CN108365761B - DC constant voltage output converter - Google Patents
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- CN108365761B CN108365761B CN201810371417.7A CN201810371417A CN108365761B CN 108365761 B CN108365761 B CN 108365761B CN 201810371417 A CN201810371417 A CN 201810371417A CN 108365761 B CN108365761 B CN 108365761B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/337—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only in push-pull configuration
- H02M3/3376—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only in push-pull configuration with automatic control of output voltage or current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
- H02H7/1213—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for DC-DC converters
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
Abstract
The invention discloses a DC constant voltage output converter which comprises a 12V or 24V low voltage power input, an auxiliary power circuit, an automatic frequency switching circuit, a PWM regulation circuit, a boosting output rectifying and filtering circuit, a potential logic protection circuit, a push-pull boosting topology circuit and an output constant voltage automatic switching circuit. The invention judges the potential logic monitoring according to different states (under voltage, overvoltage and normal) of the input bus voltage, thereby controlling the start and stop of the whole circuit by controlling the PWM module. The output constant voltage automatic switching circuit ensures safe and stable voltage output under different input voltages. The high-frequency step-up transformer connected with the push-pull topology is specially designed in winding distribution so as to adapt to two different input voltages. The automatically switched output constant voltage circuit after the step-up transformer can ensure constant voltage output at different inputs.
Description
Technical Field
The invention relates to the technical field of constant voltage output circuit design, in particular to a DC constant voltage output converter.
Background
With the rise of green renewable energy sources such as photovoltaic power generation and the like, the application and related research of the inverter power supply are increasingly extensive and deep. It is widely used in families, corporate servers, satellite relay stations and even aerospace industry. The boost circuit is a key part of the inverter power supply, and key indexes such as working stability, safety, response sensitivity and the like of the boost circuit influence the normal operation of the whole inverter power supply system.
Multiple-input boost DC constant voltage output converters are a common component in inverter power supplies. In the booster circuit, the common methods are: push-Pull (Push-Pull topology), weinberg Circuit (Winberg Circuit topology), half-Bridge (Half-Bridge topology), full-Bridge (Full-Bridge topology), etc., among which Push-Pull (Push-Pull topology) is the most common. For these topologies, the input voltage is limited to a relatively narrow range to ensure a fixed ratio, and when the input voltage changes significantly, the boost output voltage is too high, potentially burning out the high voltage power consuming components. Although the output voltage is too high, the purpose of setting the voltage output can be achieved by PWM modulation, and thus the power conversion efficiency is reduced (at this time, the pulse width of the PWM driving signal is very narrow, resulting in a reduction in the power conversion rate). Therefore, in the coupling scheme of the multi-input switching converter, each input corresponds to a respective power conversion circuit or passes through a relatively complex control circuit, so that the coupling scheme is suitable for the conditions of different input voltages, but the system scheme has higher cost and lower economy.
On the other hand, in order to ensure the normal operation of the system, the state of the input signal needs to be judged in time so as to respond. The voltage signal is used as input, the three working states of undervoltage, overvoltage and normal of the input voltage are judged, and when the input voltage is detected to be abnormal, namely undervoltage or overvoltage, the system is required to stop running or automatically implement protection. The same principle is also adopted when the input is in multiple voltage levels (hereinafter referred to as multiple levels), any input is in an abnormal state, and corresponding protection measures are required to be started. For multi-stage input logic judgment, the conventional microcontroller realizes functions through software design, and has the defects of response lag, high cost and the like.
The detection of the state of the multi-stage input voltage and the logic judgment are generally realized by two methods, namely a hardware circuit method and a singlechip software programming method.
When the hardware circuit method is adopted, the voltage signals are compared and detected through a comparator to obtain logic potential, and then the detected logic potential signals are directly transmitted to a logic composite circuit to carry out logic judgment, so that an actual control signal is obtained and supplied to a potential protection circuit. Pure hardware circuits are commonly used for single input voltage state detection.
When the single-chip microcomputer software programming method is adopted, the voltage signal must be sampled and detected through the analog-to-digital conversion module, then logic judgment is carried out through the single-chip microcomputer software programming, and judgment of the multi-stage input signal can be conveniently carried out.
The response speed of the hardware circuit method and the singlechip software programming method is influenced by the constraint factors such as semiconductor materials, working environments and the like, and the singlechip software programming method is also influenced by the singlechip clock signal, the conversion precision of the analog-to-digital conversion module, the sampling voltage range and other constraint factors.
