CN113328634A - Switch control circuit, switch control method and switch power supply - Google Patents
Switch control circuit, switch control method and switch power supply Download PDFInfo
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- CN113328634A CN113328634A CN202110561003.2A CN202110561003A CN113328634A CN 113328634 A CN113328634 A CN 113328634A CN 202110561003 A CN202110561003 A CN 202110561003A CN 113328634 A CN113328634 A CN 113328634A
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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
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
- H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
- H02H3/087—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current for dc applications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
- H02H7/1213—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for DC-DC converters
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/14—Arrangements for reducing ripples from dc input or output
- H02M1/15—Arrangements for reducing ripples from dc input or output using active elements
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/44—Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
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Abstract
The invention provides a switch control circuit, a switch control method and a switch power supply. The switch control circuit comprises a trigger circuit and a driving signal generating circuit. The reset end of the trigger circuit is coupled with the overcurrent protection signal end to receive the overcurrent protection signal; the comparison signal is obtained by comparing the first reference signal with a feedback signal indicative of an output voltage of the switching power supply. The input end of the driving signal generating circuit is coupled with the output end of the trigger circuit, the output end of the driving signal generating circuit is coupled with the switch tube, and the driving signal generating circuit is used for outputting a driving signal to control the switch tube. According to the switch control circuit, the switch control method and the switch power supply, the switching frequency of the switch tube can be controlled to be uniform, the output ripple wave is reduced, and the working noise of the switch power supply is effectively reduced.
Description
Technical Field
The invention belongs to the technical field of power electronics, relates to a power supply conversion technology, and particularly relates to a switch control circuit, a switch control method and a switch power supply.
Background
Switching power supplies are a major class of electronic power supplies, and are widely used in most electronic devices such as consumer electronics and communication devices due to their advantages of light weight, miniaturization, wide input voltage range, high power density/conversion efficiency, low standby power consumption, and the like.
The switching power supply generally includes a switching tube and a switching control circuit, an output terminal of the switching control circuit is coupled to a control terminal of the switching tube, and the switching control circuit is configured to output a switching control signal to control the switching tube to be turned on and off, so as to control a magnitude of an output voltage or an output current. As shown in fig. 1, the switch control circuit in the prior art includes a comparator, a fixed oscillator, an and gate, a flip-flop, and a driving signal generating circuit. The first input end of the comparator receives the output voltage Vout, the second input end of the comparator receives the reference voltage Vref, and the comparator outputs a comparison signal according to the output voltage Vout and the reference voltage Vref. The first input end of the AND gate is coupled with the output end of the comparator, and the second input end of the AND gate is coupled with the output end of the fixed oscillator. The fixed oscillator outputs a clock pulse signal according to a limit value of the maximum duty ratio, and the frequency of the clock pulse signal is fixed. The setting end of the trigger is coupled with the output end of the AND gate, the resetting end of the trigger is coupled with the overcurrent protection signal end, and the overcurrent protection signal end is used for outputting an overcurrent protection signal OCP. The input terminal of the driving signal generating circuit is coupled to the output terminal of the flip-flop, the output terminal of the driving signal generating circuit is coupled to the switching transistor Q1, and the driving signal generating circuit is configured to control the switching transistor Q1 to be turned on and off according to the output signal of the flip-flop. When the output voltage Vout is higher than the reference voltage Vref, the switch control circuit controls to turn off the switching tube Q1. When the output voltage Vout is lower than the reference voltage Vref, the switch control circuit controls the switching tube Q1 to be turned on and off at the frequency of the clock pulse signal output by the fixed oscillator. Based on the circuit structure, the pulse width modulation signal PWM output by the driving signal generating circuit controls the operating state of the switching tube Q1 to be a cluster of hiccup states, so that the operating noise and the output ripple of the switching power supply system are easily caused to deteriorate.
In view of the above, it is desirable to provide a new structure or control method for solving at least some of the above problems.
Disclosure of Invention
In order to solve at least part of the problems, the invention provides a switch control circuit, a switch control method and a switch power supply, which can control the switching frequency of a switch tube to be uniform, reduce output ripples and reduce the working noise of the switch power supply.
