CN212909353U

CN212909353U - Digital direct-current power supply for supplying power to photovoltaic combiner box

Info

Publication number: CN212909353U
Application number: CN202021679640.7U
Authority: CN
Inventors: 史君海; 白正阁
Original assignee: Jiangsu Blue Sky Photovoltaic Technology Co ltd
Current assignee: Jiangsu Blue Sky Photovoltaic Technology Co ltd
Priority date: 2020-08-13
Filing date: 2020-08-13
Publication date: 2021-04-06
Anticipated expiration: 2030-08-13

Abstract

The utility model discloses a digital DC power supply for supplying power to a photovoltaic combiner box, which comprises a double-tube flyback topology main circuit, a switch tube driving circuit, an output voltage feedback circuit, an MCU circuit and a current type PWM control circuit; the double-tube flyback topology main circuit is electrically connected with the photovoltaic component string; the switching tube driving circuit is electrically connected with a switching tube in the double-tube flyback topology main circuit; the output voltage feedback circuit is electrically connected with the MCU circuit and the current type PWM control circuit; the MCU circuit is electrically connected with the power supply input end, and the MCU circuit is electrically connected with the output voltage feedback circuit and the current type PWM control circuit; the current type PWM control circuit is electrically connected with the switching tube driving circuit, the double-tube flyback topology main circuit and the MCU circuit. The safety to the personnel and equipment is higher, reduces the switch tube part cost of power.

Description

Digital direct-current power supply for supplying power to photovoltaic combiner box

Technical Field

The utility model relates to a photovoltaic conflux case power supply field especially relates to a digital DC power supply for photovoltaic conflux case power supply.

Background

Photovoltaic power generation is applied in a large scale, wherein a photovoltaic power generation system of a centralized grid-connected inverter is used, and a photovoltaic combiner box is required to be configured for collecting and monitoring the electric energy of photovoltaic component strings. And a current detection device is arranged in the photovoltaic combiner box to detect the current of each group of strings. The power supply of the current detection device is obtained from the high-voltage direct current output by the photovoltaic module string through a special direct current power supply. The special direct-current power supply is usually realized by adopting a single-tube flyback topology structure.

The direct-current power supply realized by adopting the single-tube flyback topological structure has the main defect that the voltage generated in the direct-current power supply exceeds the withstand voltage value of the photovoltaic component string by hundreds of volts, thereby threatening the safety of the photovoltaic component equipment. At present, in a large-scale photovoltaic power station, a 1000V photovoltaic power generation system is continuously used, and a 1500V photovoltaic power generation system is already the mainstream, so that the defect problem is more prominent.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a digital DC power supply for photovoltaic conflux case power supply adopts double-barrelled flyback topology, and photovoltaic module cluster output voltage is equated basically to switch tube operating voltage, and is safer to the person and equipment, uses at 1000V photovoltaic power generation system and 1500V photovoltaic power generation system simultaneously, because switch tube operating voltage reduces, and then reduces the switch tube device cost of power.

The utility model discloses a realize above-mentioned utility model purpose and adopt following technical scheme:

the utility model provides a digital DC power supply for supplying power to a photovoltaic combiner box, which comprises a double-tube flyback topology main circuit, a switch tube driving circuit, an output voltage feedback circuit, an MCU circuit and a current type PWM control circuit;

the double-tube flyback topology main circuit is electrically connected with the photovoltaic component string;

the switching tube driving circuit is electrically connected with a switching tube in the double-tube flyback topology main circuit;

the output voltage feedback circuit is electrically connected with the MCU circuit and the current type PWM control circuit;

the MCU circuit is electrically connected with the power supply input end, and the MCU circuit is electrically connected with the output voltage feedback circuit and the current type PWM control circuit;

the current type PWM control circuit is electrically connected with the switching tube driving circuit, the double-tube flyback topology main circuit and the MCU circuit.

Further, the double-tube flyback topology main circuit comprises a conducting working state and a stopping working state, and the conducting working state and the stopping working state are periodically switched.

Further, the dual-transistor flyback topology main circuit comprises a switching field effect transistor TR1, a switching field effect transistor TR2, a diode D1, a diode D2, a diode D3, a diode D4, a high-frequency transformer T1, a capacitor C1, a capacitor C2, a resistor R1 and a resistor R2, wherein the drain electrode of the switching field effect transistor TR1 is connected with a high-voltage direct current positive electrode Vin, the source electrode of the switching field effect transistor TR1 is connected with a primary side winding different name end of the high-frequency transformer T1, the primary side winding different name end of the high-frequency transformer T1 is simultaneously connected with a negative electrode of a diode D1, the positive electrode of a diode D1 is connected with a high-voltage direct current negative electrode GND, the negative electrode of a diode D2 is connected with a high-voltage direct current positive electrode Vin, the positive electrode of a diode D2 is connected with a primary side winding same name end of the high-frequency transformer T1, the winding same name end of the high-frequency transformer T1 is simultaneously connected with a winding, the dotted terminal of a secondary winding of the high-frequency transformer T1 is connected with the anode of a diode D4, the cathode of a diode D4 is connected with the anode of a capacitor C2, the cathode of the capacitor C2 is connected with the dotted terminal of the secondary winding, the anode and the cathode of a capacitor C2 are correspondingly connected with the anode Vo + and the cathode Vo of low voltage required by a current detection device, the dotted terminal of the other secondary winding of the high-frequency transformer T1 is connected with the anode of a diode D3, the cathode of the diode D3 is connected with the anode of a capacitor C1, the cathode of the capacitor C1 is connected with the dotted terminal of the secondary winding, one end of a resistor R1 is connected with the anode Vaux powered by electricity, and the other end is connected with the Vin end.

