CN100511904C - Switch power source for digital relay protection - Google Patents

Abstract

The invention relates to a digital relay protection switch power, and is a switch power meeting the special technical indicators of a digital relay protection device to the power. The invention is composed of an input circuit (1), a power main circuit (2), a power output abnormal protection module (3), a startup time-sequence controller (4) as well as a startup time-sequence controller (5). The powers 5V, plus or minus 15V and 24V output in three-channel and are respectively equipped with a voltage monitoring circuit and a joint control power pulse width modulation chip to realize the output over voltage and under voltage protection. When the output occurs short circuit, voltage sag may be caused and then the short-circuit protection can be indirectly realized through the output of the under voltage protection circuit. When the power is turned on, 5V delays to electrify 24V through the control circuit to realize the startup 5V prior to 24V; when the power is turned off, an electricity loss sampling circuit rapidly cuts 24V output, 5V output maintains for a period by an input filter large capacitor to realize 5V later than 24V.

Description

Switching power supply for digital relay protection

technical field

The invention is a switching power supply designed for some special technical index requirements of a digital relay protection device for a power supply, and belongs to the technical field of electric power system relay protection.

Background technique

With the large-scale application of digital relay protection devices in substation automation systems, the reliability of relay protection devices has become a very important issue. The performance of the power supply that is part of the protection device directly affects the overall reliability of the relay protection device. The switching power supply for digital relay protection is a multi-output power supply. The input is AC and DC, and the output has three sets of voltages. Switch input and output circuits. Compared with the conventional power supply, the power supply for relay protection has added some special technical indicators, such as output overvoltage and undervoltage protection, timing coordination between 5V and 24V, and higher-level electromagnetic compatibility requirements, etc. The purpose is to improve the safety and reliability of the power supply. To prevent the misoperation of the relay protection device caused by the problem of the power supply.

Conventional power supplies require overvoltage protection for the output. The main consideration is that if the output voltage is too high, it will damage the load circuit of the subsequent stage, and undervoltage will not be designed for protection because the impact is small. Due to its special application background, the power supply for relay protection has stricter control over the output voltage.

The start-up time of the power supply is the time from when the power supply is powered on to the time when the output voltage rises to the stable voltage range, and the holding time is the time from when the power supply is powered off to the time when the output voltage drops out of the stable voltage range. Conventional multi-output power supplies have no sequential requirements for the start-up and hold times of each output. The power supply for relay protection requires that the startup time of 5V is 40~140ms before 24V, and the shutdown time of 5V is later than 24V by more than 20ms. When starting, the 5V voltage is established first, the CPU in the protection device completes the initialization program, enters the normal working state, and the state of the signal level of the output circuit is determined, which will not cause the protection device to malfunction. It is also based on this purpose that 24V disappears before 5V when shutting down.

The current power supply used in digital relay protection devices generally only has 5V output with short-circuit protection and output overvoltage protection. With power supply, 5V is established before 24V, and without power supply, 5V is later than 24V, which reduces the power supply. The reliability increases the power factor ratio in the misoperation of the relay protection device.

Contents of the invention

Technical problem: In order to realize the special technical index requirements of the digital relay protection device for the power supply, the present invention designs a switching power supply for digital relay protection, which realizes overvoltage and undervoltage protection, short circuit protection and 5V and 24V protection for each output. Timing of power on and off.

Technical solution: The switching power supply for digital relay protection of the present invention is composed of an input circuit, a main power supply circuit, a power supply output abnormality protection module, a power-on sequence controller, and a shutdown sequence controller. The output terminal of the input circuit is connected to the shutdown sequence controller, Connect to the main power circuit, the output terminal of the shutdown sequence controller is connected to the 24V power switch control circuit in the main power circuit (2), and the 5V, 15V, 24V three-way output power in the main power circuit is correspondingly connected to the power output abnormality protection module The input terminals of the 5V power monitor, 15V power monitor, and 24V power monitor, the output terminals of the 5V power monitor, 15V power monitor, and 24V power monitor are respectively connected to the input terminals of the power abnormal controller, and the power abnormal controller The output terminal of the power supply is connected to the PWM controller in the main circuit of the power supply; the input terminal of the power-on sequence controller is connected to the 5V output power supply, and the output terminal is connected to the 24V power switch control circuit in the main power supply circuit.