The invention discloses a switch control circuit, which is used for controlling a switch tube in a switch power supply, and comprises:
the trigger circuit is provided with a set end for receiving the comparison signal and an AND gate signal of the maximum frequency control signal, and a reset end coupled with the overcurrent protection signal end for receiving the overcurrent protection signal; the comparison signal is obtained by comparing the first reference signal with a feedback signal representing the output voltage of the switching power supply; and
the input end of the driving signal generating circuit is coupled to the output end of the trigger circuit, and the output end of the driving signal generating circuit is coupled to the switch tube and used for outputting a driving signal to control the switch tube.
In an embodiment of the present invention, the switch control circuit further includes:
the comparison circuit is used for comparing the first reference signal with a feedback signal representing the output voltage of the switching power supply and outputting a comparison signal; and
and the first input end of the AND gate is coupled with the output end of the comparison circuit, the second input end of the AND gate is coupled with the maximum frequency control signal end to receive the maximum frequency control signal, and the output end of the AND gate is coupled with the setting end of the trigger circuit.
In an embodiment of the present invention, the switch control circuit includes: and the maximum frequency control circuit is used for outputting a maximum frequency control signal according to the switching frequency of the switching tube and the maximum frequency reference.
In an embodiment of the present invention, the switch control circuit further includes: the first input end of the OR gate is coupled with the overcurrent protection signal end, the second input end of the OR gate is coupled with the maximum on-time signal end to receive the maximum on-time signal, and the output end of the OR gate is coupled with the reset end of the trigger circuit.
In an embodiment of the present invention, the switch control circuit further includes: the first input end of the subtracter is coupled with the feedback signal end to receive the feedback signal, the second input end of the subtracter is coupled with the ramp signal end to receive the ramp signal, and the output end of the subtracter is coupled with the comparison circuit.
In an embodiment of the present invention, the switch control circuit further includes: and the input end of the overload detection circuit is coupled with the output end of the comparison circuit and used for outputting an overload protection signal according to the comparison signal.
In an embodiment of the invention, the comparator is a comparator, a non-inverting input terminal of the comparator is coupled to the first reference signal terminal to receive the first reference signal, an inverting input terminal of the comparator is coupled to the feedback signal terminal to receive the feedback signal, and an output terminal of the comparator is coupled to the first input terminal of the and gate.
The invention also discloses a switching power supply which comprises a rectifying circuit and the switching control circuit.
The invention also discloses a switch control method for controlling the switch tube in the switch power supply, which comprises the following steps:
comparing the first reference signal with a feedback signal representing the output voltage of the switching power supply, and outputting a comparison signal;
controlling a trigger signal output by the trigger circuit according to the states of the comparison signal and the maximum frequency control signal so as to control the switching tube to be in a conducting state; the trigger signal output by the trigger circuit is controlled according to the state of the overcurrent protection signal so as to control the switching tube to be in a turn-off state; and
and outputting a driving signal according to the trigger signal to control the switching tube.
In an embodiment of the present invention, when the and gate signal of the comparison signal and the maximum frequency control signal is in the first level state, the trigger signal is in the set state; and when the overcurrent protection signal indicates that the current detection signal meets the overcurrent condition, the trigger signal is in a reset state.
In an embodiment of the present invention, the step of controlling the trigger signal output by the trigger circuit according to the state of the over-current protection signal includes: and controlling the trigger signal output by the trigger circuit according to the state of the overcurrent protection signal or the state of the maximum on-time signal.
In an embodiment of the present invention, the step of comparing the first reference signal with a feedback signal representing an output voltage of the switching power supply and outputting the comparison signal specifically includes: and performing slope compensation on the feedback signal to output a compensated feedback signal, comparing the first reference signal with the compensated feedback signal, and outputting a comparison signal.
The invention provides a switch control circuit, a switch control method and a switch power supply. The switch control circuit comprises a trigger circuit and a driving signal generating circuit. The reset end of the trigger circuit is coupled with the overcurrent protection signal end to receive the overcurrent protection signal; the comparison signal is obtained by comparing the first reference signal with a feedback signal indicative of an output voltage of the switching power supply. The input end of the driving signal generating circuit is coupled with the output end of the trigger circuit, the output end of the driving signal generating circuit is coupled with the switch tube, and the driving signal generating circuit is used for outputting a driving signal to control the switch tube. According to the switch control circuit, the switch control method and the switch power supply, the switching frequency of the switch tube can be controlled to be uniform, the output ripple wave is reduced, and the working noise of the switch power supply is effectively reduced.