Although the response speed of the semiconductor device is faster and faster under the current high-speed development wave, the single chip microcomputer software programming method has more limited factors in performance compared with the hardware circuit method. Compared with a software programming method, the hardware circuit method has the advantages of more timely and sensitive response to direct logic judgment of the voltage signal, wide potential measurement range, small error range and low realization cost of the whole circuit. Under the condition of the same performance, the response of the singlechip software programming method is not as timely as that of the hardware circuit method, the integration is not easy, and the realization cost of the whole circuit is relatively high.
Disclosure of Invention
The invention aims to provide a DC constant voltage output converter by researching a key technology of a double-voltage input boosting DC-DC constant voltage output direct current converter based on push-pull topology so as to overcome the defects in the prior art.
The technical scheme for solving the technical problems is as follows: the DC constant voltage output converter comprises a 12V or 24V low voltage power input, an auxiliary power circuit, an automatic frequency switching circuit, a PWM regulation circuit and a boost output rectifying and filtering circuit, and is characterized in that: the system also comprises a potential logic protection circuit, a push-pull type boosting topological circuit and an output constant voltage automatic switching circuit; the auxiliary power circuit is respectively connected with the automatic frequency switching circuit and the potential logic protection circuit, the automatic frequency switching circuit adjusts the parameters of the oscillating circuit according to the input voltage level to ensure PWM frequency adaptation, and the push-pull type boosting topology circuit is driven by PWM signals and is sequentially connected with the output constant-voltage automatic switching circuit and the boosting output rectifying and filtering circuit; the output constant voltage automatic switching circuit comprises a push-pull type transformer, a change-over switch K1, a switch driving circuit and a rectifying and filtering circuit, wherein the push-pull type transformer is connected with the rectifying and filtering circuit through the change-over switch K1, an input winding of the push-pull type transformer comprises two windings with the same turns and center taps, an output winding of the push-pull type transformer is two independent windings with the same turns, the switch driving circuit comprises a triode, a zener diode, a resistor and a capacitor, the anode end of the zener diode is connected with a triode base, and the cathode end of the zener diode is connected to a direct current power supply through a resistor R2; the base circuit of the triode is formed by connecting a resistor R1 and a capacitor C4 in parallel, and one end of the base circuit is grounded; the collector end of the triode is connected with a relay coil of the change-over switch K1, and a freewheeling diode D7 is connected in parallel with the relay coil, and the freewheeling diode D7 and the relay coil are connected to a direct current power supply; the change-over switch K1 is a double-pole double-throw relay, normally closed contacts of the change-over switch K1 are respectively connected with A, D ports of two output windings of the push-pull transformer, and normally open contacts of the change-over switch K1 are connected with B, C ports, so that A, D ports of the push-pull transformer are connected with diodes D1, D2, D3 and D4 to form a bridge rectifier circuit when a relay armature is in a release state; in the armature actuation state of the relay, the center tap of the push-pull transformer is connected with the cathodes of the diodes D4 and D3, and the ports of the push-pull transformer A, D are respectively connected with the anodes of the diodes D1 and D2 to form a full-wave rectifying circuit.
The reference value of the zener diode is selected between 15V and 21V.
The zener diode comprises series-connected zener diodes D5 and D6, and satisfies: 15V < (VD5+VD6) < 21V.
The rectifying and filtering circuit comprises diodes D1-D4.
The rectification filter circuit comprises two aluminum electrolytic capacitors which are connected in parallel.
The potential logic protection circuit comprises a comparator circuit and a logic compound circuit, wherein the comparator circuit is provided with n groups of comparators, n threshold point potentials U_set_1, & gt and U_set_n, each group of comparators is provided with two comparators so as to obtain 2n comparison output voltages U_out_1, & gt and U_out_2n, the input is divided into two independent voltage division type branches by the undervoltage and overvoltage sampling of the comparison voltage U_in, and the undervoltage sampling voltage division type branch comprises a resistor R 1 And R is 2 The overvoltage sampling voltage division branch comprises a resistor R 3 And R is 4 The method comprises the steps of carrying out a first treatment on the surface of the The inverting terminal of the even number comparator is connected with and connected with the R 1 And R is 2 A voltage divider circuit formed so that R 1 And R is R 2 The voltage obtained after the voltage division is respectively sent to the inverting terminal of the even-numbered comparator and is compared with the threshold potential of the non-inverting terminal, so that the even-numbered comparator obtains the under-voltage state of each of n paths; the non-inverting terminal of the odd-numbered comparator is connected with and connected with the R 3 And R is R 4 A voltage divider circuit formed so that R 3 And R is R 4 The voltage obtained after the voltage division is respectively sent to the same-phase end of the odd-numbered comparator and is compared with the threshold potential of the opposite-phase end, so that the odd-numbered comparator obtains the overvoltage state of each of n paths.
