CN108362929B - Double-circuit positive-end current sampling module, sampling circuit, switching circuit and sampling method - Google Patents

Double-circuit positive-end current sampling module, sampling circuit, switching circuit and sampling method Download PDF

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Publication number
CN108362929B
CN108362929B CN201810347792.8A CN201810347792A CN108362929B CN 108362929 B CN108362929 B CN 108362929B CN 201810347792 A CN201810347792 A CN 201810347792A CN 108362929 B CN108362929 B CN 108362929B
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resistor
sampling
output
circuit
pmos tube
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CN108362929A (en
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余东升
黄飞明
励晔
娄冬
杨潺
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WUXI SI-POWER MICRO-ELECTRONICS CO LTD
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WUXI SI-POWER MICRO-ELECTRONICS CO LTD
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
    • G01R1/30—Structural combination of electric measuring instruments with basic electronic circuits, e.g. with amplifier
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0084—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring voltage only
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
    • H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
    • H03K17/687—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being field-effect transistors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Current Or Voltage (AREA)
  • Amplifiers (AREA)

Abstract

The invention provides a double-circuit positive-end current sampling module, which comprises: one end of the resistor R5 is connected with the source electrode of the PMOS tube MP1, the source electrode of the PMOS tube MP4 and the source electrode of the PMOS tube MP 5; one end of the resistor R6 is connected with the source electrode of the PMOS tube MP 2; one end of the resistor R7 is connected with the source electrode of the PMOS tube MP 3; the grid electrode of the PMOS tube MP1 is connected with the grid electrode of the PMOS tube MP2, the grid electrode of the PMOS tube MP3 and the drain electrode of the PMOS tube MP 1; the drain electrode of the PMOS tube MP1 IS grounded through a current source IS1, the drain electrode of the PMOS tube MP2 IS grounded through a current source IS2, and the drain electrode of the PMOS tube MP3 IS grounded through a current source IS 2; the grid electrode of the PMOS tube MP4 is connected with the drain electrode of the PMOS tube MP2, and the grid electrode of the PMOS tube MP5 is connected with the drain electrode of the PMOS tube MP 3; the drains of the PMOS tubes MP4 and MP5 are connected with one end of a resistor R8, and the other end of the resistor R8 is connected with the chip ground; one end of the resistor R8 is used for outputting a voltage feedback signal V SEN . The invention realizes double-path high-precision current sampling.

Description

Double-circuit positive-end current sampling module, sampling circuit, switching circuit and sampling method
Technical Field
The invention relates to the technical field of power integrated circuits, in particular to a high-precision double-circuit positive-end current sampling control circuit applied to a switching regulator.
Background
Power converters are widely used in a variety of electronic devices to convert power from one form to another. The power converter mainly comprises a power stage circuit and a control loop. The control loop is used for keeping the output voltage or the output current of the power converter stable by adjusting the on and off time of a switching tube and a rectifying tube in the power stage circuit when the input voltage and the external load change. Therefore, whether accurate sampling can be performed on load current is important, the current sampling technology mainly tests the voltage difference between two ends of a sampling resistor, the sampling resistor can be the on-resistance of a power tube or a separated high-precision resistor, and the separated high-precision resistor is usually selected as the sampling resistor in a plurality