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EP-4064562-B1 - DRIVING DEVICE AND CONTROL METHOD

EP4064562B1EP 4064562 B1EP4064562 B1EP 4064562B1EP-4064562-B1

Inventors

  • DONG, JIE
  • XU, ZHENQING
  • ZHANG, WEIQIANG

Dates

Publication Date
20260513
Application Date
20220321

Claims (18)

  1. A method for controlling a driving device (100), the driving device (100) configured to drive a power switch (Q) and comprising a first power supply (V DD ), a second power supply (V EE ), a first bridge arm (10) coupled between the first power supply (V DD ) and the second power supply (V EE ), a second bridge arm (20) coupled in parallel to the first bridge arm (10), and a resonant inductor (L r ), the first bridge arm (10) comprising a first switch (S 1 ) and a second switch (S 2 ) connected to a first midpoint (A), the second bridge arm (20) comprising a first semiconductor element (D 1 , S 3 ) and a second semiconductor element (D 2 , S 4 ) connected to a second midpoint (B), the resonant inductor (L r ) coupled between the first midpoint (A) and the second midpoint (B), and the method comprising: turning on the first switch (S 1 ) for a first period such that the first power supply (V DD ) charges a gate electrode (G) of the power switch (Q), wherein the second midpoint (B) is connected to the gate electrode (G) of the power switch (Q); turning off the first switch (S 1 ) when a voltage of the gate electrode (G) of the power switch (Q) is increased to a voltage (VDD) of the first power supply (V DD ); turning on the first switch (S 1 ) again for a second period in response to a decrease of a current of the resonant inductor (L r ) to a first threshold value, such that a potential of the first midpoint (A) is clamped by the first switch (S 1 ) to the voltage (VDD) of the first power supply (V DD ) and the current in the resonant inductor (Lr) is freewheeled through the first switch (S 1 ) and the first semiconductor element (D1, S3), characterized in that , the first threshold value is greater than zero, a time at which the current of the resonant inductor (L r ) is decreased to the first threshold value is determined by formula calculation or current sampling.
  2. The method of claim 1, further comprising: turning on the second switch (S 2 ) for a third period to discharge the gate electrode (G) of the power switch (Q); turning off the second switch (S 2 ) when the voltage of the gate electrode (G) of the power switch (Q) is decreased to a voltage (VEE) of the second power supply (V EE ); and turning on the second switch (S 2 ) again for a fourth period in response to an increase the current of the resonant inductor (L r ) to a second threshold value, such that the potential of the first midpoint (A) is clamped by the second switch (S 2 ) to the voltage (VEE) of the second power supply (V EE ) and the current in the resonant inductor (L r ) is freewheeled through the second switch (S 2 ) and the second semiconductor element (D 2 , S 4 ), wherein the second threshold value is smaller than zero.
  3. The method of claim 2, wherein the first switch (S 1 ) turned on again is turned off when the current of the resonant inductor (L r ) is decreased to zero, and the second switch (S 2 ) turned on again is turned off when the current of the resonant inductor (L r ) is increased to zero; or the first switch (S 1 ) turned on again is turned off before the second switch (S 2 ) is turned on, and the second switch (S 2 ) turned on again is turned off before the first switch (S 1 ) is turned on in a next switching period.
  4. The method of claim 1, further comprising: calculating a time t α1 at which the current of the resonant inductor (L r ) is decreased to the first threshold value according to a first inductance-current formula; calculating a time t β1 at which the current of the resonant inductor (L r ) is decreased to zero according to a second inductance-current formula; calculating a time t µ1 at which the second switch (S 2 ) is turned on according to a duty cycle and a switching frequency of the power switch (Q); turning on the first switch (S 1 ) again when a time counted by an internal timer is equal to the time t α1 ; and turning off the first switch (S 1 ) when the time counted by the internal timer is a time in [t β1 , t µ1 ).
  5. The method of claim 2, further comprising: calculating a time t α2 at which the current of the resonant inductor (L r ) is increased to the second threshold value according to a third inductance-current formula; calculating a time t β2 at which the current of the resonant inductor (L r ) is increased to zero according to a fourth inductance-current formula; determining an ending time t 8 of a current switching period; turning on the second switch (S 2 ) again when a time counted by an internal timer is equal to the time t α2 ; and turning off the second switch (S 2 ) when the time counted by the internal timer is a time in [t β2 , t 8 ).
