TW201505481A - Driving circuit capable of switching power supply modes according to voltage value - Google Patents

Abstract

The present invention discloses a driving circuit capable of switching power supply modes according to a voltage value, which comprises a front loop, a rear loop, a switch unit and a switching control unit. The front loop is connected in parallel to a power source through a front load element (such as light emitting diode). The rear loop is connected in parallel to the front loop through a rear load element. The switch unit comprises a diode and a switching switch connected in series to each other, in which the anode of the diode is electrically connected to the anode of the power source, and the cathode is corresponded to the anode of the rear load element. The switching control unit is connected in parallel between the front loop and the rear loop, and can detect the voltage value between the front load element and the rear load element. If the detected voltage value is greater than a predetermined value, the switching control unit will keep the switching switch in an open-circuit state, so that the load elements are connected in series to each other, and the driving circuit is presented as a series power supply mode; otherwise, if the detected voltage value is less than the predetermined value, the switching control unit will keep the switching switch in a short-circuit state, so that the front load element and the rear load element are connected in parallel to each other, and the driving circuit is presented as a parallel power supply mode.

Description

Driving circuit capable of switching power supply mode according to voltage magnitude

The invention is a driving circuit capable of switching a power supply mode according to a voltage, in particular, detecting a voltage value between a front load component and a rear load component through a switching control unit, and if the voltage value is small, controlling The front load component and the rear load component are in a parallel state. If the voltage value is large, the drive circuit in which the front load component and the rear load component are in series is controlled to ensure that all load components can be driven.

Light-Emitting Diode (LED) is a kind of semiconductor electronic component that can produce bright light after being energized. Compared with traditional lighting appliances, the light-emitting diode has high efficiency, low cost and fast response speed. The advantages of long service life have been widely used in traffic signs, lighting fixtures, display panels and even optical communications in recent years, becoming one of the most influential key technologies in economic development and technology research and development.

In general, when driving a plurality of light-emitting diodes, in order to save costs or simplify the control circuit, the operator will supply a plurality of light-emitting diodes with one driving power source at the same time, as shown in FIG. The illuminating diode driving circuit 1 includes a driving power source 10, a plurality of illuminating diodes 11 and a plurality of current limiting resistors 12, wherein the driving power source 10 is provided with a rectifying module The alternating current signal can be converted into a sinusoidal direct current signal. Since the junction voltage of the light emitting diode is about 0.7 volt, whether the light emitting diode 11 can be turned on and turned on depends on the sine wave direct current. The size of the signal depends.

However, the foregoing LED driving circuit 1 has a major drawback in use: that is, when the voltage value provided by the driving power source 10 can simultaneously drive the LEDs 11, the LEDs The current on the 11 is not the same (in Figure 1, the LED is set to the right of the light-emitting diode, because the current will be shunted to each of the current-limiting resistors 12, so the current value will be smaller when turned on) As a result, not only will the brightness of the light-emitting diodes be different, At the same time, it will affect the service life of these LEDs. To this end, the inventor has devised a "control circuit with current limiting and switching function" and applied for a Taiwan invention patent (application number 102108185) to allow current to flow only through a loop through a control circuit. This ensures that each light-emitting diode produces the same light.

However, the inventor found that the circuit architecture of the design is still in the ointment. For example, if there are ten LEDs in the control circuit of a light-emitting diode, if the voltage value provided by the power supply is 3.5 volts, although the control The circuit can smoothly drive the five LEDs in the same illumination state, but the other five LEDs are not likely to be driven by the voltage strength of the power supply. As a result, it will not be able to be driven. The complete use of each of the light-emitting diodes is an intangible loss for the industry. To this end, the inventors embarked on relevant research, and were able to design a driving circuit capable of switching the power supply mode according to the voltage level to improve the aforementioned problems.

In view of the fact that the circuit for driving the light-emitting diode is still limited by the voltage of the power source, the problem that some of the light-emitting diodes cannot always remain bright is generated, and the inventor relies on years of research experience and rich electrical power. Knowledge, and after many experiments and improvements, finally designed a driving circuit capable of switching the power supply mode according to the voltage level, and can further improve the structure of the light-emitting diode driving circuit used at present.

