Three basic working modes of non-isolated switching power supply
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Three basic working modes of non-isolated switching power supply

Posted Date: 2024-01-12

Three basic working modes of non-isolated switching power supply

Non-isolated switching power supply is a common power supply design that can provide stable DC output voltage. It consists of switching tubes, inductors, capacitors, diodes and other components, and uses switches to control the flow of current to achieve efficient power conversion. Non-isolated switching power supply has the advantages of simple structure, small size and high efficiency, and is widely used in various fields, such as electronic equipment, LED lighting fixtures, etc.

The basic working methods of non-isolated switching power supplies include: fixed-frequency pulse width modulation (PWM), double pulse modulation (TPM) and current mode control (CMC). These three basic working methods will be introduced in detail below.

1. Fixed frequency pulse width modulation (PWM)

Fixed-frequency pulse width modulation is one of the most commonly used working methods in non-isolated switching power supplies. The basic principle is to control the output voltage by adjusting the conduction time of the switch tube. When the input voltage is applied to the inductor, the switch is turned on and the current increases; when the switch is turned off, the current decreases. By repeating this process, an output voltage that is directly related to the input voltage can be obtained.

In the PWM working mode, the duty cycle of the output voltage is changed by adjusting the conduction time of the switch tube. The higher the duty cycle, the closer the output voltage is to the input voltage; the lower the duty cycle, the smaller the output voltage. As needed, the required output voltage value can be achieved by controlling the duty cycle.

2. Double pulse modulation (TPM)

Double pulse modulation is a working method designed to improve the efficiency of switching power supplies. In the traditional PWM working mode, there is a certain switching loss when the switch tube is turned on and off, so the efficiency is low. Double-pulse modulation reduces switching losses and improves power conversion efficiency by introducing two pulses respectively during the turn-on and turn-off processes.

In the TPM working mode, the switch tube will perform two pulse operations in each of the two stages of turn-on and turn-off to reduce power consumption during the turn-on and turn-off processes. By precisely controlling the timing and size of the two pulses, efficient electrical energy conversion can be achieved.

3. Current Mode Control (CMC)

Current mode control is another important non-isolated switching power supply operating method. Different from PWM and TPM, the CMC working mode mainly focuses on the control of output current rather than the control of output voltage. This working method controls the opening and closing of the switch tube by measuring the output current and comparing the measurement result with the set current.

In the CMC working mode, when the measured output current is less than the set current, the switch is turned on and the current increases; when the measured output current exceeds the set current, the switch is turned off and the current decreases. Precise current control can be achieved by continuously comparing the measurement results with the set current.

Summarize:

There are three basic working modes of non-isolated switching power supply: fixed frequency pulse width modulation (PWM), double pulse modulation (TPM) and current mode control (CMC). They respectively control the output voltage and current of the power supply by adjusting the conduction time of the switch tube, introducing two pulses and comparing the output current. These working methods have different advantages and disadvantages in different application scenarios. Designers can choose the appropriate working method according to specific needs to achieve efficient and stable power supply design.


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