CN215300494U - Step-down DCDC converter and under-voltage protection circuit thereof - Google Patents
Step-down DCDC converter and under-voltage protection circuit thereof Download PDFInfo
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- CN215300494U CN215300494U CN202121088447.0U CN202121088447U CN215300494U CN 215300494 U CN215300494 U CN 215300494U CN 202121088447 U CN202121088447 U CN 202121088447U CN 215300494 U CN215300494 U CN 215300494U
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Abstract
The utility model provides a step-down DCDC converter and undervoltage protection circuit thereof, the input end of the voltage detection unit in the circuit is connected with the power supply end of the step-down DCDC converter, receives the input voltage, the output end of the voltage detection unit is connected with the first input end of the charge-discharge control unit, and outputs the detection voltage; the second input end of the charge and discharge control unit is connected with the output end of the buck DCDC converter and receives the output voltage; the output end of the charge and discharge control unit is connected with a slow start capacitor in the voltage reduction type DCDC converter to output charge and discharge control voltage; also the utility model discloses can real-time detection step-down type DCDC converter's input voltage to can frequently fall the electricity and arouse input voltage when undulant with last electricity, in time output charge-discharge control voltage control slowly starts the capacitance charge-discharge, and then control step-down type DCDC converter action, fall, go up the electricity in-process stop output voltage, avoid the damage of back level power consumption module.
Description
Technical Field
The utility model relates to a converting circuit field, concretely relates to step-down DCDC converter and undervoltage protection circuit thereof.
Background
Currently, the existing BUCK-type DCDC converter generally uses BUCK topology to realize constant voltage output. By collecting the output voltage and adding the compensation circuit, the closed-loop control is carried out on the output voltage so as to achieve the effect of stabilizing the output voltage. When the output voltage is greater than the set voltage, the driving duty ratio of a power tube in the buck DCDC converter is reduced; and when the output voltage is lower than the set voltage, increasing the driving duty ratio of the power tube.
Due to the fact that the driving duty ratio of the power tube is dynamically adjusted, the output voltage of the buck-type DCDC converter can be stabilized, and the buck-type DCDC converter can be applied to a scene that different input voltages can be output at the same voltage. However, the buck-type DCDC converter has a certain upper limit requirement on the driving duty ratio of the on-power tube, and generally requires the driving duty ratio not greater than 100%, and if the input voltage of the buck-type DCDC converter is reduced to be less than or equal to the preset minimum input voltage, the output voltage of the buck-type DCDC converter is also reduced along with the reduction of the input voltage due to the characteristics of the buck-type DCDC converter.
In practical application, a control loop of the buck-type DCDC converter needs to adjust the driving duty ratio of the power tube in real time according to the output voltage. Due to the fact that the dynamic adjustment speed of the feedback network is delayed, if frequent power failure and power up occur, the situation that the output voltage follows the input voltage and the output voltage is too large can occur at the moment of power up again, and therefore the rear-stage power utilization module is damaged.
SUMMERY OF THE UTILITY MODEL
Based on the not enough of above-mentioned prior art, the utility model provides a step-down type DCDC converter and undervoltage protection circuit thereof to there is the delay in solving current step-down type DCDC converter because of feedback network adjustment output, the easy output voltage that appears in the twinkling of an eye of frequent falling, going up electricity follows input voltage, leads to the too big problem that arouses the damage of back level power consumption module of output voltage.
In order to achieve the above object, the embodiment of the present invention provides the following technical solutions:
the utility model discloses a first aspect discloses an undervoltage protection circuit of step-down DCDC converter, include: a voltage detection unit and a charge-discharge control unit; wherein:
the input end of the voltage detection unit is connected with the power supply end of the buck DCDC converter and used for receiving the input voltage of the buck DCDC converter, and the output end of the voltage detection unit is connected with the first input end of the charge and discharge control unit and used for outputting detection voltage;
a second input end of the charge and discharge control unit is connected with an output end of the buck DCDC converter and receives the output voltage of the buck DCDC converter;
and the output end of the charge and discharge control unit is connected with a slow start capacitor in the voltage reduction type DCDC converter to output charge and discharge control voltage.
Optionally, in the undervoltage protection circuit of the step-down DCDC converter, the voltage detection unit includes: a voltage regulator diode; wherein:
the cathode of the voltage stabilizing diode is used as the input end of the voltage detection unit, and the anode of the voltage stabilizing diode is used as the output end of the voltage detection unit.
