CN102195485B - DC to DC Converter - Google Patents

Abstract

The invention provides a DC-DC converter which is suitable for generating power supply voltage required by a load and comprises a voltage reduction circuit and a voltage boosting circuit. The voltage reduction circuit is used for receiving the direct current input voltage, and outputting the power supply voltage after performing voltage reduction processing on the direct current input voltage according to the first control signal or directly outputting the direct current input voltage. The voltage boosting circuit is used for receiving the power supply voltage or the direct current input voltage output by the voltage reducing circuit, and outputting the power supply voltage to a load after boosting the direct current input voltage output by the voltage reducing circuit according to the second control signal, or directly outputting the power supply voltage output by the voltage reducing circuit to the load.

Description

DC to DC Converter

technical field

The invention relates to a power supply device, and in particular to a high-efficiency DC-to-DC converter with buck-boost function.

Background technique

Traditionally, in order to stably/accurately provide the power supply voltage required by loads (such as electronic devices), most DC-to-DC converters are designed with a buck-boost function. FIG. 1 is a schematic circuit diagram of a conventional DC-to-DC converter 100 with a buck-boost function. Referring to FIG. 1 , the DC-to-DC converter 100 includes an isolation transformer TX, a switch SW, a capacitor C, a diode D, and a voltage feedback controller VF.

Generally speaking, the voltage feedback controller VF will continuously detect the power supply voltage Vpwr received by the load LD, and accordingly generate a control signal CS with a variable duty cycle to boost the DC input voltage Vin. ) or buck (buck). In this way, the DC-to-DC converter 100 can stably/precisely provide the power supply voltage Vpwr required by the load LD.

However, since the DC-to-DC converter 100 realizes the buck-boost function at the same time mainly through the transformer TX with isolation function, the transformer TX must bear all the output power (output power), so that the volume of the transformer TX will be large, and Its efficiency is not high either. Also because of this, the DC-to-DC converter 100 is difficult to implement in the design category of today's miniaturized electronic devices.

Contents of the invention

In view of this, the present invention provides a DC-to-DC converter with a buck-boost function, small size and high efficiency.

Other purposes and advantages of the present invention can be further understood from the technical features disclosed in the present invention.

To achieve one or part or all of the above objectives or other objectives, the DC-to-DC converter provided by the present invention is suitable for generating the power supply voltage required by the load, and it includes a step-down circuit and a step-up circuit. The step-down circuit is used for receiving the DC input voltage, and outputting the power supply voltage after stepping down the DC input voltage according to the first control signal, or directly outputting the DC input voltage. The step-up circuit is coupled to the load and the step-down circuit to receive the power supply voltage or the DC input voltage output by the step-down circuit, and to boost the DC input voltage output by the step-down circuit according to the second control signal. Output the power supply voltage to the load, or directly output the power supply voltage output by the step-down circuit to the load.

In an embodiment of the present invention, the DC-to-DC converter further includes a control unit. The control unit is coupled to the step-down circuit and the step-up circuit, and is used for detecting output voltages of the step-down circuit and the step-up circuit, and generates first and second control signals to control the step-down circuit and the step-up circuit accordingly.

In an embodiment of the present invention, when the DC input voltage is higher than the power supply voltage, the control unit controls the step-down circuit to output the power supply voltage after stepping down the DC input voltage, and controls the boost circuit to directly output the voltage obtained by the step-down circuit. output power supply voltage to the load.

In an embodiment of the present invention, when the DC input voltage is lower than the power supply voltage, the control unit controls the step-down circuit to directly output the DC input voltage, and controls the step-up circuit to boost the DC input voltage output by the step-down circuit Then output the power supply voltage to the load.

In an embodiment of the present invention, the output power of the boost circuit may be less than, greater than or equal to the output power of the step-down circuit.

