WO2015176306A1

WO2015176306A1 - Voltage analog signal isolated transmission circuit

Info

Publication number: WO2015176306A1
Application number: PCT/CN2014/078283
Authority: WO
Inventors: 付明
Original assignee: 深圳航天科技创新研究院
Priority date: 2014-05-23
Filing date: 2014-05-23
Publication date: 2015-11-26

Abstract

A voltage analog signal isolated transmission circuit comprises a carrier generation circuit (2), a closed-loop control circuit (3), a PWM wave generation circuit (4), an isolation transformer (1), and m rectification circuits (5). An output end of the carrier generation circuit (2) is connected to a positive input end of the PWM wave generation circuit (4). An output end of the closed-loop control circuit (3) is connected to a negative input end of the PWM wave generation circuit (4). An output end of the PWM wave generation circuit (4) is connected to a primary winding of the isolation transformer (1). The isolation transformer (1) comprises the primary winding and m secondary windings. The i^th secondary winding is connected to an i^th output end of the isolated transmission circuit by means of the i^th rectification circuit (5), an m^th output end of the isolated transmission circuit is connected to a negative input end of the closed-loop control circuit, and a positive input end of the closed-loop control circuit is connected to an input end of the isolated transmission circuit, where m≥2, and i=1, 2, ……, m. Compared with the conventional analog voltage isolated transmission mode, the voltage analog signal isolated transmission circuit ensures the transmission precision.

Description

Voltage analog signal isolation transmission circuit

The invention relates to an isolated signal transmission circuit, which can be widely applied in various fields requiring precise isolation and transmission of analog voltage signals, such as electrical insulation, level conversion, inter-pole coupling, driving circuit, switching circuit, signal isolation, instrumentation And communication equipment, etc.

Background technique

Traditional voltage analog signal isolation transmission uses linear optocoupler, Hall voltage sensor and other transmission methods.

The optocoupler generally consists of three parts: a light-emitting part, a light receiving part and a signal amplifying part. The input electrical signal drives the light-emitting diode to emit a certain wavelength of light, which is received by the photodetector to generate a photocurrent, and then further amplified. After the output, that is, the conversion of electricity, light and electricity, thereby functioning as input and output isolation.

The Hall voltage sensor is a magnetic field sensor fabricated according to the Hall effect. When it is used to isolate the transmission voltage, a primary current is passed through the Hall element through a current limiting resistor connected to the primary side of the input terminal. The equal-proportional voltage signal generated by the Hall effect is amplified to generate a corresponding measurement signal, that is, an electrical-magnetic-Hall effect-electrical conversion.

The characteristics of the above two voltage analog signal transmission methods depend on the parameters of the optocoupler or Hall components. The influence of temperature, irradiation, aging, etc. on the semiconductor in the component will directly lead to the decrease of the linearity and accuracy of the isolated transmission circuit.

Summary of the invention

The invention solves the technical problem that the isolation and transmission mode of the existing voltage analog signal is susceptible to the linearity and precision of the isolated transmission circuit caused by the influence of temperature, irradiation and aging, and proposes a voltage analog signal isolation transmission circuit, including a carrier generation circuit, a closed loop control circuit, a PWM wave generating circuit, an isolating transformer and m rectifying circuits, wherein an output end of the carrier generating circuit is connected to a positive input end of the PWM wave generating circuit, and an output end of the closed loop control circuit is connected to the PWM wave a negative input end of the generating circuit, an output end of the PWM wave generating circuit is connected to a primary winding of the isolation transformer; the isolation transformer includes a primary winding and m secondary windings, and the i-th secondary winding is The i-th rectifier circuit is connected to the ith output end of the voltage analog signal isolation transmission circuit, and the m-th output terminal of the voltage analog signal isolation transmission circuit is connected to the negative input terminal of the closed-loop control circuit, a positive input terminal of the closed loop control circuit is connected to an input end of the voltage analog signal isolation transmission circuit; wherein, m≥2, i=l Further, the voltage analog signal isolation transmission circuit further includes m-1 output follower circuits, and the first rectifier circuit is connected to the voltage of the voltage analog signal isolation transmission circuit via the jth output follower circuit The output of the road, j=l, 2, ..,.., ml.

Further, a driving circuit is connected between the output end of the PWM wave generating circuit and the primary winding. Further, the closed loop control circuit is configured to change its output signal according to signals of its positive input terminal and negative input terminal to adjust the duty ratio of the PWM wave generating circuit so that V _in =V. _{Ut m ;} wherein V _in is the input voltage of the voltage analog signal isolation transmission circuit, V. _{Ut m} is the output voltage of the mth output terminal of the voltage analog signal isolation transmission circuit.

Further, the carrier generating circuit is a triangular wave generating circuit, a sawtooth wave generating circuit or a sine wave generating circuit.

