Band-gap reference circuit high in precision, capable of loading and fast in starting
By designing differential amplification module and reference voltage generation module in the bandgap reference circuit, and using the dynamic adjustment technology of voltage feedback, the problem of traditional bandgap reference circuits cannot carry loads and output instability is solved, achieving high-precision, load-bearing and fast start-up effects.
Patent Information
- Application Number
- CN202411665396.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-20
- Publication Date
- 2025-02-28
AI Technical Summary
Traditional bandgap reference circuits have the problem of error amplifier offset voltage amplification, and cannot carry load, the reference output voltage is unstable, and the establishment and shutdown speeds are slow.
A bandgap reference circuit including a differential amplification module and a reference voltage generation module is designed. Through dynamic adjustment of voltage feedback, the differential amplification module can adjust the stability of the reference voltage VREF to achieve accurate adjustment and dynamic stability.
It realizes a high-precision, load-bearing and fast start-up bandgap reference circuit, which can adapt to load changes and power supply fluctuations, and improves load capacity and output accuracy.
Smart Images
Figure CN119536442A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of reference voltage circuits, and in particular relates to a high-precision, loadable, and fast-starting bandgap reference circuit. Background Art
[0002] Bandgap reference circuits are widely used in circuit design because they have the following advantages: small fluctuations in reference output when the process changes, small fluctuations in reference output when the power supply changes, and small fluctuations in reference output when the temperature changes. They are particularly suitable for circuits that require high reference accuracy. Taking a low-dropout linear regulator (hereinafter referred to as LDO) as an example, the output voltage VOUT is a multiple of the reference voltage, so the characteristics of the reference voltage VREF largely determine the characteristics of the output voltage.
[0003] like Figure 1 The figure shows the circuit diagram of a traditional bandgap reference circuit. The circuit uses an error amplifier A. Therefore, the offset voltage of the error amplifier will be amplified to the output voltage of the reference circuit. In addition, the reference output voltage cannot carry a load, which will affect the value of the output voltage. The reference establishment and shutdown speeds are slow. Summary of the invention
[0004] In view of the above problems in the prior art, the purpose of the present invention is to provide a high-precision, loadable, and fast-starting bandgap reference circuit. Through the dynamic adjustment design of voltage feedback, the differential amplifier module can adjust and stabilize the reference voltage VREF generated by the reference voltage generation module, thereby achieving precise adjustment and dynamic stability.
[0005] A high-precision, loadable, and fast-starting bandgap reference circuit comprises a differential amplifier module and a reference voltage generation module, wherein the reference voltage generation module is connected to a bias current to generate a reference voltage VREF and a feedback signal VP and a feedback signal VN; the differential amplifier module comprises a transistor Q3, a transistor Q4, a transistor Q5, and a MOS transistor NM6, wherein the transistor Q3 and the transistor Q4 are used as input ends of the differential amplifier module to receive a feedback signal VN and a feedback signal VP respectively and perform differential amplification on the two feedback signals, wherein the MOS transistor NM6 is used to perform secondary amplification on an output signal outputted after differential amplification of the transistors Q3 and Q4 and output an adjustment signal, wherein the adjustment signal indirectly adjusts the bias current connected to the reference voltage generation module through the transistor Q5, thereby adjusting the reference voltage VREF generated by the reference voltage generation module to be stable at a target value, thereby realizing dynamic adjustment of voltage feedback.
[0006] Preferably, the collector of the transistor Q3 is connected to the drain of the MOS transistor PM3, the collector of the transistor Q4 is connected to the drain of the MOS transistor PM4, the emitter of the transistor Q3 is connected to the emitter of the transistor Q4 and connected to the drain of the MOS transistor NM5, the base of the transistor Q3 is connected to the feedback signal VN, the base of the transistor Q4 is connected to the feedback signal VP, the source of the MOS transistor NM5 is grounded, the gate of the MOS transistor NM5 is connected to the collector of the transistor Q3, and the MOS transistor PM3 and the MOS transistor PM4 respectively mirror the current on the MOS transistor PM2.
