Power converter with dynamic control minimum off time mechanism

Abstract

This invention discloses a power converter with a dynamic minimum turn-off time control mechanism. The upper bridge overcurrent protection circuit determines whether current flows from the upper bridge switch through the node between the second terminal of the upper bridge switch and the first terminal of the lower bridge switch towards the inductor, and determines whether the current exceeds a threshold, outputting an upper bridge overcurrent detection signal and an upper bridge overcurrent protection signal. The turn-off time control circuit outputs a minimum turn-off time signal to the drive circuit based on the upper bridge overcurrent protection signal. The drive circuit determines that an overcurrent event occurred when the upper bridge switch is turned on based on the upper bridge overcurrent detection signal, and therefore maintains the lower bridge switch on for at least the longer of the minimum turn-off time signal.

Description

Technical Field

[0001] This invention relates to power converters, and more particularly to a power converter with a dynamic control minimum shutdown time mechanism. Background Technology

[0002] In traditional power converters, the minimum off time of the lower bridge switch is a fixed value. During this minimum off time, the lower bridge overcurrent protection circuit detects whether the current flowing through the lower bridge switch exceeds the current threshold, i.e., whether an overcurrent has occurred. If an overcurrent occurs, the lower bridge switch will remain open until the current falls below the current threshold, at which point the lower bridge switch will close.

[0003] A short minimum shutdown time is generally desirable, providing optimal response time during output load transients. If the minimum shutdown time is too long, system instability or frequency throttling may occur under normal application conditions at a given transfer ratio. However, an excessively short minimum shutdown time may prevent the lower-bridge overcurrent protection circuit from detecting an overcurrent event, leading to damage to circuit components due to overcurrent. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a power converter with a dynamic control minimum turn-off time mechanism, addressing the shortcomings of existing technologies. The converter includes an upper bridge switch, a lower bridge switch, a drive circuit, an upper bridge overcurrent protection circuit, and a turn-off time adjustment circuit. The first terminal of the upper bridge switch is coupled to a shared voltage. The first terminal of the lower bridge switch is connected to the second terminal of the upper bridge switch. A node between the second terminal of the upper bridge switch and the first terminal of the lower bridge switch is connected to the first terminal of an inductor. The second terminal of the inductor is connected to the first terminal of a capacitor. The second terminal of the capacitor is grounded. The second terminal of the lower bridge switch is grounded. The drive circuit is connected to the control terminals of the upper and lower bridge switches. The drive circuit is configured to output an upper bridge turn-on signal to the upper bridge switch to drive it, and to output a lower bridge turn-on signal to the lower bridge switch to drive it. The upper bridge overcurrent protection circuit is connected to the drive circuit and the node. The upper bridge overcurrent protection circuit is configured to detect the node to determine whether current flows from the upper bridge switch through the node towards the inductor and whether the current exceeds a first current threshold, thereby outputting an upper bridge overcurrent detection signal and an upper bridge overcurrent protection signal. The turn-off time control circuit is connected to the upper bridge overcurrent protection circuit and the drive circuit. The turn-off time control circuit is configured to determine a minimum turn-off time based on the upper bridge overcurrent protection signal, and outputs the minimum turn-off time signal to the drive circuit. The drive circuit determines that an overcurrent event has occurred when the upper bridge switch is turned on based on the upper bridge overcurrent detection signal; therefore, the drive circuit maintains the lower bridge switch on for at least the longer of the minimum turn-off time signal's minimum turn-off time.

[0005] In this embodiment, the turn-off time control circuit stores multiple reference minimum turn-off times, selects one of the reference minimum turn-off times based on the overcurrent protection signal of the upper bridge, and outputs a minimum turn-off time signal with a minimum turn-off time equal to the selected reference minimum turn-off time.

[0006] In this embodiment, the turn-off time control circuit determines the duty cycle and non-duty cycle of the minimum turn-off time signal based on the overcurrent protection signal of the upper bridge, and outputs the minimum turn-off time signal. The non-duty cycle of the minimum turn-off time signal includes the minimum turn-off time.

[0007] In this embodiment, the turn-off time control circuit stores a first reference minimum turn-off time signal. When the power converter does not generate current or the current is not greater than a first current threshold, the turn-off time control circuit outputs a minimum turn-off time signal with a minimum turn-off time equal to the first reference minimum turn-off time.

[0008] In this embodiment, the turn-off time control circuit also stores a second reference minimum turn-off time signal that is greater than the first reference minimum turn-off time. When the power converter generates current and the current is greater than the first current threshold, the turn-off time control circuit outputs a minimum turn-off time signal with a minimum turn-off time equal to the second reference minimum turn-off time.

