CN213843354U

CN213843354U - Electrically isolated direct-current voltage sampling circuit

Info

Publication number: CN213843354U
Application number: CN202023132424.3U
Authority: CN
Inventors: 杨灿荣; 陈一逢
Original assignee: Xiamen Evada Electronics Co ltd
Current assignee: Xiamen Evada Electronics Co ltd
Priority date: 2020-12-23
Filing date: 2020-12-23
Publication date: 2021-07-30
Anticipated expiration: 2030-12-23

Abstract

The utility model discloses a direct current voltage sampling circuit of electrical isolation formula, including transformer T1, self-excited oscillation circuit and rectification filter circuit, self-excited oscillation circuit links to each other with transformer T1 electricity, rectification filter circuit links to each other with transformer electricity T1, the utility model belongs to the technical field of keep apart the sampling, specifically indicate a direct current voltage sampling circuit who provides lower cost's electrical isolation formula.

Description

Electrically isolated direct-current voltage sampling circuit

Technical Field

The utility model belongs to the technical field of keep apart the sampling, specifically indicate a direct current voltage sampling circuit of electrical isolation formula.

Background

In order to meet the market requirements of power supply products, input and output isolation, alternating current and direct current isolation or isolation of a power circuit and a control circuit are adopted by designers more and more, and isolation sampling of direct current voltage signals such as battery voltage or bus voltage has important significance on the performance of the power supply products, the anti-interference of a control system, even the application of some circuit topologies, and the realization of product design schemes. Generally, the existing scheme for matching the sampling linear optocoupler with the operational amplifier by using the electrical isolation sampling circuit has the following disadvantages:

1. the cost is high, the price of the linear optocoupler is high, and the matched peripheral circuit is complex and high in cost, so that the product cost is not reduced;

2. the circuit is complex, and the linear optocoupler circuit needs to restore the sampling signal by using an operational amplifier at the initial isolation time, so that the circuit is complex; and an additional set of isolated power supplies are required to power the operational amplifiers on both sides.

SUMMERY OF THE UTILITY MODEL

In order to solve the problem, the utility model provides a DC voltage sampling circuit of lower cost's electrical isolation formula is provided.

In order to realize the above functions, the utility model discloses the technical scheme who takes as follows: an electrically isolated DC voltage sampling circuit comprises a transformer T1, a self-oscillation circuit and a rectification filter circuit, wherein the self-oscillation circuit is electrically connected with a transformer T1, the rectification filter circuit is connected with a transformer T1, the self-oscillation circuit comprises a resistor R1, a diode D1, a capacitor C1, a transistor Q1 and a transistor Q1, the resistor R1 is connected with a center tap of a primary winding of the transformer T1, the diode D1 is connected with the transformer T1 and GND, the transistor Q1 is connected with the diodes D1 and GND, the resistor R1 is connected with the diode D1 and the transistor GND, the capacitor C1 is connected with the diode D1 and the transistor Q1 in parallel, the resistor R1 is connected with the capacitor C1 and the diode D1 and the transistor Q1, the diode D4 is connected with the transistor Q1 and GND, and the diode D7 is connected with the transistor Q2 and GND; the direct current voltage to be sampled is added to the center tap of the primary winding of the transformer T1 through a current limiting resistor R2, if Q1 is firstly conducted, current passes through V _ DC and forms a loop through R2, N1 and Q1, under the condition that a magnetic core is not saturated, the induced voltage generated by N1 is equal to V _ DC, and the direction is up negative and down positive; n2 also generates an induced voltage with positive and negative polarities, the induced voltage is added to the base of Q1 through a R3 and C4 network, and the generated base current maintains the saturated conduction of Q1; when the current of N1 is gradually increased, the magnetic core is finally saturated, so that the change of the N1 magnetic flux is gradually reduced until the change is not changed, and the induced electromotive force of N2 is also reduced until the induced electromotive force is zero according to the Faraday's law of electromagnetic induction; the current flowing through the base of Q1 becomes smaller, so that Q1 exits the saturation region; one part of the current flowing through N3 flows back through a collector-emitter of Q1, and the other part flows back through a base-emitter of R1 and Q2; and as the base current of Q1 is reduced, the part of the current flowing through the collector of Q1 is reduced, and the current flowing through R1 is gradually increased, so that Q2 is turned on finally; after Q2 is turned on, V _ DC will flow back along R2, N2 and Q2, the induced voltage generated by N1, which is positive, negative and up, will provide the base current of Q2, and maintain the saturated conducting state of Q2, and so on; in the period of the alternate conduction of the Q1 and the Q2, the transformer goes through the processes of forward excitation and reverse excitation, and the circuit selection parameters of the Q1 and the Q2 are the same and are completely symmetrical, so that the magnetic balance is achieved.

