只有32v电压源和电阻,如何设成5--12v连续可调电压源
\u5c06\u4e00\u53ea\u6807\u670912V.6W\u7684\u706f\u6ce1\u4e0e\u4e00\u7535\u963b\u4e32\u8054\u540e\u63a5\u5230\u7535\u538b\u4e3a12V\u7684\u7535\u6e90\u4e0a\uff0c\u7535\u963b\u6d88\u8017\u7684\u529f\u7387\u4e3a1W\u300a\u706f\u4e1d\u7535\u963b\u89c6\u505a\u4e0d\u53d8\u300b\u5219\u6b63\u786e\u7684\u9009\u9879\u662fD
\u73b0\u63d0\u4f9b\u4e24\u79cd\u7814\u7a76\u65b9\u6cd5\u2014\u2014\u5b9a\u91cf\u5206\u6790\u548c\u5b9a\u6027\u5206\u6790
\u5b9a\u91cf\u5206\u6790\uff1a
\u89e3:12V.6W\u7684\u706f\u6ce1\u989d\u5b9a\u7535\u538b\u4e3aU=12V\uff0c\u989d\u5b9a\u529f\u7387\u4e3aP=6W\uff0c\u5219\u989d\u5b9a\u7535\u6d41\u4e3aI=P/U=0.5A\uff0c\u7535\u963b\u4e3aR=U/I=24\u03a9\u3002
\u5f53\u5b83\u4e0e\u4e00\u7535\u963b\u4e32\u8054\u540e\u63a5\u5230\u7535\u538bU=12V\u7684\u7535\u6e90\u4e0a\uff0c\u4ee4\u4e32\u8054\u7684\u7535\u963b\u4e3aR1\uff0c\u5219\uff1a
\u4e32\u8054\u540e\u7535\u6d41I1\u4e3a\uff1aI1=U/\uff08R+R1\uff09
\u7531\u4e8e\u7535\u963b\u6d88\u8017\u7684\u529f\u7387P1=1W\uff0c
\u5373\uff1aP1=I1^2\u00d7R1=[U/\uff08R+R1\uff09]^2\u00d7R1=1W\uff0c
\u6c42\u5f97\uff1aR1=48+24\u221a3\u03a9\u6216R1=48-24\u221a3\u03a9\u3002
\u82e5\u662fR1=48+24\u221a3\u03a9\uff0c\u5219\uff1a
\u603b\u529f\u7387\u4e3a\uff1aP\u603b=U^2/(R+R1)=3-\u221a3W\u22481.3W
\u7535\u706f\u7684\u529f\u7387\u5219\u4e3a\uff1aP\u706f=P\u603b-P1\u22480.3W
\u82e5\u662fR1=48-24\u221a3\u03a9\uff0c\u5219\uff1a
\u603b\u529f\u7387\u4e3a\uff1aP\u603b=U^2/(R+R1)=3+\u221a3W\u22484.7W
\u7535\u706f\u7684\u529f\u7387\u5219\u4e3a\uff1aP\u706f=P\u603b-P1\u22483.7W
\u4ece\u4e0a\u9762\u4e24\u79cd\u60c5\u51b5\u6765\u770b\uff0c\u77e5\u9053\uff1a
\u706f\u6ce1\u4e0e\u7535\u963b\u6d88\u8017\u7684\u603b\u529f\u7387\u5c0f\u4e8e5W
\u706f\u6ce1\u6d88\u8017\u7684\u529f\u7387\u5c0f\u4e8e5W
\u6545\u6b63\u786e\u7684\u9009\u9879\u662fD
[\u8bf4\u660e\uff1a\u7b26\u53f7\u201c^\u201d\u8868\u793a\u7684\u662f\u5e73\u65b9]^_^
\u5b9a\u6027\u5206\u6790\uff1a