Furthermore, the switching tube driving circuit comprises a switching triode TR3, a switching triode TR4, an isolation transformer T2, a capacitor C3, a capacitor C4, a capacitor C5, a diode D5, a diode D6, a voltage regulator DZ1, a voltage regulator DZ2, a resistor R3, a resistor R4, a resistor R5 and a resistor R6 which form a driving circuit for closing or opening the switching field effect tube TR1 and the switching field effect tube TR2, a collector of the switching triode TR 9 is connected with a power-supply positive electrode Vaux, an emitter is simultaneously connected with an emitter of the switching triode TR4 and a positive electrode of the capacitor C3, a collector of the switching triode TR4 is connected with a power-supply negative electrode GND, a negative electrode of the capacitor C3 is connected with a power-supply terminal of a primary side winding of the isolation transformer T2, a different-name terminal of a primary side winding of the isolation transformer T2 is connected with a power-supply negative electrode GND, a secondary winding of the isolation transformer T2 has two secondary sides, and a secondary side of the same-name-side capacitor C, The anode of a capacitor C5, the cathodes of a capacitor C4 and a capacitor C5 are connected with the anodes of a voltage regulator tube DZ1 and a voltage regulator tube DZ2, the cathodes of a voltage regulator tube DZ1 and a voltage regulator tube DZ2 are connected with the cathodes of a diode D1 and a diode D2, the anodes of a diode D1 and a diode D2 are connected with the unlike ends of the secondary winding, the cathodes of a capacitor C4 and a capacitor C5 are simultaneously connected with one end of a resistor R3 and one end of a resistor R5, and the resistor R3, the other end of the resistor R5 is connected with the grids of a switch field effect transistor TR1 and a switch field effect transistor TR2, the sources of the switch field effect transistor TR1 and the switch field effect transistor TR2 are connected with the synonym end of a secondary winding of an isolation transformer T2, one ends of a resistor R4 and a resistor R6 are connected with the grids of a switch field effect transistor TR1 and a switch field effect transistor TR2, the other ends of the resistor R4 and a resistor R6 are connected with the sources of the switch field effect transistor TR1 and a switch field effect transistor TR2, and the bases of a switch triode TR3 and a switch triode TR4 are connected together.

Furthermore, the output voltage feedback circuit consists of an optocoupler U3, an adjustable voltage reference U4, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a capacitor C6 and a capacitor C7, one end of the capacitor C7 is connected with the cathode of a light emitting diode in an optocoupler U3 and the cathode of an adjustable voltage reference U4, the other end of the capacitor C7 is connected with a resistor R14 in series and is connected with a voltage signal output end, meanwhile, the series resistor R15 is connected with the reference end of the adjustable voltage reference U4, one end of the resistor R13 is connected with the series resistor R12 at the voltage signal output end, one end of a capacitor C7 is connected, the other end of the resistor R13 is connected with the other end of the capacitor C7 in series through a capacitor C6, the other end of the capacitor C7 is connected with the anode of the adjustable voltage reference U4, one end of the resistor R11 is connected with the cathode of a light-emitting diode in the optocoupler U3, and the other end of the resistor R11 is connected with the resistor R12 in parallel and connected with a voltage signal output end.

Further, the optocoupler U3 is a PC817 chip, and the adjustable voltage reference U4 is a TL431 chip.

Furthermore, the MCU circuit is composed of a microcontroller chip U1, a resistor R7, a resistor R8, a resistor R9 and a voltage regulator tube DZ3, wherein one end of the resistor R7 is connected with an electricity-using anode Vaux, the other end of the resistor R7 is connected with a cathode of the voltage regulator tube DZ3 and is simultaneously connected with a power supply anode of the microcontroller chip U1, a power supply cathode of the microcontroller chip U1 is connected with a power supply self-using cathode GND, an anode of the voltage regulator tube DZ3 is connected with the power supply self-using cathode GND, one ends of the resistors R8 and R9 are connected with the microcontroller chip U1, the other end of R8 is connected with a power supply input end Vin, the other end of R9 is connected with the power supply input end GND, and the microcontroller chip U1 is.

