CN110554303A - Demagnetization time detection circuit and method and power supply device - Google Patents
Demagnetization time detection circuit and method and power supply device Download PDFInfo
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- CN110554303A CN110554303A CN201910927450.8A CN201910927450A CN110554303A CN 110554303 A CN110554303 A CN 110554303A CN 201910927450 A CN201910927450 A CN 201910927450A CN 110554303 A CN110554303 A CN 110554303A
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- 230000005347 demagnetization Effects 0.000 title claims abstract description 120
- 238000001514 detection method Methods 0.000 title claims abstract description 76
- 238000000034 method Methods 0.000 title abstract description 9
- 238000004146 energy storage Methods 0.000 claims abstract description 73
- 239000003990 capacitor Substances 0.000 claims description 49
- 238000005070 sampling Methods 0.000 claims description 20
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- 230000000630 rising effect Effects 0.000 description 5
- 230000003044 adaptive effect Effects 0.000 description 4
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Abstract
the invention relates to the technical field of integrated circuits, in particular to a demagnetization time detection circuit and method and a power supply device adopting the demagnetization time detection circuit or method. The demagnetization time detection circuit is applied to a switch circuit with an energy storage inductor and a power switch, and comprises a demagnetization time detection module, wherein the demagnetization time detection module detects the end point of the demagnetization time of the energy storage inductor, and after the demagnetization time of the energy storage inductor is ended, the output end outputs a demagnetization time end signal. According to the invention, the LC resonance voltage after the demagnetization of the energy storage inductor is detected through resistance voltage division and is compared with the self-adaptive reference voltage, so that the influence caused by the parasitic capacitance of the power switch is overcome, and the accuracy and reliability of a demagnetization time detection point are improved.
Description
Technical Field
The invention relates to the technical field of integrated circuits, in particular to a demagnetization time detection circuit and method, and a power supply device adopting the demagnetization time detection circuit or method.
Background
fig. 1 shows a conventional switching circuit, in which a first end of an energy storage inductor L1 is electrically coupled to an input voltage VIN, a second end of the energy storage inductor L1 is coupled to an input end of a switching tube M1, and is also electrically coupled to an anode of a freewheeling diode D1, a control end of a switching tube M1 is electrically coupled to an output end of a control module, an output end of a switching tube M1 is electrically coupled to ground, a cathode of a freewheeling diode D1 is electrically coupled to a first end of an output capacitor C1 and a first end of a load, a second end of the output capacitor C1 and a second end of the load are electrically coupled to the input voltage VIN, an input end of the control module is electrically coupled to an output end of a demagnetization time detection module, and an input end of the demagnetization time detection. When the energy storage inductor L1 is converted into a demagnetization state from a charging state, the control module outputs a low level to disconnect the power tube M1, the rear output end is converted into a high-resistance state, the power tube M1 is kept in a disconnection state by a pull-down resistor, when demagnetization of the energy storage inductor L1 is finished, the energy storage inductor L1 and a parasitic capacitor at the input end of the power tube M1 form LC oscillation, the principle of demagnetization time detection of the existing switching circuit is that the parasitic capacitor Cgd of the power tube M1 is utilized to couple an LC oscillation voltage signal to the control end of the power tube M1 to be compared with a zero level, and when a signal at the control end of the power tube M1 becomes a negative voltage, a demagnetization time end signal ZXC output by the demagnetization time detection module is converted into a high level to realize detection of a demagnetization time end point.
The detection of the demagnetization time end point in the conventional switch circuit has the defects that the demagnetization time end point is influenced by the parasitic capacitance of the power tube M1, and the power tubes M1 with different sizes or different structures have different parasitic capacitances, so that the compatibility of the switch circuit to different power tubes M1 cannot meet the requirements of customers.
Disclosure of Invention
the invention provides a demagnetization time detection circuit and method, and a power supply device adopting the demagnetization time detection circuit or method.
