CN212343313U - Overvoltage protection circuit of switching power supply and switching power supply - Google Patents
Overvoltage protection circuit of switching power supply and switching power supply Download PDFInfo
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- CN212343313U CN212343313U CN202021264159.1U CN202021264159U CN212343313U CN 212343313 U CN212343313 U CN 212343313U CN 202021264159 U CN202021264159 U CN 202021264159U CN 212343313 U CN212343313 U CN 212343313U
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Abstract
The application provides an overvoltage protection circuit of a switching power supply and the switching power supply. The second control switch is connected in series with at least one resistor and then connected in parallel with the first control switch. When the control signal generating circuit detects that the alternating current sampling voltage is higher than the alternating current reference voltage and the direct current sampling voltage is higher than the direct current reference voltage, the first control switch and the second control switch are controlled to be switched off, a charging loop of the direct current bus capacitor is cut off, and the direct current bus capacitor discharges to the load side, so that the voltage on the direct current bus is reduced. According to the scheme, all alternating current input channels can be cut off when the alternating current input voltage is detected to be too high, so that the alternating current input power supply cannot charge the direct current bus capacitor, the direct current bus capacitor and other semiconductor devices are prevented from being damaged, and the switching power supply can continue to normally work when the alternating current input voltage is recovered to a normal range.
Description
Technical Field
The utility model relates to a switching power supply technical field especially relates to a switching power supply's overvoltage crowbar and switching power supply.
Background
An AC-DC switching power supply is a power supply that converts input single-phase alternating current into direct current and supplies the direct current to a load.
The front stage of the high-power AC-DC switching power supply is provided with a relevant power factor correction circuit (PFC circuit) so as to reduce the pollution of input current harmonic waves to a power grid. The capacitor in the PFC circuit has a certain withstand voltage value, the direct current bus voltage of the PFC circuit generally cannot exceed the withstand voltage value of the capacitor, and if the direct current bus voltage exceeds the withstand voltage value, the direct current bus capacitor and other semiconductor devices are possibly damaged. Therefore, an overvoltage protection circuit is usually designed in the AC-DC switching power supply, and when the AC input voltage is greater than the set voltage, the overvoltage protection circuit is activated to disconnect the AC input from the switching power supply. However, the maximum ac input voltage cannot exceed a certain maximum value, such as 300V, and if the ac input voltage exceeds the set maximum value, the dc bus capacitor and other internal semiconductor devices are directly damaged, so that the entire switching power supply is damaged, and the switching power supply cannot normally operate even if the input voltage is restored to the normal range.
In many application scenarios, the ac input power of the switching power supply cannot be provided through a stable ac power grid, but is provided by a high-power generator, for example, a high-power agricultural unmanned aerial vehicle is generally applied in outdoor and non-fixed operation sites. Whereas a generator typically has 2 output voltage interfaces, 230V and 380V respectively, if the ac input of the switching power supply is connected to the 380V interface, exceeding the maximum value of the ac input of the switching power supply (e.g. 318V) will cause the entire switching power supply to be damaged. In addition, even if the ac input of the switching power supply is connected to the 230V interface of the generator, when the generator is started in an idle state, the output ac voltage of the generator may overshoot a relatively high value, and the overshoot amplitude is usually as high as 1.6 times of the normal output, that is, when the 230V interface is selected, the peak voltage of the starting-up of the generator will reach 360V and exceed the set maximum value, which may cause the whole switching power supply to be damaged.
However, the related art has not provided an overvoltage protection circuit capable of effectively dealing with the ac input too high.
SUMMERY OF THE UTILITY MODEL
In view of this, the utility model provides a switching power supply's overvoltage crowbar and switching power supply to solve the technical problem that the correlation technique can't carry out too high protection to too high AC input voltage, its technical scheme that discloses as follows:
in a first aspect of embodiments of the present application, there is provided an overvoltage protection circuit for a switching power supply, including: the device comprises an alternating voltage sampling circuit, a direct voltage sampling circuit, a control signal generating circuit, a first control switch and a second control switch;
the first control switch is connected in series between the alternating current input power supply and the rectifying circuit;
the second control switch is connected in parallel with the first control switch after being connected in series with at least one resistor;
the alternating voltage sampling circuit samples alternating voltage of an alternating input power supply to obtain alternating sampling voltage and transmits the alternating sampling voltage to the control signal generating circuit;
the direct-current voltage sampling circuit samples the voltage of the direct-current bus to obtain direct-current sampling voltage and transmits the direct-current sampling voltage to the control signal generating circuit;
the control signal generating circuit is used for outputting control signals to control the first control switch and the second control switch to be switched off respectively when the alternating current sampling voltage is determined to be higher than the alternating current reference voltage and the direct current sampling voltage is determined to be higher than the direct current reference voltage.