Further, the microcontroller chip U1 is the microcontroller chip STM8S 103.

Furthermore, the current type PWM control circuit is composed of a current type PWM control chip U2, a resistor R10 and a capacitor C8, the current type PWM control chip U2 is connected with the resistor R10, the capacitor C8, the other end of the resistor R10 is connected with a conducting current signal generated by the dual-transistor flyback topology main circuit, the other end of the capacitor C8 is connected with a power supply self-powered cathode GND, the current type PWM control chip U2 is connected with a microcontroller chip U1, the current type PWM control chip U2 is connected with the power supply self-powered cathode GND, the current type PWM control chip U2 is connected with bases of switching triodes TR3 and TR4, a PWM signal output by the U2 chip controls switching of the triodes TR3 and TR4, and further controls switching of the switching field effect transistors TR1 and TR 2.

The utility model has the advantages as follows:

the double-tube flyback topological structure reduces the requirement on the voltage resistance of the switching tube, the MCU realizes the digital control on the power supply, and simultaneously meets the requirements of a 1000V photovoltaic power generation system and a 1500V photovoltaic power generation system, and the under-voltage and over-voltage function is more suitable for the requirement of photovoltaic power generation during daytime power generation;

by adopting a double-tube flyback topological structure, the working voltage of the switching tube is basically equal to the output voltage of the photovoltaic module string, the photovoltaic module string is safer for people and equipment, and the requirements of using the 1000V photovoltaic power generation system and the 1500V photovoltaic power generation system are met, because the working voltage of the switching tube is reduced, the cost of the switching tube device of the power supply is further reduced.

Drawings

Fig. 1 is a schematic diagram of a digital switching dc power supply system according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a digital switching dc power supply circuit according to an embodiment of the present invention.

Detailed Description

Fig. 1 is a schematic diagram of a digital switching dc power supply system. The power supply consists of 5 functional circuits, which are respectively: the circuit comprises a double-tube flyback topology main circuit 1, a switching tube driving circuit 2, an output voltage feedback circuit 3, an MCU circuit 4 (microcontroller circuit) and a current type PWM control circuit 5.

The double-tube flyback topology main circuit 1 is electrically connected with the photovoltaic module string to lead in high-voltage direct current as a power input end, and the output end of the main circuit serves as a power output end to supply power to a photovoltaic current detection device in the combiner box. The main circuit comprises a conducting working state and a stopping working state. The working state is switched periodically, and the double-tube flyback topology main circuit 1 realizes that electric energy is converted from high-voltage direct current of the photovoltaic module string at the input end into stable low-voltage direct current at the output end.

The switching tube driving circuit 2 is electrically connected with a switching tube in the double-tube flyback topology main circuit 1, and outputs a switching signal to drive the switching tube in the double-tube flyback topology main circuit 1 to be switched on or switched off so as to convert the state of the main circuit, including a switching-on state and a switching-off state, of the main circuit to convert electric energy from high-voltage direct current of the photovoltaic module string into stable low-voltage direct current.

The output voltage feedback circuit 3 acquires an output voltage signal, and conditions the output voltage signal into a feedback signal in the modes of amplification, filtering, comparison and the like; the output voltage feedback circuit is electrically connected with the MCU circuit 4 and the current type PWM control circuit 5 respectively, and the feedback signal is sent to the MCU circuit 4 and the current type PWM control circuit 5.

And 4, monitoring the whole power supply by the MCU circuit. The MCU circuit is electrically connected with the power input end to obtain an input voltage signal; the MCU circuit is electrically connected with the output voltage feedback circuit 3 to obtain a feedback signal; the MCU circuit is electrically connected to the current-mode PWM control circuit 5, and outputs a frequency signal, which is used as the operating frequency of the current-mode PWM control circuit. The MCU circuit adjusts the cycle control power supply operating frequency of the frequency signal according to the input voltage signal size through compiling special programs, realizes power supply frequency modulation control, and enables the power supply to meet the use requirements of a 1000V photovoltaic power generation system and a 1500V photovoltaic power generation system. The MCU circuit judges whether the voltage of the input end of the power supply is within a working range or not according to the obtained input voltage signal, and when the voltage exceeds the working range, the output of the frequency signal is stopped, so that the power supply stops working, the protection of power supply input overvoltage or input undervoltage is realized, and meanwhile, the requirement of using the power supply in photovoltaic power generation in the daytime is met.

