CN106992681B - Switch conversion circuit with multi-mode constant current control - Google Patents

Switch conversion circuit with multi-mode constant current control Download PDF

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CN106992681B
CN106992681B CN201710183551.XA CN201710183551A CN106992681B CN 106992681 B CN106992681 B CN 106992681B CN 201710183551 A CN201710183551 A CN 201710183551A CN 106992681 B CN106992681 B CN 106992681B
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circuit
constant current
output
input end
pin
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CN106992681A (en
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娄冬
杨潺
励晔
余东升
黄飞明
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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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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • 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

Abstract

The invention provides a switch conversion circuit with multi-mode constant current control, which comprises: the circuit comprises an internal voltage reduction circuit, a reference circuit, a holding circuit, a current sampling circuit, an equivalent sampling resistor R105, a switch control MOS tube Q106, a synchronous arrangement MOS tube Q107, a driving circuit, an RS trigger, an oscillator circuit, a PWM comparator, an adjustment MOS tube Q114, an error amplifier, a current input amplifier, a signal adding module, a high voltage selection circuit, an external constant current sampling signal amplification circuit, a constant current mode selection circuit, a constant current source I121, a feedback pin FB, an ILIMIT pin, a power supply pin VIN, an output pin SW and a grounding pin GND; the invention can realize the setting of the constant current value and the switching of the constant current control mode by judging the external connection mode of the single pin; so that the client can select a proper constant current control mode through external setting according to the requirement.

Description

Switch conversion circuit with multi-mode constant current control
Technical Field
The invention relates to a constant current control circuit, in particular to a switch conversion circuit with high requirements on constant current characteristics.
Background
In a switching power supply circuit, a control circuit often provides only constant voltage control. But when supplying power to a battery charging circuit, the output power supply is often required to have a constant current function. In the traditional constant current control, output current is sampled mainly through power resistor sampling and fed back to a control circuit for constant current control, and the output current needs to flow through a power sampling resistor and can generate power loss on the power sampling resistor. The constant current control is realized by sampling the internal inductive current, and because a certain deviation exists between the inductive current and the actual output current and a certain deviation also exists during the inductive current sampling, the constant current precision is not very good in the mode of realizing the constant current control by sampling the inductive current.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a switch conversion circuit with multi-mode constant current control, which can realize the setting of a constant current value and the switching of a constant current control mode by judging the external connection mode of a single pin; so that the client can select a proper constant current control mode through external setting according to the requirement. The technical scheme adopted by the invention is as follows:
a switching converter circuit with multi-mode constant current control, comprising: the circuit comprises an internal voltage reduction circuit, a reference circuit, a holding circuit, a current sampling circuit, an equivalent sampling resistor R105, a switch control MOS tube Q106, a synchronous arrangement MOS tube Q107, a driving circuit, an RS trigger, an oscillator circuit, a PWM comparator, an adjustment MOS tube Q114, an error amplifier, a current input amplifier, a signal adding module, a high voltage selection circuit, an external constant current sampling signal amplification circuit, a constant current mode selection circuit, a constant current source I121, a feedback pin FB, an ILIMIT pin, a power supply pin VIN, an output pin SW and a grounding pin GND;
the input end of the internal voltage reduction circuit is connected with a power pin VIN, and the output end of the internal voltage reduction circuit is connected with the input end of the reference circuit; the reference circuit provides reference voltage and reference current of each constant current source for the interior of the switch conversion circuit, and the reference voltage Vref generated by the reference circuit is connected with the non-inverting input end of the error amplifier;
one end of the equivalent sampling resistor R105 is connected with a power pin VIN, the other end of the equivalent sampling resistor R is connected with the input end of the current sampling circuit and the source electrode of the switch control MOS tube Q106, and the drain electrode of the Q106 is connected with the drain electrodes of the output pins SW and Q107; the output pin SW is used for being connected with an inductor L123 connected in series between the output pin SW and the positive end of an output load, the source electrode of the Q107 is connected with a ground pin GND, and the driving circuit is respectively connected with and controls the gates of the switch control MOS transistor Q106 and the synchronous sorting MOS transistor Q107; the equivalent sampling resistor R105 samples the current of the inductor L123; the drive circuit implements protection logic and provides drive and dead time control for Q106 and Q107; the output end of the RS trigger is connected with the input end of the driving circuit;
the output end of the current sampling circuit is connected with the input end of the holding circuit, and the input end of the holding circuit is connected with the non-inverting input end of the current input amplifier; the current sampling circuit samples the current of the inductor L123, and the holding circuit holds the sampled current signal of the inductor L123;
