A drive circuit with a zero-crossing detection function, and a zero-crossing detection method. The drive circuit comprises: a power switch transistor, a pull-up drive transistor, a first pull-down drive transistor and a second pull-down drive transistor. When an inductor starts to discharge, the first pull-down current and the second pull-down current jointly pull down a gate terminal of the power switch transistor, such that the power switch transistor is in a cut-off state; after a set time, the first pull-down current is turned off; and when the inductor ends discharging, a parasitic capacitance of the power switch transistor couples with the drop signal, and when the drop signal is detected, the pull-up current pulls up the gate terminal of the power switch transistor, such that the power switch transistor is in a turn-on state.

A drive circuit with a zero-crossing detection function, and a zero-crossing detection method. The drive circuit comprises: a power switch transistor, a pull-up drive transistor, a first pull-down drive transistor and a second pull-down drive transistor. When an inductor starts to discharge, the first pull-down current and the second pull-down current jointly pull down a gate terminal of the power switch transistor, such that the power switch transistor is in a cut-off state; after a set time, the first pull-down current is turned off; and when the inductor ends discharging, a parasitic capacitance of the power switch transistor couples with the drop signal, and when the drop signal is detected, the pull-up current pulls up the gate terminal of the power switch transistor, such that the power switch transistor is in a turn-on state.

Methods, systems, and devices for controlling a variable capacitor. One aspect features a variable capacitance device that includes a capacitor, a first transistor, a second transistor, and control circuitry. The control circuitry is configured to adjust an effective capacitance of the capacitor by performing operations including detecting a zero-crossing of an input current at a first time. Switching off the first transistor. Estimating a first delay period for switching the first transistor on when a voltage across the capacitor is zero. Switching on the first transistor after the first delay period from the first time. Detecting a zero-crossing of the input current at a second time. Switching off the second transistor. Estimating a second delay period for switching the second transistor on when a voltage across the capacitor is zero. Switching on the second transistor after the second delay period from the second time.

Methods, systems, and devices for controlling a variable capacitor. One aspect features a variable capacitance device that includes a capacitor, a first transistor, a second transistor, and control circuitry. The control circuitry is configured to adjust an effective capacitance of the capacitor by performing operations including detecting a zero-crossing of an input current at a first time. Switching off the first transistor. Estimating a first delay period for switching the first transistor on when a voltage across the capacitor is zero. Switching on the first transistor after the first delay period from the first time. Detecting a zero-crossing of the input current at a second time. Switching off the second transistor. Estimating a second delay period for switching the second transistor on when a voltage across the capacitor is zero. Switching on the second transistor after the second delay period from the second time.

Provided are embodiments for a system including a zero-cross circuit. The system includes a first channel and a second channel Each channel includes a generator, a generator relay, and a bus tie relay. In addition, the system includes a zero-cross circuit, wherein the zero-cross circuit synchronizes the operation of the first and second channel, and at least one controller configured to control the operation of the first channel and the second channel based on an input from the zero-cross circuit. Also provided is a method for operating the zero-cross circuit with low phase delay. The method includes receiving an inverting input, receiving a non-inverting input, and comparing the inverting input and the non-inverting input. The method also includes receiving feedback from an output of the comparator; and outputting a waveform based on the comparison of the inverting input and the non-inverting input and the feedback.

Provided are embodiments for a system including a zero-cross circuit. The system includes a first channel and a second channel Each channel includes a generator, a generator relay, and a bus tie relay. In addition, the system includes a zero-cross circuit, wherein the zero-cross circuit synchronizes the operation of the first and second channel, and at least one controller configured to control the operation of the first channel and the second channel based on an input from the zero-cross circuit. Also provided is a method for operating the zero-cross circuit with low phase delay. The method includes receiving an inverting input, receiving a non-inverting input, and comparing the inverting input and the non-inverting input. The method also includes receiving feedback from an output of the comparator; and outputting a waveform based on the comparison of the inverting input and the non-inverting input and the feedback.

Methods, systems, and devices for controlling a variable capacitor. One aspect features a variable capacitance device that includes a capacitor, a first transistor, a second transistor, and control circuitry. The control circuitry is configured to adjust an effective capacitance of the capacitor by performing operations including detecting a zero-crossing of an input current at a first time. Switching off the first transistor. Estimating a first delay period for switching the first transistor on when a voltage across the capacitor is zero. Switching on the first transistor after the first delay period from the first time. Detecting a zero-crossing of the input current at a second time. Switching off the second transistor. Estimating a second delay period for switching the second transistor on when a voltage across the capacitor is zero. Switching on the second transistor after the second delay period from the second time.

Methods, systems, and devices for controlling a variable capacitor. One aspect features a variable capacitance device that includes a capacitor, a first transistor, a second transistor, and control circuitry. The control circuitry is configured to adjust an effective capacitance of the capacitor by performing operations including detecting a zero-crossing of an input current at a first time. Switching off the first transistor. Estimating a first delay period for switching the first transistor on when a voltage across the capacitor is zero. Switching on the first transistor after the first delay period from the first time. Detecting a zero-crossing of the input current at a second time. Switching off the second transistor. Estimating a second delay period for switching the second transistor on when a voltage across the capacitor is zero. Switching on the second transistor after the second delay period from the second time.

Systems and methods are provided for measuring input voltage in an alternating current (AC) system is provided. The method includes measuring a half-cycle time of an AC signal by: detecting, using a zero crossing detector (ZCD), a first edge of the AC signal; in response to detecting the first edge, using a timer to determine a start time; detecting, using the microcontroller, a subsequent edge of the square wave output of ZCD signal; and, in response to detecting the subsequent edge, using the timer to determine a stop time and a length of time that lapsed from the start and stop times. The method further includes determining an overall value that corresponds to at least one length of time, determining, based on the overall value, an input voltage range that corresponds to the overall value, and using the input voltage to cause the AC system to take an action.

Systems and methods are provided for measuring input voltage in an alternating current (AC) system is provided. The method includes measuring a half-cycle time of an AC signal by: detecting, using a zero crossing detector (ZCD), a first edge of the AC signal; in response to detecting the first edge, using a timer to determine a start time; detecting, using the microcontroller, a subsequent edge of the square wave output of ZCD signal; and, in response to detecting the subsequent edge, using the timer to determine a stop time and a length of time that lapsed from the start and stop times. The method further includes determining an overall value that corresponds to at least one length of time, determining, based on the overall value, an input voltage range that corresponds to the overall value, and using the input voltage to cause the AC system to take an action.