CN109617429B - Voltage conversion integrated circuit, high-voltage BUCK converter and control method - Google Patents

Voltage conversion integrated circuit, high-voltage BUCK converter and control method Download PDF

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Publication number
CN109617429B
CN109617429B CN201910140949.4A CN201910140949A CN109617429B CN 109617429 B CN109617429 B CN 109617429B CN 201910140949 A CN201910140949 A CN 201910140949A CN 109617429 B CN109617429 B CN 109617429B
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signal
voltage
clamping
switch
power switch
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CN109617429A (en
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李伊珂
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Jingyi Semiconductor Co ltd
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Jingyi Semiconductor Co ltd
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS 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
    • H02M7/00Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21Conversion of ac power input into dc power output without possibility of reversal 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
    • H02M7/217Conversion of ac power input into dc power output without possibility of reversal 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

Abstract

A voltage conversion integrated circuit, a high-voltage BUCK switch converter and a control method for controlling the high-voltage BUCK switch converter are disclosed. The voltage conversion integrated circuit integrates a power switch, wherein the drain electrode of the power switch is coupled with an input pin of the integrated circuit, and the source electrode of the power switch is coupled with a grounding pin of the integrated circuit. The integrated circuit also includes a detection pin. When the current flowing through the freewheeling diode coupled outside the grounding pin of the integrated circuit is cut off, the integrated circuit generates a clamping voltage at the detection pin of the integrated circuit, and when the value of the clamping voltage is equal to the value of the output voltage when the freewheeling diode is cut off, the detection pin is floated. And when the voltage on the grounding pin is lower than the clamping voltage by a heavy load threshold value, the power switch is turned on. The integrated circuit can be used for a non-isolated high-voltage BUCK switch converter, can quickly detect load change and is beneficial to improving the dynamic response speed of a system.

Description

Voltage conversion integrated circuit, high-voltage BUCK converter and control method
Technical Field
The invention relates to an electronic circuit, in particular to an integrated circuit converter, a high-voltage buck converter and a control method thereof.
Background
Power regulators (e.g., switch mode voltage regulators) are widely used in various electronic devices for high voltage step-down applications. The non-isolated high-voltage buck switch converter is widely applied to circuits such as a small household appliance control panel power supply, an industrial control power supply, an LED lighting and the like due to the characteristics of simple circuit, few peripheral circuit elements, low loss, low heat generation and the like.
For example, fig. 1 shows a circuit schematic of a conventional non-isolated AC-DC switching converter. The non-isolated AC-DC switch converter comprises a rectifying circuit and an input filter capacitor CINAnd a high voltage BUCK switch circuit. The high-voltage BUCK switch circuit comprises an integrated circuit 51, a diode D, an output inductor LOUT, and an output capacitor COUTAnd a feedback circuit 52.
Generally, the integrated circuit 51 includes an input pin IN, a feedback pin FB, and a ground pin GND 2. The integrated circuit 51 includes a power switch tube, the drain of which is coupled to the input pin IN, and the source of which is coupled to the chip ground pin GND2, and is electrically connected to the logic ground GND1 of the non-isolated AC-DC switching converter through a diode D. The feedback pin FB receives an output voltage signal V representing the output terminal OUTOUTAccording to the feedback signal, the power switch tube is controlled to be switched on and off, and then the input capacitor C is connectedINDC input voltage V at both endsDCIs converted into an output voltage signal VOUT
In the non-isolated AC-DC switching converter shown in fig. 1, since the ground pin GND2 of the integrated circuit 51 and the logic ground GND1 of the AC-DC switching converter are two different potentials, it is difficult to directly acquire the output voltage signal V in real timeOUTTo the integrated circuit 51 for control and regulation. Generally, a feedback circuit 52 is coupled between the output OUT and the ground pin GND2 of the integrated circuit 51. When the main switch in the integrated circuit 51 is turned off and the diode D freewheels on, the ground pin GND2 of the integrated circuit 51 is electrically connected to the logic ground GND1, and a fixed voltage difference (the turn-on voltage drop of the diode D) exists between the ground pin GND2 and the logic ground GND1, so that the feedback signal generated by the feedback circuit 51 can represent the output voltage signal VOUT
However, when the non-isolated AC-DC switching converter operates in light load or no load, the voltage of the feedback pin FB is zero, and the voltage of the ground pin GND2 and the output voltage signal V are equalOUTAre equal in value, output voltage signal VOUTFrom an output capacitor COUTAnd maintaining the discharge. Meanwhile, in order to improve efficiency, the system usually enters a frequency regulation mode, and the system operates at a low frequency. Once the system recovers from light load or no load to heavy load, the feedback signal received on the feedback pin FB is collected during the diode conduction period of the previous period, so that the change of the load cannot be reflected in time, and meanwhile, because the working frequency is very low, the next switching period cannot arrive immediately, so that the transient response speed of the system is low. Output capacitor COUTIs not enough to maintain the requirement of the load, and outputs a voltage signal VOUTThe power failure of the value is serious, and the system can not work normally. Therefore, for non-isolated AC-DC switching converter systems, a dummy load is typically connected to ensure that the entire system does not operate at very low frequencies, but the dummy load increases power consumption, resulting in system inefficiency.
Therefore, it is desirable to provide a non-isolated AC-DC switching converter with fast transient response speed and low power consumption.
Disclosure of Invention
In view of one or more problems in the prior art, a voltage conversion integrated circuit, a high-voltage BUCK converter and a control method are provided.
