Reset circuit with adjustable threshold value

Abstract

The invention provides a reset circuit with an adjustable threshold value. The reset circuit comprises a first triode, a second triode, a third triode and a comparison circuit. Wherein the influence degrees of the first current and the second current by the power supply voltage are different, when the power supply voltage is small, the second current is larger than the first current, and when the power supply voltage is large, the first current is smaller than the second current, so that a special power supply voltage value exists, the first current is equal to the second current, and an overturning point of the reset circuit is set based on the special power supply voltage value. It can be seen that the first current is a negative temperature coefficient, the coefficient proportion can be adjusted by adjusting the first resistor and the second resistor, the second current is a positive temperature coefficient, and the coefficient proportion can be adjusted by adjusting the first resistor and the third resistor. When the threshold voltage is high, the ratio of the first resistor to the second resistor is adjusted, and the threshold value is increased. And meanwhile, the third resistor is adjusted to offset the positive temperature coefficient voltage and the negative temperature coefficient voltage, so that the influence of temperature drift is reduced.

Description

Technical Field

[0001] The present invention relates to the field of electronic technology, and in particular but not limited to, to a reset circuit with adjustable threshold. Background Art

[0002] Figure 1 A reset circuit is shown, which compares a power supply voltage with a threshold voltage. When the power supply voltage is higher than the threshold voltage, the output of the reset circuit changes, thereby triggering a reset signal.

[0003] Specifically, the output voltage of the reset circuit is affected by the current I1 and the current I2. When the current I1 is equal to the current I2, the output voltage of the reset circuit is 0V, and the power supply voltage is equal to the threshold voltage.

[0004]

[0005] Among them, Vbe1, Vbe2, and Vbe3 are the base-emitter voltages of transistors Q1, Q2, and Q3. The base-emitter voltage of transistors usually decreases with increasing temperature, so Vbe3 constitutes a negative temperature coefficient. For Vbe2-Vbe1, since current I1 is the mirror current of current Ic1 (MP3 and MP4 form a current mirror with a ratio of 1), and current I2 is the mirror current of current Ic2 (MP1, MP2 and MN1, MN2 each form a current mirror with a ratio of 1), combined with the transistor current-voltage relationship Ic=Is exp(Vbe / VT) and the thermodynamic formula Vt=kT / q,

[0006]

[0007] Among them, Ic1 and Ic2 are the collector currents of transistors Q1 and Q2, Is1 and Is2 are the emitter reverse saturation currents of transistors Q1 and Q2, N is the proportionality coefficient of transistors Q1 and Q2, k is the Boltzmann constant, T is the temperature, and q is the charge of the electron. It can be seen that Vbe2-Vbe1 increases with the increase of temperature, forming a positive temperature coefficient.

[0008] When the threshold voltage is low, the resistors R2 and R3 can be adjusted to make the positive temperature coefficient equal to the negative temperature coefficient, which can offset the influence of temperature drift. However, when the threshold voltage is high, this adjustment method fails. The reason is that when the threshold voltage is high, it is necessary to The positive temperature coefficient will also increase if the threshold voltage is adjusted higher. However, in circuit design, the base-emitter voltage of the transistor is usually not higher than 0.7V, so the negative temperature coefficient voltage Vbe3 has an upper limit. Therefore, when the threshold voltage is higher, the positive temperature coefficient voltage will be greater than the negative temperature coefficient voltage, making the reset circuit threshold voltage more affected by the positive temperature coefficient drift.

[0009] In view of this, it is necessary to provide a new structure or control method to solve at least part of the above problems. Summary of the invention

[0010] In view of at least one or more problems in the background technology, the present invention proposes a reset circuit with adjustable threshold value, which can meet the accuracy requirements under high threshold voltage.

