CN117873259A - A stable linear power supply circuit - Google Patents

Abstract

The invention discloses a stable linear power supply circuit, and relates to the field of power supply control; the stable linear power supply circuit can generate positive temperature coefficient current and negative temperature coefficient voltage through the branch circuit of the band gap reference circuit where the Q2 transistor is located, reduces a bipolar transistor based on the traditional band gap reference circuit structure, and the layout area occupied by the bipolar transistor in the whole band gap is the largest, so that the layout area of the whole circuit can be effectively reduced when the layout is finally drawn, the cost of circuit realization is better controlled, meanwhile, the current limiting protection circuit and the anti-surge current protection circuit are integrated by utilizing the switching effect of the MOS transistor in an intelligent control mode, and the starting rate of a grid electrode of a power tube is controlled by adopting a staged starting strategy, so that the system is in soft start during power-on, and the intelligent protection of current limiting and anti-surge current is realized.

Description

A stable linear power supply circuit

Technical Field

The invention relates to power supply control technology, and in particular to a stable linear power supply circuit.

Background technique

For analog integrated circuits, the quality of their performance depends on many factors, among which the quality of the power supply is also a key factor affecting the performance of analog integrated circuits, especially some high-precision analog circuits, such as high-precision analog-to-digital converters (ADCs), high-precision digital-to-analog converters (DACs), instrumentation amplifiers, etc. These circuits usually require a high-quality power supply, usually a linear power supply (LDO). The main functions of LDO are to perform voltage conversion and filter out noise on the power supply.

At present, linear power management technology has gradually matured. Switching power supplies are widely welcomed due to their high conversion efficiency and adjustable step-up and step-down voltages. However, linear power controllers have high switching noise due to their switching frequency, complex peripheral devices, and relatively high costs.

Summary of the invention

The object of the present invention is to provide a stable linear power supply circuit to solve the above-mentioned deficiencies in the prior art.

In order to achieve the above object, the present invention provides the following technical solution: a stable linear power supply circuit, comprising:

A bandgap reference circuit, the bandgap reference circuit is used to provide a reference voltage source desensitized to voltage and temperature fluctuations to the negative input terminal of the error amplifier;

A current bias circuit, which is used to provide a suitable bias voltage to other circuits in the system, generate a current source that does not fluctuate with the voltage on the power supply, and make the transistors in the circuit all at a suitable DC operating point;

An error amplifier, which is used to amplify the difference between the reference voltage generated by the bandgap reference circuit and the feedback voltage of the node in the feedback network. The output end of the error amplifier is connected to the gate of the power tube. The power tube can be controlled by adjusting the gate voltage through feedback to complete the voltage stabilization function.

An enabling control circuit, the enabling control circuit being used to enable and disable circuit functions in the chip;

An overshoot suppression circuit, which is used to enhance the transient response characteristics of the linear regulator and prevent overvoltage or transient noise at the input terminal from penetrating the entire circuit system;

A feedback resistor, wherein the feedback resistor is used to construct a feedback network through a resistor;

A power device, wherein the power device is used to provide a stable output current and voltage;

Over-temperature protection circuit, the over-temperature protection circuit is used to output a control signal when the chip temperature is too high and exceeds the preset temperature value, and shut down the circuit in time through the enabling logic; when the temperature drops to within the preset value range, the output control signal is reversed, and the chip starts working again to achieve the function of protecting the chip. This makes the over-temperature protection circuit have a hysteresis function, shutting down the system at high temperature and resuming normal operation at low temperature;

An overcurrent protection circuit uses a resistor to detect an output current signal and converts it into a voltage signal for comparison with a reference voltage. The MOS tube switch function is used to adjust the parallel relationship between resistors to switch the working state of the protection circuit, thereby realizing an intelligent current limiting and surge current protection circuit.

