CN215268054U

CN215268054U - Circuit for eliminating exceeding of ripple waves of Buck-Boost type power module at critical point

Info

Publication number: CN215268054U
Application number: CN202120638562.4U
Authority: CN
Inventors: 崔英杰; 邓兴培; 岳峰
Original assignee: Shijiazhuang Zerun Technology Co ltd
Current assignee: Shijiazhuang Zerun Technology Co ltd
Priority date: 2021-03-30
Filing date: 2021-03-30
Publication date: 2021-12-21
Anticipated expiration: 2031-03-30

Abstract

The utility model discloses a circuit for eliminating the supercritical point ripple superscript of a Buck-Boost type power supply module, which belongs to the technical field of switching power supplies and comprises a voltage comparison circuit, a gate circuit, a relay drive circuit, a relay and a voltage reduction circuit; the input of the voltage comparison circuit is respectively battery voltage, first set voltage and second set voltage, the voltage comparison circuit compares the first set voltage, the second set voltage and the battery voltage, an output signal of the voltage comparison circuit is subjected to logic operation through a gate circuit, an output signal of the gate circuit is sent to a relay driving circuit to control the on-off of a relay, and a relay contact is connected in parallel with a voltage reduction circuit and then connected in series in a power supply loop of the battery and the Buck-boost type non-isolated DC/DC power supply module. The circuit of the utility model is composed of discrete devices, and has simple structure and low cost.

Description

Circuit for eliminating exceeding of ripple waves of Buck-Boost type power module at critical point

Technical Field

The utility model belongs to the technical field of switching power supply, concretely relates to eliminate circuit that Buck-Boost type power module ripple exceeds standard at the critical point.

Background

When the Buck-boost type non-isolated DC/DC power supply module is used for supplying power, when the voltage of a power supply battery is reduced from a higher voltage to be very close to or equal to the output voltage (namely, the voltage is reduced to a critical point, the critical point is a range, generally the output voltage Vout +/-0.5V), ripples which are several times larger than normal ripples can be generated due to the switching of the module between the Buck mode and the boost mode, for example, the NQ60W60HGC40NRF-G non-isolated Buck-boost power supply module which is commonly used at present has normal ripples within 250KHZ and 200mVp-p at ordinary times, but when the input voltage is reduced to the critical point of 24.6V +/-0.5V (at the moment, the output voltage Vout is 25V), the ripples already exceed 500mVp-p and are seriously out of limit, which is a defect existing in the Buck-boost type non-isolated DC/DC power supply module, and the ripples are determined by a Buck-boost topology form, and cannot be eradicated at present.

FIG. 1 is a Buck-boost type non-isolated DC/DC power supply module topology diagram, which is illustrated according to the following parameters:

the battery power supply voltage range is 21V-32V, the Buck-boost type non-isolated DC/DC power supply module input voltage range is 9V-60V, and the output voltage (Vout) is adjusted to be 25V.

When the battery power supply voltage is gradually reduced from 32V in normal work, when the battery output voltage Vin is higher than the output voltage Vout of the DC/DC non-isolated Buck-boost power module, the DC/DC module works in a Buck voltage reduction topology mode, the MOS tubes on the output side SW2 are through, the lower MOS tube is turned off, the upper MOS tube and the lower MOS tube on the input side SW1 are alternately turned on, and the output voltage Vout is adjusted by adjusting the duty ratio.

When the output voltage of the battery is lower than the output voltage Vout of the Buck-Boost non-isolated DC/DC power supply module, the DC/DC module works in a Boost topological mode, the MOS transistor on the input side SW1 is straight, the lower MOS transistor is closed, and the output voltage Vout is adjusted by adjusting the duty ratios of the upper MOS transistor and the lower MOS transistor on the output side SW 2.