Drawings
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings:
FIG. 1 shows a circuit schematic of a prior art switch control circuit;
FIG. 2 shows a circuit schematic of a switch control circuit according to an embodiment of the invention;
FIG. 3 shows a circuit schematic of a switch control circuit according to another embodiment of the invention;
FIG. 4 shows a circuit schematic of a switching power supply according to an embodiment of the invention;
fig. 5 shows a circuit schematic of a switching power supply according to another embodiment of the invention.
Detailed Description
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.
The description in this section is for several exemplary embodiments only, and the present invention is not limited only to the scope of the embodiments described. Combinations of different embodiments, and substitutions of features from different embodiments, or similar prior art means may be substituted for or substituted for features of the embodiments shown and described.
The term "coupled" or "connected" in this specification includes both direct and indirect connections. An indirect connection is a connection made through an intermediate medium, such as a conductor, wherein the electrically conductive medium may contain parasitic inductance or parasitic capacitance, or through an intermediate circuit or component as described in the embodiments in the specification; indirect connections may also include connections through other active or passive devices that perform the same or similar function, such as connections through switches, signal amplification circuits, follower circuits, and so on. "plurality" or "plurality" means two or more.
The embodiment of the invention discloses a switch control circuit which is used for controlling the switch state of a switch tube in a switch power supply. The switch state of the switch tube comprises an on state and an off state. The switch control circuit comprises a trigger circuit and a driving signal generating circuit. The reset end of the trigger circuit is coupled with the overcurrent protection signal end to receive the overcurrent protection signal. The comparison signal is obtained by comparing the first reference signal with a feedback signal indicative of an output voltage of the switching power supply. The input end of the driving signal generating circuit is coupled to the output end of the trigger circuit, the output end of the driving signal generating circuit is coupled to the control end of the switch tube, and the driving signal generating circuit is used for outputting a driving signal to control the on-off state of the switch tube. According to the switch control circuit, the switch control method and the switch power supply provided by the invention, when the output voltage of the switch power supply is higher than the preset voltage, the switch control circuit controls the switch tube to stop the switching action, and when the output voltage of the switch power supply is lower than the preset voltage, the switch control circuit controls the switch tube to perform the switching action, so that the switching frequency of the switch tube can be controlled to be uniform, the output ripple wave is reduced, and the working noise of the switch power supply is effectively reduced.
The invention discloses a switch control circuit, which is used for controlling a switch tube in a switch power supply and comprises a comparison circuit, an AND gate, a trigger circuit and a driving signal generating circuit. The first input end of the comparison circuit is coupled with the first reference signal end to receive the first reference signal, the second input end of the comparison circuit is coupled with a feedback signal representing the output voltage of the switching power supply, and the comparison circuit outputs the comparison signal according to the comparison result of the first reference signal and the feedback signal. In a specific embodiment, the feedback signal may be an output voltage of the switching power supply, and the feedback signal may also be proportional or scaled to the output voltage of the switching power supply. The first input end of the AND gate is coupled with the output end of the comparison circuit, and the second input end of the AND gate is coupled with the maximum frequency control signal end to receive the maximum frequency control signal. The maximum frequency control signal is used for controlling the switching frequency of the switching tube to be not more than the maximum frequency reference fmax, and when the switching frequency of the switching tube is more than the maximum frequency reference, the switching control circuit controls the switching tube to be in an off state. The reset end of the trigger circuit is coupled with the overcurrent protection signal end to receive the overcurrent protection signal. The input end of the driving signal generating circuit is coupled to the output end of the trigger circuit, the output end of the driving signal generating circuit is coupled to the control end of the switching tube, the driving signal generating circuit is used for outputting a driving signal to control the switching state of the switching tube, and the switching state of the switching tube comprises a conducting state and a switching-off state.
