Power supply circuit capable of reducing the number of external components
View Patent ↗An inverting negative voltage DC-DC power supply circuit comprises a first resistor having one end connected to an output terminal for converting a change in output voltage into a current. A zero-volt clamp circuit is connected to the other end of the first resistor and comprises a first and second transistor. A current mirror circuit comprises a third and fourth transistor and is connected to the zero-volt clamp circuit for causing a current of the same value as that of a current flowing in the zero-volt clamp circuit to flow. A second resistor is connected to the current mirror circuit for converting a change in current flowing from the zero-volt clamp circuit into a voltage.
1. A negative voltage power supply circuit comprising:
a first voltage setting resistor having one end connected to an output terminal;
a second voltage setting resistor;
a clamp circuit connected to the other end of said first voltage setting resistor; and
a current mirror circuit adapted to cause a current flowing through said first voltage setting resistor to flow into said second voltage setting resistor through said clamp circuit.
2. An inverting negative voltage DC-DC power supply circuit comprising:
a first resistor having one end connected to an output terminal for converting a change in output voltage into a current;
a zero-volt clamp circuit comprising a first transistor and a second transistor and connected to the other end of said first resistor;
a current mirror circuit comprising a third transistor and a fourth transistor and connected to said zero-volt clamp circuit for causing a current of the same value as that of a current flowing in said zero-volt clamp circuit to flow; and
a second resistor connected to said current mirror circuit for converting a change in current flowing from said zero-volt clamp circuit into a voltage.
3. An inverting negative voltage DC-DC power supply circuit according to claim 2 , further comprising:
an error amplifier having an inverting input terminal input with the voltage across said second resistor and a non-inverting input terminal connected to a reference voltage source; and
a DC-DC control circuit input with an output of said error amplifier.
4. An inverting negative voltage DC-DC power supply circuit according to claim 3 , wherein
said zero-volt clamp circuit, said current mirror circuit, and said error amplifier are provided in a control IC, and
said first resistor and said second resistor are provided outside said control IC and connected to said zero-volt clamp circuit and said current mirror circuit through a first terminal and a second terminal of said control IC, respectively.
5. An inverting negative voltage DC-DC power supply circuit according to claim 2 , wherein
said first and second transistors are NPN transistors, and
said third and fourth transistors are PNP transistors.
6. An electronic device comprising the inverting negative voltage DC-DC power supply circuit according to claim 2 as a power supply circuit that outputs a negative voltage.