EP4292401A1

EP4292401A1 - Power supply circuit, controlling method, lighting device driver and lighting equipment

Info

Publication number: EP4292401A1
Application number: EP21936373.6A
Authority: EP
Inventors: Xiongwu ZHANG; Jiaqi Yang
Original assignee: Tridonic GmbH and Co KG
Current assignee: Tridonic GmbH and Co KG
Priority date: 2021-04-14
Filing date: 2021-04-14
Publication date: 2023-12-20
Also published as: WO2022217480A1; CN117099485A

Abstract

A power supply circuit, a controlling method and a lighting equipment. The power supply circuit includes: a controller, configured to output first PWM signal, cycle duty of the first PWM signal is controlled by an active time (t_on); control unit, configured to generate controlling signal according to the first PWM signal; drive circuit, configured to generate driving signal according to the controlling signal; switch element, configured to be turned on or off according to the driving signal; a voltage converter, configured to be connected between a first input port and two output ports; and a resistor, configured to be connected between the switch element and a ground port, the switch element being connected between the voltage converter and the resistor, when target output current of the two output ports changes, the controller changes the active time of the first PWM signal in step form, the active time being fixed in each step of the active time, and the controller changes frequency of the first PWM signal in each step of the active time.

Description

POWER SUPPLY CIRCUIT, CONTROLLING METHOD, LIGHTING DEVICE DRIVER AND LIGHTING EQUIPMENT

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field of lighting, and more particularly, to a power supply circuit, a controlling method, a lighting device driver and a lighting equipment.