[0011] In a first aspect, a reset circuit with an adjustable threshold is provided, the reset circuit comprising:

[0012] A first transistor, an emitter thereof is coupled to a reference ground, a base thereof is coupled to a collector thereof, and a collector thereof is coupled to a first resistor and a second resistor, wherein the other end of the first resistor is coupled to a supply voltage, and the other end of the second resistor is coupled to the reference ground;

[0013] A second transistor, an emitter of which is coupled to the reference ground, a base of which is coupled to the base of the first transistor, and a collector of which generates a first current;

[0014] A third triode, whose emitter is coupled to a third resistor, whose other end is coupled to a reference ground, whose base is coupled to the base of the first triode, and whose collector generates a second current; and

[0015] The comparison circuit is used to compare the first current and the second current. If the first current is higher than the second current, the comparison circuit generates a reset signal.

[0016] Optionally, the reset circuit also includes a fourth resistor and a switch, the fourth resistor is located between the supply voltage and the first resistor, the switch is connected in parallel with the fourth resistor, and the switch is turned off before the comparison circuit generates a reset signal, and the switch is turned on after the comparison circuit generates a reset signal.

[0017] Optionally, the comparison circuit includes a current mirror, which has an input terminal, a first output terminal and a second output terminal, wherein the input terminal is coupled to the supply voltage, the first output terminal is coupled to the collector of the second transistor, and the second input terminal is coupled to the collector of the third transistor.

[0018] In a second aspect, a reset circuit with an adjustable threshold is provided, the reset circuit comprising:

[0019] A first transistor, an emitter of which is coupled to a power supply voltage, a base of which is coupled to a collector, and a collector of which is coupled to a first resistor and a second resistor, wherein the other end of the first resistor is coupled to a reference ground, and the other end of the second resistor is coupled to the power supply voltage;

[0020] A second transistor, an emitter of which is coupled to a supply voltage, a base of which is coupled to the base of the first transistor, and a collector of which generates a first current;

[0021] A third triode, whose emitter is coupled to a third resistor, whose other end is coupled to a supply voltage, whose base is coupled to the base of the first triode, and whose collector generates a second current; and

[0022] The comparison circuit is used to compare the first current and the second current. If the first current is higher than the second current, the comparison circuit generates a reset signal.

[0023] In a third aspect, a reset circuit with adjustable threshold value is provided, the reset circuit comprising:

[0024] A first MOS transistor, whose source is coupled to the reference ground, whose gate is coupled to the collector, and whose drain is coupled to the first resistor and the second resistor, wherein the other end of the first resistor is coupled to the supply voltage, and the other end of the second resistor is coupled to the reference ground;

[0025] A second MOS transistor, whose source is coupled to the reference ground, whose gate is coupled to the gate of the first MOS transistor, and whose drain generates a first current;

[0026] a third MOS transistor, whose source is coupled to a third resistor, whose other end is coupled to a reference ground, whose gate is coupled to the gate of the first MOS transistor, and whose drain generates a second current; and

[0027] The comparison circuit is used to compare the first current and the second current. If the first current is higher than the second current, the comparison circuit generates a reset signal.

[0028] Optionally, the sampling circuit further includes a fourth resistor and a switch, the fourth resistor is located between the supply voltage and the first resistor, the switch is connected in parallel with the fourth resistor, and the switch is turned off before the comparison circuit generates a reset signal, and the switch is turned on after the comparison circuit generates a reset signal.

[0029] Optionally, the comparison circuit includes a current mirror, which has an input terminal, a first output terminal and a second output terminal, wherein the input terminal is coupled to the supply voltage, the first output terminal is coupled to the drain of the second MOS tube, and the second input terminal is coupled to the drain of the third MOS tube.

[0030] In a fourth aspect, a reset circuit with an adjustable threshold value is provided, the reset circuit comprising:

[0031] A first MOS transistor, whose source is coupled to the power supply voltage, whose gate is coupled to the drain, whose drain is coupled to the first resistor and the second resistor, wherein the other end of the first resistor is coupled to the reference ground, and the other end of the second resistor is coupled to the power supply voltage;

[0032] A second MOS transistor, whose source is coupled to the power supply voltage, whose gate is coupled to the gate of the first MOS transistor, and whose drain generates a first current;

[0033] a third MOS transistor, whose source is coupled to a third resistor, whose other end is coupled to a supply voltage, whose gate is coupled to the gate of the first MOS transistor, and whose drain generates a second current; and

[0034] The comparison circuit is used to compare the first current and the second current. If the first current is higher than the second current, the comparison circuit generates a reset signal.

