Voltage reference circuit based on zener diode

Abstract

The application provides a Zener diode-based voltage reference circuit, which comprises a power supply unit, a resistor R1 connected in parallel with a Zener diode Z1, a resistor R2, a resistor R3, a series branch and a voltage compensation circuit, wherein the voltage compensation circuit comprises common-gate transistors M13 and M14, common-gate transistors M11 and M12; the sources of the transistors M13 and M14 are 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 a Zener diode Z4, and the negative electrode is grounded; the source 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 Z5 is grounded; the non-inverting input of an operational amplifier OPA2 is connected to the positive electrode of the Zener diode Z4, the inverting input of the operational amplifier OPA2 is connected to the source of the transistor M12, and the output of the operational amplifier OPA2 is connected to the gate of the transistor M11. The application performs temperature compensation on the Zener voltage, so that the output voltage is more stable.

Description

TECHNICAL FIELD

[0001] The present application relates to temperature compensation circuits, and more particularly to a Zener diode based voltage reference circuit. BACKGROUND

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

[0003] SUMMARY Figure 1 As shown, a Zener voltage minus a number of transistor emitter junction bias voltages V BE can be used to achieve an output voltage with approximately zero temperature coefficient. For example, two voltage signals with opposite temperature coefficients are added together in a certain ratio to obtain a temperature independent reference voltage. Conventional techniques only have first order compensation of the positive temperature coefficient voltage and the negative temperature coefficient voltage superposition, and usually use the transistor emitter junction bias voltage V BE as the negative temperature coefficient voltage. In fact, V BE has a high order term that varies with temperature, so the temperature drift coefficient of the conventional bandgap reference circuit is high. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a Zener diode based voltage reference circuit, which compensates the Zener voltage for temperature, so that the output voltage of the voltage reference circuit is more stable.

[0005] 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 terminal of the power supply unit is connected to the negative terminal of a Zener diode Z1, and the positive terminal of the Zener diode Z1 is grounded; resistors R1, R2, and R3 form a series branch, wherein the first terminal of resistor R1 is grounded, the second terminal of resistor R1 is connected to the first terminal of resistor R2, the second terminal of resistor R2 is connected to the first terminal of resistor R3, and the second terminal of resistor R3 is connected to the negative terminal of the Zener diode Z1; the voltage at the second terminal of resistor R1 serves as the output voltage of the voltage reference circuit; and a voltage compensation circuit, comprising: common-gate transistors M13 and M14, a common-gate transistor M11, and a crystal. Transistor M12; the sources of transistors M13 and M14 are both connected to the first terminal of resistor R3, the drain of transistor M13 is connected to the gate of transistor M13 and the drain of transistor M11, the source of transistor M11 is connected to the anode of Zener diode Z4, and the cathode of Zener diode Z4 is grounded; the source of transistor M12 is connected to the anode of Zener diode Z5 through resistor Rd, and the cathode of Zener diode Z5 is grounded; operational amplifier OPA2, the non-inverting input of operational amplifier OPA2 is connected to the anode of Zener diode Z4, the inverting input of operational amplifier OPA2 is connected to the source of transistor M12, and the output of operational amplifier OPA2 is connected to the gate of transistor M11.

[0006] Optionally, the power supply unit includes: a first current mirror composed of a common-gate transistor M1 and a transistor M2, the voltage output terminal of the first current mirror being connected to the input terminal of a charge pump; and a second current mirror composed of a transistor M6 and a transistor M9, the sources of the transistors M6 and M9 being connected to the output terminal of the charge pump; and the drain of the transistor M9 being connected to the negative terminal of the Zener diode Z1.