The current type PWM control circuit 5 is electrically connected with the switching tube driving circuit 2 and outputs a PWM signal to control the switching tube driving circuit 2 to generate a corresponding switching signal; the double-tube flyback topology main circuit 1 is electrically connected to obtain a conduction current signal; and the MCU circuit 4 is electrically connected to obtain a working frequency signal. The current mode PWM control circuit periodically operates according to the frequency signal. Under normal conditions, a PWM (pulse width modulation) conduction signal is output to the switching tube driving circuit 2 to conduct the switching tube in the double-tube flyback topology main circuit 1 when the period starts, and the current flowing through the switching tube is gradually increased; the current mode PWM control circuit 5 generates a turn-off threshold value according to a feedback signal of the output voltage feedback circuit 3; the current type PWM control circuit 5 compares the obtained switch tube on current signal of the dual-tube flyback topology main circuit 1 with the turn-off threshold, and immediately outputs a PWM turn-off signal to the switch tube driving circuit 2 to turn off the switch tube in the dual-tube flyback topology main circuit 1 when the on current signal exceeds the turn-off threshold, and keeps the PWM turn-off signal to the start time of the next new working period.

According to the scheme, the current type PWM chip is used for adjusting the duty ratio of the PWM signal, and the MCU controls the frequency of the PWM signal, so that the requirements of the 1000V photovoltaic power generation system and the 1500V photovoltaic power generation system under the condition can be met simultaneously.

Fig. 2 is a schematic diagram of a digital switching dc power supply circuit. In the figure, U1-U4 are integrated circuit chips; T1-T2 is a high frequency transformer; TR1-TR2 is a switching field effect transistor; TR3-TR4 is a switching triode; D1-D6 are diodes; DZ1-DZ3 are zener diodes; R1-R15 are resistors; C1-C8 are capacitors. In the figure, a chain line block diagram divides a circuit diagram into 5 parts of functional circuits, which are respectively as follows: the circuit comprises a double-tube flyback topology main circuit 1, a switching tube driving circuit 2, an output voltage feedback circuit 3, an MCU circuit 4, namely a microcontroller circuit, and a current type PWM control circuit 5.

In this embodiment, the main circuit of the dc power supply converts the electric energy obtained by the high-voltage dc output from the photovoltaic module string into the low-voltage stable electric energy required by the current detection device, and adopts a dual-transistor flyback topology circuit structure. The double-tube flyback topology main circuit 1 comprises switching field effect transistors (TR1 and TR2), diodes (D1, D2, D3 and D4), a high-frequency transformer (T1), capacitors (C1 and C2) and resistors (R1 and R2), wherein the T2 is provided with one primary winding and two secondary windings.

When the main circuit is in a conducting state, the switching field effect transistors TR1 and TR2 are turned on, and the freewheeling diode D1 and the freewheeling diode D2 are turned off in the reverse direction. The external photovoltaic component string is formed into a loop by Vin and a GND end through a switching field effect transistor TR1, a primary winding of a high-frequency transformer T1, a switching field effect transistor TR2 and a measuring resistor R2, and a freewheeling diode D1 and a freewheeling diode D2 are reversely cut off. The high-frequency transformer T1 stores energy; and the two windings on the secondary side of the high-frequency transformer, the freewheeling diode D3 and the freewheeling diode D4 are reversely cut off.

The voltage across the measuring resistor R2 is connected as an on-current signal to the current mode PWM control circuit 5.

When the main circuit is in an off state, the switching field effect transistors TR1 and TR2 are turned off, the freewheeling diode D1 and the freewheeling diode D2 are instantaneously and positively conducted, and the leakage inductance of the primary winding of the high-frequency transformer T1 is released to generate high-voltage current. The electric energy stored in the high-frequency transformer T1 is discharged through two circuits formed by the secondary winding of the high-frequency transformer T1. One secondary winding, a freewheeling diode D3, an output capacitor C1 and a power supply internal circuit connected with the capacitor C1 in parallel form a circuit loop. And the other secondary winding, a freewheeling diode D4, an output capacitor C2 and an external load connected in parallel with the capacitor C2 through the Vo + and Vo-terminals form a circuit loop to supply power to the external load.

When the switching field effect transistor is turned off instantaneously, electric energy stored by leakage inductance of a primary winding of the high-frequency transformer T1 passes through the forward conduction fly-wheel diode D1 and the fly-wheel diode D2, and a loop formed by Vin and a GND end and the photovoltaic component in series is quickly absorbed in a short time.

The drain electrode of the field effect transistor TR1 is connected with the high-voltage direct-current positive electrode Vin, and the source electrode of the field effect transistor TR1 is connected with the synonym terminal of the primary winding of the high-frequency transformer T1. The synonym terminal of the primary winding of the high-frequency transformer T1 is simultaneously connected with the cathode of the diode D1. The anode of the diode D1 is connected with the high-voltage direct current cathode GND. The cathode of the diode D2 is connected with the anode Vin of the high-voltage direct current, and the anode of the diode D2 is connected with the dotted terminal of the primary winding of the high-frequency transformer T1. The dotted terminal of the primary winding of the high-frequency transformer T1 is simultaneously connected with the drain of a field effect transistor TR2, the source of the field effect transistor TR2 is connected with one end of a resistor R2, and the other end of the resistor R2 is connected with a high-voltage direct current negative pole GND. A dotted terminal of a secondary winding of the high-frequency transformer T1 is connected with the anode of a diode D4, the cathode of a diode D4 is connected with the anode of a capacitor C2, the cathode of the capacitor C2 is connected with the dotted terminal of the secondary winding, and the anode and the cathode of a capacitor C2 are respectively and correspondingly connected with the anode Vo + and the cathode Vo-of low voltage required by a current detection device. The dotted terminal of the other secondary winding of the high-frequency transformer T1 is connected with the anode of a diode D3, the cathode of a diode D3 is connected with the anode of a capacitor C1, the cathode of the capacitor C1 is connected with the dotted terminal of the secondary winding, and the anode and the cathode of a capacitor C1 are respectively the anode Vaux and the cathode GND for power supply self. One end of the resistor R1 is connected with the positive pole Vaux of the power source, the other end is connected with the Vin end, and the resistor R1 flows a very small current and is mainly used for providing power supply starting electric energy.