\u7535\u6e90\u7535\u538bU=12V\uff0c\u5219\u63a5\u516512V.6W\u7684\u706f\u6ce1\u65f6\u7535\u8def\u529f\u7387\u4e3aP=6W\uff0c\u5f53\u7535\u8def\u4e32\u8054\u4e00\u7535\u963bR1\u540e\uff0c\u7531\u4e8e\u7535\u8def\u7535\u963b\u53d8\u5927\uff0c\u7535\u8def\u7535\u6d41\u8981\u51cf\u5c0f\uff0c\u5219\u7535\u8def\u603b\u529f\u7387\u8981\u51cf\u5c0f\uff0c\u5373\u4e32\u8054\u7535\u963bR1\u540e\u7535\u8def\u603b\u529f\u7387\u5c0f\u4e8e6W\uff0c\u800c\u7535\u963bR1\u6d88\u8017\u7684\u529f\u7387\u4e3a1W\uff0c\u6545\u7535\u706f\u4e0a\u7684\u529f\u7387\u5c0f\u4e8e5W\u3002
\u6545\uff1a
\u201cA. \u706f\u6ce1\u4e0e\u7535\u963b\u6d88\u8017\u7684\u603b\u529f\u7387\u4e3a7W\u201d\u9519\u8bef\uff0c\u603b\u529f\u7387\u662f\u5c0f\u4e8e6W\u7684\uff1b
\u201cB. \u706f\u6ce1\u4e0e\u7535\u963b\u6d88\u8017\u7684\u603b\u529f\u7387\u4e3a6W\u201d\u9519\u8bef\uff0c\u603b\u529f\u7387\u662f\u5c0f\u4e8e6W\u7684\uff1b
\u201cC. \u706f\u6ce1\u6d88\u8017\u7684\u603b\u529f\u7387\u5927\u4e8e5W\u201d\u9519\u8bef\uff0c\u7535\u706f\u6d88\u8017\u7684\u529f\u7387\u662f\u5c0f\u4e8e5W\u7684\uff1b
\u201cD. \u706f\u6ce1\u6d88\u8017\u7684\u529f\u7387\u5c0f\u4e8e5W\u201d\u6b63\u786e\u3002
\u706f\u6ce1\u529f\u7387<5W,\u603b\u529f\u7387\u5c0f\u4e8e6W;
\u539f\u7535\u8def\uff1a\u603b\u7535\u963b = \u706f\u6ce1\u7535\u963b = \uff0812*12\uff09/ 6 = 24\u6b27\u59c6\uff1b
\u65b0\u7535\u8def\uff1a\u603b\u7535\u963b = \u706f\u6ce1\u7535\u963b + \u7535\u963b\u7535\u963b > 24\u6b27\u59c6\uff1b
\u7535\u8def\u529f\u7387 = (U*U)/ \u7535\u963b
\u7535\u538b\u4e0d\u53d8\uff0c\u5206\u6bcd\u53d8\u5927\uff0c\u503c\u53d8\u5c0f\uff0c\u6240\u4ee5\u603b\u529f\u7387 < 6W;
\u800c\u7535\u963b\u7684\u529f\u7387\u662f 1W;
\u6240\u4ee5\u706f\u6ce1\u7684\u529f\u7387 = \u603b\u529f\u7387 - 1W < 5W
只用32V电源和电阻来实现5~12V可调电压输出，这样的电源完全没有负载能力，稍微输出一点电流输出电压就会掉下来。
最好是用输出可调的开关稳压器来实现你要求的功能，例如LM2576-ADJ，用LM317不好，在输入输出电压差很大的情况下，用线性稳压器效率极低。
LM2576-ADJ的实用电路如下图——
只有电阻，只能作出有极调压，用一个317稳压块可以作出1 ---30v连续可调电压源。
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绛旓細Uab = 3 + 1 * R Rab = R 鐢垫祦婧愬舰寮忥細Is = (3 + R) / R = 3/R + 1 Rs = R
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