The logic compound circuit comprises n groups of logic input signals, each group of logic input signals is input to n operation output signals obtained by n two-input OR logic gates, and the n operation output signals are sent to AND logic gates to finally obtain a compound output signal U_out.
Resistor R 1 、R 2 、R 3 、R 4 The parameters are determined according to the following formula:
wherein, the liquid crystal display device comprises a liquid crystal display device,
the beneficial effects of the invention are as follows:
1) The invention provides a scheme of a switching power supply integrating power conversion aiming at 12V and 24V double inputs, and designs a potential logic monitoring circuit, winding distribution of a high-frequency step-up transformer and an output constant voltage automatic switching circuit corresponding to the potential logic monitoring circuit. The potential logic monitoring circuit can judge according to different states (under voltage, overvoltage and normal) of the input bus voltage, so that the starting and stopping of the whole circuit are controlled by controlling the PWM module. The output constant voltage automatic switching circuit ensures safe and stable voltage output under different input voltages. The high-frequency step-up transformer connected with the push-pull topology is specially designed in winding distribution so as to adapt to two different input voltages. The automatically switched output constant voltage circuit after the step-up transformer can ensure constant voltage output at different inputs.
The invention adopts a pure hardware circuit design scheme, has quick response and high reliability, and does not have the problem of 'dead halt' of programs in software during long-term operation. Aiming at the double-input state, a double-circuit composite window voltage comparator circuit is designed, and potential logic protection is realized; the winding structure of the traditional push-pull type boost high-frequency transformer is improved, and a constant voltage switching circuit matched with the winding structure is designed; and two different solutions of bridge\full wave are provided for the output constant voltage switching mode. The design scheme of the key technologies can provide a reference function for practical engineering application.
The invention adopts an improved window comparator, adopts a pure hardware design scheme aiming at a state detection and logic judgment circuit of multi-stage voltage input, has quick response and high reliability, and does not have the problem of 'dead halt' of programs in software during long-term operation. Based on a simple basic threshold voltage window comparator circuit, a two-stage window voltage comparator is analyzed, a two-stage and multi-stage composite window voltage comparator is designed and applied to a state detection and logic judgment circuit of 12V and 24V two-stage voltage input, the rationality and practicality of the multi-stage composite voltage window comparator are verified through simulation and experiments, and a reference function can be provided for practical related engineering application.
2) The design scheme is applied to an actual inverter power supply, and strict tests are carried out under different input voltages (12V and 24V), so that transient response tests during high-power loads are passed. The dual input function reduces the strict requirements on the input power supply and has practicability.
Drawings
Fig. 1 is a schematic diagram of a push-pull transformer circuit according to the present invention.
Fig. 2 is a schematic block diagram of the circuit of the present invention.
Fig. 3 is a diagram of a bridge or full wave rectified constant voltage output circuit of the present invention.
Fig. 4 is an equivalent schematic diagram of a bridge or full-wave rectifying constant voltage conversion circuit of the present invention, in which fig. 4 (a) is an equivalent schematic diagram of a bridge rectifying output constant voltage conversion circuit and fig. 4 (b) is an equivalent schematic diagram of a full-wave rectifying output constant voltage conversion circuit.
Fig. 5 is a diagram of the multi-stage output characteristics of the circuit of the present invention.
Fig. 6 is a circuit diagram of a multi-stage composite window comparator of the present invention.
Fig. 7 is a logic complex circuit diagram of the present invention.
Fig. 8 is an input dual voltage level logic protection circuit of the present invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the invention.
In the description of the present invention, it should be understood that the terms "center," "lateral," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," and the like indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, merely to facilitate description of the present invention and simplify the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Unless otherwise indicated, the meaning of "a plurality" is two or more.
In the description of the present invention, it should be noted that, unless explicitly stated and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixed connections; or can be detachably connected or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The above terms are understood in the specific meaning of the present invention according to circumstances, for those of ordinary skill in the art.
