TWO STAGE INDICATOR DIMMING CIRCUIT CONTROLLED BY PWM BACKLIGHTING BACK FEED AND BACKLIGHT CONTROL

摘要

A dimming circuit for an indicator switch has a control input, a dimming state and a non-dimming state. The dimming circuit is responsive to the presence of a backlight PWM signal at the control input of the dimming circuit to switch to the dimming state and responsive to the absence of the backlight PWM signal at the control input of the dimming circuit to switch to the non-dimming state. In the dimming state a high resistance of the dimming circuit is coupled in series with the indicator LED and a LED drive output of the function control module and in the non-dimming state a low resistance of the dimming circuit is coupled in series with the indicator LED and the LED drive output of the function control module. The high resistance has a resistance higher than the low resistance.

主权项

1. An dimming circuit for an indicator switch, the indicator switch including a manually actuated switch, an indicator LED that is turned on and off by a function control module to which the indicator switch is coupled wherein the indicator LED is on when a function actuated by the manually actuated switch of the indicator switch is active and off when the function actuated by the manually actuated switch of the indicator switch is off, the dimming circuit comprising:
a control input, a dimming state and a non-dimming state; and the dimming circuit responsive to the presence of a backlight PWM signal at the control input of the dimming circuit to switch to the dimming state and responsive to the absence of the backlight PWM signal at the control input of the dimming circuit to switch to the non-dimming state, when the dimming circuit is in the dimming state a high resistance of the dimming circuit is coupled in series with the indicator LED and a LED drive output of the function control module and when the dimming circuit is in the non-dimming state a low resistance of the dimming circuit is coupled in series with the indicator LED and the LED drive output of the function control module, the high resistance having a resistance higher than the low resistance.