Based on the above, it can be seen that the DC-to-DC converter proposed in the present invention is designed separately from the step-down circuit and the boost circuit and then used together to achieve multiple goals such as having a step-up and step-down function, small size and high efficiency. . To be more clear, when the DC input voltage is higher than the power supply voltage required by the load, since only the step-down circuit will perform step-down operation to generate the power supply voltage required by the load, and the boost circuit will only conduct the step-down circuit The generated power supply voltage is supplied to the load, so that under this condition, the DC-to-DC converter can achieve the goal of step-down function and improve step-down efficiency.

On the other hand, when the DC input voltage is lower than the power supply voltage required by the load, since the step-down circuit will only conduct the received DC input voltage, only the boost circuit will perform a step-up operation to generate the load required by the load. Power supply voltage, so that under this condition, the DC-to-DC converter can achieve the goal of boosting function and improving boosting efficiency. In addition, if the output power of the step-up circuit of the present invention is designed to be much smaller than the output power of the step-down circuit, the volume of the transformer used in the step-up circuit can be reduced quite a lot, so that DC-to-DC conversion The device can achieve the goal of small size.

In order to make the above-mentioned features and advantages of the present invention more obvious and easy to understand, a number of embodiments are given below, together with the accompanying drawings, for detailed description as follows, but the above-mentioned general description and the following implementation methods are only illustrative and explanatory. It is not intended to limit the scope of the present invention as claimed.

Description of drawings

FIG. 1 is a schematic circuit diagram of a conventional DC-to-DC converter with a buck-boost function.

FIG. 2 is a schematic block diagram of a DC-to-DC converter according to an embodiment of the present invention.

FIG. 3 is a schematic circuit diagram of a DC-to-DC converter according to an embodiment of the present invention.

Description of main component symbols:

100, 200: DC to DC converter 201: Step-down circuit

203: Boost circuit 205: Control unit

TX, TX’: transformer 207: first end

209: Second end 211: RBI end

SW, SW1, SW2: Switches C, C1, C2: Capacitors

L: Inductance D, D1～D3: Diodes

VF: Voltage Feedback Controller LD: Load

VF1: the first voltage feedback controller VF2: the second voltage feedback controller

Vin: DC input voltage Vpwr: Power supply voltage

CS: Control signal GND: Ground potential

CS1: The first control signal CS2: The second control signal

Detailed ways

The aforementioned and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of multiple embodiments with accompanying drawings. Additionally, reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In addition, wherever possible, elements/components using the same reference numerals in the drawings and embodiments represent the same or similar parts.

FIG. 2 is a schematic block diagram of a DC-to-DC converter (DC-to-DC converter) 200 according to an embodiment of the present invention. Please refer to FIG. 2, the DC-to-DC converter 200 is suitable for generating a power supply voltage (power voltage) Vpwr required by a load LD (such as an electronic device, but not limited thereto), and it includes a step-down circuit (buck circuit) 201, a boost circuit (boost circuit) 203 and a control unit (control unit) 205. In this embodiment, the output power of the boost circuit 203 may be less than, greater than or equal to the output power of the step-down circuit 201, all determined according to actual design requirements.

The step-down circuit 201 is used to receive the DC input voltage Vin, and output the power supply voltage Vpwr after stepping down the DC input voltage Vin according to the first control signal CS1, or output the DC input voltage Vin directly. The step-up circuit 203 is coupled to the load LD and the step-down circuit 201 for receiving the power supply voltage Vpwr or the DC input voltage Vin output by the step-down circuit 201, and according to the second control signal CS2 to output the DC output of the step-down circuit 201. The input voltage Vin is boosted to output the power supply voltage Vpwr to the load LD, or the power supply voltage Vpwr output by the step-down circuit 201 is directly output to the load LD.