Furthermore, the overcurrent protection circuit comprises:

A current detection module, which is composed of MP, resistors R1, R2, R3, R4, switches S1 and S2, wherein MP is connected in parallel with the output power tube, and the proportional mirror image I _OUT outputs the current;

COMP comparator, realizes the comparison between the voltage signal of L13 terminal and the reference voltage Vref, and outputs the gate signal drv_P for controlling the power tube. When the LDO works normally, L13 is high level, and the output drv_P is low level. When the current limiting protection circuit or the surge current protection circuit is started, the voltage of L13 decreases, the comparator jumps, the output drv_P is high level, and the power tube is turned off.

The FB voltage detection module is responsible for comparing VFB with the reference voltage resistor voltage Vref1 and outputting a signal L27. During the LDO startup phase or when the current limit returns to a smaller current value, VFB < Vref1, the output signal L27 is high level, and the control switch S1 is closed.

In the surge current protection module, when LDO starts and VFB>Vref1, S1 is closed to control the module to start delay. During the delay time, S2 is disconnected. When the delay ends, S2 is closed. After the delay ends, the normal operation of the current limiting protection circuit is not affected.

Furthermore, the power device selection requirement is to select a power device with the smallest internal resistance and capacitance while satisfying the output current and voltage difference.

Furthermore, when the startup circuit of the bandgap reference circuit starts to power on, when the output is 0, the gate voltages of the two MOS tubes M1 and M2 are close to VDD, and M7 in the startup circuit is turned on, then the gate of M5 is pulled to a low potential, and the M5 tube is turned on and generates current, so that the operational amplifier gets rid of the degeneracy point when the output is 0; when the Bandgap circuit works normally, the voltage at the output end of the operational amplifier will decrease, and this time the PMOS tube located in the inverter of the startup circuit will be turned on, that is, M6 is turned on, and M7 is turned off. At this time, the gate voltage of M5 is close to VDD, and M5 will be turned off. At this time, the startup circuit is separated from the reference circuit, and will not affect the normal operation of the bias circuit.

Furthermore, the enable control circuit includes a three-input AND gate circuit and an inverter circuit. The three-input AND gate uses a PMOS tube and an NMOS tube to be connected in a complementary manner. The gate is used as a logic signal input port and the input ports A, B, and C of the gate circuit are respectively connected to the pins Over_heat, Over_flow, and En_POWER, and the output end is connected to the enable pin EN. The input and output pins of the three-input AND gate and the inverter circuit are respectively connected to the circuit, and are connected to each module circuit to enable and control the opening and closing of the bandgap reference circuit, the error amplifier, the power tube, the overheat protection circuit, and the overcurrent protection circuit. When EN is at a high level, the system is turned on, otherwise, when EN is at a low level, the system is turned off.

Furthermore, the method for selecting the feedback resistor comprises the following steps:

A1, the value of the feedback resistor can be expressed as: ; Wherein R _f1 represents the first feedback resistor, R _f2 represents the first feedback resistor, I _Q represents the quiescent current of the power tube branch, and V _OUT represents the output voltage;

A2, based on the reference voltage V _REF , feedback voltage V _FB and output voltage V _OUT , the following expression can be written:

;

A3, and the current of the feedback resistor branch can be expressed as ; The quiescent current of the resistor is equal to the quiescent current of the PMOS power tube.

Furthermore, the overshoot suppression circuit is composed of M9-M15 and R5, and M15 is used as a capacitor. Its working principle is as follows: the resistance value of R5 is made larger, so that (W/L) ₁₁ >(W/L) ₁₂ , to ensure that the gate voltages of M11 and M12 are different. When the output generates a large overshoot voltage, the source voltage of the M12 tube will increase, and the gate voltage cannot change suddenly because it is connected in series with the capacitor M15. At this time, the M12 tube is turned on, the gate voltage of the M14 tube increases, and then Vout is pulled down to reduce the overshoot voltage. When the output voltage undershoots, M12 is turned off, its drain voltage is zero, and the M14 tube is also turned off.

