TWI382622B - Over current protection device for a power supply device and related power supply device - Google Patents

Description

Overcurrent protection device for a power supply and its associated power supply

The present invention provides an overcurrent protection device for a power supply and an associated power supply thereof, and more particularly to an overcurrent protection device capable of matching voltages corresponding to different input voltages to begin overcurrent protection and related Power Supplier.

The power supply is used to provide the power required for the operation of the electronic device. According to its circuit structure, it can be generally divided into a linear power supply (Linear Power Supply) and a switching power supply (Switching Power Supply). Among them, the switching power supply has the advantages of small size, light weight and high conversion efficiency, which has been widely used in various fields, such as mobile communication devices, personal digital assistants, computers and peripherals, servers and networks. In electronic devices such as equipment.

In order to ensure the normal and stable operation of the power supply, the protection mechanism in the control circuit of the power supply is a very important part, such as over-voltage, over-current, over-power protection, etc., in the event of an overload or short circuit, prepare A power supply with a comprehensive protection mechanism can protect internal components or related equipment from damage.

Please refer to FIG. 1 , which is a schematic diagram of a conventional power supply 100 . The power supply 100 includes a transformer 102, a power switch 104, a current detecting unit 106, a comparator 108, and a pulse width modulation control unit 110. The transformer 102 includes a primary side circuit L1 and a secondary side circuit. L2 is used to convert an input signal V _IN into an output signal V _OUT . The power switch 104 is coupled to the primary side circuit L1 for controlling the operation of the transformer 102. In the first figure, the power switch 104 is implemented by a power transistor Q1, which can be controlled to switch to the on state or the off state according to the control signal outputted by the pulse width modulation control unit 110. The current detecting unit 106 is coupled to the drain of the power transistor Q1, and is implemented by a current detecting resistor R _CS for providing a current detecting signal V _CS to estimate the lateral flow of the power transistor. The magnitude and change of the primary current I _L1 of Q1. The comparator 108 is configured to compare the current detection signal V _CS with a reference voltage V _REF such that the pulse width modulation control unit 110 can determine whether the current protection range has been reached. For example, when the current detection signal V _{CS is} higher than the reference voltage V _REF , the comparator 108 can transmit an indication signal S _OC to the pulse width modulation control unit 110 to indicate an over current, and then the pulse width modulation control Unit 110 can control power transistor Q1 to turn off to reduce the magnitude of primary side current I _L1 .

The above protection mechanism controls the current to an appropriate range by comparing the current detecting signal V _CS with the reference voltage V _REF for protection purposes. However, when the current detection signal V _{CS is} higher than the reference voltage V _REF , the power switch 104 is not immediately turned off due to the non-ideal factor in the circuit, and the pulse width modulation control unit 110 can be turned off after a period of time. Power switch 104. That is, since the detection of the overcurrent occurs until the power switch 104 actually stops conducting, there is a transfer delay time _Tdelay , and thus the current that actually stops conducting is slightly higher than the set value. In other words, the voltage at which the overcurrent protection is started (hereinafter referred to as the protection point voltage) is larger than the voltage at which the overcurrent occurs, and the protection point voltage is different under different input voltages V _IN .

In detail, please refer to Figure 2, which is a schematic diagram of the difference in the protection point voltage between different input voltages. The input voltage value V _{IN of the} power supply 100 is proportional to the rising slope of the current detection signal V _CS voltage value. That is, when the magnitude of the reference voltage V _REF is the same, a high input voltage V _H will generate a current detecting signal with a large slope, and a low input voltage V _L will generate a current detecting signal with a small slope; The same power supply has the same transfer delay time _Tdelay , and the transfer delay time _Tdelay is independent of the input voltage magnitude. As shown in FIG. 2, when the current detection signal V _CS rises to the power limit level of the reference voltage V _REF , that is, when the current detection signal V _{CS is} greater than or equal to the reference voltage V _REF , the comparator 108 transmits an indication signal. S _OC to pulse width modulation control unit 110 to turn off power transistor Q1. After the transmission delay time _Tdelay , the power switch 104 is turned off, and the primary side circuit L1 current I _{L1 is} cut off. Since the detection of the overcurrent occurs until the power switch 104 actually stops conducting, the input voltage continues to transmit power such that the protection point voltage corresponding to the high input voltage V _H is V _OPPH and the protection point corresponding to the low input voltage V _L The voltage is V _OPPL . In other words, the protection point voltage will be higher than the reference voltage V _REF , and the higher the input voltage, the more obvious the difference. Under this circumstance, when the AC input voltage is varied within a wide range of 90 to 264V, the protection point will be seriously drifted, so that the output power of the high and low input voltages is greatly varied.

