Switchover system for binary load control

A system for controlling the energization of a load-operating impedance element connected across a power supply, comprising:

• a high-resistance d-c circuit branch in series with said impedance element, said branch including a voltage limiter, a voltage multiplier with an input energized by said voltage limiter and a switching stage energized by said voltage multiplier, said switching stage having an output carrying a potential whose absolute magnitude is higher than that of the maximum output voltage of said voltage limiter in a first operational state and is lower than that of said maximum output voltage in a second operational state thereof;
• a differential amplifier having a first input connected to said voltage limiter in parallel with the input of said voltage multiplier and having a second input connected to the output of said switching stage for emitting a binary switchover signal depending on the operational state of said switching stage;
• command means connected to said switching stage for altering the operational state thereof in response to a control variable;
• and
• variable-resistance means coupled to said differential amplifier and responsive to said switchover signal connected across said branch in series with said impedance element for providing a low-resistance current path in one operational state and a high-resistance current path in the other operational state of said switching stage, thereby causing said impedance element to be traversed by a relatively large load current in said one operational state and by a relatively small load current in said other operational state, the voltage drop across said low-resistance current path being sufficient to maintain the energization of said switching stage in said one operational state.