The 24V power switch control circuit in the main power supply circuit is composed of a power switch tube whose gate-source voltage can be controlled to open and close. The first gate source of "Q1" controls the optocoupler "U1"; the shutdown timing controller is a fast sampling circuit for power failure at the AC input end of the main power circuit, and its two output terminals "off_A, off_K" are connected to the 24V power switch control circuit The second grid-source of the medium power switching tube "Q1" controls the optocoupler "U2".

The main circuit of the power supply is formed by a single-ended flyback topology. The power switch tube is driven by a current mode controller UC2842, and the 5V main output is equipped with a precision optocoupler feedback circuit with TL431. The input power supply is connected to the primary winding of the transformer after EMI filtering, full-bridge rectification and large-capacitor filtering. The input is equipped with undervoltage protection, and the three sets of separated secondary windings of the transformer output 5V, ±15V and 24V voltages respectively.

The 5V, 15V, and 24V outputs are all equipped with voltage monitoring circuits, and the outputs of each voltage monitoring are connected in series to jointly control the compensation pin of UC2842. When any output is under-voltage, the series circuit is cut off, the control turns off UC2842, and the power supply enters the "hiccup" protection state until the abnormal situation disappears. When any output is short-circuited, the instantaneous current increases sharply and the voltage drops sharply, which triggers output under-voltage protection, and short-circuit protection is included in the scope of output voltage protection.

The 24V output circuit is equipped with an IRFZ44N switch tube, and the 5V output is controlled by a delay circuit to turn on the switch tube to realize the power-on sequence. Adjusting the parameters of the delay circuit can facilitate the realization of the length of the delay. When the power is turned off, the power-off sampling circuit detects that the power is off, controls to turn off the switch tube, cuts off the 24V output, and the 5V output is maintained for a period of time by the energy stored in the large input filter capacitor to meet the shutdown sequence requirements.

Beneficial effect: the present invention obtains following beneficial effect:

(1) The overvoltage and undervoltage protection and short circuit protection of each output of the switching power supply for digital relay protection are designed and realized, and the short circuit protection and overvoltage and undervoltage protection are combined together, and the circuit is simple and effective.

(2) The design realizes the power supply output 5V and 24V switch timing coordination, which meets the timing requirements under different loading conditions.

Description of drawings

Figure 1 is a schematic diagram of the power supply structure.

FIG. 2 is a schematic circuit diagram of the input circuit 1 .

FIG. 3 a is the left half of the schematic diagram of the main power supply circuit 2 , and FIG. 3 b is the right half of the schematic diagram of the main power supply circuit 2 .

FIG. 4 is a schematic circuit diagram of the power supply output abnormality protection module 3 .

FIG. 5 is a schematic circuit diagram of the boot timing controller 4 .

FIG. 6 is a schematic circuit diagram of the shutdown timing controller 5 .

The above figure includes: input circuit 1, electromagnetic interference filter 11; power main circuit 2, input undervoltage protector 21, feedback circuit 22, PWM controller 23, 24V power switch control circuit 24; power output abnormality protection module 3 , 5V power supply monitor 31, 15V power supply monitor 32, 24V power supply monitor 33, power supply abnormality controller 34;

Detailed ways

In Fig. 1, the switching power supply for digital relay protection is composed of input circuit 1, main power circuit 2, power output abnormality protection module 3, start-up sequence controller 4, and shutdown sequence controller 5. The output terminal of input circuit 1 is connected to the shutdown The timing controller 5 is connected to the main power circuit 2, the output terminal of the shutdown timing controller 5 is connected to the 24V power switch control circuit 24 in the main power circuit 2, and the 5V, 15V, and 24V three-way output power in the main power circuit 2 are connected correspondingly To the input terminals of the 5V power monitor 31, the 15V power monitor 32, and the 24V power monitor 33 in the power output abnormality protection module 3, the output terminals of the 5V power monitor 31, the 15V power monitor 32, and the 24V power monitor 33 Connect the input terminals of the abnormal power supply controller 34 respectively, the output terminal of the abnormal power supply controller 34 is connected with the PWM controller 23 in the main power supply circuit 2; The 24V power switch control circuit 24 in 2.

The 24V power switch control circuit 24 in the main power supply circuit 2 is composed of a power switch tube whose gate-source voltage can be switched on and off. The first gate source of the medium power switch tube controls the optocoupler; the shutdown timing controller 5 is a fast sampling circuit for power loss at the AC input end of the main power circuit 2, and its two output terminals are connected to the power switch tube of the 24V power switch control circuit 24 The second gate source controls the optocoupler.