[0007] Preferably, the collector of the transistor Q4 is also connected to the gate of the MOS transistor NM6, the source of the MOS transistor NM6 is grounded, the drain of the MOS transistor NM6 is connected to the drain of the MOS transistor PM5, and the MOS transistor PM5 mirrors the bias current on the MOS transistor PM1; the drain of the MOS transistor NM6 is also connected to the base of the transistor Q5, the collector of the transistor Q5 is grounded, and the emitter of the transistor Q5 is connected to the reference voltage generation module, which is used to adjust the bias current connected to the reference voltage generation module.
[0008] Preferably, the differential amplifier module further includes a MOS tube NM3 and a MOS tube NM4, the gates of the MOS tube NM3 and the MOS tube NM4 are respectively connected to the external bias voltage VBIASN1 and the external bias voltage VBIASN2, the source of the MOS tube NM3 is grounded, the drain of the MOS tube NM3 is connected to the source of the MOS tube NM4, the drain of the MOS tube NM4 is connected to the gate and drain of the MOS tube PM2 and the gate of the MOS tube PM3 and the gate of the MOS tube PM4, and the source of the MOS tube PM2, the source of the MOS tube PM3 and the MOS tube PM4 are all connected to the power supply voltage VDD.
[0009] Preferably, a capacitor C1 is further connected between the gate and drain of the MOS transistor NM6 to improve the stability of the circuit.
[0010] Preferably, the reference voltage generating module includes a transistor Q6, a resistor R3, a resistor R4, and a resistor R5, wherein the resistor R3, the resistor R4, and the resistor R5 are connected in series in sequence, one end of the resistor R5 is connected to the MOS tube PM6 and the emitter of the transistor Q5, the other end of the resistor R3 is connected to the base and the collector of the transistor Q6, and the emitter of the transistor Q6 is grounded; the circuit between the resistor R5 and the resistor R4 outputs a feedback signal VN, and the feedback signal VP is output between the resistor R4 and the resistor R3.
[0011] Preferably, the ratio of the number of transistors Q3 and Q4 in the differential amplifier module is set to 1:k, and the ratio of the number of MOS transistors PM3 and PM4 is set to m:1, then the reference voltage VREF generated by the reference voltage generation module is VBE6 +V T *ln(k*m)*(1+R3 / R4+R5 / R4).
[0012] Preferably, the bias current is generated by MOS transistor NM1, MOS transistor NM2, and MOS transistor PM1, the gate of the MOS transistor NM1 is connected to the external bias voltage VBIASN1, the source is grounded, and the drain is connected to the source of the MOS transistor NM2, the gate of the MOS transistor NM2 is connected to the external bias voltage VBIASN2, the drain of the MOS transistor NM2 is connected to the gate and drain of the MOS transistor PM1 and the gate of the MOS transistor PM5 and the gate of the MOS transistor PM6, and the source of the MOS transistor PM1, the source of the MOS transistor PM5, and the source of the MOS transistor PM6 are all connected to the power supply voltage VDD.
[0013] The beneficial effects of the present invention are as follows: the high-precision, loadable, fast-starting bandgap reference circuit enables the differential amplifier module to adjust and stabilize the reference voltage VREF generated by the reference voltage generation module through the dynamic adjustment design of voltage feedback, thereby achieving precise adjustment and dynamic stability.
[0014] Furthermore, by adjusting the stability of the reference voltage VREF output by the reference voltage generation module through a circuit structure combining direct bias current control and indirect transistor Q5 control, the reference voltage generation module can adapt to load changes and power supply fluctuations, which is beneficial to improving its load capacity and output accuracy.
[0015] In addition, by setting capacitor C2 in the reference voltage generation module, the instantaneous charging characteristics of the capacitor are used to achieve the purpose of fast startup, thereby improving the response speed and stability of the circuit; on the other hand, transistor Q5 can quickly lower the reference voltage VREF when the bias current or the power supply voltage is not working, thereby achieving the purpose of fast shutdown. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:
[0017] Figure 1 It is a circuit diagram of the prior art involved in the present invention.
