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Power Elecronics 2 > How to Drive a Load from a Microcontroller > Flashcards

How to Drive a Load from a Microcontroller Flashcards

1
Q

What does an MCU act as in an active high

A

a source of current to the load

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2
Q

What does an MCU act as in an active low

A

a sink of current from the load

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3
Q

Which acts as a source of current, active high or active low

A

active high

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4
Q

which acts as a sink, active high or active low

A

active low

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5
Q

Why is a resistor in series with an Led

A

To limit current in LED to safe value

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6
Q

What is the voltage across the load resistor equal to (in series with LED)

A

VR=VDD-VLED

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7
Q

Which switch is between the load and the ground

A

Low side switch

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8
Q

Which switch is between the load and the supply voltage

A

High side switch

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9
Q

What type of switch must the current be reversible

A

H-bridge

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10
Q

What type of MOSFET does a low side switch use

A

n-channel

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11
Q

What type of MOSFET does a high side switch use

A

p-channel

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12
Q

What switch is more common low side or high side

A

Low side

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13
Q

For a low side switch what does the VG equal when the MCU is high

A

VGC=VsupplyMCU

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14
Q

For a high side switch what and why is the current through the load when the output of MCYU is high

A

No current as the MOSFET switches off

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15
Q

For a high side switch when the MOSFET is switched on is the MCU high or low

A

low

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16
Q

What cannot change instantaneously in a capacitor and why

A

Current, produces ver high back EMF which causes something to blow

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17
Q

What must every inductive circuit provide a path for and what is often used

A

the current when switch is turned off, diode

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18
Q

what is the name for the protective diode

A

Catch, Clamp, Flyback or freewheeling diode

19
Q

For pulse width modulation what is the equation for average voltage assuming that Voff is 0

A

Vaverage=D*Von

20
Q

What does BJT stand for

A

Bipolar Junction Transistor

21
Q

In a BTJ what does acts and the input and what is the output

A

input is base and output is the collector

22
Q

In the BJT what does the base emitter junction behave like

A

Diode

23
Q

At what value does a BTJ become saturated

A

0.2V

24
Q

What is a pair of BTJ’S

A

Darlington Pair

25
Q

When are Darlington Pairs used

A

When the current is beyond the capability of the MCU

26
Q

What is Beta

A

The current Gain

27
Q

What are MOSFETs usually the best choice for

A

Low power switches

28
Q

What works better n-channel or p-channel

A

n-channel

29
Q

What is the voltage that the Vgc must be greater

A

The Threshold Voltage

30
Q

What does a MOSFET act like

A

A capacitor

31
Q

When turned on as a switch the MOSFET acts like a

A

Resistor

32
Q

Why should the voltage drop ne kept small for a MOSFET

A

It influences the Power dissipation

33
Q

What is a relay

A

A type of Electromechanical switch

34
Q

Good qualities of Relays

A

Safety, wide choice, can switch high voltages and currents, little power loss

35
Q

Poor qualities of Relays

A

Slow, expensive, large, cannot be driven directly from MCU

36
Q

If you want a circuit to be grounded should you use an active high or an active low

A

Active low

37
Q

If you need to dissipate heat should you use an active high or active low circuit

A

Active low

38
Q

When would you use a low side circuit

A

When the Voltage supply is greater than the MCU voltage

39
Q

When would you use a high side switch

A

When the voltage supply is equal to the MCU voltage

40
Q

What type of MOSFET does a low side switch use

A

n-channel MOSFET

41
Q

What type of MOSFET does a high side switch use

A

p-channel MOSFET

42
Q

What sort of loads can be connected directly to the MCU

A

Very Light loads

43
Q

What is the voltage drop for a bipolar junction transistor

A

Constant

44
Q

When would you use a relay

A

For a load powered directly from AC Mains

Power Elecronics 2 (11 decks)

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