Optionally, in the undervoltage protection circuit of the step-down DCDC converter, the voltage detection unit includes: a reference source; wherein:
the input end of the reference source is used as the input end of the voltage detection unit, and the output end of the reference source is used as the output end of the voltage detection unit.
Optionally, in the undervoltage protection circuit of the step-down DCDC converter, the charge and discharge control unit includes: the circuit comprises a first switch tube, a second switch tube, a first resistor, a second resistor, a third resistor and a fourth resistor; wherein:
one end of the first resistor is used as a first input end of the charge and discharge control unit, and the other end of the first resistor is respectively connected with one end of the second resistor and the control end of the first switching tube;
the first end of the first switch tube is respectively connected with the control end of the second switch tube, one end of the third resistor and one end of the fourth resistor;
the other end of the third resistor is used as a second input end of the charge and discharge control unit;
the first end of the second switch tube is used as the output end of the charge and discharge control unit;
the other end of the second resistor, the second end of the first switch tube, the other end of the fourth resistor and the second end of the second switch tube are all grounded.
Optionally, in the undervoltage protection circuit of the buck DCDC converter, the voltage control circuit further includes: a filter circuit; the first end of the filter circuit is connected with the common end of the first resistor and the second resistor, and the second end of the filter circuit is grounded.
Optionally, in the undervoltage protection circuit of the buck DCDC converter, the filter circuit includes: a filter capacitor;
one end of the filter capacitor is used as a first end of the filter circuit, and the other end of the filter capacitor is used as a second end of the filter circuit.
The utility model discloses second aspect discloses a step-down DCDC converter, include: the undervoltage protection circuit comprises a DCDC control module, a DCDC driving module, and an undervoltage protection circuit of the step-down DCDC converter, wherein the undervoltage protection circuit is connected with the DCDC control module and the DCDC driving module respectively and is disclosed by any one of the first aspect;
the input end of the DCDC driving module is connected with an input power supply and receives input voltage;
the sampling end of the DCDC control module is connected with the output end of the DCDC driving module and receives output voltage;
and the control end of the DCDC drive module is connected with the output end of the DCDC control module and receives drive control voltage.
Optionally, in the step-down DCDC converter, the DCDC driving module includes: the power tube, the follow current tube, the inductor and the capacitor; wherein:
the first end of the power tube is used as the input end of the DCDC driving module, and the second end of the power tube is respectively connected with the first end of the follow current tube and one end of the inductor;
the second end of the follow current tube is connected with one end of the capacitor and is grounded;
the other end of the capacitor is connected with the other end of the inductor, and a connection point is used as an output end of the DCDC driving module;
and the control end of the power tube and the control end of the follow current tube are used as the control ends of the DCDC driving module.
Optionally, in the step-down DCDC converter, the DCDC control module includes: the device comprises a DCDC control chip, a slow start capacitor and an output sampling circuit; wherein:
a synchronous control pin of the DCDC control chip is connected with a first end of the slow starting capacitor, a connection point is used as an input end of the DCDC control module, and the other end of the slow starting capacitor is grounded;
the input end of the output sampling circuit is used as the sampling end of the DCDC control module and is connected with the output end of the DCDC driving module, and the output end of the output sampling circuit is connected with the sampling pin of the DCDC control chip;
and an output pin of the DCDC control chip is used as an output end of the DCDC control module.
Optionally, in the buck DCDC converter, the output sampling circuit includes: a fifth resistor and a sixth resistor; wherein:
one end of the fifth resistor is used as the input end of the output sampling circuit, the other end of the fifth resistor is connected with one end of the sixth resistor, and a connection point is used as the output end of the output sampling circuit;
the other end of the sixth resistor is grounded.
The embodiment of the utility model provides an under-voltage protection circuit of step-down DCDC converter, include: a voltage detection unit and a charge-discharge control unit; wherein: the input end of the voltage detection unit is connected with the power supply end of the buck DCDC converter and used for receiving the input voltage of the buck DCDC converter, and the output end of the voltage detection unit is connected with the first input end of the charge-discharge control unit and used for outputting the detection voltage; the second input end of the charge and discharge control unit is connected with the output end of the buck DCDC converter and receives the output voltage of the buck DCDC converter; the output end of the charge and discharge control unit is connected with a slow start capacitor in the voltage reduction type DCDC converter to output charge and discharge control voltage; that is, the utility model provides an undervoltage protection circuit of step-down type DCDC converter can real-time detection step-down type DCDC converter's input voltage to can be when step-down type DCDC converter frequently falls the power failure and goes up to arouse that input voltage fluctuates, in time export charge-discharge control voltage to the slow start capacitor of step-down type DCDC converter through the charge-discharge control unit, in order to control the action of step-down type DCDC converter through slow start capacitor charge-discharge, realize falling, go up the power in-process and stop output voltage; compare in current step-down type DCDC converter because of there is the delay in feedback network adjustment output, the utility model discloses can avoid the frequent falling of step-down type DCDC converter, go up the electricity and easily appear output voltage in the twinkling of an eye and follow input voltage, lead to the too big problem that arouses the damage of back level power consumption module of output voltage.
