TWI394366B - Electronic device with power switch capable of regulating power dissipation - Google Patents

Description

Electronic device capable of adjusting power dissipation of power switch

The invention relates to an electronic device capable of adjusting the heat dissipation power of the power switch, in particular to an electronic device for preventing the power switch from overheating and causing the malfunction.

Today, there are many types of electronic devices, and in order for the electronic devices to start up normally, a power-on procedure must be performed. When the power is turned on, the power supply device turns on the power switch of the main power source to each circuit component, so that the power of the main power source can be transmitted to the circuit components. The power switches used to control the power transfer to the various circuit components are usually implemented by components such as field effect transistors or bipolar transistors. Taking a field effect transistor as an example, the circuit can control the current conduction from the drain to the source by controlling the gate voltage of the field effect transistor. Under normal circumstances, when the power switch is turned on, each circuit component can start to operate.

Please refer to FIG. 1A. FIG. 1A is a schematic diagram of the architecture of the electronic device 10 according to one of the prior art. The electronic device 10 includes a power supply device 100, a transistor M1, a capacitor C1, and a load LOAD1. The transistor M1 is an N-type field effect transistor. As a power switch, when the gate voltage is changed from a low potential to a high potential, the current supplied by the power supply device 100 can be entered by the drain, and the source is Flow out to charge capacitor C1. However, it is worth noting that at the instant when the drain of the transistor M1 is turned on, the voltage across the capacitor C1 is approximately 0 volts, so the source voltage of the transistor M1 is also approximately 0 volts. Since the gate voltage of the transistor M1 is approximately equal to the voltage output by the power supply device 100, the voltage difference between the drain and the source reaches a maximum at the moment when the transistor M1 is turned on, and at this time, the conduction current of the transistor M1 is also At the same time, it increases rapidly, which causes the transistor M1 to have a large voltage difference and a large on-current. According to the principle of semiconductor operation, the thermal power released by the transistor M1 is approximately equal to the product of the voltage difference between the drain and the source and the on-current, so when the large voltage difference and the large on-current are simultaneously present, the transistor M1 will be extremely short. A large amount of thermal energy is released within the time, causing the transistor M1 to initiate the overheat protection mechanism due to overheating, and the transistor M1 is protected by the automatic power-off mode, but may also be directly burned due to the overheating of the transistor M1.

Please refer to FIG. 1B. FIG. 1B is a schematic diagram showing the time distribution of voltage drop, current magnitude and power consumption of the transistor M1 in FIG. 1A. After the electronic device 10 is turned on, the source voltage of the transistor M1 is gradually increased from 0 volts, and finally reaches the voltage level provided by the power supply device 100; on the other hand, the gate voltage of the transistor M1 is before the power-on, First, it is approximately equal to the output voltage of the power supply device 100, and after the power is turned on, the voltage difference between the drain and the source of the transistor M1 will gradually decrease as time increases. On the other hand, the current through the transistor M1 will rapidly climb upward from 0 amps and reach a maximum value IMAX at a point in time TA. As described above, when the transistor M1 is turned on, the voltage difference between the drain and the source and the on-current are large at the same time. That is to say, the transistor M1 releases a large amount of thermal energy in a very short time before and after the time point TA, causing the transistor M1 to be automatically powered off due to overheating, or directly burned.

Therefore, when the electronic device is turned on, the voltage difference between the drain and the source of the field effect transistor as the power switch is large, and if the current through the field effect transistor is suddenly raised to a certain extent, Therefore, the field effect transistor can release excessive heat energy in an instant, causing the field effect transistor to overheat, thereby starting a thermal shutdown mechanism, and even directly causing the power switch to burn, causing the electronic device to fail to operate normally.

Accordingly, it is a primary object of the present invention to provide an electronic device that can adjust the heat dissipation power of a power switch.

The invention discloses an electronic device capable of adjusting the heat dissipation power of a power switch, comprising a power supply device for providing a power supply voltage, a power switch for providing an output voltage, and a current modulation circuit including a suitable control unit. And a switch control unit is configured to output a switch control signal to control a current flowing through the power switch according to the voltage difference between the power supply voltage and the output voltage; and a switch control unit .

The present invention further discloses a current modulation circuit that can be used to adjust the heat dissipation power of a power switch, wherein the power supply relationship is used to adjust a power supply voltage outputted by a power supply device to provide an output voltage, and the current modulation circuit includes a suitability control unit for outputting a modulated signal according to a voltage difference between the power supply voltage and the output voltage; and a switch control unit for outputting a switch control signal according to the modulated signal to control flow through the The current level of the power switch.