The demagnetization time detection circuit comprises a demagnetization time detection module, a first input end, a second input end and an output end, wherein the demagnetization time detection module is provided with the first input end, the second input end and the output end, the first input end is electrically coupled with the input end of the power switch, the second input end is electrically coupled with the control end of the power switch, the demagnetization time detection module detects the end point of the demagnetization time of the energy storage inductor, and the output end outputs a demagnetization time end signal after the demagnetization time of the energy storage inductor is ended.
according to an embodiment of the present invention, the demagnetization time detection module includes: a resistive voltage divider circuit having a first terminal electrically coupled to the power switch input, a second terminal electrically coupled to ground, and a voltage divider output that outputs a divided voltage signal proportional to the voltage at the power switch input; the sampling and holding module is provided with a first input end, a second input end and an output end, wherein the first input end is electrically coupled with the voltage division signal, the second input end is electrically coupled with the power switch control end signal, and the output end outputs a sampling and holding signal; and the hysteresis comparator is provided with a first input end, a second input end and an output end, wherein the first input end is electrically coupled with the voltage division signal, the second input end is electrically coupled with the sample and hold signal, and the output end outputs a demagnetization time ending signal.
according to an embodiment of the present invention, the sample-and-hold module includes: the monopulse circuit is provided with an input end and an output end, wherein the input end is electrically coupled with the output end of an inverter, the input end of the inverter is electrically coupled with the signal of the control end of the power switch, and the monopulse circuit outputs a monopulse signal at the falling edge moment of the signal of the control end of the power switch; the first switch is provided with an input end, an output end and a control end, wherein the input end is electrically coupled with the voltage division signal output by the resistance voltage division circuit, and the control end is electrically coupled with the output end of the monopulse circuit and receives the monopulse signal; a sample-and-hold capacitor having a first terminal electrically coupled to the first switch output terminal and a second terminal electrically coupled to ground, the sample-and-hold capacitor sampling and holding the divided voltage signal output by the resistor divider circuit during the high-level time of the single pulse signal; and the second switch is provided with an input end, an output end and a control end, wherein the input end is electrically coupled with the first end of the capacitor, the control end is electrically coupled with the control end of the power switch in a signal mode, and the output end is electrically coupled with the ground.
According to an embodiment of the invention, a demagnetization time detection circuit is applied, and the applied switching circuit comprises: an energy storage inductor having a first terminal electrically coupled to the input voltage and a second terminal electrically coupled to the power switch input terminal; a freewheeling diode having a cathode and an anode, wherein the anode is electrically coupled to the power switch input and the second end of the energy storage inductor; an output capacitor and a load are connected in parallel, wherein a first end of the output capacitor and the load connected in parallel is electrically coupled to the cathode of the freewheeling diode, and a second end of the parallel connection is electrically coupled to the input voltage.
according to an embodiment of the invention, a demagnetization time detection circuit is applied, and the applied switching circuit comprises: the energy storage inductor is a primary inductor of a transformer, the primary inductor is provided with a first end and a second end, the first end is electrically coupled with the input voltage, the second end is electrically coupled with the input end of the power switch, and the secondary inductor of the transformer is provided with a first end and a second end; a freewheeling diode having a cathode and an anode, wherein the anode is electrically coupled to the first terminal of the transformer secondary inductor; an output capacitor and a load are connected in parallel, wherein a first end of the output capacitor and the load connected in parallel is electrically coupled with the cathode of the freewheeling diode, and a second end of the parallel connection is electrically coupled with the second end of the transformer secondary inductor.
According to an embodiment of the invention, a demagnetization time detection circuit is applied, and the applied switching circuit comprises: an energy storage inductor having a first terminal and a second terminal, wherein the second terminal is electrically coupled to the power switch input terminal; the output capacitor is electrically coupled with the first end of the load in parallel, and the second end of the load is electrically coupled with the first end of the energy storage inductor; and the free-wheeling diode is provided with a cathode and an anode, wherein the anode is electrically coupled with the input end of the power switch and the second end of the energy storage inductor, and the cathode is electrically coupled with the input voltage.
According to an embodiment of the invention, a demagnetization time detection circuit is applied, and the applied switching circuit comprises: an energy storage inductor having a first terminal and a second terminal, wherein the first terminal is electrically coupled to the input voltage; the output capacitor and the load are connected in parallel, wherein the first end of the output capacitor and the load which are connected in parallel is electrically coupled with the second end of the energy storage inductor, and the second end of the parallel connection is electrically coupled with the input end of the power switch; a freewheeling diode having a cathode and an anode, wherein the anode is electrically coupled to the power switch input and the cathode is electrically coupled to the input voltage.
according to an embodiment of the invention, the applied switching circuit comprises: a control module, has input and output, wherein the input with demagnetization time detection module output electricity coupling receives demagnetization time end signal, the output with power switch control end electricity coupling, the power switch output is coupled with ground electricity, control module is based on demagnetization time detection module is right the testing result at energy storage inductance demagnetization time end point controls power switch switches on for input voltage passes through power switch is right the energy storage inductance charges.
