- Ask a related questionWhat is a related question?A related question is a question created from another question. When the related question is created, it will be automatically linked to the original question.
Original question:
The input voltage of the push-pull converter is DC24V ( two 12V batteries). DC24V is output to external devices through a diode to supply power. When the push-pull output Vo (DC350V) passes through the MOSFET(Q1)
and outputs at 20KHZ (with a duty cycle of 30%), there is high-frequency interference when there is no load on 24OUT.
The schematic diagram of the push-pull converter is shown in Figure 1
The schematic diagram of the output Vo of the push-pull converter through MOSFET (Q1) is shown in Figure 2
The schematic diagram of DC24 output through D1 is shown in Figure 3
There is high-frequency interference waveform on 24OUT, as shown in Figure 4
What is the source of this interference? How to eliminate this interference?
Thank you!
Figure 4 shows the waveform of 24OUT (without load), which occurs when Q1 is switched on and off at 20KHZ
Figure 5 shows a brief schematic diagram of the entire system
Figure 5
The VO output is very stable, but there are small ripples。After adding a resistor to the 24OUT output, the waveform is OK. The 24OUT waveform is shown in Figure 6. Why can resistors eliminate this interference? Thank you!
Figure 6
the waveform of OUTA and OUTB(Figure 8)
Figure 8
the VDS waveforms of Q10 and Q13(Figure 9)
Figure 9
Figure 11 shows the waveform of a single VDS channel
When the load of a push-pull converter is an inductive load, what is the requirement for the output VO and GND of the push-pull converter to have parallel directional diodes? The reverse diode is not shown in the diagram
thank you
Figure 11
HiHong Huang,
New problems encountered after the output voltage of the push-pull converter changed
When the sum of R96 and R97 in Figure 12 decreases from 1K to 820 ohms, while other parameters remain unchanged, the MOS transistors (Q10, Q13, Q14, Q15) will be damaged. Why is this? When the output voltage Vo rises from over 400 volts to over 500 volts, this problem occurs. The load is a resistance of 2K 。The PWM frequency of push-pull is 15K。There will be no problem when the output voltage is low（about below 500V）
May I ask if this is a problem with the transformer or the loop compensation circuit?
Thank you!
Hi，
Figure 13 shows the waveforms of MOSFETs Vgs and Vds with a loaded (2K resistor) push-pull converter, while the correct waveforms of the two VDS circuits are shown in Figure 14
Figure 13
Figure 14
Figures 13 and 14 are two boards with the same design and circuit parameters. Currently, it is suspected that there is a problem with the transformer of the push-pull boost converter, but it is unclear where the problem lies?
Does the secondary current affect the primary side (when the push-pull MOSFET is not conducting)?
Thank you!