Further, the rectifying and filtering circuit comprises a diode D2, a diode D3, a diode D5, a diode D6, a capacitor C2 and a capacitor C3, the diode D2 and the diode D5 are connected with a transformer T1, the diode D3 and the diode D6 are connected with a transformer T1, the diode D2 is connected with a diode D3, the diode D5 is connected with a diode D6, the capacitor C2 and the capacitor C3 are connected in parallel and then connected with a diode D3 and a diode D6 respectively, the secondary voltage of the transformer T1 is rectified and filtered by the diodes D2-D6 and C2 and then converted into direct current voltage again, the generated VDC _ S signal can be sent to the MCU ADC for sampling processing after simple RC filtering, and the transformation ratio of the VDC 1 can be adjusted to enable the VDC _ S to be within a design range.

Furthermore, the transformer T1 adopts a magnetic core made of EP 13 PC40 material, and adopts a secondary parallel winding method, so that the high-frequency interference of the primary coupling to the magnetic core of the transformer is reduced, and the purity of the high-frequency down-sampling waveform is improved.

The utility model adopts the above structure to gain beneficial effect as follows: the utility model provides an electrically isolated DC voltage sampling circuit easy operation, reasonable in design utilizes the saturation characteristic of magnetic core of transformer, makes the triode switch on alternately, on the one hand, makes the DC voltage of waiting to sample convert alternating signal to keep apart the transmission through the transformer; on the other hand, the primary winding of the transformer alternately flows current to achieve the balance of excitation and demagnetization; the output of the transformer is converted into a direct current signal through wave shaping filtering, and the direct current signal and the input direct current voltage have a linear relation, so that the isolated sampling of the direct current voltage can be realized by using the least components; the method has wide applicability in the field of isolation sampling of direct-current voltage, and the sampling output voltage can be freely designed to meet the ADC level requirements of different control chips; the output signal is linearly related to the sampling signal, so that the sampling precision and the temperature stability are good; the device has the advantages of few elements, simplicity, easy use, long service life, strong anti-interference performance, high isolation voltage, low cost and the like.

Drawings

Fig. 1 is a circuit diagram of an electrical isolation type dc voltage sampling circuit according to the present invention.

Detailed Description

The technical solution of the present invention will be described clearly and completely with reference to the accompanying drawings, and obviously, the described embodiments are some, but not all embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

As shown in fig. 1, the utility model relates to an electrically isolated dc voltage sampling circuit, including transformer T1, self-excited oscillation circuit and rectification filter circuit, self-excited oscillation circuit is electrically connected with transformer T1, rectification filter circuit is connected with transformer electricity T1; the self-oscillation circuit comprises a resistor R1, a diode D1, a capacitor C1, a transistor Q1 and a transistor Q1, wherein the resistor R1 is connected with a center tap of a primary winding of the transformer T1, the diode D1 is connected with the transformer T1 and GND, the transistor Q1 is connected with the diode D1 and GND, the resistor R1 is connected with the capacitor C1 in parallel and then respectively connected with the diode D1 and the transistor Q1, the diode D1 is connected with the transistor GND, and the diode D1 is connected with the transistor GND.

The rectifying and filtering circuit comprises a diode D2, a diode D3, a diode D5, a diode D6, a capacitor C2 and a capacitor C3, the diode D2 and the diode D5 are connected with a transformer T1, the diode D3 and the diode D6 are connected with a transformer T1, the diode D2 and the diode D3 are connected, the diode D5 and the diode D6 are connected, and the capacitor C2 and the capacitor C3 are connected in parallel and then respectively connected with a diode D3 and a diode D6.

The transformer T1 adopts a magnetic core made of EP 13 PC 40.