The invention provides a voltage conversion integrated circuit for a high-voltage BUCK switch converter, which is provided with an input pin and a grounding pin, wherein the high-voltage BUCK switch converter comprises a diode, an output inductor and a feedback circuit, the cathode of the diode is coupled with the grounding pin, and the anode of the diode is electrically connected to the logic ground of the switch converter; the output inductor is coupled between the grounding pin and the output end of the switch converter; the feedback circuit is coupled between the output terminal of the switching converter and the ground pin and generates a feedback signal representative of the output voltage signal during the diode conduction period, the voltage conversion integrated circuit further comprising: a feedback pin coupled to the feedback circuit and receiving a feedback signal; the detection pin is electrically connected to the logic ground of the switching converter through the clamping capacitor; the power switch is provided with a first end, a second end and a control end, wherein the first end of the power switch is coupled with the input pin to receive the input voltage, and the second end of the power switch is coupled with the grounding pin; the follow current judging circuit is coupled with the feedback pin to receive the feedback signal and generates a follow current judging signal according to the feedback signal, and the follow current judging signal is effective after the diode is cut off; and the heavy load trigger circuit is coupled with the detection pin, the grounding pin and the follow current judgment circuit, when the power switch is switched off, the heavy load trigger circuit is connected with the detection pin and the grounding pin, and is disconnected with the detection pin and the grounding pin after the detection pin generates a clamping voltage signal, wherein the value of the clamping voltage signal is equal to the value of an output voltage signal when the diode follow current is switched off, the heavy load trigger circuit compares the clamping voltage signal with the voltage signal on the grounding pin to generate a heavy load trigger signal in the effective period of the follow current judgment signal, and when the value of the voltage signal on the grounding pin is lower than the value of the clamping voltage signal by a heavy load threshold value, the heavy load trigger signal is effective, and the power switch is switched on.
In another aspect, the present invention provides a high voltage BUCK switching converter, including: the power switch is provided with a first end, a second end and a control end, wherein the first end of the power switch receives an input voltage signal, and the second end of the power switch is coupled to the output end of the switching converter through an output inductor; the cathode of the freewheeling diode is coupled with the second end of the power switch, and the anode of the freewheeling diode is electrically connected to the logic ground; a feedback circuit connected between the second terminal of the power switch and the output terminal of the switching converter and generating a feedback signal representative of the output voltage during the diode conduction period; the follow current judging circuit receives the feedback signal, generates a follow current judging signal according to the feedback signal, and after the diode follow current is cut off, the follow current judging signal is effective; and the heavy-load trigger circuit is coupled with the second end of the power switch and the follow current judging circuit, generates a clamping voltage signal during the effective period of the follow current judging signal, wherein the value of the clamping voltage signal is equal to the value of the output voltage signal when the follow current of the diode is cut off, compares the clamping voltage signal with the voltage signal on the second end of the power switch to generate a heavy-load trigger signal, and when the value of the voltage signal on the second end of the power switch is lower than the value of the clamping voltage signal by a heavy-load threshold value, the heavy-load trigger signal is effective and the power switch is switched on.
Yet another aspect of the present invention provides a control method for controlling a high voltage BUCK switching converter, the high voltage BUCK switching converter including a power switch, a diode, an output inductor, a feedback circuit, and a clamp capacitor, a drain of the power switch coupled to an input of the switching converter for receiving an input voltage, a source of the power switch coupled to a cathode of the diode, an anode of the diode electrically connected to a logic ground, the output inductor coupled between the source of the power switch and an output of the switching converter, the feedback circuit coupled between the output of the switching converter and the source of the power switch, and the clamp capacitor coupled between the source of the power switch and the logic ground through one clamp switch, the control method including: when the power switch is turned off, the clamping switch is turned on, and the clamping capacitor is charged; when the voltage value of the clamping capacitor is equal to the value of the output voltage when the diode freewheeling is cut off, the clamping switch is switched off; comparing the voltage on the clamping capacitor with the voltage on the source electrode of the power switch; and when the voltage value on the source electrode of the power switch is lower than the voltage value on the clamping capacitor by a heavy load threshold value, the power switch is turned on.
Drawings
Throughout the following drawings, the same reference numerals indicate the same, similar or corresponding features or functions.
FIG. 1 illustrates a circuit schematic of a conventional non-isolated AC-DC switching converter;
FIG. 2 shows a schematic block diagram of a non-isolated AC-DC switching converter 10 according to an embodiment of the present invention;
FIG. 3 shows a schematic block diagram of the interior of integrated circuit 12 in accordance with an embodiment of the present invention;
FIG. 4 illustrates a schematic diagram of circuitry within integrated circuit 12 in accordance with one embodiment of the present invention;
FIG. 5 illustrates a schematic diagram of circuitry within integrated circuit 12 according to another embodiment of the present invention;
FIG. 6 illustrates a circuit schematic of a control module according to an embodiment of the present invention;
FIG. 7 shows a circuit schematic of a control module according to another embodiment of the invention;
fig. 8 illustrates a control method of controlling a high voltage BUCK switching converter, in accordance with an embodiment of the present invention.
Detailed Description
Specific embodiments of the present invention will be described in detail below, and it should be noted that the embodiments described herein are only for illustration and are not intended to limit the present invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that: it is not necessary to employ these specific details to practice the present invention. In other instances, well-known circuits, materials, or methods have not been described in detail in order to avoid obscuring the present invention.
Throughout the specification, reference to "one embodiment," "an embodiment," "one example," or "an example" means: the particular features, structures, or characteristics described in connection with the embodiment or example are included in at least one embodiment of the invention. Thus, the appearances of the phrases "in one embodiment," "in an embodiment," "one example" or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combination and/or sub-combination in one or more embodiments or examples. Further, those of ordinary skill in the art will appreciate that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present. Like reference numerals refer to like elements. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
Fig. 2 shows a schematic block diagram of a non-isolated AC-DC switching converter 10 according to an embodiment of the invention. As shown in FIG. 2, the non-isolated AC-DC switching converter 10 includes a rectifying circuit 11 and an input filter capacitor CINAnd a high voltage BUCK switch circuit. The rectifying circuit 11 receives an alternating voltage signal VACThe alternating voltage signal VACRectifying by a rectifying circuit 11 and filtering by an input capacitor CIN to obtain a direct current input voltage signal VDC. The high-voltage BUCK switch circuit comprises an integrated circuit 12, a diode D, and an output inductor LOUTAn output capacitor COUTAnd a feedback circuit 13.