[0009] In an embodiment, when the power converter generates current and the current is greater than the first current threshold, a pulse is generated in the upper bridge overcurrent detection signal output by the upper bridge overcurrent protection circuit and a waveform is generated in the output upper bridge overcurrent protection signal.

[0010] In this embodiment, the rising edge of the waveform of the upper bridge overcurrent protection signal is aligned with the rising edge of the pulse of the upper bridge overcurrent detection signal, and the falling edge of the waveform of the upper bridge overcurrent protection signal is aligned with the rising edge of the waveform of the upper bridge conduction signal.

[0011] In this embodiment, the time from the rising edge of the lower bridge turn-on signal to the rising edge of the minimum turn-off time signal is the minimum turn-off time.

[0012] In this embodiment, the lower bridge switch is closed when it receives a low-level lower bridge conduction signal, and is opened when it receives a high-level lower bridge conduction signal.

[0013] In one embodiment, the power converter further includes a lower-bridge overcurrent protection circuit. The lower-bridge overcurrent protection circuit is connected to the drive circuit and the node. The lower-bridge overcurrent protection circuit is configured to determine, within a minimum shutdown time, whether another current flowing through the lower-bridge switch, node, and inductor exceeds a second current threshold.

[0014] As described above, this invention provides a power converter with a dynamic minimum turn-off time control mechanism. Under normal operating conditions, the minimum turn-off time of the lower bridge switch is short. However, when the current flowing through the upper bridge switch exceeds a first current threshold, i.e., an overcurrent event occurs, the minimum turn-off time of the lower bridge switch is longer. When the lower bridge switch remains open for a longer turn-off time, the lower bridge overcurrent protection circuit has sufficient time to detect whether the current flowing through the lower bridge switch exceeds a second current threshold, i.e., an overcurrent event has occurred. This prevents overcurrent events from causing burnout of the power converter's circuit components.

[0015] To further understand the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are for reference and illustration only and are not intended to limit the present invention. Attached Figure Description

[0016] Figure 1 This is a circuit layout diagram of a power converter with a dynamic control minimum shutdown time mechanism according to the first embodiment of the present invention.

[0017] Figure 2 This is a circuit layout diagram of a power converter with a dynamic control minimum shutdown time mechanism according to a second embodiment of the present invention.

[0018] Figure 3 The graphs are of the signals of the power converters with dynamic control minimum shutdown time mechanism according to the first and second embodiments of the present invention. Detailed Implementation

[0019] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the present invention. Furthermore, the accompanying drawings of the present invention are for simple illustrative purposes only and are not depictions of actual dimensions, as stated in advance. The following embodiments will further describe the relevant technical content of the present invention in detail, but the disclosed content is not intended to limit the scope of protection of the present invention. In addition, the term "or" as used herein may, depending on the actual situation, include any combination of any one or more of the associated listed items.

[0020] Please see Figure 1 and Figure 3 ,in Figure 1 This is a circuit layout diagram of a power converter with a dynamic control minimum shutdown time mechanism according to the first embodiment of the present invention. Figure 3The graphs are of the signals of the power converters with dynamic control minimum shutdown time mechanism according to the first and second embodiments of the present invention.

[0021] The power converter of this invention may include, as in the following embodiments: Figure 1 The invention includes an upper bridge switch UG, a lower bridge switch LG, a drive circuit 100, an upper bridge overcurrent protection circuit 200, a turn-off time control circuit 300, and a lower bridge overcurrent protection circuit 400, but is not limited thereto.

[0022] The first terminal of the upper bridge switch UG can be coupled to the shared voltage VCC. The second terminal of the upper bridge switch UG can be connected to the first terminal of the lower bridge switch LG. The second terminal of the lower bridge switch LG is grounded. The node LX between the second terminal of the upper bridge switch UG and the first terminal of the lower bridge switch LG can be connected to the first terminal of the inductor L. The second terminal of the inductor L can be connected to the first terminal of the capacitor C. The second terminal of the capacitor C is grounded. The node between the second terminal of the inductor L and the first terminal of the capacitor C is the output terminal of the power converter.

[0023] The drive circuit 100 can be connected to the control terminals of the upper bridge switch UG and the lower bridge switch LG. The drive circuit 100 can output an upper bridge turn-on signal UGS to the upper bridge switch UG to drive the upper bridge switch UG. For example, when the drive circuit 100 outputs a high-level upper bridge turn-on signal UGS to the upper bridge switch UG, the upper bridge switch UG is turned on. Conversely, when the drive circuit 100 outputs a low-level upper bridge turn-on signal UGS to the upper bridge switch UG, the upper bridge switch UG is turned off.

