Self-latching H-bridge system and apparatus

A polyphase H-bridge for controlling currents through a plurality of loads, wherein the polyphase H-bridge is coupled between a supply voltage and a reference voltage, comprising:

• n high side thyristors each having a cathode, an anode, and a control gate, wherein the anodes of each of the thyristors is coupled to the supply voltage;
• n loads, each of the n loads coupled between the cathodes of two different ones of the n thyristors;
• n low side switches each coupled between the cathode of one of the n thyristors and the reference voltage, wherein each of the n low side switches comprises a control input;
• n H-bridge input terminals, each coupled to the control gate of the thyristors and the control input of the low side switches across the loads in which bi-directional current is desired to flow, whereby asserting a signal at a corresponding one of the n H-bridge input terminals enables the current to flow through the respective loads, wherein the amplitude of the asserted signal is lower than the amplitude of the supply voltage.

A system for controlling a motor, comprising:

• a motor direction control circuit to output forward and reverse direction signals;
• a hold-off circuit coupled to the motor direction control circuit to delay assertion of either the forward or reverse direction signals until the other of the forward or reverse direction signal has been disabled;
• a direct current (DC) motor capable of operation in both forward and reverse directions;
• and
• an H-bridge coupled to the DC motor and to the hold-off circuit to receive the forward and reverse direction signals, wherein the H-bridge is further coupled to a supply voltage and a reference voltage, the H-bridge comprising:
• a forward circuit coupled between the supply and reference voltages, wherein the forward circuit comprises the DC motor, a first low side switch coupled to receive the forward direction signal, and a first high side silicon-controlled rectifier (SCR) coupled to receive the forward direction signal at its control gate, and wherein assertion of the forward direction signal turns on the first low side switch and the first high side SCR to allow a current to flow through the first high side SCR, the DC motor, and the first low side switch;
• and
• a reverse circuit coupled between the supply and reference voltages, wherein the reverse circuit comprises the DC motor, a second low side switch coupled to receive a reverse direction signal, and a second high side SCR coupled to receive the reverse direction signal at its control gate, and wherein assertion of the reverse direction signal turns on the second low side switch and the second high side SCR to allow a current to flow through the second high side SCR, the DC motor, and the second low side switch.

A self-latching H-bridge, powered by a power source, for controlling bi-directional current through a load, comprising:

• a first silicon-controlled rectifier (SCR) having an anode, a cathode, and a gate input;
• wherein the first SCR is coupled to the power source via the anode;
• a first switch coupled between a reference voltage and the cathode of the first SCR through the load, wherein the first switch comprises a first control input;
• a first buffer coupled to the first SCR gate input and the first control input to turn on the first SCR and the first switch upon output of a forward direction signal to conduct current in a first direction;
• a second SCR having an anode, a cathode, and a gate input;
• wherein the second SCR is coupled to the power source via the anode;
• a second switch coupled between the reference voltage and the cathode of the second SCR through the load, wherein the second switch comprises a second control input;
• and
• a second buffer coupled to the second SCR gate input and the second control input to turn on the second SCR and the second switch upon output of a reverse direction signal to conduct current in a second direction, wherein the amplitude of the forward and reverse direction signals is lower than the amplitude of the power source.