What you are expected to learn

At the end of this module, you should be able to:

• Explain the purpose of a power supply.

• Draw a block diagram of the circuits and parts of a power supply.

• Describe the three different rectifier configurations.

• Explain the function of a filter.

• Describe the two basic types of voltage regulators and how they operate.

• Explain the function of a voltage multiplier.

• Identify over-voltage and over-current protection devices.

How to learn from this module

Going through this module can be both a fun and a meaningful learning experience. All you need to do is make use of your time and resources efficiently. To do this, here are some

tips for you:

1. Take time in reading and understanding each lesson. It is better to be slow but sure than to hurry finishing the module only to find out that you missed the concepts you are supposed to learn.

2. Do not jump from one chapter to another. Usually, the lessons are arranged such that one is built upon another, hence an understanding of the first is essential in comprehending the succeeding lessons.

3. Be honest. When answering the test items, do not turn to the key to correction page unless you are done. Likewise, when performing experiments, record only what you have really observed.

4. Safety first. Perform the experiments with extra precaution. Wear safety gears whenever necessary.

5. Don’t hesitate to ask. If you need to clarify something, approach your teacher or any knowledgeable person.

What to do before (Pretest)

• Power supplies are used to supply voltage to a variety of circuits. Their basic principles are the same.

• The primary function of the power supply is to convert alternating current (AC) to direct current (DC). The power supply may increase or decrease the incoming AC voltage by means of a transformer.

• Once the voltage is at the desired level, it is converted to a DC voltage through a process called rectification. The rectified voltage still contains an AC signal, which is referred to as a ripple frequency. The ripple is removed with a filter.

• To ensure that the output voltage remains at a constant level, a voltage regulator is used. The voltage regulator holds the output voltage at a constant level.

• Transformers are used in power supplies for isolation and to step up or step down the voltage.

• A rectifier circuit converts incoming AC voltage to pulsating DC voltage.

• The basic rectifier circuits are half-wave, full-wave, and bridge.

• Half-wave rectifiers are simpler and less expensive than either full-wave or bridge rectifiers.

• The full-wave rectifier is more efficient than the half-wave rectifier.

• The bridge rectifier can operate without a transformer.

• To convert pulsating DC voltage to a smooth DC voltage, a filter must follow the rectifier in the circuit.

• A capacitor in parallel with the load is an effective filter.

• A voltage regulator provides constant output regardless of load and input voltage changes.

• The voltage regulator is located after the filter in the circuit.

• The two basic types of regulator are the shunt regulator and the series regulator.

• The series regulator is more efficient and therefore more popular than the shunt regulator.

• Voltage multipliers are circuits capable of providing higher DC voltages than the input without the aid of a transformer.

• Voltage doublers and voltage triplers are voltage multipliers.

• A crowbar is a circuit designed for overvoltage protection.

• A fuse protects a circuit from a current overload.

• Fuses are classified as either normal or slow-blow.

• Circuit breakers perform the same job as fuses but do not have to be replaced each time there is an overload.

Simulation Activity

Rectifier Circuit

Simulate this two diagram in everycircuit

Self Check