Please refer to FIG. 2A. FIG. 2A is a schematic structural diagram of an electronic device 20 according to an embodiment of the present invention. The electronic device 20 includes a power supply device 200, a power switch 202, an output capacitor C2, a load LOAD2, and a current modulation circuit 204, which can adjust the heat dissipation power of the power switch. The power supply device 200 is used to provide an input voltage Vin. The power switch 202 adjusts the magnitude of the current through the power switch 202 according to the magnitude of the voltage of one of its control terminals 202a. The output capacitor C2 can begin to charge after the power switch 202 is turned on, while the load LOAD2 provides a load of a particular size. The current modulation circuit 204 includes a fitness control unit 210 and a switch control unit 212 for providing a modulation signal to the control terminal 202a of the power switch 202 according to the input voltage Vin and the output voltage Vout of the power switch 202 to adjust the power switch. The current size of 202. In detail, the adaptive control unit 210 is configured to output a modulated signal SIG0 according to the voltage difference between the input voltage Vin and the output voltage Vout. The switch control unit 212 outputs a switch control signal SIG1 according to the modulation signal SIG0 to control the current flowing through the power switch 202.

Briefly, the electronic device 20 regularly adjusts the magnitude of the current through the power switch 202 to avoid the occurrence of large voltage differences and large currents (or current surges) occurring across the power switch in the prior art. Looking further, please refer to FIG. 2B, and FIG. 2B is a schematic diagram of the architecture of the adaptive control unit 210. The adaptive control unit 210 includes a voltage divider 240, a multiplexer 242, a comparator 244, a counter 246, a logic controller 248, and a modulation current generator 250. Voltage divider 240 is used to provide standard voltages V_1 - V_N. The multiplexer 242 is configured to select one of the standard voltages V_1 to V_N provided by the voltage divider 240 according to a selected signal SEL_1 as a feedback reference voltage FBRV output to the comparator 244. . The comparator 244 compares the magnitudes of the feedback reference voltage FBRV and the output voltage Vout, and outputs a trigger signal CRS to the counter 246 according to the comparison result. The counter 246 can add a count value according to a timing signal (not shown) and reset the count value according to the trigger signal CRS. The logic controller 248 outputs the selection signal SEL_1 according to the count value of the counter 246 to control the selection operation of the multiplexer 242. At the same time, the logic controller 248 also generates another selection signal SEL_2 and outputs it to the modulation current generator 250. The modulation current generator 250 selects one of the reference currents II_y among the reference currents II_1 to II_K according to the selected signal SEL_2 provided by the logic controller 248 as the modulation signal SIG0 output of the adaptive control unit 210. In addition, please refer to FIG. 2C, and FIG. 2C is a schematic diagram of the structure of the switch control unit 212. The switch control unit 212 includes a current mirror CM1 and a resistor R1. The current mirror CM1 outputs a conversion current Itran according to the modulation signal SIG0 outputted by the adaptive control unit 210, and the resistor R1 converts the conversion current Itran into a voltage signal Vgate, and finally uses the voltage signal Vgate as the switching control of the switch control unit 212. The signal SIG1 is output to the control terminal 202a to control the amount of conduction current of the power switch 202.

Therefore, when the power switch 202 starts to conduct current, the current modulation circuit 204 first lowers the on current, and when the voltage across the power switch 202 is gradually decreased by the output capacitor C2, the on current can be increased step by step. The selected signal SEL_2 output by the logic controller 248 is used to implement this function, and selects a smaller reference current from among the reference currents II_1~II_K, and outputs a corresponding switch through the switch control unit 212. The small current switch controls the signal SIG1 to the control terminal 202a. Next, the current modulation circuit 204 selects a smaller standard voltage FBRV among the standard voltages V_1 to V_N supplied from the voltage divider 240 by using the selection signal SEL_1. Comparator 244 compares output voltage Vout to this smaller standard voltage FBRV. Since the output capacitor C2 is not charged when the power switch 202 is turned on at the beginning, the voltage difference across the output capacitor C2 is 0V, and the output voltage Vout is also equal to 0V. Thereby, the output voltage Vout is compared with the relatively small standard voltage FBRV. When the output voltage Vout gradually rises to a voltage level greater than the standard voltage FBRV, the output signal CRS of the comparator 244 is turned to the counter. 246 reset. Next, the logic controller 248 changes the values of the selected signal SEL_1 and the selected signal SEL_2 according to the count value of the counter 246 to increase the standard voltage FBRV and the reference current II_y, respectively. Comparator 244 then compares output voltage Vout with the regulated standard voltage FBRV and causes switch control unit 212 to update the output signal for conducting a larger current. In this way, the standard voltage FBRV and the reference current II_y are gradually increased, and finally the output voltage Vout of the power switch 202 can be made approximately equal to the input voltage Vin, and a situation in which a large voltage difference and a large current occur simultaneously is avoided.

