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參數(shù)資料
| 型號： | TS3842BCS |
| 廠商： | Electronic Theatre Controls, Inc. |
| 英文描述： | High Performance Current Mode Controller |
| 中文描述： | 高性能電流模式控制器 |
| 文件頁數(shù)： | 11/20頁 |
| 文件大?。?/td> | 521K |
| 代理商： | TS3842BCS |
Undervoltage Lockout(contd.)
This provides a low impedance path for filtering the high frequency noised. All high current loops
should be kept as short as possible using heavy copper runs to minimize radiated EMI. The Error
Amp compensation circuitry and the converter output voltage divider should be located close to
the IC and as far as possible from the power switch and other noise generating components.
Current mode converters can exhibit subharmonic oscillations when operating at a duty cycle
greater than 50% with continuous inductor current. This instability is independent of the regula-
tors closed loop characteristics and is caused by the simultaneous operating conditions of fixed
frequency and peak current detecting. Figure 19(A) shows the phenomenon graphically. At t
0
,
switch conduction begins causing the inductor current to rise at a slope of m
. This slope is a
function of the input voltage divided by the inductance. At t1, the Current Sense Input reaches the
threshold established by the control voltage. This causes the switch to turn off and the current to
decay at a slope of m
, until the next oscillator cycle. This unstable condition can be shown if a
perturbation is added to the control voltage, resulting in a small
oscillator period, the current decay time is reduced, and the minimum current at switch turn-on(t
2
)
is increased by
1+
1m
/m
. The minimum current at the next cycle (t
) decreases to (
1m
/m
)(m
/m
). This perturbation is multiplied by m
/m
on each succeeding cycle, alternately
increasing and decreasing the inductor current at switch turn-on. Several oscillator cycles may be
required before the inductor current reaches zero causing the process to commence again. If m
2
/
m
is greater than 1, the converter will be unstable. Figure 19(B) shows that by adding an artificial
ramp that is synchronized with the PWM clock to the control voltage, the
decrease to zero on succeeding cycles. This compensating ramp (m
) must have a slope equal to
or slightly greater than m
/2 for stability. With m
/2 slope compensation, the average inductor
current follows the control voltage yielding true current mode operation. The compensating ramp
can be derived from the oscillator and added to either the Voltage Feedback or Current Sense
inputs (Figure 32).
1(dashed line). With a fixed
1+
1 perturbation will
Figure 19 - Continuous Current Waveforms
(A)
1
+
+
Control Voltage
Inductor
Oscillator Period
Control Voltage
Inductor
Current
Oscillator Period
(B)
m
1
m
2
t
0
t
1
t
2
t
3
m
3
m
2
t
4
t
5
t
6
m
1
1
1m2
m1
1
1m2
m1 m2
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| TS3843B | High Performance Current Mode Controller |
| TS3843BCD | High Performance Current Mode Controller |
| TS3843BCS | High Performance Current Mode Controller |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TS3843B | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:High Performance Current Mode Controller |
| TS3843BCD | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:High Performance Current Mode Controller |
| TS3843BCS | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:High Performance Current Mode Controller |
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