The high-frequency transformer T1 plays a role of energy storage of the multi-winding inductor in the flyback power supply. And meanwhile, the switching field effect transistor TR1 and the switching field effect transistor TR2 are closed, current flows through the high-voltage direct current positive electrode Vin in sequence, and the switching field effect transistor TR1, the primary winding of the high-frequency transformer T1, the switching field effect transistor TR2, the resistor R2, the diode D1 and the diode D2 are reversely biased and cut off. Diode D3 and diode D4 are reverse biased off and there is no current in the secondary winding of high frequency transformer T1. The current of the primary winding of the high-frequency transformer T1 is increased, and the electric energy is converted into magnetic energy and stored in the high-frequency transformer T1.

And meanwhile, the switching field effect transistor TR1 and the switching field effect transistor TR2 are disconnected, the magnetic energy of the high-frequency transformer T1 is converted into electric energy, the diode D3 and the diode D4 are conducted in a forward bias mode through two windings on the secondary side, and the converted electric energy is respectively stored in a capacitor and is simultaneously supplied to a load for use. The process of converting electric energy into magnetic energy and converting magnetic energy into electric energy is continuously and periodically carried out in the high-frequency transformer T1, and the power supply stably supplies electric energy to the current detection device. The peak voltage generated by the leakage inductance of the primary winding of the high-frequency transformer T1 is clamped at the input high-voltage direct-current voltage level under the action of forward bias of the diode D1 and the diode D2, and the voltage borne by the switching field-effect tube TR1 and the switching field-effect tube TR2 does not exceed the high-voltage direct-current voltage level, so that the single-tube flyback topology circuit structure is superior to the single-tube flyback topology circuit structure.

The switching tube driving circuit 2 uses a single-ended isolation transformer driving scheme. The switching transistor TR3-TR4, the isolation transformer T2, the capacitor C3-C5, the diode D5-D6, the voltage regulator DZ1-DZ2 and the resistor R3-6 form a driving circuit for closing or opening the switching field effect transistor TR1-TR 2. The base electrodes of the switching triodes TR3-TR4 receive PWM signals generated by the current type PWM control circuit 5, and the output of the driving circuit is respectively connected to the grid electrodes and the source electrodes of the switching field effect transistors TR1 and TR2 and controls the on-off.

The base electrodes of the switching transistors TR3-TR4 receive PWM signals generated by the current type PWM control circuit 5, voltage square waves are formed at two ends of the primary side of the isolation transformer T2, and the capacitor C3 blocks direct current and conducts alternating current. The two secondary windings of the isolation transformer T2 output voltage square waves, capacitors C4 and C5 store energy and generate field effect transistors TR1 and TR2 to cut off negative voltage, a diode D5 and a voltage regulator DZ1 are connected in series to limit the terminal voltage of the capacitor C4, and a diode D6 and a voltage regulator DZ2 are connected in series to limit the terminal voltage of the capacitor C5.

The switching transistor TR3-TR4, the isolation transformer T2, the capacitor C3-C5, the diode D5-D6, the voltage regulator DZ1-DZ2 and the resistor R3-6 form a driving circuit for closing or opening the switching field effect transistor TR1-TR 2.

The collector of the switching transistor TR3(NPN tube) is connected to the positive electrode Vaux of the power source, the emitter thereof is connected to both the emitter of the transistor TR4(PNP tube) and the positive electrode of the capacitor C3, and the collector of the transistor TR4 is connected to the negative electrode GND of the power source. The negative pole of the capacitor C3 is connected to the dotted terminal of the primary winding of the isolation transformer T2. The synonym terminal of the primary winding of the isolation transformer T2 is connected with the negative pole GND of the power source. The secondary side of the isolation transformer T2 is provided with two windings, the dotted terminal of the secondary side winding is connected with the anode of a capacitor C4(C5), the cathode of a capacitor C4(C5) is connected with the anode of a voltage regulator tube DZ1(DZ2), the cathode of a voltage regulator tube DZ1(DZ2) is connected with the cathode of a diode D1(D2), and the anode of a diode D1(D2) is connected with the dotted terminal of the secondary side winding. The negative electrode of the capacitor C4(C5) is simultaneously connected with one end of the resistor R3(R5), the other end of the resistor R3(R5) is connected with the grid electrode of the switching field-effect tube TR1(TR2), and the source electrode of the switching field-effect tube TR1(TR2) is connected with the synonym end of the secondary winding of the isolation transformer T2. One end of the resistor R4(R6) is connected with the grid of the switch field effect transistor TR1(TR2), and the other end of the resistor R4(R6) is connected with the source of the switch field effect transistor TR1(TR 2). The switching transistors TR3 and TR4 are a pair of transistors, the bases of which are connected together.