the oscillator circuit provides a clock signal and a ramp compensation signal, and the clock signal is connected with the S end of the RS trigger; the signal adding module adds the current sampling signal of the inductor L123 and the ramp compensation signal and connects the added signal with the in-phase input end of the PWM comparator; the reverse input end of the PWM comparator is connected with the output end of the error amplifier; the output end of the PWM comparator is connected with the R end of the RS trigger; the PWM comparator compares the added signal of the current sampling signal of the inductor L123 and the ramp compensation signal with the output signal of the error amplifier, and outputs a PWM signal to control the on-off of the power tubes Q106 and Q107; the reverse input end of the error amplifier is connected with the output of the high-voltage selection circuit, and amplifies the feedback signal and the error signal of the internal reference voltage Vref; the output end of the error amplifier outputs a COMP signal;
the inverting input end of the current input amplifier is connected with the current output end of the constant current mode selection circuit; the output end of the current input amplifier is connected with the grid electrode of the adjusting MOS tube Q114, the drain electrode of the adjusting MOS tube Q114 is connected with the output end of the error amplifier, and the source electrode is grounded; the adjusting MOS tube Q114 is used as an adjusting MOS tube in an internal constant-current control mode, and constant-current control is realized through the output of the clamping error amplifier;
one input end of the high-voltage selection circuit is connected with the feedback pin FB, and the other input end of the high-voltage selection circuit is connected with the output end of the external constant-current sampling signal amplification circuit; the high-voltage selection circuit has the function of selecting the input signal with the higher voltage of the two input voltages to be transmitted to the output end;
the input end of the constant current mode selection circuit and the input end of the external constant current sampling signal amplification circuit are connected with the output of the constant current source I121 and an ILIMIT pin; the constant current mode selection circuit selects a corresponding constant current control mode according to the state of the ILIMIT pin; the constant current source I121 flows through a resistor on the ILIMIT pin to generate voltage so as to set a constant current value and judge a constant current control mode;
the control end of the constant current mode selection circuit is respectively connected with the low level effective enabling end of the external constant current sampling signal amplification circuit and the high level effective enabling end of the current input amplifier.
Further, the constant current mode selection circuit comprises an operational amplifier U601, an adjustment NMOS transistor Q602, a resistor R613, a PMOS transistor Q603, Q604, Q6041, Q605, Q606, Q607, Q608 and Q609; constant current sources I610, I611, I612, an inverter U614 and a NAND gate U615;
the non-inverting input end of the operational amplifier U601 serves as the input end of the constant current mode selection circuit and is connected with the grids of the PMOS tubes Q604, Q606, Q607 and Q608; the power supply positive voltage is connected with the sources of the PMOS tubes Q604, Q606, Q607 and Q608 and the input end of the constant current source I610; the output end of the constant current source I610 is connected with the source electrode of the PMOS tube Q609; the drain electrode of the PMOS tube Q604 is connected with the source electrode of the Q603, and the grid electrode of the PMOS tube Q603 is connected with the drain electrode of the PMOS tube Q603, the grid electrode of the Q6041 and the grid electrode of the Q605; the drain electrode of the PMOS tube Q603 is connected with the drain electrode of the NMOS tube Q602, the grid electrode of the NMOS tube Q602 is connected with the output end of the operational amplifier U601, and the source electrode of the NMOS tube Q602 is connected with the inverting input end of the operational amplifier U601 and is grounded through a resistor R613; the drain electrode of the PMOS tube Q606 is connected with the source electrode of the Q6041, and the drain electrode of the PMOS tube Q6041 is connected with the input end of the constant current source I611 and the input end of the phase inverter U614; the output end of the constant current source I611 is grounded; the drain of the PMOS transistor Q607 is connected with the input end of the constant current source I612, one input end of the NAND gate U615 and the grid of the Q609; the output end of the constant current source I612 is grounded; the output end of the inverter U614 is connected with the other input end of the NAND gate U615; the output end of the NAND gate U615 is used as the control end of the constant current mode selection circuit; the drain electrode of the PMOS tube Q608 is connected with the source electrode of the Q605, and the drain electrode of the PMOS tube Q605 is connected with the drain electrode of the PMOS tube Q609; the drain of the PMOS tube Q609 is used as the current output end of the constant current mode selection circuit.
Further, the high voltage selection circuit includes a comparator U401, an inverter U402, transmission gates U403 and U404; the non-inverting input end and the inverting input end of the comparator U401 are used as two input ends of the high-voltage selection circuit; the output end of the comparator U401 is connected with the input end of the inverter U402, the negative control end of the transmission gate U403 and the positive control end of the transmission gate U404; the output end of the inverter U402 is connected with the positive control end of the transmission gate U403 and the negative control end of the transmission gate U404; the input end of the transmission gate U403 is connected with the inverting input end of the comparator U401; the input end of the transmission gate U404 is connected with the non-inverting input end of the comparator U401; the output terminals of the transmission gates U403 and U404 are connected and serve as the output terminal of the high voltage selection circuit.
