# igniter/starter for HID lamps

Discussion in 'Electronic Basics' started by kfel, Sep 15, 2006.

1. ### kfelGuest

Copper ballast

240V tap 220V tap
line _________
+-------------+UUUUUUUUU+---------++
+ + |
| | |
| | |
| + |
--+--- | |
/ --- 0.1uF/ |
SIDAC / --- 275VAC |
220V --/--- | |
/ + |
---+-- | +
| | HID lamp
240Volts AC | | +
50Hz +-----+ |
| |
| |
| |
| |
| |
.-. |
| |22K/2W |
| | |
'-' |
| |
+-------------------++-----------++
neutral

(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

Circuit explanation:
This is a circuit that is generally used for starting a High Pressure
Sodium Vapour Lamp (HPSV) or a Metal Halide Lamp. The component named
as a SIDAC is basically a power diac which has a breakdown voltage of
220V. A copper ballast is used to restrict the flow current once the
HID lamp is switched on. The ballast has three tappings. One called the
240V tapping to which the SIDAC is connected. Second tapping is called
the 220V tapping to which a X2 capacitor is connected and another
tapping which is connected to one end of the HID lamp. This circuit is
called an igniter or an electronic starter for HID lamps.

Principle of operation:
Basically a HID lamp requires pulses of a minimum height of 3000V to
enable it to start. The igniter circuit does just that. It provides the
necessary high voltage pulses superimposed on the AC sine wave. Once
the lamp successfully arcs then the igniter stops giving high voltage
pulses.

Problem and/or clarifications required:
1. Unable to understand how the high voltage pulses cease once the lamp
turns on.
2. Though the igniter circuit does not provide high voltage pulses once
the lamp has turned on, but it still keeps providing pulses of a lesser
pulse height (in the range of 400V). There is a way to stop these
pulses from being supplied to the lamp by shorting the capacitor once
the lamp has turned on. Would like to know if there is any way by which
this can be achieved using passive components only. Also once the lamp
for any reason switches off while power is still present then the
igniter should start pulsing again.

Any ideas on this are welcome. Thanks in advance.

2. ### Homer J SimpsonGuest

Once the lamp fires the voltage is reduced below the firing voltage of the
Sidac.
Replace Sidac.