5. C ONCLUSION AND F UTURE W ORK
5.2 F UTURE W ORK
For further efficiency improvement, we can investigate the power losses in the SMPS. The switching loss is one of the major losses in the SMPS. We can segment the power MOSFETs into parts for reducing gate drive loss [81]. We can also adjust the gate drive voltage dynamically according to the load condition [82]. These techniques can further improve conversion efficiency in light load operation at a price of increasing cost and circuit complexity.
Another interesting topic is about improving transient response. Although the proposed current-mode converter shows good transient response compared with others, it can not meet the specifications for supplying the high speed CPUs in personal computers. There are several ways to achieve faster transient response. An interesting one is nonlinear control [22], [83]. We may find other ways to control the SMPS to achieve faster response. Another straightforward method is higher switching frequency [21], [84]. This is much depending on the manufacturing process of the semiconductor power switches. Multi-phase design can also help improving transient response, but the cost is increased proportional to the number of phases they provide [21]-[22], [85]. Other purposed techniques also have their own disadvantages [86]-[90]. Except these developing techniques, we may try to find another way to achieve our goal in the future.
in frequency spectrum that is high. Adding some random jitter may reduce the height of this tone, but the spectrum may spread into a wider range. Which one of them generates less interference to other circuits can be investigated in the future. If the spread spectrum is the answer, how to inject a random jitter but not affect the stability of the converter is another interesting topic.
R
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A
PPENDIXA perl program generates SPICE netlist for calculation of RDS(ON) of power transistor
#! /usr/bin/perl/ -w
$mos_width=4.8;
$pmos="pmos_4.8u";
$nmos="nmos_4.8u";
$M2_step=4.8;
open (INPUT,"./input_g5626a_nmos_mod") || die "$!";
open (OUTPUT,">./output_g5626a_nmos_mod") || die "$!";
# Rpp_sheet = 113;
# $R_CON_P; P-type contact resistance
# $R_CON_N; N-type contact resistance
# $R_M1; Sheet resistance of M1
# $R_VIA; VIA resistance
# $R_M2; Sheet resistance of M2
# $mos_width; Unit MOS width
# $multiplier; Transfer length into integer
# $mos_w_cal; Transferred MOS width
# $mos_cal_half; 1/2 of transferred MOS width
# $polygon_m2_d; Number of DRAIN side convex polygons in M2 layer
# $polygon_m2_s; Number of SOURCE side convex polygons in M2 layer
# $polygon_m1_p; Number of POSITIVE convex polygons in M1 layer
# $polygon_m1_n; Number of NEGATIVE convex polygons in M1 layer
# $j; Reusable counting variable
# $i; Reusable counting variable
# $xi; <STDIN> x-coordinate of the M1 convex polygon
# $yi; <STDIN> y-coordinate of the M1 convex polygon
# $right; $right>0 indicates this corner point is at the left side of the line formed by previous 2 points and vice versa.
# $max_x_m2; Maximum x-coordinate of the M2 convex polygon
# $max_y_m2; Maximum y-coordinate of the M2 convex polygon
# $min_x_m2; Minimum x-coordinate of the M2 convex polygon
# $min_y_m2; Minimum y-coordinate of the M2 convex polygon
# $max_x_p; Maximum x-coordinate of the POSITIVE M1 convex polygon
# $max_y_p; Maximum y-coordinate of the POSITIVE M1 convex polygon
# $min_x_p; Minimum x-coordinate of the POSITIVE M1 convex polygon
# $min_y_p; Minimum y-coordinate of the POSITIVE M1 convex polygon
# $max_x_n; Maximum x-coordinate of the NEGATIVE M1 convex polygon
# $max_y_n; Maximum y-coordinate of the NEGATIVE M1 convex polygon
# $min_x_n; Minimum x-coordinate of the NEGATIVE M1 convex polygon
# $min_y_n; Minimum y-coordinate of the NEGATIVE M1 convex polygon
# $perpendicular; 1:polygate perpendicular to x-axis; 0:polygate parallel to x-axis
# $width_m1; Width of each M1 line
# $gap_M1; Gap between M1 lines
# $mos_type; PMOS:0, NMOS:1
# $M2_step; $M2_step indicates the distance between the nearest M2 points alone poly-silicon (in um)
# $step_x; $step_x/$multiplier indicate the distance between the nearest M2 points alone x-axis
# $step_y; $step_y/$multiplier indicate the distance between the nearest M2 points alone y-axis
# $sync_x; Used to syncronize the x-coordinate of M2 & M1 layer
# $sync_y; Used to syncronize the y-coordinate of M2 & M1 layer
# $sync_x_pad; Used to syncronize