Voltage reference circuit based on Zener diode

Abstract

The invention provides a voltage reference circuit based on a Zener diode, which comprises a power supply unit, a series branch formed by a resistor R1, a resistor R2 and a resistor R3 which are connected in parallel with the Zener diode Z1, and a voltage compensation circuit, and the voltage compensation circuit comprises a transistor M13 and a transistor M14 which share a grid electrode, and a transistor M11 and a transistor M12 which share a grid electrode; the source electrodes of the transistors M13 and M14 are connected to the first end of the resistor R3, the drain electrode of the transistor M13 is connected to the grid electrode of the transistor M13 and the drain electrode of the transistor M11, the source electrode of the transistor M11 is connected to the positive electrode of the Zener diode Z4, and the negative electrode of the Zener diode Z4 is grounded; the source electrode of the transistor M12 is connected to the positive electrode of a Zener diode Z5 through a resistor Rd, and the negative electrode of the Zener diode Z5 is grounded; the in-phase input end of the operational amplifier OPA2 is connected to the positive electrode of the Zener diode Z4, the reverse input end of the operational amplifier OPA2 is connected to the source electrode of the transistor M12, and the output end of the operational amplifier OPA2 is connected to the grid electrode of the transistor M11. According to the invention, the Zener voltage is subjected to temperature compensation, so that the output voltage is more stable.

Description

Technical Field

[0001] The invention mainly relates to a temperature compensation circuit, and in particular to a voltage reference circuit based on a Zener diode. Background Art

[0002] Battery management chips need to measure the battery voltage with high absolute accuracy, which means that a reference voltage source is required that remains extremely stable over the service life and mechanical stress range. A known method is to use a buried Zener diode. It is also possible to add or subtract part of the diode relative voltage to the Zener voltage to achieve temperature compensation.

[0003] refer to Figure 1 As shown, the Zener voltage can be used to subtract a number of transistor emitter junction bias voltages V BE The voltage of the output is close to zero temperature coefficient. For example, two voltage signals with opposite temperature coefficients are added in a certain ratio to obtain a reference voltage that is independent of temperature. Traditional technology only has first-order compensation of positive temperature coefficient voltage and negative temperature coefficient voltage superposition. Usually, the transistor emitter junction bias voltage V BE As a negative temperature coefficient voltage, V BE There are higher-order terms that vary with temperature, so the temperature drift coefficient of traditional bandgap reference circuits is high. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a voltage reference circuit based on a Zener diode, perform temperature compensation on the Zener voltage, and make the output voltage of the voltage reference circuit more stable.

[0005] In order to solve the above technical problems, the present invention provides a voltage reference circuit based on a Zener diode, comprising: a power supply unit, wherein the positive voltage output end of the power supply unit is connected to the negative electrode of the Zener diode Z1, and the positive electrode of the Zener diode Z1 is grounded; a resistor R1, a resistor R2, and a resistor R3 form a series branch, wherein the first end of the resistor R1 is grounded, the second end of the resistor R1 is connected to the first end of the resistor R2, the second end of the resistor R2 is connected to the first end of the resistor R3, and the second end of the resistor R3 is connected to the negative electrode of the Zener diode Z1; the voltage at the second end of the resistor R1 is used as the output voltage of the voltage reference circuit; a voltage compensation circuit, wherein the voltage compensation circuit comprises: a transistor M13 and a transistor M14 with a common gate, and a transistor M11 and a transistor M14 with a common gate. tube M12; the sources of the transistors M13 and M14 are both connected to the first end of the resistor R3, the drain of the transistor M13 is connected to the gate of the transistor M13 and the drain of the transistor M11, the source of the transistor M11 is connected to the anode of the Zener diode Z4, and the cathode of the Zener diode Z4 is grounded; the source of the transistor M12 is connected to the anode of the Zener diode Z5 through the resistor Rd, and the cathode of the Zener diode Z5 is grounded; an operational amplifier OPA2, the non-inverting input terminal of the operational amplifier OPA2 is connected to the anode of the Zener diode Z4, the inverting input terminal of the operational amplifier OPA2 is connected to the source of the transistor M12, and the output terminal of the operational amplifier OPA2 is connected to the gate of the transistor M11.

[0006] Optionally, the power supply unit includes: a first current mirror composed of a transistor M1 and a transistor M2 with a common gate, wherein a voltage output end of the first current mirror is connected to an input end of a charge pump, and also includes a second current mirror composed of a transistor M6 and a transistor M9, wherein sources of the transistor M6 and the transistor M9 are both connected to an output end of the charge pump, and a drain of the transistor M9 is connected to a negative electrode of the Zener diode Z1.

