uc3842开关电源 改变启动电阻 启动电压不变 uc3842开关电源的限流电阻怎么计算
\u57fa\u4e8eUC3842\u7684\u5f00\u5173\u7535\u6e90\u8bbe\u8ba1\u4e0e\u5236\u4f5cuc3842\u8bbe\u8ba1\u5f00\u5173\u7535\u6e90
2007-07-19 19:17
1\u3001UC3842\u7684\u5185\u90e8\u7ed3\u6784\u548c\u7279\u70b9
UC3842\u662f\u7f8e\u56fdUnitrode\u516c\u53f8\u751f\u4ea7\u7684\u4e00\u79cd\u9ad8\u6027\u80fd\u5355\u7aef\u8f93\u51fa\u5f0f\u7535\u6d41\u63a7\u5236\u578b\u8109\u5bbd\u8c03\u5236\u5668\u82af\u7247\u3002
UC3842\u4e3a8\u811a\u53cc\u5217\u76f4\u63d2\u5f0f\u5c01\u88c5\uff0c\u5176\u5185\u90e8\u539f\u7406\u6846\u56fe\u5982\u56fe1\u6240\u793a\u3002\u4e3b\u8981\u75315.0V\u57fa\u51c6\u7535\u538b\u6e90\u3001\u7528\u6765\u7cbe\u786e\u5730\u63a7\u5236\u5360\u7a7a\u6bd4\u8c03\u5b9a\u7684\u632f\u8361\u5668\u3001\u964d\u538b\u5668\u3001\u7535\u6d41\u6d4b\u5b9a\u6bd4\u8f83\u5668\u3001PWM\u9501\u5b58\u5668\u3001\u9ad8\u589e\u76caE/A\u8bef\u5dee\u653e\u5927\u5668\u548c\u9002\u7528\u4e8e\u9a71\u52a8\u529f\u7387MOSFET\u7684\u5927\u7535\u6d41\u63a8\u633d\u8f93\u51fa\u7535\u8def\u7b49\u6784\u6210\u3002\u7aef1\u4e3aCOMP\u7aef\uff1b\u7aef2\u4e3a\u53cd\u9988\u7aef\uff1b\u7aef3\u4e3a\u7535\u6d41\u6d4b\u5b9a\u7aef\uff1b\u7aef4\u63a5Rt\u3001Ct\u786e\u5b9a\u952f\u9f7f\u6ce2\u9891\u7387\uff1b\u7aef5\u63a5\u5730\uff1b\u7aef6\u4e3a\u63a8\u633d\u8f93\u51fa\u7aef\uff0c\u6709\u62c9\u3001\u704c\u7535\u6d41\u7684\u80fd\u529b\uff1b\u7aef7\u4e3a\u96c6\u6210\u5757\u5de5\u4f5c\u7535\u6e90\u7535\u538b\u7aef\uff0c\u53ef\u4ee5\u5de5\u4f5c\u57288\uff5e40V\uff1b\u7aef8\u4e3a\u5185\u90e8\u4f9b\u5916\u7528\u7684\u57fa\u51c6\u7535\u538b5V\uff0c\u5e26\u8f7d\u80fd\u529b50mA\u3002
2\u3001\u7535\u8def\u7ed3\u6784\u4e0e\u5de5\u4f5c\u539f\u7406
\u56fe2\u6240\u793a\u4e3a\u7b14\u8005\u5728\u5b9e\u9645\u5de5\u4f5c\u4e2d\u4f7f\u7528\u7684\u7535\u8def\u56fe\u3002\u8f93\u5165\u7535\u538b\u4e3a24V\u76f4\u6d41\u7535\u3002\u4e09\u8def\u76f4\u6d41\u8f93\u51fa\uff0c\u5206\u522b\u4e3a+5V/4A\uff0c+12V/0.3A\u548c-12V/0.3A\u3002\u6240\u6709\u7684\u4e8c\u6781\u7ba1\u90fd\u91c7\u7528\u5feb\u901f\u53cd\u5e94\u4e8c\u6781\u7ba1\uff0c\u6838\u5fc3PWM\u5668\u4ef6\u91c7\u7528UC3842\u3002\u5f00\u5173\u7ba1\u91c7\u7528\u5feb\u901f\u5927\u529f\u7387\u573a\u6548\u5e94\u7ba1\u3002