of occasions with higher precision requirements because the on-resistance of the power tube fluctuates greatly. In order to reduce the power consumption generated on the sampling resistor, the resistance is usually very small, for example, 20 milliohms, so that the voltage difference across the sampling resistor is very small, and therefore, a high-precision amplifier is required to be designed inside the power chip to improve the sampling precision. Meanwhile, how to solve the accurate sampling under the condition of wide-range common-mode voltage is also a difficult problem. Along with the current application environment and the requirements of safety regulations becoming more and more complex, one chip can simultaneously have two or more paths of output, and how to solve the problem of realizing accurate sampling under the condition of wider common mode voltage for multiplexing output becomes more and more a urgent need to be solved.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a double-circuit positive-end current sampling module, a double-circuit positive-end current sampling circuit based on the double-circuit positive-end current sampling module and a switching circuit, so as to solve the problems that the sampling circuit in the prior art is complex in structure and low in precision, and meanwhile, the sampling consistency of the current of each output branch cannot be ensured. The technical scheme adopted by the invention is as follows:
a two-way positive side current sampling module, comprising: resistors R5, R6 and R7 with the same resistance, PMOS tubes MP1, MP2 and MP3 with the same resistance, PMOS tubes MP4 and MP5 with the same resistance R8, and current sources IS1, IS2 and IS3 with the same current;
one end of the resistor R5 is connected with the source electrode of the PMOS tube MP1, the source electrode of the PMOS tube MP4 and the source electrode of the PMOS tube MP 5; one end of the resistor R6 is connected with the source electrode of the PMOS tube MP 2; one end of the resistor R7 is connected with the source electrode of the PMOS tube MP 3; the grid electrode of the PMOS tube MP1 is connected with the grid electrode of the PMOS tube MP2, the grid electrode of the PMOS tube MP3 and the drain electrode of the PMOS tube MP 1; the drain electrode of the PMOS tube MP1 IS grounded through a current source IS1, the drain electrode of the PMOS tube MP2 IS grounded through a current source IS2, and the drain electrode of the PMOS tube MP3 IS grounded through a current source IS 2; grid electrode of PMOS tube MP4The grid electrode of the PMOS tube MP5 is connected with the drain electrode of the PMOS tube MP 3; the drains of the PMOS tubes MP4 and MP5 are connected with one end of a resistor R8, and the other end of the resistor R8 is connected with the chip ground; one end of the resistor R8 is used for outputting a voltage feedback signal V SEN 。
Further, the PMOS transistors MP1, MP2, MP3 are low voltage PMOS transistors.
Further, the PMOS tubes MP4 and MP5 are thin gate oxide high voltage PMOS tubes.
Further, the gate length of the PMOS transistors MP1, MP2 and MP3 is more than 5 μm.
Further, the gate width of the PMOS transistors MP1, MP2 and MP3 is more than 5 μm.
A double-circuit positive-end current sampling circuit comprises a first output branch, a second output branch and the double-circuit positive-end current sampling module; the first output branch comprises a sampling resistor R1 and a load R4, and the second output branch comprises a sampling resistor R2 and a load R3;
one ends of the sampling resistors R1 and R2 are connected together and connected with the other end of the resistor R5, and one end of the sampling resistor R1 connected with the sampling resistor R2 is a common end of the sampling resistors; the other end of the sampling resistor R2 is connected with the other end of the resistor R6 and one end of the load R3; the other end of the sampling resistor R1 is connected with the other end of the resistor R7 and one end of the load R4; the other ends of the loads R3 and R4 are grounded, and the chip ground of the double-circuit positive-end current sampling module is also grounded.
