Thoughts and conclusions on the role of diodes and capacitors in parallel with power supply in DC power supply circuits

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Thoughts and conclusions on the role of diodes and capacitors in parallel with power supply in DC power supply circuits [Copy link]

Question: In a DC power supply circuit, what is the function of a rectifier diode connected in parallel with the power supply?

Analysis:

1. Prevent the power supply from being connected in reverse.

a) If the power supply is connected in reverse, the diode conduction is equivalent to a short circuit, and the current is very large (2A or even larger). If the power supply is protected, it will be protected, otherwise the power supply will burn out. For a protected power supply, the diode's withstand voltage is required to be higher than the power supply voltage and the maximum forward current is required to be higher than the power supply's limiting current (the protection value of the protection circuit or the current value of the fuse), otherwise the diode will burn out, and the circuit will still burn out after the diode burns out (to be supplemented).

2. Prevent backflow from external circuits.

a) If the power supply is not reversely connected, if the external circuit is connected to an energy storage element such as an inductor, if the power is suddenly cut off, a reverse voltage will be generated on the inductor. If the power supply is connected to a diode with reversed positive and negative poles at the input end, the reverse voltage on the inductor will form a current path with the diode circuit and be clamped by the diode, so that no reverse overvoltage will be generated on the power supply to damage the power supply. Connecting the two ends of the element in parallel can prevent current reverse flow (to be supplemented).

3. Others. Connecting a diode in series in the power input loop can also protect the circuit. It is necessary to consider the maximum forward current value of the diode and whether the voltage drop of the diode has an impact on the circuit.

4. Supplement.

a) Diode 1N4001 is a rectifier diode (rectifier diodes are mainly used in various low-frequency half-wave rectifier circuits), with an operating and storage temperature range of -65~175℃. IN4007 can be replaced. The difference between rectifier diodes 1N4001 and IN4007 is only the reverse withstand voltage, and the other parameters are the same. Maximum periodic peak voltage: 50V, maximum effective value voltage: 35V, maximum forward rectifier current: 1.0A.

Question: In a DC power supply circuit, what is the role of a 1000uF electrolytic capacitor connected in parallel with the power supply?

Analysis:

1. Smooth voltage changes . The voltage across the load is the same as the voltage across the capacitor, and the bypass capacitor can stabilize the voltage change. (The characteristics of the capacitor charging and discharging points are like a reservoir. No matter how much water flows in, the water flowing out of the reservoir will be as stable as possible.)

2. Filtering. Absorb low-frequency signals and use the characteristics of capacitors that pass AC and block DC.

3. Supplement.

a) In a DC power supply circuit, a 1000uF polarized electrolytic capacitor is often connected in parallel with the power supply to stabilize voltage changes and filter out interference.

b) There are often components in the circuit that are connected in parallel with a 0.1uF capacitor. This capacitor is often a non-polar ceramic capacitor or polyester capacitor with a small capacity, and is often used to remove high-frequency noise from the power supply.

c) The function of coupling capacitor: transfer AC signal from the previous stage to the next stage, transmit AC signal and block DC connection.

d) The role of capacitors https://baijiahao.baidu.com/s?id=1595368128352786256

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