Furthermore, the invention also comprises a loop compensation circuit formed by connecting a resistor R112 and a capacitor C113 in series; one end of the loop compensation circuit is connected with the output end of the error amplifier, and the other end of the loop compensation circuit is grounded.
Furthermore, a PMOS transistor is adopted as the switching control MOS transistor Q106, and an NMOS transistor is adopted as the synchronous sorting MOS transistor Q107.
Further, the adjusting MOS transistor Q114 adopts an NMOS transistor.
Furthermore, the invention also comprises an overvoltage protection circuit and an over-temperature protection circuit; the over-temperature protection circuit is connected with the driving circuit and provides over-temperature protection for the switch conversion circuit; the overvoltage protection circuit is connected with the driving circuit and provides input overvoltage and output overvoltage protection for the switch conversion circuit.
Further, the holding circuit also filters the sampled inductor L123 current signal.
The invention has the advantages that: the invention innovates the constant current control circuit and provides the constant current control circuit which can realize the setting of the constant current value and the switching of the constant current control mode by judging the external connection mode of a single pin, so that the integrated circuit using the invention has wider application range, and a user can select a proper control mode under the constraints of factors such as precision, efficiency, cost and the like.
Drawings
FIG. 1 is a schematic diagram of an application circuit with a constant current value as an internal default value according to the present invention.
Fig. 2 is a schematic diagram of an applied circuit capable of setting a constant current value according to the present invention.
Fig. 3 is a schematic diagram of an application circuit in the external constant current control mode according to the present invention.
Fig. 4 is a schematic diagram of a high voltage selection circuit according to an embodiment of the present invention.
Fig. 5 is a schematic diagram of a constant current mode selection circuit according to an embodiment of the present invention.
Detailed Description
The invention is further illustrated by the following specific figures and examples.
The invention provides a switching conversion circuit with multi-mode constant current control, as shown in fig. 1, comprising:
an internal voltage reduction circuit 101, a reference circuit 102, a holding circuit 103, a current sampling circuit 104, an equivalent sampling resistor R105, a switch control MOS transistor Q106, a synchronous trimming MOS transistor Q107, a driving circuit 108, an RS flip-flop 109, an oscillator circuit 110, a PWM comparator 111, a resistor R112, a capacitor C113, an adjustment MOS transistor Q114, an error amplifier 115, a current input amplifier 116, a signal addition module 117, a high voltage selection circuit 118, an external constant current sampling signal amplification circuit 119, a constant current mode selection circuit 120, a constant current source I121, a feedback pin FB, an ILIMIT pin, a power supply pin VIN, an output pin SW, a ground pin GND, an overvoltage protection circuit 127 and an overheat protection circuit 128;
the internal voltage reduction circuit 101 provides power for the interior of the switch conversion circuit, the input end of the internal voltage reduction circuit is connected with a power pin VIN, and the output end of the internal voltage reduction circuit is connected with the input end of the reference circuit 102; the reference circuit 102 provides a reference voltage (such as Vref) and reference currents of each constant current source for the inside of the switch conversion circuit, and the reference voltage Vref generated by the reference circuit is connected with the non-inverting input end of the error amplifier 115;
one end of the equivalent sampling resistor R105 is connected with a power supply pin VIN, the other end of the equivalent sampling resistor R is connected with the input end of the current sampling circuit 104 and the source electrode of the switch control MOS tube Q106, the switch control MOS tube Q106 adopts a PMOS tube, the synchronous sorting MOS tube Q107 adopts an NMOS tube, and the drain electrode of the Q106 is connected with the output pins SW and the drain electrode of the Q107; the output pin SW is used for connecting an inductor L123 connected in series between the output pin SW and the positive end of an output load, the source electrode of the Q107 is connected with a ground pin GND, and the driving circuit 108 is respectively connected with and controls the gates of the switch control MOS transistor Q106 and the synchronous sorting MOS transistor Q107; the equivalent sampling resistor R105 samples the current of the inductor L123 for constant voltage control and internal constant current control of the circuit, and the Q106 charges the inductor L123 and simultaneously supplies current to a load (the load is connected to an OUT + end and an OUT-end in the figures 1, 2 and 3) when being conducted; q107 is conducted after Q106 is closed, and a follow current path is provided for the current of the inductor L123; the driver circuit 108 implements protection logic and provides drive and dead time control for the power transistors Q106 and Q107; the output end of the RS flip-flop 109 is connected to the input end of the driving circuit 108, which provides logic control for the switching conversion circuit;
the output end of the current sampling circuit 104 is connected with the input end of the holding circuit 103, and the input end of the holding circuit 103 is connected with the non-inverting input end of the current input amplifier 116; the current sampling circuit 104 samples the current of the inductor L123, and the holding circuit 103 holds and filters the sampled current signal of the inductor L123;
the oscillator circuit 110 provides a clock signal and a ramp compensation signal, and the clock signal is connected with the S end of the RS trigger; the signal adding module 117 adds the current sampling signal of the inductor L123 and the ramp compensation signal, and connects the added signal to the non-inverting input terminal of the PWM comparator 111; the inverting input of the PWM comparator 111 is connected to the output of the error amplifier 115; the output end of the PWM comparator 111 is connected with the R end of the RS trigger; the PWM comparator 111 compares the added current sampling signal of the inductor L123 and the ramp compensation signal with the output signal of the error amplifier 115, and outputs a PWM signal to control the switching of the power transistors Q106 and Q107; the inverting input terminal of the error amplifier 115 is connected to the output of the high voltage selection circuit 118, and amplifies the feedback signal and the error signal of the internal reference voltage Vref; the output terminal of the error amplifier 115 outputs the COMP signal;