When the power supply has an output overvoltage, undervoltage or short circuit, the power supply output abnormality protection module 3 controls and shuts off the main power supply circuit 2 to realize the protection of the power supply. The 5V output power of the power supply main circuit 2 is connected to the boot sequence controller 4, and the output of the start sequence controller 4 is connected to the power supply main circuit 2 to control the 24V output power of the power supply main circuit 2. The output of the input circuit 1 is connected to the shutdown timing controller 5, and the output of the shutdown timing controller 5 is connected to the main power circuit 2 to control the 24V output power of the main power circuit 2.

1) Input circuit

In Fig. 2, the power supply input is connected to the electromagnetic interference filter 11 through a transient voltage suppressor RV1 connected in parallel to filter out common-mode interference and differential-mode interference. One output end of the electromagnetic interference filter 11 is connected to a fuse F1 in series, the other output end is connected to a varistor RT1 in series, and the other end of the fuse F1 and the varistor RT1 is connected to a power switch S1.

2) Main circuit of power supply

In Fig. 3, the output of the input circuit 1 is rectified and filtered, and then connected to the primary winding of the transformer. The output voltage of the primary winding and the feedback winding, at this moment, the power supply of the PWM controller 23 is provided by the feedback winding. After single-ended flyback DC-DC conversion, the secondary outputs three sets of DC voltages: 5V, ±15V, and 24V. The input undervoltage protector 21 monitors the DC voltage value after input filtering, if it is lower than the undervoltage protection value, the triode Q6 in the input undervoltage protector 21 is saturated and turned on, and the compensation pin voltage of the PWM control circuit UC2842 in the PWM controller 23 is pulled below 1V, the PWM controller 23 is turned off. The 5V output power is connected to the feedback circuit 22, and the feedback circuit 22 is a precision optocoupler feedback circuit with a regulator tube TL431 to ensure the stable accuracy of 5V. ±15V and 24V are equipped with a voltage self-regulating circuit with a regulator tube TL431 to control the output voltage deviation. The 24V output power is connected to the 24V power switch control circuit 24, and the 24V power switch control circuit 24 is composed of a power switch tube whose gate-source voltage can be switched on and off. The output terminal of the power-on sequence controller 4 is connected to a gate-source control optocoupler of the power switch tube in the 24V power switch control circuit 24, and the two output terminals of the shutdown sequence controller 5 are connected to the power switch in the 24V power switch control circuit 24. Another gate source of the tube controls the optocoupler to control the 24V output power.

3) Power output abnormality protection module

In Fig. 4, the output terminals of 5V power monitor 31, 15V power monitor 32 and 24V power monitor 33 are connected to power abnormal controller 34, and the output of power abnormal controller 34 is connected to PWM controller 23. 5V power monitor In 31, when the output voltage is within the normal allowable range, the voltage regulator TL431 diode D5 is turned off, the diode D6 is turned on, and the optocoupler U4 is turned on. When the output is overvoltage, the diode D5 of the regulator tube TL431 is turned on, the diode D6 is turned off, and the optocoupler U4 is turned off. The overvoltage threshold is set by the resistors R67 and R47. When the output is undervoltage, the voltage regulator TL431, diode D5, diode D6 and optocoupler U4 are all turned off, and the undervoltage threshold is set by resistor R68 and resistor R49. The principles of the 15V power monitor 32 and the 24V power monitor 33 are the same as those of the 5V power monitor 31 . The output result of the voltage monitor is reflected in the corresponding state of the optocoupler. When the optocoupler is turned on, it means that the voltage is within the normal allowable range, and when the optocoupler is turned off, it means that the voltage is abnormal. When the three output voltages are all normal, the three output optocouplers are all turned on, the base voltage of the triode Q12 in the abnormal power supply controller 34 is lower than the conduction threshold, the triode is cut off, and the PWM control circuit UC2842 in the PWM controller 23 is normal Work. When any one of the three output voltages is abnormal, the base voltage of the triode Q12 is obtained from the reference output pin of the PWM control circuit UC2842, the triode is saturated and turned on, and the voltage of the compensation pin of the PWM control circuit UC2842 is pulled down to below 1V. The PWM control circuit 23 is turned off, and the power supply enters a "hiccup" protection state until the abnormal situation disappears. The resistor R70 and the capacitor C49 in the abnormal power controller 34 implement a short charging delay after power-on, and the charging delay time must be longer than the power start-up time.