the x-coordinate of PAD & M2 layer
# $sync_y_pad; Used to syncronize the y-coordinate of PAD & M2 layer
# $x; Reusable counting x-coordinate variable
# $y; Reusable counting y-coordinate variable
# $x1; (Reusable) x-Difference of current point to the 1st point of an edge of the calculating polygon
# $y1; (Reusable) y-Difference of current point to the 1st point of an edge of the calculating pol polygon
# $x2; (Reusable) x-Difference of current point to the 2nd point of an edge of the calculating pol polygon
# $y2; (Reusable) y-Difference of current point to the 2nd point of an edge of the calculating pol polygon
# $min_max_right_m2_d; $min_max_right_m2_d<0 indicates this point is inside one of the DRAIN side M2 convex polygon
# $min_max_right_m2_s; $min_max_right_m2_s<0 indicates this point is inside one of the SOURCE side M2 convex polygon
# $max_right_n; $max_right_n>0 indicates this point is outside the NEGATIVE M1 convex polygon
# $max_right_p; $max_right_n>0 indicates this point is outside the POSITIVE M1 convex polygon
# $r_m1_count; Count for M1 resistors
# $mos_count; Count for MOS transistors
# $r_con_count; Count for CONTACTs
# $r_m2_count; Count for M2 resistors
# $x_next; (Reusable)x-coordinate of next point
# $y_next; (Reusable)x-coordinate of next point
# $pmos; Name of the sub-circuit of PMOS for SPICE netlist
# @n_m2_d[$j]; Number of corner points of the $jth M2 convex polygon at DRAIN side
# @n_m2_s[$j]; Number of corner points of the $jth M2 convex polygon at SOURCE side
# @n_m1_p[$j]; Number of corner points of the $jth POSITIVE M1 convex polygon
# @n_m1_n[$j]; Number of corner points of the $jth NEGATIVE M1 convex polygon
# @x_m2_d; List x-coordinate of the corner points of the DRAIN side M2 convex polygon without index
# @y_m2_d; List y-coordinate of the corner points of the DRAIN side M2 convex polygon without index
# @x_m2_s; List x-coordinate of the corner points of the SOURCE side M2 convex polygon without index
# @y_m2_s; List y-coordinate of the corner points of the SOURCE side M2 convex polygon without index
# @x_p; List x-coordinate of the corner points of the POSITIVE M1 convex polygon without index
# @y_p; List y-coordinate of the corner points of the POSITIVE M1 convex polygon without index
# @x_n; List x-coordinate of the corner points of the NEGATIVE M1 convex polygon without index
# @y_n; List y-coordinate of the corner points of the NEGATIVE M1 convex polygon without index
# @sort_x_m2_ls; Numerically sorted (from larger to smaller) x-coordinate of the corner points of the M2 convex polygon
# @sort_y_m2_ls; Numerically sorted (from larger to smaller) y-coordinate of the corner points of the M2 convex polygon
# @sort_x_m2_sl; Numerically sorted (from smaller to larger) x-coordinate of the corner points of the M2 convex polygon
# @sort_y_m2_sl; Numerically sorted (from smaller to larger) y-coordinate of the corner points of the M2 convex polygon
# @sort_x_p_ls; Numerically sorted (from larger to smaller) x-coordinate of the corner points of the POSITIVE M1 convex polygon
# @sort_y_p_ls; Numerically sorted (from larger to smaller) y-coordinate of the corner points of the POSITIVE M1 convex polygon
# @sort_x_p_sl; Numerically sorted (from smaller to larger) x-coordinate of the corner points of the POSITIVE M1 convex polygon
# @sort_y_p_sl; Numerically sorted (from smaller to larger) y-coordinate of the corner points of the POSITIVE M1 convex polygon
# @sort_x_n_ls; Numerically sorted (from larger to smaller) x-coordinate of the corner points of the NEGATIVE M1 convex polygon
# @sort_y_n_ls; Numerically sorted (from larger to smaller) y-coordinate of the corner points of the NEGATIVE M1 convex polygon
# @sort_x_n_sl; Numerically sorted (from smaller to larger) x-coordinate of the corner points of the NEGATIVE M1 convex polygon
# @sort_y_n_sl; Numerically sorted (from smaller to larger) y-coordinate of the corner points of the NEGATIVE M1 convex polygon
# @right_m2_d; Elements in @right_m2_d indicate if one point is at the right side of the edges of the DRAIN side M2 convex polygon
# @right_m2_s; Elements in @right_m2_s indicate if one point is at the right side of the edges of the SOURCE side M2 convex polygon
# @max_right_m2_d; Minimum value of @max_right_m2_d<0 indicates the point is inside one of the DRAIN side M2 convex polygon
# @max_right_m2_d; Minimum value of @max_right_m2_d<0 indicates the point is inside one of the DRAIN side M2 convex polygon