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 under-voltage protection circuit of a buck DCDC converter according to an embodiment of the present invention;
fig. 2 is a circuit diagram of an under-voltage protection circuit of a buck DCDC converter according to an embodiment of the present invention;
fig. 3 is a circuit diagram of an under-voltage protection circuit of another step-down DCDC converter according to an embodiment of the present invention;
fig. 4 is a circuit diagram of a buck DCDC converter according to an embodiment of the present invention.
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.
It should be noted that, in the electronic controller of the automobile, the frequent power-down and power-up of the input occurs frequently. When the input voltage of the existing buck DCDC converter is in power failure, the input voltage is too low, the driving duty ratio of the power tube is 100%, and because the dynamic adjustment speed of the feedback network is not enough, when the input voltage is just electrified, the driving duty ratio of the power tube is still 100%, the output voltage can follow the input voltage to be output, so that the target output voltage of the buck DCDC converter is exceeded, and the loss of a rear-stage power utilization module is caused.
Based on the problem, the utility model provides an undervoltage protection circuit of step-down type DCDC converter to there is the delay in solving current step-down type DCDC converter because of feedback network adjustment output, the input voltage is followed to frequent falling, last electricity easy output voltage that appears in the twinkling of an eye, leads to the too big problem that arouses the damage of back level power consumption module.
Referring to fig. 1, the undervoltage protection circuit of the buck DCDC converter mainly includes: a voltage detection unit 101 and a charge/discharge control unit 102. Wherein:
the input end of the voltage detection unit 101 is connected to the power supply end of the buck-type DCDC converter, and receives the input voltage of the buck-type DCDC converter, and the output end of the voltage detection unit 101 is connected to the first input end of the charge and discharge control unit 102, and outputs the detection voltage.
It should be noted that the power supply terminal of the step-down DCDC converter is a port for receiving externally supplied power in order to ensure normal operation of the step-down DCDC converter. In practical applications, the voltage of the power supply terminal of the buck-type DCDC converter generally changes along with the change of the power supply voltage for supplying power. For example, when the power supply is an on-vehicle battery, the voltage at the power supply terminal of the step-down DCDC converter is the output voltage of the on-vehicle battery. In the embodiment shown in fig. 1, the power supply is the input power supply shown in fig. 1.
A second input terminal of the charge and discharge control unit 102 is connected to an output terminal of the buck-type DCDC converter, and receives an output voltage of the buck-type DCDC converter.
It should be noted that, as shown in fig. 1, the buck-type DCDC converter in practical application generally includes a DCDC control module and a DCDC driving module, and an output terminal of the buck-type DCDC converter generally refers to an output terminal of the DCDC driving module, and is used for outputting a voltage obtained by stepping down an input voltage.
In practical applications, as shown in fig. 2, fig. 3 or fig. 4, the voltage detection unit 101 may include: a zener diode D1; wherein:
the cathode of the zener diode D1 serves as an input terminal of the voltage detection unit 101, receives the input voltage (i.e., Vin in fig. 2, 3, and 4) provided by the input power source (i.e., B1 in fig. 2, 3, and 4), and the anode of the zener diode D1 serves as an output terminal of the voltage detection unit 101, and outputs the detection voltage.
In practical application, the zener diode D1 mainly functions to provide a relatively stable input voltage setting value for the under-voltage protection circuit by using its reverse breakdown characteristic. When the input voltage received by the cathode of the zener diode D1 is greater than the set value, the zener diode D1 is broken down, and the detection voltage is output.
Note that when the input voltage is higher than the reverse breakdown voltage of the zener diode D1, the zener diode D1 breaks down. Here, the higher the input voltage is, the higher the detection voltage output after the zener diode D1 is broken down is.
In practical applications, the voltage detection unit 101 may have other embodiments besides the embodiments shown in fig. 2, fig. 3, or fig. 4. The voltage detection unit 101 may include: a reference source; wherein: the input end of the reference source is used as the input end of the voltage detection unit 101 and receives an input voltage; the output terminal of the reference source serves as the output terminal of the voltage detection unit 101, and outputs the detection voltage.