[0035] Beneficial Effects

[0036] The present invention proposes a reset circuit with adjustable threshold, comprising a first triode, a second triode, a third triode and a comparison circuit. Among them, the current (first current) flowing through the second triode and the current (second current) flowing through the third triode are affected by the power supply voltage to different degrees. When the power supply voltage is small, the second current is greater than the first current. When the power supply voltage is large, the first current is less than the second current. Therefore, there is a special power supply voltage value, so that the first current is equal to the second current. Based on this, the flip point of the reset circuit can be set. It can be seen that the first current is a negative temperature coefficient, and the coefficient ratio can be adjusted by adjusting the first resistor and the second resistor. The second current is a positive temperature coefficient, and the coefficient ratio can be adjusted by adjusting the first resistor and the third resistor. When the threshold voltage is high, the ratio of the first resistor and the second resistor is adjusted to increase the threshold. Then adjust the third resistor and the proportional coefficient N so that the positive temperature coefficient voltage is exactly equal to the negative temperature coefficient voltage, thereby reducing the influence of temperature drift. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings are used to provide a further understanding of the present invention and are used together with the description to explain the embodiments of the present invention, but do not constitute a limitation of the present invention. In the accompanying drawings:

[0038] Figure 1 A schematic diagram of a common reset circuit structure is shown;

[0039] Figure 2 A schematic diagram of the structure of a reset circuit with adjustable threshold according to an embodiment of the present invention is shown;

[0040] Figure 3A schematic diagram of the structure of a reset circuit with adjustable threshold according to another embodiment of the present invention is shown;

[0041] Figure 4 A schematic structural diagram of a reset circuit with adjustable threshold according to yet another embodiment of the present invention is shown. DETAILED DESCRIPTION

[0042] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0043] The description in this section is only for several typical embodiments, and the present invention is not limited to the scope of the embodiments. The combination of different embodiments, the mutual replacement of some technical features in different embodiments, and the mutual replacement of the same or similar prior art means with some technical features in the embodiments are also within the scope of the description and protection of the present invention.

[0044] "Coupled" or "connected" in the specification includes both direct connection and indirect connection. Indirect connection is a connection through an intermediate medium, such as a connection through an electrical conductive medium such as a conductor, wherein the electrical conductive medium may contain parasitic inductance or parasitic capacitance, or a connection through an intermediate circuit or component described in the embodiments in the specification; indirect connection may also include a connection through other active or passive devices on the basis of achieving the same or similar functions, such as a connection through circuits or components such as switches, signal amplification circuits, and follower circuits. "Multiple" or "many" means two or more.

[0045] Reference Figure 2 The present invention provides a reset circuit with adjustable threshold, including a comparison circuit, a first transistor (Q1 in the figure), a second transistor (Q2 in the figure) and a third transistor (Q3 in the figure). The base of the first transistor and the base of the second transistor are both coupled to the first resistor, and the emitter of the first transistor and the emitter of the second transistor are both coupled to the reference ground. Therefore, if the ratio of the first transistor to the second transistor is N, the ratio of the current flowing through the first transistor to the current flowing through the second transistor is also N, that is, I1=Ic1 / N.

[0046] The base of the second transistor and the base of the third transistor are both coupled to the first resistor, the emitter of the second transistor is coupled to the reference ground, the emitter of the third transistor is coupled to the third resistor, and the other end of the third resistor is coupled to the reference ground. Therefore, the base-emitter voltage of the second transistor is equal to the sum of the base-emitter voltage of the third transistor and the voltage of the third resistor, that is, Vbe2 = Vbe3 + VR3. The current I2 flowing through the third transistor = (Vbe2-Vbe3) / R3.

