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参数资料
| 型号： | GM38C42S8T |
| 厂商： | American Power Management Inc. |
| 英文描述： | HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS |
| 中文描述： | 高性能电流模式PWM控制器 |
| 文件页数： | 9/11页 |
| 文件大小： | 166K |
| 代理商： | GM38C42S8T |
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Application Information
Familiarity with 384x converter designs is assumed.
GM38C4x has been designed to be compatible with 384xA series controllers.
GM38C4x Advantages
Start-up Current
Start-up current has been reduced to an ultra-low 50A(typical) permitting higher-valued, lower-wattage, and
start-up resistors (power controller during power supply start-up). The reduced resistor wattage reduces cost and
printed circuit space.
Operating Current
Operating current has been reduced to 4mA compared to 11mA for a typical bipolar controller. The controller runs
cooler and the V
hold-up capacitance required during start-up may be reduced.
DD
Output Driver
Complementary internal P-and N-channel MOSFETs produce rail-to-rail output voltages for better performance
driving external power MOSFETs. The driver transistor's low on resistance and high peak current capability can
drive gate capacitances of greater than 1000pF. The value of output
capacitance which can be driven is
determined only by the rise/fall time requirements. Within the restrictions of output capacity and controller power
dissipation, maximum switching frequency can approach 500kHz.
Design Precautions
When operating near 20V, circuit transients can easily exceed 20V absolute maximum rating and permanently
damaging the controller's CMOS construction. To reduce transients, use a 0.1F low-ESR capacitor to next to
the controller's supply V
(or V for '-1' versions)and ground connections.
DD
D
Film type capacitors, such as Wima MKS2, are recommended.
When designing high -frequency converters, avoid capacitive and inductive coupling of the switching waveform
into high impedance circuitry such as the error amplifier, oscillator, and current sense amplifier. Avoid long
printed-circuit traces and component leads. Locate oscillator and compensation circuitry neat the IC. Use high
frequency decoupling capacitors on V
, and if necessary, on V . Return high di/dt currents directly to their
ERF
DD
source and use large ground planes.
Buck Converter
Refer to Figure 7. When at lest 26V is applied to the input, C5 is charged through R2 until the voltage V
is
DD
greater than 14.5V(the undervoltage lockout value of the GM38C42), output switching begins when Q1is turned
on by the gate drive transformer T1 and charging the output filter capacitor C3 through L1. D5 supplies a
regulated +12V to V
once the circuit is running.
DD
Current sense transformer CT1 provides current feedback to ISNS for current-mode operation and cycle-by-cycle
current limiting. This is more efficient than a high- power sense resistor and provides the required ground-
referenced level shift.
When Q1 turns off, current flow continues from ground through D1 and L1 until Q1 is turned on again.
The 100V Schottky diode D1 reduces the forward voltage drop in the main current path, resulting in higher
efficiency than could be accomplished by using an ultra-fast recovery diode. R1 and C2 suppress parasitic
oscillations from D1.
Using a high-value inductance for L1 and a low-ESR capacitor for C3 permits small capacitance with minimum
output ripple. This inductance value also improves circuit efficiency by reducing the flux swing in L1.
Magnetic components are carefully chosen for minimal loss at 500kHz.
相关PDF资料 |
PDF描述 |
|---|---|
| GM38C42 | HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS |
| GM38C43D8T | HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS |
| GM38C43S8R | HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS |
| GM38C43S8T | HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS |
| GM38C43 | HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS |
相关代理商/技术参数 |
参数描述 |
|---|---|
| GM38C43 | 制造商:GAMMA 制造商全称:GAMMA 功能描述:HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS |
| GM38C43D8T | 制造商:GAMMA 制造商全称:GAMMA 功能描述:HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS |
| GM38C43S8R | 制造商:GAMMA 制造商全称:GAMMA 功能描述:HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS |
| GM38C43S8T | 制造商:GAMMA 制造商全称:GAMMA 功能描述:HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS |
| GM38C44 | 制造商:GAMMA 制造商全称:GAMMA 功能描述:HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS |
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