It should be noted that the electronic device 20 is an embodiment of the present invention, and those skilled in the art can make different changes according to the present invention, and are not limited thereto. For example, please refer to FIG. 3A. FIG. 3A is a schematic structural diagram of an electronic device 30 according to an embodiment of the present invention. The structure of the electronic device 30 is similar to that of the electronic device 20, so the same components are denoted by the same names and symbols, and the components having the same function and different architectures are denoted by the same name but different symbols, such as the current modulation circuit 304 and the included therein. The suitability control unit 310 and the switch control unit 312. The electronic device 30 is different from the electronic device 20 in that the electronic device 30 adds a sensing resistor Rsense to the electronic device 20, and the voltage signal Vsense at one end of the sensing resistor Rsense is coupled to the switch control unit 312. In this case, as shown in FIG. 3B, a modulation voltage generator 350 of the adaptive control unit 310 adds a resistance RR to the modulation current generator 250 of FIG. 2B for converting the selected reference current into a reference. The voltage signal VV_y is used as the modulation signal SIG0 output by the adaptive control unit 310, and is output to the switch control unit 312. In this case, as shown in FIG. 3C, the switch control unit 312 is implemented by a comparator CMP1 for comparing the terminal voltages of the modulation signal SIG0 and the sense resistor Rsense, and accordingly controlling the current of the power switch 202 to be turned on. Therefore, the electronic device 30 can also adjust the magnitude of the current through the power switch 202 step by step.

In FIG. 3A, the modulation signal SIG0 output by the adaptive control unit 310 is a reference voltage (instead, the output shown in FIG. 2B is a reference current). In this case, the switch control unit 312 is also changed to become the comparator CMP1 for comparing the voltages of the modulation signal SIG0 and the sense resistor Rsense for the purpose of the terminal voltage and input according to the sense resistor Rsense. The voltage difference of the voltage Vin detects the magnitude of the current passing through the sensing resistor Rsense (this is also equivalent to the magnitude of the current through the power switch 202). Then, the output of the comparator CMP1 is used as the switch control signal SIG1 to control the current of the power switch 202 to be turned on. In this way, the electronic device 30 can adjust the current through the power switch 202 step by step according to the magnitude of the current passing through the power switch 202 and according to the voltage of the input end and the output end of the power switch 202. The components of the remaining electronic device 30 and their functions are the same as those of the electronic device 20, and therefore will not be described again.

Please refer to FIG. 4, which is a schematic diagram showing the time distribution of voltage drop, current magnitude and thermal energy distribution of the power switch 202 during startup according to an embodiment of the invention. Compared with the current and thermal energy distribution diagrams of the prior art shown in FIG. 1B, the present invention achieves a curve distribution for controlling the power consumption of the power switch by controlling the current of the power switch, and the peak of the heat energy distribution curve can be large. In order to reduce, the shape of the heat distribution curve is also changed from a mountain shape having a sharp peak to a relatively gentle plateau shape. According to the thermal energy distribution curve shown in Fig. 4, the possibility that the power switch 202 is overheated at the time of starting up is greatly reduced.

In short, whether it is the embodiment shown in Figures 2A to 2C or the variation embodiment shown in Figures 3A to 3C, the operation is based on the principle of the present invention. First, the function of the adaptive control unit is the same. The state machine can be used to detect the on-current of the next stage by detecting the voltage difference or the on-current of the input and output of the power switch 202, so that the on-current can be compared. The gentle speed is stepped up, so as to gently increase the current flowing through the power switch 202 so that the power switch does not have a large voltage difference and a large on-current (or current surge) simultaneously, and the power switch is also moderated. The ground releases heat. Then, after the power switch is turned on normally, the rest of the circuit can also start to operate. It is worth noting that in order to make the current rise slowly, the rising order of the conduction current should not be too small. Preferably, its ascending order must be greater than three. According to the experimental results, the more the order of ascending, the more accurately the present invention can control the variation of the on-current, but the disadvantage is that the control circuit will become more complicated and the occupied wafer area will increase more, so it is necessary to Select the appropriate ascending order depending on the application.