An object of the present invention is to provide a driving circuit capable of switching a power supply mode according to a voltage, comprising a power source, at least one pre-circuit, a switching unit, a rear circuit and a switching control unit, wherein the pre-loop is transmitted through a front load component (such as a light-emitting diode) connected in parallel with the power source, wherein a positive pole of the front load component is electrically connected to a positive pole of the power source, and a negative pole is electrically connected to the front loop a negative pole of the power supply, wherein the front loop is provided with a control end for receiving a feedback control signal; the rear loop is connected to the front loop through a rear load component, the rear end The positive pole of the load component is electrically connected to the negative pole of the front load component, and the negative pole is electrically connected to the negative pole of the power supply through the rear loop, and the rear loop is provided with a feedback end, and the feedback end is electrically connected Connected to the control end of the pre-loop, so that a voltage value on the rear loop can be used as the feedback control signal, and fed back to the control end of the pre-loop, where the feedback control signal is In a case where the reference voltage value, the The pre-loop will be set to the open state. When the feedback control signal is less than the reference voltage value, the pre-loop will be set to the on-state; the switch unit includes a first diode connected in series with each other and a switching switch, the positive pole of the first diode is electrically connected to the anode of the power source, and in the case that the switching switch is open, the front load component and the rear load component can be connected in series to each other, so that the driving circuit pair The power supply of the front load component and the rear load component exhibits a series power supply mode; conversely, when the switch is short circuited, the front load component and the rear load component are connected in parallel with the power source, thereby enabling The driving circuit presents a parallel power supply mode for the power supply of the front load component and the rear load component; the switching control unit is connected in parallel between the front loop and the rear loop, and an input end thereof can detect the same a voltage value between the load components, an output terminal is electrically connected to a control terminal on the switch, so that the voltage value detected at the input end of the switch control unit is greater than a pre- In the case of a value, the output of the switching control unit can generate a disconnection control signal, so that the switching switch is in an open state, so that the driving circuit is maintained in the series power supply mode; otherwise, at the input end of the switching control unit When the voltage value is less than a predetermined value, the output of the switching control unit can generate a short-circuit control signal, so that the switching switch is in a short-circuit state, so that the driving circuit is maintained in the parallel power supply mode. In this way, the driving circuit can automatically switch to the parallel power supply mode or the series power supply mode according to the voltage provided by the power source, so that the load components can operate normally regardless of the power supply mode, thereby ensuring.

Another object of the present invention is that the driving circuit further includes a capacitor, the positive pole of the capacitor is electrically connected to the switch unit, and the negative pole thereof is electrically connected to the rear loop to be in the series power supply mode of the driving circuit. In the case that the power source can simultaneously charge the capacitor, when the driving circuit is switched to the parallel power supply mode, the power stored in the capacitor can be supplied to the rear load circuit through the switch unit, thereby When the parallel power supply mode is ensured, the rear load circuit can obtain sufficient voltage to operate in an ideal working state, and at the same time, improve the power factor of the driving circuit during operation.

Another object of the present invention is that a feedback end of the rear circuit is electrically connected to one of the control terminals of the pre-circuit, so that the voltage value on the rear circuit is greater than the reference voltage value. The rear loop can generate a feedback control signal to cause the pre-loop to be in an open state. According to this, it can be ensured that the current will only be returned to the power supply by the front circuit or the rear circuit, so that The load elements can all be in the same working state (ie, projecting the same light).

For your review, you can have a better understanding and understanding of the design concept, circuit architecture and purpose of the present invention. The embodiments are described in conjunction with the drawings, which are described in detail as follows:

[study]

1‧‧‧Lighting diode drive circuit

10‧‧‧Drive power supply

11‧‧‧Lighting diode

12‧‧‧ Current limiting resistor

〔this invention〕

2‧‧‧Drive circuit

20‧‧‧front control unit

200‧‧‧front control terminal

21‧‧‧Power supply

22‧‧‧First front loop

23‧‧‧Second pre-circuit

230‧‧‧Pre-return terminal

24‧‧‧ Rear loop

240‧‧‧post feedback

25‧‧‧Switch unit

26‧‧‧Switch control unit

A‧‧‧ input

B‧‧‧output

C‧‧‧ capacitor

D1‧‧‧First Diode

D2‧‧‧ second diode

L1‧‧‧First front load component

L2‧‧‧Second preload component

L3‧‧‧ rear load component

P1‧‧‧First Operational Amplifier

P2‧‧‧Second operational amplifier

Q1‧‧‧Pre-limit current limiting crystal

Q2‧‧‧ front switch transistor

Q3‧‧‧Reset current limiting crystal

Q4‧‧‧Switching transistor

R, R1, R2, R3, R4‧‧‧ resistance

S‧‧‧Toggle switch

V1‧‧‧Non-inverting power supply

V2‧‧‧ rear power supply end

V3, V5‧‧‧ first power supply end

V4, V6‧‧‧ reference power supply

1 is a schematic diagram of a conventional LED driving circuit; FIG. 2 is a schematic view showing a first preferred embodiment of the driving circuit of the present invention; and FIG. 3 is a first preferred embodiment of the pre-control unit of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 4 is a schematic view showing a second preferred embodiment of the front control unit of the present invention.

