Differential circuit, capacitance detection circuit, touch detection device and terminal device

A capacitance detection circuit for detecting capacitance of N to-be-detected capacitors, wherein N is greater than or equal to 2, and the capacitance detection circuit comprises at least N−1 first front-end circuits configured to convert capacitance signals of to-be-detected capacitors into first voltage signals and perform a difference operation on the first voltage signals, at least one second front-end circuit configured to convert the capacitance signals of the to-be-detected capacitors into second voltage signals and perform a difference operation on the second voltage signals, and a processing circuit, wherein:

• each of the at least N−1 first front-end circuits comprises a first input end and a second input end, and each of the at least one second front-end circuit comprises a third input end and a fourth input end,
• a first input end and a second input end of each of at least N−2 first front-end circuits are connected to two different to-be-detected capacitors respectively,
• a first input end of a first front-end circuit other than the at least N−2 first front-end circuits is connected to both a third input end of a second front-end circuit and a to-be-detected capacitor, a second input end of the first front-end circuit other than the at least N−2 first front-end circuits is connected to both a first input end of a first front-end circuit of the at least N−2 first front-end circuits and a to-be-detected capacitor, and the to-be-detected capacitors connected to the two input ends of the first front-end circuit other than the at least N−2 first front-end circuits are different to-be-detected capacitors, wherein:
• each of the first front-end circuits comprises a first control circuit and a first programmable gain amplification (PGA) circuit, and the first control circuit is connected to a power supply, two to-be-detected capacitors connected to the first front-end circuit and the first PGA circuit,
• the first control circuit is configured to:
• control, at a first stage of a detection period, the power supply to charge the two to-be-detected capacitors connected to the first front-end circuit and control the two to-be-detected capacitors connected to the first front-end circuit to discharge to the first PGA circuit;
• and control, at a second stage of the detection period, the first PGA circuit to charge the two to-be-detected capacitors connected to the first front-end circuit,
• the first PGA circuit is configured to convert the capacitance signals of the two to-be-detected capacitors connected to the first front-end circuit into the first voltage signals at the first stage and the second stage respectively, and perform a difference operation on the first voltage signals of the two to-be-detected capacitors connected to the first front-end circuit, to obtain a first differential signal of voltages corresponding to the two to-be-detected capacitors connected to the first front-end circuit at the first stage and a first differential signal of voltages corresponding to the two to-be-detected capacitors connected to the first front-end circuit at the second stage;
• a third input end of each of the at least one second front-end circuit is connected to a to-be-detected capacitor, and a fourth input end is connected to a reference capacitor, wherein:
• each second front-end circuit comprises a second control circuit and a second PGA circuit, and the second control circuit is connected to a power supply, the second PGA circuit, the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit,
• the second control circuit is configured to:
• control, at the first stage, the power supply to charge the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit and control the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit to discharge to the second PGA circuit;
• and control, at the second stage, the second PGA circuit to charge the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit,
• the second PGA circuit is configured to convert capacitance signals of the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit into the second voltage signals at the first stage and the second stage respectively, and perform a difference operation on the second voltage signals of the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit, to obtain a second differential signal of voltages corresponding to the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit at the first stage and a second differential signal of voltages corresponding to the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit at the second stage;
• each of the at least N−1 first front-end circuits outputs the first differential signal of the two to-be-detected capacitors connected to the front-end circuit at the first stage and outputs the first differential signal of the two to-be-detected capacitors connected to the front-end circuit at the second stage,
• each of the at least one second front-end circuit outputs the second differential signal of the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit at the first stage and outputs the second differential signal of the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit at the second stage;
• and
• the processing circuit is connected to an output end of each first front-end circuit and an output end of each second front-end circuit and is configured to:
• determine, according to the first differential signal output by the first front-end circuit at the first stage and the first differential signal output by the first front-end circuit at the second stage, a target differential signal of voltages corresponding to the two to-be-detected capacitors connected to the first front-end circuit;
• determine, according to the second differential signal output by the second front-end circuit at the first stage and the second differential signal output by the second front-end circuit at the second stage, a target differential signal of voltages corresponding to the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit;
• and determine, according to the target differential signal of the two to-be-detected capacitors connected to the first front-end circuit and the target differential signal of the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit, a capacitance value of each of the N to-be-detected capacitors.