A switching circuit, comprising: a switching tube M1, a rectifying tube M2, an inductance L, an output capacitor Cout, a double-circuit positive-side current sampling module according to any one of claims 1-5, sampling resistors R1 and R2, feedback resistors R23 and R24, loads R3 and R4, a driving circuit, an RS trigger, a PWM comparator, an operational amplifier and a level selection circuit;
the drain electrode of the switch tube M1 is connected with the input voltage signal V IN The grid electrode is connected with one output end of the driving circuit, and the other output end of the driving circuit is connected with the grid electrode of the rectifying tube M2; the source electrode of the rectifying tube M2 is grounded; the source electrode of the switching tube M1 is connected with the drain electrode of the rectifying tube M2 and one end of an inductor L, and the other end of the inductor L is connected with one end of an output capacitor Cout and one end of sampling resistors R1 and R2; the other end of the output capacitor Cout is grounded;the other end of the resistor R5 in the double-circuit positive end current sampling module is connected with one ends of sampling resistors R1 and R2, the other end of the resistor R6 in the double-circuit positive end current sampling module is connected with the other end of the sampling resistor R2, and the other end of the resistor R7 in the double-circuit positive end current sampling module is connected with the other end of the sampling resistor R1; the other end of the sampling resistor R1 is grounded through a load R4; the other end of the sampling resistor R2 is connected with one end of the feedback resistor R23 and is grounded through a load R3; the other end of the feedback resistor R23 is grounded through a feedback resistor R24; the chip of the double-circuit positive-end current sampling module is grounded;
voltage feedback signal V obtained from double-circuit positive-side current sampling module SEN And a voltage feedback signal V obtained from the connection node of the feedback resistors R23, R24 FB Respectively input into level selection circuits for comparing voltage feedback signals V SEN And V FB Will be V SEN And V FB The larger signal of the first signal is transmitted to the inverting input end of the operational amplifier; the non-inverting input end of the operational amplifier is connected with the reference voltage V REF The method comprises the steps of carrying out a first treatment on the surface of the The output end of the operational amplifier is connected with the inverting input end of the PWM comparator, and the non-inverting input end of the PWM comparator is connected with the triangular wave signal V ramp The method comprises the steps of carrying out a first treatment on the surface of the The output end of the PWM comparator is connected with the R end of the RS trigger, and the S end of the RS trigger is connected with the pulse signal V pulse The method comprises the steps of carrying out a first treatment on the surface of the The Q end of the RS trigger is connected with the input end of the driving circuit.
Further, the output end of the operational amplifier is grounded through a compensating resistor R25 and a compensating capacitor C21 which are connected in series.
Further, the switching tube M1 and the rectifying tube M2 are NMOS tubes.
A method of current sampling, comprising:
two output branches are arranged, wherein the two output branches comprise a first output branch and a second output branch; the first output branch comprises a sampling resistor R1 and a load R4 which are connected in series, and the second output branch comprises a sampling resistor R2 and a load R3 which are connected in series; one ends of the sampling resistors R1 and R2 are connected together to serve as a common end of the sampling resistors;
detecting the positive terminal voltage of the common terminal of the sampling resistor to obtain a positive terminal voltage feedback signal representing output current information;
detecting the negative terminal voltage of a sampling resistor in the first output branch to obtain a negative terminal voltage feedback signal representing the output current information of the first output branch;
detecting the negative terminal voltage of the sampling resistor in the second output branch to obtain a negative terminal voltage feedback signal representing the output current information of the second output branch;
by comparing the voltage feedback differential pressure signals on sampling resistors in two output branches and converting the output current information of the output branch with larger differential pressure into a voltage feedback signal V SEN 。
The invention has the advantages that:
1) The consistency of the current sampling of the two positive ends is ensured by utilizing the complete consistency of the first detection branch circuit and the second detection branch circuit; the high-precision double-circuit positive-end current sampling circuit can be realized.
2) The common-mode voltage range of the high-precision double-circuit positive-end current sampling circuit can reach 1.8V to input voltage.
3) Only the second detection branch circuit in the two-way positive-end current sampling module is required to be copied, three or more detection branches can be easily expanded, and therefore high-precision multipath positive-end current sampling is achieved.
Drawings
Fig. 1 is a schematic diagram of a two-way positive side current sampling module and a two-way positive side current sampling circuit according to the present invention.
Fig. 2 is a schematic diagram of a switching circuit according to the present invention.
Fig. 3 is a timing diagram of a constant current/constant voltage mode of operation of the switching circuit of the present invention.
Detailed Description
The invention will be further described with reference to the following specific drawings and examples.
