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http://www.learnabout-electronics.org/PSU/psu32.php
Boost Converter
Switched mode supplies can be used for many purposes
including DC to DC converters.
Often, although a DC supply, such as a battery may be available,
its available voltage is not suitable for the system being supplied.
DC공급기라도, 그 전압이 시스템에 적합하진않다.
For example,
the motors used in driving electric automobiles require much higher voltages,
in the region of 500V, than could be supplied by a battery alone.
전기차 운용에 쓰이는 모터들은 요구한다. much higher 전압들을
500V의 일부는 could be 공급될수있다. by a 베터리 자체에의해.
Even if banks of batteries were used,
the extra weight and space taken up
would be too great to be practical.
The answer to this problem
is to use fewer batteries
and
to boost the available DC voltage
to the required level
by using a boost converter.
이 문제에 대한 대답
은 to 사용하는거다. 더 낮은 베터리들을
and
to 부스트하는거다. the available DC 전압을
to the 요구하는 레벨까지
by 사용함으로써 a 부스트 컨버터를.
Another problem with batteries, large or small,
is that their output voltage varies as the available charge is used up, and at some point the battery voltage becomes too low to power the circuit being supplied.
다른 문제
는 that their 출력 전압은 변한다. as the available한 charge를 다쓴만큼,
and at 어떤 의미에선 the 베터리 전압은 becomes 너무 낮게된다. to 파워공급하기에 the 회로가 being 공급되게끔.
However, if this low output level can be boosted back up to a useful level again,
by using a boost converter,
the life of the battery can be extended.
하지만 만약 this 낮은 출력 레벨이 can be 부스티드되면 back upto쓸모있는 레벨로 다시,
by 사용함으로써 a 부스트 컨버터를,
the life of the 베터리는 can be 확장된다.
The DC input to a boost converter
can be from many sources as well as batteries,
such as rectified AC from the mains supply,
or DC from solar panels, fuel cells, dynamos and DC generators.
The boost converter is different to the Buck Converter in that it’s output voltage is equal to, or greater than its input voltage.
However it is important to remember that, as power (P) = voltage (V) x current (I), if the output voltage is increased, the available output current must decrease.
Fig. 3.2.1 illustrates the basic circuit of a Boost converter.
However, in this example the switching transistor is a power MOSFET, both Bipolar power transistors and MOSFETs are used in power switching, the choice being determined by the current, voltage, switching speed and cost considerations.
The rest of the components are the same as those used in the buck converter illustrated in Fig. 3.1.2, except that their positions have been rearranged.
Boost converter Operation
Fig 3.2.2 illustrates the circuit action
during the initial high period of the high frequency square wave
applied to the MOSFET gate at start up.
그림3.2.2는 설명한다. the 회로 액션을
during the 초기 high 주기동안 of the high frequency 사각파의
적용된 to the MOSFET 게이트에 at 스타트업에서.
During this time
MOSFET conducts, placing a short circuit
from the right hand side of L1 to the negative input supply terminal.
Therefore a current flows between the positive and negative supply terminals through L1, which stores energy in its magnetic field.
There is virtually no current flowing in the remainder of the circuit
as the combination of D1, C1 and the load
represent a much higher impedance than the path directly through the heavily
conducting MOSFET.
Fig. 3.2.3 shows the current path during the low period
of the switching square wave cycle.
그림 3.2.3은 보여준다. the 전류 경로를 during the low 주기 동안
of the 스위칭 사각파 사이클의.
As the MOSFET is rapidly turned off the sudden drop in current causes L1 to produce a back e.m.f. in the opposite polarity to the voltage across L1 during the on period, to keep current flowing.
This results in two voltages, the supply voltage VINand the back e.m.f.(VL) across L1 in series with each other.
This higher voltage (VIN +VL), now that there is no current path through the MOSFET, forward biases D1. The resulting current through D1 charges up C1 to VIN +VL minus the small forward voltage drop across D1, and also supplies the load.
Fig.3.2.4 shows the circuit action during MOSFET on periods after the initial start up. Each time the MOSFET conducts, the cathode of D1 is more positive than its anode, due to the charge on C1. D1 is therefore turned off so the output of the circuit is isolated from the input, however the load continues to be supplied with VIN +VL from the charge on C1. Although the charge C1 drains away through the load during this period, C1 is recharged each time the MOSFET switches off, so maintaining an almost steady output voltage across the load.
