穩(wěn)壓芯片并聯(lián)的問題

一、前言

如果一個穩(wěn)壓芯片輸出電流不能夠滿足要求，是否可以簡單的將兩個穩(wěn)壓芯片進行并聯(lián)提供更大的輸出電流呢？?下面簡單測試一下，看會出現(xiàn)什么問題。

二、測試電路

設計兩路穩(wěn)壓芯片并聯(lián)電路。這里給出了兩路獨立的穩(wěn)壓芯片 7805。它們的輸出可以并聯(lián)在一起，為負載提供輸出電流。輸入分開，由不同的直流電源提供工作電流，也間接獲得每個穩(wěn)壓器的工作電流。下面也設計了 1117 ，3.3V的穩(wěn)壓芯片。該電路板也可以對1117 穩(wěn)壓芯片進行測試。使用單面板制作測試電路。

一分鐘之后獲得測試電路板。檢查一下制作的情況。非常完美。焊接電路板。先測試兩個 AS1117 穩(wěn)壓芯片的并聯(lián)情況。通過可編程直流電源和電子負載對其進行測試。

▲ 圖1.2.1 測試電路圖

▲ 圖1.2.2 測試PCB圖

三、測試結果

下面使用電子負載，分別測試兩個 AS1117 的輸出特性。負載電流范圍是 300mA。兩個1117 ?的輸入電壓為9V。記錄每個電流下對應的芯片輸出。這是第一個芯片的輸出特性。右面電壓下降快，猜測是芯片發(fā)熱造成的。第二個芯片特性比較平直。估計它的溫度特性比較穩(wěn)定。從這里可以看到 ，兩個穩(wěn)壓芯片輸出特性差別還是蠻大的。

▲ 圖1.3.1 AS1117芯片1的電壓與電流特性

cdim=[0.0000,0.0030,0.0061,0.0091,0.0121,0.0152,0.0182,0.0212,0.0242,0.0273,0.0303,0.0333,0.0364,0.0394,0.0424,0.0455,0.0485,0.0515,0.0545,0.0576,0.0606,0.0636,0.0667,0.0697,0.0727,0.0758,0.0788,0.0818,0.0848,0.0879,0.0909,0.0939,0.0970,0.1000,0.1030,0.1061,0.1091,0.1121,0.1152,0.1182,0.1212,0.1242,0.1273,0.1303,0.1333,0.1364,0.1394,0.1424,0.1455,0.1485,0.1515,0.1545,0.1576,0.1606,0.1636,0.1667,0.1697,0.1727,0.1758,0.1788,0.1818,0.1848,0.1879,0.1909,0.1939,0.1970,0.2000,0.2030,0.2061,0.2091,0.2121,0.2152,0.2182,0.2212,0.2242,0.2273,0.2303,0.2333,0.2364,0.2394,0.2424,0.2455,0.2485,0.2515,0.2545,0.2576,0.2606,0.2636,0.2667,0.2697,0.2727,0.2758,0.2788,0.2818,0.2848,0.2879,0.2909,0.2939,0.2970,0.3000]
vdim=[3.2967,3.2967,3.2967,3.2967,3.2934,3.2925,3.2917,3.2909,3.2902,3.2895,3.2887,3.2881,3.2870,3.2863,3.2855,3.2848,3.2841,3.2833,3.2826,3.2817,3.2809,3.2801,3.2794,3.2787,3.2780,3.2773,3.2766,3.2756,3.2748,3.2741,3.2734,3.2727,3.2720,3.2713,3.2705,3.2698,3.2691,3.2682,3.2675,3.2668,3.2661,3.2654,3.2646,3.2640,3.2633,3.2625,3.2616,3.2609,3.2601,3.2594,3.2588,3.2580,3.2573,3.2566,3.2557,3.2550,3.2543,3.2536,3.2529,3.2522,3.2514,3.2507,3.2500,3.2493,3.2486,3.2477,3.2470,3.2463,3.2456,3.2450,3.2442,3.2434,3.2428,3.2418,3.2412,3.2404,3.2396,3.2389,3.2382,3.2375,3.2367,3.2357,3.2350,3.2342,3.2334,3.2328,3.2321,3.2314,3.2307,3.2295,3.2287,3.2279,3.2270,3.2262,3.2253,3.2245,3.2236,3.2225,3.2214,3.2205]