In a possible implementation manner of the first aspect, a first output end of the control signal generation circuit is connected to the first control switch, a second output end of the control signal generation circuit is connected to the second control switch, when the switching power supply is turned on, a signal of the second output end is used to control the second control switch to be turned on, and a signal of the first output end is used to keep the first control switch turned off.
In another possible implementation manner of the first aspect, the control signal generating circuit is configured to output an electrical signal for controlling the first control switch tube to be closed by a first output terminal of the control signal generating circuit when the dc sampling voltage is greater than a preset voltage and less than the dc reference voltage.
In yet another possible implementation manner of the first aspect, the first control switch is controlled to be closed when the first output end of the control signal generation circuit is a high-level signal, and the second control switch is controlled to be closed when the second output end of the control signal generation circuit is a low-level signal.
In another possible implementation manner of the first aspect, the first control switch is a normally open relay; the second control switch is a normally closed relay;
when the first output end of the control signal generating circuit is a high level signal, the normally open relay is closed, and when the first output end of the control signal generating circuit is a low level signal, the normally open relay is opened;
when the second output end of the control signal generating circuit is a low level signal, the normally closed relay keeps a closed state, and when the second output end of the control signal generating circuit is a high level signal, the normally closed relay is disconnected.
In yet another possible implementation manner of the first aspect, the control signal generation circuit includes: the circuit comprises a first comparator, a second comparator and a signal conversion circuit;
the non-inverting input end of the first comparator inputs the alternating current reference voltage, the inverting input end of the first comparator is connected with the output end of the alternating current voltage sampling circuit, and the output end of the first comparator is connected with the first input end of the signal conversion circuit;
the non-inverting input end of the second comparator is connected with the output end of the direct-current voltage sampling circuit, and the output end of the second comparator is connected with the second input end of the signal conversion circuit;
and a first output end of the signal conversion circuit is connected with the control end of the first control switch, and a second output end of the signal conversion circuit is connected with the control end of the second control switch.
In another possible implementation manner of the first aspect, the control signal generating circuit is an MCU chip.
In yet another possible implementation manner of the first aspect, the alternating voltage sampling circuit includes: the first rectifying branch, the second rectifying branch and the series resistance branch formed by connecting at least two divider resistors in series;
the input end of the first rectifying branch circuit is connected with a first alternating current end of the alternating current input power supply, the output end of the first rectifying branch circuit is connected with one end of the series resistance branch circuit, and the other end of the series resistance branch circuit is connected with the grounding end;
the input end of the second rectifying branch is connected with the second alternating current end of the alternating current input power supply, and the output end of the second rectifying branch is connected with one end of the series resistance branch which is connected with the first rectifying branch;
and the connecting end between any two adjacent resistors in the series resistor branch is the sampling voltage output end of the alternating voltage sampling circuit.
In yet another possible implementation manner of the first aspect, the dc voltage sampling circuit includes: and the at least two divider resistors are connected in series between the direct current bus and a grounding end, wherein a connecting end between any two adjacent resistors is a sampling voltage output end of the direct current voltage sampling circuit.
In a second aspect of the embodiments of the present application, there is provided a switching power supply, including a front-stage circuit, a rear-stage circuit, and an overvoltage protection circuit according to any one of the possible implementation manners of the first aspect;
the overvoltage protection circuit is connected in series with an input line of a rectification circuit in the preceding stage circuit.