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

[0008] Optionally, it also includes a current compensation loop configured to detect the 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 comprises: 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 pole of a 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 the gate of the transistor M4 and the positive pole of a Zener diode Z2, the negative pole of the Zener diode Z2 is connected to the drain of a transistor M6; a transistor M7, the positive and negative poles of the current source I1 are connected to the drain and source of the transistor M7 respectively; a transistor M8, the drain of the transistor M8 is grounded through a resistor Rc, and the source of the transistor M8 is connected to the source of the transistor M7; an operational amplifier OPA1, the output of the operational amplifier OPA1 is connected to the gate of the transistor M7 and the gate of the transistor M8 respectively, the inverting input of the operational amplifier OPA1 is connected to the drain of the transistor M8, and the non-inverting input is connected to the first end of the resistor R2.

[0010] Optionally, the circuit further comprises a transistor M10, the drain of the transistor M10 is connected to the inverting input of the operational amplifier OPA1, the source of the transistor M10 is connected to the positive pole of a diode Z3, and the negative pole of the diode Z3 is grounded.

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

[0012] Compared with the prior art, the application has the following advantages: the improved voltage compensation circuit is introduced to compensate the reference voltage, so that the output voltage of the voltage reference circuit is more stable. BRIEF DESCRIPTION OF DRAWINGS

[0013] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the principle of the application. In the drawings:

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

[0015] Figure 2 is a structural schematic diagram of a resistance voltage dividing circuit;

[0016] Figure 3 is a structural schematic diagram of another resistance voltage dividing circuit;

[0017] Figure 4 is a circuit schematic diagram for generating a compensation voltage AV be ;

[0018] Figure 5 Fig. 1 is a schematic diagram of a Zener diode-based voltage reference circuit according to an embodiment of the present application. DETAILED DESCRIPTION

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some examples or embodiments of the present application, and for those skilled in the art, the present application can also be applied to other similar scenarios without creative labor on the basis of these drawings. Unless it is clear from the language context or otherwise stated, the same reference numbers in the drawings represent the same structure or operation.

[0020] As shown in the present application and claims, unless the context clearly indicates otherwise, the words "one", "an", "a", and / or "the" do not mean a single number, but can also include a plurality. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of the steps and elements explicitly identified, and these steps and elements do not constitute an exclusive list, and the method or device can also include other steps or elements.

[0021] In addition, it should be noted that the use of the words "first", "second", and the like, to define elements, is merely intended to distinguish between corresponding elements, and unless otherwise stated, the above words have no special meaning and therefore cannot be understood as limiting the scope of protection of the present application. In addition, although the terms used in the present application are selected from commonly known terms, some terms mentioned in the specification of the present application can be selected by the applicant according to his or her judgment, and the detailed meanings of these terms are described in the relevant part of the description. In addition, the present application is not only understood 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 "on", "connected to", "coupled to", or "contacting" another component, it can be directly on, connected to, coupled to, or contacting the other component, or intervening components can be present. In contrast, when a component is referred to as being "directly on", "directly connected to", "directly coupled to", or "directly contacting" another component, there are no intervening components present. 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 can include capacitors, coupled inductors, and / or other components that allow current to flow, even without direct contact between conductive components.

[0023] Battery management systems contain chips responsible for measuring the state of the battery cells, one of the key measurements is the measurement of the battery voltage, it is necessary to measure a voltage value very close to the real battery voltage. Therefore, it is necessary to create a very accurate voltage reference (voltage reference) in the chip.

[0024] The considerations for a voltage reference generally include: 1. The voltage reference must be very stable during the lifetime of the chip, i.e. maintain its stability after production testing. During production testing, the drift of the standard value provided by the individual chip due to random variables can be reduced by trimming, calibration methods. If this standard value has a drift and instability during the lifetime, the chip can no longer be compensated by calibration. 2. The voltage reference must be very stable under mechanical stress. The chip is subjected to mechanical stress due to packaging. Possible causes are soldering and other factors of 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 the change in reference voltage with temperature can be compensated by trimming or calibration in the form of a prediction, if the reference voltage changes greatly with temperature, and considering the corresponding changes in many other parameters in the chip, accurate calibration will become very difficult to achieve. At the same time, calibration relies on environmental temperature control, if the environmental temperature cannot be very accurately controlled during calibration or trimming, this will cause temperature errors to be introduced into the measurement value, ultimately leading to errors in calibration or trimming 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 lifetime and mechanical stress. However, a single battery management chip needs to consider the following two characteristics of the Zener diode: 1. The (positive) temperature coefficient of the Zener diode is about 1.5 mV / K, which means that during production testing, a temperature control instrument with better than 1 K accuracy 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 measurement. 2. Buried Zener diodes with good stability usually have a breakdown voltage of about 5.6 V, which is much higher than the typical lithium-ion battery voltage (depending on the technology of about 2.5-4.5 V), which means that the Zener diode will have to be powered by a charge pump, and also means that the operating current of the Zener diode and other circuits connected to high voltage should be low enough to minimize the area of the charge pump.