Accordingly, it is a primary object of the present invention to provide an overcurrent protection device for a power supply and its associated power supply.

The present invention discloses a power supply for preventing overcurrent damage, comprising an input stage for rectifying and filtering an input signal to generate a first power signal; a transformer device comprising a primary side circuit coupled to the An input stage, and a secondary side circuit for converting the first power signal into a second power signal; a power switch coupled to the primary side circuit; and a current detecting unit coupled to the power switch a current detecting signal is generated to generate a current detecting signal; an output stage is coupled to the voltage transforming device for outputting the second power signal to a load; And an overcurrent protection device coupled to the current detection unit and the power switch, comprising a receiving end for receiving the current detection signal; a compensation current unit coupled to the receiving end for compensating a current detection signal for generating a current detection compensation signal; a first reference voltage generating unit for generating a first reference voltage; a comparator coupled to the compensation current unit and the a reference voltage generating unit for comparing the current detecting compensation signal and the first reference voltage to generate a comparison result; a control unit coupled to the comparator and the power switch for determining, according to the comparison result, Control the conduction of the power switch.

The invention further discloses an overcurrent protection device for a power supply, comprising a receiving end for receiving a current detecting signal; a compensating current unit coupled to the receiving end for compensating the current detecting signal to generate a current detecting compensation signal; and a first reference voltage generating unit For generating a first reference voltage, a comparator coupled to the compensation current unit and the first reference voltage generating unit for comparing the current detection compensation signal and the first reference voltage to generate a comparison As a result, a control unit is coupled to the comparator for controlling an on state of the power switch of one of the power supplies according to the comparison result.

Please refer to FIG. 3, which is a schematic diagram of a power supply 300 according to an embodiment of the present invention. Power supply 300 is preferably a switched power supply. The power supply 300 includes an input stage 302, a voltage transforming device 304, a power switch 306, a current detecting unit 308, an output stage 310, and an overcurrent protection device 312. The input stage 302 is configured to rectify and filter an input signal V _IN to generate a first power signal V _PS1 . The transformer unit 304 is coupled to the input stage 302 and includes a primary side circuit L1 and a secondary side circuit L2 for converting the first power signal V _PS1 into a second power signal V _PS2 . The power switch 306 is preferably implemented by a power transistor Q1 coupled to the primary side circuit L1 for switching the operation of the transformer device 304. The current detecting unit 308 is coupled to the power switch 306, which is preferably implemented by a resistor R _CS for detecting the current of the primary side circuit L1 to generate a current detecting signal V _CS . The output stage 310 is coupled to the transformer device 304 for outputting the second power signal V _PS2 to a load 324. The overcurrent protection device 312 is coupled to the power switch 306 and the current detecting unit 308 for monitoring whether the primary side current I _L1 is within an appropriate protection range. When the safety protection range is exceeded, the power switch 306 is turned off to Over the purpose of current protection.

The architecture and operation of the overcurrent protection device 312 are further described. The overcurrent protection device 312 includes a receiving end 314, a compensation current unit 316, a first reference voltage generating unit 318, a comparator 320, and a control unit 322. The receiving end 314 is coupled to the current detecting unit 308 for receiving the current detecting signal V _CS . The compensation current unit 316 is coupled to the receiving end 314 for compensating the current detecting signal V _CS to generate a current detecting compensation signal V _{S — CS} . The first reference voltage generating unit 318 is configured to generate a first reference voltage V _REF1 . The comparator 320 is coupled to the compensation current unit 316 and the first reference voltage generating unit 318 for comparing the current detection compensation signal V _{S_CS} and the first reference voltage V _REF1 to generate a comparison result. The control unit 322 is coupled to the comparator 320 and the power switch 306 for controlling the conduction state of the power switch 306 according to the comparison result of the comparator 320. When the comparison result shows that the current detection compensation signal V _{S_CS is} smaller than the first reference voltage V _REF1 , the conduction state of the power switch 306 is maintained. When the comparison result shows that the current detection compensation signal V _{S_CS is} greater than or equal to the first reference voltage V _REF1 , the control unit 322 turns off the conduction state of the power switch 306 .