When the battery output voltage Vin and the Buck-boost non-isolated DC/DC power module input voltage are close or equal, the module enters Buck, boost rotation mode (see fig. 2), i.e.:

during the periods from t0 to t1 and from t2 to t3, the module enters a freewheeling mode, the upper MOS transistors of the input side SW1 and the output side SW2 are simultaneously switched on, and the other 2 MOS transistors are switched off;

during the period from t1 to t2, the module enters a charging mode, an upper MOS transistor of an input side SW1 and a lower MOS transistor of an output side SW2 are simultaneously turned on, the other 2 MOS transistors are simultaneously turned off, and the voltage of an inductor L1 is equal to the input voltage Vin;

during the period from t3 to t4, the module enters a discharge mode, a MOS transistor on the input side SW1 and a MOS transistor on the output side SW2 are simultaneously turned on, the other 2 MOS transistors are simultaneously turned off, and the voltage of the inductor L1 is equal to the output voltage Vout;

it can be seen from the above examples that when the input voltage and the output voltage are very close to or equal to each other, although the internal management chip of the Buck-boost non-isolated DC/DC power module also sets the sampling return difference, chip sampling always has a certain error, which causes a power supply to judge a Buck-boost mode fault, and a ripple exceeds the standard, which is determined by a Buck-boost topology mode and cannot be overcome at present, and this will affect the normal operation of the following devices.

At present, engineers take the following solutions:

firstly, improve battery output cut-off voltage, be exactly with battery output cut-off voltage higher than Buck-boost power module critical point, Buck-boost non-isolation DC/DC type power module works at Buck step-down topological mode all the time like this, can not get into the critical point and just can not have the ripple to exceed standard, in fact cut the boost function of module, weakened the advantage of Buck-boost non-isolation DC/DC type power module "input voltage wide range", and the battery utilization ratio is on the low side, extravagant equipment resource, fund etc..

Secondly, the output capacitance is increased to tens of thousands of uF, the electrolytic capacitance of the tens of thousands of uF is large in volume, no space is installed in the equipment, and the effect is not ideal, because the frequency of Buck and Boost mode switching at the critical point of the input voltage is very low, about hundreds of Hz, when the current of the equipment is about 20A, according to the relation formula of ripple waves and capacitance: σ Vout (Iout × D × Ts)/C (σ Vout is ripple amplitude, C is capacitance value, Iout is output current size, Ts is ripple period, D is duty ratio), if the ripple is limited within 200mVp-p, an electrolytic capacitor with tens of thousands uF or even larger needs to be matched, the method is limited by factors such as equipment space, the anode and cathode of the electrolytic capacitor are mistakenly connected to cause explosion danger, and the larger the capacitance value is, the larger the damage is, the method is not ideal.

SUMMERY OF THE UTILITY MODEL

The utility model discloses the technical problem that needs to solve provides a small, with low costs, compatible capacitive load and possess prevent the direct current switch controller of reverse connection and overcurrent protection function.

In order to solve the above problems, the utility model adopts the following technical proposal:

a circuit for eliminating the exceeding of ripples of a Buck-Boost type power module at a critical point is characterized in that: the voltage comparison circuit comprises a voltage comparison circuit, a gate circuit, a relay driving circuit, a relay and a voltage reduction circuit; the input of the voltage comparison circuit is respectively battery voltage, first set voltage and second set voltage, the voltage comparison circuit compares the first set voltage, the second set voltage and the battery voltage, an output signal of the voltage comparison circuit is subjected to logic operation through a gate circuit, an output signal of the gate circuit is sent to a relay driving circuit to control the on-off of a relay, and a relay contact is connected in parallel with a voltage reduction circuit and then connected in series in a power supply loop of the battery and the Buck-boost type non-isolated DC/DC power supply module.

Preferably, the voltage reduction circuit is a diode voltage reduction circuit and is formed by connecting one diode or a plurality of diodes in series in sequence.

Further, the number of the diodes is 4.

Preferably, the voltage reduction circuit is a diode voltage reduction circuit and is formed by connecting a plurality of diode series components in parallel, and each diode series component is formed by sequentially connecting one diode or a plurality of diodes in series.

Furthermore, the number of diodes of each diode series assembly is 4, and the number of the diode series assemblies is more than 2 groups.

Preferably, the gate circuit includes a not gate and a gate, the not gate is used for logically negating a comparison result of the first setting voltage and the battery output voltage monitored in real time, and the or gate is used for logically operating a comparison result of the second setting voltage and the battery output voltage monitored in real time and an output of the not gate.

