Method for reducing EMI interference of secondary circuit
A technology of secondary circuit and primary circuit, which is applied to electrical components, adjusting electrical variables, and output power conversion devices, etc., can solve the problems of high cost, poor effect, and occupation of layout space.
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Embodiment 1
[0024] Such as figure 1 In the secondary circuit shown, the pre-adjustment circuit 1 is a BUCK circuit, and the resonant circuit 2 is a full-bridge circuit. The closed-loop stability of the entire output voltage is mainly regulated by the duty cycle of the pre-adjustment circuit. If the center frequency of resonant circuit 2 is 100kHz, and the center frequency of pre-adjustment circuit 1 is 70kHz, the EMI test result is as follows Figure 4 shown. If the frequency of the resonant circuit 2 is set to be 100kHz as the center, + / -9kHz to change; the center frequency of the pre-adjustment circuit 1 is 70kHz, + / -5kHz to change; the change period is 5ms. Test results such as Figure 5 shown. It can be seen that by dithering the frequency of the secondary circuit, the quasi-peak value and average value of the EMI test can be greatly reduced to improve the EMI performance of the circuit.
Embodiment 2
[0026] Such as figure 2 The secondary circuit shown is a circuit structure composed of a BOOST circuit and a half-bridge circuit. If the center frequency of the resonant circuit 2 is 160kHz and the center frequency of the pre-adjustment circuit 1 is 100kHz, the EMI test results are as follows when frequency shaking is not performed. Figure 6 Shown: If the frequency of the resonant circuit 2 is set around 160kHz, it will vary by + / -16kHz; the center frequency of the pre-adjustment circuit 2 is centered around 100kHz, and it will vary by + / -8kHz. The change period is 4ms. The frequency of the pre-adjustment circuit 1 and the frequency of the resonant circuit 2 change in opposite directions. When the frequency of the resonant circuit 2 increases, the frequency of the pre-adjustment circuit 1 decreases; when the frequency of the resonant circuit 2 decreases, the pre-adjustment circuit 1 frequency increases. EMI test results such as Figure 7 shown. It can be seen that by dit...
Embodiment 3
[0028] Please refer to image 3 The secondary circuit shown is a circuit structure composed of a BUCK circuit and a half-bridge circuit. If the center frequency of the resonant circuit 2 is 240kHz and the center frequency of the pre-adjustment circuit 1 is 200kHz, the EMI test result is close to Figure 4 or Figure 6 As shown, the waveform jitter of the EMI test is very complex, the peak value changes greatly, and it is extremely unstable. If the frequency of the resonant circuit 2 is set to make round-trip jumps at 230-250kHz intervals of 2kHz; the center frequency of pre-adjustment circuit 1 is made to make round-trip jumps at intervals of 190-210kHz to 2kHz. The test results were close to Figure 5 or Figure 7 As shown, by dithering the frequency of the secondary circuit, the quasi-peak value and average value of the EMI test can be greatly reduced to improve the EMI performance of the circuit.
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