Input open-phase sampling circuit based on transformer step-down

Abstract

The utility model relates to the technical field of circuit protection devices, in particular to an input open-phase sampling circuit based on transformer step-down, which comprises a power supply circuit, a rectifying circuit, a switching power supply transformer circuit, a feedback loop, an analog quantity signal output circuit and a DSP (Digital Signal Processor) which are connected with one another, the switching power supply transformer circuit comprises the transformer and an MOS tube, a primary coil of the transformer is connected with the MOS tube and the rectification circuit, a secondary coil of the transformer is connected with the feedback loop and the analog quantity signal output circuit, and the analog quantity signal output circuit is connected with the DSP; and the other end of the feedback loop is connected with the MOS tube. The sampling circuit is simple in structure, high in reliability and easy to realize; the open-phase sampling circuit can be used as a bus voltage sampling circuit while realizing input open-phase sampling, so that the circuit is simplified, and the cost is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of circuit protection devices, in particular to an input phase-loss sampling circuit based on transformer voltage reduction. Background Art

[0002] With the vigorous development of industrial automation and new energy, motor drivers are widely used in various occasions, such as automated production lines, fans, oil pump control, electric vehicles, logistics AGV carts, air conditioners and other equipment. When the power supply is poor, such as when the wiring is missing a phase or the power supply voltage is too low, the input and output currents of the driver are abnormal. If the current exceeds the rated current for a long time, the driver will have alarms, explode, or burn out.

[0003] Therefore, a technology is urgently needed to perform input phase loss sampling on the driver power input terminal. Utility Model Content

[0004] The purpose of the utility model is to overcome the above-mentioned problems of the prior art and provide an input phase loss sampling circuit based on transformer step-down to solve the technical problem that frequency conversion, servo and other drives are prone to failure when the input power supply is phase-lost.

[0005] The above objectives are achieved through the following technical solutions:

[0006] A transformer-based input phase-loss sampling circuit comprises a power supply circuit, a rectifier circuit, a switching power supply transformer circuit, a feedback loop, an analog signal output circuit and a DSP which are connected to each other; the switching power supply transformer circuit comprises the transformer and a MOS tube, the primary coil of the transformer is connected to the MOS tube and the rectifier circuit, the secondary coil of the transformer is connected to the feedback loop and the analog signal output circuit, and the analog signal output circuit is connected to the DSP; the other end of the feedback loop is connected to the MOS tube for controlling the on and off of the MOS tube.

[0007] Furthermore, the rectifier circuit includes a twelfth diode, a seventh diode and an eighth diode, and the twelfth diode, the seventh diode and the eighth diode are connected to each other to form a three-phase rectifier bridge, the input end of the three-phase rectifier bridge is connected to the first phase line, the second phase line and the third phase line of the power supply circuit, and the output end of the three-phase rectifier bridge is connected to the primary coil and the MOS tube.

[0008] Furthermore, the S pole of the MOS tube is connected to the output end of the three-phase rectifier bridge, the D pole of the MOS tube is connected to the third pin of the secondary coil, and the G pole of the MOS tube is connected to the feedback loop.

[0009] Furthermore, an RCD clamping circuit is arranged between the third pin and the first pin of the secondary coil, and the RCD clamping circuit includes a thirteenth diode and a twenty-fourth resistor and a twentieth capacitor connected in parallel with each other, the same end of the twenty-fourth resistor and the twentieth capacitor is connected to the cathode of the thirteenth diode, and the anode of the thirteenth diode is connected to the third pin of the secondary coil.

[0010] Furthermore, a thirtieth resistor is arranged between the S pole of the MOS tube and the output end of the three-phase rectifier bridge.

[0011] Furthermore, a twenty-eighth resistor is provided between the S pole and the G pole of the MOS tube as a pull-down resistor.

[0012] Furthermore, the feedback loop includes a power controller, a linear isolation circuit and an error amplifier circuit which are interconnected, the power controller is connected to the G pole of the MOS tube, and the error amplifier circuit is connected to the tenth pin of the secondary coil.