The overvoltage protection circuit of the switching power supply comprises a first control switch, a second control switch, an alternating-current voltage sampling circuit, a direct-current voltage sampling circuit and a control signal generating circuit, wherein the first control switch is connected between an alternating-current input power supply and a rectifying circuit in series. The second control switch is connected in series with at least one resistor and then connected in parallel with the first control switch. The alternating current voltage sampling circuit samples alternating current input voltage of the switch power supply to obtain alternating current sampling voltage, and the direct current voltage sampling circuit samples voltage of a direct current bus of the switch power supply to obtain direct current sampling voltage. The control signal generating circuit compares the alternating current sampling voltage with the alternating current reference voltage, compares the direct current sampling voltage with the direct current reference voltage, generates control signals for respectively controlling the first control switch and the second control switch to be disconnected if the alternating current sampling voltage is higher than the alternating current reference voltage and the direct current sampling voltage is higher than the direct current reference voltage, cuts off a charging loop of the direct current bus capacitor, and simultaneously discharges the direct current bus capacitor to a load side, so that the voltage on the direct current bus is reduced. According to the scheme, all alternating current input channels can be cut off when the alternating current input voltage is detected to be too high, so that the alternating current input power supply cannot charge the direct current bus capacitor, the direct current bus capacitor and other semiconductor devices are prevented from being damaged, and the switching power supply can continue to normally work when the alternating current input voltage is recovered to a normal range.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an overvoltage protection circuit of a switching power supply according to an embodiment of the present disclosure;
fig. 2 is a schematic circuit diagram of an overvoltage protection circuit of another switching power supply according to an embodiment of the present application;
FIG. 3 is a waveform diagram of a power-on key point voltage of the switching power supply;
FIG. 4 is a circuit diagram of a control signal generating circuit according to an embodiment of the present disclosure;
fig. 5 is a schematic circuit diagram of an ac voltage sampling circuit according to an embodiment of the present application;
fig. 6 is a circuit schematic diagram of a dc voltage sampling circuit according to an embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.
Referring to fig. 1, a schematic structural diagram of an overvoltage protection circuit of a switching power supply according to an embodiment of the present disclosure is shown, where the overvoltage protection circuit is applied to a high-power switching power supply, such as a high-power supply with a power of more than 500W.
As shown in fig. 1, the overvoltage protection circuit of the switching power supply includes: the circuit comprises a first control switch K1, a second control switch K2, an alternating voltage sampling circuit 1, a direct voltage sampling circuit 2 and a control signal generating circuit 3.
The first control switch K1 is connected in series between the ac input power 101 and the rectifier circuit 102 in the switching power supply. The second control switch K2 is connected in series with at least one starting resistor R0 and then connected in parallel with the first control switch K1.
The input end of the alternating voltage sampling circuit 1 is connected with the alternating input power supply 101 and is used for collecting the alternating voltage of the alternating input power supply 101 to obtain the alternating sampling voltage. The output end of the alternating voltage sampling circuit 1 is connected with one input end of the control signal generating circuit 3, and the alternating voltage sampling circuit transmits the alternating voltage sampling to the control signal generating circuit 3.
The input end of the direct current voltage sampling circuit 2 is connected with a direct current bus VBUS and used for collecting the voltage of the VBUS to obtain direct current sampling voltage. The output end of the direct current voltage sampling circuit 2 is connected with the other input end of the control signal generating circuit 3, and the direct current sampling voltage is transmitted to the control signal generating circuit 3.
The first output terminal of the control signal generating circuit 3 is connected to the control terminal of the first control switch K1, and the second output terminal is connected to the control terminal of the second control switch K2.
Wherein the initial state of the first control switch K1 is an open state, and the initial state of the second control switch K2 is a closed state.
When the switching power supply is turned on, the first control switch K1 is kept in an open state, and the second control switch K2 is kept in a closed state. At this time, the branch where the ac input power 101 passes through the second control switch K2 charges the dc bus capacitor C1, and the dc bus voltage gradually increases.
When the voltage of the direct current bus rises to a low voltage set value (for example, 120V), the internal circuit of the switching power supply is started, and the alternating current voltage sampling circuit 1, the direct current voltage sampling circuit 2 and the control signal generating circuit 3 start to work. After that, the control signal generating circuit 3 controls the first control switch K1 to be closed, at this time, the branch of the second control switch K2 connected in series with R0 is shorted by the first control switch K1, and the ac input power 101 charges the dc bus capacitor C1 only through the branch where the first control switch K1 is located.
When the ac voltage of the ac input power 101 is greater than a predetermined ac voltage, for example, 318V, the rectified ac voltage rises to a predetermined dc voltage, for example, 450V, and the rectified ac voltage exceeds the withstand voltage of the dc bus capacitor C1, which may cause damage to the dc bus capacitor C1 and other semiconductor devices.
