A kind of positive 10V dc sources protection circuit for frequency converter
Technical field
A kind of positive 10V dc sources protection circuit for frequency converter is the utility model is related to, belongs to electric circuit safety
Protection technique field.
Background technology
It is well known that need to be powered device with positive 10V dc sources in frequency converter, existing+10V DC power supply circuits
It is to recall+10V voltages by one piece of entitled U32 pressure regulation chip, three resistance of external resistor.This circuit is not protected voluntarily
The function of shield, its carrying load ability depend on the power of U32 pressure regulation chips, and when external+10V power output ends occur
When short-circuit, easily occur burning out U32 chips, or even the serious accidents such as fire occur, both influence manufacturing schedule, give enterprise again
Cause economic loss.
The content of the invention
To overcome the drawbacks described above of positive 10V power supplys in existing frequency converter, the utility model provides a kind of for frequency converter
Positive 10V dc source protection circuits, protected to allow positive 10V dc sources to carry out self in the case where there is load excessive
Shield, prevents to burn out unsafe accident such as chip.
To solve its technical problem, the technical solution adopted in the utility model is:The positive 10V for frequency converter designed
Dc source protection circuit, it is after the positive 10V DC power supply circuits of existing frequency converter, increases this protection circuit again and carry out excessively stream
Protection circuit, the current foldback circuit, including:One piece of operational amplifier, two transistors and resistance capacitance, its spy
Putting is:
1st, operational amplifier positive 10V DC power supply circuits output end, pass through a resistance and a filter capacitor
The base stage with first transistor is connected afterwards, while is connected with the colelctor electrode of second transistor, first crystal
The colelctor electrode of triode ,+15V power supply, the hair of first transistor are followed by by the parallel circuit of two resistance
Machine is penetrated by wire with the base stage of second transistor to be connected, at the same by a resistance also with second transistor
Emitter stage be connected, the emitter stage is connected to the output end of+10V voltages;
2nd, the model of first and second transistor is:MMBT4401LT1;
3rd, the parameter of the capacitor is:104/25V.
Compared with prior art, the utility model has following features and progress:Because the utility model is defeated using arithmetic unit
Go out after+10V DC voltages and pass through the automatic protection circuit being made up of two transistors and the resistance of three, therefore can be right
The abnormal conditions that face terminals external positive 10V occur carry out self-protection, with exempt pick out outside existing exception it is short-circuit when cause
Frequency converter terminal faults, or even burn out component, improve the sense of security of product.
Brief description of the drawings
Fig. 1 is electrical structure signal schematic diagram of the present utility model.
In figure:U7B is arithmetic unit, and Q15 and Q16 are transistor, and C48 is filter condenser, R19, R37, R65,
R66, R76 and R93 are resistance.
Embodiment
The utility model is further illustrated with reference to the accompanying drawings and examples:
The positive 10V dc sources protection circuit designed, including the existing+10V power supplys exported by arithmetic unit U7B output ends
Circuit and the current protecting circuit newly increased, it is in the positive 10V direct currents of existing frequency converter being made up of R37, R76 and arithmetic unit U8
Pass through this protection circuit again after power supply, it is carried out to stablize protection, finally stable+10V the dc sources of output.It is described to newly increase
The automatic protection circuit that is made up of two transistors and the resistance of three of protection circuit include:One piece of model:
LF347D operational amplifier U7B, two model MMBT4401LT1 transistor Q15 and Q16, and resistance R19,
R37, R65, R66, R76 and R93, parameter are 104/25V filter condenser C48, and their annexation is:
The existing positive 10V DC power supply circuits of frequency converter are:An arithmetic unit U7B input 5 is grounded, and calculates the another of device U7B
One input 6 is connected by the resistance R37 that resistance is 10KF with -2.5V power supplys, while the resistance R76 by resistance for 47KF
It is connected with arithmetic unit U7B output end 7, makes output end output+10V voltages;
The utility model exports in existing arithmetic unit U7B output ends 7 increases the utility model institute on+10V voltage output ends
The following protection circuit stated:
The input power of the protection circuit is the+10V voltages that the arithmetic unit U7B output ends 7 of existing frequency converter export, and is led to
Cross behind one end of the resistance R93 that resistance is 2KF and the filter condenser C48 that parameter is 104/25V with first transistor
Q15 base stage is connected, while is connected with second transistor Q16 colelctor electrode, capacitor C48 other end ground connection;The
One transistor Q15 colelctor electrode ,+15V is followed by by resistance R65, R66 that two resistances are 499RF parallel circuit
Power supply, the base stage phase that first transistor Q15 emitter passes through wire and second transistor Q16
Even, while by emitter stages of the resistance R19 also with second transistor Q16 that a resistance is 100RF it is connected, this is sent out
Emitter-base bandgap grading is connected to the output end of+10V voltages.
During work, the resistance R37 and R76 that first pass through operational amplifier U7B connections adjust out 10V voltage, then pass through
Resistance R93 first drives first transistor Q15 base stage to operational amplifier U7B output current limiting, then by it is external+
15V power supplys and the right+10V voltages of resistance R65, R66 are powered, and when+10V voltage loads are excessive, then resistance R19 voltage can increase
Greatly, so as to drive the second transistor Q16, after the Q16 is driven, first transistor Q15 base voltage
Reduce, reduce output current, to have the function that protection device, load-carrying capacity of water can be entered with resistance R19 resistance
Row regulation, is advisable with the rated current no more than first transistor Q15.This positive 10V protection circuit, to external terminal
When positive 10V is if there is abnormal conditions, self-protection can be carried out, with exempt pick out outside existing exception it is short-circuit when caused frequency converter
Terminal faults, or even burn out component.