Bright book tri-level switch power amplifier
One, technical field
Tri-level switch power amplifier of the present invention belongs to voltage-current mode switch power amplifier.
Two, background technology
Shortcomings such as early stage voltage-current mode power amplifier is a linear power amplifier, because its power loss is big, efficient is low, adopts two level switch power amplifiers afterwards, but that two level power amplifiers have a current ripples is big, and dynamic characteristic is limited.The scholar had proposed three level modulation technology in recent years, and digital tri-level switch power amplifier is many with DSP, and chips such as CPLD or FPGA are main control circuit, what have also will add the A/D module, price is more expensive, also will consider the interference problem of digital and analogue signals, and reliability is not high; The simulation tri-level switch power amplifier utilizes ripe pulse modulation technology, and the reliability height is with low cost, is fit to commercial Application.
Three, summary of the invention
The object of the present invention is to provide tri-level switch power amplifier simple in structure, that cost is low, efficient is high, reliability is high.
Power amplifier comprises following circuit:
1. signal mixed processing circuit: the current signal in the inductive load that current sensor is fed back, (the unipolarity switch power amplifier has the voltage signal that quiescent current is regulated, the bipolarity switch power amplifier does not have this voltage signal) and the signal plus of PID controller, control signal produced.In order to make power amplifier control accurate, adopt the proportional integral circuit.
2. pulse-width modulation circuit, protection and optical couple isolation drive circuit: pulse-width modulation circuit is used for the control signal from signal mixed processing circuit is compared with triangular wave, produces the pwm pulse signal that duty ratio changes with control signal.Optical couple isolation drive circuit flows through corresponding electric current with the switching tube of this pulse signal output driving bridge circuit in load, produce magnetic force.Protective circuit can be protected power switch pipe, and the restriction maximum current is avoided damaging because of electric current is excessive.
3. bridge circuit: adopted improved half-bridge structure for unipolar power amplifier, be used for the occasion that the requirement load has quiescent current more.Ambipolar power amplifier has adopted full bridge structure, is used for the occasion that the requirement load need not quiescent current more.
Technical scheme of the present invention is: the output that the signal that comprises voltage signal that the current signal, quiescent current of the inductive load that current sensor is fed back are regulated and PID controller from the solenoid of power switch bridge circuit carries out the signal mixed processing circuit that addition handles is connected in by triangular-wave generator and is connected in the pulse-width modulation circuit that comparator is formed; the output of this pulse-width modulation circuit is connected in protective circuit and optical couple isolation drive circuit, and the output of this optical couple isolation drive circuit is connected in the power switch bridge circuit.
Described signal mixed processing circuit, comprise the PID controller output signal through operational amplifier oppositely after the PID signal of resistance, carry out proportional integral with raising current response speed through the bias voltage three of the resistance control signal that produces that superposes through operational amplifier through the current feedback signal of resistance and-5 volts voltages.
Described pulse-width modulation circuit and optical couple isolation drive circuit, comprise by the output signal of higher level's treatment circuit and pass through the triangular wave comparator, pulse voltage through NAND gate circuit output high-low level is input to the optocoupler driver again and offers the power switch bridge circuit, makes bridge circuit work.
Described protective circuit; comprise by flow through the differential coil load current from current sensor senses and convert voltage signal to through resistance; through behind the two-stage calculation amplifier with the output signal power controlling switching bridge circuit of magnitude of voltage behind comparator of setting in the shutoff of switching tube, realize defencive function to switching tube.
Good effect of the present invention is:
Principle based on three level modulation technology, unipolarity and bipolarity switch power amplifier have switching frequency to be fixed, output ripple is little, can control minimum turn-on and turn-off pulse duration, the power amplifier capacitance power dissipation is little, characteristics such as efficient height can make load current rapid track and control signal, can regulate bias current according to the needs at scene.Photoelectric coupled circuit adopts the bootstrapping supply power mode, makes to drive the power supply that each road load all will be lacked one tunnel isolation, will lack ten road power supplys for the driving that resembles ten coils of five degrees of freedom in the magnetic levitation bearing system, and this will significantly reduce cost.Bipolarity switch power amplifier bridge circuit has gate charge repid discharge loop, has reduced the due to voltage spikes that switching tube turns on and off generation effectively, prevents that same brachium pontis conducting from causing short circuit overcurrent and damaging switching tube.
Four, description of drawings
Fig. 1 is a unipolarity power amplifier theory diagram of the present invention.
Fig. 2 is unipolarity power amplifier signal mixed processing circuit theory diagrams of the present invention.
Fig. 3 is unipolarity power amplifier pulse-width modulation circuit of the present invention and optical couple isolation drive circuit schematic diagram.
Fig. 4 is a unipolarity power amplifier protective circuit schematic diagram of the present invention.
Fig. 5 is a unipolarity power amplifier bridge circuit schematic diagram of the present invention.
Fig. 6 is a bipolarity power amplifier theory diagram of the present invention.
Fig. 7 is the pulse-width modulation circuit schematic diagram of bipolarity power amplifier of the present invention.
Fig. 8 is a bipolarity power amplifier bridge circuit schematic diagram of the present invention.