#!/usr/local/bin/python
#?-*-?coding:?gbk?-*-
#******************************
#?TEST1.PY???????????????????-?by?Dr.?ZhuoQing?2023-12-21
#
#?Note:
#******************************

from?headm?import?*
from?tsmodule.tsvisa????????import?*

dl3021open(109)


dl3021setcurrent(0)
dl3021on()

cdim?=?linspace(0,?0.3,?100)
vdim?=?[]


for?c?in?cdim:
????dl3021setcurrent(c)
????time.sleep(1)
????v?=?dl3021volt()
????printff(c,?v)
????vdim.append(v)
????tspsave('u1',?cdim=cdim,?vdim=vdim)


dl3021setcurrent(0)
dl3021off()

plt.plot(cdim,?vdim,?lw=3)

plt.xlabel("Current(A)")
plt.ylabel("Voltage(VA)")
plt.grid(True)
plt.tight_layout()
plt.show()


#------------------------------------------------------------
printf("a")



#------------------------------------------------------------
#????????END?OF?FILE?:?TEST1.PY
#******************************

▲ 圖1.3.2 第二個芯片對應的輸出電流與電壓

cdim=[0.0000,0.0030,0.0061,0.0091,0.0121,0.0152,0.0182,0.0212,0.0242,0.0273,0.0303,0.0333,0.0364,0.0394,0.0424,0.0455,0.0485,0.0515,0.0545,0.0576,0.0606,0.0636,0.0667,0.0697,0.0727,0.0758,0.0788,0.0818,0.0848,0.0879,0.0909,0.0939,0.0970,0.1000,0.1030,0.1061,0.1091,0.1121,0.1152,0.1182,0.1212,0.1242,0.1273,0.1303,0.1333,0.1364,0.1394,0.1424,0.1455,0.1485,0.1515,0.1545,0.1576,0.1606,0.1636,0.1667,0.1697,0.1727,0.1758,0.1788,0.1818,0.1848,0.1879,0.1909,0.1939,0.1970,0.2000,0.2030,0.2061,0.2091,0.2121,0.2152,0.2182,0.2212,0.2242,0.2273,0.2303,0.2333,0.2364,0.2394,0.2424,0.2455,0.2485,0.2515,0.2545,0.2576,0.2606,0.2636,0.2667,0.2697,0.2727,0.2758,0.2788,0.2818,0.2848,0.2879,0.2909,0.2939,0.2970,0.3000]
vdim=[3.3192,3.3187,3.3188,3.3182,3.3152,3.3149,3.3142,3.3134,3.3128,3.3121,3.3115,3.3109,3.3100,3.3093,3.3088,3.3081,3.3075,3.3068,3.3061,3.3052,3.3046,3.3039,3.3032,3.3026,3.3020,3.3013,3.3006,3.2997,3.2990,3.2984,3.2977,3.2970,3.2964,3.2957,3.2950,3.2944,3.2937,3.2927,3.2920,3.2913,3.2907,3.2900,3.2893,3.2885,3.2879,3.2872,3.2862,3.2855,3.2848,3.2840,3.2832,3.2824,3.2817,3.2808,3.2798,3.2789,3.2781,3.2774,3.2767,3.2759,3.2748,3.2738,3.2730,3.2722,3.2713,3.2702,3.2693,3.2686,3.2677,3.2665,3.2655,3.2649,3.2640,3.2626,3.2613,3.2600,3.2589,3.2579,3.2565,3.2551,3.2539,3.2519,3.2504,3.2488,3.2472,3.2457,3.2442,3.2424,3.2406,3.2385,3.2365,3.2336,3.2306,3.2280,3.2247,3.2216,3.2181,3.2136,3.2086,3.2029]

▲ 圖1.3.3 將兩個穩(wěn)壓芯片電流電壓曲線繪制在一起

#!/usr/local/bin/python
#?-*-?coding:?gbk?-*-
#******************************
#?TEST2.PY???????????????????-?by?Dr.?ZhuoQing?2023-12-21
#
#?Note:
#******************************

from?headm?import?*

cdim0,?vdim0?=?tspload('u1',?'cdim',?'vdim')
cdim1,?vdim1?=?tspload('u2',?'cdim',?'vdim')

plt.plot(cdim0,?vdim0,?lw=3,?label='U1')
plt.plot(cdim1,?vdim1,?lw=3,?label='U2')

plt.xlabel("Current(A)")
plt.ylabel("Voltage(V)")
plt.grid(True)
plt.legend(loc="upper?right")
plt.tight_layout()
plt.show()


