Starting circuit

Abstract

The embodiment of the invention provides a starting circuit, which comprises a band-gap reference module, an operational amplifier, a feedback module, a first switch, a starting module and a voltage output module, and is characterized in that the operational amplifier is used for receiving reference voltage output by the band-gap reference module and feedback voltage output by the feedback module, and comparing the reference voltage with the feedback voltage; and adjusting the first voltage output by the output end according to the comparison result so as to control the working state of the first switch, and outputting a high level to the control end of the first switch at the moment when the starting module receives the signal from the low level to the high level through the starting module of which one end is connected between the output end of the operational amplifier and the control end of the first switch. The first switch is switched on before receiving the first voltage output by the output end of the operational amplifier, so that the output voltage of the voltage output module can be quickly established, the starting speed of the circuit is increased, and the slow starting speed of the circuit caused by long charging time of the load capacitor is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply circuits, and in particular to a starting circuit. Background Art

[0002] In power management systems, LDO (Low dropout regulator) has become an indispensable power source due to its high efficiency and stability. With the rapid development of technology, low-power design has become a common goal pursued by the industry, especially in low-power application fields such as the Internet of Things, wearable devices and biological detection products. The system needs to switch frequently between low-power mode and normal working mode. During this switching process, LDO needs to have the ability to respond quickly and be able to start in a very short time to ensure that a stable output voltage can be maintained even when power consumption increases.

[0003] The working principle of LDO is based on the reference voltage generated by the bandgap reference module, and a negative feedback control loop is used to achieve a stable output voltage that is not affected by the external environment. However, during the operation of LDO, the introduction of noise sources will inevitably affect the stability of the output voltage.

[0004] In low-power application scenarios, in order to suppress the impact of these noise sources, on-chip capacitors are usually used for filtering. However, the presence of on-chip capacitors will introduce a certain delay in the LDO power-on process. Since the on-chip capacitors require a certain amount of time to charge, this will reduce the response speed of the LDO and affect its startup speed. Summary of the invention

[0005] In view of the above problems, embodiments of the present invention are proposed to provide a startup circuit that overcomes the above problems or at least partially solves the above problems.

[0006] In order to solve the above problems, an embodiment of the present invention discloses a startup circuit, which includes: a bandgap reference module, an operational amplifier, a feedback module, a first switch, a startup module and a voltage output module;

[0007] The operational amplifier has a first input terminal connected to the bandgap reference module, a second input terminal connected to the feedback module, and an output terminal connected to the control terminal of the first switch; and is used to receive a reference voltage output by the bandgap reference module and a feedback voltage output by the feedback module, and compare the reference voltage and the feedback voltage, and adjust the first voltage output by the output terminal according to the comparison result, so as to control the working state of the first switch;

[0008] The output end of the first switch is connected to the voltage output module, and is used to output a second voltage to the voltage output module when it is turned on;

[0009] One end of the feedback module is connected between the output end of the first switch and the voltage output module, and is used to output the feedback voltage according to the second voltage;

[0010] One end of the startup module is connected between the output end of the operational amplifier and the control end of the first switch, and is used for outputting a third voltage to the output end of the first switch to control the first switch to be turned on before the output end of the operational amplifier outputs the first voltage to the control end of the first switch;

[0011] The voltage output module includes a load capacitor, which is used to output a fourth voltage after the load capacitor is fully charged.

[0012] Optionally, the startup module includes a converter and a second switch;

[0013] The converter is connected to the second switch, and is used to receive a digital signal and output a voltage signal to a control end of the second switch according to the digital signal;

[0014] The output end of the second switch is grounded, and the input end is connected between the output end of the operational amplifier and the control end of the first switch, and is used to control the first switch to be turned on before receiving the first voltage output by the output end of the operational amplifier.

[0015] Optionally, the startup module also includes a filtering circuit, which includes a filtering capacitor and a filtering resistor, one end of the filtering capacitor is connected to the converter, and the other end is connected to the filtering resistor; one end of the filtering resistor is connected between the filtering capacitor and the control end of the second switch, and the other end is grounded.

[0016] Optionally, the circuit further includes a third switch, and the startup module further includes a first inverter connected to the converter, and a second inverter connected to the first inverter;

[0017] The first inverter is used to invert the voltage signal and output the inverted voltage signal to the second inverter;

[0018] The output end of the second inverter is connected to the control end of the third switch, and is used to invert the voltage signal after the first inversion, and output the voltage signal after the second inversion to the control end of the third switch;

[0019] The output end of the third switch is connected between the output end of the operational amplifier and the control end of the first switch, and is used for being turned on when the voltage signal after the secondary inversion is at a low level, so as to disconnect the first switch.