When the feedback voltage representing the output voltage of the switching power supply is lower than the first reference signal, the switching tube is controlled to be conducted, namely when the output voltage of the switching power supply is lower than the preset voltage, the switching tube is timely conducted to raise the output voltage. If the overcurrent condition is met, the current signal is not higher than the preset current by timely turning off the switch tube, so that the normal work of the switch control circuit is protected. The switching power supply is limited to work at an unstable working point by limiting the maximum switching frequency of the switching tube so as to ensure the normal work of the switching power supply. The switching frequency of the controllable switching tube based on the switching control circuit is uniform, output ripples are reduced, and the working noise of the switching power supply is reduced.
In an embodiment of the invention, the switch control circuit includes a switch, and the output terminal of the driving signal generating circuit is coupled to the control terminal of the switch. In another embodiment, the switch control circuit does not include a switch tube, and the output terminal of the switch control circuit is coupled to the control terminal of the switch tube.
In an embodiment of the present invention, as shown in fig. 2, the switch control circuit includes a comparator 100, a trigger circuit 200, a driving signal generating circuit 300, and an and gate 500. The non-inverting input terminal of the comparator 100 is coupled to the first reference signal terminal to receive a first reference signal, which is a first reference voltage Vref. The inverting input terminal of the comparator 100 is coupled to the feedback signal terminal to receive the feedback signal VFB, and the feedback signal VFB represents the output voltage of the switching power supply. In this embodiment, the feedback signal VFB is a divided voltage of the output voltage of the switching power supply, and the feedback signal VFB is proportional to the output voltage of the switching power supply. A first input terminal of the and gate 500 is coupled to the output terminal of the comparator 100, and a second input terminal of the and gate 500 is coupled to the maximum frequency control signal terminal to receive the maximum frequency control signal fs _ max. The set terminal of the trigger circuit 200 is coupled to the output terminal of the and gate 500, and the reset terminal of the trigger circuit 200 is coupled to the over-current protection signal terminal to receive the over-current protection signal OCP. The input terminal of the driving signal generating circuit 300 is coupled to the output terminal of the trigger circuit 200, the output terminal of the driving signal generating circuit 300 is coupled to the switch Q1, and the driving signal generating circuit 300 is configured to generate a driving signal according to the output signal of the trigger circuit 200 to drive the switch. In the embodiment of the present invention, the switch tube may be one of a metal oxide semiconductor field effect transistor (MOSFET for short), a junction field effect transistor (JFET for short), and an insulated gate bipolar transistor (IGBT for short).
In an embodiment of the present invention, the trigger circuit 200 is a flip-flop. In a specific embodiment, the flip-flop is an RS flip-flop, a set terminal of the RS flip-flop is coupled to the output terminal of the and gate, and a reset terminal of the RS flip-flop is coupled to the overcurrent protection signal terminal to receive the overcurrent protection signal OCP. The input end of the driving signal generating circuit is coupled with the output end of the RS trigger.
In the embodiment shown in fig. 2, the switch control circuit further includes an overload detection circuit 400, an input terminal of the overload detection circuit 400 is coupled to an output terminal of the comparator 100, and the overload detection circuit 400 is configured to output the overload protection signal OLP according to the comparison signal. Specifically, the overload detection circuit 400 determines the overload detection by means of overcurrent detection timing, and when the timing time satisfies a condition, the overload protection is triggered, and the switching control circuit controls the switching tube Q1 to stop the switching action.
In an embodiment of the invention, the switch control circuit further includes a maximum frequency control circuit, and a second input terminal of the and gate 500 is coupled to an output terminal of the maximum frequency control circuit, and an output terminal of the maximum frequency control circuit is a maximum frequency control signal terminal. The maximum frequency control circuit is used for outputting a maximum frequency control signal fs _ max according to the switching frequency of the switching tube and a maximum frequency reference. When the switching frequency of the switching tube is lower than the maximum frequency reference, the maximum frequency control signal is in a first level state (for example, a high level). When the switching frequency of the switching tube reaches or is higher than the maximum frequency reference, the maximum frequency control signal is in a second level state (for example, a low level), the trigger circuit is not set at the moment, and the switching tube is not controlled to be conducted at the moment.