The theoretical DC output voltage is determined by the input voltage (VIN) divided by 1 minus the duty cycle (D) of the switching waveform, which will be some figure between 0 and 1 (corresponding to 0 to 100%) and therefore can be determined using the following formula:
Example:
If the switching square wave has a period of 10µs,
the input voltage is 9V and the ON is half of the periodic time, i.e. 5µs,
then the output voltage will be:
만약 the 스위칭 사각파가 갖고있으면 주기를 of 10us의,
the 입력 전압은 9V이다. and the ON이 절반 주기이다. i.e. 5us,
그럼 출력전압은 will be:
VOUT = 9/(1- 0.5) = 9/0.5 = 18V (minus output diode voltage drop)
Because the output voltage is dependent on the duty cycle,
it is important that this is accurately controlled.
For example if the duty cycle increased from 0.5 to 0.99
the output voltage produced would be:
because the 출력 전압이 의존하기때문에. on the 듀티 사이클에
이건 중요하다. that 이건 정확히 컨트롤된다.
For example, 만약 듀티 사이클 증가했다면 from 0.5 ~ 0.99까지
그 출력 전압 만들어진 would be:
VOUT = 9/(1- 0.99) = 9/0.01 = 900V
Before this level of output voltage was reached however, there would of course be some serious damage (and smoke) caused, so in practice,
unless the circuit is specifically designed for very high voltages, the changes in duty cycle are kept much lower than indicated in this example.
Boost Converter Animation
Click play to start.
See the current paths during the on and off periods of the switching transistor.
See the magnetic field around the inductor grow and collapse, and observe the changing polarity of the voltage across L.
Watch the effect of ripple during the on and off states of the switching transistor.
See the input voltage and the back e.m.f. of VL add to give an output voltage greater than the input voltage.
Click pause to hold the animation in either the on or the off state.
Click back to reset the animation.
I.C. Boost Converter
In this circuit,
an appropriate fraction of the output voltage (VOUT),
dependent on the ratio of R2:R3
is used as a sample
and
compared with a reference voltage within the I.C.
이 회로에서,
an 근사치 fraction of the 출력전압(Vout),
의존하는 on the 비율에 of R2:R3
는 사용된다. as a 셈플로
and
비교된다. with a 참조 전압에 within the IC내의.
This produces an error voltage that is used to alter the duty cycle of the switching oscillator,
enabling a range of automatically regulated boost voltages between 5V and 28V to be obtained.
Because of the ease with which boost converters can supply large over voltages, they will almost always include some regulation to control the output voltage, and there are many I.Cs. manufactured for this purpose A typical example of an I.C. boost converter is shown in Fig. 3.2.6, in this example the LM27313 from Texas Instruments.
This chip is designed for use in low power systems such as PDAs, cameras, mobile phones, and GPS devices.
The LM27313 contains an internal oscillator
operating at a fixed frequency of about 1.6MHz.
The FET switching transistor is also internal
and switches the current through L1 via the SW terminal.
Notice also that
a Schottky diode with an appropriate voltage
and
current rating is used for D1 to keep losses
due to the forward voltage drop of the diode as small as possible,
and to enable high switching speeds to be achieved.
The I.C. also has a shut down (SHDN) facility, operated by external logic, by which the boost converter may be disabled when not required, to save battery power.
▼사용된부품
Protection Circuits
Other safety features provided by the I.C. are over current shut down, which disables the switch on a cycle-by-cycle basis if too much current is sensed, and an over temperature shut down facility.
Stability
Another problem facing designers of high frequency boost converters is that of stability, as at MHz frequencies both negative and positive feedback can occur simply due to electromagnetic fields radiating between components within the circuit, especially where the circuit components are in very close proximity as in surface mount layouts. C2 is therefore added to improve stability and prevent possible oscillation due to unwanted positive feedback occurring.
https://reibot.org/2011/08/07/intro-to-boost-converter/
BuckConverter VS BoostConverter
DC-DC Converter
용도 :: AC-DC컨버터를 거쳐서 나온 DC전압을 각 용도에 맞춰서 낮춰야 할경우
DC-DC컨버터를 사용하게 된다.
전압을 낮추는 방법에는 여러가지 방법이 있겠지만 대체로 PWM을 이용한 High/Low 빈도를 이용하여 출력 전압을 내보낸다.
Pspice로 설계시 자료(영문 PDF)
4763126.ppthttp://www.circuitstoday.com/12v-to-120v-dc-dc-converter
555timer는
PSpice에서 anl_misc.olb 에 있다. 여기서 555B를 사용한다.
▼Buck Converter (스위치에 따른 상태변화)
Buck Converter is controlled by Active Switch S1.
▼Pulse 주기는 아래 공식에 따라 결정된다. (Duty비 라고 불린다.)
ON Time divided by the Total Period as shown in this equation.
ΔiL
Δvc
What is the voltage over the inductor during the switch is ON.
Vi는 initial Volate라는 뜻이다. (초기전압)
