Patent Description:
In the field of lighting technology, it is often needed to configure a driving current, which is used to drive a lighting device. The lighting device is LED (Light Emitting Diode) for example.

The lighting device is driven by a driver, which outputs direct current to the lighting device. For most of low cost drivers, output current has high ripple coefficient, e.g. ±<NUM>% or even higher. High ripple coefficient may make the lighting device to flicker. One transistor can be used as voltage regulator to cut ripple.

In many applications of constant voltage (CV) circuits, pulse width modulation (PWM) dimming is needed. One transistor is used as a voltage switch to switch output voltage on or off. <CIT> discloses a dimmable voltage regulating circuit combining DC/PWM dimming and linear dimming methods.

This invention is defined by a voltage regulating circuit according to claim <NUM> and by a controlling method according to claim <NUM>. Further embodiments are set out in the dependent claims.

Inventor of this disclosure found: in a circuit with functions of ripple suppression and PWM dimming, two transistors are needed, one is for ripple suppression, and the other one is for output voltage switching of PWM dimming. Two transistors will bring a higher cost.

In general, embodiments of the present disclosure provide a voltage regulating circuit, a controlling method and a driving equipment. In the embodiments, one transistor is used for both purpose of ripple suppression and output voltage switching of PWM dimming. Therefore, lower cost is obtained, and less space is need in the voltage regulating circuit.

In a first aspect, there is provided a voltage regulating circuit, including:.

In another embodiment, the voltage regulator <NUM> includes:.

In another embodiment, the voltage regulator <NUM> further comprises:
a first capacitor C2 and a third resistor R11, configured to be in series connection between the cathode and the reference terminal of the reference voltage generator.

In another embodiment, a fourth resistor R10 and a fifth resistor R12 are in serials connection between the first output port and the controlling port of the first transistor Q3,
a sixth resistor R9 is connected between the controlling port of the first transistor Q3 and the second input port.

In another embodiment, the voltage detector <NUM> includes:.

In another embodiment, the voltage detector 300a includes:.

In a second aspect, there is provided a controlling method of a ripple suppression circuit, includes: when voltage of the dimming signal being higher than a threshold, the second transistor Q2 turning off the first transistor.

In a third aspect, there is provided a driving equipment, includes a driving circuit and the voltage regulator circuit according to the first aspect of the disclosure, the input voltage is provided by the driving circuit.

According to various embodiments of the present disclosure, one transistor is used for both purpose of ripple suppression and output voltage switching of PWM dimming. Therefore, lower cost is obtained, and less space is need in the voltage regulating circuit.

The above and other aspects, features, and benefits of various embodiments of the disclosure will become more fully apparent, by way of example, from the following detailed description with reference to the accompanying drawings, in which like reference numerals or letters are used to designate like or equivalent elements.

The present disclosure will now be discussed with reference to several example embodiments.

As used herein, the terms "first" and "second" refer to different elements. The terms "comprises," "comprising," "has," "having," "includes" and/or "including" as used herein, specify the presence of stated features, elements, and/or components and the like, but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof. The term "based on" is to be read as "based at least in part on. " The term "one embodiment" and "an embodiment" are to be read as "at least one embodiment. " The term "another embodiment" is to be read as "at least one other embodiment. " Other definitions, explicit and implicit, may be included below.

A voltage regulating circuit is provided in a first embodiment.

<FIG> is a diagram of a voltage regulating circuit in accordance with an embodiment of the present disclosure. As shown in <FIG>, a voltage regulating circuit <NUM> includes a first input port X1-a, a second input port X1-b, a first output port X2-a, a second output port X2-b, an output circuit <NUM>, a voltage regulator <NUM>, a first transistor Q3, a voltage detector <NUM>, and a second transistor Q2.

In the embodiment, the first input port X1-a and the second input port X1-b are configured to receive an input voltage. The input voltage may be direct current/voltage which has ripples. The input voltage may be provided by a driving circuit, for example, the driving circuit is single stage constant voltage (CV) circuit.

