Nowadays, from all aspects of life, to all walks of life, the use of switching power adapters is inseparable. While switching power supplies develop rapidly, switching power supplies are popular in human applications with the characteristics of high efficiency, small size, convenience, etc., but now The structure of switching power supply is not so simple. Due to the requirements of wide frequency band and diversified application scenarios, the power supply mechanism is not so simple. It is still difficult for beginners to develop switching power supplies. The types of components used in switching power supplies are very different. More, then I will introduce the function of multiple components of the switching power supply.
Switching power supply components are divided into two categories, one is general components and the other is special components
1. Sampling resistor—composes the sampling circuit of the output voltage, and sends the sampling voltage to the feedback circuit.
2. Equalizing resistor—plays a voltage equalizing role in the symmetrical DC input circuit of the switching power supply, also known as a balancing resistor.
3. Voltage divider resistors - form a resistor divider.
4. Bleeding Resistor—The charge stored in the capacitor in the electromagnetic interference (EMI) filter can be drained when the power is turned off.
5. Current-limiting resistor—plays the role of current-limiting protection, such as current-limiting resistors used as voltage regulators, optocouplers and input filter capacitors.
6. Current detection resistor—used with overcurrent protection circuit to limit the output current limit of switching power supply.
7. Shunt Resistor—Bypassing the current.
8. Load resistance—the load resistance of the switching power supply (including the equivalent load resistance).
9. Minimum load resistance - the minimum load resistance required to maintain the normal operation of the switching power supply, to avoid excessive output voltage due to open load.
10. Dummy load - temporarily connected load (such as resistance wire, cement resistance) when testing the performance indicators of switching power supply.
11. Filter resistor—used as filter resistor in LC-type filter, RC-type filter and π-type filter.
12. Bias resistor—provides a bias voltage to the control terminal of the switching power supply, or is used to stabilize the operating point of the transistor.
13. Protection resistor - commonly used in RC-type absorption circuit or VD, R, C-type clamp protection circuit.
14. Frequency Compensation Resistors—for example, an RC-type frequency compensation network that forms an error amplifier.
15. Damping Resistor—Prevents resonance in the circuit.
1. Filter capacitors—constitute input filters, output filters, etc.
2. Coupling capacitor - also known as DC blocking capacitor, when it acts, it blocks the DC signal and only allows the AC signal to pass.
3. Decoupling capacitors—such as power supply decoupling capacitors, can prevent self-oscillation.
4. Soft-start capacitor—composes a soft-start circuit, which makes the output voltage and output current slowly build up during the soft-start process.
5. Compensation capacitor - constitutes an RC type frequency compensation network.
6. Speed-up capacitors - used to increase the switching speed of transistors.
7. Oscillation capacitor - can form RC type, LC type oscillator.
8. Differential capacitance - form a differential circuit to obtain sharp pulses.
9. Bootstrap capacitor - used to increase the power supply voltage of the input stage, and can also form a voltage feedforward circuit.
10. Delay capacitor - and resistor form an RC-type delay circuit.
11. Storage capacitors—such as pump capacitors in polarity-reversing DC/DC converters.
12. Phase-shifting capacitors - form a phase-shifting circuit.
13. Voltage-doubling capacitors—and diodes form a voltage-doubling rectifier circuit.
14. Noise-cancelling capacitors—used to filter out noise interference in circuits.
15. Neutralizing Capacitor - Eliminates self-oscillation of the amplifier.
16. Capacitors to suppress interference—In EMI filters, series mode and common mode interference can be filtered out respectively.
17. Safety capacitors - including X capacitors and Y capacitors.
18. X capacitor—can filter out the common mode interference generated by the primary winding and the secondary winding coupling capacitor, provide a return path for the interference current coupled from the primary side to the secondary side, and prevent the current from being coupled to the ground through the secondary side .
19. Y capacitor—can filter out series-mode interference between power grids, and is often used in EMI filters.
1. Filter inductance—constitute an LC filter.
2. Energy storage inductors - commonly used in buck or boost DC/DC converter circuits.
3. Oscillating inductance - constitutes an LC oscillator.
4. Common mode inductance—also known as common mode choke coil, is often used in EMI filters to suppress common mode interference.
5. Series mode inductance - also known as series mode choke coil, it adopts a single winding structure and is generally connected in series in the input circuit of the switching power supply.
6. Frequency Compensation Inductor—Constitute LC type, LCR type frequency compensation network.
1. Power frequency transformer—transforms and isolates the AC power supply, and then supplies power to the DC/DC converter (ie, switching regulator) after being rectified and filtered.
2. High frequency transformer—energy storage, transformation and isolation of high frequency power supply, suitable for switching power supply without power frequency transformer.
1. Rectifier diodes - low frequency rectification, high frequency rectification.
2. Freewheeling diode - commonly used in step-down DC/DC converters; if a freewheeling diode is connected in parallel at both ends of the windings of relays, motors, etc., it can provide a discharge circuit for the back electromotive force to avoid damage to the drive tube.
3. Clamping diodes - form VD, R, C clamp circuits, absorb peak voltages, and protect MOSFET power field effect transistors.
4. Blocking diodes - diodes in clamping protection circuits, also known as damping diodes.
5. Protection diodes—used in half-wave rectifier circuits to provide a loop for alternating current during the negative half cycle.
6. Isolation diodes—can achieve signal isolation.
7. Anti-saturation diode - connecting a diode in series with the base of the power switch tube can reduce the saturation depth of the power switch tube and improve the turn-off speed.
6. Rectifier bridge:
Convert the AC voltage into a pulsating DC voltage and send it to the filter. The rectifier bridge can be composed of four rectifier diodes, and a finished rectifier bridge can also be used.