[0020] Optionally, the first switch is a PMOS tube, the control end of the first switch is a gate, the output end of the first switch is a drain, the input end of the first switch is a source, and the source is connected to a power supply voltage.

[0021] Optionally, the second switch is an NMOS tube, the control end of the second switch is a gate, the output end of the second switch is a source, and the input end of the second switch is a drain.

[0022] Optionally, the third switch is a PMOS tube, the control end of the third switch is a gate, the output end of the third switch is a drain, the input end of the third switch is a source, and the input end of the third switch is connected to the power supply voltage.

[0023] Optionally, the feedback module includes a first resistor and a second resistor, one end of the first resistor is connected to the output end of the first switch, and the other end is connected to the second resistor, the second resistor is grounded, and the second input end of the operational amplifier is connected between the first resistor and the second resistor.

[0024] Optionally, the first resistor is an adjustable resistor.

[0025] Optionally, the voltage output module further includes a load resistor, one end of the load resistor is grounded, and the other end is connected to the output end of the first switch.

[0026] The embodiments of the present invention include the following advantages:

[0027] The startup circuit of the embodiment of the present invention includes a bandgap reference module, an operational amplifier, a feedback module, a first switch, a startup module and a voltage output module, wherein the first input terminal of the operational amplifier is connected to the bandgap reference module, the second input terminal is connected to the feedback module, and the output terminal is connected to the control terminal of the first switch; the operational amplifier is used to receive the reference voltage output by the bandgap reference module and the feedback voltage output by the feedback module, and compare the reference voltage and the feedback voltage, and adjust the first voltage output by the output terminal according to the comparison result to control the working state of the first switch; the output terminal of the first switch is connected to the voltage output module, and is used to output a second voltage to the voltage output module when it is turned on; one end of the feedback module is connected between the output terminal of the first switch and the voltage output module, and is used to output a feedback voltage according to the second voltage; one end of the startup module is connected between the output terminal of the operational amplifier and the control terminal of the first switch, and is used to output a third voltage to the output terminal of the first switch before the output terminal of the operational amplifier outputs the first voltage to the control terminal of the first switch to control the first switch to be turned on; the voltage output module includes a load capacitor, and is used to output a fourth voltage after the load capacitor is charged. Through a startup module having one end connected between the output end of the operational amplifier and the control end of the first switch, at the moment when the startup module receives a signal that changes from a low level to a high level, a high level is output to the control end of the first switch, so that the first switch is turned on before receiving the first voltage output by the output end of the operational amplifier, so that the output voltage of the voltage output module can quickly reach its set value and then be output, thereby accelerating the startup speed of the circuit and avoiding the slow startup speed of the circuit caused by the long charging time of the load capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a structural schematic diagram of a starting circuit according to an embodiment of the present invention;

[0029] Figure 2 It is a structural schematic diagram of another starting circuit according to an embodiment of the present invention.

[0030] Figure numerals: bandgap reference module 10, operational amplifier 20, first switch 30, feedback module 40, first resistor 41, second resistor 42, startup module 50, converter 51, second switch 52, filter circuit 53, filter capacitor 531, filter resistor 532, first inverter 54, second inverter 55, voltage output module 60, load capacitor 61, load resistor 62, third switch 70. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] In power management systems, LDO has become an indispensable power source due to its high efficiency and stability. With the rapid development of technology, low-power design has become a common goal pursued by the industry, especially in low-power application fields such as the Internet of Things, wearable devices and biological detection products. The system needs to switch frequently between low-power mode and normal working mode. During this switching process, LDO needs to have the ability to respond quickly and be able to start in a very short time to ensure that a stable output voltage can be maintained when power consumption increases.

[0033] The working principle of LDO is based on the reference voltage generated by the bandgap reference module, and a negative feedback control loop is used to achieve a stable output voltage that is not affected by the external environment. However, during the operation of LDO, the introduction of noise sources will inevitably affect the stability of the output voltage. Common noise sources include the output noise of the bandgap reference, the error amplifier noise, and the feedback network noise. In order to suppress the influence of the above noise sources, traditional LDOs require large loads and will have a filter capacitor installed outside the chip for filtering. The commonly used capacitance is nF or uF level.