The first output port X2-a and the second output port X2-b are configured to output an output voltage. The first input port X1-a is connected with the first output port X2-a, thus the first input port X1-a and the first output port X2-a may have the same voltage.

The output circuit <NUM> is configured to be connected between the first output port X2-a and the second output port X2-b. The output circuit <NUM> includes a resistor R4, a capacitor C5 and a diode D5. The resistor R4, the capacitor C5 and the diode D5 are in parallel connection between the first output port X2-a and the second output port X2-b. An anode of the diode D5 is connected to the second output port X2-b, a cathode of the diode D5 is connected to the first output port X2-a.

The voltage regulator <NUM> is configured to be connected between the first output port X2-a and the second output port X2-b, setting the output voltage to a predetermined value according to a reference voltage U1.

For example, as shown in <FIG>, the voltage regulator <NUM> includes: a first resistor R3, a second resistor R7 and a reference voltage generator <NUM>.

The first resistor R3 and the second resistor R7 are configured to be in series connection between the first output port X2-a and the second output port X2-b.

The reference voltage generator <NUM> generates the reference voltage U1. An anode of the reference voltage generator <NUM> is connected to the second output port X2-b, a cathode of the reference voltage generator <NUM> is connected to the voltage detector <NUM>, a reference terminal of the voltage generator <NUM> is connected to a connecting node A of the first resistor R3 and the second resistor R7, the cathode of the reference voltage generator <NUM> outputs the reference voltage U1. The resistance of R3 and R7 is tuned, the reference voltage U1 may change. The output voltage that is outputted from the first output port X2-a and the second output port X <NUM>-b will be set to the predetermined value, for example, the predetermined value is 24V. As the reference voltage U1 changes, the predetermined value changes.

As shown in <FIG>, the voltage regulator <NUM> further includes: a first capacitor C2 and a third resistor R11. The capacitor C2 and the resistor R11 is configured to be in series connection between the cathode and the reference terminal of the reference voltage generator <NUM>. The capacitor C2 is used for filtering out ripples in the output voltage.

As shown in <FIG>, the first transistor Q3 is configured to be connected between the second output port X2-b and the second input port X1-b. A controlling terminal of the first transistor Q3 is coupled to the first output port X2-a, for example, a resistor R10 and a resistor R12 are in serials connection between the first output port X2-a and the controlling port of the first transistor Q3. A resistor R9 is connected between the controlling port of the first transistor Q3 and the second input port X1-b.

As shown in <FIG>, the first transistor Q3 is a MOS FET (Metal-Oxide-Semiconductor Field-Effect Transistor). The controlling terminal of the first transistor Q3 is a gate. A drain of the first transistor Q3 is connected to the second output port X2-b. A source of the first transistor Q3 is connected to the second input port X1-b. The embodiment will not be limited thereto; the first transistor Q3 can be of other type, for example a bipolar transistor, such as an NPN bipolar transistor.

The voltage detector <NUM> is configured to be connected with the first output port X2-a and the voltage regulator <NUM>. When the output voltage is detected to be higher than the predetermined value, the voltage detector <NUM> pulls down the driving voltage of the first transistor Q3. The pulled down driving voltage of Q3 will increase Ron (on-resistance) of Q3, then voltage drop on the first transistor Q3 is increased, thus ripple of output voltage is suppressed. Therefore, the first transistor Q3 can work as a ripple suppressor.

The second transistor Q2 is configured to be coupled between the controlling terminal of the first transistor Q3 and the second input port X1-b. A controlling terminal of the second transistor Q2 receives a dimming signal. The dimming signal is provided by an external PWM dimming signal generator V4. A resistor R6 is connected between the controlling terminal of the second transistor Q2 and the external PWM dimming signal generator V4. A resistor R8 is connected between the controlling terminal of the second transistor Q2 and the second input port X1-b.

As shown in <FIG>, the second transistor Q2 is NPN bipolar transistor, and the controlling terminal of the second transistor Q2 is a base of the NPN bipolar transistor. The embodiment will not be limited thereto; the second transistor Q2 can be of other type, for example a MOS FET.