Please refer to FIG. 4 again. FIG. 4 is a schematic diagram of the compensation current unit 316 compensating the current detecting signal V _CS in FIG. As shown in the figure, the current detection signal V _{CS is} subjected to a slope compensation operation, that is, the current detection signal V _{CS is added} to a compensation signal V _{S to} form a current detection compensation signal V _{S_CS} , current detection compensation The signal V _{S_CS} allows the input voltage to start switching early. Please refer to FIG. 5, which is a schematic diagram of the correction of the transfer delay of the overcurrent protection device 312 in FIG. The delay time T _delay is the same in different input voltage situations. As shown in the figure, the signals with high and low input voltages V _H and V _L after slope compensation (ie V _{S_CS(H)} , V _{S_CS(L)} ) can be used. The first reference voltage V _{REF1 is} reached in advance, so that the power is continuously consumed due to the transmission delay time, and the voltage corresponding to the high input voltage and the low input voltage starting to be overcurrent protection is consistent, so that the difference of the protection point voltage is solved.

It is to be noted that FIG. 3 is only a schematic view of an embodiment of the present invention, and those skilled in the art can make different modifications. For example, please refer to Figure 6. FIG. 6 is a schematic diagram of a preferred embodiment of the current detecting compensation unit 316 in FIG. The operation of the current detection compensation unit 316 is further described. The current detection compensation unit 316 includes a compensation signal generator 602 and an adder 604. The compensation signal generator 602 is used to generate the compensation signal V _S as shown in FIG. 4 , and the adder 604 is coupled between the compensation signal generator 602 , the receiving end 314 and the comparator 320 for detecting the current detection signal. The V _CS and the compensation signal V _S are added to generate a current detection compensation signal V _{S — CS} to the comparator 320.

In FIG. 6, the compensation signal generator 602 is used to generate the compensation signal V _S to compensate for the slope of the current detection signal V _CS , the implementation of which is not limited to a particular circuit or component. For example, please refer to FIG. 7. FIG. 7 is a schematic diagram of a preferred embodiment of the compensation signal generator 602 in FIG. The compensation signal generator 602 includes a triangular wave generator 702, a second reference voltage generator 704, and a subtractor 706. The triangular wave generator 702 is used to generate a triangular wave signal V _T (or an oscillating signal). The second reference voltage generator 704 is configured to generate a second reference voltage V _REF2 . The subtracter 706 is coupled between the triangular wave generator 702, the second reference voltage generator 704, and the adder 604 for subtracting the triangular wave signal V _T and the second reference voltage V _REF2 to generate the compensation signal V _S to Adder 604.

In summary, the present invention can perform slope compensation on the input signal of the power supply, so that the power supply does not continue to consume power due to the transmission delay time. More importantly, in the present invention, the voltages for which overcurrent protection is started corresponding to different input voltages are identical, and thus the difference in the protection point voltage can be improved.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

100‧‧‧Power supply

102‧‧‧Transformers

104‧‧‧Power switch

106‧‧‧current detection unit

108‧‧‧ comparator

110‧‧‧ Pulse width modulation control unit

300‧‧‧Power supply

302‧‧‧Input level

304‧‧‧Transformer

306‧‧‧Power switch

308‧‧‧current detection unit

310‧‧‧Output level

312‧‧‧Overcurrent protection device

314‧‧‧ Receiver

316‧‧‧Compensated current unit

318‧‧‧First reference voltage generating unit

320‧‧‧ Comparator 320

322‧‧‧Control unit

324‧‧‧load

602‧‧‧Compensation signal generator

604‧‧‧Adder

702‧‧‧ triangle wave generator

704‧‧‧Second reference voltage generator

706‧‧‧Subtractor

Figure 1 is a schematic diagram of a conventional power supply.

Figure 2 is a schematic diagram of the difference in the protection point voltage of the different input voltages in the transfer delay time in Figure 1.

FIG. 3 is a schematic diagram of a power supply according to an embodiment of the present invention.

Figure 4 is a schematic diagram of a compensation current unit compensating for a current detection signal in Figure 3.

Figure 5 is a schematic diagram of the modified transfer delay of an overcurrent protection device in Figure 3.

Figure 6 is a schematic view of a preferred embodiment of a current detecting compensation unit in Figure 3

Figure 7 is a schematic diagram of a preferred embodiment of a compensation signal generator in Figure 6.

