CN117597857A

CN117597857A - Power supply circuit, driver, and control method

Info

Publication number: CN117597857A
Application number: CN202180100036.5A
Authority: CN
Inventors: 杨嘉琦; 王双红; 张建锋; 郑海
Original assignee: Tridonic GmbH and Co KG
Current assignee: Tridonic GmbH and Co KG
Priority date: 2021-06-29
Filing date: 2021-08-10
Publication date: 2024-02-23
Also published as: WO2023272885A1; EP4338275A1

Abstract

The invention discloses a power supply circuit, a driver and a control method. The power supply circuit includes: a step-down circuit configured to convert an input DC (direct current) voltage into an output DC voltage, the step-down circuit including a diode, an inductor, a capacitor, and a switch, the output DC voltage being output from an output port (vout+, VOUT-); a controller (MCU) configured to output a control signal (PWM signal) according to a feedback voltage (Vout) obtained by a voltage detection circuit connected between one output port and a ground port; and a MOS driving circuit configured to drive the switch of the step-down circuit according to the control signal, the off-state time (Toff) of each period of the control signal being set according to an Output Comparison (OC) reference voltage.

Description

Power supply circuit, driver, and control method

Technical Field

Embodiments of the present disclosure relate generally to the field of lighting, and more particularly, to power supply circuits, drivers, and control methods.

Background

This section presents a simplified summary that may facilitate a better understanding of aspects of the disclosure. Accordingly, the statements of this section are to be read in this light, and not as admissions of prior art.

The step-down circuit includes a diode, an inductor, a capacitor, and a switch. The control signal may control the switch to turn on and off such that the buck circuit may convert an input voltage to an output voltage that is lower than the input voltage. The control signal may be a PWM (pulse width modulation) signal.

Disclosure of Invention

In the related art, an auxiliary winding is used to detect a current flowing through an inductor of a step-down circuit and perform zero-crossing detection on the detected current so as to control a switch according to a zero-crossing detection result.

The inventors found that in a step-down circuit, the auxiliary winding would result in high costs.

Generally, embodiments of the present disclosure provide power supply circuits, drivers, and control methods. In an embodiment, the power supply circuit sets the off-state time (Toff) of each period of the control signal using an Output Comparison (OC) reference voltage, and an auxiliary winding is not required to control the switch, thereby reducing the cost of the step-down circuit.

In a first aspect, there is provided a power supply circuit comprising:

a step-down circuit configured to convert an input DC (direct current) voltage into an output DC voltage, the step-down circuit including a diode, an inductor, a capacitor, and a switch, the output DC voltage being output from an output port (vout+, VOUT-);

a controller (MCU) configured to output a control signal (PWM signal) according to a feedback voltage (Vout) obtained by a voltage detection circuit connected between one output port and a ground port; and

a MOS driving circuit configured to drive a switch of the step-down circuit according to a control signal,

an off-state time (Toff) of each period of the control signal is set according to an Output Comparison (OC) reference voltage.

In one embodiment, the on-state time (Ton) of each cycle of the control signal is determined by the detected peak current (Ipeak) flowing through the switch.

In one embodiment, the power supply circuit further comprises:

a current peak limiter configured to detect the peak current and send an off signal to an off pin of the controller, the off signal causing the control signal to drop to a low level, thereby ending the on state.

In one embodiment, the current peak limiter includes a first comparator (comp_break) that compares a voltage corresponding to the peak current with a first reference voltage (Ref), and when the voltage corresponding to the peak current is higher than the first reference voltage, an off signal having a low level is generated by the first comparator.

In one embodiment, the controller includes:

a first timer (Tim 1) configured to define each cycle of the control signal by counting when the first timer is reset, a new cycle starts; and

a second timer (Tim 2) configured to be reset when an off-state of the control signal starts,

when the count value of the second timer reaches a value corresponding to an Output Comparison (OC) reference voltage, the first timer is reset, thereby ending the off state of the control signal.

In one embodiment, when the controller controls the buck circuit to operate in CCM (continuous conduction mode) or BCM (boundary conduction mode), the off-state time (Toff) is determined by the fixed Δipeak, the inductance of the inductor and the feedback voltage (Vout),

where Δipeak represents the difference between the upper Ipeak limit and the lower Ipeak limit.

In one embodiment, when the controller controls the buck circuit to operate in DCM (discontinuous conduction mode), the off-state time (Toff) is determined by a fixed Δipeak, the inductance of the inductor, a fixed output current (iLED), an input DC (direct current) voltage (Vin), and a feedback voltage (Vout), where Δipeak is equal to the Ipeak upper limit.

