CN103094875B - A kind of solid-state power controller based on microcontroller implementation - Google Patents

Abstract

Based on a solid-state power controller for microcontroller implementation, comprise signal isolation circuit, insulating power supply, microcontroller, AD analog to digital converter, amplifier, comparator, drive circuit, detection resistance and power MOSFET composition.Instantaneous tripping guard signal is produced by comparator, instantaneous tripping reference voltage.By detecting resistance, amplifier, AD analog to digital converter, line current signal forms the digital current signal of microcontroller.Microcontroller utilizes the method in the present invention can realize calculating the thermal accumlation of line current; inverse time lag trip protection signal is produced to the overload situations exceeding rated current; drive supply line's switch to turn off in time, play protection circuit effect, the present invention has heat memory function.The present invention can monitoring load electric current, tripped condition.

Description

A kind of solid-state power controller based on microcontroller implementation

Technical field

The present invention relates to the solid-state power controller of microcontroller implementation, belong to power electronics and electrical technology field.

Background technology

Field of power distribution generally adopts electromagnetic relay or solid state relay to realize switch control rule, coordinates fuse to realize line current overload protection.Under overload situations, fuse thermal accumlation makes himself conductor temperature raise, and after reaching fusing point, fusing conductor material, open-circuit line plays a protective role.Fusing time depends on the size of circuit overload electric current, and overload current is larger, and fusing speed is faster.After fuse blows, only have and again could recover conducting by changing intact fuse.Solid-state power controller of the present invention, can by the function i ntegration of switch control rule, fuse protection based on the inverse time lag trip protection of microcontroller implementation electronic type, has trip protection simultaneously and to reset the feature of conducting again, line status monitoring.

Summary of the invention

The technology of the present invention is dealt with problems and is: overcome the deficiencies in the prior art, provides a kind of solid-state power controller based on microcontroller implementation, has the feature of Protection parameters alterability, overload trip protection, greatly improves the validity of system overload protection.

Technical solution of the present invention: a kind of solid-state power controller based on microcontroller implementation comprises: signal isolation circuit, insulating power supply, microcontroller, AD analog to digital converter, amplifier, comparator, drive circuit, detection resistance and power MOSFET; Insulating power supply receives after outside 5V powers and produces internal insulation 5V, 10V power supply, for whole controller is powered; External control order produces isolation signals through signal isolation circuit and delivers to microcontroller, microcontroller controls drive circuit according to the control command of isolation signals, drive circuit receives and drives ON command rear drive power MOSFET ON, line current is through detecting resistance to load, and load obtains distribution; Line current enters comparator and AD analog to digital converter in the ohmically current voltage drop of detection respectively through amplifier conditioning amplification; When load current reaches short-circuit condition, the current signal after conditioning causes comparator to overturn, and forms instantaneous tripping signal, and microcontroller to receive after this state switch-off power MOSFET immediately; When load current overload not yet reaches short-circuit condition, microcontroller receives the current signal after AD analog-to-digital conversion, the software tripping operation algorithm of microcontroller carries out inverse time lag thermal accumlation computing, obtain heat result, described heat result is compared with the reference value of setting, when reaching protection limit value, microcontroller outputs signal immediately and controls switch-off power MOSFET output by drive circuit; Load current load, at rated value and following, controls power MOSFET according to control order and exports conducting or shutoff; Microcontroller according to load current value size, whether be in tripped condition, indicate corresponding state, externally export through signal isolation circuit;

The operational formula that described software tripping operation algorithm carries out inverse time lag thermal accumlation is:

$V_A\left(n\right)=\frac{T}{T+\mathrm{RC}}[I_w^2\left(n\right)R+\frac{\mathrm{RC}}{T}{V}_A(n-1)]$

Wherein: T is the sampling time, R is the resistance in algorithm model, and C is the electric capacity in algorithm model, V _an () is n-th thermal accumlation value, I _wn () is n-th sampling circuit electric current.

Described microcontroller can be worked with bus serial communication mode by Protocol Design; Trip time parameter R, C in described software program can pass through communication instruction online change, to realize the line power grade changing solid-state power controller.

