Basic principle of pwm control of switching power supply
Basic principle of pwm control of switching power supply
With the increasing demand for electricity, power management technology is becoming more and more important. As a high-efficiency and high-reliability power supply, switching power supply has found a wide range of applications. In switching power supply, pwm control technology is a common way to control the output of power supply. Aiming at the basic principle of pwm control of switching power supply, this paper expounds in detail from the following three aspects: introduction of basic working principle of switching power supply, pwm control principle and application of pwm control in switching power supply.
First, the basic working principle of switching power supply is introduced
Switching power supply is a voltage-type power supply, which can convert input voltage into output voltage. Its basic components include input filter circuit, rectifier circuit, filter circuit, boost circuit, boost inverter circuit and control circuit. Its basic principle is to realize the stability of output voltage by intermittent switching of switch tubes. Switching power supply has the following advantages: high output voltage stability, high efficiency, light weight and so on.
The whole switching power supply can be divided into two parts: DC/DC converter and controller. DC/DC converter includes rectifier circuit, filter circuit, boost circuit and boost inverter circuit. The whole process is to convert input voltage into stable output voltage. At the same time, the switching power supply needs to control the switching tube through the controller, so as to keep the output voltage stable. The task of the controller is to adjust the output voltage to keep it stable within the working range by controlling the switch tube according to the change of the input voltage.
Second, the principle of pwm control
Pulse Width Modulation (PWM for short) means that the output voltage is adjusted by changing the duty ratio at a certain switching frequency. Its essence is a steady-state control technology. The working principle of PWM technology is to set the high-level time as T1 and the low-level time as idle time T2 in a certain period of time. The duty ratio calculation formula is D = T1/(T1+T2), where d is the duty ratio. By changing the duty ratio d, the output voltage can be controlled.
Third, the application of pwm control in switching power supply
In switching power supply, pwm control is widely used. Specifically, pwm control can be applied to the full-wave rectification circuit of input AC voltage and the transformation of output voltage. In switching power supply, pwm control can realize the following functions:
1. Stability adjustment of output voltage and current. Pwm control technology can control the output voltage and current by adjusting the duty ratio, and realize accurate electric quantity adjustment.
2. Low noise control. In the switching power supply system, it is necessary to output current and voltage in a bridge mode, and pwm technology can realize this and reduce noise interference at the same time.
3. Feedback control. In the switching power supply system, pwm control can realize accurate control of output voltage and current by means of feedback control. At the same time, pwm control usually needs to be combined with filtering technology to make the output voltage more stable.
