The principle of generation circuit graph of negative voltage

 

In electronic circuit we often need to use negative tension, often need to build a negative voltage to him when use carry is put e.g. us. Below simple with 5V voltage is a circuit that says him to negative voltage 5V.

 

When normally I need to use negative tension, general meeting chooses to use appropriative negative pressure to produce chip, but these chip are more expensive for instance ICL7600, LT1054 is waited a moment. Oh within an inch of forgot MC34063 what this chip uses is most, produce circuit about the negative pressure of 34063 did not say to be in Datasheet here some. We look to be in please below odd two kinds of negative pressure that middling uses a machine electron circuit produce circuit.

 

 

Present sheet piece machine a lot of contain PWM to output, we are using sheet piece machine when a lot of moment of PWM are assisting generation negative pressure with him without what use is right choice.

 

The circuit above is a circuit of the simplest negative pressure generation. The original that he uses is least the square wave that we need to offer 1kHZ to control to him only is OK, those who comparative is simple. The acting laden capability that needs to notice this circuit here is very weak, the descent of the voltage after increasing load at the same time is bigger also.

 

Because the reason above produced this circuit below:

 

 

Negative voltage produces circuit to analyse

 

The definition of voltage: Voltage (Voltage) , also call electromotive force difference or voltage, it is to measure unit charge to differ as a result of electromotive force in electrostatic field the physical quantity with the poor energy of a generation. Because suffer effect of electric field strength to nod shift to choose the work that does to B from A,its size is equal to unit positive electrical charge, the directional regulation of voltage is the direction that points to low potential from high potential.

 

Spoken parts in an opera is: Voltage of a certain bits is opposite the poor value between the electromotive force of a reference point. V some =E some – E ginseng. General we regard negative pole of power supply source as reference point. Power source voltage is Vcc=E power source – E power source is lost.

 

Think generation loses voltage, make his photograph lower to the electromotive force of power source negative pole can. Want lower, must have another power supply intervene, fundamentality is the series connection that uses two power source. 2 anode series connection is in power source referenced power source after the negative pole of 1. Power source 2 negative pole are negative voltage.

 

 

A negative voltage produces circuit: Use capacitance to charge equivalent gives a new power supply, capacitance series connection is after GND, equivalent is power source 2. Produce negative tension.

 

 

1, capacitance charges: When PWM is low n, q2 is opened, q1 is shut, VCC charges to C1 through Q2, charge loop is VCC-Q2-C1-D2-GND. The Zun Zheng on C1 is right negative.

 

 

2, capacitance C1 fills report

 

 

3, capacitance C1 serves as power source, c1 is tall series connection of electromotive force pole is in reference point. C1 discharge, from C2 follow on current, generation loses voltage.

 

When PWM is low n, q2 is shut, q1 is opened, c1 begins to discharge, discharge loop is C1-C2-D1, this also is the process that has charging to C2 actually. After C2 fills good report, going up below negative, if the electromotive force of VCC is at 5 o’clock a few bend over, can output – the voltage of 5V.

 

 

Generation negaive electricity is pressed (- 5V) plan

 

 

7660 output ability with MAX232 finite, do oscillograph to take high speed carry to put very demanding, so Wei Kun also must use 4 shunt-wound means enlarge to flow.

 

The first edition is two 7660 paralell connection.

 

With common DC/DC chip can produce negative tension, and voltage accuracy is pressed with positive electricity same, drive capability is very strong also, can achieve 300mA above.

 

Chip of general switch power source can produce negative tension, be no good really go pushing charge pump with the PWM that outputs with switch power source, also can produce bigger electricity, cost is very low also, do not know ripple to ask how many, ripple is quite small after charge pump uses LC filter wave. 7660 it is charge pump electric current is very so small.

 

Of the design number power source of whole oscillograph + of 5V and imitate power source + 5 V is apart power supply, but how should be digital ground and imitate ground handled?

 

Digital ground and imitate ground must be together repeatedly, otherwise circuit does not have law job.

 

The ground of digital part returns electric current to cannot have shed imitate part ground, two ground should be connected together in stable ground reference point.

 

Lose the sense of voltage

 

1, factitious regulation. It is to use in phone system for example – 48V comes of power supply, can avoid line to be corroded by electrochemistry so. Of course, turning over picking up the telephone also can work, no more than is voltage reference point changes just.

 

2, communication interface need. For example RS232 interface, must use negative tension. – 3V ～ – 15V expresses 1, + 3 ～ + 15V expresses 0. This is the agreement when designing communication interface at the outset, can abide by cough up only. PS:MThe interface chip of AX232 and so on takes charge pump oneself, can oneself produce negative tension.

 

3, for (blame course arrives course) carry is put offer power source course. Vintage carry is put is to do not have course to be inputted to course / those who output ability, for example OP07, input voltage limits always parts than limits of power source voltage small 1V, output parts small 2V. Such if VEE uses 0V, so the input carries voltage to must exceed 1V, output voltage won’t under 2V. Such word may not satisfy the design of certain circuitry to ask. The input to can be close to 0V / output works below the condition, put to carry with respect to need offer negative voltage, for example – 5V, such ability make carry is put around 0V to work normally. Gain ground as what course puts to rail transport nevertheless, this kind of circumstance is scarcer and scarcer also.

 

4, this has Chinese distinguishing feature quite, self-destruction circuit. Generally speaking the protective circuit of chip interior is pressed to negaive electricity is not of fortify, should have electricity only so largish, voltage need not very tall negative voltage is added to chip, can destroy chip successfully.