The integrated circuit 12 includes an input pin IN, a ground pin GND2, and a feedback pin FB. The integrated circuit 12 includes a power switch therein, which in one embodiment includes a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), a Junction Field Effect Transistor (JFET), an Insulated Gate Bipolar Transistor (IGBT), and other suitable power devices. The drain D of the power switch is coupled to the input pin IN, and the source S of the power switch is coupled to the ground pin GND2 of the integrated circuit 12. The anode of the diode D external to the integrated circuit is coupled to the logic ground GND1 of the switching converter 10, and the cathode of the diode D is coupled to the ground pin GND2 of the integrated circuit 12. Output inductor LOUTCoupled between the ground pin GND2 of the integrated circuit 12 and the output OUT of the switching converter 10. Output capacitor COUTCoupled between the output terminal OUT and the logic ground GND 1. A feedback circuit 13 coupled to the output terminalOUT and a ground pin GND2, and generates a signal V representative of the output voltage during the conduction period of the diode DOUTIs fed back toFBAnd to the feedback pin FB of the integrated circuit 12. In one embodiment, the feedback circuit 13 includes a first resistor R1 and a second resistor R2 connected in series between the output terminal OUT and the ground pin GND2, wherein a common terminal of the first resistor R1 and the second resistor R2 is coupled to the feedback pin FB to provide the feedback signal VFB. During the conduction of the diode D, the feedback signal VFBAnd an output voltage signal VOUTProportional relation; when the diode D turns off, the current flows through the inductor LOUTIs zero, feedback signal VFBEqual to zero, the voltage of the ground pin GND2 and the output voltage signal VOUTAre equal.
The integrated circuit 12 further includes a control circuit therein, and the control circuit receives the feedback signal VFBAnd according to the feedback signal VFBGenerating a control signal to the grid of the power switch tube for controlling the on-off switching of the power switch tube so as to input a DC voltage signal VDCIs converted into an output voltage signal VOUT
Furthermore, the integrated circuit 12 comprises a detection pin DET which is connected to the logic ground GND1 via the clamping capacitance 14. In another embodiment, the detection pin DET is connected to the logic ground GND1 through a clamp capacitor 14 and a resistor 15 connected in series. In the embodiment shown in fig. 2, when the power switch inside the integrated circuit 12 is turned off, the detection pin DET is forcibly connected to the ground pin GND2, so that the voltage on the detection pin DET and the voltage on the ground pin GND2 are equal. Outputting a voltage signal V when the voltage on the detection pin DET is equal to the freewheeling cut-off of the diode DOUTAt value (v), the float detection pin DET is floating. In the embodiment shown in fig. 2, floating means that the voltage on the detection pin DET does not change any more by disconnecting the detection pin DET from the ground pin GND 2. It should be noted that, since the detection pin DET is connected to the ground pin GND2, when the freewheeling of the diode D is turned off, the voltage at the detection pin DET is equal to the voltage at the ground pin GND2, but there is a dynamic state in the process of turning off the freewheeling of the diode D from on to offThe process is that the voltage on the ground pin GND2 has ringing and jitter, and when the diode D becomes stable after the end of turning off, the voltage on the detection pin DET is equal to the voltage on the ground pin GND2 and equal to the output voltage VOUT. When the load changes, the output voltage VOUTAs a result, the voltage on the ground pin GND2 changes relative to the voltage on the detection pin DET. When the voltage on the ground pin GND2 is lower than the voltage on the detection pin DET by a heavy loading threshold, the power switch tube inside the integrated circuit 12 is turned on. The non-isolated AC-DC switching converter 10 quickly reverts from the light load or no load mode to the heavy load mode of operation. In the embodiment shown in fig. 2, the clamping capacitor 14 and the resistor 15 are illustrated outside the integrated circuit 12, but in other embodiments, the clamping capacitor 14 and the resistor 15 may be integrated inside the integrated circuit 12 as desired.
In the embodiment shown in fig. 2, the integrated circuit 12 further includes a power supply pin BST coupled to the ground pin GND2 of the integrated circuit 12 through the bootstrap capacitor 16. The bootstrap capacitor 16 will generate a supply voltage on the supply pin BST for driving the power switches inside the integrated circuit 12 and for powering the other circuits inside.
Fig. 3 shows a schematic block diagram of the interior of integrated circuit 12 in accordance with an embodiment of the present invention. As shown in fig. 3, the integrated circuit 12 includes a control module 21, a free-wheeling judgment circuit 22, a heavy-duty trigger circuit 23, a logic circuit 24, a power switch 26 and a driving circuit.
In the embodiment shown in FIG. 3, control module 21 is coupled to a feedback pin of integrated circuit 12 for receiving feedback signal VFBAnd generates the control signal PWM according to the feedback signal VFB. The control signal PWM is a high-low logic level signal. In one embodiment, when the control signal PWM is logic high, the power switch 26 is turned on; when the control signal PWM is logic low, the power switch 26 is turned off. The control module 21 may adopt various control modes, such as pulse width modulation (e.g. voltage control, current control, voltage-current dual-loop control, etc.), pulse frequency modulation (constant time conduction control, frequency hopping control, etc.), or a combination of pulse width modulation and pulse frequency modulation. For example, in normal loading of the systemIn the case of (3), a control method of pulse width modulation may be employed; under the condition of light load or no load of the system, a control mode of pulse frequency can be adopted.
The follow current judging circuit 22 receives the feedback signal VFBAnd according to the feedback signal VFBGenerating a follow current determination signal DTHWhen the diode D in the embodiment shown in fig. 2 freewheels off, the freewheel decision signal DTHIs effective. Follow current determination signal DTHA high-low logic level signal. In one embodiment, the current-follow decision signal DTHWhen logic high, follow current decision signal DTHIs effective.