A touch detection apparatus, comprising a capacitance detection circuit for detecting capacitance of N to-be-detected capacitors, wherein N is greater than or equal to 2, and the capacitance detection circuit comprises at least N−1 first front-end circuits configured to convert capacitance signals of to-be-detected capacitors into first voltage signals and perform a difference operation on the first voltage signals, at least one second front-end circuit configured to convert the capacitance signals of the to-be-detected capacitors into second voltage signals and perform a difference operation on the second voltage signals, and a processing circuit, wherein:

• each of the at least N−1 first front-end circuits comprises a first input end and a second input end, and each of the at least one second front-end circuit comprises a third input end and a fourth input end,
• a first input end and a second input end of each of at least N−2 first front-end circuits are connected to two different to-be-detected capacitors respectively,
• a first input end of a first front-end circuit other than the at least N−2 first front-end circuits is connected to both a third input end of a second front-end circuit and a to-be-detected capacitor, a second input end of the first front-end circuit other than the at least N−2 first front-end circuits is connected to both a first input end of a first front-end circuit of the at least N−2 first front-end circuits and a to-be-detected capacitor, and the to-be-detected capacitors connected to the two input ends of the first front-end circuit other than the at least N−2 first front-end circuits are different to-be-detected capacitors, wherein:
• each of the first front-end circuits comprises a first control circuit and a first programmable gain amplification (PGA) circuit, and the first control circuit is connected to a power supply, two to-be-detected capacitors connected to the first front-end circuit and the first PGA circuit,
• the first control circuit is configured to:
• control, at a first stage of a detection period, the power supply to charge the two to-be-detected capacitors connected to the first front-end circuit and control the two to-be-detected capacitors connected to the first front-end circuit to discharge to the first PGA circuit;
• and control, at a second stage of the detection period, the first PGA circuit to charge the two to-be-detected capacitors connected to the first front-end circuit,
• the first PGA circuit is configured to convert the capacitance signals of the two to-be-detected capacitors connected to the first front-end circuit into the first voltage signals at the first stage and the second stage respectively, and perform a difference operation on the first voltage signals of the two to-be-detected capacitors connected to the first front-end circuit, to obtain a first differential signal of voltages corresponding to the two to-be-detected capacitors connected to the first front-end circuit at the first stage and a first differential signal of voltages corresponding to the two to-be-detected capacitors connected to the first front-end circuit at the second stage;
• a third input end of each of the at least one second front-end circuit is connected to a to-be-detected capacitor, and a fourth input end is connected to a reference capacitor, wherein:
• each second front-end circuit comprises a second control circuit and a second PGA circuit, and the second control circuit is connected to a power supply, the second PGA circuit, the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit,
• the second control circuit is configured to:
• control, at the first stage, the power supply to charge the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit and control the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit to discharge to the second PGA circuit;
• and control, at the second stage, the second PGA circuit to charge the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit,
• the second PGA circuit is configured to convert capacitance signals of the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit into the second voltage signals at the first stage and the second stage respectively, and perform a difference operation on the second voltage signals of the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit, to obtain a second differential signal of voltages corresponding to the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit at the first stage and a second differential signal of voltages corresponding to the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit at the second stage;
• each of the at least N−1 first front-end circuits outputs the first differential signal of the two to-be-detected capacitors connected to the front-end circuit at the first stage and outputs the first differential signal of the two to-be-detected capacitors connected to the front-end circuit at the second stage,
• each of the at least one second front-end circuit outputs the second differential signal of the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit at the first stage and outputs the second differential signal of the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit at the second stage;
• and
• the processing circuit is connected to an output end of each first front-end circuit and an output end of each second front-end circuit and is configured to:
• determine, according to the first differential signal output by the first front-end circuit at the first stage and the first differential signal output by the first front-end circuit at the second stage, a target differential signal of voltages corresponding to the two to-be-detected capacitors connected to the first front-end circuit;
• determine, according to the second differential signal output by the second front-end circuit at the first stage and the second differential signal output by the second front-end circuit at the second stage, a target differential signal of voltages corresponding to the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit;
• and determine, according to the target differential signal of the two to-be-detected capacitors connected to the first front-end circuit and the target differential signal of the to-be-detected capacitor and the reference capacitor that are connected to the second front-end circuit, a capacitance value of each of the N to-be-detected capacitors,
• wherein the touch detection apparatus determines a touch position of a user according to a capacitance value of each of the N to-be-detected capacitors determined by the capacitance detection circuit.