[0024] The driving circuit 100 can output a lower bridge turn-on signal LGS to the lower bridge switch LG to drive the lower bridge switch LG. For example, when the driving circuit 100 outputs a high-level lower bridge turn-on signal LGS to the lower bridge switch LG, the lower bridge switch LG is turned on. Conversely, when the driving circuit 100 outputs a low-level lower bridge turn-on signal LGS to the lower bridge switch LG, the lower bridge switch LG is turned off.

[0025] The upper bridge overcurrent protection circuit 200 can be connected to the drive circuit 100 and the turn-off time control circuit 300. Additionally, the upper bridge overcurrent protection circuit 200 can be connected to node LX between the second terminal of the upper bridge switch UG and the first terminal of the lower bridge switch LG.

[0026] The overcurrent protection circuit 200 can detect data from node LX and generate a function based on the detected data from node LX. Figure 3The node detection signal LXS shown is used to determine whether there is a current IU flowing from the upper bridge switch UG through node LX toward the inductor L, and can further determine whether this current IU is greater than the first current threshold, so as to output an upper bridge overcurrent detection signal OCH to the drive circuit 100, and output an upper bridge overcurrent protection signal CHA to the turn-off time control circuit 300.

[0027] It is worth noting that when the upper bridge overcurrent protection circuit 200 determines that the power converter generates a current IU and that the current IU is greater than the first current threshold, the upper bridge overcurrent protection circuit 200 can output the following: Figure 3 The diagram shows an upper bridge overcurrent detection signal OCH with a pulse to the drive circuit 100, and an upper bridge overcurrent protection signal CHA with a waveform to the turn-off time control circuit 300.

[0028] like Figure 3 As shown, the rising edge of the upper bridge overcurrent protection signal CHA is aligned with the rising edge of the upper bridge overcurrent detection signal OCH, and the falling edge of the upper bridge overcurrent protection signal CHA is aligned with the rising edge of the upper bridge turn-on signal UGS. In other words, the timing of the falling edge of the upper bridge overcurrent protection signal CHA can be aligned with the timing of the current IL of inductor L discharging to the low-trough current value OCPL.

[0029] The overcurrent protection signal CHA stores the value of the overcurrent detection signal OCH in an edge-triggered manner and resets its value to zero at the beginning of the next cycle.

[0030] The turn-off time control circuit 300 can be connected to the drive circuit 100. The turn-off time control circuit 300 can determine the duration of a minimum turn-off time signal TFM, Toffmin, based on the upper bridge overcurrent protection signal CHA, and output the minimum turn-off time signal TFM to the drive circuit 100. The drive circuit 100 must maintain the lower bridge switch LG open at least during the minimum turn-off time Toffmin of the minimum turn-off time signal TFM.

[0031] like Figure 3 As shown, the minimum turn-off time Toffmin can be the time from the rising edge of the lower bridge turn-on signal LGS to the rising edge of the minimum turn-off time signal TFM.

[0032] For example, the turn-off time control circuit 300 can store multiple reference minimum turn-off times. The lengths of these multiple reference minimum turn-off times are not equal. When the turn-off time control circuit 300 receives an upper-bridge overcurrent protection signal CHA from the upper-bridge overcurrent protection circuit 200, it can select one of the multiple reference minimum turn-off times based on the current IU value indicated by the upper-bridge overcurrent protection signal CHA to output a minimum turn-off time signal TFM. The minimum turn-off time Toffmin of this minimum turn-off time signal TFM is equal to the selected reference minimum turn-off time.

[0033] For example, the multiple reference minimum turn-off times stored in the aforementioned turn-off time control circuit 300 may include a first reference minimum turn-off time and a second reference minimum turn-off time. The second reference minimum turn-off time is greater than the first reference minimum turn-off time.

[0034] When the power converter does not generate current IU or the current IU is not greater than the first current threshold, the minimum turn-off time Toffmin of the minimum turn-off time signal TFM output by the turn-off time control circuit 300 is equal to the first reference minimum turn-off time.

[0035] Conversely, when the power converter generates a current IU and the current IU is greater than the first current threshold, the minimum turn-off time Toffmin of the minimum turn-off time signal TFM output by the turn-off time control circuit 300 is equal to the second reference minimum turn-off time.