Referring to fig. 1 to 4, the invention provides a DC constant voltage output converter, which comprises a 12V or 24V low voltage power input, an auxiliary power circuit, an automatic frequency switching circuit, a PWM regulation circuit, a boost output rectifying and filtering circuit, and is characterized in that: the system also comprises a potential logic protection circuit, a push-pull type boosting topological circuit and an output constant voltage automatic switching circuit; the auxiliary power circuit is respectively connected with the automatic frequency switching circuit and the potential logic protection circuit, the automatic frequency switching circuit adjusts the parameters of the oscillating circuit according to the input voltage level to ensure PWM frequency adaptation, and the push-pull type boosting topology circuit is driven by PWM signals and is sequentially connected with the output constant-voltage automatic switching circuit and the boosting output rectifying and filtering circuit; the output constant voltage automatic switching circuit comprises a push-pull type transformer, a change-over switch K1, a switch driving circuit and a rectifying and filtering circuit, wherein the push-pull type transformer is connected with the rectifying and filtering circuit through the change-over switch K1, an input winding of the push-pull type transformer comprises two windings with the same turns and center taps, an output winding of the push-pull type transformer is two independent windings with the same turns, the switch driving circuit comprises a triode, a zener diode, a resistor and a capacitor, the anode end of the zener diode is connected with a triode base, and the cathode end of the zener diode is connected to a direct current power supply through a resistor R2; the base circuit of the triode is formed by connecting a resistor R1 and a capacitor C4 in parallel, and one end of the base circuit is grounded; the collector end of the triode is connected with a relay coil of the change-over switch K1, and a freewheeling diode D7 is connected in parallel with the relay coil, and the freewheeling diode D7 and the relay coil are connected to a direct current power supply; the change-over switch K1 is a double-pole double-throw relay, normally closed contacts of the change-over switch K1 are respectively connected with A, D ports of two output windings of the push-pull transformer, and normally open contacts of the change-over switch K1 are connected with B, C ports, so that A, D ports of the push-pull transformer are connected with diodes D1, D2, D3 and D4 to form a bridge rectifier circuit when a relay armature is in a release state; in the armature actuation state of the relay, the center tap of the push-pull transformer is connected with the cathodes of the diodes D4 and D3, and the ports of the push-pull transformer A, D are respectively connected with the anodes of the diodes D1 and D2 to form a full-wave rectifying circuit. The specific description is as follows:
in Push-Pull topologies (Push-Pull), the transformer input and output windings are typically made up of two sets of symmetrical windings with taps in the middle. And symmetrical input windings enable the transformer core to work in a third type of working state, and the power supply topology has good magnetic core utilization rate in the conversion process. At an input DC voltage of U i In the case of (2), if the transformation ratio is set to K, the output voltage satisfies U o ＝U i K; if a new DC voltage U is to be applied at this time i ’＝2U i As input, then the new output voltage now satisfies U o ’＝U i ’/K＝2U o . It can be seen that under different input voltages, an overvoltage input will be generatedAnd (3) a phenomenon occurs.
To solve the above problem, the output of the transformer of the push-pull topology is designed as two independent windings, as shown in fig. 1. And the series or parallel connection mode of two independent output windings is switched through the peripheral circuit, or the rectification mode corresponding to the alternating voltage of the output winding of the transformer is switched, so that the circuit output is constant voltage, and the overvoltage phenomenon is solved. The input winding of the transformer is composed of two windings with the same number of turns and is provided with a center tap, and n is used for each 11 、n 12 Indicating the number of turns. The output winding is composed of two independent windings with the same number of turns, and n is used for each 21 、n 22 Indicating the number of turns. Assuming a number of turns n 11 ＝n 12 ＝N 1 Number of turns n 21 ＝n 22 ＝N 2 . According to known conditions, e.g. input voltage U i Output voltage U o Output power P o The PWM frequency f and the duty ratio D are used for estimating the conversion efficiency eta, the coil current density i can be solved, and parameters such as the required transformer core specification, the enamelled wire diameter and the like are selected. N (N) 1 、N 2 The value can be solved according to the following formula:
the automatic switching output constant voltage circuit behind the step-up transformer can ensure constant voltage output in different inputs, and is applied to a step-up circuit of a two-stage input inverter power supply. The overall design block diagram is shown in fig. 2. The low voltage power supply (12V or 24V) serves as an input to the overall power supply circuit. The stable 15V and 5V output by the auxiliary power circuit are provided for the control circuit to be used as power supply; the automatic frequency switching circuit can adjust the parameters of the oscillating circuit according to the input voltage level to ensure the PWM frequency adaptation; the push-pull type boost circuit is driven by PWM signals, is matched with an output constant voltage automatic adjustment circuit, is switched according to automatic judgment (12V or 24V) of input voltage, converts different low-voltage direct current inputs into 380V (effective value) square wave high voltage with constant output voltage, and obtains a path of 380V rear-stage bus high voltage after passing through the output rectifying and filtering circuit.
