Current detection circuit, integrated circuit, and power supply circuit
A current detection circuit for a power supply circuit configured to generate an output voltage from an input voltage thereof, the power supply circuit including an inductor configured to receive the input voltage, a transistor configured to control an inductor current flowing through the inductor, and a diode coupled to a first node that is a node at which the inductor and the transistor are coupled. The current detection circuit is configured to detect the inductor current, and includes: a first capacitor coupled to the first node; and a second capacitor provided between the first capacitor and a ground, the second capacitor being coupled in series with the first capacitor.
1 . A current detection circuit for a power supply circuit configured to generate an output voltage from an input voltage thereof, the power supply circuit including
an inductor configured to receive the input voltage,
a transistor configured to control an inductor current flowing through the inductor, and
a diode coupled to a first node, which is a node at which the inductor and the transistor are coupled,
the current detection circuit being configured to detect the inductor current, the current detection circuit comprising:
a first capacitor coupled to the first node;
a second capacitor provided between the first capacitor and a ground, the second capacitor being coupled in series with the first capacitor at a second node; and
a setting circuit, including a resistor, configured to set a direct-current (DC) level of a voltage at the second node, wherein
the second capacitor and the resistor form a RC parallel circuit, which has a time constant longer than a switching period of the transistor.
2 . A current detection circuit for a power supply circuit configured to generate an output voltage from an input voltage thereof, the power supply circuit including
an inductor configured to receive the input voltage,
a transistor configured to control an inductor current flowing through the inductor, and
a diode coupled to a first node, which is a node at which the inductor and the transistor are coupled,
the current detection circuit being configured to detect the inductor current, the current detection circuit comprising:
a first capacitor coupled to the first node;
a second capacitor provided between the first capacitor and a ground, the second capacitor being coupled in series with the first capacitor; and
a setting circuit configured to set a direct-current (DC) level of a voltage at a second node, which is a node at which the first capacitor and the second capacitor are coupled, wherein
the setting circuit is a clamp circuit configured to clamp the voltage at the second node to a first level, when the transistor is off.
3 . The current detection circuit according to claim 2 , wherein the clamp circuit includes a first diode having a cathode that is grounded and an anode coupled to the second node.
4 . The current detection circuit according to claim 2 , wherein the clamp circuit clamps the voltage at the second node to a second level, when the transistor is on.
5 . The current detection circuit according to claim 4 , wherein the clamp circuit includes
a second diode having a cathode that is grounded and an anode coupled to the second node, and
a third diode having a cathode coupled to the second node and an anode that is grounded.
6 . The current detection circuit according to claim 4 , wherein the clamp circuit is a Zener diode.
7 . The current detection circuit according to claim 6 , wherein
the Zener diode has a cathode coupled to the second node and an anode that is grounded,
the first level is a level of a Zener voltage of the Zener diode, and
the second level is a level of a forward voltage of the Zener diode.
8 . The current detection circuit according to claim 1 , wherein a first capacitance value of the first capacitor is smaller than a second capacitance value of the second capacitor.
9 . The current detection circuit according to claim 8 , wherein a first rated voltage of the first capacitor is higher than a second rated voltage of the second capacitor.
10 . A power supply circuit configured to generate an output voltage from an input voltage thereof, the power supply circuit comprising:
an inductor configured to receive the input voltage;
a transistor configured to control an inductor current flowing through the inductor;
a diode coupled to a first node, which is a node at which the inductor and the transistor are coupled;
a current detection circuit configured to detect the inductor current; and
an integrated circuit configured to switch the transistor, based on a detection voltage outputted from the current detection circuit, wherein
the current detection circuit includes
a first capacitor coupled to the first node, and
a second capacitor provided between the first capacitor and a ground, the second capacitor being coupled in series with the first capacitor at a second node,
a setting circuit, including a resistor, configured to set a direct-current (DC) level of a voltage at the second node, the second capacitor and the resistor forming a RC parallel circuit, which has a time constant longer than a switching period of the transistor, the current detection circuit being configured to output, as the detection voltage, the voltage at the second node; and
the integrated circuit includes
a terminal configured to receive the voltage at the second node,
a comparator circuit configured to compare the received voltage at the terminal with a reference voltage, and
a driver circuit configured to
turn on the transistor, based on a result of comparison of the comparator circuit, and
turn off the transistor, based on another voltage corresponding to the output voltage.
11 . A power supply circuit configured to generate an output voltage from an input voltage thereof, the power supply circuit comprising:
an inductor configured to receive the input voltage;
a transistor configured to control an inductor current flowing through the inductor;
a diode coupled to a first node, which is a node at which the inductor and the transistor are coupled;
a current detection circuit configured to detect the inductor current; and
an integrated circuit configured to switch the transistor, based on a detection voltage outputted from the current detection circuit, wherein
the current detection circuit includes
a first capacitor coupled to the first node, and
a second capacitor provided between the first capacitor and a ground, the second capacitor being coupled in series with the first capacitor,
a setting circuit configured to set a direct-current (DC) level of a voltage at a second node, which is a node at which the first capacitor and the second capacitor are coupled, the setting circuit being a clamp circuit configured to clamp the voltage at the second node to a first level, when the transistor is off,
the current detection circuit being configured to output, as the detection voltage, the voltage at the second node; and
the integrated circuit includes
a terminal configured to receive the voltage at the second node,
a comparator circuit configured to compare the received voltage at the terminal with a reference voltage, and
a driver circuit configured to
turn on the transistor, based on a result of comparison of the comparator circuit, and
turn off the transistor, based on another voltage corresponding to the output voltage.