[0018] Figure 2 It is a circuit diagram of the present invention. DETAILED DESCRIPTION
[0019] Embodiment 1
[0020] like Figure 2As shown, a high-precision, loadable, and fast-starting bandgap reference circuit includes a differential amplifier module and a reference voltage generation module. The reference voltage generation module is connected to a bias current to generate a reference voltage VREF and a feedback signal VP and a feedback signal VN; the differential amplifier module outputs an adjustment signal according to the input feedback signal VP and the feedback signal VN, which is used to adjust the reference voltage VREF generated by the reference voltage generation module to be constant at a target value.
[0021] like Figure 2 As shown, the differential amplifier module includes MOS transistors NM3, NM4, NM5, NM6, PM2, PM3, PM4, PM5, triodes Q3, Q4 and Q5, and capacitor C1.
[0022] Among them, the gate of the MOS tube NM3 is connected to the external bias voltage VBIASN1, the source is grounded, the drain is connected to the source of the MOS tube NM4, the gate of the MOS tube NM4 is connected to the external bias voltage VBIASN2, the drain of the MOS tube NM4 is connected to the gate and drain of the MOS tube PM2 and the gate of the MOS tube PM3 and the gate of the MOS tube PM4, the source of the MOS tube PM2, the source of the MOS tube PM3 and the MOS tube PM4 are all connected to the power supply voltage VDD, the drain of the MOS tube PM3 is connected to the collector of the transistor Q3, and the drain of the MOS tube PM4 is connected to the collector of the transistor Q4.
[0023] Specifically, MOS tubes NM3 and NM4 are both NMOS tubes, and external bias voltages VBIASN1 and VBIASN2 are used to set gate voltages of MOS tubes NM3 and NM4, and determine the magnitude of current flowing through MOS tubes NM3 and NM4. MOS tubes PM2, PM3 and PM4 are all PMOS tubes, and MOS tubes PM2, PM3 and PM4 form a current mirror structure. The current generated by MOS tubes NM3 and NM4 passes through MOS tube PM2 and is mirrored to MOS tubes PM3 and PM4, thereby affecting the collector currents of transistors Q3 and Q4, and are used for reference voltage adjustment.
[0024] like Figure 2 As shown, the emitter of the transistor Q3 is connected to the emitter of the transistor Q4 and connected to the drain of the MOS transistor NM5, the base of the transistor Q3 is connected to the feedback signal VN, the base of the transistor Q4 is connected to the feedback signal VP, the source of the MOS transistor NM5 is grounded, and the gate of the MOS transistor NM5 is connected to the collector of the transistor Q3.
[0025] Transistors Q3 and Q4 are PNP transistors. Transistors Q3 and Q4 are used as the input terminals of the first-stage amplifier to differentially amplify the feedback signal VN and the feedback signal VP generated by the reference voltage generation module. Since the transconductance of transistors Q3 and Q4 is relatively large, they are more sensitive to input errors and can effectively reduce error offset, thereby improving the accuracy of the generated reference voltage VREF. Among them, MOS transistor NM5 is an NMOS transistor, which serves as a current source for transistors Q3 and Q4 to provide a stable current.
[0026] like Figure 2 As shown, the collector of the transistor Q4 is also connected to the gate of the MOS transistor NM6, the source of the MOS transistor NM6 is grounded, and the drain of the MOS transistor NM6 is connected to the drain of the MOS transistor PM5. Among them, the MOS transistor PM5 is a PMOS transistor, and the MOS transistor PM5 and the MOS transistor PM1 form a current mirror structure. The MOS transistor PM5 replicates the bias current on the MOS transistor PM1 and provides a stable current for the MOS transistor NM6, ensuring the position of the zero pole of the error amplifier and providing a reasonable phase margin, thereby ensuring the stability of the entire system. In addition, a capacitor C1 is also connected between the gate and the drain of the MOS transistor NM6, and Miller compensation is performed through the capacitor C1 to improve the stability of the system.
