Receiving circuit and signal receiving method

A receiving circuit that operates in a power supply system different from a transmitting circuit outputting a transmission signal and receives the transmission signal through an AC coupling device where a primary coil through which the transmission signal flows and a secondary coil having first and second ends and a center tap to which a specified voltage is supplied from an external terminal are magnetically coupled, comprising:

• a pulse width amplifier circuit including a first bottom hold circuit that holds a first pulse signal with a negative amplitude appearing at a first end of the secondary coil for a first specified period of time and outputs the signal as a first hold signal, and a second bottom hold circuit that holds a pulse signal with a negative amplitude appearing at the second end of the secondary coil for a second specified period of time and outputs the signal as a second hold signal;
• and
• a comparator circuit having a first anode and a second anode that compares a voltage of the first hold signal and a voltage of the second hold signal and outputs a comparison result,
• wherein the first bottom hold circuit includes:
• a first diode element having a cathode connected to a first end of the secondary coil and an anode connected to the first anode of the comparator circuit;
• and
• a first resistor element having one end connected to the anode of the first diode element and another end to which a reference voltage is supplied, and
• the second bottom hold circuit includes:
• a second diode element having a cathode connected to the second end of the secondary coil and an anode connected to the second anode of the comparator circuit;
• and
• a second resistor element having one end connected to the anode of the second diode element and another end to which the reference voltage is supplied, and
• wherein the pulse width amplifier circuit includes either a third capacitor element having one end connected to the anode of the first diode element and another end connected to the anode of the second diode element, or a first capacitor element that releases accumulated charges toward the first end of the secondary coil through the first diode element and a second capacitor element that releases accumulated charges toward the second end of the secondary coil through the first diode element.

A receiving circuit that operates in a power supply system different from a transmitting circuit outputting a transmission signal and receives the transmission signal through an AC coupling device where a primary coil through which the transmission signal flows and a secondary coil having first and second ends and a center tap to which a specified voltage is supplied from an external terminal are magnetically coupled, comprising:

• a pulse width amplifier circuit that holds a first pulse signal appearing at a first end of the secondary coil for a first specified period of time and outputs the signal as a first hold signal and holds a second pulse signal appearing at the second end of the secondary coil for a second specified period of time and outputs the signal as a second hold signal;
• and
• a comparator circuit having a first anode and a second anode that compares a voltage of the first hold signal and a voltage of the second hold signal and outputs a comparison result,
• wherein the pulse width amplifier circuit includes:
• a first threshold circuit including first and third diode elements through which current flows when a voltage difference between an anode and a cathode of the first and third diode elements becomes a specified value or larger, the first diode having an anode connected to the first end of the secondary coil and a cathode connected to the first anode of the comparator circuit, the third diode having a cathode connected to the first end of the secondary coil and an anode connected to the first anode of the comparator circuit;
• a first resistor element having one end connected to the cathode of the first diode and another end to which a reference voltage is supplied;
• a second threshold circuit including second and fourth diode elements through current flows when a voltage difference between an anode and a cathode of the second and fourth diode elements becomes a specified value or larger, the second diode having an anode connected to the second end of the secondary coil and a cathode connected to the second anode of the comparator circuit, and the fourth diode having a cathode connected to the second end of the secondary coil and an anode connected to the second anode of the comparator circuit;
• and
• a second resistor element having one end connected to the cathode of the second diode element and another end to which the reference voltage is supplied,
• wherein the pulse width amplifier circuit further includes either a third capacitor element having one end connected to the cathode of the first diode element and another end connected to the cathode of the second diode or a first capacitor element having one end connected to the cathode of the first diode element and another end to which the reference voltage is supplied and a second capacitor element having one end connected to the cathode of the second diode element and another end to which the reference voltage is supplied.