A demagnetization time detection method comprises the following steps: when the power switch is disconnected, sampling the voltage of a drain electrode at the input end of the power switch to obtain drain electrode partial pressure; sampling and holding the divided voltage of the drain electrode to obtain a comparative reference voltage; and comparing the divided voltage of the drain electrode with the reference voltage, and outputting a demagnetization time ending signal when the divided voltage of the drain electrode is smaller than the reference voltage.
According to an embodiment of the present invention, the power supply device includes any one of the demagnetization time detection circuits or adopts the demagnetization time detection method.
the demagnetization time detection circuit provided by the invention detects the LC resonance voltage after the demagnetization of the energy storage inductor is finished through resistance voltage division and compares the LC resonance voltage with the self-adaptive reference voltage, thereby overcoming the influence caused by the parasitic capacitance of the power switch and improving the accuracy and reliability of a demagnetization time detection point.
Drawings
fig. 1 is a schematic diagram of a conventional demagnetization time detection circuit;
fig. 2A is a schematic diagram of a demagnetization time detection circuit according to an embodiment of the invention;
fig. 2B is a schematic diagram of a demagnetization time detection module according to an embodiment of the invention;
FIG. 2C is a schematic diagram of a sample and hold module according to an embodiment of the invention;
FIG. 2D is a schematic diagram of a single pulse circuit according to an embodiment of the invention;
FIG. 2E is a schematic diagram of a demagnetization time detection circuit according to a second embodiment of the present invention;
FIG. 2F is a schematic diagram of a demagnetization time detection circuit according to a third embodiment of the invention;
Fig. 2G is a schematic diagram of a demagnetization time detection circuit according to a fourth embodiment of the invention;
FIG. 3A illustrates exemplary operating waveforms in accordance with one embodiment of the present invention;
FIG. 3B illustrates exemplary operating waveforms of another embodiment of the present invention;
FIG. 3C is a waveform illustrating an exemplary operation of yet another embodiment of the present invention;
Fig. 4 is a flowchart of a demagnetization time detection method according to an embodiment of the 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 drawings 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. 2A shows a demagnetization time detection circuit according to an embodiment of the present invention, which is applied to a switch circuit 200 having an energy storage inductor 201 and a power switch 205, and includes a demagnetization time detection module 220 having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is electrically coupled to the input terminal Vdrain of the power switch 205, the second input terminal is electrically coupled to the control terminal of the power switch 205 (for convenience of description, the input terminal or the output terminal of a component is equal to the signal name of the input terminal or the output terminal), the demagnetization time detection module 220 detects the end point of the demagnetization time of the energy storage inductor 201, and after the demagnetization time of the energy storage inductor 201 ends, the output terminal outputs a demagnetization time end signal ZXC.
Fig. 2B is a schematic circuit diagram of a demagnetization time detection module 220 according to an embodiment of the invention, including: a resistor divider circuit 221, wherein the resistor divider circuit 221 has a first terminal electrically coupled to the input terminal of the power switch 205 for receiving the input terminal voltage Vdrain, a second terminal electrically coupled to ground, and a divider output terminal for outputting a divider signal VN2 proportional to the input terminal voltage Vdrain of the power switch 205, VN2 k Vdrain, where k is a constant; a sample-and-hold module 222 having a first input electrically coupled to the voltage-divided signal VN2, a second input electrically coupled to the control signal PWM of the power switch 205, and an output outputting a sample-and-hold signal Vsmp; a hysteresis comparator 223 having a first input electrically coupled to the voltage-dividing signal VN2, a second input electrically coupled to the sample-and-hold signal Vsmp, and an output outputting a demagnetization-time-end signal ZXC.
In one embodiment, the resistance voltage divider circuit 221 includes an upper voltage dividing resistor and a lower voltage dividing resistor, wherein a first end of the upper voltage dividing resistor is electrically coupled to the input end of the power switch 205 and receives the input end voltage Vdrain, a second end of the upper voltage dividing resistor is electrically coupled to the first end of the lower voltage dividing resistor, a second end of the lower voltage dividing resistor is electrically coupled to ground, a common end of the upper voltage dividing resistor and the lower voltage dividing resistor is a voltage dividing output end, and outputs a voltage dividing signal VN2, where VN2 ═ k Vdrain.
