1 / 17

EE 136 Power Electronics Class Project

EE 136 Power Electronics Class Project. Power Supply Handbook Chapter 11and 12 Over voltage and Under voltage Protection By Gordon Wong. Today’s Topics. Over Voltage Protection Under Voltage Protection Why are these types of protection needed? Circuit Analysis Simulations in Simplorer

odette-everett
Télécharger la présentation

EE 136 Power Electronics Class Project

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. EE 136 Power ElectronicsClass Project Power Supply Handbook Chapter 11and 12 Over voltage and Under voltage Protection By Gordon Wong

  2. Today’s Topics • Over Voltage Protection • Under Voltage Protection • Why are these types of protection needed? • Circuit Analysis • Simulations in Simplorer • Advantages and Disadvantages

  3. Dangers of Over Voltage • Overheating • Increase Thermal Stress on Components • MTBF will decrease • Waste of energy • Safety Hazards increase risk of fire and electric shock

  4. Example of Over Voltage Protection in Industry • The following circuit is from Maxim. • This is a over voltage protection circuit in automotive systems. • Input Voltage 16V maximum • Output Voltage 5 V • How does this work?

  5. Desired Characteristics of a Good Over Voltage Protection Circuit • Fast Response • Able to handle large input voltages, from voltage spikes and surges. • Doesn’t intrude with the normal operation of the circuit • Doesn’t overheat

  6. A common Over Voltage Protection Circuit is the SCR crowbar

  7. What does this circuit do? • To prevent the output from going over 5 volts the circuit is designed to short the output to ground if Rload goes over 5 volts.

  8. How does the SCR crowbar circuit work? • E1 and R6 are the Thevenin equivalent for the DC power supply. • R1 and C2 introduce a time delay in the circuit. • S2 is zener diode that closes if E1 goes over a certain value • S3 is the SCR that closes if the C1 voltage goes over a certain value.

  9. Results

  10. Advantages Easy to create The value of C1 can be adjusted to accommodate a wide range of time delays and let thru voltages. Disadvantages Premature shutdown of circuit might occur is the C1 value is too low. The SCR require a manual reset if it goes off. Advantages and Disadvantages

  11. A more precise SCR circuit using a voltage comparator.

  12. What does this circuit do? • This circuit also prevents the output from receiving more then 5 volts. • This is done by shorting the output to ground if it goes over 5 volts. • However this circuit has a much faster response time then the SCR crowbar circuit.

  13. How does the SCR voltage comparator works? • E2 and R6 are the Thevenin equivalent of the DC power supply. • R2, R3 form a voltage divider. • E1 is the reference voltage. • R4, C1 introduce a time delay. • S2 closes if the voltage across C1 gets too high.

  14. Results

  15. Second type of over voltage protection • This is a voltage clamping circuit. • The zener diode automatically limits the voltages across the load.

  16. Simulation results of Voltage limiting circuit.

  17. Advantages Simple easy to use. Cost effective Disadvantages Zener diode characteristic depend on temperature You have find a Zener diode with exactly the breakdown voltage you want. Advantages and Disadvantages to voltage limiting circuits.

More Related