The heavy duty trigger circuit 23 has a first terminal, a second terminal, a third terminal, and an output terminal. A first terminal of the heavy-duty trigger circuit 23 is coupled to the freewheel decision circuit 22 for receiving the freewheel decision signal DTH(ii) a The second terminal of the heavy trigger circuit 23 is coupled to the ground pin GND2 of the integrated circuit 12 for receiving the voltage signal V on the ground pinGND2(ii) a The third terminal of the reload trigger circuit 23 is coupled to the detect pin DET of the integrated circuit 12. The heavy-duty trigger circuit 23 determines the signal D according to the follow currentTHAnd a voltage signal V on the ground pin GND2GND2Generating a clamping voltage signal V on the detection pin DETDETWherein the voltage signal V is clampedDETIs equal to the output voltage signal V when the diode D freewheeling is cut offOUTI.e., the voltage on ground pin GND2 after diode D is fully turned off (the voltage signal on ground pin GND2 has ringing and jitter before diode D is not fully turned off). The heavy-duty trigger circuit 23 also clamps the voltage signal VDETAnd a voltage signal V on the ground pinGND2Comparison to generate a heavy-duty trigger signal CH. Heavy duty trigger signal CHA high-low logic level signal. In one embodiment, when the voltage signal V on the ground pin GND2GND2Is lower than the clamping voltage signal VDETA reload threshold of △ VTHHTime, heavy load trigger signal CHActive (e.g., logic high), power switch 26 is on. Similarly, in the embodiment shown in FIG. 3, the clamping capacitor 14 and resistor 15 are illustrated as being external to the integrated circuit 12, in other implementationsFor example, the clamping capacitor 14 and the resistor 15 may be integrated into the integrated circuit 12 according to the requirement, and in this case, the clamping capacitor 14 and the resistor 15 may be included in the heavy-duty trigger circuit 23.
The logic circuit 24 has a first input, a second input and an output. A first input terminal of the logic circuit 24 is coupled to the control module 21 for receiving the control signal PWM; a second input terminal of the logic circuit 24 is coupled to the reload trigger circuit 23 for receiving the reload trigger signal CH(ii) a The logic circuit 24 outputs the control signal PWM and the overload trigger signal CHPerforms a logic operation and generates a control signal SW. The control signal SW is a high/low logic level signal, and in one embodiment, when the control signal PWM and the override trigger signal C are appliedHWhen either is active (e.g., logic high), control signal SW is active (e.g., logic high), and power switch 26 is on.
In the embodiment shown in fig. 3, the driving circuit includes a driver 25 and a bootstrap voltage generating circuit. The driver 25 has a first supply terminal, a second supply terminal, an input terminal and an output terminal. A first power supply terminal of the driver 25 is coupled to the power supply pin BST; a second power supply terminal of the driver 25 is coupled to the ground pin GND2 of the integrated circuit 12; an input of the driver 25 receives the control signal SW; the driver 25 generates a drive signal Dr at an output terminal based on the control signal SW, wherein the drive signal Dr is used to drive the on and off switching of the power switch 26. The bootstrap voltage generation circuit includes a diode 27 inside the integrated circuit 12, a linear Regulator (LDO) 28, and a bootstrap capacitor 16 outside the integrated circuit 12. The input end of the LDO is coupled with the input pin IN to receive the DC input voltage VDCThe output terminal of the LDO is coupled to the anode of the diode 27, and the cathode of the diode 27 is coupled to the power supply pin BST. At the same time, the output voltage of the LDO is also used as the supply voltage signal V inside the integrated circuit 12CC
The drain D of the power switch tube 26 is coupled to the input pin IN; the source S of the power switch tube 26 is coupled to the ground pin GND 2; the gate G of the power switch 26 is coupled to the output terminal of the driver 25 for receiving the driving signal Dr. The high-voltage BUCK switching circuit inputs the direct current voltage V through the on-off switching of the power switch tube 26DCConversionFor outputting a voltage signal VOUT
Fig. 4 shows a schematic diagram of circuitry within integrated circuit 12 in accordance with an embodiment of the present invention. In the embodiment shown in fig. 4, a specific circuit schematic diagram of the free-wheeling judgment circuit 22, the heavy-duty trigger circuit 23 and the logic circuit 24 in the embodiment shown in fig. 3 is mainly illustrated.
In the embodiment shown in fig. 4, the freewheel decision circuit 22 comprises a voltage comparator 201. The non-inverting input terminal of the voltage comparator 201 receives the freewheel reference signal VTHThe inverting input terminal of the voltage comparator 201 receives the feedback signal VFBThe voltage comparator 201 will feed back the signal VFBAnd a follow current reference signal VTHComparing and outputting a follow current decision signal D at an output terminalTH. When the feedback signal VFBDown to a freewheel reference signal VTHWhen the value of (D) is reached, the follow current determination signal DTHActive (e.g., logic high). In one embodiment, the freewheel reference signal VTHIncluding a zero voltage signal. That is, ideally, when the diode D is interrupted, the feedback signal V is fed backFBEqual to 0V represents the freewheel decision signal DTHIs effective.
In the embodiment shown in fig. 4, the heavy duty flip flop 23 comprises a pulse flip flop 301, a clamp switch 302, a voltage source 303 and a voltage comparator 304.
The pulse flip-flop 301 receives the freewheel decision signal DTHAnd determining a signal D according to the follow currentTHGenerating a pulse signal in which the pulse signal is at a follow current determination signal DTHActive for a period of time from the start of the active (logic high), i.e. the pulse signal is active with respect to the freewheel decision signal DTHIs a narrow pulse signal, and only the follow current determination signal DTHThe active period is active for a short period of time. In one embodiment, the width of the pulse signal is the width of the signal for charging the clamping capacitor 14 to the output voltage signal VOUTThe time length required for the value when the diode D turns off, the width of the pulse signal, the capacitance of the clamping capacitor 14 selected by the detection pin DET, the resistance of the resistor 15 and the output voltage signal VOUTAnd (4) correlating. Generally, a reasonable width range of the pulse signalBetween tens of microseconds to hundreds of microseconds.
The clamp switch 302 has a first terminal, a second terminal, and a control terminal. The first terminal of the clamp switch 302 is coupled to the ground pin GND2 (i.e., the source of the power switch 26), and the control terminal of the clamp switch 302 receives the pulse signal, and when the pulse signal is asserted, the clamp switch 302 is turned on.