Adopt the produced beneficial effect of above-mentioned technical scheme to lie in:

the utility model discloses utilize the step-down circuit of concatenating in power supply loop, when battery voltage reduces Buck-boost non-isolation DC/DC type power module critical point, utilize diode step-down circuit to reduce the supply voltage of this module, successfully avoid Buck-boost non-isolation DC/DC type power module's critical point, when battery voltage is less than the critical point, the supply voltage who resumes this module is battery voltage, has eliminated Buck-boost non-isolation DC/DC type power module's critical point ripple that exceeds standard effectively, the utility model discloses the circuit comprises the discrete device, simple structure, with low costs.

Drawings

FIG. 1 is a Buck-boost type non-isolated DC/DC power supply module topology;

FIG. 2 is a voltage timing diagram of Buck-boost type non-isolated DC/DC power module when the input voltage operates in Buck and boost rotation modes at a critical point;

fig. 3 is a schematic block diagram of the present invention.

Fig. 4 is a schematic circuit diagram of the present invention.

Detailed Description

The utility model is described in further detail below with reference to the attached drawings:

as shown in fig. 3, the circuit of the present invention includes a voltage comparison circuit, a gate circuit, a relay driving circuit, a relay and a voltage reduction circuit; the input of the voltage comparison circuit is respectively battery voltage, first set voltage and second set voltage, the voltage comparison circuit compares the first set voltage, the second set voltage and the battery voltage, an output signal of the voltage comparison circuit is subjected to logic operation through a gate circuit, an output signal of the gate circuit is sent to a relay driving circuit to control the on-off of a relay, and a relay contact is connected in parallel with a voltage reduction circuit and then connected in series in a power supply loop of the battery and the Buck-boost type non-isolated DC/DC power supply module.

The gate circuit comprises a NOT gate and an OR gate, wherein the NOT gate is used for logically negating a comparison result of the first set voltage and the battery output voltage monitored in real time, and the OR gate is used for logically operating a comparison result of the second set voltage and the battery output voltage monitored in real time and the NOT gate output.

In order to ensure the power supply current of the Buck-boost type non-isolated DC/DC power supply module and effectively avoid critical points, the voltage reduction circuit of the utility model adopts a diode voltage reduction circuit which is formed by connecting a plurality of diode series components in parallel, and the diode series components are formed by connecting one diode or a plurality of diodes in series in sequence; the diode quantity of every diode series connection subassembly is 4 in this novel, and according to the work current that Buck-boost type non-isolation DC/DC power module model and diode series connection subassembly can provide, the quantity of diode series connection subassembly can be a set of, also can be more than 2 groups.

According to the determined critical point (voltage reduction range), the forward conduction voltage drop Vf value of the diodes is selected, the quantity of the forward conduction voltage drop Vf values is determined, and the diodes are judged to be required to be used in series and parallel according to the requirement of the load on the current.

The diodes commonly used at present are as follows:

a diode 1N4007, the forward current IF is 1A, and the forward conduction voltage drop VF is 0.7V;

diode SBL3050PT, forward current IF is 30A, forward conduction voltage drop VF is 0.7V;

a diode RHRP15120, the forward current IF is 15A, and the forward conduction voltage drop VF is 2.6V;

additionally the contact current of relay J1 should be greater than the load maximum current.

Description of the principle:

fig. 4 is a schematic circuit diagram of an embodiment of the present invention. The concrete description is as follows:

the battery output voltage range of the embodiment is 21V-32V, the Buck-boost non-isolated DC/DC power supply module is NQ60W60HGC40NRF-G, the output voltage is 25V, when the output voltage is 25V, the critical point of the input voltage of the Buck-boost non-isolated DC/DC power supply module is 24.6V +/-0.5V, through the embodiment of serially connecting the battery and the Buck-boost non-isolated DC/DC power supply module, the output ripple of the Buck-boost non-isolated DC/DC power supply module cannot exceed the standard within the full battery power supply range of 21V-32V.