The whole design scheme also comprises an overcurrent protection circuit and an overvoltage protection circuit, and the two protection circuits are used as feedback signals and introduced into the PWM enabling end. The overcurrent protection circuit judges whether overcurrent and short circuit phenomena exist in the boosting process by monitoring the on-voltage drop voltage of the transistor by utilizing the internal resistance characteristic of the transistor, and if so, the PWM output is turned off in time; the overvoltage protection circuit immediately turns off the PWM output under the overvoltage condition by monitoring the condition of the output voltage.
The input windings of the push-pull topology connected transformer are two N 1 The winding of the turn coil has two independent turns N 2 Is formed by windings. When the input voltage is U i When the two output windings output effective values U o Is a square wave voltage of (a); when the input voltage is 2U i When each output winding outputs an effective value of 2U o Is a square wave voltage of (a). Based on this, the following scheme of output constant voltage automatic switching is designed:
the properties of bridge rectification and full-wave rectification are as follows: the rectification object of a bridge rectification circuit is only one coil winding, and the voltage of rectification filtering output is determined by the number of turns of the coil; the rectification object of a full-wave rectification circuit is two symmetrical coil windings, the two coils form a combined coil with a tap at the center, the voltage of the rectification filtering output is determined by the two symmetrical coils at the same time, and the voltage of the rectification filtering output is determined by the same coil because of the symmetry of the coils (the number of turns of the coils is equal and the polarities of the two coils are different at the center tap).
Referring to fig. 3, two output windings of the step-up transformer are connected to a double pole double throw relay, and the relay coil K1 is controlled by a 17.1V voltage state flip circuit consisting of R2, D6, D5, R1, C4, and Q1.
When the input voltage (V-BAT) is lower than 17.1V (12V input), the relay armature is in a released state (state of the relay in fig. 3), and the circuit analysis shows that the ports 'OUT B' and 'OUT C' are in a short-circuited state (the output windings are equivalent to series output) and have no connection with the rectifying circuit, and the ports 'OUT a' and 'OUT D' are taken as outputs, and form a bridge rectifying mode with four diodes (D4, D3, D1 and D2 in the figure), and the rectifying objects are two identical N 2 2N formed by serially connecting turns 2 The turn coil, so the voltage after rectifying and filtering is 2U o The equivalent principle is shown in fig. 4 (a); similarly, when the input voltage (V-BAT) is higher than 17.1V (24V input), the relay armature is in the pull-in state, and the circuit analysis shows that the ports 'OUT B' and 'OUT C' are in the short-circuited state, the transformer center tap formed by the ports 'OUT C' and 'OUT B' is connected with the cathodes of the diodes D4 and D3, and the ports 'OUT a' and 'OUT D' are respectively connected with the anodes of the diodes D1 and D2 to form a full-wave rectification mode, and the rectification objects are two identical N 2 The turns are connected in series to form a coil with a tap at the center, and the actual rectification object is equivalent to N 2 A coil of turns, so that the voltage after rectifying and filtering is 2U o The equivalent principle is shown in fig. 4 (b). In this way, the constant voltage conversion is also achieved.
Referring to fig. 5-8, the potential logic protection circuit includes a comparator circuit, a logic complex circuit, and is characterized in that: the comparator circuit has n groups of comparators, n threshold point potentials u_set_1, & gt, u_set_n, each group of comparators having two comparators to obtain 2n comparison output voltages u_out_1, & gt, u_out_2n, the input being divided into two independent voltage dividing branches by undervoltage and overvoltage samples of the comparison voltage u_in, the undervoltage sampling voltage dividing branch comprising a resistor R 1 And R is 2 The overvoltage sampling voltage division branch comprises a resistor R 3 And R is 4 . R is R 1 And R is R 2 The divided voltages are respectively sent to the inverting terminals of the even numbered (A2, A4,) and (A2 n) comparators in FIG. 2, and are electrically connected with the threshold values of the non-inverting terminalsThe phase comparison, the even number comparator obtains the under-voltage state of each path in n paths (under-voltage state when outputting high level, non-under-voltage state when outputting low level); r is R 3 And R is R 4 The voltage obtained after voltage division is respectively sent to the same phase end of the odd number (A1, A3, &..A (2 n-1)) comparator and is compared with the threshold potential of the opposite phase end, at the moment, the odd number comparator obtains the overvoltage state of each of the n paths (the overvoltage state when the output high level is the overvoltage state, and the non-overvoltage state when the output low level is the non-overvoltage state). The specific description is as follows:
the design of the circuit is divided into two parts, wherein one part is a multi-stage composite window comparator circuit, and the other part is a logic composite circuit. And the circuit output characteristic diagram is shown in fig. 5.
