Control device of power switch
A control device of a power switch includes a voltage boost circuit, a discharge circuit and a bias voltage generating circuit. The voltage boost circuit generates a control voltage at a control end of the power switch by boosting a base voltage. The discharge circuit provides a discharge path between the control end of the power switch and a reference ground end according to a bias voltage. The bias voltage generating circuit compares an output voltage on an output end of the power switch with the control voltage to generate a comparison result, and generates the bias voltage according to the comparison result.
1. A control device of a power switch, comprising:
a voltage boost circuit coupled to a control end of the power switch and boosting a base voltage to generate a control voltage at the control end of the power switch;
a discharge circuit coupled between the control end of the power switch and a reference ground end and generating a discharge path between the control end of the power switch and the reference ground end according to a bias voltage; and
a bias voltage generating circuit coupled to the discharge circuit, comparing an output voltage at an output end of the power switch to the control voltage to generate a comparison result, and generating the bias voltage according to the comparison result.
2. The control device according to claim 1 , wherein the bias voltage generating circuit further generates the bias voltage according to a switch on/off signal, an abnormal signal, and the comparison result.
3. The control device according to claim 1 , wherein the bias voltage generating circuit generates the bias voltage to enable the discharge circuit to generate the discharge path when the control voltage is greater than a difference between the output voltage and an offset voltage.
4. The control device according to claim 1 , wherein the bias voltage generating circuit comprises:
a comparator comprising a positive input end to receive the control voltage, a negative input end of the comparator to receive the output voltage, and an output end of the comparator to generate the comparison result; and
a logic operator performing a logic operation on a switch on/off signal, an abnormal signal, and the comparison result and generating the bias voltage according to the operation result.
5. The control device according to claim 4 , wherein the logic operator comprises:
an inverter receiving the switch on/off signal and generating a reverse switch on/off signal;
an OR gate receiving the reverse switch on/off signal and the abnormal signal and generating a first operation signal;
an AND gate receiving the comparison result and the first operation signal to generate a second operation signal and providing the bias voltage through the second operation signal.
6. The control device according to claim 1 , wherein the bias voltage generating circuit comprises:
a first current mirror receiving the output voltage and the control voltage, generating a first current according to a difference between the output voltage and the control voltage, and mirroring the first current to generate a second current;
a second current mirror receiving the second current and mirroring the second current to generate a third current;
a reference current source providing a reference current to a reference end of the second current mirror to generate the third current;
a logic operator performing a logic operation on a switch on/off signal, an abnormal signal, and the voltage on the reference end and providing the bias voltage according to the operation result.
7. The control device according to claim 6 , wherein the bias voltage generating circuit further comprises:
an offset voltage generator coupled between the first current mirror and the control end of the power switch to provide an offset voltage.
8. The control device according to claim 1 , wherein the bias voltage generating circuit comprises:
a current mirror receiving the output voltage and the control voltage, generating a first current according to a difference between the output voltage and the control voltage, and mirroring the first current to generate a second current;
a reference current source coupled to a reference end of the current mirror that generates the second current;
a logic operator performing a logic operation on a switch on/off signal, an abnormal signal, and the voltage on the reference end and providing the bias voltage according to the operation result.
9. The control device according to claim 8 , wherein the logic operator comprises:
a first inverter receiving the switch on/off signal and generating a reverse switch on/off signal;
a second inverter receiving the abnormal signal and generating a reverse abnormal signal;
a reverse OR gate receiving the reverse abnormal signal and the voltage on the reference end to generate a first operation signal; and
an OR gate receiving the reverse switch on/off signal and the first operation signal, generating a second operation signal, and providing the bias voltage according to the second operation signal.
10. The control device according to claim 9 , wherein the bias voltage generating circuit further comprises:
an offset voltage generator coupled between the first current mirror and the control end of the power switch to provide an offset voltage.