Compared with the prior art, the present invention provides a stable linear power supply circuit, which can generate both a current with a positive temperature coefficient and a voltage with a negative temperature coefficient by setting a bandgap reference circuit in the branch where the Q2 transistor is located. On the basis of the traditional bandgap reference circuit structure, a bipolar transistor is reduced, and the layout area occupied by the bipolar transistor in the entire bandgap is the largest proportion. Such a design can effectively reduce the layout area of the entire circuit when the layout is finally drawn, and better control the cost of circuit implementation. At the same time, by utilizing the switching effect of the MOS tube and adopting an intelligent control method, the current limiting protection circuit and the surge current protection circuit are integrated, and a phased startup strategy is adopted to control the power tube gate startup rate, so that the system is soft-started when powered on, and the intelligent protection of current limiting and surge current is realized.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

FIG1 is a schematic diagram of the overall structure provided by an embodiment of the present invention;

FIG2 is a schematic diagram of the structure of an overcurrent protection circuit provided by an embodiment of the present invention;

FIG3 is a schematic diagram of the structure of an anti-surge current protection module provided in an embodiment of the present invention;

FIG4 is a schematic diagram of a bandgap reference circuit structure provided by an embodiment of the present invention;

FIG5 is a schematic diagram of the structure of an enabling control circuit provided in an embodiment of the present invention;

FIG. 6 is a schematic diagram of the structure of an overshoot suppression circuit provided in an embodiment of the present invention.

Detailed ways

In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

Please refer to FIG1-6, a stable linear power supply circuit includes:

A bandgap reference circuit, the bandgap reference circuit is used to provide a reference voltage source desensitized to voltage and temperature fluctuations to the negative input terminal of the error amplifier;

Current bias circuit, the current bias circuit is used to provide a suitable bias voltage to other circuits in the system, generate a current source that does not fluctuate with the voltage on the power supply, so that the transistors in the circuit are at a suitable DC operating point;

Error amplifier: The error amplifier is used to amplify the difference between the reference voltage generated by the bandgap reference circuit and the feedback voltage of the node in the feedback network. The output of the error amplifier is connected to the gate of the power tube. By adjusting the gate voltage through feedback, the power tube can be controlled to complete the voltage regulation function.

An enabling control circuit, the enabling control circuit is used to turn on and off the circuit functions in the chip;

Overshoot suppression circuit: The overshoot suppression circuit is used to enhance the transient response characteristics of the linear regulator and prevent overvoltage or transient noise at the input end from penetrating the entire circuit system;

Feedback resistor, feedback resistor is used to build a feedback network through resistor;

Power devices, which are used to provide stable output current and voltage;

Over-temperature protection circuit: When the chip temperature is too high and exceeds the preset temperature value, the over-temperature protection circuit outputs a control signal and shuts down the circuit in time through the enabling logic; when the temperature drops to within the preset value range, the output control signal flips, and the chip restarts to protect the chip. This makes the over-temperature protection circuit have a hysteresis function, shutting down the system at high temperature and resuming normal operation at low temperature;

Overcurrent protection circuit, the overcurrent protection circuit uses resistors to detect the output current signal, and converts it into a voltage signal to compare with the reference voltage. By using the MOS tube switch function, the parallel relationship between the resistors is adjusted to switch the working state of the protection circuit, thereby realizing a current limiting and surge current protection intelligent circuit.

The overcurrent protection circuit includes:

The current detection module is composed of MP, resistors R1, R2, R3, R4, switch S1 and switch S2. MP is connected in parallel with the output power tube, and the proportional mirror image I _OUT outputs the current.

COMP comparator, realizes the comparison between the voltage signal of L13 terminal and the reference voltage Vref, and outputs the gate signal drv_P for controlling the power tube. When the LDO works normally, L13 is high level, and the output drv_P is low level. When the current limiting protection circuit or the surge current protection circuit is started, the voltage of L13 decreases, the comparator jumps, the output drv_P is high level, and the power tube is turned off.

