Currently USB chargers , PD chargers , and PD power adapters are developing in a small, efficient, energy-saving, and environmentally friendly direction. Understanding and selecting various components correctly is the foundation for developing, designing, producing and manufacturing chargers and power adapters. There are dozens to hundreds of components assembled on the charging circuit board, each with a different function, which can be divided into two categories: special components and general components. The types and main uses of general components in the charging circuit are as follows:
Capacitors:
Noise suppression capacitor: used to filter out noise interference in the circuit, mostly ceramic capacitors.
Decoupling capacitor: for example, the power supply decoupling capacitor can prevent self-excited oscillation. Most of these capacitors are ceramic capacitors.
Acceleration capacitor: used to improve the switching speed of transistors.
Safety capacitor: contains X capacitors and Y capacitors.
X capacitor: can filter out common mode interference generated by the coupling capacitors between the primary and secondary windings, and provide a return path for the interference current from the primary side to the secondary side to prevent the current from being coupled to ground through the secondary side.
Differential capacitor: used in differential circuits to obtain sharp pulses.
Energy storage capacitor: for example, the pump capacitor in a polarity reversing DC/DC converter.
Oscillation capacitor: can form RC-type and LC-type oscillators.
Phase-shifting capacitor: forms a phase-shifting circuit.
Soft start capacitor: forms a soft start circuit, which slowly establishes the output voltage and current during the soft start process.
Compensation capacitor: forms an RC-type frequency compensation network.
Voltage multiplier capacitor: forms a voltage multiplier rectification circuit with a diode.
Neutralizing capacitor: eliminates amplifier self-excited oscillation.
Bootstrap capacitor: used to increase the input stage voltage of the PD charger , and can also form a voltage feedback circuit.
Delay capacitor: forms an RC-type delay circuit with a resistor.
Filter capacitor: used as a capacitor for input circuit filter, output circuit filter or auxiliary circuit filter, mostly electrolytic capacitors.
Coupling capacitor: also called DC-blocking capacitor, its function is to block DC signals and only let AC signals pass.
Interference suppression capacitor: in EMI filters, can respectively filter out differential mode and common mode interference.
Y capacitor: can filter out common mode interference between the power grid, commonly used in EMI filters, mostly high-voltage ceramic capacitors.
Resistors:
Load resistor: the load resistor at the output end of the fast charger, also called a dummy load resistor, is used to make the charger circuit work normally when there is no load device attached to it (load open).
Minimum load resistor: the minimum dummy load resistor required to maintain the normal operation of the charger circuit, which can prevent the output voltage of the charger from being too high due to load open.
Frequency compensation resistor: such as the resistor in an RC-type frequency compensation network that forms an error amplifier.
Damping resistor: used to prevent circuit resonance.
Current limiting resistor: serves as a current limiting protection, such as the current limiting resistor used in a voltage regulator tube, optocoupler, and input filter capacitor to prevent damage to the device due to excessive operating current.
Bias resistor: provides a working voltage to the PWM control terminal of the charger or stabilizes the working point of the transistor.
Current sensing resistor: paired with the overcurrent or short circuit protection circuit to provide feedback signal to the PWC circuit, limiting the output current limit of the charger.
Voltage divider resistor: forms a voltage dividing circuit to divide the total voltage into different voltages.
Discharge resistor: can discharge the charge on the energy storage capacitor or energy storage inductor when the circuit is powered off.
Shunt resistor: provides an alternative current path and distributes different currents.
Electronic load: a temporary electronic load connected during the testing of the charger’s performance indicators, and the size of the load is adjusted according to the rated output of the charger (or a resistor wire or cement resistor can be used).
Filter resistor: used as a resistor in π-type filters, LC-type filters, and RC-type filters.
Protection resistor: used to absorb the resistance of the circuit loop, such as in RC-type, VD, R, and C-type clamp protection circuits.
Sampling resistor: forms an output voltage or current sampling loop to collect sampled current or voltage feedback to the PWC circuit.
Balancing resistor: plays a balancing role in the symmetric DC input circuit of the charger, also known as a balancing resistor.
Transformers:
Power frequency transformer: also known as a low-frequency transformer, which transforms and isolates AC mains, and then supplies power to the circuit after rectification and filtering. The input usually works with a single voltage segment.
High-frequency transformer: stores energy, transforms, and isolates high-frequency voltage, and is suitable for chargers without power frequency transformers. This type of circuit usually has a wide voltage working range.
Inductors:
Oscillation inductor: forms an LC-type oscillator.
Series-mode choke: also called a series-mode inductor, it uses a single-winding structure and is generally connected in series in the input circuit of the charger.
Filter inductor: forms an LC-type filter.
Frequency compensation inductor: forms an LC-type or LCR-type frequency compensation network.
Common-mode choke: also known as a common
Energy storage inductor – commonly used in step-down or step-up DC/DC converter circuits.
5. Diodes:
Clamp diode – forms a VD, R, C type clamp circuit, absorbs spike voltage, and provides protection for MOSFET power field-effect transistors.
Anti-saturation diode – connected in series with the base of a power switch transistor, can reduce the saturation depth of the power switch transistor and improve its turn-off speed.
Protection diode – used in half-wave rectification circuits, provides a path for AC signal during the negative half-cycle.
Freewheeling diode – commonly used in step-down DC/DC converters. By connecting a freewheeling diode in parallel with the winding ends of a relay, motor, etc., a discharge path can be provided for the reverse electromotive force to avoid damaging the drive transistor.
Isolation diode – can achieve signal isolation.
Damper diode – a diode in the clamp protection circuit, also called a blocking diode.
Rectifier diode – low-frequency rectification, high-frequency rectification, converting AC voltage to pulsating DC voltage.
6. Bridge rectifier – converts AC voltage to pulsating DC voltage and sends it to the filter. The bridge rectifier can be composed of four rectifier diodes or an integrated rectifier bridge.
7.Voltage regulator – forms a simple voltage stabilizing circuit, connected to the output of the charger to stabilize the output voltage under no-load conditions. It is composed of a voltage regulator, a fast recovery diode, and a resistance-capacitance element, forming a primary side clamp protection circuit and an overvoltage protection circuit.
8.Operational amplifier – forms an external error amplifier, voltage control loop, current control loop, etc.
9.MOS field-effect transistor – used as a power switch transistor for PWM modulator, forms voltage control and current control loops for constant voltage/constant current output power chargers, forms a cutoff control loop for cutoff output power chargers, and forms switch control, undervoltage protection, overvoltage protection, overcurrent protection and other circuits for switch stabilizers.
Post time: May-29-2023