参数资料
| 型号： | NCP4331DR2G |
| 厂商： | ON Semiconductor |
| 文件页数： | 11/22页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM 16-SOIC |
| 标准包装： | 2,500 |
| PWM 型： | 控制器 |
| 输出数： | 2 |
| 频率 - 最大： | 400kHz |
| 电源电压： | 最高 30V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 16-SOIC（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
NCP4331
DETAILED OPERATING DESCRIPTION
Introduction
The NCP4331 is ideal in multi-outputs applications
where efficiency, ease of implementation and compactness
are key requirements. Since it is often impossible to tightly
regulate all the outputs and since a further regulation of the
sequencing in a smart manner so that three over the
four transitions are soft. The high gate drive capability
of the NCP4331 and the utilization of N-MOSFETs for
both the high and low sides reduce the conduction
losses to a minimum (synchronous rectification).
outputs is not an efficient option, it is preferable to do as
follows:
? Traditionally regulate the highest output voltage.
? Post-regulate the other ones, by directly drawing the
energy from the transformer secondary ac voltage. The
NCP4331 is a controller developed to drive such buck
converters that have the ability to operate from pulsed
voltage.
Typically, NCP4331 driven post-regulators are
associated to forward converters as portrayed by Figure 20.
For the sake of the simplicity, the forward of Figure 20
consists of a simple demagnetization winding and output
?
?
Ease of implementation and compactness: The
NCP4331 is housed in a small SO16 package and it
incorporates all the functions necessary for a reliable
post-regulation (synchronization block, accurate
regulation block, soft-start, current control). Hence,
NCP4331 driven post-regulation requires few external
components. Also the high switching frequency levels
it can handle (up to 400 kHz) allows the utilization of
small output coil and capacitor. An internal regulator
highly eases the circuit feeding.
Robustness: The NCP4331 embeds powerful features
to protect the application from possible over-stresses
diodes, but more sophisticated options including active
clamp and synchronous rectification, would lead to a better
global efficiency of the solution.
Also, one can associate the NCP4331 to other
architectures (like two switches' forward or half-bridge
converters). Any converter able to provide the NCP4331
post-regulator with a square wave source could use this
concept, as long as the NCP4331 maximum ratings are not
exceeded (in particular, the “BST” and “HB” maximum
voltage).
Finally, the NCP4331 has the following main benefits:
? Efficiency: The NCP4331 concept avoids the
implementation of downstream converters to re-process
the main converter output voltage when two or more
outputs are to be tightly regulated. Instead, like
Mag-amp systems, NCP4331 driven post-regulators
directly draw the energy from the secondary side of the
main converter transformer, for a more efficient power
processing. In addition, the circuit manages the
and make the post-regulator very rugged. In particular,
it incorporates a second operational amplifier to lower
the duty-cycle and ultimately clamp the coil current
when it tends to become excessive (CCCV
characteristic). Also, the soft-start and the undervoltage
protections improve reliability. In addition, they help
control the start and end of the post-regulator
operation. Ultimately, the integration within the whole
system is eased.
Post-Regulation Operation
Figure 20 illustrates the concept where two outputs are to
be regulated (”V out1 ” and “V out2 ”). The highest output
(V out1 ) is traditionally regulated thanks to a regulation
arrangement that modulates the forward converter duty
cycle. The other output (V out2 ) is regulated by a dual
MOSFET arrangement driven by the NCP4331. The
high-side MOSFET turns on during one part of the forward
converter on-time, while the low-side power switch is ON
for the rest of the period (free wheeling).
http://onsemi.com
11
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