In a second aspect, there is provided a driver for driving a lighting device, the driver comprising a power supply circuit according to the first aspect of the embodiment, the power supply circuit providing power to the lighting device, and a control circuit in communication with the power supply circuit, the control circuit in communication with a peripheral device.

In a second aspect, there is provided a control method of the power supply circuit according to the first aspect of the embodiment. The control method comprises the following steps:

the off-state time (Toff) of each cycle of the control signal is set according to the Output Comparison (OC) reference voltage.

According to various embodiments of the present disclosure, an off-state time (Toff) of each period of a control signal is set according to an Output Comparison (OC) reference voltage, and an auxiliary winding is not required to control a switch, thereby reducing the cost of a step-down circuit.

Drawings

The above and other aspects, features and advantages of various embodiments of the present disclosure will become more 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 figures are illustrated for the sake of a better understanding of the embodiments of the disclosure and are not necessarily drawn to scale, wherein:

fig. 1 is a diagram of a power supply circuit according to a first aspect of an embodiment of the present disclosure;

fig. 2 is a simple circuit topology of a power supply circuit according to a first aspect of an embodiment of the present disclosure;

fig. 3 is a complete circuit topology of a power supply circuit according to a first aspect of an embodiment of the present disclosure;

FIG. 4 is a diagram of a controller MCU according to a first aspect of an embodiment of the present disclosure;

fig. 5 is a diagram illustrating an operation principle of a controller MCU according to a first aspect of an embodiment of the present disclosure;

FIG. 6 is a timing diagram of the buck circuit when operating in CCM or BCM;

FIG. 7 is a timing diagram of the buck circuit operating in DCM;

fig. 8 is a diagram of a control method of Toff control with fixed Δipeak (or Ipeak) in DCM;

fig. 9 is a diagram of a state machine for Toff control of a power supply circuit according to a first aspect of an embodiment of the present disclosure;

fig. 10 is an illustration of a driver.

Detailed Description

The present disclosure will now be discussed with reference to several exemplary embodiments. It should be understood that these embodiments are discussed only in order to enable those skilled in the art to better understand the present disclosure and thus practice the present disclosure, and are not intended to limit the scope of the present disclosure in any way.

The terms "first" and "second" as used herein refer to different elements. The singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the terms "comprises," "comprising," "includes," "including," "having," "containing," and/or "containing" specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof. The term "based on" should be understood as "based at least in part on". The terms "one embodiment" and "an embodiment" should be understood as "at least one embodiment". The term "another embodiment" should be understood as "at least one other embodiment". Other explicit and implicit definitions may be included below.

First aspect of the embodiments

In a first embodiment, a power supply circuit is provided.

Fig. 1 is a diagram of a power supply circuit according to a first aspect of an embodiment of the present disclosure. Fig. 2 is a simple circuit topology of a power supply circuit according to a first aspect of an embodiment of the present disclosure. Fig. 3 is a complete circuit topology of a power supply circuit according to a first aspect of an embodiment of the present disclosure.

As shown in fig. 1, 2, and 3, the power supply circuit 1 includes:

a step-down circuit 10 configured to convert an INPUT DC (direct current) voltage (received from the INPUT ports input+ and INPUT-) into an output DC voltage, the step-down circuit 10 including a diode, an inductor, a capacitor, and a switch Q1, the output DC voltage being output from the output port (vout+, VOUT-;

a controller (MCU, also denoted 20) configured to output a control signal (PWM signal) in accordance with a feedback voltage (Vout), obtained by a voltage detection circuit 21 connected between an output port (Vout-) and a ground port; and

a MOS drive circuit 30 configured to drive the switch Q1 of the step-down circuit 10 according to the control signal.

As shown in fig. 3, the MOS drive circuit 30 may drive the switch Q1 according to a control signal. For example, the MOS drive circuit 30 includes a totem pole circuit.

In fig. 3, the use of each pin of the controller MCU is explained as follows:

vin: DC input voltage detection.

Vout: the LED output voltage detection, for example, the Vout pin may receive a feedback voltage (Vout).

Isns: RShunt average voltage detection

PWM: a MOS gate driver (to a MOS drive circuit), for example, a control signal may be output from the PWM pin.

BREAK: a PWM circuit breaker trigger, for example, the BREAK pin may receive an open signal.

Ref: the current limit reference, e.g., the Ref pin, receives a first reference voltage.

In at least one embodiment, the off-state time (Toff) of each cycle of the control signal is set according to an Output Comparison (OC) reference voltage.

