Circuit Diagram Schematic Request

1:13

Below is a two-step plan to replicate the SMPS circuit shown in your image using discrete, readily available components. Step 1 adds all components; Step 2 wires them as per the diagram.

Step 1: Add All Required Components

PWM Controller
- Add UC3842 as U1.
Power MOSFET
- Add IRF840 as Q1 (N-channel MOSFET).
Optocoupler (Feedback Isolation)
- Add PC817 as U2.
Voltage Reference/Regulator
- Add TL431 as U3 for the feedback loop reference.
Diodes
- Add a high-speed diode (e.g., UF4007) as D1 on the secondary output.
- Add a general diode (e.g., 1N4148) as D2 for any small-signal needs in the primary/auxiliary circuits, if visible in the diagram.
Main Transformer
- Add a flyback-type Transformer as T1.
  (Exact specs will depend on output power/voltage you want. Choose one rated appropriately.)
Resistors
- Add the following resistors (adjust values to match the diagram as closely as possible):
  - R1: 10 kΩ
  - R2: 22 Ω
  - R3: 68 Ω
  - R4: 1 kΩ
  - R5: 33 kΩ
  - R6: 4.7 kΩ
  - R7: 10 Ω (gate resistor or sense resistor, depending on diagram details)
  - R8: 10 kΩ (feedback or pull-up)
  - …and any additional resistors you see in the original image.
Capacitors
- Add the following capacitors (adjust values to match the diagram):
  - C1: 0.1 µF bypass
  - C2: 22 µF or 100 µF (input bulk filter or timing cap)
  - C3: e.g., 47 µF for the output filter
  - C4: small RC timing or feedback capacitor (e.g., 1 nF–100 nF)
  - Any additional filtering capacitors visible in the original diagram.
Inductors or Chokes (If Shown)
- If there is a secondary inductor for output filtering, add L1 with a value matching the diagram.
Ground Symbol

Use the standard Ground component for the common reference and any isolated grounds.

Step 2: Wire Them According to the Diagram

U1 (UC3842) Primary Connections:
- VCC pin to the primary supply rail (through any startup resistor if shown).
- GND pin to primary ground.
- Sense pin to the MOSFET source (via a low-value sense resistor, if present) and to R2.
- Feedback pin to PC817 output side and/or TL431 reference path as in the diagram.
- Timing or compensation pins to the appropriate RC network (e.g., [C4], [R4]) as shown.
Q1 (IRF840) as the Main Switch:
- Gate to UC3842 Gate drive pin (through R7 if shown).
- Drain to the primary winding of T1.
- Source to sense resistor and primary ground reference as in the diagram.
Transformer (T1):
- Primary side from drain of Q1 to supply rail.
- Secondary side feeding the diode D1 and filter capacitor C3.
- Auxiliary winding (if present) for powering UC3842 or for feedback referencing.
Feedback (Optocoupler + TL431):
- PC817 LED side connected to the secondary or reference circuit that senses output voltage.
- TL431 reference and cathode connected across output rails with resistor dividers as in the diagram. Its output drives the optocoupler LED.
- The optocoupler transistor side returns a signal to UC3842’s feedback pin.
Output Filtering:
- Secondary of T1 → D1 → C3 → Output.
- If the diagram shows an LC filter, place L1 in series and an additional capacitor if indicated.
Ground Connections:
- Tie all primary grounds to the same reference node.
- Tie all secondary grounds to the isolated reference node as shown.
- Optocoupler provides isolation between the two.

Match all resistor/capacitor values and net names to the hand-drawn schematic as closely as possible. Once these components and connections are in place, you’ll have a practical SMPS schematic equivalent to the provided diagram.

You can use the “Apply changes” button below to add and connect these components in your schematic.

Clarify feedback wiring

Specify transformer requirements

Review MOSFET branch

Startup resistor details

370 days

Reviews

Ground
A common return path for electric current. Commonly known as ground.
jharwinbarrozo
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Net Portal
Wirelessly connects nets on schematic. Used to organize schematics and separate functional blocks. To wirelessly connect net portals, give them same designator. #portal
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Power Net Portal
Wirelessly connects power nets on schematic. Identical to the net portal, but with a power symbol. Used to organize schematics and separate functional blocks. To wirelessly connect power net portals, give them the same designator. #portal #power
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jharwinbarrozo
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Generic Capacitor
A generic fixed capacitor ideal for rapid circuit topology development. You can choose between polarized and non-polarized types, its symbol and the footprint will automatically adapt based on your selection. Supported options include standard SMD sizes for ceramic capacitors (e.g., 0402, 0603, 0805), SMD sizes for aluminum electrolytic capacitors, and through-hole footprints for polarized capacitors. Save precious design time by seamlessly add more information to this part (value, footprint, etc.) as it becomes available. Standard capacitor values: 1.0pF, 10pF, 100pF, 1000pF, 0.01uF, 0.1uF, 1.0uF, 10uF, 100uF, 1000uF, 10000uF 1.1pF, 11pF, 110pF, 1100pF 1.2pF, 12pF, 120pF, 1200pF 1.3pF, 13pF, 130pF, 1300pF 1.5pF, 15pF, 150pF, 1500pF, 0.015uF, 0.15uF, 1.5uF, 15uF, 150uF, 1500uF 1.6pF, 16pF, 160pF, 1600pF 1.8pF, 18pF, 180pF, 1800pF 2.0pF, 20pF, 200pF, 2000pF 2.2pF, 22pF, 220pF, 2200pF, 0.022uF, 0.22uF, 2.2uF, 22uF, 220uF, 2200uF 2.4pF, 24pF, 240pF, 2400pF 2.7pF, 27pF, 270pF, 2700pF 3.0pF, 30pF, 300pF, 3000pF 3.3pF, 33pF, 330pF, 3300pF, 0.033uF, 0.33uF, 3.3uF, 33uF, 330uF, 3300uF 3.6pF, 36pF, 360pF, 3600pF 3.9pF, 39pF, 390pF, 3900pF 4.3pF, 43pF, 430pF, 4300pF 4.7pF, 47pF, 470pF, 4700pF, 0.047uF, 0.47uF, 4.7uF, 47uF, 470uF, 4700uF 5.1pF, 51pF, 510pF, 5100pF 5.6pF, 56pF, 560pF, 5600pF 6.2pF, 62pF, 620pF, 6200pF 6.8pF, 68pF, 680pF, 6800pF, 0.068uF, 0.68uF, 6.8uF, 68uF, 680uF, 6800uF 7.5pF, 75pF, 750pF, 7500pF 8.2pF, 82pF, 820pF, 8200pF 9.1pF, 91pF, 910pF, 9100pF #generics #CommonPartsLibrary
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