The control signal generating circuit 3 determines whether the ac input voltage exceeds the ac voltage setting value, for example, 318V, by comparing the ac sampled voltage with the ac reference voltage, and determines whether the dc bus voltage exceeds the dc voltage setting value, for example, 450V, by comparing the dc sampled voltage with the dc reference voltage.
The ac reference voltage is an ac sampling voltage value sampled by the ac sampling circuit 1 when the ac input voltage is the ac voltage set value. Similarly, the dc reference voltage is a dc sampling voltage value obtained by sampling the dc bus by the dc sampling circuit 2 when the dc input voltage is the set dc voltage value.
When the control signal generating circuit 3 detects that the ac sampling voltage is higher than the ac reference voltage (i.e., the sampling value corresponding to the ac voltage setting value) and the dc sampling voltage is higher than the dc reference voltage (i.e., the sampling value corresponding to the dc voltage setting value), the first control switch K1 and the second control switch K2 are controlled to be turned off, at this time, all the ac input channels are cut off, the ac input power supply cannot charge the dc bus capacitor C1, and the C1 discharges naturally, so that the dc bus voltage is lowered.
In an application scenario, K1 is currently in an open state, and K2 is currently in a closed state, at this time, if the control signal generation circuit 3 detects that the ac sampling voltage is higher than the ac reference voltage and the dc sampling voltage is higher than the dc sampling voltage, then K1 is kept in the open state, and K2 is controlled to be open.
In another application scenario, both K1 and K2 are currently in a closed state, and at this time, if the control signal generating circuit 3 detects that the ac sampling voltage is higher than the ac reference voltage and the dc sampling voltage is higher than the dc sampling voltage, K1 and K2 are turned off.
In the overvoltage protection circuit of the switching power supply provided by this embodiment, the first control switch is connected in series between the ac input power supply and the rectification circuit. The second control switch is connected in series with at least one resistor and then connected in parallel with the first control switch. The alternating current voltage sampling circuit samples alternating current input voltage of the switching power supply, and the direct current voltage sampling circuit samples voltage of a direct current bus of the switching power supply. The control signal generating circuit compares the alternating current sampling voltage with the alternating current reference voltage, compares the direct current sampling voltage with the direct current reference voltage, and controls the first control switch and the second control switch to be switched off if the alternating current sampling voltage is higher than the alternating current reference voltage and the direct current sampling voltage is higher than the direct current reference voltage. Therefore, all the alternating current input channels are cut off, the alternating current input power supply cannot charge the direct current bus capacitor, and meanwhile, the direct current bus capacitor discharges to the load side, so that the voltage on the direct current bus is reduced, the direct current bus capacitor and other semiconductor devices are prevented from being damaged, and the switching power supply can continue to work normally when the alternating current input voltage is restored to a normal range.
Fig. 2 is a schematic circuit diagram of an overvoltage protection circuit of another switching power supply according to an embodiment of the present application. In this embodiment, the first control switch and the second control switch both use relays.
As shown in fig. 2, the contact of RY1 is connected in series between the live end of the ac input power source 101 and the first ac input terminal of the rectifier circuit 102. The coil of RY1 is connected to the first power supply control circuit 103, the positive electrode of the first power supply control circuit 103 is connected to the positive electrode PVCC of the auxiliary power supply, and the negative electrode of the first power supply control circuit 103 is grounded PGND.
The first power supply control circuit 103 includes a switch Q1 connected in series between the positive electrode PVCC and the negative electrode PGND, and a control terminal of the switch Q1 is connected to the first output terminal of the control signal generating circuit. In addition, the first power supply control circuit 103 includes other devices, which are not described in detail herein.
In one embodiment of the present application, the first control switch employs a normally open relay RY1, the contact of which defaults to an open state. When the control signal RLY1_ ONOFF output by the control signal generating circuit is low level, Q1 is turned off, the first power supply control circuit 103 is turned off, the coil of RY1 is not energized, and the contact maintains the off state; when RLY1_ ONOFF is high level, Q1 is closed, and first power supply control circuit 103 supplies power to the coil of RY1, and the contact pulls in.