[0027] On the other hand, the drain of MOS transistor NM6 is also connected to the base of transistor Q5, the collector of transistor Q5 is grounded, and the emitter of transistor Q5 is connected to the reference voltage generation module. Among them, transistor Q5 is a PNP transistor, the emitter of transistor Q5 is also connected to the drain of MOS transistor PM6, MOS transistor PM6 and MOS transistor PM1 form a current mirror structure, MOS transistor PM6 copies the bias current on MOS transistor PM1, when the bias current or the power supply voltage VDD is not working, transistor Q5 can quickly pull down the reference voltage VREF to achieve the purpose of rapid shutdown.
[0028] MOS tube NM6 is an NMOS tube. MOS tube NM6 is used as a second-stage amplifier to perform secondary amplification on the output signal output after differential amplification of transistors Q3 and Q4. The output signal of MOS tube NM6 is used as an adjustment signal output by the differential amplifier module to adjust the reference voltage generation module.
[0029] The bias current on the MOS transistor PM1 is generated by the MOS transistor NM1, the MOS transistor NM2, the external bias voltage VBIASN1 and the external bias voltage VBIASN2. Specifically, the gate of the MOS transistor NM1 is connected to the external bias voltage VBIASN1, the source is grounded, the drain is connected to the source of the MOS transistor NM2, the gate of the MOS transistor NM2 is connected to the external bias voltage VBIASN2, the drain of the MOS transistor NM2 is connected to the gate and drain of the MOS transistor PM1, the gate of the MOS transistor PM5, and the gate of the MOS transistor PM6, and the source of the MOS transistor PM1, the source of the MOS transistor PM5, and the source of the MOS transistor PM6 are all connected to the power supply voltage VDD.
[0030] Among them, MOS tube NM1 and MOS tube NM2 are NMOS tubes, which are used to provide a constant bias current according to an external bias voltage to form a reference current. MOS tube PM1, MOS tube PM5, and MOS tube PM6 are PMOS tubes, and a current mirror structure is formed between the three, so that MOS tube PM5 and MOS tube PM6 can accurately mirror the bias current flowing through MOS tube PM1.
[0031] Among them, MOS tube PM5 is used to provide a stable current for MOS tube NM6, and MOS tube PM6 is used to transmit a stable bias current to the reference voltage generation module. The size of the mirror current on MOS tube PM6 can be adjusted by adjusting the parameter ratio between MOS tube PM6 and MOS tube PM1, so as to adjust the number of MOS tubes PM6 to adjust the size of the mirror current to adapt to different load capacity requirements, and can effectively improve the accuracy and stability of the reference voltage.
[0032] The reference voltage generation module includes a transistor Q6, a resistor R3, a resistor R4, and a resistor R5. The resistors R3, R4, and R5 are connected in series in sequence, one end of the resistor R5 is connected to the MOS tube PM6 and the emitter of the transistor Q5, the other end of the resistor R3 is connected to the base and collector of the transistor Q6, and the emitter of the transistor Q6 is grounded. The circuit between the resistor R5 and the resistor R4 outputs a feedback signal VN, and the resistor R4 and the resistor R3 output a feedback signal VP, and the feedback signal VN and the feedback signal VP are used as input signals of the differential amplifier module.
[0033] Transistor Q6, as the core component of the reference voltage generation module, is controlled by the adjustment signal of the differential amplifier module to output the corresponding reference voltage VREF. When the reference voltage VREF deviates from the target value, the adjustment signal output by the differential amplifier module can be dynamically adjusted according to the feedback signal VN and the feedback signal VP to make the reference voltage VREF return to the target value.