[0007] Optionally, the output voltage of the charge pump is 7V to 10V.

[0008] Optionally, a current compensation loop is further included, and the current compensation loop is configured to: detect an average current at the second end of the resistor R1 to adjust the output voltage of the charge pump.

[0009] Optionally, the current compensation loop includes: a transistor M5, the drain of the transistor M5 is connected to the drain of the transistor M1, and the source of the transistor M5 is grounded; a transistor M3, the drain of the transistor M3 is connected to the positive electrode of the current source I1 and the gate of the transistor M5, and the source of the transistor M3 is grounded; a transistor M4, the gate of the transistor M4 is connected to the gate of the transistor M3, the source of the transistor M4 is grounded, the drain of the transistor M4 is connected to its gate and to the positive electrode of the Zener diode Z2, and the negative electrode of the Zener diode Z2 is connected The drain of the transistor M6; the transistor M7, the positive and negative electrodes of the current source I1 are respectively connected to the drain and source of the transistor M7; the transistor M8, the drain of the transistor M8 is grounded through the resistor Rc, and the source of the transistor M8 is connected to the source of the transistor M7; the operational amplifier OPA1, the output end of the operational amplifier OPA1 is respectively connected to the gate of the transistor M7 and the gate of the transistor M8, the inverting input end of the operational amplifier OPA1 is connected to the drain of the transistor M8, and the in-phase input end is connected to the first end of the resistor R2.

[0010] Optionally, a transistor M10 is further included, wherein the drain of the transistor M10 is connected to the inverting input terminal of the operational amplifier OPA1, the source of the transistor M10 is connected to the anode of the diode Z3, and the cathode of the diode Z3 is grounded.

[0011] Optionally, the diode Z3 is a Zener diode.

[0012] Compared with the prior art, the present invention has the following advantages: by introducing an improved voltage compensation circuit to compensate for the reference voltage, the output voltage of the voltage reference circuit is made more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings are included to provide a further understanding of the present application. They are included and constitute a part of the present application. The accompanying drawings illustrate embodiments of the present application and together with the present specification serve to explain the principles of the present application. In the accompanying drawings:

[0014] Figure 1 It is a schematic diagram of a temperature compensation circuit of a Zener diode;

[0015] Figure 2 It is a structural schematic diagram of a resistor voltage divider circuit;

[0016] Figure 3 It is a structural diagram of another resistor voltage divider circuit;

[0017] Figure 4 Is a way to generate a compensation voltage ΔV be Circuit diagram of

[0018] Figure 5 It is a schematic structural diagram of a voltage reference circuit based on a Zener diode according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0020] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0021] In addition, it should be noted that the use of words such as "first" and "second" to define components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above words have no special meaning and cannot be understood as limiting the scope of protection of this application. In addition, although the terms used in this application are selected from well-known and commonly used terms, some terms mentioned in the specification of this application may be selected by the applicant at his or her discretion, and their detailed meanings are explained in the relevant parts of the description of this article. In addition, it is required to understand this application not only by the actual terms used, but also by the meaning implied by each term.

[0022] It should be understood that when a component is referred to as being "on another component," "connected to another component," "coupled to another component," or "contacting another component," it may be directly on, connected to, coupled to, or contacting the other component, or there may be intervening components. In contrast, when a component is referred to as being "directly on another component," "directly connected to," "directly coupled to," or "directly contacting" another component, there are no intervening components. Similarly, when a first component is referred to as being "electrically in contact with" or "electrically coupled to" a second component, there is an electrical path between the first component and the second component that allows current to flow. The electrical path may include capacitors, coupled inductors, and / or other components that allow current to flow, even without direct contact between conductive components.

[0023] The battery management system contains chips responsible for measuring the status of the battery cells. One of the key measurements is the battery voltage, which must be very close to the actual battery voltage. Therefore, a very accurate voltage reference (reference voltage) needs to be created in the chip.

[0024] Considerations for voltage references generally include: 1. The voltage reference must be very stable during the life of the chip, that is, it must maintain its stability after production testing. During production testing, fine-tuning and calibration methods can be used to reduce the drift of the standard value provided by a single chip due to random variables. If this standard value drifts and is unstable during its service life, the chip can no longer be calibrated to compensate. 2. The voltage reference must be very stable under mechanical stress. The chip is subjected to mechanical stress due to the package. Possible causes are soldering and other factors in some production processes. Many components on the chip are sensitive to mechanical stress, such as resistors and the Vbe voltage commonly used in bandgap references. 3. The temperature coefficient of the device should be as low as possible (flat temperature curve). Although it is possible to fine-tune or calibrate in a predictive manner to compensate for the change in the reference voltage with temperature, if the reference voltage changes greatly with temperature and consider the corresponding changes in many other chip parameters, accurate calibration will become very difficult to achieve. At the same time, calibration relies on ambient temperature control. During the calibration or fine-tuning stage, if the ambient temperature cannot be controlled very accurately, this will cause temperature errors to be introduced into the measured value, ultimately resulting in errors in the calibration or fine-tuning accuracy.

