Voltage detecting device for half bridge circuit

摘要

There is described a detecting device for the midpoint voltage (Va) of a half bridge circuit of transistors (M1, M2) comprising first (M1) and second (M2) transistors; the half bridge is connected between a voltage supply (Vcc) and a reference voltage (GND) and it is adapted to drive a load (LOAD). The first and second transistors are driven so that said midpoint voltage (Va) undergoes transitions from a low voltage value (LW) to a high voltage value (HW) and vice versa; the circuit comprises a bootstrap capacitor (Cboot) having one terminal connected to the midpoint node and the other terminal connected to a supply circuit (15) of said bootstrap capacitor. The detecting device comprises a further capacitor (Cgd) adapted to be connected between said other terminal of the bootstrap capacitor and circuit means (12, Cpump) adapted to form a low impedance node for the current signal (Isink, Isource) circulating in said further capacitor (Cgd) during the transitions from the low value to the high value and from the high value to the low value of the midpoint voltage (Va). The device comprises detecting means (10) adapted to detect said current signal circulating in said further capacitor and adapted to output at least a first signal (HL_comm, LH_comm) indicating the transitions from the low value to the high value or from the high value to the low value of the midpoint voltage according to said current signal.