5v to 15v level shifter problem

Thread Starter

BramLabs

Joined Nov 21, 2013
98
Hello,
Sir, i want to ask. I've made 5v to 15v level shifter with using a transistor 2n2222.
snip.PNG
I'm using 5v PWM (40 kHz) from microcontroller as an input of the base transistor.
The problem is :

1). The transistor itself, become hot.
I've calculated the transistor dissipation :
When transistor in saturation :
Ib = (Vin - Vbe) / R1 = (5v - 0.65v)/1k = 4.35 mA
And then i get :
Ic = hfe.ib = 10 * 4.35 mA = 43.5 mA
And the power dissipation of the transistor would be :
Vce(sat) * Ic(sat) = 43.5 mA * 0.2v = around 8.7 mW (the maximum dissipation of transistor on datasheet is about 1.8 Watt)
I get Ic(sat) = 0.2v and Vbe = 0.65v from the datasheet of transistor 2n2222.

2). The output only give me 15v DC (i think the output voltage is latching to the voltage supply), not inverting of the PWM. I thought that the output would be such as like this :
snip 2.jpg

And also can you give me a recommendation for making 5v to 15v level shifter ?
I've been thinking to use IR2110 as the level shifter, is that good sir ?

For the problem number 2, can i use this kind of circuit, to avoid the 'latching' problem :
snip3.PNG

And for the problem number 1, i don't have any solution yet.

Thank you sir for your reply,
 

Picbuster

Joined Dec 2, 2013
1,047
Take the first drawing and replace Q1 with a Nmos fet. reduce the 1K to 100R. max current 15/(2K+Rfet) in mA =15/(2+0,02) 7.5 mA approx.
heat in 0,02Ohm 57 x 10^-6 Watt
Next step; invert PWM signal in software.
That's all.
 

MrChips

Joined Oct 2, 2009
30,714
What is the exact part number of your 2N2222 transistor?
There are two very different lead identification. Make sure you get it right.
 

Thread Starter

BramLabs

Joined Nov 21, 2013
98
Take the first drawing and replace Q1 with a Nmos fet. reduce the 1K to 100R. max current 15/(2K+Rfet) in mA =15/(2+0,02) 7.5 mA approx.
heat in 0,02Ohm 57 x 10^-6 Watt
Next step; invert PWM signal in software.
That's all.
Thank you sir, can you give me a recommendation for the nmos-fet type ? Because there aren't many type of nmos that works as a logic level on the market in my country, i prefer to choose BJT transistor, rather than nmos-fet. But there're many types of 10v gate mosfet.

Hello,

MrChips is right, the 2N2222 (the metal case) and the PN2222 (the plastic case) have different connections:

View attachment 108103

Bertus
What is the exact part number of your 2N2222 transistor?
There are two very different lead identification. Make sure you get it right.
Oh i'm sorry sir, i forgot to attach the transistor part number.
The transistor itself : KN 2222A 341
And then it looks like a case TO-92A but with BENT LEAD

VLtUx.png

And based on your configuration and the configuration i found in internet, i think there's different between the collector and the emitter.
Which one is wrong and which one is right sir ?

Thank your so much for your reply.
I really appreciate it.
 
Last edited:

EM Fields

Joined Jun 8, 2016
583
Hello,
Sir, i want to ask. I've made 5v to 15v level shifter with using a transistor 2n2222.
View attachment 108097
I'm using 5v PWM (40 kHz) from microcontroller as an input of the base transistor.
The problem is :

1). The transistor itself, become hot.
I've calculated the transistor dissipation :
When transistor in saturation :
Ib = (Vin - Vbe) / R1 = (5v - 0.65v)/1k = 4.35 mA
And then i get :
Ic = hfe.ib = 10 * 4.35 mA = 43.5 mA
And the power dissipation of the transistor would be :
Vce(sat) * Ic(sat) = 43.5 mA * 0.2v = around 8.7 mW (the maximum dissipation of transistor on datasheet is about 1.8 Watt)
I get Ic(sat) = 0.2v and Vbe = 0.65v from the datasheet of transistor 2n2222.

2). The output only give me 15v DC (i think the output voltage is latching to the voltage supply), not inverting of the PWM. I thought that the output would be such as like this :
View attachment 108099

And also can you give me a recommendation for making 5v to 15v level shifter ?
I've been thinking to use IR2110 as the level shifter, is that good sir ?

For the problem number 2, can i use this kind of circuit, to avoid the 'latching' problem :
View attachment 108100

And for the problem number 1, i don't have any solution yet.

Thank you sir for your reply,
Here are the results of an LTspice simulation showing that there's nothing wrong with your circuit, so you must have made a wiring error.

5 to 15 volt translator.jpg
 

Alec_t

Joined Sep 17, 2013
14,280
If the transistor is wired correctly and has a 2k collector load there is no way it should get hot. Max collector current would be ~7.5mA, so if the collector-emitter saturation voltage were say ~0.2V the transistor dissipation would be only 7.5mA x 0.2V + ~5mA x 0.7V = 5mW. I'd guess that either the 2k resistor is shorted out by something or has gone low resistance (unlikely).
 
Last edited:

Thread Starter

BramLabs

Joined Nov 21, 2013
98
Hello,

It could be that the transistor already has blown.
Do you have an other to try?

Bertus
Yeah, i think so sir. Because it smells like a burn thing. ahahaha... I'll try later with new transistor ^^
Thank you so much sir for your support !

Here are the results of an LTspice simulation showing that there's nothing wrong with your circuit, so you must have made a wiring error.

View attachment 108151
Yeah sir, i've simulated too with multisim and it works. I thought that maybe because the wiring error as Sir Bertus have already said before, i made an error of the transistor configuration. Maybe i'll try another transistor later.
Thank you for your information.

If the transistor is wired correctly and has a 2k collector load there is no way it should get hot. Max collector current would be ~7.5mA, so if the collector-emitter saturation voltage were say ~0.2V the transistor dissipation would be only 7.5mA x 0.2V + ~5mA x 0.7V = 5mW. I'd guess that either the 2k resistor is shorted out by something or has gone low resistance (unlikely).
Yeah, i've calculated it too. But it gets hot. Maybe i'll try to use using a breadboard first rather than to use single side prototype board.
Thank you so much sir for your information.
 
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