[0026] One possible way to reduce the temperature coefficient of the Zener diode is to subtract ΔV be from the Zener voltage, because ΔV beThe voltage also has a positive temperature coefficient; by subtracting it from the Zener diode (which also has a positive temperature coefficient), the desired flat temperature profile can be obtained. (With V) be The absolute values ​​of the voltages are opposite, ΔV be The voltage is very stable in terms of lifespan and mechanical stress.

[0027] This embodiment is based on a Zener diode voltage reference circuit, using a Zener diode to create V. be and ΔV be Thus, V be and ΔV be It will be more stable in terms of stability and stress during its lifespan, without using any external two-stage transistors, and uses a resistor divider network to subtract n times ΔV from the output voltage of the Zener diode resistor divider. be The function.

[0028] refer to Figure 2 As shown, the current is drawn from the resistor divider network by connecting a branch in parallel with the resistor to ground. V s As a voltage source, V1 and V2 are node voltages or node names. It can be seen that resistors r3 and r4 receive current from node V1 that should have originally flowed through resistor r2. Therefore, the voltage at the first node changes, being subtracted by a value.

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

[0030] The output voltage Vref at this time

[0031]

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

[0033] Assume that Zener diode Z1 has a temperature coefficient k znr Its relationship with temperature is as follows:

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

[0035] Substituting equation (2) into equation (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 For saturation current, VBE is the voltage between the base and the emitter of the triode, n is the exponential ideal factor, V T is the thermal voltage.

[0038] V BE may be expressed as

[0039]

[0040] The voltage between A and B is ΔV be may be expressed as:

[0041]

[0042] The relationship between the voltage difference between A and B 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, the embodiment provides a voltage reference circuit based on Zener diode, as shown in the reference Figure 5 The current It is drawn from the first end of the resistor R3, and then ΔV beThe two-stage transistor is replaced by a Zener diode, and the circuit is connected to the resistance R3. The entire voltage reference circuit includes: a power supply unit, the positive voltage output 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. The resistance R1, the resistance R2, and the resistance R3 form a series branch, wherein the first end of the resistance R1 is grounded, the second end of the resistance R1 is connected to the first end of the resistance R2, the second end of the resistance R2 is connected to the first end of the resistance R3, the second end of the resistance R3 is connected to the negative electrode of the Zener diode Z1, and the voltage at the second end of the resistance R1 is taken as the output voltage of the voltage reference circuit. The voltage compensation circuit includes the common-gate transistors M13 and M14, the common-gate transistors M11 and M12, the sources of the transistors M13 and M14 are both connected to the first end of the resistance 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 resistance Rd, and the negative electrode of the Zener diode Z5 is grounded. The operational amplifier OPA2, the non-inverting input of the operational amplifier OPA2 is connected to the positive electrode of the Zener diode Z4, the inverting input of the operational amplifier OPA2 is connected to the source of the transistor M12, and the output of the operational amplifier OPA2 is connected to the gate of the transistor M11.

[0046] In the embodiment, the improved voltage compensation circuit is introduced to compensate the reference voltage, so that the output voltage of the voltage reference circuit is more stable.

