CN109245052B - Short-circuit protection circuit and switching power supply comprising same - Google Patents
Short-circuit protection circuit and switching power supply comprising same Download PDFInfo
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- CN109245052B CN109245052B CN201810995074.1A CN201810995074A CN109245052B CN 109245052 B CN109245052 B CN 109245052B CN 201810995074 A CN201810995074 A CN 201810995074A CN 109245052 B CN109245052 B CN 109245052B
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- 238000006243 chemical reaction Methods 0.000 claims abstract description 14
- 238000002955 isolation Methods 0.000 claims description 32
- 239000003990 capacitor Substances 0.000 claims description 20
- 230000003111 delayed effect Effects 0.000 claims description 4
- 230000001934 delay Effects 0.000 claims description 3
- 238000010586 diagram Methods 0.000 description 6
- 238000004804 winding Methods 0.000 description 3
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 230000004075 alteration Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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Classifications
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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
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Abstract
The invention discloses a short-circuit protection circuit, which comprises a first input port, a second input port, an output port, a switch circuit and a reset circuit, wherein the first input port is connected with the second input port; the first input port and the second input port are both used for inputting PWM signals, the first input port inputs high level, the second input port inputs high level after high level delay for a first time, and the second input short-circuit port turns to low level after the first input port turns to low level and delay for a second time; when the input of the first input port is turned to be at a low level, the level of the output port can be directly pulled down by the switch circuit, so that the output port can output a control signal at the low level without delaying for a second time; after the short-circuit protection circuit is used for the switching power supply, the output port of the short-circuit protection circuit is connected with the driving end of the main power switching tube in the power conversion circuit, so that the main power switching tube in the power conversion circuit of the switching power supply can be rapidly turned off.
Description
Technical field:
the invention discloses a short-circuit protection circuit and a switching power supply comprising the same, and particularly relates to short-circuit protection of the switching power supply using an isolation driving chip.
The background technology is as follows:
in the existing module power supply, high-power products generally use complex circuit topologies such as double-tube flyback, push-pull, half-bridge and full-bridge, and the like, and because the circuit topologies comprise two or more switching tubes to be controlled, part of the circuit topologies need to be driven in an isolated mode, such as double-tube flyback and full-bridge, so that the circuit topologies cannot be directly controlled by a pulse width modulation chip (hereinafter, pulse width modulation is called PWM for short), and the circuit topologies need to use an isolated driving chip to transmit control signals of the PWM chip to the power switching tubes so as to control the switching tubes in the power circuit.
The existing isolation driving chips have longer on and off time delays, the off time delay of the full-bridge circuit isolation driving chip is about 100ns, and the half-bridge circuit isolation driving chip reaches 200ns. The existing PWM chip generally integrates a single-period peak current protection function, when the output is short-circuited, the main power current is rapidly increased, when the peak value of the primary current reaches a protection set value, the PWM chip turns off a driving signal, but the primary power switch tube is turned off after the time length of turn-on-off time delay due to the turn-off time delay of the isolation driving chip, and the current of the primary main power continuously rises in the time period. Under most short-circuit conditions, the short-circuit current of the main power can saturate the transformer core, and the inductance can be drastically reduced after the transformer core is saturated. As can be seen from the inductor current formula, when the input voltage Vin is 160V and the inductance Lp of the primary side transformer is reduced to 0.5 μh, the magnitude of the short-circuit current corresponding to the on-time Ton of 200ns is:
therefore, the longer turn-off delay time of the isolation driving chip can cause short-circuit current to increase, so that the main power device is required to meet the specification of larger current stress, and the selection of the device is influenced.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide a short-circuit protection circuit and a switching power supply including the same, which solves the problem of overlarge short-circuit current of the existing switching power supply using an isolated driving chip in a high-voltage short-circuit state.
In order to solve the above technical problems, the present invention provides a short-circuit protection circuit, including:
the switching circuit comprises a first input port, a second input port, an output port, a switching circuit and a reset circuit;
the switch circuit is provided with a first input port, a second input port and an output port, and the reset circuit is connected with the switch circuit;
the first input port inputs PWM signals;
when the level input by the first input port is high level, the switching circuit does not work, the second input port delays for a first time and then inputs a second high level, and the switching circuit receives the second high level and outputs a third high level to the output port;
when the level input by the first input port is turned to the low level, the switching circuit works and pulls down the voltage of the output port, the second input port inputs the second low level after being delayed for a second time, the switching circuit stops working, the reset circuit starts working, and the working is stopped before the first input port is turned to the high level again.
