DC-DC converter with short-circuit protection
A DC-DC converter includes a voltage converter circuit having an FET 1 , a short-circuit protection FET 3 that blocks a large current from flowing in the voltage converter circuit when a short-circuit failure occurs in the FET 1 or capacitors, and a detector that detects a short-circuit failure in the FET 1 or the capacitors to turn off the FET 3 . The FET 1 is connected to a power supply line and also in series to the FET 3 . The capacitors are connected to the power supply line and to a connection point between the FET 1 and FET 3 . The detector detects a failure on the basis of the voltage at the connection point.
1. A DC-DC converter comprising:
an input terminal to which a positive electrode of a DC power supply is connected;
an output terminal to which a load is connected;
a power supply line of the DC power supply extending from the input terminal to the output terminal;
a voltage converter circuit that is disposed between the input terminal and the output terminal, has a first switching element having one end connected to the power supply line, and boosts or steps down a voltage of the DC power supply depending on an on/off-operation of the first switching element to supply the voltage to the load; and
a capacitor having one end connected to the power supply line, and further comprising:
a short-circuit protection second switching element connected in series with the first switching element on the other end side of the first switching element; and
a detector that detects a short-circuit failure in the first switching element or the capacitor to turn off the second switching element, wherein
the other end of the capacitor is connected to a connection point between the first switching element and the second switching element, and
the detector detects a failure on the basis of a voltage at the connection point.
2. The DC-DC converter according to claim 1 , further comprising
an input filter disposed between the input terminal and the voltage converter circuit, wherein
the capacitor is a noise removing capacitor included in the input filter.
3. The DC-DC converter according to claim 2 , wherein
the detector includes:
a voltage-dividing resistor that divides the voltage at the connection point; and
a third switching element that is turned on/off when the voltage divided by the voltage-dividing resistor is equal to or higher than a constant value, and
the second switching element is turned off by turning on/off the third switching element.
4. The DC-DC converter according to claim 2 , wherein
the detector includes a first detector and a second detector,
the first detector includes
a voltage-dividing resistor that divides the voltage at the connection point, and
a third switching element that is turned on/off when the voltage divided by the voltage-dividing resistor is equal to or higher than a predetermined value,
the second detector includes
a controller that determines the presence/absence of a failure on the basis of the voltage at the connection point and outputs a control signal when the second detector determines that the failure occurs, and
a fourth switching element that is turned on/off on the basis of the control signal, and
the second switching element is turned off by turning on/off the third switching element in the first detector or turning on/off the fourth switching element in the second detector.
5. The DC-DC converter according to claim 2 , further comprising
a reverse connection protection fifth switching element that blocks a large current from flowing into the voltage converter circuit when the negative electrode of the DC power supply is connected to the input terminal, wherein
the fifth switching element is connected in series with the second switching element and disposed between the second switching element and the ground.
6. The DC-DC converter according to claim 1 , further comprising
an output filter disposed between the voltage converter circuit and the output terminal, wherein
the capacitor is a noise removing capacitor included in the output filter.
7. The DC-DC converter according to claim 6 , wherein
the detector includes:
a voltage-dividing resistor that divides the voltage at the connection point; and
a third switching element that is turned on/off when the voltage divided by the voltage-dividing resistor is equal to or higher than a constant value, and
the second switching element is turned off by turning on/off the third switching element.
8. The DC-DC converter according to claim 6 , wherein
the detector includes a first detector and a second detector,
the first detector includes
a voltage-dividing resistor that divides the voltage at the connection point, and
a third switching element that is turned on/off when the voltage divided by the voltage-dividing resistor is equal to or higher than a predetermined value,
the second detector includes
a controller that determines the presence/absence of a failure on the basis of the voltage at the connection point and outputs a control signal when the second detector determines that the failure occurs, and
a fourth switching element that is turned on/off on the basis of the control signal, and
the second switching element is turned off by turning on/off the third switching element in the first detector or turning on/off the fourth switching element in the second detector.
9. The DC-DC converter according to claim 6 , further comprising
a reverse connection protection fifth switching element that blocks a large current from flowing into the voltage converter circuit when the negative electrode of the DC power supply is connected to the input terminal, wherein
the fifth switching element is connected in series with the second switching element and disposed between the second switching element and the ground.