[0047] In the embodiment, the power supply unit includes: the first current mirror composed of the common-gate transistors M1 and M2, the voltage output of the first current mirror is connected to the input of the charge pump, and the second current mirror composed of the transistors M6 and M9, the sources of the transistors M6 and M9 are both connected to the output of the charge pump, and the drain of the transistor M9 is connected to the negative electrode of the Zener diode Z1. More preferably, the output voltage of the charge pump is 7V-10V.

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

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

[0050] Specifically, the current compensation loop comprises: 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 pole 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, and the drain of the transistor M4 is connected to the gate thereof and connected to the positive pole of the Zener diode Z2, and the negative pole of the Zener diode Z2 is connected to the drain of the transistor M6. A transistor M7, the positive and negative poles of the current source I1 are connected to the drain and source of the transistor M7, respectively. A transistor M8, the drain of the transistor M8 is grounded through a resistor Rc, and the source of the transistor M8 is connected to the source of the transistor M7. An operational amplifier OPA1, the output of the operational amplifier OPA1 is connected to the gate of the transistor M7 and the gate of the transistor M8, respectively, the inverting input of the operational amplifier OPA1 is connected to the drain of the transistor M8, and the non-inverting input is connected to the first end of the resistor R2.

[0051] Since the resistance varies greatly with the manufacturing process deviation, the resistance branch composed of the resistor R3, the resistor R2 and the resistor R1 will shunt the current on the Zener diode Z1 due to the manufacturing deviation, and will also slightly affect the direct current voltage output by the Zener diode Z1, so the current compensation loop composed of the transistor M1, the transistor M2, the transistor M5, the transistor M3, the transistor M4, the current source I1, the transistor M7, the transistor M8, the resistor Rc, the operational amplifier OPA1 and the transistor M10 is needed to detect the average current at the output voltage Vref to adjust the voltage of the charge pump and thus adjust the current through the Zener diode Z1.

[0052] The voltage reference circuit based on the Zener diode of the embodiment further comprises a transistor M10, the drain of the transistor M10 is connected to the inverting input of the operational amplifier OPA1, the source of the transistor M10 is connected to the positive pole of the diode Z3, and the negative pole of the diode Z3 is grounded. More preferably, the diode Z3 is a Zener diode.

[0053] To compensate for the variation of the resistance current branch, compensation is needed on the feedback path. In the semiconductor manufacturing process, the transistor is a surface element, and the Zener diode is a deep-embedded element. The surface element is subjected to a greater change in electrical parameters under stress than the deep-embedded element, so the compensation circuit uses a Zener diode.

[0054] Having described the basic concepts, it is obvious that the above-described disclosure of the application is merely meant to be exemplary and not restrictive of the application. Although not explicitly described, various modifications, improvements, and changes can be made to the application by those skilled in the art. Such modifications, improvements, and changes are contemplated by the present application and are still within the spirit and scope of the exemplary embodiments of the present application.

[0055] Also, the present application has used certain language which could be construed as limiting the application to the specific embodiments described. It is emphasized and should be construed that "one embodiment," "an embodiment," and / or "some embodiments" of the present application refer to some but not necessarily all possible embodiments of the present application. Furthermore, to the extent that the application does not require a particular feature of any of the claims, the application should not be limited to embodiments that include that feature.

[0056] Although the present application has been described with reference to the current exemplary embodiments, it is apparent that equivalent changes and modifications can be applied to the present application without departing from the spirit and scope of the application. Therefore, the above-described embodiments are merely meant to be illustrative of the present application and the scope of the present application should be limited only by the claims.