The contact of RY2 is connected in series with starting resistor R0, and then connected in parallel with the contact of RY 1. The coil of RY2 is connected to the second power supply control circuit 104, the positive pole of the power supply control circuit is connected to the positive pole PVCC of the auxiliary power supply, the negative pole of the power supply control circuit is connected to PGND, and the power supply control circuit includes a switch tube Q2 connected in series between PVCC and PGND, and the control end of Q2 is connected to the second output end of the control signal generating circuit. In addition, the power supply control circuit also comprises other devices which are not described in detail here.
In one embodiment of the present application, the second control switch employs a normally closed relay RY2, the contact defaults to a closed state. When the control signal RLY2_ ONOFF output by the control signal generating circuit is low level, Q2 is opened, the second power supply control circuit 104 is opened, the coil of RY2 is not energized, and the contact keeps a closed state; when RLY2_ ONOFF is high, Q2 is closed, second power supply control circuit 104 supplies power to the coil of RY2, and the contact is opened.
The different modes of operation of the overvoltage protection circuit will be described below with reference to fig. 2 and 3:
fig. 3 is a schematic waveform diagram of a voltage at a key point of startup of the switching power supply, where VBUS is a schematic waveform diagram of a dc bus voltage, Vac is a schematic waveform diagram of an ac input voltage, and Pvcc is a schematic waveform diagram of an auxiliary power supply voltage inside the switching power supply.
The auxiliary power supply inside the switching power supply takes power from the dc bus and converts the power into a dc voltage required for normal operation of other circuits inside the power supply.
(1) AC input normal of switching power supply
As shown in fig. 3, at time T0, the switching power supply is turned on, RY1 is in an open state, and RY2 is in a closed state. The ac input voltage Vac charges the dc bus capacitor C1 through RY2 and the starting resistor R0, and the voltage of C1 gradually increases, i.e., the dc bus voltage VBUS gradually increases.
At time T1, when the dc bus voltage VBUS rises to the low voltage set point (e.g., 120V), the auxiliary power supply inside the power supply is turned on, generating auxiliary power supply voltages PVCC and +5V _ P. The +5V _ P is a dc voltage of 5V, PVCC may be a dc voltage of other values, such as +12V, +24V, and the internal auxiliary power supply may be designed according to the actual requirement of the internal circuit of the switching power supply.
In one embodiment of the present application, the control signal generating circuit is an MCU chip. When the PVCC is established, the control signal generating circuit can work normally.
Under the condition that the alternating current input power supply of the switching power supply is normal, the control signal generating circuit detects that both Vac and VBUS are in a normal range. Specifically, when VBUS rises to 320V, the control signal generation circuit output RLY1_ ONOFF is high, RY1 is closed, RLY2_ ONOFF does not give the control signal, that is, RY2 is in a closed state.
After RY1 is closed, because the on-resistance of RY1 is far less than the resistance of the branch where RY2 is located, the branch where RY2 and R0 are connected in series is shorted by RY1, the AC input power supply charges C1 through closed RY1, and the switching power supply works normally.
(2) Direct abnormal over-high of AC input power
After the AC input power is turned on and PVCC is generated, the control signal generating circuit detects Vac and VBUS, and if directly detects that Vac is larger than the AC voltage set value 318V and VBUS is larger than the DC voltage set value 450V, the AC input voltage is determined to be abnormally too high. At this time, RY1 is still in the off state, so the control signal generating circuit only needs to output RLY2_ ONOFF at high level to turn off RY2, and at this time, all the ac input channels (i.e., the branch where RY1 is located and the branch where RY2 is located) are cut off, so that the ac input power source cannot charge dc bus capacitor C1, and at the same time, C1 discharges to the load, and VBUS gradually decreases.
When VBUS is reduced to the low voltage set value of 120V, the auxiliary power supply in the switching power supply stops working, PVCC and +5V _ P disappear, the first output end and the second output end of the control signal generation circuit naturally become low level, namely RLY1_ ONOFF and RLY2_ ONOFF are both low level, RY2 becomes closed state, the alternating current input power supply charges C1 through the branch where RY2 is located, and then the process of detecting Vac and VBUS is repeated.
If Vac is always greater than the AC voltage set point 318V, the above-mentioned C1 charging and discharging process is performed cyclically, and the cycle time is related to the C1 discharging time constant. If Vac returns to normal, the process of switching power supply AC input is normal.
