Pulse width modulated dimming arrangement for fluorescent lamps

Claim 2

A relatively high efficiency, adjustable pulse width modulator energizing circuit for a fluorescent lamp for illuminating a surface which is also illuminated by ambient light, comprising: a transformer having a primary winding, and a secondary winding for connection to said fluorescent lamp; transistorized push-pull inverter means connected to said primary winding of said transformer for providing pulses of alternating polarity thereto when driven, pulse width modulator drive means for driving said inverter means with drive pulses at a relatively high frequency; means for adjusting the width of said drive pulses to control the power which is applied to said fluorescent lamp; said means for adjusting the width of said drive pulses including photo-responsive control means directed at said surface for sensing ambient light and florescent lamp light reflected from said surface.

Claim 3

The circuit of claim 1, wherein the transistors of said inverter are mounted in heat sinks, and wherein thermostat means are mounted on one or more of said heat sinks, said thermostat means being connected in parallel with an on-off switch for shutting the circuit off when the transistors overheat.

Claim 4

The circuit of claim 2, wherein said circuit is comprised of a high voltage portion including said inverter, said transformer and said lamp and a low voltage portion including said pulse width modulator drive means, and said on-off switch is connected in said low voltage portion of said circuit for controlling said lamp.

Claim 5

A relatively high efficiency, adjustable pulse width modulator energizing circuit for a fluorescent lamp for providing variable power at a high frequency to said lamp, comprising: an on-off switch; a transformer having a primary winding, and a secondary winding for connection to said fluorescent lamp; transistorized push-pull inverter means connected to said primary winding of said transformer for providing pulses of alternating polarity thereto when driven; pulse width modulated drive means for driving said inverter means with drive pulses at a relatively high frequency; means for adjusting the width of said drive pulses to control the power which is applied to said fluorescent lamp; and the transistors of said inverter being mounted in heat sinks, and thermostat means being mounted on one or more of said heat sinks, said thermostat means being connected in parallel with said on-off switch for controlling said pulse width modulated drive means for shutting the circuit off when transistors overheat.

Claim 6

A relatively high efficiency, adjustable pulse width modulator energizing circuit for a fluorescent lamp for providing variable power at a high frequency to said lamp, comprising: an on-off switch; a transformer having a primary winding, and a secondary winding for connection to said fluorescent lamp; transistorized push-pull inverter means connected to said primary winding of said transformer for providing pulses of alternating polarity thereto when driven; pulse width modulated drive means for driving said inverter means with drive pulses at a relatively high frequency; means for adjusting the width of said drive pulses to control the power which is applied to said fluorescent lamp; and the transistors of said inverter being mounted in heat sinks, and thermostat means being mounted on one or more of said heat sinks, said thermostat means being connected in parallel with said on-off switch for controlling said pulse width modulated drive means for shutting the circuit off when transistors overheat.

Claim 7

A relatively high efficiency, adjustable pulse width modulator energizing circuit for a fluorescent lamp for illuminating a surface which is also illuminated by ambient light, comprising: an on-off switch; a transformer having a primary winding, and a secondary winding for connection to said fluorescent lamp; transistorized push-pull inverter means connected to said primary winding of said transformer for providing pulses of alternating polarity thereto when driven; pulse width modulated drive means for driving said inverter means with drive pulses at a relatively high frequency; means for ajusting the width of said drive pulses to control the power which is applied to said fluorescent lamp; and said means for adjusting the width of said drive pulses including photo-responsive control means for sensing ambient light and fluorescent lamp light at said surface; the transistors of said inverter being mounted in heat sinks, and thermostat means being mounted on one or more of said heat sinks, said thermostat means being connected in parallel with said on-off switch for controlling said pulse width modulator drive means for shutting the circuit off when the transistors overheat.

Claim 8

A relatively high efficiency, adjustable pulse width modulator energizing circuit for a fluorescent lamp for illuminating a surface which is also illuminated by ambient light, comprising: an on-off switch; a transformer having a primary winding, and a secondary winding for connection to said fluorescent lamp; transistorized push-pull inverter means connected to said primary winding of said transformer for providing pulses of alternating polarity thereto when driven; pulse width modulated drive means for driving said inverter means with drive pulses at a relatively high frequency; means for ajusting the width of said drive pulses to control the power which is applied to said fluorescent lamp; and said means for adjusting the width of said drive pulses including photo-responsive control means for sensing ambient light and fluorescent lamp light at said surface; the transistors of said inverter being mounted in heat sinks, and thermostat means being mounted on one or more of said heat sinks, said thermostat means being connected in parallel with said on-off switch for controlling said pulse width modulator drive means for shutting the circuit off when the transistors overheat.