阅读说明：本技术 电平移位电路 (Level shift circuit ) 是由 高田幸辅 宇野正幸 于 2019-05-31 设计创作，主要内容包括：电平移位电路具有：两个电阻,它们在两个输入端子成为低电平时将逻辑固定；逻辑电路,其通过固定的逻辑将输出端子的逻辑设定为期望的值；以及晶体管,即使两个输入端子变为低电平,输出电压也不会变得不确定,输出期望的输出逻辑。(The level shift circuit includes: two resistors that fix logic when two input terminals become low level; a logic circuit that sets the logic of the output terminal to a desired value by fixed logic; and a transistor which outputs a desired output logic without an output voltage becoming indefinite even if both input terminals become low level.)

1. A level shift circuit, characterized in that,

The level shift circuit includes:

A first transistor having a source connected to a first power supply terminal;

a second transistor having a source connected to the first power supply terminal, a gate connected to the drain of the first transistor, and a drain connected to the gate of the first transistor;

a first resistance element connected between the first power supply terminal and a drain of the first transistor;

A second resistance element connected between the first power supply terminal and a drain of the second transistor;

a third transistor having a source connected to the second power supply terminal, a gate connected to the first input terminal, and a drain connected to the drain of the first transistor;

a fourth transistor having a source connected to the second power supply terminal, a gate connected to the second input terminal, and a drain connected to the drain of the second transistor;

A fifth transistor having a source connected to the first power supply terminal, a gate connected to the drain of the second transistor, and a drain connected to the output terminal of the level shift circuit;

A logic circuit having a first input terminal connected to the drain of the first transistor and a second input terminal connected to the drain of the second transistor; and

And a sixth transistor having a source connected to the first power supply terminal, a gate connected to the output terminal of the logic circuit, and a drain connected to the output terminal of the level shift circuit.

2. The level shifting circuit of claim 1,

the logic circuit turns on the sixth transistor when the voltages of the first and second input terminals are equal to the voltage of the first power supply terminal.

3. Level shifting circuit according to claim 1 or 2,

the level shift circuit includes:

a constant voltage part having one end connected to the first power supply terminal;

A seventh transistor having a gate connected to the other end of the constant voltage part, the seventh transistor being connected between the drain of the first transistor and the drain of the third transistor; and

and an eighth transistor having a gate connected to the other end of the constant voltage part, the eighth transistor being connected between the drain of the second transistor and the drain of the fourth transistor.

Technical Field

The present invention relates to a level shift circuit.

Background

Fig. 2 shows a circuit diagram of a conventional level shift circuit 200.

The conventional level shift circuit 200 includes a power supply terminal 201, a ground terminal 202, a constant voltage unit 211, input terminals 223 and 224, NMOS transistors 212 and 213, PMOS transistors 214, 215, 217, 218 and 220, and an output terminal 222.

The constant voltage section 211 has one end connected to the power supply terminal 201 and the other end connected to the gate of the PMOS transistor 214 and the gate of the PMOS transistor 215. The NMOS transistor 212 has a gate connected to the input terminal 223, a source connected to the ground terminal 202, and a drain connected to the drain of the PMOS transistor 214. The NMOS transistor 213 has a gate connected to the input terminal 224, a source connected to the ground terminal 202, and a drain connected to the drain of the PMOS transistor 215. The PMOS transistor 217 has a source connected to the power supply terminal 201 and a drain connected to a source of the PMOS transistor 214 and a gate of the PMOS transistor 218. The PMOS transistor 218 has a source connected to the power supply terminal 201 and a drain connected to a source of the PMOS transistor 215, a gate of the PMOS transistor 217, and a gate of the PMOS transistor 220. The PMOS transistor 220 has a source connected to the power supply terminal 201 and a drain connected to the output terminal 222. Normally, an NMOS transistor 226 that pulls down the output terminal 222 when the PMOS transistor 220 is turned off is connected to the output terminal 222.

When the voltage across the constant voltage part 211 is VREF, the voltage VBIAS at the other end of the constant voltage part 211 is a value obtained by subtracting the voltage VREF from the voltage VDD of the power supply terminal 201. The gates of the PMOS transistors 214, 215 are supplied with a voltage VBIAS, and the respective source voltages VP1, VP2 are clamped to be greater than the voltage VBIAS plus the threshold voltage | VHTP | of the PMOS transistor. The reason why such clamping is required is that all transistors have a lower gate-source withstand voltage than the voltage VDD. For example, the voltage VDD is 12V, the gate-source withstand voltage is 6V, the voltage VREF is 4V, and the voltage | VTHP | is 1V for each voltage.

