Above all the basic develop that we understand half bridge circuit first attacks:

 

The basic develop of half bridge circuit attacks circuit graph

 

Capacitor C1 and C2 and switch canal Q1, Q2 constitutes the bridge, the diagonal of the bridge receives the former edge winding of transformer T1, friend calls half bridge transformer. If right now C1=C2, so when some switch the canal guides when connecting, the voltage on winding has the in part of power source voltage only.

 

 

Consult the basic develop of half bridge circuit attacks circuit graph, among them Q1 is enlightened, q2 closes, the tension that right now two end increase transformer is the half of bus voltage, at the same time energy is delivered to deputy edge by former edge. Q1 closes, q2 closes, right now transformer deputy edge two winding because rectification diode two pipe at the same time follow on current and be in short circuit condition, former edge winding also is equivalent to short circuit condition. Q1 closes, q2 is enlightened. The tension that right now two end increase transformer basically also is the half of bus voltage, at the same time energy is delivered to deputy edge by former edge. Two diode complete deputy side change stream.

 

 

 

Reason: Because two capacitance join the potential of bit of A is,follow Q1, Q2 to guide open a case and floating, the Fu Miao that can balance every transistor switch automatically so is worth, when float does not satisfy a requirement, hypothesis Q1, Q2 has different switch character, fall in T=t1 of identical base pulse width namely, q1 closes slower, q2 closes faster, the tension that hints to B is met influential, with respect to what can have the A1 in having gray area, A2 lopsided Fu Miao is worth, the reason is Q1 involves delay.

 

If want this kind of lopsided undee drive transformer, will happen slant magnetism phenomenon, cause core saturation and had produced big transistor collector electricity, reduced the efficiency of transformer thereby, make transistor out of control, even burn down.

 

In series connection of transformer former edge the working weaveform of a capacitance pursues

 

Settle way: C3 of capacitance of a series connection is added in coil of transformer former edge, be worth the dc bias voltage of direct ratio to will be dropped by second capacitance filter with lopsided Fu Miao, guide in transistor so during connecting, be worth with respect to the Fu Miao of meeting balance voltage, achieve eliminate slant the purpose of magnetism.

 

 

Look from structure of half bridge circuit, those who consider capacitance need to all press an issue when choosing the two capacitance C1 on bridge arm, C2, choose the capacitance of C1=C2 as far as possible, so when some switch the canal guides when connecting, the voltage on winding has the in part of power source voltage only, achieve all press the effect, usually, be in even two capacitance two end each are shunt-wound a resistor (the R1 that the principle pursues medium and R2) and R1=R2 satisfies a requirement further, in the choice right now block is worth and need to notice to fall when power the forehead. Right now, the action of capacitance C1, C2 uses the Fu Miao that every switch is in charge of self-poise to be worth namely, (the distinction with C3: C3 is the dc heft that filter goes to affecting Fu Miao to balance) .

 

Can try to restrict to the maximum of drive pulse width, make guide current flow angle is spent won’t arise direct.

 

Still can attack to solve a problem from develop, just close with alternate coupling circuit, make one pipe guides when connecting, another pipe drive is in close condition, close till a pipe, close to just cancel, the canal just has after guide the possibility that open, this kind of automatic block has self-reacting advantage to storing time, parameter distributings, and use to occupying sky comparing to be able to be spent completely.

 

Deputy edge is complete wave circuit

 

Deputy edge is complete bridge circuit

 

 

1, the discretion according to outputting voltage, consider the safe problem; of pipe
2, the problem of power loss, basically be the loss problem; of switch canal and deputy edge winding

 

 

1, limitation of overload of former edge coil: The power canal that wants former limit offers independent electric current to restrict;
2, soft start: When starting, should restrict arteries and veins wide, make arteries and veins wide what starting is original a certain number of; rises slowly in cycle
3, the control of magnetism: Width of pulse of control transistor drive is equal, want to make magnetic flux of positive and negative equal, do not arise slant magnetism;
4, prevent direct: Want control to occupy sky comparing upper limit contractible;
5, the control of voltage and segregation: Circuit wants closed-loop control, segregation can be the; such as photoelectricity isolator, transformer or magnetism amplifier
6, press protection too: It is to close normally the switch pulse of transformer protects; with undertaking pressing
7, voltaic limitation: Electric current restricts installation to be on input or output loop, in short-circuit moment is effective;
8, input voltage crosses low protection: What the regulation is developing good performance only is enough the ability below tall voltage starts;
9, in addition, have appropriate auxiliary function even: Be restricted like surge electric current and output filter wave link to wait.

 

 

1, fluctuation bridge arm not in all, namely the switch of former edge circuit is in charge of not in all.
2, keep apart drive.

 

 

The imitate circuit architect of great majority knows how the condition in voltage of double power source issues use operation amplifier, pursue for instance that circuit of 1 left, a double power source is by source of a positive electricity and a negaive electricity of equal voltage the source is comprised. It is to losing 15V commonly, losing 12V and losing 5V often also is used. Inputting voltage and output voltage give out referencedly, still include what losing voltage to swing extent limit Vom and amplitude of the biggest output.

 

The circuit of power supply of only power source (graph 1 in right) the power source foot that carry puts receives positive electricity source and land repeatedly. Positive electricity source brings a foot to receive VCC ＋ , the ground or VCC – bring a foot to join to GND. The input that the voltage after positive electricity pressing cent becomes an in part regards empty ground as to receive carry to put brings a foot to go up, carry put output voltage also is voltage of this empty ground at this moment, carry put output voltage is a center with empty ground, amplitude is in Vom. A few new use put the highest output voltage that two differ and lowermost output voltage. The meeting in the data manual that this kind of carry puts is special part demonstrate Voh and Vol. Those who need special attention is to the not little architect’s very can optional ground that use theory will consult input voltage and output voltage, but in applying for the most part, input and output are ground of referenced power source, the place that so the architect must be being inputted and outputs is joined lie between straight capacitance, use the volts d.c. between segregation empty ground and ground.

 

 

Normally the voltage of power supply of only power source is 5V commonly, the output voltage amplitude that this fortune puts will be lower. The power supply voltage that additionally carry puts now also can be 3V perhaps also is met lower. Stemming from the motion that this reason uses in the circuit in power supply of only power source to put basically is Rail – To – the carry of Rail is put (like AD820, AD822, AD824) , eliminated missing dynamic limits so. Need is special those who point out is input and output can not bear certainly Rail – To – the voltage of Rail. Although parts of an apparatus by demonstrate it is course to course (Rail – To – Rail) , if carry put output perhaps is inputted,do not support course to course, be close to the voltage that input or approachs output voltage limit to may make carry put function degrades, whether is the referenced data manual with so careful need inputted and output is course to course.

 

Conclusion

An article undertook the major ABC of half bridge circuit sum up and inducing almost. God-given is, the problem that still appears among half-and-half bridge circuit undertook detailed analysis, gave out corresponding solution. Hope everybody can master these knowledge in the round, the design career that is oneself thereby has laid solid foundation. Introduced how to carry double power source circuit of only power source of discharge road instead is designed next, better serve for circuit architect.