The present invention is a driving circuit capable of switching a power supply mode according to a voltage. Referring to FIG. 2, which is a first preferred embodiment of the present invention, the driving circuit 2 includes a first pre-loop 22 and a second a pre-circuit 23, a rear circuit 24, a switch unit 25 and a switching control unit 26, the first pre-circuit 22 is transmitted through a first pre-load component L1 (eg, a light-emitting diode) and a power source The 21 phases are connected in parallel, and the second pre-circuit 23 is connected in parallel with the first pre-circuit 22 through a second pre-load element L2.

The positive poles of the pre-loading elements L1, L2 are electrically connected to the positive pole of the power source 21, and the negative poles are respectively transmitted through the corresponding pre-circuits 22, 23 to the negative pole of the power source 21; the rear loop 24 is Connected to the second pre-circuit 23 through a rear load element L3, the positive pole of the rear load element L3 is electrically connected to the negative pole of the second pre-load element L2, and the negative pole is transmitted through the rear loop 24, electrically connected to the negative pole of the power source 21; the switch unit 25 includes a first diode D1 and a switch S, the first diode D1 is connected in series with the switch S, and the positive pole is electrically Connected to the positive electrode of the power source 21, the negative electrode is electrically connected to the positive electrode of the rear load element L3.

In the case where the switch S is open, the pre-load elements L1, L2 and the post-load element L3 can be connected in series with each other. At this time, the drive circuit 2 pairs the pre-load elements L1, L2. And the power supply of the rear load component L3 will present a "series power supply mode". A second diode D2 is further disposed between the second front load component L2 and the rear load component L3. The positive pole of the second diode D2 corresponds to the negative pole of the second pre-loading element L2, so that the pre-loading components L1, L2 and the rear load component are in the case that the switching switch S is short-circuited. L3 will be connected in parallel with the power source 21, and the drive circuit 2 will assume a "parallel power supply mode".

The switching control unit 26 is connected in parallel between the second pre-circuit 23 and the rear circuit 24. The input terminal A of the switching control unit 26 can detect the second pre-load component L2 and the rear load component. The voltage value between L3, one output terminal B is electrically connected to the control terminal of the switch S, so that the voltage value detected at the input terminal A of the switching control unit 26 is greater than a predetermined value (for example, 0.7 volt). In this case, the output terminal B of the switching control unit 26 can generate a disconnection control signal to cause the switch S to be in an open state, so that the drive circuit 2 is maintained in the series power supply mode. For example, if the driving voltage of each of the light-emitting diodes is 0.7 volts, when the voltage value provided by the power source 21 is greater than 2.1 volts, since the power source 21 can simultaneously drive all the load components L1 to L3, the switching is performed. The voltage value detected by the input terminal A of the control unit 26 is necessarily greater than the predetermined value (for example, the detection result is 0.7 volt). Therefore, the switching control unit 26 will ensure that the switch S is in an open state, and the power source is 21 can drive all load components L1~L3 simultaneously in series power mode.

On the other hand, if the voltage detected by the input terminal A of the switching control unit 26 is less than the predetermined value, the output of the switching control unit 26 can generate a short-circuit control signal to make the switch S short-circuit. The state causes the drive circuit 2 to remain in the parallel power supply mode. For example, in the case where the voltage value provided by the power source 21 is less than 2.1 volts (eg, 1.5 volts), since the power source 21 cannot drive the load elements L1 LL3 in series, the input terminal A of the switching control unit 26 The detected voltage value must be less than the predetermined value (eg, the detection result is 0 volts). Therefore, the switching control unit 26 will ensure that the switch S is in a short-circuit state, so that the power source 21 can be in the parallel power supply mode. The pre-load elements L1, L2 and the post-load element L3 are driven at 1.5 volts, respectively.

Referring to FIG. 2 to FIG. 4, in the first preferred embodiment of the present invention, the switching control unit 26 belongs to a differential amplifying circuit, and includes a plurality of resistors R, a non-inverting power supply terminal V1, and a The first operational amplifier P1, the input terminal A of the switching control unit 26 is connected to the inverting input terminal of the first operational amplifier P1 through a resistor R, and the non-inverting power supply terminal V1 is connected to the non-inverting power supply terminal P1. Inverting input, so the switching control unit 26 loses When the voltage value received by the input terminal A is greater than the non-inverting power supply terminal V1, the output terminal B of the switching control unit 26 can generate a very low voltage value, so that the switch S is in an open state.

