Control circuit for a boost converter in DCM
A control circuit for a boost converter wherein the control circuit comprises switching means configured to switch the boost converter to perform cycles wherein each cycle comprises an energy charging state in which an inductor stores energy provided by an input voltage and an energy discharging state in which the inductor provides energy to an output of the boost converter, comparison means configured to decide whether a frequency of a switching event is lower than a predetermined minimum frequency and on-time signal generation means configured to generate an on-time signal based on whether a frequency of a switching event is lower than a predetermined minimum frequency, wherein the on-time signal determines a duration of a charging state of a next switching event and wherein the switching means is configured to switch the boost converter based on the generated on-time signal.
1 . A control circuit for a boost converter, wherein the control circuit comprises:
switching means configured to switch the boost converter to perform cycles wherein each cycle comprises an energy charging state in which an inductor stores energy provided by an input voltage and an energy discharging state in which the inductor provides energy to an output of the boost converter;
comparison means configured to decide whether a frequency of a switching event is lower than a predetermined minimum frequency; and
on-time signal generation means configured to generate an on-time signal based on whether the frequency of a switching event is lower than the predetermined minimum frequency, wherein the on-time signal determines a duration of a charging state of a next switching event and wherein the switching means is configured to switch the boost converter based on the generated on-time signal;
wherein the on-time signal generation means comprises a current Digital Analogic Converter (DAC) configured to generate a charge current.
2 . The control circuit according to claim 1 , wherein the comparison means is further configured to decide whether the frequency of the switching event is higher than a first predetermined maximum frequency and the on-time signal generation means is configured to generate the on-time signal based on whether the frequency of the switching event is higher than the first predetermined maximum frequency;
wherein the on-time signal generation means further comprises a control value configured to decrease when the frequency of the switching event is higher than the first predetermined maximum frequency, and wherein the on-time signal is generated based on the control value.
3 . The control circuit according to claim 1 , the on-time signal generation means comprises a current source connected to the current DAC and the current source is configured to generate a reference current, wherein the current DAC is configured to generate the charge current based on the control value and the reference current.
4 . A control circuit for a boost converter, wherein the control circuit comprises:
switching means configured to switch the boost converter to perform cycles wherein each cycle comprises an energy charging state in which an inductor stores energy provided by an input voltage and an energy discharging state in which the inductor provides energy to an output of the boost converter;
comparison means configured to decide whether a frequency of a switching event is lower than a predetermined minimum frequency; and
on-time signal generation means configured to generate an on-time signal based on whether the frequency of a switching event is lower than the predetermined minimum frequency, wherein the on-time signal determines a duration of a charging state of a next switching event and wherein the switching means is configured to switch the boost converter based on the generated on-time signal;
wherein the on-time signal generation means further comprises a control value configured to increase when the frequency of the switching event is lower than the predetermined minimum frequency, and wherein the on-time signal is generated based on the control value.
5 . The control circuit according to claim 4 , further comprising generating a charge current based on the control value and the current in the inductor.
6 . The control circuit according to claim 4 , wherein the on-time signal generation means further comprises a register configured to store the control value (NSET), wherein the control value (NSET) is a signal generated by the comparison means at an output and indicates whether the frequency of a switching event is lower than a first threshold, and/or higher than a second threshold and/or higher than a third threshold.
7 . The control circuit according to claim 4 , wherein the comparison means is further configured to decide whether the frequency of the switching event is higher than a first predetermined maximum frequency and the on-time signal generation means is configured to generate the on-time signal based on whether the frequency of the switching event is higher than the first predetermined maximum frequency;
wherein the on-time signal generation means further comprises a control value configured to decrease when the frequency of the switching event is higher than the first predetermined maximum frequency, and wherein the on-time signal is generated based on the control value.
8 . The control circuit according to claim 4 , wherein the on-time signal generation means comprises a feedback circuit wherein the feedback circuit comprises a feedback input and is configured to receive a charge current (I CHARGE ) at the feedback input and to generate the on-time signal based on the charge current.
9 . A control circuit for a boost converter, wherein the control circuit comprises:
switching means configured to switch the boost converter to perform cycles wherein each cycle comprises an energy charging state in which an inductor stores energy provided by an input voltage and an energy discharging state in which the inductor provides energy to an output of the boost converter;
comparison means configured to decide whether a frequency of a switching event is lower than a predetermined minimum frequency; and
on-time signal generation means configured to generate an on-time signal based on whether the frequency of a switching event is lower than the predetermined minimum frequency, wherein the on-time signal determines a duration of a charging state of a next switching event and wherein the switching means is configured to switch the boost converter based on the generated on-time signal;
measurement means configured to receive a reference clock signal from a reference clock, to count a number of clock cycles during the switching event, and to determine the frequency of the switching event based on the number of clock cycles.
10 . The control circuit according to claim 9 , wherein the comparison means is further configured to decide whether the frequency of the switching event is higher than a first predetermined maximum frequency and the on-time signal generation means is configured to generate the on-time signal based on whether the frequency of the switching event is higher than the first predetermined maximum frequency;
wherein the on-time signal generation means further comprises a control value configured to decrease when the frequency of the switching event is higher than the first predetermined maximum frequency, and wherein the on-time signal is generated based on the control value.