Five, embodiment
With the unipolarity power amplifier of controlling two coil load electric currents is example, and the bipolarity power amplifier is identical with unipolarity power amplifier principle major part, and difference illustrates in addition.
Unipolarity power amplifier circuit principle as shown in Figure 1, designation among Fig. 1: Q1, Q3 are switching tube, D2, D4 are power diode.Mainly comprise signal mixed processing circuit, pulse-width modulation circuit, protective circuit, optical couple isolation drive circuit and bridge circuit.Signal mixed processing circuit as shown in Figure 2 because the PID signal will be controlled two differential coil loads up and down of one degree of freedom respectively, one of them PID signal is through operational amplifier U
1COppositely.-5V provides the required bias voltage of quiescent current, through the PID of resistance R 4 signal, through resistance R
6-the 5V bias voltage with through resistance R
3Current feedback signal stack produce control signal through operational amplifier U
1DCarry out the one-level proportional integral and improve current response speed.Pulse-width modulation circuit and optical couple isolation drive circuit are as shown in Figure 3.Designation among Fig. 3: G
1And G
2Be higher level's treatment circuit output signal, TANG is a triangular signal, U
3, U
13, U
5, U
15Be comparator, U
4A, U
14A, U
6A, U
16ABe NAND gate, TP1, TP2, TP3, TP4 are the optocoupler driver.Forward and reverse triangular wave TANG is as carrier frequency, the output signal G of higher level's treatment circuit
1, G
2With triangular wave TANG through the comparator pulse voltage of back output high-low level relatively, offer half-bridge circuit two MOSFET pipe Q1 up and down by the high speed photo coupling driver, the Q3 gate drive signal makes bridge circuit work.Resistance R 10 and R32, resistance R 15 and R37 by with resistance R 8, R28, the dividing potential drop of R13 and R35 can change the Dead Time of gate drive signal, guarantees not conducting simultaneously of upper and lower bridge arm, prevents short circuit overcurrent.Diode D4, resistance R 18 and capacitor C 3 are formed upward coil load high-side driver bootstrapping power supply circuits, when bridge is worked down, + 15V power supply is through diode D4, resistance R 18, and load and following bridge charge for capacitor C 3, to guarantee that bridge turn-offs down, the grid of going up bridge when last bridge is opened has enough energy storage to drive.Diode D6, resistance R 40 and capacitor C 8 are lower coil load high-side driver boostrap circuit, principle is the same.Diode D1, D2, D3 and D5 connect protective circuit.Protective circuit as shown in Figure 4, designation among Fig. 4: U
8, U
9, U
17, U
18Be operational amplifier, L1, L2 are green LED, and L3, L4 are red light emitting diodes.Flow through the current i of two differential coil loads respectively by current sensor senses
a, i
b, be converted to the correspondent voltage signal through resistance R 20 and resistance R 41 respectively, with potentiometer W3, W6 and W7 set point are relatively, when current value in the load during greater than the current minimum set, green diode L1, L2 lights, red diode L3, L4 does not work, and shows the power amplifier operate as normal; When current value in the load surpasses the current maxima of setting, green diode L1, L2 does not work, red diode L3, L4 lights, and shows that power amplifier has fault, answer the power cutoff inspection, turn-off the pulse signal of optocoupler driver input end simultaneously, bridge circuit is quit work.Diode D1, D3 in the M point map interlinking 3 among Fig. 4, diode D2, D5 in the N point map interlinking 3.The used bridge circuit of unipolarity power amplifier is an improvement half-bridge structure commonly used as shown in Figure 5.Symbol Q1, Q3 are switching tube among Fig. 5, and D2, D4 are diode.
Bipolarity power amplifier principle as shown in Figure 6.Symbol Q1, Q2, Q3, Q4 are switching tube among the figure.Mainly comprise signal mixed processing circuit, pulse-width modulation circuit, protective circuit, optical couple isolation drive circuit and bridge circuit.Signal mixed processing circuit, protective circuit is basic identical with the unipolarity power amplifier with the optical couple isolation drive circuit theory structure.The pulse-width modulation circuit of bipolarity power amplifier as shown in Figure 7.Designation among Fig. 7: U4, U5 are comparator, and U6C, U7C, U6D, U7D are NAND gate, and X1C, X1D, X2E, X2F, X1E, X1F, X1A, X1B are trigger, and T1, T2, T3, T4 are the optocoupler driver, and Q1, Q2, Q3, Q4 connect the switching tube grid.Diode D1, resistance R 8, capacitor C 13 is formed the RC charge-discharge circuits, comes the Dead Time of the same brachium pontis of controlling and driving bridge circuit by the RC time constant, the rising edge time-delay, trailing edge descends fast.Diode D2, resistance R 10, capacitor C 15, diode D6, resistance R 14, capacitor C 20, diode D7, resistance R 17, capacitor C 23 also are the RC charging and discharging circuit.Because the bipolarity power amplifier need drive 4 switching tubes,, drive two switching tube Q2 in addition, Q4 so increase by 2 the road than 2 of the unipolarity power amplifier drivings of Duoing.G point among the figure is the output signal of higher level's signal processing circuit, and the P point connects protective circuit.The used bridge circuit of bipolarity power amplifier as shown in Figure 8.Symbol Q1 ~ the Q4 that indicates among the figure is a switching tube.