the resistor R112 and the capacitor C113 are connected in series to form a loop compensation circuit; one end of the loop compensation circuit is connected with the output end of the error amplifier 115, and the other end is grounded;
the inverting input terminal of the current input amplifier 116 is connected to the current output terminal of the constant current mode selection circuit 120; the output end of the current input amplifier 116 is connected with the grid electrode of the adjusting MOS transistor Q114, the adjusting MOS transistor Q114 adopts an NMOS transistor, the drain electrode is connected with the output end of the error amplifier 115, and the source electrode is grounded; the adjusting MOS transistor Q114 serves as an adjusting MOS in the internal constant current control mode, and constant current control is realized by the output of the clamping error amplifier 115; the current input amplifier 116 operates in an internal constant current control mode;
one input end of the high voltage selection circuit 118 is connected with the feedback pin FB, and the other input end is connected with the output end of the external constant current sampling signal amplification circuit 119; the function of the high voltage selection circuit 118 is to select the higher of the two input voltages for transmission to the output;
the input end of the constant current mode selection circuit 120 and the input end of the external constant current sampling signal amplification circuit 119 are connected with the output of the constant current source I121 and an ILIMIT pin; the constant current mode selection circuit 120 selects a corresponding constant current control mode according to the ILIMIT pin state; the ILIMIT pin is suspended or externally connected with a resistor, and the constant current source I121 generates voltage by flowing through the resistor on the ILIMIT pin to set a constant current value and judge a constant current control mode; the control end of the constant current mode selection circuit 120 is respectively connected with the low level effective enabling end of the external constant current sampling signal amplification circuit 119 and the high level effective enabling end of the current input amplifier 116;
the over-temperature protection circuit 128 is connected with the driving circuit 108 and provides over-temperature protection for the switch conversion circuit; the overvoltage protection circuit 127 is connected with the driving circuit 108 and provides input overvoltage and output overvoltage protection for the switch conversion circuit;
in the application circuit of the invention, one end of an inductor L123 is connected with an output pin SW, the other end is connected with one end of a resistor R124 and one end of a capacitor C126, and the other end of the resistor R124 is connected with one end of a resistor R125 and a feedback pin FB; the other end of the resistor R125 and the other end of the capacitor C126 are grounded; the inductor L123 and the capacitor C126 form an LC output filter circuit; the resistors R125 and R126 form a feedback network and can feed back a voltage signal;
the invention realizes constant current control in various modes by arranging pins on the integrated circuit; when the ILIMIT pin is suspended, as shown in fig. 1, the ILIMIT pin works in an internal constant current control mode at this time, and the output constant current value is an internal default value at this time; when the ILIMIT pin is connected to a resistor (greater than 10k Ω) to ground, as shown in fig. 2, the internal constant current control mode is operated, but the constant current can be controlled by the resistance R of the resistor R201 201 Determining that the larger the resistance value is, the larger the constant current value is; when the ILIMIT pin is connected to a voltage drop signal of a sampling resistor R301 serially connected to the negative terminal of the output load, as shown in fig. 3, the circuit works in an external constant current control mode, and the constant current value output by the circuit is determined by the sampling resistor R301 to be smaller in resistance value and larger in constant current value;
FIG. 1 is a first embodiment of the present invention; an ILIMIT pin is suspended; the positive end and the negative end of the output load are respectively connected with the two ends of the capacitor C126;
the error amplifier 115 amplifies the difference between the feedback signal and the internal reference voltage Vref, outputs a COMP signal, and R112 and C113 constitute an internal loop compensation circuit; the equivalent sampling resistor R105 and the current sampling circuit 104 form an inductive current sampling circuit; when the power tube Q106 is turned on, the current signal of the inductor L123 is sampled, and the output signal of the current signal is compared with the COMP signal through the PWM comparator 111 after being added with the ramp compensation signal generated by the oscillator circuit 110; at the beginning of each cycle, the clock signal generated by the oscillator circuit 110 controls the power tube Q106 to be switched on, and the follow current power tube Q107 is switched off; when the output signal of the PWM comparator 111 is high, the RS trigger 109 outputs a signal to control the power transistor Q106 to be turned off, and the follow current power transistor Q107 is turned on; the driving circuit 108 provides a driving signal for the power tube and controls the dead time at the same time, so that two power tubes Q106 and Q107 are prevented from being conducted at the same time to form punch-through; when the power tube Q106 is conducted, the follow current power tube Q107 is closed, the current of the inductor L123 is linearly increased, a part of the current is supplied to an output load, and a part of the current charges the output capacitor C126; when the power tube Q106 is turned off, the follow current power tube Q107 is turned on, and due to the existence of the inductive electromotive force of the inductor, the current of the inductor L123 does not change instantly, the original current direction is kept unchanged, and the inductor current is linearly reduced; the resistors R124 and R125 form a voltage division network, the sampling output voltage is fed back to a voltage control loop, and the stability of the output voltage is kept;
