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CN-115729296-B - Circuit for keeping conduction impedance of power tube constant in load switch

CN115729296BCN 115729296 BCN115729296 BCN 115729296BCN-115729296-B

Abstract

A circuit for keeping the on-resistance of a power tube constant in a load switch is characterized by comprising a voltage-controlled current source unit, a reference voltage generating unit, a charge pump unit and the power tube, wherein the voltage-controlled current source unit is used for generating voltage-controlled current of the reference voltage generating unit based on load voltage of the power tube, the reference voltage generating unit is respectively connected with the voltage-controlled current source unit and the charge pump unit and used for receiving the voltage-controlled current input by the voltage-controlled current source unit, generating control voltage based on the voltage-controlled current and inputting the control voltage into the charge pump unit, and the charge pump unit is connected with a grid electrode of the power tube and used for receiving the control voltage output by the reference voltage generating unit and pumping out a switching voltage which is multiple of the control voltage to the grid electrode of the power tube so as to control the output voltage of a source electrode of the power tube. The method has the advantages of simple circuit structure, low cost and low cost, and can effectively ensure the constant on-resistance of the power tube on the premise of unchanged load.

Inventors

  • LIN KELONG

Assignees

  • 圣邦微电子（北京）股份有限公司

Dates

Publication Date
20260512
Application Date
20210825

Claims (9)

  1. 1. A circuit for maintaining constant on-resistance of a power tube in a load switch, comprising: The circuit comprises a voltage-controlled current source unit, a reference voltage generating unit, a charge pump unit and a power tube, wherein, The voltage-controlled current source unit is connected with the reference voltage generation unit and is used for generating voltage-controlled current of the reference voltage generation unit based on the load voltage of the power tube; the voltage-controlled current source unit comprises a first error amplifier EA1, an NMOS tube Mn0, positive phase input end voltage dividing resistors R1 and R2 and a negative phase input end voltage dividing resistor R3, The device power supply of the first error amplifier EA1 is connected with bias voltage Vbias; The positive input end of the first error amplifier EA1 is respectively connected with one ends of voltage dividing resistors R1 and R2 at the positive input end, the other end of the R1 is connected with load voltage, and the other end of the R2 is grounded; the negative phase input end of the first error amplifier EA1 is respectively connected with the source electrode of the NMOS tube Mn0 and one end of a divider resistor R3 at the negative phase input end, and the other end of the divider resistor R3 is grounded; the output end of the first error amplifier EA1 is connected with the grid electrode of an NMOS tube Mn0, and the drain electrode of the NMOS tube Mn0 is used as the output end of the voltage-controlled current source unit; The reference voltage generating unit is respectively connected with the voltage-controlled current source unit and the charge pump unit, and is used for receiving the voltage-controlled current input by the voltage-controlled current source unit, generating a control voltage based on the voltage-controlled current and inputting the control voltage into the charge pump unit; the charge pump unit is connected with the grid electrode of the power tube, and is used for receiving the control voltage output by the reference voltage generating unit and pumping the switch voltage with the multiple of the control voltage to the grid electrode of the power tube so as to control the output voltage of the source electrode of the power tube.
  2. 2. A circuit for maintaining constant on-resistance of a power transistor in a load switch as recited in claim 1, wherein: the first error amplifier EA1 is used for converting the voltage of the positive input terminal based on output feedback With negative phase input voltage Is set equal and the voltage controlled current is generated accordingly.
  3. 3. A circuit for maintaining constant on-resistance of a power transistor in a load switch as recited in claim 2, wherein: when the resistance values of the voltage dividing resistors R1 and R2 at the non-inverting input end are equal, the voltage-controlled current 。
  4. 4. A circuit for maintaining constant on-resistance of a power transistor in a load switch as recited in claim 2, wherein: The reference voltage generating unit comprises a second error amplifier EA2, an inverter, a PMOS tube Mp0, and voltage dividing resistors R4 and R5 at the non-inverting input end, The device power supply of the second error amplifier EA2 and the source electrode of the PMOS tube MP0 are respectively connected with bias voltage Vbias; The positive input end of the second error amplifier EA2 is respectively connected with voltage dividing resistors R4 and R5 at the positive input end and the output end of the voltage-controlled current source unit, the other end of the R4 is connected with the drain electrode of the PMOS tube MP0, and the other end of the R5 is grounded; The negative phase input end of the second error amplifier EA2 is connected with the reference voltage Vref, and the output end of the second error amplifier EA2 is connected with the grid electrode of the PMOS tube MP0 through an inverter; the drain electrode of the PMOS tube MP0 and the other end of the resistor R4 are respectively used as the output ends of the reference voltage generating unit.
  5. 5. The circuit for maintaining constant on-resistance of a power transistor in a load switch as recited in claim 4, wherein: The second error amplifier EA2 is used for converting the voltage of the positive input terminal based on the output feedback With negative phase input voltage Is set equal and a control voltage is generated accordingly.
  6. 6. The circuit for maintaining constant on-resistance of a power transistor in a load switch as recited in claim 5, wherein: The control voltage is 。
  7. 7. The circuit for maintaining constant on-resistance of a power transistor in a load switch as recited in claim 6, wherein: when the resistance value of the negative phase input end voltage dividing resistor R3 of the first error amplifier EA1 is equal to that of the positive phase input end voltage dividing resistor R4 of the second error amplifier EA2, and the resistance values of the positive phase input end voltage dividing resistors R1 and R2 of the first error amplifier EA1 are equal to each other, the generated control voltage is obtained 。
  8. 8. The circuit for maintaining constant on-resistance of a power transistor in a load switch as recited in claim 7, wherein: the selection mode of the resistance value of the resistor in the circuit is as follows Equal to the inverse of the pumping multiple of the charge pump unit.
  9. 9. The circuit for maintaining constant on-resistance of a power transistor in a load switch as recited in claim 8, wherein: When the power tube works in a linear region, the voltage difference between the gate and the source of the power tube The gate-source voltage difference The value of (2) is constant.