[0034] In low-power application scenarios, LDO is the main power source. The load it supplies is generally within 100mA, so the off-chip capacitor is omitted and a non-off-chip capacitor method is used for filtering. This requires capacitor integration within the chip. Considering the chip area control requirements, the capacitance of this on-chip capacitor is generally not large (usually at the pF level), so it also brings challenges to noise processing. At the same time, due to the existence of this capacitor, this capacitor will be charged during the LDO power-on process, thereby affecting the startup speed of the LDO.

[0035] One of the core concepts of the embodiment of the present invention is that, through a startup module whose one end is connected between the output end of the operational amplifier and the control end of the first switch, at the moment when the startup module receives a signal that changes from a low level to a high level, a high level is output to the control end of the first switch, so that the first switch is turned on before receiving the first voltage output by the output end of the operational amplifier, so that the output voltage of the voltage output module can quickly reach its set value and then be output, thereby accelerating the startup speed of the circuit and avoiding the slow startup speed of the circuit caused by the long charging time of the load capacitor.

[0036] Reference Figure 1 , shows a schematic diagram of the structure of a startup circuit of an embodiment of the present invention, which may specifically include the following structures: a bandgap reference module 10, an operational amplifier 20, a first switch 30, a feedback module 40, a startup module 50 and a voltage output module 60.

[0037] The first input terminal of the operational amplifier 20 is connected to the bandgap reference module 10, the second input terminal is connected to the feedback module 40, and the output terminal is connected to the control terminal of the first switch 30, and is used to receive the reference voltage output by the bandgap reference module 10 and the feedback voltage output by the feedback module 40, and compare the reference voltage and the feedback voltage, and adjust the first voltage output by the output terminal according to the comparison result to control the working state of the first switch 30.

[0038] The bandgap reference module 10 is powered by a power supply voltage VCC, and is used to generate a reference voltage, and output the reference voltage to the first input terminal of the operational amplifier 20. The bandgap reference module 10 also outputs IBIAS (Input Bias Current) to the operational amplifier 20. The first input terminal of the operational amplifier 20 is connected to the bandgap reference module 10, and is used to receive the reference voltage output by the bandgap reference module 10. The second input terminal of the operational amplifier 20 is connected to the feedback module 40, and is used to receive the feedback voltage output by the feedback module 40. The output terminal of the operational amplifier 20 is connected to the control terminal of the first switch 30. The operational amplifier 20 is used to compare the reference voltage and the feedback voltage, and adjust the first voltage outputted from the output terminal according to the comparison result, so as to control the working state of the first switch 30 and adjust the output voltage of the voltage output module 60.

[0039] Exemplarily, the first input terminal can be a negative input terminal, the second input terminal can be a positive input terminal, the feedback voltage RFB is input to the positive input terminal of the operational amplifier 20, and the reference voltage is input to the negative input terminal of the operational amplifier 20. The operational amplifier 20 compares the feedback voltage and the reference voltage to adjust the output voltage of the voltage output module 60 to ensure the stable output of the voltage output module 60.

[0040] An output end of the first switch 30 is connected to the voltage output module 60 , and is configured to output a second voltage to the voltage output module 60 when the first switch 30 is turned on.

[0041] One end of the feedback module 40 is connected between the output end of the first switch 30 and the voltage output module 60, and is used to output a feedback voltage according to the second voltage. The first switch 30 outputs the second voltage to the voltage output module 60, the control end of the first switch 30 is connected to the output end of the operational amplifier 20, and the feedback module 40 outputs a feedback voltage according to the second voltage.

[0042] In an operational amplifier circuit, the feedback voltage is usually returned to the input of the operational amplifier through a feedback network. The feedback network can be composed of components such as resistors and capacitors, which are used to return part of the output signal to the input to form a closed-loop control. Feedback voltage refers to the voltage signal returned from the output to the input. In an operational amplifier circuit, the feedback voltage is usually obtained through a feedback network and used to compare with a reference voltage to adjust the output voltage. The feedback network is usually composed of components such as resistors and capacitors, which are used to return part of the output signal to the input.

[0043] One end of the startup module 50 is connected between the output end of the operational amplifier 20 and the control end of the first switch 30, and is used to output a third voltage to the output end of the first switch 30 to control the first switch 30 to be turned on before the output end of the operational amplifier 20 outputs the first voltage to the control end of the first switch 30.

[0044] The output end of the operational amplifier 20 is connected to the control end of the first switch 30. Normally, the first switch 30 is controlled by the output change of the output end of the operational amplifier 20. However, in low-power applications, the start-up time of the first switch 30 will be slower due to the change of the overall current. The start-up time of the first switch 30 can be accelerated by controlling the switch of the first switch 30 through a start-up module 50 whose one end is connected between the output end of the operational amplifier 20 and the control end of the first switch 30.

