KR20190027566A - Apparatus and method for power supply - Google Patents

Abstract

The present invention relates to an apparatus and a method for supplying electric power, wherein the apparatus minimizes switching loss in the switching control of the apparatus for supplying electric power. The apparatus for supplying electric power according to the present invention comprises: a main switch which is turned on and off by a control signal to output a load current; and a drive control unit for variably controlling a voltage level and a duty ratio of the control signal applied to the main switch to turn on and off the main switch according to the magnitude of the load current.

Description

[0001] APPARATUS AND METHOD FOR POWER SUPPLY [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply apparatus, and more particularly to a switching control of a power supply apparatus.

Generally, a vehicle means a moving means or a transportation means that travels on a road or a line using fossil fuel, electricity, or the like as a power source.

Vehicles using fossil fuels can emit fine dust, water vapor, carbon dioxide, carbon monoxide, hydrocarbons, nitrogen, nitrogen oxides, and / or sulfur oxides due to the combustion of fossil fuels. Water vapor and carbon dioxide are known to cause global warming, and fine dust, carbon monoxide, hydrocarbons, nitrogen oxides, and / or sulfur oxides are known as air pollutants that can harm people.

For this reason, vehicles using environmentally friendly energy that replace fossil fuels are being developed recently. For example, Hybrid Electric Vehicle (HEV) and Electric Vehicle (EV) that use both fossil fuel and electricity are being developed.

Hybrid cars and electric cars have separate high-voltage batteries that power the motor that drives the vehicle and low-voltage batteries that power the vehicle's electrical components. In addition, hybrid vehicles and electric vehicles generally include a power supply that converts the voltage of a high-voltage battery into a voltage of a low-voltage battery and supplies the voltage to a load in order to supply power from the high-voltage battery to the low-voltage battery.

According to one aspect, there is a need to minimize switching losses in switching control of a power supply.

The power supply apparatus according to the present invention for the above purpose comprises: a main switch which is turned on / off by a control signal to output a load current; And a drive control unit for variably controlling a voltage level and a duty ratio of the control signal applied to the main switch to turn on / off the main switch according to the magnitude of the load current.

The power supply apparatus may further include: a switch power source section for variably controlling a voltage level of the control signal; And a switch control unit for variably controlling the duty ratio of the control signal.

In the power supply device described above, the voltage level of the control signal increases as the load current increases.

In the power supply apparatus described above, the switch power supply section includes: a transformer for converting an input voltage and outputting the converted voltage; And a first switch for interrupting an input voltage of the transformer.

In the power supply apparatus described above, the switch control section includes a second switch and a third switch that are serially connected to the output side of the switch power source section and are alternately turned on / off.

In the power supply device described above, the second switch is an N-channel MOSFET and the third switch is a P-channel MOSFET.

In the power supply device described above, the main switch is an N-channel MOSFET; The control signal is a gate voltage of the N-channel MOSFET.

According to another aspect of the present invention, there is provided a power supply apparatus including: a main switch which is turned on / off by a control signal to output a load current; A switch power source for variably controlling a voltage level of the control signal; A switch control unit for variably controlling a duty ratio of the control signal; And a drive control unit for variably controlling a voltage level and a duty ratio of the control signal applied to the main switch to turn on / off the main switch according to the magnitude of the load current.

In the power supply device described above, the voltage level of the control signal increases as the load current increases.

In the power supply apparatus described above, the switch power supply section includes: a transformer for converting an input voltage and outputting the converted voltage; And a first switch for interrupting an input voltage of the transformer.

In the power supply apparatus described above, the switch control section includes a second switch and a third switch that are serially connected to the output side of the switch power source section and are alternately turned on / off.

In the power supply device described above, the second switch is an N-channel MOSFET and the third switch is a P-channel MOSFET.

In the power supply device described above, the main switch is an N-channel MOSFET; The control signal is a gate voltage of the N-channel MOSFET.

