This is a diagram drawn by my online friend, and he actually got it to work! Does anyone know how it works?

Line AC voltage is connected to series circuit of 12uF capacitor, ballast, lamp

Lets assume that if we succeed to start the lamp, it can then keep going in this circuit with leading power factor

An initial pulse for starting the lamp can be made by short circuiting parallel to the lamp, you can try it with an ordinary on/off switch manually. Switch it on for <1 sec and immediately off

The rest of the circuit is supplying 141V DC to a relay (probably with 110V DC or 220V DC coil), which will switch it on and keep it switched on permanently as long as the circuit is powered

This means that in the beginning the relay contact is closed, and it disconnects when the relay is turned on. The connected relay contacts are C and NC (11 and 12 for typical DIN relay)

The 2nd capacitor is there to try to limit sparking in the relay contacts



The problems with this circuit :

Lamp starting by high voltage pulse can sometimes not work. The starter must check if the lamp works, if no then try again. All starting circuits do it : Fluorescent starter (if the fluorescent lamp is not working, the glow lamp will light again), HPS ignitor (it checks the voltage), and so on

This circuit does not. If the lamp did not start in the 1st time, or if it was interrupted by a power blink, it will remain off, and you will have to switch it off and on again

There is no delay in the operation of the relay. If your switch has bad connection or contact jitter, the voltage at turn on will rise slowly. At some moment the voltage may be sufficient to switch the relay, but not sufficient to keep the arc in the lamp, the lamp won't start

The voltage supplied to the relay in this circuit (with 100V AC in) is 141V DC. The closest relay coil ratings i know are 110V DC and 220V DC. For 110V DC, this may be a little high (the relay may overheat over extended use). For 220V DC, 141V may or may not suffice to switch the relay at all

The moment the power is connected, the 250-volt 10-microfarad capacitor connected to that bridge rectifier will charge through the relay coil. Current flows through the relay coil, which then triggers the contacts, ensuring that it can only be triggered once during a single power-up process. In contrast, traditional 110-volt starters may accidentally trigger and cause the light to go out when the voltage rises to 95 volts or above

You are right, it is in series and not parallel with the relay coil. In this case there is some starting delay and a 110V DC relay would be ok

However this circuit still does not try again if the lamp did not start or if it goes out