in fig. 1, an equivalent sampling resistor R105, a current sampling circuit 104, a holding circuit 103, a current input amplifier 116, an adjusting MOS transistor Q114, a high voltage selection circuit 118, an external constant current sampling signal amplification circuit 119, a constant current source I121, and a constant current mode selection circuit 120 form a constant current control circuit; when the ILIMIT pin is suspended as shown in fig. 1, an internal constant current source I121 pulls the ILIMIT pin high, and the constant current mode selection circuit 120 outputs a CC _ mode signal which is high and operates in an internal constant current control mode; an internal sampling constant current loop is formed by the equivalent sampling resistor R105, the current sampling circuit 104, the holding circuit 103, the current input amplifier 116 and the adjusting MOS transistor Q114, and the average current of the inductor is calculated through sampling and holding; the inductor average current and the default reference current (hereinafter, I) generated by the constant current mode selection circuit 120 are compared REF1 I.e. default internal settingThe recognized constant current value) controls an output end (COMP end) of the error amplifier 115 through the current input amplifier 116 and the adjusting MOS transistor Q114, when the output load current is small, the corresponding average current of the inductor is also small, at this time, the adjusting MOS transistor Q114 is turned off, the system works in a constant voltage control mode, as the output load current increases, the average current of the inductor correspondingly increases, the sampling current thereof also increases, when the sampling current is equal to the internal default reference current, the current input amplifier 116 turns on the adjusting MOS transistor Q114 by the output signal, and the duty ratio of the PWM signal is changed to realize constant current control.
FIG. 2 is a second embodiment of the present invention; the ILIMIT pin is grounded through a resistor R201; the positive end and the negative end of the output load are respectively connected with the two ends of the capacitor C126;
when the ILIMIT pin connects a resistor R201 larger than 10K omega to the ground, the system works in an internal constant current control mode; however, the constant current value can be determined by the resistance value of the resistor R201;
FIG. 3 is a third embodiment of the present invention; the negative end of the output load is connected with the sampling resistor R301 to the ground, the negative end of the output load is connected with the ILIMIT pin, and the other end of the inductor L123 is connected with the positive end of the output load; the output load current will flow through the sampling resistor R301, which generates loss, so the smaller the resistor R301, the better; at this time, the voltage of the ILIMIT pin is lower than the internal judgment threshold, the output signal CC _ mode of the constant current mode selection circuit is low, and the current input amplifier 116 is turned off; the external constant-current sampling signal amplifying circuit 119 works; in this example, the amplification factor of the external constant-current sampling signal amplification circuit 119 is 10, and the circuit works in an external constant-current control mode; the working principle is as follows: load current flows through the sampling resistor R301 to generate voltage drop, because the internal current source 121 is microampere current, the voltage drop on the sampling resistor R301 is far smaller than the voltage drop generated by the load current; a voltage drop signal generated by the load current flowing through the sampling resistor R301 is amplified by 10 times through the external constant current sampling signal amplification circuit 119, and a constant voltage feedback signal on the feedback pin FB is output to the error amplifier 115 through the high voltage selection module 118 by selecting the largest one of the voltage drop signal and the constant voltage feedback signal; when the voltage of the sampling resistor R301 is amplified by 10 times and is greater than the voltage on the feedback pin FB, the system enters an external constant current control mode, and the output is output at the momentConstant current I OUT It can be calculated to yield:
I OUT ·R 301 10= Vref thus
Figure BDA0001254223810000061
R 301 Is the resistance value of the resistor R301;
it can be seen from the above formula that the output constant current precision is mainly determined by the precision of the internal reference voltage Vref, the external current sampling resistor R301 and the amplification factor, and in practical application, the internal reference voltage and the amplification factor can be both maintained by programming fuse trimming or other technical means, so that the constant current control mode has good constant current precision;
FIG. 4 is an embodiment of the high voltage selection circuit 118; the circuit comprises a comparator U401, an inverter U402, a transmission gate U403 and a transmission gate U404; the non-inverting input terminal and the inverting input terminal of the comparator U401 are used as two input terminals of the high voltage selection circuit 118; the output end of the comparator U401 is connected with the input end of the inverter U402, the negative control end of the transmission gate U403 and the positive control end of the transmission gate U404; the output end of the inverter U402 is connected with the positive control end of the transmission gate U403 and the negative control end of the transmission gate U404; the input end of the transmission gate U403 is connected with the inverting input end of the comparator U401; the input end of the transmission gate U404 is connected with the non-inverting input end of the comparator U401; the output ends of the transmission gates U403 and U404 are connected and used as the output end of the high voltage selection circuit 118; the working principle is that when the input 1 is larger than the input 2, the output of the comparator U401 is low, the output of the inverter U402 is high, the transmission gate U403 is gated, and the input 1 is transmitted to the output; when input 1 is less than input 2, the output of comparator U401 is high and the output of inverter U402 is low, the transmission gate U404 is gated and input 2 is transmitted to the output.