A control method of a power supply apparatus according to the present invention for a purpose of controlling a power supply apparatus includes a main switch that is turned on and off by a control signal to output a load current, Detecting a magnitude of the load current; And varying the voltage level and the duty ratio of the control signal applied to the main switch to turn on / off the main switch according to the magnitude of the load current.

In the above-described control method for a power supply apparatus, the voltage level of the control signal is increased as the load current is increased.

In the above-mentioned method of controlling a power supply device, the main switch is an N-channel MOSFET; The control signal is a gate voltage of the N-channel MOSFET.

According to one aspect, the efficiency of the power supply can be improved by minimizing the switching loss in switching control of the power supply. In addition, the heat generation can be reduced by minimizing the loss of the power supply device, thereby reducing the size and number of the heat sink for heat dissipation, thereby contributing to miniaturization of the power supply device.

1 is a view showing an electric vehicle according to an embodiment of the present invention.
2 is a view showing a power system of an electric vehicle according to an embodiment of the present invention.
3 is a view illustrating a charging apparatus for an electric vehicle according to an embodiment of the present invention.
4 is a view illustrating a power supply apparatus according to an embodiment of the present invention.
5 is a diagram illustrating current control characteristics of a power supply apparatus according to an embodiment of the present invention.

1 is a view showing an electric vehicle according to an embodiment of the present invention.

The electric vehicle 100 shown in Fig. 1 has a motor (see 212 in Fig. 2). Thus requiring a high voltage battery 102 to store the power for driving the motor 212. [ A secondary battery (see 208 in FIG. 2) is provided on one side of the engine room in a common internal combustion engine vehicle. However, in the case of the electric vehicle 100, a large-capacity, high-capacity battery 212 having a large size is required. In the electric vehicle 100 according to the embodiment of the present invention, the high voltage battery 102 is installed in the lower space of the two row passenger seat. The power stored in the high voltage battery 102 may be used to drive the motor 212 to generate power. The high-voltage battery 102 according to the embodiment of the present invention may be a lithium battery.

The electric vehicle (100) is provided with a charging socket (104). Charging of the high-voltage battery 102 can be performed by connecting the charging connector 152 of the external charging facility to the charging socket 104. [ That is, when the charging connector 152 of the charging facility is connected to the charging socket 104 of the electric vehicle 100, the high-voltage battery 102 of the electric vehicle 100 is charged.

2 is a view showing a power system of an electric vehicle according to an embodiment of the present invention. The power system shown in Fig. 2 is for supplying electric power to the motor 212 and the electric field load 214. Fig.

2, the power system of the electric vehicle 100 according to the embodiment of the present invention includes a high-voltage battery 102 and a low-voltage DC-DC converter 204, An inverter 206, an auxiliary battery 208, and a control unit 210. [

The LDC 204 converts the high voltage DC voltage of the high voltage battery 102 into a DC voltage of a lower voltage. The LDC 204 converts the high DC voltage (DC) of the high voltage battery 102 into an AC voltage, downconverts the AC voltage through a coil, a transformer, a capacitor, and the like, and then rectifies the DC voltage DC to a DC voltage of a lower voltage. The DC voltage that is lowered by the LDC 204 is supplied to each electric field load 214 requiring a low voltage.

The DC voltage of the high-voltage battery 102 is converted into an AC voltage having a predetermined phase and frequency by the inverter 206 and then supplied to the motor 212. [ The rotational force and speed of the motor 212 are determined by the output voltage of the inverter 206. [ The control unit 210 controls overall operation of the power supply.

3 is a view illustrating a charging apparatus for an electric vehicle according to an embodiment of the present invention.

Various types of external chargers including a rapid charger 352 and a slow charger 356 may be used to charge the high voltage battery 102 of the electric vehicle 100. [ The high voltage battery 102 has a charging voltage of 500V to 800V.

The rapid charger 352 can charge the high voltage battery 102 with a first voltage (e.g., a high DC voltage of 800V). The rapid charger 352 converts the commercial AC power to a DC voltage of 800 V and supplies it to the electric vehicle 100.

The slow charger 356 supplies the commercial AC power AC to the electric vehicle 100 in the form of AC power. The alternating-current power supplied through the slow charging device 356 is converted into a direct-current voltage of a preset level in the electric vehicle 100.