In fig. 5, u_low_1, u_high_1, u_low_2, u_high_2, …, u_low_n, and u_high_n represent the first-stage low threshold voltage point, the first-stage high threshold voltage point, the second-stage low threshold voltage point, the second-stage high threshold voltage point, the nth-stage low threshold voltage point, and the nth-stage high threshold voltage point of the multi-stage input voltage, respectively (there are other stages of high and low threshold voltage points therebetween not shown). Meanwhile, the threshold point potential satisfies U_high_n > U_low_n > … > U_high_2 > U_low_2 > U_high_1 > U_low_1. If U_in is less than U_low_x, the condition is called as corresponding to the under-voltage condition under the x-th stage; if U_low_x is less than U_in and less than U_high_x, the normal condition under the corresponding x-th level is called; if U_in > U_high_x, this is referred to as an overpressure condition at stage x.
The structure of the multi-stage composite window comparator circuit is shown in fig. 6, and the structure of the logic composite circuit is shown in fig. 7.
The multi-stage composite window comparator circuit has 2n comparators (A1, A2, A3, A4,) a (2 n-1), A2 n), n threshold point potentials (u_set_1, u_set_2,) and u_set_n), and 2n comparison output voltages (u_out_1, u_out_2, u_out_3, u_out_4,) and u_out_ (2 n-1) and u_out_2 n.
Here, as is clear from the properties of the upper and lower limit values of the threshold point potential, the upper and lower limit values of each level potential satisfy u_high_n > u_low_n > u_high_ (n-1) > u_low_ (n-1) > u_high_1 > u_low_1 in the n-level input. Meanwhile, the respective threshold point potentials of the multi-stage composite window comparator circuit should satisfy u_set_n > u_set_ (n-1) > u_set_1.
The circuit divides the under-voltage and over-voltage sampling of the input compared voltage U_in into two independent voltage division branches. R in undervoltage sampling partial pressure branch route diagram 1 And R is 2 R in component, overvoltage sampling partial pressure branch route diagram 3 And R is 4 Composition is prepared.
R is R 1 And R is R 2 The voltage obtained after voltage division is respectively sent to the inverting terminals of the comparators with even numbers (A2, A4, &..and A2 n) and is compared with the threshold potential of the non-inverting terminal, and at the moment, the comparator with even numbers obtains the under-voltage state of each of n paths (under-voltage state when outputting high level and non-under-voltage state when outputting low level); r is R 3 And R is R 4 The divided voltages are respectively sent to the non-inverting terminal of the odd-numbered (A1, A3,..and a (2 n-1)) comparator in fig. 2, and compared with the threshold voltage of the inverting terminal, at this time, the odd-numbered comparator obtains an overvoltage state (an overvoltage state when a high level is output, and a non-overvoltage state when a low level is output) of each of the n paths. The comparison output voltages (u_out_1, u_out_2, u_out_3, u_out_4, i.e., u_out_ (2 n-1), u_out_2n) obtained by the 2 n-way comparator are subjected to voltage logic combination by the logic circuit of fig. 2, so that a one-way multi-stage input potential logic judgment signal output can be obtained.
As can be seen, the lower limit values u_low_1, u_low_2, u_low_n and the upper limit values u_high_1, u_high_2 of the n-way voltage inputs become threshold point potentials in the equivalent undervoltage state and overvoltage state under the corresponding inputs. The input voltage is compared with u_set_1, u_set_2, and u_set_n after being valued by the voltage dividing circuit, which is equivalent to the input voltage being directly compared with u_low_1, u_high_1, u_low_2, u_high_2, u_low_n, and u_high_n. The method converts the undervoltage area and the overvoltage area into two ways, and the needed potential discrimination can be formed by using n comparison threshold point potentials in the circuit, which is also the principle that the circuit has fewer than the conventional multi-limit comparator circuit on the threshold point potentials.