As a specific embodiment of the switching circuit, it includes: the first capacitor, the first diode, first resistance, the second resistance, first PNP triode, the one end of first capacitor links to each other with the second input port, the other end of first capacitor links to each other with the projecting pole of first PNP triode after linking to each other with the one end of first resistance, the other end of first resistance links to each other with output port, the one end of second resistance links to each other with first input port, the other end of second resistance links to each other with the negative pole of first diode, the positive pole of first diode links to each other with the base of first PNP triode, the collector ground of first PNP triode.
One specific embodiment of the reset circuit includes: and the cathode of the second diode is connected with the emitter of the first PNP triode, and the anode of the second diode is grounded.
Another specific embodiment of the switching circuit includes: the first capacitor, the first resistor and the first diode are connected, one end of the first capacitor is connected with the second input port, the other end of the first capacitor is connected with one end of the first resistor and then connected with the anode of the first diode, and the cathode of the first diode is connected with the first input port; the other end of the first resistor is connected with the output port.
Another specific embodiment as a reset circuit includes: and the cathode of the second diode is connected with the anode of the first diode, and the anode of the second diode is grounded.
The invention also provides a switching power supply comprising the short-circuit protection circuit, which comprises a PWM chip, an isolation driving chip and a power conversion circuit, wherein a first input port is connected with an output port of the PWM chip and an output port of the isolation driving chip, a second input port is connected with another output port of the secondary isolation driving chip, the output port is connected with a driving end of a main power switching tube in the power conversion circuit, the first time is the on delay time of the isolation driving chip, and the second time is the off delay time of the isolation driving chip.
Term interpretation:
isolation driving chip conduction delay time: the time between the isolation driving chip receiving the on signal and outputting the driving signal, for example, the time between the FAN7382 of the FAN company being high from the LIN pin to the LO being high;
isolation drive chip off delay time: the time between the isolation driving chip receiving the turn-off signal and the turn-off driving signal, for example, the time between the FAN7382 of the FAN company from the LIN pin being low to the LO being low;
the beneficial effects of the invention are as follows:
the short-circuit protection circuit can directly pull down the level of the output port, when the primary current peak reaches a protection set value in a high-voltage short-circuit state, the PWM chip outputs and turns off, and simultaneously, the level of the output port is immediately pulled down, after the PWM chip is used for switching a power supply, the output port is connected with the driving end of a main power switching tube in a power conversion circuit, the main power switching tube in the power conversion circuit is rapidly turned off, the turn-off delay of the main power switching tube is reduced to about 5ns, and the problem that the short-circuit current of the main power circuit is overlarge in the high-voltage short-circuit state caused by longer turn-off delay of an isolation driving chip is effectively solved.
Drawings
FIG. 1 is a schematic block diagram of a switching power supply incorporating the short circuit protection circuit of the present invention;
FIG. 2 is a circuit diagram of a first embodiment of a switching power supply incorporating the short-circuit protection circuit of the present invention;
fig. 3 is a circuit diagram of a second embodiment of a switching power supply incorporating the short-circuit protection circuit of the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings:
fig. 1 is a schematic block diagram of a switching power supply incorporating the short-circuit protection circuit of the present invention, the switching power supply comprising: the power conversion circuit comprises a short-circuit protection circuit, a PWM control chip, an isolation driving chip and a power conversion circuit; the short-circuit protection circuit includes: a first input port GATE, a second input port OUT, an output port G, a switching circuit, and a reset circuit; the first input port GATE is connected with the switch circuit, the second input port is connected with the switch circuit, the output port G is connected with the switch circuit, and the reset circuit is connected with the switch circuit; the first input port GATE is connected with the output port of the PWM chip, the first input port OUT is connected with the output port of the isolation driving chip, and the output port G is connected with the input port of the power conversion circuit.