It can be seen from the above that according to the architecture of the driving circuit of the present invention, when the voltage outputted by the power source 21 is small and not enough to drive the load elements L1 to L3 connected in series, the driving circuit 2 can switch to the parallel circuit by itself. The power supply mode enables the power supply 21 to drive the front load components L1 and L2 and the rear load component L3, respectively, so that the load components L1 to L3 can operate normally regardless of the power supply mode (eg, projection) A sufficient light is emitted to improve the overall operational efficiency of the driving circuit 2.

In addition, in the present embodiment, each of the pre-circuits 22 and 23 includes a pre-current limiting transistor Q1, a pre-switching transistor Q2, and a pre-control unit 20, respectively. The input end of the pre-current limiting transistor Q1 is connected to the negative poles of the corresponding pre-loading elements L1 and L2; the input end of the pre-switching transistor Q2 is connected to the output of the pre-current limiting transistor Q1. The terminal is connected to the anode of the power supply 21; the front control unit 20 is connected to the front current limiting transistor Q1 and the front switching transistor Q2 The control terminal, and the input end thereof is a pre-control loop 200 corresponding to the pre-loop 22, 23, and the pre-control unit 20 can provide a current limiting signal to the control end of the pre-current limiting transistor Q1. The front control unit 20 can provide a switching signal to the control end of the pre-switch transistor Q2 to control the front switch transistor Q2. The input terminal and the output terminal are maintained in an on state or an open state.

A pre-return terminal 230 is disposed between the front current limiting transistor Q1 and the front switching transistor Q2, and the pre-return terminal 230 is electrically connected to the first front The control circuit 200 is disposed before the loop 22, and the pre-control terminal 200 can control the voltage between the front current limiting transistor Q1 and the front switching transistor Q2 in the second pre-circuit 23 as a feedback control. The signal is sent back to the first pre-loop 22 before the control terminal 200, and the feedback control signal is greater than a reference voltage value (ie, a threshold voltage sufficient to drive the pre-switch transistor Q2 into an on state) In the case of a value, the pre-control unit 20 in the first pre-circuit 22 can cause the pre-switch transistor Q2 to enter an open state; otherwise, if the feedback control signal is less than the reference voltage value, The pre-switching transistor Q2 in the first pre-circuit 22 will be controlled In the short circuit state.

The rear circuit 24 includes a rear current limiting transistor Q3 and a rear power supply terminal V2. The input end of the rear current limiting transistor Q3 is connected to the negative terminal of the rear load component L3, and the output end thereof is connected. Connected to a rear feedback terminal 240 of the rear circuit 24; the rear power supply terminal V2 is connected to the control terminal of the rear current limiting transistor Q3 to control the pass current limiting transistor Q3 The maximum current value. As described above, the feedback structure between the pre-circuits 22 and 23, the post-return terminal 240 of the post-circuit 24 can use the voltage value at the output end of the post-current limiting transistor Q3 as a feedback control signal. And returning to the second pre-circuit 23 to pre-control the terminal 200. Accordingly, the feedback structure of each of the pre-circuits 22, 23 and the rear circuit 24 ensures that the load elements L1 to L3 can be driven in the same state (for example, the light-emitting diode can be driven). Produces light of the same brightness).

For example, if the voltage value provided by the power source 21 is between 0 and 2.1 volts, when the voltage value provided by the power source is 1.4 volts, the driving circuit 2 will assume a parallel power supply mode, and the current is passing through the After the second pre-loading element L2, the power supply 21 is returned along the second pre-circuit 23, and the feedback control signal generated by the pre-return terminal 230 of the second pre-circuit 23 will result in a feedback control signal. The front switch transistor Q2 in the first pre-circuit 22 is in an open state, so the current flowing through the first pre-load element L1 and the second pre-load element L2 is necessarily equal; similarly, When the voltage value provided by the power source 21 is 2.1 volts, and the driving circuit 2 is in the series power supply mode, the rear circuit 24 can turn off the front switching transistors Q2 by the same principle.

Moreover, the driving circuit further includes a capacitor C, the positive pole of the capacitor C is electrically connected to the switch unit 25, and the negative pole thereof is electrically connected to the rear loop 23, so that the driving circuit 2 is in the series power supply mode and the power source 21, when a large voltage signal is provided, the power source 21 can simultaneously charge the capacitor C, and the driving circuit 2 switches to the parallel power supply mode, and when the voltage supplied by the power source 21 is small, the capacitor C is at this time. The stored energy is greater than the power source 21, so the capacitor C can pass through the switch unit 25 to supply the stored power to the rear load component L3, so that the rear load component L3 can be driven by a sufficient voltage. Therefore, the power factor of the driving circuit 2 during operation can be effectively improved, and the voltage supply cannot be stably supplied to all the load components L1 to L3 when the driving circuit 2 switches between different power supply modes. question.

