Constant current source circuit and a sampling circuit
View Patent ↗A constant current source circuit includes a main circuit, wherein the main circuit includes a first three-terminal regulator, a transistor, a sample resistor and a load, an output terminal of the first three-terminal regulator is connected with a control Electrode of the transistor, a reference Electrode of the transistor is connected with a voltage input terminal, a working Electrode is connected with one end of the load, and the other end of the load is connected with one end of the sample resistor, and the other end of the sample resistor and an input terminal of the first three-terminal regulator are connected to a reference potential, respectively, wherein the constant current source circuit further includes an adjusting unit that includes a voltage stabilizing unit, a fourth resistor and a fifth resistor.
1. A constant current source circuit comprising a main circuit, wherein the main circuit comprises a first three-terminal regulator, a transistor, a sample resistor and a load, an output terminal of the first three-terminal regulator is connected with a control Electrode of the transistor, a reference Electrode of the transistor is connected with a voltage input terminal, a working Electrode is connected with one end of the load, and the other end of the load is connected with one end of the sample resistor, and the other end of the sample resistor and an input terminal of the first three-terminal regulator are connected to a reference potential, respectively, wherein the constant current source circuit further comprises an adjusting unit that comprises a voltage stabilizing unit, a fourth resistor and a fifth resistor, wherein the voltage stabilizing unit generates a second reference voltage higher than a first reference voltage of the first three-terminal regulator and supplies the second reference voltage to an adjusting terminal of the first three-terminal regulator through the fourth resistor, and the fifth resistor is connected between the adjusting terminal of the first three-terminal regulator and a node that is between the load and the sample resistor.
2. The constant current source circuit according to claim 1 further comprising a third resistor, wherein the output terminal of the first three-terminal regulator is connected with the voltage input terminal through the third resistor, and the third resistor is connected between the control Electrode of the transistor and the voltage input terminal.
3. The constant current source circuit according to claim 1 , wherein the voltage stabilizing unit is a second three-terminal regulator that has an adjusting terminal connected with an adjusting terminal of the first three-terminal regulator through the fourth resistor, an output terminal connected with the voltage input terminal, and an input terminal connected with the reference potential.
4. The constant current source circuit according to claim 3 further comprising a second resistor, through which the output terminal of the second three-terminal regulator is connected with the voltage input terminal.
5. The constant current source circuit according to claim 3 , wherein the second three-terminal regulator is TL431.
6. The constant current source circuit according to claim 5 , wherein the second three-terminal regulator has the adjusting terminal thereof short connected to the output terminal thereof.
7. The constant current source circuit according to claim 1 , wherein the voltage regulating unit is a Zener Diode that has one end connected with the adjusting terminal of the first three-terminal regulator through the fourth resistor and the other end connected with the reference potential.
8. The constant current source circuit according to claim 1 , wherein the first three-terminal regulator is LM317.
9. The constant current source circuit according to claim 1 , wherein the load is an LED that has a Anode connected with the working Electrode of the transistor and a Cathode connected to one end of sample resistor.
10. The constant current source circuit according to claim 9 , wherein the load is a plurality of LEDs in serial connection.
11. A sampling circuit, for a DC-DC switch converter, comprising a main circuit, wherein the main circuit comprises a load having one end connected with a voltage input terminal and the other end connected with one end of a sample resistor, the other end of the sample resistor is connected with a reference potential, wherein the sampling circuit further comprising an adjusting unit, and the adjusting unit comprises a voltage stabilizing unit, a fourth resistor and a fifth resistor, wherein the voltage stabilizing unit generates a reference voltage and supplies the reference voltage to a sampling circuit output terminal through the fifth resistor, and the fourth resistor is connected between the sampling circuit output terminal and a node that is between the load and the sample resistor.
12. The sampling circuit according to claim 11 , wherein the voltage stabilizing unit is a three-terminal regulator that has an adjusting terminal connected with the sampling circuit output terminal through the fifth resistor, an output terminal connected with the voltage input terminal, and an input terminal connected with the reference potential.
13. The sampling circuit according to claim 12 further comprising a second resistor, through which the output terminal of the three-terminal regulator is connected with the voltage input terminal.
14. The sampling circuit according to claim 12 , wherein the three-terminal regulator has the adjusting terminal short connected to the output terminal.