11 . A control circuit for a boost converter, wherein the control circuit comprises:
switching means configured to switch the boost converter to perform cycles wherein each cycle comprises an energy charging state in which an inductor stores energy provided by an input voltage and an energy discharging state in which the inductor provides energy to an output of the boost converter;
comparison means configured to decide whether a frequency of a switching event is lower than a predetermined minimum frequency; and
on-time signal generation means configured to generate an on-time signal based on whether the frequency of a switching event is lower than the predetermined minimum frequency, wherein the on-time signal determines a duration of a charging state of a next switching event and wherein the switching means is configured to switch the boost converter based on the generated on-time signal;
wherein the on-time signal generation means comprises a feedback circuit wherein the feedback circuit comprises a feedback input and is configured to receive a charge current (I CHARGE ) at the feedback input and to generate the on-time signal based on the charge current;
the feedback circuit further comprises a capacitor and comparison circuit wherein the capacitor is configured to store a capacitor voltage based on the charge current, wherein the comparison circuit comprises a first input, a second input, wherein the comparison circuit is configured to receive a reference voltage at the first input, to receive the capacitor voltage at the second input, and to generate the on-time signal by comparing the reference voltage and the capacitor voltage; and
the reference voltage is generated by a variable voltage source controlled based on the determined duration of the charging state of the next switching event.
12 . The control circuit according to claim 11 , wherein the on-time signal generation means is configured to generate the charge current (I CHARGE ) based on the determined duration of the charging state of the next switching event and a current in the inductor.
13 . The control circuit according to claim 11 , wherein the charge current (I CHARGE ) is proportional to an output voltage (V BST ) of the switching means and the reference voltage (V REF ) is proportional to (V BST −V BAT ) to obtain a required target frequency in continuous conduction mode (CCM), and V BAT is an input voltage of the switching means.
14 . The control circuit according to claim 11 , the reference voltage (V REF ) is scaled based on a control value (N SET ) by using a variable voltage source, and the on-time signal (T ON ) is manipulated to scale the capacitor size or to scale the reference voltage (V REF ) with 1/factor.
15 . A control circuit for a boost converter, wherein the control circuit comprises:
switching means configured to switch the boost converter to perform cycles wherein each cycle comprises an energy charging state in which an inductor stores energy provided by an input voltage and an energy discharging state in which the inductor provides energy to an output of the boost converter;
comparison means configured to decide whether a frequency of a switching event is lower than a predetermined minimum frequency; and
on-time signal generation means configured to generate an on-time signal based on whether the frequency of a switching event is lower than the predetermined minimum frequency, wherein the on-time signal determines a duration of a charging state of a next switching event and wherein the switching means is configured to switch the boost converter based on the generated on-time signal;
wherein the on-time signal generation means comprises a feedback circuit wherein the feedback circuit comprises a feedback input and is configured to receive a charge current (I CHARGE ) at the feedback input and to generate the on-time signal based on the charge current;
the feedback circuit further comprises a capacitor and comparison circuit wherein the capacitor is configured to store a capacitor voltage based on the charge current, wherein the comparison circuit comprises a first input, a second input, wherein the comparison circuit is configured to receive a reference voltage at the first input, to receive the capacitor voltage at the second input, and to generate the on-time signal by comparing the reference voltage and the capacitor voltage; and
the capacitor comprises variable capacitor controlled based on the determined duration of the charging state of the next switching event.
16 . The control circuit according to claim 15 , wherein the on-time signal generation means is configured to generate the charge current (I CHARGE ) based on the determined duration of the charging state of the next switching event and a current in the inductor.
17 . The control circuit according to claim 15 , wherein the charge current (I CHARGE ) is proportional to an output voltage (V BST ) of the switching means and the reference voltage (V REF ) is proportional to (V BST −V BAT ) to obtain a required target frequency in continuous conduction mode (CCM), and V BAT is an input voltage of the switching means.
18 . The control circuit according to claim 15 , the reference voltage (V REF ) is scaled based on a control value (N SET ) by using a variable voltage source, and the on-time signal (T ON ) is manipulated to scale the capacitor size or to scale the reference voltage (V REF ) with 1/factor.
19 . A control circuit for a boost converter, wherein the control circuit comprises:
switching means configured to switch the boost converter to perform cycles wherein each cycle comprises an energy charging state in which an inductor stores energy provided by an input voltage and an energy discharging state in which the inductor provides energy to an output of the boost converter;
comparison means configured to decide whether a frequency of a switching event is lower than a predetermined minimum frequency; and
on-time signal generation means configured to generate an on-time signal based on whether the frequency of a switching event is lower than the predetermined minimum frequency, wherein the on-time signal determines a duration of a charging state of a next switching event and wherein the switching means is configured to switch the boost converter based on the generated on-time signal;
wherein the comparison means is further configured to decide whether the frequency of the switching event is higher than a first predetermined maximum frequency and the on-time signal generation means is configured to generate the on-time signal based on whether the frequency of the switching event is higher than the first predetermined maximum frequency;
the comparison means is further configured to decide whether the frequency of the switching event is higher than a predetermined second maximum frequency and the on-time signal generation means is configured to generate the on-time signal based further on whether the frequency of the switching event is higher than the predetermined second maximum frequency;
wherein the second predetermined frequency is greater than 2.25 multiply by the first predetermined frequency;
wherein the on-time signal generation means further comprises a control value configured to reset when the frequency of the switching event is higher than the second predetermined maximum frequency, and wherein the on-time signal is generated based on the control value.
20 . The control circuit according to claim 19 , wherein the on-time signal generation means further comprises a control value configured to decrease when the frequency of the switching event is higher than the first predetermined maximum frequency, and wherein the on-time signal is generated based on the control value.