2.1 \u542f\u52a8\u8fc7\u7a0b
\u9996\u5148\u7531\u7535\u6e90\u901a\u8fc7\u542f\u52a8\u7535\u963bR 1\u63d0\u4f9b\u7535\u6d41\u7ed9\u7535\u5bb9C2\u5145\u7535\uff0c\u5f53C2\u7535\u538b\u8fbe\u5230UC3842\u7684\u542f\u52a8\u7535\u538b\u95e8\u69db\u503c16V\u65f6\uff0cUC3842\u5f00\u59cb\u5de5\u4f5c\u5e76\u63d0\u4f9b\u9a71\u52a8\u8109\u51b2\uff0c\u75316\u7aef\u8f93\u51fa\u63a8\u52a8\u5f00\u5173\u7ba1\u5de5\u4f5c\uff0c\u8f93\u51fa\u4fe1\u53f7\u4e3a\u9ad8\u4f4e\u7535\u538b\u8109\u51b2\u3002\u9ad8\u7535\u538b\u8109\u51b2\u671f\u95f4\uff0c\u573a\u6548\u5e94\u7ba1\u5bfc\u901a\uff0c\u7535\u6d41\u901a\u8fc7\u53d8\u538b\u5668\u539f\u8fb9\uff0c\u540c\u65f6\u628a\u80fd\u91cf\u50a8\u5b58\u5728\u53d8\u538b\u5668\u4e2d\u3002\u6839\u636e\u540c\u540d\u7aef\u6807\u8bc6\u60c5\u51b5\uff0c\u6b64\u65f6\u53d8\u538b\u5668\u5404\u8def\u526f\u8fb9\u6ca1\u6709\u80fd\u91cf\u8f93\u51fa\u3002\u5f536\u811a\u8f93\u51fa\u7684\u9ad8\u7535\u5e73\u8109\u51b2\u7ed3\u675f\u65f6\uff0c\u573a\u6548\u5e94\u7ba1\u622a\u6b62\uff0c\u6839\u636e\u695e\u6b21\u5b9a\u5f8b\uff0c\u53d8\u538b\u5668\u539f\u8fb9\u4e3a\u7ef4\u6301\u7535\u6d41\u4e0d\u53d8\uff0c\u4ea7\u751f\u4e0b\u6b63\u4e0a\u8d1f\u7684\u611f\u751f\u7535\u52a8\u52bf\uff0c\u6b64\u65f6\u526f\u8fb9\u5404\u8def\u4e8c\u6781\u7ba1\u5bfc\u901a\uff0c\u5411\u5916\u63d0\u4f9b\u80fd\u91cf\u3002\u540c\u65f6\u53cd\u9988\u7ebf\u5708\u5411UC3842\u4f9b\u7535\u3002UC3842\u5185\u90e8\u8bbe\u6709\u6b20\u538b\u9501\u5b9a\u7535\u8def\uff0c\u5176\u5f00\u542f\u548c\u5173\u95ed\u9608\u503c\u5206\u522b\u4e3a16V\u548c10V\uff0c\u5982\u56fe3\u6240\u793a\u3002\u5728\u5f00\u542f\u4e4b\u524d\uff0cUC3842\u6d88\u8017\u7684\u7535\u6d41\u57281mA\u4ee5\u5185\u3002\u7535\u6e90\u7535\u538b\u63a5\u901a\u4e4b\u540e\uff0c\u5f537\u7aef\u7535\u538b\u5347\u81f316V\u65f6UC3842\u5f00\u59cb\u5de5\u4f5c\uff0c\u542f\u52a8\u6b63\u5e38\u5de5\u4f5c\u540e\uff0c\u5b83\u7684\u6d88\u8017\u7535\u6d41\u7ea6\u4e3a15mA\u3002\u56e0\u4e3aUC3842\u7684\u542f\u52a8\u7535\u6d41\u57281mA\u4ee5\u5185\uff0c\u8bbe\u8ba1\u65f6\u53c2\u7167\u8fd9\u4e9b\u53c2\u6570\u9009\u53d6R1\uff0c\u6240\u4ee5\u5728R1\u4e0a\u7684\u529f\u8017\u5f88\u5c0f\u3002