The control unit 205 is coupled to the step-down circuit 201 and the step-up circuit 203, and is used to detect the output voltages of the step-down circuit 201 and the step-up circuit 203, and generate a first control signal CS1 and a second control signal CS2 accordingly to control Buck circuit 201 and boost circuit 203 . In this embodiment, when the DC input voltage Vin is higher than the power supply voltage Vpwr, the control unit 205 controls the step-down circuit 201 to output the power supply voltage Vpwr after stepping down the DC input voltage Vin, and controls the boost circuit 203 to directly output The power supply voltage Vpwr output by the step-down circuit 201 is supplied to the load LD. On the other hand, when the DC input voltage Vin is lower than the power supply voltage Vpwr, the control unit 205 controls the step-down circuit 201 to directly output the DC input voltage Vin, and controls the step-up circuit 203 to output the DC input voltage Vin output by the step-down circuit 201. After boosting, the power supply voltage Vpwr is output to the load LD.

To be more clear, FIG. 3 is a schematic circuit diagram of a DC-to-DC converter 200 according to an embodiment of the present invention. Please refer to FIG. 2 and FIG. 3 together. The buck circuit 201 may be, for example, a buck converter (but not limited thereto), and includes a switch SW1, a diode D1, an inductor L, and a capacitor C1. The switch SW1 is realized by using a MOS transistor, and its first terminal is used to receive the DC input voltage Vin, and its control terminal is used to receive the first control signal CS1. The anode of the diode D1 is coupled to the ground potential GND, and the cathode of the diode D1 is coupled to the second terminal of the switch SW1. The first end of the inductor L is coupled to the second end of the switch SW1, and the second end of the inductor L is used to output the power supply voltage Vpwr or the DC input voltage Vin. The first end of the capacitor C1 is coupled to the second end of the inductor L, and the second end of the capacitor C1 is coupled to the ground potential GND.

In addition, the boost circuit 203 can be, for example, a flyback-boost converter (but not limited thereto), and it includes a transformer TX', diodes D2 and D3, a switch SW2, and a capacitor C2. The transformer TX' has a first terminal 207, a second terminal 209 and a dotted terminal 211. Wherein, the dotted terminal 211 of the transformer TX' is coupled to the second terminal of the inductor L. The anode of the diode D2 is coupled to the first terminal 207 of the transformer TX', and the cathode of the diode D2 is used to output the power voltage Vpwr. The anode of the diode D3 is coupled to the second end of the inductor L, and the cathode of the diode D3 is coupled to the cathode of the diode D2. The switch SW2 is implemented by using a MOS transistor, and its control terminal is used to receive the second control signal CS2, its first terminal is coupled to the second terminal 209 of the transformer TX', and its second terminal is coupled to the ground potential GND.

Furthermore, the control unit 205 includes a first voltage feedback controller (voltage feedback controller) VF1 and a second voltage feedback controller VF2. The first voltage feedback controller VF1 is used to detect the output voltage of the step-down circuit 201 and generate the first control signal CS1 accordingly. The second voltage feedback controller VF2 is used to detect the output voltage of the boost circuit 203 and generate a second control signal CS2 accordingly.

Based on the above, assuming that the power supply voltage Vpwr required by the load LD is 12V, and the DC input voltage Vin is 12.5V at this time, since the DC input voltage Vin is higher than the power supply voltage Vpwr, the first voltage feedback controller VF1 generates the first A control signal CS1 turns on and off the switch SW1 multiple times, so that the step-down circuit 201 steps down the DC input voltage Vin (ie, 12.5V) to output the power supply voltage Vpwr (ie, 12V). At this time, because the second voltage feedback controller VF2 will detect that the output voltage of the boost circuit 203 has already reached the power supply voltage Vpwr (i.e. 12V) required by the load LD, so that the second voltage feedback controller VF2 will generate the first The second control signal CS2 is used to continuously close the switch SW2, so that the power supply voltage Vpwr (i.e. 12V) output by the step-down circuit 201 will be directly provided to the load LD through the path of the diode D3, that is, the step-up circuit 203 will directly output a step-down voltage The power supply voltage Vpwr output by the circuit 201 is given to the load LD.

It can be seen that, under the condition that the DC input voltage Vin is higher than the power supply voltage Vpwr required by the load LD, only the step-down circuit 201 will perform step-down operation/processing to generate the power supply voltage Vpwr required by the load LD, while the boost circuit 203 only conducts the power supply voltage Vpwr generated by the step-down circuit 201 to the load LD, so that under this condition, the DC-to-DC converter 200 can achieve the step-down function and improve the step-down efficiency.