It should be noted that the main function of the reference source is to provide a relatively stable input voltage setting value for the under-voltage protection circuit by using its own characteristics. Wherein, regard as the visual specific application environment of input voltage setting value and user's demand with the absolute voltage of reference source, set for by oneself the absolute voltage of reference source, the utility model discloses do not make its concrete limit, all belong to the utility model discloses a protection range. Moreover, regarding the relevant description of the reference source, refer to the prior art, and the present invention is not repeated.
The output end of the charge and discharge control unit 102 is connected to the slow start capacitor in the buck DCDC converter, and outputs a charge and discharge control voltage.
The slow start capacitor in the step-down DCDC converter is a capacitor that can be started up slowly by the DCDC control chip in the step-down DCDC converter, and is used to realize the slow start function of the step-down DCDC converter, and for example, as shown in C2 in fig. 2, 3, or 4, the slow start capacitor can be charged and discharged by adjusting the magnitude of the output charge and discharge control voltage.
In practical applications, as shown in fig. 2, 3 or 4, the charge/discharge control unit 102 includes: the circuit comprises a first switch tube Q3, a second switch tube Q4, a first resistor R1, a second resistor R2, a third resistor R3 and a fourth resistor R4. Wherein:
one end of the first resistor R1 serves as a first input end of the charge and discharge control unit 102, and the other end of the first resistor R1 is connected to one end of the second resistor R2 and a control end of the first switch tube Q3, respectively.
In practical application, the first resistor R1 and the second resistor R2 form a voltage division loop of the first switch tube Q3, and mainly divide the output detection voltage of the zener diode D1 after reverse breakdown, so as to provide a corresponding voltage for the subsequent first switch tube Q3, so as to ensure normal operation of the subsequent first switch tube Q3. The voltage generated between the connection point of the first resistor R1 and the second resistor R2 is in a direct proportion relation with the voltage of the breakdown voltage stabilizing diode D1.
A first end of the first switch tube Q3 is connected to a control end of the second switch tube Q4, an end of the third resistor R3, and an end of the fourth resistor R4, respectively.
In practical applications, the first switch tube Q3 and the second switch tube Q4 may be power tubes or transistors, and mainly function to amplify the influence of the input voltage variation outputted by the input power source. Specifically, first switch tube Q3 and second switch tube Q4 can be NPN type triode, and it can to look at concrete application environment and user's demand, the utility model discloses do not do the restriction to the concrete type of first switch tube Q3 and second switch tube Q4, all belong to the utility model discloses a protection scope.
It should be noted that in practical applications, the first switch tube Q3 and the second switch tube Q4 are generally the same type of switch tube, power tube or other types of transistors.
The other end of the third resistor R3 serves as a second input terminal of the charge and discharge control unit 102, and receives the output voltage (i.e., Vout in fig. 2, 3, and 4) of the buck-type DCDC converter.
A first end of the second switching tube Q4 serves as an output end of the charge/discharge control unit 102, and outputs a charge/discharge control voltage.
The other end of the second resistor R2, the second end of the first switch transistor Q3, the other end of the fourth resistor R4, and the second end of the second switch transistor Q4 are all grounded.
In practical application, the third resistor R3 and the fourth resistor R4 form a voltage division loop of the second switch tube Q4, and mainly divide the output voltage of the buck DCDC converter to provide a corresponding voltage for the second switch tube Q4, so that normal operation of the second switch tube Q4 is ensured.
In this embodiment, the first ends of the first switch Q3 and the second switch Q4 represent collectors of the switch transistors, the second ends of the first switch Q3 and the second switch Q4 represent emitters of the switch transistors, and the control ends of the first switch Q3 and the second switch Q4 represent bases of the switch transistors.
It should be noted that, after the voltage received by the base of the first switch Q3 and the voltage between the emitter of the first switch Q3 are greater than or equal to the turn-on voltage of the first switch Q3, the turn-on between the collector and the emitter of the first switch Q3 is turned on, the base and the emitter of the second switch Q4 are short-circuited, that is, the voltage between the base and the emitter of the second switch Q4 is 0V. When the voltage between the base of the first switch Q3 and the emitter of the first switch Q3 is smaller than the turn-on voltage of the first switch Q3, the first switch Q3 cannot turn on, the collector and the emitter of the first switch Q3 are not conductive, the third resistor R3 and the fourth resistor R4 divide the received output voltage, a voltage drop is generated across the base and the emitter of the second switch Q4, and when the voltage drop across the base and the emitter of the second switch Q4 is larger than the turn-on voltage of the second switch Q4, the second switch Q4 is turned on.