Referring to FIGS. 2 and 3, in the first preferred embodiment of the present invention, the pre-control unit 20 includes a first power supply terminal V3, a reference power supply terminal V4, and a second operational amplifier P2. The first power supply terminal V3 is connected to the control terminal of the pre-current limiting transistor Q1 to provide the current limiting signal to the pre-current limiting transistor Q1; the output terminal of the second operational amplifier P2 is connected to the front end The control terminal of the switching transistor Q2 is provided to provide the switching signal to the pre-switching transistor Q2, and the non-inverting input terminal of the second operational amplifier P2 is connected to the reference power supply terminal V4 to receive the reference power supply The voltage input signal provided by the terminal V4, the inverting input terminal of the second operational amplifier P2 is respectively connected to the output end of the second operational amplifier P2 and the front control end of the pre-control unit 20 through a resistor R1, R2 200. When the feedback control signal received by the inverting input terminal of the second operational amplifier P2 is greater than the reference voltage value, the voltage value outputted by the output end of the second operational amplifier P2 can enable the front end Switching transistor Q2 is in an open state, reverse In the case where the feedback control signal is less than the reference voltage value, the voltage value of the output of the second operational amplifier output P2 of the switching transistor enables the pre-rendering Q2 conductive state.

Referring to FIGS. 2 and 4, in the second preferred embodiment of the present invention, the front control unit 20 includes a first power supply terminal V5, a switching transistor Q4, and a reference power supply terminal V6. The first power supply terminal V5 is connected to the control terminal of the pre-current limiting transistor Q1 to provide the current limiting signal to the pre-current limiting transistor Q1; the control terminal of the switching transistor Q4 is transmitted through a resistor R3. Connected to the front control unit 20 to receive the feedback control signal, the output end of the switching transistor Q4 is connected to the ground terminal; the reference power supply terminal V6 is transmitted through another resistor R4, The control terminal of the front switch transistor Q2 and the input end of the switching transistor Q4 are respectively connected to provide the switching signal to the pre-switch transistor Q2.

And, when the feedback control signal is greater than the reference voltage value (for example, a voltage value sufficient to cause the switching transistor Q4 to enter a saturation state of the bipolar junction transistor), since the switching transistor Q4 is The output terminal and the input terminal can be regarded as a short circuit, so the front switch transistor Q2 will be in an open state. Otherwise, when the feedback control signal is smaller than the reference voltage value, the switching transistor Q4 will be present. In the open state, the switching signal generated by the pre-control unit 20 can be regarded as equivalent to the voltage of the reference power supply terminal V6, so that the front-switching transistor Q2 can be in an on state.

In addition, the driving circuit 2 of the present invention is characterized by "better compatibility", that is, since the driving circuit 2 can switch between different power supply modes according to the magnitude of the voltage, the voltage value provided by the power source 21 is 110V. Or 220V, the drive circuit can work normally without damage. For example, when the voltage value is 220V, the driving circuit 2 can drive all the load components L1~L3 in the series power supply mode, and when the voltage value is 110V, the driving circuit 2 can be connected in parallel because the voltage is small. In the power supply mode, the pre-load elements L1, L2 and the post-load element L3 are driven, respectively.

In the foregoing embodiment, the driving circuit 2 includes two pre-circuits 22, 23 and a rear circuit 24, but the driving circuit 2 can also be provided with a plurality of pre-circuits and The number of the rear circuit can be adjusted according to the needs of the designer. For example, in the driving circuit 2 shown in FIG. 2, the rear circuit 24 and the second diode D2 can be additionally connected in parallel with each other. a circuit, and the other rear circuit structures will be the same as the second pre-circuit 23, so that the rear circuit 24 can pass through the rear feedback terminal 240 to control the conduction of other newly added rear circuits. Since the circuit structure and application system of the pre-circuit and the rear-end circuit have been described in detail in the invention patent "control circuit with current limiting and switching function" which the inventor has applied for in the past, it will not be described in detail here. In addition, in other preferred embodiments of the present invention, the number of the pre-loops may be only one (eg, removing the first pre-loop 22, leaving only the second pre-circuit 23). The effect of the "switching power supply mode" expected by the present invention can be constructed.

