![[UNIFIVE]AC/DC Power Adapter&Switching Power Supply Manufacturer](common/img/header-logo.svg){kind=logo}
What Is an MCU-Integrated Battery Charger? Next-Generation Charging Technology Enabling Miniaturization, High Efficiency, and Long Lifespan
MCU-equipped battery chargers control charging profiles and protection functions such as OVP/OCP with high precision on a single chip. Specifications can be easily changed through firmware updates, and UNIFIVE provides custom support tailored to your application.
目次
Key Points of This Article
- An MCU-equipped battery charger is a next-generation charging technology that digitally controls charging management, protection functions, and status monitoring with high precision on a single chip.
- Charging profiles and protection thresholds can be changed simply by updating the firmware, enabling specification changes and feature additions without modifying the hardware.
- UNIFIVE provides custom MCU-equipped chargers tailored to your application and battery specifications. Please feel free to contact us from the planning stage.
MCU-equipped battery chargers/chargers are charging technologies in which charging profiles (methods) and various protection functions such as OVP/OCP are controlled on a single chip by a microcontroller (MCU). Compared with conventional analog-controlled chargers, advanced digital control using an MCU enables highly accurate charging and enhanced safety, while also allowing flexible specification changes through firmware updates.
This article explains the mechanisms, advantages, configurable parameters, and charging control methods of MCU-equipped chargers from the technical perspective of an AC/DC Power Adapter manufacturer.
What is an MCU? - Basics of Microcontrollers
MCU (Microcontroller Unit) is an ultra-compact computer that integrates the CPU, memory, and I/O on a single chip. It is widely used in home appliances and industrial equipment, and in recent years has also been built into battery chargers/charging devices to enable advanced digital control.
By performing charging control via software, which was traditionally handled by analog ICs and hardware circuits, functional integration and flexible control become possible. In chargers with a built-in MCU, battery voltage, current, and temperature information are read in real time and adjusted to optimal charging current and voltage through software algorithms.
Three Reasons MCU-Equipped Battery Chargers Are Chosen
Figure 1: Three Reasons MCU-Equipped Chargers Are Chosen
1. Multifunctionality and System Integration
Battery state diagnostics (voltage and temperature monitoring), charge control, communication with external devices, and protection controls such as OVP (overvoltage protection) and OCP (overcurrent protection) can all be integrated into a single chip. Functions that previously required separate ICs or circuits can now be handled by a single MCU, leading to a reduction in component count and greater flexibility in circuit design.
2. Flexible Specification Changes via Software
Charging algorithms and profiles can be adjusted simply by rewriting the software. For example, it is possible to switch from standard CC-CV charging to a pulse charging method, or to customize charge voltage and current thresholds according to the battery manufacturer's recommended values through firmware updates. Since functions can be added or improved without hardware changes, this approach shortens development time and enables a design that is robust against future updates.
3. Multiple Protection and Real-Time Monitoring
Because the MCU can process sensor information at high speed, it can execute multiple protection functions such as OVP, OCP, and OTP (over-temperature protection) with high precision. When an abnormality is detected, it can immediately stop charging or perform a safe shutdown, enabling real-time protection. Since voltage, current, and temperature values during charging can be continuously monitored and recorded, it can also be used to understand battery conditions and predict degradation.
Key Features of MCU-Based Battery Chargers
| Feature | Description |
|---|---|
| Custom Protection Settings | Thresholds and delay times for various protections such as OVP, OCP, and OTP can be freely configured according to the application. This protects equipment reliably while preventing unnecessary shutdowns. |
| Automatic Control of Long-Duration Peak Current | Even when a temporary high current is required, the duration of the peak current can be programmatically controlled. For example, flexible current profiles such as allowing 150% of maximum output for 5 seconds can be implemented. |
| Integrated Monitoring of Multiple Outputs | A single MCU can monitor and control the output voltage and current of multiple channels collectively. This simplifies wiring and control systems while optimizing overall system efficiency. |
| Temperature-Linked Fan ON/OFF Control | Fan operation is automatically controlled according to temperature sensor readings. It runs only when necessary, reducing noise, saving energy, and minimizing dust intake. |
| External Alarm Signal Output | When power supply or battery abnormalities are detected, the MCU immediately outputs an alarm signal to external systems. This enables compatibility with smart monitoring in the IoT era. |
AC/DC Power Adapter Where is the MCU circuit integrated?
Figure 2: MCU Placement Inside the AC/DC Power Adapter (Configuration Diagram)
The MCU circuit is generally integrated into the low-voltage side (secondary-side circuit) inside the AC/DC Power Adapter. In the case of an isolated AC/DC Power Adapter, the MCU is placed on the transformer-isolated secondary side and controls the primary-side switching IC via a photocoupler or similar device.
While monitoring the battery voltage and current, the MCU drives the charging DC-DC converter and switching elements, thereby achieving digital feedback control across the primary and secondary sides. The MCU software replaces the role traditionally handled by analog controller ICs and functions as the "brain" of the charger.