The parameters of the design are determined according to the following formula:
wherein the method comprises the steps of
In designing the determination parameters, u_low_1, u_high_1, u_low_2, u_high_2, u_low_n, u_high_n are to be specified. The values for u_set_1, u_set_2, and u_set_n can then be determined first, and R can be determined using the above formula 1 、R 2 、R 3 、R 4 Parameter setting of the whole circuit is realized.
The multi-stage composite window comparator circuit scheme is applied to electronic circuits of two different input voltage levels, 12V and 24V. An input dual voltage level logic protection circuit as shown in fig. 8 is obtained. As shown, the under-voltage and over-voltage sampling of the input voltage (V-BAT) is divided into two independent voltage dividing branches. R in undervoltage sampling partial pressure branch route diagram 1 And R is 2 R in component, overvoltage sampling partial pressure branch route diagram 3 And R is 4 Composition is prepared.
Meanwhile, under the input level of 12V, the undervoltage and overvoltage values are respectively 10.5V and 15V; at 24V input level, the undervoltage and overvoltage values are 21V and 30V, respectively.
By calculation, the four resistors can take on values:
R 1 ＝24K ohm，R 2 ＝11K ohm，R 3 ＝39K ohm，R 4 =11kohm. The two divided sampling signals are respectively sent to four comparator units A, B, C, D of the LM339 chip. Two zener diodes (zener diodes, BZV-B3V 3) are connected in series to form comparison reference voltages of four comparators, wherein each zener diode is connected in parallel with a ceramic capacitor with the capacity of 10nF as a high-frequency bypass capacitor, and interference signals from the inside and outside of the circuit of the comparison reference voltages are filtered. Since the LM339 comparator belongs to the "open drain" output, a "pull-up" resistor with a resistance of 2Kohm is added at the output of each comparator cell,to ensure that the correct state can be output.
The outputs of the four comparators are coupled to subsequent logic gates. Because the CMOS logic chip works in 5V mode, one level voltage divider circuit is added to the output end of each comparator to make the input voltage reach the input standard of the CMOS logic chip. The circuit is connected according to fig. 2, when the comparator output is high, the input voltage is indicated to be in an undervoltage or overvoltage state; when the comparator outputs a low level, it indicates that the input voltage is within a reasonable operating range.
As can be analyzed, the output terminals OA and OB of the comparator unit A, B output high levels, corresponding to the overvoltage and undervoltage protection outputs at the 12V battery input; and the output ends OC and OD of the comparator unit C, D respectively correspond to the overvoltage and undervoltage protection outputs when the 24V battery is input when the output ends OC and OD are at high level.
The four-way logic signal OA, OB, OC, OD is fed into a logic complex circuit conforming to the logic expression "control_out=oa·od+ob+oc", and finally the complex output signal control_out is obtained.
While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents, and modifications which are not to be construed as being within the scope of the invention.
Claims (6)
1. The DC constant voltage output converter comprises a 12V or 24V low voltage power input, an auxiliary power circuit, an automatic frequency switching circuit, a PWM regulation circuit and a boost output rectifying and filtering circuit, and is characterized in that: the system also comprises a potential logic protection circuit, a push-pull type boosting topological circuit and an output constant voltage automatic switching circuit; the auxiliary power circuit is respectively connected with the automatic frequency switching circuit and the potential logic protection circuit, the automatic frequency switching circuit adjusts the parameters of the oscillating circuit according to the input voltage level to ensure PWM frequency adaptation, and the push-pull type boosting topology circuit is driven by PWM signals and is sequentially connected with the output constant-voltage automatic switching circuit and the boosting output rectifying and filtering circuit;
the output constant voltage automatic switching circuit comprises a push-pull type transformer, a change-over switch K1, a switch driving circuit and a rectifying and filtering circuit, wherein the push-pull type transformer is connected with the rectifying and filtering circuit through the change-over switch K1, an input winding of the push-pull type transformer comprises two windings with the same turns and center taps, an output winding of the push-pull type transformer is two independent windings with the same turns, the switch driving circuit comprises a triode, a zener diode, a resistor and a capacitor, the anode end of the zener diode is connected with a triode base, and the cathode end of the zener diode is connected to a direct current power supply through a resistor R2; the base circuit of the triode is formed by connecting a resistor R1 and a capacitor C4 in parallel, and one end of the base circuit is