[0025] Compared to the standard voltage provided by the transistor attached to the silicon surface, the voltage provided by the buried Zener diode is very stable in terms of chip life and mechanical stress. However, the single-cell management chip needs to consider the following two characteristics of the Zener diode: 1. The (positive) temperature coefficient of the Zener diode is about 1.5mV / K, which means that during production testing, temperature control instruments with better accuracy than 1K must be used to obtain accurate results. Although absolute temperature control is not required, it still poses a fundamental challenge to test insertion, ultimately limiting the accuracy of chip measurements. 2. The buried Zener diode with good stability usually has a breakdown voltage of about 5.6V, which is much higher than the typical lithium-ion battery voltage (depending on the technology of about 2.5 to 4.5V), which means that the Zener diode will have to be powered by a charge pump, which also means that the operating current of the Zener diode and other circuits connected to the high voltage should be low enough to minimize the area of ​​the charge pump.

[0026] One possible way to reduce the temperature coefficient of a Zener diode is to subtract ΔV from the Zener voltage. be voltage, because ΔV beThe voltage also has a positive temperature coefficient, and by subtracting it from the Zener diode (which also has a positive temperature coefficient), the result can be the desired flat temperature curve. be The absolute value of the voltage is opposite, ΔV be The voltage is very stable over lifetime and mechanical stress.

[0027] This embodiment is based on a Zener diode voltage reference circuit, using a Zener diode to create a V be and ΔV be , so that V be and ΔV be The stability and stress during the life span will be more stable. No other bipolar transistors are used, and a resistor divider network is used to subtract n times ΔV from the output voltage of the Zener diode resistor divider. be function.

[0028] refer to Figure 2 As shown, the current is extracted from the resistor divider network in the form of a branch connected in parallel to the resistor to ground. s is a voltage source, V1 and V2 are node voltages or node names, it can be seen that resistors r3 and r4 divide the current that should originally flow through resistor r2 from node V1. As a result, the voltage at the first node changes and is subtracted by a value.

[0029] Similarly, reference Figure 3 As shown, if current is drawn from the lower end of the resistor R3, the voltage on the resistor R1 will change.

[0030] The output voltage Vref at this time

[0031]

[0032] Among them, V znr is the output voltage of Zener diode Z1.

[0033] Assume that the Zener diode Z1 has a temperature coefficient k znr , which is related to temperature as

[0034] V znr =V znr0 +k znr T (2)

[0035] Substituting (2) into (1), the part that needs to be compensated is

[0036]

[0037] refer to Figure 4 The circuit shown, Where α is a coefficient, its value is approximately 1, I s is the saturation current, VBE is the voltage between the base and emitter of the transistor, n is the exponential ideal factor, V T is the thermal voltage.

[0038] Then V BE It can be expressed as

[0039]

[0040] The voltage between AB is ΔV be It can be expressed as:

[0041]

[0042] The relationship between the voltage difference between AB and the resistance R can be expressed as:

[0043]

[0044] Where, ΔV be =nV T ln(x), x is the ratio of the area of ​​the bipolar transistor in the B branch to the area of ​​the bipolar transistor in the A branch, n is the exponential ideal factor, k is the Boltzmann constant, and q is the elementary charge.

[0045] According to the above principle, this embodiment provides a voltage reference circuit based on a Zener diode. Figure 5 As shown, by extracting the current It from the first end of the resistor R3, it is possible to subtract ΔV from the output voltage. be. Replace the bipolar transistor with a Zener diode and connect the circuit to the resistor R3. The entire voltage reference circuit includes: a power supply unit, the positive voltage output end of the power supply unit is connected to the cathode of the Zener diode Z1, and the anode of the Zener diode Z1 is grounded. Resistors R1, R2, and R3 form a series branch, wherein the first end of resistor R1 is grounded, the second end of resistor R1 is connected to the first end of resistor R2, the second end of resistor R2 is connected to the first end of resistor R3, the second end of resistor R3 is connected to the cathode of the Zener diode Z1, and the voltage at the second end of resistor R1 is used as the output voltage of the voltage reference circuit. A voltage compensation circuit, the voltage compensation circuit includes a transistor M13 and a transistor M14 with a common gate, a transistor M11 and a transistor M12 with a common gate, the source of the transistor M13 and the transistor M14 are both connected to the first end of the resistor R3, the drain of the transistor M13 is connected to the gate of the transistor M13 and the drain of the transistor M11, the source of the transistor M11 is connected to the positive electrode of the Zener diode Z4, the negative electrode of the Zener diode Z4 is grounded, the source of the transistor M12 is connected to the positive electrode of the Zener diode Z5 through the resistor Rd, and the negative electrode of the Zener diode Z5 is grounded. An operational amplifier OPA2, the non-inverting input terminal of the operational amplifier OPA2 is connected to the positive electrode of the Zener diode Z4, the inverting input terminal of the operational amplifier OPA2 is connected to the source of the transistor M12, and the output terminal of the operational amplifier OPA2 is connected to the gate of the transistor M11.

