Over-power protection apparatus with programmable over-current threshold

1. An over-power protection apparatus with programmable over-current threshold for a power converter, comprising:

an oscillator, generating a pulse signal;

a control unit, generating a clear signal in response to a current sense signal, a voltage feedback signal and a maximum power threshold of said power converter;

a driving unit, connected to said oscillator and said control unit for generating a driving signal in response to said pulse signal and said clear signal;

a threshold unit, connected to said driving unit for generating a current limit signal as said driving signal is in high-level;

an over-power comparative unit, connected to said threshold unit for comparing said current limit signal and said current sense signal to generate a protection signal as said current sense signal is higher than said current limit signal;

an accumulating trigger unit, connected to said over-power comparative unit and said oscillator for receiving said protection signal and said pulse signal, wherein said accumulating trigger unit accumulates and counts said protection signal, and further generates a first off-signal as said protection signal is enabled and the count of said protection signal reaches a predetermined value; and

a latch unit, connected to said accumulating trigger unit and said driving unit for generating a latch signal to said driving unit in response to said first off-signal;

wherein said driving unit latch-off said driving signal in response to said latch signal and adjusts a pulse width of said driving signal in response to said clear signal outputted by said control unit.

2. The over-power protection apparatus with programmable over-current threshold of claim 1 , wherein said accumulating trigger unit comprising:

a holding unit, connected to said over-power comparative unit and said oscillator for generating an up-down signal to delay the state of said protection signal in accordance with said protection signal and said pulse signal;

a switch, connected to said holding unit for generating an on/off state in response to said up-down signal and the states of said protection signal;

a programmable capacitor, connected to a charging current source via said switch for generating a charging current and a charging voltage in response to the on state of said switch, wherein said programmable capacitor further connects to a discharging current source via said switch, said discharging current source generates a discharging current to discharge said programmable capacitor in response to the off state of said switch; and

a delay comparator, connected to said programmable capacitor and a fourth threshold signal, which comparing said charging voltage with said fourth threshold signal for generating said first off-signal as said charging voltage is higher than said fourth threshold signal;

wherein said predetermined value of said accumulating trigger unit can be adjusted by said programmable capacitor.

3. The over-power protection apparatus with programmable over-current threshold of claim 1 , wherein said threshold unit comprises a constant current source, a first controlled switch and a programmable resistor, wherein said constant current source connects to said programmable resistor via said first controlled switch, further, said first controlled switch is at on state as said driving signal is in high-level, and said constant current source follows through said programmable resistor for generating said current limit signal.

4. The over-power protection apparatus with programmable over-current threshold of claim 1 , wherein the magnitude of said current limit signal can be adjusted by said programmable resistor.

5. The over-power protection apparatus with programmable over-current threshold of claim 1 , further comprising a voltage feedback terminal, a current sense terminal, a voltage input terminal, a driving terminal, an over-power/over-temperature protection terminal and an adjustable delay time terminal.

6. An over-power protection apparatus with programmable over-current threshold for a power converter, comprising:

an oscillator, generating a pulse signal;

a control unit, generating a clear signal in response to a current sense signal, a voltage feedback signal and a maximum power threshold of said power converter;

a driving unit, connected to said oscillator and said control unit for generating a driving signal in response to said pulse signal and said clear signal;

a threshold unit, connected to said driving unit for generating a current limit signal as said driving signal is in high-level;

an over-temperature protection unit, connected to said driving unit for receiving an over-temperature threshold to generate a second off-signal in response to a thermal limit signal is lower than said over-temperature threshold and said driving signal is in low-level;

an over-power comparative unit, connected to said threshold unit for comparing said current limit signal and said current sense signal to generate a protection signal as said current sense signal is higher than said current limit signal;

an accumulating trigger unit, connected to said over-power comparative unit and said oscillator for receiving said protection signal and said pulse signal, wherein said accumulating trigger unit accumulates and counts said protection signal, and further generates a first off-signal as said protection signal is enabled and the count of said protection signal reaches a predetermined value; and

a connecting unit, connected to said over-temperature protection unit and said accumulating trigger unit for executing an or-gate operation and generating a third off-signal in response to said second off-signal and said first off-signal; and

a latch unit, connected to said connecting unit and said driving unit for generating a latch signal to said driving unit in response to said third off-signal;

wherein said driving unit latch-off said driving signal in response to said latch signal and adjusts a pulse width of said driving signal in response to said clear signal of said control unit.

7. The over-power protection apparatus with programmable over-current threshold of claim 6 , wherein said over-temperature protection unit comprising:

a thermal sensor, connected to said driving unit and a ground via a threshold diode and a programming resistor of said threshold unit;

an over-temperature current source, connected to said programming resistor via a second controlled switch, wherein said second controlled switch connects to said driving unit via an inverter; and

an over-temperature comparator, connected to said programmable resistor, said over-temperature comparator comparing said over-temperature threshold with said thermal limit signal across said programmable resistor, said over-temperature comparator further connected to said connecting unit via a third controlled switch, wherein said third controlled switch connects to said driving unit via said inverter;

whereby said threshold diode, said second and said third controlled switches are turned on in response to said driving signal of said driving unit is in low-level, and said over-temperature comparator generates said second off-signal as said thermal limit signal is lower than said over-temperature threshold.

8. The over-power protection apparatus with programmable over-current threshold of claim 6 , wherein said accumulating trigger unit comprising:

a holding unit, connected to said over-power comparative unit and said oscillator for generating an up-down signal to delay the state of said protection signal in accordance with said protection signal and said pulse signal;

a switch, connected to said holding unit for generating an on/off state in response to said up-down signal and the states of said protection signal;

a programmable capacitor, connected to a charging current source via said switch for generating a charging current and a charging voltage in response to the on state of said switch, wherein said programmable capacitor further connects to a discharging current source via said switch, said discharging current source generates a discharging current to discharge said programmable capacitor in response to the off state of said switch; and

a delay comparator, connected to said programmable capacitor and a fourth threshold signal, said delay comparator comparing said charging voltage with said fourth threshold signal for generating said first off-signal as said charging voltage is higher than said fourth threshold signal;

wherein said predetermined value of said accumulating trigger unit can be adjusted by said programmable capacitor.

9. The over-power protection apparatus with programmable over-current threshold of claim 6 , wherein said threshold unit comprises a constant current source, a first controlled switch, a programmable resistor and a fourth controlled switch, wherein said constant current source connects with said programmable resistor via said first controlled switch, further, said first and said fourth controlled switches are turned on as said driving signal is in high-level, and said constant current source follows through said programmable resistor for generating said current limit signal.

10. The over-power protection apparatus with programmable over-current threshold of claim 6 , wherein the magnitude of said current limit signal and said thermal limit signal can be adjusted by said programmable resistor.

11. The over-power protection apparatus with programmable over-current threshold of claim 6 , further comprising a voltage feedback terminal, a current sense terminal, a voltage input terminal, a driving terminal, an over-power/over-temperature protection terminal and an adjustable delay time terminal.