Digital slope compensation for current mode control
A digital slope compensation apparatus and method for a switched-mode power supply use a sensor for sensing and generating an analog inductor current (i L ) of the switched-mode power supply, a comparator ( 2 ) for generating a trigger signal according to a comparison of an analog current threshold level and the analog inductor current (i L ), and a pulse width modulator (PWM) for controlling the operation of a switched-mode power supply, wherein the pulse width modulator (PWM) is arranged to be triggered by the trigger signal of the comparator. A first analog to digital converter is arranged for converting an analog output voltage (V out ) of the switched-mode power supply into a digital output voltage, means are arranged for transforming the digital output voltage into a digital current threshold level (i cmp ) and a digital to analog converter is arranged for generating the analog current threshold level according to the digital current threshold level (i cmp ).
1. A digital slope compensation apparatus for a switched-mode power supply, comprising:
a sensor for sensing an analog inductor current (i L ) of the switched-mode power supply,
a comparator for generating a trigger signal according to a comparison of an analog current threshold level and the analog inductor current (i L ), and
a pulse width modulator (PWM) for controlling the operation of the switched-mode power supply, wherein the pulse width modulator (PWM) is arranged to be triggered by the trigger signal of the comparator,
characterised in that
a first analog to digital converter is arranged for converting an analog output voltage (V out ) of the switched-mode power supply into a digital output voltage,
at least one transformation module is arranged for transforming the digital output voltage into a digital current threshold level (i cmp ),
a digital to analog converter is arranged for generating the analog current threshold level according to the digital current threshold level (i cmp ),
a voltage controller is arranged to receive the digital output voltage and to generate a digital current reference (i*),
a second analog to digital converter is arranged to convert the analog inductor current (i L ) of the switched-mode power supply into a digital inductor current, and
a digital slope compensation module is arranged to receive the digital current reference (i*), the digital inductor current, and a compensation factor (k sc ) to generate the digital current threshold level (i cmp ).
2. Apparatus according to claim 1 , characterised in that the compensation factor (k sc ) is arranged to be a constant value.
3. Apparatus according to claim 1 , characterised in that an adaptive slope compensation factor module is arranged to generate the compensation factor (k sc ).
4. Apparatus according to claim 3 , characterised in that:
a third analog to digital converter is arranged to convert an analog input voltage (V in ) of the switched-mode power supply into a digital input voltage, and
the adaptive slope compensation factor module is arranged to receive the digital output voltage and the digital input voltage to generate the compensation factor (k sc ).
5. Apparatus according to claim 1 , characterized in that the apparatus is integrated as a part of a microcontroller.
6. A digital slope compensation method for a switched-mode power supply, wherein:
an analog inductor current (i L ) of the switched-mode power supply is sensed,
a trigger signal according to a comparison of an analog current threshold level and the analog inductor current (i L ) is generated, and
a pulse width modulated signal is triggered by the trigger signal to control operation of the switched-mode power supply,
characterised in that
an analog output voltage of the switched-mode power supply is converted into a digital output voltage,
the digital output voltage is transformed into a digital current threshold level,
the analog current threshold level is generated according to the digital current threshold level (i cmp ),
the digital current reference (i*) is generated according to the digital output voltage,
the analog inductor current (i L ) of the switched-mode power supply is converted into a digital inductor current, and
the digital current threshold level (i cmp ) is generated according to the digital current reference (i*), the digital inductor current, and a compensation factor (k sc ).
7. Method according to claim 6 , characterised in that a compensation factor (k sc ) with a constant value is used.
8. Method according to claim 6 , characterised in that an adaptive slope compensation factor module generates the compensation factor (k sc ).
9. Method according to claim 8 , characterised in that:
an analog input voltage (V in ) of the switched-mode power supply is converted into a digital input voltage, and
the compensation factor (k sc ) is generated according to the digital output voltage and the digital input voltage.
10. Method according to claim 6 , characterized in that a microcontroller is used to carry out the method.
11. Apparatus according to claim 1 , characterised in that the compensation factor (k sc ) is arranged to be a constant value.
12. Apparatus according to claim 1 , characterised in that an adaptive slope compensation factor module is arranged to generate the compensation factor (k sc ).
13. Apparatus according to claim 1 , characterized in that the apparatus is integrated as a part of a microcontroller.
14. Apparatus according to claim 2 , characterized in that the apparatus is integrated as a part of a microcontroller.
15. Apparatus according to claim 3 , characterized in that the apparatus is integrated as a part of a microcontroller.
16. Apparatus according to claim 4 , characterized in that the apparatus is integrated as a part of a microcontroller.
17. Method according to claim 6 , characterised in that a compensation factor (k sc ) with a constant value is used.
18. Method according to claim 6 , characterised in that an adaptive slope compensation factor module generates the compensation factor (k sc ).