\u5f53\u7136\uff0c\u82e5VCC\u7aef\u7535\u538b\u8f83\u5c0f\u65f6\uff0c\u5728R1\u4e0a\u7684\u538b\u964d\u5f88\u5c0f\uff0c\u5168\u90e8\u4f9b\u7535\u5de5\u4f5c\u90fd\u53ef\u7531R1\u964d\u538b\u540e\u6765\u5b8c\u6210\u3002\u4f46\u662f\uff0c\u901a\u5e38\u60c5\u51b5\u4e0b\uff0cVCC\u7aef\u7535\u538b\u90fd\u6bd4\u8f83\u5927\uff0c\u8fd9\u6837\u5b8c\u5168\u901a\u8fc7R1\u6765\u63d0\u4f9b\u6b63\u5e38\u5de5\u4f5c\u7535\u538b\u5c31\u4f1a\u4f7fR1\u81ea\u8eab\u529f\u8017\u592a\u5927\uff0c\u5bf9\u6574\u4e2a\u7535\u6e90\u6765\u8bf4\u6548\u7387\u592a\u4f4e\u3002\u4e00\u822c\u6765\u8bf4\uff0c\u968f\u7740UC3842\u7684\u542f\u52a8\uff0cR1\u7684\u5de5\u4f5c\u4e5f\u5c31\u57fa\u672c\u7ed3\u675f\uff0c\u4f59\u4e0b\u7684\u4efb\u52a1\u4ea4\u7ed9\u53cd\u9988\u7ed5\u7ec4\uff0c\u7531\u53cd\u9988\u7ed5\u7ec4\u4ea7\u751f\u7535\u538b\u6765\u4e3aUC3842\u4f9b\u7535\u3002\u6545R1\u7684\u529f\u7387\u4e0d\u5fc5\u9009\u5f97\u5f88\u5927\uff0c1W\u30012W\u5c31\u8db3\u591f\u4e86\u3002\u7b14\u8005\u8ba4\u4e3a\uff0c\u867d\u7136\u7406\u8bba\u4e0aUC3842\u542f\u52a8\u7535\u6d41\u57281mA\u4ee5\u5185\uff0c\u4f46\u5b9e\u9645\u5e94\u7528\u65f6\uff0c\u63091.6\uff5e2.0mA\u8bbe\u8ba1\u5219\u5de5\u4f5c\u6bd4\u8f83\u4fbf\u5229\u3002\u5373\u5f53VCC\u7aef\u7535\u538b\u4e3aU\u4f0f\u65f6
2.2 \u7a33\u538b\u8fc7\u7a0b
\u4ece\u56fe2\u4e2d\u53ef\u77e5\uff0c\u5f53\u573a\u6548\u5e94\u7ba1\u5bfc\u901a\u65f6\uff0c\u6574\u6d41\u7535\u538b\u52a0\u5728\u53d8\u538b\u5668T\u521d\u7ea7\u7ed5\u7ec4Np\u4e0a\u7684\u7535\u80fd\u53d8\u6210\u78c1\u80fd\u50a8\u5b58\u5728\u53d8\u538b\u5668\u4e2d\uff0c\u5728\u573a\u6548\u5e94\u7ba1\u5bfc\u901a\u7ed3\u675f\u65f6\uff0cNp\u7ed5\u7ec4\u4e2d\u7535\u6d41\u8fbe\u5230\u6700\u5927\u503cIpmax\uff0c\u6839\u636e\u6cd5\u62c9\u7b2c\u7535\u78c1\u611f\u5e94\u5b9a\u5f8b\uff1a
\u5f0f\u4e2d\uff1aE\u2014\u2014\u6574\u6d41\u7535\u538b\uff1bLp\u2014\u2014\u53d8\u538b\u5668\u521d\u7ea7\u7ed5\u7ec4\u7535\u611f\uff1bTon\u2014\u2014\u573a\u6548\u5e94\u7ba1\u5bfc\u901a\u65f6\u95f4\u3002
\u5728\u573a\u6548\u5e94\u7ba1\u5173\u95ed\u77ac\u95f4\uff0c\u53d8\u538b\u5668\u6b21\u7ea7\u7ed5\u7ec4\u653e\u7535\u7535\u6d41\u4e3a\u6700\u5927\u503cIsmax\uff0c\u82e5\u5ffd\u7565\u5404\u79cd\u635f\u8017\u5e94\u4e3a
