SG3525 PWM inverter circuit board is a square wave inverter that oscillates the 12V DC input voltage at a high frequency of 18–24 kHz, using an onboard ATX transformer to generate a 220V AC output. This compact inverter is suitable for use as an emergency power supply for AC LED bulbs and adapters.
Specification
The quick technical specification of the circuit board is given below.
| Module Type | PWM Inverter |
| Chip Used | SG3525 |
| Input Type | DC |
| Input Voltage | 12V |
| Input Current | ≤ 2 Ampere |
| Input Terminal | H1 |
| Operating Frequency | 18kHz to 24kHz |
| Output Type | AC |
| Output Voltage | 220V |
| Output Terminal | H2 |
| Max Load | 5W to 100W |
| PCB Colour | Purple |
Circuit Diagram
Schematic of sg3525 pwm inverter module circuit as shown below.
The components are used in the circuit boards are - U1: SG3525 IC, Q1 Q2: IRF3205 N-Channel MOSFET, TRF1: EE16 High Frequency Transformer, R1: 1K 1/4W Resistor, D1: 3MM Red LED, R2 R3 R6 R7: 2K 1/4W Resistor, R4: 4K7 1/4W Resistor, R5: 200R 1/4W Resistor, R8 R10: 10R 1/4W Resistor, R9 R11: 8K2 1/4W Resistor, C1: 1000uF 16V Electrolytic Capacitor, C2: 1uF Ceramic Capacitor, C3: 1uF 25V Electrolytic Capacitor, and C4: 5nF Ceramic Capacitor.
Circuit Working Explanation
The working principle of the SG3525 inverter circuit is simple. It converts a 12V DC input into a 220V square wave output at a high frequency.
The input DC supply is smoothed and filtered by the parallel-connected capacitors (C1 & C2) and powers the SG3525 IC (U1) through its VC pin (13). A series circuit consisting of a current-limiting resistor (R1) and an LED (D1) emits light to indicate the device is turned on.
The IC is typically a multifunction PWM generator, it is set up in an inverting/non-inverting or push-pull configuration in this module.
Therefore, the inverting input pin (1) receives a low logic signal from the ground through resistor (R1). An internal 5.1V reference is provided through the VREF pin (16), which supplies a high logic signal from the voltage divider formed by resistors (R3 & R6) to the non-inverting input pin (2).
External resistors (R4 & R5) and a capacitor (C4) are used to set the frequency of the IC's internal oscillator circuit. The CT pin (5) is connected to the capacitor (C4), while the RT pin (6) is connected to resistor (R4) to optimize the frequency. The Discharge pin (7) is connected to resistor (R5) to determine the IC's dead time.
The electrolytic capacitor (C5) is connected to the Soft-start pin (9) to initiate the operation of the IC gradually, preventing a sudden or abrupt start.
The two outputs of the IC (pin-11 & in-14) are switched by the supply connected to the VC pin (13). These push-pull switching outputs efficiently control the n-channel MOSFETs (Q1 & Q2) at high frequencies, typically around 18kHz to 24kHz.
Case 1: When pin (11) is high and pin (14) is low, the gate of MOSFET (Q1) is triggered through resistor (R8). The 12V input supply flows through the primary winding (L1) and completes the circuit via the Drain-Source path of MOSFET (Q1) to ground. This induces mutual induction, stepping up the voltage to 220VAC in the secondary winding (L3). Resistor (R9) acts as a pull-down resistor to keep the gate of (Q1) low during the off condition.
Case 2: When pin (11) is low and pin (14) is high, the gate of MOSFET (Q2) is triggered through resistor (R10). The 12V input supply flows through the primary winding (L2) and completes the circuit via the Drain-Source path of MOSFET (Q2) to ground. This induces mutual induction, stepping up the voltage to 220VAC in the secondary winding (L3). Resistor (R12) acts as a pull-down resistor to keep the gate of (Q2) low during the off condition.
Hence, this oscillation creates an square wave 220V AC voltage in the secondary winding of the transformer (TRF1). The transformer winding turns are: L1 and L2 = 7 turns each, L3 = 150 turns. The switching pulse of IC (U1) is continuously monitored at the Drain of the MOSFETs through resistor (R7).
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