Inside the electric vehicle 100, an on board charger (OBC) 302 and a converter 304 are involved in charging the high voltage battery 102.

The in-vehicle charger 302 called OBC converts the commercial AC power supplied from the constant rate charger 356 to a DC voltage of 800 V to charge the high voltage battery 102. The fast charger 356 supplies the commercial alternating-current power to the electric vehicle 100 in the form of alternating current, unlike the rapid charging device 352 which converts the alternating-current voltage to the direct-current voltage and supplies it to the electric vehicle 100. The AC voltage supplied from the constant rate charger 356 is used to charge the high voltage battery 102 after being converted into a DC voltage by the vehicle-mounted charger 302 inside the electric vehicle 100. [

The 800V DC voltage supplied from the rapid charger 352 is supplied to the high voltage battery 102 as it is. Since the charging voltage of the high-voltage battery 102 is 500V to 800V, the high-voltage battery 102 can be charged without boosting the 800V DC voltage supplied from the rapid charger 352.

4 is a view illustrating a power supply apparatus according to an embodiment of the present invention. The power supply device shown in Fig. 4 can be applied to the low-voltage DC-DC converter 204 (LDC) 204 described in Fig. 2 or the vehicle-mounted charger (OBC) 302 described in Fig.

The DC input voltage Vdc may be a DC voltage rectified at the previous stage or a DC voltage stored in a power storage unit or the like. The DC input voltage Vdc is input to the switch power supply unit 402. The switch power supply unit 402 includes a high frequency transformer 408, a smoothing circuit unit 410, and a first drive switch 412.

The high frequency transformer 408 can change the value of the alternating voltage and / or the value of the alternating current by using the electromagnetic induction phenomenon. The high frequency transformer 408 may include a primary coil on the input side, a secondary coil on the output side, and an iron core for transmitting a magnetic field from the primary coil to the secondary coil. The AC voltage and AC current input to the primary coil generate a magnetic field that changes with time in the iron core, and alternating voltage and alternating current can be generated in the secondary coil by the magnetic field of the iron core. The alternating voltage appearing on the output side of the high frequency transformer 408 is converted into a direct current voltage through the smoothing circuit portion 410. The first drive switch 412 is connected between the cathode of the DC input voltage Vdc and the primary side of the high frequency transformer 408. When the first drive switch 412 is repeatedly turned on and off by the pulse signal output from the drive control unit 450 to be described later, the DC input voltage Vdc is converted into the AC type, and is supplied to the primary side of the high frequency transformer 408 . The magnitude of the voltage applied to the primary side of the high frequency transformer 408 is determined by the on / off period of the first drive switch 412. Accordingly, the magnitude of the voltage applied to the primary side of the high frequency transformer 408 is determined according to the duty ratio of the pulse signal generated by the driving control unit 450 and applied to the gate of the first driving switch 412.

The drain-source current Ids of the main switch 406 is a direct current supplied to the load side (for example, a battery). The magnitude of the drain-source current Ids of the main switch 406 is determined by the on / off period (duty ratio) of the main switch 406. [ That is, the larger the duty ratio of the control signal applied to the gate of the main switch 406, the more the drain-source current Ids increases. The ON / OFF control of the main switch 406 is performed by the switch control section 404 described below.

The switch control section 404 is applied to the gate of the main switch 406 to generate a control signal for on / off control of the main switch 406. To this end, the switch control unit 404 connects the N-channel second drive switch 442 and the P-channel third drive switch 444 in series to the output side of the switch power supply unit 402. Since the second drive switch 442 and the third drive switch 444 are N channel and P channel, respectively, the same switching control signal (pulse signal) is applied to the second drive switch 442 and the third drive switch 444 The on / off operations of the second drive switch 442 and the third drive switch 444 are alternately performed.

