Image display apparatus and high voltage driver circuit
View Patent ↗A driver circuit of an image display apparatus comprises driver circuit with a class A/B push-pull stage (T 3 , T 5 ). The driver circuit contains an n-type pull transistor (T 3 ), an n-type control transistor (T 2 ) with a main current channel terminal coupled to a control electrode of the pull transistor (T 2 ) and a voltage source (V) applying a predetermined voltage over a series connection of the control electrode-main current channel terminals of the control transistor (T 2 ) and the pull transistor (T 3 ). The current from the control transistor (T 2 ) flows to a p-type push transistor (T 5 ) via a current mirror (T 4 , T 5 ). An input transistor (T 1 ) draws all of the current from the control transistor (T 2 ) via a node ( 142 ) between the control transistor (T 2 ) and the pull transistor (T 3 ) to control the ratio between the currents through these transistors (T 2 , T 3 ). The input of the driver circuit has a direct control over the current through the input transistor (T 1 ) that does not include a feedback through the control transistor (T 2 ).
1. An image display apparatus, comprising:
a display screen device with a drive input; and
a driver circuit comprising a push-pull stage with an output coupled to the drive input, the driver circuit comprising:
an n-type pull transistor with a main current channel coupled to the drive input;
an n-type control transistor with a main current channel terminal coupled to a control electrode of the pull transistor via a node;
a voltage source for applying a predetermined voltage over a series connection of the control electrode-main current channel terminals of the control transistor and the pull transistor;
a p-type current mirror with an output transistor that serves as push transistor for the push-pull stage and an input fed by the main current channel of the control transistor; and
an input transistor with a main current channel coupled to said node, the input transistor having a control electrode coupled to an input of the driver circuit, the input transistor being arranged to draw substantially all of a variable part of the current from the control transistor, an external input of the apparatus having a coupling to the control electrode of the input transistor that does not include the main current channel through the control transistor.
2. An image display apparatus according to claim 1 , the driver circuit comprising a first and a second branch, the first branch comprising the pull transistor, the control transistor and the input transistor, the second branch comprising a further pull transistor, a further control transistor and a further input transistor, interconnected as the pull transistor, the control transistor and the input transistor in the first branch, the driver circuit comprising a current source that connects the main current channels of the input transistor and the further input transistor in common to a supply voltage.
3. An image display apparatus according to claim 2 , wherein the main current channel of the further pull transistor of the second branch is coupled to the input of the current mirror in parallel with the main current channel of the control transistor of the first branch.
4. An image display apparatus according to claim 2 , wherein the main current channel of the further control transistor of the second branch is coupled to the drive input in parallel with the main current channel of the pull transistor of the first branch.
5. An integrated circuit with an output contact and a push-pull stage with an output coupled to the output contact, the integrated circuit comprising:
an n-type pull transistor with a main current channel coupled to the output;
an n-type control transistor with a main current channel terminal coupled to a control electrode of the pull transistor via a node;
a voltage source for applying a predetermined voltage over a series connection of the control electrode-main current channel terminals of the control transistor and the pull transistor;
a p-type current mirror with an input fed by the main current channel of the control transistor and an output transistor that serves as push transistor for the push-pull stage; and
an input transistor with a main current output coupled to said node, the input transistor having a control electrode coupled to an input of the driver circuit, arranged to control substantially all of a variable part of the current through the control transistor, an external input of the apparatus having a coupling to the control electrode of the input transistor that does not include the main current channel through the control transistor.
6. An integrated circuit according to claim 5 , comprising a first and a second branch, the first branch comprising the pull transistor, the control transistor and the input transistor, the second branch comprising a further pull transistor, a further control transistor and a further input transistor, interconnected as the pull transistor, the control transistor and the input transistor in the first branch, the driver circuit comprising a current source that connects the main current channels of the input transistor and the further input transistor in common to a supply voltage.
7. An integrated circuit according to claim 6 , wherein the main current channel of the further pull transistor of the second branch is coupled to the input of the current mirror in parallel with the main current channel of the control transistor of the first branch.
8. A driver circuit comprising a push-pull stage comprising:
an output;
a pull transistor of a first conductivity type with a main current channel coupled to the output;
a control transistor of the first conductivity type with a main current channel terminal coupled to a control electrode of the pull transistor via a node;
a voltage source for applying a voltage across a series connection of the control electrode-main current channel terminals of the control transistor and the pull transistor;
a current mirror of a second conductivity type opposite to the first conductivity type, with an input fed by the main current channel of the control transistor and an output transistor that serves as push transistor for the push-pull stage; and
an input transistor with a main current output coupled to said node, the input transistor having a control electrode coupled to an input of the driver circuit, arranged to control substantially all of a variable part of the current through the control transistor, an external input of the driver circuit having a coupling to the control electrode of the input transistor that does not include the main current channel through the control transistor.
9. A driver circuit according to claim 8 , comprising a first and a second branch, the first branch comprising the pull transistor, the control transistor and the input transistor, the second branch comprising a further pull transistor, a further control transistor and a further input transistor, interconnected as the pull transistor, the control transistor and the input transistor in the first branch, the driver circuit comprising a current source that connects the main current channels of the input transistor and the further input transistor in common to a supply voltage.