Circuit arrangement for accurately adjusting each color channel of a picture signal generator using digital control signals

A circuit arrangement for adaptive white-compression of video signals of a color picture signal generator, having a color signal channel for processing each of three color signals (R, G, B), each of said color channels including a signal minimum detector circuit having a first input for receiving a respective one of said color signals (R, G, B), and a second input for receiving respective compressed color signals, and an output for furnishing a respective color output signal (R', G', B') which is the smaller of the signals applied to the first and second inputs, each of said color channels further comprising a multiplier circuit having a signal input for receiving a respective one of the color signals (R, G, B), a control input for receiving a digital control signal derived from the color output signals (R', G', B') of the minimum detector circuits, and an output for supplying a respective one of said compressed color signals coupled to the second input of the respective minimum detector circuit, characterized in that said circuit arrangement further comprises means for generating a digitized steering signal from the color output signals (R', G', B') by line-sequential measurement of the energy contents of the largest of said color output signals over a period of one line, and comparison of said energy contents with a threshold value reference signal;

• and an up/down counter for furnishing said digital control signal, said up/down counter having a control input for receiving said digitized steering signal, and an output coupled to the control inputs of the multiplier circuits, whereby the color signals (R, G, B) respectively applied to the multiplier circuits are multiplied by a factor between 0 and 1 in response to the digital control signal thereby forming the compressed color signals.