(3) The AC input power is normal when starting up, but is abnormally high in the working process
After the ac input power is turned on and PVCC is generated, the control signal generation circuit detects Vac and VBUS. When the power is turned on, the alternating current input power supply is normal, at the moment, Vac and VBUS detected by the control signal generating circuit are both in a normal range, RLY1_ ONOFF high level is output, RY1 is closed, RY1 is in short circuit with RY2 and a starting resistor R0, the alternating current input power supply charges C1 through RY1, and the power supply works normally.
When the alternating current input voltage is suddenly overhigh in the working process of the power supply, at the moment, the control signal generation circuit detects that Vac is larger than the alternating current voltage set value 318V and VBUS is larger than the direct current voltage set value 450V, the fact that the alternating current input voltage is abnormally overhigh is determined, the output RLY1_ ONOFF is in a low level, RY1 is disconnected, the output RLY2_ ONOFF is in a high level, RY2 is disconnected, at the moment, all alternating current input channels are cut off, and the alternating current input voltage cannot charge C1. Meanwhile, the C1 discharges naturally, when the VBUS voltage discharges to the low voltage set value of 120V, the auxiliary power supply stops working, PVCC and +5V _ P disappear, at this time, RLY1_ ONOFF and RLY2_ ONOFF naturally become low level, RY2 closes, and the detection process of Vac and VBUS is repeated again.
If Vac is always greater than the AC voltage set point 318V, the above-mentioned C1 charging and discharging process is performed cyclically, and the cycle time is related to the C1 discharging time constant. If Vac returns to normal, the process of switching power supply AC input is normal.
In the overvoltage protection circuit of the switching power supply provided by this embodiment, the control switches, that is, the first control switch and the second control switch, are arranged on the two ac input channels of the switching power supply. No matter the alternating current input is directly abnormally too high or the alternating current input is suddenly changed into abnormally too high in the normal working process, the overvoltage protection circuit can cut off all the alternating current input channels, so that the alternating current input power supply cannot charge the direct current bus capacitor, and meanwhile, the direct current bus capacitor discharges to the load side, so that the voltage on the direct current bus is reduced. Therefore, the direct current bus capacitor and other semiconductor devices are prevented from being damaged, and the switching power supply can continue to work normally when the alternating current input voltage is recovered to a normal range.
Referring to fig. 4, a circuit diagram of a control signal generating circuit according to an embodiment of the present disclosure is shown, and as shown in fig. 4, the control signal generating circuit includes: a first comparator U1, a second comparator U2 and a signal conversion circuit U3.
An AC reference voltage VREF1 is input to a non-inverting input end of the first comparator U1, an AC sampling voltage VAC _ SNS is input to an inverting input end of the first comparator U1, and an output end of the first comparator U1 is connected with a first input end of the signal conversion circuit U3.
The non-inverting input terminal of the second comparator U2 inputs the dc reference voltage VREF2, the inverting input terminal thereof inputs the dc sampling voltage VBULK _ SENSE, and the output terminal of U2 is connected to the second input terminal of the signal conversion circuit U3.
A first output terminal of the signal conversion circuit U3 outputs a control signal RLY1_ ONOFF for controlling the first control switch, and a second output terminal outputs a control signal RLY2_ ONOFF for controlling the second control switch.
When VAC _ SNS is greater than VREF1, U1 outputs a low level, and when VBULK _ SENSE is greater than VREF2, U2 outputs a low level, at which time two control signals RLY1_ ONOFF output by U3 are low and RLY2_ ONOFF are high; if RLY1_ ONOFF was low at the last time, RLY1_ ONOFF remains low; if RLY1_ ONOFF was high at the last time, RLY1_ ONOFF switches to low.
In other embodiments of the present application, the control signal generating circuit may also be implemented by an MCU chip, and the control logic of the MCU is the same as the working principle of the circuit shown in fig. 4, which is not described herein again.
Referring to fig. 5, a schematic circuit diagram of an ac voltage sampling circuit according to an embodiment of the present application is shown, and as shown in fig. 5, the ac voltage sampling circuit includes: the first rectifying branch, the second rectifying branch and the series resistance branch formed by connecting at least two divider resistors in series.
