Membrane keyboard scan circuit, scan method and keyboard having the same

摘要

A membrane keyboard scan circuit, a scan method and a keyboard having the same are provided. A row scan-port circuit of the scan circuit comprises a first and a second select branches corresponding to a first type of the membrane keyboard and a second type of the membrane keyboard respectively. A column scan-port circuit of the scan circuit comprises a fifth switch connected between a power supply voltage and an output port of the row scan-port circuit and a sixth switch connected between a ground line and the output port. The column scan-port circuit performs a scan output process to provide a row-scan timing signal to a key circuit of the membrane keyboard such that one of the first and the second select branches generates a sensing signal when the key circuit is triggered.

主权项

1. A membrane keyboard scan circuit used in a membrane keyboard having a key circuit, wherein the membrane keyboard scan circuit comprises:
a row scan-port circuit comprising:
a first select branch configured to be close when the membrane keyboard is a first type of the membrane keyboard, wherein the first select branch comprises:
a first branch comprising a first switch and a first pull-up resistor connected to each other in series; anda third branch comprising a first input voltage control circuit and a third switch connected to each other in series; anda second select branch configured to be close when the membrane keyboard is a second type of the membrane keyboard, wherein the second select branch comprises:
a second branch connected in parallel with the first branch between a first node and a second node, wherein the second branch comprises a second pull-up resistor having a different resistive value from that of the first pull-up resistor and a second switch connected to each other in series, and wherein the first node is connected to a power supply voltage;a fourth branch connected in parallel with the third branch between a third node and a fourth node, wherein the fourth branch comprises a second input voltage control circuit and a fourth switch connected to each other in series, the third node is a row output port of the row scan-port circuit, the second node and the fourth node are connected to a signal input port that is further connected to the key circuit, and the second input voltage control circuit has a different effective low threshold voltage level from that of the first input voltage control circuit; and a column scan-port circuit comprising:
a fifth switch connected between the power supply voltage and a column output port of the column scan-port circuit; anda sixth switch having a first end connected to ground and a second end connected to the column output port of the column scan-port circuit; wherein the column scan-port circuit performs a scan output process repetitively to output a low voltage level in a first specific time period through the use of the fifth switch and the sixth switch and to output and maintain a high voltage level after the first specific time period to provide a row-scan timing signal to the key circuit of the membrane keyboard such that one of the first select branch and the second select branch generates a sensing signal when the key circuit is triggered.