On the other hand, assuming that the power supply voltage Vpwr required by the load LD is 12V and the DC input voltage Vin is 11.5V at this time, since the DC input voltage Vin is lower than the power supply voltage Vpwr, the first voltage feedback controller VF1 generates The first control signal CS1 continuously turns on the switch SW1 , so that the step-down circuit 201 directly outputs the DC input voltage Vin (ie, 11.5V). At this time, since the second voltage feedback controller VF2 will detect that the output voltage of the boost circuit 203 is not the power supply voltage Vpwr (i.e. 12V) required by the load LD, the second voltage feedback controller VF2 will generate the first The second control signal CS2 turns on and off the switch SW2 multiple times. Moreover, since the primary side and one end of the secondary side of the transformer TX' are stacked together (that is, the dotted end 211), the transformer TX' does not have the function of isolation, so that the output power required to be provided by the transformer TX' is not sufficient. It needs to be very large, so that the DC input voltage Vin (i.e. 11.5V) output by the step-down circuit 201 only needs to be boosted by a small power of the boost circuit 203, and the power supply voltage Vpwr (i.e. 12V) is output through the path of the diode D2. ) to the load LD. In other words, at this time, the boost circuit 203 only needs to slightly supplement the insufficient output power of the step-down circuit 201 .

It can be seen that, under the condition that the DC input voltage Vin is lower than the power supply voltage Vpwr required by the load LD, the step-down circuit 201 will only conduct the received DC input voltage Vin, and only the step-up circuit 203 will perform boosting operation/ Processing is performed to generate the power supply voltage Vpwr required by the load LD, so that under this condition, the DC-to-DC converter 200 can achieve the boost function and improve the boost efficiency. In addition, in this embodiment, if the output power of the boost circuit 203 is designed to be much smaller than the output power of the step-down circuit 201 (for example, the output power of the boost circuit 203 only needs to be 10% of the output power of the step-down circuit 201 %, but not limited thereto), the volume of the transformer TX' applied in the booster circuit 203 can be reduced considerably (compared to the transformer TX of the DC-to-DC converter 100 in the prior art) , so that the DC-to-DC converter 200 can achieve the goal of small size, so that it can be easily implemented in the scope of today's miniaturized electronic device design. On the other hand, in other embodiments of the present invention, the output power of the boost circuit 203 can also be designed to be greater than or equal to the output power of the step-down circuit 201, so as to meet certain design and application requirements.

To sum up, the DC-to-DC converter proposed by the present invention is designed separately and independently from the step-down circuit and the step-up circuit and then used together, so as to achieve multiple functions such as step-down and step-down functions, small size and high efficiency. Target. To be more clear, when the DC input voltage is higher than the power supply voltage required by the load, since only the step-down circuit will perform step-down operation to generate the power supply voltage required by the load, and the boost circuit will only conduct the step-down circuit The generated power supply voltage is supplied to the load, so that under this condition, the DC-to-DC converter can achieve the goal of step-down function and improve step-down efficiency.

On the other hand, when the DC input voltage is lower than the power supply voltage required by the load, since the step-down circuit will only conduct the received DC input voltage, only the boost circuit will perform a step-up operation to generate the load required by the load. Power supply voltage, so that under this condition, the DC-to-DC converter can achieve the goal of boosting function and improving boosting efficiency. In addition, if the output power of the step-up circuit of the present invention is designed to be much smaller than the output power of the step-down circuit, the volume of the transformer used in the step-up circuit can be reduced quite a lot, so that DC-to-DC conversion The device can achieve the goal of small size.

However, the above-mentioned content is only a preferred embodiment of the present invention, and cannot limit the scope of the present invention. That is, as long as simple equivalent changes and modifications are made according to the patent scope of the present invention and the description of the invention, All still belong to the scope that the patent of the present invention covers. In addition, any embodiment or scope of claims of the present invention does not necessarily achieve all the objects or advantages or features disclosed in the present invention. In addition, the abstract and titles are only used to assist patent document search, and are not used to limit the claims of the present invention.