The input end of the first rectifying branch circuit is connected with the L end of the alternating current input power supply, the input end of the second rectifying branch circuit is connected with the N end of the alternating current input power supply, the output ends of the two rectifying branch circuits are connected in series with the series resistance branch circuit after being connected, and the other end of the series resistance branch circuit is connected with the PGND.
And the connecting end between any two resistors in the series resistor branch is a sampling voltage output end VAC _ SNS of the alternating voltage sampling circuit.
In one embodiment of the present application, the first rectifying branch and the second rectifying branch each comprise at least two unidirectional conducting devices, such as diodes, connected in series and/or in parallel. In this embodiment, the two rectifying branches each include a diode series branch formed by two diodes connected in series, an anode of the diode series branch is an input end of the rectifying branch, and a cathode of the diode series branch is an output end of the rectifying branch.
In this embodiment, the resistor series branch includes R1 to R4 connected in series in sequence, where R1 is the head end of the resistor series branch, R4 is the tail end, and the common end of R3 and R4 is VAC _ SNS. R5 and C2 are RC parallel filter circuits connected in parallel at two ends of R4.
And the voltage of the VAC _ SNS, namely the voltage drop obtained by dividing the alternating current input voltage by R1-R4 after rectification, and R4.
Referring to fig. 6, a schematic circuit diagram of a dc voltage sampling circuit provided in an embodiment of the present application is shown, and as shown in fig. 6, the dc voltage sampling circuit includes a resistor series branch formed by at least two voltage dividing resistors sequentially connected in series, where one end of the resistor series branch is connected to a VBUS end of a dc bus, and the other end of the resistor series branch is connected to a PGND. The common end of any two resistors in the resistor series branch is a sampling voltage output end VBULK _ SENSE.
In this embodiment, the resistor series branch includes R6-R9 connected in series in sequence, where VBULK _ SENSE is the common end of R9 and R8. After the voltage of VBULK _ SENSE, namely the voltage of the direct current bus VBUS is divided by R6-R9, the voltage is reduced by R9.
In addition, two ends of the R9 are connected in parallel with an RC parallel filter circuit formed by connecting R10 and C3 in parallel so as to filter clutter signals in the direct current sampling voltage signal.
On the other hand, the application also provides a switching power supply using the overvoltage protection circuit, and the working process of other circuits in the switching power supply is the same as that of the conventional switching power supply, and is not repeated here.
The embodiments of the present invention are described in a progressive manner, each embodiment is mainly described as different from other embodiments, and the same similar parts between the embodiments are referred to each other.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. An overvoltage protection circuit for a switching power supply, comprising: the device comprises an alternating voltage sampling circuit, a direct voltage sampling circuit, a control signal generating circuit, a first control switch and a second control switch;
the first control switch is connected in series between the alternating current input power supply and the rectifying circuit;
the second control switch is connected in parallel with the first control switch after being connected in series with at least one resistor;
the alternating voltage sampling circuit samples alternating voltage of an alternating input power supply to obtain alternating sampling voltage and transmits the alternating sampling voltage to the control signal generating circuit;
the direct-current voltage sampling circuit samples the voltage of the direct-current bus to obtain direct-current sampling voltage and transmits the direct-current sampling voltage to the control signal generating circuit;
the control signal generating circuit is used for outputting control signals to control the first control switch and the second control switch to be switched off respectively when the alternating current sampling voltage is determined to be higher than the alternating current reference voltage and the direct current sampling voltage is determined to be higher than the direct current reference voltage.
2. The over-voltage protection circuit of the switching power supply according to claim 1, wherein a first output terminal of the control signal generating circuit is connected to the first control switch, a second output terminal of the control signal generating circuit is connected to the second control switch, when the switching power supply is turned on, a signal of the second output terminal is used to control the second control switch to be turned on, and a signal of the first output terminal is used to keep the first control switch off.
3. The overvoltage protection circuit of the switching power supply according to claim 2, wherein the control signal generating circuit is configured to output an electrical signal for controlling the first control switch tube to close when the dc sampling voltage is greater than a preset voltage and less than the dc reference voltage.
4. The over-voltage protection circuit of the switching power supply according to claim 2 or 3, wherein the first control switch is controlled to be closed when the first output terminal of the control signal generating circuit is a high-level signal, and the second control switch is controlled to be closed when the second output terminal of the control signal generating circuit is a low-level signal.