When a high level (for example, 5V) is input to the input terminal 223 and a low level (for example, 0V) is input to the input terminal 224, the NMOS transistor 212 is turned on and the NMOS transistor 213 is turned off. The voltage VP1 is clamped by PMOS transistor 214 to VDD-VREF + | VTHP |. At this time, since the PMOS transistor 218 is turned on, the voltage VP2 becomes the voltage VDD, and the PMOS transistors 217 and 220 are turned off. The voltage VOUT of the output terminal 222 becomes 0V because the NMOS transistor 226 is turned on.

when a low level is input to the input terminal 223 and a high level is input to the input terminal 224, the NMOS transistor 213 is turned on and the NMOS transistor 212 is turned off. The voltage VP2 is clamped by PMOS transistor 215 to VDD-VREF + | VTHP |. At this time, since the PMOS transistors 217 and 220 are turned on, the voltage VP1 becomes the voltage VDD, and the PMOS transistor 218 is turned off. At this time, since the NMOS transistor 226 is turned off, the voltage VOUT of the output terminal 222 is the voltage VDD.

In this way, according to the conventional level shift circuit 200, the PMOS transistor 220 is switched according to the signals of the input terminal 223 and the input terminal 224, and the voltage VDD or 0V after the level shift is obtained from the output terminal 222 (for example, see patent document 1).

Patent document

Patent document 1: japanese laid-open patent publication No. 11-205123

In the conventional level shift circuit 200 as described above, when the voltage VN1 at the input terminal 223 and the voltage VN2 at the input terminal 224 are low, the voltage VP1 and the voltage VP2 become indeterminate, and the NMOS transistor 226 is also turned off, so that the voltage VOUT becomes indeterminate.

when the PMOS transistor 227 receiving the voltage VOUT from the gate is connected to the output terminal 222, if the voltage VDD rises rapidly in a state where the voltage VOUT is indeterminate, a potential difference is generated between the voltage VDD and the voltage VOUT due to a parasitic capacitance between the drain and the source of the NMOS transistor 226, and the PMOS transistor 227 is turned on.

The level shift circuit does not prefer that the output logic becomes indeterminate, and it is preferable that the transistor receiving the signal be turned off when the output logic becomes indeterminate.

Disclosure of Invention

The present invention has been made to solve the above-described problems, and provides a level shift circuit in which even when the voltage VN1 and the voltage VN2 are low, the output terminal 222 is fixed to the voltage VDD with low impedance, and the voltage VOUT does not become indefinite.

A level shift circuit according to an embodiment of the present invention is characterized by comprising: a first transistor having a source connected to a first power supply terminal; a second transistor having a source connected to the first power supply terminal, a gate connected to the drain of the first transistor, and a drain connected to the gate of the first transistor; a first resistance element connected between a first power supply terminal and a drain of the first transistor; a second resistance element connected between the first power supply terminal and the drain of the second transistor; a third transistor having a source connected to the second power supply terminal, a gate connected to the first input terminal, and a drain connected to the drain of the first transistor; a fourth transistor having a source connected to the second power supply terminal, a gate connected to the second input terminal, and a drain connected to the drain of the second transistor; a fifth transistor having a source connected to the first power supply terminal, a gate connected to the drain of the second transistor, and a drain connected to the output terminal of the level shift circuit; a logic circuit having a first input terminal connected to the drain of the first transistor and a second input terminal connected to the drain of the second transistor; and a sixth transistor having a source connected to the first power supply terminal, a gate connected to the output terminal of the logic circuit, and a drain connected to the output terminal of the level shift circuit.

According to the level shift circuit of the present invention, since the level shift circuit includes two resistors, a logic circuit, and a transistor, the two resistors fix a logic when the two input terminals are at a low level, and the logic circuit sets the logic of the output terminal to a desired value by the fixed logic, the output voltage does not become indefinite, and a desired output logic can be output.

Drawings

Fig. 1 is a circuit diagram showing a level shift circuit according to an embodiment of the present invention.

Fig. 2 is a circuit diagram of a conventional level shift circuit.

Description of the reference symbols

100: a level shift circuit; 111: a constant pressure part; 125: a NAND circuit.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

fig. 1 is a circuit diagram of a level shift circuit 100 according to an embodiment of the present invention.

The level shift circuit 100 of the present embodiment includes a power supply terminal 101, a ground terminal 102, a constant voltage unit 111, input terminals 123 and 124, NMOS transistors 112 and 113, PMOS transistors 114, 115, 117, 118, 120 and 121, an output terminal 122, resistors 116 and 119, and a NAND circuit 125.