Claims (10)

1. A DC-to-DC converter adapted to produce a power supply voltage required by a load, the DC-to-DC converter comprising: A step-down circuit, used to receive a DC input voltage, and output the power supply voltage after performing step-down processing on the DC input voltage according to a first control signal, or directly output the DC input voltage, wherein the The step-down circuit includes: a first switch, the first terminal of which is used to receive the DC input voltage, and the control terminal thereof is used to receive the first control signal; a first diode, its anode is coupled to a ground potential, and its cathode is coupled to the second end of the first switch; an inductor whose first end is coupled to the second end of the first switch, and whose second end is used to output the power supply voltage or the DC input voltage; and a first capacitor, the first end of which is coupled to the second end of the inductor, and the second end thereof is coupled to the ground potential; a step-up circuit, coupled to the load and the step-down circuit, for receiving the power supply voltage or the DC input voltage output by the step-down circuit, and controlling the voltage according to a second control signal The DC input voltage output by the step-down circuit is boosted to output the power supply voltage to the load, or directly output the power supply voltage output by the step-down circuit to the load, wherein the The boost circuit includes: A transformer has a first end, a second end, and a dotted end, wherein the primary side of the transformer and the same-named end of the secondary side are stacked together to form the dotted end, and the dotted end of the transformer end coupled to the second end of the inductor; a second diode, its anode is coupled to the first end of the transformer, and its cathode is used to output the power supply voltage; a third diode, its anode is coupled to the second end of the inductor, and its cathode is coupled to the cathode of the second diode; and a second switch, the control terminal of which is used to receive the second control signal, the first terminal of which is coupled to the second terminal of the transformer, and the second terminal of which is coupled to the ground potential; and A control unit, coupled to the step-down circuit and the step-up circuit, the control unit is used to detect the output voltage of the step-down circuit and generate the first control signal accordingly to control the The step-down circuit, the control unit is used to detect the output voltage of the step-up circuit and generate the second control signal accordingly to control the step-up circuit. the 2. The DC-to-DC converter according to claim 1, wherein the step-down circuit is a step-down converter. the 3. The DC-to-DC converter according to claim 1, wherein the boost circuit is a flyback boost converter. the 4. The DC-to-DC converter according to claim 1, wherein the control unit comprises: A first voltage feedback controller, used to detect the output voltage of the step-down circuit, and generate the first control signal accordingly; and A second voltage feedback controller is used to detect the output voltage of the boost circuit and generate the second control signal accordingly. the 5. The DC-to-DC converter according to claim 4, wherein when the DC input voltage is higher than the power supply voltage, the first voltage feedback controller generates the first control signal to turn on and closing the first switch, so that the step-down circuit outputs the power supply voltage after stepping down the DC input voltage, and the second voltage feedback controller generates the second control signal to continuously closing the second switch, thereby causing the boost circuit to directly output the power supply voltage output by the step-down circuit to the load. the 6. The DC-to-DC converter according to claim 4, wherein when the DC input voltage is lower than the power supply voltage, the first voltage feedback controller generates the first control signal to continuously turn on the the first switch, so that the step-down circuit directly outputs the DC input voltage, and the second voltage feedback controller generates the second control signal to turn on and off the second switch multiple times, thereby causing the The step-up circuit boosts the DC input voltage output by the step-down circuit to output the power supply voltage to the load. the 7. The DC-to-DC converter according to claim 1, wherein the output power of the step-up circuit is smaller than the output power of the step-down circuit. the 8. The DC-to-DC converter according to claim 1, wherein the output power of the boost circuit is greater than the output power of the step-down circuit. the 9. The DC-to-DC converter according to claim 1, wherein the output power of the step-up circuit is equal to the output power of the step-down circuit. the 10. The DC-to-DC converter according to claim 1, wherein the load comprises at least one electronic device. the