A voltage comparator 304 having an inverting input, a non-inverting input, and an output. The non-inverting input terminal of the voltage comparator 304 is coupled to the second terminal of the clamp switch 302, and the inverting input terminal of the voltage comparator 304 is coupled to the ground pin GND2 through the voltage source 303 and receives the voltage signal V on the ground pin GND2GND2Wherein the voltage value of the voltage source 304 is equal to the reloading threshold △ VTHH. The voltage signal V at the ground pin GND2 during the time when the clamp switch 302 is turned onGND2A clamp capacitor 14 connected to the detection pin DET is charged by a clamp switch and generates a clamp voltage signal V on the detection pin DETDET. When clamping voltage signal VDETEqual to output voltage signal V when diode D freewheeling is cut offOUTAt value (v), the clamp switch 302 is turned off, and the detection pin DET is floating. In one embodiment, floating means that the detection pin DET is disconnected from the ground pin GND2 and the voltage on the detection pin DET does not change any more. The voltage comparator 304 converts the voltage signal V on the ground pin GND2GND2And a reload threshold of △ VTHHSum of (d) and clamp voltage signal VDETComparing and generating a heavy duty trigger signal C at the outputH. It will be appreciated by those skilled in the art that in another embodiment, the voltage source 303 can also be coupled between the non-inverting input terminal of the voltage comparator 304 and the second terminal of the clamp switch 302, and the voltage comparator 304 can couple the voltage signal V on the ground pin GND2GND2And a clamp voltage signal VDETAnd a reload threshold of △ VTHHAnd generating a heavy-duty trigger signal C at the outputH. When the voltage signal V on the ground pin GND2GND2Is lower than the clamping voltage signal VDETA reload threshold of △ VTHHTime, heavy load trigger signal CHActive (e.g., logic high). Similarly, in FIG. 4In the illustrated embodiment, the clamping capacitor 14 and the resistor 15 are illustrated external to the integrated circuit 12, and the clamping capacitor 14 and the resistor 15 are connected to the inverting input of the internal voltage comparator 304 via the detection pin DET. In other embodiments, the clamping capacitor 14 and the resistor 15 may be integrated into the integrated circuit 12 according to requirements, and in this case, the clamping capacitor 14 and the resistor 15 may be included in the heavy-duty trigger circuit 23.
The logic circuit 24 comprises an OR gate 401 receiving the control signal PWM and the override trigger signal CHAnd for the control signal PWM and the heavy-duty trigger signal CHA logic operation is performed to generate a control signal SW for controlling the on/off switching of the power switch 26. In one embodiment, the control signal PWM and the override trigger signal CHWhen either is active (e.g., logic high), power switch 26 is on.
Fig. 5 shows a schematic diagram of circuitry within integrated circuit 12 according to another embodiment of the present invention. The schematic diagram of integrated circuit 12 shown in fig. 5 differs from the schematic diagram of integrated circuit 12 shown in fig. 4 in the design of reload trigger circuit 23.
As shown in fig. 5, the heavy duty flip-flop 23 includes a delay circuit 501, an RS flip-flop 502, a clamp switch 503, a voltage source 504, and a voltage comparator 505.
The delay circuit 501 receives the follow current determination signal DTHAnd determines a signal D for the follow currentTHAnd delaying to generate a delay signal DLY. In one embodiment, delay circuit 501 determines signal D for free-wheelingTHThe delay time is the time required to charge the clamp capacitor 14 to the output voltage signal VOUTThe time length of the value when the freewheeling of the diode D is cut off, the delay time, the capacitance of the clamping capacitor 14 selected by the detection pin DET, the resistance of the resistor 15 and the output voltage signal VOUTAnd (4) correlating. In general, a reasonable width of the delay time ranges from tens of microseconds to hundreds of microseconds.
An RS flip-flop 502 having a set terminal S for receiving the switch control signal SW controlling the switching of the power switch 26, a reset terminal R for receiving the delay signal DLY, and an output terminal Q for delaying the switch control signal SWThe signal DLY is used for logic operation and outputs a clamping control signal C at the output endLAMP. In one embodiment, the set terminal S of the RS flip-flop 502 sets the clamp control signal C at the time of the falling edge of the switch control signal SWLAMP(logic high). That is, the clamp control signal C is set when the control signal SW changes from active to inactive (at the time when the power switch 26 changes from on to off)LAMP. When the delay signal DLY is active (i.e., when the feedback signal V is activeFBDown to a freewheel reference signal VTHAnd delayed for a period of time), resets the clamp control signal CLAMP(logic low).
Clamp switch 503 has a first terminal, a second terminal, and a control terminal. A first terminal of the clamp switch 503 is coupled to the ground pin GND2 (i.e., the source of the power switch 26), and a control terminal of the clamp switch 503 receives a clamp control signal CLAMPWhen clamping control signal CLAMPDuring being set (logic high), clamp switch 503 is turned on.
And a voltage comparator 505 having an inverting input terminal, a non-inverting input terminal, and an output terminal. The non-inverting input terminal of the voltage comparator 505 is coupled to the second terminal of the clamp switch 503, and the inverting input terminal of the voltage comparator 505 is coupled to the ground pin GND2 through the voltage source 504, and receives the voltage signal V on the ground pin GND2GND2Wherein the voltage value of the voltage source 504 is equal to the reloading threshold △ VTHH. The voltage signal V at the ground pin GND2 during the time when the clamp switch 503 is turned onGND2A clamp capacitor 14 connected to the detection pin DET is charged by a clamp switch and generates a clamp voltage signal V on the detection pin DETDET. When clamping voltage signal VDETEqual to output voltage signal V when diode D freewheeling is cut offOUTAt value (3), the clamp switch 503 is turned off, and the detection pin DET floats. In one embodiment, floating means that the detection pin DET is disconnected from the ground pin GND2 and the voltage on the detection pin DET does not change any more. The voltage comparator 505 converts the voltage signal V on the ground pin GND2GND2And a clamp voltage signal VDETComparing and generating a heavy duty trigger signal C at the outputH. When the voltage signal V on the ground pin GND2GND2Value of (3) is lower than the clamping voltage signalNumber VDETA reload threshold of △ VTHHTime, heavy load trigger signal CHActive (e.g., logic high). Likewise, in the embodiment shown in fig. 5, the clamping capacitor 14 and the resistor 15 are illustrated outside the integrated circuit 12, and the clamping capacitor 14 and the resistor 15 are connected to the inverting input terminal of the internal voltage comparator 505 through the detection pin DET. In other embodiments, the clamping capacitor 14 and the resistor 15 may be integrated into the integrated circuit 12 according to requirements, and in this case, the clamping capacitor 14 and the resistor 15 may be included in the heavy-duty trigger circuit 23.