In at least one embodiment, the on-state time (Ton) of each cycle of the control signal is determined by the detected peak current (Ipeak) flowing through the switch Q1.

As shown in fig. 3, the power supply circuit 1 further includes:

a current peak limiter 40 configured to detect the peak current and send an off signal to an off pin (i.e., BREAK pin in fig. 3) of the controller 20, which drops the control signal to a low level, thereby ending the on state of the switch Q1.

As shown in fig. 3, the current peak limiter 40 includes a first comparator (comp_break) 41 that compares a voltage corresponding to the peak current with a first reference voltage (denoted Ref, which is also received by the Ref pin of the controller 20). The first comparator generates a low-level off signal when a voltage corresponding to the peak current is higher than a first reference voltage. Thus, the first reference voltage defines an Ipeak upper limit. The voltage corresponding to the peak current can be obtained by a resistor denoted R-shot 1.

Fig. 4 is a diagram of a controller MCU according to a first aspect of an embodiment of the present disclosure. Fig. 5 is a diagram illustrating an operation principle of the controller MCU according to the first aspect of the embodiment of the present disclosure.

As shown in fig. 4, the numeral (1) indicates "falling edge trigger". The numeral (2) denotes "support external reference or internal DAC module", which means that the comparator COMP in the controller MCU shown in fig. 4 can replace the first comparator (comp_break) 41 in fig. 3 in order to use the MCU external comparator, thereby using fewer components and saving space. Numeral (3) in fig. 5 indicates "use OC (output comparison) reference to set Toff hold time".

As shown in fig. 4, the controller MCU (also denoted as 41 in fig. 3) includes:

a second timer (Tim 2) configured to be reset when an off-state of the control signal starts (e.g., a low-level off signal is sent to an off pin of the controller MCU).

As shown in fig. 5, when the count value of the second timer reaches a value corresponding to the Output Comparison (OC) reference voltage, the first timer (Tim 1) is reset, thereby ending the off state of the control signal.

In at least one embodiment, the first reference voltage may be a sampled voltage. The first reference voltage determines the maximum value of the current flowing through the switch Q1. The Output Comparison (OC) reference voltage (denoted OC ref) is a parameter in the controller 20 for controlling the off-state time (Toff), for example, the Output Comparison (OC) reference voltage may be stored in the controller 20 and updated.

In at least one embodiment, the first reference voltage and the Output Comparison (OC) reference voltage are the same or different.

Fig. 6 is a timing diagram when the step-down circuit operates in CCM or BCM.

In at least one embodiment, as shown in fig. 6, when the controller controls the buck circuit to operate in CCM (continuous conduction mode) or BCM (boundary conduction mode), the off-state time (Toff) is determined by the fixed Δipeak, the inductance of the inductor, and the feedback voltage (Vout). Δipeak represents the difference between the upper Ipeak limit and the lower Ipeak limit. The upper and lower Ipeak limits represent the maximum and minimum values, respectively, of the current flowing through the switch Q1.

As shown in fig. 6, the output of the first comparator is connected to the BREAK pin, so that the output current can be controlled cycle by cycle.

Since the Ipk upper limit is obtained, the following equation (1) can be used to calculate the target of Toff (i.e., toff _target ) Thereby setting a fixed Δipeak:

for example, in step 1, when an Ipeak upper limit is set, the first reference voltage may be determined by the Ipeak upper limit; in step 2, toff can be calculated according to the above formula by using Δipeak, inductance L and detected Vout _target The method comprises the steps of carrying out a first treatment on the surface of the In step 3, the calculated Toff can be used _target The Output Comparison (OC) reference voltage is determined, and the Output Comparison (OC) reference voltage stored in the controller MCU 20 may be updated by using the determined Output Comparison (OC) reference voltage.

As shown in fig. 6, v_rshunt represents the voltage across resistor R-shunt 1 in fig. 3.

Fig. 7 is a timing diagram of the buck circuit when operating in DCM.

As shown in fig. 7, when the controller 20 controls the buck circuit 10 to operate in DCM (discontinuous conduction mode), the off-state time (Toff) is determined by a fixed Δipeak, the inductance L of the inductor, a fixed output current (iLED), an input DC (direct current) voltage (denoted Vin), and a feedback voltage (Vout). Δipeak is equal to the Ipeak upper limit.

Wherein the fixed Δipeak, the inductance L of the inductor and the fixed output current (iLED) are fixed values. The input DC (direct current) voltage (Vin) and the feedback voltage (Vout) are variables. Vout may also be a low site voltage.

