CN203827186U - DC equal-proportion isolating power supply - Google Patents

Abstract

The utility model discloses a DC equal-proportion isolated power supply, which comprises a non-gate RC multivibrator circuit and at least one isolation circuit connected to its output end, and the output end of each isolation circuit is connected with a corresponding output rectification filter circuit; The isolation circuit includes a driving transistor and a pulse transformer connected in sequence. Compared with the traditional switching power supply, the DC equal-proportion isolation power supply of the utility model has no feedback circuit between the output voltage and the input voltage of the circuit, and the output voltage depends on the input voltage and the transformation ratio of the pulse transformer; the output rectification The filter circuit utilizes the conduction process (positive process) of the previous stage switching circuit. The circuit of the isolated power supply is simple and low in cost. Under the condition that the load current at the output terminal fluctuates from tens of mA to tens of mA, the fluctuation of the output power supply voltage is only a few tenths of a volt, which can well meet the requirements of the DC electric energy meter for the power supply. requirements.

Description

A DC Equal Proportional Isolation Power Supply

technical field

The utility model relates to a DC equal-proportion isolation power supply.

Background technique

The traditional DC isolated power supply generally adopts flyback switching power supply technology or self-excited oscillation DC-DC conversion technology. Flyback switching power supply technology can obtain better output characteristics, but the circuit needs closed-loop feedback, the structure is more complicated, and the cost is higher. As shown in Figure 1, the flyback switching power supply circuit is mainly composed of driver chip U1, pulse transformer T1, flyback rectifier diodes D1~D3, filter capacitors C1~C3, reference voltage regulator DW1, feedback sampling circuit, photocoupler Composed of O1, etc., its working principle is as follows: the driver chip outputs a switch signal generated by the internal signal generating circuit, whose pulse width and frequency are controlled by the feedback voltage; The secondary side output is then rectified by diodes and filtered by capacitors to form a DC output; the stability of the output depends on the reference stabilized voltage source, feedback sampling circuit, photocoupler, etc. to feed back to the driver chip to adjust the switch signal output, so as to achieve the final stable two The purpose of secondary output. However, for circuits that require two sets of secondary DC outputs, since the two sets of DC outputs are isolated from each other and their load characteristics are not the same, only one set of outputs can be used for feedback (DC OUT1 in the figure), and this can only be guaranteed. The stability of the output of one group, the accuracy of the output of the other group (DC OUT2) will be poor.

As shown in Figure 2, the self-oscillating DC-DC conversion technology circuit is compared with the flyback switching power supply structure diagram. The circuit structure is simple and the cost is low, but the disadvantage is that the output characteristics are poor and the conversion efficiency is low.

In the vehicle-mounted DC electronic watt-hour meter, the power supply is taken from the DC working power system of the vehicle itself, and the metering part of the watt-hour meter is directly connected to the high-voltage power supply of the vehicle. In order to ensure safety, the power input of the watt-hour meter is The main circuit of the electric energy meter requires isolation; at the same time, the communication circuit of the electric energy meter also requires a separate isolated power supply; the power consumption of the electric energy meter is limited in the relevant standards, so the power supply of the electric energy meter requires high conversion efficiency; the power supply of the electric energy meter The consumption has a large fluctuation range, so the output characteristics of the power supply are required to be better; the current market competition in the electric energy meter industry is relatively fierce, so the cost is required to be controllable. Based on the above factors, the power supply of the electric energy meter is required to meet the four requirements of dual high-isolation output, high conversion efficiency, good output characteristics, and low cost at the same time. It is very difficult to use the current power supply technical solution.

Utility model content

The purpose of the utility model is to provide a DC equal-proportion isolated power supply to solve the problems of poor multi-channel output accuracy and low conversion efficiency of the existing DC isolated power supply.