FIG. 6 illustrates a circuit schematic of a control module according to an embodiment of the present invention. Fig. 6 shows a schematic circuit diagram of a Constant On Time (COT) controlled control module 21. As shown in fig. 6, the control module 21 includes a feedback voltage sample-and-hold circuit 601, a voltage comparator 602, a constant on-time generation circuit 603, and an RS flip-flop 604. The feedback voltage sample-and-hold circuit 601 is coupled to the feedback pin FB to receive the feedback voltage signal VFBAnd for the feedback voltage signal VFBSampling and holding to output a first feedback voltage signal VFB1Wherein the first feedback voltage signal VFB1Representing the feedback voltage signal V during the period when the power switch 26 is off and the diode D is freewheelingFBThe value of (c). The first input terminal of the voltage comparator 602 receives a reference voltage signal VREFThe second input terminal of the voltage comparator 501 receives the first feedback voltage signal VFB1The voltage comparator 602 outputs a first feedback voltage signal VFB1And a reference voltage signal VREFComparing and outputting a set signal T at an output terminalON. The constant on-time generating circuit 603 generates a reset signal T with a fixed on-timeOFF. The set terminal S of the RS flip-flop 604 receives the set signal TONThe reset terminal R of the RS flip-flop 503 receives the reset signal TOFFAnd outputs a control signal PWM at an output terminal Q.
FIG. 7 shows a circuit schematic of a control module according to another embodiment of the present invention. Fig. 7 shows a circuit schematic of a voltage-controlled control module 21. As shown in FIG. 7, the control module includes a feedback voltage sample-and-hold circuit 701,An error amplifier 702, a first voltage comparator 703, a second voltage comparator 704, and an RS flip-flop 705. The feedback voltage sample-and-hold circuit 701 is coupled to the feedback pin FB to receive the feedback voltage signal VFBAnd for the feedback voltage signal VFBSampling and holding to output a first feedback voltage signal VFB1Wherein the first feedback voltage signal VFB1Representing the feedback voltage signal V during the period when the power switch 26 is off and the diode D is freewheelingFBThe value of (c). A first input terminal of the error amplifier 702 receives a reference voltage signal VREFThe second input terminal of the error amplifier 702 receives the first feedback voltage signal VFB1The error amplifier 702 provides the first feedback voltage signal VFB1And a reference voltage signal VREFComparing and amplifying the error, and outputting an error signal EA at an output end. The first input terminal of the first voltage comparator 703 receives the error signal EA, the second input terminal of the first voltage comparator 703 receives the RAMP signal RAMP, and the first voltage comparator 703 compares the error signal EA with the RAMP signal RAMP and outputs a first comparison signal CS at the output terminal. The first input terminal of the second voltage comparator 704 receives the current reference signal VREF_CSA second input terminal of the second voltage comparator 704 receives the current sampling signal VCSThe second voltage comparator 704 provides a current reference signal VREF_CSAnd current sampling signal VCSAnd comparing and outputting a second comparison signal CR at an output terminal. In one embodiment, the current sampling signal VCSRepresenting the value of current flowing through the power switch 26. The set terminal S of the RS flip-flop 705 receives the first comparison signal CSThe reset terminal R of the RS flip-flop 503 receives the second comparison signal CRAnd outputs a control signal PWM at an output terminal Q.
Fig. 8 illustrates a control method of controlling a high voltage BUCK switching converter, in accordance with an embodiment of the present invention. The control method shown in fig. 8 can be applied to the high-voltage BUCK switching converter shown in fig. 2-7. As shown in fig. 2-7, the high-voltage BUCK switching converter includes a power switch 26, a diode D, and an output inductor LOUTA feedback circuit 13, a clamping capacitor 14, and a power switch 26 having a drain coupled to an input of the switching converter for receiving a DC input voltageVDCThe source of the power switch is coupled to the cathode of the diode D, the anode of the diode D is electrically connected to the logic ground GND1, and the output inductor LOUTCoupled between the source of the power switch 26 and the output OUT of the switching converter, the feedback circuit 13 is connected between the output OUT of the switching converter and the source of the power switch 26 and generates a signal representative of the output voltage V during the conduction period of the diode DOUTThe clamping capacitor 14 is coupled between the source of the power switch 26 and the logic ground GND1 through a clamping switch (302 or 503), and the control method includes steps 81-85.
In step 81, when the power switch 26 is turned off, the clamp switch (302 or 503) is turned on, and the clamp capacitor is charged. In one embodiment, the clamp switch is turned on (302) by the power switch control signal SW immediately after the power switch 26 is turned off. In yet another embodiment, after the power switch 26 is turned off, the clamp switch may be turned on (503) after the diode D freewheel is turned off.
Step 82, when the voltage on the clamping capacitor 14 is equal to the freewheeling cut-off of the diode D, outputting a voltage signal VOUTAt a value of (3), the clamp switch (302 or 503) is turned off. In one embodiment, the output voltage signal V is when the voltage on the clamping capacitor 14 equals the diode freewheel cutoffOUTThe value of (A) is that the voltage on the clamping capacitor 14 is charged and rises to the output voltage signal VOUTThe clamp switch can be turned off at this value. After the clamp switch is turned off, the voltage on the clamp capacitor 14 does not change any more, and the voltage signal V is outputOUTWill continue to change as the load changes. In one embodiment, the output voltage signal V may be based on the selected capacitance of the clamping capacitor 14 and the steady state output voltage signal VOUTThe voltage value of (a) calculates the charging time of one clamping capacitor 14.