[0047] Based on Hofkiel's law, Iin=Ic1+It, then (Vdd-Vbe1) / R1=Vbe1 / R2+Ic1. When the first current is equal to the second current, the voltage value of the supply voltage is the threshold voltage, then Vfp=(Vbe1 / R2+Ic1)×R1+Vbe1. Combining the first current formula and the second current formula to replace Ic1, Vfp=(Vbe1 / R2+N×(Vbe2-Vbe3) / R3)×R1+Vbe l , after extracting the common factors, we have

[0048]

[0049] By adjusting the coefficient (R1+R2) / R2 and then adjusting the coefficient R3 or the coefficient N, the positive temperature coefficient voltage can be made exactly equal to the negative temperature coefficient voltage, thereby reducing the influence of temperature drift on the flip point.

[0050] In one embodiment, the reset circuit further includes a fourth resistor and a switch, wherein the fourth resistor is located between the supply voltage and the first resistor, and the switch is connected in parallel with the fourth resistor. In the initial stage, the switch is turned off, and the fourth resistor is in a path. When the supply voltage is higher than the threshold voltage, the comparison circuit sends a reset signal, and the switch tube is turned on, and the fourth resistor is short-circuited. It can be seen that when the fourth resistor is in the on state, the threshold voltage is higher, and when the fourth resistor is in the short circuit state, the threshold voltage is lower, so the reset signal generated will produce a hysteresis effect. For example, by controlling the circuit to be powered on through the reset signal, the initial threshold voltage is higher, which can cause power-on hysteresis; after power-on, the threshold voltage is lowered, which can cause power-off hysteresis.

[0051] In one embodiment, if Figure 2 As shown, the comparison circuit includes a current mirror, which has an input terminal, a first output terminal and a second output terminal. The input terminal is coupled to the supply voltage, the first output terminal is coupled to the collector of the second transistor, and the second transistor is coupled to the collector of the third transistor. In this way, the first current is copied by the current mirror and is in the same path as the second current. Based on Hofkiel's law, the branch current drawn from this path is detected. If the branch current is in the outflow direction, it indicates that the first current is greater than the second current at this time. If the branch current is in the inflow direction, it indicates that the first current is less than the second current at this time. Specifically, the current mirror is composed of a pair of transistors, MOS tubes or other transistors that can form a current mirror with equal proportional coefficients.

[0052] The above describes the use of an NPN transistor to implement a reset circuit. In another embodiment, Figure 3 As shown, a PNP transistor can also be used to implement the reset circuit. In another embodiment, as Figure 4 As shown, a MOS tube can also be used to implement the reset circuit. The reset circuit implemented by using a PNP transistor, a PMOS tube, and an NMOS tube has no obvious difference from the reset circuit implemented by an NPN transistor except that the accuracy and coupling method are slightly different. Therefore, the structures of the PNP transistor reset circuit, the PMOS tube reset circuit, and the NMOS tube reset circuit can refer to the description of the NPN transistor reset circuit above, and will not be repeated here.

[0053] Those skilled in the art should know that the logic controls such as "high level" and "low level", "set" and "reset", "AND gate" and "OR gate", "non-inverting input terminal" and "inverting input terminal" in the logic controls involved in the specification or drawings can be interchanged or changed with each other, and the same function or purpose as the above embodiment can be achieved by adjusting the subsequent logic controls.

[0054] The description and application of the present invention here are illustrative, and it is not intended to limit the scope of the present invention to the above-mentioned embodiments. The effects or advantages involved in the specification may not be reflected in the actual experimental examples due to the uncertainty of specific condition parameters or other factors, and the effects or advantages are not used to limit the scope of the invention. The deformation and change of the embodiments disclosed here are possible, and the replacement of the embodiments and the various equivalent parts are well known to those of ordinary skill in the art. It should be clear to those skilled in the art that the present invention can be implemented in other forms, structures, arrangements, proportions, and with other components, materials and parts without departing from the spirit or essential features of the present invention. Other deformations and changes can be made to the embodiments disclosed here without departing from the scope and spirit of the present invention.