BACKGROUND

This section introduces aspects that may facilitate better understanding of the present disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
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.
In related art, for a power supply circuit, 2 PWM channels are used in dimming control. During dimming control, high dimming level range (for example above 10%) one of the PWM channel (PWMH) generate PWM signal to influence current sense detection. When dimming level lower, another PWM channel (PWML) is used to achieve lower dimming level. That is to say, 2 PWM channels are used to control the dimming curve, thus 2 consecutive linear curves can be obtained in whole dimming range (normally 1-100%, various based on product specification) . Also keeps the BUCK circuit operating in CCM (continuous current Mode) even output current range is wide, for example, output current range of LocoDALI2 20W is 5mA～1050mA.
The DC power outputted from the power supply circuit can rise from minimum to maximum value according to dimming signal. DALI (Digital Addressable Lighting Interface) , NFC (Near Field Communication) , etc., may be used to regulate the DC power, thus an output power of the lighting device rises from minimum to maximum value.
The power supply circuit usually includes a PFC (Power Factor Correction) circuit. Switching frequency of a switch in the PFC circuit will be designed to around 50kHZ to 100kHZ at full load.
SUMMARY
In deep dimming level, as the LED device executing a DALI level command to dim up from deep dimming level or dim down to deep dimming, it could be possible to find that dim curves not strictly monotonic enough. Because it could be captured by current probe when the device was in the fading performance.
FIG. 1 shows the fade time of LED current outputted by the power supply circuit. The dimming curve 100 in deep dimming level drops step by step. This fading performance in deep dimming level would cause flickering issue which can be observed by human eyes.
The inventor found that: in deep dimming level, Buck switching cycles are very long, which means the switching frequency may be small enough for PWML to control. For example, as dim down to 3%, Buck cycle frequency might be 30K～40K, but the duty cycle of PWML is 4～5%. The result is that there are not enough Buck pulses to drive the LED current to change. Therefore, even if dim up higher than 3%or to 6～8%, cycle duty of PWML was not large enough, for example, only 2～3 Buck switch cycles were held. That is the root cause why the LED current stay at a stage during fading, typically in deep dimming level and low I-sel LED current state.
In general, embodiments of the present disclosure provide a power supply circuit, a controlling method, a lighting device driver and a lighting equipment. In the embodiments, a controller of a power supply circuit may change the active time of the first PWM (PWML) signal in step form, and change frequency of the first PWM signal in each step of the active time. Therefore, an ideal fading performance behavior can be obtained.
In a first aspect, there is provided a power supply circuit, includes:
a controller, configured to output first PWM (Pulse Width Modulation) signal, cycle duty of the first PWM signal is controlled by an active time (t_on) ;
control unit, configured to generate controlling signal according to the first PWM signal;
drive circuit, configured to generate driving signal according to the controlling signal;
switch element, configured to be turned on or off according to the driving signal;
a voltage converter, configured to be connected between a first input port and two output ports; and
a resistor, configured to be connected between the switch element and a ground port,
the switch element being connected between the voltage converter and the resistor,
when target output current of the two output ports changes,
the controller changes the active time of the first PWM signal in step form, the active time being fixed in each step of the active time,
and the controller changes frequency of the first PWM signal in each step of the active time.
In an embodiment, the controller monotonically changes frequency of the first PWM signal in each step of the active time.
In an embodiment, when target output current of the two output ports drops,
the controller reduces the active time of the first PWM signal in step form, and the controller reduces the frequency of the first PWM signal from a maximum frequency to a minimum frequency in each step of the active time.
In an embodiment, when target output current of the two output ports increases,
the controller raises the active time of the first PWM signal in step form, and the controller raises the frequency of the first PWM signal from a minimum frequency to a maximum frequency in each step of the active time.
In an embodiment, differences among the maximum frequencies in the steps of the active time are less than a first predetermined value.
In an embodiment, the maximum frequencies in the steps of the active time are with the same value.
In an embodiment, differences among the minimum frequencies in the steps of the active time are less than a second predetermined value.
In an embodiment, the minimum frequencies in the steps of the active time are with the same value.
In an embodiment, when the target output current is lower than a first critical value and/or higher than a second critical value,
the controller changes the active time of the first PWM signal in step form, and changes frequency of the first PWM signal in each step of the active time.
In an embodiment, when the target output current is higher than the first critical value,
the controller keeps frequency of the first PWM signal to a first frequency (maximum dynamic frequency) .
In an embodiment, when the target output current is lower than the second critical value,
the controller keeps frequency of the first PWM signal to a second frequency (minimum dynamic frequency) .
In an embodiment, at least two area are involved between the first critical value and the second critical value,
differences (t_on interval_1 or t_on interval_2) between adjacent steps of the active times keeps fixed in each area,
differences (t_on interval_1 and t_on interval_2) between adjacent steps of the active times are different among the at least two area.
In an embodiment, the control unit is further configured to generate second PWM signal, which is provided to a connecting node between the resistor and the switch element.
In a second aspect, there is provided a lighting device driver which includes the power supply circuit according to the first aspect of embodiment, the lighting device driver providing the second direct current (DC) power to a lighting device.
In an embodiment, the lighting device driver is an LED (Light Emitting Diode) driver.
In a third aspect, there is provided a lighting equipment, including a lighting device, and the power supply circuit according to the first aspect of embodiment, the power supply circuit providing the second direct current (DC) power to the lighting device.
In a fourth aspect, there is provided a controlling method of a power supply circuit according to the first aspect, the controlling method includes: when target output current of the two output ports changes, the controller changes the active time of the first PWM signal in step form, the active time being fixed in each step of the active time, and the controller changes frequency of the first PWM signal in each step of the active time.
According to various embodiments of the present disclosure, a controller of a power supply circuit may change the active time of the first PWM (PWML) signal in step form, and change frequency of the first PWM signal in each step of the active time, therefore, an ideal fading performance behavior can be obtained, and the flickering issue can be resolved.