#------------------------------------------------------------
#????????END?OF?FILE?:?TEST2.PY
#******************************

在測試過程中，不小心短路將第二芯片燒壞了。更換了一支新的芯片。重新測量它的輸出特性。對比三個1117 的輸出特性，可以看到它們之間的差別還是比較大的。

▲ 圖1.3.4 第三只1117 的電壓電流特性

cdim=[0.0000,0.0030,0.0061,0.0091,0.0121,0.0152,0.0182,0.0212,0.0242,0.0273,0.0303,0.0333,0.0364,0.0394,0.0424,0.0455,0.0485,0.0515,0.0545,0.0576,0.0606,0.0636,0.0667,0.0697,0.0727,0.0758,0.0788,0.0818,0.0848,0.0879,0.0909,0.0939,0.0970,0.1000,0.1030,0.1061,0.1091,0.1121,0.1152,0.1182,0.1212,0.1242,0.1273,0.1303,0.1333,0.1364,0.1394,0.1424,0.1455,0.1485,0.1515,0.1545,0.1576,0.1606,0.1636,0.1667,0.1697,0.1727,0.1758,0.1788,0.1818,0.1848,0.1879,0.1909,0.1939,0.1970,0.2000,0.2030,0.2061,0.2091,0.2121,0.2152,0.2182,0.2212,0.2242,0.2273,0.2303,0.2333,0.2364,0.2394,0.2424,0.2455,0.2485,0.2515,0.2545,0.2576,0.2606,0.2636,0.2667,0.2697,0.2727,0.2758,0.2788,0.2818,0.2848,0.2879,0.2909,0.2939,0.2970,0.3000]
vdim=[3.3015,3.3014,3.3012,3.3008,3.2982,3.2976,3.2969,3.2963,3.2957,3.2951,3.2945,3.2938,3.2930,3.2924,3.2918,3.2913,3.2907,3.2901,3.2896,3.2887,3.2881,3.2876,3.2870,3.2865,3.2859,3.2853,3.2847,3.2839,3.2833,3.2828,3.2822,3.2817,3.2811,3.2806,3.2799,3.2794,3.2789,3.2781,3.2775,3.2769,3.2763,3.2757,3.2752,3.2746,3.2740,3.2735,3.2726,3.2720,3.2714,3.2709,3.2702,3.2696,3.2691,3.2684,3.2675,3.2669,3.2663,3.2657,3.2651,3.2644,3.2635,3.2629,3.2622,3.2616,3.2609,3.2600,3.2593,3.2586,3.2580,3.2572,3.2565,3.2558,3.2550,3.2539,3.2531,3.2524,3.2516,3.2508,3.2500,3.2492,3.2484,3.2473,3.2465,3.2457,3.2449,3.2441,3.2434,3.2425,3.2417,3.2406,3.2398,3.2389,3.2382,3.2372,3.2363,3.2353,3.2342,3.2329,3.2317,3.2304]

▲ 圖1.3.5 三個芯片輸出特性

??將兩個1117并聯(lián)在一起，輸入電壓同樣為9V，此時可以看到，它們各自的靜態(tài)電流不太一樣。一個為 0.9mA，另外一個為 5.6mA。下面使用電子負載測量兩個 1117 并聯(lián)后各自的電流變化。

使用電子負載測試并聯(lián)后的兩個 1117 工作電流。工作電流可以通過DH1766 直接讀出。測量結果令人感到驚訝。居然在整個輸出電流范圍內，兩個 1117 只有一個為負載提供電流。另外一個始終輸出 0mA。這讓我破防了。實在是沒有想到。手觸碰兩個 1117，會發(fā)現(xiàn)一個已經發(fā)燙，另外一個沒有溫度。

▲ 圖1.3.6 并聯(lián)后兩個1117在不同負載下輸出電流

#!/usr/local/bin/python
#?-*-?coding:?gbk?-*-
#******************************
#?TEST3.PY???????????????????-?by?Dr.?ZhuoQing?2023-12-21
#
#?Note:
#******************************

from?headm?import?*


from?tsmodule.tsvisa????????import?*

dl3021open(109)
dl3021setcurrent(0)
dl3021on()