In addition, the power switch as an electronic device can be replaced by a bipolar transistor in addition to a field effect transistor, and via the method of the present invention, the base of the bipolar transistor is controlled. The current or voltage regulates the magnitude of the collector-to-emitter conduction current in the bipolar transistor. Therefore, the principle of the present invention can also be used, so that the bipolar transistor as a power switch also has the effect of adjusting the heat dissipation power of the power switch. This should be well known to those of ordinary skill in the art and will not be described.

In summary, according to the present invention, the electronic device can control the current through the power switch of the electronic device when the power is turned on, so that the thermal energy released by the power switch is controlled within an allowable range, thereby preventing the power switch from being activated due to overheating. The overheat protection device causes the electronic device to fail to operate normally, or directly burns due to overheating, resulting in loss of property, thereby greatly improving the reliability of the product and reducing the cost.

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, 200. . . Power supply unit

102, 202. . . switch

204, 304. . . Current modulation circuit

210, 310. . . Adaptive control unit

212, 312. . . Switch control unit

C1, C2. . . Output capacitor

LOAD1, LOAD2. . . load

10, 20, 30. . . Electronic device

202a. . . Control terminal

M1. . . N-type field effect transistor

TA. . . Time point

IMAX. . . Current maximum

240. . . Voltage divider

242. . . Multiplexer

244, CMP1. . . Comparators

246. . . counter

248. . . Logic controller

250. . . Modulation current generator

350. . . Modulation voltage generator

V_1~V_N, V_x. . . Standard Voltage

FBRV. . . Feedback reference voltage

Vout. . . The output voltage

CRS. . . Trigger signal

SEL_1, SEL_2. . . Select signal

II_1～II_K, II_y. . . Reference current

SIG0. . . Modulation signal

SIG1. . . Switch control signal

CM1. . . Current mirror

R1. . . resistance

Rsense. . . Sense resistor

VV_y, Vsense. . . Voltage signal

FIG. 1A is a schematic diagram showing the architecture of an electronic device of one of the prior art.

FIG. 1B is a schematic diagram showing the time distribution of voltage drop, current magnitude, and power consumption of a power switch of FIG. 1A when it is turned on.

FIG. 2A is a schematic structural diagram of an electronic device according to an embodiment of the present invention.

Figure 2B is a schematic diagram of the architecture of an adaptive control unit in Figure 2A.

Figure 2C is a schematic diagram of the structure of a switch control unit in Figure 2A.

FIG. 3A is a schematic structural diagram of an electronic device according to a variation of the embodiment of the present invention.

Figure 3B is a schematic diagram of the architecture of an adaptive control unit in Figure 3A.

Figure 3C is a schematic diagram of the structure of a switch control unit in Figure 3A.

Figure 4 is a schematic diagram showing the time distribution of voltage drop, current magnitude and power consumption of a power switch of Figure 2A or Figure 3A.

200. . . Power supply unit

202. . . switch

204. . . Current modulation circuit

210. . . Adaptive control unit

212. . . Switch control unit

C2. . . Output capacitor

LOAD2. . . load

Claims (14)

