Explore the intricate circuit details and IC pinouts of the KM-809A rechargeable hair trimmer. Get insights on CL4056A, 9926B, and connection wires.
Rechargeable Hair Trimmer Circuit Diagram
General Overview of the Circuit
The KM 809A hair trimmer circuit board is designed for powering, charging, and displaying the battery status of the trimmer. The main components include:
A 7-segment display showing battery charge in percentage.
A CL4056A IC for battery charging control.
A 9926B IC for power control and switching.
An Analog-to-Digital Converter (ADC) IC to interface with the display and battery.
External components such as the motor, battery, and switch are also connected to this board.
External Component Details
Motor
M- and M+ terminals on the board connect directly to the motor of the hair trimmer. The motor's main function is to drive the blades for trimming hair.
The motor is typically powered by the battery (via the switch), and these connection points control the direction and operation of the motor.
Battery
The trimmer uses a lithium battery with a 4.2V rating and 2A capacity.
The battery is connected to the B- and B+ terminals on the board.
The CL4056A charging IC manages the charging and discharging cycles of the battery, ensuring it is charged properly and safely.
Switch
The power switch connects to the On/Off terminals.
The switch is a simple mechanism that controls the power flow to the motor. In the ON position, it allows the battery power to reach the motor (via the power control IC, 9926B).
Internal Component Details
7-Segment Digital Display
This display shows the battery charge level in percentage, from 0% (empty) to 100% (fully charged).
The display works in conjunction with the Analog-to-Digital Converter (ADC) IC. The ADC IC converts the battery voltage to a digital signal, which is then displayed as a percentage on the 7-segment display.
IC CL4056A - Battery Charging IC
The CL4056A is an 8-pin charging IC responsible for managing the charging process of the lithium battery.
CL4056A IC PinOut
Pin 1 (BAT): Connected to the B+ terminal. This pin monitors the battery voltage.
Pin 2 (GND): Ground pin, connected to the B- terminal and other ground points on the board.
Pin 3 (VCC): This is where the charger input voltage is connected (usually from the DC adapter via DC+ and DC- points).
Pin 4 (CHRG): Status pin that indicates the charging state (high or low depending on whether the battery is charging or full).
Pin 5 (STDBY): This pin indicates the standby state when the battery is fully charged.
Pin 6 (PROG): A pin that connects to a resistor to set the charging current.
Pin 7 (TEMP): Monitors the temperature of the battery to avoid overheating during charging.
Pin 8 (VSS): Ground pin (common ground).
The CL4056A ensures that the battery is charged safely, stopping the process when the battery reaches 4.2V to avoid overcharging.
IC 9926B - Power Control IC / Switching IC
The 9926B is a dual N-channel MOSFET IC, often used for load switching and power control in small devices.
Pin configuration (8-pin)
Pins 1 & 2 (Source1): These pins may be connected to the battery's B+.
Pin 3 (Gate1): The gate for the first MOSFET, controls switching.
Pins 4 & 5 (Drain1): This connects to the motor (M+).
Pin 6 (Drain2): Connects to the DC+ for charging.
Pin 7 (Gate 2): Gate for the second MOSFET (charging path control).
Pin 8 (Source 2): Connects to the ground or B-.
Function: The 9926B switches the power between charging mode and operational mode, controlling when the motor is powered and when the battery is charging.
Analog-to-Digital Converter IC
The ADC IC, with a total of 16 pins, interfaces with the battery and the 7-segment display.
This IC takes the analogue battery voltage and converts it to a digital value. The digital output is used to display the battery's charge status on the 7-segment display. Typically, the voltage is mapped to a percentage scale (0-100%).
Connection Points
M- and M+ (Motor)
These two points connect the motor of the hair trimmer.
When the switch is turned on, the power flows from the battery through the 9926B MOSFET, which acts as a switch for controlling the motor operation.
On and Off (Power Switch)
These terminals are connected to the external power switch. The switch controls whether the motor receives power from the battery.
In the ON state, the switch allows current to pass from the battery to the motor. In the OFF state, the motor is disconnected from the power supply.
DC- and DC+ (Charger Input)
These two points are for the charger adapter input. The DC+ connects to the positive terminal of the charger, and DC- connects to the ground.
The charger adapter is responsible for supplying power to charge the battery via the CL4056A IC.
B- and B+ (Battery)
These are the battery terminals. The B+ is the positive terminal, and B- is the ground connection.
These terminals are connected to the battery and supply power to the motor via the 9926B power control IC.
Working Step-by-Step
Powering the Motor
When the switch is turned on (connecting the ON/OFF terminals), the battery power is directed to the motor via the 9926B MOSFET.
The 9926B acts as a gate, controlling when the motor is powered and ensuring efficient power management.
Charging the Battery
When a charger is connected to the DC+ and DC- points, the charging current flows through the CL4056A IC.
The CL4056A monitors the battery voltage and current to ensure safe charging.
Once the battery reaches 4.2V, the CL4056A stops the charging process to prevent overcharging.
Battery Status Display
The battery voltage is constantly monitored by the ADC IC.
The ADC converts the analogue battery voltage into a digital signal and sends this information to the 7-segment display, showing the charge percentage.
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