Transmitting type electronic pen and signal transmitting circuit thereof
Abstract:
A signal transmitting circuit prevents oscillation efficiency from dropping regardless of changes in transmission signal frequency. The signal transmitting circuit includes a switch circuit that enables a current to flow to a resonance circuit including a capacitor and a coil to provide energy that sustains resonance of the resonance circuit, and a control signal generating circuit that generates a control signal to control changeover of the switch circuit, thereby outputting a transmission signal having a resonance frequency of the resonance circuit. The control signal generating circuit includes a detection circuit that detects a cycle of the transmission signal, a timing generating circuit that generates a timing point at which the changeover control signal is generated based on a detection result of the detection circuit, and a drive circuit that generates the control signal at the timing point generated by the timing generating circuit to control changeover of the switch circuit.
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