Fig. 2C is a circuit diagram of a sample-and-hold module 222 according to an embodiment of the invention, which includes: a monopulse circuit 2221 having an input terminal and an output terminal, wherein the input terminal is electrically coupled to the output terminal of an inverter 2222, the input terminal of the inverter 2222 is electrically coupled to the control terminal signal PWM of the power switch 205, and the monopulse circuit 2221 outputs a monopulse signal Vpulse at the time of the falling edge of the control terminal signal PWM of the power switch 205; a first switch 2223 having an input terminal, an output terminal, and a control terminal, wherein the input terminal is electrically coupled to the voltage-dividing signal VN2 outputted by the voltage-dividing resistor circuit 221, and the control terminal is electrically coupled to the output terminal of the single pulse circuit 2221 for receiving the single pulse signal Vpulse; a sample-and-hold capacitor 2224 having a first terminal electrically coupled to the output terminal of the first switch 2223 and a second terminal electrically coupled to ground, wherein the sample-and-hold capacitor 2224 samples and holds the voltage-dividing signal VN2 output from the resistor voltage-dividing circuit 221 during the time of the high level of the single pulse signal Vpulse; a second switch 2225 having an input terminal, an output terminal, and a control terminal, wherein the input terminal is electrically coupled to the first terminal of the capacitor 2224, the control terminal is electrically coupled to the control terminal signal PWM of the power switch 205, and the output terminal is electrically coupled to ground, and when the control terminal signal PWM of the power switch 205 becomes high level, the second switch 2225 clears the sample-and-hold signal Vsmp on the sample-and-hold capacitor 2224.
in one embodiment, the single pulse circuit 2221 includes a rising edge delay circuit 2221a, wherein the rising edge delay circuit 2221a delays the rising edge of the signal PWMB at its input terminal, and has an input terminal and an output terminal, and wherein the input terminal is electrically coupled to the output terminal of the inverter 2222; an inverter 2221b having an input electrically coupled to the output of the rising edge delay circuit 2221a and an output electrically coupled to a first input of an and gate 2221 c; a second input terminal of the and gate 2221c is electrically coupled to the input terminal of the rising edge delay circuit 2221a, and an output terminal of the and gate 2221c outputs a single pulse signal Vpulse.
in one embodiment, as shown in fig. 2A, the switch circuit 200 applied by the demagnetization time detection circuit includes: an energy storage inductor 201 having a first terminal electrically coupled to the input voltage VIN and a second terminal electrically coupled to the input terminal of the power switch 205; a freewheeling diode 202 having a cathode and an anode, wherein the anode is electrically coupled to the input of the power switch 205 and the second end of the energy storage inductor 201; an output capacitor 203 and a load 204, wherein a first end of the output capacitor 203 and the load 204 connected in parallel is electrically coupled to the cathode of the freewheeling diode 202, and a second end of the parallel connection is electrically coupled to the input voltage VIN, and the switching circuit 200 constitutes a buck-boost circuit structure.
Referring to fig. 3A, with reference to a typical operating waveform diagram of a buck-boost circuit structure, when a signal PWM at a control terminal of the power switch 205 is at a high level, the power switch 205 is turned on, a voltage Vdrain at an input terminal thereof becomes a low level, the sampling capacitor 2224 is reset to a zero level, the energy storage inductor 201 is charged, and an inductor current IL increases linearly; when the control end signal PWM of the power switch 205 is at a low level, the power switch 205 is turned off, the voltage Vdrain at the input end of the power switch 205 changes to a high level, and for the buck-boost circuit structure, Vdrain is VIN + Vout, where Vout is a load voltage, the resistance voltage-dividing circuit 221 in the demagnetization time detection module 220 divides the voltage Vdrain at the input end of the power switch 205 to obtain a divided voltage signal VN2 is k Vdrain, the single pulse circuit in the sample-and-hold circuit 222 outputs a sampling pulse Vpulse, during the high level period, the sample-and-hold module 222 sample-holds the divided voltage signal VN2 in the capacitor 2224 as a non-inverting end reference voltage Vsmp of the comparator 223, and when the voltage Vdrain is high, the reference voltage Vsmp is high, and when the voltage rain is low, the reference voltage vdmp is low, so that the reference voltage Vsmp has a function of adaptive adjustment. During the period that the power switch 205 is turned off, the energy storage inductor 201 is in a demagnetization discharge state, and the current IL of the energy storage inductor 201 is linearly reduced; when the current IL of the energy storage inductor 201 drops to zero and after demagnetization ends, LC resonance occurs between the energy storage inductor 201 and the capacitor parasitic at the second end of the energy storage inductor, which causes the voltage Vdrain at the input end of the power switch 205 to oscillate, and the voltage division signal VN2 also oscillates, and when the voltage amplitude of the voltage division signal VN2 oscillates to a set threshold value lower than the reference voltage Vsmp of the comparator, the demagnetization time ending signal ZXC output by the comparator 223 becomes a high level, which indicates that demagnetization of the energy storage inductor 201 ends at this time.