When the dimming signal is low or the external PWM dimming signal generator V4 is not connected with the controlling terminal of the transistor Q2, voltage drop on R8 is not able to turn on the second transistor Q2, driving voltage of the first transistor Q3 is not pulled down, and the first transistor Q3 works in a linear region for ripple suppression. The output voltage is outputted from the first output port X2-a and the second output port X2-b. When the dimming signal is high , voltage drop on R8 is able to turn on the second transistor Q2, driving voltage of the first transistor Q3 is pulled down, and the first transistor Q3 is turned off, there is no output voltage being outputted from the first output port X2-a and the second output port X2-b. Therefore, the first transistor Q3 can work as an output voltage switching of PWM dimming.

According to the embodiments of the present disclosure, the first transistor Q3 is used for two purposes: one is ripple suppression, and the other one is output voltage switching of PWM dimming. Therefore, one transistor can be omitted, lower cost is obtained, and less space is need in the voltage regulating circuit.

As shown in <FIG>, in at least one embodiment, the voltage detector <NUM> includes: a resistor R1, a resistor R2, a diode D6 and an optical coupler U3.

The resistor R1, the resistor R2 and the diode D6 are configured to be in serials connection between the first input port X1-a and the voltage regulator <NUM>. For example, an anode of the diode D6 is connected to the resistor R2, a cathode of the diode D6 is connected to the cathode of the reference voltage generator <NUM>.

The optical coupler U3 includes an input LED and an output transistor. An anode of the input LED in the optical coupler U3 is connected to a node connecting the resistor R1 and the resistor R2, a cathode of the input LED is connected to a node connecting the resistor R2 and the diode D6. A collector of the output transistor in the optical coupler U3 is connected to the collector of the second transistor Q2, and the emitter of the output transistor in the optical coupler U3 is connected to the second input port X1-b.

As shown in <FIG>, when the output voltage is higher than the predetermined value as ripple peak, voltage of the cathode of the reference voltage generator <NUM> pulls the input LED in U3 to conduct, and output transistor pulls down driving voltage of Q3, then voltage drop on Q3 is increased, so the excessive voltage is on Q3 to keep the output voltage to the predetermined value and ripple peak is cut.

<FIG> is a diagram of a voltage regulating circuit according to another embodiment of the disclosure. A voltage detector 300a in <FIG> is different from the voltage detector <NUM> in <FIG>. Descriptions for the same element with the same labels in <FIG> and <FIG> are omitted.

As shown in <FIG>, a voltage regulating circuit 10a includes the voltage detector 300a. The voltage detector 300a includes: a resistor R1, a resistor R2, a diode D6 and a third transistor Q1.

As shown in <FIG>, the resistor R1, the resistor R2 and the diode D6 are configured to be in serials connection between the first input port X1-a and the voltage regulator <NUM>. For example, an anode of the diode D6 is connected to the resistor R2, a cathode of the diode D6 is connected to the cathode of the reference voltage generator <NUM>.

An emitter of the third transistor Q1 is coupled to the first input port X1-a via a resistor R14, a collector of the third transistor Q1 is coupled to a base of the second transistor Q2 via a resistor R13, a base of the third transistor Q1 is connected to a connecting node between the resistor R1 and the resistor R2.

The third transistor Q1 is a PNP bipolar transistor. The embodiment will not be limited thereto; the third transistor Q3 can be of other type, for example a MOS FET.

As shown in <FIG>, when the output voltage is higher than the predetermined value as ripple peak, voltage of the cathode of the reference voltage generator <NUM> pulls the third transistor Q1 to conduct, and pulls up the second transistor Q2 to conduct. Then, the driving voltage of Q3 is pulled down, voltage drop on Q3 is increased, so the excessive voltage is on Q3 to keep the output voltage to the predetermined value and ripple peak is cut.

Besides, as shown in <FIG> and <FIG>, the voltage regulating circuit <NUM> and 10a may further include a resistor R5 and a capacitor C1.

