Circuit arrangement for producing a control signal for the purpose of dimming at least one lamp
View Patent ↗A circuit arrangement for producing a control signal (U s ) for the purpose of dimming at least one lamp, including a device ( 10 ) for modifying the phase gating angle corresponding to a dimming input value ( 8 ), it being possible for the device ( 10 ) for modifying the phase gating angle to be fed, at its input, an input signal (U e ), whose phase gating angle is to be modified, and for an output signal (U 1 ) having a modified phase gating angle to be provided at its output; and an output at which the control signal (U s ) can be provided; it also includes a device ( 14 ) for comparing the output signal (U 1 ) with a predeterminable signal (U c ) for the purpose of producing the control signal (U s ), the amplitude of the predeterminable signal (U c ) depending on the amplitude of the input signal (U e ).
1. A circuit for producing a control signal for the purpose of dimming at least one lamp, the circuit comprising:
a device for receiving an input voltage and a dimming input value, and for providing an output voltage having a modified phase gating angle, wherein the device is operable to modify the phase gating angle in dependence upon the dimming input value;
a rectifier circuit for receiving the output voltage from the device and for providing a rectified version of the output voltage;
a control output at which a control signal is provided;
an amplitude detection device coupled to the rectifier circuit, wherein the amplitude detection device is operable to detect the amplitude of the input voltage and to provide a predeterminable voltage in dependence upon the amplitude of the input voltage; and
a comparison device coupled to the rectifier circuit, the amplitude detection device, and the control output, wherein the comparison device is operable to:
(i) compare the rectified output voltage with the predeterminable voltage; and
(ii) provide the control signal in dependence upon the phase gating angle of the output voltage, wherein the control signal has an amplitude that is substantially independent of the magnitude of the input voltage.
2. The circuit of claim 1 , wherein the comparison device comprises a subtraction circuit for receiving the rectified output voltage and the predeterminable voltage, wherein the substraction circuit is operable to provide a subtraction voltage that is representative of a difference between the rectified output voltage and the predeterminable voltage.
3. The circuit of claim 2 , wherein the comparison device further comprises a toggle circuit coupled between the subtraction circuit and the control output, wherein the toggle circuit is operable to receive the subtraction voltage and to provide the control signal such that:
(i) if the difference between the rectified output voltage and the predeterminable voltage is positive, the control signal is a nonzero positive voltage; and
(ii) if the difference between the rectified output voltage and the predeterminable voltage is negative, the control signal has a magnitude that is approximately zero.
4. The circuit of claim 1 , wherein the amplitude detection device comprises:
a resistive voltage divider comprising at least a first resistor and a second resistor;
a diode coupled to a junction between the first resistor and the second resistor; and
a holding element coupled to the diode.
5. The circuit of claim 4 , wherein the holding element comprises a parallel combination of a capacitor and a third resistor.
6. A method for producing a control signal for the purpose of dimming at least one lamp, the method comprising the steps of:
receiving an input voltage and a dimming input value;
providing an output voltage having a modified phase gating angle, the modified phase gating angle being set in dependence upon the dimming input value;
rectifying the output voltage;
detecting the amplitude of the input voltage;
providing a predeterminable voltage in dependence upon the detected amplitude of the input voltage;
comparing the rectified output voltage with the predeterminable voltage; and
setting the control signal in dependence upon the phase gating angle of the output voltage, wherein the control signal has an amplitude that is substantially independent of the magnitude of the output voltage.
7. The method of claim 6 , wherein the step of comparing the rectified output voltage with the predeterminable voltage includes subtracting the predeterminable voltage from the rectified output voltage.
8. The method of claim 7 , wherein the step of providing the control signal includes setting the control signal such that:
(i) if the difference between the rectified output voltage and the predeterminable voltage is positive, the control signal is a nonzero positive voltage; and
(ii) if the difference between the rectified output voltage and the predeterminable voltage is negative, the control signal has a magnitude that is approximately zero.