Claims

1. A Zener diode based voltage reference circuit, characterized by, The application relates to a voltage reference circuit, comprising: a power supply unit, a negative electrode of a Zener diode Z1 being connected to a positive voltage output end of the power supply unit, and a positive electrode of the Zener diode Z1 being grounded; the power supply unit comprises a first current mirror composed of a common-gate transistor M1 and a common-gate transistor M2, a voltage output end of the first current mirror being connected to an input end of a charge pump, and the power supply unit further comprises a second current mirror composed of a transistor M6 and a transistor M9, source electrodes of the transistor M6 and the transistor M9 being both connected to an output end of the charge pump, and a drain electrode of the transistor M9 being connected to a negative electrode of the Zener diode Z1; a series branch composed of a resistor R1, a resistor R2 and a resistor R3, wherein a first end of the resistor R1 is grounded, a second end of the resistor R1 is connected to a first end of the resistor R2, a second end of the resistor R2 is connected to a first end of the resistor R3, and a second end of the resistor R3 is connected to a negative electrode of the Zener diode Z1; a voltage at the second end of the resistor R1 is taken as an output voltage of the voltage reference circuit; a voltage compensation circuit, the voltage compensation circuit comprising: a common-gate transistor M13 and a common-gate transistor M14, and a common-gate transistor M11 and a common-gate transistor M12; source electrodes of the common-gate transistor M13 and the common-gate transistor M14 are both connected to the first end of the resistor R3, a drain electrode of the common-gate transistor M13 is connected to a gate electrode of the common-gate transistor M13 and a drain electrode of the common-gate transistor M11, a source electrode of the common-gate transistor M11 is connected to a positive electrode of a Zener diode Z4, and a negative electrode of the Zener diode Z4 is grounded; a source electrode of the common-gate transistor M12 is connected to a positive electrode of a Zener diode Z5 through a resistor Rd, and a negative electrode of the Zener diode Z5 is grounded; an operational amplifier OPA2, a non-inverting input end of the operational amplifier OPA2 being connected to the positive electrode of the Zener diode Z4, an inverting input end of the operational amplifier OPA2 being connected to the source electrode of the common-gate transistor M12, and an output end of the operational amplifier OPA2 being connected to the gate electrode of the common-gate transistor M11; the voltage compensation circuit further comprises a current compensation loop, the current compensation loop being configured to detect an average current at the second end of the resistor R1 so as to adjust the output voltage of the charge pump.

2. The Zener diode-based voltage reference circuit of claim 1, wherein, The output voltage of the charge pump is 7V-10V.

3. The Zener diode-based voltage reference circuit of claim 1, wherein, The current compensation loop comprises: a transistor M5, a drain electrode of the transistor M5 being connected to a drain electrode of the transistor M1, and a source electrode of the transistor M5 being grounded; a transistor M3, a drain electrode of the transistor M3 being connected to a positive electrode of a current source I1 and a gate electrode of the transistor M5, and a source electrode of the transistor M3 being grounded; a transistor M4, a gate electrode of the transistor M4 being connected to a gate electrode of the transistor M3, a source electrode of the transistor M4 being grounded, and a drain electrode of the transistor M4 being connected to the gate electrode of the transistor M4 and a positive electrode of a Zener diode Z2, and a negative electrode of the Zener diode Z2 being connected to a drain electrode of the transistor M6; a transistor M7, a positive electrode of the current source I1 being connected to a drain electrode of the transistor M7, and a negative electrode of the current source I1 being connected to a source electrode of the transistor M7; a transistor M8, a drain electrode of the transistor M8 being connected to the source electrode of the transistor M7 through a resistor Rc, and a source electrode of the transistor M8 being grounded. An operational amplifier OPA1, an output terminal of the operational amplifier OPA1 is connected to a gate of the transistor M7 and a gate of the transistor M8 respectively, an inverting input terminal of the operational amplifier OPA1 is connected to a drain of the transistor M8, and a non-inverting input terminal is connected to a first terminal of the resistor R2.

4. The Zener diode-based voltage reference circuit of claim 3, wherein, Further comprising a transistor M10, a drain of the transistor M10 is connected to the inverting input terminal of the operational amplifier OPA1, a source of the transistor M10 is connected to a positive electrode of a diode Z3, and a negative electrode of the diode Z3 is grounded.

5. The Zener diode-based voltage reference circuit of claim 4, wherein, The diode Z3 is a Zener diode.

Images