To reduce the power consumption of switching power supplies - Database & Sql Blog Articles

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The power consumption of a switching power supply includes a fixed loss due to a parasitic resistance of a semiconductor switch, a magnetic element, and a wiring, and a switching loss at the time of switching operation. For fixed loss, since it mainly depends on the characteristics of the component itself, it needs to be suppressed by the improvement of the component technology. In terms of magnetic components, research on a low-loss winding method that takes into account the skin effect and the adjacent wire effect has been in existence for a long time. In order to reduce the switching loss caused by the switching surge of the transformer leakage inductance, a new circuit technology such as a snubber circuit with a surge energy regeneration function has been developed. The following are circuits and system methods to improve the efficiency of switching power supplies:

(1) ZVS (Zero Voltage Switching), ZCS (Zero Current Switching), etc., which use a resonant switch to reduce switching loss.

(2) Reduce the switching loss by using Edge Resonance represented by an active clamp circuit.

(3) The fixed loss is reduced by extending the on-time of the switching element to suppress the peak current.

(4) In the case of low voltage and large current, the fixed loss is reduced by improving the synchronous rectification circuit.

(5) Use the parallel structure of the converter to reduce the fixed loss.

Among them, the first method is extremely effective for reducing the switching loss, but the problem is that the fixed loss due to the peak current and the peak voltage will increase. The second method is an active buffer (Active Snubber) developed to solve this problem. It is a very practical ZVS method; however, the problem of efficiency degradation caused by reactive current under light load conditions is A big flaw. In the third method, the tap inductor is effective, and it can cope with the surge caused by the leakage inductance. Regarding the fourth method, the two-stage structure is one of the methods for realizing the efficient operation of the synchronous rectification circuit. It adopts a fixed time ratio (Time Ratio) close to 0.5, and the output voltage control is performed by the converter of the preceding stage. It is a traditional thinking mode that “two-stage structure will lead to a decrease in efficiency” and is very effective in low voltage and high current applications. As for the fifth method, the entire converter circuit can be connected in parallel, or a parallel structure can be partially used like the Current Doubler.