The voltage reduction circuit of the embodiment adopts 4 diodes to be connected in series and then connected in parallel, so that the voltage reduction is 0.7 × 4-2.8V, the range of the voltage critical point selected to be avoided is 24.6 ± 1.4V, when the voltage of the battery is reduced to 26V (first set voltage), the voltage reduction circuit is connected, the input voltage directly skips the critical point, the Buck-boost non-isolated DC/DC power supply module is switched from a voltage reduction mode to a voltage boosting mode for transfer, and when the voltage of the battery is reduced to 23.2V (second set voltage), the connection of the voltage reduction circuit is cancelled, and the power consumption is reduced.

The reference voltage of the first setting voltage is divided by resistors R10 and R15 in series and then is input to the same-phase end of a comparator U1A through a resistor R6, a resistor R8 is a feedback resistor, positive feedback is added through a feedback resistor R8, a hysteresis comparator is formed by a comparator U1A, the reference voltage of the second setting voltage is divided by resistors R7 and R14 in series and then is input to the same-phase end of the comparator U1B through a resistor R3, a resistor R5 is a feedback resistor, positive feedback is added through the feedback resistor R5, the comparator U1B forms a hysteresis comparator, the battery output voltage monitored in real time is divided by resistors R1 and R2 in series and then is input to the opposite-phase end of U1A, the resistors R4 and R13 in series and then is input to the opposite-phase end of U1B, and the comparison of the battery real-time output voltage with the first setting voltage and the second setting voltage is completed by the opposite-phase input hysteresis comparator U1A and U1B. In order to ensure that the level of the comparator is stable during the inversion, the hysteresis comparator is adopted in the embodiment, the return difference voltage is about 0.1V, and the return difference voltage can be adjusted according to the actual situation.

And according to the range of the voltage critical point needing to be avoided, the voltage value of the avoidance critical point is set by adjusting the resistance values of the resistors R1, R2, R4 and R13.

In this embodiment, when the battery voltage is lower than 26V (the first setting voltage), the output voltage of the comparator U1A needs to be inverted to a high level, and then the output voltage is output as a low level to the or gate U2 through the not gate U3, and the input voltage at the inverting terminal of U1A is calculated through the first setting voltage: R2/(R1+ R2) × 26V ═ 2.49, the comparator U1A and its peripheral circuits form a hysteresis comparator, the voltage at the same phase end, which is input to the comparator U1A through the resistor R6 after the resistors R10 and R15 are serially divided, is in a range of 2.49V to 2.59V, i.e., Vref R8/(R6+ R8) +5V R6/(R6+ R8) ═ 2.59, Vref R8/(R6+ R8) -OV R6/(R6+ R8) ═ 2.49, then Vref ═ R15/(R10+ R15) ═ 5V ═ 2.54V, an example given in this embodiment is: R15-2K 7, then R10-R15-5V/2.54V-R15-2K 7-5V/2.54V-2K 7-2K 6.

Similarly, when the battery voltage is lower than 23.2V (second setting voltage), the present embodiment gives an example in which: r14 is 2K7, then R7 is 3K1, R13 is 10K, R4 is 91K 3.

The resistances of the resistors R1, R2, R4, R7, R14 and R15 can be selected and calculated according to actual conditions, and in order to ensure sampling accuracy, the resistors adopt 1% accuracy.

When the output voltage of the battery is smaller than 32V and larger than 26V, the comparator U1A outputs low level, high level is output to an OR gate U2 after passing through an NOT gate U3, the comparator U1B outputs low level, output signals of the OR gate U2 and the comparator U1B output high level after being operated through an OR gate U2, a triode Q1 is driven to be conducted, a relay J1 is attracted, a normally open contact of a relay J1 is used for short-circuiting a voltage reduction circuit, and the positive electrode of the battery directly supplies power to the Buck-boost non-isolated DC/DC power supply module normally through the normally open contact of the relay J1.