The FB voltage detection module is responsible for comparing VFB with the reference voltage resistor voltage Vref1 and outputting a signal L27. During the LDO startup phase or when the current limit returns to a smaller current value, VFB < Vref1, the output signal L27 is high level, and the control switch S1 is closed.

In the surge current protection module, when LDO starts and VFB>Vref1, S1 is closed, and the module starts to delay. S2 is disconnected during the delay time. When the delay ends, S2 is closed. The module does not affect the normal operation of the current limiting protection circuit after the delay ends. Refer to Figure 3 for the specific circuit of the surge current protection module, where L45 is the enable control signal, Vbias1 and Vbias5 are bias signals, N31, N49 and N36 are MOS capacitors with large capacitance, L27 is the output signal for detecting the FB potential, and Lrush is the output signal of the surge current protection control circuit. This part of the circuit mainly realizes the delay of the high-level signal of L27. When L27 turns from a low level to a high level, the delay is realized by signal transmission and the right branch current charging the large MOS capacitor, so as to control the startup stage. After VFB>300mV, the S2 closing time is extended to realize soft start and reduce the surge current.

At the same time, the large capacitor is charged by the surge current protection module to extend the startup time of the power tube, so as to achieve the effect of suppressing the surge current. When the circuit is just started or the circuit returns to a smaller current after current limiting, L27 and Lrush are both low-level signals. At this time, the input current charges the input capacitor, which will generate a large surge current. An I _short current is generated through the current detection circuit. The Ishort current size can be controlled by adjusting the size of the MOS capacitor N120. At this time, the LDO starts slowly with this low current. When VOUT gradually rises to about 1V, the FB terminal voltage is detected to be greater than 300mV, and L27 outputs a high level. The L27 signal is used as the input signal of the surge current protection module. After signal transmission, N22 is controlled to turn on. At this time, the surge current charges the three MOS large capacitors N31, N49 and N36, thereby delaying the time for Lrush to become a high-level signal, so as to achieve the effect of suppressing the surge current. At this time, L27 and Lrush are both high-level signals, the LDO is fully started, the current detection circuit monitors the output current at all times, and the output voltage is also stable at 2.45V.

The power device selection requirement is to select the power device with the smallest internal resistance and capacitance while meeting the output current and voltage difference.

Bandgap reference circuit When the startup circuit starts to power on, when the output is 0, the gate voltage of the two MOS tubes M1 and M2 above is close to VDD, and M7 in the startup circuit is turned on, then the gate of M5 is pulled to a low potential, and the M5 tube is turned on and generates current, so that the op amp gets rid of the degeneracy point when the output is 0; when the Bandganp circuit works normally, the voltage at the output of the op amp will decrease, and this time the PMOS tube located in the inverter of the startup circuit will be turned on, that is, M6 is turned on, and M7 is turned off. At this time, the gate voltage of M5 is close to VDD, and M5 will be turned off. At this time, the startup circuit is separated from the reference circuit and will not affect the normal operation of the bias circuit.

The enable control circuit includes a three-input AND gate circuit and an inverter circuit. The three-input AND gate adopts a PMOS tube and an NMOS tube to be connected in a complementary manner. The gate is used as a logic signal input port and the input ports A, B, and C of the AND gate circuit are respectively connected to the pins Over_heat, Over_flow, and En_POWER, and the output end is connected to the enable pin EN. The input and output pins of the three-input AND gate and the inverter circuit are respectively connected to the circuit, and are connected to each module circuit to enable and control the opening and closing of the bandgap reference circuit, the error amplifier, the power tube, the overheat protection circuit, and the overcurrent protection circuit. When EN is a high level, the system is turned on, otherwise, when EN is a low level, the system is turned off. By setting the enable control circuit, when a high level signal is received, the enable control circuit will activate the relevant circuit function and start working. The enable control circuit is used to turn on or off the circuit function in the chip. When a high level signal is received, the enable control circuit will activate the relevant circuit function and start working.