An electronic device capable of adjusting a heat dissipation power of a power switch, comprising: a power supply device for providing a power voltage; a power switch for providing an output voltage; and a current modulation circuit comprising: a suitability control unit, And a switch control unit is configured to output a switch control signal according to the modulation signal to control a current flowing through the power switch; and a sensing The resistor is coupled between the power supply device and the power switch, and the voltage drop of the sensing resistor corresponds to a current flowing through the power switch; wherein the adaptive control unit comprises: a voltage divider, Providing a plurality of standard voltages; a multiplexer coupled to the voltage divider for selecting a standard voltage among the plurality of standard voltages according to a first selected signal, and outputting the output as a feedback reference a comparator for comparing the feedback reference voltage and the output voltage to output a trigger signal; a counter for using a time Increasing a counter value signal, and according to the trigger signal resets the counter value; a logic controller, coupled to the counter, according to the counter value, the output of the first select signal and a second selection signal; and A modulation voltage generator is configured to select one of the plurality of reference voltages according to the second selection signal, and output the modulation signal as the adaptive control unit. The electronic device of claim 1, further comprising: an output capacitor coupled to the power switch for receiving the output voltage provided by the power switch to store electrical energy; and a load for providing a load. The electronic device of claim 1, wherein the switch control unit comprises: a current mirror for outputting a conversion current according to the modulation signal of the adaptive control unit; and a resistor for converting the conversion current It is a voltage signal and is output as the switch control signal. The electronic device of claim 1, wherein the switch control unit is a comparator for comparing the voltage of the modulation signal and the sensing resistor to output the switch control signal. A current modulation circuit for adjusting a heat dissipation power of a power switch, wherein the power supply relationship is used to adjust a power supply voltage outputted by a power supply device to provide an output voltage, and the current modulation circuit includes: an adaptive control a unit for outputting one according to the power supply voltage and the output voltage a modulation signal; and a switch control unit for outputting a switch control signal to control a current flowing through the power switch according to the modulation signal; and a sensing resistor coupled to the power supply device and the power switch The voltage drop of the sense resistor corresponds to the current flowing through the power switch; wherein the adaptive control unit comprises: a voltage divider for providing a plurality of standard voltages; a multiplexer, coupled Connected to the voltage divider for selecting a standard voltage among the plurality of standard voltages according to a first selected signal, and outputting the reference voltage as a feedback reference voltage; a comparator for comparing the feedback a reference voltage and the output voltage for outputting a trigger signal; a counter for increasing a count value according to a timing signal, and resetting the count value according to the trigger signal; a logic controller coupled to the counter for use And outputting the first selected signal and a second selected signal according to the count value; and a modulation voltage generator for using the plurality of selected signals according to the second selected signal Among the test voltage, selecting one of the reference voltage, and outputs the modulation signal for the adaptive control unit. The current modulation circuit of claim 5, wherein the switch control unit comprises: a current mirror for outputting a conversion current according to the modulation signal of the adaptive control unit; A resistor is used to convert the converted current into a voltage signal and output the switch control signal. The current modulation circuit of claim 5, wherein the switch control unit is a comparator for comparing the voltage of the modulation signal and the sensing resistor to output the switch control signal. An electronic device capable of adjusting a heat dissipation power of a power switch, comprising: a power supply device for providing a power supply voltage; a power switch for providing an output voltage; and a current modulation circuit comprising: a adaptive control unit And outputting a modulation signal according to the power voltage and the output voltage; and a switch control unit for outputting a switch control signal according to the modulation signal to control a current flowing through the power switch; wherein The adaptive control unit includes: a voltage divider for providing a plurality of standard voltages; a multiplexer coupled to the voltage divider for using the plurality of standard voltages according to a first selected signal Selecting a standard voltage and outputting as a feedback reference voltage; a comparator for comparing the feedback reference voltage and the output voltage to output a trigger signal; and a counter for adding a meter according to a timing signal Numerical and based The trigger signal resets the count value; a logic controller coupled to the counter for outputting the first selected signal and a second selected signal according to the count value; and a modulation current generator for The second selected signal, among the plurality of reference currents, selects one of the reference currents and outputs the modulated signal of the adaptive control unit. The electronic device of claim 8, further comprising: an output capacitor coupled to the power switch for receiving the output voltage provided by the power switch to store electrical energy; and a load for providing a load. The electronic device of claim 8, wherein the switch control unit comprises: a current mirror for outputting a conversion current according to the modulation signal of the adaptive control unit; and a resistor for converting the conversion current It is a voltage signal and is output as the switch control signal. The electronic device of claim 8, wherein the switch control unit is a comparator for comparing the voltage of the modulation signal and the sensing resistor to output the switch control signal. a current modulation circuit for adjusting a heat dissipation power of a power switch, wherein the current modulation circuit The power-on relationship is used to adjust a power supply voltage outputted by a power supply device to provide an output voltage. The current modulation circuit includes: a suitability control unit for outputting a modulated signal according to the power supply voltage and the output voltage And a switch control unit for outputting a switch control signal to control a current flowing through the power switch according to the modulation signal; and a sense resistor coupled between the power supply device and the power switch The voltage drop of the sense resistor corresponds to the current flowing through the power switch; wherein the adaptive control unit comprises: a voltage divider for providing a plurality of standard voltages; a multiplexer coupled to The voltage divider is configured to select a standard voltage among the plurality of standard voltages according to a first selected signal, and output the signal as a feedback reference voltage; a comparator for comparing the feedback reference voltage And the output voltage to output a trigger signal; a counter for adding a count value according to a timing signal, and resetting the trigger signal according to the trigger signal a logic controller coupled to the counter for outputting the first selected signal and a second selected signal according to the count value; and a modulation current generator for using the second selected signal according to the second selected signal Among the plurality of reference currents, one of the reference currents is selected to output the modulated signal of the adaptive control unit. The current modulation circuit of claim 12, wherein the switch control unit comprises: a current mirror for outputting a conversion current according to the modulation signal of the adaptive control unit; and a resistor for converting the current Converted to a voltage signal and output as the switch control signal. The current modulation circuit of claim 12, wherein the switch control unit is a comparator for comparing the voltage of the modulation signal and the sensing resistor to output the switch control signal.