As shown in fig. 1, a DC voltage to be sampled is applied to a center tap of a primary winding of a transformer T1 through a current limiting resistor R2, and assuming that Q1 is turned on first, a current is looped through V _ DC through R2, N1, and Q1, and when a magnetic core is not saturated, an induced voltage generated by N1 is equal to V _ DC, and the direction is up-negative and down-positive; n2 also generates an induced voltage with positive and negative polarities, the induced voltage is added to the base of Q1 through a R3 and C4 network, and the generated base current maintains the saturated conduction of Q1; when the current of N1 is gradually increased, the magnetic core is finally saturated, so that the change of the N1 magnetic flux is gradually reduced until the change is not changed, and the induced electromotive force of N2 is also reduced until the induced electromotive force is zero according to the Faraday's law of electromagnetic induction; the current flowing through the base of Q1 becomes smaller, so that Q1 exits the saturation region; one part of the current flowing through N3 flows back through a collector-emitter of Q1, and the other part flows back through a base-emitter of R1 and Q2; and as the base current of Q1 is reduced, the part of the current flowing through the collector of Q1 is reduced, and the current flowing through R1 is gradually increased, so that Q2 is turned on finally; after Q2 is turned on, V _ DC will flow back along R2, N2 and Q2, the induced voltage generated by N1, which is positive, negative and up, will provide the base current of Q2, and maintain the saturated conducting state of Q2, and so on; in the period of the alternate conduction of the Q1 and the Q2, the transformer goes through the processes of forward excitation and reverse excitation, and the circuit selection parameters of the Q1 and the Q2 are the same and are completely symmetrical, so that the magnetic balance is achieved.

The secondary voltage of the transformer is rectified and filtered by D2-D6 and C2 and then converted into direct current voltage again, and the generated VDC _ S signal can be sent to the MCU ADC for sampling processing after simple RC filtering. The transformation ratio of T1 can be adjusted to make VDC _ S within the design range.

The triode is conducted alternately by utilizing the saturation characteristic of the magnetic core of the transformer, and on one hand, the direct current voltage to be sampled is converted into an alternating signal, so that the alternating signal is transmitted in an isolated manner through the transformer; on the other hand, the primary winding of the transformer alternately passes through current, so that the balance of excitation and demagnetization is achieved. The output of the transformer is converted into a direct current signal through wave shaping filtering, and the direct current signal and the input direct current voltage have a linear relation, so that the isolated sampling of the direct current voltage can be realized by using the minimum components.

The present invention and the embodiments thereof have been described above, but the description is not limited thereto, and the embodiment shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. In summary, those skilled in the art should understand that they should not be limited to the embodiments described above, and that they can design the similar structure and embodiments without departing from the spirit of the invention.

Claims

1. The utility model provides a direct current voltage sampling circuit of electrical isolation formula which characterized in that: the transformer T1, the self-excited oscillation circuit and the rectification filter circuit are included, the self-excited oscillation circuit is electrically connected with the transformer T1, and the rectification filter circuit is connected with the transformer T1; the self-oscillation circuit comprises a resistor R1, a diode D1, a capacitor C1, a transistor Q1 and a transistor Q1, wherein the resistor R1 is connected with a center tap of a primary winding of the transformer T1, the diode D1 is connected with the transformer T1 and GND, the transistor Q1 is connected with the diode D1 and GND, the resistor R1 is connected with the capacitor C1 in parallel and then respectively connected with the diode D1 and the transistor Q1, the diode D1 is connected with the transistor GND, and the diode D1 is connected with the transistor GND.

2. The electrically isolated dc voltage sampling circuit of claim 1, wherein: the rectifying and filtering circuit comprises a diode D2, a diode D3, a diode D5, a diode D6, a capacitor C2 and a capacitor C3, the diode D2 and the diode D5 are connected with a transformer T1, the diode D3 and the diode D6 are connected with a transformer T1, the diode D2 and the diode D3 are connected, the diode D5 and the diode D6 are connected, and the capacitor C2 and the capacitor C3 are connected in parallel and then respectively connected with a diode D3 and a diode D6.

3. An electrically isolated dc voltage sampling circuit according to claim 2, wherein: the transformer T1 adopts a magnetic core made of EP 13 PC 40.