The feedback resistor selection method includes the following steps:

A1, the value of the feedback resistor can be expressed as: ; Wherein R _f1 represents the first feedback resistor, R _f2 represents the first feedback resistor, I _Q represents the quiescent current of the power tube branch, and V _OUT represents the output voltage;

A2, based on the reference voltage V _REF , feedback voltage V _FB and output voltage V _OUT , the following expression can be written:

;

A3, and the current of the feedback resistor branch can be expressed as: ; The quiescent current of the resistor is equal to the quiescent current of the PMOS power tube.

The overshoot suppression circuit is composed of M9-M15 and R5. M15 is used as a capacitor. Its working principle is as follows: the resistance value of R5 is set larger, so that (W/L) ₁₁ > (W/L) ₁₂ , to ensure that the gate voltages of M11 and M12 are different. When the output generates a large overshoot voltage, the source voltage of the M12 tube will increase, and the gate voltage cannot change suddenly because it is connected in series with the capacitor M15. At this time, the M12 tube is turned on, the gate voltage of the M14 tube increases, and then Vout is pulled down to reduce the overshoot voltage. When the output voltage undershoots, M12 is turned off, its drain voltage is zero, and the M14 tube is also turned off. The overshoot suppression circuit can effectively prevent the input overvoltage or transient noise from having an adverse effect on the downstream circuit, thereby improving the transient response characteristics of the entire circuit.

The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that, for those skilled in the art, the described embodiments can be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims (7)

1. A stabilized linear power supply circuit, comprising:

the band-gap reference circuit is used for providing a reference voltage source for desensitizing voltage and temperature fluctuation for the negative input end of the error amplifier;

the current bias circuit is used for providing proper bias voltage for other circuits in the system, generating a current source which does not fluctuate with the voltage on a power supply, and enabling transistors in the circuit to be at proper direct current working points;

the error amplifier is used for amplifying the difference value between the reference voltage generated by the band gap reference circuit and the feedback voltage of the node in the feedback network, the output end of the error amplifier is connected with the grid electrode of the power tube, and the power tube can be controlled by adjusting the voltage of the grid electrode through feedback, so that the voltage stabilizing function is completed;

an enable control circuit for turning on and off circuit functions in the chip;

the overshoot suppression circuit is used for enhancing the transient response characteristic of the linear voltage stabilizer and preventing overvoltage or transient noise at the input end from penetrating through the whole circuit system;

the feedback resistor is used for constructing a feedback network through the resistor;

a power device for providing a stable output current and voltage;

the over-temperature protection circuit is used for outputting a control signal when the temperature of the chip is over high and exceeds a preset temperature value, and the circuit is turned off in time through the enabling logic; when the temperature is reduced to a preset value range, the output control signal is turned over, the chip begins to work again, the effect of protecting the chip is achieved, the hysteresis function of the overheat protection circuit is achieved, the system is closed at high temperature, and normal work is resumed at low temperature;

and the overcurrent protection circuit adopts resistors to realize detection of output current signals, converts the output current signals into voltage signals and compares the voltage signals with reference voltages, and switches the working state of the protection circuit by adjusting the parallel relation among the resistors by utilizing the switching function of the MOS tube, so that the intelligent protection circuit for limiting current and preventing surge current is realized.