Claims

1. A reset circuit with adjustable threshold, characterized in that: The reset circuit comprises: A first transistor, an emitter thereof is coupled to a reference ground, a base thereof is coupled to a collector thereof, and a collector thereof is coupled to a first resistor and a second resistor, wherein the other end of the first resistor is coupled to a supply voltage, and the other end of the second resistor is coupled to the reference ground; A second transistor, an emitter of which is coupled to the reference ground, a base of which is coupled to the base of the first transistor, and a collector of which generates a first current; A third triode, whose emitter is coupled to a third resistor, whose other end is coupled to a reference ground, whose base is coupled to the base of the first triode, and whose collector generates a second current; and The comparison circuit is used to compare the first current and the second current. If the first current is higher than the second current, the comparison circuit generates a reset signal.

2. The reset circuit according to claim 1, wherein: The reset circuit also includes a fourth resistor and a switch, wherein the fourth resistor is located between the supply voltage and the first resistor, and the switch is connected in parallel with the fourth resistor. Before the comparison circuit generates a reset signal, the switch is turned off, and after the comparison circuit generates a reset signal, the switch is turned on.

3. The reset circuit according to any one of claims 1 or 2, characterized in that: The comparison circuit includes a current mirror having an input terminal, a first output terminal and a second output terminal, wherein the input terminal is coupled to a supply voltage, the first output terminal is coupled to the collector of the second transistor, and the second input terminal is coupled to the collector of the third transistor.

4. A reset circuit with adjustable threshold, characterized in that: The reset circuit comprises: A first transistor, an emitter of which is coupled to a power supply voltage, a base of which is coupled to a collector, and a collector of which is coupled to a first resistor and a second resistor, wherein the other end of the first resistor is coupled to a reference ground, and the other end of the second resistor is coupled to the power supply voltage; A second transistor, an emitter of which is coupled to a supply voltage, a base of which is coupled to the base of the first transistor, and a collector of which generates a first current; A third triode, whose emitter is coupled to a third resistor, whose other end is coupled to a supply voltage, whose base is coupled to the base of the first triode, and whose collector generates a second current; and The comparison circuit is used to compare the first current and the second current. If the first current is higher than the second current, the comparison circuit generates a reset signal.

5. A reset circuit with adjustable threshold, characterized in that: The reset circuit comprises: A first MOS transistor, whose source is coupled to the reference ground, whose gate is coupled to the collector, and whose drain is coupled to the first resistor and the second resistor, wherein the other end of the first resistor is coupled to the supply voltage, and the other end of the second resistor is coupled to the reference ground; A second MOS transistor, whose source is coupled to the reference ground, whose gate is coupled to the gate of the first MOS transistor, and whose drain generates a first current; a third MOS transistor, whose source is coupled to a third resistor, whose other end is coupled to a reference ground, whose gate is coupled to the gate of the first MOS transistor, and whose drain generates a second current; and The comparison circuit is used to compare the first current and the second current. If the first current is higher than the second current, the comparison circuit generates a reset signal.

6. The reset circuit according to claim 5, characterized in that: The sampling circuit also includes a fourth resistor and a switch, wherein the fourth resistor is located between the supply voltage and the first resistor, and the switch is connected in parallel with the fourth resistor. Before the comparison circuit generates a reset signal, the switch is turned off, and after the comparison circuit generates a reset signal, the switch is turned on.

7. The reset circuit according to any one of claims 5 or 6, characterized in that: The comparison circuit includes a current mirror having an input terminal, a first output terminal and a second output terminal, wherein the input terminal is coupled to the supply voltage, the first output terminal is coupled to the drain of the second MOS tube, and the second input terminal is coupled to the drain of the third MOS tube.

8. A reset circuit with adjustable threshold, characterized in that: The reset circuit comprises: A first MOS transistor, whose source is coupled to the power supply voltage, whose gate is coupled to the drain, whose drain is coupled to the first resistor and the second resistor, wherein the other end of the first resistor is coupled to the reference ground, and the other end of the second resistor is coupled to the power supply voltage; A second MOS transistor, whose source is coupled to the power supply voltage, whose gate is coupled to the gate of the first MOS transistor, and whose drain generates a first current; a third MOS transistor, whose source is coupled to a third resistor, whose other end is coupled to a supply voltage, whose gate is coupled to the gate of the first MOS transistor, and whose drain generates a second current; and The comparison circuit is used to compare the first current and the second current. If the first current is higher than the second current, the comparison circuit generates a reset signal.

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