In another embodiment of the present invention, the switch control circuit further includes an over-current detection circuit, a first input terminal of the over-current detection circuit receives a current detection signal, the current detection signal is indicative of a current flowing through the switch tube, and a second input terminal of the over-current detection circuit receives a second reference signal. When the current detection signal is lower than the second reference signal, the overcurrent protection signal is in a second level state (e.g., low level), and the trigger circuit may not be reset. When the current detection signal reaches or is higher than the second reference signal, the overcurrent protection signal is in a first level state (for example, a high level), and the overcurrent protection can be triggered to reset the trigger circuit, so that the switching tube is controlled to be switched off.
In an embodiment of the present invention, as shown in fig. 3, the switch control circuit includes a comparator 100, a trigger circuit 200, a driving signal generating circuit 300, an overload detecting circuit 400, an and gate 500, and an or gate 600. A first input terminal of the or gate 600 is coupled to the over-current protection signal terminal to receive the over-current protection signal OCP, a second input terminal of the or gate 600 is coupled to the maximum on-time signal terminal to receive the maximum on-time signal Ton _ max, and an output terminal of the or gate 600 is coupled to the reset terminal of the trigger circuit 200. The maximum on-time signal Ton _ max is used to control the switching tube to turn off when the on-time in the switching period of the switching tube reaches the set maximum on-time. In another embodiment of the present invention, the switch control circuit further includes a subtractor 700, a first input terminal of the subtractor 700 is coupled to the feedback signal terminal to receive the feedback signal VFB, a second input terminal of the subtractor 700 is coupled to the ramp signal terminal to receive the ramp signal slope, and an output terminal of the subtractor 700 is coupled to the inverting input terminal of the comparator 100. By introducing slope compensation, the working stability of a system where the switch control circuit is located can be increased.
The embodiment of the invention also discloses a switching power supply which comprises a rectifying circuit and the switching control circuit. The switching power supply can be one of a Buck type switching power supply, a Boost type switching power supply, a Buckboost type switching power supply, a flyback type switching power supply and the like, and the switching power supply in the embodiment of the invention comprises a voltage feedback circuit of the output voltage of the switching power supply, so that the loop control of the output voltage is realized. The switching power supply can control the switching frequency of the switching tube to be uniform, reduce output ripples and reduce the working noise of the switching power supply.
In an embodiment of the invention, as shown in fig. 4, the switching power supply is a Buck switching power supply, and the Buck switching power supply includes a rectifying circuit (not shown), a first capacitor C1, a switch control circuit, a sampling resistor Rcs, an inductor L, a third capacitor C3, a first diode D1, a second diode D2, and a second capacitor C2. The switch control circuit is provided with a Drain terminal Drain, a current sampling terminal CS and a power supply terminal VDD. The Drain terminal Drain is coupled to a first terminal of a first capacitor C1 that serves as an input filter capacitor. The current sampling terminal CS is coupled to a first terminal of the sampling resistor Rcs, and a second terminal of the sampling resistor Rcs is coupled to a first terminal of the inductor L. The power supply terminal VDD is coupled to the second terminal of the third capacitor C3, and the first terminal of the third capacitor C3 is coupled to the second terminal of the sampling resistor Rcs. The anode of the first diode D1 is coupled to ground, and the cathode of the first diode D1 is coupled to the first terminal of the inductor L. An anode of the second diode D2 is coupled to the second terminal of the inductor L, and a cathode of the second diode D2 is coupled to the second terminal of the third inductor C3. The second capacitor C2 is an output capacitor, a first terminal of the second capacitor C2 is coupled to the second terminal of the inductor L, and a second terminal of the second capacitor C2 is coupled to ground. The output voltage of the switching power supply can be fed back to the power supply terminal VDD through the second diode D2, so that the output voltage of the switching power supply can be obtained in real time.