The invention provides a high-precision double-circuit positive-end current sampling module and a double-circuit positive-end current sampling circuit, which are shown in figure 1; the dotted line frame part is a double-path positive end current sampling module which can be made into a chip;
the double-circuit positive-end current sampling module comprises resistors R5, R6 and R7 with the same resistance, PMOS (P-channel metal oxide semiconductor) transistors MP1, MP2 and MP3 with the same resistance, PMOS transistors MP4 and MP5 with the same resistance, resistor R8 and current sources IS1, IS2 and IS3 with the same current; wherein MP1, MP2 and MP3 are low-voltage PMOS tubes, MP4 and MP5 are thin gate oxide high-voltage PMOS tubes; the peripheral devices of the chip are arranged outside the dotted line frame, and a double-circuit positive-end current sampling circuit is formed by the peripheral devices and the chip; wherein R1 and R2 are high-precision sampling resistors on two output branches respectively, and R3 and R4 are loads on two output branches respectively;
one end of the resistor R5 is connected with the source electrode of the PMOS tube MP1, the source electrode of the PMOS tube MP4 and the source electrode of the PMOS tube MP 5; one end of the resistor R6 is connected with the source electrode of the PMOS tube MP 2; one end of the resistor R7 is connected with the source electrode of the PMOS tube MP 3; the grid electrode of the PMOS tube MP1 is connected with the grid electrode of the PMOS tube MP2, the grid electrode of the PMOS tube MP3 and the drain electrode of the PMOS tube MP 1; the drain electrode of the PMOS tube MP1 IS grounded through a current source IS1, the drain electrode of the PMOS tube MP2 IS grounded through a current source IS2, and the drain electrode of the PMOS tube MP3 IS grounded through a current source IS 2; the grid electrode of the PMOS tube MP4 is connected with the drain electrode of the PMOS tube MP2, and the grid electrode of the PMOS tube MP5 is connected with the drain electrode of the PMOS tube MP 3; the drains of the PMOS tubes MP4 and MP5 are connected with one end of a resistor R8, and the other end of the resistor R8 is connected with the chip ground; one end of the resistor R8 is used for outputting a voltage feedback signal V SEN The method comprises the steps of carrying out a first treatment on the surface of the The currents of the current sources IS1, IS2 and IS3 are I 1 ；
A high-precision double-circuit positive-end current sampling circuit comprises a first output branch, a second output branch and the double-circuit positive-end current sampling module; the first output branch comprises a sampling resistor R1 and a load R4, and the second output branch comprises a sampling resistor R2 and a load R3;
one ends of the sampling resistors R1 and R2 are connected together and connected with the other end of the resistor R5, and one end of the sampling resistor R1 connected with the sampling resistor R2 is a common end of the sampling resistors; the other end of the sampling resistor R2 is connected with the other end of the resistor R6 and one end of the load R3; the other end of the sampling resistor R1 is connected with the other end of the resistor R7 and one end of the load R4; the other ends of the loads R3 and R4 are grounded, and the chip ground of the double-circuit positive-end current sampling module is also grounded.
The working principle of the high-precision two-way positive-side current sampling circuit and related formula derivation will be explained in detail below. The voltage at each node and the current at each branch are as indicated in fig. 1; in fig. 1, MP2, MP3 are the same, neglecting channel modulation effect, assuming that MP4 and MP5 have current, MP1 to MP3 all operate in saturation region, and the formula of saturation region combined with MOS transistor easily knows v4=v5=v6, and simultaneously obtains the following equation:
V 1 -(I 1 +I 2 +I 3 )*R 5 ＝V 2 -I 1 *R 6 (1)
V 1 -(I 1 +I 2 +I 3 )*R 5 ＝V 3 -I 1 *R 7 (2)
due to R 5 ＝R 6 ＝R 7 Therefore, the following steps are obtained:
V 1 -V 2 ＝(I 2 +I 3 )*R 5 (3)
V 1 -V 3 ＝(I 2 +I 3 )*R 5 (4)
when V is 1 -V 2 And V 1 -V 3 When equal, I 2 And I 3 Can be arbitrarily combined, and is assumed to be I 3 =0, then:
when V is 1 -V 2 And V 1 -V 3 When the two are not equal, the combination of formulas (3) and (4) can show that the current of MP4 and MP5 is incorrect, only one of them can be conducted, and the other is in the off state, and the PMOS tube connected with the grid electrode of the PMOS tube MP4 or MP5 in the off state works in the linear region. Reasoning easy-to-know V 1 -V 2 And V 1 -V 3 The PMOS tube MP4 or MP5 corresponding to the output branch with larger medium pressure difference is conducted. For example V 1 -V 2 ＞V 1 -V 3 MP2 is operated in the saturation region, MP3 is operated in the linear region, MP4 is conducted with current flowing, MP5 is in the off state, i.e. I3=0, then
Comprehensive synthesisThe analysis above and formulas (5) and (6) show that the two-way positive current sampling module in the dashed box can compare and screen out the branch with larger differential pressure between the two ends of the high-precision sampling resistor in the two output branches, and convert the load current signal into the voltage feedback signal V SEN The ratio of R8 to R5 is the amplification factor of the load current signal, and the sampling formula of the double-path positive-end current sampling module is as follows:
wherein the ratio of the resistors R8 and R5 can be used to adjust the amplification of the sampling circuit, and the type of resistors R8 and R5 can be used to adjust the temperature coefficient of the sampling circuit.