#------------------------------------------------------------

cdim?=?linspace(0,?0.3,?100)
c1dim?=?[]
c2dim?=?[]


for?c?in?cdim:
????dl3021setcurrent(c)
????time.sleep(1)
????ca?=?dh1766call1()

????printff(c,?ca)
????c1dim.append(ca[0])
????c2dim.append(ca[1])

????tspsave('1117',?cdim=cdim,?c1dim=c1dim,?c2dim=c2dim)


dl3021setcurrent(0)
dl3021off()

plt.plot(cdim,?c1dim,?lw=3,?label='U1')
plt.plot(cdim,?c2dim,?lw=3,?label='U2')

plt.xlabel("Current(A)")
plt.ylabel("Current(A)")
plt.grid(True)
plt.tight_layout()
plt.show()


#------------------------------------------------------------
#????????END?OF?FILE?:?TEST3.PY
#******************************

cdim=[0.0000,0.0030,0.0061,0.0091,0.0121,0.0152,0.0182,0.0212,0.0242,0.0273,0.0303,0.0333,0.0364,0.0394,0.0424,0.0455,0.0485,0.0515,0.0545,0.0576,0.0606,0.0636,0.0667,0.0697,0.0727,0.0758,0.0788,0.0818,0.0848,0.0879,0.0909,0.0939,0.0970,0.1000,0.1030,0.1061,0.1091,0.1121,0.1152,0.1182,0.1212,0.1242,0.1273,0.1303,0.1333,0.1364,0.1394,0.1424,0.1455,0.1485,0.1515,0.1545,0.1576,0.1606,0.1636,0.1667,0.1697,0.1727,0.1758,0.1788,0.1818,0.1848,0.1879,0.1909,0.1939,0.1970,0.2000,0.2030,0.2061,0.2091,0.2121,0.2152,0.2182,0.2212,0.2242,0.2273,0.2303,0.2333,0.2364,0.2394,0.2424,0.2455,0.2485,0.2515,0.2545,0.2576,0.2606,0.2636,0.2667,0.2697,0.2727,0.2758,0.2788,0.2818,0.2848,0.2879,0.2909,0.2939,0.2970,0.3000]
c1dim=[0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009,0.0009]
c2dim=[0.0056,0.0056,0.0056,0.0124,0.0162,0.0192,0.0222,0.0250,0.0277,0.0307,0.0338,0.0366,0.0405,0.0434,0.0463,0.0491,0.0519,0.0549,0.0579,0.0617,0.0647,0.0674,0.0705,0.0733,0.0763,0.0792,0.0822,0.0861,0.0891,0.0921,0.0950,0.0979,0.1009,0.1038,0.1066,0.1094,0.1123,0.1163,0.1192,0.1219,0.1250,0.1278,0.1308,0.1337,0.1367,0.1396,0.1434,0.1461,0.1491,0.1520,0.1549,0.1579,0.1607,0.1636,0.1676,0.1704,0.1733,0.1763,0.1792,0.1820,0.1858,0.1888,0.1917,0.1945,0.1974,0.2014,0.2043,0.2072,0.2100,0.2129,0.2158,0.2186,0.2216,0.2255,0.2284,0.2313,0.2343,0.2372,0.2401,0.2430,0.2458,0.2498,0.2527,0.2556,0.2583,0.2614,0.2642,0.2671,0.2700,0.2738,0.2769,0.2798,0.2827,0.2854,0.2886,0.2913,0.2941,0.2980,0.3009,0.3038]

更換了另外一對1117重新進行測量。使用電子負載為并聯(lián)1117 提供負載。它們輸出電流相差 50% 左右。

▲ 圖1.3.7 另外兩組1117 并聯(lián)輸出電流

??最后測試兩個 7805 并聯(lián)的結果。輸入電壓為 9V。負載電流從0變化到300mA，可以看到兩個7805 的工作電流相差很大。

▲ 圖1.3.8 兩個 7805 并聯(lián)輸出

※ 總??結 ※

本文對于兩個穩(wěn)壓芯片的并聯(lián)進行了測試，可以看到這種情況如果不使用均流方法，是無法工作的。與其并聯(lián)這些穩(wěn)壓芯片，不如采用其它方式進行擴容。