  6. The method of claim 1, further comprising: sampling the current of the resonant inductor (L r ); comparing a sampled value with the first threshold value, and turning on the first switch (S 1 ) again when the sampled value is equal to the first threshold value; and comparing the sampled value with zero, and turning off the first switch (S 1 ) when the sampled value is equal to zero.
  7. The method of claim 1, further comprising: sampling the current of the resonant inductor (L r ); comparing a sampled value with the first threshold value, and turning on the first switch (S 1 ) again when the sampled value is equal to the first threshold value; comparing the sampled value with zero, and recording a time t β1 counted by an internal timer when the sampled value is equal to zero; and obtaining a turn-on time t µ1 of the second switch (S 2 ), and turning off the first switch (S 1 ) when the time counted by the internal timer is a time in (t β1 , t µ1 ).
  8. The method of claim 2, further comprising: sampling the current of the resonant inductor (L r ); comparing a sampled value with the second threshold value, and turning on the second switch (S 2 ) again when the sampled value is equal to the second threshold value; and comparing the sampled value with zero, and turning off the second switch (S 2 ) when the sampled value is equal to zero.
  9. The method of claim 2, further comprising: sampling the current of the resonant inductor (L r ); comparing a sampled value with the second threshold value, and turning on the second switch (S 2 ) again when the sampled value is equal to the second threshold value; comparing the sampled value with zero, and recording a time t β2 counted by an internal timer when the sampled value is equal to zero; and obtaining an ending time t 8 of a current switching period, and turning off the second switch (S 2 ) when the time counted by the internal timer is a time in (t β2 , t 3 ).
  10. A device for driving a power switch, comprising: a first power supply (V DD ) and a second power supply (V EE ); a first bridge arm (10) coupled between the first power supply (V DD ) and the second power supply (V EE ), and comprising a first switch (S 1 ) and a second switch (S 2 ) connected to a first midpoint (A); a second bridge arm (20) coupled in parallel to the first bridge arm (10), and comprising a first semiconductor element (D 1 , S 3 ) and a second semiconductor element (D 2 , S 4 ) connected to a second midpoint (B); and a resonant inductor (L r ) coupled between the first midpoint (A) and the second midpoint (B); the device is configured to operate the first switch (S 1 ) such that the first switch (S 1 ) is turned on for a first period such that the first power supply (V DD ) charges a gate electrode (G) of the power switch (Q); and the first switch (S 1 ) is turned off when a voltage of the gate electrode (G) of the power switch (Q) is increased to a voltage (VDD) of the first power supply (V DD ), wherein the second midpoint (B) is connected to the gate electrode (G) of the power switch (Q), the device is configured to operate the first switch (S 1 ) such that, in response to a decrease of a current of the resonant inductor (L r ) to a first threshold value, the first switch (S 1 ) is turned on again for a second period such that a potential of the first midpoint (A) is clamped by the first switch (S 1 ) to the voltage (VDD) of the first power supply (V DD ) and the current in the resonant inductor (L r ) is freewheeled through the first switch (S 1 ) and the first semiconductor element (D 1 , S 3 ), characterized in that , the first threshold value is greater than zero, a time at which the current of the resonant inductor (L r ) is decreased to the first threshold value is determined by formula calculation or current sampling.
  11. The device of claim 10, wherein the device is configured to operate the second switch (S 2 ) such that the second switch (S 2 ) is turned on for a third period to discharge the gate electrode (G) of the power switch (Q); the second switch (S 2 ) is turned off when the voltage of the gate electrode (G) of the power switch (Q) is decreased to a voltage (VEE) of the second power supply (V EE ); and in response to an increase of the current of the resonant inductor (L r ) to a second threshold value, the second switch (S 2 ) is turned on again for a fourth period such that the potential of the first midpoint (A) is clamped by the second switch (S 2 ) to the voltage (VEE) of the second power supply (V EE ) and the current in the resonant inductor (L r ) is freewheeled through the second switch (S 2 ) and the second semiconductor element (D 2 , S 4 ), wherein the second threshold value is smaller than zero.