5. The overvoltage protection circuit of the switching power supply according to claim 4, wherein the first control switch is a normally open relay; the second control switch is a normally closed relay;
when the first output end of the control signal generating circuit is a high level signal, the normally open relay is closed, and when the first output end of the control signal generating circuit is a low level signal, the normally open relay is opened;
when the second output end of the control signal generating circuit is a low level signal, the normally closed relay keeps a closed state, and when the second output end of the control signal generating circuit is a high level signal, the normally closed relay is disconnected.
6. The overvoltage protection circuit of the switching power supply according to any one of claims 1 to 3, wherein the control signal generating circuit comprises: the circuit comprises a first comparator, a second comparator and a signal conversion circuit;
the non-inverting input end of the first comparator inputs the alternating current reference voltage, the inverting input end of the first comparator is connected with the output end of the alternating current voltage sampling circuit, and the output end of the first comparator is connected with the first input end of the signal conversion circuit;
the non-inverting input end of the second comparator is connected with the output end of the direct-current voltage sampling circuit, and the output end of the second comparator is connected with the second input end of the signal conversion circuit;
and a first output end of the signal conversion circuit is connected with the control end of the first control switch, and a second output end of the signal conversion circuit is connected with the control end of the second control switch.
7. The overvoltage protection circuit of the switching power supply according to any one of claims 1 to 3, wherein the control signal generating circuit is an MCU chip.
8. The overvoltage protection circuit of the switching power supply according to any one of claims 1 to 3, wherein the alternating voltage sampling circuit comprises: the first rectifying branch, the second rectifying branch and the series resistance branch formed by connecting at least two divider resistors in series;
the input end of the first rectifying branch circuit is connected with a first alternating current end of the alternating current input power supply, the output end of the first rectifying branch circuit is connected with one end of the series resistance branch circuit, and the other end of the series resistance branch circuit is connected with the grounding end;
the input end of the second rectifying branch is connected with the second alternating current end of the alternating current input power supply, and the output end of the second rectifying branch is connected with one end of the series resistance branch which is connected with the first rectifying branch;
and the connecting end between any two adjacent resistors in the series resistor branch is the sampling voltage output end of the alternating voltage sampling circuit.
9. The overvoltage protection circuit of the switching power supply according to any one of claims 1 to 3, wherein the DC voltage sampling circuit comprises: and the at least two divider resistors are connected in series between the direct current bus and a grounding end, wherein a connecting end between any two adjacent resistors is a sampling voltage output end of the direct current voltage sampling circuit.
10. A switching power supply comprising a front stage circuit, a rear stage circuit, and the overvoltage protection circuit of any one of claims 1 to 9;
the overvoltage protection circuit is connected in series with an input line of a rectification circuit in the preceding stage circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN202021264159.1U CN212343313U (en) | 2020-06-30 | 2020-06-30 | Overvoltage protection circuit of switching power supply and switching power supply |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202021264159.1U CN212343313U (en) | 2020-06-30 | 2020-06-30 | Overvoltage protection circuit of switching power supply and switching power supply |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113131445A (en) * | 2021-03-31 | 2021-07-16 | 联想(北京)有限公司 | Power supply protection device and control method thereof |
| CN113473579A (en) * | 2021-04-27 | 2021-10-01 | 北京安诺信科技股份有限公司 | Intelligent control power-saving terminal of 5G base station based on Internet of things technology and embedded application technology |
-
2020
- 2020-06-30 CN CN202021264159.1U patent/CN212343313U/en active Active
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113131445A (en) * | 2021-03-31 | 2021-07-16 | 联想(北京)有限公司 | Power supply protection device and control method thereof |
| CN113131445B (en) * | 2021-03-31 | 2023-03-21 | 联想(北京)有限公司 | Power supply protection device and control method thereof |
| CN113473579A (en) * | 2021-04-27 | 2021-10-01 | 北京安诺信科技股份有限公司 | Intelligent control power-saving terminal of 5G base station based on Internet of things technology and embedded application technology |
| CN113473579B (en) * | 2021-04-27 | 2024-04-12 | 无锡专心智制科技有限公司 | Intelligent control electricity-saving terminal of 5G base station based on Internet of things technology and embedded application technology |
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