Fig. 5 is an embodiment of the constant current mode selection circuit 120; the device comprises an operational amplifier U601, a regulating NMOS tube Q602, a resistor R613, PMOS tubes Q603, Q604, Q6041, Q605, Q606, Q607, Q608 and Q609; constant current sources I610, I611 and I612, an inverter U614 and a NAND gate U615; wherein the reference current of the constant current source I610 is I REF1 Reference current of constant current source I611The flow is I REF2 ；
The non-inverting input end of the operational amplifier U601 serves as the input end of the constant current mode selection circuit 120 and is connected with the gates of the PMOS transistors Q604, Q606, Q607 and Q608; the power supply positive voltage is connected with the sources of PMOS tubes Q604, Q606, Q607 and Q608 and the input end of a constant current source I610; the output end of the constant current source I610 is connected with the source electrode of the PMOS tube Q609; the drain electrode of the PMOS tube Q604 is connected with the source electrode of the Q603, and the grid electrode of the PMOS tube Q603 is connected with the drain electrode of the PMOS tube Q603, the grid electrode of the Q6041 and the grid electrode of the Q605; the drain electrode of the PMOS tube Q603 is connected with the drain electrode of the NMOS tube Q602, the grid electrode of the NMOS tube Q602 is connected with the output end of the operational amplifier U601, and the source electrode of the NMOS tube Q602 is connected with the inverting input end of the operational amplifier U601 and is grounded through a resistor R613; the drain electrode of the PMOS tube Q606 is connected with the source electrode of the Q6041, and the drain electrode of the PMOS tube Q6041 is connected with the input end of the constant current source I611 and the input end of the phase inverter U614; the output end of the constant current source I611 is grounded; the drain of the PMOS tube Q607 is connected with the input end of the constant current source I612, one input end of the NAND gate U615 and the grid of the Q609; the output end of the constant current source I612 is grounded; the output end of the inverter U614 is connected with the other input end of the NAND gate U615; the output end of the nand gate U615 serves as the control end of the constant current mode selection circuit 120; the drain electrode of the PMOS tube Q608 is connected with the source electrode of the Q605, and the drain electrode of the PMOS tube Q605 is connected with the drain electrode of the PMOS tube Q609; the drain of the PMOS transistor Q609 serves as the current output terminal of the constant current mode selection circuit 120;
the working principle is as follows: when the ILIMIT pin is empty, the constant current source I121 pulls up the voltage of the ILIMIT pin at this time; the PMOS transistors Q604, Q606, Q607, Q608 are turned off, the control end of the constant current mode selection circuit 120 outputs a CC _ mode signal high, and the current in the internal sampling constant current loop is selected to be input to the amplifier 116; at this time, Q609 is turned on, and the constant current mode selection circuit 120 outputs the constant current reference current I REF Equal to the internally set default reference current I REF1 ；
When the ILIMIT pin connects the resistor R201 to ground as shown in fig. 2, the PMOS transistors Q604, Q606, Q607, and Q608 are turned on, the operational amplifier U601, the NMOS transistor Q602, and the resistor R613 form a voltage-current conversion circuit, and the Q603, Q6041, and Q605 form a current mirror; at the moment, the PMOS tube Q609 is closed; constant current reference current I output by constant current mode selection circuit 120 REF It can be calculated that:
Figure BDA0001254223810000071
in which I 121 Is a reference current of a constant current source I121, R 201 Is the resistance value of the resistor R201, R 613 Is the resistance of the resistor R613; at the same time need to satisfy
Figure BDA0001254223810000072
The switch conversion circuit works in an internal constant current control mode to ensure that the CC _ mode signal is high;
when the negative terminal of the output load is connected with the sampling resistor R301 to the ground and the negative terminal of the output load is connected with the ILIMIT pin as shown in FIG. 3, the equivalent resistance of the ILIMIT pin meets the requirement
Figure BDA0001254223810000073
The CC _ mode signal is low, and the external constant current sampling signal amplifier 119 is gated, while the shielding current input amplifier 116 and the switching conversion circuit operate in the external constant current control mode.