[0045] The voltage output module 60 includes a load capacitor 61 , and is configured to output a fourth voltage after the load capacitor 61 is fully charged.

[0046] In the power supply circuit, the load capacitor 61 is used to filter out the ripple and noise in the output voltage. The fourth voltage output by the voltage output module 60 is the output voltage of the output end of the LDO. The load capacitor (LC) refers to the capacitor connected to the output end of the circuit, which is used to smooth the output voltage or current and reduce the ripple and noise of the output signal. The load capacitor smoothes the output voltage through the charging and discharging process. When the output voltage of the LDO regulator changes, the load capacitor absorbs or releases the charge to keep the output voltage stable. When the output voltage of the LDO regulator rises, the load capacitor charges and absorbs excess charge, thereby slowing down the rise rate of the output voltage. When the output voltage of the LDO regulator drops, the load capacitor discharges and releases the stored charge, thereby slowing down the fall rate of the output voltage. The voltage output module 60 is used to output the fourth voltage after the load capacitor 61 is fully charged.

[0047] During the LDO power-on process, during the process of the output establishment of the voltage output module 60, the load capacitor 61 needs to be charged. Establishment is the process of the circuit transitioning from one state to another stable state. The establishment time refers to the time required for the circuit to transition from one state to another stable state. For an LDO regulator, the establishment time generally refers to the time required from the input voltage change or the load change to the output voltage stabilizing within a specified error range. The presence of the load capacitor 61 will affect the establishment time of the LDO regulator. Since the load capacitor needs to be charged, the establishment time of the output voltage becomes longer. Specifically, the charging process of the load capacitor will introduce a time constant, thereby extending the stabilization time of the output voltage. The faster the response speed of the LDO regulator, the shorter the establishment time. The establishment time depends on the charging time constant of the load capacitor and the response speed of the LDO regulator.

[0048] The startup circuit of the embodiment of the present invention includes a bandgap reference module, an operational amplifier, a feedback module, a first switch, a startup module and a voltage output module, wherein the first input terminal of the operational amplifier is connected to the bandgap reference module, the second input terminal is connected to the feedback module, and the output terminal is connected to the control terminal of the first switch; the operational amplifier is used to receive the reference voltage output by the bandgap reference module and the feedback voltage output by the feedback module, and compare the reference voltage and the feedback voltage, and adjust the first voltage output by the output terminal according to the comparison result to control the working state of the first switch; the output terminal of the first switch is connected to the voltage output module, and is used to output a second voltage to the voltage output module when it is turned on; one end of the feedback module is connected between the output terminal of the first switch and the voltage output module, and is used to output a feedback voltage according to the second voltage; one end of the startup module is connected between the output terminal of the operational amplifier and the control terminal of the first switch, and is used to output a third voltage to the output terminal of the first switch before the output terminal of the operational amplifier outputs the first voltage to the control terminal of the first switch to control the first switch to be turned on; the voltage output module includes a load capacitor, and is used to output a fourth voltage after the load capacitor is charged. Through a startup module having one end connected between the output end of the operational amplifier and the control end of the first switch, at the moment when the startup module receives a signal that changes from a low level to a high level, a high level is output to the control end of the first switch, so that the first switch is turned on before receiving the first voltage output by the output end of the operational amplifier, thereby improving the response speed of the first switch being turned on, so that the output voltage of the voltage output module can quickly reach its set value and then be output, thereby accelerating the startup speed of the circuit and avoiding the slow startup speed of the circuit caused by the long charging time of the load capacitor.

[0049] Reference Figure 2 , shows a schematic diagram of the structure of another startup circuit according to an embodiment of the present invention, which may specifically include the following structure:

[0050] The startup module 50 includes a converter 51 and a second switch 52 .

[0051] The converter 51 is connected to the second switch 52 , and is configured to receive a digital signal and output a voltage signal to a control end of the second switch 52 according to the digital signal.

[0052] The converter 51 is also called LV shift (Low Voltage Shift, low voltage conversion module). The converter 51 receives a control signal. The converter 51 is used to convert a digital signal into an analog signal. Generally, the control signal is given by a digital module and is a low voltage signal. It needs to be converted into a VCC power supply voltage for use by the analog circuit by the converter 51. The converter 51 is connected to the second switch 52, and is used to receive a digital control signal, and convert the digital control signal into a VCC power supply voltage and output it to the control end of the second switch 52.