Main Parameters Adjustable via MCU Software
In MCU-based battery chargers, the following charging control parameters can be finely configured and adjusted through software. By customizing optimal values according to the battery type and application, charging safety and efficiency can be enhanced.
| Parameter | Overview | Example Setting |
|---|---|---|
| Pre-Charge Transition Voltage | Voltage threshold for switching from pre-charge to main charge. The starting point for safely recovering deeply discharged batteries. | Lithium-ion battery: approx. 3.0V |
| Pre-Charge Current | Initial pre-charge current applied to deeply discharged batteries. Typically about 10% (0.1C) of the full-charge current. | 2000mAh battery: approx. 200mA |
| Post-Charge Start Voltage | Voltage threshold to start supplementary charging (trickle charging) after main charging is complete. | Lead-acid battery float charge transition point |
| Post-Charge Current | Small trickle current to maintain full charge. For long durations, it must be limited to an appropriate value. | "Maintain charging at XXmA for XX hours," etc. |
| Charge Termination Voltage | Target voltage to determine full charge (float voltage). Can be set lower to prioritize safety and extend lifespan. | Lithium-ion: 4.2V/cell (adjustable from 4.1V to 4.35V) |
| Recharge Voltage | Threshold to automatically restart charging after full charge when voltage drops. Set with hysteresis. | Lithium: approx. 4.1V relative to full charge 4.2V |
| Battery Detection Time | Detection time to determine battery presence and status. If voltage does not recover within a certain period, it is judged as abnormal or not connected. | Test with micro current for several seconds |
| Output Overvoltage Protection (OVP) | If voltage tends to exceed the set level during charging, the MCU immediately reduces or cuts off the output. The threshold is programmable. | Lithium: cut off above 4.25V |
| Output Overcurrent Protection (OCP) | Limits or cuts off current when excessive current is detected. Delay time can also be finely configured. | Immediate cut-off in case of terminal short circuit or internal short |
| Safety Timer Duration | Overall charging timeout. If charging is not completed within a certain time, it is considered abnormal and forcibly terminated as a safety measure. | Set according to battery capacity |
| Pre-Charge Timer | Dedicated timeout for pre-charging. If voltage does not recover within the specified time, the battery is judged defective and charging is stopped. | Error if specified value is not reached within 30 minutes |
By optimizing various thresholds, timers, and current and voltage values, a custom charging profile tailored to the battery type and condition can be achieved, enabling both fast charging and safety assurance while extending battery lifespan.
Typical Charging Control Methods
Chargers equipped with an MCU can implement various charging methods through software, allowing the optimal control algorithm to be selected according to the application.
Constant Current/Constant Voltage Control (CC-CV Method)
Figure 3: Conceptual diagram of CC-CV charging profile
This is the standard method used in lithium-ion batteries. First, during CC (constant current) charging, the battery voltage gradually increases, and when it reaches the specified maximum voltage (charge termination voltage), it switches to CV (constant voltage) charging, continuing to charge while reducing the current. Charging is terminated when the current becomes sufficiently small during the CV stage. In MCU control, the CC current value, CV voltage value, and termination current (cutoff current) can be set flexibly.
Pulse Charging & Refresh Charging
Pulse charging is a method that charges using intermittent current pulses and is effective for lead-acid batteries. By applying high-voltage pulses, lead sulfate crystals (sulfation) accumulated inside the battery are removed, helping to restore capacity and reduce internal resistance.
For nickel-metal hydride batteries (Ni-MH) and nickel-cadmium batteries, refresh charging is used to mitigate capacity loss caused by the memory effect by discharging once before recharging. With MCU control, these complex patterns can also be executed via software, enabling optimal charging tailored to the characteristics of the battery.
Contact Us
MCU-equipped battery chargers are a key technology that dramatically enhances charging accuracy, safety, and operational flexibility.
UNIFIVE provides charging solutions optimized to meet customer requirements through multi-layer protection design based on extensive experience and firmware customization support.
From implementing special charging profiles to mass production, we support you from the planning stage.
Frequently Asked Questions (Q&A)
What is the difference between an MCU-equipped charger and a conventional analog charger?
Conventional analog chargers control charging through hardware circuits, whereas MCU-equipped chargers perform digital control via software. This enables flexible modification of charging parameters, highly accurate execution of multiple protection functions, and specification changes through firmware updates.
What types of batteries are compatible with MCU-equipped chargers?
They are compatible with a wide range of batteries, including lithium-ion, nickel-metal hydride, and lead-acid batteries. Since charging profiles (CC-CV, pulse charging, refresh charging, etc.) can be switched via software, optimal charging control can be achieved according to the battery type.
To what extent can charging parameters be customized?
Nearly all charging-related parameters can be configured and modified via software, including charge voltage and current thresholds, protection functions (OVP・OCP・OTP) operating points, safety timer duration, and pre-charge conditions. Adjustments to meet battery manufacturers' recommended values are also supported.
Is it possible to change the charging specifications after mass production?
One of the major advantages of an MCU-equipped charger is the ability to modify specifications through firmware updates. Since the charging profile and threshold values can be changed without altering the hardware, it is easy to implement updates after mass production or adapt to new batteries.
UNIFIVEWhat kind of custom support is available?
We provide comprehensive support from the planning stage to mass production, including designing charging profiles tailored to your battery specifications and applications, optimizing protection threshold values, custom firmware development, and compact design. Please feel free to contact our sales team for more information.