[0013] Furthermore, the analog signal output circuit includes an RC filter circuit, a resistor voltage divider circuit and a low-pass filter circuit which are connected to each other.

[0014] Further, the RC filter circuit includes a sixteenth resistor and a twelfth capacitor connected to the eighth pin and the ninth pin of the secondary coil, the resistance voltage divider circuit includes a seventeenth resistor and a twenty-seventh resistor connected to the eighth pin and the ninth pin of the secondary coil, and the low-pass filter circuit includes an eighteenth resistor and a thirteenth capacitor connected to the eighth pin and the ninth pin of the secondary coil.

[0015] Furthermore, an eleventh diode is arranged between the eighth pin of the secondary coil and the sixteenth resistor.

[0016] The utility model provides an input phase loss sampling circuit based on transformer step-down. The transformer steps down the high-voltage direct current rectified by the rectifier bridge, and cooperates with the rear-end resistor voltage divider circuit to make the voltage reach the range that the DSP can bear. While realizing the step-down function, the transformer can also realize high-low voltage electrical isolation of the entire circuit, thereby improving the circuit safety and anti-interference ability. The sampling circuit has a simple structure, high reliability, and is easy to implement. While realizing input phase loss sampling, it can also be used as a bus voltage sampling circuit to simplify the circuit and reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of an input phase loss sampling circuit based on transformer step-down described in the utility model. DETAILED DESCRIPTION

[0018] The utility model is further described in detail below based on the accompanying drawings and embodiments. The described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0019] like Figure 1 As shown, an input phase loss sampling circuit based on transformer step-down includes a power supply circuit, a rectifier circuit, a switching power supply transformer circuit, a feedback loop, an analog signal output circuit and a DSP connected to each other;

[0020] The switching power supply transformer circuit includes the transformer T1 and the MOS tube D15, the primary coil T1A of the transformer is connected to the MOS tube D15 and the rectifier circuit, the secondary coil T1B of the transformer T1 is connected to the feedback loop and the analog signal output circuit, and the analog signal output circuit is connected to the DSP; the other end of the feedback loop is connected to the MOS tube for controlling the conduction and closing of the MOS tube so as to control the charging and discharging of the primary coil.

[0021] Working principle:

[0022] Based on the flyback switching power supply of the driver's main power supply, transformers and MOS tubes are used to achieve electrical isolation, energy transmission, electro-magnetic-electrical and voltage reduction, and the frequency and period information of the power supply is transmitted to the DSP of the signal system through the switching power supply (due to the switching frequency of the switching power supply 60kHz >> the pulsation frequency of the power supply after rectification), and then ADC sampling is performed through the DSP (sampling frequency is 12kHz) to determine the frequency or period of the analog quantity. According to the Nyquist sampling theorem, when the sampling frequency is greater than twice the highest frequency in the signal, the digital signal after sampling completely retains the information in the original signal to detect whether the input power supply is missing a phase.

[0023] In this embodiment, the rectifier circuit includes a twelfth diode D12, a seventh diode D7 and an eighth diode D8. The twelfth diode D12, the seventh diode D7 and the eighth diode D8 are connected to each other to form a three-phase rectifier bridge. The input end of the three-phase rectifier bridge is connected to the first phase line L1, the second phase line L2 and the third phase line L3 of the power supply circuit, and the output end of the three-phase rectifier bridge is connected to the primary coil T1A and the MOS tube D15.

[0024] The S pole of the MOS tube D15 is connected to the output end of the three-phase rectifier bridge, the D pole of the MOS tube D15 is connected to the third pin of the secondary coil T1B, and the G pole of the MOS tube D15 is connected to the feedback loop.

[0025] In this embodiment, an RCD clamping circuit is provided between the third pin and the first pin of the secondary coil T1B, and the RCD clamping circuit includes a thirteenth diode D13 and a twenty-fourth resistor D24 and a twentieth capacitor C20 connected in parallel, the same end of the twenty-fourth resistor D24 and the twentieth capacitor C20 is connected to the cathode of the thirteenth diode D13, and the anode of the thirteenth diode D13 is connected to the third pin of the secondary coil T1B.

