bridge rectifier circuit?
D1 and D2
What is the approximate peak output voltage of the bridge rectifier circuit?
16.3 V
What is the purpose of the reservoir capacitor C1 in the bridge rectifier circuit?
To maintain the output voltage when the diodes are not conducting
During negative half-cycles, which point is positive with respect to the other?
Point B is positive with respect to Point A
What is the advantage of using a bridge rectifier circuit over other rectifier circuits?
Current is routed through the load in the same direction on successive half-cycles
What is the voltage drop across each diode in the bridge rectifier circuit?
0.7 V
What is the approximate r.m.s. voltage output of the secondary winding of transformer T1?
12 V
What is the primary function of a reservoir capacitor in a DC power supply?
To smooth out the voltage pulses produced by the rectifier
What type of rectifier uses four diodes and operates in both positive and negative half cycles?
Bridge rectifier
What device is commonly used to regulate the output voltage in a DC power supply?
Series transistor regulator
What is the purpose of a step-down transformer in a DC power supply?
To step down the input voltage
What is the relationship between Vrms and Vpeak?
Vrms is equal to Vpeak
What is the function of a Zener diode in a voltage regulator circuit?
To regulate the output voltage
What type of rectifier uses a single diode and operates on only either positive or negative half-cycles of the supply?
Half-wave rectifier
What is the purpose of a stabilizing circuit in a DC power supply?
To regulate the output voltage
Study Notes
DC Power Supply
- More sophisticated circuits based on discrete components produce values of between 1% and 5% and integrated circuit regulators often provide values of 1% or less.
Load Test and Regulation Test
- Load test: Output voltage (no-load) = 12 V, Output voltage (2 A load current) = 11.5 V
- Regulation test: Output voltage (mains input, 220 V) = 12 V, Output voltage (mains input, 200 V) = 11.9 V
Voltage Doubler
- Increases the output of a simple half-wave rectifier
- C1 charges to the positive peak secondary voltage while C2 charges to the negative peak secondary voltage
- The resulting output voltage is twice that produced by one diode alone
Voltage Tripler
- Operation is similar to a voltage doubler, but with an additional capacitor and diode
DC Power Supply
- A DC power supply consists of an iron-cored step-down transformer, a rectifier arrangement, a high-value reservoir capacitor, and a stabilizing circuit
- The stabilizing circuit provides a constant output voltage
Rectifiers
- A rectifier is a device that converts alternating current (ac) to direct current (dc)
- Types of rectifiers: Half-wave rectifier, Full-wave rectifier, Bridge rectifier
- Semiconductor diodes are commonly used as rectifiers
Half-Wave Rectifier
- Uses a single diode and operates on only either positive or negative half-cycles of the supply
- The secondary of the step-down transformer provides a reduced voltage to the rectifier circuit
- The diode is forward biased during each positive half-cycle and reverse biased during each negative half-cycle
Full-Wave Rectifier
- Uses two diodes with a centre tap transformer and operates in both positive and negative half-cycles
Bridge Rectifier
- Uses four diodes and operates in both positive and negative half-cycles
- On positive half-cycles, two diodes conduct while the other two do not conduct
- On negative half-cycles, the opposite two diodes conduct while the other two do not conduct
Voltage and Current
- Vrms – Root mean square voltage
- Vm (= Vpeak) – peak voltage
- Vavg (= Vdc) – Average voltage
Bridge Rectifier with Reservoir Capacitor
- A reservoir capacitor can be added to maintain the output voltage when the diodes are not conducting
- The capacitor charges to approximately 16.3 V at the peak of the positive half-cycle and holds the voltage at this level when the diodes are in their non-conducting states
This quiz is about determining the regulation of a DC power supply based on load test and regulation test data. It involves calculating the equivalent output resistance and regulation percentage of the power supply.
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