In another embodiment of the present invention, as shown in fig. 5, the switching power supply is a pseudo-isolation flyback switching power supply, and the pseudo-isolation flyback switching power supply includes a switching control circuit, and the switching control circuit is respectively coupled to the primary side circuit and the secondary side circuit, so that the switching power supply is called a pseudo-isolation flyback switching power supply. The switch control circuit is provided with a DRAIN terminal DRAIN, a power supply terminal VDD, a feedback terminal FB and a reference ground terminal GND. The DRAIN terminal DRAIN is coupled with the primary winding, the power supply terminal VDD is coupled with the output terminal of the pseudo-isolation flyback switching power supply, and the reference ground terminal GND is coupled with the reference ground. The feedback terminal FB is coupled to a node between the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2, wherein the first voltage-dividing resistor R1 is coupled to the output terminal of the pseudo-isolated flyback switching power supply, the second terminal of the first voltage-dividing resistor R1 is coupled to the first terminal of the second voltage-dividing resistor R2, and the second terminal of the second voltage-dividing resistor R2 is coupled to the ground reference. The divided voltage of the output voltage of the switching power supply can be fed back to the feedback terminal FB through the first voltage dividing resistor R1 and the second voltage dividing resistor R2.
The embodiment of the invention also discloses a switch control method, which is used for controlling the switch tube in the switch power supply, and the switch control method comprises the following steps:
comparing the first reference signal with a feedback signal representing the output voltage of the switching power supply, and outputting a comparison signal;
controlling a trigger signal output by the trigger circuit according to the states of the comparison signal and the maximum frequency control signal so as to control the switching tube to be in a conducting state; the trigger signal output by the trigger circuit is controlled according to the state of the overcurrent protection signal so as to control the switching tube to be in a turn-off state; and
and outputting a driving signal according to the trigger signal to control the switching tube.
In an embodiment of the invention, when the states of the comparison signal and the maximum frequency control signal are both in the first level state (for example, high level), the trigger signal output by the control trigger circuit is in high level, so as to control the switch tube to be in the conducting state. In another embodiment, when the state of the over-current protection signal is a first level state (for example, a high level), that is, the over-current protection is triggered in the switching power supply, the trigger signal output by the control trigger circuit is a low level at this time, so that the switching tube is controlled to be in an off state.
In an embodiment of the present invention, when the and gate signal of the comparison signal and the maximum frequency control signal is in a first level state (such as high level), the trigger signal is in a set state; and when the overcurrent protection signal indicates that the current detection signal meets the overcurrent condition, the trigger signal is in a reset state.
In another embodiment of the present invention, the step of controlling the trigger signal output by the trigger circuit according to the state of the over-current protection signal further includes: and controlling the trigger signal output by the trigger circuit according to the state of the overcurrent protection signal or the state of the maximum on-time signal so as to control the switching tube to be in an off state.
In another embodiment of the present invention, the step of comparing the first reference signal with a feedback signal representing an output voltage of the switching power supply and outputting the comparison signal specifically includes: and performing slope compensation on the feedback signal to output a compensated feedback signal, comparing the first reference signal with the compensated feedback signal, and outputting a comparison signal.
Based on the above embodiments, the PWM signal PWM outputted from the driving signal generating circuit of the present invention controls the switching transistor Q1 to switch at a uniform frequency instead of a cluster-by-cluster hiccup state. According to the switch control circuit, the switch control method and the switch power supply, the switching frequency of the switch tube can be controlled to be uniform, the output ripple is reduced, and the working noise of the switch power supply is effectively reduced.
Those skilled in the art should understand that the logic controls such as "high" and "low", "set" and "reset", "and gate" and "or gate", "non-inverting input" and "inverting input" in the logic controls referred to in the specification or the drawings may be exchanged or changed, and the subsequent logic controls may be adjusted to achieve the same functions or purposes as the above-mentioned embodiments.
The description and applications of the invention herein are illustrative and are not intended to limit the scope of the invention to the embodiments described above. The descriptions related to the effects or advantages in the specification may not be reflected in practical experimental examples due to uncertainty of specific condition parameters or influence of other factors, and the descriptions related to the effects or advantages are not used for limiting the scope of the invention. Variations and modifications of the embodiments disclosed herein are possible, and alternative and equivalent various components of the embodiments will be apparent to those skilled in the art. It will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, and with other components, materials, and parts, without departing from the spirit or essential characteristics thereof. Other variations and modifications of the embodiments disclosed herein may be made without departing from the scope and spirit of the invention.