in one embodiment, as shown in fig. 2E, the switch circuit 300 applied by the demagnetization time detection circuit includes an energy storage inductor 301 as a primary inductor of a transformer T1, where the primary inductor 301 has a first terminal electrically coupled to the input voltage VIN and a second terminal electrically coupled to the input terminal of the power switch 205, and the secondary inductor 305 of the transformer T1 has a first terminal and a second terminal; a freewheeling diode 302 having a cathode and an anode, wherein the anode is electrically coupled to a first terminal of the secondary inductor 305 of the transformer T1; an output capacitor 303 and a load 304 are connected in parallel, wherein a first end of the parallel connection of the output capacitor 303 and the load 304 is electrically coupled to the cathode of the freewheeling diode 302, and a second end of the parallel connection is electrically coupled to a second end of the secondary inductor 305 of the transformer T1, and the switching circuit 300 forms a flyback circuit structure.
Referring to fig. 3C, with reference to a typical operating waveform diagram of a flyback circuit structure, when a signal PWM at a control end of the power switch 205 is at a high level, the power switch 205 is turned on, a voltage Vdrain at an input end of the power switch is changed to a low level, the sampling capacitor 2224 is reset to a zero level, the energy storage inductor 301 is charged, and an inductor current IL increases linearly; when the control terminal signal PWM of the power switch 205 is at low level, the power switch 205 is turned off, the input end voltage Vdrain becomes high level, and for the flyback circuit structure, the Vdrain becomes VIN + Nps Vout, wherein Vout is a load voltage, Nps is a winding turn ratio of a primary side and a secondary side of the transformer, a resistance voltage dividing circuit 221 in the demagnetization time detection module 220 divides a voltage Vdrain at an input end of the power switch 205 to obtain a divided voltage signal VN2 k Vdrain, a single pulse circuit in the sample-and-hold circuit 222 outputs a sampling pulse Vpulse, during its high level, the sample-and-hold module 222 sample-holds the divided voltage signal VN2 in the capacitor 2224, as the non-inverting terminal reference voltage Vsmp of the comparator 223, the reference voltage Vsmp is high when the Vdrain voltage is high, and is high when the Vdrain voltage is low, the reference voltage Vamp is low and thus the reference voltage Vsmp has a function of adaptive adjustment. During the off period of the power switch 205, the secondary inductor 305 of the transformer T1 is in a demagnetized discharge state, and the current IL decreases linearly; when the secondary inductor current IL drops to zero and after demagnetization ends, the energy storage inductor 301 and the capacitor parasitic at the second end of the energy storage inductor generate LC resonance, so that the voltage Vdrain at the input end of the power switch 205 also oscillates, and the voltage division signal VN2 also oscillates at the same time, when the voltage amplitude of the voltage division signal VN2 oscillates to a set threshold value lower than the reference voltage Vsmp of the comparator, the demagnetization time ending signal ZXC output by the comparator 223 becomes a high level, which indicates that demagnetization of the secondary inductor 305 of the transformer T1 ends at this time.