Description

Circuit for keeping conduction impedance of power tube constant in load switch Technical Field The invention relates to the field of integrated circuits, in particular to a circuit for keeping the on-resistance of a power tube constant in a load switch. Background In the prior art, the internal structure of a load switch chip powered by a dual power supply generally comprises a charge pump, which is used for generating a higher gate voltage at the output end of a power tube so as to realize a higher output voltage for a later stage load. However, due to the effect of the charge pump, the gate voltage of the power tube doubles on the basis of the bias voltage, so that when the power tube works in a linear interval, the gate-source voltage difference of the power tube is influenced by the load current and the load voltage of the later stage to be in a changed state. Further, the voltage difference between the gate and the source of the power tube can cause the on-resistance of the power tube to change, thereby affecting the output constancy of the power tube. Therefore, a new circuit for keeping the on-resistance of the power transistor constant in the load switch is needed. Disclosure of Invention In order to solve the defects in the prior art, the invention aims to provide a circuit for keeping the on-resistance of a power tube constant in a load switch, which adopts a voltage-controlled current source unit and a reference voltage generating unit to generate the input voltage of a charge pump, and the input voltage counteracts the influences of bias voltage and load voltage, so that the switch voltage of a grid electrode of the power tube generated by the charge pump is constant and effective. The invention adopts the following technical scheme. The circuit for keeping the on-resistance of the power tube constant in the load switch comprises a voltage-controlled current source unit, a reference voltage generation unit, a charge pump unit and a power tube, wherein the voltage-controlled current source unit is connected with the reference voltage generation unit and used for generating voltage-controlled current of the reference voltage generation unit based on load voltage of the power tube, the reference voltage generation unit is respectively connected with the voltage-controlled current source unit and the charge pump unit and used for receiving voltage-controlled current input by the voltage-controlled current source unit and generating control voltage based on the voltage-controlled current and inputting the control voltage into the charge pump unit, and the charge pump unit is connected with a grid electrode of the power tube and used for receiving the control voltage output by the reference voltage generation unit and pumping out a switching voltage which is multiple of the control voltage to the grid electrode of the power tube so as to control the output voltage of a source electrode of the power tube. The voltage-controlled current source unit comprises a first error amplifier EA1, an NMOS tube Mn0, positive input end voltage dividing resistors R1 and R2 and a negative input end voltage dividing resistor R3, wherein a device power supply of the first error amplifier is connected with bias voltage Vbias, one ends of the positive input end voltage dividing resistors R1 and R2 of the first error amplifier EA1 are respectively connected with a load voltage Vin, the other end of the R1 is grounded, the negative input end of the first error amplifier EA1 is respectively connected with a source electrode of the NMOS tube Mn0 and one end of the negative input end voltage dividing resistor R3, the other end of the R3 is grounded, an output end of the first error amplifier EA1 is connected with a grid electrode of the NMOS tube Mn0, and a drain electrode of the NMOS tube Mn0 serves as an output end of the voltage-controlled current source unit. Preferably, a first error amplifier for inverting the voltage at the positive input based on the output feedbackIs set equal to the negative input voltage V 1-＝I·R3 and generates a voltage-controlled current accordingly. Preferably, when the resistances of the voltage dividing resistors R1 and R2 at the non-inverting input are equal, the current is controlled The reference voltage generating unit preferably comprises a second error amplifier EA2, an inverter, a PMOS tube MP0 and positive-phase input end voltage dividing resistors R4 and R5, wherein a device power supply of the second error amplifier and a source electrode of the PMOS tube MP0 are respectively connected with bias voltage Vbias, the positive-phase input end of the second error amplifier is respectively connected with the positive-phase input end voltage dividing resistors R4 and R5 and an output end of a voltage-controlled current source unit, the other end of the R4 is connected with a drain electrode of the PMOS tube MP0, the other end of the R5 is grounded, a negative-phase input end of the second er