The advantage of the present invention compared with conventional electrical distribution switch, fuse is:

(1) the present invention realizes panel switches and controls, and can monitoring switch tripped condition, the size of electric current in monitoring load circuit;

(2) present invention achieves software tripping operation algorithm realization inverse time lag trip protection curve, there is fuse inverse time lag trip avoidance function, and according to circumstances can realize circuit reset, do not need to change circuit protecting device;

(3) the present invention can online updating microcontroller trip protection parameter, thus realizes the trip protection of different rated current or the renewal of trip time;

(4) the present invention is based on electronic devices and components and microcontroller program, greatly improve trip protection curve accuracy, consistency;

(5) the software tripping operation algorithm described in is that charging voltage compares with reference voltage based on the current source after line current square to the charging of RC parallel circuits.Trip signal can be produced during load overcurrent.

Accompanying drawing explanation

Fig. 1 is circuit theory diagrams of the present invention;

Fig. 2 is fuse schematic diagram of the prior art;

Fig. 3 realizes the present invention to trip the circuit theory diagrams of algorithm;

Fig. 4 is A point voltage waveform in Fig. 3 under different loads electric current;

Fig. 5 is inverse time lag tripping operation curve.

Embodiment

As shown in Figure 1, the present invention includes: signal isolation circuit 1, insulating power supply 2, microcontroller 3, AD analog to digital converter 4, amplifier 5, comparator 6, drive circuit 7, detection resistance 8 and power MOSFET 9.

Solid-state power controller control inputs of the present invention and power take-off electrical isolation, can realize switch control rule, status monitoring, overcurrent tripping defencive function.

1, switch control functions.Insulating power supply 2 receives after outside 5V powers and produces internal insulation 5V, 10V power supply, for whole controller is powered; External control order produces isolation signals through signal isolation circuit 1 and delivers to microcontroller 3, microcontroller 3 controls drive circuit 7 according to the control command of isolation signals, drive circuit 7 receives and drives the conducting of ON command rear drive power MOSFET 9, line current is through detecting resistance 8 to load, and load 10 obtains distribution.

2, overcurrent tripping defencive function.The current voltage drop of line current on detection resistance 8 is nursed one's health to amplify through amplifier 5 and is entered comparator 6 and AD analog to digital converter 4 respectively; When load 10 electric current reaches short-circuit condition, the current signal after conditioning causes comparator 6 to overturn, and forms instantaneous tripping signal, and microcontroller 3 to receive after this state switch-off power MOSFET9 immediately; When load 10 current overload not yet reaches short-circuit condition, microcontroller 3 receives the current signal after AD analog to digital converter 4, the software tripping operation algorithm of microcontroller 3 inside carries out inverse time lag thermal accumlation computing, obtain heat result, described heat result is compared with the reference value of setting, when reaching protection limit value, microcontroller 3 outputs signal immediately and controls switch-off power MOSFET9 by drive circuit 7 and export; Load 10 will keep tripped condition after exporting tripping operation, until resetted to microcontroller by control command, again can control power MOSFET 9 by control command and export conducting.

3, status monitoring function.Status monitoring can be divided into the monitoring of loaded line current status, the monitoring of solid-state power controller output state.Load current status monitoring is in course of normal operation, and microcontroller 3 compares 15% of the output line current detected and load current value, exceedes 15% of rated current, state instruction low level; Lower than rated current 15%, state instruction high level.Can judge that switch closes loaded line whether exception or open circuit with this.Because of loaded line overcurrent, microcontroller 3 is in tripped condition, and tripped condition is indicated output by signal isolation circuit 2 by microcontroller 3.

Microcontroller 3 can be worked with bus serial communication mode by Protocol Design; Trip time parameter R, C in software tripping operation algorithm can pass through communication instruction online change, to realize the line power grade changing solid-state power controller.

The inverse time lag tripping operation theory of algorithm of microcontroller 3 inside of the present invention is as follows with realization:

Figure 2 shows that the schematic diagram of fuse of the prior art.The differential equation that formula (1) is heating conductor power and own temperature.P (t) is heater own power, and a is the intensification coefficient of heating conductor, and b is the coefficient of heat transfer of conductor, and θ (t) is t temperature rise of conductor.Temperature rise of conductor will be made to raise if conductor self-heating power exceedes heat dissipation capacity, otherwise temperature rise of conductor decline, until reach heating and heat dissipation balancing.The fever model of fuse and operation principle can use formula (1) to describe, after current overload temperature rise exceedes fusing point, and fuse blows protection circuit.