BRIEF DESCRIPTION OF THE DRAWINGS

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 drawings are illustrated for facilitating better understanding of the embodiments of the disclosure and not necessarily drawn to scale, in which:
FIG. 1 shows the fade time of LED current outputted by the power supply circuit;
Fig. 2 is a diagram of a power supply circuit in accordance with an embodiment of the present disclosure;
FIG. 3 is sequence chart of the target current, the active time t_on and frequency of the first PWM;
FIG. 4 is sequence chart of the target current, the active time t_on, switch element Q1 cycles and frequency of the first PWM;
Fig. 5 shows a flowchart of a controlling method of the power supply circuit 10.

DETAILED DESCRIPTION

The present disclosure will now be discussed with reference to several example embodiments. It should be understood that these embodiments are discussed only for the purpose of enabling those skilled persons in the art to better understand and thus implement the present disclosure, rather than suggesting any limitations on the scope of the present disclosure.
As used herein, the terms “first” and “second” refer to different elements. The singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 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.
First aspect of embodiments
A power supply circuit is provided in a first embodiment.
Fig. 2 is a diagram of a power supply circuit in accordance with an embodiment of the present disclosure. As shown in Fig. 2, a power supply circuit 10 includes a controller 100, a control unit 200, a drive circuit 300, a switch element Q1, a voltage converter 400 and a resistor R.
The controller 100 is configured to output first PWM (Pulse Width Modulation) signal, cycle duty of the first PWM signal is controlled by an active time t_on. For example, the first PWM is PWML.
The control unit 200 is configured to generate controlling signal according to the first PWM signal.
The drive circuit 300 is configured to generate driving signal according to the controlling signal.
The switch element Q1 is configured to be turned on or off according to the driving signal. For example, Q1 is a MOS transistor.
The voltage converter 400 is configured to be connected between a first input port (INPUT+) and two output ports (VOUT+ and VOUT_) . For example, as shown in FIG. 2, the voltage converter 400 includes a diode D1, an inductor L1 and a capacitor C1.
The resistor R is configured to be connected between the switch element Q1 and a ground port.
As shown in FIG. 2, the switch element Q1 is connected between the voltage converter 400 and the resistor R.
As shown in FIG. 2, the control unit 100 is further configured to generate second PWM signal (for example, PWMH) , which is provided to a connecting node A between the resistor R and the switch element Q1.
In at least one embodiment, when target output current of the two output ports (VOUT+ and VOUT_) changes, the controller 100 changes the active time t_on of the first PWM signal in step form. The active time t_on decides the duty cycle of the first PWM signal. The active time t_on is fixed in each step, that is to say, the switching cycles of the switch element Q1 in each step is fixed, but duty cycle of the first PWM signal in each step changes as the PWM frequency monitoring accordingly.
The controller 100 changes frequency of the first PWM signal in each step of the active time.
According to the first aspect of the embodiments, the controller 100 of the power supply circuit may change the active time of the first PWM (PWML) signal in step form, and change frequency of the first PWM signal in each step of the active time, therefore, an ideal fading performance behavior can be obtained, and the flickering issue can be resolved.
FIG. 3 is sequence chart of the target current, the active time t_on and frequency of the first PWM. FIG. 4 is sequence chart of the target current, the active time t_on, switch element Q1 cycles and frequency of the first PWM.
In at least one embodiment, the controller 100 monotonically changes frequency of the first PWM signal in each step of the active time t_on.
For one example, as shown in FIG. 3, when target output current of the two output ports drops, the controller 100 reduces the active time t_on of the first PWM signal in step form (for example, step 1, step 2, …) , and the controller 100 reduces the frequency of the first PWM signal from a maximum frequency to a minimum frequency in each step of the active time, i.e, in step 1, the frequency of the first PWM signal drops from maximum frequency fmax1 to minimum frequency fmin1; in step 2, the frequency of the first PWM signal drops from maximum frequency fmax2 to minimum frequency fmin2, fmax2 is higher than fmin1 .
For another example, when target output current of the two output ports increases, the controller 100 raises the active time of the first PWM signal in step form, and the controller raises the frequency of the first PWM signal from a minimum frequency to a maximum frequency in each step of the active time.