It should be further noted that, after the first switching tube Q3 is turned on and the second switching tube Q4 is turned off, the charge/discharge control voltage output by the charge/discharge control unit 102 is not zero, the slow start capacitor in the buck DCDC converter is no longer bypassed by the second switching tube Q4, and the DCDC control chip in the buck DCDC converter starts to charge the slow start capacitor; when the charging of the slow start capacitor reaches a set threshold value, the DCDC control chip starts to work again, the output voltage is judged again, the drive duty ratio of the output power tube is controlled in a closed loop mode, and the normal mode is entered. After the first switch tube Q3 is turned off and the second switch tube Q4 is turned on, the charge and discharge control voltage output by the charge and discharge control unit 102 is zero, and the slow start capacitor in the step-down DCDC converter is bypassed by the second switch tube Q4, the slow start capacitor is discharged, and when the voltage of the slow start capacitor is lower than a set threshold, the DCDC control chip stops working.
Based on the above principle, the utility model provides an undervoltage protection circuit of step-down DCDC converter can real-time detection step-down DCDC converter's input voltage to can frequently fall the power down and when going up and arouse that input voltage fluctuates at step-down DCDC converter, in time export charge-discharge control voltage to the slow start capacitor of step-down DCDC converter through charge-discharge control unit 102, in order to control the action of step-down DCDC converter through slow start capacitor charge-discharge, realize falling, the power up in-process stops output voltage; compare in current step-down type DCDC converter because of there is the delay in feedback network adjustment output, the utility model discloses can avoid the frequent falling of step-down type DCDC converter, go up the electricity and easily appear output voltage in the twinkling of an eye and follow input voltage, lead to the too big problem that arouses the damage of back level power consumption module of output voltage.
And, the utility model discloses a pure hardware design, when falling the electricity, DCDC control chip in the step-down type DCDC converter can quick response, has solved under the frequent upper and lower electric operating mode of input that automotive electronics probably met, the condition of input is followed in the output. In addition, through the setting of parameters in the undervoltage protection circuit of the step-down DCDC converter, the output voltage is ensured not to exceed a target set threshold value, the output overvoltage condition is avoided, and the normal work of a rear-stage chip is ensured.
It is worth to be noted that there is also an under-voltage protection scheme for the buck-type DCDC converter, where the slow start capacitor in the existing under-voltage protection scheme can only delay the start of the buck-type DCDC converter in a charging manner when the power is first turned on, so as to prevent the output of the buck-type DCDC converter from being abnormal in a short time; however, after the first start, if the buck DCDC converter has frequent power-off and power-on conditions, the slow start capacitor in the conventional buck DCDC converter will not be recharged and discharged, so that the DCDC control chip in the buck DCDC converter only monitors the undervoltage state, and if the undervoltage state disappears soon, the output will follow the input to generate an overvoltage condition, that is, the output voltage will follow the input voltage at the moment of power-off and power-on, so that the problem that the output voltage is too large to cause the damage of the rear-stage power module occurs; and the utility model provides an under-voltage protection circuit of step-down type DCDC converter can combine together the delay start-up function of slowly starting electric capacity with input short-time undervoltage, carries out the input closed-loop control of step-down type DCDC converter, also can real-time detection input voltage to slowly starting electric capacity to in the step-down type DCDC converter carries out charge-discharge control, can guarantee when input voltage tends to the stability, just restart step-down type DCDC converter, avoided the emergence of above-mentioned problem.
Optionally, referring to fig. 3, in another embodiment provided by the present invention, the charging and discharging control unit 102 further includes: a filter circuit 103; the first end of the filter circuit 103 is connected to the common end of the first resistor R1 and the second resistor R2, and the second end of the filter circuit 103 is grounded.
In practical applications, as shown in fig. 3, the filter circuit 103 mainly includes: a filter capacitor C1; one end of the filter capacitor C1 is used as the first end of the filter circuit 103, and the other end of the filter capacitor C1 is used as the second end of the filter circuit 103.
If a plurality of filter capacitors are present in the filter circuit 103, the plurality of filter capacitors are sequentially connected in series, and both ends of the series connection are respectively used as a first end and a second end of the filter circuit 103. Alternatively, the plurality of filter capacitors are connected in parallel in sequence, and the two ends of the parallel connection are respectively used as the first end and the second end of the filter circuit 103.