$P\left(t\right)=a\frac{\mathrm{d\θ}\left(t\right)}{\mathrm{dt}}+\mathrm{b\θ}\left(t\right)---\left(1\right)$

Figure 3 shows that realizing the present invention trips the circuit theory diagrams of algorithm.The line electricity flow valuve that operation principle is forms current source through multiplying and exports, and to the charging of RC parallel circuits, can have equation (2)

$I_w^2\left(t\right)=C\frac{d{V}_A\left(t\right)}{\mathrm{dt}}+\frac{V_A\left(t\right)}{R}---\left(2\right)$

Matching test (1) and formula (2), in equation (1), P (t) is and current squaring be directly proportional.Adjusting resistance R, electric capacity C value can make voltage V in formula (2) _atemperature rise θ (t) in (t) analog (1).Timeconstantτ=RC in circuit.Therefore obtain the electronic circuit of simulating fuse temperature rise, work as V _at () voltage exceedes reference comparison voltages V _ref, namely think that temperature rise exceedes protection point, form trip signal.

Figure 4 shows that the voltage rise waveform that different current source charges to RC parallel circuits, i.e. A point voltage rising waveform in Fig. 3 circuit.Current curve 3 and current curve 4 corresponding A point burning voltage do not exceed reference comparison voltages, therefore can not form trip signal.Current curve 1 can exceed reference voltage V with the burning voltage of current curve 2 _ref, reach V in voltage rise process _refnamely form trip signal, disconnect output.

Fig. 5 is different time constant τ=RC and reference voltage V _refthe inverse time lag tripping operation waveform formed, τ ₂> τ ₁.

The function of the software tripping operation algorithm realization Fig. 3 circuit in microcontroller 3, peer-to-peer (2) discretization, sampling time T, can obtain formula (3), solves formula (4).Write software inverse time lag tripping operation program according to equation (4), can protection algorism be realized.

$\frac{V_A\left(n\right)}{R}+C\frac{V_A\left(n\right)-V_A(n-1)}{T}=I_w^2\left(n\right)---\left(3\right)$

$V_A\left(n\right)=\frac{T}{T+\mathrm{RC}}[I_w^2\left(n\right)R+\frac{\mathrm{RC}}{T}{V}_A(n-1)]---\left(4\right)$

Wherein: T is the sampling time, R is the resistance in algorithm model, and C is the electric capacity in algorithm model, V _an () is n-th thermal accumlation value, I _wn () is n-th sampling circuit electric current.

The content be not described in detail in specification of the present invention belongs to the known technology of those skilled in the art.

Claims (2)

1. based on a solid-state power controller for microcontroller implementation, its feature comprises: signal isolation circuit, insulating power supply, microcontroller, AD analog to digital converter, amplifier, comparator, drive circuit, detection resistance and power MOSFET; Insulating power supply receives after outside 5V powers and produces internal insulation 5V, 10V power supply, for whole controller is powered; External control order produces isolation signals through signal isolation circuit and delivers to microcontroller, microcontroller controls drive circuit according to the control command of isolation signals, drive circuit receives and drives ON command rear drive power MOSFET ON, line current is through detecting resistance to load, and load obtains distribution; Line current enters comparator and AD analog to digital converter in the ohmically voltage drop of detection respectively through amplifier conditioning amplification; When load current reaches short-circuit condition, the current signal after conditioning causes comparator to overturn, and forms instantaneous tripping signal, and microcontroller to receive after this state switch-off power MOSFET immediately; When load current overload not yet reaches short-circuit condition, microcontroller receives the current signal after AD analog-to-digital conversion, the software tripping operation algorithm of microcontroller carries out inverse time lag thermal accumlation computing, obtain heat result, described heat result is compared with the reference value of setting, when reaching protection limit value, microcontroller outputs signal immediately and controls switch-off power MOSFET output by drive circuit; Load current, at rated value and following, controls power MOSFET according to control order and exports conducting or shutoff; Microcontroller according to load current value size, whether be in tripped condition, indicate corresponding state, externally export through signal isolation circuit;

The operational formula that described software tripping operation algorithm carries out inverse time lag thermal accumlation is:

$V_A\left(n\right)=\frac{T}{T+\mathrm{RC}}[I_w^2\left(n\right)R+\frac{\mathrm{RC}}{T}{V}_A(n-1)]$

Wherein: T is the sampling time, R is the resistance in algorithm model, and C is the electric capacity in algorithm model, V _an () is n-th thermal accumlation value, I _wn () is n-th sampling circuit electric current.

2. a kind of solid-state power controller based on microcontroller implementation according to claim 1, is characterized in that: described microcontroller can be worked with bus serial communication mode by Protocol Design; Trip time parameter R, C in described software program can pass through communication instruction online change, to realize the object changing solid-state power controller power grade.