| CPC H03K 17/063 (2013.01) [H03K 17/04123 (2013.01); H03K 17/6871 (2013.01); H03K 2217/0081 (2013.01)] | 23 Claims |
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1. A charge pump gate driver (CPGD) circuit with an adjustable pump voltage for active dv/dt control, comprising:
a first power supply that provides a positive voltage reference;
a second power supply that provides a negative voltage reference;
a first charge pump, wherein the first charge pump controls a turn-on switching speed of a power device, said first charge pump comprising two MOSFETSs, one diode (D1), and one flying capacitor (Cf1);
a second charge pump, wherein the second charge pump controls a turn-off switching speed of the power device, said second charge pump comprising two MOSFETS, one diode (D2), and one flying capacitor (Cf2); and
a totem-pole driver comprising two decoupling capacitors (Cd1 and Cd2) and split outputs to connect external ON and OFF gate resistors of the power device to the CPGD circuit,
wherein during a turn-on process a pulse width of a control signal (Sc1) of the first charge pump is adjusted so that the flying capacitor (Cf1) of the first charge pump is pre-charged to varying levels, allowing a voltage (vCf1) across the flying capacitor (Cf1) of the first charge pump to attain different magnitudes at a first time period (t1), then, a first one of the decoupling capacitors (Cd1) of the totem-pole driver is charged by discharging the flying capacitor (Cf1) of the first charge pump, which in turn pumps a voltage (vCd1) across the first one of the decoupling capacitors (Cd1) of the totem-pole driver to varying voltage levels during a second time subinterval [t1˜t2], wherein a different pump voltage of the voltage across the first one of the decoupling capacitors (Cd1) of the totem-pole driver at time period t2 leads to a varying gate current of the power device after the totem-pole driver is tied to a high output voltage at t2, providing different current rising rate and voltage falling rate of the power device, resulting in a faster switching speed, including an accelerated current rising rate, i.e., (t4-t3)<(t4x-t3), and an accelerated voltage falling rate, i.e., (t5-t4)<(t15x-t4x) of the power device,
wherein during a turn-off process a pulse width of a control signal (Sc2) is adjusted so that the flying capacitor (Cf2) of the second charge pump is pre-charged to varying levels, allowing a voltage (vCf2) across the flying capacitor (Cf2) of the second charge pump to attain different magnitudes at a first time period (t1), then a second one of the decoupling capacitors (Cd2) of the totem-pole driver is charged by discharging the flying capacitor (Cf2) of the second charge pump, which in turn pumps a voltage (vCd2) across the second one of the decoupling capacitors (Cd2) of the totem-pole driver to varying voltage levels during a second time subinterval [t1˜t2], wherein a different pump voltage of the voltage (vCd2) across the second one of the decoupling capacitors (Cd2) of the totem-pole driver at t2 leads to a varying gate current of the power device after the totem-pole driver is tied to a low output voltage at t2, providing different voltage rising rate and current falling rate of the power device, resulting in a faster switching speed, including an accelerated voltage rising rate, i.e., (t4-t3)<(T4X-t3), and an accelerated current falling rate, i.e., (t5-t4)<(t15x-t4x), and
wherein to prevent an overcharging issue, a value of Cf1 is selected to guarantee that a maximum pre-charged charge of Cf1 during a time subinterval [t0-t1] aligns with a total gate charge needed for the power device during the turn-on process, which is determined by:
 where Qgd is an equivalent gate-to-drain charge of SiC MOSFET at Vdc.
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