[0026] The RCD clamp circuit is used to absorb the instantaneous high voltage when the primary coil T1A is powered off to prevent it from causing breakdown of the MOS tube.

[0027] As an optimization of this embodiment, a thirtieth resistor R30 is further provided between the S pole of the MOS tube D15 and the output end of the three-phase rectifier bridge as a switch current sampling resistor.

[0028] A twenty-eighth resistor R28 is provided between the S pole and the G pole of the MOS tube D15 as a pull-down resistor, which can accelerate the falling speed of the gate voltage, thereby protecting the MOS tube.

[0029] In this embodiment, the feedback loop includes a power controller PWN, a linear isolation circuit and an error amplifier circuit connected to each other. The power controller PWN is connected to the G pole of the MOS tube D15, and the error amplifier circuit is connected to the tenth pin of the secondary coil T1B.

[0030] A fourteenth diode D14 is further provided between the tenth pin of the secondary coil T1B and the error amplifier circuit for rectifying the output voltage.

[0031] The analog signal output circuit in this embodiment includes an RC filter circuit, a resistor voltage divider circuit and a low-pass filter circuit that are connected to each other.

[0032] Among them, the RC filtering circuit includes a sixteenth resistor R16 and a twelfth capacitor C12 connected to the eighth pin and the ninth pin of the secondary coil T1B, the resistance voltage divider circuit includes a seventeenth resistor R17 and a twenty-seventh resistor R27 connected to the eighth pin and the ninth pin of the secondary coil T1B, and the low-pass filtering circuit includes an eighteenth resistor R18 and a thirteenth capacitor C13 connected to the eighth pin and the ninth pin of the secondary coil T1B.

[0033] Specifically, in this embodiment, the sixteenth resistor R16 and the twelfth capacitor C12 constitute the RC filter circuit, which is used to filter out the harmonic voltage spike of the switching power supply;

[0034] The seventeenth resistor R17 and the twenty-seventh resistor R27 form the resistor voltage divider circuit, and then pass through the low-pass filter circuit composed of the eighteenth resistor R18 and the thirteenth capacitor C13 to output the CVD signal to the ADC of the DSP for sampling and judgment. The amplitude of this signal is proportional to the primary bus voltage, and the frequency is the pulsating frequency after rectification of the industrial frequency power supply.

[0035] In addition, an eleventh diode D11 is provided between the eighth pin of the secondary coil T1B and the sixteenth resistor R16 for rectifying the output voltage.

[0036] Specifically, the eleventh diode D11 and the fourteenth diode D14 in this embodiment are output rectifier diodes, the winding output of the fourteenth diode D14 is the feedback voltage of the switching power supply, the winding where the eleventh diode D11 is located works in the forward working mode, and the output voltage of this winding is proportional to the rectified pulsating DC voltage according to the turns ratio of the transformer.

[0037] In this embodiment, three-phase or single-phase industrial frequency AC is rectified into pulsating DC through a rectifier bridge (the frequency of the pulsating DC after rectification of the three-phase industrial frequency AC is 300Hz, and the frequency of the pulsating DC after rectification of the single-phase industrial frequency AC is 100Hz), and then the pulsating high-voltage DC is stepped down into pulsating low-voltage DC through a flyback switching power supply (the power switching frequency is 60kHz) (the voltage ratio is proportional to the transformer turns ratio, and the transformer turns ratio can be determined according to actual conditions), the output of the transformer secondary coil is rectified by a diode, and capacitor filtering is added, and the TTL level analog signal is input to the DSP after resistor voltage division.

[0038] DSP is a digital signal processor, which determines whether there is a phase loss based on the period of the collected signal. Taking three-phase 380V AC input as an example, in normal state, the signal period is 3.3ms (frequency is 300Hz), and when there is a phase loss, it is 10ms (frequency is 100Hz).