[0046] This embodiment introduces an improved voltage compensation circuit to compensate for the reference voltage, so that the output voltage of the voltage reference circuit is more stable.

[0047] In this embodiment, the power supply unit includes: a transistor M1 and a transistor M2 with a common gate forming a first current mirror, the voltage output end of the first current mirror is connected to the input end of the charge pump, and a second current mirror composed of a transistor M6 and a transistor M9, the source of the transistor M6 and the transistor M9 are connected to the output end of the charge pump, and the drain of the transistor M9 is connected to the negative electrode of the Zener diode Z1. More optimally, the output voltage of the charge pump is 7V to 10V.

[0048] In this embodiment, transistor M1 and transistor M2 are directly powered by battery voltage VBAT, and the current mirror formed by transistor M1 and transistor M2 continuously supplies current to the charge pump (charge pump 6x vdda) so that the charge pump output is between 7 and 10 V. The output of the charge pump supplies power to transistors M6 and M9, and the voltage of 7 V to 10 V is also sufficient to generate a Zener voltage in Zener diode Z1.

[0049] The voltage reference circuit based on the Zener diode in this embodiment further includes a current compensation loop, which is configured to detect an average current at the second end of the resistor R1 to adjust the output voltage of the charge pump.

[0050] Specifically, the current compensation loop includes: a transistor M5, the drain of which is connected to the drain of the transistor M1, and the source of which is grounded. A transistor M3, the drain of which is connected to the positive electrode of the current source I1 and the gate of the transistor M5, and the source of which is grounded. A transistor M4, the gate of which is connected to the gate of the transistor M3, the source of which is grounded, the drain of which is connected to its gate and to the positive electrode of the Zener diode Z2, and the negative electrode of the Zener diode Z2 is connected to the drain of the transistor M6. A transistor M7, the positive and negative electrodes of the current source I1 are respectively connected to the drain and source of the transistor M7. A transistor M8, the drain of which is grounded through a resistor Rc, and the source of which is connected to the source of the transistor M7. The operational amplifier OPA1 has an output terminal connected to the gate of the transistor M7 and the gate of the transistor M8 respectively, an inverting input terminal of the operational amplifier OPA1 connected to the drain of the transistor M8, and a non-inverting input terminal connected to the first end of the resistor R2.

[0051] Since the resistance has a large deviation due to the manufacturing process, the resistance branch composed of resistors R3, R2 and R1 will shunt the current on the Zener diode Z1 due to the manufacturing deviation, and will also slightly affect the DC voltage output by the Zener diode Z1. Therefore, it is necessary to use transistor M1, transistor M2, transistor M5, transistor M3, transistor M4, current source I1, transistor M7, transistor M8, resistor Rc, operational amplifier OPA1, transistor M10 and the like to form a current compensation loop to detect the average current at the output voltage Vref to adjust the voltage of the charge pump and thus adjust the current passing through the Zener diode Z1.

[0052] The voltage reference circuit based on the Zener diode in this embodiment further includes a transistor M10, the drain of the transistor M10 is connected to the reverse input terminal of the operational amplifier OPA1, the source of the transistor M10 is connected to the anode of the diode Z3, and the cathode of the diode Z3 is grounded. More preferably, the diode Z3 is a Zener diode.

[0053] In order to compensate for the change in the resistance current branch, compensation is required on the feedback path. In the semiconductor manufacturing process, the triode is a surface component and the Zener diode is a deeply buried component. The electrical parameters of the surface component are subject to greater changes than those of the deeply buried component, so the compensation circuit uses the Zener diode.

[0054] The basic concepts have been described above. Obviously, for those skilled in the art, the above invention disclosure is only used as an example and does not constitute a limitation of the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and amendments to the present application. Such modifications, improvements and amendments are suggested in the present application, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of the present application.

