H-Bridge Motor Driver Power Problem

[skyglin]

74hc14 circuits

I'm building a H-Bridge to control the operation of a DC brush motor, this works fine except that the transistors get very hot immediately after the circuit powers up. The power consumption of this circuit is very large as I have tested in PSPICE. After spending some time searching the web for a solution, on one website, I found Steve Bolt's 4-transistor H-bridge, and it has a 74HC14 inverter on each of the control input. So I add the inverters to my circuit and connected between the pull-up resistor and the controlling input, tested using PSPICE, amazingly, the power consumption dropped dramatically. [/img]

Why is the addition of 74HC14 solve the power problem? Is it because the pull-up resistor can influence the h-bridge without the inverters? but how?
Can someone help me on this?

*A schematic for the H-Bridge without the 74HC14 is attached

 

[Regnum]

motor ic burnt

skyglin,

When the first switch is open, the control voltage at R12,R4,R8 node isn't 5Volt but some intermediate voltage, so both transistors of a same stage turn on simultaneously (and trust me, you'll fry them!)

The same concept is valid for the second switch and R13-R10-R11 node.

You must lower R12 and R13, or use a low-impedance source (such as the 74HC14 you're talking about). This all is easy to check by using Spice.

Supply-current must be just the motor consumption plus 7milliampere (approx)

Regards

 

[skyglin]

sg3535

hi, what I still don't understand is how does the addition of 74HC14 solve the problem? What did the 74HC14 do to the circuit? I still need more clarification. Thanks a lot.

 

[petarpav]

h bridge motor

Hi. Regnum is right, I tning same.

Best Regards.

 

[Regnum]

h bridge free wheeling diode

What did the 74HC14 do to the circuit?

- Bridge inputs need over 3.5V for granting upper transistors be off.
- Bridge-input thevening image is a 2.5V voltage-source with a 500Ohm source-resistance

so, watch the driving circuits...

Such a high Voh and low output-impedance of HC14 drive bridge-inputs perfectly,

Oppositely, 2K resistors driving the inputs from +5V, mean a bridge input voltage around 3.3V, so that upper transistors keep always on.

Regards

 

[batdin]

h bridge power amplifier + transistor burn out

It is possible to overheat it if R12 is not connected to +5V because Q5 and Q7 are open in the same time by the base current through R4,R8.(the same for the right part)
Another drawback: when using darlingtons the minimum saturation voltage accross them is about 0.8V.The same for the other side of the bridge,i.e. 1.6V loss out of 5V.
Not a good design.
Replace darlingtons with singular high-beta transistors to cut the loss dramatically.

 

[skyglin]

h-bridge circuit problems

What about using MOSFET to do the design because they are low power consumption? Any drawback?

Also, How does the value of each of the bias resistor affect the circuit? What is recommended value for the pull-up resistor?

 

[bimbla]

h-bridge motor

What you need to do is design a drive circuit which will have dead-zone to avoid simultaneous conduction of the upper and lower Tr.
Tr. takes more time to turn off than turn on. So make sure that the conducting pair is full off before you turn on the next pair.

Use SG3535 (not 3524) to get oomplimentary o/p with zead=zone.

Do post the sesults.

bimbla.

 

[bimbla]

h bridge problem when connected to motors

The motor connected as load is inductive. Make sure that the o/p darlington's have built-in free- wheeling diodes. TIP142/147 have it. Don't remember about TIP122/127.

If they don't then connect one across each of the four o/p devices.
Also you need to connect a resistor between base and emitter of all the four o/p devices. The value of this is calculated as: R=0.3/Icbo.

This ensures thermal stability.

bimbla.

 

[skyglin]

thermal calculations for h-bridge

Hi bimbla, what is SG3535, I can't find any information on the net about it.

TIP122/127 do contain a built-in free wheeling diode.

skyglin

 

[bimbla]

20 a h bridge driver

Sorry, its SG3525.
Sorry again.

bimbla

 

[seinfield]

h-bridge tip122

I use an H-bridge ic, like a L293, i use the L293D to control servos (it can be used to control bipolar step motors) for robots but it only supports 5 volts or it gets to hot and burned.

There is a Toshiba ic that supports 3 amp, i have some of those but i do not remember teh number ic.

 

[ahmad_imran]

h bridge dc motor freewheeling diode

Is there any ic that can support up to 16 amp?

 

[seinfield]

h-bridge motor driver tr

I founded the number of teh IC: Toshiba TA7279P
It supports 3 Amp

 

[bimbla]

on off circuit 74hc14

I will suggest drivers before the TIP122/127 devices.

Give me 12hrs I will put up a 'Tested OK' ckt from Elektor.

bimbla.

 

[Regnum]

how does to control power h-bridge

What's the motor supply current ?

Hard to design anything if you don't know it...

 

[skyglin]

h-bridge 540

The motor is drawing 0.36A at 5V.

bimbla, can you explain how did you get the formular for thermal stability calculation, and what is Icbo?

 

[tocal09]

h-bridge pull up resistors

I've done this kit .You can use POWER part of it