When the battery voltage is reduced to be less than or equal to 26V and greater than 23.2V, the output of the comparator U1A is inverted to a high level, a low level is output after passing through the not gate U3, the output of the comparator U1B is still a low level, the output of the or gate U2 is a low level at this time, the triode Q1 is cut off, the relay J1 is disconnected, the positive electrode of the battery is supplied to the Buck-boost non-isolated DC/DC power supply module for power supply after passing through a voltage reduction circuit (high-power diodes D1, D2, D3, Dn, D21, D22, D23, D2n), the voltage reduction range selected in the embodiment is 2.8V, so that the power supply voltage supplied to the later Buck-boost non-isolated DC/DC power supply module is 26V-2.8V ═ 23.2V, and the critical point range of the Buck-boost non-isolated DC/DC power supply module is 24.6V ± 0.5V, thereby eliminating the overproof ripple.

When the voltage of the battery is continuously reduced to be less than 23.2V, the output of the comparator U1A is continuously at a high level, the output of the comparator U1B is at a low level after passing through the NOT gate U3, the output of the comparator U1B is inverted to be at a high level, two signals are output as a high level after passing through the OR gate U2, the triode Q1 is conducted, the relay J1 is attracted, the positive electrode of the battery directly supplies power to the Buck-boost non-isolated DC/DC power supply module normally through a normally open contact of the relay J1, and the voltage of the power supply is 23.2V and 24.6V +/-0.5V of the critical point voltage is avoided.

What has just been the utility model discloses a specific embodiment, because Buck-boost non-isolation DC/DC power module and output voltage's difference, circuit parameter need do the adjustment, consequently the settlement of above-mentioned parameter does not restrict the utility model discloses a protection scope.

The voltage critical point is determined by the output voltage of the Buck-boost non-isolated DC/DC power supply module, the input voltage critical point of the general Buck-boost non-isolated DC/DC power supply module is in the range of Vo +/-0.5V, the voltage reduction size is determined after the critical point is found, the voltage reduction range is too small to completely contain the critical point, energy is wasted greatly, heat dissipation needs to be considered, and a heat dissipation fin, a fan and the like are added.

Claims

1. A circuit for eliminating the exceeding of ripples of a Buck-Boost type power module at a critical point is a circuit for eliminating the exceeding of ripples of a Buck-Boost type non-isolated DC-DC power module at the critical point, and is characterized in that: the voltage comparison circuit comprises a voltage comparison circuit, a gate circuit, a relay driving circuit, a relay and a voltage reduction circuit; the input of the voltage comparison circuit is respectively battery voltage, first set voltage and second set voltage, the voltage comparison circuit compares the first set voltage, the second set voltage and the battery voltage, an output signal of the voltage comparison circuit is subjected to logic operation through a gate circuit, an output signal of the gate circuit is sent to a relay driving circuit to control the on-off of a relay, and a relay contact is connected in parallel with a voltage reduction circuit and then connected in series in a power supply loop of the battery and the Buck-boost type non-isolated DC/DC power supply module.

2. The circuit for eliminating the excess ripple of the Buck-Boost type power supply module at the critical point according to claim 1, wherein: the voltage reduction circuit is a diode voltage reduction circuit and is formed by sequentially connecting one diode or a plurality of diodes in series.

3. The circuit for eliminating the excess ripple of the Buck-Boost type power supply module at the critical point according to claim 2, wherein: the number of the diodes is 4.

4. The circuit for eliminating the excess ripple of the Buck-Boost type power supply module at the critical point according to claim 1, wherein: the voltage reduction circuit is a diode voltage reduction circuit and is formed by connecting a plurality of diode series components in parallel, and each diode series component is formed by sequentially connecting one diode or a plurality of diodes in series.

5. The circuit for eliminating the excess ripple of the Buck-Boost type power supply module at the critical point according to claim 4, wherein: the number of diodes of each diode series assembly is 4, and the number of the diode series assemblies is more than 2 groups.

6. A circuit for eliminating the excess ripple of a Buck-Boost type power supply module at a critical point according to any one of claims 1 to 5, wherein: the gate circuit comprises a NOT gate and an OR gate, wherein the NOT gate is used for logically negating a comparison result of the first set voltage and the battery output voltage monitored in real time, and the OR gate is used for logically operating a comparison result of the second set voltage and the battery output voltage monitored in real time and the NOT gate output.