Claims (12)
1. A switch control circuit for controlling a switching tube in a switching power supply, the switch control circuit comprising:
the trigger circuit is provided with a set end for receiving the comparison signal and an AND gate signal of the maximum frequency control signal, and a reset end coupled with the overcurrent protection signal end for receiving the overcurrent protection signal; the comparison signal is obtained by comparing a first reference signal with a feedback signal representing the output voltage of the switching power supply; and
and the input end of the driving signal generating circuit is coupled with the output end of the trigger circuit, and the output end of the driving signal generating circuit is coupled with the switching tube and used for outputting a driving signal to control the switching tube.
2. The switch control circuit of claim 1, further comprising:
the comparison circuit is used for comparing the first reference signal with a feedback signal representing the output voltage of the switching power supply and outputting a comparison signal; and
and the first input end of the AND gate is coupled with the output end of the comparison circuit, the second input end of the AND gate is coupled with the maximum frequency control signal end to receive the maximum frequency control signal, and the output end of the AND gate is coupled with the position end of the trigger circuit.
3. The switch control circuit of claim 1, wherein the switch control circuit comprises:
and the maximum frequency control circuit is used for outputting the maximum frequency control signal according to the switching frequency of the switching tube and the maximum frequency reference.
4. The switch control circuit of claim 1, further comprising:
the first input end of the OR gate is coupled with the overcurrent protection signal end, the second input end of the OR gate is coupled with the maximum on-time signal end to receive the maximum on-time signal, and the output end of the OR gate is coupled with the reset end of the trigger circuit.
5. The switch control circuit of claim 2, further comprising:
the first input end of the subtracter is coupled with the feedback signal end to receive the feedback signal, the second input end of the subtracter is coupled with the ramp signal end to receive the ramp signal, and the output end of the subtracter is coupled with the comparison circuit.
6. The switch control circuit of claim 2, further comprising:
and the input end of the overload detection circuit is coupled with the output end of the comparison circuit and is used for outputting an overload protection signal according to the comparison signal.
7. The switch control circuit of claim 2, wherein the comparator is a comparator, a non-inverting input of the comparator is coupled to the first reference signal terminal to receive the first reference signal, an inverting input of the comparator is coupled to the feedback signal terminal to receive the feedback signal, and an output of the comparator is coupled to the first input of the and gate.
8. A switching power supply, characterized in that it comprises a rectifying circuit and a switch control circuit according to any one of claims 1 to 7.
9. A switch control method is used for controlling a switch tube in a switch power supply, and is characterized by comprising the following steps:
comparing the first reference signal with a feedback signal representing the output voltage of the switching power supply, and outputting a comparison signal;
controlling a trigger signal output by a trigger circuit according to the states of the comparison signal and the maximum frequency control signal so as to control the switch tube to be in a conducting state; the trigger signal output by the trigger circuit is controlled according to the state of the overcurrent protection signal so as to control the switching tube to be in a turn-off state; and
and outputting a driving signal according to the trigger signal to control the switching tube.
10. The switching control method according to claim 9, wherein the trigger signal is in a set state when and gate signals of both the comparison signal and the maximum frequency control signal are in a first level state; and when the overcurrent protection signal indicates that the current detection signal meets the overcurrent condition, the trigger signal is in a reset state.
11. The switch control method according to claim 9, wherein the step of controlling the trigger signal output by the trigger circuit according to the state of the overcurrent protection signal comprises:
and controlling the trigger signal output by the trigger circuit according to the state of the overcurrent protection signal or the state of the maximum on-time signal.
12. The switching control method of claim 9, wherein the step of comparing the first reference signal with a feedback signal indicative of the output voltage of the switching power supply and outputting the comparison signal specifically comprises:
and performing slope compensation on the feedback signal to output a compensated feedback signal, comparing the first reference signal with the compensated feedback signal, and outputting a comparison signal.
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| CN202110561003.2A CN113328634A (en) | 2021-05-19 | 2021-05-19 | Switch control circuit, switch control method and switch power supply |
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| CN202110561003.2A CN113328634A (en) | 2021-05-19 | 2021-05-19 | Switch control circuit, switch control method and switch power supply |
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