When the output is short-circuited, the output current rises sharply and the voltage drops sharply, which triggers output undervoltage protection and indirectly realizes the short-circuit protection function.

4) Boot sequence controller

In Figure 5, the cathode pin 1 of TL431 U7 is connected to one end of resistors R53 and R54, the reference pin 3 is connected to one end of resistor R80 and capacitor C51, and the anode pin 2 is connected to 5V ground. The other ends of resistors R80 and R53 are connected to +5V output, and the other end of capacitor C51 is connected to 5V ground. The other end of the resistor R54 is connected to the negative end of the LED of the optocoupler U1 in the 24V power switch control circuit 24 .

In Fig. 5, the 5V output charges the capacitor C51 through the resistor R80. When the voltage of the capacitor C51 reaches 2.5V, the regulator tube TL431 U7 is turned on, and the photocoupler U1 in the control circuit 24 of the 24V power switch is controlled to be turned on, and the 24V power switch controls The switching tube Q1 in the circuit 24 obtains the gate voltage, and the Q1 is turned on to provide a 24V output. The delay time of 24V relative to 5V output is determined by the charging time constant formed by resistor R80 and capacitor C51. Adjusting the two parameters can flexibly adjust the delay time.

5) Shutdown sequence controller

In Figure 6, diodes D10, D11, D12, and D28 form a rectifier bridge, one of its input terminals is connected to the input pin 1 of the rectifier bridge BR1 in the main power supply circuit 2 through a resistor R78, and the other input terminal is connected to the main power supply circuit 2 Input pin 3 of rectifier bridge BR1. The output end of the rectifier bridge is connected in parallel with the capacitor C50, one output end of which is connected to the positive end of the light-emitting diode of the optocoupler U2 in the 24V power switch control circuit 24 through the resistor R79, and the other output end is connected to the light emitting diode in the 24V power switch control circuit 24. LED negative terminal of coupler U2.

In Fig. 6, the rectification and filtering completes the sampling of the AC power supply information of the power supply, and the resistors R78 and R79 are used to control the output voltage value of the sampling circuit. When the power supply is normal, the circuit maintains the output and controls the optocoupler U2 in the 24V power switch control circuit 24 to conduct. When the power is off, the capacitor C50 is discharged quickly, and the photocoupler U2 in the 24V power switch control circuit 24 is controlled to turn off, the switch tube Q1 in the 24V power switch control circuit 24 loses the gate voltage, the switch tube Q1 is turned off, and the 24V output is cut off. The parameters of resistor R78, resistor R79, and capacitor C50 should be properly selected so that the sampling circuit maintains a certain voltage output during normal power supply, and the voltage output of the sampling circuit quickly disappears when power is off.

Claims (2)

1. switch power source for digital relay protection, by input circuit (1), electric power main circuit (2), power supply output abnormality protection module (3), start time schedule controller (4), shutdown time schedule controller (5) is formed, it is characterized in that: the output of input circuit (1) respectively with the shutdown time schedule controller (5), electric power main circuit (2) connects, 24V power on-off control circuit (24) in the output termination electric power main circuit (2) of shutdown time schedule controller (5), 5V in the electric power main circuit (2), 15V, 24V three road out-put supply correspondences are connected to the 5V supply monitor (31) in the power supply output abnormality protection module (3), 15V supply monitor (32), the input of 24V supply monitor (33), 5V supply monitor (31), 15V supply monitor (32), the output of 24V supply monitor (33) connects the input of abnormity of power supply controller (34) respectively, the PWM controller (23) in the output termination electric power main circuit (2) of abnormity of power supply controller (34); The input termination 5V out-put supply of start time schedule controller (4), the 24V power on-off control circuit (24) in the output termination electric power main circuit (2).

2. switch power source for digital relay protection according to claim 1, it is characterized in that: the 24V power on-off control circuit (24) in the electric power main circuit (2) is made of the power switch pipe of gate source voltage may command folding, start time schedule controller (4) is a charging delay control circuit, and its output inserts the first grid source control optical coupler (U1) of power switch pipe (Q1) in the 24V power on-off control circuit (24); Shutdown time schedule controller (5) is electric power main circuit (a 2) ac input end dead electricity quick sampling circuit, and two output (off_A, off_K) inserts the second grid source control optical coupler (U2) of power switch pipe (Q1) in the 24V power on-off control circuit (24).

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