It should be further noted that the filter capacitor C1 is mainly used for filtering high-frequency noise to eliminate interference of the high-frequency noise on the subsequent switching tube. Under the action of the filter capacitor C1, the first switch tube Q3 is opened slowly.
Alternatively, in other embodiments, the charging and discharging control unit 102 may have other embodiments, and a filter capacitor may be configured for the second switching tube Q4 in practical use.
Based on the undervoltage protection circuit of the step-down DCDC converter that above-mentioned embodiment provided, please refer to fig. 4, another embodiment of the present invention further provides a step-down DCDC converter, which mainly includes: the undervoltage protection circuit comprises a DCDC control module 201, a DCDC driving module 202 and an undervoltage protection circuit 200 of the step-down DCDC converter according to any one of the embodiments, wherein the undervoltage protection circuit 200 is connected with the DCDC control module 201 and the DCDC driving module 202 respectively. Wherein:
the input terminal of the DCDC driving module 202 is connected to the output terminal of the input power source and receives the input voltage.
In practical application, the input power source is an external power source input of the step-down DCDC converter, and specifically, the input power source may be any storage battery or energy storage battery capable of providing electric energy for the step-down DCDC converter. For example, a whole vehicle battery, a vehicle-mounted battery and the like in a new energy charging automobile.
It should be noted that the input end of the DCDC driving module 202 serves as a power supply end of the buck-type DCDC converter, and receives the electric energy provided by the external power supply for the buck-type DCDC converter.
The sampling terminal of the DCDC control module 201 is connected to the output terminal of the DCDC driving module 202, and receives the output voltage.
The control terminal of the DCDC driving module 202 is connected to the output terminal of the DCDC control module 201, and receives the driving control voltage.
It should be noted that the DCDC driving module 202 is configured to perform power conversion, and store energy of an input high voltage through an output inductor and an output capacitor by controlling a driving duty ratio of a power tube, so as to achieve a final voltage reduction purpose.
In practical applications, as shown in fig. 2, fig. 3 or fig. 4, the DCDC control module 201 mainly includes: DCDC control chip U1, slowly start-up capacitance C2 and output sampling circuit 2011. Wherein:
the synchronous control pin SS of the DCDC control chip U1 is connected with the first end of the slow starting capacitor C2, the connection point is used as the input end of the DCDC control module 201, and the other end of the slow starting capacitor C2 is grounded.
The input end of the output sampling circuit 2011 serves as the sampling end of the DCDC control module 201 and is connected with the output end of the DCDC driving module 202, and the output end of the output sampling circuit 2011 is connected with the sampling pin of the DCDC control chip U1.
The output pin of the DCDC control chip U1 serves as the output terminal of the DCDC control module 201.
As also shown in fig. 2, 3, or 4, the output sampling circuit 2011 mainly includes: a fifth resistor R5 and a sixth resistor R6. Wherein:
one end of the fifth resistor R5 serves as an input end of the output sampling circuit 2011, the other end of the fifth resistor R5 is connected with one end of the sixth resistor R6, a connection point serves as an output end of the output sampling circuit 2011, and the other end of the sixth resistor R6 is grounded.
In practical applications, referring also to fig. 2, fig. 3 or fig. 4, the DCDC driving module 202 mainly includes: power tube Q1, follow current tube Q2, inductor Lout and capacitor Cout. Wherein:
a first terminal of the power transistor Q1 serves as an input terminal of the DCDC driving module 202, and receives an input voltage; a second terminal of the power transistor Q1 is connected to a first terminal of the follow current transistor Q2 and one terminal of the inductor Lout, respectively.
The second terminal of follow tube Q2 is connected to one terminal of capacitor Cout and is grounded.
The other end of the capacitor Cout is connected to the other end of the inductor Lout, and the connection point is used as an output end of the DCDC driving module 202 to output the output voltage.
The control terminal of the power transistor Q1 and the control terminal of the follow current transistor Q2 serve as control terminals of the DCDC driving module 202, and receive a driving control voltage.
In practical applications, the power transistor Q1 is mainly used for reducing the output voltage. The follow current tube Q2 is mainly used for matching with the power tube Q1 to realize the voltage reduction function. The inductor Lout is an output inductor, and the capacitor Cout is an output capacitor.
In this embodiment, the first terminal represents the drain of the power transistor Q1, the second terminal represents the source of the power transistor Q1, and the control terminal represents the gate of the power transistor Q1.