The constant voltage unit 111 has one end connected to the power supply terminal 101 and the other end connected to the gate of the PMOS transistor 114 and the gate of the PMOS transistor 115. The NMOS transistor 112 has a gate connected to the input terminal 123, a source connected to the ground terminal 102, and a drain connected to the drain of the PMOS transistor 114. The NMOS transistor 113 has a gate connected to the input terminal 124, a source connected to the ground terminal 102, and a drain connected to the drain of the PMOS transistor 115. The PMOS transistor 117 has a source connected to the power supply terminal 101, and a drain connected to a source of the PMOS transistor 114, a gate of the PMOS transistor 118, the other end of the resistor 116, and a first input terminal of the NAND circuit 125. The PMOS transistor 118 has a source connected to the power supply terminal 101 and a drain connected to a source of the PMOS transistor 115, a gate of the PMOS transistor 117, a gate of the PMOS transistor 120, the other end of the resistor 119, and a second input terminal of the NAND circuit 125. The PMOS transistor 120 has a source connected to the power supply terminal 101 and a drain connected to the output terminal 122. One end of the resistor 116 is connected to the power supply terminal 101. One end of the resistor 119 is connected to the power supply terminal 101. The PMOS transistor 121 has a source connected to the power supply terminal 101 and a drain connected to the output terminal 122. The output of the NAND circuit 125 is connected to the gate of the PMOS transistor 121. An NMOS transistor 126 for pulling down the output terminal 122 is connected to the output terminal 122.

When the voltage across the constant voltage unit 111 is set to the voltage VREF and the voltage of the power supply terminal 101 is set to the voltage VDD, the voltage VBIAS at the other end of the constant voltage unit 111 is a value obtained by subtracting the voltage VREF from the voltage VDD. The voltage VBIAS is supplied to the gates of the PMOS transistors 114, 115, and the respective source voltages VP1, VP2 are clamped to be greater than a voltage obtained by adding the threshold voltage | VHTP | of the PMOS transistor to the voltage VBIAS. The reason why such clamping is required is that all transistors have a lower gate-source withstand voltage than the voltage VDD. Although an example, the voltage VDD is 12V, the gate-source withstand voltage is 6V, the voltage VREF is 4V, and the voltage | VTHP | is 1V for the voltages of the respective nodes.

Next, the operation of the level shift circuit 100 of the present embodiment will be described.

In the first state, when a high level (for example, 5V) is input to the input terminal 123 and a low level (for example, 0V) is input to the input terminal 124, the NMOS transistor 112 is turned on and the NMOS transistor 113 is turned off. The voltage VP1 is clamped by PMOS transistor 114 to VDD-VREF + | VTHP |. At this time, since the PMOS transistor 118 is turned on, the voltage VP2 becomes the voltage VDD, and the PMOS transistors 117 and 120 are turned off. The NAND circuit 125 operates with the voltage VBIAS as a reference potential, and outputs the voltage VDD in accordance with the voltage VP1 and the voltage VP2 that are input. Therefore, the PMOS transistor 121 is turned off. The voltage VOUT of the output terminal 122 becomes 0V due to the NMOS transistor 126 being turned on.

In the second state, when a low level is input to the input terminal 123 and a high level is input to the input terminal 124, the NMOS transistor 113 is turned on and the NMOS transistor 112 is turned off. The voltage VP2 is clamped by PMOS transistor 115 to VDD-VREF + | VTHP |. At this time, since the PMOS transistors 117 and 120 are turned on, the voltage VP1 becomes the voltage VDD, and the PMOS transistor 118 is turned off. The NAND circuit 125 outputs the voltage VDD according to the voltages of the voltage VP1 and the voltage VP 2. Therefore, the PMOS transistor 121 is turned off. The voltage VOUT of the output terminal 222 becomes the voltage VDD by the NMOS transistor 126 being turned off.

as a third state, when a low level is input to the input terminal 123 and the input terminal 124, the NMOS transistors 113 and 112 are turned off. The voltages VP2 and VP1 become the voltage VDD through the resistor 116 and the resistor 119, and the PMOS transistors 117, 118, and 120 are turned off. The NAND circuit 125 outputs a voltage VBIAS according to the voltages of the voltage VP1 and the voltage VP 2. Accordingly, the PMOS transistor 121 is turned on. Since the NMOS transistor 126 is turned off, the voltage VOUT of the output terminal 122 becomes the voltage VDD through the PMOS transistor 121.

as described above, since the level shift circuit 100 of the present embodiment includes the resistors 116 and 119, the NAND circuit 125, and the PMOS transistor 121, the output terminal 122 does not become indefinite even when a low level is input to the input terminal 123 and the input terminal 124, and the voltage VOUT can be set to a voltage equal to the voltage VDD. Therefore, even if the PMOS transistor 127 is connected to the output terminal 122, the PMOS transistor 227 is not unintentionally turned on.

While the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications may be made without departing from the scope of the present invention.

For example, in the above embodiment, the NAND circuit 125 may be replaced with an AND circuit, AND the PMOS transistor 121 may be replaced with an NMOS transistor. For example, the resistors 116 and 119 may be depletion transistors or JFETs as long as they have a pull-up function. For example, in the above embodiment, a circuit configuration in which the polarities of the PMOS transistor and the NMOS transistor are inverted may be used. For example, although an example in which a MOS transistor is used as the level shift circuit has been described, a bipolar transistor or the like may be used.