\u5f0f\u4e2d\uff1an\u2014\u2014\u53d8\u538b\u5668\u53d8\u6bd4\uff0cn=Np/Ns\uff0cNp\u3001Ns\u4e3a\u53d8\u538b\u5668\u521d\u3001\u6b21\u7ea7\u7ed5\u7ec4\u531d\u6570\u3002
\u9ad8\u9891\u53d8\u538b\u5668\u5728\u573a\u6548\u5e94\u7ba1\u5bfc\u901a\u671f\u95f4\u521d\u7ea7\u7ed5\u7ec4\u50a8\u5b58\u7684\u80fd\u91cf\u4e0e\u573a\u6548\u5e94\u7ba1\u5173\u95ed\u671f\u95f4\u6b21\u7ea7\u7ed5\u7ec4\u91ca\u653e\u7684\u80fd\u91cf\u76f8\u7b49\uff1a
\u5f0f\u4e2d\uff1aLs\u2014\u2014\u53d8\u538b\u5668\u6b21\u7ea7\u7ed5\u7ec4\u7535\u611f\uff1bUo\u2014\u2014\u8f93\u51fa\u7535\u538b\uff1bToff\u2014\u2014\u573a\u6548\u5e94\u7ba1\u5173\u95ed\u65f6\u95f4\u3002
\u4e0a\u5f0f\u8bf4\u660e\uff0c\u8f93\u51fa\u7535\u538bUo\u4e0eTon\u6210\u6b63\u6bd4\uff0c\u4e0e\u531d\u6bd4n\u53caToff\u6210\u53cd\u6bd4\u3002\u6bd4\u5982\uff0c\u7531\u4e8e\u7535\u6e90\u7535\u538b\u53d8\u5316\u6216\u8d1f\u8f7d\u53d8\u5316\u800c\u5f15\u8d77\u8f93\u51fa\u7535\u538b\u964d\u4f4e\u65f6\uff0c\u53cd\u9988\u7ebf\u5708\u7684\u8f93\u51fa\u7535\u538b\u5219\u4f1a\u53d8\u4f4e\uff0c\u4ece\u800c\u4f7f2\u7aef\u7535\u538b\u53d8\u4f4e\uff0c\u5219\u8109\u5bbd\u8c03\u5236\u5668\u4f1a\u76f8\u5e94\u7684\u589e\u5927\u8f93\u51faPWM\u6ce2\u5f62\u7684\u5360\u7a7a\u6bd4\uff0c\u4f7f\u5927\u529f\u7387\u6676\u4f53\u7ba1\u5bfc\u901a\u7684\u65f6\u95f4\u53d8\u957f\uff1b\u53cd\u4e4b\uff0c\u5f53\u7535\u6e90\u7535\u538b\u53d8\u5316\u6216\u8d1f\u8f7d\u53d8\u5316\u800c\u5f15\u8d77\u8f93\u51fa\u7535\u538b\u5347\u9ad8\u65f6\uff0c\u5219\u8109\u5bbd\u8c03\u5236\u5668\u4f1a\u76f8\u5e94\u7684\u51cf\u5c0fPWM\u8f93\u51fa\u8109\u51b2\u6ce2\u5f62\u7684\u5360\u7a7a\u6bd4\uff0c\u4f7f\u5927\u529f\u7387\u6676\u4f53\u7ba1\u5bfc\u901a\u7684\u65f6\u95f4\u53d8\u77ed\uff0c\u4ece\u800c\u7ef4\u6301\u8f93\u51fa\u7535\u538b\u4e3a\u4e00\u6052\u5b9a\u503c\u3002
UC3842\u4e3a\u56fa\u5b9a\u5de5\u4f5c\u9891\u7387\u8109\u5bbd\u8c03\u5236\u65b9\u5f0f\uff0c\u8f93\u51fa\u7535\u538b\u6216\u8d1f\u8f7d\u53d8\u5316\u65f6\u4ec5\u8c03\u6574\u5360\u7a7a\u6bd4\uff0c\u63a7\u5236\u573a\u6548\u5e94\u7ba1\u7684\u5bfc\u901a\u65f6\u95f4\u3002\u53cd\u9988\u7535\u538b\u8f93\u51652\u811a\uff0c\u6b64\u811a\u7535\u538b\u4e0e\u5185\u90e82.5V\u57fa\u51c6\u8fdb\u884c\u6bd4\u8f83\uff0c\u4ea7\u751f\u63a7\u5236\u7535\u538b\uff0c\u4ece\u800c\u63a7\u5236\u8109\u51b2\u5bbd\u5ea6\uff1b\u8f93\u51fa\u8109\u51b2\u7684\u9891\u7387\u75314\u811a\u5916\u63a5\u5b9a\u65f6\u7535\u963bRt\u53ca\u5b9a\u65f6\u7535\u5bb9Ct\u51b3\u5b9a\uff0cf