It should be noted that a closed-loop control loop is formed between the DCDC control module 201 and the DCDC driving module 202, so as to acquire the output voltage output by the output end of the DCDC driving module 202 in real time, and compare the acquired output voltage with the set output voltage of the DCDC control chip U1 in the DCDC control module 201; when the output voltage is higher than the set output voltage, the power tube Q1 is controlled to be closed, the follow current tube Q2 is controlled to be opened, and the output voltage is released; when the output voltage is lower than the set output voltage, the driving duty ratio of the power tube Q1 is adjusted, the follow current tube Q2 is closed, and the output voltage is increased to the set output voltage.
It should be further noted that the under-voltage protection circuit 200 is configured to detect the stability of the input power in real time, and when the voltage of the input power is lower than a set value, discharge the charge stored in the slow start capacitor C2 of the DCDC control module 201, so that the step-down DCDC converter enters the standby mode. When the voltage of the input power is higher than the set value, the slow start capacitor C2 in the DCDC control module 201 is recharged, and after the slow start capacitor C2 is fully charged again, the buck DCDC converter enters the working mode again.
It should be further noted that, for the related description of the under-voltage protection circuit 200, reference may be made to the above-mentioned embodiments, and details are not repeated herein; similarly, the relevant explanation about DCDC control module 201 and DCDC drive module 202 still can refer to prior art, the utility model discloses no longer describe, all belong to the utility model discloses a protection scope.
Combine the step-down DCDC converter that fig. 4 shows, assume that the setting value of zener diode or reference source is 5V, when the input power supply appearance is unusual, also when input voltage reduces suddenly, the utility model discloses specifically there is following implementation: the voltage at the anode of D1 becomes almost 0V, and Q3 cannot meet the turn-on requirement. Q3 is closed, after Q3 is closed, the Q4 can work due to the partial pressure of R3 and R4 in the later stage, at the moment, Q4 is conducted, the electric charge of the slow starting capacitor C2 is released, and therefore the voltage at two ends of the slow starting capacitor C2 is 0V. The DCDC controller U1 detects that the voltage across the soft start capacitor C2 is 0V and stops controlling the power transistor Q1, and thus does not connect the input power source to the output, thereby cutting off the relationship between the input and the output.
And when the input voltage increases suddenly, the utility model discloses specifically there is following implementation: due to the filtering effect of C1, Q3 will turn on slowly; when Q3 is turned on, Vce of Q3 is turned on, the voltage across Vbe of Q4 becomes 0V, and Q4 is turned off. After the Q4 is turned off, the slow start capacitor C2 is no longer bypassed by the Q4, the DCDC control module 201 starts to charge the slow start capacitor C2, when the charge of the slow start capacitor C2 reaches a set threshold of the buck DCDC converter, the buck DCDC converter works again, the output voltage is judged again, the drive duty ratio of the power tube is controlled in a closed loop mode, and therefore the normal mode is entered.
Based on the above, the step-down DCDC converter does not have the condition of outputting short-time overvoltage, and further does not burn out the later-stage electric devices.
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.
It is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising a … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
Claims (10)
1. An undervoltage protection circuit of a buck-type DCDC converter, comprising: a voltage detection unit and a charge-discharge control unit; wherein:
the input end of the voltage detection unit is connected with the power supply end of the buck DCDC converter and used for receiving the input voltage of the buck DCDC converter, and the output end of the voltage detection unit is connected with the first input end of the charge and discharge control unit and used for outputting detection voltage;
a second input end of the charge and discharge control unit is connected with an output end of the buck DCDC converter and receives the output voltage of the buck DCDC converter;
and the output end of the charge and discharge control unit is connected with a slow start capacitor in the voltage reduction type DCDC converter to output charge and discharge control voltage.
2. The undervoltage protection circuit of step-down DCDC converter according to claim 1, wherein said voltage detection unit comprises: a voltage regulator diode; wherein:
the cathode of the voltage stabilizing diode is used as the input end of the voltage detection unit, and the anode of the voltage stabilizing diode is used as the output end of the voltage detection unit.
3. The undervoltage protection circuit of step-down DCDC converter according to claim 1, wherein said voltage detection unit comprises: a reference source; wherein:
the input end of the reference source is used as the input end of the voltage detection unit, and the output end of the reference source is used as the output end of the voltage detection unit.
