How to convert energy-saving lamps into efficient LED lamps

LED lamps are also called white light-emitting diodes. Their characteristic is that they have obvious energy-saving effects. Generally speaking, under the premise of the same power consumption, they are at least 5 times brighter than current energy-saving lamps, and they have a long life. They generate less heat, and have many advantages over other types of lighting appliances. However, there are too few similar household lighting products on the market, and even if there are, the prices are too high. For this reason, here is an LED lamp modified from the main component (converter) of waste IEL energy-saving lamps that most households have, for readers with hands-on ability to modify, and can also further use their imagination to make various LED energy-saving lighting appliances.

Recently, I was lucky enough to find the information of medium-power LED on Taobao and remit money to buy dozens of 0.5W white light-emitting diodes. According to the boss who supplies the tube, the ignition voltage of this light-emitting tube is between 3-4V, the working current is 150mA, and the consistency is good. After purchasing it, it was measured that its stable ignition voltage (stable current at 100mA) is 3.56V, and the consistency is really good. Basically, under the working current of 1OOmA, the voltage drop is 3.56 V (measured with a digital multimeter), which brings convenience to parallel use. The maximum working current of this light-emitting tube is 150mA. For safe and stable operation, the working current is selected between 13O~140mA. A fluorescent desk lamp made of 4 such light-emitting tubes can basically meet the requirements of reading and writing. If there are higher requirements, a desk lamp with 6 such white light-emitting tubes can already be comparable to a conventional 40W desk lamp (the brightness is only higher, not lower). And it can be easily changed into a high-end dimming desk lamp. Through structural changes, it can also be made into bathroom or kitchen lighting, living room ceiling lamps, workbench lighting commonly used by electronics enthusiasts, corridor lights... and so on.

The commonly used LED light-emitting tube power supply adopts a DC current-stabilized power supply. Under AC conditions, some adopt a capacitor current-stabilized method, but all light-emitting tubes are often damaged at the moment of power-on. For the sake of safety, the author uses an AC converter made of waste I19 energy-saving lamps. The electrical schematic diagram of its electronic transformer is shown in Figure 1. In the figure, L1, L2, and L3 are wound on a ring-shaped magnetic core, and L4 and L5 play the role of voltage conversion.

The author also disassembled the circuits in the lamp holders of various energy-saving lamps. Two common circuit diagrams are shown in Figures 2 and 3.

Comparing Figure 1 with Figure 2 and Figure 3, we can see that most of the basic circuits are the same or similar. The only difference is in the second half. In Figure 2 and Figure 3, the inductor and the resonant capacitor (2n7) behind it form a starting (ignition) and current stabilization circuit with the filament of the fluorescent tube, while in Figure 1, the high-frequency transformer replaces the starting and current stabilization circuit required for the above-mentioned fluorescent lamp, so it also has the conditions for modification.

The specific modified circuit is shown in Figure 4. It removes the resonant capacitor in the original energy-saving lamp circuit. The simplest method is to only retain the DC blocking capacitor (C7 in the figure). Modify the resonant inductor L1. Just use 0-25~1 mm enameled wire to wind 8-9 turns in the free space of the resonant inductor; a 15Q resistor is used as a current limiting resistor here to control the current at 100~140mA.

Here, the electronic converter circuit in the original energy-saving lamp is modified into an electronic transformer, and the original resonant inductor is converted into a voltage, so that the secondary of the inductor induces a high-frequency voltage of about 7.5V~9V; the light-emitting tube adopts a series-parallel circuit, and only uses a current-limiting resistor to achieve the purpose of reliability and simplicity. It should be noted that it is better to use a larger current-limiting resistor. I use a 1W resistor, and the temperature rise of long-term operation is tolerable.

It is worth pointing out that, from the principle of electronic circuit, the energy-saving lamp circuit is a changed electronic converter circuit. In principle, it is not appropriate to use the original inductor directly. If conditions permit, it is best to rewind the inductor and leave no gap in the middle of the magnetic core. Of course, it is better to use a larger size magnetic core for winding. Generally, the primary is wound with 0.15mm enameled wire for 80~110 turns, and the secondary is wound with 0.25~2mm enameled wire (it is best to use thinner multi-strand enameled wire). If possible, like an electronic transformer, a capacitor of the same capacity is connected in series below the 47n capacitor connected to the upper power tube, and the other end of the capacitor is connected to the emitter of the lower power tube (the same as the electronic transformer circuit) to become a standard half-bridge conversion circuit, which can be safely used for a long time. As for the circuit after the secondary of the converter, various rectification and current stabilization circuits can be used to achieve the purpose of long-term safe use. It will not be described here. Readers can refer to the relevant circuits in this magazine. The
energy-saving LED lamp modified with the waste energy-saving lamp converter is shown in Figure 5 for readers' reference.

Figure 5 Energy-saving LED lamp

In fact, it is also very convenient to use electronic transformers to modify LED lamps. Now many lamps use electronic transformers to convert 220V voltage into 12V high-frequency voltage to power 12V/20~30W small incandescent lamps. It is even simpler to change such lamps into LED lamps. You only need to add current limiting resistors or rectification and current stabilization circuits to power the LEDs. It has become a new generation of energy-saving lamps.