- #1
yungman
- 5,726
- 242
Hi all.
I am using LM311 comparator to design a speaker protection circuit. I read quite a few data sheet of LM311. Seems like it's such an old IC that they assume people know the IC already. I happen to be a first time user and I am not sure I design it right. Mainly strobe pin #6. From reading, it seems like if I use a transistor to pull it down, the output transistor turns off regardless and become open circuit pulled up by the pull up resistor. Also the output transistor how I can use it off ground. Anyone that familiar with the LM311, please confirm I designed the circuit correctly.
Also, this is a speaker protection circuit for SS amp that can drive a DC voltage if something gone wrong. This circuit will:
1) monitor the output by using a low pass filter to filter out the audio frequency, only the very very low frequency or DC passes through. Two window comparators using LM311(U1 & U3, U2 & U4) are used to monitor the DC and turn off the transistor if over 0.7V DC is detected.
2) monitor circuit to monitor +/-24V supply (R3, D3 and relay S1). If total voltage drop by say 5V, the relay opens.
3) Power on delay (Q1 C15). The drain of the Q1 connects to pin 6 of all the comparators. when Q1 is on and pull all the pin 6 to ground, the LM311 turns off.
The /OUTPUT EN are use to turn on the speaker output relay when it is pulled to ground.
I am connecting the two LM311 output transistors in series with the relay contact, so if anyone opens, the chain opens and loss the ground, the speaker relay will be turned off. Only if both NPN output transistor of LM311 and the relay are on, then the /OUTPUT EN will be low to turn on the speaker relay. Please confirm that I am doing everything correctly.
Thanks
Alan
I am using LM311 comparator to design a speaker protection circuit. I read quite a few data sheet of LM311. Seems like it's such an old IC that they assume people know the IC already. I happen to be a first time user and I am not sure I design it right. Mainly strobe pin #6. From reading, it seems like if I use a transistor to pull it down, the output transistor turns off regardless and become open circuit pulled up by the pull up resistor. Also the output transistor how I can use it off ground. Anyone that familiar with the LM311, please confirm I designed the circuit correctly.
Also, this is a speaker protection circuit for SS amp that can drive a DC voltage if something gone wrong. This circuit will:
1) monitor the output by using a low pass filter to filter out the audio frequency, only the very very low frequency or DC passes through. Two window comparators using LM311(U1 & U3, U2 & U4) are used to monitor the DC and turn off the transistor if over 0.7V DC is detected.
2) monitor circuit to monitor +/-24V supply (R3, D3 and relay S1). If total voltage drop by say 5V, the relay opens.
3) Power on delay (Q1 C15). The drain of the Q1 connects to pin 6 of all the comparators. when Q1 is on and pull all the pin 6 to ground, the LM311 turns off.
The /OUTPUT EN are use to turn on the speaker output relay when it is pulled to ground.
I am connecting the two LM311 output transistors in series with the relay contact, so if anyone opens, the chain opens and loss the ground, the speaker relay will be turned off. Only if both NPN output transistor of LM311 and the relay are on, then the /OUTPUT EN will be low to turn on the speaker relay. Please confirm that I am doing everything correctly.
Thanks
Alan