[0034] For the differential amplifier module, the ratio of the number of transistors Q3 and Q4 is set to 1:k, and the ratio of the number of MOS tubes PM3 and PM4 is set to m:1. Since the amplification factor of the differential amplifier module is large and the base current can be ignored, the reference voltage VREF is V BE6 +V T *ln(k*m)*(1+R3 / R4+R5 / R4), that is, V REF =V BE6 +V T *ln(k*m)*(1+R3 / R4+R5 / R4). Among them, V BE6 is the difference between the base voltage and emitter voltage of transistor Q6, V T is the thermal voltage, V T ≈26mv. By setting the values of k and m and the ratio of the resistors R3, R4 and R5, different bandgap reference voltage values can be obtained.
[0035] It should be noted that, in order to realize the rapid startup of the circuit, a capacitor C2 is provided, and one end of the capacitor C2 is connected to one end of the resistor R5, the drain of the MOS tube PM6, and the emitter of the transistor Q5. By utilizing the instantaneous charging characteristics of the capacitor, a large instantaneous current is provided when the circuit is started, which speeds up the process of establishing the reference voltage and bias current, improves the response speed of the circuit, and improves the stability of the circuit.
[0036] Specifically, when the circuit starts, capacitor C2 starts to charge. Since capacitor C2 has a lower voltage in the initial state, it absorbs a larger instantaneous current, which pushes the reference voltage VREF to rise rapidly through various components in the circuit, so that the reference voltage VREF quickly reaches a target value close to stability, thereby improving the startup speed and stability of the circuit. As the charging process proceeds, the voltage on capacitor C2 gradually increases, and the charging current gradually decreases. When the voltage of capacitor C2 approaches the final value, the charging current gradually approaches zero. At this time, the startup process is completed, the circuit enters a stable working state, and capacitor C2 no longer has a significant impact on the circuit.
[0037] Working principle: This high-precision, loadable, fast-starting bandgap reference circuit, when started, generates a bias current on the MOS tube PM1 through the external bias voltage VBIASN1 and the external bias voltage VBIASN2, and the MOS tube PM6 and the MOS tube PM1 form a current mirror structure to mirror the bias current on the MOS tube PM1, so that the reference voltage generation module generates the corresponding reference voltage VREF and the feedback signal VP and the feedback signal VN.
[0038] During the startup process, the instantaneous charging characteristics of capacitor C2 are used to speed up the process of establishing the reference voltage and bias current, thereby achieving rapid startup of the circuit.
[0039] When the reference voltage VREF deviates from the target value, the feedback signal VP and the feedback signal VN are connected to the differential amplifier module, and differential amplification is performed through transistors Q3 and Q4, and secondary amplification is performed through MOS tube NM6. The output signal of MOS tube NM6 indirectly adjusts the bias current connected to the reference voltage generation module through transistor Q5, thereby adjusting the generated reference voltage VREF to stabilize at the target value, and realizing dynamic adjustment of voltage feedback. Among them, when the bias current or the power supply voltage VDD is not working, the transistor Q5 can quickly pull down the reference voltage VREF to achieve the purpose of rapid shutdown.
[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A high-precision, loadable, fast-starting bandgap reference circuit, characterized in that: The invention comprises a differential amplifier module and a reference voltage generation module. The reference voltage generation module is connected to a bias current to generate a reference voltage VREF and a feedback signal VP and a feedback signal VN. The differential amplifier module comprises a transistor Q3, a transistor Q4, a transistor Q5 and a MOS transistor NM6. The transistor Q3 and the transistor Q4 are used as input ends of the differential amplifier module to receive a feedback signal VN and a feedback signal VP respectively and perform differential amplification on the two feedback signals. The MOS transistor NM6 is used to perform secondary amplification on the output signal outputted by the transistor Q3 and the transistor Q4 after differential amplification and output an adjustment signal. The adjustment signal indirectly adjusts the bias current connected to the reference voltage generation module through the transistor Q5, thereby adjusting the reference voltage VREF generated by the reference voltage generation module to be stable at a target value, thereby realizing dynamic adjustment of voltage feedback.