Claims (8)

1. A switching converter circuit with multi-mode constant current control, comprising: the circuit comprises an internal voltage reduction circuit (101), a reference circuit (102), a holding circuit (103), a current sampling circuit (104), an equivalent sampling resistor R105, a switch control MOS tube Q106, a synchronous sorting MOS tube Q107, a driving circuit (108), an RS trigger (109), an oscillator circuit (110), a PWM comparator (111), an adjusting MOS tube Q114, an error amplifier (115), a current input amplifier (116), a signal adding module (117), a high voltage selection circuit (118), an external constant current sampling signal amplification circuit (119), a constant current mode selection circuit (120), a constant current source I121, a feedback pin FB, an ILIMIT pin, a power supply pin VIN, an output pin SW and a grounding pin GND;
the input end of the internal voltage reduction circuit (101) is connected with a power pin VIN, and the output end of the internal voltage reduction circuit is connected with the input end of the reference circuit (102); the reference circuit (102) provides reference voltage and reference current of each constant current source for the interior of the switch conversion circuit, and the reference voltage Vref generated by the reference circuit is connected with the non-inverting input end of the error amplifier (115);
one end of the equivalent sampling resistor R105 is connected with a power supply pin VIN, the other end of the equivalent sampling resistor R is connected with the input end of the current sampling circuit (104) and the source electrode of the switch control MOS tube Q106, and the drain electrode of the Q106 is connected with the drain electrodes of the output pins SW and Q107; the output pin SW is used for connecting an inductor L123 connected in series between the output pin SW and the positive end of an output load, the source electrode of the Q107 is connected with a ground pin GND, and the driving circuit (108) is respectively connected with and controls the gates of the switch control MOS tube Q106 and the synchronous sorting MOS tube Q107; the equivalent sampling resistor R105 samples the current of the inductor L123; a drive circuit (108) implements protection logic and provides drive and dead time control for Q106 and Q107; the output end of the RS trigger (109) is connected with the input end of the driving circuit (108);
the output end of the current sampling circuit (104) is connected with the input end of the holding circuit (103), and the output end of the holding circuit (103) is connected with the non-inverting input end of the current input amplifier (116); the current sampling circuit (104) samples the current of the inductor L123, and the holding circuit (103) holds the sampled current signal of the inductor L123;
the oscillator circuit (110) provides a clock signal and a ramp compensation signal, and the clock signal is connected with the S end of the RS trigger; the signal adding module (117) adds the inductance L123 current sampling signal and the ramp compensation signal, and connects the added signal with the non-inverting input end of the PWM comparator (111); the inverting input end of the PWM comparator (111) is connected with the output end of the error amplifier (115); the output end of the PWM comparator (111) is connected with the R end of the RS trigger; the PWM comparator (111) compares the added current sampling signal of the inductor L123 and the ramp compensation signal with the output signal of the error amplifier (115) and outputs a PWM signal to control the power transistors Q106 and Q107 to be switched on and off; the inverting input end of the error amplifier (115) is connected with the output of the high-voltage selection circuit (118) and amplifies the feedback signal and the error signal of the internal reference voltage Vref; the output end of the error amplifier (115) outputs a COMP signal;
the inverting input end of the current input amplifier (116) is connected with the current output end of the constant current mode selection circuit (120); the output end of the current input amplifier (116) is connected with the grid electrode of the adjusting MOS tube Q114, the drain electrode of the adjusting MOS tube Q114 is connected with the output end of the error amplifier (115), and the source electrode is grounded; the adjusting MOS tube Q114 is used as an adjusting MOS tube in an internal constant current control mode, and constant current control is realized through the output of a clamping error amplifier (115);
one input end of the high-voltage selection circuit (118) is connected with the feedback pin FB, and the other input end is connected with the output end of the external constant-current sampling signal amplification circuit (119); the function of the high voltage selection circuit (118) is to select the input signal with the higher voltage of the two input voltages to be transmitted to the output terminal;
the input end of the constant current mode selection circuit (120) and the input end of the external constant current sampling signal amplification circuit (119) are connected with the output of a constant current source I121 and an ILIMIT pin; the constant current mode selection circuit (120) selects a corresponding constant current control mode according to the state of the ILIMIT pin; the constant current source I121 flows through a resistor on the ILIMIT pin to generate voltage so as to set a constant current value and judge a constant current control mode;
the control end of the constant current mode selection circuit (120) is respectively connected with the low level effective enabling end of the external constant current sampling signal amplification circuit (119) and the high level effective enabling end of the current input amplifier (116).