[0036] The lower bridge overcurrent protection circuit 400 can be connected to the drive circuit 100 and can be connected to node LX between the second terminal of the upper bridge switch UG and the first terminal of the lower bridge switch LG. The lower bridge overcurrent protection circuit 400 can detect the data at node LX within the minimum off-time of the minimum off-time signal TFM to determine whether the current flowing through the lower bridge switch LG, node LX, and inductor L is greater than the second current threshold, and output a lower bridge overcurrent detection signal OCL.

[0037] In other words, when current IU flows from the upper bridge switch UG through node LX to inductor L, and current IU is greater than the second current threshold (i.e., when an overcurrent event occurs when the upper bridge switch UG is turned on), the minimum turn-off time Toffmin of the minimum turn-off time signal TFM is adjusted to a second reference minimum turn-off time with a longer duration. Thus, the lower bridge overcurrent protection circuit 400 has sufficient time to determine whether the current flowing through the lower bridge switch LG, node LX, and inductor L is greater than the second current threshold, thereby determining whether an overcurrent event has occurred when the lower bridge switch LG is turned on. This allows for real-time execution of measures to prevent damage to the power converter's circuit components due to overcurrent.

[0038] Please see Figure 2This is a circuit layout diagram of a power converter with a dynamic control minimum shutdown time mechanism according to a second embodiment of the present invention.

[0039] In addition to including the upper bridge switch UG, the lower bridge switch LG, the drive circuit 100, the upper bridge overcurrent protection circuit 200, the turn-off time control circuit 300, and the lower bridge overcurrent protection circuit 400, the power converter of this embodiment may also include an operational amplifier 500, a ramp signal generator 600, a comparator 700, a pulse signal generator 800, and a feedback circuit 900, but this invention is not limited thereto. The similarities to the first embodiment will not be repeated below.

[0040] The input of feedback circuit 900 can be connected to the node between the second end of inductor L and the first end of capacitor C (i.e., the output of the power converter). Feedback circuit 900 can detect the voltage at this node (i.e., the output voltage VOUT of the power converter) as the feedback voltage FB. The first input of operational amplifier 500, such as the inverting input, can be coupled to a reference voltage VREF. The second input of operational amplifier 500, such as the non-inverting input, can be connected to the output of feedback circuit 900 to receive the feedback voltage FB from the output of the power converter.

[0041] Operational amplifier 500 multiplies the difference between the feedback voltage FB at the output of the power converter and the reference voltage VREF by a gain, and outputs an amplified signal. The output of operational amplifier 500 can be connected to the first terminal of resistor Rc. The second terminal of resistor Rc can be connected to the first terminal of capacitor Cc. The second terminal of capacitor Cc can be grounded.

[0042] The first input terminal of comparator 700, such as the non-inverting input terminal, can be connected to the output terminal of operational amplifier 500. The second input terminal of comparator 700, such as the inverting input terminal, can be connected to the output terminal of ramp signal generator 600. Comparator 700 compares the voltage of the amplified signal output by operational amplifier 500 (i.e., the voltage at the first end of resistor Rc) with the voltage of the ramp signal generated by ramp signal generator 600 to output a comparison signal.

[0043] The pulse signal generator 800 can be connected to the output of the comparator 700 and the input of the drive circuit 100. The pulse signal generator 800 can output a pulse width modulation (PWM) signal to the drive circuit 100 based on the comparison signal received from the comparator 700. The drive circuit 100 can, based on the PWM signal, output an upper bridge on signal UGS to the upper bridge switch UG and an lower bridge on signal LGS to the lower bridge switch LG, as described above.

[0044] In summary, this invention provides a power converter with a dynamic minimum turn-off time control mechanism. Under normal operating conditions, the minimum turn-off time of the lower bridge switch is short. However, when the current flowing through the upper bridge switch exceeds a first current threshold, i.e., an overcurrent event occurs, the minimum turn-off time of the lower bridge switch is longer. When the lower bridge switch remains open during the longer turn-off time, the lower bridge overcurrent protection circuit has sufficient time to detect whether the current flowing through the lower bridge switch exceeds a second current threshold, i.e., an overcurrent event has occurred. This prevents overcurrent events from causing burnout of the power converter's circuit components.

[0045] The above-disclosed content is only a preferred embodiment of the present invention and is not intended to limit the claims of the present invention. Therefore, all equivalent technical changes made based on the description and drawings of the present invention are included in the claims of the present invention.