\u7684\u5355\u4f4d\u53d6k\u03a9\uff0cCt\u53d6\u03bcF\u30023\u811a\u4e3a\u7535\u611f\u7535\u6d41\u4f20\u611f\u5668\u7aef\uff0c\u5f53\u53d6\u6837\u8d85\u8fc71V\u65f6\uff0c\u7f29\u5c0f\u5bfc\u901a\u8109\u5bbd\uff0c\u4f7f\u7535\u6e90\u5904\u4e8e\u95f4\u9699\u5de5\u4f5c\u72b6\u6001\uff1b6\u811a\uff0c\u8f93\u51fa\u7aef\uff0c\u5185\u90e8\u4e3a\u56fe\u817e\u67f1\u5f0f\uff0c\u4e0a\u5347\u3001\u4e0b\u964d\u65f6\u95f4\u4ec550ns\uff0c\u9a71\u52a8\u80fd\u529b\u4e3a\u00b11A\uff1b7\u811a\uff0c\u4f9b\u7535\u8f93\u5165\uff0c\u8d77\u632f\u540e\u5de5\u4f5c\u7535\u538b\u4e3a10\uff5e13V\uff0c\u4f4e\u4e8e10V\u505c\u6b62\u5de5\u4f5c\uff0c\u529f\u8017\u4e3a15mW\uff1b8\u811a\uff0c\u5185\u90e8\u57fa\u51c65V(50mA)\u3002
2.3 \u8fc7\u6d41\u4fdd\u62a4\u539f\u7406
\u5f53\u8d1f\u8f7d\u7535\u6d41\u8d85\u8fc7\u989d\u5b9a\u503c\u6216\u77ed\u8def\u65f6\uff0c\u573a\u6548\u5e94\u7ba1\u7535\u6d41\u589e\u52a0\uff0cR9\u4e0a\u7684\u7535\u538b\u53cd\u9988\u81f33\u811a(\u7535\u538b\u5927\u4e8e1V)\uff0c\u901a\u8fc7\u5185\u90e8\u7535\u6d41\u653e\u5927\u5668\u4f7f\u5bfc\u901a\u5bbd\u5ea6\u53d8\u7a84\uff0c\u8f93\u51fa\u7535\u538b\u4e0b\u964d\uff0c\u76f4\u81f3\u4f7fUC3842\u505c\u6b62\u5de5\u4f5c\uff0c\u6ca1\u6709\u89e6\u53d1\u8109\u51b2\u8f93\u51fa\uff0c\u4f7f\u573a\u6548\u5e94\u7ba1\u622a\u6b62\uff0c\u8fbe\u5230\u4fdd\u62a4\u529f\u7387\u7ba1\u7684\u76ee\u7684\u3002\u77ed\u8def\u73b0\u8c61\u6d88\u5931\u540e\uff0c\u7535\u6e90\u81ea\u52a8\u6062\u590d\u6b63\u5e38\u5de5\u4f5c\u3002
2.4 \u8fc7\u538b\u4fdd\u62a4\u539f\u7406
\u5f53\u56e0\u67d0\u79cd\u539f\u56e0\u4f7f\u8f93\u51fa\u7535\u538b\u8fc7\u9ad8\u65f6\uff0c\u7531\u53cd\u9988\u7ed5\u7ec4\u5f62\u6210\u7684\u7535\u538b\u4e5f\u9ad8\uff0c\u4ece\u800c\u4f7f2\u811a\u7684\u7535\u538b\u8fc7\u9ad8\uff0c\u5185\u90e8\u4fdd\u62a4\u7535\u8def\u8d77\u52a8\uff0c\u4f7f6\u811a\u8f93\u51fa\u8109\u51b2\u9ad8\u7535\u5e73\u65f6\u95f4\u53d8\u77ed\uff0c\u6216\u4e0d\u8f93\u51fa\u9ad8\u7535\u5e73\u4f7f\u5f00\u5173\u7ba1\u622a\u6b62\u3002
