The NiMH battery charging circuit is relatively complex, and some SMD components cannot be found in the specification sheet.

童心老叟

The NiMH battery charging circuit is relatively complex, and some SMD components cannot be found in the specification sheet. [Copy link]

I want to replace the rechargeable battery of an imported experimental instrument, so I disassembled its charger and drew a circuit diagram. There are some chip components whose specifications cannot be found and cannot be judged based on the silk screen printing, so I come here for help. The following are the components that cannot be found and are uncertain. Chip U2 of the main control board: silk screen marked "GYEG", suspected to be "MK3498", packaged as SOT-753 or SC-74a, the code library website gave a brief introduction, but no information. Diodes D2 and D3: silk screen marked "605 1334", packaged as SMC or DO-214. Diode D4: silk screen marked "S1A", packaged as SMA. Transistor Q1: silk screen marked "N7A3E", SOT-23. Diodes D5 and D4' in the battery compartment: silk screen marked "S1S1" or "1S1S", packaged as 0805, and not very clear under the microscope. Put the main schematic diagram here (the 232 interface and USB interface circuit are not included), maybe it will help to analyze it? This charger is a seat type, and it also needs a power adapter to power it, the voltage is DC12V. The charger itself has a microprocessor. During the charging process of the NiMH battery, there is a voltage and current detection chip, and its signal is converted through an AD converter and connected to the microprocessor. In addition, there are RS232 and USB interfaces to communicate with the host computer, and real-time monitoring during charging? Most of the components of this circuit are not commonly used. I have found some information about some rare things. If you need it, I can also provide it.

qwqwqw2088

Now that I have the schematic, I am still worried about not being able to find the device.

dcexpert

The schematic diagram should be drawn by yourself. It is normal that the model is difficult to find. Some components are difficult to find only by silk screen.

天地摩登恒

After understanding its function, just replace it with common components

童心老叟

qwqwqw2088 posted on 2019-4-16 17:47 Now that I have the schematic, I am still worried about not being able to find the device

I just drew the schematic myself. I searched the Internet but found nothing.

Based on this picture, what device can be determined?

童心老叟

Tian Di Modern Heng published on 2019-4-16 20:18 After understanding its function, just replace it with common components

Replace with common components? I'm not so confident.

Even if you know what the component is, you may not be able to analyze the principle clearly, let alone know what it is?