The transistors TR3-TR4 are turned on and off alternately to generate square wave voltage, and the high level and the 0 level are alternated in sequence. The square wave voltage is applied to the primary side of the isolation transformer T2 through the capacitor C3, and the secondary side of the isolation transformer T2 generates an in-phase voltage square wave. The capacitor C3 plays a role of isolating direct current and preventing unbalanced saturation of the magnetic core of the isolation transformer T2 through alternating current. The high level is output from the dotted terminal of the secondary side of the isolation transformer T2, and is applied to the gate of the switching fet TR1(TR2) through the capacitor C4(C5) and the resistor R3(R5), thereby driving the switching fet TR1(TR2) to close and maintain the on state. When the secondary dotted terminal of the isolation transformer T2 outputs a 0 level, the capacitor C4(C5) applies a negative voltage to the gate of the switching fet TR1(TR2) via the resistor R3(R5) and the secondary winding of the isolation transformer T2, and accelerates the switching fet TR1(TR2) to turn off and maintain the off state. The terminal voltage of the capacitor C4(C5) is limited within a given range by a regulator tube DZ1(DZ2) and a diode D5 (D6). The resistor R4(R6) plays a role of protecting the effect transistor TR1(TR2) and providing a charging current loop of the capacitor C4 (C5).

The output voltage feedback circuit 3 adopts a scheme that TL431 and optical couplers form an isolation feedback amplifying circuit. The circuit is composed of an optocoupler U3, an adjustable voltage reference U4, resistors R11-R15 and capacitors C6-C7. The optocoupler U3 is selected from a PC817 or similar functional chip, and the adjustable voltage reference U4 is selected from a TL431 or similar compatible chip.

The optocoupler U3 plays roles of electrical isolation and signal transmission, the adjustable voltage reference U4 provides reference voltage and plays a role of a signal amplifier, the optocoupler U4 is matched with the resistors R11-R15 and the capacitors C6-C7 to realize the functions of signal comparison, amplification, filtering and the like, an output voltage signal is converted into a feedback signal, and the feedback signal is output to the pin 20 of the U1 and the pin 1 of the U2 through the pin 4 of the U3.

The MCU circuit 4, i.e., a microcontroller circuit, is composed of a microcontroller chip STM8S103 produced by semiconductor manufacturing by the intentional method, or a microcontroller chip having a similar function as a core. Only the part of the MCU circuit for realizing the power supply function is provided, and other parts are omitted. The controller consists of a microcontroller chip U1, resistors R7-R9 and a voltage regulator tube DZ 3. The microcontroller chip U1 adopts a microcontroller chip STM8S103, and can normally work within a wide voltage range of 2.95-5.5V; u1 contains a timing/counter for generating PWM wave signal as frequency signal; u1 contains an analog to digital converter that collects the input voltage signal. One end of the resistor R7 is connected with a power supply anode Vaux, the other end is connected with a cathode of a voltage regulator tube DZ3, and the anode of the voltage regulator tube DZ3 is connected with a power supply anode GND to form a voltage-stabilized power supply; they generate the MCU working voltage, and are connected with the pin 9 of the power supply positive input pin of U1. The power negative input pin 7 of the U1 is connected with the power self-using power negative GND, so that the U1 obtains working power.

Pins

19 and 20 of U1 are provided as analog signal input pins. The pin 19 of the U1 is connected with one end of a resistor R8 and one end of a resistor R9, the other end of the resistor R8 is connected with a power input end Vin, the other end of the resistor R9 is connected with a power input end GND, and the resistor R8-9 forms a voltage divider. The 20 pins of U1 are connected to the feedback signal output by the 4 pins of U3 in the output voltage feedback circuit 3. The 16 pins of the U1 are set as PWM signal output pins and are connected with the 4 pins of the U2 in the current-mode PWM control circuit 5. The PWM signal generated by the timing/counter of U1 is output to pin 4 of U2 via pin 16 as a frequency signal.