[0039] The above description is only for illustrating the implementation mode of the present invention and is not intended to limit the present invention. For those skilled in the art, any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An input phase loss sampling circuit based on transformer step-down, characterized in that: It includes a power supply circuit, a rectifier circuit, a switching power supply transformer circuit, a feedback loop, an analog signal output circuit and a DSP that are interconnected; The switching power supply transformer circuit comprises the transformer (T1) and the MOS tube (D15), the primary coil (T1A) of the transformer is connected to the MOS tube (D15) and the rectifier circuit, the secondary coil (T1B) of the transformer (T1) is connected to the feedback loop and the analog signal output circuit, and the analog signal output circuit is connected to the DSP; the other end of the feedback loop is connected to the MOS tube for controlling the on and off of the MOS tube.

2. The input phase loss sampling circuit based on transformer step-down according to claim 1 is characterized in that: The rectifier circuit comprises a twelfth diode (D12), a seventh diode (D7) and an eighth diode (D8); the twelfth diode (D12), the seventh diode (D7) and the eighth diode (D8) are connected to each other to form a three-phase rectifier bridge; an input end of the three-phase rectifier bridge is connected to a first phase line (L1), a second phase line (L2) and a third phase line (L3) of the power supply circuit; and an output end of the three-phase rectifier bridge is connected to the primary coil (T1A) and the MOS tube (D15).

3. The input phase loss sampling circuit based on transformer step-down according to claim 2 is characterized in that: The S pole of the MOS tube (D15) is connected to the output end of the three-phase rectifier bridge, the D pole of the MOS tube (D15) is connected to the third pin of the secondary coil (T1B), and the G pole of the MOS tube (D15) is connected to the feedback loop.

4. The input phase loss sampling circuit based on transformer step-down according to claim 3 is characterized in that: An RCD clamping circuit is provided between the third pin and the first pin of the secondary coil (T1B), and the RCD clamping circuit comprises a thirteenth diode (D13) and a twenty-fourth resistor (D24) and a twentieth capacitor (C20) connected in parallel with each other, the same end of the twenty-fourth resistor (D24) and the twentieth capacitor (C20) is connected to the cathode of the thirteenth diode (D13), and the anode of the thirteenth diode (D13) is connected to the third pin of the secondary coil (T1B).

5. The input phase loss sampling circuit based on transformer step-down according to claim 3 is characterized in that: A thirtieth resistor (R30) is also provided between the S pole of the MOS tube (D15) and the output end of the three-phase rectifier bridge.

6. The input phase loss sampling circuit based on transformer step-down according to claim 3 is characterized in that: A twenty-eighth resistor (R28) is provided between the S pole and the G pole of the MOS tube (D15) as a pull-down resistor.

7. The input phase loss sampling circuit based on transformer step-down according to claim 3 is characterized in that: The feedback loop comprises a power controller (PWN), a linear isolation circuit and an error amplifier circuit which are connected to each other, the power controller (PWN) is connected to the G pole of the MOS tube (D15), and the error amplifier circuit is connected to the tenth pin of the secondary coil (T1B).

8. The input phase loss sampling circuit based on transformer step-down according to claim 1, characterized in that: The analog signal output circuit includes an RC filter circuit, a resistor voltage divider circuit and a low-pass filter circuit which are connected to each other.

9. The input phase loss sampling circuit based on transformer step-down according to claim 8, characterized in that: The RC filter circuit includes a sixteenth resistor (R16) and a twelfth capacitor (C12) connected to the eighth pin and the ninth pin of the secondary coil (T1B), the resistance voltage divider circuit includes a seventeenth resistor (R17) and a twenty-seventh resistor (R27) connected to the eighth pin and the ninth pin of the secondary coil (T1B), and the low-pass filter circuit includes an eighteenth resistor (R18) and a thirteenth capacitor (C13) connected to the eighth pin and the ninth pin of the secondary coil (T1B).

10. The input phase loss sampling circuit based on transformer step-down according to claim 9, characterized in that: An eleventh diode (D11) is also provided between the eighth pin of the secondary coil (T1B) and the sixteenth resistor (R16).

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