<FIG> is a diagram of a driving equipment. As shown in <FIG>, a driving equipment <NUM> includes the voltage regulating circuit <NUM> and a driving circuit <NUM>.

The driving equipment <NUM> further includes a rectifier <NUM>, which includes a diode D1, a diode D, a diode D3 and a diode D1. The rectifier <NUM> rectifies a voltage provided by a power source V1 and a power source V2. V1 provides DC voltage, V2 provides a sine signal added on the DC voltage.

The driving circuit <NUM> is a constant voltage circuit, for example, a single stage constant voltage circuit, which provides the input voltage to the voltage regulating circuit <NUM>.

In another embodiment, the driving equipment <NUM> in <FIG> can be replace by the voltage detector 300a in <FIG>.

The driving circuit <NUM> may be formed by a flyback converter or resonant halfbridge converter or LLC converter including a transformer. Instead of the transformer there might from an inductor a part of a switched converter e.g. a buck converter or boost converter which forms the driving circuit. The clocking of the driving circuit and especially the transformer by at least one controllable switch which is clocked at high frequency may depend on a controlling signal inputted to a control input of the driving circuit. For instance the frequency and / or the duty cycle of the controllable switch of the driving circuit may be adjusted in dependency on the controlling signal inputted to an input of the driving circuit.

The driving circuit may generate a driving current or driving voltage for the lighting device. The driving circuit may output the driving current or driving voltage for the lighting device at the first input port X1-a and the second input port X1-b in order to output the input voltage to the voltage regulating circuit <NUM> (or 10a).

A controlling method of a voltage regulating circuit. The voltage regulating circuit of the first aspect of embodiments is provided in an embodiment. The same contents as those in the first aspect of embodiments are omitted.

<FIG> shows a flowchart of a controlling method <NUM> of the voltage regulating circuit.

As shown in <FIG>, the method <NUM> includes:.

Block <NUM>: when the output voltage being higher than the predetermined value, the voltage detector (<NUM>) turning off the first transistor; or, when voltage of the dimming signal being higher than a threshold, the second transistor (Q2) turning off the first transistor (Q3).

As can be seen from the above mentioned embodiments, the first transistor Q3 is used for two purposes: one is ripple suppression, and the other one is output voltage switching of PWM dimming. Therefore, one transistor can be omitted, lower cost is obtained, and less space is need in the voltage regulating circuit.

A driving equipment is provided in an embodiment. The driving equipment includes a driving circuit and the voltage regulating circuit according to the first aspect of embodiments.

In the embodiment, the voltage regulating circuit receives the input voltage provided by the driving circuit, and outputs signal with low ripple coefficient. The signal with low ripple coefficient may be provided to a lighting device, so that flicker of the lighting device can be reduced.

Claim 1:
A voltage regulating circuit, comprising:
a first input port (X1-a) and a second input port (X1-b), configured to receive an input voltage;
a first output port (X2-a) and a second output port (X2-b), configured to output an output voltage, the first input port connects with the first output port;
an output circuit (<NUM>), configured to be connected between the first output port and the second output port;
a voltage regulator (<NUM>), configured to be connected between the first output port and the second output port, setting the output voltage to a predetermined value according to a reference voltage (U1);
a voltage detector (<NUM>, 300a), configured to be connected with the first output port and the voltage regulator (<NUM>),
a first transistor (Q3), configured to be connected between the second output port and the second input port, a controlling terminal of the first transistor (Q3) being coupled to the first output port and the voltage detector (<NUM>, 300a);
when the output voltage being higher than the predetermined value, the voltage detector (<NUM>) being configured to turn off the first transistor (Q3); and
a second transistor (Q2), configured to be coupled between the controlling terminal of the first transistor (Q3) and the second input port, a controlling terminal of the second transistor (Q2) receiving a dimming signal, when voltage of the dimming signal being higher than a threshold, the second transistor (Q2) being configured to turn off the first transistor (Q3).