In one embodiment, as shown in fig. 2F, the switch circuit 400 applied to the demagnetization time detection circuit includes: an energy storage inductor 401 having a first terminal and a second terminal, wherein the second terminal is electrically coupled to the input terminal of the power switch 205; an output capacitor 403 and a load 404 are connected in parallel, wherein a first end of the parallel connection of the output capacitor 403 and the load 404 is electrically coupled to the input voltage VIN, and a second end of the parallel connection is electrically coupled to the first end of the energy storage inductor 401; a freewheeling diode 402 having a cathode and an anode, wherein the anode is electrically coupled to the input terminal of the power switch 205 and the second terminal of the energy storage inductor 401, and the cathode is electrically coupled to the input voltage VIN, and the switching circuit 400 constitutes a buck circuit configuration.
Referring to fig. 3B, when the control end signal PWM of the power switch 205 is at a high level, the power switch 205 is turned on, the voltage Vdrain at the input end thereof changes to a low level, the sampling capacitor 2224 is reset to a zero level, the energy storage inductor 401 is charged, and the inductor current IL increases linearly; when the control end signal PWM of the power switch 205 is at a low level, the power switch 205 is turned off, the voltage Vdrain at the input end of the power switch 205 is at a high level, and for the voltage-reducing circuit structure, Vdrain is VIN-Vout, where Vout is a load voltage, the resistance voltage-dividing circuit 221 in the demagnetization time detection module 220 divides the voltage Vdrain at the input end of the power switch 205 to obtain a divided voltage signal VN2, k is Vdrain, the single-pulse circuit in the sample-and-hold circuit 222 outputs a sampling pulse Vpulse, during the high level period, the sample-and-hold module 222 sample-holds the divided voltage signal VN2 in the capacitor 2224 as a non-inverting end reference voltage Vsmp of the comparator 223, and when the Vdrain voltage is high, the reference voltage Vsmp is high, and when the rain voltage is low, the reference voltage Vamp is low, so the reference voltage Vsmp has a function of adaptive adjustment. During the period that the power switch 205 is turned off, the energy storage inductor 401 is in a demagnetization discharge state, and the current IL of the energy storage inductor 401 is linearly reduced; when the current IL of the energy storage inductor 401 drops to zero, and after demagnetization ends, the energy storage inductor 401 and the capacitor parasitic at the second end thereof generate LC resonance, which causes the voltage Vdrain at the input end of the power switch 205 to oscillate, and the voltage division signal VN2 also oscillates, and when the voltage amplitude of the voltage division signal VN2 oscillates to a set threshold value lower than the reference voltage Vsmp of the comparator, the demagnetization time ending signal ZXC output by the comparator 223 becomes a high level, which indicates that demagnetization of the energy storage inductor 401 ends at this time.
In one embodiment, as shown in fig. 2G, the switch circuit 500 applied to the demagnetization time detection circuit includes: an energy storage inductor 501 has a first terminal and a second terminal, wherein the first terminal is electrically coupled to the input voltage VIN; an output capacitor 503 and a load 504 are connected in parallel, wherein a first end of the parallel connection of the output capacitor 503 and the load 504 is electrically coupled with a second end of the energy storage inductor 501, and the second end of the parallel connection is electrically coupled with the input end of the power switch 205; a freewheeling diode 502 having a cathode and an anode, wherein the anode is electrically coupled to the input of the power switch 205 and the cathode is electrically coupled to the input voltage VIN, and the switching circuit 500 constitutes a buck circuit configuration.
Referring to fig. 3B, when the control end signal PWM of the power switch 205 is at a high level, the power switch 205 is turned on, the voltage Vdrain at the input end thereof changes to a low level, the sampling capacitor 2224 is reset to a zero level, the energy storage inductor 501 is charged, and the inductor current IL increases linearly; when the control end signal PWM of the power switch 205 is at a low level, the power switch 205 is turned off, the voltage Vdrain at the input end of the power switch 205 is at a high level, and for the voltage-reducing circuit structure, Vdrain is VIN-Vout, where Vout is a load voltage, the resistance voltage-dividing circuit 221 in the demagnetization time detection module 220 divides the voltage Vdrain at the input end of the power switch 205 to obtain a divided voltage signal VN2, k is Vdrain, the single-pulse circuit in the sample-and-hold circuit 222 outputs a sampling pulse Vpulse, during the high level period, the sample-and-hold module 222 sample-holds the divided voltage signal VN2 in the capacitor 2224 as a non-inverting end reference voltage Vsmp of the comparator 223, and when the Vdrain voltage is high, the reference voltage Vsmp is high, and when the rain voltage is low, the reference voltage Vamp is low, so the reference voltage Vsmp has a function of adaptive adjustment. During the period that the power switch 205 is turned off, the energy storage inductor 501 is in a demagnetization discharge state, and the current IL of the energy storage inductor 501 is linearly reduced; when the current IL of the energy storage inductor 501 drops to zero and demagnetization ends, the energy storage inductor 501 and the capacitor parasitic at the second end of the energy storage inductor 501 generate LC resonance, and the voltage Vdrain at the input end of the power switch 205 also oscillates through the coupling of the output capacitor 503, and meanwhile, the voltage division signal VN2 also oscillates, and when the voltage amplitude of the voltage division signal VN2 oscillates to a set threshold value lower than the reference voltage Vsmp of the comparator, the demagnetization time ending signal ZXC output by the comparator 223 becomes a high level, which indicates that demagnetization of the energy storage inductor 501 ends at the moment.