Claims

1. A power converter with a dynamic control minimum shutdown time mechanism, characterized in that, The power converter with a dynamic control minimum shutdown time mechanism includes: An upper bridge switch, wherein the first terminal of the upper bridge switch is coupled to a shared voltage; A lower bridge switch, the first end of which is connected to the second end of the upper bridge switch, the node between the second end of the upper bridge switch and the first end of the lower bridge switch is connected to the first end of an inductor, the second end of the inductor is connected to the first end of a capacitor, the second end of the capacitor is grounded, and the second end of the lower bridge switch is grounded. A driving circuit is connected to the control terminal of the upper bridge switch and the control terminal of the lower bridge switch, and is configured to output an upper bridge conduction signal to the upper bridge switch to drive the upper bridge switch, and output a lower bridge conduction signal to the lower bridge switch to drive the lower bridge switch. An upper bridge overcurrent protection circuit is connected to the drive circuit and the node, and is configured to detect the node to determine whether there is current flowing from the upper bridge switch through the node toward the inductor and whether the current is greater than a first current threshold, so as to output an upper bridge overcurrent detection signal to the drive circuit and output an upper bridge overcurrent protection signal. as well as A turn-off time control circuit is connected to the upper bridge overcurrent protection circuit and the drive circuit, and is configured to determine the minimum turn-off time of the minimum turn-off time signal based on the upper bridge overcurrent protection signal, and output the minimum turn-off time signal to the drive circuit. The drive circuit determines that an overcurrent event has occurred when the upper bridge switch is turned on based on the upper bridge overcurrent detection signal, and therefore the drive circuit maintains the lower bridge switch on for at least the longer of the off time of the minimum off time signal.

2. The power converter with a dynamic control minimum shutdown time mechanism according to claim 1, characterized in that, The off-time control circuit stores multiple reference minimum off-times, selects one of the reference minimum off-times based on the upper bridge overcurrent protection signal, and outputs a minimum off-time signal having the minimum off-time equal to the selected reference minimum off-time.

3. The power converter with a dynamic control minimum shutdown time mechanism according to claim 1, characterized in that, The shutdown time control circuit determines the working period and non-working period of the minimum shutdown time signal based on the overcurrent protection signal of the upper bridge, and outputs the minimum shutdown time signal. The non-working period includes the minimum shutdown time.

4. The power converter with a dynamic control minimum shutdown time mechanism according to claim 1, characterized in that, The shutdown time control circuit stores a first reference minimum shutdown time. When the power converter does not generate the current or the current is not greater than the first current threshold, the shutdown time control circuit outputs a minimum shutdown time signal with the minimum shutdown time being equal to the first reference minimum shutdown time.

5. The power converter with a dynamic control minimum shutdown time mechanism according to claim 4, characterized in that, The shutdown time control circuit also stores a second reference minimum shutdown time that is greater than the first reference minimum shutdown time. When the power converter generates the current and the current is greater than the first current threshold, the shutdown time control circuit outputs a minimum shutdown time signal that has the minimum shutdown time equal to the second reference minimum shutdown time.

6. The power converter with a dynamic control minimum shutdown time mechanism according to claim 1, characterized in that, When the power converter generates the current and the current is greater than the first current threshold, a pulse is generated in the upper bridge overcurrent detection signal output by the upper bridge overcurrent protection circuit and a waveform is generated in the output upper bridge overcurrent protection signal.

7. The power converter with a dynamic control minimum shutdown time mechanism according to claim 6, characterized in that, The rising edge of the waveform of the upper bridge overcurrent protection signal is aligned with the rising edge of the pulse of the upper bridge overcurrent detection signal, and the falling edge of the waveform of the upper bridge overcurrent protection signal is aligned with the rising edge of the waveform of the upper bridge conduction signal.

8. The power converter with a dynamic control minimum shutdown time mechanism according to claim 1, characterized in that, The time from the rising edge of the lower bridge turn-on signal to the rising edge of the minimum turn-off time signal is the minimum turn-off time.

9. The power converter with a dynamic control minimum shutdown time mechanism according to claim 1, characterized in that, When the lower bridge switch receives a low-level lower bridge conduction signal, the lower bridge switch is closed; when the lower bridge switch receives a high-level lower bridge conduction signal, the lower bridge switch is opened.

10. The power converter with a dynamic control minimum shutdown time mechanism according to claim 1, characterized in that, The power converter with a dynamic control minimum turn-off time mechanism also includes a lower bridge overcurrent protection circuit connected to the drive circuit and the node, configured to determine whether another current flowing through the lower bridge switch, the node and the inductor is greater than a second current threshold during the minimum turn-off time.

Images