For example, when the switching control signal applied to the gates of the second drive switch 442 and the third drive switch 444 is low level, the second drive switch 442 of the N channel is turned on and the third drive switch 442 of the N- The drive switch 444 is turned off. At this time, a high level voltage is applied to the gate of the main switch 406 through the second driving switch 442, which is outputted from the switch control unit 404 and turned on, so that the N-channel main switch 406 is turned off.

On the other hand, when the switching control signal applied to the gates of the second drive switch 442 and the third drive switch 444 is high level, the second drive switch 442 of the N channel is turned off and the third drive The switch 444 is turned on. At this time, a low level voltage is applied to the gate of the main switch 406 through the third drive switch 444 which is outputted from the switch control unit 404 and turned on, so that the N-channel main switch 406 is turned on.

As described above, the ON / OFF period of the main switch 406 is determined by the duty ratio of the signal applied to the gate of the main switch 406 in the switch control unit 404. It is determined by the duty ratio of the pulse signal for on / off control of the second drive switch 442 and the third drive switch 444 of the switch control unit 404.

The drive control unit 450 generates a control signal for on / off control of the first drive switch 412. The duty ratio of the control signal generated by the driving control unit 450 varies according to the magnitude of the drain-source current Ids of the main switch 406. [

For example, as the magnitude of the drain-source current Ids of the main switch 406 increases, the output voltage of the switch control section 404, that is, the voltage Vgs applied to the gate of the main switch 406, The duty ratio is variable. In contrast, the smaller the magnitude of the drain-source current Ids of the main switch 406, the smaller the output voltage of the switch control unit 404, that is, the voltage Vgs applied to the gate of the main switch 406, The ratio is variable.

5 is a diagram illustrating current control characteristics of a power supply apparatus according to an embodiment of the present invention. FIG. 5A is a diagram showing the drain-source current of the main switch 406. FIG. 5B is a diagram showing a control signal in the form of a pulse signal which is outputted from the drive control unit 450 and applied to the gate of the first drive switch 412. In FIG. 5C is a diagram showing a gate voltage (Vgs) applied to the gate of the main switch 406. In FIG. The gate voltage Vgs of the main switch 406 shown in Fig. 5 (C) can be varied by the control signal shown in Fig. 5 (B).

4, the drive control unit 450 of the power supply apparatus has described that the duty ratio of the control signal varies depending on the magnitude of the drain-source current Ids of the main switch 406. [ 5A and 5B, the drive control section 450 increases the pulse width (duty ratio) of the control signal as the drain-source current Ids of the main switch 406 increases, .

The power loss that can occur in the main switch 406 includes a conduction loss and a switching loss.

The conduction loss can be expressed by the product of the square of the effective current (RMS current) flowing through the main switch 406 and the conduction resistance (Rds (on) of the main switch 406).

The switching loss of the main switch 406 is in a functional relationship with the load current, that is, the drain-source current Ids and the switching frequency fsw of the switch control unit 404,

(1) " Psw = Vin X Iout X fsw X ((Qgs + Qgd) / Ig)

Source voltage Vds of the main switch 406 and Iout is the drain-source current Ids of the main switch 406, fsw is the switching frequency, and Qgs and Qgd are the drain- Is the gate-source charge and gate-drain charge of switch 406, and Ig is the gate current of main switch 406.

The switching loss of the main switch 406 may be caused by the energy Qg (TOT) required to charge the gate when the main switch 406 is turned on / off. The gate drive loss of the main switch 406 depends on the switching frequency fsw and is in a functional relationship with the gate capacitance of the main switch 406. When turning on / off the main switch 406, the higher the switching frequency fsw, the greater the gate drive loss. This is another reason why the power supply efficiency of the main switch 406 is lowered when the switching frequency fsw rises. As the size of the main switch 406 is large and the conduction resistance Rds (on) is low, the conduction loss decreases, but the gate capacitance increases, thereby increasing the gate drive loss. Such losses can result in significant power loss of the power supply at very high switching frequencies in the megahertz range. Lowering the gate power Pgate and the gate voltage Vg of the main switch 406 can lower the power loss of the power supply device and increase the switching frequency fsw of the main switch 406. [

The following equation (2) shows the gate power (Pgate) of the main switch 406.