As can be seen from the deduction of the formula, the two-way positive current sampling circuit can realize completely equal current sampling coefficients as long as the absolute matching performance of the first detection branch circuit (R6, MP2, IS2 and MP 4) and the second detection branch circuit (R7, MP3, IS3 and MP 5) IS ensured, so that the influence caused by process mismatch IS also needed to be considered in the real design process. Considering that the parameter control of the low-voltage device is much easier than that of the high-voltage device in the process of production, and higher precision can be realized, the MP 1-MP 3 in the circuit are all low-voltage tubes, and the gate length of MP 1-MP 3 is recommended to be more than 5 mu m in order to further weaken the influence of the channel modulation effect; it is also recommended to take more than 5 μm in order to improve the matching degree and reduce the influence gate width caused by mismatch.
In summary, the current sampling method provided in the present invention includes:
two output branches are arranged, wherein the two output branches comprise a first output branch and a second output branch; the first output branch comprises a sampling resistor R1 and a load R4, and the second output branch comprises a sampling resistor R2 and a load R3; one ends of the sampling resistors R1 and R2 are connected together to serve as a common end of the sampling resistors; the sampling resistor R1 is connected with the load R4 in series, and the sampling resistor R2 is connected with the load R3 in series;
detecting the positive terminal voltage of the common terminal of the sampling resistor to obtain a positive terminal voltage feedback signal representing output current information;
detecting the negative terminal voltage of a sampling resistor in the first output branch to obtain a negative terminal voltage feedback signal representing the output current information of the first output branch;
detecting the negative terminal voltage of the sampling resistor in the second output branch to obtain a negative terminal voltage feedback signal representing the output current information of the second output branch;
by comparing the voltage feedback differential pressure signals on sampling resistors in two output branches and converting the output current information of the output branch with larger differential pressure into a voltage feedback signal V SEN The current is transmitted to the next stage to realize overcurrent protection or constant current function;
the switch circuit provided by the invention is shown in fig. 2, and comprises: the switching tube M1, the rectifying tube M2, the inductance L, the output capacitor Cout, the double-circuit positive-end current sampling module, the sampling resistors R1 and R2, the feedback resistors R23 and R24, the loads R3 and R4, the driving circuit 21, the RS trigger 22, the PWM comparator 23, the operational amplifier 24, the level selection circuit 25, the compensation resistor R25 and the compensation capacitor C21; the switching tube M1 and the rectifying tube M2 are NMOS tubes, and the RS trigger 22 is effective for high-level input;
the drain electrode of the switch tube M1 is connected with the input voltage signal V IN The grid electrode is connected with one output end of the driving circuit 21, and the other output end of the driving circuit 21 is connected with the grid electrode of the rectifying tube M2; the source electrode of the rectifying tube M2 is grounded; the source electrode of the switching tube M1 is connected with the drain electrode of the rectifying tube M2 and one end of an inductor L, and the other end of the inductor L is connected with one end of an output capacitor Cout and one end of sampling resistors R1 and R2; the other end of the output capacitor Cout is grounded; the other end of the resistor R5 in the double-circuit positive end current sampling module is connected