Power supply voltage detection circuit
View Patent ↗A power supply voltage detection circuit of the present invention includes a reference signal generation circuit that generates a reference signal according to a power supply voltage, a first transistor having a current flowing between a first terminal and a second terminal, where the current is controlled according to the reference signal, a voltage generation circuit that generates a control voltage according to a potential difference between the power supply voltage and the first terminal of the first transistor, and a second transistor that controls whether or not to output the power supply voltage according to the control voltage. Such circuit configuration enables to accurately detect a low voltage state of the power supply voltage.
1. A power supply voltage detection circuit comprising:
a reference signal generation circuit that generates a reference signal according to a power supply voltage;
a first transistor having a current flowing between a first terminal and a second terminal, the current being controlled according to the reference signal;
a voltage generation circuit that generates a control voltage according to a potential difference between the power supply voltage and the first terminal of the first transistor, the voltage generation circuit being connected in series with the first transistor; and
a second transistor that controls whether or not to output the power supply voltage according to the control voltage,
wherein the reference signal generation circuit comprises:
a reference current generation circuit that generates a reference current according to the power supply voltage and outputs the reference current as the reference signal; and
a current mirror circuit that includes the first transistor and passes a current corresponding to the reference signal, between the first terminal and the second terminal of the first transistor.
2. The power supply voltage detection circuit according to claim 1 , wherein the current mirror circuit comprises:
the first transistor; and
a third transistor that is connected in a current mirror configuration with the first transistor.
3. The power supply voltage detection circuit according to claim 2 , wherein the first transistor and the third transistor are N-channel MOS transistors.
4. The power supply voltage detection circuit according to claim 2 , wherein the first transistor and the third transistor are NPN bipolar transistors.
5. The power supply voltage detection circuit according to claim 1 , wherein the voltage generation circuit comprises:
a first resistor; and
a voltage drop circuit that is connected in series with the first resistor,
wherein a node for connecting the first resistor and the voltage drop circuit generates the control voltage.
6. The power supply voltage detection circuit according to claim 5 , wherein the voltage drop circuit is a diode.
7. The power supply voltage detection circuit according to claim 5 , wherein the voltage drop circuit is a second resistor.
8. The power supply voltage detection circuit according to claim 5 , wherein the voltage drop circuit is a Zener diode.
9. The power supply voltage detection circuit according to claim 1 , wherein the second transistor is a P-channel MOS transistor.