m 1 2 wattcapacitor 4 0 1 u03bcf 50 vzener 5 1 n 968resistor 6 10 m 1 2 wattfet 7 mtm 1 n 100resistor 8 1k 1 wattdiode 9 1 n 3647resistor 10 100 1 4 watt______________________________________ when the flashlamp is pulsed the pfn power supply is generally inhibited for a period of time to allow turn off of the lamp switching device generally an scr it then takes some time for the pfn to be recharged to the level that will forward bias diode 2 thus allowing capacitor 1 to recharge during the time that diode 2 is reverse biased the constant simmer current is being supplied by discharging capacitor 1 through the fet into the lamp at a constant current capacitor 1 is chosen to have sufficient electrical capacitance to supply the desired simmer current for the maximum recharge time typically less than 30 ms with a starting voltage at the minimum design pfn voltage and ending at approximately 30 volts above the maximum simmer voltage capacitor 1 is thus typically 1 microfarad giving a large margin of safety for temperature effects and aging since capacitor 1 is initially charged to the pfn voltage in most applications and since the maximum voltage across the flashlamp is less than the initial pfn voltage in all cases diode 2 can be eliminated in many applications the resistor 6 is also not needed in applications in which lamp voltage is sensed by a resistor from the anode of diode 9 for the purpose of providing trigger pulses to the flashlamp to initiate simmer a function generally provided in simmer applications the resistor 10 is a parasitic oscillation suppression resistor generally used.