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Types and main functions of each component of the power adapter
The types and main functions of general-purpose components are as follows:
First, the resistor:
1. Sampling resistor—A sampling circuit that forms the output voltage and sends the sampled voltage to the feedback circuit.
2. Voltage equalization resistor—The voltage equalization function is also used in the symmetrical DC input circuit of the power adapter, also known as the balance resistor.
3. Voltage divider resistors - form a resistor divider.
4. Bleed Resistor—Discharges the charge stored in the capacitor in the electromagnetic interference (EMI) filter when the power is turned off.
5. Current limiting resistor - acts as a current limiting resistor, such as a current limiting resistor for a Zener, optocoupler, and input filter capacitor.
6. Current Sense Resistor—Used with an overcurrent protection circuit to limit the output current limit of the power adapter.
7. Shunt Resistor—Bypass the current.
8. Load resistance—The load resistance of the power adapter (including the equivalent load resistance).
9. Minimum Load Resistance—The minimum load resistance required to maintain proper operation of the power adapter avoids excessive output voltage due to open load.
10. Fake load—A load that is temporarily connected when testing the power adapter performance specifications (such as resistance wire, cement resistance).
11. Filter resistor—Used as a filter resistor in LC type filters, RC type filters, and π type filters.
12. Bias Resistor—Provides a bias to the control terminal of the power adapter or stabilizes the operating point of the transistor.
13. Protection Resistor—Commonly used in RC type absorption circuits or VD, R, and C type clamp protection circuits.
14. Frequency compensation resistor—for example, an RC type frequency compensation network that forms an error amplifier.
15. Damping resistor—Prevents resonance in the circuit.
Second, the capacitor:
1. Filter capacitors—constituting input filters, output filters, and so on.
2. Coupling Capacitor - Also known as a DC-blocking capacitor, it acts to block the DC signal and only allows the AC signal to pass.
3. Unbuckling capacitors—such as the power adapter's untwisting capacitor—can prevent self-oscillation.
4. Soft-Start Capacitor—This constitutes a soft-start circuit that slowly establishes the output voltage and output current during soft-start.
5. Compensation Capacitor - constitutes a RC type frequency compensation network.
6. Acceleration Capacitor - used to increase the switching speed of the transistor.
7. Oscillation Capacitor - Forms an RC type, LC type oscillator.
8. Differential Capacitor—Constructs a differential circuit to obtain a sharp pulse.
9. Bootstrap capacitor—used to boost the power adapter voltage of the input stage and also form a voltage feedforward circuit.
10. Delay Capacitor—The resistor forms a RC delay circuit.
11. Energy storage capacitors—such as pump capacitors in a polarity inverting DC/DC converter.
12. Phase Shift Capacitor - Forms a phase shifting circuit.
13. Doubled Capacitor—The diode forms a voltage doubler rectifier circuit.
14. Noise Cancellation Capacitor—Used to filter out noise interference in the circuit.
15. Neutralize Capacitor—Remove the self-oscillation of the amplifier.
16. Capacitor to suppress interference—In the EMI filter, serial mode and common mode interference can be filtered out separately.
17. Safety Capacitor—Contains X and Y capacitors.
18. X Capacitor—Filters the common mode interference generated by the primary winding and secondary winding coupling capacitors, providing a return path for the interference current coupled from the primary side to the secondary side, preventing this current from coupling to the earth through the secondary side. .
19. Y Capacitor—Filters the string-mode interference between the grids and is commonly used in EMI filters.
Third, the inductor:
1. Filter Inductor - Forms an LC filter.
2. Energy storage inductors—usually used in buck or boost DC/DC converter circuits.
3. Oscillation Inductor - Forms an LC type oscillator.
4. Common mode inductors—also known as common mode chokes—are commonly used in EMI filters to suppress common mode interference.
5. Series-mode inductors—also known as series-mode chokes—have a single-winding structure that is typically connected in series with the input circuit of the power adapter.
6. Frequency compensation inductor—constructs LC type and LCR type frequency compensation network.
Fourth, the transformer:
1. Power frequency transformer—The AC power adapter is transformed and isolated, and then rectified and filtered to supply power to the DC/DC converter (ie, the switching regulator).
2. High-frequency transformer—Energy storage, voltage transformation and isolation for high-frequency power adapters, suitable for power adapters without power frequency transformers.
Five, diode:
1. Rectifier diode - low frequency rectification, high frequency rectification.
2. Freewheeling diodes - commonly used in buck DC/DC converters; if a freewheeling diode is connected across the windings of relays, motors, etc., a bleeder circuit can be provided for the back EMF to avoid damage to the drive tube.
3. Clamping diodes—constituting VD, R, and C clamp circuits that absorb the spike voltage and protect the MOSFET power FET.
4. Blocking Diode - A diode in a clamp protection circuit, also known as a damper diode.
5. Protection Diode—Used in a half-wave rectification circuit to provide a loop to the AC during the negative half cycle.
6. Isolation Diode - Signal isolation.
7. Anti-saturation diode—Connecting the diode in series with the base of the power switch tube reduces the saturation depth of the power switch tube and increases the turn-off speed.
6. Rectifier Bridge—Changes the AC voltage to a pulsating DC voltage and sends it to the filter. The rectifier bridge can be composed of four rectifier diodes, and a finished rectifier bridge can also be used.
Seventh, the voltage regulator tube - constitutes a simple voltage regulator circuit; is connected to the output end of the power adapter, used to stabilize the output voltage when no load; the Zener tube, the fast recovery diode and the RC component constitute a primary side clamp protection circuit; Form an overvoltage protection circuit.
VIII. Transistor—a power switch tube used as a PWM modulator; a voltage control and current control loop that constitutes a constant voltage/constant current output type power adapter; a cut-off control loop that constitutes a cut-off output power adapter; constitutes a switching regulator On/off control, under voltage, over voltage protection, over current protection and other circuits.
9. Field Effect Transistor—The MOSFET is used as a power switch for a PWM modulator or a switching regulator controller.
X. Operational Amplifiers - constitute external error amplifiers, voltage control loops, and current control loops.
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