As shown in fig. 7, the 1/2 Δipeak value is greater than i_led. The buck circuit will enter DCM (discontinuous conduction mode). The off-time control depends on Vin and Vout, on stored parameters (e.g., parameters in a look-up table). The stored parameters may be a fixed Δipeak, the inductance L of the inductor, and a fixed output current (iLED). An iLED refers to the average current flowing through a load (e.g., an LED) connected between output ports VOUT+ and VOUT-. The iLED has the same meaning as the i_led in fig. 7.

Fig. 8 is a diagram of a control method of Toff control with fixed Δipeak (or Ipeak) in DCM.

As shown in fig. 8, the control method for Toff control with fixed Δipeak (or Ipeak) in DCM includes:

step 1, sending a maximum on-state time Ton (expressed as pwm_ton (max)) control signal of the switch Q1 to the step-down circuit 10;

step 2, generating a reference (denoted as ipeak_ref) of a current peak according to the current selection signal, wherein the ipeak_ref corresponds to the Δipeak or the Ipeak upper limit;

step 3. The step-down circuit 10 generates the output voltage Vout from ipeak_ref, pwm_ton (max) and Toff (max), where Toff (max) is a preset constant, which is about 50 microseconds and can be defined by the designer;

step 4.Vout and bus voltage are sent to the ADC converter to generate vbus_adc and vout_adc as digital signals;

step 5: CCM or DCM calculations are performed based on vbus_adc and vout_adc to obtain the actual off-state time (Toff) of the switch Q1.

Step 5 may comprise two sub-steps:

a first substep: determining the operation mode as CCM or DCM, for example, when the 1/2 Δipeak value is greater than i_led, as shown in fig. 7, determining the operation mode as DCM;

a second substep: toff is calculated based on vbus_adc and vout_adc.

For example, toff may be calculated using a lookup table based on vbus_adc and vout_adc. For example, toff may be calculated using a formula related to VBus and Vout, such as formula (1). Toff can be calculated based on VBus_adc and Vout_adc using other methods in the art

Step 6: generating a reference value of Toff (denoted as toff_ref) from the current selection signal, e.g. the current selection signal determines that ilent, ipeak_ref is available as ilent fixed value, and then determining toff_ref corresponding to ilent and ipeak_ref by using a look-up table;

step 7: PI (proportional-integral) control is performed based on the difference between toff_ref and actual Toff, whereby Toff in the control signal is updated, and the updated Toff is sent to the step-down circuit 10.

After a number of cycles of step 3, step 4, step 5 and step 7, the output voltage Vout will become stable.

Fig. 9 is a diagram of a state machine for Toff control of a power supply circuit according to a first aspect of an embodiment of the present disclosure.

As shown in fig. 9, when the output voltage is stable, a slow Toff control may be used; when the output voltage is unstable, a fast Toff control may be used. The update rate of the PI control loop in the fast Toff control is higher than the update rate of the PI control loop in the slow Toff control.

For example, two sets of PI parameters may be defined, one for fast Toff control and the other for slow Toff control. The fast t_off control and the slow t_off control correspond to the PI control of step 7 in fig. 8.

The fast Toff control may be enabled at start-up or when the output voltage is in an unstable state. When the output voltage is in an unstable state, the slow Toff control may be enabled.

According to the first aspect of the embodiment, the power supply circuit 1 has the following advantages:

1. digital solutions-flexible use in different products (hardware parameters can be configured in software lists);

2. cost savings-zero crossing detection without additional auxiliary windings;

3. space saving-fewer elements (MCU internal comparators can be used);

4. the operating window supporting CCM/DCM performance-output power is wider.

The power supply circuit 1 has the following features:

1. using the formula-calculate for control in DCM operation;

2. the totem circuit is used for driving the MOSFET;

3. vin and Vout detection is required without measurement of average LED current.

Second aspect of the embodiment

A control method of a power supply circuit is provided. In a first aspect of an embodiment, a power supply circuit is provided. Those same as those in the first aspect of the embodiment are omitted.

Third aspect of the embodiment

In a third aspect of the embodiments, a driver is provided.

Fig. 10 is an illustration of a driver. As shown in fig. 10, the driver 50 includes:

an EMI filter 51 for filtering electromagnetic interference;

a boost PFC circuit 52 that converts the input AC power to DC power;

a DC-DC converter 53 that uses a step-down circuit to convert the DC voltage of the step-up PFC circuit 52 into an output voltage that is used to drive a lighting device, for example, an LED;

the controller 54 controls the DC-DC converter 53; and is also provided with

The control circuit 55 communicates with the controller 54. The control circuit 54 communicates with peripheral devices via an interface.