[0053] The output end of the second switch 52 is grounded, and the input end is connected between the output end of the operational amplifier 20 and the control end of the first switch 30 , and is used to control the first switch 30 to be turned on before receiving the first voltage outputted from the output end of the operational amplifier 20 .

[0054] The input end of the second switch 52 is connected between the output end of the operational amplifier 20 and the control end of the first switch 30, that is, the control end of the first switch 30 is affected by the input end of the second switch 52. During the power-on process, the bandgap reference module 10 first establishes and outputs the reference voltage and bias current IBIAS to the operational amplifier 20, the operational amplifier 20 starts to work, and controls the working state of the first switch 30. At the same time, the digital module gives a high-level signal to the converter 51, and the converter 51 converts the high-level digital control signal into a voltage signal and outputs it to the control end of the second switch 52. The second switch 52 conducts Since the input end of the second switch 52 is connected between the output end of the operational amplifier 20 and the control end of the first switch 30, when the second switch 52 is turned on, the first switch 30 is controlled to be turned on before receiving the first voltage outputted from the output end of the operational amplifier 20. Since the switching control of the first switch 30 is usually formed by the output change of the output end of the operational amplifier 20, however, in low-power applications, the startup time of the first switch 30 will be slowed down due to the change of the overall current. By controlling the first switch 30 to be turned on when the second switch 52 is turned on, the startup time of the first switch 30 can be accelerated.

[0055] In an embodiment of the present invention, the startup module 50 also includes a filter circuit 53, which includes a filter capacitor 531 and a filter resistor 532. One end of the filter capacitor 531 is connected to the converter 51, and the other end is connected to the filter resistor 532; one end of the filter resistor 532 is connected between the filter capacitor 531 and the control end of the second switch 52, and the other end is grounded.

[0056] The filter circuit 53 is a high-pass filter circuit, which is used to pass high-frequency signals and block low-frequency signals to remove low-frequency noise or DC offset. The basic principle of the high-pass filter circuit is to use the characteristics of capacitors and resistors to achieve frequency selection. The capacitor presents low impedance at high frequencies and high impedance at low frequencies; the resistor presents a constant impedance for all frequencies. By reasonably selecting the values ​​of the capacitor and the resistor, the high-frequency signal can be passed and the low-frequency signal can be blocked.

[0057] The filter circuit 53 includes a filter capacitor 531 and a filter resistor 532. At low frequencies, the filter capacitor 531 presents high impedance, the voltage drop across the filter resistor 532 is large, the output voltage is small, and the low-frequency signal is blocked. At high frequencies, the filter capacitor 531 presents low impedance, the voltage drop across the filter resistor 532 is small, the output voltage is large, and the high-frequency signal passes.

[0058] One end of the filter capacitor 531 is connected to the converter 51, and the other end is connected to the filter resistor 532. One end of the filter resistor 532 is connected between the filter capacitor 531 and the control end of the second switch 52, and the other end is grounded. The control signal Controlsignal is equivalent to a high-frequency signal at the moment of changing from a low level to a high level. At this time, the high-pass filter circuit composed of the filter capacitor 531 and the filter resistor 532 can quickly pass this high-frequency signal to the control end of the second switch 52. The second switch 52 is turned on instantly, directly controlling the first switch 30 to turn on, so that the output of the voltage output module 60 can be quickly established, avoiding the influence of the long charging time of the load capacitor 61. The control signal can be provided by the bandgap reference module 10, or it can be given by program setting, and the embodiment of the present invention does not limit this.

[0059] In the embodiment of the present invention, the circuit further includes a third switch 70 , and the startup module 50 further includes a first inverter 54 connected to the converter 51 , and a second inverter 55 connected to the first inverter 54 .

[0060] The first inverter 54 is used to invert the voltage signal and output the inverted voltage signal to the second inverter 55 .

[0061] The output end of the second inverter 55 is connected to the control end of the third switch 70 , and is used to invert the voltage signal after the first inversion, and output the voltage signal after the second inversion to the control end of the third switch 70 .

[0062] The output end of the third switch 70 is connected between the output end of the operational amplifier 20 and the control end of the first switch 30 , and is used to be turned on when the voltage signal after the secondary inversion is at a low level, so as to disconnect the first switch.