  12. The device of claim 11, wherein the device is configured to operate the first switch (S 1 ) and the second switch (S 2 ) such that, the first switch (S 1 ) turned on again is turned off when the current of the resonant inductor (L r ) is decreased to zero, and the second switch (S 2 ) turned on again is turned off when the current of the resonant inductor (L r ) is increased to zero; or the first switch (S 1 ) turned on again is turned off before the second switch (S 2 ) is turned on, and the second switch (S 2 ) turned on again is turned off before the first switch (S 1 ) is turned on in a next switching period.
  13. The device of claim 10, further comprising a control unit electrically connected to the first switch (S 1 ) and the second switch (S 2 ) and configured to: calculate a time t α1 at which the current of the resonant inductor (L r ) is decreased to the first threshold value according to a first inductance-current formula; calculate a time t β1 at which the current of the resonant inductor (L r ) is decreased to zero according to a second inductance-current formula; calculate a time t µ1 at which the second switch (S 2 ) is turned on according to a duty cycle and a switching frequency of the power switch; turn on the first switch (S 1 ) again when a time counted by an internal timer is equal to the time t α1 ; and turn off the first switch (S 1 ) when the time counted by the internal timer is a time in [t β1 , t µ1 ).
  14. The device of claim 11, further comprising a control unit electrically connected to the first switch (S 1 ) and the second switch (S 2 ) and configured to: calculate a time t α2 at which the current of the resonant inductor (L r ) is increased to the second threshold value according to a third inductance-current formula; calculate a time t β2 at which the current of the resonant inductor (L r ) is increased to zero according to a fourth inductance-current formula; determine an ending time t 8 of a current switching period; turn on the second switch (S 2 ) again when a time counted by an internal timer is equal to the time t α2 ; and turn off the second switch (S 2 ) when the time counted by the internal timer is a time in [t β2 t 8 ).
  15. The device of claim 10, further comprising a control unit electrically connected to the first switch (S 1 ) and the second switch (S 2 ), and a sampling unit electrically connected to the resonant inductor (L r ) and the control unit, wherein, the sampling unit is configured to sample the current of the resonant inductor (L r ); and the control unit is configured to: receive a sampled value; compare the sampled value with the first threshold value, and turn on the first switch (S 1 ) again when the sampled value is equal to the first threshold value; and compare the sampled value with zero, and turn off the first switch (S 1 ) when the sampled value is equal to zero.
  16. The device of claim 10, further comprising a control unit electrically connected to the first switch (S 1 ) and the second switch (S 2 ), and a sampling unit electrically connected to the resonant inductor (L r ) and the control unit, wherein, the sampling unit is configured to sample the current of the resonant inductor (L r ); and the control unit is configured to: receive a sampled value; compare the sampled value with the first threshold value, and turn on the first switch (S 1 ) again when the sampled value is equal to the first threshold value; compare the sampled value with zero, and record a time t β1 counted by an internal timer when the sampled value is equal to zero; and obtain a turn-on time t µ1 of the second switch (S 2 ), and turn off the first switch (S 1 ) when the time counted by the internal timer is a time in (t β1 , t µ1 ).
  17. The device of claim 10, further comprising a control unit electrically connected to the first switch (S 1 ) and the second switch (S 2 ), and a sampling unit electrically connected to the resonant inductor (L r ) and the control unit, wherein, the sampling unit is configured to sample the current of the resonant inductor (L r ); and the control unit is configured to: receive a sampled value; compare the sampled value with the second threshold value, and turn on the second switch (S 2 ) again when the sampled value is equal to the second threshold value; and compare the sampled value with zero, and turn off the second switch (S 2 ) when the sampled value is equal to zero.
  18. The device of claim 10, further comprising a control unit electrically connected to the first switch (S 1 ) and the second switch (S 2 ), and a sampling unit electrically connected to the resonant inductor (L r ) and the control unit, wherein, the sampling unit is configured to sample the current of the resonant inductor (L r ); and the control unit is configured to: receive a sampled value; compare the sampled value with the second threshold value, and turn on the second switch (S 2 ) again when the sampled value is equal to the second threshold value; compare the sampled value with zero, and record a time t β2 counted by an internal timer when the sampled value is equal to zero; and obtain an ending time t 8 of a current switching period, and turn off the second switch (S 2 ) when the time counted by the internal timer is a time in (t β2 , t 8 ).