The above description is only a few preferred embodiments of the present invention, but the technical features of the present invention are not limited thereto, and those skilled in the relevant art can easily think about it after considering the technical content of the present invention. Modifications should not depart from the scope of protection of the present invention.

2‧‧‧Drive circuit

20‧‧‧front control unit

200‧‧‧front control terminal

21‧‧‧Power supply

22‧‧‧First front loop

23‧‧‧Second pre-circuit

230‧‧‧Pre-return terminal

24‧‧‧ Rear loop

240‧‧‧post feedback

25‧‧‧Switch unit

26‧‧‧Switch control unit

A‧‧‧ input

B‧‧‧output

C‧‧‧ capacitor

D1‧‧‧First Diode

D2‧‧‧ second diode

L1‧‧‧First front load component

L2‧‧‧Second preload component

L3‧‧‧ rear load component

P1‧‧‧First Operational Amplifier

Q1‧‧‧Pre-limit current limiting crystal

Q2‧‧‧ front switch transistor

Q3‧‧‧Reset current limiting crystal

R‧‧‧resistance

S‧‧‧Toggle switch

V1‧‧‧Non-inverting power supply

V2‧‧‧ rear power supply end

Claims (16)

A driving circuit capable of switching a power supply mode according to a voltage, comprising: a pre-loop, wherein the pre-circuit is connected in parallel with a power source through a pre-load component, wherein a positive pole of the pre-load component is electrically connected to the The positive pole of the power source has a negative pole that is electrically connected to the negative pole of the power supply through the front loop, and a control terminal is disposed on the front loop, the control terminal is configured to receive a feedback control signal; and a rear loop, the rear loop The rear circuit is connected in parallel with the pre-circuit through a rear load component, the positive pole of the rear load component is electrically connected to the negative pole of the pre-load component, and the negative pole is electrically connected to the rear loop through the rear loop. a negative pole of the power supply, the back circuit is provided with a feedback end electrically connected to the control end of the front loop, so that a voltage value on the rear loop can be used as the feedback control signal And feeding back to the control end of the pre-loop, if the feedback control signal is greater than a reference voltage value, the pre-loop will be set to the open circuit state, or the feedback control signal is small In the case of the reference voltage value, the pre-circuit will be set in an on state; a switching unit includes a first diode and a switch in series with each other, and the anode of the first diode is electrically connected to The anode of the power source has a negative pole electrically connected to the anode of the rear load component, and in the case that the switch is open, the front load component and the rear load component can be connected in series to each other, so that the drive circuit is front The power supply of the load component and the rear load component assumes a series power supply mode. Conversely, in the case that the switch is short-circuited, the front load component and the rear load component will be connected in parallel with the power supply, and the drive is driven. The circuit presents a parallel power supply mode for the power supply of the front load component and the rear load component; a second diode is connected in series between the front loop and the rear load component, and the positive pole thereof Corresponding to the negative pole of the pre-load component; and a switching control unit connected in parallel between the pre-loop and the rear loop, the input end of the switching control unit can detect the pre-load component and the rear The voltage value between the load components is electrically connected to one of the control terminals of the switch, so that the voltage detected by the input end of the switch control unit is greater than a predetermined value, the switch control The output end of the unit can generate a breaking control signal, so that the switching switch is in an open state, so that the driving circuit is maintained in the series power supply mode; otherwise, the voltage value detected at the input end of the switching control unit is less than the predetermined value. In the case, the output of the switching control unit will be able to generate a short-circuit control signal to keep the switching switch in a short-circuit state, so that the driving circuit is maintained in the parallel power supply mode. The driving circuit of claim 1, wherein the driving circuit further comprises a capacitor, the positive pole of the capacitor is electrically connected to the switching unit, and the negative pole is electrically connected to the rear loop, so that the driving circuit is in series power supply In the case of the mode, the power source can simultaneously charge the capacitor. When the driving circuit is switched to the parallel power supply mode, the power stored in the capacitor can be supplied to the rear load component through the switch unit. The driving circuit of claim 2, wherein the pre-circuit comprises: a pre-current limiting transistor, the input end of which is connected to the negative pole of the pre-loading component; and a pre-switching transistor, the input end thereof Connected to the output end of the pre-current limiting transistor, and the output end of the pre-switching transistor is electrically connected to the negative pole of the power supply; and a front control unit is respectively connected to the pre-current limiting current a control end of the transistor and the front switch transistor, and an input end thereof is connected to the control end of the pre-loop, the pre-control unit can provide a current limiting signal to the control end of the pre-current limiting transistor, Making the front current limiting transistor capable According to the current limiting signal, setting a maximum current value that can pass through the pre-current limiting transistor; the pre-control unit can further provide a switching signal to the control end of the pre-switching transistor, so that the pre-switching transistor The input end and the output end can be maintained in a conducting state, so that the current provided by the output end of the pre-current limiting current transistor can smoothly pass