Further, the closed loop control circuit is a PID controller.

Further, the PWM wave generating circuit is a PWM comparator.

Further, the output follower circuit is a voltage follower.

The invention has the following beneficial effects: The invention applies the closed-loop feedback idea to the scheme of the analog voltage signal isolation transmission, and utilizes the idea that the switching power supply transformer output turns ratio is equal to the voltage ratio of the output winding rectification. Ben Compared with the traditional analog voltage isolation transmission mode, the output winding ratio of the transformer in the topology scheme is strictly equal to the output rectification voltage ratio of each output winding, which ensures the transmission precision; the circuit design of the present invention is completed. After that, the transformer turns ratio is fixed, and it is not affected by environmental temperature, irradiation, aging and other factors, which makes the transmission accuracy of the circuit lower. Overcoming the accuracy of the traditional analog voltage isolation transmission mode relies heavily on optocoupler and Hall element. Disadvantages of the parameters of the device.

DRAWINGS

1 is a schematic diagram showing the circuit structure of a voltage analog signal isolation transmission circuit of the present invention;

2 is a circuit structural diagram of a specific example of an isolated transmission circuit of the present invention.

detailed description

The invention is further described below in conjunction with the drawings and specific embodiments.

The invention adopts an electric-magnetic-electrical conversion mode, and the working principle thereof is as follows: The output voltages of the isolated transmission circuits are strictly proportional to the turns ratio of the transformer, and one of the two outputs of the secondary side is connected to the primary side. Closed-loop feedback enables accurate transmission of analog signals.

The voltage analog signal isolation transmission circuit of the embodiment shown in FIG. 1 includes an isolation transformer 1, a carrier generation circuit 2, a closed loop control circuit 3, a PWM wave generation circuit 4, and m rectifier circuits 5, and an output end of the carrier generation circuit 2 Connected to the positive input terminal of the PWM wave generating circuit 4, the output end of the closed loop control circuit 3 is connected to the negative input terminal of the PWM wave generating circuit 4, and the output end of the PWM wave generating circuit 4 is connected to the primary winding of the isolating transformer 1; the isolating transformer 1 includes The primary winding and the m secondary windings, the i-th secondary winding is connected to the i-th output of the isolated transmission circuit via the i-th rectifying circuit 5, and the m-th output of the isolated transmission circuit is connected to the negative of the closed-loop control circuit 3. At the input end, the positive input terminal of the closed loop control circuit 3 is connected to the input end of the isolated transmission circuit; wherein, m ≥ 2, i = 1, 2 m. The closed-loop control circuit 3 is for changing its output signal according to the signals of its positive input terminal and negative input terminal to adjust the duty ratio of the PWM wave generating circuit 4 so that V _in = V. _{Ut m ;} where ^ is the input voltage of the isolated transmission circuit, V. _UT Ϊ _m is the m-th transmission circuit isolation output terminal voltage Yu.

The closed loop control circuit 3 may be an integrating circuit, such as a PID controller; the carrier generating circuit 4 is a triangular wave generating circuit, a sawtooth wave generating circuit or a sine wave generating circuit, etc., for generating a PWM wave carrier signal compared with the integrated signal, in FIG. 2 In the middle, the triangular wave generating circuit is selected; the PWM wave generating circuit is a PWM comparator.

When the output signal of the PWM wave generating circuit 4 is sufficient to drive the primary winding, the primary winding end does not need to be provided with an additional driving circuit; when it is insufficient to drive the primary winding, the output of the PWM wave generating circuit 4 is connected to the primary winding. Into the drive circuit 6, for example, in the isolated flyback circuit shown in Fig. 1, that is, the drive circuit 6 is employed.

The signals of the carrier generating circuit 2 and the closed-loop control circuit 3 are compared in the PWM wave generating circuit 4 to generate a PWM wave having an adjustable duty ratio, and the primary winding N of the isolation transformer 1 is driven by the driving circuit 6. The isolation transformer 1 secondary winding and N ₂ N _m generate equal proportions of the output voltages according to the turns ratio relationship of the windings. That is: the turns ratio of each winding of the transformer 1 is N _1: N _2: ...:N _m — : T _2: ...:T _m — _1: 1, the output voltage ratio of each winding is: V . _{Ut 1:} V. _Ut ₂ :...:V _{0Ut m} _!: V _{out m} =T _1: T _2: ...:T _m — _1: 1. The m-th output voltage is connected to the negative input terminal of the closed-loop control circuit 3, and the input signal of the isolated transmission circuit is connected to the positive input terminal of the closed-loop control circuit 3. The closed-loop control circuit 3 adjusts the PWM wave generation by changing the output signal. The duty cycle of circuit 4, thereby adjusting the output voltage of each winding of the secondary side of transformer 1, ultimately achieving V _in =V. _{Ut m} , then V. _Ut _k =T _k _{xV 0Ut m} =T _k _xV _in , provides a constant ratio of isolated linear transmission of the input signal to the output signal; where k = 1, 2 ml.