2. The high-precision, loadable, fast-starting bandgap reference circuit according to claim 1, characterized in that: The collector of the transistor Q3 is connected to the drain of the MOS transistor PM3, the collector of the transistor Q4 is connected to the drain of the MOS transistor PM4, the emitter of the transistor Q3 is connected to the emitter of the transistor Q4 and connected to the drain of the MOS transistor NM5, the base of the transistor Q3 is connected to the feedback signal VN, the base of the transistor Q4 is connected to the feedback signal VP, the source of the MOS transistor NM5 is grounded, the gate of the MOS transistor NM5 is connected to the collector of the transistor Q3, and the MOS transistor PM3 and the MOS transistor PM4 respectively mirror the current on the MOS transistor PM2.
3. The high-precision, loadable, fast-starting bandgap reference circuit according to claim 1, characterized in that: The collector of the transistor Q4 is also connected to the gate of the MOS transistor NM6, the source of the MOS transistor NM6 is grounded, the drain of the MOS transistor NM6 is connected to the drain of the MOS transistor PM5, and the MOS transistor PM5 mirrors the bias current on the MOS transistor PM1; The drain of the MOS transistor NM6 is also connected to the base of the transistor Q5, the collector of the transistor Q5 is grounded, and the emitter of the transistor Q5 is connected to the reference voltage generation module for adjusting the bias current connected to the reference voltage generation module.
4. The high-precision, loadable, fast-starting bandgap reference circuit according to claim 2, characterized in that: The differential amplifier module also includes a MOS transistor NM3 and a MOS transistor NM4. The gates of the MOS transistor NM3 and the MOS transistor NM4 are respectively connected to the external bias voltage VBIASN1 and the external bias voltage VBIASN2. The source of the MOS transistor NM3 is grounded. The drain of the MOS transistor NM3 is connected to the source of the MOS transistor NM4. The drain of the MOS transistor NM4 is connected to the gate and drain of the MOS transistor PM2 and the gate of the MOS transistor PM3 and the gate of the MOS transistor PM4. The source of the MOS transistor PM2, the source of the MOS transistor PM3 and the MOS transistor PM4 are all connected to the power supply voltage VDD.
5. The high-precision, loadable, fast-starting bandgap reference circuit according to claim 1, characterized in that: A capacitor C1 is also connected between the gate and drain of the MOS transistor NM6 to improve the stability of the circuit.
6. The high-precision, loadable, fast-starting bandgap reference circuit according to claim 1, characterized in that: The reference voltage generation module includes a transistor Q6, a resistor R3, a resistor R4, and a resistor R5, wherein the resistors R3, R4, and R5 are connected in series in sequence, one end of the resistor R5 is connected to the MOS tube PM6 and the emitter of the transistor Q5, the other end of the resistor R3 is connected to the base and collector of the transistor Q6, and the emitter of the transistor Q6 is grounded; The circuit between the resistor R5 and the resistor R4 outputs a feedback signal VN, and the circuit between the resistor R4 and the resistor R3 outputs a feedback signal VP.
7. The high-precision, loadable, fast-starting bandgap reference circuit according to claim 2, characterized in that: The ratio of the number of transistors Q3 and Q4 in the differential amplifier module is set to 1:k, and the ratio of the number of MOS transistors PM3 and PM4 is set to m:
1. Then the reference voltage VREF generated by the reference voltage generation module is V BE6 +V T *ln(k*m)*(1+R3 / R4+R5 / R4).
8. The high-precision, loadable, fast-starting bandgap reference circuit according to claim 1, characterized in that: The bias current is generated by MOS transistor NM1, MOS transistor NM2, and MOS transistor PM1. The gate of the MOS transistor NM1 is connected to the external bias voltage VBIASN1, the source is grounded, and the drain is connected to the source of the MOS transistor NM2. The gate of the MOS transistor NM2 is connected to the external bias voltage VBIASN2. The drain of the MOS transistor NM2 is connected to the gate and drain of the MOS transistor PM1 and the gate of the MOS transistor PM5 and the gate of the MOS transistor PM6. The source of the MOS transistor PM1, the source of the MOS transistor PM5, and the source of the MOS transistor PM6 are all connected to the power supply voltage VDD.