Name and function of the components of the switching power supply
T1, T2, R11, R12, D6, C2, Q1, D5, U1, U6,
This is a single-ended flyback switching power supply circuit, in this switching power supply,
T2 is a high-frequency transformer, the role of voltage conversion,
R11 is the starting resistance of U1, the input voltage of 85 - 2-265 AC, the choice should be in the 1--2W, 150 - 330K resistance between, usually need to use multiple resistors in series, otherwise it is easy to damage.
R12 is the current limiting resistor of the switch, but also U1 overcurrent current detection resistor, the output short circuit when the voltage drop on the resistor will become high, U1 protection to stop the output drive signal.
D6 is the transformer provided to the U1 supply voltage rectifier.
C2 is the main filter capacitor, usually with electrolytic capacitors, voltage is greater than the maximum voltage input of 1/3, the capacity of about 1W / micro-law output.
Q1 is the FET, is the switch tube. Generally also mos.
D5 and R7, C5 are connected to the transformer primary to form the transformer spike voltage absorption circuit. When the switch is turned off, the moment the transformer will have a very high induced voltage generated, this circuit can be absorbed by this spike voltage (or is limited to a safe Of the range). Also called DRC or RCD spike voltage absorption circuit.
U1 is the switch tube drive circuit, here should be a PWM integrated circuit, also known as pulse width modulation, is the English "Pulse Width Modulation" abbreviation, referred to as pulse width modulation.
U6 is a photocoupler,
T2: high frequency transformer
R11: constitute the RC filter circuit R12: current limiting effect
D6: auxiliary power supply rectifier
C2: filter capacitor
D5: and R7 and C5 constitute the absorption circuit, which absorbs the instantaneous spikes of the switch
U1: drive the chip
U6: optical coupling circuit, the main feedback loop.
The main principle of this circuit diagram: AC input, through the EMC filter bridge rectifier filter, and then through the drive chip control switch and then drive the high-frequency transformer, secondary AC and then re-rectifier filter output.
Output after the stage through the comparison, optical feedback, adjust the PWM duty cycle, control output stability.
commonly used as PC817. Since the switching power supply between the primary and secondary need to be isolated, there is no circuit between them can be directly connected, so the secondary voltage signal with it into an optical signal, and then in its internal and then become an electrical signal to complete the feedback Regulator process, while achieving isolation.
