DC motor full load current and no load – I have a DC motor with 24V and 11A written on its face plate but in the datasheet its nominal current is 4A. When I applied a 24V on its terminal at no load it draws 0.5A. I want to know what is the wrong data (face plate or datasheet )? Read more
PWM generation using PIC microcontroller – Does anyone know how to generate the waveforms as shown below? I have made it by switching a pin on and off with fixed frequency but I want a more intelligent program for this purpose. Can anyone suggest some module of any PIC microcontroller that can implement such PWMs? The duty cycle needs to be same for both of them and they both are delivering the required duty cycle in the same period delayed in phase. Read more
Hard-switched bridge spiking even after snubber – I have a hard-switched MOSFET bridge running at 100KHz. The output capacitance is nearly 5nF and the ringing frequency at transients is 48MHz. After snubbing the FETs with an RC snubber of 20nF and 1Ω to suppress this spike.The two photos show the output at 10A load and 25A load. The bridge drives a 12V:240V transformer with approximately 100nH leakage. The HV side of the transformer is connected directly to a resistive load without rectification. Read more
LT3650 Li-ion battery charger heat issue – Have someone ever used the LT3650?I have designed a circuit charging a 18650 battery. It works ok but the IC gets very hot (50C) at 12V input and over 65C at 28V. The IC has about 20mm² of copper on the bottom side and about 10mm² on the top side. Charging current is set to 1.5A. The IC should have thermal shutdown but is this heating normal? I built about 10 units and all have the same heat issue but now I’ve got two of them back with a blown IC. The client said he plugged them in cigarette lighter socket of a truck but that should be 12V and if by mistake it was 24V, it should still not get over 30V while the IC takes a max of 32V. Read more
Triac circuit normally closed – I am looking for a way to make a Triac (controlled by optotriac), to switch ON when no signal is driving the opto and switch OFF when the opto has a signal.
Is this possible? (Just need OFF/ON switching no phase control). Read more
MOSFET heating problem in H-bridge – I am trying to drive an H-bridge using the MC33883. But at more than 2A, my upper-side MOSFET is heating too much. Why? Read more
Can an offline LED driver last 20 years? – The Cu-Beam light is certainly the best LED light that the worldwide market has to offer. However, the spec says that the LED lasts 180,000 hours (20 years) and that the offline LED driver that ships with it lasts as long as the LED (ie, 20 years). The offline LED driver is said to last the 20 years because of having big heatsinks and special capacitors. Surely no offline LED driver can last 20 years? I mean, in 20 years, it is likely to succumb to mains transients which will result in the MOV failing short and thereby blowing the input fuse…this happening well before 20 years? If mains transients are not such a problem, then why does Littelfuse sell these LED lighting mains surge protectors? Read more
MC34063 boost configuration dropped voltage – I am facing a problem working with the MC34063 under standard Boost configuration. Vin is 3.2V and Vout is 5V. Iout is 375mA.
When checked on a DMM, the Vout is 5V but if even a small load is applied – say a microcontroller – the voltage drops to 1.5V.
The component values are as follows:
– Rsc: 0.22 ohms
– R: 180 ohms
– Cin: 10uF
– Cout: 10uF
– L: 22uH
– R3:R4 (for 5V): 3.3K and 10Kohms
– Diode: 1N5817
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2kW battery charger topology – I want to build a 2kW battery charger for a solar system. I’ll use a portable generator as a power source and a step-down/isolation LF transformer (former welding machine) to get around 30VAC. As the load consists of a big battery bank (48VDC / 500A) I can’t use an output voltage control thus I have to use a current control topology. I was thinking of a regular CCM boost converter driven by a UC3845 chip. But, as the input/output current is quite big I prefer not to use a current sense resistor. I’ve never used a current transformer before (hence I don’t have one available) but I’m wondering if I could make a separate winding (few turns) around the input toroidal inductor to get a feedback voltage proportional to the inductor current. I don’t mind about output ripple and such, I just need a higher PFC to protect the gas generator. Do you have any other suggestion? Read more
Inductor core saturation – I am currently working on a boost converter. The current waveform of the inductor is this:
It has no similarity with the theoretical waveform. I think the core is getting saturated.
Any idea what could be the reason?? Read more
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