Direct current control circuit
First Claim
1. A control circuit for turning off a flow of direct current through a load (12) to ground, the load being at least partly an inductive load (14);
- the control circuit comprising;
a semiconductor switch (11) having a first terminal (D), a control terminal (G), and a second terminal (S) coupled to the load;
a semiconductor freewheel component (16) coupled between the second terminal and ground in parallel with the load, the freewheel component having a current-conducting state and a current non-conducting state;
a switching-off current source (19), coupled between the second terminal and the control terminal, comprising means to reduce a magnitude of switching control current (-IGS) flowing through the control terminal of the switch as a function of voltage at the second terminal of the switch;
the function including a minimum value (-IGSmin) of the switching control current being reached when the voltage at the second terminal of the switch is at ground potential;
whereby when the load is disconnected the control current is reduced from a higher initial value so as to open the semiconductor switch completely only when the freewheel component is in the current-conducting state.
1 Assignment
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Accused Products
Abstract
A control circuit for turning off or on direct current flowing through an inductive load (12) to ground uses a semiconductor switch (11), for example a MOSFET, having a first input terminal (D), a control terminal (G), and a second output terminal (S) to the load. A semiconductor freewheel diode (16) is coupled between the switch second terminal and ground, in parallel with the load. The freewheel diode has a current-conducting state and a current non-conducting state. A switching-off current source (19) is coupled between the second terminal and the control terminal; it reduces the magnitude of the switching control current (±IGS) flowing into the control terminal of the MOSFET, as a function of voltage at the second terminal of the switch and the input to the freewheel diode. A minimum value (±IIGSmin) of the switching control current is reached when the voltage at the second terminal of the switch reaches ground potential. The current-increase or current-decrease time intervals are influenced by the current sources 18 and 19 in response to the freewheel voltage causing rapid switching without spikes and power loss.
13 Citations
17 Claims
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1. A control circuit for turning off a flow of direct current through a load (12) to ground, the load being at least partly an inductive load (14);
- the control circuit comprising;
a semiconductor switch (11) having a first terminal (D), a control terminal (G), and a second terminal (S) coupled to the load; a semiconductor freewheel component (16) coupled between the second terminal and ground in parallel with the load, the freewheel component having a current-conducting state and a current non-conducting state; a switching-off current source (19), coupled between the second terminal and the control terminal, comprising means to reduce a magnitude of switching control current (-IGS) flowing through the control terminal of the switch as a function of voltage at the second terminal of the switch; the function including a minimum value (-IGSmin) of the switching control current being reached when the voltage at the second terminal of the switch is at ground potential; whereby when the load is disconnected the control current is reduced from a higher initial value so as to open the semiconductor switch completely only when the freewheel component is in the current-conducting state. - View Dependent Claims (2, 3, 4)
- the control circuit comprising;
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5. A control circuit for turning on a flow of direct current through at least one load (12) to ground, the load being at least partly an inductive load (14);
- the control circuit comprising;
a semiconductor switch (11) having a first terminal (D), a control terminal (G), and a second terminal (S) coupled to the load; a semiconductor freewheel component (16) coupled between the second terminal and ground in parallel with the at least one load, the freewheel component having a current-conducting state and a current non-conducting state; a switching-on current source (18), coupled between the first terminal and the control terminal, comprising means to set a magnitude of switching control current (IGS) flowing through the control terminal of the switch as a function of voltage at the second terminal of the switch; the function including a minimum value (IGSmin) of the switching control current being reached when the voltage at the second terminal of the switch is at ground potential prior to going below a threshold value thereof; whereby when the load is disconnected the control current is reduced from a higher initial value so as to open the semiconductor switch completely only when the freewheel component is in the current non-conducting state. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
- the control circuit comprising;
Specification