The microcontroller chip U1 realizes power supply monitoring through a program burned in the U1. The microcontroller chip U1 obtains the value corresponding to the input voltage signal through the internal analog-digital converter from the 19-pin voltage signal of U1, judges that the power input voltage is in a reasonable range through the number, and outputs the PWM signal generated by the timing/counter of U1 to the 4 pins of U2 through 16 pins as a frequency signal, so that the U2 works and the power supply works; otherwise, the timer/counter of the microcontroller chip U1 stops outputting the frequency signal to the U2, so that the U2 stops working and the power supply stops working. The microcontroller chip U1 obtains the corresponding value of the feedback signal output by the 4 pin of U3 by passing the 20 pin voltage signal of U1 through an internal analog-digital converter. The amplitude of the input voltage signal detected by the U1 is high or the amplitude of the feedback signal is low, the period of the frequency signal is enlarged, and the working frequency of the U2 is reduced; the amplitude of the input voltage signal detected by the U1 is low or the amplitude of the feedback signal is high, the period of the frequency signal is shortened, and the working frequency of the U2 is improved; the control of the power supply frequency is realized in such a way, and the output voltage of the power supply is regulated.

The current type PWM control circuit 5 is formed by using a current type PWM control chip UC3844 or a compatible chip as a core. The current-mode PWM control circuit is composed of a current-mode PWM control chip U2, a resistor R10 and a capacitor C8. The 3 pins of the current type PWM control chip U2 are current signal input pins, the current type PWM control chip U2 is connected with a resistor R10 and a capacitor C8, the other end of the resistor R10 is connected with a conducting current signal generated by the double-tube flyback topology main circuit 1, the other end of the capacitor C8 is connected with a power utilization cathode GND, and the capacitor C8 and the resistor R10 form an RC filter circuit to filter sharp pulses contained in the conducting current signal. The 4 pins of the U2 are connected with the 16 pins of the U1, and the 16 pins of the U1 output frequency signals as the working frequency of the U2. The pins 2 and 5 of the U2 are connected with a self-powered cathode GND. The 6 feet of the U2 chip is connected with the bases of the switching transistors TR3 and TR4, the PWM signal output by the U2 chip controls the switching of the transistors TR3 and TR4, and further controls the switching of the switching field effect transistors TR1 and TR 2. Pin 1 of U2 is connected to pin 20 of U1 and pin 4 of U3, and pin 4 of U3 outputs a feedback signal into pin 1 of U2. The PWM control chip U2 compares the signal of the 3 pin with the signal of the 1 pin, and changes the duty ratio of the PWM output by the 6 pin according to the comparison result, thereby regulating the output voltage of the DC power supply to be stable.

The above description specifically describes the preferred embodiment of the present invention, but of course, the present invention can also adopt different forms from the above embodiments, and equivalent changes or corresponding modifications made by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope of the present invention.

Claims

1. A digital direct current power supply for supplying power to a photovoltaic combiner box is characterized by comprising a double-tube flyback topology main circuit, a switching tube driving circuit, an output voltage feedback circuit, an MCU circuit and a current type PWM control circuit;

2. The digital direct-current power supply for supplying power to the photovoltaic combiner box according to claim 1, wherein the double-tube flyback topology main circuit comprises a conducting working state and a stopping working state, and the conducting working state and the stopping working state are periodically switched.

3. The digital DC power supply for supplying power to the photovoltaic combiner box of claim 2, wherein the main circuit of the double-tube flyback topology is composed of a switching field effect tube TR1, a switching field effect tube TR2, a diode D1, a diode D2, a diode D3, a diode D4, a high-frequency transformer T1, a capacitor C1, a capacitor C2, a resistor R1 and a resistor R2, the drain of the switching field effect tube TR1 is connected with the positive pole Vin of high-voltage DC, the source of the switching field effect tube TR1 is connected with the different-name end of the primary winding of the high-frequency transformer T1, the different-name end of the primary winding of the high-frequency transformer T1 is simultaneously connected with the negative pole of the diode D1, the positive pole of the diode D1 is connected with the negative pole GND of high-voltage DC, the negative pole of the diode D2 is connected with the positive pole of high-voltage DC, the positive pole of the diode D2 is connected with the same-name end of the winding of, the source of the field effect transistor TR2 is connected with one end of a resistor R2, the other end of R2 is connected with a high-voltage direct current cathode GND, the dotted terminal of a secondary winding of a high-frequency transformer T1 is connected with the anode of a diode D4, the cathode of a diode D4 is connected with the anode of a capacitor C2, the cathode of a capacitor C2 is connected with the dotted terminal of the secondary winding, the anode Vo + and the cathode Vo of low voltage required by a current detection device are correspondingly connected from the anode and the cathode of the capacitor C2, the dotted terminal of the other secondary winding of the high-frequency transformer T1 is connected with the anode of a diode D3, the cathode of a diode D3 is connected with the anode of a capacitor C1, the cathode of a capacitor C1 is connected with the dotted terminal of the secondary winding, one end of the resistor R1 is connected with an anode Va.