through the pre-switching transistor crystal; or the input of the pre-switching transistor transistor A disconnection state is present between the terminal and the output terminal, so that the current supplied from the output terminal of the pre-current limiting transistor cannot pass through the front switch transistor. The driving circuit of claim 3, wherein the rear circuit comprises: a rear current limiting transistor, the input end of which is connected to the negative pole of the rear load component, and the output end of which is connected to the rear circuit The feedback terminal and a rear power supply terminal are connected to the control terminal of the rear current limiting transistor to control the maximum current value of the current limiting transistor. The driving circuit of claim 4, wherein the switching control unit comprises a differential amplifying circuit. The driving circuit of claim 5, wherein the front load component and the rear load component are a light emitting diode. The driving circuit of claim 3, 4, 5 or 6, wherein the pre-control unit further comprises: a first power supply end connected to the control end of the pre-current limiting transistor to provide the current limiting Signaling to the pre-current limiting transistor; a reference power supply terminal; and an operational amplifier having an output terminal coupled to the control terminal of the pre-switch transistor to provide the switching signal to the pre-switching transistor The non-inverting input terminal of the amplifier is connected to the reference power supply end, and the inverting input end thereof is respectively connected to the operational amplification by a resistor The output end of the operational amplifier and the control end of the pre-control unit, the output voltage of the output terminal of the operational amplifier is obtained when the feedback control signal received by the control terminal of the pre-control unit is greater than the reference voltage value The value enables the front switch transistor to be in an open state. Conversely, when the feedback control signal is less than the reference voltage value, the output voltage output from the operational amplifier enables the front switch transistor to be presented. On state. The driving circuit of claim 3, 4, 5 or 6, wherein the pre-control unit further comprises: a first power supply end connected to the control end of the pre-current limiting transistor to provide the current limiting Signaling to the pre-current limiting transistor; a switching transistor whose control terminal is connected to the control terminal of the pre-control unit through a resistor to receive the feedback control signal, and the output end of the switching transistor is Connected to the ground terminal; and a reference power supply terminal is connected to the control terminal of the front switch transistor and the input end of the switching transistor through another resistor to provide the switching signal to the front switch transistor In the case that the feedback control signal is greater than the reference voltage value, the switch signal can cause the front switch transistor to be in an open state, and vice versa, if the feedback control signal is less than the reference voltage value, the switch The signal enables the front switch transistor to be in an on state. A driving circuit capable of switching a power supply mode according to a voltage, comprising: at least two pre-circuits, wherein the first pre-loop is connected to a power supply through a pre-load component, and the positive pole of the pre-load component is electrically Connected to the positive pole of the power source, the negative pole is electrically connected to the negative pole of the power supply through the first pre-loop, and the first front loop is provided with a front control end, and the front control end is used for Receiving a feedback control signal, the second pre-loop is connected in parallel with the first pre-loop through another pre-load element, and the The second pre-loop has a pre-return terminal electrically connected to the pre-control terminal of the first pre-loop to enable the second pre-loop A voltage value is used as the feedback control signal, and is fed back to the first pre-loop pre-control terminal. When the feedback control signal is greater than a reference voltage value, the first pre-loop will be Set in the open state, or when the feedback control signal is less than the reference voltage value, the first pre-loop will be set to the on state, and so on; a rear loop, the rear loop is transmitted through a rear load component is connected in parallel with the last pre-circuit, the positive pole of the rear load component is electrically connected to the negative pole of the load component before the last pre-circuit, and the negative pole is transmitted through the rear loop, electrical Connected to the negative pole of the power supply, the rear loop is provided with a rear feedback end, and the rear feedback end is electrically connected to the front control loop of the last pre-circuit, so that the rear loop can be One of the voltage values as another feedback control No. and feedback to the last pre-loop pre-control terminal, in the case that the other feedback control signal is greater than a reference voltage value, the last pre-loop will be set to the open state, or When the other feedback control signal is less than the reference voltage value, the last pre-loop is set to be in a conducting state; a switching unit includes a first diode and a switch in series with each other, the first The anode of the diode is electrically connected to the anode of the power source, and the cathode of the diode is electrically connected to the anode of the rear load component. When the switch is open, the preload component and the rear load component are The series circuit can be connected to each other, so that the driving circuit presents a series power supply mode for the power supply of the pre-load component and the rear load component, and vice versa, if the switch is short-circuited, the pre-load component and the rear device The load component will be connected in parallel with the power source, so that the driving circuit presents a parallel power supply mode for the power supply of