Homemade 24V energy-saving lamp

The general energy-saving lamp can only work under the voltage of 220V, and cannot be used in the occasions of vehicles and ships powered by batteries. The energy-saving lamp introduced in this article can use the 24V DC low voltage to make the energy-saving lamp light normally.

The working principle
is shown in Figure 1. When the power is turned on, the current passes through the resistor R1 and the coil n2 to the base of the transistor V, making the transistor V conductive. At this time, there is current passing through the coil n1, causing the pulse transformer T to generate magnetic flux. The change in magnetic flux causes the coil n2 to generate an induced electromotive force. This electromotive force is added to the base and emitter of the transistor V through R2, generating base current to form self-excitation, so that the transistor is quickly saturated. Since the collector current of the transistor continues to increase at this time, the magnetic flux also continues to increase. When the magnetic flux is saturated, the induced electromotive force in n2 drops to zero, and the magnetic flux decreases accordingly. The transformer coils n1 and n2 induce electromotive forces of opposite polarity, causing the transistor to be quickly cut off. Then the transistor starts from cutoff to saturation under the action of the power supply voltage, and this cycle produces oscillation. At this time, a pulse high voltage is induced on the coil n3 to ignite the lamp.
In the figure, R1 is a starting resistor to enable the circuit to work normally at the beginning. Resistor R2 is a bias resistor, which provides a suitable base current to the transistor V. Capacitor C1 is an accelerating capacitor, which is used to improve the waveform of the pulse voltage applied to the transistor V. The function of C2 is to reduce the peak voltage applied to the collector-emitter of the transistor to prevent the transistor from being broken down.

Component selection:
The transistor V uses MJE13005 plastic tube. The transformer T uses EE25 ferrite core. The coils n1 and n2 are both wound with 0.35mm enameled wire, of which n1 is wound 60 times, n2 is wound 7 times, and n3 is wound with 0.28mm enameled wire 100 times. The resistors R1 and R2 use 1/8W carbon film resistors, C1 uses 15n polyester capacitor with a withstand voltage of 63V, and C2 uses 100p ceramic capacitor with a withstand voltage of 400V. The lamp uses a 9W energy-saving lamp.

Production and debugging
First, wind the transformer T according to the requirements. Wind the coil n1 on the plastic frame first, then the coil n2, and finally the coil n3, and pay attention to the same-name ends of each coil. After winding, install the magnetic core and seal it with adhesive tape to prevent loosening. Then make the circuit board according to Figure 2. First install the transformer and weld it, install the 18mm*25mm U-shaped heat sink on the transistor and weld it to the circuit board, and then weld other components. Find a 9W/220V energy-saving lamp, weld the original circuit board, install the prepared 24V circuit board and fix it. In order to allow the heat of the transistor in the energy-saving lamp to dissipate when it is working, it is necessary to open some small holes on the shell. The energy-saving lamp can work at a voltage of 20-26V and a working current of about 300mA, but be careful not to reverse the polarity of the power supply.