The invention is characterized in that the short-circuit protection circuit is additionally arranged on the basis of the existing switching power supply, when the output of the PWM chip is high level, the short-circuit protection circuit does not work, the isolation driving chip outputs high level to the primary side MOS tube after normal conduction delay, when the output of the PWM chip is turned from high level to low level, the short-circuit protection circuit rapidly pulls down the grid voltage of the primary side MOS tube, and the primary side MOS tube is turned off.
In order that the invention may be more readily understood, a more particular description thereof will be rendered by reference to specific embodiments that are illustrated in the appended drawings. It should be noted that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
First embodiment
As shown in fig. 2, a circuit diagram of a switching power supply including a short-circuit protection circuit according to a first embodiment of the present invention is shown.
The switching circuit comprises a first capacitor C1, a first diode D1, a first resistor R1, a second resistor R2 and a first PNP triode Q1, wherein one end of the capacitor C1 is connected with a second input port, the other end of the capacitor C1 is connected with an emitter of the PNP triode Q1 after being connected with the resistor R1, the other end of the resistor R1 is connected with an output port, one end of the resistor R2 is connected with the first input port, the other end of the resistor R2 is connected with a cathode of the diode D1, an anode of the diode D1 is connected with a base electrode of the PNP triode Q1, and a collector of the PNP triode Q1 is grounded.
One specific embodiment of the reset circuit includes: and the cathode of the second diode D2 is connected with the emitter of the PNP triode Q1, and the anode of the diode D2 is grounded.
The power conversion circuit comprises an input voltage source VIN, a first winding Np, a first N-channel MOS tube TR1 and a second N-channel MOS tube TR2, wherein the drain electrode of the MOS tube TR1 is connected with the input voltage source VIN, the grid electrode of the MOS tube TR1 is connected with the isolation driving end of the isolation driving chip, the source electrode of the MOS tube TR1 is connected with one end of the first winding Np, the other end of the winding Np is connected with the drain electrode of the MOS tube TR2, the grid electrode of the MOS tube TR2 is connected with a port G, and the source electrode of the MOS tube TR2 is connected with a ground wire port GND.
Term interpretation:
isolation driving end of isolation driving chip: ports for implementing isolation driving of NMOS transistors with floating source voltages, such as port HO of FAN7382, for example, from fawn corporation;
the working principle of the circuit is as follows:
after the switching power supply is started, the PWM chip and the isolation driving chip start to work, after the port GATE outputs a high level, the port OUT outputs a high level after being conducted and delayed by the isolation driving chip, the port OUT charges the grid electrode of the MOS tube TR2 through the capacitor C1 and the resistor R1, the MOS tube TR1 is conducted, and the control port G changes to a high level.
When the output of the port GATE is changed from high level to low level, the connection point of the capacitor C1 and the resistor R1 is at high level, the emitter and the base of the PNP triode are positively conducted, the diode D1 is conducted, so that the PNP triode Q1 is saturated and conducted, the voltage of the control port G is rapidly pulled down, the MOS tube TR2 is turned off, meanwhile, the capacitor C1 starts to charge, the output of the port OUT is changed from high level to low level after the port OUT is turned off and delayed by the isolation driving circuit, the diode D2 is conducted, and the capacitor C1 is rapidly discharged by the isolation driving chip and the diode D2.
Second embodiment
Fig. 3 is a circuit diagram of a second embodiment of a switching power supply including a short-circuit protection circuit according to the present invention, which is mainly different in that the pull-down circuit is driven by a diode D1, instead of a resistor R2 and a transistor Q1, the anode of the diode D1 is connected to the cathode of the diode D2 and then to a connection point between the capacitor C1 and the resistor R1. The working principle and the first embodiment of the PWM control chip are basically identical, and the main difference is that when the GATE driving level is changed from high level to low level, the GATE pin output by the PWM control chip pulls down the GATE voltage of the MOS transistor TR2 through the diode D1, so that the GATE pin of the PWM control chip is required to have a stronger current filling capability, and all other working processes and the first embodiment are identical and are not repeated herein.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that the above-mentioned preferred embodiment should not be construed as limiting the invention, and that modifications and alterations can be made by those skilled in the art without departing from the spirit and scope of the invention, which is also regarded as the protection scope of the invention, which is defined by the claims without further description of the examples.