10. The DC-DC converter according to claim 1 , wherein
the capacitor is a smoothing capacitor that smooths a voltage switched by the first switching element and is included in the voltage converter circuit.
11. The DC-DC converter according to claim 10 , wherein
the detector includes:
a voltage-dividing resistor that divides the voltage at the connection point; and
a third switching element that is turned on/off when the voltage divided by the voltage-dividing resistor is equal to or higher than a constant value, and
the second switching element is turned off by turning on/off the third switching element.
12. The DC-DC converter according to claim 10 , wherein
the detector includes a first detector and a second detector,
the first detector includes
a voltage-dividing resistor that divides the voltage at the connection point, and
a third switching element that is turned on/off when the voltage divided by the voltage-dividing resistor is equal to or higher than a predetermined value,
the second detector includes
a controller that determines the presence/absence of a failure on the basis of the voltage at the connection point and outputs a control signal when the second detector determines that the failure occurs, and
a fourth switching element that is turned on/off on the basis of the control signal, and
the second switching element is turned off by turning on/off the third switching element in the first detector or turning on/off the fourth switching element in the second detector.
13. The DC-DC converter according to claim 10 , further comprising
a reverse connection protection fifth switching element that blocks a large current from flowing into the voltage converter circuit when the negative electrode of the DC power supply is connected to the input terminal, wherein
the fifth switching element is connected in series with the second switching element and disposed between the second switching element and the ground.
14. The DC-DC converter according to claim 1 , further comprising:
an input filter disposed between the input terminal and the voltage converter circuit; and
an output filter disposed between the voltage converter circuit and the output terminal, wherein
the capacitor includes:
a noise removing first capacitor included in the input filter;
a noise removing second capacitor included in the output filter; and
a smoothing third capacitor that smooths a voltage switched by the first switching element and is included in the voltage converter circuit.
15. The DC-DC converter according to claim 14 , wherein
the detector includes:
a voltage-dividing resistor that divides the voltage at the connection point; and
a third switching element that is turned on/off when the voltage divided by the voltage-dividing resistor is equal to or higher than a constant value, and
the second switching element is turned off by turning on/off the third switching element.
16. The DC-DC converter according to claim 14 , wherein
the detector includes a first detector and a second detector,
the first detector includes
a voltage-dividing resistor that divides the voltage at the connection point, and
a third switching element that is turned on/off when the voltage divided by the voltage-dividing resistor is equal to or higher than a predetermined value,
the second detector includes
a controller that determines the presence/absence of a failure on the basis of the voltage at the connection point and outputs a control signal when the second detector determines that the failure occurs, and
a fourth switching element that is turned on/off on the basis of the control signal, and
the second switching element is turned off by turning on/off the third switching element in the first detector or turning on/off the fourth switching element in the second detector.
17. The DC-DC converter according to claim 1 , wherein
the detector includes:
a voltage-dividing resistor that divides the voltage at the connection point; and
a third switching element that is turned on/off when the voltage divided by the voltage-dividing resistor is equal to or higher than a constant value, and
the second switching element is turned off by turning on/off the third switching element.
18. The DC-DC converter according to claim 1 , wherein
the detector includes:
a controller that determines the presence/absence of a failure on the basis of a voltage at the connection point and outputs a control signal when the detector determines that the failure occurs; and
a fourth switching element that is turned on/off on the basis of the control signal, and
the second switching element is turned off by turning on/off the fourth switching element.
19. The DC-DC converter according to claim 1 , wherein
the detector includes a first detector and a second detector,
the first detector includes
a voltage-dividing resistor that divides the voltage at the connection point, and
a third switching element that is turned on/off when the voltage divided by the voltage-dividing resistor is equal to or higher than a predetermined value,
the second detector includes
a controller that determines the presence/absence of a failure on the basis of the voltage at the connection point and outputs a control signal when the second detector determines that the failure occurs, and
a fourth switching element that is turned on/off on the basis of the control signal, and
the second switching element is turned off by turning on/off the third switching element in the first detector or turning on/off the fourth switching element in the second detector.
20. The DC-DC converter according to claim 1 , further comprising
a reverse connection protection fifth switching element that blocks a large current from flowing into the voltage converter circuit when the negative electrode of the DC power supply is connected to the input terminal, wherein
the fifth switching element is connected in series with the second switching element and disposed between the second switching element and the ground.