For example, the peripheral device may be a dimmer, a sensor, a controller, a safety device, or the like. The interface may be a DALI (digital addressable lighting interface).

In the driver 50, the controller 54 corresponds to the MCUs in fig. 1, 2 and 3. The DC-DC converter 53 corresponds to the step-down circuit, the MOS drive circuit, and the current peak limiter in fig. 3.

The driver 50 may supply Direct Current (DC) power to the lighting device. The driver 50 may be an LED driver and the lighting device may be an LED device.

The output power, output voltage or output current of the lighting device may vary between a minimum value to a maximum value depending on a dimming signal (e.g. 1V-10V) received via DALI (digital addressable lighting interface), NFC (near field communication), bluetooth, etc. Preferably, the DC-DC converter supplies that the lighting device will change its output parameters (current and/or voltage) in accordance with the dimming signal.

In addition, while operations are illustrated in a particular order, this should not be construed as requiring that such operations be performed in the particular order illustrated or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous. Also, while several specific implementation details are included in the above discussion, these specific implementation details should not be construed as limiting the scope of the present disclosure, but as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination.

Although the disclosure has been described in language specific to structural features and/or methodological acts, it is to be understood that the 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

1. A power supply circuit, the power supply circuit comprising:

a MOS drive circuit configured to drive the switch of the step-down circuit according to the control signal,

2. The power supply circuit of claim 1, wherein,

the on-state time (Ton) of each period of the control signal is determined by the detected peak current (Ipeak) flowing through the switch.

3. The power supply circuit according to claim 2, wherein,

the power supply circuit further includes:

a current peak limiter configured to detect the peak current and send an off signal to an off pin of the controller, the off signal dropping the control signal to a low level, thereby ending the on state.

4. The power supply circuit according to claim 3, wherein,

the current peak limiter comprises a first comparator (comp_break) comparing a voltage corresponding to the peak current with a first reference voltage (Ref), the off signal having a low level being generated by the first comparator when the voltage corresponding to the peak current is higher than the first reference voltage.

5. The power supply circuit according to claim 4, wherein,

the controller includes:

a first timer (Tim 1) configured to define each cycle of the control signal by counting when the first timer is reset, a new cycle starting; and

a second timer (Tim 2) configured to be reset when the off-state of the control signal begins,

when the count value of the second timer reaches a value corresponding to the Output Comparison (OC) reference voltage, the first timer is reset, ending the off state of the control signal.

6. The power supply circuit according to claim 2, wherein,

when the controller controls the step-down circuit to operate in CCM (continuous conduction mode) or BCM (boundary conduction mode), the off-state time (Toff) is determined by a fixed Δipeak, the inductance of the inductor and the feedback voltage (Vout),

wherein Δipeak represents the difference between the upper Ipeak limit and the lower Ipeak limit.

7. The power supply circuit according to claim 2, wherein,

when the controller controls the buck circuit to operate in DCM (discontinuous conduction mode), the off-state time (Toff) is determined by a fixed Δipeak, the inductance of the inductor, a fixed output current (iLED), the input DC voltage (Vin) and the feedback voltage (Vout),

wherein Δipeak is equal to the Ipeak upper limit.

8. A driver for driving a lighting device, the driver comprising the power supply circuit according to any one of claims 1 to 7 and a control circuit, wherein,

the power supply circuit provides power to the lighting device,

the control circuit is in communication with the power supply circuit,

the control circuit communicates with a peripheral device.

9. A control method of an electric power supply circuit, the electric power supply circuit comprising:

the control method comprises the following steps:

10. The control method of an electric power supply circuit according to claim 9, wherein,

11. The control method of an electric power supply circuit according to claim 10, wherein,

the power supply circuit further includes:

the peak current limiter is provided with a current peak limiter,

the method further comprises the steps of:

the current peak limiter detects the peak current and sends an off signal to an off pin of the controller,

wherein the off signal drops the control signal to a low level, thereby ending the on state.

12. The control method of an electric power supply circuit according to claim 11, wherein,

the current peak limiter includes a first comparator (comp_break) that compares a voltage corresponding to the peak current with a first reference voltage, and the off signal having a low level is generated by the first comparator when the voltage corresponding to the peak current is higher than the first reference voltage.

13. The control method of an electric power supply circuit according to claim 12, wherein,

the controller includes:

14. The control method of an electric power supply circuit according to claim 10, wherein,

15. The control method of an electric power supply circuit according to claim 10, wherein,

wherein Δipeak is equal to the Ipeak upper limit.