with one ends of sampling resistors R1 and R2, the other end of the resistor R6 in the double-circuit positive end current sampling module is connected with the other end of the sampling resistor R2, and the other end of the resistor R7 in the double-circuit positive end current sampling module is connected with the other end of the sampling resistor R1; the other end of the sampling resistor R1 is grounded through a load R4; the other end of the sampling resistor R2 is connected with one end of the feedback resistor R23 and is grounded through a load R3; the other end of the feedback resistor R23 is grounded through a feedback resistor R24; the chip of the double-circuit positive-end current sampling module is grounded;
from the two-way positive endVoltage feedback signal V obtained by current sampling module SEN And a voltage feedback signal V obtained from the connection node of the feedback resistors R23, R24 FB Respectively input to the level selection circuits 25, the level selection circuits 25 compare the voltage feedback signals V SEN And V FB Will be V SEN And V FB The larger of which is passed to the inverting input of op amp 24; the non-inverting input of the operational amplifier 24 is connected with the reference voltage V REF The method comprises the steps of carrying out a first treatment on the surface of the The output end of the operational amplifier 24 is connected with the inverting input end of the PWM comparator 23, and the non-inverting input end of the PWM comparator is connected with the triangular wave signal V ramp The method comprises the steps of carrying out a first treatment on the surface of the The output end of the PWM comparator 23 is connected with the R end of the RS trigger 22, and the S end of the RS trigger 22 is connected with the pulse signal V pulse The method comprises the steps of carrying out a first treatment on the surface of the The Q terminal of the RS flip-flop 22 is connected to the input terminal of the driving circuit 21.
More preferably, the output of the operational amplifier 24 is also grounded through a compensation resistor R25 and a compensation capacitor C21 connected in series.
In FIG. 2, V out To sample the positive terminal voltage of the common terminal of the resistor, V SEN1 For the negative voltage of the sampling resistor R1 in the first output branch, V SEN2 For the negative voltage of the sampling resistor R2 in the second output branch, the two-way positive current sampling module compares V out -V SEN1 And V out -V SEN2 Then converting the value with larger difference into a voltage feedback signal V SEN The method comprises the steps of carrying out a first treatment on the surface of the Is passed to a level selection circuit 25, the level selection circuit 25 feeding back a signal V by comparing the voltages SEN And V FB Will be V SEN And V FB The larger signal of the signal is transmitted to the inverting input end of the operational amplifier 24 to participate in loop control of the circuit; signal V SEN Greater than V FB In this case, the constant-voltage loop (loop in which the feedback resistors R23 and R24 and the level selection circuit 25 are located) is shielded, the constant-current loop (loop in which the sampling resistors R1 and R2, the two-way positive-side current sampling module, and the level selection circuit 25 are located) is operated, and the load current is always stabilized at the set constant-current point. The constant current point is set by a double-circuit positive end current sampling module, a high-precision sampling resistor R1 of the first output branch and a high-precision sampling resistor R2 of the second output branch. When VS is EN Small signalAt V FB When the constant current loop is shielded, the constant voltage loop acts, and the output voltage is always stabilized at a set value. Where the output voltage is derived from the reference voltage V REF Feedback resistor R23 and feedback resistor R24.
