In the design of switching power supply, the input power is smaller, switching transformer primary side of the inductance but the greater the? Transformer primary side of the greater the amount of inductance, the transformer is not the volume will increase?
DC "can have a different meaning, and if the voltage through the resistor does not produce a voltage drop through the resistor voltage drop is called" DC "voltage, then the DC refers to a constant voltage that does not change with time, or from the Fourier decomposition Is the DC component of the periodic signal (the DC component is equal to the mean in one cycle when the input is a periodic signal and the circuit has a periodic steady state).
High frequency "DC voltage" is clearly not a constant voltage, it is estimated that the PWM thing, if it is a cycle input, then it will not only contain the DC component, but also contains the various sinusoidal AC component. Among them, the DC component in the inductor there is no pressure drop, and its components in the inductor voltage drop, so the coil inductance is certainly not short circuit. Of course, if the input signal DC component is too large, sinusoidal AC component is too small, then it may be too small inductance voltage, the entire coil current is too large.
The above is the meaning of DC from the perspective of frequency domain analysis. Of course, if you avoid the concept of DC directly to the time domain analysis, that is, on the first floor zchy4610 analysis, high level charge, the current index rises, low level discharge, current index decreased, in any case, the peak current and average current are not The voltage is only added to the resistor so much.
(1) Low power is corresponding to large inductance
Lp is inversely proportional to Ippk Lp = Vin (min) * Dmax / Ippk * f * k (Ippk: primary peak current K: current ripple rate)
Ippk is proportional to the input power Ippk = 2Pin / (1 + k) Vin (min) * Dmax
∴Lp is inversely proportional to Pin
(2) inductance volume and energy, and the relationship between the inductance is not absolute, large power is to correspond to the large volume of the inductor.
In the case of a selected core L = AL * N? (AL: inductance (material dependent) N: number of turns)
∴ sense and the core material and the number of turns
In the input voltage must be certain, the switching frequency of a certain situation, the smaller the input power, switching transformer primary side of the inductance but the greater the general, if the input voltage, switching frequency uncertainty, there is no comparable. On the forward power and counterattack power, the meaning of some different. The purpose of the counterattack is to allow the transformer to store the appropriate energy when the switch is turned on because the counterattack power supply does not output energy to the load during the turn-on of the switch and is only stored by the transformer during the switch Energy on the load output power, inductance is small, the excitation current is large, energy storage on more. On the forward, the purpose is to reduce the no-load energy consumption, because the forward power is in the switch tube conduction time to the load output power, do not rely on excitation energy storage. Transformer primary side of the volume of the transformer with the volume of the transformer is not necessarily related to the number of turns by the coil, the transformer is based on the power required to select the power, usually see the situation is the power of the smaller power supply, transformer volume small.