2.5 \u5f00\u5173\u7ba1\u4fdd\u62a4\u7535\u8def
\u7531D3\u3001R10\u3001C1\u53caR11\u3001C14\u3001D4\u6784\u6210\uff0c\u6d88\u9664\u7531\u53d8\u538b\u5668\u6f0f\u611f\u4ea7\u751f\u7684\u53cd\u5cf0\u7535\u538b\uff0c\u4ece\u800c\u4f7f\u5f00\u5173\u5de5\u4f5c\u7535\u538b\u4e0d\u81f3\u4e8e\u592a\u9ad8\u800c\u6bc1\u574f\u3002
3\u3001\u8bbe\u8ba1\u4e2d\u7684\u6ce8\u610f\u4e8b\u9879
3.1 \u8d77\u52a8\u7535\u8def\u7684\u8bbe\u8ba1
\u7535\u8def\u5982\u56fe4\u6240\u793a\uff0c\u7535\u5bb9C2\u50a8\u5b58\u7684\u80fd\u91cf\u8981\u80fd\u6ee1\u8db3\u7535\u6e90\u5f00\u59cb\u6b63\u5e38 \u5de5\u4f5c\u7684\u9700\u8981\uff0c\u4f7f\u5f97UC3842\u7b2c7\u811a\u6709\u7a33\u5b9a\u3001\u5145\u8db3\u7684\u8f93\u5165\u4f9b\u7ed9\u3002\u5373\u7535\u5bb9C2\u7684\u653e\u7535\u65f6\u95f4\u8981\u5927\u4e8eUC3 842\u8f93\u51fa\u8109\u51b2\u7684\u9ad8\u7535\u5e73\u6301\u7eed\u65f6\u95f4\u3002\u5426\u5219\uff0c\u7535\u6e90\u5c06\u51fa\u73b0\u6253\u55dd\u73b0\u8c61\u3002\u56e0\u6b64\uff0c\u7535\u5bb9C2\u7684\u5bb9\u91cf\u548c \u8d28\u91cf\u7684\u9009\u53d6\u975e\u5e38\u91cd\u8981\u3002\u7b14\u8005\u5728\u5b9e\u9645\u8bbe\u8ba1\u8fc7\u7a0b\u4e2d\uff0cC2\u66fe\u7528100\u03bcF\u94dd\u7535\u89e3\u7535\u5bb9\uff0c\u7ecf\u5e38\u53d1\u73b0 \u7535\u6e90\u6253\u55dd\uff1b\u6d4b\u91cf\u53cd\u9988\u7aef\u7535\u538b\uff0c\u603b\u662f\u592a\u4f4e\uff0c\u4ee5\u81f3\u4e8e\u53cd\u9988\u7aef\u7684\u6574\u6d41\u4e8c\u6781\u7ba1\u90fd\u6ca1\u6709\u5de5\u4f5c\uff0c\u8bf4\u660e\u53cd\u9988 \u7aef\u7535\u538b\u5e45\u5ea6\u4e0d\u591f\u3002\u539f\u56e0\u5728\u4e8eC2\u5bb9\u91cf\u4e0d\u591f\uff0c\u4e0d\u80fd\u63d0\u4f9b\u8db3\u591f\u7684\u80fd\u91cf\u6765\u4f7fUC3842\u5145\u5206\u5de5\u4f5c\uff0c\u56e0\u6b64 \uff0c\u5bb9\u91cf\u6700\u597d\u5728100\u03bcF\u4ee5\u4e0a\u3002
3.2 \u53cd\u9988\u7ed5\u7ec4\u7684\u8bbe\u8ba1
