外接电源为目标板供电，经板上稳压管稳压到4.7V，PICkit3探测到的电压是2.3V，我进行烧写出现下面的错误信息，大侠们帮忙看看是什么原因造成的

PICkit 3 detected
Connecting to PICkit 3...
Running self test...
Self test completed
Firmware Suite Version...... 01.26.43
Firmware type......................Midrange
PICkit 3 Connected.
PK3Err0045: You must connect to a target device to use PICkit
3.Target Detected
Device ID Revision = 00000006

Erasing...
Erase device complete

Programming...
The following memory regions failed to program correctly:
Program Memory
Address: 00000000 Expected Value: 0000118a Received Value: 00000000
Programming failed

Target Removed