Step 83, comparing the voltage on the clamp capacitor 14 with the voltage on the source of the power switch 26, and determining whether the difference between the voltage on the source of the power switch and the voltage on the clamp capacitor is greater than the overload threshold. In one embodiment, the inductor current L is set to be equal to or less than the inductor current L when the diode D is turned offOUTZero current flowing in it, voltage at source of power switch 26 after steady state, etcOutput voltage signal V at output terminal OUTOUTThe value of (c).
And step 84, when the difference value between the voltage on the source electrode of the power switch and the voltage on the clamping capacitor is larger than the heavy load threshold value, the power switch is turned on.
The above description of the control method and steps according to the embodiments of the present invention is only exemplary and not intended to limit the present invention. In addition, some well-known control steps, control parameters used, etc. are not shown or described in detail to make the invention clear, concise, and understandable. Those skilled in the art should understand that the step numbers used in the above description of the control method and steps according to the embodiments of the present invention are not used to indicate the absolute sequence of the steps, and the steps are not implemented according to the step number sequence, but may be implemented in different sequences, or may be implemented in parallel, and are not limited to the described embodiments.
While the present invention has been described with reference to several exemplary embodiments, it is understood that the terminology used is intended to be in the nature of words of description and illustration, rather than 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, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.

Claims (13)

1. A voltage conversion integrated circuit for a high-voltage BUCK switch converter is provided with an input pin and a grounding pin, wherein the high-voltage BUCK switch converter comprises a diode, an output inductor and a feedback circuit, the cathode of the diode is coupled with the grounding pin, and the anode of the diode is electrically connected to the logic ground of the switch converter; the output inductor is coupled between the grounding pin and the output end of the switch converter; a feedback circuit coupled between the output terminal of the switching converter and the ground pin and generating a feedback signal representative of the output voltage signal during diode conduction, said voltage conversion integrated circuit comprising:
a feedback pin coupled to the feedback circuit and receiving a feedback signal;
the detection pin is electrically connected to the logic ground of the switching converter through the clamping capacitor;
the power switch is provided with a first end, a second end and a control end, wherein the first end of the power switch is coupled with the input pin to receive the input voltage, and the second end of the power switch is coupled with the grounding pin;
the follow current judging circuit is coupled with the feedback pin to receive the feedback signal and generates a follow current judging signal according to the feedback signal, and the follow current judging signal is effective after the diode is cut off; and
the heavy-load trigger circuit is coupled with the detection pin, the grounding pin and the follow current judgment circuit, when the power switch is switched off, the heavy-load trigger circuit is connected with the detection pin and the grounding pin, and the connection between the detection pin and the grounding pin is disconnected after the detection pin generates a clamping voltage signal, wherein the value of the clamping voltage signal is equal to the value of an output voltage signal when the diode follow current is cut off, the heavy-load trigger circuit compares the clamping voltage signal with the voltage signal on the grounding pin to generate a heavy-load trigger signal in the effective period of the follow current judgment signal, and when the value of the voltage signal on the grounding pin is lower than the value of the clamping voltage signal by a heavy-load threshold value, the heavy-load trigger signal is effective, and the power.
2. The voltage converting integrated circuit of claim 1, wherein the heavy duty trigger circuit comprises:
the pulse trigger receives the follow current judgment signal and generates a pulse signal according to the follow current judgment signal, wherein the pulse signal is effective within a period of time from the initial moment when the follow current judgment signal is effective;
the clamping switch is provided with a first end, a second end and a control end, the first end of the clamping switch is coupled with the grounding pin, the second end of the clamping switch is coupled with the detection pin, the control end of the clamping switch receives the pulse signal, and when the pulse signal is effective, the clamping switch is switched on; and
the voltage comparator is provided with a first input end, a second input end and an output end, the first input end of the voltage comparator is coupled with the detection pin to receive the clamping voltage signal, the second input end of the voltage comparator is coupled with the grounding pin through a voltage source to receive the voltage signal on the grounding pin, the voltage comparator compares the sum value of the voltage signal on the grounding pin and the voltage source with the clamping voltage signal, and outputs a heavy-load trigger signal at the output end of the voltage comparator, wherein the voltage value of the voltage source is equal to a heavy-load threshold value.
3. The voltage converting integrated circuit of claim 1, wherein the heavy duty trigger circuit comprises:
the delay circuit receives the follow current judging signal, delays the follow current judging signal and generates a delay signal;
the RS trigger is provided with a setting end, a resetting end and an output end, wherein the setting end receives a switch control signal for controlling the switching of the power switch, the resetting end receives a delay signal, and the RS trigger performs logic operation on the switch control signal and the delay signal and outputs a clamping control signal at the output end;
the clamp switch is provided with a first end, a second end and a control end, the first end of the clamp switch is coupled with the grounding pin, the second end of the clamp switch is coupled with the detection pin, and the control end of the clamp switch receives a clamp control signal; and
the voltage comparator is provided with a first input end, a second input end and an output end, the first input end of the voltage comparator is coupled with the detection pin to receive the clamping voltage signal, the second input end of the voltage comparator is coupled with the grounding pin through a voltage source to receive the voltage signal on the grounding pin, the voltage comparator compares the sum value of the voltage signal on the grounding pin and the voltage source with the clamping voltage signal, and outputs a heavy-load trigger signal at the output end of the voltage comparator, wherein the voltage value of the voltage source is equal to a heavy-load threshold value.
4. A voltage conversion integrated circuit as claimed in claim 1, wherein the freewheel decision circuit comprises a freewheel comparator having a first input receiving the feedback signal, a second input receiving the freewheel threshold signal and an output, the freewheel comparator comparing the feedback signal with the freewheel threshold signal and generating a freewheel decision signal at the output of the freewheel comparator, the freewheel decision signal being active when the feedback signal is less than the freewheel threshold signal.
5. The voltage converting integrated circuit of claim 1, further comprising:
the control module receives the feedback signal and generates a first control signal according to the feedback signal; and
and the logic circuit receives the first control signal and the heavy-load trigger signal, performs logic operation on the first control signal and the heavy-load trigger signal, and generates a switch control signal, wherein when any one of the first control signal and the heavy-load trigger signal is effective, the switch control signal controls the power switch to be switched on.
