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110W输出开关电源应用中的MC44603的设计方法说明

更新时间：2019-11-20 08:28:56 大小：193K 上传用户：梦留香查看TA发布的资源 标签：开关电源 下载积分：2分 评价赚积分 （如何评价?） 打赏 收藏 评论(0) 举报

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本申请说明的目的是提供一种在两种不同情况下设计MC44603的方法，即110 Vrms主电源和220 Vrms主电源。


　　对于这一功率范围，由于它限制了电源开关和输出二极管上的应力，必须改变不连续模式。由于MC44603的退磁装置，这种工作是可以保证的。


　　本应用说明考虑了高和低电源电压。


　　-在高压交流线路的情况下，它涉及到bothMOSFET和双极晶体管的使用。


　　-在低电源电压的情况下，只有MOSFET的解决方案被认为是电感峰值电流高。


　　MC40603是一种高灵活性的SMPS控制器，它提供了多种保护（精确的最大电流限制，VCC过电压检测，折回，退磁，软启动）。


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110W输出开关电源应用中的MC44603的设计方法说明.pdf 193K

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Order this document  
by AN1669/D  
SEMICONDUCTOR APPLICATION NOTE  
by Joël Turchi  
Power Management Products Operation  
Application Laboratory, Motorola, Toulouse, France  
The purpose of this application note is to present a way of  
designing the MC44603 in a fly–back dedicated to a 110 W  
output power supply in two distinct cases: 110 Vrms mains  
and 220 Vrms mains.  
For this range of power, the discontinuous mode must be  
chosen as it limits the stress on the power switch and the out-  
put diodes. This kind of working can be guaranteed, thanks to  
the demagnetization arrangement of the MC44603.  
This application note considers both high and low mains  
voltages.  
The outputs:  
120 V  
28 V  
15 V  
8 V  
0.5 A  
1.0 A  
1.0 A  
1.0 A  
Consequences for the Transformer  
This output voltage values are obtained using four second-  
ary windings of the transformer. Now, as a diode is located  
between the output capacitor and the winding, this diode volt-  
age must be taken into account in the choice of the number of  
turns of each of the windings.  
So, if the diode voltage is considered equal to 1 V, the  
desired voltages on the windings are nearly:  
121 V  
— In the high voltage a.c. line case, it deals with both  
MOSFET and BIPOLAR transistor use.  
— In the low mains voltage case, only the MOSFET solu-  
tion is considered as the inductor peak current is high.  
The MC44603 is a high flexibility SMPS controller. It offers  
a wide variety of protection (accurate maximum current limita-  
tion, Vcc overvoltage detection, fold–back, demagnetization,  
soft start).  
29 V  
16 V  
9 V  
In addition, distinct working modes can be used with this  
circuit:  
To obtain the output voltage values of the specification with  
a good accuracy, we need at least 3 turns for the 9 V and then:  
9 V  
3 turns  
— a fixed frequency working mode  
16 V  
5 turns  
Here, the frequency is given by the circuit oscillator.  
29 V  
10 turns  
40 turns  
— a variable frequency working mode  
This kind of working can be obtained when the chosen  
oscillator period is shorter than the cycle time for trans-  
former magnetization and complete demagnetization.  
121 V  
This solution seems to be correct, since with three turns, the  
9 V should be well coupled; also, 40 turns (for the 120 V) is not  
too large a value (no ferrite saturation).  
— a stand–by mode  
In our application, in order to obtain a very well regulated  
high voltage output, an opto coupler is used. By this means,  
the regulation uses feedback drawn from the 120 V output.  
This reduces the working frequency during this phase.  
This method reduces the stand–by losses that are  
mainly proportional to the switching frequency, and  
avoids the unstable very high frequency working that  
is generally associated with traditional free frequency  
systems.  
II — GENERAL DESIGN EQUATIONS  
Calculation of the Main SMPS Parameters  
II–1 — Fixed frequency working mode:  
In the MC44603 design proposed here, the variable  
frequency mode is not used. Indeed, as shown later, the fixed  
frequency mode enables a more accurate control of the power  
that is drawn from the mains.  
To obtain a fixed frequency discontinuous working mode  
(the discontinuous mode is guaranteed by the demagnetiza-  
tion section), the transformer primary inductor magnetization  
and demagnetization cycle must be shorter than the oscillator  
period (that is the chosen working period) for any working  
point.  
I — THE APPLICATIONS  
OUTPUT: 110 W  
In the following calculations, the maximum input power will  
This condition can be expressed by the following inequality:  
be considered equal to 135 W (η  
80%).  
(ineq 1)  
Ton Toff  
Tosc  
Application 1: 110 V mains 80 Vrms ↔ 140 Vrms  
Application 2: European mains 180 Vrms ↔ 280 Vrms  
Motorola, Inc.1998

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