"Current" control is a big issue using ClassD ?  - Page 1
Forum section: electronics / projects

author: Md Mubdiul Hasan
author_rank: Regular Contributor
timestamp: October 22, 2019, 04:29:41 am
content: Hi there,I think people who works in 'Analog or Power electronics" understand this issue.I am having a project on, "3 phase power Calibrator"Like me previous post I was trying to go with a ClassAB for current and voltage amplifier,https://www.edaboard.com/showthread.php?386525-Lets-take-a-look-on-a-linear-amplifierComparable study shows, ClassAB is less suitable than ClassD.ClassD is a voltage source device, so current transformer may not be use,https://www.diyaudio.com/forums/class-d/343198-class-amplifier-suitable-60hz-potential-transformer.html#post5927022I think potential transformer can be use with ClassD,https://www.element14.com/community/thread/73845/l/classd-amplifier-for-transformerSince my project need to get Current transformer output, kindly suggest me what should I do.I'am not sure with this solution,https://e2e.ti.com/support/motor-drivers/f/38/t/848028

author: rvalente
author_rank: Frequent Contributor
timestamp: October 22, 2019, 03:08:01 pm
content: Check the classic irs2092 from old international rectifier, now infineon.The mosfets current sensing is made through the reading of the rdson of the mosfet, feedback to a voltage comparator. A little trick to set but, works fine.You may use 3x irs2092 or other pwm generator from your uC or similar.

author: Md Mubdiul Hasan
author_rank: Regular Contributor
timestamp: October 24, 2019, 01:47:12 am
content: Thnak you very much Sir Rvalente!Let me post a similar application schemetic where user wanted to do some thing !This application is for 400W, user said " I have connected additional parallel resistors to R117A, R118A, R17A, because amp was clipping, when power supply was circa 2x35V, is possible that leads of that resistors was to long?"Now lets see other ( attached 2)The main part of this protection circuit is a transistor FET which is connected in the power supply branch amplifier integrated circuit IRS2092. When applying a positive voltage to the control electrode of the transistor, the ground power supply voltage and the comparator halts the modulation process. The transistor FET is switched on the circuit that brings together a number of protections. One of them is check the power supply, which detects whether the supply voltage is in the range of 68 to 100 volts. If this the condition is not met, the class d protection will react. Additional protection is temperature. Circuit controls the voltage on the thermistor, which is located on the heatsink of the power switching Mosfet. Last class d amplifier protection detects the amplified audio signal at the output of the amplifier and responds when congestion or limitation.Lets disscuss how we can adapt my requirement !

author: rvalente
author_rank: Frequent Contributor
timestamp: October 24, 2019, 11:40:48 am
content: Have you checked your power supply? Is is capable of delivering steady voltagem during the current surges of bass and etc?

author: Md Mubdiul Hasan
author_rank: Regular Contributor
timestamp: October 25, 2019, 12:33:11 am
content: Quote from: rvalente on October 24, 2019, 11:40:48 amI was trying to say "wheather this kind of circuit can be use or not"?Take a look on my previous post that has no solution here,https://ez.analog.com/audio/f/q-a/116542/need-a-suitable-class-d-amplifer-for-transformer-applicationI think as Class D is a voltage source it just limit the current , then it might not fit for Current transformer.Now let us move for a individual solution on for "Current" .Requirments are modified here:1. The amp input should be plus and minus 7volt AC, 45-65Hz( 1 Hz has been converted to 1024)2. Amp operating voltage should be more or less 24v.3. Only single channel "current" signal should be amplify.4. 7.5 ohm load.5. Output should be 16.5 V/1.5 A. 25 Watt.6. SC protection and current sensing capabilities.