The principle of operation of this topology is described below in connection with the timing diagram of the constant current/constant voltage mode of operation given in fig. 3. Before time t1, the load current i of the first output branch out1 Less than the constant current point, less load, and load current i of the second output branch out2 Is 0. V obtained by sampling by the double-circuit positive-end current sampling module SEN The voltage is smaller than V FB The constant current loop is shielded, the constant voltage loop acts, V FB The level is regulated and stabilized at the reference voltage V through a constant voltage loop REF Up and down, output voltage V out Constant. the load of the first output branch is suddenly switched to a constant voltage source at the time t1 to output voltage V out Pulled low. At this time V FB The same proportion is reduced, the upper tube M1 is controlled to be conducted for a long time through the constant voltage loop, enough energy is provided for the output, and along with the load current i of the first output branch out1 Gradually increasing, and V obtained by sampling by the double-path positive-end current sampling module SEN The voltage also gradually rises, when V SEN Voltage higher than V FB When the constant voltage loop is shielded, the constant current loop starts to control the whole loop, and finally the load current i of the first output branch circuit out1 Stabilize at constant current point and output voltage V out The same constant voltage source load as the first output branch.
While the invention has been described with reference to exemplary embodiments, it is to be understood that the terminology used is intended to be in the nature of words of description and of limitation. As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, but rather should be construed broadly within its spirit and scope as defined in the appended claims. It is therefore intended that all changes and modifications that fall within the scope of the claims or the equivalents thereof be covered thereby.

Claims (10)

1. A two-way positive side current sampling module, comprising: resistors R5, R6 and R7 with the same resistance, PMOS tubes MP1, MP2 and MP3 with the same resistance, PMOS tubes MP4 and MP5 with the same resistance R8, and current sources IS1, IS2 and IS3 with the same current;
one end of the resistor R5 is connected with the source electrode of the PMOS tube MP1, the source electrode of the PMOS tube MP4 and the source electrode of the PMOS tube MP 5; one end of the resistor R6 is connected with the source electrode of the PMOS tube MP 2; one end of the resistor R7 is connected with the source electrode of the PMOS tube MP 3; the grid electrode of the PMOS tube MP1 is connected with the grid electrode of the PMOS tube MP2, the grid electrode of the PMOS tube MP3 and the drain electrode of the PMOS tube MP 1; the drain electrode of the PMOS tube MP1 IS grounded through a current source IS1, the drain electrode of the PMOS tube MP2 IS grounded through a current source IS2, and the drain electrode of the PMOS tube MP3 IS grounded through a current source IS3; the grid electrode of the PMOS tube MP4 is connected with the drain electrode of the PMOS tube MP2, and the grid electrode of the PMOS tube MP5 is connected with the drain electrode of the PMOS tube MP 3; the drains of the PMOS tubes MP4 and MP5 are connected with one end of a resistor R8, and the other end of the resistor R8 is connected with the chip ground; one end of the resistor R8 is used for outputting a voltage feedback signal V SEN 。
2. The two-way positive side current sampling module of claim 1, wherein,
the PMOS tubes MP1, MP2 and MP3 are low-voltage PMOS tubes.
3. The two-way positive side current sampling module of claim 1, wherein,
the PMOS tubes MP4 and MP5 are thin gate oxide high-voltage PMOS tubes.
4. The two-way positive side current sampling module of claim 1, wherein,
the gate length of the PMOS tubes MP1, MP2 and MP3 is more than 5 mu m.
5. The two-way positive side current sampling module of claim 1, wherein,
the gate width of the PMOS transistors MP1, MP2 and MP3 is more than 5 mu m.
6. A two-way positive-side current sampling circuit comprising a first output branch, a second output branch, and the two-way positive-side current sampling module according to any one of claims 1 to 5; the first output branch comprises a sampling resistor R1 and a load R4, and the second output branch comprises a sampling resistor R2 and a load R3;
one ends of the sampling resistors R1 and R2 are connected together and connected with the other end of the resistor R5, and one end of the sampling resistor R1 connected with the sampling resistor R2 is a common end of the sampling resistors; the other end of the sampling resistor R2 is connected with the other end of the resistor R6 and one end of the load R3; the other end of the sampling resistor R1 is connected with the other end of the resistor R7 and one end of the load R4; the other ends of the loads R3 and R4 are grounded, and the chip ground of the double-circuit positive-end current sampling module is also grounded.