[0063] During the power-on process, first, the bandgap reference module 10 establishes and outputs the reference voltage and bias current IBIAS to the operational amplifier 20, and the operational amplifier 20 starts to work and controls the working state of the first switch 30. At the same time, the digital module gives a high-level signal to the converter 51, and outputs a PD high-level signal to the control end of the third switch 70 through the converter 51, the first inverter 54 and the second inverter 55. After receiving the PD high-level signal, the control end of the third switch 70 is in a high-resistance cut-off state, so that the first switch 30 is controlled by the output voltage of the operational amplifier 20, the first switch 30 is turned on, the output of the voltage output module 60 is established normally, and the feedback voltage output by the feedback module 40 is received through the operational amplifier 20 to adjust the output voltage of the voltage output module 60. In this process, due to the existence of the load capacitor 61, the load capacitor 61 needs to be charged during the establishment process, so that the establishment time of the output of the voltage output module 60 becomes longer, generally in the millisecond level. When the digital module gives a high-level signal to the converter 51, the converter 51 will output to the filter circuit 53, and the control signal Control At the moment when the signal changes from a low level to a high level, it is equivalent to a high-frequency signal. At this time, through the high-pass filter circuit, this high-frequency signal can be quickly transmitted to the control end of the second switch 52. The second switch 52 is turned on instantly, directly controlling the first switch 30 to be turned on, so that the output of the voltage output module 60 can be quickly established, avoiding the influence caused by the long charging time of the load capacitor 61.

[0064] PD signal usually refers to "power off signal" or "power-off signal". It is a control signal used to instruct a circuit or system to enter a low-power or shutdown state. PD signals are often used in power management circuits to achieve energy saving and extend battery life. When the PD signal is high, the circuit or system enters a low-power mode to reduce power consumption. This is a low-power mode. When the PD signal is low, the circuit or system is completely shut down and stops working. This is a shutdown mode. In battery-powered devices, PD signals are used to control the power management of the device and extend battery life. In power management chips, PD signals are used to control the switching and regulation of the power supply.

[0065] When the circuit is in the closed state, the PD signal is at a low level, and the third switch 70 is in the open state. Since the output end of the third switch 70 is connected to the control end of the first switch 30, the first switch 30 is in the cut-off state at this time, the voltage output module 60 has no output, and the current in the overall circuit is very small.

[0066] In the embodiment of the present invention, the first switch 30 is a PMOS tube, the control end of the first switch 30 is a gate, the output end of the first switch 30 is a drain, the input end of the first switch 30 is a source, and the source is connected to the power supply voltage VCC.

[0067] In the embodiment of the present invention, the second switch 52 is an NMOS transistor, the control end of the second switch 52 is a gate, the output end of the second switch 52 is a source, and the input end of the second switch 52 is a drain.

[0068] In the embodiment of the present invention, the third switch 70 is a PMOS tube, the control end of the third switch 70 is a gate, the output end of the third switch 70 is a drain, the input end of the third switch 70 is a source, and the input end of the third switch 70 is connected to the power supply voltage VCC.

[0069] When the circuit is in the closed state, the PD signal is at a low level, the gate of the third switch PMOS tube 70 receives the low level, the third switch PMOS tube 70 is in the open state, and the channel region is in the on state. Since the drain of the third switch PMOS tube 70 is connected to the gate of the first switch PMOS tube 30, the gate of the first switch PMOS tube 30 is pulled to the high level of the power supply voltage VCC, the first switch PMOS tube 30 is in the cut-off state, the voltage output module 60 has no output, and the current in the overall circuit is very small.

[0070] During the power-on process, the bandgap reference module 10 first establishes and outputs the reference voltage and bias current IBIAS to the operational amplifier 20, and the operational amplifier 20 starts to work and controls the working state of the first switch 30. At the same time, the control signal Control signal is a high-level signal, and after passing through the converter 51, the first inverter 54 and the second inverter 55, a PD high-level signal is output to the gate of the third switch PMOS tube 70. The gate of the third switch PMOS tube 70 receives the PD high-level signal, and the channel of the third switch PMOS tube 70 is in a high-resistance cut-off state, so that the first switch PMOS tube 30 is directly controlled by the output of the operational amplifier 20, the channel of the first switch PMOS tube 30 is turned on, and the output of the voltage output module 60 is normally established, and the feedback voltage output from the feedback module 40 is received through the operational amplifier 20, and the output voltage of the voltage output module 60 is adjusted.

[0071] In this process, due to the existence of the load capacitor 61, the load capacitor 61 needs to be charged during the establishment process, so that the establishment time of the voltage output module 60 becomes longer, generally in the millisecond level.