6. The voltage converting integrated circuit of claim 1, further comprising a supply pin, wherein the supply pin is coupled to the ground pin through a bootstrap capacitor.
7. A high-voltage BUCK switching converter, comprising:
the power switch is provided with a first end, a second end and a control end, wherein the first end of the power switch receives an input voltage signal, and the second end of the power switch is coupled to the output end of the switching converter through an output inductor;
the cathode of the freewheeling diode is coupled with the second end of the power switch, and the anode of the freewheeling diode is electrically connected to the logic ground;
a feedback circuit coupled between the second terminal of the power switch and the output terminal of the switching converter and generating a feedback signal representative of the output voltage signal during the diode conduction period;
the follow current judging circuit receives the feedback signal, generates a follow current judging signal according to the feedback signal, and after the diode follow current is cut off, the follow current judging signal is effective; and
and the heavy-load trigger circuit is coupled with the second end of the power switch and the follow current judging circuit, generates a clamping voltage signal during the effective period of the follow current judging signal, wherein the value of the clamping voltage signal is equal to the value of the output voltage signal when the follow current of the diode is cut off, compares the clamping voltage signal with the voltage signal on the second end of the power switch to generate a heavy-load trigger signal, and when the value of the voltage signal on the second end of the power switch is lower than the value of the clamping voltage signal by a heavy-load threshold value, the heavy-load trigger signal is effective and the power switch is switched on.
8. The high-voltage BUCK switching converter of claim 7, wherein the heavy-duty trigger circuit includes:
the pulse trigger receives the follow current judgment signal and generates a pulse signal according to the follow current judgment signal, wherein the pulse signal is effective within a period of time from the initial moment when the follow current judgment signal is effective;
the clamping switch is provided with a first end, a second end and a control end, the first end of the clamping switch is coupled with the second end of the power switch, the control end of the clamping switch receives the pulse signal, and when the pulse signal is effective, the clamping switch is conducted;
the clamping capacitor is connected between the second end of the clamping switch and logic ground, and a voltage signal on the clamping capacitor is a clamping voltage signal; and
and the voltage comparator is provided with a first input end, a second input end and an output end, the first input end of the voltage comparator is coupled with the second end of the clamping switch to receive a clamping voltage signal, the second input end of the voltage comparator is coupled with the second end of the power switch to receive a voltage signal on the second end of the power switch through a voltage source, the voltage comparator compares the sum of the voltage signal on the second end of the power switch and the voltage source with the clamping voltage signal and outputs a heavy-load trigger signal at the output end of the voltage comparator, wherein the voltage value of the voltage source is equal to the heavy-load threshold value.
9. The high-voltage BUCK switching converter of claim 7, wherein the heavy-duty trigger circuit includes:
the delay circuit receives the follow current judging signal, delays the follow current judging signal and generates a delay signal;
the RS trigger is provided with a setting end, a resetting end and an output end, wherein the setting end receives a switch control signal for controlling the switching of the power switch, the resetting end receives a delay signal, and the RS trigger performs logic operation on the switch control signal and the delay signal and outputs a clamping control signal at the output end;
the clamping switch is provided with a first end, a second end and a control end, the first end of the clamping switch is coupled with the second end of the power switch, and the control end of the clamping switch receives a clamping control signal;
the clamping capacitor is connected between the second end of the clamping switch and logic ground, and a voltage signal on the clamping capacitor is a clamping voltage signal; and
and the voltage comparator is provided with a first input end, a second input end and an output end, the first input end of the voltage comparator is coupled with the second end of the clamping switch to receive a clamping voltage signal, the second input end of the voltage comparator is coupled with the second end of the power switch to receive a voltage signal on the second end of the power switch through a voltage source, the voltage comparator compares the sum of the voltage signal on the second end of the power switch and the voltage source with the clamping voltage signal and outputs a heavy-load trigger signal at the output end of the voltage comparator, wherein the voltage value of the voltage source is equal to the heavy-load threshold value.
10. The high-voltage BUCK switching converter of claim 7, further comprising:
the control module receives the feedback signal and generates a first control signal according to the feedback signal; and
and the logic circuit receives the first control signal and the heavy-load trigger signal, performs logic operation on the first control signal and the heavy-load trigger signal, and generates a switch control signal, wherein when any one of the first control signal and the heavy-load trigger signal is effective, the switch control signal controls the power switch to be switched on.
11. The high-voltage BUCK switching converter of claim 7, wherein the freewheel decision circuit includes a freewheel comparator having a first input receiving the feedback signal, a second input receiving the freewheel threshold signal, and an output, the freewheel comparator comparing the feedback signal to the freewheel threshold signal and generating a freewheel decision signal at the output of the freewheel comparator, the freewheel decision signal being active when the feedback signal is less than the freewheel threshold signal.
12. A control method for controlling a high voltage BUCK switching converter, the high voltage BUCK switching converter including a power switch, a diode, an output inductor, a feedback circuit, and a clamping capacitor, a drain of the power switch coupled to an input of the switching converter to receive an input voltage signal, a source of the power switch coupled to a cathode of the diode, an anode of the diode electrically coupled to a logic ground, the output inductor coupled between the source of the power switch and an output of the switching converter, the feedback circuit coupled between the output of the switching converter and the source of the power switch, the clamping capacitor coupled between the source of the power switch and the logic ground through a clamping switch, the control method comprising:
when the power switch is turned off, the clamping switch is turned on, and the clamping capacitor is charged;
when the voltage value of the clamping capacitor is equal to the value of the output voltage signal when the diode freewheeling is cut off, the clamping switch is switched off;
comparing the voltage on the clamping capacitor with the voltage on the source electrode of the power switch; and
and when the voltage value of the source electrode of the power switch is lower than the voltage value of the clamping capacitor by a heavy load threshold value, the power switch is turned on.
13. The control method of claim 12, wherein said step of turning on the clamp switch after the power switch is turned off comprises turning on the clamp switch after the power switch is turned off and the diode freewheel is turned off.
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