In order to achieve the above purpose, the technical solution adopted by the utility model is: a DC equal-proportion isolated power supply, including at least one isolation circuit connected to the NOT gate RC multivibrator circuit and its output end, and the output end of each isolation circuit is A corresponding output rectification and filtering circuit is connected; the isolation circuit includes sequentially connected drive triodes and pulse transformers, and the output terminal of the NOT gate RC multivibrator circuit is used to connect with the base of the drive triode to drive the emitter of the triode One end of the primary winding of the pulse transformer is connected to the input power supply; one end of the secondary winding of the pulse transformer is connected to the input end of the corresponding output rectification filter circuit , and the other end is grounded; the output end of the output rectification filter circuit is the voltage output end of the isolated power supply.

The NOT gate RC multivibrator circuit is composed of a three-stage inverter, resistors R1, R2 and capacitor C1, the three NOT gates of the three-stage inverter are connected in series, and one end of the resistor R1 is connected to the first NOT gate One end of resistor R2 is connected between the first NOT gate and the second NOT gate, one end of capacitor C1 is connected to the output end of the second NOT gate, the other end of resistors R1, R2 and capacitor C1 Short.

The inverting gate RC multivibrator circuit is connected to the base of the driving transistor through a current limiting resistor.

The rectification filter circuit includes a rectification diode and a filter capacitor, the anode of the rectification diode is connected to the secondary winding of the pulse transformer, the cathode of the rectification diode is grounded through the filter capacitor, and the cathode terminal of the rectification diode is the voltage of the isolated power supply output.

Compared with the traditional switching power supply, the DC equal-proportion isolation power supply of the utility model has no feedback circuit between the output voltage and the input voltage of the circuit, and the output voltage depends on the input voltage and the transformation ratio of the pulse transformer; the output rectification The filter circuit utilizes the conduction process (positive process) of the previous stage switching circuit. The circuit of the isolated power supply is simple and low in cost. Under the condition that the load current at the output terminal fluctuates from tens of mA to tens of mA, the fluctuation of the output power supply voltage is only a few tenths of a volt, which can well meet the requirements of the DC electric energy meter for the power supply. requirements.

Description of drawings

Figure 1 is a flyback dual output switching power supply;

Figure 2 is a self-excited DC/DC conversion isolated power supply;

Fig. 3 is a circuit diagram of the DC equal-proportion isolated power supply of the present invention.

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment the utility model is further introduced.

As shown in Figure 3, it is the circuit diagram of the embodiment of the DC equal-proportion isolation power supply of the present invention. As can be seen from the figure, the power supply includes a NOT gate RC multivibrator circuit and two isolation circuits connected to its output terminals, and the output of each isolation circuit Both terminals are connected with corresponding output rectification and filtering circuits; the isolation circuit includes sequentially connected drive triodes and pulse transformers, the output terminal of the NOT gate RC multivibrator circuit is used to connect with the base of the drive triode, and the emitter of the drive triode is grounded , its collector is used to connect to one end of the primary winding of the pulse transformer, and the other end of the primary winding of the pulse transformer is used to connect to the input power supply VCC; one end of the secondary winding of the pulse transformer is connected to the input end of the corresponding output rectification filter circuit, The other end is grounded; the output end of the output rectification filter circuit is the voltage output end of the isolated power supply.

The NOT gate RC multivibrator circuit of the utility model is respectively connected to the bases of the corresponding driving transistors Q1 and Q2 through the current limiting resistors R3 and R4. The NOT gate RC multivibrator circuit is composed of three-stage inverter IC1 and resistors R1, Composed of R2 and capacitor C1, the three NOT gates of the three-stage inverter are connected in series, one end of the resistor R1 is connected to the input of the first NOT gate, and one end of the resistor R2 is connected to the first and second NOT gates. Between the two NOT gates, one end of the capacitor C1 is connected to the output end of the second NOT gate, and the resistors R1, R2 and the other end of the capacitor C1 are short-circuited.