[0055] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0056] Although the present application has been described with reference to the current specific embodiments, ordinary technicians in this technical field should recognize that the above embodiments are only used to illustrate the present application, and various equivalent changes or substitutions may be made without departing from the spirit of the present application. Therefore, as long as the changes and modifications to the above embodiments are within the essential spirit of the present application, they will fall within the scope of the claims of the present application.

Claims

1. A voltage reference circuit based on a Zener diode, characterized in that: include: A power supply unit, wherein a positive voltage output terminal of the power supply unit is connected to a cathode of a Zener diode Z1, and an anode of the Zener diode Z1 is grounded; The resistor R1, the resistor R2 and the resistor R3 form a series branch, wherein the first end of the resistor R1 is grounded, the second end of the resistor R1 is connected to the first end of the resistor R2, the second end of the resistor R2 is connected to the first end of the resistor R3, and the second end of the resistor R3 is connected to the cathode of the Zener diode Z1; the voltage at the second end of the resistor R1 is used as the output voltage of the voltage reference circuit; A voltage compensation circuit, the voltage compensation circuit comprising: A transistor M13 and a transistor M14 with a common gate, and a transistor M11 and a transistor M12 with a common gate; the sources of the transistor M13 and the transistor M14 are both connected to the first end of the resistor R3, the drain of the transistor M13 is connected to the gate of the transistor M13 and the drain of the transistor M11, the source of the transistor M11 is connected to the positive electrode of the Zener diode Z4, and the negative electrode of the Zener diode Z4 is grounded; the source of the transistor M12 is connected to the positive electrode of the Zener diode Z5 through the resistor Rd, and the negative electrode of the Zener diode Z5 is grounded; An operational amplifier OPA2, wherein the non-inverting input terminal of the operational amplifier OPA2 is connected to the anode of the Zener diode Z4, the inverting input terminal of the operational amplifier OPA2 is connected to the source of the transistor M12, and the output terminal of the operational amplifier OPA2 is connected to the gate of the transistor M11.

2. The voltage reference circuit based on a Zener diode as claimed in claim 1, characterized in that: The power supply unit comprises: The transistor M1 and the transistor M2 with a common gate form a first current mirror, the voltage output end of the first current mirror is connected to the input end of the charge pump, and the second current mirror is also composed of a transistor M6 and a transistor M9, the sources of the transistor M6 and the transistor M9 are connected to the output end of the charge pump, and the drain of the transistor M9 is connected to the negative electrode of the Zener diode Z1.

3. The voltage reference circuit based on a Zener diode as claimed in claim 2, characterized in that: The output voltage of the charge pump is 7V-10V.

4. The voltage reference circuit based on a Zener diode as claimed in claim 2, characterized in that: A current compensation loop is also included, and the current compensation loop is configured to: detect an average current at the second end of the resistor R1 to adjust the output voltage of the charge pump.

5. The voltage reference circuit based on a Zener diode as claimed in claim 4, characterized in that: The current compensation loop comprises: a transistor M5, wherein a drain of the transistor M5 is connected to a drain of the transistor M1, and a source of the transistor M5 is grounded; A transistor M3, wherein a drain of the transistor M3 is connected to the positive electrode of the current source I1 and the gate of the transistor M5, and a source of the transistor M3 is grounded; A transistor M4, wherein the gate of the transistor M4 is connected to the gate of the transistor M3, the source of the transistor M4 is grounded, the drain of the transistor M4 is connected to the gate and the anode of the Zener diode Z2, and the cathode of the Zener diode Z2 is connected to the drain of the transistor M6; Transistor M7, the positive and negative electrodes of the current source I1 are connected to the drain and source of the transistor M7 respectively; a transistor M8, wherein a drain of the transistor M8 is grounded via a resistor Rc, and a source of the transistor M8 is connected to a source of the transistor M7; An operational amplifier OPA1, wherein the output terminal of the operational amplifier OPA1 is respectively connected to the gate of the transistor M7 and the gate of the transistor M8, the inverting input terminal of the operational amplifier OPA1 is connected to the drain of the transistor M8, and the non-inverting input terminal is connected to the first end of the resistor R2.

6. The voltage reference circuit based on a Zener diode as claimed in claim 5, characterized in that: It also includes a transistor M10, wherein the drain of the transistor M10 is connected to the inverting input terminal of the operational amplifier OPA1, the source of the transistor M10 is connected to the anode of the diode Z3, and the cathode of the diode Z3 is grounded.

7. The voltage reference circuit based on a Zener diode as claimed in claim 6, characterized in that: The diode Z3 is a Zener diode.

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