According to an embodiment of the present invention, a demagnetization time detection circuit, where a switching circuit is applied to the demagnetization time detection circuit as shown in fig. 2A, fig. 2E, fig. 2F, and fig. 2G, further includes: a control module 240, has input and output, wherein the input with demagnetization time detection module 220 output electricity coupling receives demagnetization time end signal ZXC, the output with power switch 205 control end electricity is coupled, power switch 205 output is coupled with ground electricity, control module 240 is based on demagnetization time detection module 220 is right the testing result at energy storage inductance demagnetization time end point controls power switch 205 switches on for input voltage VIN passes through power switch 205 is right the energy storage inductance charges.
The power switch 205 according to an embodiment of the present invention is an NMOS transistor, a gate of a control terminal of the NMOS transistor is electrically coupled to an output terminal of the control module 240, a source of the output terminal is electrically coupled to ground, and a drain of the input terminal is electrically coupled to the energy storage inductor; or the power switch 205 is an NPN transistor, a base of a control terminal of the NPN transistor is electrically coupled to the output terminal of the control module 240, an emitter of the input terminal is electrically coupled to ground, and a collector of the output terminal is electrically coupled to the energy storage inductor.
FIG. 4 is a flowchart of a demagnetization time detection method according to an embodiment of the invention, including steps 401 to 403
Step 401, when the power switch is turned off, sampling the drain voltage of the input end of the power switch to obtain drain voltage division;
Step 402, sampling and holding the divided voltage of the drain electrode to obtain a comparative reference voltage;
And 403, comparing the divided voltage of the drain with the reference voltage, and outputting a demagnetization time ending signal when the divided voltage of the drain is smaller than the reference voltage.
According to an embodiment of the invention, the power supply device comprises any one of the demagnetization time detection circuits or the demagnetization time detection method.
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. It will be apparent to those skilled in the art that various modifications and enhancements can be made without departing from the principles of the invention, and such modifications and enhancements are intended to be included within the scope of the invention.
Claims (10)
1. A demagnetization time detection circuit is applied to a switch circuit with an energy storage inductor and a power switch, and is characterized by comprising:
A demagnetization time detection module has first input, second input and output, wherein first input with power switch input electricity coupling, the second input with power switch control end electricity coupling, demagnetization time detection module detects the end point of energy storage inductance demagnetization time after the end of energy storage inductance demagnetization time, a demagnetization time end signal is exported to the output.
2. the demagnetization time detection circuit according to claim 1, wherein the demagnetization time detection module comprises:
A resistive voltage divider circuit having a first terminal electrically coupled to the power switch input, a second terminal electrically coupled to ground, and a voltage divider output that outputs a divided voltage signal proportional to the voltage at the power switch input;
the sampling and holding module is provided with a first input end, a second input end and an output end, wherein the first input end is electrically coupled with the voltage division signal, the second input end is electrically coupled with the power switch control end signal, and the output end outputs a sampling and holding signal;
and the hysteresis comparator is provided with a first input end, a second input end and an output end, wherein the first input end is electrically coupled with the voltage division signal, the second input end is electrically coupled with the sample and hold signal, and the output end outputs a demagnetization time ending signal.
