The analysis of the power adapter circuit three states the working condition of _

The analysis of the power adapter circuit three states the working condition of 2020-897 08 - 04 16:16:26 learning power adapter circuit, learn to circuit analysis, to understand the three states of the circuit from the beginning. Circuit which has three states: pathways ( Load) , short circuit, open circuit ( No-load) Under the three states of the ac adapter voltage U = E -, respectively IR， U=0。 U = E, the following content respectively introduce the three states of the specific circumstances. 1, the on-state: channel is in the circuit switch is closed, there are electric current flows through the load. In this state, the voltage of the power adapter and the relationship between the load current can be used outside characteristics determine the power adapter, according to the size of the load, is divided into full load, light load and overload conditions. Under rated power load working condition called rated working condition or full load; The working state is called light load under rated power; Higher than the rated power working condition is overload. Due to the overload are easy to burn out electrical later, so in general, are not allowed to appear overload. 2, short circuit state if the external circuit is approximate to zero resistance of conductors connected, power adapter is in short circuit condition at this moment, in this state, the current in the circuit, Short circuit current) I≈E/R 。 We know that the power adapter resistance are generally small, and thus could reach very large values of short-circuit current, the power adapter is in danger of burning, must be strictly prevent and avoid. To prevent the short circuit of the most common method is to install insurance tube in the circuit. Insurance of the fuse tube is made of low melting point of lead tin alloy, silver. When the current increases to a certain value, the fuse is first fuse, so as to cut off the circuit. In the condition of short circuit power supply voltage of the adapter is: U = E - IR≈E- E/R * R = 0, short circuit state of the main features are: large short-circuit current, voltage of the power adapter is zero. To note here, usually power adapter resistance basically remain unchanged and the value is very small, so can approximate think power supply voltage of the adapter is equal to the power adapter electromotive force. In the future if not particularly pointed out that the bid opening out the power adapter resistance, it means the internal resistance is small, can be neglected. 3. Open circuit state open is open circuit disconnect somewhere on both ends of the power adapter, no current in circuit, the power adapter is not sending power to the load. For the power adapter, this state is called light. Open circuit state of the main features are: the current in the circuit is zero. The voltage of the power adapter is equal to the electromotive force. The three state, can be seen everywhere in our life, such as the electric light switch is closed, the light shine, this is a state of channel, if the light, at the same time open the refrigerator, air conditioner, electric cooker, TV, computer, speakers, electric frying pans, when the load is more, let overload phenomenon in a night, when overload wire smoke fire easily. When the switch is closed, the lights went out, this is an open circuit condition. And when the two wires ( Firewire, zero line) Skin damaged by the mouse and a second wire touch together, can cause a short circuit, flow switch, if any, is flow switch work immediately, such as no flow switch, is smoking immediately burst into flames.