Regulators

Question 1

What are the four reasons that we need power control, regulation and distribution?

Answer 1

• Power output from a solar array fluctuates depending on whether it is in an eclipse or not
• Battery voltage fluctuates dependent upon how much charge remains
• Spacecraft payload and subsystems generally need a stable voltage and isolation from the effects of other systems
• Need to be able to switch on and off other spacecraft loads

Question 2

What are the advantages and disadvantages of a linear regulator?

Answer 2

• Simple device
• Highly inefficient ( 70 % efficient)
• Can only step voltage down

Question 3

What are the three advantages and disadvantages of switch-mode regulators?

Answer 3

• More complex circuitry
• Highly efficient (90 to 95 %)
• Can step voltage up, down and perform polarity reversal

Question 4

What are the four types of regulator described?

Answer 4

• Buck regulator, steps down voltage
• boost regulator, steps up voltage
• Buck/boost regulator, can perform polarity reversal
• Shunt regulator, dumps excess power through shunt resistors

Question 5

What is meant by a redundancy scheme when designing shunt regulator circuits?

Answer 5

• Extra lines allowing pathways back to the dump resistor in case one or a number of switches fail.
• Parallel switches mitigate open circuit failures and series switches mitigate short circuit failures

Question 6

What kind of switch architecture is required for protection against a single switch failure?

Answer 6

2s2p

Question 7

How do the three different regulator circuits vary?

Answer 7

see notes

Question 8

What’s the difference between centralised, distributed and hybrid power conditioning?

Answer 8

• Centralised: When the raw unregulated power is immediately conditioned and fed into a stabilised battery supply which can then be distributed as needed to the different subsystems
• Distributed: raw power is fed to the unregulated bus and power is then regulated at each different subsytems depending on the subsystems needs
  -n Hybrid: mixture of 1 and 2

Question 9

What does the circuit diagram look like for the unregulated bus, quasi-regulated bus and regulated bus? What does the diode do for the quasi-regulated bus?

Answer 9

See notes. The diode Allows the battery to discharge in one direction and prevents return currents through unwanted paths by making the discharge line look high impedance