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参数资料
| 型号： | GM3255S8R |
| 厂商： | American Power Management Inc. |
| 元件分类： | DC/DC变换器 |
| 英文描述： | 1.5A 280kHz DC-DC CONVERTOR BOOST REGULATOR |
| 中文描述： | 1.5A的为280kHz的DC - DC转换器升压稳压器 |
| 文件页数： | 19/19页 |
| 文件大小： | 234K |
| 代理商： | GM3255S8R |
When the power switch turns off, there exists a volt-
age spike superimposed on top of the steady-state
voltage. Usually, this voltage spike is caused by
transformer leakage inductance charging stray ca-
pacitance between the V
and PGND pins. To pres-
SW
ent the voltage at the V
pin from exceeding the
SW
maximum rating, a transient voltage suppressor in
series with a diode is paralleled with the primary
windings. Another method of clamping switch volt-
age is to connect a transient voltage suppressor be-
tween the V
pin and ground.
SW
Magnetic Component Selection
When choosing a magnetic component, one must
consider factors such as peak current, core and fer-
rite material, output voltage ripple, EMI, temperature
range, physical size, and cost. In boost circuits, the
average inductor current is the product of output cur-
rent and voltage gain (V
/ V
), assuming 100%
OUT
CC
energy transfer efficiency. In continuous conduction
mode, inductor ripple current is
where:
f = 280kHz.
The peak inductor current is equal to average cur-
rent plus half of the ripple current, which should not
cause inductor saturation. The above equation can
also be referenced when selecting the value of the
inductor based on the tolerance of the ripple current
in the circuits. Small ripple current provides the bene-
fits of small input capacitors and greater output cur-
rent capability. A core geometry like a rod or barrel is
prone to generating high magnetic field radiation,
but is relatively cheap and small. Other core geome-
tries, such as toroids, provide a closed magnetic
loop to prevent EMI.
Input Capacitor Selection
In boost circuits, the inductor becomes part of the
input filter, as shown in Figure 11. In continuous
mode, the input current waveform is triangular and
does not contain a large pulsed current, During con-
tinuous conduction mode, the peak to peak inductor
ripple current is given in the previous section.
In
most applications, input capacitors in the range of
10F to 100F with an ESR less than 0.3W work
well up to a full 1.5A switch current.
The phase lead provided by this zero ensures that
the loop has at least a 45°C phase margin at the cross-
over frequency. Therefore, this zero should be placed
close to the pole generated in the power stage, which
can be identified at frequency:
where:
The high frequency pole, f , can be placed at the out-
P2
put filter's ESR zero or at half the switching frequency.
Placing the pole at this frequency will cut down on
switching noise. The frequency of this pole is deter-
mined by the value of C2 and R1:
One simple method to ensure adequate phase margin
is to design the frequency response with a - 20 dB per
decade slope, until unity-gain crossover. The crossover
frequency should be selected at the midpoint between
f
and f
where the phase margin is maximized.
Z1
P2
V
Voltage Limit
SW
In the boost topology, V
pin maximum voltage is set
SW
by the maximum output voltage plus the output diode
forward voltage. The diode forward voltage is typically
0.5V for Schottky diodes and 0.8V for ultrafast diodes
Where:
N = transformer turns ratio, primary over secondary
C = equivalent output capacitance of the error
O
amplifier 120pF;
R
= load resistance.
LOAD
f
=
P1
1
2pCR
O LOAD
V
= V
+ V
SW(MAX)
OUT(MAX)
F
V = output diode forward voltage.
F
In the flyback topology, peak V
voltage is governed by:
SW
V
= V
+ (V
+ V ) X N
SW(MAX)
CC(MAX)
OUT
F
f
=
P2
1
2pC1R1
G
a
in
(d
B
)
D
C
G
a
in
Frequency(LOG)
f
P1
F
P2
f
Z1
Figure 10. Bode Plot of the Compensation
Network Shown in Figure 9.
I
=
RIPPLE
V
(V
- V
)
CC
OUT
CC
( f )( L )(V
)
OUT
G
M
3
2
5
9
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相关代理商/技术参数 |
参数描述 |
|---|---|
| GM3255S8T | 制造商:GAMMA 制造商全称:GAMMA 功能描述:1.5A 280kHz DC-DC CONVERTOR BOOST REGULATOR |
| GM330K | 制造商:Mallory Sonalert Products Inc 功能描述:Cap Ceramic 33pF 500V SL 10% (6 X 4mm) Radial 6.4mm 85°C 制造商:CORNELL DUBILIER ELECTRONICS 功能描述:Cap Ceramic 33pF 500V SL 10% (6 X 4mm) Radial 6.4mm 85°C |
| GM331K | 功能描述:瓷片电容器 500V 330pF DISC RoHS:否 制造商:Vishay/Cera-Mite 电容:0.01 uF 容差:20 % 电压额定值:3 kV 工作温度范围:- 25 C to + 105 C 损耗因数 DF: 端接类型:Radial 产品:High Voltage Ceramic Disc Capacitors |
| GM3326 | 制造商:GAMMA 制造商全称:GAMMA 功能描述:PWM,PWM/PFM SWITCHING STEP-UP & DOWN DC/DC CONVERTER CONTROLLER ICS |
| GM3326-2.5ST25R | 制造商:GAMMA 制造商全称:GAMMA 功能描述:PWM,PWM/PFM SWITCHING STEP-UP & DOWN DC/DC CONVERTER CONTROLLER ICS |
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