Claims (6)
1. The utility model provides a short-circuit protection circuit is applied to switching power supply, switching power supply includes PWM chip, isolation drive chip and power conversion circuit, its characterized in that: comprising the following steps: the switching circuit comprises a first input port, a second input port, an output port, a switching circuit and a reset circuit;
the switch circuit is provided with a first input port, a second input port and an output port, and the reset circuit is connected with the switch circuit;
the first input port inputs PWM signals;
when the level input by the first input port is high level, the switching circuit does not work, the second input port delays for a first time and then inputs a second high level, the switching circuit receives the second high level and outputs a third high level to the output port, and the signal input by the second input port is a signal output by the PWM signal through the isolation driving chip;
when the level input by the first input port is turned to the low level, the switching circuit works and pulls down the voltage of the output port, the second input port inputs the second low level after being delayed for a second time, the switching circuit stops working, the reset circuit starts working, and the working is stopped before the first input port is turned to the high level again.
2. The short-circuit protection circuit of claim 1, wherein: the switching circuit includes: the first capacitor, the first diode, first resistance, the second resistance, first PNP triode, the one end of first capacitor links to each other with the second input port, the other end of first capacitor links to each other with the projecting pole of first PNP triode after linking to each other with the one end of first resistance, the other end of first resistance links to each other with output port, the one end of second resistance links to each other with first input port, the other end of second resistance links to each other with the negative pole of first diode, the positive pole of first diode links to each other with the base of first PNP triode, the collector ground of first PNP triode.
3. The short-circuit protection circuit of claim 2, wherein: the reset circuit includes: and the cathode of the second diode is connected with the emitter of the first PNP triode, and the anode of the second diode is grounded.
4. The short-circuit protection circuit of claim 1, wherein: the switching circuit comprises a first capacitor, a first resistor and a first diode, one end of the first capacitor is connected with the second input port, the other end of the first capacitor is connected with one end of the first resistor and then connected with the anode of the first diode, and the cathode of the first diode is connected with the first input port; the other end of the first resistor is connected with the output port.
5. The short-circuit protection circuit of claim 4, wherein: the reset circuit comprises a second diode, wherein the cathode of the second diode is connected with the anode of the first diode, and the anode of the second diode is grounded.
6. A switching power supply comprising the short-circuit protection circuit of any one of claims 1 to 5, characterized in that: the power conversion circuit also comprises a PWM chip, an isolation driving chip and a power conversion circuit, wherein a first input port is connected with an output port of the PWM chip, a second input port is connected with an output port of the isolation driving chip, and the output port is connected with a driving end of a main power switching tube in the power conversion circuit.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810995074.1A CN109245052B (en) | 2018-08-29 | 2018-08-29 | Short-circuit protection circuit and switching power supply comprising same |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201810995074.1A CN109245052B (en) | 2018-08-29 | 2018-08-29 | Short-circuit protection circuit and switching power supply comprising same |
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| CN109245052B true CN109245052B (en) | 2024-04-12 |
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| CN110378155B (en) * | 2019-06-25 | 2021-06-29 | 苏州浪潮智能科技有限公司 | Server serial port forbidding protection circuit and method |
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| CN103579995A (en) * | 2012-08-01 | 2014-02-12 | 艾默生网络能源有限公司 | Direct-current input switching power source and undervoltage protection circuit thereof |
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| CN206099313U (en) * | 2016-08-12 | 2017-04-12 | 武汉港迪电气传动技术有限公司 | Converter switching power supply's short -circuit protection circuit |
| CN208753970U (en) * | 2018-08-29 | 2019-04-16 | 广州金升阳科技有限公司 | A kind of short-circuit protection circuit and the Switching Power Supply comprising the circuit |
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2018
- 2018-08-29 CN CN201810995074.1A patent/CN109245052B/en active Active
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4890020A (en) * | 1987-06-08 | 1989-12-26 | U.S. Philips Corporation | Circuit for driving a semiconductor device with protection against transients |
| CN102332705A (en) * | 2011-10-25 | 2012-01-25 | 杭州日鼎控制技术有限公司 | Short-circuit protection circuit of insulated gate bipolar translator (IGBT) of high-power frequency conversion device |
| CN103579995A (en) * | 2012-08-01 | 2014-02-12 | 艾默生网络能源有限公司 | Direct-current input switching power source and undervoltage protection circuit thereof |
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