<Formula 2> Pgate = Qg (TOT) X Vgs X fsw

In Equation 2, Pgate is the gate power of the main switch 406, Vgs is the gate-source voltage, and fsw is the switching frequency. As can be seen from equation (1), the gate power (Pgate) is an important factor in the switching loss. In the conventional power supply device, the power loss is increased by applying a constant-sized gate-source voltage (Vgs) to the switch regardless of the frequency.

5, the gate-source voltage Vgs of the main switch 406 is changed according to the magnitude of the drain-source current Ids of the main switch 406. In this case, The gate-source voltage Vgs is increased as the switching frequency fsw of the main switch 406 is increased, thereby minimizing the power loss. Source voltage Ids supplied to the gate of the main switch 406 through the variable control of the control signal of the drive controller 450 as the drain-source current Ids of the main switch 406 increases, (Vgs) increases the level (amplitude) so that the switching loss of the main switch 406 is minimized.

The description above is merely illustrative of the technical idea, and various modifications, alterations, and substitutions are possible without departing from the essential characteristics of the present invention. Therefore, the embodiments and the accompanying drawings described above are intended to illustrate and not limit the technical idea, and the scope of technical thought is not limited by these embodiments and the accompanying drawings. The scope of which is to be construed in accordance with the following claims, and all technical ideas which are within the scope of the same shall be construed as being included in the scope of the right.

100: Electric vehicle
104: Charging socket
152: Charging connector
204: LDC
206: Inverter
208: auxiliary battery
210:
212: motor
214: Electric field load
302: On-board charger (OBC)
354: Quick Charger
356: Slow Charger
402: Switch power source
404: Switch control section
406: Main switch
450:

Claims (16)

A main switch which is turned on / off by a control signal to output a load current;
And a drive control unit for variably controlling a voltage level and a duty ratio of the control signal applied to the main switch to turn on / off the main switch according to the magnitude of the load current. The method according to claim 1,
A switch power source for variably controlling a voltage level of the control signal;
And a switch control unit for variably controlling the duty ratio of the control signal. 3. The method of claim 2,
And the voltage level of the control signal increases as the load current increases. The power supply unit according to claim 2,
A transformer for converting and outputting an input voltage;
And a first switch for interrupting an input voltage of the transformer. The apparatus according to claim 2,
And a second switch and a third switch connected in series to the output side of the switch power supply unit and alternately turned on / off. 6. The method of claim 5,
The second switch is an N-channel MOSFET, and the third switch is a P-channel MOSFET. The method according to claim 1,
The main switch is an N-channel MOSFET;
Wherein the control signal is a gate voltage of the N-channel MOSFET. A main switch which is turned on / off by a control signal to output a load current;
A switch power source for variably controlling a voltage level of the control signal;
A switch control unit for variably controlling a duty ratio of the control signal;
And a drive control unit for variably controlling a voltage level and a duty ratio of the control signal applied to the main switch to turn on / off the main switch according to the magnitude of the load current. 9. The method of claim 8,
And the voltage level of the control signal increases as the load current increases. The power supply unit according to claim 1,
A transformer for converting and outputting an input voltage;
And a first switch for interrupting an input voltage of the transformer. The apparatus according to claim 1,
And a second switch and a third switch connected in series to the output side of the switch power supply unit and alternately turned on / off. 12. The method of claim 11,
The second switch is an N-channel MOSFET, and the third switch is a P-channel MOSFET. 9. The method of claim 8,
The main switch is an N-channel MOSFET;
Wherein the control signal is a gate voltage of the N-channel MOSFET. And a main switch which is turned on / off by a control signal to output a load current,
Detecting a magnitude of the load current output through the main switch;
And varying a voltage level and a duty ratio of the control signal applied to the main switch to turn on / off the main switch according to the magnitude of the load current. 15. The method of claim 14,
And increases the voltage level of the control signal as the load current increases. 15. The method of claim 14,
The main switch is an N-channel MOSFET;
Wherein the control signal is a gate voltage of the N-channel MOSFET.

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