**Simple LED Desk Lamp Dimming Circuit Diagram (1)**
This energy-saving LED desk lamp uses a combination of high-power 1W LEDs and low-power φ5mm LEDs. It features a unique trigger dimming circuit, making the design simple and efficient. The circuit utilizes an operational amplifier and offers illumination comparable to a 25W incandescent bulb, while being energy-efficient, reliable, and long-lasting.
The power supply is derived from a transformer T followed by a bridge rectifier D1-D4, converting 220V AC into 14V DC. The operational amplifier A1 and regulator IC1 create a reference voltage for A2, with resistors R3-R6 forming a non-inverting input for the flip-flop circuit. The inverting input is sampled via resistor R9, and the output pulse width is adjusted using a potentiometer RP. This signal is then amplified by transistors BG1 and BG2, driving the LED array (LED1-LED15). A freewheeling diode D5 and inductor L1 help smooth the current.
Components include a 8W 9V transformer, φ5mm LEDs (LED1-LED6 and LED10-LED15) with natural light color, and two 1W high-power LEDs (LED7-LED8) with heat sinks. The op amps used are LM358 or LM324, and the regulator is TL31, providing a 2.5V reference. The inductor L1 is wound with 40 turns of 0.25mm enameled wire around a φ15mm ferrite ring, and R9 is a 1W resistor with a value between 2.2Ω and 3.0Ω.
After power is applied, the capacitor C1 should show about 14V, dropping to 10.5V under full load. The LED current is controlled by R9, ensuring that the 1W LEDs receive at least 350mA, while the φ5mm LEDs stay below 20mA. Small 20Ω resistors can be added in series with the smaller LEDs for current regulation. A power switch is recommended for the mains input.
**Simple LED Desk Lamp Dimming Circuit Diagram (2)**
This basic dimming circuit allows for adjustable brightness using a potentiometer. By adjusting the resistance, the white LEDs can be made to glow brighter or dimmer. Multiple groups of LEDs can be connected in parallel for different lighting effects.
In Figure 1, one group can function as a night light, while multiple groups can be used for more general lighting. Adjusting R1 or R2 can increase brightness, but the dimming effect may not be very noticeable. The CZ socket can be used to test the temperature of a soldering iron, where the LED brightness indicates the temperature level. Alternatively, it can be connected to an LED lamp in Figure 2, allowing the same circuit to act as a dimmable light.
Figure 2 shows a small LED panel made with high-gloss white LEDs, measuring 146mm x 16mm. Each board has 8 LEDs in 4 strings, powered by a 15V regulator. Using 72 such boards, the user created a large LED array with 18 strings, operating on 12V. This is a cost-effective and energy-efficient solution for lighting, suitable for reading or nighttime use.
**Simple LED Desk Lamp Dimming Circuit Diagram (3)**
12V LED lamp dimming circuit diagram.
**Simple LED Desk Lamp Dimming Circuit Diagram (4)**
Dimming circuit using CD4017.
**Simple LED Desk Lamp Dimming Circuit Diagram (5)**
This design uses a transistor-based driver circuit. Transistors are used to control current flow, with the base controlling the collector current. The amplification factor β determines how much the current is increased. Choosing the right transistor allows for effective LED drive with low cost and ease of implementation.
The LED driver circuit in this design uses 12 LEDs arranged in series and parallel, simulating a desk lamp. The SS8550 PNP transistor is used to drive the LEDs.
**Dimming Implementation**
LED brightness is controlled by current. By adjusting the duty cycle of a PWM signal, the average current through the LED can be varied. This changes the perceived brightness.
In this design, the STC89C51 microcontroller outputs a PWM signal on pin P1.3. When the signal is high, the transistor Q1 conducts a small current; when low, it conducts a larger current. Adjusting the duty ratio changes the average current, thus controlling the brightness of the LED lamp.
**Simple LED Desk Lamp Dimming Circuit Diagram (6)**
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