Detailed explanation of the main component types and functions of switching power supply

The switch power supply circuit generally consists of fuses, thermistors, mutual inductance filters, bridge rectifier circuits, filter capacitors, switch impulse integrated circuits, switch transformers, optocouplers, three end regulators, etc. If you want to produce switching power supplies with powerful characteristics, you must understand the types and basic functions of each component in the switching power supply. The types and basic functions of common components in switching power supplies are as follows:

1、 Resistance 1, Sampling Resistance - The sampling circuit that forms the voltage and sends the sampling voltage to the feedback circuit.

2. Equalizing resistor - plays a voltage balancing role in the symmetrical DC input circuit of a switching power supply, also known as balancing resistor.

3. Divider resistor - forms a resistive voltage divider.

4. Release resistor - EMI during power outage releases the charges stored in the capacitor in the filter.

5. Current limiting resistor - Starting current limiting buffer, such as current limiting resistors for voltage regulators, optocouplers, and input filter capacitors.

6. Current detection resistor - combined with overcurrent protection circuit to limit the output current limit of the switching power supply.

7. Shunt resistor - provides a bypass for current.

8. Load resistance - Switching power supply load resistance (including equivalent load resistance).

9. Minimum load resistance - The minimum load resistance required to maintain the normal operation of a switching power supply, which can avoid excessive output voltage caused by load routing.

10. False load - a load that is temporarily connected during testing the performance parameters of a switching power supply (such as a heating wire or cement resistor).

11. Filter resistance - used as a filter resistance in LC filters, RC filters, and π type filters.

12. Bias resistor - provides bias voltage to the control terminal of a switching power supply or to the operating point used to stabilize transistors.

13. RC type absorption circuits or VD types are commonly used for maintaining resistors, R, and in C-type clamp protection circuits.

14. Frequency compensation resistor - for example, RC type Frequency compensation network, which constitutes an error amplifier.

15. Damping resistor - avoids resonance in the circuit.

2、 Capacitor 1, filter capacitor - composed of input filter, output filter, etc.

2. Coupling capacitors, also known as direct isolation capacitors, are used to isolate DC signals and only allow AC signals to be relied on.

3. Decoupling capacitance - For example, power decoupling capacitance can prevent Self-oscillation.

4. Soft start capacitor - forms a soft start circuit, allowing voltage and output current to slowly establish during the soft start process.

5. Compensation capacitance - forms an RC Frequency compensation network.

6. Accelerated capacitance - increases the switching rate of transistors.

7. Impulse capacitors can be composed of RC and LC types.

8. Differential capacitance - forms a differential circuit to obtain sharp pulses.

9. Boosting capacitance - used to increase the input stage power supply current and can also form a voltage feedforward circuit.

10. The RC type delay circuit consists of a delay capacitor resistor.

11. Energy storage capacitors - such as pump capacitors in polarity reversal DC/DC converters.

12. Phase shifting capacitor - forms a phase shifting circuit.

13. Voltage doubling capacitor - forms a voltage doubling rectifier circuit with a diode.

14. Noise cancelling capacitor - used to filter out noise interference in circuits.

15. Neutralize capacitance - clear the Self-oscillation of the amplifier.

16. Capacitor series mode and Common-mode interference that can suppress the influence can be filtered out in EMI filter respectively.

17. Safety capacitors - X capacitors and Y capacitors.

X capacitance - it can filter out the Common-mode interference generated by the coupling capacitor of the primary and secondary windings, provide a return path for the influence current of coupling from the primary side to the secondary side, and prevent the current from coupling to the ground through the secondary side.

Y capacitor - can filter out the series mode effects between power grids, commonly used in EMI filters.

3、 Inductance 1, Filter Inductance - Constitutes an LC filter.

2. Energy storage inductor - commonly used in buck or variable voltage DC/DC converter circuits.

3. The composition of an oscillating inductor LC oscillator.

4. Common mode inductance, also called common mode choke, is commonly used in EMI filters to suppress Common-mode interference.

5. Series mode inductance, also known as series mode choke, adopts a single winding structure and is generally connected in series in the input circuit of a switching power supply.

6. Frequency compensation inductance - forms LC and LCR Frequency compensation networks.

4、 Transformer 1, Power Frequency Transformer - Transforms and protects AC power, and then supplies power to DC/DC transformers (i.e. switching regulators) through rectifier filters.

2. High frequency transformer - Energy storage, voltage transformation, and isolation high-frequency power supply, suitable for switching power supplies without power frequency transformers.

5、 Diode 1, diode rectification - low-frequency rectification, high-frequency rectification.

2. Flyback diode - commonly used in buck DC/DC converters; If flow diodes are connected on both sides of the windings of the solenoid valve and the motor, a release circuit can be provided for the Counter-electromotive force to prevent damage to the drive tube.

3. Clamping diode - constituting VDD, R, C clamping circuit, absorbing peak voltage, and buffering MOSFET power Field-effect transistor.

4. Blocking diode - A diode in a clamping protection circuit, also known as a damping diode.

5. Maintenance diode - used in half wave rectifier circuits to provide circuit for AC power during negative half cycle.

6. Protective diode - can achieve signal isolation.

7. Anti saturation diode - Connecting a diode to the base of a power switch can reduce the saturation depth of the power switch and increase the shutdown rate.

6、 The rectifier bridge converts AC current into pulsating DC voltage and sends it to the filter. The rectifier bridge can be composed of four rectifier diodes or finished rectifier bridges.

7、 The regulator tube forms a simple regulator circuit; Connect to the output terminal of the switching power supply to stabilize the voltage at full load; The primary side clamp protection circuit consists of a voltage regulator, a fast recovery diode, and a resistor element; Form an overvoltage protection circuit.

8、 The Field Effect of Transistors

MOSFETs are used as power switches for PWM modulators or switching regulators.

9、 Operating amplifier

Form an external error amplifier, voltage control loop, and current control loop.

10、 Crystal tubes are used as power switching tubes for PWM modulators; Forming a voltage control and current control loop for constant voltage/constant current output switching power supply; Forming a interception control loop for intercepting the output switching power supply; Forming circuits for on-off operation, undervoltage, overvoltage protection, overcurrent protection, etc. of switch voltage regulators.

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