grounded; the collector end of the triode is connected with a relay coil of the change-over switch K1, and a freewheeling diode D7 is connected in parallel with the relay coil, and the freewheeling diode D7 and the relay coil are connected to a direct current power supply; the change-over switch K1 is a double-pole double-throw relay, normally closed contacts of the change-over switch K1 are respectively connected with A, D ports of two output windings of the push-pull transformer, and normally open contacts of the change-over switch K1 are connected with B, C ports, so that A, D ports of the push-pull transformer are connected with diodes D1, D2, D3 and D4 to form a bridge rectifier circuit when a relay armature is in a release state; in the relay armature attraction state, the center tap of the push-pull transformer is connected with the cathodes of the diodes D4 and D3, and the ports of the push-pull transformer A, D are respectively connected with the anodes of the diodes D1 and D2 to form a full-wave rectifying circuit; the reference value of the voltage stabilizing diode is selected from 15V to 21V;
the potential logic protection circuit comprises a comparator circuit and a logic compound circuit, wherein the comparator circuit is provided with n groups of comparators, n threshold point potentials U_set_1, & gt and U_set_n, each group of comparators is provided with two comparators so as to obtain 2n comparison output voltages U_out_1, & gt and U_out_2n, the input is divided into two independent voltage division type branches by the undervoltage and overvoltage sampling of the comparison voltage U_in, and the undervoltage sampling voltage division type branch comprises a resistor R 1 And R is 2 The overvoltage sampling voltage division branch comprises a resistor R 3 And R is 4 The method comprises the steps of carrying out a first treatment on the surface of the The inverting terminal of the even number comparator is connected withConnect and connect with the R 1 And R is 2 A voltage divider circuit formed so that R 1 And R is R 2 The voltage obtained after the voltage division is respectively sent to the inverting terminal of the even-numbered comparator and is compared with the threshold potential of the non-inverting terminal, so that the even-numbered comparator obtains the under-voltage state of each of n paths; the non-inverting terminal of the odd-numbered comparator is connected with and connected with the R 3 And R is R 4 A voltage divider circuit formed so that R 3 And R is R 4 The voltage obtained after the voltage division is respectively sent to the same-phase end of the odd-numbered comparator and is compared with the threshold potential of the opposite-phase end, so that the odd-numbered comparator obtains the overvoltage state of each of n paths.
2. The DC constant voltage output converter of claim 1, wherein: the zener diode comprises series-connected zener diodes D5 and D6, and satisfies: 15V < (VD5+VD6) < 21V.
3. A DC constant voltage output converter according to claim 1 or 2, characterized in that: the rectifying and filtering circuit comprises diodes D1-D4.
4. A DC constant voltage output converter as claimed in claim 3, wherein: the rectification filter circuit comprises two aluminum electrolytic capacitors which are connected in parallel.
5. The DC constant voltage output converter of claim 1, wherein: the logic compound circuit comprises n groups of logic input signals, each group of logic input signals is input to n operation output signals obtained by n two-input OR logic gates, and the n operation output signals are sent to AND logic gates to finally obtain a compound output signal U_out.
6. A DC constant voltage output converter as claimed in claim 1 or 5, wherein: resistor R 1 、R 2 、R 3 、R 4 The parameters are determined according to the following formula:
wherein, the liquid crystal display device comprises a liquid crystal display device,
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| WO2007118400A1 (en) * | 2006-04-13 | 2007-10-25 | Emerson Network Power Energy Systems Ab | A hardware overvoltage breakaway circuit |
| CN106134509B (en) * | 2009-09-15 | 2013-06-19 | 北京卫星制造厂 | The tandem type DC/DC converter that a kind of constant pressure and flow regulates automatically |
| CN106849683A (en) * | 2017-01-12 | 2017-06-13 | 南京工业大学 | A kind of converter based on push-pull topology structure of input-series and output-parallel |
| CN208015596U (en) * | 2018-04-23 | 2018-10-26 | 顺德职业技术学院 | A kind of DC constant pressures output translator |
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| WO2007118400A1 (en) * | 2006-04-13 | 2007-10-25 | Emerson Network Power Energy Systems Ab | A hardware overvoltage breakaway circuit |
| CN106134509B (en) * | 2009-09-15 | 2013-06-19 | 北京卫星制造厂 | The tandem type DC/DC converter that a kind of constant pressure and flow regulates automatically |
| CN106849683A (en) * | 2017-01-12 | 2017-06-13 | 南京工业大学 | A kind of converter based on push-pull topology structure of input-series and output-parallel |
| CN208015596U (en) * | 2018-04-23 | 2018-10-26 | 顺德职业技术学院 | A kind of DC constant pressures output translator |
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