求翻译：开关电源是利用现代电力电子技术，控制开关晶体管开通和关断的时间比率，维持稳定输出电压的一种电源，开关电源一般由脉冲宽度调制（PWM）控制IC和开关器件（MOSFET、BJT等）构成。开关电源和线性电源相比，二者的成本都随着输出功率的增加而增长，但二者增长速率各异。线性电源成本在某一输出功率点上，反而高于开关电源。随着电力电子技术的发展和创新，使得开关电源技术在不断地创新，这一成本反转点日益向低输出电力端移动，这为开关电源提供了广泛的发展空间。是什么意思？

The switching power supply is the use of modern power electronics technology to control the ratio of the switching transistor to turn on and off, maintaining a stable output voltage power supply, switching power supply in general by the pulse width modulation (pwm) ic and switch devices (the mosfet,

Switching power supply is to use modern electronic technology, the control switch transistor opened and shut-off of the percentage of time to maintain a stable output voltage of a power supply, switching power supply by a pulse width modulation (PWM IC ) control and switch devices, such as BJT , (MO