the pre-load component and the rear load component; a second diode connected in series between the last pre-circuit and the rear load component, and the positive pole corresponding to the negative pole of the load element before the last pre-circuit; and a switching control unit, Parallel between the last pre-loop and the post-loop, the input of one of the switching control units can detect the voltage value between the last pre-load component and the post-load component, and an output terminal thereof Electrically connected to one of the control terminals of the switch to generate a trip control signal at the output of the switch control unit when the voltage detected by the input of the switch control unit is greater than a predetermined value The switch is in an open state, so that the drive circuit is maintained in the series power supply mode; conversely, if the voltage value detected at the input end of the switch control unit is less than the predetermined value, the output of the switch control unit will be A short circuit control signal can be generated to cause the switch to be in a short circuit condition to maintain the drive circuit in the parallel power supply mode. The driving circuit of claim 9, wherein the driving circuit further comprises a capacitor, the positive pole of the capacitor is electrically connected to the switching unit, and the negative pole is electrically connected to the rear loop, so that the driving circuit is in series power supply In the case of the mode, the power source can simultaneously charge the capacitor. When the driving circuit is switched to the parallel power supply mode, the power stored in the capacitor can be supplied to the rear load component through the switch unit. The driving circuit of claim 10, wherein each of the pre-circuits comprises: a pre-current limiting transistor, the input end of which is connected to the negative pole of the pre-loading component; and a pre-switching transistor, the input thereof The end system is connected to the output end of the pre-current limiting transistor, and the output end of the pre-switching transistor is electrically connected to the negative pole of the power supply; and a front control unit is respectively connected to the pre-limit a control terminal of the galvanic crystal and the front switch transistor, and an input end thereof is connected to the front control end of the pre-loop, the pre-control The control unit can provide a current limiting signal to the control end of the pre-current limiting transistor, so that the pre-current limiting transistor can set a maximum current value that can pass through the pre-current limiting transistor according to the current limiting signal; The front control unit can further provide a switching signal to the control end of the front switch transistor, so that the input end and the output end of the front switch transistor can be maintained in a conducting state, so that the front limit current is The current provided at the output end of the crystal can smoothly pass through the front switch transistor; or an open circuit state between the input end and the output end of the front switch transistor, so that the output end of the pre-current limiting transistor The supplied current cannot pass through the front switch transistor. The driving circuit of claim 11, wherein the rear circuit comprises: a rear current limiting transistor, the input end of which is connected to the negative pole of the rear load component, and the output end of which is connected to the rear circuit Then, the rear end is provided; and a rear power supply end is connected to the control end of the rear current limiting transistor to control the maximum current value that can pass through the rear current limiting transistor. The driving circuit of claim 12, wherein the switching control unit comprises a differential amplifying circuit. The driving circuit of claim 13, wherein the front load component and the rear load component are a light emitting diode. The driving circuit of claim 11, wherein the front control unit further comprises: a first power supply end connected to the control end of the pre-current limiting transistor to provide the current limiting Signal to the pre-current limiting transistor; a reference power supply terminal; An operational amplifier having an output connected to a control terminal of the front switch transistor to provide the switching signal to the pre-switch transistor, wherein the non-inverting input terminal of the operational amplifier is connected to the reference power supply terminal The inverting input terminal is respectively connected to the output end of the operational amplifier and the front control end of the pre-loop through a resistor, so that the feedback control signal received at the control end of the pre-control unit is greater than the reference In the case of a voltage value, the voltage value outputted by the output terminal of the operational amplifier can cause the front switch transistor to be in an open state, and vice versa, if the feedback control signal is smaller than the reference voltage value, the operational amplifier The voltage value outputted at the output enables the front switch transistor to assume an on state. The driving circuit of claim 11, wherein the front control unit further comprises: a first power supply end connected to the control end of the pre-current limiting transistor to provide the current limiting Signaling to the pre-current limiting transistor; a switching transistor, the control terminal is connected to the front control terminal of the pre-loop through a resistor to receive the feedback control signal, and the output end of the switching transistor Connected to the ground terminal; and a reference power supply terminal is connected to the control terminal of the front switch transistor and the input end of the switching transistor through another resistor to provide the switching signal to the front switch a crystal; if the feedback control signal is greater than the reference voltage value, the switching signal can cause the front switch transistor to be in an open state; and if the feedback control signal is less than the reference voltage value, The switching signal enables the front switch transistor to be in an on state.