Voltage and PFC based OBC pre-charge system
An on-board charger for an electric vehicle a silicon controlled rectifier circuit configured to receive an AC input voltage and output a first AC rectified voltage, a power factor correction circuit configured to receive the rectified AC voltage and output a DC voltage, a DC Link capacitor that receives DC voltage as a capacitor voltage; and a controller configured to operate in a first mode and a second mode depending on the DC voltage.
1. An on-board charger comprises:
a silicon controlled rectifier circuit configured to receive an AC input voltage and output a rectified AC voltage;
a power factor correction circuit configured to receive the rectified AC voltage and output a DC voltage; and
a DC-link capacitor loaded with the DC voltage as a DC-link capacitor voltage; and
a controller configured to trigger the silicon controlled rectifier circuit in a first mode that occurs when the AC input voltage is at a position of a half-cycle of the AC input voltage having a slope pointing to 0 volts wherein when an instantaneous capacitor voltage is below a voltage threshold, the voltage threshold is incremented for a next half-cycle such that the DC-link capacitor voltage incrementally increases until eventually being loaded at a pre-defined DC-link working voltage or a voltage within a pre-defined amount of the pre-defined DC-Link working voltage.
2. The on-board charger of claim 1 , wherein the first mode is implemented when the DC voltage is below or equal to a pre-defined voltage value.
3. The on-board charger of claim 2 wherein the DC-link capacitor is charged in voltage steps with the voltage threshold for triggering the silicon controlled rectifier circuit increased after each voltage step until the voltage threshold reaches the predetermined voltage value with charging continuing while the voltage threshold is below the pre-defined voltage value so that during charging periods the silicon controlled rectifier circuit is triggered with trigger pulses to enable energy flow such that the DC-Link capacitor charges as the voltage threshold increases after each voltage step.
4. The on-board charger of claim 3 wherein the controller is further operable to operate in a second mode in which the DC-link capacitor voltage is above the pre-defined voltage value, the power factor correction circuit operates to boost the DC-link capacitor voltage.
5. The on-board charger of claim 4 wherein in the second mode, the power factor correction circuit is active.
6. The on-board charger of claim 1 wherein the silicon controlled rectifier circuit comprises a full-wave rectifier including a first thyristor in a first rectifier arm and a second thyristor in a second rectifier arm.
7. The on-board charger of claim 6 wherein the silicon controlled rectifier circuit the full-wave rectifier further includes a first diode in the first rectifier arm and a second diode in the second rectifier arm.
8. The on-board charger of claim 1 wherein a measured AC input voltage is within a predetermined voltage difference from a previously measured peak AC input voltage.
9. The on-board charger of claim 8 wherein the predetermined voltage difference is at least 20 V.
10. The on-board charger of claim 1 wherein a measured AC input voltage is less that than an average peak voltage for a predetermined number of consecutive measurement samples.
11. The on-board charger of claim 1 wherein the time period between consecutive trigger pulses is less than half the time period for the AC input voltage by a predetermined time difference.
12. The on-board charger of claim 11 wherein the predetermined time difference is about 500 μs.
13. The on-board charger of claim 1 wherein charging is implemented every AC half-cycle during descending quarters of the rectified AC voltage.
14. An on-board charger for an electric vehicle, the on-board charger comprising:
a silicon controlled rectifier circuit configured to receive an AC input voltage and output a rectified AC voltage;
a power factor correction circuit configured to receive the rectified AC voltage and output a DC voltage;
a DC-Link capacitor loaded with the DC voltage as a DC-link capacitor voltage; and
a controller configured to operate in a first mode and a second mode depending on the DC voltage, wherein in the first mode while the DC voltage is below or equal to a pre-defined voltage value, the DC-link capacitor is charged in voltage steps with a voltage threshold for triggering the silicon controlled rectifier circuit increased after each voltage step until the voltage threshold reaches the predetermined voltage value wherein charging continues while the voltage threshold is below the pre-defined voltage value so that during charging periods the silicon controlled rectifier circuit is triggered with trigger pulses to enable energy flow such that the DC-Link capacitor charges as the voltage threshold increases after each voltage step and wherein in the second mode while the DC voltage is above the pre-defined voltage value, the power factor correction circuit operates to boost the DC-link capacitor voltage.
15. The on-board charger of claim 14 wherein the silicon controlled rectifier circuit comprises a full-wave rectifier including a first thyristor in a first rectifier arm and a second thyristor in a second rectifier arm and a first diode in the first rectifier arm and a second diode in the second rectifier arm.
16. The on-board charger of claim 14 wherein a measured AC input voltage is within a predetermined voltage difference from a previously measured peak AC input voltage.
17. The on-board charger of claim 14 wherein a measured AC input voltage is less that than an average peak voltage for a predetermined number of consecutive measurement samples.
18. The on-board charger of claim 15 wherein the time period between consecutive trigger pulses is less than half the time period for the AC input voltage by a predetermined time difference.
19. The on-board charger of claim 15 wherein charging is implemented every AC half-cycle during descending quarters of the rectified AC voltage.
20. The on-board charger of claim 15 wherein the pre-charge function in boost mode is stopped when the DC-link capacitor voltage greater than the AC peak voltage by a predetermined voltage amount.
21. An on-board charger comprises:
a silicon controlled rectifier circuit configured to receive an AC input voltage and output a rectified AC voltage;
a power factor correction circuit configured to receive the rectified AC voltage and output a DC voltage; and
a DC-link capacitor loaded with the DC voltage as a DC-link capacitor voltage; and
a controller configured to trigger the silicon controlled rectifier circuit in a first mode that occurs when the AC input voltage is at a position of a half-cycle of the AC input voltage having a slope pointing to 0 volts wherein when an instantaneous capacitor voltage is below a voltage threshold, the voltage threshold is incremented for a next half-cycle such that the DC-link capacitor voltage incrementally increases until eventually being loaded at a pre-defined DC-link working voltage or a voltage within a pre-defined amount of the pre-defined DC-Link working voltage; and
wherein the controller is further operable to operate in a second mode in which the DC-link capacitor voltage is above the pre-defined voltage value, the power factor correction circuit operates to boost the DC-link capacitor voltage.