Driving circuit and a desaturation circuit of a power circuit
A power circuit includes a power transistor and a driving circuit. The power transistor draws a power current from a loading node according to a voltage of a driving node and stops drawing the power current according to an over-current signal. The driving circuit includes a high-side transistor, a low-side transistor, a charge pump, a pre-driver, and a desaturation circuit. The high-side transistor provides a supply voltage to the driving node according to a high-side voltage of a high-side node. The low-side transistor couples the driving node to the ground according to a first internal signal. The charge pump generates a high-side voltage that exceeds the supply voltage according to the first internal signal. The pre-driver generates the first internal signal according to a control signal. The desaturation circuit determines that the power current exceeds a threshold to generate the over-current signal.
1. A power circuit, comprising:
a power transistor, drawing a power current from a loading node according to a driving voltage of a driving node and stopping drawing the power current according to an over-current signal; and
a driving circuit, comprising:
a high-side transistor, providing a supply voltage to the driving node according to a high-side voltage of a high-side node;
a low-side transistor, coupling the driving node to a ground according to a first internal signal;
a charge pump, coupled to the high-side node and the driving node, wherein the charge pump is configured to generate the high-side voltage that exceeds the supply voltage according to the first internal signal;
a pre-driver, generating the first internal signal according to a control signal, wherein the pre-driver is configured to improve driving capability of the control signal; and
a desaturation circuit, determining that the power current exceeds a threshold to generate the over-current signal.
2. The power circuit of claim 1 , further comprising:
a first hysteresis circuit, coupled between the control signal and the pre-driver, wherein the first hysteresis circuit receives the control signal to generate a second internal signal, so that the pre-driver generates the first internal signal according to the second internal signal, wherein the first hysteresis circuit is configured to provide a hysteresis for the control signal.
3. The power circuit of claim 1 , wherein the desaturation circuit comprises:
a first desaturation resistor, coupled between the supply voltage and a first desaturation node;
a first desaturation normally-on transistor, comprising a gate terminal coupled to the first desaturation node, a source terminal coupled to the first desaturation node, and a drain terminal coupled to the loading node;
a second desaturation normally-on transistor, comprising a gate terminal coupled to a second desaturation node, a source terminal coupled to the second desaturation node, and a drain terminal coupled to the supply voltage;
a low-pass filter, filtering out a ripple at the first desaturation node to generate a detection voltage at a detection node;
a first desaturation normally-off transistor, comprising a gate terminal coupled to the driving node, a source terminal coupled to the ground, and a drain terminal coupled to the second desaturation node;
a second desaturation normally-off transistor, supplying the supply voltage to the second desaturation node according to the first internal signal;
a third desaturation normally-off transistor, coupling the detection node to the ground according to a voltage of the second desaturation node; and
a second hysteresis circuit, determining whether the detection voltage exceeds the threshold and generating the over-current signal when the detection voltage exceeds the threshold.
4. The power circuit of claim 3 , wherein the low-pass filter comprises:
a second desaturation resistor, coupled between the first desaturation node and a third desaturation node;
a first desaturation unidirectional conducting device, having a first forward voltage, wherein the first desaturation unidirectional conducting device is turned ON when the ripple is lower than the ground by the first forward voltage;
a third desaturation resistor, coupled between the third desaturation node and the detection node; and
a second desaturation unidirectional conducting device, having a second forward voltage, wherein the second desaturation unidirectional conducting device is turned ON when the ripple exceeds the second forward voltage.
5. The power circuit of claim 3 , wherein the second hysteresis circuit comprises:
a fourth desaturation resistor, coupled between the supply voltage and a fourth desaturation node;
a fourth desaturation normally-off transistor, coupling a fifth desaturation node to the ground according to the detection voltage;
a fifth desaturation normally-off transistor, coupling the fourth desaturation node to the fifth desaturation node according to the detection voltage;
a sixth desaturation normally-off transistor, supplying the supply voltage to the fifth desaturation node according to a voltage of the fourth desaturation node;
a seventh desaturation normally-off transistor, coupling an over-current node to the ground according to the voltage of the fourth desaturation node; and
a third desaturation normally-on transistor, comprising a gate terminal coupled to the over-current node, a source terminal coupled to the over-current node, and a drain terminal coupled to the supply voltage, wherein the over-current signal is generated on the over-current node.
6. The power circuit of claim 5 , wherein the desaturation circuit further comprises:
a pull-down transistor, coupling the driving node to the ground in response to the over-current signal.
7. The power circuit of claim 5 , wherein the desaturation circuit further comprises:
a pull-down transistor, pulling the first sub-internal signal down to the ground in response to the over-current signal.
8. The power circuit of claim 5 , wherein the desaturation circuit further comprises:
a pull-down transistor, pulling the third sub-internal signal down to the ground in response to the over-current signal.
9. The power circuit of claim 5 , wherein the control signal is generated by a controller, wherein the controller stops generating the control signal in response to the over-current signal.