[0072] The control signal Control signal gives a high level signal. After passing through the converter 51, in addition to being output to the first inverter 54 and the second inverter 55, it is also output to the filter circuit 53. At the moment when the control signal Control signal changes from a low level to a high level, it is equivalent to a high-frequency signal. At this time, through the high-pass filter network composed of the filter capacitor 531 and the filter resistor 532, this high-frequency signal can be quickly transmitted to the gate of the second switch NMOS tube 52. According to the characteristics of the NMOS tube device, the channel of the second switch NMOS tube 52 is instantly turned on, generating a large current flowing to the ground. Because the drain of the second switch NMOS tube 52 is connected to the gate of the first switch PMOS tube 30, the gate of the first switch PMOS tube 30 is directly pulled to a low level, which speeds up the time for the channel of the first switch PMOS tube 30 to open, so that the channel area of ​​the first switch PMOS tube 30 quickly enters the low-resistance channel, so that the output of the voltage output module 60 can be quickly established, avoiding the influence caused by the long charging time of the load capacitor 61.

[0073] Usually, the switching control of the first switch PMOS tube 30 is formed by the output change of the operational amplifier 20. In low-power applications, the startup time will be slower due to the decrease in the overall current. Therefore, the use of this startup module 50 can speed up the startup time of the first switch PMOS tube 30 and filter out some interference signals at the same time.

[0074] The startup module 50 of the embodiment of the present invention enables the LDO to start quickly when switching from a low power consumption mode (such as a power-down mode) to a normal working mode, that is, the LDO can be turned on quickly. The high-pass filter circuit composed of the filter capacitor 531 and the filter resistor 532 of the startup module 50 is connected to the gate of the second switch NMOS tube 52, and the drain of the second switch NMOS tube 52 is connected to the gate of the first switch PMOS tube 30. The input voltage of the startup module 50 is an external shutdown voltage signal. When the external shutdown voltage signal is switched from a low level to a high level, the quick startup module starts working from a dormant state. Since the current of each branch in the LDO main circuit is very small, but the internal load capacitance is very large (pF level), at the moment of switching of the external shutdown signal, the input voltage is equivalent to a high-frequency signal in the signal spectrum. At this time, the high-pass filter circuit of the charging device will sense the high-frequency signal and transmit the signal to the gate of the second switch NMOS tube 52. The second switch NMOS tube 52 instantly generates a large current to pull the gate voltage of the first switch PMOS tube 30 of the LDO output stage to 0V. At the same time, the external switching switch controls other switch tubes to start the LDO circuit instantly, so as to achieve the purpose of accelerating the startup without increasing the static power consumption. By adopting the structure of the high-pass filter and combining the fast switching of the main structure, it is possible to reduce the influence of noise and ensure that the LDO starts quickly during the switching process, achieving a start-up speed of microseconds.

[0075] In the embodiment of the present invention, the feedback module 40 includes a first resistor 41 and a second resistor 42, one end of the first resistor 41 is connected to the output end of the first switch 30, and the other end is connected to the second resistor 42, the second resistor 42 is grounded, and the second input end of the operational amplifier 20 is connected between the first resistor 41 and the second resistor 42. The first resistor 41 is an adjustable resistor. The feedback voltage is generated by a voltage divider resistor network and finally input to the second input end of the operational amplifier 20.

[0076] Feedback networks play a vital role in electronic circuits, especially in operational amplifier circuits. The feedback network returns part of the output signal to the input terminal to form a closed-loop control, thereby achieving multiple functions, such as stabilizing the amplification factor, reducing distortion, and improving the stability of the circuit. Feedback networks can be divided into two main types: negative feedback, which refers to connecting part of the output signal to the input terminal in reverse to reduce the amplitude of the output signal. Negative feedback can improve the stability of the circuit, reduce distortion, expand bandwidth, reduce noise, etc., and is widely used in amplifiers, oscillators, filters and other circuits; positive feedback, which refers to connecting part of the output signal to the input terminal in the forward direction to increase the amplitude of the output signal. Positive feedback can be used in circuits such as oscillators and comparators to generate oscillations or enhance signals, and is commonly found in circuits such as oscillators and Schmitt triggers. The feedback network of an embodiment of the present invention may be positive feedback.

[0077] In the embodiment of the present invention, the voltage output module 60 further includes a load resistor 62, one end of which is grounded and the other end is connected to the output end of the first switch 30. The load capacitor 61 and the load resistor 62 are used to filter out ripples and noise in the output voltage. The load capacitor 61 is used to smooth the voltage and reduce high-frequency noise, and the load resistor 62 is used to absorb the power at the output end of the circuit and convert it into heat energy.