The output rectification filter circuit includes corresponding rectification diodes D1, D2 and filter capacitors C2, C3, the anodes of rectification diodes D1, D2 are connected to the secondary windings of corresponding pulse transformers T1, T2, and the cathodes of rectification diodes D1, D2 pass through the corresponding filter The capacitors C2 and C3 are grounded, and the cathode terminal of the rectifier diode is the voltage output terminal of the isolated power supply.

The non-gate RC multivibrator circuit of this embodiment has fast start-up, stable output, and low cost; the driving transistors Q1 and Q2 are ordinary bipolar medium-power transistors, which work in the switching state, so the loss is low and the efficiency is high. ; The pulse transformer is made of high-frequency ferrite magnetic surround, which has the advantages of small size and low loss; D1 and D2 of the rectification filter circuit are Schottky fast diodes. Because the operating frequency is high, the capacitors C2 and C3 do not need Large-capacity electrolytic capacitors are used, so this part of the circuit has the advantages of voltage drop, high efficiency, and small size.

The working principle and process of the utility model are as follows: the high-frequency oscillating signal generated by the NOT-gate RC multivibrator circuit directly controls the switch state of the rear-stage driving triode, and when the driving triode is turned on, the input power passes through the pulse transformer and the triode to form a path. The triode is working in the switching state. At this time, the input power supply voltage is fully added to the primary winding of the pulse transformer. Because of electromagnetic induction, a voltage proportional to the primary input voltage will be induced in the secondary of the pulse transformer (the secondary induced voltage is the same as The voltage ratio of the primary input is equal to the turns ratio of the secondary winding to the primary winding). The output voltage of the pulse transformer is rectified and filtered through the Schottky diode and capacitor at the output end, and then the voltage output corresponding to the input power supply voltage can be output.

According to the test and verification results, the circuit form of the DC equal-proportion isolation power supply of the present invention is applied to the DC vehicle-mounted electronic electric energy meter, and the product application condition is good and the work is stable.

The above embodiments are only used to help understand the core idea of the utility model, and cannot limit the utility model with this. For those skilled in the art, any modification or equivalent replacement of the utility model according to the idea of the utility model shall be carried out in specific implementation. Any changes done in the manner and scope of application should be included in the protection scope of the present utility model.

Claims (4)

1. a direct current equal proportion insulating power supply, is characterized in that: comprise at least one road buffer circuit that not gate RC multi-resonant oscillating circuit and output thereof connect, the output of every road buffer circuit is all connected with corresponding output rectifier and filter; Described buffer circuit comprises the driving triode and the pulse transformer that connect in turn, the output of described not gate RC multi-resonant oscillating circuit is for being connected with the base stage that drives triode, drive the grounded emitter of triode, its collector electrode is for being connected with one end of pulse transformer armature winding, and the other end of pulse transformer armature winding is for being connected with input power; One end of the secondary winding of pulse transformer connects with the input of corresponding output rectifier and filter, other end ground connection; The output of described output rectifier and filter is the voltage output end of this insulating power supply.

2. direct current equal proportion insulating power supply according to claim 1, it is characterized in that: described not gate RC multi-resonant oscillating circuit is made up of three grades of inverters and resistance R 1, R2 and capacitor C 1, three not gate serial connections of three grades of inverters are connected, one end of resistance R 1 is connected in the input of first not gate, between that one end of resistance R 2 is connected in first not gate and second not gate, one end of capacitor C 1 is connected in the output of second not gate, the other end short circuit of resistance R 1, R2 and capacitor C 1.

3. direct current equal proportion insulating power supply according to claim 1, is characterized in that: described not gate RC multi-resonant oscillating circuit is connected to the base stage of described driving triode by current-limiting resistance.

4. according to the direct current equal proportion insulating power supply described in claim 1～3 any one, it is characterized in that: described current rectifying and wave filtering circuit comprises rectifier diode and filter capacitor, the anode of described rectifier diode is connected with the secondary winding of pulse transformer, the negative electrode of rectifier diode is by filter capacitor ground connection, and the cathode terminal of this rectifier diode is the voltage output end of this insulating power supply.