Abstract: A tracking circuit for a power supply comprises an inverter (68), a summing network (70), and a driver circuit (72). The inverter inverts a feedback voltage, which is a variable load voltage level, about an inverter reference voltage level to provide an inverter output voltage level. The inverter output voltage level is summed or averaged with the output voltage of the power supply with respect to the voltage of the return line (54) to provide a summing voltage. The driver circuit signals the primary control circuit (35) to adjust the power supply output voltage level so that the summing voltage is held constant and equal with a driver reference voltage level.

Abstract: A battery pack (10) is connected to a load or charger (12) and includes battery cells (20), under-voltage switch (22), a first voltage controlled switch (24), over-voltage switch (28), and second voltage controlled switch (30). Under-voltage switch (22) can block only discharge current, any recharge current may pass through it regardless of its switch state. Over-voltage switch (28) can block only recharge current when switched off and will always allow discharge current to flow regardless of its switch state. First voltage controlled switch (24) maintains under-voltage switch (22) on while battery voltage V1 is above a predetermined under-voltage level. When V1 drops to, or below, the under-voltage level first voltage controlled switch (24) switches off under-voltage switch (22) with a switch signal on line (26). Second voltage controlled switch (30) maintains over-voltage switch (28) on while battery voltage V1 is below a predetermined over-voltage level.