2. The switching converter circuit with multi-mode constant current control of claim 1,
the constant current mode selection circuit (120) comprises an operational amplifier U601, an adjustment NMOS tube Q602, a resistor R613, PMOS tubes Q603, Q604, Q6041, Q605, Q606, Q607, Q608 and Q609; constant current sources I610, I611 and I612, an inverter U614 and a NAND gate U615;
the non-inverting input end of the operational amplifier U601 serves as the input end of the constant current mode selection circuit (120) and is connected with the grids of the PMOS tubes Q604, Q606, Q607 and Q608; the power supply positive voltage is connected with the sources of the PMOS tubes Q604, Q606, Q607 and Q608 and the input end of the constant current source I610; the output end of the constant current source I610 is connected with the source electrode of the PMOS tube Q609; the drain electrode of the PMOS tube Q604 is connected with the source electrode of the Q603, and the grid electrode of the PMOS tube Q603 is connected with the drain electrode of the PMOS tube Q603, the grid electrode of the Q6041 and the grid electrode of the Q605; the drain electrode of the PMOS tube Q603 is connected with the drain electrode of the NMOS tube Q602, the grid electrode of the NMOS tube Q602 is connected with the output end of the operational amplifier U601, and the source electrode of the NMOS tube Q602 is connected with the inverting input end of the operational amplifier U601 and is grounded through a resistor R613; the drain electrode of the PMOS tube Q606 is connected with the source electrode of the Q6041, and the drain electrode of the PMOS tube Q6041 is connected with the input end of the constant current source I611 and the input end of the phase inverter U614; the output end of the constant current source I611 is grounded; the drain of the PMOS transistor Q607 is connected with the input end of the constant current source I612, one input end of the NAND gate U615 and the grid of the Q609; the output end of the constant current source I612 is grounded; the output end of the inverter U614 is connected with the other input end of the NAND gate U615; the output end of the NAND gate U615 is used as the control end of the constant current mode selection circuit (120); the drain electrode of the PMOS tube Q608 is connected with the source electrode of the Q605, and the drain electrode of the PMOS tube Q605 is connected with the drain electrode of the PMOS tube Q609; the drain of the PMOS tube Q609 is used as the current output end of the constant current mode selection circuit (120).
3. The switching converter circuit with multi-mode constant current control of claim 1,
the high voltage selection circuit (118) comprises a comparator U401, an inverter U402, transmission gates U403 and U404; the non-inverting input end and the inverting input end of the comparator U401 are used as two input ends of a high-voltage selection circuit (118); the output end of the comparator U401 is connected with the input end of the inverter U402, the negative control end of the transmission gate U403 and the positive control end of the transmission gate U404; the output end of the inverter U402 is connected with the positive control end of the transmission gate U403 and the negative control end of the transmission gate U404; the input end of the transmission gate U403 is connected with the inverting input end of the comparator U401; the input end of the transmission gate U404 is connected with the non-inverting input end of the comparator U401; the output terminals of the transmission gates U403 and U404 are connected and serve as the output terminal of the high voltage selection circuit (118).
4. The switching converter circuit with multi-mode constant current control of claim 1,
the circuit also comprises a loop compensation circuit formed by serially connecting a resistor R112 and a capacitor C113; one end of the loop compensation circuit is connected with the output end of the error amplifier (115), and the other end is grounded.
5. The switching converter circuit with multi-mode constant current control of claim 1,
the switch control MOS tube Q106 adopts a PMOS tube, and the synchronous arrangement MOS tube Q107 adopts an NMOS tube.
6. The switching converter circuit with multi-mode constant current control of claim 1,
and an NMOS transistor is adopted for the adjusting MOS transistor Q114.
7. The switching converter circuit with multi-mode constant current control of claim 1,
the over-voltage protection circuit is characterized by further comprising an over-voltage protection circuit (127) and an over-temperature protection circuit (128); the over-temperature protection circuit (128) is connected with the driving circuit (108) and provides over-temperature protection for the switch conversion circuit; the overvoltage protection circuit (127) is connected with the driving circuit (108) and provides input overvoltage and output overvoltage protection for the switch conversion circuit.
8. The switching converter circuit with multi-mode constant current control of claim 1,
the hold circuit (103) also filters the sampled inductor L123 current signal.
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