7. A switching circuit, comprising: a switching tube M1, a rectifying tube M2, an inductance L, an output capacitor Cout, a double-circuit positive-side current sampling module according to any one of claims 1 to 5, sampling resistors R1 and R2, feedback resistors R23 and R24, loads R3 and R4, a driving circuit (21), an RS trigger (22), a PWM comparator (23), an operational amplifier (24) and a level selection circuit (25);
the drain electrode of the switch tube M1 is connected with the input voltage signal V IN The grid electrode is connected with one output end of the driving circuit (21), and the other output end of the driving circuit (21) is connected with the grid electrode of the rectifying tube M2; the source electrode of the rectifying tube M2 is grounded; the source electrode of the switching tube M1 is connected with the drain electrode of the rectifying tube M2 and one end of an inductor L, and the other end of the inductor L is connected with one end of an output capacitor Cout and one end of sampling resistors R1 and R2; the other end of the output capacitor Cout is grounded; the other end of the resistor R5 in the double-circuit positive end current sampling module is connected with one ends of sampling resistors R1 and R2, the other end of the resistor R6 in the double-circuit positive end current sampling module is connected with the other end of the sampling resistor R2, and the other end of the resistor R7 in the double-circuit positive end current sampling module is connected with the other end of the sampling resistor R1; the other end of the sampling resistor R1 is grounded through a load R4; the other end of the sampling resistor R2 is connected with one end of the feedback resistor R23 and is grounded through a load R3; the other end of the feedback resistor R23 is grounded through a feedback resistor R24; the chip of the double-circuit positive-end current sampling module is grounded;
voltage feedback signal V obtained from double-circuit positive-side current sampling module SEN And from feedback resistors R23, R24Voltage feedback signal V obtained at node FB Respectively input with a level selection circuit (25), the level selection circuit (25) compares the voltage feedback signal V SEN And V FB Will be V SEN And V FB The larger of which is passed to the inverting input of the operational amplifier (24); the non-inverting input of the operational amplifier (24) is connected with the reference voltage V REF The method comprises the steps of carrying out a first treatment on the surface of the The output end of the operational amplifier (24) is connected with the inverting input end of the PWM comparator (23), and the non-inverting input end of the PWM comparator is connected with the triangular wave signal V ramp The method comprises the steps of carrying out a first treatment on the surface of the The output end of the PWM comparator (23) is connected with the R end of the RS trigger (22), and the S end of the RS trigger (22) is connected with the pulse signal V pulse The method comprises the steps of carrying out a first treatment on the surface of the The Q end of the RS trigger (22) is connected with the input end of the driving circuit (21).
8. The switching circuit according to claim 7, wherein,
the output end of the operational amplifier (24) is also grounded through a compensating resistor R25 and a compensating capacitor C21 which are connected in series.
9. The switching circuit according to claim 7, wherein,
the switching tube M1 and the rectifying tube M2 are NMOS tubes.
10. A method of current sampling adapted for use in a two-way positive side current sampling circuit according to claim 6, comprising:
two output branches are arranged, wherein the two output branches comprise a first output branch and a second output branch; the first output branch comprises a sampling resistor R1 and a load R4 which are connected in series, and the second output branch comprises a sampling resistor R2 and a load R3 which are connected in series; one ends of the sampling resistors R1 and R2 are connected together to serve as a common end of the sampling resistors;
detecting the positive terminal voltage of the common terminal of the sampling resistor to obtain a positive terminal voltage feedback signal representing output current information;
detecting the negative terminal voltage of a sampling resistor in the first output branch to obtain a negative terminal voltage feedback signal representing the output current information of the first output branch;
detecting the negative terminal voltage of the sampling resistor in the second output branch to obtain a negative terminal voltage feedback signal representing the output current information of the second output branch;
by comparing the voltage feedback differential pressure signals on sampling resistors in two output branches and converting the output current information of the output branch with larger differential pressure into a voltage feedback signal V SEN 。
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