In at least one embodiment, differences among the maximum frequencies in the steps of the active time are less than a first predetermined value. For example, difference between fmax1 and fmax2 are less than a first predetermined value; for another example, the maximum frequencies in the steps of the active time are with the same value, i.e. fmax1 is equal to fmax2.
In at least one embodiment, differences among the minimum frequencies in the steps of the active time are less than a second predetermined value. For example, difference between fmin1 and fmin2 are less than a second predetermined value; for another example, the fmin1 is equal to fmin2.
As shown in FIG. 4, fmax1 and fmax2 may be 1KHz, fmin1 may be 500Hz.
As shown in FIG. 3, the t_on interval is time difference between adjacent step of active time. For example, the t_on interval is time difference between step 1 and step 2.
As shown in FIG. 3, in at least one embodiment, when the target output current is lower than a first critical value ct1 and/or higher than a second critical value ct2, the controller 100 may change the active time t_on of the first PWM signal in step form, and change frequency of the first PWM signal in each step of the active time.
In at least one embodiment, when the target output current is higher than the first critical value, the controller keeps frequency of the first PWM signal to a first frequency (maximum dynamic frequency) .
In at least one embodiment, when the target output current is lower than the second critical value, the controller keeps frequency of the first PWM signal to a second frequency (minimum dynamic frequency) .
In at least one embodiment, at least two area are involved between the first critical value and the second critical value. Differences between adjacent steps of the active times keeps fixed in each area, for example, t_on interval_1 in area 1 keeps fixed, t_on interval_2 in area 2 keeps fixed. Differences between adjacent steps of the active times are different among the at least two area, for example, t_on interval_1 differs from t_on interval_2.
According to the first aspect of the embodiments, the controller 100 of the power supply circuit may change the active time of the first PWM (PWML) signal in step form, and change frequency of the first PWM signal in each step of the active time, therefore, an ideal fading performance behavior can be obtained, and the flickering issue can be resolved.
Second aspect of embodiments
A controlling method of a power supply circuit. The power supply circuit is provided in the first aspect of embodiments. The same contents as those in the first aspect of embodiments are omitted.
Fig. 5 shows a flowchart of a controlling method of the power supply circuit 10.
As shown in Fig. 5, the method 50 includes:
Block 51: when target output current of the two output ports changes, the controller changes the active time of the first PWM signal in step form, the active time being fixed in each step of the active time, and the controller changes frequency of the first PWM signal in each step of the active time.
According to the first aspect of the embodiments, the controller 100 of the power supply circuit may change the active time of the first PWM (PWML) signal in step form, and change frequency of the first PWM signal in each step of the active time, therefore, an ideal fading performance behavior can be obtained, and the flickering issue can be resolved.
Third aspect of embodiments
A lighting equipment is provided in an embodiment. The lighting equipment includes a power supply circuit and a lighting device. The power supply circuit is provided in the first aspect of embodiments. The lighting device maybe LED.
In the embodiment, the power supply circuit 10 (shown in Fig. 2) provides direct current (DC) power to the lighting device.
Fourth aspect of embodiments
A lighting device driver is provided in an embodiment. The lighting device driver includes the power supply circuit 10 (shown in Fig. 2) according to the first aspect of embodiments.
The lighting device driver may supply direct current (DC) power to a lighting device. The lighting device driver may be an LED driver, the lighting device may be an LED device.
An output power, output voltage or output current of the lighting device may be changed from a minimum to maximum value according to dimming signal, e.g. 1-10V, which is received via DALI (Digital Addressable Lighting Interface) , NFC (Near Field Communication) , Bluetooth etc.. Preferably the DC-DC-converter supplying the lighting device will change its output parameters (current and/or voltage) depending on the dimming signal. This change may lead to a change of loading of the power supply circuit 10 (shown in Fig. 2) .
Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.
Although the present disclosure has been described in language specific to structural features and/or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A power supply circuit, comprising:

a controller, configured to output first PWM (Pulse Width Modulation) signal, cycle duty of the first PWM signal is controlled by an active time (t_on) ;

control unit, configured to generate controlling signal according to the first PWM signal;

drive circuit, configured to generate driving signal according to the controlling signal;

switch element, configured to be turned on or off according to the driving signal;

a voltage converter, configured to be connected between a first input port and two output ports; and

a resistor, configured to be connected between the switch element and a ground port,

wherein,

the switch element being connected between the voltage converter and the resistor,

when target output current of the two output ports changes,

the controller changes the active time of the first PWM signal in step form, the active time being fixed in each step of the active time,

and the controller changes frequency of the first PWM signal in each step of the active time.
The power supply circuit according to claim 1, wherein,

the controller monotonically changes frequency of the first PWM signal in each step of the active time.
The power supply circuit according to claim 2, wherein,

when target output current of the two output ports drops,

the controller reduces the active time of the first PWM signal in step form, and the controller reduces the frequency of the first PWM signal from a maximum frequency to a minimum frequency in each step of the active time.
The power supply circuit according to claim 2, wherein,

when target output current of the two output ports increases,

the controller raises the active time of the first PWM signal in step form, and the controller raises the frequency of the first PWM signal from a minimum frequency to a maximum frequency in each step of the active time.
The power supply circuit according to claim 3 or 4, wherein,

differences among the maximum frequencies in the steps of the active time are less than a first predetermined value.
The power supply circuit according to claim 5, wherein,

the maximum frequencies in the steps of the active time are with the same value.
The power supply circuit according to claim 3 or 4, wherein,

differences among the minimum frequencies in the steps of the active time are less than a second predetermined value.
The power supply circuit according to claim 5, wherein,

the minimum frequencies in the steps of the active time are with the same value.
The power supply circuit according to claim 1, wherein,

when the target output current is lower than a first critical value and/or higher than a second critical value,

the controller changes the active time of the first PWM signal in step form, and changes frequency of the first PWM signal in each step of the active time.
The power supply circuit according to claim 9, wherein,

when the target output current is higher than the first critical value,

the controller keeps frequency of the first PWM signal to a first frequency (maximum dynamic frequency) .
The power supply circuit according to claim 9, wherein,

when the target output current is lower than the second critical value,

the controller keeps frequency of the first PWM signal to a second frequency (minimum dynamic frequency) .
The power supply circuit according to claim 1, wherein,

at least two area are involved between the first critical value and the second critical value,

differences (t_on interval_1 or t_on interval_2) between adjacent steps of the active times keeps fixed in each area,

differences (t_on interval_1 and t_on interval_2) between adjacent steps of the active times are different among the at least two area.
The power supply circuit according to claim 1, wherein,

the control unit is further configured to generate second PWM signal, which is provided to a connecting node between the resistor and the switch element,
A lighting equipment, comprising a lighting device, and the power supply circuit according to any one of claims 1-13, wherein,

the power supply circuit providing power to the lighting device.
A controlling method of a power supply circuit, the power supply circuit comprising:

a controller, configured to output first PWM (Pulse Width Modulation) signal, each cycle of the first PWM signal comprising an active time (t_on) ;

control unit, configured to generate controlling signal according to the first PWM signal;

driving circuit, configured to generate driving signal according to the controlling signal;

switch element, configured to be turned on or off according to the driving signal;

a voltage converter, configured to be connected between a first input port and two output ports; and

a resistor, configured to be connected between the switch element and a ground port,

wherein,

the switch element being connected between the voltage converter and the switch element,

the controlling method comprising:

when target output current of the two output ports changes,

the controller changes the active time of the first PWM signal in step form, the active time being fixed in each step of the active time,

and the controller changes frequency of the first PWM signal in each step of the active time.