Load driving circuit, display driver, display apparatus and semiconductor device

Abstract

Provided is an output amplifier having: a push-pull output-stage formed by first and second output-stage transistors; and a detection circuit detecting an abnormal output current output by the output amplifier and including: a coupling circuit, generating first and second currents mirroring current flowing in the first output-stage transistor and third and fourth currents mirroring current flowing in the second output-stage transistor, coupling the first and third currents at a first output node, outputting a first voltage at the first output node, coupling the second and fourth currents at a second output node, and outputting a second voltage at the second output node; and a determination circuit, outputting a determination signal indicating normality of an output current based on the first and second voltages. The coupling circuit generates the first to fourth currents. In the reference state, the third current>the first current, the second current>the fourth current.

What is claimed is: 
     
         1 . A display driver, comprising a load driving circuit, the load driving circuit comprising:
 an output amplifier, having a push-pull output-stage formed by a first output-stage transistor and a second output-stage transistor having different conductivity types, and outputting an output current output from the push-pull output-stage 5 to a load; and   
       a detection circuit, detecting a change of the output current, 
       wherein the detection circuit comprises: 
       a coupling circuit, respectively generating a first current and a second current that are mirror currents with respect to a current flowing in one of the first output-stage transistor and the second output-stage transistor, respectively generating a third current and a fourth current that are mirror currents with respect to a current flowing in an other of the first output-stage transistor and the second output-stage transistor, coupling the first current and the third current at a first output node to output a voltage generated at the first output node as a first voltage, and coupling the second current and the fourth current at a second output node to output a voltage generated at the second output node as a second voltage; 
       wherein the coupling circuit respectively generates the first to fourth currents, so that, in a reference state in which the output current is stable within a predetermined range, the third current is greater than the first current and the second current is greater than the fourth current, 
       wherein the detection circuit detects, based on the first voltage and the second voltage output from the coupling circuit, whether the output current is changed from the reference state or not, 
       wherein the load driving circuit includes k output amplifiers, k being an integer of 2 or more, 
       wherein the detection circuit: 
       comprises a selection switch selecting, in order, each of k mirror current pairs respectively generated by the k output amplifiers and respectively formed by a first mirror current with respect to the current flowing in the one of the first output-stage transistor and the second output-stage transistor and a second mirror current with respect to the current flowing in the other of the first output-stage transistor and the second output-stage transistor, 
       respectively generates the first current and the second current as mirror currents with respect to the first mirror current in the mirror current pair selected by the selection switch, and respectively generates the third current and the fourth current as minor currents with respect to the second mirror current in the minor current pair selected by the selection switch, and 
       wherein the display driver outputs the a determination signal, which indicates whether the output current is changed from the reference state or not, to outside while respectively outputting k output currents output from the respective k output amplifiers of the load driving circuit to k data lines of a display panel. 
     
     
         2 . A display apparatus, comprising the display driver as claimed in  claim 1 . 
     
     
         3 . A semiconductor device, comprising:
 an output amplifier, having a push-pull output-stage formed by a first output-stage transistor and a second output-stage transistor having different conductivity types, and outputting an output current output from the push-pull output-stage to a load; and   a detection circuit, detecting a change of the output current,   wherein the detection circuit comprises:   a coupling circuit, respectively generating a first current and a second current that are mirror currents with respect to a current flowing in one of the first output-stage transistor and the second output-stage transistor, respectively generating a third current and a fourth current that are mirror currents with respect to a current flowing in an other of the first output-stage transistor and the second output-stage transistor, coupling the first current and the third current at a first output node to output a voltage generated at the first output node as a first voltage, and coupling the second current and the fourth current at a second output node to output a voltage generated at the second output node as a second voltage;   wherein the coupling circuit respectively generates the first to fourth currents, so that, in the reference state, the third current is greater than the first current and the second current is greater than the fourth current, and   wherein the detection circuit detects, based on the first voltage and the second voltage output from the coupling circuit, whether the output current is changed from the reference state or not.   
     
     
         4 . The semiconductor device as claimed in  claim 3 , wherein the detection circuit further comprises a determination circuit, outputting, based on the first voltage and the second voltage, a determination signal indicating that the output current is abnormal when the output current is changed from the reference state and a determination signal indicating that the output current is normal when the output current is not changed.