[0078] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0079] It will be appreciated by those skilled in the art that the embodiments of the present invention may be provided as methods, devices, or computer program products. Therefore, the embodiments of the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the embodiments of the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0080] The embodiments of the present invention are described with reference to the flowcharts and / or block diagrams of the methods, terminal devices (systems), and computer program products according to the embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing terminal device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing terminal device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0081] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing terminal device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0082] These computer program instructions can also be loaded onto a computer or other programmable data processing terminal device so that a series of operating steps are executed on the computer or other programmable terminal device to produce a computer-implemented process, thereby providing instructions for executing on the computer or other programmable terminal device to implement the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0083] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0084] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements.

[0085] A starting circuit provided by the present invention is introduced in detail above. Specific examples are used in this article to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A starting circuit, characterized in that: The circuit comprises: a bandgap reference module, an operational amplifier, a feedback module, a first switch, a start-up module and a voltage output module; The operational amplifier has a first input terminal connected to the bandgap reference module, a second input terminal connected to the feedback module, and an output terminal connected to the control terminal of the first switch, and is used to receive a reference voltage output by the bandgap reference module and a feedback voltage output by the feedback module, and compare the reference voltage and the feedback voltage, and adjust the first voltage output by the output terminal according to the comparison result, so as to control the working state of the first switch; The output end of the first switch is connected to the voltage output module, and is used to output a second voltage to the voltage output module when it is turned on; One end of the feedback module is connected between the output end of the first switch and the voltage output module, and is used to output the feedback voltage according to the second voltage; One end of the startup module is connected between the output end of the operational amplifier and the control end of the first switch, and is used for outputting a third voltage to the output end of the first switch to control the first switch to be turned on before the output end of the operational amplifier outputs the first voltage to the control end of the first switch; The voltage output module includes a load capacitor, which is used to output a fourth voltage after the load capacitor is fully charged.

2. The circuit according to claim 1, characterized in that The startup module includes a converter and a second switch; The converter is connected to the second switch, and is used to receive a digital signal and output a voltage signal to a control end of the second switch according to the digital signal; The output end of the second switch is grounded, and the input end is connected between the output end of the operational amplifier and the control end of the first switch, and is used to control the first switch to be turned on before receiving the first voltage output by the output end of the operational amplifier.

3. The circuit according to claim 2, characterized in that The startup module also includes a filter circuit, which includes a filter capacitor and a filter resistor. One end of the filter capacitor is connected to the converter, and the other end is connected to the filter resistor; one end of the filter resistor is connected between the filter capacitor and the control end of the second switch, and the other end is grounded.

4. The circuit according to claim 2, characterized in that The circuit further includes a third switch, and the startup module further includes a first inverter connected to the converter and a second inverter connected to the first inverter; The first inverter is used to invert the voltage signal and output the inverted voltage signal to the second inverter; The output end of the second inverter is connected to the control end of the third switch, and is used to invert the voltage signal after the first inversion, and output the voltage signal after the second inversion to the control end of the third switch; The output end of the third switch is connected between the output end of the operational amplifier and the control end of the first switch, and is used for being turned on when the voltage signal after the secondary inversion is at a low level, so as to disconnect the first switch.

5. The circuit according to claim 1, characterized in that The first switch is a PMOS tube, the control end of the first switch is a gate, the output end of the first switch is a drain, the input end of the first switch is a source, and the source is connected to a power supply voltage.

6. The circuit according to claim 2, characterized in that The second switch is an NMOS tube, the control end of the second switch is a gate, the output end of the second switch is a source, and the input end of the second switch is a drain.

7. The circuit according to claim 4, characterized in that The third switch is a PMOS tube, the control end of the third switch is a gate, the output end of the third switch is a drain, the input end of the third switch is a source, and the input end of the third switch is connected to the power supply voltage.

8. The circuit according to claim 1, characterized in that The feedback module includes a first resistor and a second resistor, one end of the first resistor is connected to the output end of the first switch, and the other end is connected to the second resistor, the second resistor is grounded, and the second input end of the operational amplifier is connected between the first resistor and the second resistor.

9. The circuit according to claim 1, characterized in that The first resistor is an adjustable resistor.

10. The circuit according to claim 1, characterized in that The voltage output module further includes a load resistor, one end of which is grounded, and the other end of which is connected to the output end of the first switch.

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