300‧‧‧Power supply

302‧‧‧Input level

304‧‧‧Transformer

306‧‧‧Power switch

308‧‧‧current detection unit

310‧‧‧Output level

312‧‧‧Overcurrent protection device

314‧‧‧ Receiver

316‧‧‧Compensated current unit

318‧‧‧First reference voltage generating unit

320‧‧‧ comparator

322‧‧‧Control unit

324‧‧‧load

Claims (16)

An overcurrent protection device for a power supply, comprising: a receiving end for receiving a current detecting signal; and a compensating current unit coupled to the receiving end for compensating the current detecting signal, a first reference voltage generating unit for generating a first reference voltage; a comparator coupled to the compensation current unit and the first reference voltage generating unit for comparing the The current detection compensation signal and the first reference voltage are used to generate a comparison result. A control unit is coupled to the comparator for controlling the conduction state of the power switch of the power supply according to the comparison result. The overcurrent protection device of claim 1, wherein the current detection signal is provided by a current detecting unit of the power supply. The overcurrent protection device of claim 1, wherein the compensation current unit comprises: a compensation signal generator for generating a compensation signal; and an adder coupled to the compensation signal generator and the receiving end And the comparator is configured to add the current detection signal and the compensation signal to generate the current detection compensation signal to the comparator. The overcurrent protection device of claim 3, wherein the compensation signal generator comprises: a triangular wave generator for generating a triangular wave signal; and a second reference voltage generator for generating a second reference voltage; And a subtractor coupled between the triangular wave generator, the second reference voltage generator, and the adder for subtracting the triangular wave signal and the second reference voltage to generate the compensation signal to the Adder. The overcurrent protection device of claim 4, wherein the triangular wave generator is further configured to provide an oscillation signal. The overcurrent protection device of claim 1, wherein the power supply is a switched power supply. The overcurrent protection device of claim 1, wherein the control unit turns off the on state of the power switch when the comparison result indicates that the current detection compensation signal is greater than or equal to the first reference voltage. The overcurrent protection device of claim 1, wherein the control unit maintains the conduction state of the power switch when the comparison result indicates that the current detection compensation signal is smaller than the first reference voltage. A power supply for preventing overcurrent damage, comprising: An input stage for rectifying and filtering an input signal to generate a first power signal; a transformer device comprising a primary side circuit coupled to the input stage and a secondary side circuit for The first power signal is converted into a second power signal; a power switch is coupled to the primary circuit; a current detecting unit is coupled to the power switch for detecting the primary circuit flowing through the power switch The current is generated to generate a current detection signal; an output stage coupled to the voltage transformation device for outputting the second power signal to a load; and an overcurrent protection device coupled to the current detection The unit and the power switch include: a receiving end for receiving the current detecting signal; and a compensating current unit coupled to the receiving end for compensating the current detecting signal to generate a current detecting compensation a first reference voltage generating unit for generating a first reference voltage; a comparator coupled to the compensating current unit and the first reference voltage generating unit for comparing the current detecting compensation signal And the first reference voltage to generate a comparison result; a control unit, coupled to the comparator and the power switch, according to the comparison result, controls the conduction of the power switch case. The power supply of claim 9, wherein the compensation current unit comprises: a compensation signal generator for generating a compensation signal; and an adder coupled to the compensation signal generator, the receiving end and the comparator for adding the current detection signal and the compensation signal To generate the current detection compensation signal to the comparator. The power supply device of claim 10, wherein the compensation signal generator comprises: a triangular wave generator for generating a triangular wave signal; and a second reference voltage generator for generating a second reference voltage; a subtractor coupled between the triangular wave generator, the second reference voltage generator, and the adder for subtracting the triangular wave signal and the second reference voltage to generate the compensation signal to the adding Device. The power supply of claim 11, wherein the triangular wave generator is further configured to provide an oscillation signal. The power supply of claim 9, wherein the power supply is a switched power supply. The power supply device of claim 9, wherein the control unit turns off the on state of the power switch when the comparison result indicates that the current detection compensation signal is greater than or equal to the first reference voltage. The power supply device of claim 9, wherein the control unit maintains the on state of the power switch when the comparison result indicates that the current detection compensation signal is less than the first reference voltage. The power supply of claim 9, wherein the power is related to a power transistor.