10. The power circuit of claim 1 , wherein the driving circuit further comprises:
a high-side normally-on transistor, comprising a source terminal coupled to the driving node, a gate terminal coupled to the driving node, and a drain terminal supplied by the supply voltage, wherein the high-side normally-on transistor is configured to improve driving capability of the high-side transistor.
11. A driving circuit for driving a power transistor, wherein the power transistor draws a power current according to a driving voltage of a driving node, the driving circuit comprising:
a high-side transistor, providing a supply voltage to the driving node according to a high-side voltage of a high-side node;
a low-side transistor, coupling the driving node to a ground according to a first internal signal;
a charge pump, coupled to the high-side node and the driving node, wherein the charge pump is configured to generate a high-side voltage that exceeds the supply voltage according to the first internal signal;
a pre-driver, generating the first internal signal according to a control signal, wherein the pre-driver is configured to improve driving capability of the control signal, wherein the pre-driver stops generating the first internal signal according to an over-current signal; and
a desaturation circuit, determining that the power current exceeds a threshold to generate the over-current signal, wherein the power transistor stops drawing the power current according to the over-current signal.
12. The driving circuit of claim 11 , further comprising:
a first hysteresis circuit, coupled between the control signal and the pre-driver, wherein the first hysteresis circuit receives the control signal to generate a second internal signal, so that the pre-driver generates the first internal signal according to the second internal signal, wherein the first hysteresis circuit is configured to provide a hysteresis for the control signal.
13. The driving circuit of claim 12 , wherein the desaturation circuit comprises:
a first desaturation resistor, coupled between the supply voltage and a first desaturation node;
a first desaturation normally-on transistor, comprising a gate terminal coupled to the first desaturation node, a source terminal coupled to the first desaturation node, and a drain terminal coupled to a loading node;
a second desaturation normally-on transistor, comprising a gate terminal coupled to a second desaturation node, a source terminal coupled to the second desaturation node, and a drain terminal coupled to the supply voltage;
a low-pass filter, filtering out a ripple at the first desaturation node to generate a detection voltage at a detection node;
a first desaturation normally-off transistor, comprising a gate terminal coupled to the driving node, a source terminal coupled to the ground, and a drain terminal coupled to the second desaturation node;
a second desaturation normally-off transistor, supplying the supply voltage to the second desaturation node according to the first internal signal;
a third desaturation normally-off transistor, coupling the detection node to the ground according to a voltage of the second desaturation node; and
a second hysteresis circuit, determining whether the detection voltage exceeds the threshold and generating an over-current signal when the detection voltage exceeds the threshold.
14. The driving circuit of claim 13 , wherein the low-pass filter comprises:
a second desaturation resistor, coupled between the first desaturation node and a third desaturation node;
a first desaturation unidirectional conducting device, having a first forward voltage, wherein the first desaturation unidirectional conducting device is turned ON when the ripple is lower than the ground by the first forward voltage;
a third desaturation resistor, coupled between the third desaturation node and the detection node; and
a second desaturation unidirectional conducting device, having a second forward voltage, wherein the second desaturation unidirectional conducting device is turned ON when the ripple exceeds the second forward voltage.
15. The driving circuit of claim 13 , wherein the second hysteresis circuit comprises:
a fourth desaturation resistor, coupled between the supply voltage and a fourth desaturation node;
a fourth desaturation normally-off transistor, coupling a fifth desaturation node to the ground according to the detection voltage;
a fifth desaturation normally-off transistor, coupling the fourth desaturation node to the fifth desaturation node according to the detection voltage;
a sixth desaturation normally-off transistor, supplying the supply voltage to the fifth desaturation node according to a voltage of the fourth desaturation node;
a seventh desaturation normally-off transistor, coupling an over-current node to the ground according to the voltage of the fourth desaturation node; and
a third desaturation normally-on transistor, comprising a gate terminal coupled to the over-current node, a source terminal coupled to the over-current node, and a drain terminal coupled to the supply voltage, wherein the over-current signal is generated on the over-current node.
16. The driving circuit of claim 15 , wherein the desaturation circuit further comprises:
a pull-down transistor, coupling the driving node to the ground in response to the over-current signal.
17. The driving circuit of claim 15 , wherein the desaturation circuit further comprises:
a pull-down transistor, pulling the first sub-internal signal down to the ground in response to the over-current signal.
18. The driving circuit of claim 15 , wherein the desaturation circuit further comprises:
a pull-down transistor, pulling the third sub-internal signal down to the ground in response to the over-current signal.
19. The driving circuit of claim 15 , wherein the control signal is generated by a controller, wherein the controller stops generating the control signal in response to the over-current signal.
20. The driving circuit of claim 11 , wherein the driving circuit further comprises:
a high-side normally-on transistor, comprising a source terminal coupled to the driving node, a gate terminal coupled to the driving node, and a drain terminal supplied by the supply voltage, wherein the high-side normally-on transistor is configured to improve driving capability of the high-side transistor.