Power management

Description

A PWM Controller (Pulse Width Modulation Controller) is an integrated circuit (IC) used to generate a square wave signal with a variable duty cycle and control the power output by adjusting the pulse width. The core principle is to adjust the average voltage or current by changing the on-time (duty cycle) of the switching device, and it is widely used in power management, motor drive, LED dimming and other fields.

Key features:

Duty cycle adjustment: The ratio of the conduction time (Ton) to the period (T) of the output pulse (D = Ton/T).
Frequency adjustable: The frequency of the PWM signal can be fixed or programmable (e.g. 20kHz to 1MHz).
Control modes: Voltage mode, current mode, digital control, etc.
Protection features: Overcurrent protection (OCP), overvoltage protection (OVP), undervoltage lock (UVLO), etc.

2. Classification of PWM controllers

PWM controllers can be classified according to topology, control mode and application scenario:
(1) By topology
Buck (step-down) : Used for DC-DC step-down conversion.
Boost: For DC-DC boost conversion.
Buck-Boost: Input voltage can be higher/lower than output voltage.
Flyback: For isolated power supplies.
Half-bridge/full bridge: For high-power motor drives.
(2) By control mode
Voltage mode: Adjust duty cycle by feedback voltage (simple but slow response).
Current mode: Simultaneously detect inductor current and output voltage (fast dynamic response, strong anti-interference).
Digital control: With high flexibility through MCU or DSP programming (such as TI's 2000 series).
(3) By integration
Pure PWM controller: Requires an external MOSFET and inductor (e.g. SG3525).
PWM IC with integrated switch: Built-in power switch (e.g. TPS5430).

3 Core applications for PWM controllers

PWM controllers are widely used in scenarios that require efficient energy conversion or precise control:
(1) Switching Power Supply (SMPS)
DC-DC converters: Buck, Boost, and other topologies that provide a stable voltage for electronic devices.
¢Example: CPU power supply on a laptop motherboard (multiphase Buck controllers like 95858).
AC-DC power supply: such as charger, adapter (flyback controller).
(2) Motor drive
Dc motor speed regulation: Control the speed by adjusting the PWM duty cycle.
¢Example: Electric vehicle controller.
Stepper/servo motor: Precise control of position and torque.
(3) LED dimming
Backlight driver: Adjust the brightness of the LED.
Smart Lighting: PWM dimming avoids color shift.
(4) Audio Class D amplifiers
Convert the audio signal into a PWM wave to drive the speaker.
(5) New energy systems
Solar MPPT controller: Optimizes photovoltaic panel output.
Battery charging management: Constant current/constant voltage charging.

4. Key points for selecting PWM controllers

When choosing a PWM controller, the following parameters should be considered:

5 Notes

EMI issues: High-frequency PWM may introduce noise and need to optimize the PCB layout (shorten the switching loop).
Dead time: For half-bridge/full-bridge drives, configure dead time to prevent direct connection between the upper and lower tubes.
Efficiency optimization: Select synchronous rectification or low on-resistance (RDS(on)) MOSFETs.

Summary

PWM controllers are the core of power electronics systems, enabling efficient energy conversion and precise control by flexibly adjusting duty cycles. The selection should take into account topology, power requirements and control complexity, as well as cost and reliability.