\u5f53UC3842\u542f\u52a8\u540e\uff0c\u82e5\u53cd\u9988\u7ed5\u7ec4\u4e0d\u80fd\u63d0\u4f9b\u8db3\u591f\u7684UF\uff0c\u7535\u8def\u5c31\u4f1a\u4e0d\u505c\u5730\u8d77\u52a8 \uff0c\u51fa\u73b0\u6253\u55dd\u73b0\u8c61\u3002\u53e6\u5916\uff0c\u6839\u636e\u7b14\u8005\u7684\u7ecf\u9a8c\uff0c\u82e5UF\u5927\u4e8e17.5V\u65f6\uff0c \u4e5f\u4f1a\u5f15\u8d77UC3842\u5de5\u4f5c\u5f02\u5e38\uff0c\u5bfc\u81f4\u8f93\u51fa\u8109\u51b2\u5360\u7a7a\u6bd4\u53d8\u5c0f\uff0c\u8f93\u51fa\u7535\u538b\u53d8\u4f4e\u3002\u6545\u800c\u53cd\u9988\u7ed5\u7ec4\u531d\u6570\u7684 \u9009\u53d6\u53ca\u5176\u7f20\u7ed5\u662f\u975e\u5e38\u91cd\u8981\u7684\uff0c\u4e00\u822c\u53ef\u630913\uff5e15V\u8bbe\u8ba1\uff0c\u4f7fUC3842\u6b63\u5e38\u5de5\u4f5c\u65f6\uff0c7\u811a\u7684\u7535\u538b\u7ef4\u6301 \u572813V\u5de6\u53f3\u3002
4\u3001\u7ed3\u675f\u8bed
UC3842\u662f\u4e00\u79cd\u6027\u80fd\u4f18\u826f\u7684\u7535\u6d41\u63a7\u5236\u578b\u8109\u5bbd\u8c03\u5236\u5668\u3002\u5047\u5982\u7531\u4e8e\u67d0\u79cd\u539f\u56e0\u4f7f\u8f93\u51fa\u7535\u538b\u5347\u9ad8\u65f6\uff0c\u8109 \u5bbd\u8c03\u5236\u5668\u5c31\u4f1a\u6539\u53d8\u9a71\u52a8\u4fe1\u53f7\u7684\u8109\u51b2\u5bbd\u5ea6\uff0c\u4ea6\u5373\u5360\u7a7a\u6bd4D\uff0c\u4f7f\u65a9\u6ce2\u540e\u7684\u5e73\u5747 \u503c\u7535\u538b\u4e0b\u964d\uff0c\u4ece\u800c\u8fbe\u5230\u7a33\u538b\u76ee\u7684\uff0c\u53cd\u4e4b\u4ea6\u7136\u3002UC3842\u53ef\u4ee5\u76f4\u63a5\u9a71\u52a8MOS\u7ba1\u3001IGBT\u7b49\uff0c\u9002\u5408\u4e8e \u5236\u4f5c20\uff5e80W\u5c0f\u529f\u7387\u5f00\u5173\u7535\u6e90\u3002\u7531\u4e8e\u5668\u4ef6\u8bbe\u8ba1\u5de7\u5999\uff0c\u7531\u4e3b\u7535\u6e90\u7535\u538b\u76f4\u63a5\u542f\u52a8\uff0c\u6784\u6210\u7535\u8def\u6240\u9700 \u5143\u4ef6\u5c11\uff0c\u975e\u5e38\u7b26\u5408\u7535\u8def\u8bbe\u8ba1\u4e2d\u201c\u7b80\u6d01\u81f3\u4e0a\u201d\u7684\u539f\u5219\u3002
\u3000\u3000\u6839\u636e\u8f93\u5165\u7535\u538b\u7528\u6b27\u59c6\u5b9a\u5f8b\u8ba1\u7b97\uff0c\u4fdd\u8bc1\u80fd\u7ed93842\u82af\u7247\u63d0\u4f9b1mA\u4ee5\u4e0a\u7684\u542f\u52a8\u7535\u6d41\u3002
3842的7脚到300V的电阻常见的是120K-150K，但既然原来设计用190K能工作，应该不是电阻的问题。3842启动原理是：由300V经启动电阻给电容充电，充到16V时3842便开始工作，然后由高频变压器供电绕组维持3842的正常供电，电压在11V以上都能正常工作。7脚的电压为12.3V而不启动，问题应该在47uF电容和芯片本身上，要么是电容漏电，要么是3842坏，使启动时对电容的充电到不了16V。如果8脚没有5V电压，至少说明3842没有启动，7脚12.3V不能说明说明问题。加我三六二，我一步一步教你，你有示波器和稳压源最好。
扩展阅读：维修3842芯片开关电源 ... 3842改0-60可调电源 ... 3845开关电源通病维修 ... 3842开关电源输电压低 ... 3842不起振维修视频 ... 3845开关电源维修讲解 ... 代替3842的电源芯片 ... 开关电源芯片uc3842 ... 3842电动车充电器改可调 ...