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority on Patent Application No. 202110322065.8 filed in P.R. China on March 25, 2021. BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a power electronics device, and particularly to a driving device and a control method. 2. Related Art As a development of a power unit of a solid state transformer (SST), a frequency is increased in order to achieve high efficiency and high power density. Increasing a switching frequency is effective for achieving high power density, and fewer number of turns can be used in a high frequency to reduce a dimension and loss of windings of the transformer, thereby leaving more space for insulation. Driving loss of a power switch of a high frequency power converter is increased linearly along with rising of the frequency. A ratio of the driving loss to a total loss is increased under a light load, and the issue of the driving loss is more significant. When the frequency is further increased, the ratio of the driving loss to the total loss becomes unacceptable, so the driving loss of a gate electrode of the power switch must be reduced. Generally, the power output is performed by using a push-pull circuit, which mainly controls on and off of the power switch by controlling a gate voltage of the power switch. FIG. 1 shows a topological structure of a push-pull circuit applied in a conventional driving method. When the switch S1 is turned on, and the switch S2 is turned off, a power supply VDD charges a gate capacitor Cgs of the power switch Q through the switch S1, a gate external resistor Rg-ex and an internal resistor Rg-in, and the gate voltage is increased, thereby turning on the power switch Q. When the switch S2 is turned on, and the switch S1 is turned off, the gate capacitor Cgs is discharged to a power supply VEE through the internal resistor Rg-in, the gate external resistor Rq-ex and the switch S2, and the gate voltage is decreased, thereby turning off the power switch Q. In the conventional driving method, the driving loss is: Pgating=Qg×Vgs×fs wherein Qg is a gate charge of the power switch Q, Vgs is a voltage between a gate electrode G and a source electrode S of the power switch Q, and fs is a switching frequency of the power switch Q. As can be seen from the formula, in the conventional driving method, the driving loss Pgating is proportional to the switching frequency fs. With an increase of the switching frequency fs, the driving loss Pgating is significantly increased. The conventional driving method is characterized by: (1) outputting power using the push-pull circuit; (2) controlling a switching speed of the power switch Q by the gate external driving resistor Rg-ex. However, the conventional driving method has the following disadvantages: (1) the driving loss is high and proportional to the switching frequency, and the high frequency dramatically increase the loss; (2) a ratio of the driving loss to the total loss is increased under a light load. There is also a lossless driving method in the prior art, as shown in FIGS. 2A and 2B. In the lossless driving method, a resonant inductor Lr and diodes D1, D2 are added on the basis of push-pull output. At a time t0, the switch S1 is turned on, the power supply VDD charges the gate capacitor Cgs of the power switch Q through the switch S1, the resonant inductor Lr and the internal resistor Rg-in, the gate voltage is increased, and turning on of the power switch Q is initiated. At a time t1, the gate voltage is increased to VDD, the power switch Q is stably turned on. As shown in FIG. 2C, the switch S1 is turned off, the diode D1 is turned on, and a current of the resonant inductor is freewheeled through the diode D1 and a body diode of the switch S2 until the current is zero, such that the energy is fed back to the power supply to reduce the loss. At times t1-t3, the power switch Q is stably turned on, and the switches S1 and S2 are maintained to be turned off. At the time t3, the switch S2 is turned on, the gate capacitor Cgs is discharged to the power supply VEE through the internal resistor Rg-in, the resonant inductor Lr and the switch S2, the gate voltage is decreased, and turning off of the power switching Q is initiated. At the time t4, the gate voltage is decreased to VEE, the power switch Q is completely turned off, and the switch S2 is turned off, the diode D2 is turned on. The current of the resonant inductor is freewheeled through the diode D2 and a body diode of the switch S1 until the current is zero, such that energy is fed back to the power supply to reduce the loss. However, the lossless driving method has the following problems: at the time t2, the current of the resonant inductor is decreased to zero, and since potentials of the two nodes a and b are different (Va≈VEE, Vb≈VDD), a direction of the current of the resonant inductor is reversed due to the voltage difference, causing a oscillation occurring