In order to ensure the accuracy of the isolation feedback, the equivalent load of each output winding of the transformer 1 side must be kept the same, so the output follower circuit 7 is added at each output winding end to ensure that each output has load capacity. That is, the isolated transmission circuit includes m-1 output follower circuits 7, such as a voltage follower (as shown in FIG. 2), and the jth rectifier circuit 5 is connected to the jth output of the isolated transmission circuit via the jth output follower circuit 7. End, j=l, 2 ml.

As shown in FIG. 2, a circuit diagram using a flyback topology scheme is adopted. The carrier generation circuit 2 uses a triangular wave generation circuit, the closed loop control circuit 3 uses a PID controller, the PWM wave generation circuit 4 uses a PWM comparator, and the drive circuit 6 uses a triode. The rectifier circuit 5 is mainly composed of a diode and a capacitor, and the output follower circuit 7 is adopted. The voltage follower, the transformer in Figure 2 has two secondary windings, wherein the second secondary winding is connected to the negative input of the PID controller for closed-loop feedback, and the first secondary winding is an analog voltage signal isolated output winding.

The above embodiment only describes an isolated transmission scheme using a flyback topology. In the isolated closed-loop feedback voltage transmission method described in the present invention, flyback, forward, double-switch forward, push-pull, full-bridge, and half can be used. A variety of isolated topologies such as bridges, which mainly utilize the following working principle of the isolated topology: The turns ratio of each winding of the transformer is strictly equal to the output rectified voltage ratio of each winding. At the same time, the bandwidth of the isolated signal transmission can be improved by increasing the closed-loop feedback bandwidth and the triangular wave frequency.

The detailed description of the present invention has been described in connection with the specific preferred embodiments, and the specific embodiments of the present invention are not limited to the description. It will be apparent to those skilled in the art that the present invention may be practiced without departing from the spirit and scope of the invention.

Claims

Claim

A voltage analog signal isolation transmission circuit, comprising an isolation transformer (1), the isolation transformer (1) comprising a primary winding; wherein the voltage analog signal isolation transmission circuit further comprises a carrier generation circuit (2) a closed loop control circuit (3), a PWM wave generating circuit (4), and m rectifier circuits (5), wherein an output end of the carrier generating circuit (2) is connected to a positive input terminal of the PWM wave generating circuit (4), Closed loop control circuit

The output terminal of (3) is connected to the negative input terminal of the PWM wave generating circuit (4), and the PWM wave generating circuit

The output terminal of (4) is connected to the primary winding of the isolation transformer (1); the isolation transformer (1) comprises m secondary windings, and the i-th secondary winding is subjected to the i-th rectifier circuit ( 5) connected to the ith output end of the voltage analog signal isolation transmission circuit, the mth output end of the voltage analog signal isolation transmission circuit is connected to the negative input end of the closed loop control circuit (3), the closed loop control The positive input terminal of the circuit (3) is connected to the input end of the voltage analog signal isolation transmission circuit; wherein, m ≥ 2, i = 1, 2 m.

2. The voltage analog signal isolation transmission circuit according to claim 1, further comprising: m-1 output follower circuits (7), wherein said jth said rectifier circuit (5) follows said output of said jth The circuit (7) is connected to the jth output terminal of the voltage analog signal isolation transmission circuit, j=l, 2 ml.

The voltage analog signal isolation transmission circuit according to claim 1, characterized in that: a driving circuit (6) is connected between the output end of the PWM wave generating circuit (4) and the primary winding.

4. The voltage analog signal isolation transmission circuit according to claim 1, wherein: said closed loop control circuit

(3) It is used to change its output signal according to the signals of its positive input terminal and negative input terminal to adjust the duty ratio of the PWM wave generating circuit (4) so that V _in =V. _{Ut m ;} where ^ is the input voltage of the voltage analog signal isolated transmission circuit, V. _{Ut m} is the output voltage of the mth output terminal of the voltage mode signal isolation transmission circuit.

The isolated transmission circuit according to claim 1, wherein the carrier generating circuit (2) is a triangular wave generating circuit, a sawtooth wave generating circuit or a sine wave generating circuit.

6. The isolated transmission circuit according to claim 1, wherein: said closed loop control circuit (3) is a PID controller.

7. The isolated transmission circuit according to claim 1, wherein: said PWM wave generating circuit (4) is a PWM comparator.

8. The isolated transmission circuit of claim 2, wherein: said output follower circuit (7) is a voltage follower.