3. The demagnetization time detection circuit of claim 2 wherein the sample and hold module comprises:
The monopulse circuit is provided with an input end and an output end, wherein the input end is electrically coupled with the output end of an inverter, the input end of the inverter is electrically coupled with the signal of the control end of the power switch, and the monopulse circuit outputs a monopulse signal at the falling edge of the signal of the control end of the power switch;
The first switch is provided with an input end, an output end and a control end, wherein the input end is electrically coupled with the voltage division signal output by the resistance voltage division circuit, and the control end is electrically coupled with the output end of the monopulse circuit and receives the monopulse signal;
A sample-and-hold capacitor having a first terminal electrically coupled to the first switch output terminal and a second terminal electrically coupled to ground, the sample-and-hold capacitor sampling and holding the divided voltage signal output by the resistor divider circuit during the high-level time of the single pulse signal;
and the second switch is provided with an input end, an output end and a control end, wherein the input end is electrically coupled with the first end of the capacitor, the control end is electrically coupled with the control end of the power switch in a signal mode, and the output end is electrically coupled with the ground.
4. A demagnetization time detection circuit as claimed in claim 1, characterized in that the switching circuit used comprises:
an energy storage inductor having a first terminal electrically coupled to the input voltage and a second terminal electrically coupled to the power switch input terminal;
A freewheeling diode having a cathode and an anode, wherein the anode is electrically coupled to the power switch input and the second end of the energy storage inductor;
an output capacitor and a load are connected in parallel, wherein a first end of the output capacitor and the load connected in parallel is electrically coupled to the cathode of the freewheeling diode, and a second end of the parallel connection is electrically coupled to the input voltage.
5. A demagnetization time detection circuit as claimed in claim 1, characterized in that the switching circuit used comprises:
The energy storage inductor is a primary inductor of a transformer, the primary inductor is provided with a first end and a second end, the first end is electrically coupled with the input voltage, the second end is electrically coupled with the input end of the power switch, and the secondary inductor of the transformer is provided with a first end and a second end;
A freewheeling diode having a cathode and an anode, wherein the anode is electrically coupled to the first terminal of the transformer secondary inductor;
An output capacitor and a load are connected in parallel, wherein a first end of the output capacitor and the load connected in parallel is electrically coupled with the cathode of the freewheeling diode, and a second end of the parallel connection is electrically coupled with the second end of the transformer secondary inductor.
6. a demagnetization time detection circuit as claimed in claim 1, characterized in that the switching circuit used comprises:
An energy storage inductor having a first terminal and a second terminal, wherein the second terminal is electrically coupled to the power switch input terminal;
The output capacitor is electrically coupled with the first end of the load in parallel, and the second end of the load is electrically coupled with the first end of the energy storage inductor;
and the free-wheeling diode is provided with a cathode and an anode, wherein the anode is electrically coupled with the input end of the power switch and the second end of the energy storage inductor, and the cathode is electrically coupled with the input voltage.
7. a demagnetization time detection circuit as claimed in claim 1, characterized in that the switching circuit used comprises:
An energy storage inductor having a first terminal and a second terminal, wherein the first terminal is electrically coupled to the input voltage;
the output capacitor and the load are connected in parallel, wherein the first end of the output capacitor and the load which are connected in parallel is electrically coupled with the second end of the energy storage inductor, and the second end of the parallel connection is electrically coupled with the input end of the power switch;
A freewheeling diode having a cathode and an anode, wherein the anode is electrically coupled to the power switch input and the cathode is electrically coupled to the input voltage.
8. a demagnetization time detection circuit as claimed in claim 1, characterized in that the switching circuit applied thereto further comprises:
A control module, has input and output, wherein the input with demagnetization time detection module output electricity coupling receives demagnetization time end signal, the output with power switch control end electricity coupling, the power switch output is coupled with ground electricity, control module is based on demagnetization time detection module is right the testing result at energy storage inductance demagnetization time end point controls power switch switches on for input voltage passes through power switch is right the energy storage inductance charges.
9. A demagnetization time detection method comprises the following steps:
When the power switch is disconnected, sampling the voltage of a drain electrode at the input end of the power switch to obtain drain electrode partial pressure;
sampling and holding the divided voltage of the drain electrode to obtain a comparative reference voltage;
And comparing the divided voltage of the drain electrode with the reference voltage, and outputting a demagnetization time ending signal when the divided voltage of the drain electrode is smaller than the reference voltage.
10. A power supply device characterized by comprising the demagnetization time detection circuit according to any one of claims 1 to 8 or adopting the demagnetization time detection method according to claim 9.
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