2. The stabilized linear power supply circuit of claim 1 wherein the over-current protection circuit comprises:

the current detection module consists of MP, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a switch S1 and a switch S2, wherein MP is connected with the output power tube in parallel and is a proportion mirror image I _OUT Outputting a current;

the COMP comparator is used for comparing an L13 terminal voltage signal with a reference voltage Vref, outputting a control power tube grid signal drv_P, wherein when the LDO works normally, L13 is high level, drv_P is low level, when the current limiting protection circuit or the anti-surge current protection circuit is started, the L13 voltage is reduced, the comparator jumps, drv_P is high level, and the power tube is closed;

the FB voltage detection module is responsible for comparing the voltage of VFB with the voltage division Vref1 of the reference voltage resistor and outputting a signal L27; when the LDO starts or the current is limited and returns to a smaller current value, the VFB is smaller than Vref1, the output signal L27 is high level, and the switch S1 is controlled to be closed;

and when the LDO is started and VFB is larger than Vref1, S1 is closed, the module is controlled to start delaying, S2 is in an open state within delay time, S2 is closed after delay is finished, and normal operation of the current-limiting protection circuit is not influenced after the delay of the module is finished.

3. The stabilized linear power supply circuit of claim 1 wherein the power device type selection requirement is to select the power device with the smallest internal resistance and capacitance of the device under conditions of satisfying output current and voltage difference.

4. The stabilized linear power supply circuit according to claim 1, wherein when the start-up circuit starts to power up and the output is 0, the gate voltages of the upper two MOS transistors M1 and M2 are close to VDD, M7 in the startup circuit is turned on, the gate of M5 is pulled to a low potential, and the M5 transistor is turned on and generates a current, so that the op-amp gets rid of a degeneracy point when the output is 0; when the Bandganp circuit works normally, the voltage of the output end of the operational amplifier is reduced, the PMOS tube of the inverter in the startup circuit is turned on this time, namely M6 is turned on, M7 is turned off, the grid voltage of M5 is close to VDD, M5 is turned off, and the starting circuit is separated from the reference circuit at the moment, so that the normal work of the bias circuit is not influenced.

5. The stabilized linear POWER supply circuit according to claim 1, wherein the enable control circuit comprises a three-input and gate circuit and an inverter circuit, the three-input and gate circuit is connected with the NMOS transistor by adopting a PMOS transistor and an NMOS transistor by adopting a complementary mode, the gate electrode is used as a logic signal input port and the input port A, B, C of the gate circuit is respectively connected with the pins over_heat, over_flow and en_power, the output end is connected with the enable pin En, the input and output pins of the three-input and gate circuit and the inverter circuit are respectively connected into the circuit, and the three-input and gate circuit and the inverter circuit are connected with the module circuits so as to control the turn-on and turn-off of the bandgap reference circuit, the error amplifier, the POWER transistor, the overheat protection circuit and the overcurrent protection circuit, when En is at a high level, otherwise, the system is turned-off when En is at a low level.

6. A stabilized linear power supply circuit as claimed in claim 1, wherein the method of selecting the feedback resistor comprises the steps of:

a1, the value of the feedback resistance can be expressed as:

the method comprises the steps of carrying out a first treatment on the surface of the Wherein R is _f1 Represents a first feedback resistance, R _f2 Represents a first feedback resistance, I _Q Representing the quiescent current of the power tube branch, V _OUT Representing an output voltage;

a2, according to the reference voltage V _REF Feedback voltage V _FB And output voltage V _OUT The following expression can be written:

；

a3, and the current of the feedback resistor branch can be expressed as:the method comprises the steps of carrying out a first treatment on the surface of the The static current of the resistor is equal to that of the PMOS power tube.

7. The stabilized linear power supply circuit as claimed in claim 1, wherein said overshoot suppression circuit is composed of M9-M15 and R5, M15 is used as a capacitor, and the working principle is as follows, R5 is made larger in resistance value to give (W/L) ₁₁ >(W/L) ₁₂ Ensure that the grid voltage of M11 is different from that of M12, and the source end of the M12 tube is powered when the output generates larger overshoot voltageThe voltage will rise, and the gate voltage can not be suddenly changed because of the string on the capacitor M15, at this time, the M12 tube is turned on, the gate voltage of the M14 tube is raised, then Vout is pulled down to reduce the overshoot voltage, when the output voltage is undershooted, M12 is turned off, its drain voltage is zero, and the M14 tube is also turned off.