Yes. The biggest part of that refund is the Earned Income Credit (EIC). The basic EIC works on a "bell curve," rising as a worker's wages rise reaching a maximum when annual earnings are between $13,650 and $17850 (Single with 2 or 3 children 2014) and then declining gradually until it phases out altogether. If your income is on the up slope of the EIC curve more earned income will increase your EIC but if your income is on the down slope, more income (of any kind) will reduce you EIC.
http://www.taxpolicycenter.org/briefing-book/key-elements/family/eitc.cfm
If you have not been receiving EIC, more income can still lower your refund depending on your withholding. A refund is the balance left over after you compare the amount withheld for taxes with the amount you actually owe. Sometimes when you get a raise or change jobs, your withholding might not keep up with your wages. This is especially true if you have two jobs, since the withholding system is not very smart and will under-withhold if you have two jobs, unless you make special adjustments to your withholding.
The answer is twofold. Not only did you make more money, but perhaps you have less deductions. Did exemptions change? Also, to insure a greater refund, you can have an additional amount with held from each pay check. Ask your employers hr. Dept. On how to go about this