4. The digital DC power supply of claim 3, wherein the switching transistor driving circuit comprises a switching transistor TR3, a switching transistor TR4, an isolation transformer T2, a capacitor C3, a capacitor C4, a capacitor C5, a diode D5, a diode D6, a voltage regulator DZ1, a voltage regulator DZ2, a resistor R3, a resistor R4, a resistor R5 and a resistor R6, which form a driving circuit for closing or opening the switching field effect transistor TR1 and the switching field effect transistor TR2, a collector of the switching transistor TR3 is connected to a power-using positive electrode Vaux, an emitter is connected to both the emitter of the switching transistor TR4 and the positive electrode of the capacitor C3, a collector of the switching transistor TR4 is connected to a power-using negative electrode GND, a negative electrode of the capacitor C3 is connected to a power-using positive electrode GND of a primary winding of the isolation transformer T2, and a power-using a negative electrode of a primary winding of the isolation transformer T2, the secondary side of the isolation transformer T2 is provided with two windings, the dotted terminal of the secondary side winding is connected with the anode of a capacitor C4 and a capacitor C5, the cathode of the capacitor C4 and the cathode of the capacitor C4 are connected with the anode of a voltage regulator tube DZ 4 and the anode of the voltage regulator tube DZ 4, the cathodes of the voltage regulator tube DZ 4 and the voltage regulator tube DZ 4 are connected with the cathode of a diode D4 and the cathode of a diode D4, the anodes of the diode D4 and the anode of the diode D4 are connected with the dotted terminal of the secondary side winding, the cathodes of the capacitor C4 and the capacitor C4 are simultaneously connected with one end of a resistor R4 and one end of a resistor R4, the other end of the resistor R4 is connected with a gate of a switch field effect tube TR4 and the gate of the switch field effect tube TR4, the sources of the switch field effect tube TR4 and the switch TR4 are connected with the source of the switch field effect tube TR4 and the switch TR4 of the switch TR4 and the other end of the field effect tube TR4 is connected with the switch TR 4. The bases of the switching transistor TR3 and the switching transistor TR4 are connected together.

5. The digital DC power supply of claim 4, wherein the output voltage feedback circuit is composed of an optocoupler U3, an adjustable voltage reference U4, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a capacitor C6, and a capacitor C7, one end of the capacitor C7 is connected to the cathode of the light emitting diode in the optocoupler U3 and the cathode of the adjustable voltage reference U4, the other end of the capacitor C7 is connected in series with a resistor R14 to the voltage signal output end, the series resistor R15 is connected to the reference end of the adjustable voltage reference U4, one end of the resistor R13 is connected in series with the R12 to the voltage signal output end and is connected to one end of the capacitor C7, the other end of the resistor R13 is connected in series with a capacitor C6 to the other end of the capacitor C7, the other end of the capacitor C7 is connected to the anode of the adjustable voltage reference U4, one end of the R11 is connected to the cathode of the light emitting diode in the optocoupler U3, the other end of the resistor R11 is connected with a resistor R12 in parallel and connected with a voltage signal output end.

6. The digital direct current power supply for supplying power to the photovoltaic combiner box of claim 5, wherein the optocoupler U3 is a PC817 chip, and the adjustable voltage reference U4 is a TL431 chip.

7. The digital direct-current power supply for supplying power to the photovoltaic combiner box according to claim 5, wherein the MCU circuit is composed of a microcontroller chip U1, a resistor R7, a resistor R8, a resistor R9 and a voltage regulator tube DZ3, one end of the resistor R7 is connected with a power-using positive electrode Vaux, the other end of the resistor R7 is connected with a negative electrode of the voltage regulator tube DZ3 and is simultaneously connected with a power supply positive electrode of the microcontroller chip U1, a power supply negative electrode of the microcontroller chip U1 is connected with a power-using negative electrode GND, a power supply positive electrode of the voltage regulator tube DZ3 is connected with the power-using negative electrode GND, one ends of the resistors R8 and R9 are connected with the microcontroller chip U1, the other end of R8 is connected with a power supply input end Vin, the other end of R9 is connected with the power supply input end, and the microcontroller chip U.

8. The digital direct current power supply for supplying power to the photovoltaic combiner box of claim 7, wherein the microcontroller chip U1 is a microcontroller chip STM8S 103.

9. The digital direct current power supply for supplying power to the photovoltaic combiner box of claim 7, wherein the current type PWM control circuit is composed of a current type PWM control chip U2, a resistor R10 and a capacitor C8, the current type PWM control chip U2 is connected with the resistor R10, the capacitor C8, the other end of the resistor R10 is connected with a conducting current signal generated by the double-tube flyback topology main circuit, the other end of the capacitor C8 is connected with a power source from an electric negative pole GND, the current type PWM control chip U2 is connected with a microcontroller chip U1, the current type PWM control chip U2 is connected with the power source from the electric negative pole GND, the current type PWM control chip U2 is connected with bases of switching transistors TR3 and TR4, PWM signals output by the U2 control the switching of the transistors TR3 and TR4, and further control the switching of the switching field effect transistors TR1 and TR 2.