4. The undervoltage protection circuit of step-down DCDC converter according to claim 1, wherein said charge-discharge control unit comprises: the circuit comprises a first switch tube, a second switch tube, a first resistor, a second resistor, a third resistor and a fourth resistor; wherein:
one end of the first resistor is used as a first input end of the charge and discharge control unit, and the other end of the first resistor is respectively connected with one end of the second resistor and the control end of the first switching tube;
the first end of the first switch tube is respectively connected with the control end of the second switch tube, one end of the third resistor and one end of the fourth resistor;
the other end of the third resistor is used as a second input end of the charge and discharge control unit;
the first end of the second switch tube is used as the output end of the charge and discharge control unit;
the other end of the second resistor, the second end of the first switch tube, the other end of the fourth resistor and the second end of the second switch tube are all grounded.
5. The undervoltage protection circuit of a buck DCDC converter as recited in claim 4, wherein said voltage control circuit further comprises: a filter circuit; the first end of the filter circuit is connected with the common end of the first resistor and the second resistor, and the second end of the filter circuit is grounded.
6. The undervoltage protection circuit of a buck DCDC converter as recited in claim 5, wherein said filter circuit comprises: a filter capacitor;
one end of the filter capacitor is used as a first end of the filter circuit, and the other end of the filter capacitor is used as a second end of the filter circuit.
7. A buck DCDC converter, comprising: a DCDC control module, a DCDC driving module, and an under-voltage protection circuit of the step-down DCDC converter according to any one of claims 1 to 6, connected to the DCDC control module and the DCDC driving module, respectively;
the input end of the DCDC driving module is connected with an input power supply and receives input voltage;
the sampling end of the DCDC control module is connected with the output end of the DCDC driving module and receives output voltage;
and the control end of the DCDC drive module is connected with the output end of the DCDC control module and receives drive control voltage.
8. The buck DCDC converter according to claim 7, wherein the DCDC driving module includes: the power tube, the follow current tube, the inductor and the capacitor; wherein:
the first end of the power tube is used as the input end of the DCDC driving module, and the second end of the power tube is respectively connected with the first end of the follow current tube and one end of the inductor;
the second end of the follow current tube is connected with one end of the capacitor and is grounded;
the other end of the capacitor is connected with the other end of the inductor, and a connection point is used as an output end of the DCDC driving module;
and the control end of the power tube and the control end of the follow current tube are used as the control ends of the DCDC driving module.
9. The buck DCDC converter according to claim 7, wherein the DCDC control module comprises: the device comprises a DCDC control chip, a slow start capacitor and an output sampling circuit; wherein:
a synchronous control pin of the DCDC control chip is connected with a first end of the slow starting capacitor, a connection point is used as an input end of the DCDC control module, and the other end of the slow starting capacitor is grounded;
the input end of the output sampling circuit is used as the sampling end of the DCDC control module and is connected with the output end of the DCDC driving module, and the output end of the output sampling circuit is connected with the sampling pin of the DCDC control chip;
and an output pin of the DCDC control chip is used as an output end of the DCDC control module.
10. The buck DCDC converter according to claim 9, wherein the output sampling circuit comprises: a fifth resistor and a sixth resistor; wherein:
one end of the fifth resistor is used as the input end of the output sampling circuit, the other end of the fifth resistor is connected with one end of the sixth resistor, and a connection point is used as the output end of the output sampling circuit;
the other end of the sixth resistor is grounded.
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| CN202121088447.0U CN215300494U (en) | 2021-05-20 | 2021-05-20 | Step-down DCDC converter and under-voltage protection circuit thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116799915A (en) * | 2023-06-29 | 2023-09-22 | 航天锂电科技(江苏)有限公司 | Voltage reduction equalization circuit of lithium battery pack and control method thereof |
| CN117277823A (en) * | 2023-11-20 | 2023-12-22 | 宁德时代新能源科技股份有限公司 | DC-DC converter, state control method and device thereof and storage medium |
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2021
- 2021-05-20 CN CN202121088447.0U patent/CN215300494U/en active Active
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116799915A (en) * | 2023-06-29 | 2023-09-22 | 航天锂电科技(江苏)有限公司 | Voltage reduction equalization circuit of lithium battery pack and control method thereof |
| CN116799915B (en) * | 2023-06-29 | 2023-12-29 | 航天锂电科技(江苏)有限公司 | Voltage reduction equalization circuit of lithium battery pack and control method thereof |
| CN117277823A (en) * | 2023-11-20 | 2023-12-22 | 宁德时代新能源科技股份有限公司 | DC-DC converter, state control method and device thereof and storage medium |
| CN117277823B (en) * | 2023-11-20 | 2024-04-12 | 宁德时代新能源科技股份有限公司 | DC-DC converter and state control method, device and storage medium thereof |
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